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Sample records for soot formation secondary

  1. Ice nucleation activity of diesel soot particles at cirrus relevant temperature conditions: Effects of hydration, secondary organics coating, soot morphology, and coagulation

    Science.gov (United States)

    Kulkarni, Gourihar; China, Swarup; Liu, Shang; Nandasiri, Manjula; Sharma, Noopur; Wilson, Jacqueline; Aiken, Allison C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail; Shilling, John; Shutthanandan, Vaithiyalingam; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-01

    Ice formation by diesel soot particles was investigated at temperatures ranging from -40 to -50°C. Size-selected soot particles were physically and chemically aged in an environmental chamber, and their ice nucleating properties were determined using a continuous flow diffusion type ice nucleation chamber. Bare (freshly formed), hydrated, and compacted soot particles, as well as α-pinene secondary organic aerosol (SOA)-coated soot particles at high relative humidity conditions, showed ice formation activity at subsaturation conditions with respect to water but below the homogeneous freezing threshold conditions. However, SOA-coated soot particles at dry conditions were observed to freeze at homogeneous freezing threshold conditions. Overall, our results suggest that heterogeneous ice nucleation activity of freshly emitted diesel soot particles are sensitive to some of the aging processes that soot can undergo in the atmosphere.

  2. Investigating the formation mechanism of soot-like materials present in blast furnace coke samples

    Energy Technology Data Exchange (ETDEWEB)

    S. Dong; P. A' lvarez; N. Paterson; D.R. Dugwell; R. Kandiyoti [Imperial College London, London (United Kingdom). Department of Chemical Engineering

    2008-09-15

    An attempt to gain an understanding of the formation mechanism of these 'soot-like' materials has been made by means of tracing the changes in the molecular-mass distribution and molecular structure of the NMP-extractable materials from an injectant coal as well as its partially gasified chars and its pyrolytic tars. Variations in the SEC chromatograms provide clues about changes in the apparent molecular-mass distributions of these NMP extracts. Results suggest that the build-up of 'soot-like' materials follows from the secondary reactions of tars evolved from the injectant coal. The likely secondary-reaction pathways have been probed by collating structural information on these NMP extracts. The time-resolved 13-16 and 22-25 min elution fractions from the SEC column have been characterized using UV fluorescence (UV F) spectroscopy. Greater concentrations of larger aromatic ring systems are found present in samples formed under conditions appearing more prone for soot formation. The 11-16 min (large apparent molecular mass) effluent from SEC has been examined by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). Results from FTIR spectroscopy are consistent with the UV F data, showing more significant extents of dehydrogenation under conditions more prone to form soot. Similarly, TEM results show that larger amount of graphene layers exist in samples exposed to more soot-prone conditions. The emerging picture for the formation of 'soot-like' materials involves a well-defined sequence. Tars evolved from the injectant coal undergo secondary dehydrogenation, condensation, and repolymerization reactions, which eventually lead to the formation of the NMP-extractable 'soot-like' materials of large apparent molecular mass. 44 refs., 7 figs., 3 tabs.

  3. Soot Formation in Freely-Propagating Laminar Premixed Flames

    Science.gov (United States)

    Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

    1997-01-01

    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

  4. Effect of relative humidity on soot - secondary organic aerosol mixing: A case study from the Soot Aerosol Aging Study (PNNL-SAAS)

    Science.gov (United States)

    Sharma, N.; China, S.; Zaveri, R. A.; Shilling, J. E.; Pekour, M. S.; Liu, S.; Aiken, A. C.; Dubey, M. K.; Wilson, J. M.; Zelenyuk, A.; OBrien, R. E.; Moffet, R.; Gilles, M. K.; Gourihar, K.; Chand, D.; Sedlacek, A. J., III; Subramanian, R.; Onasch, T. B.; Laskin, A.; Mazzoleni, C.

    2014-12-01

    Atmospheric processing of fresh soot particles emitted by anthropogenic as well as natural sources alters their physical and chemical properties. For example, fresh and aged soot particles interact differently with incident solar radiation, resulting in different overall radiation budgets. Varying atmospheric chemical and meteorological conditions can result in complex soot mixing states. The Soot Aerosol Aging Study (SAAS) was conducted at the Pacific Northwest National Laboratory in November 2013 and January 2014 as a step towards understanding the evolution of mixing state of soot and its impact on climate-relevant properties. Aging experiments on diesel soot were carried out in a controlled laboratory chamber, and the effects of condensation and coagulation processes were systematically explored in separate sets of experiments. In addition to online measurement of aerosol properties, aerosol samples were collected for offline single particle analysis to investigate the evolution of the morphology, elemental composition and fine structure of sample particles from different experiments. Condensation experiments focused on the formation of α-pinene secondary organic aerosol on diesel soot aerosol seeds. Experiments were conducted to study the aging of soot under dry (RH < 2%) and humid conditions (RH ~ 80%). We present an analysis of the morphology of soot, its evolution, and its correlation with optical properties, as the condensation of α-pinene SOA is carried out for the two different RH conditions. The analysis was performed by using scanning electron microscopy, transmission electron microscopy, scanning transmission x-ray microscopy and atomic force microscopy for single particle characterization. In addition, particle size, mass, composition, shape, and density were characterized in-situ, as a function of organics condensed on soot seeds, using single particle mass spectrometer.

  5. Aromatics Oxidation and Soot Formation in Flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J. B.; Richter, H.

    2005-03-29

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and the growth process to polycyclic aromatic hydrocarbons (PAH) of increasing size, soot and fullerenes formation in flames. The overall objective of the experimental aromatics oxidation work is to extend the set of available data by measuring concentration profiles for decomposition intermediates such as phenyl, cyclopentadienyl, phenoxy or indenyl radicals which could not be measured with molecular-beam mass spectrometry to permit further refinement and testing of benzene oxidation mechanisms. The focus includes PAH radicals which are thought to play a major role in the soot formation process while their concentrations are in many cases too low to permit measurement with conventional mass spectrometry. The radical species measurements are used in critical testing and improvement of a kinetic model describing benzene oxidation and PAH growth. Thermodynamic property data of selected species are determined computationally, for instance using density functional theory (DFT). Potential energy surfaces are explored in order to identify additional reaction pathways. The ultimate goal is to understand the conversion of high molecular weight compounds to nascent soot particles, to assess the roles of planar and curved PAH and relationships between soot and fullerenes formation. The specific aims are to characterize both the high molecular weight compounds involved in the nucleation of soot particles and the structure of soot including internal nanoscale features indicative of contributions of planar and/or curved PAH to particle inception.

  6. Soot formation characteristics of gasoline surrogate fuels in counterflow diffusion flames

    KAUST Repository

    Choi, Byungchul

    2011-01-01

    The characteristics of polycyclic aromatic hydrocarbon (PAH) and soot for gasoline surrogate fuels have been investigated in counterflow diffusion flames by adopting laser-induced fluorescence (LIF) and laser-induced incandescence (LII) techniques for both soot formation and soot formation/oxidation flames. Tested fuels were three binary mixtures from the primary reference fuels of n-heptane, iso-octane, and toluene. The result showed that PAH and soot maintained near zero level for all mixtures of n-heptane/iso-octane case under present experimental conditions. For n-heptane/toluene and iso-octane/toluene mixtures, PAH initially increased and then decreased with the toluene ratio, exhibiting a synergistic effect. The soot formation increased monotonically with the toluene ratio, however the effect of toluene on soot formation was minimal for relatively small toluene ratios. These results implied that even though toluene had a dominant role in soot and PAH formations, small amount of toluene had a minimal effect on soot formation. Numerical simulations have also been conducted by adopting recently proposed two kinetic mechanisms. The synergistic behavior of aromatic rings was predicted similar to the experimental PAH measurement, however, the degree of the synergistic effect was over-predicted for the soot formation flame, indicating the need for refinements in the kinetic mechanisms. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  7. Numerical Investigation of Soot Formation in Non-premixed Flames

    KAUST Repository

    Abdelgadir, Ahmed Gamaleldin

    2017-05-01

    Soot is a carbon particulate formed as a result of the combustion of fossil fuels. Due to the health hazard posed by the carbon particulate, government agencies have applied strict regulations to control soot emissions from road vehicles, airplanes, and industrial plants. Thus, understanding soot formation and evolution is critical. Practical combustion devices operate at high pressure and in the turbulent regime. Elevated pressures and turbulence on soot formation significantly and fundamental understanding of these complex interactions is still poor. In this study, the effects of pressure and turbulence on soot formation and growth are investigated numerically. As the first step, the evolution of the particle size distribution function (PSDF) and soot particles morphology are investigated in turbulent non-premixed flames. A Direct Simulation Monte Carlo (DSMC) code is developed and used. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of an n-heptane turbulent non-premixed flame. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a broad tail, which implies significant polydispersity induced by turbulence. Secondly, the effect of the flow and mixing fields on soot formation at atmospheric and elevated pressures is investigated in coflow laminar diffusion flames. The experimental observation and the numerical prediction of the spatial distribution are in good agreement. Based on the common scaling methodology of the flames (keeping the Reynolds number constant), the scalar dissipation rate decreases as pressure increases, promoting the formation of PAH species and soot. The decrease of the scalar dissipation rate significantly contributes to soot formation occurring closer to the nozzle and outward on the flames wings as pressure

  8. Formation of Soot in Counterflow Diffusion Flames with Carbon Dioxide Dilution

    KAUST Repository

    Wang, Yu

    2016-05-04

    Experimental and numerical modeling studies have been performed to investigate the effect of CO2 dilution on soot formation in ethylene counterflow diffusion flames. Thermal and chemical effects of CO2 addition on soot growth was numerically identified by using a fictitious CO2 species, which was treated as inert in terms of chemical reactions. The results showed that CO2 addition reduces soot formation both thermodynamically and chemically. In terms of chemical effect, the addition of CO2 decreases soot formation through various pathways, including: (1) reduced soot precursor (PAH) formation leading to lower inception rates and soot number density, which in turn results in lower surface area for soot mass addition; (2) reduced H, CH3, and C3H3 concentrations causing lower H abstraction rate and therefore less active site per surface area for soot growth; and (3) reduced C2H2 mole fraction and thus a slower C2H2 mass addition rate. In addition, the sooting limits were also measured for ethylene counterflow flames in both N2 and CO2 atmosphere and the results showed that sooting region was significantly reduced in the CO2 case compared to the N2 case. © 2016 Taylor & Francis.

  9. Stochastic Simulation of Soot Formation Evolution in Counterflow Diffusion Flames

    Directory of Open Access Journals (Sweden)

    Xiao Jiang

    2018-01-01

    Full Text Available Soot generally refers to carbonaceous particles formed during incomplete combustion of hydrocarbon fuels. A typical simulation of soot formation and evolution contains two parts: gas chemical kinetics, which models the chemical reaction from hydrocarbon fuels to soot precursors, that is, polycyclic aromatic hydrocarbons or PAHs, and soot dynamics, which models the soot formation from PAHs and evolution due to gas-soot and soot-soot interactions. In this study, two detailed gas kinetic mechanisms (ABF and KM2 have been compared during the simulation (using the solver Chemkin II of ethylene combustion in counterflow diffusion flames. Subsequently, the operator splitting Monte Carlo method is used to simulate the soot dynamics. Both the simulated data from the two mechanisms for gas and soot particles are compared with experimental data available in the literature. It is found that both mechanisms predict similar profiles for the gas temperature and velocity, agreeing well with measurements. However, KM2 mechanism provides much closer prediction compared to measurements for soot gas precursors. Furthermore, KM2 also shows much better predictions for soot number density and volume fraction than ABF. The effect of nozzle exit velocity on soot dynamics has also been investigated. Higher nozzle exit velocity renders shorter residence time for soot particles, which reduces the soot number density and volume fraction accordingly.

  10. Empirical soot formation and oxidation model

    Directory of Open Access Journals (Sweden)

    Boussouara Karima

    2009-01-01

    Full Text Available Modelling internal combustion engines can be made following different approaches, depending on the type of problem to be simulated. A diesel combustion model has been developed and implemented in a full cycle simulation of a combustion, model accounts for transient fuel spray evolution, fuel-air mixing, ignition, combustion, and soot pollutant formation. The models of turbulent combustion of diffusion flame, apply to diffusion flames, which one meets in industry, typically in the diesel engines particulate emission represents one of the most deleterious pollutants generated during diesel combustion. Stringent standards on particulate emission along with specific emphasis on size of emitted particulates have resulted in increased interest in fundamental understanding of the mechanisms of soot particulate formation and oxidation in internal combustion engines. A phenomenological numerical model which can predict the particle size distribution of the soot emitted will be very useful in explaining the above observed results and will also be of use to develop better particulate control techniques. A diesel engine chosen for simulation is a version of the Caterpillar 3406. We are interested in employing a standard finite-volume computational fluid dynamics code, KIVA3V-RELEASE2.

  11. Towards predictive simulations of soot formation: from surrogate to turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Blanquart, Guillaume [California Inst. of Technology (CalTech), Pasadena, CA (United States)

    2017-03-28

    The combustion of transportation fuels leads to the formation of several kinds of pollutants, among which are soot particles. These particles, also formed during coal combustion and in fires, are the source of several health problems and environmental issues. Unfortunately, our current understanding of the chemical and physical phenomena leading to the formation of soot particles remains incomplete, and as a result, the predictive capability of our numerical tools is lacking. The objective of the work was to reduce the gap in the present understanding and modeling of soot formation both in laminar and turbulent flames. The effort spanned several length scales from the molecular level to large scale turbulent transport.

  12. A computational study of soot formation in opposed-flow diffusion flame interacting with vortices

    KAUST Repository

    Selvaraj, Prabhu

    2017-01-05

    The flame-vortex interaction enables the study of basic phenomena that control the coupling between combustion and turbulence. Employing a gas phase reaction mechanism considering polycyclic aromatic hydrocarbons (PAH), a two dimensional counterflow ethylene-air flame is simulated. A reduced mechanism with PAH pathways that includes until coronene and method of moments with interpolative closure (MOMIC) has been employed to calculate the soot characteristics. Interaction of sooting flame with a prescribed decaying random velocity field is being investigated. Counterflow nonpremixed flames at low strain rate sooting conditions are considered. Effects of vortices are studied on the flame structures and its sensitivity on the soot formation characteristics. As the vortex rolls up the flame, integrated soot volume fraction is found to be larger for the air-side vortex. A detailed analysis on the flame structure and its influence on the formation of soot were carried out. The results indicate that the larger PAH species contributes to the soot formation in the airside perturbation regimes, whereas the soot formation is dominated by the soot transport in fuel-side perturbation.

  13. On the formation and early evolution of soot in turbulent nonpremixed flames

    KAUST Repository

    Bisetti, Fabrizio

    2012-01-01

    A Direct Numerical Simulation (DNS) of soot formation in an n-heptane/air turbulent nonpremixed flame has been performed to investigate unsteady strain effects on soot growth and transport. For the first time in a DNS of turbulent combustion, Polycyclic Aromatic Hydrocarbons (PAH) are included via a validated, reduced chemical mechanism. A novel statistical representation of soot aggregates based on the Hybrid Method of Moments is used [M.E. Mueller, G. Blanquart, H. Pitsch, Combust. Flame 156 (2009) 1143-1155], which allows for an accurate state-of-the-art description of soot number density, volume fraction, and morphology of the aggregates. In agreement with previous experimental studies in laminar flames, Damköhler number effects are found to be significant for PAH. Soot nucleation and growth from PAH are locally inhibited by high scalar dissipation rate, thus providing a possible explanation for the experimentally observed reduction of soot yields at increasing levels of mixing in turbulent sooting flames. Furthermore, our data indicate that soot growth models that rely on smaller hydrocarbon species such as acetylene as a proxy for large PAH molecules ignore or misrepresent the effects of turbulent mixing and hydrodynamic strain on soot formation due to differences in the species Damköhler number. Upon formation on the rich side of the flame, soot is displaced relative to curved mixture fraction iso-surfaces due to differential diffusion effects between soot and the gas-phase. Soot traveling towards the flame is oxidized, and aggregates displaced away from the flame grow primarily by condensation of PAH on the particle surface. In contrast to previous DNS studies based on simplified soot and chemistry models, surface reactions are found to contribute barely to the growth of soot, for nucleation and condensation processes occurring in the fuel stream are responsible for the most of soot mass generation. Furthermore, the morphology of the soot aggregates is

  14. Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure

    Science.gov (United States)

    Xu, F.; Lin, K.-C.; Faeth, G. M.

    1998-01-01

    Flame structure and soot formation were studied within soot-containing laminar premixed mc1hane/oxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt: the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogen-abstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames. for reasons that still must be explained.

  15. Understanding Combustion and Soot Formation in Diesel Engines

    Science.gov (United States)

    2016-09-09

    distributions of PLII signals help understand the soot distributions within diesel/ biodiesel flames. In addition, planar laser-induced Figure 1. Transported ...Prescribed by ANSI Std. Z39.18 Page 1 of 1FORM SF 298 9/14/2016https://livelink.ebs.afrl.af.mil/livelink/llisapi.dll This project investigated biodiesel ...emissions testing. 1 FINAL REPORT Project title: Understanding combustion and soot formation in biodiesel fuelled diesel engines Lead Institute and

  16. Effects of Large Polycyclic Aromatic Hydrocarbons on the Soot Formation in Ethylene-Air Nonpremixed Flames

    KAUST Repository

    Prabhu, S.; Arias, P.G.; Wang, Y.; Gao, Y.; Park, S.; Im, Hong G.; Sarathy, Mani; Chung, Suk-Ho; Lu, T.

    2015-01-01

    This study presents updated comprehensive gas-phase kinetic mechanism and aerosol models to predict soot formation characteristics in ethylene-air nonpremixed flames. A main objective is to investigate the sensitivity of the soot formation rate to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph (DRG) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames of pure ethylene at low strain rate sooting conditions are considered, for which the sensitivity of soot formation characteristics with respect to hetrogeneous nucleation is investigated. Results show that higher PAH concentrations result in higher soot nucleation rate, and that the average size of the particles are in good agreement with experimental results. It is found that the nucleation processes (i.e., soot inception) from higher PAH precursors, coronene in particular, is critical for accurate prediction of the overall soot formation.

  17. Effects of Large Polycyclic Aromatic Hydrocarbons on the Soot Formation in Ethylene-Air Nonpremixed Flames

    KAUST Repository

    Prabhu, S.

    2015-03-30

    This study presents updated comprehensive gas-phase kinetic mechanism and aerosol models to predict soot formation characteristics in ethylene-air nonpremixed flames. A main objective is to investigate the sensitivity of the soot formation rate to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph (DRG) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames of pure ethylene at low strain rate sooting conditions are considered, for which the sensitivity of soot formation characteristics with respect to hetrogeneous nucleation is investigated. Results show that higher PAH concentrations result in higher soot nucleation rate, and that the average size of the particles are in good agreement with experimental results. It is found that the nucleation processes (i.e., soot inception) from higher PAH precursors, coronene in particular, is critical for accurate prediction of the overall soot formation.

  18. Investigation of soot formation and temperature field in laminar diffusion flames of LPG-air mixture

    Energy Technology Data Exchange (ETDEWEB)

    Shahad, Haroun A.K.; Mohammed, Yassar K.A. [Babylon Univ., Dept. of Mechanical Engineering, Babylon (Israel)

    2000-11-01

    Soot formation and burnout were studied at atmospheric pressure in co-flowing, axisymmetric buoyant laminar diffusion flames and double flames of liquefied petroleum gases (LPG)-air mixtures. In diffusion flames, two different fuel flow rates were examined. In double flames, three different primary air flow rates were examined. A soot sampling probe and a thermocouple were used to measure the local soot mass concentration and flame temperature, respectively. Flame residence time was predicted using a uniformly accelerated motion model as function of axial distance of the flame. The increase of primary air flow rate was found to suppress the energy transfer from the annular region, at which the soot is produced, to the flame axis. The time required to initiate soot formation at the flame axis becomes longer as the primary air is increased. The trend rate of soot formation was found to be similar along the flame axis in all tested diffusion flames. The increase of primary air by 10% of the stoichiometric air requirement of the fuel results in a 70% reduction in maximum soot concentration. The final exhaust of soot, which is determined by the net effect of soot formation and burnout, is much lower in double flames than that in diffusion flames. (Author)

  19. Soot Formation Modeling of n-dodecane and Diesel Sprays under Engine-Like Conditions

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Poon, Hiew Mun; Ng, Hoon Kiat

    2015-01-01

    This work concerns the modelling of soot formation process in diesel spray combustion under engine-like conditions. The key aim is to investigate the soot formation characteristics at different ambient temperatures. Prior to simulating the diesel combustion, numerical models including a revised...

  20. Role of Fluid-Dynamics in Soot Formation and Microstructure in Acetylene-Air Laminar Diffusion Flames

    Directory of Open Access Journals (Sweden)

    Praveen Pandey

    2015-03-01

    Full Text Available Residence time and thermo-chemical environment are important factors in the soot-formation process in flames. Studies have revealed that flow-dynamics plays a dominant role in soot formation process. For understanding the effect of flow dynamics on soot formation and physical structure of the soot formed in different combustion environments two types of laminar diffusion flames of Acetylene and air, a normal diffusion flame (NDF and an inverse diffusion flame (IDF have been investigated. The fuel and air supply in the reaction zone in two flame types were kept constant but the interchange of relative position of fuel and air altered the burner exit Reynolds and Froude numbers of gases, fuel/air velocity ratio and flame shape. Soot samples were collected using thermophoretic sampling on transmission electron microscope (TEM grids at different flame heights and were analyzed off-line in a Transmission Electron Microscope. Soot primary particle size, soot aggregate size and soot volume fraction were measured using an image analysis software. In NDF the maximum flame temperature was about 1525 K and 1230 K for IDF. The soot primary particles are distinctly smaller in size in IDF (between 19 – 26 nm compared to NDF (between 29–34 nm. Both NDF and IDF show chainlike branched structure of soot agglomerate with soot particles of a nearly spherical shape. The average number of soot primary particles per aggregate in NDF was in the range of 24 to 40 and in IDF it varied between 16 to 24. Soot volume fraction was between 0.6 to 1.5 ppm in NDF where as it was less than 0.2 ppm in IDF. The change in sooting characteristics of the two flame types is attributed to changed fuel/air velocity ratio, entrainment of gas molecules and thermophoresis on soot particles.

  1. Heterogeneous reaction of SO2 with soot: The roles of relative humidity and surface composition of soot in surface sulfate formation

    Science.gov (United States)

    Zhao, Yan; Liu, Yongchun; Ma, Jinzhu; Ma, Qingxin; He, Hong

    2017-03-01

    The conversion of SO2 to sulfates on the surface of soot is still poorly understood. Soot samples with different fractions of unsaturated hydrocarbons and oxygen-containing groups were prepared by combusting n-hexane under well-controlled conditions. The heterogeneous reaction of SO2 with soot was investigated using in situ attenuated total internal reflection infrared (ATR-IR) spectroscopy, ion chromatography (IC) and a flow tube reactor at the ambient pressure and relative humidity (RH). Water promoted SO2 adsorption and sulfate formation at the RH range from 6% to 70%, while exceeded water condensed on soot was unfavorable for sulfate formation due to inhibition of SO2 adsorption when RH was higher than 80%. The surface composition of soot, which was governed by combustion conditions, also played an important role in the heterogeneous reaction of SO2 with soot. This effect was found to greatly depend on RH. At low RH of 6%, soot with the highest fuel/oxygen ratio of 0.162 exhibited a maximum uptake capacity for SO2 because it contained a large amount of aromatic Csbnd H groups, which acted as active sites for SO2 adsorption. At RH of 54%, soot produced with a fuel/oxygen ratio of 0.134 showed the highest reactivity toward SO2 because it contained appropriate amounts of aromatic Csbnd H groups and oxygen-containing groups, subsequently leading to the optimal surface concentrations of both SO2 and water. These results suggest that variation in the surface composition of soot from different sources and/or resulting from chemical aging in the atmosphere likely affects the conversion of SO2 to sulfates.

  2. Compositional effects on PAH and soot formation in counterflow diffusion flames of gasoline surrogate fuels

    KAUST Repository

    Park, Sungwoo

    2017-02-05

    Gasoline surrogate fuels are widely used to understand the fundamental combustion properties of complex refinery gasoline fuels. In this study, the compositional effects on polycyclic aromatic hydrocarbons (PAHs) and soot formation were investigated experimentally for gasoline surrogate mixtures comprising n-heptane, iso-octane, and toluene in counterflow diffusion flames. A comprehensive kinetic model for the gasoline surrogate mixtures was developed to accurately predict the fuel oxidation along with the formation of PAHs and soot in flames. This combined model was first tested against ignition delay times and laminar burning velocities data. The proposed model for the formation and growth of PAHs up to coronene (C24H12) was based on previous studies and was tested against existing and present new experimental data. Additionally, in the accompanied soot model, PAHs with sizes larger than (including) pyrene were used for the inception of soot particles, followed by particle coagulations and PAH condensation/chemical reactions on soot surfaces. The major pathways for the formation of PAHs were also identified for the surrogate mixtures. The model accurately captures the synergistic PAH formation characteristics observed experimentally for n-heptane/toluene and iso-octane/toluene binary mixtures. Furthermore, the present experimental and modeling results also elucidated different trends in the formation of larger PAHs and soot between binary n-heptane/iso-octane and ternary n-heptane/iso-octane/toluene mixtures. Propargyl radicals (C3H3) were shown to be important in the formation and growth of PAHs for n-heptane/iso-octane mixtures when the iso-octane concentration increased; however, reactions involving benzyl radicals (C6H5CH2) played a significant role in the formation of PAHs for n-heptane/iso-octane/toluene mixtures. These results indicated that the formation of PAHs and subsequently soot was strongly affected by the composition of gasoline surrogate mixtures.

  3. Compositional effects on PAH and soot formation in counterflow diffusion flames of gasoline surrogate fuels

    KAUST Repository

    Park, Sungwoo; Wang, Yu; Chung, Suk-Ho; Sarathy, Mani

    2017-01-01

    Gasoline surrogate fuels are widely used to understand the fundamental combustion properties of complex refinery gasoline fuels. In this study, the compositional effects on polycyclic aromatic hydrocarbons (PAHs) and soot formation were investigated experimentally for gasoline surrogate mixtures comprising n-heptane, iso-octane, and toluene in counterflow diffusion flames. A comprehensive kinetic model for the gasoline surrogate mixtures was developed to accurately predict the fuel oxidation along with the formation of PAHs and soot in flames. This combined model was first tested against ignition delay times and laminar burning velocities data. The proposed model for the formation and growth of PAHs up to coronene (C24H12) was based on previous studies and was tested against existing and present new experimental data. Additionally, in the accompanied soot model, PAHs with sizes larger than (including) pyrene were used for the inception of soot particles, followed by particle coagulations and PAH condensation/chemical reactions on soot surfaces. The major pathways for the formation of PAHs were also identified for the surrogate mixtures. The model accurately captures the synergistic PAH formation characteristics observed experimentally for n-heptane/toluene and iso-octane/toluene binary mixtures. Furthermore, the present experimental and modeling results also elucidated different trends in the formation of larger PAHs and soot between binary n-heptane/iso-octane and ternary n-heptane/iso-octane/toluene mixtures. Propargyl radicals (C3H3) were shown to be important in the formation and growth of PAHs for n-heptane/iso-octane mixtures when the iso-octane concentration increased; however, reactions involving benzyl radicals (C6H5CH2) played a significant role in the formation of PAHs for n-heptane/iso-octane/toluene mixtures. These results indicated that the formation of PAHs and subsequently soot was strongly affected by the composition of gasoline surrogate mixtures.

  4. Numerical modeling of soot formation in a turbulent C2H4/air diffusion flame

    Directory of Open Access Journals (Sweden)

    Manedhar Reddy Busupally

    2016-06-01

    Full Text Available Soot formation in a lifted C2H4-Air turbulent diffusion flame is studied using two different paths for soot nucleation and oxidation; by a 2D axisymmetric RANS simulation using ANSYS FLUENT 15.0. The turbulence-chemistry interactions are modeled using two different approaches: steady laminar flamelet approach and flamelet-generated manifold. Chemical mechanism is represented by POLIMI to study the effect of species concentration on soot formation. P1 approximation is employed to approximate the radiative transfer equation into truncated series expansion in spherical harmonics while the weighted sum of gray gases is invoked to model the absorption coefficient while the soot model accounts for nucleation, coagulation, surface growth, and oxidation. The first route for nucleation considers acetylene concentration as a linear function of soot nucleation rate, whereas the second route considers two and three ring aromatic species as function of nucleation rate. Equilibrium-based and instantaneous approach has been used to estimate the OH concentration for soot oxidation. Lee and Fenimore-Jones soot oxidation models are studied to shed light on the effect of OH on soot oxidation. Moreover, the soot-radiation interactions are also included in terms of absorption coefficient of soot. Furthermore, the soot-turbulence interactions have been invoked using a temperature/mixture fraction-based single variable PDF. Both the turbulence-chemistry interaction models are able to accurately predict the flame liftoff height, and for accurate prediction of flame length, radiative heat loss should be accounted in an accurate way. The soot-turbulence interactions are found sensitive to the PDF used in present study.

  5. The effect of ethanol blending on mixture formation, combustion and soot emission studied in an optical DISI engine

    International Nuclear Information System (INIS)

    Storch, Michael; Hinrichsen, Florian; Wensing, Michael; Will, Stefan; Zigan, Lars

    2015-01-01

    Highlights: • Catalyst heating points were analyzed using optical measurement techniques. • E20 shows stronger soot radiation and higher soot concentration as isooctane. • Different mixing formation of isooctane and E20 was determined. • Strong mixture stratification was identified for both fuels. • Remaining droplets and fuel rich regions are the main source for soot formation. - Abstract: In various research studies, ethanol blended fuels have shown reduced particulate matter (PM) emissions in comparison to gasoline and its surrogate fuels in direct-injection spark-ignition (DISI) engines. However, there are also studies reporting increased particulate concentration for fuels with low ethanol content. In this work the mixture formation and sooting combustion behavior of isooctane and the mixture E20 (20 vol% of ethanol in isooctane) is analyzed for catalyst heating operation. These operating conditions are critical as they strongly contribute to overall soot emissions in driving cycles. Simultaneous high speed imaging of OH ∗ –chemiluminescence and natural soot luminosity measurements are performed in combination with primary particle concentration measurements using a laser induced incandescence (LII) sensor in the engine exhaust duct. At these operating conditions E20 exhibits a higher sooting tendency as compared to isooctane. In order to identify the reason for increased soot formation, the mixture formation process is analyzed by planar laser induced fluorescence (LIF) measurements. The results show that soot was formed in fuel rich regions with incomplete evaporated fuel droplets remaining from the injection event. A different evaporation process of E20 fuel spray and mixing behavior is indicated showing a more compact rich mixture cloud with surrounding lean areas near the spark plug region. This mixture stratification is characterized by higher cyclic variations and constitutes a significant source of soot formation

  6. Aromatics oxidation and soot formation in flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J.B.; Pope, C.J.; Shandross, R.A.; Yadav, T. [Massachusetts Institute of Technology, Cambridge (United States)

    1993-12-01

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and soot and fullerenes formation in flames. The scope includes detailed measurements of profiles of stable and radical species concentrations in low-pressure one-dimensional premixed flames. Intermediate species identifications and mole fractions, fluxes, and net reaction rates calculated from the measured profiles are used to test postulated reaction mechanisms. Particular objectives are to identify and to determine or confirm rate constants for the main benzene oxidation reactions in flames, and to characterize fullerenes and their formation mechanisms and kinetics.

  7. Instabilities and soot formation in spherically expanding, high pressure, rich, iso-octane-air flames

    International Nuclear Information System (INIS)

    Lockett, R D

    2006-01-01

    Flame instabilities, cellular structures and soot formed in high pressure, rich, spherically expanding iso-octane-air flames have been studied experimentally using high speed Schlieren cinematography, OH fluorescence, Mie scattering and laser induced incandescence. Cellular structures with two wavelength ranges developed on the flame surface. The larger wavelength cellular structure was produced by the Landau-Darrieus hydrodynamic instability, while the short wavelength cellular structure was produced by the thermal-diffusive instability. Large negative curvature in the short wavelength cusps caused local flame quenching and fracture of the flame surface. In rich flames with equivalence ratio φ > 1.8, soot was formed in a honeycomb-like structure behind flame cracks associated with the large wavelength cellular structure induced by the hydrodynamic instability. The formation of soot precursors through low temperature pyrolysis was suggested as a suitable mechanism for the initiation of soot formation behind the large wavelength flame cracks

  8. Instabilities and soot formation in spherically expanding, high pressure, rich, iso-octane-air flames

    Energy Technology Data Exchange (ETDEWEB)

    Lockett, R D [School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V OHB (United Kingdom)

    2006-07-15

    Flame instabilities, cellular structures and soot formed in high pressure, rich, spherically expanding iso-octane-air flames have been studied experimentally using high speed Schlieren cinematography, OH fluorescence, Mie scattering and laser induced incandescence. Cellular structures with two wavelength ranges developed on the flame surface. The larger wavelength cellular structure was produced by the Landau-Darrieus hydrodynamic instability, while the short wavelength cellular structure was produced by the thermal-diffusive instability. Large negative curvature in the short wavelength cusps caused local flame quenching and fracture of the flame surface. In rich flames with equivalence ratio {phi} > 1.8, soot was formed in a honeycomb-like structure behind flame cracks associated with the large wavelength cellular structure induced by the hydrodynamic instability. The formation of soot precursors through low temperature pyrolysis was suggested as a suitable mechanism for the initiation of soot formation behind the large wavelength flame cracks.

  9. Effects of Fuel Quantity on Soot Formation Process for Biomass-Based Renewable Diesel Fuel Combustion

    KAUST Repository

    Jing, Wei; Wu, Zengyang; Roberts, William L.; Fang, Tiegang

    2016-01-01

    Soot formation process was investigated for biomass-based renewable diesel fuel, such as biomass to liquid (BTL), and conventional diesel combustion under varied fuel quantities injected into a constant volume combustion chamber. Soot measurement

  10. Formation, growth, and transport of soot in a three-dimensional turbulent non-premixed jet flame

    KAUST Repository

    Attili, Antonio; Bisetti, Fabrizio; Mü eller, Michael E.; Pitsch, Heinz G.

    2014-01-01

    The formation, growth, and transport of soot is investigated via large scale numerical simulation in a three-dimensional turbulent non-premixed n-heptane/air jet flame at a jet Reynolds number of 15,000. For the first time, a detailed chemical mechanism, which includes the soot precursor naphthalene and a high-order method of moments are employed in a three-dimensional simulation of a turbulent sooting flame. The results are used to discuss the interaction of turbulence, chemistry, and the formation of soot. Compared to temperature and other species controlled by oxidation chemistry, naphthalene is found to be affected more significantly by the scalar dissipation rate. While the mixture fraction and temperature fields show fairly smooth spatial and temporal variations, the sensitivity of naphthalene to turbulent mixing causes large inhomogeneities in the precursor fields, which in turn generate even stronger intermittency in the soot fields. A strong correlation is apparent between soot number density and the concentration of naphthalene. On the contrary, while soot mass fraction is usually large where naphthalene is present, pockets of fluid with large soot mass are also frequent in regions with very low naphthalene mass fraction values. From the analysis of Lagrangian statistics, it is shown that soot nucleates and grows mainly in a layer close to the flame and spreads on the rich side of the flame due to the fluctuating mixing field, resulting in more than half of the total soot mass being located at mixture fractions larger than 0.6. Only a small fraction of soot is transported towards the flame and is completely oxidized in the vicinity of the stoichiometric surface. These results show the leading order effects of turbulent mixing in controlling the dynamics of soot in turbulent flames. Finally, given the difficulties in obtaining quantitative data in experiments of turbulent sooting flames, this simulation provides valuable data to guide the development of

  11. Formation, growth, and transport of soot in a three-dimensional turbulent non-premixed jet flame

    KAUST Repository

    Attili, Antonio

    2014-07-01

    The formation, growth, and transport of soot is investigated via large scale numerical simulation in a three-dimensional turbulent non-premixed n-heptane/air jet flame at a jet Reynolds number of 15,000. For the first time, a detailed chemical mechanism, which includes the soot precursor naphthalene and a high-order method of moments are employed in a three-dimensional simulation of a turbulent sooting flame. The results are used to discuss the interaction of turbulence, chemistry, and the formation of soot. Compared to temperature and other species controlled by oxidation chemistry, naphthalene is found to be affected more significantly by the scalar dissipation rate. While the mixture fraction and temperature fields show fairly smooth spatial and temporal variations, the sensitivity of naphthalene to turbulent mixing causes large inhomogeneities in the precursor fields, which in turn generate even stronger intermittency in the soot fields. A strong correlation is apparent between soot number density and the concentration of naphthalene. On the contrary, while soot mass fraction is usually large where naphthalene is present, pockets of fluid with large soot mass are also frequent in regions with very low naphthalene mass fraction values. From the analysis of Lagrangian statistics, it is shown that soot nucleates and grows mainly in a layer close to the flame and spreads on the rich side of the flame due to the fluctuating mixing field, resulting in more than half of the total soot mass being located at mixture fractions larger than 0.6. Only a small fraction of soot is transported towards the flame and is completely oxidized in the vicinity of the stoichiometric surface. These results show the leading order effects of turbulent mixing in controlling the dynamics of soot in turbulent flames. Finally, given the difficulties in obtaining quantitative data in experiments of turbulent sooting flames, this simulation provides valuable data to guide the development of

  12. Numerical Modelling of Soot Formation in Laminar Axisymmetric Ethylene-Air Coflow Flames at Atmospheric and Elevated Pressures

    KAUST Repository

    Rakha, Ihsan Allah

    2015-05-01

    The steady coflow diffusion flame is a widely used configuration for studying combustion kinetics, flame dynamics, and pollutant formation. In the current work, a set of diluted ethylene-air coflow flames are simulated to study the formation, growth, and oxidation of soot, with a focus on the effects of pressure on soot yield. Firstly, we assess the ability of a high performance CFD solver, coupled with detailed transport and kinetic models, to reproduce experimental measurements, like the temperature field, the species’ concentrations and the soot volume fraction. Fully coupled conservation equations for mass, momentum, energy, and species mass fractions are solved using a low Mach number formulation. Detailed finite rate chemistry describing the formation of Polycyclic Aromatic Hydrocarbons up to cyclopenta[cd]pyrene is used. Soot is modeled using a moment method and the resulting moment transport equations are solved with a Lagrangian numerical scheme. Numerical and experimental results are compared for various pressures. Reasonable agreement is observed for the flame height, temperature, and the concentrations of various species. In each case, the peak soot volume fraction is predicted along the centerline as observed in the experiments. The predicted integrated soot mass at pressures ranging from 4-8 atm, scales as P2.1, in satisfactory agreement with the measured integrated soot pressure scaling (P2.27). Significant differences in the mole fractions of benzene and PAHs, and the predicted soot volume fractions are found, using two well-validated chemical kinetic mechanisms. At 4 atm, one mechanism over-predicts the peak soot volume fraction by a factor of 5, while the other under-predicts it by a factor of 5. A detailed analysis shows that the fuel tube wall temperature has an effect on flame stabilization.

  13. Modelling thermal radiation and soot formation in buoyant diffusion flames

    International Nuclear Information System (INIS)

    Demarco Bull, R.A.

    2012-01-01

    The radiative heat transfer plays an important role in fire problems since it is the dominant mode of heat transfer between flames and surroundings. It controls the pyrolysis, and therefore the heat release rate, and the growth rate of the fire. In the present work a numerical study of buoyant diffusion flames is carried out, with the main objective of modelling the thermal radiative transfer and the soot formation/destruction processes. In a first step, different radiative property models were tested in benchmark configurations. It was found that the FSCK coupled with the Modest and Riazzi mixing scheme was the best compromise in terms of accuracy and computational requirements, and was a good candidate to be implemented in CFD codes dealing with fire problems. In a second step, a semi-empirical soot model, considering acetylene and benzene as precursor species for soot nucleation, was validated in laminar co flow diffusion flames over a wide range of hydrocarbons (C1-C3) and conditions. In addition, the optically-thin approximation was found to produce large discrepancies in the upper part of these small laminar flames. Reliable predictions of soot volume fractions require the use of an advanced radiation model. Then the FSCK and the semi-empirical soot model were applied to simulate laboratory-scale and intermediate-scale pool fires of methane and propane. Predicted flame structures as well as the radiant heat flux transferred to the surroundings were found to be in good agreement with the available experimental data. Finally, the interaction between radiation and turbulence was quantified. (author)

  14. Effects of Fuel Quantity on Soot Formation Process for Biomass-Based Renewable Diesel Fuel Combustion

    KAUST Repository

    Jing, Wei

    2016-12-01

    Soot formation process was investigated for biomass-based renewable diesel fuel, such as biomass to liquid (BTL), and conventional diesel combustion under varied fuel quantities injected into a constant volume combustion chamber. Soot measurement was implemented by two-color pyrometry under quiescent type diesel engine conditions (1000 K and 21% O2 concentration). Different fuel quantities, which correspond to different injection widths from 0.5 ms to 2 ms under constant injection pressure (1000 bar), were used to simulate different loads in engines. For a given fuel, soot temperature and KL factor show a different trend at initial stage for different fuel quantities, where a higher soot temperature can be found in a small fuel quantity case but a higher KL factor is observed in a large fuel quantity case generally. Another difference occurs at the end of combustion due to the termination of fuel injection. Additionally, BTL flame has a lower soot temperature, especially under a larger fuel quantity (2 ms injection width). Meanwhile, average soot level is lower for BTL flame, especially under a lower fuel quantity (0.5 ms injection width). BTL shows an overall low sooting behavior with low soot temperature compared to diesel, however, trade-off between soot level and soot temperature needs to be carefully selected when different loads are used.

  15. Sooting limit in counterflow diffusion flames of ethylene/propane fuels and implication to threshold soot index

    KAUST Repository

    Joo, Peter H.

    2013-01-01

    Sooting limits in counterflow diffusion flames of propane/ethylene fuels have been studied experimentally using a light scattering technique, including the effects of dilution, fuel mixing, and strain rate. The results are discussed in view of the threshold soot index (TSI). In soot-formation (SF) flames, where the flame is located on the oxidizer side of the stagnation plane, the sooting limit depends critically on fuel type and subsequently on flame temperature. The sooting limit has a non-linear dependence on the fuel-mixing ratio, which is similar to the non-linear mixing rule for TSI observed experimentally in rich premixed flames, where soot oxidation is absent for both SF and rich premixed flames. In soot-formation-oxidation (SFO) flames, where the flame is located on the fuel side, the sooting limit depends critically on flame temperature, while it is relatively independent on fuel type. This result suggests a linear mixing rule for sooting limits in SFO flames, which is similar to the TSI behavior for coflow diffusion flames. Soot oxidation takes place for both types of flames. The aerodynamic strain effect on the sooting limits has also been studied and an appreciable influence has been observed. Under sooting conditions, soot volume fraction was measured using a light extinction technique. The soot loadings in SF flames of the mixture fuels demonstrated a synergistic effect, i.e., soot production increased for certain mixture fuels as compared to the respective singlecomponent fuels. © 2012 The Combustion Institute.

  16. Numerical investigation on soot particles emission in compression ignition diesel engine by using particulate mimic soot model

    Directory of Open Access Journals (Sweden)

    Ibrahim Fadzli

    2017-01-01

    Full Text Available Research via computational method, specifically by detailed-kinetic soot model offers much more advantages than the simple model as more detailed formation/oxidation process is taken into consideration, thus providing better soot mass concentration, soot size, soot number density as well as information regarding other related species. In the present computational study, investigation of in-cylinder soot concentration as well as other emissions in a single cylinder diesel engine has been conducted, using a commercial multidimensional CFD software, CONVERGE CFD. The simulation was carried out for a close-cycle combustion environment from inlet valve closing (IVC to exhaust valve opening (EVO. In this case, detailed-kinetic Particulate Mimic (PM soot model was implemented as to take benefit of the method of moment, instead of commonly implemented simple soot model. Analyses of the results are successfully plotted to demonstrate that the soot size and soot mass concentration are strongly dependent on the detailed soot formation and oxidation process rates. The calculated of soot mass concentration and average soot size at EVO provide the end value of 29.2 mg/m3 and 2.04 × 10−8 m, respectively. Besides, post-processing using EnSight shows the qualitative results of soot concentration along simulation period in the combustion chamber.

  17. Sooting Characteristics and Modeling in Counterflow Diffusion Flames

    KAUST Repository

    Wang, Yu

    2013-11-01

    Soot formation is one of the most complex phenomena in combustion science and an understanding of the underlying physico-chemical mechanisms is important. This work adopted both experimental and numerical approaches to study soot formation in laminar counterfl ow diffusion flames. As polycyclic aromatic hydrocarbons (PAHs) are the precursors of soot particles, a detailed gas-phase chemical mechanism describing PAH growth upto coronene for fuels with 1 to 4 carbon atoms was validated against laminar premixed and counter- flow diffusion fl ames. Built upon this gas-phase mechanism, a soot model was then developed to describe soot inception and surface growth. This soot model was sub- sequently used to study fuel mixing effect on soot formation in counterfl ow diffusion flames. Simulation results showed that compared to the baseline case of the ethylene flame, the doping of 5% (by volume) propane or ethane in ethylene tends to increase the soot volume fraction and number density while keeping the average soot size almost unchanged. These results are in agreement with experimental observations. Laser light extinction/scattering as well as laser induced fluorescence techniques were used to study the effect of strain rate on soot and PAH formation in counterfl ow diffusion ames. The results showed that as strain rate increased both soot volume fraction and PAH concentrations decreased. The concentrations of larger PAH were more sensitive to strain rate compared to smaller ones. The effect of CO2 addition on soot formation was also studied using similar experimental techniques. Soot loading was reduced with CO2 dilution. Subsequent numerical modeling studies were able to reproduce the experimental trend. In addition, the chemical effect of CO2 addition was analyzed using numerical data. Critical conditions for the onset of soot were systematically studied in counterfl ow diffusion ames for various gaseous hydrocarbon fuels and at different strain rates. A sooting

  18. Role of soot in the transport of chlorine in hydrocarbon-air diffusion flames

    International Nuclear Information System (INIS)

    Venkatesh, S.; Saito, K.; Stencel, J.M.; Majidi, V.; Owens, M.

    1991-01-01

    Soot is an inevitable product of incomplete combustion in many practical combustion systems such as automobiles, incinerators and furnaces. Recent studies on chlorinated hydrocarbon combustion have shown that soot and other praticulates (eg. fly ash) play an important role in secondary reactions leading to the formation of chlorine substituted polyaromatic hydrocarbons (PAHs). In order to attain very high destruction efficiencies the fundamental chemical and physical processes that are associated with combustion, and post-combustion cleanup must be well understood. In order to understand the effect of chlorine on the soot formed in a combustion system, fundamental studies using a coflow laminar hydrocarbon-air diffusion flame have been carried out. Phenomenological studies have revealed the effect of chlorine on the visible structure of the flame. Soot inception activation energies were estimated for methane, ethane and ethylene diffusion flames for the case of with and without chlorine addition. No significant difference in the activation energy was estimated for either case. The effect of chlorine on the soot escape rate of an acetylene diffusion flame was estimated. The soot formed in these diffusion flames was analyzed for chlorine using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and by laser induced plasma spectroscopy (LIPS). REsults from these techniques indicate the presence of chlorine in the soot formed. In this paper a chemical scheme to explain the chlorine found in the soot is proposed based on known theories of soot formation

  19. Soot formation in a blast furnace - Prediction via a parametric study, using detailed kinetic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Nordstroem, T.; Kilpinen, P.; Hupa, M. [Aabo Akademi, Turku (Finland). Combustion Chemistry Group

    1996-12-31

    The objective of this work has been to investigate the soot formation in a blast furnace fired with heavy fuel oil, using detailed kinetic modelling. This work has been concentrated on parameter studies that could explain under which conditions soot is formed and how that formation could be avoided. The parameters investigated were temperature, pressure, stoichiometric ratio, pyrolysis gas composition and reactor model. The calculations were based on a reaction mechanism that consists of 100 species and 446 reactions including polyaromatic hydrocarbons (PAM) up to 7 aromatic rings SULA 2 Research Programme; 4 refs.

  20. Soot formation in a blast furnace - Prediction via a parametric study, using detailed kinetic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Nordstroem, T; Kilpinen, P; Hupa, M [Aabo Akademi, Turku (Finland). Combustion Chemistry Group

    1997-12-31

    The objective of this work has been to investigate the soot formation in a blast furnace fired with heavy fuel oil, using detailed kinetic modelling. This work has been concentrated on parameter studies that could explain under which conditions soot is formed and how that formation could be avoided. The parameters investigated were temperature, pressure, stoichiometric ratio, pyrolysis gas composition and reactor model. The calculations were based on a reaction mechanism that consists of 100 species and 446 reactions including polyaromatic hydrocarbons (PAM) up to 7 aromatic rings SULA 2 Research Programme; 4 refs.

  1. Smog chamber study on aging of combustion soot in isoprene/SO2/NOx system: Changes of mass, size, effective density, morphology and mixing state

    Science.gov (United States)

    Li, Kangwei; Chen, Linghong; Han, Ke; Lv, Biao; Bao, Kaiji; Wu, Xuecheng; Gao, Xiang; Cen, Kefa

    2017-02-01

    Atmospheric soot aging process is always accompanied by secondary particle formation, which is a comprehensive environmental issue that deserves great attention. On one hand, aging of primary soot could change its own physicochemical properties; on the other hand, complex air pollution caused by pollutant emission from various sources (e.g., vehicle exhausts, coal-fired flue gases and biogenic VOCs emission) may contribute to secondary particle formation onto primary particle surface. In this study, aging of combustion soot in isoprene/SO2/NOx system was investigated under controlled laboratory conditions in several smog chamber experiments. During the evolution of soot, several physical properties such as mass, size, effective density, morphology and mixing state were determined simultaneously by an integrated aerosol analytical system of Scanning Mobility Particle Sizer (SMPS), Differential Mobility Analyzer-Aerosol Particle Mass Analyzer-Condensation Particle Counter (DMA-APM-CPC) and Transmission Electron Microscopy coupled with Energy-dispersive X-ray Spectrometry (TEM/EDX) techniques. Here, based on the experimental results of soot aging under different gas-phase composition and relative humidity (RH), we firstly proposed possible aging pathways of soot in isoprene/SO2/NOx system. A synergetic effect was speculated to exist between SO2 and isoprene on soot aging process, which led to more secondary particle formation. At the same time, TEM/EDX analysis showed that a competitive mechanism between H2SO4(g) and isoprene oxidation vapor may exist: H2SO4(g) firstly condensed onto fresh soot, then an acceleration of isoprene oxidation products formed onto H2SO4 pre-coated soot. In isoprene/SO2/NOx system, high RH conditions could contribute to soot aging and new particle formation. The changes of effective density and dynamic shape factor of soot also indicated that high RH conditions could accelerate soot aging process, and led chain-like soot into more spherical

  2. Effect of strain rate on sooting limits in counterflow diffusion flames of gaseous hydrocarbon fuels: Sooting temperature index and sooting sensitivity index

    KAUST Repository

    Wang, Yu

    2014-05-01

    The effect of the strain rate on the sooting limits in counterflow diffusion flames was investigated in various gaseous hydrocarbon fuels by varying the nitrogen dilution in the fuel and oxidizer streams. The sooting limit was defined as the critical fuel and oxygen mole fraction at which soot started to appear in the elastic light scattering signal. The sooting region for normal alkane fuels at a specified strain rate, in terms of the fuel and oxygen mole fraction, expanded as the number of carbon atoms increased. The alkene fuels (ethylene, propene) tested had a higher propensity for sooting as compared with alkane fuels with the same carbon numbers (ethane, propane). Branched iso-butane had a higher propensity for sooting than did n-butane. An increase in the strain rate reduced the tendency for sooting in all the fuels tested. The sensitivity of the sooting limit to the strain rate was more pronounced for less sooting fuels. When plotted in terms of calculated flame temperature, the critical oxygen mole fraction exhibited an Arrhenius form under sooting limit conditions, which can be utilized to significantly reduce the effort required to determine sooting limits at different strain rates. We found that the limiting temperatures of soot formation flames are viable sooting metrics for quantitatively rating the sooting tendency of various fuels, based on comparisons with threshold soot index and normalized smoke point data. We also introduce a sooting temperature index and a sooting sensitivity index, two quantitative measures to describe sooting propensity and its dependence on strain rate. © 2013 The Combustion Institute.

  3. NATO Workshop on Soot in Combustion Systems

    CERN Document Server

    Prado, G

    1983-01-01

    Our interest in Mulhouse for carbon black and soot began some 30 years ago when J.B. Donnet developed the concept of surface chemistry of carbon and its involvement in interactions with gas, liquid and solid phases. In the late sixties, we began to study soot formation in pyrolytic systems and later on in flames. The idea of organ1z1ng a meeting on soot formation originated some four or five years ago, through discussions among Professor J.B. Howard, Dr. A. D'Alessio and ourselves. At that time the scientific community was becoming aware of the necessity to strictly control soot formation and emission. Being involved in the study of surface properties of carbon black as well as of formation of soot, we realized that the combustion community was not always fully aware of the progress made by the physical-chemists on carbon black. Reciprocally, the carbon specialists were often ignoring the research carried out on soot in flames. One objective of this workshop was to stimulate discussions between these two scie...

  4. Simulation of soot size distribution in an ethylene counterflow flame

    KAUST Repository

    Zhou, Kun

    2014-01-06

    Soot, an aggregate of carbonaceous particles produced during the rich combustion of fossil fuels, is an undesirable pollutant and health hazard. Soot evolution involves various dynamic processes: nucleation soot formation from polycyclic aromatic hydrocarbons (PAHs) condensation PAHs condensing on soot particle surface surface processes hydrogen-abstraction-C2H2-addition, oxidation coagulation two soot particles coagulating to form a bigger particle This simulation work investigates soot size distribution and morphology in an ethylene counterflow flame, using i). Chemkin with a method of moments to deal with the coupling between vapor consumption and soot formation; ii). Monte Carlo simulation of soot dynamics.

  5. Simulation of temporal and spatial soot evolution in an automotive diesel engine using the Moss–Brookes soot model

    International Nuclear Information System (INIS)

    Pang, Kar Mun; Ng, Hoon Kiat; Gan, Suyin

    2012-01-01

    Highlights: ► Numerical models were validated against experimental data of two diesel engines. ► Soot model constant values were calibrated to predict in-cylinder soot processes. ► Effects of split-main injection parameters on soot distributions were determined. ► Soot cloud was distributed towards cylinder wall when using large dwell period. ► Greater soot deposition expected with large dwell period and retarded injection. - Abstract: In this reported work, computational study on the formation processes of soot particles from diesel combustion is conducted using an approach where Computational Fluid Dynamics (CFD) is coupled with a chemical kinetic model. A multi-step soot model which accounts for inception, surface growth, coagulation and oxidation was applied. Model constant values in the Moss–Brookes soot formation and Fenimore–Jones soot oxidation models were calibrated, and were validated against in-cylinder soot evolution and exhaust soot density of both heavy- and light-duty diesel engines, respectively. Effects of various injection parameters such as start of injection (SOI) timing, split-main ratio and dwell period of the split-main injection strategy on in-cylinder temporal/spatial soot evolution in a light-duty diesel engine were subsequently investigated. The spatial soot distributions at each crank angle degree after start of injection were found to be insensitive to the change of values in SOI and split-main ratio when close-coupled injection was implemented. Soot cloud was also observed to be distributed towards the cylinder wall when a large separation of 20° was used, even with an advanced SOI timing of −6° after top dead centre (ATDC). The use of large separation is hence not desired for this combustion system as it potentially leads to soot deposition on surface oil film and greater tailpipe soot emissions.

  6. Large eddy simulation of soot evolution in an aircraft combustor

    Science.gov (United States)

    Mueller, Michael E.; Pitsch, Heinz

    2013-11-01

    An integrated kinetics-based Large Eddy Simulation (LES) approach for soot evolution in turbulent reacting flows is applied to the simulation of a Pratt & Whitney aircraft gas turbine combustor, and the results are analyzed to provide insights into the complex interactions of the hydrodynamics, mixing, chemistry, and soot. The integrated approach includes detailed models for soot, combustion, and the unresolved interactions between soot, chemistry, and turbulence. The soot model is based on the Hybrid Method of Moments and detailed descriptions of soot aggregates and the various physical and chemical processes governing their evolution. The detailed kinetics of jet fuel oxidation and soot precursor formation is described with the Radiation Flamelet/Progress Variable model, which has been modified to account for the removal of soot precursors from the gas-phase. The unclosed filtered quantities in the soot and combustion models, such as source terms, are closed with a novel presumed subfilter PDF approach that accounts for the high subfilter spatial intermittency of soot. For the combustor simulation, the integrated approach is combined with a Lagrangian parcel method for the liquid spray and state-of-the-art unstructured LES technology for complex geometries. Two overall fuel-to-air ratios are simulated to evaluate the ability of the model to make not only absolute predictions but also quantitative predictions of trends. The Pratt & Whitney combustor is a Rich-Quench-Lean combustor in which combustion first occurs in a fuel-rich primary zone characterized by a large recirculation zone. Dilution air is then added downstream of the recirculation zone, and combustion continues in a fuel-lean secondary zone. The simulations show that large quantities of soot are formed in the fuel-rich recirculation zone, and, furthermore, the overall fuel-to-air ratio dictates both the dominant soot growth process and the location of maximum soot volume fraction. At the higher fuel

  7. An investigation of late-combustion soot burnout in a DI diesel engine using simultaneous planar imaging of soot and OH radical

    Energy Technology Data Exchange (ETDEWEB)

    John E. Dec; Peter L. Kelly-Zion

    1999-10-01

    Diesel engine design continues to be driven by the need to improve performance while at the same time achieving further reductions in emissions. The development of new designs to accomplish these goals requires an understanding of how the emissions are produced in the engine. Laser-imaging diagnostics are uniquely capable of providing this information, and the understanding of diesel combustion and emissions formation has been advanced considerably in recent years by their application. However, previous studies have generally focused on the early and middle stages of diesel combustion. These previous laser-imaging studies do provide important insight into the soot formation and oxidation processes during the main combustion event. They indicate that prior to the end of injection, soot formation is initiated by fuel-rich premixed combustion (equivalence ratio > 4) near the upstream limit of the luminous portion of the reacting fuel jet. The soot is then oxidized at the diffusion flame around the periphery of the luminous plume. Under typical diesel engine conditions, the diffusion flame does not burn the remaining fuel and soot as rapidly as it is supplied, resulting in an expanding region of rich combustion products and soot. This is evident in natural emission images by the increasing size of the luminous soot cloud prior to the end of injection. Hence, the amount of soot in the combustion chamber typically increases until shortly after the end of fuel injection, at which time the main soot formation period ends and the burnout phase begins. Sampling valve and two-color pyrometry data indicate that the vast majority (more than 90%) of the soot formed is oxidized before combustion ends; however, it is generally thought that a small fraction of this soot from the main combustion zones is not consumed and is the source of tail pipe soot emissions.

  8. Modelling soot formation from wall films in a gasoline direct injection engine using a detailed population balance model

    International Nuclear Information System (INIS)

    Wang, Buyu; Mosbach, Sebastian; Schmutzhard, Sebastian; Shuai, Shijin; Huang, Yaqing; Kraft, Markus

    2016-01-01

    Highlights: • Soot formation from a wall film in a GDI engine is simulated. • Spray impingement and wall film evaporation models are added to SRM Engine Suite. • Soot is modelled using a highly detailed population balance model. • Particle size distributions are measured experimentally. • Evolution of wall region is shown in equivalence ratio-temperature diagrams. - Abstract: In this study, soot formation in a Gasoline Direct Injection (GDI) engine is simulated using a Stochastic Reactor Model (SRM Engine Suite) which contains a detailed population balance soot model capable of describing particle morphology and chemical composition. In order to describe the soot formation originating from the wall film, the SRM Engine Suite is extended to include spray impingement and wall film evaporation models. The cylinder is divided into a wall and a bulk zone to resolve the equivalence ratio and temperature distributions of the mixture near the wall. The combustion chamber wall is assumed to exchange heat directly only with the wall zone. The turbulent mixing within each zone and between the two zones are simulated with different mixing models. The effects of key parameters on the temperature and equivalence ratio in the two zones are investigated. The mixing rate between the wall and bulk zone has a significant effect on the wall zone, whilst the mixing rate in the wall zone only has a negligible impact on the temperature and equivalence ratio below a certain threshold. Experimental data are obtained from a four-cylinder, gasoline-fuelled direct injection spark ignition engine operated stoichiometrically. An injection timing sweep, ranging from 120 CAD BTDC to 330 CAD BTDC, is conducted in order to investigate the effect of spray impingement on soot formation. The earliest injection case (330 CAD BTDC), which produces significantly higher levels of particle emissions than any other case, is simulated by the current model. It is found that the in-cylinder pressure

  9. Effects of soot formation on shape of a nonpremixed laminar flame established in a shear boundary layer in microgravity

    International Nuclear Information System (INIS)

    Wang, H Y; Merino, J L Florenciano; Dagaut, P

    2011-01-01

    A numerical study was performed to give a quantitative description of a heavily sooting, nonpremixed laminar flame established in a shear boundary layer in microgravity. Controlling mechanisms of three dimensional flow, combustion, soot and radiation are coupled. Soot volume fraction were predicted by using three approaches, referred respectively to as the fuel, acetylene and PAH inception models. It is found that the PAH inception model, which is based on the formation of two and three-ringed aromatic species, reproduces correctly the experimental data from a laminar ethylene diffusion flame. The PAH inception model serves later to better understand flame quenching, flame stand-off distance and soot formation as a function of the dimensionless volume coefficient, defined as C q = V F /V ox where V F is the fuel injection velocity, and V ox air stream velocity. The present experiments showed that a blue unstable flame, negligible radiative feedback, may change to a yellow stable flame, significant radiative loss with an increase of C q ; this experimental trend was numerically reproduced. The flame quenching occurs at the trailing edge due to radiative heat loss which is significantly amplified by increasing V F or decreasing V ox , favouring soot formation. Along a semi-infinite fuel zone, the ratio, d f /d b , where d f is the flame standoff distance, and d b the boundary layer thickness, converges towards a constant value of 1.2, while soot resides always within the boundary layer far away from the flame sheet.

  10. Investigation of Chemical Kinetics on Soot Formation Event of n-Heptane Spray Combustion

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song

    2014-01-01

    . Numerical computation is performed using OpenFOAM and chemistry coordinate mapping (CCM) approach is used to expedite the calculation. Three n-heptane kinetic mechanisms with different chemistry sizes and comprehensiveness in oxidation pathways and soot precursor formation are adopted. The three examined...

  11. Internally mixed soot, sulfates, and organic matter in aerosol particles from Mexico City

    Science.gov (United States)

    Adachi, K.; Buseck, P. R.

    2008-05-01

    Soot particles are major aerosol constituents that result from emissions of burning of fossil fuel and biomass. Because they both absorb sunlight and contribute to cloud formation, they are an influence on climate on local, regional, and global scales. It is therefore important to evaluate their optical and hygroscopic properties and those effects on the radiation budget. Those properties commonly change through reaction with other particles or gases, resulting in complex internal mixtures. Using transmission electron microscopy, we measured ~8000 particles (25 samples) with aerodynamic diameters from 0.05 to 0.3 μm that were collected in March 2006 from aircraft over Mexico City (MC) and adjacent areas. More than 50% of the particles consist of internally mixed soot, organic matter, and sulfate. Imaging combined with chemical analysis of individual particles show that many are coated, consist of aggregates, or both. Coatings on soot particles can amplify their light absorption, and coagulation with sulfates changes their hygroscopic properties, resulting in shorter lifetime. Our results suggest that a mixture of materials from multiple sources such as vehicles, power plants, and biomass burning occurs in individual particles, thereby increasing their complexity. Through changes in their optical and hygroscopic properties, internally mixed soot particles have a greater effect on the regional climate than uncoated soot particles. Moreover, soot occurs in more than 60% of all particles in the MC plumes, suggesting its important role in the formation of secondary aerosol particles.

  12. Numerical investigation of soot formation and oxidation processes under large two-stroke marine diesel engine-like conditions using integrated CFD-chemical kinetics

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Karvounis, Nikolas; Walther, Jens Honore

    2016-01-01

    n-heptane mechanism and a revised multi-step soot model using laser extinction measurements of diesel soot obtained at different ambient pressure levels in an optical accessible, constant volume chamber experiment. It is revealed that ignition delay times and liftoff lengths generated using the new......In this reported work, multi-dimensional computational fluid dynamics studies of diesel combustion and soot formation processes in a constant volume combustion chamber and a marine diesel engine are carried out. The key interest here is firstly to validate the coupling of a newly developed skeletal...... using the revised soot model agrees reasonably well with the measurements in terms of peak values. The numerical model is subsequently applied to investigate the flame development, soot/nitrogen monoxide formation and heat transfer in a two-stroke, low-speed uniflow-scavenged marine diesel engine...

  13. Soot Formation and Destruction in High-Pressure Flames with Real Fuels

    Science.gov (United States)

    2013-08-18

    Temperature and Oxygen Concentration on Diesel Spray Combustion Using a Single- Nozzle Injector in a Constant Volume Combustion Chamber, Combustion...enable the design of more efficient diesel engines. Higher efficiency will help reduce the logistical demand transportation fuels place on the entire...understanding of the soot formation processes at elevated pressure (e.g., 30 atm) will enable the design of more efficient diesel engines. Higher

  14. Numerical Investigation of Soot Formation in Non-premixed Flames

    KAUST Repository

    Abdelgadir, Ahmed Gamaleldin

    2017-01-01

    Soot is a carbon particulate formed as a result of the combustion of fossil fuels. Due to the health hazard posed by the carbon particulate, government agencies have applied strict regulations to control soot emissions from road vehicles, airplanes

  15. Estimating soot emissions from an elevated flare

    Science.gov (United States)

    Almanza, Victor; Sosa, Gustavo

    2009-11-01

    Combustion aerosols are one of the major concerns in flaring operations, due to both health and environmental hazards. Preliminary results are presented for a 2D transient simulation of soot formation in a reacting jet with exit velocity of 130 m/s under a 5 m/s crossflow released from a 50 m high elevated flare and a 50 cm nozzle. Combustion dynamics was simulated with OpenFOAM. Gas-phase non-premixed combustion was modeled with the Chalmers PaSR approach and a κ-ɛ turbulence model. For soot formation, Moss model was used and the ISAT algorithm for solving the chemistry. Sulfur chemistry was considered to account for the sourness of the fuel. Gas composition is 10 % H2S and 90 % C2H4. A simplified Glassman reaction mechanism was used for this purpose. Results show that soot levels are sensitive to the sulfur present in the fuel, since it was observed a slight decrease in the soot volume fraction. NSC is the current oxidation model for soot formation. Predicted temperature is high (about 2390 K), perhaps due to soot-radiation interaction is not considered yet, but a radiation model implementation is on progress, as well as an oxidation mechanism that accounts for OH radical. Flame length is about 50 m.

  16. Soot Formation In Turbulent Combusting Flows

    National Research Council Canada - National Science Library

    Santoro, Robert

    1998-01-01

    .... Laser-based techniques were used to measure the soot volume fraction, particle size and number density as well as the temperature and relative concentration of hydroxyl radicals and polycyclic aromatic hydrocarbons...

  17. Dynamics of flow–soot interaction in wrinkled non-premixed ethylene–air flames

    KAUST Repository

    Arias, Paul G.

    2015-08-17

    A two-dimensional simulation of a non-premixed ethylene–air flame was conducted by employing a detailed gas-phase reaction mechanism considering polycyclic aromatic hydrocarbons, an aerosol-dynamics-based soot model using a method of moments with interpolative closure, and a grey gas and soot radiation model using the discrete transfer method. Interaction of the sooting flame with a prescribed decaying random velocity field was investigated, with a primary interest in the effects of velocity fluctuations on the flame structure and the associated soot formation process for a fuel-strip configuration and a composition with mature soot growth. The temporally evolving simulation revealed a multi-layered soot formation process within the flame, at a level of detail not properly described by previous studies based on simplified soot models utilizing acetylene or naphthalene precursors for initial soot inception. The overall effect of the flame topology on the soot formation was found to be consistent with previous experimental studies, while a unique behaviour of localised strong oxidation was also noted. The imposed velocity fluctuations led to an increase of the scalar dissipation rate in the sooting zone, causing a net suppression in the soot production rate. Considering the complex structure of the soot formation layer, the effects of the imposed fluctuations vary depending on the individual soot reactions. For the conditions under study, the soot oxidation reaction was identified as the most sensitive to the fluctuations and was mainly responsible for the local suppression of the net soot production. © 2015 Taylor & Francis

  18. A computational study of radiation and gravity effect on temperature and soot formation in a methane air co-flow diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    Bhowal, Arup Jyoti, E-mail: arupjyoti.bhowal@heritageit.edu [Department of Mechanical Engineering, Heritage Institute of Technology, Chowbaga Road, Anandapur, Kolkata-700 107, West Bengal (India); Mandal, Bijan Kumar, E-mail: bkm375@yahoo.co.in [Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah – 711103, West Bengal (India)

    2016-07-12

    An effort has been made for a quantitative assessment of the soot formed under steady state in a methane air co flow diffusion flame by a numerical simulation at normal gravity and at lower gravity levels of 0.5 G, 0.1 G and 0.0001 G (microgravity). The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. There is an augmentation of soot formation at lower gravity levels. Peak value at microgravity multiplies by a factor of ∼7 of that at normal gravity. However, if radiation is not considered, soot formation is found to be much more.

  19. Delayed condensation and frost formation on superhydrophobic carbon soot coatings by controlling the presence of hydrophilic active sites

    Science.gov (United States)

    Esmeryan, Karekin D.; Castano, Carlos E.; Mohammadi, Reza; Lazarov, Yuliyan; Radeva, Ekaterina I.

    2018-02-01

    Condensation frosting is an undesired natural phenomenon that could be impeded efficiently using appropriate wettability and morphologically patterned surfaces. The icephobic properties of carbon soot and the fabrication scalability of its synthesis method are a good foundation for anti-frosting applications; however, the fundamentals of frost growth and spreading on sooted surfaces have not been examined yet. In this study, we investigate the anti-frosting performance of three groups of superhydrophobic soot coatings by means of 16 MHz quartz crystal microbalances (QCMs). The analysis of the real-time sensor signal of each soot coated QCM pattern shows that frost formation and its propagation velocity depend on the quantity of oxygen functionalities and structural defects in the material. In turn, the reduction of both parameters shifts the onset of frost growth to temperatures below  -20 °C, whereas the interdroplet ice bridging is slowed by a factor of four. Moreover, high-resolution scanning electron micrographs of the samples imply delamination upon defrosting of the soot with spherical-like morphology via polar interactions driven mechanism. These results reveal an opportunity for control of frost incipiency on sooted surfaces by adjusting the synthesis conditions and depositing soot coatings with as low as possible content of hydrophilic active sites.

  20. Dielectric properties of PMMA/Soot nanocomposites.

    Science.gov (United States)

    Clayton, Lanetra M; Cinke, Martin; Meyyappan, M; Harmon, Julie P

    2007-07-01

    Dielectric analysis (DEA) of relaxation behavior in poly(methyl methacrylate) (PMMA) soot nanocomposites is described herein. The soot, an inexpensive material, consists of carbon nanotubes, amorphous and graphitic carbon and metal particles. Results are compared to earlier studies on PMMA/multi-walled nanotube (MWNT) composites and PMMA/single-walled nanotube (SWNT) composites. The beta relaxation process appeared to be unaffected by the presence of the soot, as was noted earlier in nanotube composites. The gamma relaxation region in PMMA, normally dielectrically inactive, was "awakened" in the PMMA/soot composite. This occurrence is consistent with previously published data on nanotube composites. The dielectric permittivity, s', increased with soot content. The sample with 1% soot exhibited a permittivity (at 100 Hz and 25 degrees C) of 7.3 as compared to 5.1 for neat PMMA. Soot increased the dielectric strength, deltaE, of the composites. The 1% soot sample exhibited a dielectric strength of 6.38, while the neat PMMA had a value of 2.95 at 40 degrees C. The symmetric broadening term (alpha) was slightly higher for the 1% composite at temperatures near the secondary relaxation and near the primary relaxation, but all samples deviated from symmetrical semi-circular behavior (alpha = 1). The impact of the soot filler is seen more clearly in dielectric properties than in mechanical properties studies conducted earlier.

  1. Computational Investigation of Soot and Radiation in Turbulent Reacting Flows

    Science.gov (United States)

    Lalit, Harshad

    over prediction effect of the DD model. It is shown that the effect of species Lewis number on soot evolution is a secondary phenomenon and that soot is primarily transported by advection of the fluid in a turbulent flame. The effect of hydrogen dilution on the soot formation and transport process is also studied. It is noted that the decay of soot volume fraction and flame length with hydrogen addition follows trends observed in laminar sooting flame measurements. While hydrogen enhances mixing shown by the laminar flamelet solutions, the mixing effect does not significantly contribute to differential molecular diffusion effects in the soot nucleation regions downstream of the flame and has a negligible effect on soot transport. The sensitivity of computations of soot volume fraction towards the chemical reaction mechanism is shown. It is concluded that modeling reaction pathways of C3 and C4 species that lead up to Polycyclic Aromatic Hydrocarbon (PAH) molecule formation is paramount for accurate predictions of soot in the flame. (Abstract shortened by ProQuest.).

  2. Understanding and predicting soot generation in turbulent non-premixed jet flames.

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hai (University of Southern California, Los Angeles, CA); Kook, Sanghoon; Doom, Jeffrey; Oefelein, Joseph Charles; Zhang, Jiayao; Shaddix, Christopher R.; Schefer, Robert W.; Pickett, Lyle M.

    2010-10-01

    This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation

  3. Simulation of soot size distribution in an ethylene counterflow flame

    KAUST Repository

    Zhou, Kun; Abdelgadir, Ahmed Gamaleldin; Bisetti, Fabrizio

    2014-01-01

    Soot, an aggregate of carbonaceous particles produced during the rich combustion of fossil fuels, is an undesirable pollutant and health hazard. Soot evolution involves various dynamic processes: nucleation soot formation from polycyclic aromatic

  4. Study on soot particle formation and oxidation in DI diesel engine; Chokufunshiki diesel kikan ni okeru susu ryushi no seicho sanka ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Kurata, K; Senda, J; Fujimoto, H [Doshisha University, Kyoto (Japan); Asai, G [Yanmar Diesel Engine Co. Ltd., Osaka (Japan)

    1997-10-01

    To clarify soot formation and oxidation process in diesel combustion, the natural emission of OH radical and the flame temperature were obtained in the combustion chamber of D.I. diesel engine. Further, soot were detected by LII (Laser Induced Incandescence) and LIS (Laser Induced Scattering) technique to assess the relative soot diameter and its number density. OH emission and flame temperature were compared with data of soot diameter and number- density. The results show that : (1) OH emission has relation to flame temperature. (2) OH emission arises latter than soot emission, because early soot at early combustion consume OH to oxidate. (3) As soon as it is ignited, soot particles are formed in the region of low temperature. 6 refs., 7 figs., 2 tabs.

  5. Monte carlo simulation for soot dynamics

    KAUST Repository

    Zhou, Kun

    2012-01-01

    A new Monte Carlo method termed Comb-like frame Monte Carlo is developed to simulate the soot dynamics. Detailed stochastic error analysis is provided. Comb-like frame Monte Carlo is coupled with the gas phase solver Chemkin II to simulate soot formation in a 1-D premixed burner stabilized flame. The simulated soot number density, volume fraction, and particle size distribution all agree well with the measurement available in literature. The origin of the bimodal distribution of particle size distribution is revealed with quantitative proof.

  6. Cosmic: Carbon Monoxide And Soot In Microgravity Inverse Combustion

    Science.gov (United States)

    Mikofski, M. A.; Blevins, L. G.; Davis, R. W.; Moore, E. F.; Mulholland, G. W.; Sacksteder, Kurt (Technical Monitor)

    2003-01-01

    Almost seventy percent of fire related deaths are caused by the inhalation of toxins such as CO and soot that are produced when fires become underventilated.(1) Although studies have established the importance of CO formation during underventilated burning,(2) the formation processes of CO (and soot) in underventilated fires are not well understood. The goal of the COSMIC project is to study the formation processes of CO and soot in underventilated flames. A potential way to study CO and soot production in underventilated flames is the use of inverse diffusion flames (IDFs). An IDF forms between a central air jet and a surrounding fuel jet. IDFs are related to underventilated flames because they may allow CO and soot to escape unoxidized. Experiments and numerical simulations of laminar IDFs of CH4 and C2H4 were conducted in 1-g and micro-g to study CO and soot formation. Laminar flames were studied because turbulent models of underventilated fires are uncertain. Microgravity was used to alter CO and soot pathways. A IDF literature survey, providing background and establishing motivation for this research, was presented at the 5th IWMC.(3) Experimental results from 1-g C2H4 IDFs and comparisons with simulations, demonstrating similarities between IDFs and underventilated fires, were presented at the 6th IWMC.(4) This paper will present experimental results from micro-g and 1-g IDFs of CH4 and C2H4 as well as comparisons with simulations, further supporting the relation between IDFs and underventilated flames.

  7. Numerical Modelling of Soot Formation in Laminar Axisymmetric Ethylene-Air Coflow Flames at Atmospheric and Elevated Pressures

    KAUST Repository

    Abdelgadir, Ahmed

    2015-03-30

    A set of coflow diffusion flames are simulated to study the formation, growth, and oxidation of soot in flames of diluted hydrocarbon fuels, with focus on the effects of pressure. Firstly, we assess the ability of a high performance CFD solver, coupled with detailed transport and kinetic models, to reproduce experimental measurements of a series of ethylene-air coflow flames. Detailed finite rate chemistry describing the formation of Polycyclic Aromatic Hydro-carbons is used. Soot is modeled with a moment method and the resulting moment transport equations are solved with a Lagrangian numerical scheme. Numerical and experimental results are compared for various pressures. Finally, a sensitivity study is performed assessing the effect of the boundary conditions and kinetic mechanisms on the flame structure and stabilization properties.

  8. Ice Nucleation of Soot Particles in the Cirrus Regime: Is Pore Condensation and Freezing Relevant for Soot?

    Science.gov (United States)

    Kanji, Z. A.; Mahrt, F.; David, R.; Marcolli, C.; Lohmann, U.; Fahrni, J.; Brühwiler, D.

    2017-12-01

    Heterogeneous ice nucleation (HIN) onto soot particles from previous studies have produced inconsistent results of temperature and relative humidity conditions required for freezing depending on the source of soot particle investigated. The ability of soot to act as HIN depended on the type of soot and size of particle. Often homogenous freezing conditions or water saturation conditions were required to freeze soot particles, rendering HIN irrelevant. Using synthesised mesoporous silica particles, we show pore condensation and freezing works with experiments performed in the Zurich Ice Nucleation Chamber (ZINC). By testing a variety of soot particles in parallel in the Horizontal Ice Nucleation Chamber (HINC), we suggest that previously observed HIN on soot particles is not the responsible mechanism for ice formation. Laboratory generated CAST brown and black soot, commercially available soot and acid treated soot were investigated for their ice nucleation abilities in the mixed-phase and cirrus cloud temperature regimes. No heterogeneous ice nucleation activity is inferred at T > -38 °C (mixed-phase cloud regime), however depending on particle size and soot type, HIN was observed for T nucleation of ice in the pores or cavities that are ubiquitous in soot particles between the primary spherules. The ability of some particles to freeze at lower relative humidity compared to others demonstrates why hydrophobicity plays a role in ice nucleation, i.e. controlling the conditions at which these cavities fill with water. Thus for more hydrophobic particles pore filling occurs at higher relative humidity, and therefore freezing of pore water and ice crystal growth. Future work focusses on testing the cloud processing ability of soot particles and water adsorption isotherms of the different soot samples to support the hydrophobicity inferences from the ice nucleation results.

  9. A small porous-plug burner for studies of combustion chemistry and soot formation

    Science.gov (United States)

    Campbell, M. F.; Schrader, P. E.; Catalano, A. L.; Johansson, K. O.; Bohlin, G. A.; Richards-Henderson, N. K.; Kliewer, C. J.; Michelsen, H. A.

    2017-12-01

    We have developed and built a small porous-plug burner based on the original McKenna burner design. The new burner generates a laminar premixed flat flame for use in studies of combustion chemistry and soot formation. The size is particularly relevant for space-constrained, synchrotron-based X-ray diagnostics. In this paper, we present details of the design, construction, operation, and supporting infrastructure for this burner, including engineering attributes that enable its small size. We also present data for charactering the flames produced by this burner. These data include temperature profiles for three premixed sooting ethylene/air flames (equivalence ratios of 1.5, 1.8, and 2.1); temperatures were recorded using direct one-dimensional coherent Raman imaging. We include calculated temperature profiles, and, for one of these ethylene/air flames, we show the carbon and hydrogen content of heavy hydrocarbon species measured using an aerosol mass spectrometer coupled with vacuum ultraviolet photoionization (VUV-AMS) and soot-volume-fraction measurements obtained using laser-induced incandescence. In addition, we provide calculated mole-fraction profiles of selected gas-phase species and characteristic profiles for seven mass peaks from AMS measurements. Using these experimental and calculated results, we discuss the differences between standard McKenna burners and the new miniature porous-plug burner introduced here.

  10. 3-D simulation of soot formation in a direct-injection diesel engine based on a comprehensive chemical mechanism and method of moments

    Science.gov (United States)

    Zhong, Bei-Jing; Dang, Shuai; Song, Ya-Na; Gong, Jing-Song

    2012-02-01

    Here, we propose both a comprehensive chemical mechanism and a reduced mechanism for a three-dimensional combustion simulation, describing the formation of polycyclic aromatic hydrocarbons (PAHs), in a direct-injection diesel engine. A soot model based on the reduced mechanism and a method of moments is also presented. The turbulent diffusion flame and PAH formation in the diesel engine were modelled using the reduced mechanism based on the detailed mechanism using a fixed wall temperature as a boundary condition. The spatial distribution of PAH concentrations and the characteristic parameters for soot formation in the engine cylinder were obtained by coupling a detailed chemical kinetic model with the three-dimensional computational fluid dynamic (CFD) model. Comparison of the simulated results with limited experimental data shows that the chemical mechanisms and soot model are realistic and correctly describe the basic physics of diesel combustion but require further development to improve their accuracy.

  11. Flame experiments at the advanced light source: new insights into soot formation processes.

    Science.gov (United States)

    Hansen, Nils; Skeen, Scott A; Michelsen, Hope A; Wilson, Kevin R; Kohse-Höinghaus, Katharina

    2014-05-26

    The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory(1-4). This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range(5,6). The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species' profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates(7). The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles(4). The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation

  12. Investigations of Sooting Laminar Coflow Diffusion Flames at Elevated Pressures

    KAUST Repository

    Steinmetz, Scott A.

    2016-12-01

    Soot is a common byproduct of hydrocarbon based combustion systems. It poses a risk to human and environmental health, and can negatively or positively affect combustor performance. As a result, there is significant interest in understanding soot formation in order to better control it. More recently, the need to study soot formation in engine relevant conditions has become apparent. One engine relevant parameter that has had little focus is the ambient pressure. This body of work focuses on the formation of soot in elevated pressure environments, and a number of investigations are carried out with this purpose. Laminar coflow diffusion flames are used as steady, simple soot producers. First, a commonly studied flame configuration is further characterized. Coflow flames are frequently used for fundamental flame studies, particularly at elevated pressures. However, they are more susceptible to buoyancy induced instabilities at elevated pressures. The velocity of the coflow is known to have an effect on flame stability and soot formation, though these have not been characterized at elevated pressures. A series of flames are investigated covering a range of flowrates, pressures, and nozzle diameters. The stability limits of coflow flames in this range is investigated. Additionally, an alternative strategy for scaling these flames to elevated pressures is proposed. Finally, the effect of coflow rate on soot formation is evaluated. Identification of fundamental flames for coordinated research can facilitate our understanding of soot formation. The next study of this work focuses on adding soot concentration and particle size information to an existing fundamental flame dataset for the purpose of numerical model validation. Soot volume fraction and average particle diameters are successfully measured in nitrogen-diluted ethylene-air laminar coflow flames at pressures of 4, 8, 12, and 16 atm. An increase in particle size with pressure is found up to 12 atm, where particle

  13. A computational study of ethylene–air sooting flames: Effects of large polycyclic aromatic hydrocarbons

    KAUST Repository

    Selvaraj, Prabhu

    2015-11-05

    An updated reduced gas-phase kinetic mechanism was developed and integrated with aerosol models to predict soot formation characteristics in ethylene nonpremixed and premixed flames. A primary objective is to investigate the sensitivity of the soot formation to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). The gas-phase chemical mechanism adopted the KAUST-Aramco PAH Mech 1.0, which utilized the AramcoMech 1.3 for gas-phase reactions validated for up to C2 fuels. In addition, PAH species up to coronene (C24H12 or A7) were included to describe the detailed formation pathways of soot precursors. In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph with expert knowledge (DRG-X) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames at low strain rate sooting conditions were considered, for which the sensitivity of soot formation characteristics to different nucleation pathways were investigated. Premixed flame experiment data at different equivalence ratios were also used for validation. The findings show that higher PAH concentrations result in a higher soot nucleation rate, and that the total soot volume and average size of the particles are predicted in good agreement with experimental results. Subsequently, the effects of different pathways, with respect to pyrene- or coronene-based nucleation models, on the net soot formation rate were analyzed. It was found that the nucleation processes (i.e., soot inception) are sensitive to the choice of PAH precursors, and consideration of higher PAH species beyond pyrene is critical for accurate prediction of the overall soot formation.

  14. Numerical Modelling of Soot Formation in Laminar Axisymmetric Ethylene-Air Coflow Flames at Atmospheric and Elevated Pressures

    KAUST Repository

    Abdelgadir, Ahmed; Rakha, Ihsan Allah; Steinmetz, Scott A.; Attili, Antonio; Bisetti, Fabrizio; Roberts, William L.

    2015-01-01

    , coupled with detailed transport and kinetic models, to reproduce experimental measurements of a series of ethylene-air coflow flames. Detailed finite rate chemistry describing the formation of Polycyclic Aromatic Hydro-carbons is used. Soot is modeled

  15. Formation of polycyclic aromatic hydrocarbons and soot in fuel-rich oxidation of methane in a laminar flow reactor

    DEFF Research Database (Denmark)

    Skjøth-Rasmussen, Martin Skov; Glarborg, Peter; Østberg, M.

    2004-01-01

    Conversion of methane to higher hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and soot was investigated under fuel-rich conditions in a laminar flow reactor. The effects of stoichiometry, dilution, and water vapor addition were studied at temperatures between 1073 and 1823 K. A chemical...... kinetic mechanism was established for methane oxidation, with emphasis on formation of higher hydrocarbons and PAH. A submodel for soot formation was adopted from the work of Frenklach and co-workers without changes. Modeling predictions showed good agreement with experimental results. Reactants, stable...... decrease with increasing addition of water vapor. The effect is described qualitatively by the reaction mechanism. The enhanced oxidation of acetylene is attributed to higher levels of hydroxyl radicals, formed from the reaction between the water vapor and hydrogen atoms....

  16. Quantitative characterization of steady and time-varying, sooting, laminar diffusion flames using optical techniques

    Science.gov (United States)

    Connelly, Blair C.

    In order to reduce the emission of pollutants such as soot and NO x from combustion systems, a detailed understanding of pollutant formation is required. In addition to environmental concerns, this is important for a fundamental understanding of flame behavior as significant quantities of soot lower local flame temperatures, increase overall flame length and affect the formation of such temperature-dependent species as NOx. This problem is investigated by carrying out coupled computational and experimental studies of steady and time-varying sooting, coflow diffusion flames. Optical diagnostic techniques are a powerful tool for characterizing combustion systems, as they provide a noninvasive method of probing the environment. Laser diagnostic techniques have added advantages, as systems can be probed with high spectral, temporal and spatial resolution, and with species selectivity. Experimental soot volume fractions were determined by using two-dimensional laser-induced incandescence (LII), calibrated with an on-line extinction measurement, and soot pyrometry. Measurements of soot particle size distributions are made using time-resolved LII (TR-LII). Laser-induced fluorescence measurements are made of NO and formaldehyde. These experimental measurements, and others, are compared with computational results in an effort to understand and model soot formation and to examine the coupled relationship of soot and NO x formation.

  17. Particulate matter emission modelling based on soot and SOF from direct injection diesel engines

    International Nuclear Information System (INIS)

    Tan, P.Q.; Hu, Z.Y.; Deng, K.Y.; Lu, J.X.; Lou, D.M.; Wan, G.

    2007-01-01

    Particulate matter (PM) emission is one of the major pollutants from diesel engines, and it is harmful for human health and influences the atmospheric visibility. In investigations for reducing PM emission, a simulation model for PM emission is a useful tool. In this paper, a phenomenological, composition based PM model of direct injection (DI) diesel engines has been proposed and formulated to simulate PM emission. The PM emission model is based on a quasi-dimensional multi-zone combustion model using the formation mechanisms of the two main compositions of PM: soot and soluble organic fraction (SOF). First, the quasi-dimensional multi-zone combustion model is given. Then, two models for soot and SOF emissions are established, respectively, and after that, the two models are integrated into a single PM emission model. The soot emission model is given by the difference between a primary formation model and an oxidation model of soot. The soot primary formation model is the Hiroyasu soot formation model, and the Nagle and Strickland-Constable model is adopted for soot oxidation. The SOF emission model is based on an unburned hydrocarbons (HC) emission model, and the HC emission model is given by the difference between a HC primary formation model and a HC oxidation model. The HC primary formation model considers fuel injected and mixed beyond the lean combustion limit during ignition delay and fuel effusing from the nozzle sac volume at low pressure and low velocity. In order to validate the PM emission model, experiments were performed on a six cylinder, turbocharged and intercooled DI diesel engine. The simulation results show good agreement with the experimental data, which indicates the validity of the PM emission model. The calculation results show that the distinctions between PM and soot formation rates are mainly in the early combustion stage. The SOF formation has an important influence on the PM formation at lower loads, and soot formation dominates the

  18. Sooting turbulent jet flame: characterization and quantitative soot measurements

    Science.gov (United States)

    Köhler, M.; Geigle, K. P.; Meier, W.; Crosland, B. M.; Thomson, K. A.; Smallwood, G. J.

    2011-08-01

    Computational fluid dynamics (CFD) modelers require high-quality experimental data sets for validation of their numerical tools. Preferred features for numerical simulations of a sooting, turbulent test case flame are simplicity (no pilot flame), well-defined boundary conditions, and sufficient soot production. This paper proposes a non-premixed C2H4/air turbulent jet flame to fill this role and presents an extensive database for soot model validation. The sooting turbulent jet flame has a total visible flame length of approximately 400 mm and a fuel-jet Reynolds number of 10,000. The flame has a measured lift-off height of 26 mm which acts as a sensitive marker for CFD model validation, while this novel compiled experimental database of soot properties, temperature and velocity maps are useful for the validation of kinetic soot models and numerical flame simulations. Due to the relatively simple burner design which produces a flame with sufficient soot concentration while meeting modelers' needs with respect to boundary conditions and flame specifications as well as the present lack of a sooting "standard flame", this flame is suggested as a new reference turbulent sooting flame. The flame characterization presented here involved a variety of optical diagnostics including quantitative 2D laser-induced incandescence (2D-LII), shifted-vibrational coherent anti-Stokes Raman spectroscopy (SV-CARS), and particle image velocimetry (PIV). Producing an accurate and comprehensive characterization of a transient sooting flame was challenging and required optimization of these diagnostics. In this respect, we present the first simultaneous, instantaneous PIV, and LII measurements in a heavily sooting flame environment. Simultaneous soot and flow field measurements can provide new insights into the interaction between a turbulent vortex and flame chemistry, especially since soot structures in turbulent flames are known to be small and often treated in a statistical manner.

  19. Damköhler number effects on soot formation and growth in turbulent nonpremixed flames

    KAUST Repository

    Attili, Antonio

    2015-01-01

    The effect of Damköhler number on turbulent nonpremixed sooting flames is investigated via large scale direct numerical simulation in three-dimensional n-heptane/air jet flames at a jet Reynolds number of 15,000 and at three different Damköhler numbers. A reduced chemical mechanism, which includes the soot precursor naphthalene, and a high-order method of moments are employed. At the highest Damköhler number, local extinction is negligible, while flames holes are observed in the two lowest Damköhler number cases. Compared to temperature and other species controlled by fuel oxidation chemistry, naphthalene is found to be affected more significantly by the Damköhler number. Consequently, the overall soot mass fraction decreases by more than one order of magnitude for a fourfold decrease of the Damköhler number. On the contrary, the overall number density of soot particles is approximately the same, but its distribution in mixture fraction space is different in the three cases. The total soot mass growth rate is found to be proportional to the Damköhler number. In the two lowest Da number cases, soot leakage across the flame is observed. Leveraging Lagrangian statistics, it is concluded that soot leakage is due to patches of soot that cross the stoichiometric surface through flame holes. These results show the leading order effects of turbulent mixing in controlling the dynamics of soot in turbulent flames. © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  20. Studies of propane flame soot acting as heterogeneous ice nuclei in conjunction with single particle soot photometer measurements

    Directory of Open Access Journals (Sweden)

    I. Crawford

    2011-09-01

    Full Text Available The ice nucleation efficiency of propane flame soot particles with and without a sulphuric acid coating was investigated using the aerosol and cloud chamber facility AIDA (Aerosol Interaction and Dynamics in the Atmosphere. The test soot for cloud formation simulations was produced using a propane flame Combustion Aerosol Standard generator (CAST, Jing-CAST Technologies. The organic carbon content (OC of the test soot was altered in a reproducible fashion by changing the fuel/air mixture of the generator. The soot content of ice nuclei was subsequently investigated using a combination of a pumped counterflow virtual impactor (PCVI to separate and evaporate the ice crystals, and a DMT single particle soot photometer (SP2 to examine the mixing state of the BC containing ice residuals.

    Ice nucleation was found to be most efficient for uncoated soot of low organic carbon content (~5 % organic carbon content where deposition freezing occurred at an ice saturation ratio Sice ~ 1.22 at a temperature T = 226.6 K with 25 % of the test soot becoming active as ice nuclei. Propane flame soot of higher organic carbon content (~30 % and ~70 % organic carbon content showed significantly lower ice nucleation efficiency (an activated fraction of the order of a few percent in the experiments than the low organic carbon content soot, with water saturation being required for freezing to occur. Ice nucleation occurred over the range Sice = 1.22–1.70, and T = 223.2–226.6 K. Analysis of the SP2 data showed that the 5 % organic carbon content soot had an undetectable OC coating whereas the 30 % organic carbon content soot had a thicker or less volatile OC coating.

    The application of a sulphuric acid coating to the flame soot shifted the threshold of the onset of freezing towards that of the homogeneous freezing of sulphuric acid; for the minimum OC flame soot this inhibited nucleation since the

  1. Developing a predictive model for the chemical composition of soot nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Violi, Angela [Univ. of Michigan, Ann Arbor, MI (United States); Michelsen, Hope [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Hansen, Nils [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilson, Kevin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-04-07

    In order to provide the scientific foundation to enable technology breakthroughs in transportation fuel, it is important to develop a combustion modeling capability to optimize the operation and design of evolving fuels in advanced engines for transportation applications. The goal of this proposal is to develop a validated predictive model to describe the chemical composition of soot nanoparticles in premixed and diffusion flames. Atomistic studies in conjunction with state-of-the-art experiments are the distinguishing characteristics of this unique interdisciplinary effort. The modeling effort has been conducted at the University of Michigan by Prof. A. Violi. The experimental work has entailed a series of studies using different techniques to analyze gas-phase soot precursor chemistry and soot particle production in premixed and diffusion flames. Measurements have provided spatial distributions of polycyclic aromatic hydrocarbons and other gas-phase species and size and composition of incipient soot nanoparticles for comparison with model results. The experimental team includes Dr. N. Hansen and H. Michelsen at Sandia National Labs' Combustion Research Facility, and Dr. K. Wilson as collaborator at Lawrence Berkeley National Lab's Advanced Light Source. Our results show that the chemical and physical properties of nanoparticles affect the coagulation behavior in soot formation, and our results on an experimentally validated, predictive model for the chemical composition of soot nanoparticles will not only enhance our understanding of soot formation since but will also allow the prediction of particle size distributions under combustion conditions. These results provide a novel description of soot formation based on physical and chemical properties of the particles for use in the next generation of soot models and an enhanced capability for facilitating the design of alternative fuels and the engines they will power.

  2. Soot reduction under DC electric fields in counterflow non-premixed laminar ethylene flames

    KAUST Repository

    Park, Daegeun

    2014-04-23

    The effects of DC electric fields on non-premixed ethylene flames in a counterflow burner were studied experimentally with a focus on the reduction of soot particles. The experiment was conducted by connecting a high voltage terminal and a ground terminal to a lower (fuel) and upper (oxidizer) nozzle, respectively. We applied direct current (DC) potentials in a range of -5 kV < Vdc < 5 kV. Uniform electric fields were then generated in the gap between the two nozzles. The experimental conditions were selected to cover both soot formation (SF) and soot formation oxidation (SFO) flames. The flames subjected to the negative electric fields moved toward the fuel nozzle because of an ionic wind due to the Lorentz force acting on the positive ions in the flames. In addition, the yellow luminosity significantly decreased, indicating changes in the sooting characteristics. To analyze the sooting characteristics under the electric fields, planar laser induced incandescence (PLII) and fluorescence (PLIF) techniques were used to visualize the soot, polycyclic aromatic hydrocarbons (PAHs), and OH radicals. The sooting limits in terms of the fuel and oxygen mole fractions were measured. No substantial soot formation due to the effects of the DC electric fields for the tested range of voltages and reactant mole fractions could be identified. The detailed flame behaviors and sooting characteristics under the DC electric fields are discussed. Copyright © Taylor & Francis Group, LLC.

  3. Cloud condensation nuclei and ice nucleation activity of hydrophobic and hydrophilic soot particles.

    Science.gov (United States)

    Koehler, Kirsten A; DeMott, Paul J; Kreidenweis, Sonia M; Popovicheva, Olga B; Petters, Markus D; Carrico, Christian M; Kireeva, Elena D; Khokhlova, Tatiana D; Shonija, Natalia K

    2009-09-28

    Cloud condensation nuclei (CCN) activity and ice nucleation behavior (for temperaturesnucleation experiments below -40 degrees C, AEC particles nucleated ice near the expected condition for homogeneous freezing of water from aqueous solutions. In contrast, GTS, TS, and TC1 required relative humidity well in excess of water saturation at -40 degrees C for ice formation. GTS particles required water supersaturation conditions for ice activation even at -51 degrees C. At -51 to -57 degrees C, ice formation in particles with electrical mobility diameter of 200 nm occurred in up to 1 in 1000 TS and TC1 particles, and 1 in 100 TOS particles, at relative humidities below those required for homogeneous freezing in aqueous solutions. Our results suggest that heterogeneous ice nucleation is favored in cirrus conditions on oxidized hydrophilic soot of intermediate polarity. Simple considerations suggest that the impact of hydrophilic soot particles on cirrus cloud formation would be most likely in regions of elevated atmospheric soot number concentrations. The ice formation properties of AEC soot are reasonably consistent with present understanding of the conditions required for aircraft contrail formation and the proportion of soot expected to nucleate under such conditions.

  4. Experimental and computational investigation of temperature effects on soot mechanisms

    Directory of Open Access Journals (Sweden)

    Bi Xiaojie

    2014-01-01

    Full Text Available Effects of initial ambient temperatures on combustion and soot emission characteristics of diesel fuel were investigated through experiment conducted in optical constant volume chamber and simulation using phenomenological soot model. There are four difference initial ambient temperatures adopted in our research: 1000 K, 900 K, 800 K and 700 K. In order to obtain a better prediction of soot behavior, phenomenological soot model was revised to take into account the soot oxidation feedback on soot number density and good agreement was observed in the comparison of soot measurement and prediction. Results indicated that ignition delay prolonged with the decrease of initial ambient temperature. The heat release rate demonstrated the transition from mixing controlled combustion at high ambient temperature to premixed combustion mode at low ambient temperature. At lower ambient temperature, soot formation and oxidation mechanism were both suppressed. But finally soot mass concentration reduced with decreasing initial ambient temperature. Although the drop in ambient temperature did not cool the mean in-cylinder temperature during the combustion, it did shrink the total area of local high equivalence ratio, in which soot usually generated fast. At 700 K initial ambient temperature, soot emissions were almost negligible, which indicates that sootless combustion might be achieved at super low initial temperature operation conditions.

  5. THE EFFECTS OF EQUIVALENCE RATIO ON THE FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND SOOT IN PREMIXED ETHANE FLAMES. (R825412)

    Science.gov (United States)

    AbstractThe formation of polycyclic aromatic hydrocarbons (PAH) and soot has been investigated in atmospheric-pressure, laminar, ethane/oxygen/argon premixed flames as a function of mixture equivalence ratio. Mole fraction profiles of major products, trace aromatics, ...

  6. Lanthanum-promoted copper-based hydrotalcites derived mixed oxides for NO{sub x} adsorption, soot combustion and simultaneous NO{sub x}-soot removal

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhongpeng [School of Resources and Environment, University of Jinan, 106 Jiwei Road, Jinan 250022 (China); Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Yan, Xiaotong; Bi, Xinlin; Wang, Liguo [School of Resources and Environment, University of Jinan, 106 Jiwei Road, Jinan 250022 (China); Zhang, Zhaoliang, E-mail: chm_zhangzl@ujn.edu.cn [School of Resources and Environment, University of Jinan, 106 Jiwei Road, Jinan 250022 (China); Jiang, Zheng; Xiao, Tiancun [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Umar, Ahmad [Department of Chemistry, College of Science and Arts, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Wang, Qiang, E-mail: qiang.wang.ox@gmail.com [College of Environmental Science and Engineering, Beijing Forestry University, 35 Tsinghua East Road, Beijing 100083 (China)

    2014-03-01

    Graphical abstract: - Highlights: • The addition of La in Cu-based oxides increased the types of active oxygen. • NO{sub x} adsorption, soot oxidation and simultaneous NO{sub x}-soot removal were enhanced. • The possible catalytic mechanism was studied via in situ FTIR analysis. • Soot oxidation was promoted by the NO{sub 2} intermediate. - Abstract: La-promoted Cu-based hydrotalcites derived mixed oxides were prepared and their catalytic activities for NO{sub x} adsorption, soot oxidation, and simultaneous NO{sub x}-soot removal were investigated. The catalysts were characterized by XRD, DTG, BET, FTIR, H2-TPR, TPD and TPO techniques. The oxides catalysts exhibited mesoporous properties with specific surface area of 45–160 m{sup 2}/g. The incorporation of La and Cu decreased the amount of basic sites due to the large decrease in surface areas. Under O{sub 2} atmosphere, La incorporation is dominant for soot oxidation activity, while Cu favors high selectivity to CO{sub 2} formation. A synergetic effect between La and Cu for catalyzed soot oxidation lies in the improved redox property and suitable basicity. The presence of NO in O{sub 2} significantly promoted soot oxidation on the catalysts with the ignition temperature decreased to about 300 °C. In O{sub 2}/NO atmosphere, NO{sub 2} acts as an intermediate which oxidizes soot to CO{sub 2} at a lower temperature with itself reduced to NO or N{sub 2}, contributing to the high catalytic performance in simultaneous removal of NO{sub x} and soot.

  7. Soot modeling of counterflow diffusion flames of ethylene-based binary mixture fuels

    KAUST Repository

    Wang, Yu

    2015-03-01

    A soot model was developed based on the recently proposed PAH growth mechanism for C1-C4 gaseous fuels (KAUST PAH Mechanism 2, KM2) that included molecular growth up to coronene (A7) to simulate soot formation in counterflow diffusion flames of ethylene and its binary mixtures with methane, ethane and propane based on the method of moments. The soot model has 36 soot nucleation reactions from 8 PAH molecules including pyrene and larger PAHs. Soot surface growth reactions were based on a modified hydrogen-abstraction-acetylene-addition (HACA) mechanism in which CH3, C3H3 and C2H radicals were included in the hydrogen abstraction reactions in addition to H atoms. PAH condensation on soot particles was also considered. The experimentally measured profiles of soot volume fraction, number density, and particle size were well captured by the model for the baseline case of ethylene along with the cases involving mixtures of fuels. The simulation results, which were in qualitative agreement with the experimental data in the effects of binary fuel mixing on the sooting structures of the measured flames, showed in particular that 5% addition of propane (ethane) led to an increase in the soot volume fraction of the ethylene flame by 32% (6%), despite the fact that propane and ethane are less sooting fuels than is ethylene, which is in reasonable agreement with experiments of 37% (14%). The model revealed that with 5% addition of methane, there was an increase of 6% in the soot volume fraction. The average soot particle sizes were only minimally influenced while the soot number densities were increased by the fuel mixing. Further analysis of the numerical data indicated that the chemical cross-linking effect between ethylene and the dopant fuels resulted in an increase in PAH formation, which led to higher soot nucleation rates and therefore higher soot number densities. On the other hand, the rates of soot surface growth per unit surface area through the HACA mechanism were

  8. Oxidation kinetics and soot formation

    Science.gov (United States)

    Glassman, I.; Brezinsky, K.

    1983-01-01

    The research objective is to clarify the role of aromaticity in the soot nucleation process by determining the relative importance of phenyl radical/molecular oxygen and benzene/atomic oxygen reactions in the complex combustion of aromatic compounds. Three sets of chemical flow reactor experiments have been designed to determine the relative importance of the phenyl radical/molecular oxygen and benzene/atomic oxygen reactions. The essential elements of these experiments are 1) the use of cresols and anisole formed during the high temperature oxidation of toluene as chemical reaction indicators; 2) the in situ photolysis of molecular oxygen to provide an oxygen atom perturbation in the reacting aromatic system; and 3) the high temperature pyrolysis of phenol, the cresols and possibly anisole.

  9. Characteristics of non-premixed oxygen-enhanced combustion: II. Flame structure effects on soot precursor kinetics resulting in soot-free flames

    Energy Technology Data Exchange (ETDEWEB)

    Skeen, S.A.; Axelbaum, R.L. [Department of Energy, Environmental, Chemical Engineering, Washington University in St. Louis, St. Louis, MO (United States); Yablonsky, G. [Department of Energy, Environmental, Chemical Engineering, Washington University in St. Louis, St. Louis, MO (United States); Parks College, Saint Louis University, St. Louis, MO (United States)

    2010-09-15

    A detailed computational study was performed to understand the effects of the flame structure on the formation and destruction of soot precursors during ethylene combustion. Using the USC Mech Version II mechanism the contributions of different pathways to the formation of benzene and phenyl were determined in a wide domain of Z{sub st} values via a reverse-pathway analysis. It was shown that for conventional ethylene-air flames two sequential reversible reactions play primary roles in the propargyl (C{sub 3}H{sub 3}) chemistry, namely (1) C{sub 2}H{sub 2}+CH{sub 3}= pC{sub 3} H{sub 4}+H, (2) pC{sub 3} H{sub 4}= C{sub 3} H{sub 3}+ H with the corresponding overall endothermic reaction of propargyl formation (3) C{sub 2} H{sub 2}+CH{sub 3}= C{sub 3} H{sub 3}+2H. The contributions of these reactions to propyne (pC{sub 3}H{sub 4}) and propargyl formation and propargyl self-combination leading to benzene and phenyl were studied as a function of physical position, temperature, Z{sub st}, and H concentration. In particular, the role of H radicals on soot precursor destruction was studied in detail. At low Z{sub st}, Reactions 1 and 2 contribute significantly to propyne and propargyl formation on the fuel side of the radical pool at temperatures greater than approx. 1600 K. At higher local temperatures near the radical pool where the concentration of H is significant, the reverse reactions begin to dominate resulting in soot precursor destruction. As Z{sub st} is increased, these regions merge and only net propargyl consumption is observed. Based on the equilibrium constant of Reaction 3, a Z{sub st} value was estimated above which the rate of propargyl formation as a soot precursor is greatly reduced (Z{sub st} = 0.3). This condition compares well with the experimental results for permanently blue counterflow flames in the literature. (author)

  10. A computational study of soot formation in opposed-flow diffusion flame interacting with vortices

    KAUST Repository

    Selvaraj, Prabhu; Im, Hong G.

    2017-01-01

    ethylene-air flame is simulated. A reduced mechanism with PAH pathways that includes until coronene and method of moments with interpolative closure (MOMIC) has been employed to calculate the soot characteristics. Interaction of sooting flame with a

  11. Reductions of PAH and Soot by Center Air Injection

    Directory of Open Access Journals (Sweden)

    Kazuhiro Yamamoto

    2014-07-01

    Full Text Available In this study, to reduce the amount of pollutant PAH and soot in the flame, we examined the burner system equipped with a center air injection. For this purpose, by using PAH-LIF and soot LII, we evaluated relative PAH and soot amounts in both the triple port burner and the conventional co-axial burner (double port burner to discuss effects of center air injection on the formation of PAH and soot. The fuel was propane. In the triple port burner, two different blue flames are observed near the burner rim, followed by bright luminous flames with soot. The flame length is longer when the fuel flow velocity is increased. On the other hand, the flame length is shorter with an increase in internal air flow velocity. As for PAH and soot, these amounts of the triple port burner are much smaller than those of the double port burner. For the triple port burner, due to the center air injection, the fuel consumption occurs in both inner and outer flames. On the other hand, for the double port burner, the oxygen is supplied from one side air, and as a result, the fuel consumption rate is relatively lower. Hence, by the center air injection, the fuel consumption is largely accelerated, resulting in the reduction of PAH and soot.

  12. Comparison of soot formation for diesel and jet-a in a constant volume combustion chamber using two-color pyrometry

    KAUST Repository

    Jing, Wei

    2014-04-01

    The measurement of the two-color line of sight soot and KL factor for NO.2 diesel and jet-A fuels was conducted in an optical constant volume combustion chamber by using a high speed camera under 1000 K ambient temperature and varied oxygen concentration conditions. The ambient conditions were set as follows: four oxygen cases including 10%, 15%, 18% and 21% at 1000 K ambient temperature. KL factor and soot temperature were determined based on the two-color pyrometry technique using two band-pass filters with wavelengths of 650 nm and 550 nm. The results show that low soot temperature is observed in the upstream inner flame along the centerline, which is surrounded by high soot temperature regions, and a high KL factor is found in the same region with a low soot temperature. The results under different times suggest that soot temperature is higher for high O2 conditions during the entire flame development; meanwhile, both integrated KL factor and soot area decrease with the increase of O2 concentration. The two fuels share a similar trend of soot temperature and KL factor, however, diesel flame has a higher soot temperature and a larger high soot temperature area compared to jet-A flame. On the other hand, diesel flame shows a lower soot level during the quasi-steady state with a higher total soot level at the end of the combustion under low O2 conditions. A lower O2 concentration range from 10% to 15% is expected to have the possibility to achieve a simultaneous reduction of soot and NOx in sooting flames under the 1000 K ambient temperature condition. Copyright © 2014 SAE International.

  13. Numerical simulation of combustion and soot under partially premixed combustion of low-octane gasoline

    KAUST Repository

    An, Yanzhao

    2017-09-23

    In-cylinder combustion visualization and engine-out soot particle emissions were investigated in an optical diesel engine fueled with low octane gasoline. Single injection strategy with an early injection timing (−30 CAD aTDC) was employed to achieve partially premixed combustion (PPC) condition. A high-speed color camera was used to record the combustion images for 150 cycles. The regulated emission of carbon dioxide, carbon monoxide, nitrogen oxides and soot mass concentration were measured experimentally. Full cycle engine simulations were performed using CONVERGE™ and the simulation results matched with the experimental results. The in-cylinder soot particle evolution was performed by coupling a reduced toluene reference fuel mechanism including the PAHs formation/oxidation reactions with particulate size mimic model. The results showed that PPC presents typical stratified combustion characteristics, which is significantly different from the conventional diesel spray-driven combustion. The in-cylinder temperature and equivalence ratio overlaid with soot-NO formation regime revealed that PPC operating condition under study mostly avoided the main sooting conditions throughout the entire combustion. The evaluation of temperature distribution showed formaldehyde could be regarded as an indicator for low temperature reactions, while hydroxyl group represents the high temperature reactions. Soot evolution happened during the combustion process, hydroxyl radicals promoted the soot oxidation.

  14. Numerical simulation of combustion and soot under partially premixed combustion of low-octane gasoline

    KAUST Repository

    An, Yanzhao; Jaasim, Mohammed; Vallinayagam, R.; Vedharaj, S.; Im, Hong G.; Johansson, Bengt.

    2017-01-01

    In-cylinder combustion visualization and engine-out soot particle emissions were investigated in an optical diesel engine fueled with low octane gasoline. Single injection strategy with an early injection timing (−30 CAD aTDC) was employed to achieve partially premixed combustion (PPC) condition. A high-speed color camera was used to record the combustion images for 150 cycles. The regulated emission of carbon dioxide, carbon monoxide, nitrogen oxides and soot mass concentration were measured experimentally. Full cycle engine simulations were performed using CONVERGE™ and the simulation results matched with the experimental results. The in-cylinder soot particle evolution was performed by coupling a reduced toluene reference fuel mechanism including the PAHs formation/oxidation reactions with particulate size mimic model. The results showed that PPC presents typical stratified combustion characteristics, which is significantly different from the conventional diesel spray-driven combustion. The in-cylinder temperature and equivalence ratio overlaid with soot-NO formation regime revealed that PPC operating condition under study mostly avoided the main sooting conditions throughout the entire combustion. The evaluation of temperature distribution showed formaldehyde could be regarded as an indicator for low temperature reactions, while hydroxyl group represents the high temperature reactions. Soot evolution happened during the combustion process, hydroxyl radicals promoted the soot oxidation.

  15. Influence of turbulence-chemistry interaction for n-heptane spray combustion under diesel engine conditions with emphasis on soot formation and oxidation

    Science.gov (United States)

    Bolla, Michele; Farrace, Daniele; Wright, Yuri M.; Boulouchos, Konstantinos; Mastorakos, Epaminondas

    2014-03-01

    The influence of the turbulence-chemistry interaction (TCI) for n-heptane sprays under diesel engine conditions has been investigated by means of computational fluid dynamics (CFD) simulations. The conditional moment closure approach, which has been previously validated thoroughly for such flows, and the homogeneous reactor (i.e. no turbulent combustion model) approach have been compared, in view of the recent resurgence of the latter approaches for diesel engine CFD. Experimental data available from a constant-volume combustion chamber have been used for model validation purposes for a broad range of conditions including variations in ambient oxygen (8-21% by vol.), ambient temperature (900 and 1000 K) and ambient density (14.8 and 30 kg/m3). The results from both numerical approaches have been compared to the experimental values of ignition delay (ID), flame lift-off length (LOL), and soot volume fraction distributions. TCI was found to have a weak influence on ignition delay for the conditions simulated, attributed to the low values of the scalar dissipation relative to the critical value above which auto-ignition does not occur. In contrast, the flame LOL was considerably affected, in particular at low oxygen concentrations. Quasi-steady soot formation was similar; however, pronounced differences in soot oxidation behaviour are reported. The differences were further emphasised for a case with short injection duration: in such conditions, TCI was found to play a major role concerning the soot oxidation behaviour because of the importance of soot-oxidiser structure in mixture fraction space. Neglecting TCI leads to a strong over-estimation of soot oxidation after the end of injection. The results suggest that for some engines, and for some phenomena, the neglect of turbulent fluctuations may lead to predictions of acceptable engineering accuracy, but that a proper turbulent combustion model is needed for more reliable results.

  16. Experimental study of the interaction of HO2 radicals with soot surface.

    Science.gov (United States)

    Bedjanian, Yuri; Lelièvre, Stéphane; Le Bras, Georges

    2005-01-21

    The reaction of HO2 with toluene and kerosene flame soot was studied over the temperature range 240-350 K and at P = 0.5-5 Torr of helium using a discharge flow reactor coupled to a modulated molecular beam mass spectrometer. A flat-flame burner was used for the preparation and deposition of soot samples from premixed flames of liquid fuels under well controlled and adjustable combustion conditions. The independent of temperature in the range 240-350 K value of gamma = (7.5 +/- 1.5) x 10(-2) (calculated with geometric surface area) was found for the uptake coefficient of HO2 on kerosene and toluene soot. No significant deactivation of soot surface during its reaction with HO2 was observed. Experiments on soot ageing under ambient conditions showed that the reactivity of aged soot is similar to that of freshly prepared soot samples. The results show that the HO2 + soot reaction could be a significant loss process for HOx in the urban atmosphere with a potential impact on photochemical ozone formation. In contrast this process will be negligible in the upper troposphere even in flight corridors.

  17. Evaluation and optimisation of phenomenological multi-step soot model for spray combustion under diesel engine-like operating conditions

    Science.gov (United States)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song; Schramm, Jesper

    2015-05-01

    In this work, a two-dimensional computational fluid dynamics study is reported of an n-heptane combustion event and the associated soot formation process in a constant volume combustion chamber. The key interest here is to evaluate the sensitivity of the chemical kinetics and submodels of a semi-empirical soot model in predicting the associated events. Numerical computation is performed using an open-source code and a chemistry coordinate mapping approach is used to expedite the calculation. A library consisting of various phenomenological multi-step soot models is constructed and integrated with the spray combustion solver. Prior to the soot modelling, combustion simulations are carried out. Numerical results show that the ignition delay times and lift-off lengths exhibit good agreement with the experimental measurements across a wide range of operating conditions, apart from those in the cases with ambient temperature lower than 850 K. The variation of the soot precursor production with respect to the change of ambient oxygen levels qualitatively agrees with that of the conceptual models when the skeletal n-heptane mechanism is integrated with a reduced pyrene chemistry. Subsequently, a comprehensive sensitivity analysis is carried out to appraise the existing soot formation and oxidation submodels. It is revealed that the soot formation is captured when the surface growth rate is calculated using a square root function of the soot specific surface area and when a pressure-dependent model constant is considered. An optimised soot model is then proposed based on the knowledge gained through this exercise. With the implementation of optimised model, the simulated soot onset and transport phenomena before reaching quasi-steady state agree reasonably well with the experimental observation. Also, variation of spatial soot distribution and soot mass produced at oxygen molar fractions ranging from 10.0 to 21.0% for both low and high density conditions are reproduced.

  18. Simulation and analysis of the soot particle size distribution in a turbulent nonpremixed flame

    KAUST Repository

    Lucchesi, Marco; Abdelgadir, Ahmed Gamaleldin; Attili, Antonio; Bisetti, Fabrizio

    2017-01-01

    to the simulation of soot formation and growth in simplified configurations featuring a constant concentration of soot precursors and the evolution of the size distribution in time is found to depend on the intensity of the nucleation rate. Higher nucleation rates

  19. Morphology and nano-structure analysis of soot particles sampled from high pressure diesel jet flames under diesel-like conditions

    Science.gov (United States)

    Jiang, Hao; Li, Tie; Wang, Yifeng; He, Pengfei

    2018-04-01

    Soot particles emitted from diesel engines have a significant impact on the atmospheric environment. Detailed understanding of soot formation and oxidation processes is helpful for reducing the pollution of soot particles, which requires information such as the size and nano-structure parameters of the soot primary particles sampled in a high-temperature and high-pressure diesel jet flame. Based on the thermophoretic principle, a novel sampling probe minimally disturbing the diesel jet flame in a constant volume combustion vessel is developed for analysing soot particles. The injected quantity of diesel fuel is less than 10 mg, and the soot particles sampled by carriers with a transmission electron microscope (TEM) grid and lacey TEM grid can be used to analyse the morphologies of soot aggregates and the nano-structure of the soot primary particles, respectively. When the quantity of diesel fuel is more than 10 mg, in order to avoid burning-off of the carriers in higher temperature and pressure conditions, single-crystal silicon chips are employed. Ultrasonic oscillations and alcohol extraction are then implemented to obtain high quality soot samples for observation using a high-resolution transmission electron microscope. An in-house Matlab-based code is developed to extract the nano-structure parameters of the soot particles. A complete sampling and analysis procedure of the soot particles is provided to study the formation and oxidation mechanism of soot.

  20. Investigating Soot Morphology in Counterflow Flames at Elevated Pressures

    KAUST Repository

    Amin, Hafiz Muhammad Fahid

    2018-01-01

    volume fraction from 2 to 10 atm. Local soot volume fraction increased with pressure and soot concentration profiles showed good agreements when measured by both techniques. Experimental data obtained in this work is very helpful for the modelers for validating their codes and predicting the soot formation in pressurized flames.

  1. Physical and chemical comparison of soot in hydrocarbon and biodiesel fuel diffusion flames: A study of model and commercial fuels

    Energy Technology Data Exchange (ETDEWEB)

    Matti Maricq, M. [Research and Advanced Engineering, Ford Motor Company, Dearborn, MI (United States)

    2011-01-15

    Data are presented to compare soot formation in both surrogate and practical fatty acid methyl ester biodiesel and petroleum fuel diffusion flames. The approach here uses differential mobility analysis to follow the size distributions and electrical charge of soot particles as they evolve in the flame, and laser ablation particle mass spectrometry to elucidate their composition. Qualitatively, these soot properties exhibit a remarkably similar development along the flames. The size distributions begin as a single mode of precursor nanoparticles, evolve through a bimodal phase marking the onset of aggregate formation, and end in a self preserving mode of fractal-like particles. Both biodiesel and hydrocarbon fuels yield a common soot composition dominated by C{sub x}H{sub y}{sup +} ions, stabilomer PAHs, and fullerenes in the positive ion mass spectrum, and C{sub x}{sup -} and C{sub 2x}H{sup -} in the negative ion spectrum. These ion intensities initially grow with height in the diffusion flames, but then decline during later stages, consistent with soot carbonization. There are important quantitative differences between fuels. The surrogate biodiesel fuel methyl butanoate substantially reduces soot levels, but soot formation and evolution in this flame are delayed relative to both soy and petroleum fuels. In contrast, soots from soy and hexadecane flames exhibit nearly quantitative agreement in their size distribution and composition profiles with height, suggesting similar soot precursor chemistry. (author)

  2. Investigation of mass and energy coupling between soot particles and gas species in modelling ethylene counterflow diffusion flames

    NARCIS (Netherlands)

    Zimmer, L.; Pereira, F.M.; van Oijen, J.A.; de Goey, L.P.H.

    2017-01-01

    A numerical model is developed aiming at investigating soot formation in ethylene counterflow diffusion flames. The mass and energy coupling between soot solid particles and gas-phase species is investigated in detail. A semi-empirical two-equation model is chosen for predicting soot mass fraction

  3. Soot formation characteristics of gasoline surrogate fuels in counterflow diffusion flames

    KAUST Repository

    Choi, Byungchul; Choi, Sangkyu; Chung, Suk-Ho

    2011-01-01

    The characteristics of polycyclic aromatic hydrocarbon (PAH) and soot for gasoline surrogate fuels have been investigated in counterflow diffusion flames by adopting laser-induced fluorescence (LIF) and laser-induced incandescence (LII) techniques

  4. Effects of diluents on soot surface temperature and volume fraction in diluted ethylene diffusion flames at pressure

    KAUST Repository

    Kailasanathan, Ranjith Kumar Abhinavam

    2014-05-20

    Soot surface temperature and volume fraction are measured in ethylene/air coflowing laminar diffusion flames at high pressures, diluted with one of four diluents (argon, helium, nitrogen, and carbon dioxide) using a two-color technique. Both temperature and soot measurements presented are line-of-sight averages. The results aid in understanding the kinetic and thermodynamic behavior of the soot formation and oxidation chemistry with changes in diluents, ultimately leading to possible methods of reducing soot emission from practical combustion hardware. The diluted fuel and coflow exit velocities (top-hat profiles) were matched at all pressures to minimize shear effects. In addition to the velocity-matched flow rates, the mass fluxes were held constant for all pressures. Addition of a diluent has a pronounced effect on both the soot surface temperature and volume fraction, with the helium diluted flame yielding the maximum and carbon dioxide diluted flame yielding minimum soot surface temperature and volume fraction. At low pressures, peak soot volume fraction exists at the tip of the flame, and with an increase in pressure, the location shifts lower to the wings of the flame. Due to the very high diffusivity of helium, significantly higher temperature and volume fraction are measured and explained. Carbon dioxide has the most dramatic soot suppression effect. By comparing the soot yield with previously measured soot precursor concentrations in the same flame, it is clear that the lower soot yield is a result of enhanced oxidation rates rather than a reduction in precursor formation. Copyright © 2014 Taylor & Francis Group, LLC.

  5. Evaluation of a Lagrangian Soot Tracking Method for the prediction of primary soot particle size under engine-like conditions

    DEFF Research Database (Denmark)

    Cai Ong, Jiun; Pang, Kar Mun; Walther, Jens Honore

    2018-01-01

    This paper reports the implementation and evaluation of a Lagrangian soot tracking (LST) method for the modeling of soot in diesel engines. The LST model employed here has the tracking capability of a Lagrangian method and the ability to predict primary soot particle sizing. The Moss-Brookes soot...... in predicting temporal soot cloud development, mean soot diameter and primary soot size distribution is evaluated using measurements of n-heptane and n-dodecane spray combustion obtained under diesel engine-like conditions. In addition, sensitivity studies are carried out to investigate the influence of soot....... A higher rate of soot oxidation due to OH causes the soot particles to be fully oxidized downstream of the flame. In general, the LST model performs better than the Eulerian method in terms of predicting soot sizing and accessing information of individual soot particles, both of which are shortcomings...

  6. Implementation of two-equation soot flamelet models for laminar diffusion flames

    Energy Technology Data Exchange (ETDEWEB)

    Carbonell, D.; Oliva, A.; Perez-Segarra, C.D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), ETSEIAT, Colom 11, E-08222, Terrassa (Barcelona) (Spain)

    2009-03-15

    The two-equation soot model proposed by Leung et al. [K.M. Leung, R.P. Lindstedt, W.P. Jones, Combust. Flame 87 (1991) 289-305] has been derived in the mixture fraction space. The model has been implemented using both Interactive and Non-Interactive flamelet strategies. An Extended Enthalpy Defect Flamelet Model (E-EDFM) which uses a flamelet library obtained neglecting the soot formation is proposed as a Non-Interactive method. The Lagrangian Flamelet Model (LFM) is used to represent the Interactive models. This model uses direct values of soot mass fraction from flamelet calculations. An Extended version (E-LFM) of this model is also suggested in which soot mass fraction reaction rates are used from flamelet calculations. Results presented in this work show that the E-EDFM predict acceptable results. However, it overpredicts the soot volume fraction due to the inability of this model to couple the soot and gas-phase mechanisms. It has been demonstrated that the LFM is not able to predict accurately the soot volume fraction. On the other hand, the extended version proposed here has been shown to be very accurate. The different flamelet mathematical formulations have been tested and compared using well verified reference calculations obtained solving the set of the Full Transport Equations (FTE) in the physical space. (author)

  7. Role of engine age and lubricant chemistry on the characteristics of EGR soot

    Science.gov (United States)

    Adeniran, Olusanmi Adeniji

    Exhaust products of Diesel Engines serves as an environmental hazard, and to curtail this problem a Tier 3 emission standard was introduced which involves change in engine designs and introduction of EGR systems in Diesel engines. EGR systems, however has the challenge of generating soot which are abrasive and are major causes of wear in Diesel engines. This work has studied the characteristics of EGR soot formed in different range of engine age and in different lubricant chemistries of Mineral and Synthetic based diesel Oils. It is found that lubricant degradation is encouraged by less efficient combustion as engine age increases, and these are precursors to formation of crystalline and amorphous particles that are causes of wear in Diesel Engines. It is found that soot from new engine is dominated by calcium based crystals which are from calcium sulfonate detergent, which reduces formation of second phase particles that can be abrasive. Diversity and peak intensity is seen to increase in soot samples as engine age increases. This understanding of second phase particles formed in engines across age ranges can help in the durability development of engine, improvement of Oil formulation for EGR engines, and in development of chemistries for after-treatment Oil solutions that can combat formation of abrasive particles in Oils.

  8. A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

    KAUST Repository

    Skeen, Scott A.

    2016-04-05

    The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.

  9. A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

    KAUST Repository

    Skeen, Scott A.; Manin, Julien; Pickett, Lyle M.; Cenker, Emre; Bruneaux, Gilles; Kondo, Katsufumi; Aizawa, Tets; Westlye, Fredrik; Dalen, Kristine; Ivarsson, Anders; Xuan, Tiemin; Garcia-Oliver, Jose M; Pei, Yuanjiang; Som, Sibendu; Hu, Wang; Reitz, Rolf D.; Lucchini, Tommaso; D'Errico, Gianluca; Farrace, Daniele; Pandurangi, Sushant S.; Wright, Yuri M.; Chishty, Muhammad Aqib; Bolla, Michele; Hawkes, Evatt

    2016-01-01

    The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.

  10. The effect of soot on ammonium nitrate species and NO2 selective catalytic reduction over Cu-zeolite catalyst-coated particulate filter.

    Science.gov (United States)

    Mihai, Oana; Tamm, Stefanie; Stenfeldt, Marie; Olsson, Louise

    2016-02-28

    A selective catalytic reduction (SCR)-coated particulate filter was evaluated by means of dynamic tests performed using NH3, NO2, O2 and H2O. The reactions were examined both prior to and after soot removal in order to study the effect of soot on ammonium nitrate formation and decomposition, ammonia storage and NO2 SCR. A slightly larger ammonia storage capacity was observed when soot was present in the sample, which indicated that small amounts of ammonia can adsorb on the soot. Feeding of NO2 and NH3 in the presence of O2 and H2O at low temperature (150, 175 and 200°C) leads to a large formation of ammonium nitrate species and during the subsequent temperature ramp using H2O and argon, a production of nitrous oxides was observed. The N2O formation is often related to ammonium nitrate decomposition, and our results showed that the N2O formation was clearly decreased by the presence of soot. We therefore propose that in the presence of soot, there are fewer ammonium nitrate species on the surface due to the interactions with the soot. Indeed, we do observe CO2 production during the reaction conditions also at 150°C, which shows that there is a reaction with these species and soot. In addition, the conversion of NOx due to NO2 SCR was significantly enhanced in the presence of soot; we attribute this to the smaller amount of ammonium nitrate species present in the experiments where soot is available since it is well known that ammonium nitrate formation is a major problem at low temperature due to the blocking of the catalytic sites. Further, a scanning electron microscopy analysis of the soot particles shows that they are about 30-40 nm and are therefore too large to enter the pores of the zeolites. There are likely CuxOy or other copper species available on the outside of the zeolite crystallites, which could have been enhanced due to the hydrothermal treatment at 850°C of the SCR-coated filter prior to the soot loading. We therefore propose that soot is

  11. Effect of diluents on soot precursor formation and temperature in ethylene laminar diffusion flames

    KAUST Repository

    Abhinavam Kailasanathan, Ranjith Kumar

    2013-03-01

    Soot precursor species concentrations and flame temperature were measured in a diluted laminar co-flow jet diffusion flame at pressures up to eight atmospheres while varying diluent type. The objective of this study was to gain a better understanding of soot production and oxidation mechanisms, which could potentially lead to a reduction in soot emissions from practical combustion devices. Gaseous samples were extracted from the centerline of an ethylene-air laminar diffusion flame, which was diluted individually with four diluents (argon, helium, nitrogen, and carbon dioxide) to manipulate flame temperature and transport properties. The diluted fuel and co-flow exit velocities (top-hat profiles) were matched at all pressures to minimize shear-layer effects, and the mass fluxes were fixed over the pressure range to maintain constant Reynolds number. The flame temperature was measured using a fine gauge R-type thermocouple at pressures up to four atmospheres. Centerline concentration profiles of major non-fuel hydrocarbons collected via extractive sampling with a quartz microprobe and quantification using GC/MS+FID are reported within. The measured hydrocarbon species concentrations are vary dramatically with pressure and diluent, with the helium and carbon dioxide diluted flames yielding the largest and smallest concentrations of soot precursors, respectively. In the case of C2H2 and C6H6, two key soot precursors, helium diluted flames had concentrations more than three times higher compared with the carbon dioxide diluted flame. The peak flame temperature vary with diluents tested, as expected, with carbon dioxide diluted flame being the coolest, with a peak temperature of 1760K at 1atm, and the helium diluted flame being the hottest, with a peak temperature of 2140K. At four atmospheres, the helium diluted flame increased to 2240K, but the CO2 flame temperature increased more, decreasing the difference to approximately 250K. © 2012 The Combustion Institute.

  12. Fullerene Soot in Eastern China Air: Results from Soot Particle-Aerosol Mass Spectrometer

    Science.gov (United States)

    Wang, J.; Ge, X.; Chen, M.; Zhang, Q.; Yu, H.; Sun, Y.; Worsnop, D. R.; Collier, S.

    2015-12-01

    In this work, we present for the first time, the observation and quantification of fullerenes in ambient airborne particulate using an Aerodyne Soot Particle - Aerosol Mass Spectrometer (SP-AMS) deployed during 2015 winter in suburban Nanjing, a megacity in eastern China. The laser desorption and electron impact ionization techniques employed by the SP-AMS allow us to differentiate various fullerenes from other aerosol components. Mass spectrum of the identified fullerene soot is consisted by a series of high molecular weight carbon clusters (up to m/z of 2000 in this study), almost identical to the spectral features of commercially available fullerene soot, both with C70 and C60 clusters as the first and second most abundant species. This type of soot was observed throughout the entire study period, with an average mass loading of 0.18 μg/m3, accounting for 6.4% of the black carbon mass, 1.2% of the total organic mass. Temporal variation and diurnal pattern of fullerene soot are overall similar to those of black carbon, but are clearly different in some periods. Combining the positive matrix factorization, back-trajectory and analyses of the meteorological parameters, we identified the petrochemical industrial plants situating upwind from the sampling site, as the major source of fullerene soot. In this regard, our findings imply the ubiquitous presence of fullerene soot in ambient air of industry-influenced area, especially the oil and gas production regions. This study also offers new insights into the characterization of fullerenes from other environmental samples via the advanced SP-AMS technique.

  13. A comparative study on the sooting tendencies of various 1-alkene fuels in counterflow diffusion flames

    KAUST Repository

    Wang, Yu

    2018-02-19

    Alkenes are important components in transportation fuels, and are known to have increased sooting tendencies compared to analogous saturated hydrocarbons with the same carbon number. This work aims to understand the sooting tendencies of various 1-alkenes through experiments and numerical simulations for counterflow diffusion flames. Soot and PAH formation tendencies of 1-alkene fuels, including ethylene (C2H4), propene (C3H6), 1-butene (1-C4H8), 1-pentene (1-C5H10), 1-hexene (1-C6H12) and 1-octene (1-C8H16), were experimentally studied using laser induced-incandescence (LII) and laser-induced fluorescence (LIF) techniques, respectively. From the LII results, 1-C4H8 was found to be the most sooting fuel, followed by C3H6 > 1-C5H10 > 1-C6H12 > 1-C8H16 > C2H4. The LIF data with a detection wavelength of 500 nm indicated the PAH formation tendencies followed the order of 1-C4H8 > 1-C5H10 ∼1-C6H12 > C3H6 > 1-C8H16 > C2H4, which were different from the order of sooting tendencies. Numerical simulations with a comprehensive chemical kinetic model including PAH growth chemistry for the tested 1-alkene fuels were conducted to elucidate the aromatic formation pathways and rationalize the experimentally observed trends. The numerical results highlighted the importance of intermediate species with odd carbon numbers in aromatic species formation, such as propargyl, allyl, cyclopentadienyl and indenyl radicals. Their concentration differences, which could be traced back to the parent fuel molecules through rate of production analysis, rationalize the experimentally observed differences in soot and PAH formation tendencies.

  14. Soot and Spectral Radiation Modeling in ECN Spray A and in Engines

    Energy Technology Data Exchange (ETDEWEB)

    Haworth, Daniel C [Pennsylvania State Univ., University Park, PA (United States); Ferreyro-Fernandez, Sebastian [Pennsylvania State Univ., University Park, PA (United States); Paul, Chandan [Pennsylvania State Univ., University Park, PA (United States); Sircar, Arpan [Pennsylvania State Univ., University Park, PA (United States); Imren, Abdurrahman [Pennsylvania State Univ., University Park, PA (United States); Roy, Somesh P [Marquette University (United States); Modest, Michael F [University of California Merced (United States); Ge, Wenjun [University of California Merced (United States)

    2017-04-03

    The amount of soot formed in a turbulent combustion system is determined by a complex system of coupled nonlinear chemical and physical processes. Different physical subprocesses can dominate, depending on the hydrodynamic and thermochemical environments. Similarly, the relative importance of reabsorption, spectral radiation properties, and molecular gas radiation versus soot radiation varies with thermochemical conditions, and in ways that are difficult to predict for the highly nonhomogeneous in-cylinder mixtures in engines. Here it is shown that transport and mixing play relatively more important roles as rate-determining processes in soot formation at engine-relevant conditions. It is also shown that molecular gas radiation and spectral radiation properties are important for engine-relevant conditions.

  15. The Toxicological Mechanisms of Environmental Soot (Black Carbon and Carbon Black: Focus on Oxidative Stress and Inflammatory Pathways

    Directory of Open Access Journals (Sweden)

    Rituraj Niranjan

    2017-06-01

    Full Text Available The environmental soot and carbon blacks (CBs cause many diseases in humans, but their underlying mechanisms of toxicity are still poorly understood. Both are formed after the incomplete combustion of hydrocarbons but differ in their constituents and percent carbon contents. For the first time, “Sir Percival Pott” described soot as a carcinogen, which was subsequently confirmed by many others. The existing data suggest three main types of diseases due to soot and CB exposures: cancer, respiratory diseases, and cardiovascular dysfunctions. Experimental models revealed the involvement of oxidative stress, DNA methylation, formation of DNA adducts, and Aryl hydrocarbon receptor activation as the key mechanisms of soot- and CB-induced cancers. Metals including Si, Fe, Mn, Ti, and Co in soot also contribute in the reactive oxygen species (ROS-mediated DNA damage. Mechanistically, ROS-induced DNA damage is further enhanced by eosinophils and neutrophils via halide (Cl− and Br− dependent DNA adducts formation. The activation of pulmonary dendritic cells, T helper type 2 cells, and mast cells is crucial mediators in the pathology of soot- or CB-induced respiratory disease. Polyunsaturated fatty acids (PUFAs were also found to modulate T cells functions in respiratory diseases. Particularly, telomerase reverse transcriptase was found to play the critical role in soot- and CB-induced cardiovascular dysfunctions. In this review, we propose integrated mechanisms of soot- and CB-induced toxicity emphasizing the role of inflammatory mediators and oxidative stress. We also suggest use of antioxidants and PUFAs as protective strategies against soot- and CB-induced disorders.

  16. Experimental and numerical investigation of fuel mixing effects on soot structures in counterflow diffusion flames

    KAUST Repository

    Choi, Byungchul

    2011-03-26

    Experimental and numerical analyses of laminar diffusion flames were performed to identify the effect of fuel mixing on soot formation in a counterflow burner. In this experiment, the volume fraction, number density, and particle size of soot were investigated using light extinction/scattering systems. The experimental results showed that the synergistic effect of an ethylene-propane flame is appreciable. Numerical simulations showed that the benzene (C6H6) concentration in mixture flames was higher than in ethylene-base flames because of the increase in the concentration of propargyl radicals. Methyl radicals were found to play an important role in the formation of propargyl, and the recombination of propargyl with benzene was found to lead to an increase in the number density for cases exhibiting synergistic effects. These results imply that methyl radicals play an important role in soot formation, particularly with regard to the number density. © 2011 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

  17. Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame

    KAUST Repository

    Li, Zepeng

    2016-04-21

    As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals

  18. On the formation and early evolution of soot in turbulent nonpremixed flames

    KAUST Repository

    Bisetti, Fabrizio; Blanquart, Guillaume; Mü eller, Michael E.; Pitsch, Heinz G.

    2012-01-01

    (2009) 1143-1155], which allows for an accurate state-of-the-art description of soot number density, volume fraction, and morphology of the aggregates. In agreement with previous experimental studies in laminar flames, Damköhler number effects are found

  19. In situ measurements of soot formation in simple flames using small angle X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, C. [Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth SY23 3BZ (United Kingdom); Greaves, G.N. [Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth SY23 3BZ (United Kingdom)]. E-mail: gng@aber.ac.uk; Hargrave, G.K. [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU (United Kingdom); Jarvis, S. [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU (United Kingdom); Wildman, P. [Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough LE11 3TU (United Kingdom); Meneau, F. [Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth SY23 3BZ (United Kingdom); Netherlands Organisation for Scientific Research (NWO), DUBBLE CRG/ESRF, P.O. Box 220, F38043 Grenoble Cedex (France); Bras, W. [Netherlands Organisation for Scientific Research (NWO), DUBBLE CRG/ESRF, P.O. Box 220, F38043 Grenoble Cedex (France); Thomas, G. [Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth SY23 3BZ (United Kingdom)

    2005-08-15

    Direct SAXS measurements of soot formation from ethylene have been made using laminar pre-mixed flames for the first time. The slot burner was configured to maximise the signal from particulates. The geometry also enabled the thermal background from the surrounding hot gasses to be accurately removed. With cold flame speeds of 40 cm s{sup -1} we have been able to identify particle sizes and densities from moderately sooty to rich flame conditions. By adjusting the height of the burner in the beam, the development of particles as a function of position above the flame tip and therefore as a function of time from ignition have been obtained. These reveal evidence for bimodal particle nucleation and growth at different stages in the continuous combustion of ethylene.

  20. In situ measurements of soot formation in simple flames using small angle X-ray scattering

    International Nuclear Information System (INIS)

    Gardner, C.; Greaves, G.N.; Hargrave, G.K.; Jarvis, S.; Wildman, P.; Meneau, F.; Bras, W.; Thomas, G.

    2005-01-01

    Direct SAXS measurements of soot formation from ethylene have been made using laminar pre-mixed flames for the first time. The slot burner was configured to maximise the signal from particulates. The geometry also enabled the thermal background from the surrounding hot gasses to be accurately removed. With cold flame speeds of 40 cm s -1 we have been able to identify particle sizes and densities from moderately sooty to rich flame conditions. By adjusting the height of the burner in the beam, the development of particles as a function of position above the flame tip and therefore as a function of time from ignition have been obtained. These reveal evidence for bimodal particle nucleation and growth at different stages in the continuous combustion of ethylene

  1. In situ measurements of soot formation in simple flames using small angle X-ray scattering

    Science.gov (United States)

    Gardner, C.; Greaves, G. N.; Hargrave, G. K.; Jarvis, S.; Wildman, P.; Meneau, F.; Bras, W.; Thomas, G.

    2005-08-01

    Direct SAXS measurements of soot formation from ethylene have been made using laminar pre-mixed flames for the first time. The slot burner was configured to maximise the signal from particulates. The geometry also enabled the thermal background from the surrounding hot gasses to be accurately removed. With cold flame speeds of 40 cm s-1 we have been able to identify particle sizes and densities from moderately sooty to rich flame conditions. By adjusting the height of the burner in the beam, the development of particles as a function of position above the flame tip and therefore as a function of time from ignition have been obtained. These reveal evidence for bimodal particle nucleation and growth at different stages in the continuous combustion of ethylene.

  2. Variation of diesel soot characteristics by different types and blends of biodiesel in a laboratory combustion chamber

    Energy Technology Data Exchange (ETDEWEB)

    Omidvarborna, Hamid; Kumar, Ashok [Department of Civil Engineering, The University of Toledo, Toledo, OH (United States); Kim, Dong-Shik, E-mail: dong.kim@utoledo.edu [Department of Chemical and Environmental Engineering, The University of Toledo, Toledo, OH (United States)

    2016-02-15

    Very little information is available on the physical and chemical properties of soot particles produced in the combustion of different types and blends of biodiesel fuels. A variety of feedstock can be used to produce biodiesel, and it is necessary to better understand the effects of feedstock-specific characteristics on soot particle emissions. Characteristics of soot particles, collected from a laboratory combustion chamber, are investigated from the blends of ultra-low sulfur diesel (ULSD) and biodiesel with various proportions. Biodiesel samples were derived from three different feedstocks, soybean methyl ester (SME), tallow oil (TO), and waste cooking oil (WCO). Experimental results showed a significant reduction in soot particle emissions when using biodiesel compared with ULSD. For the pure biodiesel, no soot particles were observed from the combustion regardless of their feedstock origins. The overall morphology of soot particles showed that the average diameter of ULSD soot particles is greater than the average soot particles from the biodiesel blends. Transmission electron microscopy (TEM) images of oxidized soot particles are presented to investigate how the addition of biodiesel fuels may affect structures of soot particles. In addition, inductively coupled plasma mass spectrometry (ICP-MS), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were conducted for characterization of soot particles. Unsaturated methyl esters and high oxygen content of biodiesel are thought to be the major factors that help reduce the formation of soot particles in a laboratory combustion chamber. - Highlights: • The unsaturation of biodiesel fuel was correlated with soot characteristics. • Average diameters of biodiesel soot were smaller than that of ULSD. • Eight elements were detected as the marker metals in biodiesel soot particles. • As the degree of unsaturation increased, the oxygen content in FAMEs increased. • Biodiesel

  3. Formation of secondary organic aerosol coating on black carbon particles near vehicular emissions

    Science.gov (United States)

    Lee, Alex K. Y.; Chen, Chia-Li; Liu, Jun; Price, Derek J.; Betha, Raghu; Russell, Lynn M.; Zhang, Xiaolu; Cappa, Christopher D.

    2017-12-01

    Black carbon (BC) emitted from incomplete combustion can result in significant impacts on air quality and climate. Understanding the mixing state of ambient BC and the chemical characteristics of its associated coatings is particularly important to evaluate BC fate and environmental impacts. In this study, we investigate the formation of organic coatings on BC particles in an urban environment (Fontana, California) under hot and dry conditions using a soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated in a configuration that can exclusively detect refractory BC (rBC) particles and their coatings. Using the -log(NOx / NOy) ratio as a proxy for photochemical age of air masses, substantial formation of secondary organic aerosol (SOA) coatings on rBC particles was observed due to active photochemistry in the afternoon, whereas primary organic aerosol (POA) components were strongly associated with rBC from fresh vehicular emissions in the morning rush hours. There is also evidence that cooking-related organic aerosols were externally mixed from rBC. Positive matrix factorization and elemental analysis illustrate that most of the observed SOA coatings were freshly formed, providing an opportunity to examine SOA coating formation on rBCs near vehicular emissions. Approximately 7-20 wt % of secondary organic and inorganic species were estimated to be internally mixed with rBC on average, implying that rBC is unlikely the major condensation sink of SOA in this study. Comparison of our results to a co-located standard high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) measurement suggests that at least a portion of SOA materials condensed on rBC surfaces were chemically different from oxygenated organic aerosol (OOA) particles that were externally mixed with rBC, although they could both be generated from local photochemistry.

  4. Diffusion air effects on the soot axial distribution concentration in a premixed acetylene/air flame

    Energy Technology Data Exchange (ETDEWEB)

    Fassani, Fabio Luis; Santos, Alex Alisson Bandeira; Goldstein Junior, Leonardo [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia Termica e de Fluidos]. E-mails: fassani@fem.unicamp.br; absantos@fem.unicamp.br; leonardo@fem.unicamp.br; Ferrari, Carlos Alberto [Universidade Estadual de Campinas, SP (Brazil). Inst. de Fisica. Dept. de Eletronica Quantica]. E-mail: ferrari@ifi.unicamp.br

    2000-07-01

    Soot particles are produced during the high temperature pyrolysis or combustion of hydrocarbons. The emission of soot from a combustor, or from a flame, is determined by the competition between soot formation and its oxidation. Several factors affect these processes, including the type of fuel, the air-to-fuel ratio, flame temperature, pressure, and flow pattern. In this paper, the influence of the induced air diffusion on the soot axial distribution concentration in a premixed acetylene/air flame was studied. The flame was generated in a vertical axis burner in which the fuel - oxidant mixture flow was surrounded by a nitrogen discharge coming from the annular region between the burner tube and an external concentric tube. The nitrogen flow provided a shield that protected the flame from the diffusion of external air, enabling its control. The burner was mounted on a step-motor driven, vertical translation table. The use of several air-to-fuel ratios made possible to establish the sooting characteristics of this flame, by measuring soot concentration along the flame height with a non-intrusive laser light absorption technique. (author)

  5. Nitro-PAH formation studied by interacting artificially PAH-coated soot aerosol with NO 2 in the temperature range of 295-523 K

    Science.gov (United States)

    Carrara, Matteo; Wolf, Jan-Christoph; Niessner, Reinhard

    2010-10-01

    Diesel particulate matter poses a threat to human health, and in particular nitrated polycyclic aromatic hydrocarbons (NPAHs) found within and on the surface of these particles. Although diesel particulate filters (DPFs) have been designed and implemented to reduce these and other harmful diesel emissions, the particle loaded filters may act as a reaction chamber for the enhanced production of NPAHs from the nitration of PAHs with NO 2. Focus is on the investigation of the heterogeneous reactions that occur on soot particles by exposing laboratory produced pyrene- or benzo(a)pyrene-coated spark discharge soot particles to varying concentrations of NO 2 and temperatures while following the formation of products over time. The sole nitration product that was observed throughout the experiments with pyrene-coated soot was 1-nitropyrene (1-NPYR), which increased linearly with reaction time for all NO 2 concentrations chosen (0.11, 1.0, 2.0, 4.0 ppm, m m -1). Resulting 1-NPYR formation rate increased exponentially with [NO 2]. Throughout the 3-h experiments less than 10% of pyrene has been converted to 1-NPYR and the partial reaction order with regard to [NO 2] was estimated to 1.52. Benzo(a)pyrene (BaP) was more reactive than pyrene. After 3 h reaction time almost 80% of the BaP has been converted to 6-NBaP. Highest 1-NPYR concentrations on particles were detected at 373 K, and at higher temperatures a considerable decrease in particulate 1-NPYR was observed. A similar trend was observed in a DPF simulation system (PM-Kat ®-like) with BaP-coated soot. In this case, highest 6-NBaP concentration on particles was detected at 423 K. Backed by corroborating results from separate gas/solid-phase partition experiments with 1-NPYR and 6-NBaP, it is likely that the newly formed 1-NPYR and 6-NBaP became transferred from particle to gas phase at higher temperatures. Results from this study confirm the presence of 1-NPYR and 6-NBaP in particulate and gas phase under conditions

  6. Effects of Lignocellulosic Compounds on the Yield, Nanostructure and Reactivity of Soot from Fast Pyrolysis at High Temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Broström, Markus; Kling, Jens

    reactor. The specific objectives of this study were to: (1) obtain knowledge about lignocellulosic compounds and monolignols influence on the yield, nanostructure, composition, and reactivity of soot during high-temperature gasification, (2) understand the influence of Soxhlet extraction on the soot......Gasification offers the utilization of biomass to a wide variety of applications such as heat, electricity, chemicals and transport fuels in an efficient and sustainable manner. High soot yields in the high-temperature entrained flow gasification lead to intensive gas cleaning and can cause...... primary, secondary and teriary pyrolysis products such as organic acids, aldehydes and phenolics [1]. In this study, therefore, the impacts of lignocellulosic compounds and monolignols (syringol, guaiacol, p-hydroxyphenol) on the yield and characteristics of soot were investigated at 1250°C in a drop tube...

  7. Measuring and predicting sooting tendencies of oxygenates, alkanes, alkenes, cycloalkanes, and aromatics on a unified scale

    Energy Technology Data Exchange (ETDEWEB)

    Das, Dhrubajyoti D.; St. John, Peter C.; McEnally, Charles S.; Kim, Seonah; Pfefferle, Lisa D.

    2018-04-01

    Databases of sooting indices, based on measuring some aspect of sooting behavior in a standardized combustion environment, are useful in providing information on the comparative sooting tendencies of different fuels or pure compounds. However, newer biofuels have varied chemical structures including both aromatic and oxygenated functional groups, which expands the chemical space of relevant compounds. In this work, we propose a unified sooting tendency database for pure compounds, including both regular and oxygenated hydrocarbons, which is based on combining two disparate databases of yield-based sooting tendency measurements in the literature. Unification of the different databases was made possible by leveraging the greater dynamic range of the color ratio pyrometry soot diagnostic. This unified database contains a substantial number of pure compounds (greater than or equal to 400 total) from multiple categories of hydrocarbons important in modern fuels and establishes the sooting tendencies of aromatic and oxygenated hydrocarbons on the same numeric scale for the first time. Using this unified sooting tendency database, we have developed a predictive model for sooting behavior applicable to a broad range of hydrocarbons and oxygenated hydrocarbons. The model decomposes each compound into single-carbon fragments and assigns a sooting tendency contribution to each fragment based on regression against the unified database. The model's predictive accuracy (as demonstrated by leave-one-out cross-validation) is comparable to a previously developed, more detailed predictive model. The fitted model provides insight into the effects of chemical structure on soot formation, and cases where its predictions fail reveal the presence of more complicated kinetic sooting mechanisms. This work will therefore enable the rational design of low-sooting fuel blends from a wide range of feedstocks and chemical functionalities.

  8. Investigation of soot morphology and particle size distrib ution in a turbulent nonpremixed flame via Monte Carlo simulations

    KAUST Repository

    Abdelgadir, Ahmed

    2015-03-30

    Recently, our group performed a set of direct numerical simulations (DNS) of soot formation and growth in a n-heptane three dimensional non-premixed jet flame [Attili et al., Proc. Comb. Inst, 35, 2015], [Attili et al., Comb. Flame, 161, 2014], [Bisetti et al.,Trans of the Royal Soc, 372, 2014]. The evolution of species relevant to soot formation and growth have been sampled along a large number of Lagrangian trajectories in the DNS. In this work, the DNS results are post-processed to compute the soot evolution along selected Lagrangian trajectories using a Monte Carlo method. An operator splitting approach is adopted to split the deterministic processes (nucleation, surface growth and oxidation) from coagulation, which is treated stochastically. The morphological properties of soot and the particlesize distribution are investigated. For trajectories that experience an early strong nucleation event, the particle size distribution is found to be bimodal, as the soot particles have enough time to coagulate and grow while it is unimodal for trajectories characterized by only late nucleation events. As a results, the average size distribution at two different crosswise positions in the flame is unimodal.

  9. Development of high fidelity soot aerosol dynamics models using method of moments with interpolative closure

    KAUST Repository

    Roy, Subrata P.

    2014-01-28

    The method of moments with interpolative closure (MOMIC) for soot formation and growth provides a detailed modeling framework maintaining a good balance in generality, accuracy, robustness, and computational efficiency. This study presents several computational issues in the development and implementation of the MOMIC-based soot modeling for direct numerical simulations (DNS). The issues of concern include a wide dynamic range of numbers, choice of normalization, high effective Schmidt number of soot particles, and realizability of the soot particle size distribution function (PSDF). These problems are not unique to DNS, but they are often exacerbated by the high-order numerical schemes used in DNS. Four specific issues are discussed in this article: the treatment of soot diffusion, choice of interpolation scheme for MOMIC, an approach to deal with strongly oxidizing environments, and realizability of the PSDF. General, robust, and stable approaches are sought to address these issues, minimizing the use of ad hoc treatments such as clipping. The solutions proposed and demonstrated here are being applied to generate new physical insight into complex turbulence-chemistry-soot-radiation interactions in turbulent reacting flows using DNS. © 2014 Copyright Taylor and Francis Group, LLC.

  10. Condensed-phase biogenic-anthropogenic interactions with implications for cold cloud formation.

    Science.gov (United States)

    Charnawskas, Joseph C; Alpert, Peter A; Lambe, Andrew T; Berkemeier, Thomas; O'Brien, Rachel E; Massoli, Paola; Onasch, Timothy B; Shiraiwa, Manabu; Moffet, Ryan C; Gilles, Mary K; Davidovits, Paul; Worsnop, Douglas R; Knopf, Daniel A

    2017-08-24

    Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA-soot biogenic-anthropogenic interactions and their impact on ice nucleation in relation to the particles' organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (T g ) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core-shell configuration (i.e. a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respective T g and FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas.

  11. The immersion freezing behavior of size-segregated soot and kaolinite particles

    Science.gov (United States)

    Hartmann, S.; Augustin, S.; Clauss, T.; Niedermeier, D.; Raddatz, M.; Wex, H.; Shaw, R. A.; Stratmann, F.

    2011-12-01

    Heterogeneous ice nucleation plays a crucial role for ice formation in mixed-phase and cirrus clouds and has an important impact on precipitation formation, global radiation balances, and therefore Earth's climate (Cantrell and Heymsfield, 2005). Mineral dust and soot particles are found to be a major component of ice crystal residues (e.g., Pratt et al., 2009) so these substances are potential sources of atmospheric ice nuclei (IN). Experimental studies investigating the immersion freezing behavior of size-segregated soot and kaolinite particles conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS) are presented. In our measurements only one aerosol particle is immersed in an air suspended water droplet which can trigger ice nucleation. The method facilitates very precise examinations with respect to temperature, ice nucleation time and ice nucleus size. Considering laboratory studies, the picture of the IN ability of soot particles is quite heterogeneous. Our studies show that submicron flame, spark soot particles and optionally coated with sulfuric acid to simulate chemically aging do not act as IN at temperatures higher than homogeneous freezing taking place. Therefore soot particles might not be an important source of IN for immersion freezing in the atmosphere. In contrast, kaolinite being representative for natural mineral dust with a well known composition and structure is found to be very active in forming ice for all freezing modes (e.g., Mason and Maybank, 1958). Analyzing the immersion freezing behavior of different sized kaolinite particles (300, 500 and 700 nm in diameter) the size effect was clearly observed, i.e. the ice fraction (number of frozen droplets per total number) scales with particle surface, i.e. the larger the ice nucleus surface the higher the ice fraction. The slope of the logarithm of the ice fraction as function of temperature is similar for all particle sizes investigated and fits very well with the results of L

  12. Thermal fragmentation and deactivation of combustion-generated soot particles

    KAUST Repository

    Raj, Abhijeet

    2014-09-01

    The effect of thermal treatment on diesel soot and on a commercial soot in an inert environment under isothermal conditions at intermediate temperatures (400-900°C) is studied. Two important phenomena are observed in both the soot samples: soot fragmentation leading to its mass loss, and loss of soot reactivity towards O2. Several experimental techniques such as high resolution transmission electron microscopy, electron energy loss spectroscopy, thermo-gravimetric analysis with mass spectrometry, elemental analysis, Fourier transform infrared spectroscopy and X-ray diffraction have been used to identify the changes in structures, functional groups such as oxygenates and aliphatics, σ and π bonding, O/C and H/C ratios, and crystallite parameters of soot particles, introduced by heat. A decrease in the size of primary particles and an increase in the average polycyclic aromatic hydrocarbon (PAH) size was observed in soots after thermal treatment. The activation energies of soot oxidation for thermally treated soot samples were found to be higher than those for the untreated ones at most conversion levels. The cyclic or acyclic aliphatics with sp3 hybridization were present in significant amounts in all the soot samples, but their concentration decreased with thermal treatment. Interestingly, the H/C and the O/C ratios of soot particles increased after thermal treatment, and thus, they do not support the decrease in soot reactivity. The increase in the concentration of oxygenates on soot surface indicate that their desorption from soot surface in the form of CO, CO2 and other oxygenated compounds may not be significant at the temperatures (400-900°C) studied in this work. © 2014 The Combustion Institute.

  13. Validation of an LES Model for Soot Evolution against DNS Data in Turbulent Jet Flames

    Science.gov (United States)

    Mueller, Michael

    2012-11-01

    An integrated modeling approach for soot evolution in turbulent reacting flows is validated against three-dimensional Direct Numerical Simulation (DNS) data in a set of n-heptane nonpremixed temporal jet flames. As in the DNS study, the evolution of the soot population is described statistically with the Hybrid Method of Moments (HMOM). The oxidation of the fuel and formation of soot precursors are described with the Radiation Flamelet/Progress Variable (RFPV) model that includes an additional transport equation for Polycyclic Aromatic Hydrocarbons (PAH) to account for the slow chemistry governing these species. In addition, the small-scale interactions between soot, chemistry, and turbulence are described with a presumed subfilter PDF approach that accounts for the very large spatial intermittency characterizing soot in turbulent reacting flows. The DNS dataset includes flames at three different Damköhler numbers to study the influence of global mixing rates on the evolution of PAH and soot. In this work, the ability of the model to capture these trends quantitatively as Damköhler number varies is investigated. In order to reliably assess the LES approach, the LES is initialized from the filtered DNS data after an initial transitional period in an effort to minimize the hydrodynamic differences between the DNS and the LES.

  14. Processes and problems in secondary star formation

    International Nuclear Information System (INIS)

    Klein, R.I.; Whitaker, R.W.; Sandford, M.T. II.

    1984-03-01

    Recent developments relating the conditions in molecular clouds to star formation triggered by a prior stellar generation are reviewed. Primary processes are those that lead to the formation of a first stellar generation. The secondary processes that produce stars in response to effects caused by existing stars are compared and evaluated in terms of the observational data presently available. We discuss the role of turbulence to produce clumpy cloud structures and introduce new work on colliding inter-cloud gas flows leading to non-linear inhomogeneous cloud structures in an intially smooth cloud. This clumpy morphology has important consequences for secondary formation. The triggering processes of supernovae, stellar winds, and H II regions are discussed with emphasis on the consequences for radiation driven implosion as a promising secondary star formation mechanism. Detailed two-dimensional, radiation-hydrodynamic calculations of radiation driven implosion are discussed. This mechanism is shown to be highly efficient in synchronizing the formation of new stars in congruent to 1-3 x 10 4 years and could account for the recent evidence for new massive star formation in several UCHII regions. It is concluded that, while no single theory adequately explains the variety of star formation observed, a uniform description of star formation is likely to involve several secondary processes. Advances in the theory of star formation will require multiple dimensional calculations of coupled processes. The important non-linear interactions include hydrodynamics, radiation transport, and magnetic fields

  15. Processes and problems in secondary star formation

    International Nuclear Information System (INIS)

    Klein, R.I.; Whitaker, R.W.; Sandford, M.T. II

    1985-01-01

    Recent developments relating the conditions in molecular clouds to star formation triggered by a prior stellar generation are reviewed. Primary processes are those that lead to the formation of a first stellar generation. The secondary processes that produce stars in response to effects caused by existing stars are compared and evaluated in terms of observational data presently available. We discuss the role of turbulence to produce clumpy cloud structures and introduce new work on colliding intercloud gas flows leading to nonlinear inhomogeneous cloud structures in an initially smooth cloud. This clumpy morphology has important consequences for secondary formation. The triggering processes of supernovae, stellar winds, and H II regions are discussed with emphasis on the consequences for radiation-driven implosion as a promising secondary star formation mechanism. Detailed two-dimensional, radiation-hydrodynamic calculations of radiation-driven implosion are discussed. This mechanism is shown to be highly efficient in synchronizing the formation of new stars in -- 1-3 x 10/sup 4/ yr and could account for the recent evidence for new massive star formation in several ultracompact H II regions. It is concluded that, while no single theory adequately explains the variety of star formation observed, a uniform description of star formation is likely to involve several secondary processes. Advances in the theory of star formation will require multi-dimensional calculations of coupled processes. Important nonlinear interactions include hydrodynamics, radiation transport, and magnetic fields

  16. Soot oxidation over NOx storage catalysts. Activity and deactivation

    International Nuclear Information System (INIS)

    Krishna, K.; Makkee, M.

    2006-01-01

    Soot oxidation activity and deactivation of NO x storage and reduction (NSR) catalysts containing Pt, K, and Ba supported on Al 2 O 3 , are studied under a variety of reaction conditions. K-containing catalysts decrease soot oxidation temperature with O 2 alone and the presence of Pt further enhance the activity due to synergetic effect. The active species responsible for synergism on Pt/K-Al 2 O 3 are unstable and cannot be regenerated. Soot oxidation temperature decreases by about 150 o C with NO+O 2 exhaust feed gas and under lean conditions NSR system acts as catalysed soot filter (CSF). The reactions that are mainly responsible for decreasing soot oxidation temperature are: (1) soot oxidation with NO 2 followed by NO recycles to NO 2 , and (2) soot oxidation with O 2 assisted by NO 2 . Only a part of the stored NO x that is decomposed at high temperatures under lean conditions is found to be useful for soot oxidation. NO x storage capacity of NSR catalysts decreases upon ageing under soot oxidising conditions. This will lead to a decreased soot oxidation activity on stored nitrate decomposition. Pt/K-Al 2 O 3 catalyst is more active, but least stable compared with Pt/Ba-Al 2 O 3 . (author)

  17. Dynamics of very small soot particles during soot burnout in diesel engines; Dynamik kleinster Russteilchen waehrend der Russausbrandphase im Dieselmotor

    Energy Technology Data Exchange (ETDEWEB)

    Bockhorn, H. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Chemische Technik; Peters, N. [RWTH Aachen (DE). Institut fuer Technische Mechanik (ITM); Pittermann, R. [WTZ fuer Motoren- und Maschinenforschung Rosslau gGmbH (Germany); Hentschel, J.; Weber, J.

    2003-07-01

    The investigations used advanced laser-optical methods for measuring soot particle size distributions, temporally and spectrally resolved measurements of engine combustion, measurements of composition and size distribution of particles in exhaust, and further development and validation of reaction-kinetic models. In all, it can be stated that mixing will affect not only soot particle formation but also soot particle emissions. Mixing can be influenced by using a fuel-water emulsion and by CR injection. Experiments and models both showed the advantageous effects of water added to the diesel fuels and of CR injection. The higher OH radical concentrations in the later combustion stages also serve to ensure faster oxidation of soot. (orig.) [German] Ziel des Projektes war es, Informationen ueber die Bildung und Oxidation von Russ sowie die Teilchendynamik der Russteilchen waehrend der Ausbrandphase zu erhalten. Dies wurde erreicht durch die Weiterentwicklung laseroptischer Methoden zur Bestimmung der Groessenverteilung von Russpartikeln, durch zeit- und spektral aufgeloeste Erfassung der motorischen Verbrennung, durch die Bestimmung von Zusammensetzung und Groessenverteilung von Partikeln im Abgas sowie durch die Weiterentwicklung und Validierung von reaktionskinetischen Modellen. Zusammenfassend laesst sich sagen, dass sich die Gemischbildung im Dieselmotor nicht nur auf die Bildung der Russpartikel sondern auch auf die Russpartikelemission auswirkt. Die Verwendung einer Kraftstoff-Wasser-Emulsion und die Common-Rail-Einspritzung stellen zwei Verfahren zur Beeinflussung der Gemischbildung dar. Sowohl die experimentellen Untersuchungen als auch die Modellierung zeigen den die Gemischbildung foerdernden Einfluss des Zusatzes von Wasser zum Dieselbrennstoff. Ein erhoehter Anteil an vorgemischter Verbrennung, wie er auch durch die Verwendung hoher Einspritzdruecke bei der Common-Rail-Einspritzung erreicht werden kann, verringert die waehrend der Verbrennung entstehende

  18. Technical Note: The single particle soot photometer fails to reliably detect PALAS soot nanoparticles

    Directory of Open Access Journals (Sweden)

    M. Gysel

    2012-12-01

    Full Text Available The single particle soot photometer (SP2 uses laser-induced incandescence (LII for the measurement of atmospheric black carbon (BC particles. The BC mass concentration is obtained by combining quantitative detection of BC mass in single particles with a counting efficiency of 100% above its lower detection limit. It is commonly accepted that a particle must contain at least several tenths of a femtogram BC in order to be detected by the SP2.

    Here we show the result that most BC particles from a PALAS spark discharge soot generator remain undetected by the SP2, even if their BC mass, as independently determined with an aerosol particle mass analyser (APM, is clearly above the typical lower detection limit of the SP2. Comparison of counting efficiency and effective density data of PALAS soot with flame generated soot (combustion aerosol standard burner, CAST, fullerene soot and carbon black particles (Cabot Regal 400R reveals that particle morphology can affect the SP2's lower detection limit. PALAS soot particles are fractal-like agglomerates of very small primary particles with a low fractal dimension, resulting in a very low effective density. Such loosely packed particles behave like "the sum of individual primary particles" in the SP2's laser. Accordingly, most PALAS soot particles remain undetected as the SP2's laser intensity is insufficient to heat the primary particles to their vaporisation temperature because of their small size (Dpp ≈ 5–10 nm. Previous knowledge from pulsed laser-induced incandescence indicated that particle morphology might have an effect on the SP2's lower detection limit, however, an increase of the lower detection limit by a factor of ∼5–10, as reported here for PALAS soot, was not expected.

    In conclusion, the SP2's lower detection limit at a certain laser power depends primarily on the total BC mass per particle for compact particles with sufficiently high effective

  19. Emissions of soot particles from heat generators

    Science.gov (United States)

    Lyubov, V. K.; Popov, A. N.; Popova, E. I.

    2017-11-01

    «Soot carbon» or «Soot» - incomplete combustion or thermal decomposition particulate carbon product of hydrocarbons consisting of particles of various shapes and sizes. Soot particles are harmful substances Class 2 and like a dust dispersed by wind for thousands of kilometers. Soot have more powerful negative factor than carbon dioxide. Therefore, more strict requirements on ecological and economical performance for energy facilities at Arctic areas have to be developed to protect fragile Arctic ecosystems and global climate change from degradation and destruction. Quantity of soot particles in the flue gases of energy facilities is a criterion of effectiveness for organization of the burning process. Some of heat generators do not provide the required energy and environmental efficiency which results in irrational use of energy resources and acute pollution of environment. The paper summarizes the results of experimental study of solid particles emission from wide range of capacity boilers burning different organic fuels (natural gas, fuel oil, coal and biofuels). Special attention is paid to environmental and energy performance of the biofuels combustion. Emissions of soot particles PM2.5 are listed. Structure, composition and dimensions of entrained particles with the use of electronic scanning microscope Zeiss SIGMA VP were also studied. The results reveal an impact of several factors on soot particles emission.

  20. Catalytic Oxidation of Soot on a Novel Active Ca-Co Dually-Doped Lanthanum Tin Pyrochlore Oxide

    Directory of Open Access Journals (Sweden)

    Lijie Ai

    2018-04-01

    Full Text Available A novel active Ca-Co dually-doping pyrochlore oxide La2−xCaxSn2−yCoyO7 catalyst was synthesized by the sol-gel method for catalytic oxidation of soot particulates. The microstructure, atomic valence, reduction, and adsorption performance were investigated by X-ray powder diffraction (XRD, scanning electron microscope (SEM, Fourier-transform infrared spectroscopy (FT-IR, X-ray photoelectron spectroscopy (XPS, H2-TPR (temperature-programmed reduction, and in situ diffuse reflection infrared Fourier transformed (DRIFTS techniques. Temperature programmed oxidation (TPO tests were performed with the mixture of soot-catalyst under tight contact conditions to evaluate the catalytic activity for soot combustion. Synergetic effect between Ca and Co improved the structure and redox properties of the solids, increased the surface oxygen vacancies, and provided a suitable electropositivity for oxide, directly resulting in the decreased ignition temperature for catalyzed soot oxidation as low as 317 °C. The presence of NO in O2 further promoted soot oxidation over the catalysts with the ignition temperature decreased to about 300 °C. The DRIFTS results reveal that decomposition of less stable surface nitrites may account for NO2 formation in the ignition period of soot combustion, which thus participate in the auxiliary combustion process.

  1. Damköhler number effects on soot formation and growth in turbulent nonpremixed flames

    KAUST Repository

    Attili, Antonio; Bisetti, Fabrizio; Mueller, Michael E.; Pitsch, Heinz

    2015-01-01

    numbers. A reduced chemical mechanism, which includes the soot precursor naphthalene, and a high-order method of moments are employed. At the highest Damköhler number, local extinction is negligible, while flames holes are observed in the two lowest

  2. Mutagenicity of diesel exhaust soot dispersed in phospholipid surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, W.; Keane, M.; Xing, S.; Harrison, J.; Gautam, M.; Ong, T.

    1994-06-01

    Organics extractable from respirable diesel exhaust soot particles by organic solvents have been known for some time to be direct acting frameshift mutagens in the Ames Salmonella typhimurium histidine reversion assay. Upon deposition in a pulmonary alveolus or respiratory bronchiole, respirable diesel soot particles will contact first the hypophase which is coated by and laden with surfactants. To model interactions of soot and pulmonary surfactant, the authors dispersed soots in vitro in the primary phospholipid pulmonary surfactant dipalmitoyl glycerophosphorylcholine (lecithin) (DPL) in physiological saline. They have shown that diesel soots dispersed in lecithin surfactant can express mutagenic activity, in the Ames assay system using S. typhimurium TA98, comparable to that expressed by equal amounts of soot extracted by dichloromethane/dimethylsulfoxide (DCM/DMSO). Here the authors report additional data on the same system using additional exhaust soots and also using two other phospholipids, dipalmitoyl glycerophosphoryl ethanolamine (DPPE), and dipalmitoyl phosphatidic acid (DPPA), with different ionic character hydrophilic moieties. A preliminary study of the surfactant dispersed soot in an eucaryotic cell test system also is reported.

  3. Soot Aerosol Particles as Cloud Condensation Nuclei: from Ice Nucleation Activity to Ice Crystal Morphology

    Science.gov (United States)

    Pirim, Claire; Ikhenazene, Raouf; Ortega, Isamel Kenneth; Carpentier, Yvain; Focsa, Cristian; Chazallon, Bertrand; Ouf, François-Xavier

    2016-04-01

    Emissions of solid-state particles (soot) from engine exhausts due to incomplete fuel combustion is considered to influence ice and liquid water cloud droplet activation [1]. The activity of these aerosols would originate from their ability to be important centers of ice-particle nucleation, as they would promote ice formation above water homogeneous freezing point. Soot particles are reported to be generally worse ice nuclei than mineral dust because they activate nucleation at higher ice-supersaturations for deposition nucleation and at lower temperatures for immersion freezing than ratios usually expected for homogeneous nucleation [2]. In fact, there are still numerous opened questions as to whether and how soot's physico-chemical properties (structure, morphology and chemical composition) can influence their nucleation ability. Therefore, systematic investigations of soot aerosol nucleation activity via one specific nucleation mode, here deposition nucleation, combined with thorough structural and compositional analyzes are needed in order to establish any association between the particles' activity and their physico-chemical properties. In addition, since the morphology of the ice crystals can influence their radiative properties [3], we investigated their morphology as they grow over both soot and pristine substrates at different temperatures and humidity ratios. In the present work, Combustion Aerosol STandart soot samples were produced from propane using various experimental conditions. Their nucleation activity was studied in deposition mode (from water vapor), and monitored using a temperature-controlled reactor in which the sample's relative humidity is precisely measured with a cryo-hygrometer. Formation of water/ice onto the particles is followed both optically and spectroscopically, using a microscope coupled to a Raman spectrometer. Vibrational signatures of hydroxyls (O-H) emerge when the particle becomes hydrated and are used to characterize ice

  4. Investigation of black soot staining in houses

    Energy Technology Data Exchange (ETDEWEB)

    Fugler, D. [Canada Mortgage and Housing Corp., Ottawa, ON (Canada)

    2000-07-01

    Air quality investigators are frequently called upon to determine the origin of streaking, staining or soot marks in both new and old homes. Those marks display common characteristics: black marks along baseboards at interior or exterior walls, behind furniture and at doorways; black smudges on window frames and plastic cabinets; and even shadowing of studs on exterior wall drywall in a few cases. In most instances, carbon soot from a combustion source is the culprit. The combustion sources include furnaces, water heaters, fireplaces, gas dryers, gas ranges, smoking, vehicle exhaust and candle burning. Scepticism about candle soot is prevalent among callers. As a result, a study was initiated in homes where occupants burn candles regularly to investigate soot problems. Samples were collected from five homes, and included stained carpets, filters, and swab samples of black dust or soot. All the houses selected for the study had been built within a three-year period. Some samples of candles commonly burned in those homes were burnt in a laboratory. Air quality audits had been performed in the homes and had revealed other potential pollutant sources. Best practices for cost-effective clean up and control of soot were researched in industry information. The tests conducted in the laboratory found materials consistent with candle soot or residue during microscopic investigations, but no link was established with the stained material obtained from the homes. A few tips for homeowners were included concerning candle burning, and tips for builders were also offered. 1 tab.

  5. Candle Soot-Driven Performance Enhancement in Pyroelectric Energy Conversion

    Science.gov (United States)

    Azad, Puneet; Singh, V. P.; Vaish, Rahul

    2018-05-01

    We observed substantial enhancement in pyroelectric output with the help of candle soot coating on the surface of lead zirconate titanate (PZT). Candle soot of varying thicknesses was coated by directly exposing pyroelectric material to the candle flame. The open-circuit pyroelectric voltage and closed-circuit pyroelectric current were recorded while applying infrared heating across the uncoated and candle soot-coated samples for different heating and cooling cycles. In comparison to the uncoated sample, the maximum open-circuit voltage improves seven times for the candle soot-coated sample and electric current increases by eight times across a resistance of 10Å. Moreover, the harvested energy is enhanced by 50 times for candle soot-coated sample. Results indicate that candle soot coating is an effective and economic method to improve infrared sensing performance of pyroelectric materials.

  6. Steady State Investigations of DPF Soot Burn Rates and DPF Modeling

    DEFF Research Database (Denmark)

    Cordtz, Rasmus Lage; Ivarsson, Anders; Schramm, Jesper

    2011-01-01

    and soot mass concentrations are used as model boundary conditions. An in-house developed raw exhaust gas sampling technique is used to measure the soot concentration upstream the DPF which is also needed to find the DPF soot burn rate. The soot concentration is measured basically by filtering the soot...... characteristics are used to fit model constants of soot and filter properties. Measured DPF gas conversions and soot burn rates are used to fit model activation energies of four DPF regeneration reactions using O2 and NO2 as reactants. Modeled DPF pressure drops and soot burn rates are compared to the steady...... state DPF experiments in the temperature range between 260 and 480 °C. The model widely reproduces the experimental results. Especially the exponential soot burn rate versus temperature is accurately reproduced by the model....

  7. Monomer-dependent secondary nucleation in amyloid formation.

    Science.gov (United States)

    Linse, Sara

    2017-08-01

    Secondary nucleation of monomers on the surface of an already existing aggregate that is formed from the same kind of monomers may lead to autocatalytic amplification of a self-assembly process. Such monomer-dependent secondary nucleation occurs during the crystallization of small molecules or proteins and self-assembled materials, as well as in protein self-assembly into fibrous structures. Indications of secondary nucleation may come from analyses of kinetic experiments starting from pure monomers or monomers supplemented with a low concentration of pre-formed aggregates (seeds). More firm evidence requires additional experiments, for example those employing isotope labels to distinguish new aggregates arising from the monomer from those resulting from fragmentation of the seed. In cases of amyloid formation, secondary nucleation leads to the formation of toxic oligomers, and inhibitors of secondary nucleation may serve as starting points for therapeutic developments. Secondary nucleation displays a high degree of structural specificity and may be enhanced by mutations or screening of electrostatic repulsion.

  8. Ignition delay and soot oxidative reactivity of MTBE blended diesel fuel

    KAUST Repository

    Yang, Seung Yeon; Naser, Nimal; Chung, Suk-Ho; Al-Qurashi, Khalid

    2014-01-01

    Methyl tert-butyl ether (MTBE) was added to diesel fuel to investigate the effect on ignition delay and soot oxidative reactivity. An ignition quality tester (IQT) was used to study the ignition propensity of MTBE blended diesel fuels in a reactive spray environment. The IQT data showed that ignition delay increases linearly as the MTBE fraction increases in the fuel. A four-stroke single cylinder diesel engine was used to generate soot samples for a soot oxidation study. Soot samples were pre-treated using a tube furnace in a nitrogen environment to remove any soluble organic fractions and moisture content. Non-isothermal oxidation of soot samples was conducted using a thermogravimetric analyzer (TGA). It was observed that oxidation of 'MTBE soot' started began at a lower temperature and had higher reaction rate than 'diesel soot' across a range of temperatures. Several kinetic analyses including an isoconversional method and a combined model fitting method were carried out to evaluate kinetic parameters. The results showed that Diesel and MTBE soot samples had similar activation energy but the pre-exponential factor of MTBE soot was much higher than that of the Diesel soot. This may explain why MTBE soot was more reactive than Diesel soot. It is suggested that adding MTBE to diesel fuel is better for DPF regeneration since an MTBE blend can significantly influence the ignition characteristics and, consequently, the oxidative reactivity of soot. Copyright © 2014 SAE International.

  9. Ignition delay and soot oxidative reactivity of MTBE blended diesel fuel

    KAUST Repository

    Yang, Seung Yeon

    2014-04-01

    Methyl tert-butyl ether (MTBE) was added to diesel fuel to investigate the effect on ignition delay and soot oxidative reactivity. An ignition quality tester (IQT) was used to study the ignition propensity of MTBE blended diesel fuels in a reactive spray environment. The IQT data showed that ignition delay increases linearly as the MTBE fraction increases in the fuel. A four-stroke single cylinder diesel engine was used to generate soot samples for a soot oxidation study. Soot samples were pre-treated using a tube furnace in a nitrogen environment to remove any soluble organic fractions and moisture content. Non-isothermal oxidation of soot samples was conducted using a thermogravimetric analyzer (TGA). It was observed that oxidation of \\'MTBE soot\\' started began at a lower temperature and had higher reaction rate than \\'diesel soot\\' across a range of temperatures. Several kinetic analyses including an isoconversional method and a combined model fitting method were carried out to evaluate kinetic parameters. The results showed that Diesel and MTBE soot samples had similar activation energy but the pre-exponential factor of MTBE soot was much higher than that of the Diesel soot. This may explain why MTBE soot was more reactive than Diesel soot. It is suggested that adding MTBE to diesel fuel is better for DPF regeneration since an MTBE blend can significantly influence the ignition characteristics and, consequently, the oxidative reactivity of soot. Copyright © 2014 SAE International.

  10. Soot and smoke emissions numerical evaluation for a direct injection (DI diesel engine

    Directory of Open Access Journals (Sweden)

    Radu Bogdan

    2017-01-01

    Full Text Available The reduction of Diesel internal combustion engines emissions is one of the major concerns of the engines manufacturers. Despite the fact that the efficiency of the gas post-treatment systems has been significantly improved, decreasing the smoke and the soot from the cylinder inside remains a main research goal. This work is proposing a theoretical study on these pollutants formation for different kinds of direct injection methods. By dividing the in-cylinder injection the heat release characteristic could be modified, leading to different temperature and pressure levels. Using exhaust gas recirculation (EGR the reduction of the gas temperatures might also be decreased, limiting NOx formation. To evaluate the level of the cylinder gas emissions formation a two-step procedure could be followed. First, by using a numerical calculation system the heat release characteristic can be highlighted concerning a Diesel engine with stratified injection; then, using an experimental relationship applying a large data base, the amount of the gas emissions can be subsequently provided. The authors propose some combinations between injection characteristics and EGR used fractions which could generate successfully results speaking in terms of NOx, soot and smoke formation.

  11. Experiments and Model Development for the Investigation of Sooting and Radiation Effects in Microgravity Droplet Combustion

    Science.gov (United States)

    Choi, Mun Young; Yozgatligil, Ahmet; Dryer, Frederick L.; Kazakov, Andrei; Dobashi, Ritsu

    2001-01-01

    Today, despite efforts to develop and utilize natural gas and renewable energy sources, nearly 97% of the energy used for transportation is derived from combustion of liquid fuels, principally derived from petroleum. While society continues to rely on liquid petroleum-based fuels as a major energy source in spite of their finite supply, it is of paramount importance to maximize the efficiency and minimize the environmental impact of the devices that burn these fuels. The development of improved energy conversion systems, having higher efficiencies and lower emissions, is central to meeting both local and regional air quality standards. This development requires improvements in computational design tools for applied energy conversion systems, which in turn requires more robust sub-model components for combustion chemistry, transport, energy transport (including radiation), and pollutant emissions (soot formation and burnout). The study of isolated droplet burning as a unidimensional, time dependent model diffusion flame system facilitates extensions of these mechanisms to include fuel molecular sizes and pollutants typical of conventional and alternative liquid fuels used in the transportation sector. Because of the simplified geometry, sub-model components from the most detailed to those reduced to sizes compatible for use in multi-dimensional, time dependent applied models can be developed, compared and validated against experimental diffusion flame processes, and tested against one another. Based on observations in microgravity experiments on droplet combustion, it appears that the formation and lingering presence of soot within the fuel-rich region of isolated droplets can modify the burning rate, flame structure and extinction, soot aerosol properties, and the effective thermophysical properties. These observations led to the belief that perhaps one of the most important outstanding contributions of microgravity droplet combustion is the observation that in the

  12. NASA: Black soot fuels global warming

    CERN Multimedia

    2003-01-01

    New research from NASA's Goddard Space Center scientists suggests emissions of black soot have been altering the way sunlight reflects off Earth's snow. The research indicates the soot could be responsible for as much as 25 percent of global warming over the past century (assorted news items, 1 paragraph each).

  13. Method for removing soot from exhaust gases

    Science.gov (United States)

    Suib, Steven L.; Dharmarathna, D. A. Saminda; Pahalagedara, Lakshitha R.

    2018-01-16

    A method for oxidizing soot from diesel exhaust gas from a diesel engine. The method involves providing a diesel particulate filter for receiving the diesel exhaust gas; coating a catalyst composition on the diesel particulate filter; and contacting the soot from the diesel exhaust gas with the catalyst coated diesel particulate filter at a temperature sufficient to oxidize the soot to carbon dioxide. The catalyst composition is a doped or undoped manganese oxide octahedral molecular sieve (OMS-2) material. A diesel exhaust gas treatment system that includes a diesel particulate filter for receiving diesel exhaust gas from a diesel engine and collecting soot; and a catalyst composition coated on the diesel particulate filter. The catalyst composition is a doped or undoped manganese oxide octahedral molecular sieve (OMS-2).

  14. Strain rate effect on sooting characteristics in laminar counterflow diffusion flames

    KAUST Repository

    Wang, Yu

    2016-01-20

    The effects of strain rate, oxygen enrichment and fuel type on the sooting characteristics of counterflow diffusion flames were studied. The sooting structures and relative PAH concentrations were measured with laser diagnostics. Detailed soot modeling using recently developed PAH chemistry and surface reaction mechanism was performed and the results were compared with experimental data for ethylene flames, focusing on the effects of strain rates. The results showed that increase in strain rate reduced soot volume fraction, average size and peak number density. Increase in oxygen mole fraction increased soot loading and decreased its sensitivity on strain rate. The soot volume fractions of ethane, propene and propane flames were also measured as a function of global strain rate. The sensitivity of soot volume fraction to strain rate was observed to be fuel dependent at a fixed oxygen mole fraction, with the sensitivity being higher for more sooting fuels. However, when the soot loadings were matched at a reference strain rate for different fuels by adjusting oxygen mole fraction, the dependence of soot loading on strain rate became comparable among the tested fuels. PAH concentrations were shown to decrease with increase in strain rate and the dependence on strain rate is more pronounced for larger PAHs. Soot modeling was performed using detailed PAH growth chemistry with molecular growth up to coronene. A qualitative agreement was obtained between experimental and simulation results, which was then used to explain the experimentally observed strain rate effect on soot growth. However, quantitatively, the simulation result exhibits higher sensitivity to strain rate, especially for large PAHs and soot volume fractions.

  15. SO2 influence on the K/La2O3 soot combustion catalyst deactivation

    International Nuclear Information System (INIS)

    Peralta, M.A.; Ulla, M.A.; Querini, C.A.

    2008-01-01

    In the present work, K/La 2 O 3 was prepared and tested as a potential catalyst to be used in a diesel engine exhaust. The soot combustion activity was evaluated by temperature-programmed-oxidation (TPO), and the NO x -catalyst interaction was studied using a microbalance experiment. The SO 2 poisoning process and the regeneration of a poisoned K/La 2 O 3 catalyst were analyzed. The fresh catalyst presented a good soot combustion activity. After being treated with a 1000 ppm SO 2 stream, the catalyst was poisoned due to lanthanum sulfate and potassium sulfate formation. The NO x treatment contributed to the K 2 (SO 4 ) decomposition at the expense of extra La 2 (SO 4 ) 3 formation and the H 2 treatment contributed to the La 2 (SO 4 ) 3 decomposition. (author)

  16. Effects of DME mixing on number density and size properties of soot particles in counterflow non-premixed ethylene flames

    KAUST Repository

    Choi, J. H.

    2015-05-01

    In order to investigate the effect of DME mixing on the number density and size of soot particles, DME was mixed in a counter flow non-premixed ethylene flame with mixture ratios of 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and mean size of soot particles. The experimental results showed that the highest soot concentrations were observed for flames with mixture ratios of 5% and 14%; however, for a mixture ratio of 30% the soot concentration decreased. Numerical results showed that the concentrations of propargyl radicals (C3H3) at the 5% and 14% ratios were higher than those measured in the ethylene-based flame, and the production of benzene (C6H6) in the 5% and 14% DME mixture flames was also increased. This indicates the crucial role of propargyl in benzene ring formation. These reactions generally become stronger with increased DME mixing, except for A1- + H2 → A1 + H (-R554) and n-C4H5 + C2H2 → A1 + H (R542). Therefore, it is indicated that adding DME to ethylene flames promotes benzene ring formation. Note that although the maximum C6H6 concentration is largest in the 30% DME mixing flame, the soot volume fraction is smaller than those for the 5% and 14% mixture ratios. This is because the local C6H6 concentration decreases in the relatively low temperature region in the fuel side where soot growth occurs. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

  17. Effects of DME mixing on number density and size properties of soot particles in counterflow non-premixed ethylene flames

    KAUST Repository

    Choi, J. H.; Choi, B. C.; Lee, S. M.; Chung, Suk-Ho; Jung, K. S.; Jeong, W. L.; Choi, S. K.; Park, S. K.

    2015-01-01

    In order to investigate the effect of DME mixing on the number density and size of soot particles, DME was mixed in a counter flow non-premixed ethylene flame with mixture ratios of 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and mean size of soot particles. The experimental results showed that the highest soot concentrations were observed for flames with mixture ratios of 5% and 14%; however, for a mixture ratio of 30% the soot concentration decreased. Numerical results showed that the concentrations of propargyl radicals (C3H3) at the 5% and 14% ratios were higher than those measured in the ethylene-based flame, and the production of benzene (C6H6) in the 5% and 14% DME mixture flames was also increased. This indicates the crucial role of propargyl in benzene ring formation. These reactions generally become stronger with increased DME mixing, except for A1- + H2 → A1 + H (-R554) and n-C4H5 + C2H2 → A1 + H (R542). Therefore, it is indicated that adding DME to ethylene flames promotes benzene ring formation. Note that although the maximum C6H6 concentration is largest in the 30% DME mixing flame, the soot volume fraction is smaller than those for the 5% and 14% mixture ratios. This is because the local C6H6 concentration decreases in the relatively low temperature region in the fuel side where soot growth occurs. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

  18. Durable superhydrophobic carbon soot coatings for sensor applications

    Science.gov (United States)

    Esmeryan, K. D.; Radeva, E. I.; Avramov, I. D.

    2016-01-01

    A novel approach for the fabrication of durable superhydrophobic (SH) carbon soot coatings used in quartz crystal microbalance (QCM) based gas or liquid sensors is reported. The method uses modification of the carbon soot through polymerization of hexamethyldisiloxane (HMDSO) by means of glow discharge RF plasma. The surface characterization shows a fractal-like network of carbon nanoparticles with diameter of ~50 nm. These particles form islands and cavities in the nanometer range, between which the plasma polymerized hexamethyldisiloxane (PPHMDSO) embeds and binds to the carbon chains and QCM surface. Such modified surface structure retains the hydrophobic nature of the soot and enhances its robustness upon water droplet interactions. Moreover, it significantly reduces the insertion loss and dynamic resistance of the QCM compared to the commonly used carbon soot/epoxy resin approach. Furthermore, the PPHMDSO/carbon soot coating demonstrates durability and no aging after more than 40 probing cycles in water based liquid environments. In addition, the surface layer keeps its superhydrophobicity even upon thermal annealing up to 540 °C. These experiments reveal an opportunity for the development of soot based SH QCMs with improved electrical characteristics, as required for high-resolution gas or liquid measurements.

  19. Th effectiveness of soot removal techniques for the recovery of fingerprints on glass fire debris in petrol bomb cases

    International Nuclear Information System (INIS)

    Umi Kalthom Ahmad; Mei, Y.S.; Mohd Shahru Bahari; Raramasivam, V.K.

    2011-01-01

    The increased use of petrol bombs as an act of vengeance in Malaysia has heightened awareness for the need of research relating physical evidence found at the crime scene to the perpetrator of the crime. A study was therefore carried out to assess the effectiveness of soot removal techniques on glass fire debris without affecting the fingerprints found on the evidence. Soot was removed using three methods which were brushing, 2 % NaOH solution and tape lifting. Depending on the visibility of prints recovered, prints which were visible after soot removal were lifted directly while prints that were not visible were subjected to enhancement. Glass microscope slides were used in laboratory experiment and subjected to control burn for the formation of soot. Soot was later removed following enhancement of the prints over time (within 1 day, within 2 days and after 2 days). While in simulated petrol bomb ground experiment, petrol bombs were hurled in glass bottles and the fragments were collected. Favorable results were obtained in varying degrees using each soot removal methods. In laboratory testing, brushing and 2 % NaOH solution revealed fingerprints that were visible after removal of excess soot and were lifted directly. As for tape lifting technique, some prints were visible and were successfully lifted while those that were not visible were subjected to super glue fuming for effective fingerprint identification. (author)

  20. The impact of carbon dioxide and exhaust gas recirculation on the oxidative reactivity of soot from ethylene flames and diesel engines

    Science.gov (United States)

    Al-Qurashi, Khalid O.

    Restrictive emissions standards to reduce nitrogen oxides (NOx) and particulate matter (PM) emissions from diesel engines necessitate the development of advanced emission control technology. The engine manufacturers in the United States have implemented the exhaust gas recirculation (EGR) and diesel particulate filters (DPF) to meet the stringent emissions limits on NOx and PM, respectively. Although the EGR-DPF system is an effective means to control diesel engine emissions, there are some concerns associated with its implementation. The chief concern with this system is the DPF regenerability, which depends upon several factors, among which are the physicochemical properties of the soot. Despite the plethora of research that has been conducted on DPF regenerability, the impact of EGR on soot reactivity and DPF regenerability is yet to be examined. This work concerns the impact of EGR on the oxidative reactivity of diesel soot. It is part of ongoing research to bridge the gap in establishing a relationship between soot formation conditions, properties, and reactivity. This work is divided into three phases. In the first phase, carbon dioxide (CO2) was added to the intake charge of a single cylinder engine via cylinders of compressed CO2. This approach simulates the cold-particle-free EGR. The results showed that inclusion of CO2 changes the soot properties and yields synergistic effects on the oxidative reactivity of the resulting soot. The second phase of this research was motivated by the findings from the first phase. In this phase, post-flame ethylene soot was produced from a laboratory co-flow laminar diffusion flame to better understand the mechanism by which the CO2 affects soot reactivity. This phase was accomplished by successfully isolating the dilution, thermal, and chemical effects of the CO2. The results showed that all of these effects account for a measurable increase in soot reactivity. Nevertheless, the thermal effect was found to be the most

  1. On the Response of Nascent Soot Nanostructure and Oxidative Reactivity to Photoflash Exposure

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2017-07-01

    Full Text Available Soot particles are a kind of major pollutant from fuel combustion. To enrich the understanding of soot, this work focuses on investigating detailed influences of instantaneous external irradiation (conventional photoflash exposure on nanostructure as well as oxidation reactivity of nascent soot particles. By detailed soot characterizations flash can reduce the mass of soot and soot nanostructure can be reconstructed substantially without burning. After flash, the degree of soot crystallization increases while the soot reactive rate decreases and the activation energy increases. In addition, nanostructure and oxidative reactivity of soot in air and Ar after flash are different due to their different thermal conductivities.

  2. Effect of Morphology and Composition on the Hygroscopicity of Soot Aerosols

    Science.gov (United States)

    Williams, L.; Slowik, J.; Davidovits, P.; Jayne, J.; Kolb, C.; Worsnop, D.; Rudich, Y.

    2003-12-01

    Freshly generated soot aerosols are initially hydrophobic and unlikely to act as cloud condensation nuclei (CCN). However, during combustion many low vapor pressure gas products are formed that may then condense on existing soot aerosols. Additionally, soot particles may acquire coatings as they age, such as acids, salts, and oxygenated organics. An understanding of this aging process and its effect on soot hygroscopicity is necessary to address the potential of soot to act as a CCN. The transformation of soot from hydrophobic to hydrophilic is the focus of this work. An aim here is to determine the minimum coating required for hygroscopic growth. Soot particles produced by combustion of mixtures of fuel and air are size selected by a Differential Mobility Analyzer (DMA) and entrained in a laminar flow passing through a flow tube. The size selected soot particles are mixed with a controlled amount of the gas phase precursors to produce the coatings to be studied. Initial studies are focused on coatings of H2SO4, NH4NO3, and selected organics. The number of particles per unit volume of air is counted by a Condensation Particle Counter (CPC) and the particles are isokinetically sampled into an Aerosol Mass Spectrometer (AMS). Two distinct types of soot aerosols have been observed depending on the type of fuel and air mixture. With soot produced by the combustion of propane and air, the AMS shows a polydisperse particle size distribution with aerodynamic diameters ranging from 100 nm to 400 nm. The aerodynamic diameter is linearly related to the DMA-determined mobility diameter with the product density x shape factor = 1.2. The organic molecules in this soot are mostly PAH compounds. However, when kerosene is added to the propane flame, the soot particle morphology and composition is strikingly altered. While the DMA shows an essentially unchanged mobility diameter distribution, in the range 100 nm to 400, aerodynamic particle diameter is constant at about 100 nm

  3. Simulation and analysis of the soot particle size distribution in a turbulent nonpremixed flame

    KAUST Repository

    Lucchesi, Marco

    2017-02-05

    A modeling framework based on Direct Simulation Monte Carlo (DSMC) is employed to simulate the evolution of the soot particle size distribution in turbulent sooting flames. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of a n-heptane turbulent nonpremixed flame. The DSMC method is validated against experimentally measured size distributions in laminar premixed flames and found to reproduce quantitatively the experimental results, including the appearance of the second mode at large aggregate sizes and the presence of a trough at mobility diameters in the range 3–8 nm. The model is then applied to the simulation of soot formation and growth in simplified configurations featuring a constant concentration of soot precursors and the evolution of the size distribution in time is found to depend on the intensity of the nucleation rate. Higher nucleation rates lead to a higher peak in number density and to the size distribution attaining its second mode sooner. The ensemble-averaged PSDF in the turbulent flame is computed from individual samples of the PSDF from large sets of Lagrangian trajectories. This statistical measure is equivalent to time-averaged, scanning mobility particle size (SMPS) measurements in turbulent flames. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a long, broad tail, which implies significant polydispersity induced by turbulence. Our results agree very well with SMPS measurements available in the literature. Conditioning on key features of the trajectory, such as mixture fraction or radial locations does not reduce the scatter in the size distributions and the ensemble-averaged PSDF remains broad. The results highlight and explain the important role of turbulence in broadening the size distribution of

  4. Characterization and reactivity of soot from fast pyrolysis of lignocellulosic compounds and monolignols

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Brown, Avery; Tompsett, Geoffrey

    2018-01-01

    spectroscopy. The CO2 reactivity of soot was investigated by thermogravimetric analysis. Soot from cellulose was more reactive than soot produced from extractives, lignin and monolignols. Soot reactivity was correlated with the separation distances between adjacent graphene layers, as measured using...... transmission electron microscopy. Particle size, free radical concentration, differences in a degree of curvature and multi-core structures influenced the soot reactivity less than the interlayer separation distances. Soot yield was correlated with the lignin content of the feedstock. The selection...... of the extraction solvent had a strong influence on the soot reactivity. The Soxhlet extraction of softwood and wheat straw lignin soot using methanol decreased the soot reactivity, whereas acetone extraction had only a modest effect....

  5. Small particles big effect? - Investigating ice nucleation abilities of soot particles

    Science.gov (United States)

    Mahrt, Fabian; David, Robert O.; Lohmann, Ulrike; Stopford, Chris; Wu, Zhijun; Kanji, Zamin A.

    2017-04-01

    Atmospheric soot particles are primary particles produced by incomplete combustion of biomass and/or fossil fuels. Thus soot mainly originates from anthropogenic emissions, stemming from combustion related processes in transport vehicles, industrial and residential uses. Such soot particles are generally complex mixtures of black carbon (BC) and organic matter (OM) (Bond et al., 2013; Petzold et al., 2013), depending on the sources and the interaction of the primary particles with other atmospheric matter and/or gases BC absorbs solar radiation having a warming effect on global climate. It can also act as a heterogeneous ice nucleating particle (INP) and thus impact cloud-radiation interactions, potentially cooling the climate (Lohmann, 2002). Previous studies, however, have shown conflicting results concerning the ice nucleation ability of soot, limiting the ability to predict its effects on Earth's radiation budget. Here we present a laboratory study where we systematically investigate the ice nucleation behavior of different soot particles. Commercial soot samples are used, including an amorphous, industrial carbon frequently used in coatings and coloring (FW 200, Orion Engineered Carbons) and a fullerene soot (572497 ALDRICH), e.g. used as catalyst. In addition, we use soot generated from a propane flame Combustion Aerosol Standard Generator (miniCAST, JING AG), as a proxy for atmospheric soot particles. The ice nucleation ability of these soot types is tested on size-selected particles for a wide temperature range from 253 K to 218 K, using the Horizontal Ice Nucleation Chamber (HINC), a Continuous Flow Diffusion Chamber (CFDC) (Kanji and Abbatt, 2009). Ice nucleation results from these soot surrogates will be compared to chemically more complex real world samples, collected on filters. Filters will be collected during the 2016/2017 winter haze periods in Beijing, China and represent atmospheric soot particles with sources from both industrial and residential

  6. Influence of fuel properties on fundamental spray characteristics and soot emissions using different tailor-made fuels from biomass

    International Nuclear Information System (INIS)

    García, Antonio; Monsalve-Serrano, Javier; Heuser, Benedikt; Jakob, Markus; Kremer, Florian; Pischinger, Stefan

    2016-01-01

    Highlights: • TMFB show clear potential to reduce soot emissions under mixing-controlled combustion. • The larger lift-off-length of 2-MTHF and 1-octanol promotes soot emissions reduction. • Oxidation process governs the improved soot emissions of DNBE. - Abstract: This work evaluates the potential of some new biomass-derived fuels as candidates for compression ignition operation. Thus, fundamental spray characteristics related to fuel vaporization and fuel/air mixing process for 2-Methyltetrahydrofuran, Di-n-butyl ether and 1-octanol has been studied and compared with conventional EN590 Diesel fuel. For this purpose, OH"∗ chemiluminescence and shadowgraphy measurements in a high pressure chamber as well as 1D simulations with a spray model have been carried out at different operating conditions representative of the NEDC driving cycle. Finally, measured soot emissions in the single-cylinder engine were presented and discussed. Results from the high pressure chamber presented very good agreement in terms of liquid length and vapor penetration with simulation results. Thus, some analytical expressions related to macroscopic spray characteristics have been proposed and validated experimentally for all four fuels. Finally, the single-cylinder engine results confirmed the relevant role of soot formation on final emissions for 1-octanol and 2-MTHF. In addition, DNBE showed greater soot oxidation potential than diesel and other TMFB candidates.

  7. Effects of ambient oxygen concentration on soot temperature and concentration for biodiesel and diesel spray combustion

    KAUST Repository

    Zhang, Ji

    2015-06-01

    Ambient oxygen concentration, a key variable directly related to exhaust gas recirculation (EGR) levels in diesel engines, plays a significant role in particulate matter (PM) and nitrogen oxides (NOx) emissions. The utilization of biodiesel in diesel engines has been investigated over the last decades for its renewable characteristics and lower emissions compared to diesel. In an earlier work, we demonstrated that the soot temperature and concentration of biodiesel were lower than diesel under regular diesel engine conditions without EGR. Soot concentration was quantified by a parameter called KL factor. As a continuous effort, this paper presents an experimental investigation of the ambient oxygen concentration on soot temperature and KL factor during biodiesel and diesel spray combustion. The experiment was implemented in a constant volume chamber system, where the ambient oxygen concentration varied from 21 to 10% and the ambient temperature was kept to 1,000 K. A high speed two-color pyrometry technique was used to measure transient soot temperature and the KL factor of the spray flame. The soot temperature of biodiesel is found to be lower than that of diesel under the same conditions, which follows the same trend from our previous results found when the ambient temperature changes to 21% oxygen conditions. A reduction in ambient oxygen concentration generally reduces the soot temperature for both fuels. However, this is a complicated effect on soot processes as the change of oxygen concentration greatly affects the balance between soot formation and oxidation. The KL factor is observed to be the highest at 12% O2 for diesel and 18% O2 for biodiesel, respectively. On the other hand, the 10% O2 condition shows the lowest KL factor for both fuels. These results can provide quantitative experimental evidences to optimize the ambient oxygen concentration for diesel engines using different fuels for better emissions characteristics. © 2014 American Society of

  8. Soot emissions from turbulent diffusion flames burning simple alkane fuels

    Energy Technology Data Exchange (ETDEWEB)

    Canteenwalla, P.M.; Johnson, M.R. [Carleton Univ., Ottawa, ON (Canada). Dept. of Mechanical and Aerospace Engineering; Thomson, K.A.; Smallwood, G.J. [National Research Council of Canada, Ottawa, ON (Canada). Inst. for Chemical Process and Environmental Technology

    2007-07-01

    A classic problem in combustion involves measurement and prediction of soot emissions from turbulent diffusion flames. Very high-sensitivity measurements of particulate matter (PM) from very low-sooting diffusion flames burning methane and other simple alkane fuels have been enabled from recent advances in laser-induced incandescence (LII). In order to quantify soot emissions from a lab-scale turbulent diffusion flame burner, this paper presented a study that used LII to develop a sampling protocol. The purpose of the study was to develop an experimentally based model to predict PM emissions from flares used in industry using soot emissions from lab-scale flares. Quantitative results of mass of soot emitted per mass of fuel burned were presented across a range of flow conditions and fuels. The experiment used digital imaging to measure flame lengths and estimate flame residence times. Comparisons were also made between current measurements and results of previous researchers for soot in the overfire region. The study also considered the validity applicability of buoyancy based models for predicting and scaling soot emissions. The paper described the experimental setup including sampling system and flame length imaging. Background information on soot yield and a comparison of flame residence time definitions were provided. The results and discussion of results were also presented. It was concluded that the results highlighted the subjective nature of flame length measurements. 10 refs., 4 figs.

  9. Potassium and soot interaction in fast biomass pyrolysis at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Hofmann Larsen, Flemming; Shchukarev, Andrey

    2018-01-01

    2 reactivity was studied by thermogravimetric analysis. The XPS results showed that potassium incorporation with oxygen-containing surface groups in the soot matrix did not occur during high temperature pyrolysis. The potassium was mostly found as water-soluble salts such as KCl, KOH, KHCO3 and K2CO...... potassium amount was incorporated in the soot matrix during pyrolysis. Raman spectroscopy results showed that the carbon chemistry of biomass soot also affected the CO2 reactivity. The less reactive pinewood soot was more graphitic than herbaceous biomass soot samples with the disordered carbon structure...

  10. High-throughput approach to the catalytic combustion of diesel soot

    Energy Technology Data Exchange (ETDEWEB)

    Iojoiu, Eduard Emil; Bassou, Badr; Guilhaume, Nolven; Farrusseng, David; Desmartin-Chomel, Arnold; Bianchi, Daniel; Mirodatos, Claude [Institut de recherches sur la catalyse et l' environnement de Lyon IRCELYON, UMR5256 CNRS Universite Lyon 1, 2 avenue Albert Einstein, F-69626 Villeurbanne Cedex (France); Lombaert, Karine [Renault, Diesel Innovative Catalytic Materials, Direction de l' Ingenierie Materiaux, 1 Allee Cornuel, 91510 Lardy (France)

    2008-08-30

    A methodology for the evaluation of diesel soot oxidation catalysts by high-throughput (HT) screening was developed. The optimal experimental conditions (soot amount, catalyst/soot ratio, type of contact, composition and flow rate of gas reactants) ensuring a reliable and reproducible detection of light-off temperatures in a 16 parallel channels reactor were set up. The temperature profile measured in the catalyst/soot bed under TPO conditions when the exothermic combustion of soot takes place was shown to provide an accurate measurement of the ignition. Its reproducibility and relevance were checked. The results obtained with a reference noble metal free catalyst (La{sub 0.8}Cr{sub 0.8}Li{sub 0.2}O{sub 3} perovskite) agree very well with literature data. Qualitative mechanistic features could be derived from these experiments, stressing the likely limiting step of oxygen transfer from catalyst surface to soot particulates to ignite the soot combustion. Ceria material was shown to be more appropriate than perovskite one. From an HT screening of a large diverse library (over 100 mixed oxides catalysts) under optimized conditions, about 10 new formulations were found to perform better than selected noble metal free reference materials. (author)

  11. Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot

    Directory of Open Access Journals (Sweden)

    R. Prasad

    2011-01-01

    Full Text Available To comply with the stringent emission regulations on soot, diesel vehicles manufacturers more and more commonly use diesel particulate filters (DPF. These systems need to be regenerated periodically by burning soot that has been accumulated during the loading of the DPF. Design of the DPF requires rate of soot oxidation. This paper describes the kinetics of catalytic oxidation of diesel soot with air under isothermal conditions. Kinetics data were collected in a specially designed mini-semi-batch reactor. Under the high air flow rate assuming pseudo first order reaction the activation energy of soot oxidation was found to be, Ea = 160 kJ/ mol. ©2010 BCREC UNDIP. All rights reserved(Received: 14th June 2010, Revised: 18th July 2010, Accepted: 9th August 2010[How to Cite: R. Prasad, V.R. Bella. (2010. Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot. Bulletin of Chemical Reaction Engineering and Catalysis, 5(2: 95-101. doi:10.9767/bcrec.5.2.796.95-101][DOI:http://dx.doi.org/10.9767/bcrec.5.2.796.95-101 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/796]Cited by in: ACS 1 |

  12. Time-resolved analysis of primary volatile emissions and secondary aerosol formation potential from a small-scale pellet boiler

    Science.gov (United States)

    Czech, Hendryk; Pieber, Simone M.; Tiitta, Petri; Sippula, Olli; Kortelainen, Miika; Lamberg, Heikki; Grigonyte, Julija; Streibel, Thorsten; Prévôt, André S. H.; Jokiniemi, Jorma; Zimmermann, Ralf

    2017-06-01

    Small-scale pellet boilers and stoves became popular as a wood combustion appliance for domestic heating in Europe, North America and Asia due to economic and environmental aspects. Therefore, an increasing contribution of pellet boilers to air pollution is expected despite their general high combustion efficiency. As emissions of primary organic aerosol (POA) and permanent gases of pellet boilers are well investigated, the scope of this study was to investigate the volatile organic emissions and the formation potential of secondary aerosols for this type of appliance. Fresh and aged emissions were analysed by a soot-particle aerosol time-of-flight mass spectrometry (SP-AMS) and the molecular composition of the volatile precursors with single-photon ionisation time-of-flight mass spectrometry (SPI-TOFMS) at different pellet boiler operation conditions. Organic emissions in the gas phase were dominated by unsaturated hydrocarbons while wood-specific VOCs, e.g. phenolic species or substituted furans, were only detected during the starting phase. Furthermore, organic emissions in the gas phase were found to correlate with fuel grade and combustion technology in terms of secondary air supply. Secondary organic aerosols of optimised pellet boiler conditions (OPT, state-of-the-art combustion appliance) and reduced secondary air supply (RSA, used as a proxy for pellet boilers of older type) were studied by simulating atmospheric ageing in a Potential Aerosol Mass (PAM) flow reactor. Different increases in OA mass (55% for OPT, 102% for RSA), associated with higher average carbon oxidation state and O:C, could be observed in a PAM chamber experiment. Finally, it was found that derived SOA yields and emission factors were distinctly lower than reported for log wood stoves.

  13. Effect of Coatings on the Uptake Rate and HONO Yield in Heterogeneous Reaction of Soot with NO2

    Science.gov (United States)

    Cruz-Quiñones, M.; Khalizov, A. F.; Zhang, R.

    2009-12-01

    Heterogeneous reaction of nitrogen dioxide on carbon soot aerosols has been suggested as a possible source of nighttime nitrous acid (HONO) in atmosphere boundary layer. Available laboratory data show significant variability in the measured reaction probabilities and HONO yields, making it difficult to asses the atmospheric significance of this process. Moreover, little is known of how aging of soot aerosol through internal mixing with other atmospheric trace constituents will affect the heterogeneous reactivity and HONO production. In this work, the heterogeneous reaction of NO2 on fresh and aged soot films leading to HONO formation was studied through a series of kinetic uptake experiments and HONO yield measurements. Soot samples were prepared by incomplete combustion of propane and kerosene fuels under lean and rich flame conditions. Experiments were performed in a low-pressure, fast-flow reactor coupled to a chemical ionization mass spectrometer (CIMS), using atmospheric-level NO2 concentrations. Heterogeneous uptake coefficients, γ(geom) and γ(BET), were calculated using geometric and internal BET soot surface areas, respectively. The uptake coefficient and the HONO yield depend on the type of fuel and combustion regime and are the highest for soot samples prepared using rich kerosene flame. Although, the internal surface area of soot measured by BET method is a factor of 50 to 500 larger than the geometric surface area, only the top soot layers are involved in heterogeneous reaction with NO2 as follows from the observed weak dependence of γ(geom) and decrease in γ(BET) with increasing sample mass. Heating the soot samples before exposure to NO2 increases the BET surface area, the HONO yield, and the NO2 uptake coefficient due to the removal of the organic fraction from the soot backbone that unblocks active sites and makes them accessible for physical adsorption and chemical reactions. Our results support the oxidation-reduction mechanism involving

  14. Strain rate effect on sooting characteristics in laminar counterflow diffusion flames

    KAUST Repository

    Wang, Yu; Chung, Suk-Ho

    2016-01-01

    The effects of strain rate, oxygen enrichment and fuel type on the sooting characteristics of counterflow diffusion flames were studied. The sooting structures and relative PAH concentrations were measured with laser diagnostics. Detailed soot

  15. Soot in the air may have serious climatic consequences

    International Nuclear Information System (INIS)

    Seip, Hans Martin

    2002-01-01

    Emissions of soot in China and India may be an important cause of changed summer weather in China, with increasing floods in the south-east and increasing droughts in the north-east. In addition to the greenhouse gases, the particulate matter (aerosols) in the air has an important effect on the climate. Most particles have a cooling effect since they reflect solar radiation. However, some particles are dark as they contain soot ('black carbon'). Such particles, which are formed by incomplete combustion of coal, oil and biomass, absorb solar radiation and thus have a warming effect, even if they reduce the solar irradiation on the ground. Soot particles do not have quite the same effect as the greenhouse gases. The soot particles absorb solar radiation, while the greenhouse gases absorb terrestrial heat radiation. In addition, the residence time of the soot particles in the atmosphere is shorter than that of, say, carbon dioxide. The concentration is therefore much higher in areas close to emission sources than elsewhere

  16. Experimental determination of soot refractive index in the infrared

    International Nuclear Information System (INIS)

    Ouf, F.X.; Vendel, J.; Ouf, F.X.; Coppalle, A.; Weil, M.E.; Yon, J.

    2007-01-01

    The study of physical properties of soot particles produced during combustion is a complex subject but of a great interest within the framework of the study of the safety of an installation, with respect to the fire hazard. These characteristics are, in this case, particularly useful in order to predict the behaviour of containment barriers in situation of fire, but also in order to estimate the contribution of these particles to radiative transfers. The aim of this study is to determine the radiative properties of soot particles produced during combustion. A specific device, which establishes extinction and vertical-vertical scattering coefficients, has been developed and has allowed to determine the refractive index of soot particles in the infrared. This determination also needed the establishment of size distribution and morphological properties of soot aggregates. We present in this document the experimental device developed, and the validation of this device on latex spheres which optical properties are well known. First results of extinction coefficients will be presented and will underline the similar optical behaviour of different soot aggregates. Values of refractive index will be detailed and discussed, and a direct application of these values will be carried out in order to determine the soot volume fraction. A comparison with reference method will underline the efficiency of our method. We will conclude on the validity of the information brought by this device and on the prospects of this study. A discussion is included, on the utility of mean values of refractive index and on the determination of total emissivity of soot particles. (authors)

  17. T-matrix modeling of linear depolarization by morphologically complex soot and soot-containing aerosols

    International Nuclear Information System (INIS)

    Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

    2013-01-01

    We use state-of-the-art public-domain Fortran codes based on the T-matrix method to calculate orientation and ensemble averaged scattering matrix elements for a variety of morphologically complex black carbon (BC) and BC-containing aerosol particles, with a special emphasis on the linear depolarization ratio (LDR). We explain theoretically the quasi-Rayleigh LDR peak at side-scattering angles typical of low-density soot fractals and conclude that the measurement of this feature enables one to evaluate the compactness state of BC clusters and trace the evolution of low-density fluffy fractals into densely packed aggregates. We show that small backscattering LDRs measured with ground-based, airborne, and spaceborne lidars for fresh smoke generally agree with the values predicted theoretically for fluffy BC fractals and densely packed near-spheroidal BC aggregates. To reproduce higher lidar LDRs observed for aged smoke, one needs alternative particle models such as shape mixtures of BC spheroids or cylinders. -- Highlights: ► New superposition T-matrix code is applied to soot aerosols. ► Quasi-Rayleigh side-scattering peak in linear depolarization (LD) is explained. ► LD measurements can be used for morphological characterization of soot aerosols

  18. Diesel soot oxidation under controlled conditions

    OpenAIRE

    Song, Haiwen

    2003-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 11/12/2003. In order to improve understanding of diesel soot oxidation, an experimental rig was designed and set up, in which the soot oxidation conditions, such as temperature, oxygen partial pressure, and CO2 partial pressure, could be varied independently of each other. The oxidizing gas flow in the oxidizer was under laminar condition. This test rig comprised a naturally-aspirated single ...

  19. Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the properties of contrail ice particles in the jet regime

    Directory of Open Access Journals (Sweden)

    H.-W. Wong

    2013-10-01

    Full Text Available Contrails and contrail-induced cirrus clouds are identified as the most uncertain components in determining aviation impacts on global climate change. Parameters affecting contrail ice particle formation immediately after the engine exit plane (< 5 s in plume age may be critical to ice particle properties used in large-scale models predicting contrail radiative forcing. Despite this, detailed understanding of these parametric effects is still limited. In this paper, we present results from recent laboratory and modeling studies conducted to investigate the effects of water and soot emissions and ambient conditions on near-field formation of contrail ice particles and ice particle properties. The Particle Aerosol Laboratory (PAL at the NASA Glenn Research Center and the Aerodyne microphysical parcel model for contrail ice particle formation were employed. Our studies show that exhaust water concentration has a significant impact on contrail ice particle formation and properties. When soot particles were introduced, ice particle formation was observed only when exhaust water concentration was above a critical level. When no soot or sulfuric acid was introduced, no ice particle formation was observed, suggesting that ice particle formation from homogeneous nucleation followed by homogeneous freezing of liquid water was unfavorable. Soot particles were found to compete for water vapor condensation, and higher soot concentrations emitted into the chamber resulted in smaller ice particles being formed. Chamber conditions corresponding to higher cruising altitudes were found to favor ice particle formation. The microphysical model captures trends of particle extinction measurements well, but discrepancies between the model and the optical particle counter measurements exist as the model predicts narrower ice particle size distributions and ice particle sizes nearly a factor of two larger than measured. These discrepancies are likely due to particle

  20. Experimental studies on spray and gas entrainment characteristics of biodiesel fuel: Implications of gas entrained and fuel oxygen content on soot formation

    International Nuclear Information System (INIS)

    Kuti, Olawole Abiola; Nishida, Keiya; Zhu, Jingyu

    2013-01-01

    Experiments were performed inside the constant volume vessel to simulate the real diesel engine conditions. The LIF–PIV (Laser Induced Florescence – Particulate Image Velocimetry) technique was used to characterize the spray and gas entrainment characteristics of the fuels while the OH-chemiluminescence and two color pyrometry were applied to obtain information about the combustion processes. Biodiesel from palm oil (BDF (Biodiesel Fuel)) and the JIS #2 diesel fuel were utilized. It was observed that the SMD (Sauter mean diameter) obtained through an empirical equation decreased by increasing the injection pressure from 100 to 300 MPa and reducing the nozzle diameter from 0.16 to 0.08 mm. BDF has higher SMD values compared to diesel thus signifying inferior atomization. By increasing the injection pressure up to 300 MPa and reducing the nozzle diameter to 0.08 mm, the normal velocity and total mass flow rate of the entrained gas by the fuels increased. Due to higher viscosity and density properties, BDF possessed inferior atomization characteristics which made the normal velocity and total mass flow rate of the entrained gas lower compared to diesel. Due to inferior atomization which led to less gas being entrained upstream of the lift-off flame, the fuel oxygen content in BDF played a significant role in soot formation processes. - Highlights: • Spray and gas entrainment characteristics of biodiesel (BDF (Biodiesel Fuel)) and fuel were investigated. • Effect of injector parameters on BDF spray and gas entrainment characteristics was identified. • Higher viscosity and density of BDF yielded inferior spray atomization processes. • Gas entrainment velocity and mass flow rate of gas entrained by BDF lower. • Gas entrained had less effect on BDF's soot formation

  1. Phototransformation rate constants of PAHs associated with soot particles

    International Nuclear Information System (INIS)

    Kim, Daekyun; Young, Thomas M.; Anastasio, Cort

    2013-01-01

    Photodegradation is a key process governing the residence time and fate of polycyclic aromatic hydrocarbons (PAHs) in particles, both in the atmosphere and after deposition. We have measured photodegradation rate constants of PAHs in bulk deposits of soot particles illuminated with simulated sunlight. The photodegradation rate constants at the surface (k p 0 ), the effective diffusion coefficients (D eff ), and the light penetration depths (z 0.5 ) for PAHs on soot layers of variable thickness were determined by fitting experimental data with a model of coupled photolysis and diffusion. The overall disappearance rates of irradiated low molecular weight PAHs (with 2–3 rings) on soot particles were influenced by fast photodegradation and fast diffusion kinetics, while those of high molecular weight PAHs (with 4 or more rings) were apparently controlled by either the combination of slow photodegradation and slow diffusion kinetics or by very slow diffusion kinetics alone. The value of z 0.5 is more sensitive to the soot layer thickness than the k p 0 value. As the thickness of the soot layer increases, the z 0.5 values increase, but the k p 0 values are almost constant. The effective diffusion coefficients calculated from dark experiments are generally higher than those from the model fitting method for illumination experiments. Due to the correlation between k p 0 and z 0.5 in thinner layers, D eff should be estimated by an independent method for better accuracy. Despite some limitations of the model used in this study, the fitted parameters were useful for describing empirical results of photodegradation of soot-associated PAHs. - Highlights: ► PAHs on soot were evaluated by a model of coupled photolysis and diffusion. ► Photodegradation rate at the surface, diffusion coefficient, and light penetration path were determined. ► Low MW PAHs were influenced by fast photodegradation and fast diffusion. ► High MW PAHs were controlled either by slow

  2. Fractal-like dimension of nanometer Diesel soot particles

    Energy Technology Data Exchange (ETDEWEB)

    Skillas, G.; Baltensperger, U. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegmann, K. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-11-01

    Measurements with a low-pressure impactor and a differential mobility analyser were conducted for Diesel soot at various engine loads. By means of these measurements a fractal-like dimension of Diesel soot particles, with diameters ranging from 55 up to 260 nm, was established. (author) 2 figs., 7 refs.

  3. Catalytic oxidation of soot over alkaline niobates

    International Nuclear Information System (INIS)

    Pecchi, G.; Cabrera, B.; Buljan, A.; Delgado, E.J.; Gordon, A.L.; Jimenez, R.

    2013-01-01

    Highlights: ► No previous reported studies about alkaline niobates as catalysts for soot oxidation. ► NaNbO 3 and KNbO 3 perovskite-type oxides show lower activation energy than other lanthanoid perovskite-type oxides. ► The alkaline niobate does not show deactivation by metal loss. - Abstract: The lack of studies in the current literature about the assessment of alkaline niobates as catalysts for soot oxidation has motivated this research. In this study, the synthesis, characterization and assessment of alkaline metal niobates as catalysts for soot combustion are reported. The solids MNbO 3 (M = Li, Na, K, Rb) are synthesized by a citrate method, calcined at 450 °C, 550 °C, 650 °C, 750 °C, and characterized by AAS, N 2 adsorption, XRD, O 2 -TPD, FTIR and SEM. All the alkaline niobates show catalytic activity for soot combustion, and the activity depends basically on the nature of the alkaline metal and the calcination temperature. The highest catalytic activity, expressed as the temperature at which combustion of carbon black occurs at the maximum rate, is shown by KNbO 3 calcined at 650 °C. At this calcination temperature, the catalytic activity follows an order dependent on the atomic number, namely: KNbO 3 > NaNbO 3 > LiNbO 3 . The RbNbO 3 solid do not follow this trend presumably due to the perovskite structure was not reached. The highest catalytic activity shown by of KNbO 3 , despite the lower apparent activation energy of NaNbO 3 , stress the importance of the metal nature and suggests the hypothesis that K + ions are the active sites for soot combustion. It must be pointed out that alkaline niobate subjected to consecutive soot combustion cycles does not show deactivation by metal loss, due to the stabilization of the alkaline metal inside the perovskite structure.

  4. Parametric studies of contrail ice particle formation in jet regime using microphysical parcel modeling

    Directory of Open Access Journals (Sweden)

    H.-W. Wong

    2010-04-01

    Full Text Available Condensation trails (contrails formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age <5 s, systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a microphysical parcel modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index >1×1015 (kg-fuel−1 at cruise. The effects of dilution history, ion-mediated nucleation, ambient relative humidity, fuel sulfur contents, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles in the soot-rich regime, and the effect of fuel sulfur contents is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles. Further modeling and experimental studies are needed to verify if our findings can provide a possible approach for contrail mitigation.

  5. Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames

    KAUST Repository

    Attili, Antonio

    2016-02-13

    Turbulence statistics from two three-dimensional direct numerical simulations of planar n-heptane/air turbulent jets are compared to assess the effect of the gas-phase species diffusion model on flame dynamics and soot formation. The Reynolds number based on the initial jet width and velocity is around 15, 000, corresponding to a Taylor scale Reynolds number in the range 100 ≤ Reλ ≤ 150. In one simulation, multicomponent transport based on a mixture-averaged approach is employed, while in the other the gas-phase species Lewis numbers are set equal to unity. The statistics of temperature and major species obtained with the mixture-averaged formulation are very similar to those in the unity Lewis number case. In both cases, the statistics of temperature are captured with remarkable accuracy by a laminar flamelet model with unity Lewis numbers. On the contrary, a flamelet with a mixture-averaged diffusion model, which corresponds to the model used in the multi-component diffusion three-dimensional DNS, produces significant differences with respect to the DNS results. The total mass of soot precursors decreases by 20-30% with the unity Lewis number approximation, and their distribution is more homogeneous in space and time. Due to the non-linearity of the soot growth rate with respect to the precursors\\' concentration, the soot mass yield decreases by a factor of two. Being strongly affected by coagulation, soot number density is not altered significantly if the unity Lewis number model is used rather than the mixture-averaged diffusion. The dominant role of turbulent transport over differential diffusion effects is expected to become more pronounced for higher Reynolds numbers. © 2016 The Combustion Institute.

  6. Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames

    KAUST Repository

    Attili, Antonio; Bisetti, Fabrizio; Mueller, Michael E.; Pitsch, Heinz

    2016-01-01

    Turbulence statistics from two three-dimensional direct numerical simulations of planar n-heptane/air turbulent jets are compared to assess the effect of the gas-phase species diffusion model on flame dynamics and soot formation. The Reynolds number based on the initial jet width and velocity is around 15, 000, corresponding to a Taylor scale Reynolds number in the range 100 ≤ Reλ ≤ 150. In one simulation, multicomponent transport based on a mixture-averaged approach is employed, while in the other the gas-phase species Lewis numbers are set equal to unity. The statistics of temperature and major species obtained with the mixture-averaged formulation are very similar to those in the unity Lewis number case. In both cases, the statistics of temperature are captured with remarkable accuracy by a laminar flamelet model with unity Lewis numbers. On the contrary, a flamelet with a mixture-averaged diffusion model, which corresponds to the model used in the multi-component diffusion three-dimensional DNS, produces significant differences with respect to the DNS results. The total mass of soot precursors decreases by 20-30% with the unity Lewis number approximation, and their distribution is more homogeneous in space and time. Due to the non-linearity of the soot growth rate with respect to the precursors' concentration, the soot mass yield decreases by a factor of two. Being strongly affected by coagulation, soot number density is not altered significantly if the unity Lewis number model is used rather than the mixture-averaged diffusion. The dominant role of turbulent transport over differential diffusion effects is expected to become more pronounced for higher Reynolds numbers. © 2016 The Combustion Institute.

  7. Molecular mechanics and quantum mechanical modeling of hexane soot structure and interactions with pyrene

    Directory of Open Access Journals (Sweden)

    Kubicki JD

    2000-09-01

    Full Text Available Molecular simulations (energy minimizations and molecular dynamics of an n-hexane soot model developed by Smith and co-workers (M. S. Akhter, A. R. Chughtai and D. M. Smith, Appl. Spectrosc., 1985, 39, 143; ref. 1 were performed. The MM+ (N. L. Allinger, J. Am. Chem. Soc., 1977, 395, 157; ref. 2 and COMPASS (H. Sun, J. Phys. Chem., 1998, 102, 7338; ref. 3 force fields were tested for their ability to produce realistic soot nanoparticle structure. The interaction of pyrene with the model soot was simulated. Quantum mechanical calculations on smaller soot fragments were carried out. Starting from an initial 2D structure, energy minimizations are not able to produce the observed layering within soot with either force field. Results of molecular dynamics simulations indicate that the COMPASS force field does a reasonably accurate job of reproducing observations of soot structure. Increasing the system size from a 683 to a 2732 atom soot model does not have a significant effect on predicted structures. Neither does the addition of water molecules surrounding the soot model. Pyrene fits within the soot structure without disrupting the interlayer spacing. Polycyclic aromatic hydrocarbons (PAH, such as pyrene, may strongly partition into soot and have slow desorption kinetics because the PAH-soot bonding is similar to soot–soot interactions. Diffusion of PAH into soot micropores may allow the PAH to be irreversibly adsorbed and sequestered so that they partition slowly back into an aqueous phase causing dis-equilibrium between soil organic matter and porewater.

  8. Measurement of Soot Deposition in Automotive Components Using Neutron Radiography

    Energy Technology Data Exchange (ETDEWEB)

    Zekveld, David; Liu, Liaohui [AMEC NSS, 700 University Ave, Toronto, Ontario, M5G 1X6 (Canada); UOIT, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada); Harrison, Andrew; Gill, Spencer; Harvel, Glenn [UOIT, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada); Chang, Jen-Shih [McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8 (Canada)

    2008-07-01

    About 40% of air pollution is generated by vehicles and transportation. The particulate matter (PM) emission significantly impacts human health. Fine particles below 2.5 {mu}m (PM2.5) can enter the lungs and lead to respiratory problems. These particles not only influence human health, but also reduce the capability of many automobile exhaust heat exchanging devices. Neutron radiography is a non-destructive method of analyzing carbonaceous PM. While neutron radiography has been demonstrated for soot measurement in the past, the application has not considered the presence of unburned hydrocarbons, significant amounts of moisture nor examined complex geometrical configurations. The purpose of this work is to study a reliable non-destructive testing methodology using neutron radiography for measurement of soot distribution in automotive components. A soot standard (aluminium target) was designed and manufactured as a calibration tool. The standard is radiographed and used to measure the differences between various soot thickness and compositions. The radiograph images are analyzed to determine a calibration curve based upon the composition of the materials which can then be used for analysis of the automotive components. Experiments are performed using a diesel engine to produce soot deposits on exhaust piping. Soot distribution on exhaust piping is measured using neutron radiography. (authors)

  9. Measurement of Soot Deposition in Automotive Components Using Neutron Radiography

    International Nuclear Information System (INIS)

    Zekveld, David; Liu, Liaohui; Harrison, Andrew; Gill, Spencer; Harvel, Glenn; Chang, Jen-Shih

    2008-01-01

    About 40% of air pollution is generated by vehicles and transportation. The particulate matter (PM) emission significantly impacts human health. Fine particles below 2.5 μm (PM2.5) can enter the lungs and lead to respiratory problems. These particles not only influence human health, but also reduce the capability of many automobile exhaust heat exchanging devices. Neutron radiography is a non-destructive method of analyzing carbonaceous PM. While neutron radiography has been demonstrated for soot measurement in the past, the application has not considered the presence of unburned hydrocarbons, significant amounts of moisture nor examined complex geometrical configurations. The purpose of this work is to study a reliable non-destructive testing methodology using neutron radiography for measurement of soot distribution in automotive components. A soot standard (aluminium target) was designed and manufactured as a calibration tool. The standard is radiographed and used to measure the differences between various soot thickness and compositions. The radiograph images are analyzed to determine a calibration curve based upon the composition of the materials which can then be used for analysis of the automotive components. Experiments are performed using a diesel engine to produce soot deposits on exhaust piping. Soot distribution on exhaust piping is measured using neutron radiography. (authors)

  10. The pH-dependent adsorption of tributyltin to charcoals and soot

    International Nuclear Information System (INIS)

    Fang Liping; Borggaard, Ole K.; Marcussen, Helle; Holm, Peter E.; Bruun Hansen, Hans Christian

    2010-01-01

    Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m 2 g -1 have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m -2 ) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity. - Tributyltin adsorption to black carbon increases at increasing pH but charcoal exhibits electrostatic and hydrophobic adsorption, whereas soot only adsorbs hydrophobically.

  11. Reaction mechanism for the free-edge oxidation of soot by O 2

    KAUST Repository

    Raj, Abhijeet

    2012-11-01

    The reaction pathways for the oxidation by O 2 of polycyclic aromatic hydrocarbons present in soot particles are investigated using density functional theory at B3LYP/6-311++G(d,p) level of theory. For this, pyrene radical (4-pyrenyl) is chosen as the model molecule, as most soot models present in the literature employ the reactions involving the conversion of 4-pyrenyl to 4-phenanthryl by O 2 and OH to account for soot oxidation. Several routes for the formation of CO and CO 2 are proposed. The addition of O 2 on a radical site to form a peroxyl radical is found to be barrierless and exothermic with reaction energy of 188kJ/mol. For the oxidation reaction to proceed further, three pathways are suggested, each of which involve the activation energies of 104, 167 and 115kJ/mol relative to the peroxyl radical. The effect of the presence of H atom on a carbon atom neighboring the radical site on the energetics of carbon oxidation is assessed. Those intermediate species formed during oxidation with seven-membered rings or with a phenolic group are found to be highly stable. The rate constants evaluated using transition state theory in the temperature range of 300-3000K for the reactions involved in the mechanism are provided. © 2012 The Combustion Institute.

  12. Reaction mechanism for the free-edge oxidation of soot by O 2

    KAUST Repository

    Raj, Abhijeet; da Silva, Gabriel; Chung, Suk-Ho

    2012-01-01

    The reaction pathways for the oxidation by O 2 of polycyclic aromatic hydrocarbons present in soot particles are investigated using density functional theory at B3LYP/6-311++G(d,p) level of theory. For this, pyrene radical (4-pyrenyl) is chosen as the model molecule, as most soot models present in the literature employ the reactions involving the conversion of 4-pyrenyl to 4-phenanthryl by O 2 and OH to account for soot oxidation. Several routes for the formation of CO and CO 2 are proposed. The addition of O 2 on a radical site to form a peroxyl radical is found to be barrierless and exothermic with reaction energy of 188kJ/mol. For the oxidation reaction to proceed further, three pathways are suggested, each of which involve the activation energies of 104, 167 and 115kJ/mol relative to the peroxyl radical. The effect of the presence of H atom on a carbon atom neighboring the radical site on the energetics of carbon oxidation is assessed. Those intermediate species formed during oxidation with seven-membered rings or with a phenolic group are found to be highly stable. The rate constants evaluated using transition state theory in the temperature range of 300-3000K for the reactions involved in the mechanism are provided. © 2012 The Combustion Institute.

  13. Soot modeling of counterflow diffusion flames of ethylene-based binary mixture fuels

    KAUST Repository

    Wang, Yu; Raj, Abhijeet Dhayal; Chung, Suk-Ho

    2015-01-01

    of ethylene and its binary mixtures with methane, ethane and propane based on the method of moments. The soot model has 36 soot nucleation reactions from 8 PAH molecules including pyrene and larger PAHs. Soot surface growth reactions were based on a modified

  14. Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame

    KAUST Repository

    Li, Zepeng

    2016-01-01

    As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding

  15. Soot temperature and KL factor for biodiesel and diesel spray combustion in a constant volume combustion chamber

    KAUST Repository

    Zhang, Ji

    2013-07-01

    This paper presents measurements of the soot temperature and KL factor for biodiesel and diesel combustion in a constant volume chamber using a two-color technique. This technique uses a high-speed camera coupled with two narrowband filters (550. nm and 650. nm, 10. nm FWHM). After calibration, statistical analysis shows that the uncertainty of the two-color temperature is less than 5%, while it is about 50% for the KL factor. This technique is then applied to the spray combustion of biodiesel and diesel fuels under an ambient oxygen concentration of 21% and ambient temperatures of 800, 1000 and 1200. K. The heat release result shows higher energy utilization efficiency for biodiesel compared to diesel under all conditions; meanwhile, diesel shows a higher pressure increase due to its higher heating value. Biodiesel yields a lower temperature inside the flame area, a longer soot lift-off length, and a smaller soot area compared to diesel. Both the KL factor and the total soot with biodiesel are lower than with diesel throughout the entire combustion process, and this difference becomes larger as the ambient temperature decreases. Biodiesel shows approximately 50-100. K lower temperatures than diesel at the quasi-steady stage for 1000 and 1200. K ambient temperature, while diesel shows a lower temperature than biodiesel at 800. K ambient. This result may raise the question of how important the flame temperature is in explaining the higher NO. x emissions often observed during biodiesel combustion. Other factors may also play an important role in controlling NO. x emissions. Both biodiesel and diesel temperature measurements show a monotonic dependence on the ambient temperature. However, the ambient temperature appears to have a more significant effect on the soot formation and oxidation in diesel combustion, while biodiesel combustion soot characteristics shows relative insensitivity to the ambient temperature. © 2013 Elsevier Ltd.

  16. The pH-dependent adsorption of tributyltin to charcoals and soot

    Energy Technology Data Exchange (ETDEWEB)

    Fang Liping, E-mail: fang@life.ku.d [Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C (Denmark); Borggaard, Ole K.; Marcussen, Helle; Holm, Peter E.; Bruun Hansen, Hans Christian [Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C (Denmark)

    2010-12-15

    Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m{sup 2} g{sup -1} have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 {mu}mol m{sup -2}) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity. - Tributyltin adsorption to black carbon increases at increasing pH but charcoal exhibits electrostatic and hydrophobic adsorption, whereas soot only adsorbs hydrophobically.

  17. A Phenomenological Model for Prediction Auto-Ignition and Soot Formation of Turbulent Diffusion Combustion in a High Pressure Common Rail Diesel Engine

    Directory of Open Access Journals (Sweden)

    Qinghui Zhou

    2011-06-01

    Full Text Available A new phenomenological model, the TP (Temperature Phase model, is presented to carry out optimization calculations for turbulent diffusion combustion in a high-pressure common rail diesel engine. Temperature is the most important parameter in the TP model, which includes two parts: an auto-ignition and a soot model. In the auto-ignition phase, different reaction mechanisms are built for different zones. For the soot model, different methods are used for different temperatures. The TP model is then implemented in KIVA code instead of original model to carry out optimization. The results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP model, KIVA standard model and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics and can be a useful tool to study turbulent diffusion combustion.

  18. Spectral Signature of Radiative Forcing by East Asian Dust-Soot Mixture

    Science.gov (United States)

    Zhu, A.; Ramanathan, V.

    2007-12-01

    The Pacific Dust Experiment (PACDEX) provides the first detailed sampling of dust-soot mixtures from the western Pacific to the eastern Pacific Ocean. The data includes down and up spectral irradiance, mixing state of dust and soot, and other aerosol properties. This study attempts to simulate the radiative forcing by dust-soot mixtures during the experimental period. The MODTRAN band model was employed to investigate the spectral signatures of solar irradiance change induced by aerosols at moderate spectral resolutions. For the short wave band (300-1100nm) used in this study, the reduction of downward irradiance at surface by aerosols greatly enhances with increasing wavelength in the UV band (300-400nm), reaches a maximum in the blue band, then gradually decreases toward the red band. In the near-IR band (700-1100nm), irradiance reduction by aerosols shows great fluctuations in the band with center wavelength at around 940nm, 820nm, 720nm, 760nm, 690nm, where the aerosol effect is overwhelmed by the water vapor and O2 absorptions. The spectral pattern of irradiance reduction varies for different aerosol species. The maximum reduction lies at around 450nm for soot, and shifting to about 490nm for East Asian mineral dust. It's worth noting that although soot aerosols reduce more irradiance than East Asian dust in the UV and blue band, the impact of dust to the irradiance exceeds that by soot at the longer wavelength band (i.e. around 550nm). The reduction of irradiance by East Asian dust (soot) in the UV band, visible band, and near-IR accounts for about 6% (10%), 56% (64%), and 38% (26%) of total irradiance reduction. As large amount of soot aerosols are involved during the long range transport of East Asian dust, the optical properties of dust aerosols are modified with different mixing state with soot, the spectral pattern of the irradiance reduction will be changed. The study of aerosol forcing at moderate spectral resolutions has the potential application for

  19. Development and implementation of Intelligent Soot Blowing Optimization System for TNB Janamanjung

    Directory of Open Access Journals (Sweden)

    Sundaram Taneshwaren

    2017-01-01

    Full Text Available With an ever increasing demand for energy, Malaysia has become a nation that thrives on solid power generation sector to meet the energy demand and supply market. In a coal fired power plant, soot blowing operation is commonly used as a cleaning mechanism inside the boiler. There are many types of sequence available for this soot blowing operation. Hence, there is no efficient ways in utilizing the soot blowing operation to enhance the efficiency of boiler. Soot blowing optimization requires specific set of data preparation and simulation in order to achieve the best modal. Computational Fluid Dynamics (CFD is used to model a 700MW super-critical boiler, whereby parameters with effect to soot blowing operation is studied. Two different boiler condition is studied to analyze parameters in a clean and faulty boiler. Artificial Neural Network (ANN is used to train neural network modal with back propagation method to determine the best modal that will be used to predict soot blowing operation. Combination of neural network different number of neurons, hidden layers, training algorithm, and training functions is trained to find the modal with lowest error. By improving soot blowing sequence, efficiency of boiler can be improved by providing best parameter and model. This model is then used as a reference for advisory tool whereby a Neural Network Predictive Tool is suggested to the station to predict the soot blowing operation that occurs.

  20. Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

    Directory of Open Access Journals (Sweden)

    A. T. Ahern

    2016-12-01

    Full Text Available Biomass burning is a large source of light-absorbing refractory black carbon (rBC particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV ablation LAAPTOF and the IR vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.

  1. Effect of NO2 and water on the catalytic oxidation of soot

    DEFF Research Database (Denmark)

    Christensen, Jakob Munkholt; Grunwaldt, Jan-Dierk; Jensen, Anker Degn

    2017-01-01

    The influence of adding NO2 to 10 vol% O2/N2 on non-catalytic soot oxidation and soot oxidation in intimate or loose contact with a catalyst has been investigated. In non-catalytic soot oxidation the oxidation rate is increased significantly at lower temperatures by NO2. For soot oxidation in tig...... exhibited a volcano-curve dependence on the heat of oxygen chemisorption, and among the tested pure metals and oxides Cr2O3 was the most active catalyst. Further improvements were achieved with a FeaCrbOx binary oxide catalyst....

  2. Characterization of Diesel Soot Aggregates by Scattering and Extinction Methods

    Science.gov (United States)

    Kamimoto, Takeyuki

    2006-07-01

    Characteristics of diesel soot particles sampled from diesel exhaust of a common-rail turbo-charged diesel engine are quantified by scattering and extinction diagnostics using newly build two laser-based instruments. The radius of gyration representing the aggregates size is measured by the angular distribution of scattering intensity, while the soot mass concentration is measured by a two-wavelength extinction method. An approach to estimate the refractive index of diesel soot by an analysis of the extinction and scattering data using an aggregates scattering theory is proposed.

  3. Characterization of Diesel Soot Aggregates by Scattering and Extinction Methods

    International Nuclear Information System (INIS)

    Kamimoto, Takeyuki

    2006-01-01

    Characteristics of diesel soot particles sampled from diesel exhaust of a common-rail turbo-charged diesel engine are quantified by scattering and extinction diagnostics using newly build two laser-based instruments. The radius of gyration representing the aggregates size is measured by the angular distribution of scattering intensity, while the soot mass concentration is measured by a two-wavelength extinction method. An approach to estimate the refractive index of diesel soot by an analysis of the extinction and scattering data using an aggregates scattering theory is proposed

  4. Investigations of the long-term effects of LII on soot and bath gas

    KAUST Repository

    Cenker, Emre

    2017-08-24

    A combination of high-repetition rate imaging, laser extinction measurements, two-colour soot pyrometry imaging, and high-resolution transmission electron microscopy of thermophoretically sampled soot is used to investigate the long-term and permanent effects of rapid heating of in-flame soot during laser-induced incandescence (LII). Experiments are carried out on a laminar non-premixed co-annular ethylene/air flame with various laser fluences. The high-repetition rate images clearly show that the heated and the neighbouring laser-border zones undergo a permanent transformation after the laser pulse, and advect vertically with the flow while the permanent marking is preserved. The soot volume fraction at the heated zone reduces due to the sublimation of soot and the subsequent enhanced oxidation. At the laser-border zones, however, optical thickness increases that may be due to thermophoretic forces drawing hot particles towards relatively cooler zones and the rapid compression of the bath gas induced by the pressure waves created by the expansion of the desorbed carbon clusters. Additionally sublimed carbon clusters can condense onto existing particles and contribute to increase of the optical thickness. Time-resolved two-colour pyrometry imaging show that the increased temperature of soot both in the heated and neighbouring laser-border zones persists for several milliseconds. This can be associated to the increase in the bath-gas temperature, and a change in the wavelength-dependent emissivity of soot particles induced by the thermal annealing of soot. Ex-situ analysis show that the lattice structure of the soot sampled at the laser-border zones tend to change and soot becomes more graphitic. This may be attributed to thermal annealing induced by elevated temperature.

  5. Source identification of individual soot agglomerates in Arctic air by transmission electron microscopy

    Science.gov (United States)

    Weinbruch, S.; Benker, N.; Kandler, K.; Schütze, K.; Kling, K.; Berlinger, B.; Thomassen, Y.; Drotikova, T.; Kallenborn, R.

    2018-01-01

    Individual soot agglomerates collected at four different locations on the Arctic archipelago Svalbard (Norway) were characterised by transmission electron microscopy and energy-dispersive X-ray microanalysis. For source identification of the ambient soot agglomerates, samples from different local sources (coal burning power plants in Longyearbyen and Barentsburg, diesel and oil burning for power generation in Sveagruva and Ny Ålesund, cruise ship) as well as from other sources which may contribute to Arctic soot concentrations (biomass burning, aircraft emissions, diesel engines) were investigated. Diameter and graphene sheet separation distance of soot primary particles were found to be highly variable within each source and are not suited for source identification. In contrast, concentrations of the minor elements Si, P, K, Ca and Fe showed significant differences which can be used for source attribution. The presence/absence of externally mixed particle groups (fly ashes, tar balls, mercury particles) gives additional hints about the soot sources. Biomass/wood burning, ship emissions and coal burning in Barentsburg can be excluded as major source for ambient soot at Svalbard. The coal power plant in Longyearbyen is most likely a major source of soot in the settlement of Longyearbyen but does not contribute significantly to soot collected at the Global Atmosphere Watch station Zeppelin Mountain near Ny Ålesund. The most probable soot sources at Svalbard are aircraft emissions and diesel exhaust as well as long range transport of coal burning emissions.

  6. New Nanotech from an Ancient Material: Chemistry Demonstrations Involving Carbon-Based Soot

    Science.gov (United States)

    Campbell, Dean J.; Andrews, Mark J.; Stevenson, Keith J.

    2012-01-01

    Carbon soot has been known since antiquity, but has recently been finding new uses as a robust, inexpensive nanomaterial. This paper describes the superhydrophobic properties of carbon soot films prepared by combustion of candle wax or propane gas and introduces some of the optical absorption and fluorescence properties of carbon soot particles.…

  7. The Ice Nucleation Activity of Surface Modified Soot

    Science.gov (United States)

    Häusler, Thomas; Witek, Lorenz; Felgitsch, Laura; Hitzenberger, Regina; Grothe, Hinrich

    2017-04-01

    The ice nucleation efficiency of many important atmospheric particles remains poorly understood. Since soot is ubiquitous in the Earth's troposphere, they might have the potential to significantly impact the Earth's climate (Finlayson-Pitts and Pitts, 2000; Seinfeld and Pandis, 1998). Here we present the ice nucleation activity (INA) in immersion freezing mode of different types of soot. Therefor a CAST (combustion aerosol standard) generator was used to produce different kinds of soot samples. The CAST generator combusts a propane-air-mixture and deposits thereby produced soot on a polyvinyl fluoride filter. By varying the propane to air ratio, the amount of organic portion of the soot can be varied from black carbon (BC) with no organic content to brown carbon (BrC) with high organic content. To investigate the impact of functional sites of ice nuclei (IN), the soot samples were exposed to NO2 gas for a certain amount of time (30 to 360 minutes) to chemically modify the surface. Immersion freezing experiments were carried out in a unique reaction gadget. In this device a water-in-oil suspension (with the soot suspended in the aqueous phase) was cooled till the freezing point and was observed through a microscope (Pummer et al., 2012; Zolles et al., 2015) It was found that neither modified nor unmodified BC shows INA. On the contrary, unmodified BrC shows an INA at -32˚ C, which can be increased up to -20˚ C. The INA of BrC depends on the duration of NO2- exposure. To clarify the characteristics of the surface modifications, surface sensitive analysis like infrared spectroscopy and X-ray photoelectron spectroscopy were carried out. Finlayson-Pitts, B. J. and Pitts, J. N. J.: Chemistry of the Upper and Lower Atmosphere, Elsevier, New York, 2000. Pummer, B. G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos Chem Phys, 12, 2541-2550, 2012. Seinfeld, J

  8. An analysis of direct-injection spark-ignition (DISI) soot morphology

    Science.gov (United States)

    Barone, Teresa L.; Storey, John M. E.; Youngquist, Adam D.; Szybist, James P.

    2012-03-01

    We have characterized particle emissions produced by a 4-cylinder, 2.0 L DISI engine using transmission electron microscopy (TEM) and image analysis. Analyses of soot morphology provide insight to particle formation mechanisms and strategies for prevention. Particle emissions generated by two fueling strategies were investigated, early injection and injection modified for low particle number concentration emissions. A blend of 20% ethanol and 80% emissions certification gasoline was used for the study given the likelihood of increased ethanol content in widely available fuel. In total, about 200 particles and 3000 primary soot spherules were individually measured. For the fuel injection strategy which produced low particle number concentration emissions, we found a prevalence of single solid sub-25 nm particles and fractal-like aggregates. The modal diameter of single solid particles and aggregate primary particles was between 10 and 15 nm. Solid particles as small as 6 nm were present. Although nanoparticle aggregates had fractal-like morphology similar to diesel soot, the average primary particle diameter per aggregate had a much wider range that spanned from 7 to 60 nm. For the early fuel injection strategy, liquid droplets were prevalent, and the modal average primary particle diameter was between 20 and 25 nm. The presence of liquid droplets may have been the result of unburned fuel and/or lubricating oil originating from fuel impingement on the piston or cylinder wall; the larger modal aggregate primary particle diameter suggests greater fuel-rich zones in-cylinder than for the low particle number concentration point. However, both conditions produced aggregates with a wide range of primary particle diameters, which indicates heterogeneous fuel and air mixing.

  9. Comparative Study of Different Methods for Soot Sensing and Filter Monitoring in Diesel Exhausts

    Science.gov (United States)

    Feulner, Markus; Hagen, Gunter; Hottner, Kathrin; Redel, Sabrina; Müller, Andreas; Moos, Ralf

    2017-01-01

    Due to increasingly tighter emission limits for diesel and gasoline engines, especially concerning particulate matter emissions, particulate filters are becoming indispensable devices for exhaust gas after treatment. Thereby, for an efficient engine and filter control strategy and a cost-efficient filter design, reliable technologies to determine the soot load of the filters and to measure particulate matter concentrations in the exhaust gas during vehicle operation are highly needed. In this study, different approaches for soot sensing are compared. Measurements were conducted on a dynamometer diesel engine test bench with a diesel particulate filter (DPF). The DPF was monitored by a relatively new microwave-based approach. Simultaneously, a resistive type soot sensor and a Pegasor soot sensing device as a reference system measured the soot concentration exhaust upstream of the DPF. By changing engine parameters, different engine out soot emission rates were set. It was found that the microwave-based signal may not only indicate directly the filter loading, but by a time derivative, the engine out soot emission rate can be deduced. Furthermore, by integrating the measured particulate mass in the exhaust, the soot load of the filter can be determined. In summary, all systems coincide well within certain boundaries and the filter itself can act as a soot sensor. PMID:28218700

  10. Comparative Study of Different Methods for Soot Sensing and Filter Monitoring in Diesel Exhausts.

    Science.gov (United States)

    Feulner, Markus; Hagen, Gunter; Hottner, Kathrin; Redel, Sabrina; Müller, Andreas; Moos, Ralf

    2017-02-18

    Due to increasingly tighter emission limits for diesel and gasoline engines, especially concerning particulate matter emissions, particulate filters are becoming indispensable devices for exhaust gas after treatment. Thereby, for an efficient engine and filter control strategy and a cost-efficient filter design, reliable technologies to determine the soot load of the filters and to measure particulate matter concentrations in the exhaust gas during vehicle operation are highly needed. In this study, different approaches for soot sensing are compared. Measurements were conducted on a dynamometer diesel engine test bench with a diesel particulate filter (DPF). The DPF was monitored by a relatively new microwave-based approach. Simultaneously, a resistive type soot sensor and a Pegasor soot sensing device as a reference system measured the soot concentration exhaust upstream of the DPF. By changing engine parameters, different engine out soot emission rates were set. It was found that the microwave-based signal may not only indicate directly the filter loading, but by a time derivative, the engine out soot emission rate can be deduced. Furthermore, by integrating the measured particulate mass in the exhaust, the soot load of the filter can be determined. In summary, all systems coincide well within certain boundaries and the filter itself can act as a soot sensor.

  11. Comparative Study of Different Methods for Soot Sensing and Filter Monitoring in Diesel Exhausts

    Directory of Open Access Journals (Sweden)

    Markus Feulner

    2017-02-01

    Full Text Available Due to increasingly tighter emission limits for diesel and gasoline engines, especially concerning particulate matter emissions, particulate filters are becoming indispensable devices for exhaust gas after treatment. Thereby, for an efficient engine and filter control strategy and a cost-efficient filter design, reliable technologies to determine the soot load of the filters and to measure particulate matter concentrations in the exhaust gas during vehicle operation are highly needed. In this study, different approaches for soot sensing are compared. Measurements were conducted on a dynamometer diesel engine test bench with a diesel particulate filter (DPF. The DPF was monitored by a relatively new microwave-based approach. Simultaneously, a resistive type soot sensor and a Pegasor soot sensing device as a reference system measured the soot concentration exhaust upstream of the DPF. By changing engine parameters, different engine out soot emission rates were set. It was found that the microwave-based signal may not only indicate directly the filter loading, but by a time derivative, the engine out soot emission rate can be deduced. Furthermore, by integrating the measured particulate mass in the exhaust, the soot load of the filter can be determined. In summary, all systems coincide well within certain boundaries and the filter itself can act as a soot sensor.

  12. Asymptotic analysis soot model and experiment for a directed injection engine

    Science.gov (United States)

    Liu, Yongfeng; Pei, Pucheng; Xiong, Qinghui; Lu, Yong

    2012-09-01

    The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many researchers within the error range in the current computer speed. On the basis of the latest experimental results, TP (temperature phases) model is presented as a new soot model to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature and excess air factor are the most important two parameters in this model. When zone temperature T0.6, only the soot precursors—polycyclic aromatic hydrocarbons(PAH) is created and there is no soot emission. When zone temperature T ⩾ 1 500 K and excess air factor Φinjection time, variation of rail pressure and variation of speed among TP models. The experimental results indicate that the TP model can carry out optimization and computational fluid dynamics can be a tool to calculate for a high-pressure common rail directed injection diesel engine. The TP model result is closer than the use of the original KIVA-3V results of soot model accuracy by about 50% and TP model gives a new method for engine researchers.

  13. Experimental investigation on the morphology of soot aggregates from the burning of typical solid and liquid fuels

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Dongmei, E-mail: 20021567@163.com; Guo, Chenning [China Jiliang University, College of Quality and Safety Engineering (China); Shi, Long [RMIT University, Civil and Infrastructure Engineering Discipline, School of Engineering (Australia)

    2017-03-15

    Soot particles from the burning of typical fuels are one of the critical sources causing environmental problems and human disease. To understand the soot formation of these typical fuels, the size and morphology of soot aggregates produced from the burning of typical solid and liquid fuels, including diesel, kerosene, natural rubber (NR) latex foam, and wood crib, were studied by both extractive sampling and subsequent image analysis. The 2D and 3D fractal dimensions together with the diameter distribution of agglomerate and primary particles were analyzed for these four typical fuels. The average diameters of the primary particles were within 45–85 nm when sampling from different heights above the fire sources. Irregular sheet structures and flake-like masses were observed from the burning of NR latex foam and wood cribs. Superaggregates with a mean maximum length scale of over 100 μm were also found from the burning of all these four tested fuels. The fractal dimension of a single aggregate was 3 for all the tested fuels.

  14. Conductometric Sensor for Soot Mass Flow Detection in Exhausts of Internal Combustion Engines.

    Science.gov (United States)

    Feulner, Markus; Hagen, Gunter; Müller, Andreas; Schott, Andreas; Zöllner, Christian; Brüggemann, Dieter; Moos, Ralf

    2015-11-13

    Soot sensors are required for on-board diagnostics (OBD) of automotive diesel particulate filters (DPF) to detect filter failures. Widely used for this purpose are conductometric sensors, measuring an electrical current or resistance between two electrodes. Soot particles deposit on the electrodes, which leads to an increase in current or decrease in resistance. If installed upstream of a DPF, the "engine-out" soot emissions can also be determined directly by soot sensors. Sensors were characterized in diesel engine real exhausts under varying operation conditions and with two different kinds of diesel fuel. The sensor signal was correlated to the actual soot mass and particle number, measured with an SMPS. Sensor data and soot analytics (SMPS) agreed very well, an impressing linear correlation in a double logarithmic representation was found. This behavior was even independent of the used engine settings or of the biodiesel content.

  15. Conductometric Sensor for Soot Mass Flow Detection in Exhausts of Internal Combustion Engines

    Science.gov (United States)

    Feulner, Markus; Hagen, Gunter; Müller, Andreas; Schott, Andreas; Zöllner, Christian; Brüggemann, Dieter; Moos, Ralf

    2015-01-01

    Soot sensors are required for on-board diagnostics (OBD) of automotive diesel particulate filters (DPF) to detect filter failures. Widely used for this purpose are conductometric sensors, measuring an electrical current or resistance between two electrodes. Soot particles deposit on the electrodes, which leads to an increase in current or decrease in resistance. If installed upstream of a DPF, the “engine-out” soot emissions can also be determined directly by soot sensors. Sensors were characterized in diesel engine real exhausts under varying operation conditions and with two different kinds of diesel fuel. The sensor signal was correlated to the actual soot mass and particle number, measured with an SMPS. Sensor data and soot analytics (SMPS) agreed very well, an impressing linear correlation in a double logarithmic representation was found. This behavior was even independent of the used engine settings or of the biodiesel content. PMID:26580621

  16. Conductometric Sensor for Soot Mass Flow Detection in Exhausts of Internal Combustion Engines

    Directory of Open Access Journals (Sweden)

    Markus Feulner

    2015-11-01

    Full Text Available Soot sensors are required for on-board diagnostics (OBD of automotive diesel particulate filters (DPF to detect filter failures. Widely used for this purpose are conductometric sensors, measuring an electrical current or resistance between two electrodes. Soot particles deposit on the electrodes, which leads to an increase in current or decrease in resistance. If installed upstream of a DPF, the “engine-out” soot emissions can also be determined directly by soot sensors. Sensors were characterized in diesel engine real exhausts under varying operation conditions and with two different kinds of diesel fuel. The sensor signal was correlated to the actual soot mass and particle number, measured with an SMPS. Sensor data and soot analytics (SMPS agreed very well, an impressing linear correlation in a double logarithmic representation was found. This behavior was even independent of the used engine settings or of the biodiesel content.

  17. Impacts of fuel formulation and engine operating parameters on the nanostructure and reactivity of diesel soot

    Science.gov (United States)

    Yehliu, Kuen

    This study focuses on the impacts of fuel formulations on the reactivity and nanostructure of diesel soot. A 2.5L, 4-cylinder, turbocharged, common rail, direct injection light-duty diesel engine was used in generating soot samples. The impacts of engine operating modes and the start of combustion on soot reactivity were investigated first. Based on preliminary investigations, a test condition of 2400 rpm and 64 Nm, with single and split injection strategies, was chosen for studying the impacts of fuel formulation on the characteristics of diesel soot. Three test fuels were used: an ultra low sulfur diesel fuel (BP15), a pure soybean methyl-ester (B100), and a synthetic Fischer-Tropsch fuel (FT) produced in a gas-to-liquid process. The start of injection (SOI) and fuel rail pressures were adjusted such that the three test fuels have similar combustion phasing, thereby facilitating comparisons between soots from the different fuels. Soot reactivity was investigated by thermogravimetric analysis (TGA). According to TGA, B100 soot exhibits the fastest oxidation on a mass basis followed by BP15 and FT derived soots in order of apparent rate constant. X-ray photoelectron spectroscopy (XPS) indicates no relation between the surface oxygen content and the soot reactivity. Crystalline information for the soot samples was obtained using X-ray diffraction (XRD). The basal plane diameter obtained from XRD was inversely related to the apparent rate constants for soot oxidation. For comparison, high resolution transmission electron microscopy (HRTEM) provided images of the graphene layers. Quantitative image analysis proceeded by a custom algorithm. B100 derived soot possessed the shortest mean fringe length and greatest mean fringe tortuosity. This suggests soot (nano)structural disorder correlates with a faster oxidation rate. Such results are in agreement with the X-ray analysis, as the observed fringe length is a measure of basal plane diameter. Moreover the relation

  18. A comparative study on the sooting tendencies of various 1-alkene fuels in counterflow diffusion flames

    KAUST Repository

    Wang, Yu; Park, Sungwoo; Sarathy, Mani; Chung, Suk-Ho

    2018-01-01

    -alkenes through experiments and numerical simulations for counterflow diffusion flames. Soot and PAH formation tendencies of 1-alkene fuels, including ethylene (C2H4), propene (C3H6), 1-butene (1-C4H8), 1-pentene (1-C5H10), 1-hexene (1-C6H12) and 1-octene

  19. Laser-induced incandescence: Towards quantitative soot volume fraction measurements

    Energy Technology Data Exchange (ETDEWEB)

    Tzannis, A P; Wienbeucker, F; Beaud, P; Frey, H -M; Gerber, T; Mischler, B; Radi, P P [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Laser-Induced Incandescence has recently emerged as a versatile tool for measuring soot volume fraction in a wide range of combustion systems. In this work we investigate the essential features of the method. LII is based on the acquisition of the incandescence of soot when heated through a high power laser pulse. Initial experiments have been performed on a model laboratory flame. The behaviour of the LII signal is studied experimentally. By applying numerical calculations we investigate the possibility to obtain two-dimensional soot volume fraction distributions. For this purpose a combination of LII with other techniques is required. This part is discussed in some extent and the future work is outlined. (author) 4 figs., 3 refs.

  20. Intake condition requirements for biodiesel modulated kinetic combustion concept to achieve a simultaneous NOx and soot removal

    International Nuclear Information System (INIS)

    Kim, Keunsoo; Oh, Seungmook; Lee, Yonggyu; Lee, Sunyoup; Kim, Junghwan

    2015-01-01

    Highlights: • MK LTC combustion was investigated under various intake conditions. • BD20 MK combustion achieved NO x and soot removal at achievable intake conditions. • The BD20 best point showed lower ISFC and COV IMEP than the diesel best point. • Higher intake pressure showed higher efficiency at all intake oxygen concentrations. • Simultaneous NO x and soot removal required 200 kPa intake pressure at a medium load. - Abstract: The fuel oxygen contained in oxygenated fuels can help reduce harmful engine-out emissions and improve the combustion process in compression-ignition engines. The use of soybean methylene ether biodiesel in the low-temperature combustion (LTC) regime has the potential to suppress soot formation and nitrogen oxides (NO x ) emissions even further, which eventually alleviates the burden of the after-treatment system. In the present study, the effects of the intake pressure and injection timing on the combustion and emissions of the modulated kinetic (MK) combustion concept with ultra-low sulfur diesel and 20% biodiesel blended fuel (BD20) were investigated in a single-cylinder CI engine. The intake pressure was varied from 100 kPa to 250 kPa for the intake oxygen concentration range of 11–17%. The engine test results indicate that simultaneous reductions in both the NO x and soot emissions were realized under the MK LTC combustion regime. At the best operating point, BD20 achieved the simultaneous NO x and soot removal at a lower intake pressure and lower EGR level than diesel, which led to better fuel economy. In addition, BD20 achieved acceptable levels of combustion stability and noise level

  1. CFD studies of soot production in a coflow laminar diffusion flame under conditions of micro-gravity in fire safety

    Directory of Open Access Journals (Sweden)

    Arnaud Mbainguebem

    2017-07-01

    Full Text Available This work which is in the fire safety framework is focused on a numerical study of the production of soot in a laminar diffusion flame, under different conditions of micro-gravity in unsteady regime. It is intended to evaluate the temperature and rate at which the production of soot is predominant, to quantify their concentrations and volume fraction in dispersion. It has been accomplished by modification of the ReactingFOAM application source code of the OpenFOAM-2.3.0 by introducing for the first time, the equations of concentration transport and of volume fractions of soot. The results of the different values of gravity obtained are compared with the normal value of gravity and we ascertain that the results obtained were satisfactory and show the ability of the code to predict the speed and temperature of the formation of soot, their concentrations and their volume fractions. The maximum peak of the volume fraction varies from 7 × 10−8 to 4.5 × 10−6. The maximum temperature, which was 2423 K before changing the code, is about 2410 K after implementation of our modifications due to the taking into account of the numerical model.

  2. Detection of Soot Using a Resistivity Sensor Device Employing Thermophoretic Particle Deposition

    Directory of Open Access Journals (Sweden)

    Doina Lutic

    2010-01-01

    Full Text Available Results are reported for thermophoretic deposition of soot particles on resistivity sensors as a monitoring technique for diesel exhaust particles with the potential of improved detection limit and sensitivity. Soot with similar characteristics as from diesel exhausts was generated by a propane flame and diluted in stages. The soot in a gas flow at 240–270C∘ was collected on an interdigitated electrode structure held at a considerably lower temperature, 105–125C∘. The time delay for reaching measurable resistance values, the subsequent rate, and magnitude of resistance decrease were a function of the distance between the fingers in the electrodes and the degree of dilution of the soot containing flow. Soot deposition and subsequent removal by heating the sensor support was also performed in a real diesel exhaust. Good similarities between the behavior in our laboratory system and the real diesel exhaust were noticed.

  3. Soot measurements for diesel and biodiesel spray combustion under high temperature highly diluted ambient conditions

    KAUST Repository

    Zhang, Ji

    2014-11-01

    This paper presents the soot temperature and KL factor for biodiesel, namely fatty acid methyl ester (FAME) and diesel fuel combustion in a constant volume chamber using a two-color technique. The KL factor is a parameter for soot concentration, where K is an absorption coefficient and proportional to the number density of soot particles, L is the geometric thickness of the flame along the optical detection axis, and KL factor is proportional to soot volume fraction. The main objective is to explore a combustion regime called high-temperature and highly-diluted combustion (HTHDC) and compare it with the conventional and low-temperature combustion (LTC) modes. The three different combustion regimes are implemented under different ambient temperatures (800 K, 1000 K, and 1400 K) and ambient oxygen concentrations (10%, 15%, and 21%). Results are presented in terms of soot temperature and KL factor images, time-resolved pixel-averaged soot temperature, KL factor, and spatially integrated KL factor over the soot area. The time-averaged results for these three regimes are compared for both diesel and biodiesel fuels. Results show complex combined effects of the ambient temperature and oxygen concentration, and that two-color temperature for the HTHDC mode at the 10% oxygen level can actually be lower than the conventional mode. Increasing ambient oxygen and temperature increases soot temperature. Diesel fuel results in higher soot temperature than biodiesel for all three regimes. Results also show that diesel and biodiesel fuels have very different burning and sooting behavior under the three different combustion regimes. For diesel fuel, the HTHDC regime offers better results in terms of lower soot than the conventional and LTC regimes, and the 10% O2, 1400 K ambient condition shows the lowest soot concentration while maintaining a moderate two-color temperature. For biodiesel, the 15% O2, 800 K ambient condition shows some advantages in terms of reducing soot

  4. Interdigitated Pt-GaN Schottky interfaces for high-temperature soot-particulate sensing

    Science.gov (United States)

    So, Hongyun; Hou, Minmin; Jain, Sambhav R.; Lim, Jongwoo; Senesky, Debbie G.

    2016-04-01

    A microscale soot-particulate sensor using interdigitated platinum-gallium nitride (Pt-GaN) Schottky interfaces was developed to monitor fine soot particles within high-temperature environments (e.g., combustion exhausts and flues). Upon exposure to soot particles (30 to 50 nm in diameter) from an experimental chimney, an increased current (∼43.6%) is observed through the back-to-back Schottky contact to n-type GaN. This is attributed to a reduction in the effective Schottky barrier height (SBH) of ∼10 meV due to the electric field from the charged soot particles in the depletion region and exposed GaN surface. Furthermore, the microfabricated sensor was shown to recover sensitivity and regenerate the sensing response (∼11 meV SBH reduction) after exposure to temperature as high as 550 °C. This study supports the feasibility of a simple and reliable soot sensor to meet the increasing market demand for particulate matter sensing in harsh environments.

  5. Subsonic aircraft soot. A tracer documenting barriers to inter-hemispheric mixing

    Energy Technology Data Exchange (ETDEWEB)

    Pueschel, R F [NASA Ames Research Center, Moffett Field, CA (United States)

    1998-12-31

    Meridional observations of soot aerosols and radioactive {sup 14}C, and models of the geographic distribution of nuclear bomb-released {sup 14}C and aircraft-emitted NO{sub x}, all show strong gradients between the hemispheres. Reason for it are decade-long inter-hemispheric mixing times which are much in excess of yearlong stratospheric residence times of tracers. Vertical mixing of soot aerosol is not corroborated by {sup 14}C observations. The reason could be radiometric forces that act on strongly absorbing soot. (author) 10 refs.

  6. Subsonic aircraft soot. A tracer documenting barriers to inter-hemispheric mixing

    Energy Technology Data Exchange (ETDEWEB)

    Pueschel, R.F. [NASA Ames Research Center, Moffett Field, CA (United States)

    1997-12-31

    Meridional observations of soot aerosols and radioactive {sup 14}C, and models of the geographic distribution of nuclear bomb-released {sup 14}C and aircraft-emitted NO{sub x}, all show strong gradients between the hemispheres. Reason for it are decade-long inter-hemispheric mixing times which are much in excess of yearlong stratospheric residence times of tracers. Vertical mixing of soot aerosol is not corroborated by {sup 14}C observations. The reason could be radiometric forces that act on strongly absorbing soot. (author) 10 refs.

  7. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts

    Directory of Open Access Journals (Sweden)

    R. Prasad

    2011-05-01

    Full Text Available CuO-CeO2 systems have been proposed as a promising catalyst for low temperature diesel-soot oxidation. CuO-CeO2 catalysts prepared by various methods were examined for air oxidation of the soot in a semi batch tubular flow reactor. The air oxidation of soot was carried out under tight contact with soot/catalyst ratio of 1/10. Air flow rate was 150 ml/min, soot-catalyst mixture was 110 mg, heating rate was 5 0C/min. Prepared catalysts were calcined at 500 0C and their stability was examined by further heating to 800 0C for 4 hours. It was found that the selectivity of all the catalysts was nearly 100% to CO2 production. It was observed that the activity and stability of the catalysts greatly influenced by the preparation methods. The strong interaction between CuO and CeO2 is closely related to the preparation route that plays a crucial role in the soot oxidation over the CuO-CeO2 catalysts. The ranking order of the preparation methods of the catalysts in the soot oxidation performance is as follows: sol-gel > urea nitrate combustion > Urea gelation method > thermal decomposition > co-precipitation. Copyright © 2011 BCREC UNDIP. All rights reserved.(Received: 27th June 2010, Revised: 7th August 2010; Accepted: 13rd October 2010[How to Cite: R. Prasad, V.R. Bella. (2011. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 15-21. doi:10.9767/bcrec.6.1.822.15-21][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.822.15-21 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/822 | View in 

  8. Potential of secondary aerosol formation from Chinese gasoline engine exhaust.

    Science.gov (United States)

    Du, Zhuofei; Hu, Min; Peng, Jianfei; Guo, Song; Zheng, Rong; Zheng, Jing; Shang, Dongjie; Qin, Yanhong; Niu, He; Li, Mengren; Yang, Yudong; Lu, Sihua; Wu, Yusheng; Shao, Min; Shuai, Shijin

    2018-04-01

    Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds (VOCs). However, little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4-5hr simulation, which was estimated to represent more than 10days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol (SOA) production was 426±85mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China. Copyright © 2017. Published by Elsevier B.V.

  9. Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames

    International Nuclear Information System (INIS)

    Demarco, R.; Nmira, F.; Consalvi, J.L.

    2013-01-01

    The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C 1 –C 3 hydrocarbon–air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated

  10. Simultaneous measurement of the concentrations of soot particles and gas species in light hydrocarbon flames using mass spectrometry

    International Nuclear Information System (INIS)

    Li, Qingxun; Liu, Fang; Wang, Dezheng; Wang, Tiefeng

    2014-01-01

    Besides gas species concentrations, soot volume fractions are also important data in the study of flames. This work describes the simultaneous measurement of the concentrations of soot and gas species in light hydrocarbon flames by in situ sampling and mass spectrometry (MS).The reaction medium was frozen by sampling into a very low-pressure tube, and the soot selectivity (proportion of carbon atoms in the reactant converted to soot) was determined from the C and H mass balances using the measured concentrations of the gas species and the mass of soot present per unit gas volume. The H/C ratio of the soot was measured by a thermogravimetry–mass spectrometry combination. The soot volume fraction was calculated from the soot selectivity and density of the soot. The soot selectivity measured by this reduced pressure sampling mass spectrometry (RPSMS) method was verified by measurements using the gravimetric sampling technique where the mass of soot collected in a volume of gas was weighed by a high precision balance. For most of the measurements, the uncertainty in the soot volume fraction was ±5%, but this would be larger when the soot volume fractions are less than 1 ppm. For demonstration, the RPSMS method was used to study a methane fuel-rich flame where the soot volume fractions were 1–5 ppm. The simultaneous measurement of concentrations of soot and gas species is useful for the quantitative study of flames. (paper)

  11. Soot Reactivity in Conventional Combustion and Oxy-fuel Combustion Environments

    DEFF Research Database (Denmark)

    Abián, María; Jensen, Anker D.; Glarborg, Peter

    2012-01-01

    A study of the reactivity of soot produced from ethylene pyrolysis at different temperatures and CO2 atmospheres toward O2 and CO2 has been carried out using a thermogravimetric analyzer. The purpose was to quantify how soot reactivity is affected by the gas environment and temperature history of...

  12. A multi-probe thermophoretic soot sampling system for high-pressure diffusion flames

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, Alex M.; Gülder, Ömer L. [Institute for Aerospace Studies, University of Toronto, Toronto, Ontario M3H 5T6 (Canada)

    2016-05-15

    Optical diagnostics and physical probing of the soot processes in high pressure combustion pose challenges that are not faced in atmospheric flames. One of the preferred methods of studying soot in atmospheric flames is in situ thermophoretic sampling followed by transmission electron microscopy imaging and analysis for soot sizing and morphology. The application of this method of sampling to high pressures has been held back by various operational and mechanical problems. In this work, we describe a rotating disk multi-probe thermophoretic soot sampling system, driven by a microstepping stepper motor, fitted into a high-pressure chamber capable of producing sooting laminar diffusion flames up to 100 atm. Innovative aspects of the sampling system design include an easy and precise control of the sampling time down to 2.6 ms, avoidance of the drawbacks of the pneumatic drivers used in conventional thermophoretic sampling systems, and the capability to collect ten consecutive samples in a single experimental run. Proof of principle experiments were performed using this system in a laminar diffusion flame of methane, and primary soot diameter distributions at various pressures up to 10 atm were determined. High-speed images of the flame during thermophoretic sampling were recorded to assess the influence of probe intrusion on the flow field of the flame.

  13. The formation of aromatics and PAH's in laminar flames

    International Nuclear Information System (INIS)

    Marinov, N M; Pitz, W J; Westbrook, C K

    1999-01-01

    The formation of aromatics and PAH's is an important problem in combustion. These compounds are believed to contribute to the formation of soot whose emission from diesel engines is regulated widely throughout the industrial world. Additionally, the United States Environmental Protection Agency regulates the emission of many aromatics and PAH species from stationary industrial burners, under the 1990 Clean Air Act Amendments. The above emission regulations have created much interest in understanding how these species are formed in combustion systems. Much previous work has been done on aromatics and PAH's. The work is too extensive to review here, but is reviewed in Reference 1. A few recent developments are highlighted here. McEnally, Pfefferle and coworkers have studied aromatic, PAH and soot formation in a variety of non-premixed flames with hydrocarbon additives[2-4]. They found additives that contain a C5 ring increase the concentration of aromatics and soot[4]. Howard and coworkers have studied the formation of aromatic and PAH's in low pressure, premixed, laminar hydrocarbon flames. They found the cyclopentadienyl radical to be a key species in naphthalene formation in a fuel-rich, benzene/Ar/O2 flame[5

  14. Comparison of soot formation for diesel and jet-a in a constant volume combustion chamber using two-color pyrometry

    KAUST Repository

    Jing, Wei; Roberts, William L.; Fang, Tiegang

    2014-01-01

    The measurement of the two-color line of sight soot and KL factor for NO.2 diesel and jet-A fuels was conducted in an optical constant volume combustion chamber by using a high speed camera under 1000 K ambient temperature and varied oxygen

  15. Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames

    Science.gov (United States)

    Demarco, R.; Nmira, F.; Consalvi, J. L.

    2013-05-01

    The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C1-C3 hydrocarbon-air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated k (FSCK

  16. Buildup of aerosol precursor gases and sulfur-induced activation of soot in nascent jet aircraft exhaust plumes

    Energy Technology Data Exchange (ETDEWEB)

    Kaercher, B.; Hirschberg, M.M.; Fabian, P. [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung; Gerz, T. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere

    1997-12-31

    Research issues concerning the chemical transformation of exhaust trace gases are summarized. The photochemical evolution of NO{sub x} early in the plume is strongly coupled to plume mixing. Substantial amounts of HNO{sub 3} are generated in nascent plumes even if no NO{sub 2} is emitted. The production of H{sub 2}SO{sub 4} becomes very efficient if part of the fuel sulfur is emitted as SO{sub 3}. Each emitted soot particle can acquire 1-10% by mass fully oxidized sulfur molecules prior to binary homogeneous nucleation, if a few percent of the exhaust SO{sub x} are emitted as SO{sub 3}, indicating an important activation pathway for soot, and leading to a marked enhancement of new aerosol formation and growth rates. (author) 11 refs.

  17. Buildup of aerosol precursor gases and sulfur-induced activation of soot in nascent jet aircraft exhaust plumes

    Energy Technology Data Exchange (ETDEWEB)

    Kaercher, B; Hirschberg, M M; Fabian, P [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung; Gerz, T [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere

    1998-12-31

    Research issues concerning the chemical transformation of exhaust trace gases are summarized. The photochemical evolution of NO{sub x} early in the plume is strongly coupled to plume mixing. Substantial amounts of HNO{sub 3} are generated in nascent plumes even if no NO{sub 2} is emitted. The production of H{sub 2}SO{sub 4} becomes very efficient if part of the fuel sulfur is emitted as SO{sub 3}. Each emitted soot particle can acquire 1-10% by mass fully oxidized sulfur molecules prior to binary homogeneous nucleation, if a few percent of the exhaust SO{sub x} are emitted as SO{sub 3}, indicating an important activation pathway for soot, and leading to a marked enhancement of new aerosol formation and growth rates. (author) 11 refs.

  18. Electrometric aviation soot monitor, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a highly sensitive and portable device to monitor soot particle mass distribution from aircraft engine exhaust. The proposed method is based on...

  19. A mechanistic study on the simultaneous elimination of soot and nitric oxide from engine exhaust

    KAUST Repository

    Raj, Abhijeet; Zainuddin, Zakwan; Sander, Markus; Kraft, Markus

    2011-01-01

    The non-catalytic interaction between soot and nitric oxide (NO) resulting in their simultaneous elimination was studied on different types of reactive site present on soot. The reaction mechanism proposed previously was extended by including seven new reaction pathways for which the reaction energetics and kinetics were studied using density functional theory and transition state theory. This has led to the calculation of a new rate for the removal of carbon monoxide (CO) from soot. The new pathways have been added to our polycyclic aromatic hydrocarbon (PAH) growth model and used to simulate the NO-soot interaction to form CO, N2 and N2O. The simulation results show satisfactory agreement with experiment for the new CO removal rate. The NO-soot reaction was found to depend strongly on the soot site type and temperature. For a set of temperatures, computed PAH structures were analysed to determine the functional groups responsible for the decrease in the reactivity of soot with NO with increasing reaction time. In isothermal conditions, it was found that as temperature is increased, the number of oxygen atoms remaining on the soot surface decreases, while the number of nitrogen atoms increases for a given reaction time. © 2010 Elsevier Ltd. All rights reserved.

  20. A mechanistic study on the simultaneous elimination of soot and nitric oxide from engine exhaust

    KAUST Repository

    Raj, Abhijeet

    2011-04-01

    The non-catalytic interaction between soot and nitric oxide (NO) resulting in their simultaneous elimination was studied on different types of reactive site present on soot. The reaction mechanism proposed previously was extended by including seven new reaction pathways for which the reaction energetics and kinetics were studied using density functional theory and transition state theory. This has led to the calculation of a new rate for the removal of carbon monoxide (CO) from soot. The new pathways have been added to our polycyclic aromatic hydrocarbon (PAH) growth model and used to simulate the NO-soot interaction to form CO, N2 and N2O. The simulation results show satisfactory agreement with experiment for the new CO removal rate. The NO-soot reaction was found to depend strongly on the soot site type and temperature. For a set of temperatures, computed PAH structures were analysed to determine the functional groups responsible for the decrease in the reactivity of soot with NO with increasing reaction time. In isothermal conditions, it was found that as temperature is increased, the number of oxygen atoms remaining on the soot surface decreases, while the number of nitrogen atoms increases for a given reaction time. © 2010 Elsevier Ltd. All rights reserved.

  1. Secondary organic aerosols: Formation potential and ambient data

    DEFF Research Database (Denmark)

    Barthelmie, R.J.; Pryor, S.C.

    1997-01-01

    Organic aerosols comprise a significant fraction of the total atmospheric particle loading and are associated with radiative forcing and health impacts. Ambient organic aerosol concentrations contain both a primary and secondary component. Herein, fractional aerosol coefficients (FAC) are used...... in conjunction with measurements of volatile organic compounds (VOC) to predict the formation potential of secondary organic aerosols (SOA) in the Lower Fraser Valley (LEV) of British Columbia. The predicted concentrations of SOA show reasonable accord with ambient aerosol measurements and indicate considerable...

  2. The competition between mineral dust and soot ice nuclei in mixed-phase clouds (Invited)

    Science.gov (United States)

    Murray, B. J.; Atkinson, J.; Umo, N.; Browse, J.; Woodhouse, M. T.; Whale, T.; Baustian, K. J.; Carslaw, K. S.; Dobbie, S.; O'Sullivan, D.; Malkin, T. L.

    2013-12-01

    The amount of ice present in mixed-phase clouds, which contain both supercooled liquid water droplets and ice particles, affects cloud extent, lifetime, particle size and radiative properties. The freezing of cloud droplets can be catalysed by the presence of aerosol particles known as ice nuclei. In this talk our recent laboratory and global aerosol modelling work on mineral dust and soot ice nuclei will be presented. We have performed immersion mode experiments to quantify ice nucleation by the individual minerals which make up desert mineral dusts and have shown that the feldspar component, rather than the clay component, is most important for ice nucleation (Atkinson et al. 2013). Experiments with well-characterised soot generated with eugenol, an intermediate in biomass burning, and n-decane show soot has a significant ice nucleation activity in mixed-phase cloud conditions. Our results for soot are in good agreement with previous results for acetylene soot (DeMott, 1990), but extend the efficiency to much higher temperatures. We then use a global aerosol model (GLOMAP) to map the distribution of soot and feldspar particles on a global basis. We show that below about -15oC that dust and soot together can explain most observed ice nuclei in the Earth's atmosphere, while at warmer temperatures other ice nuclei types are needed. We show that in some regions soot is the most important ice nuclei (below -15oC), while in others feldspar dust dominates. Our results suggest that there is a strong anthropogenic contribution to the ice nuclei population, since a large proportion of soot aerosol in the atmosphere results from human activities. Atkinson, J. D., Murray, B. J., Woodhouse, M. T., Carslaw, K. S., Whale, T. F., Baustian, K. J., Dobbie, S., O'Sullivan, D., and Malkin, T. L.: The importance of feldspar for ice nucleation by mineral dust in mixed-phase clouds, Nature, 10.1038/nature12278, (2013). Demott, P. J. 1990. An Exploratory-Study of Ice Nucleation by Soot

  3. Soot particle size measurements in ethylene diffusion flames at elevated pressures

    KAUST Repository

    Steinmetz, Scott

    2016-05-07

    Soot particle size is investigated in laminar nitrogen-diluted ethylene coflow diffusion flames at 4, 8, 12 and 16 atm. Line of sight attenuation and scattering are used to measure two-dimensional soot volume fraction and particle size fields for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh-Debye-Gans polydisperse fractal aggregate theories to provide two estimates of particle size. An increase in overall particle sizes with pressure is found, consistent with similar one-dimensional studies. Particle diameters in the annulus of the flame increase faster with pressure than those on centerline. Contrary to previous studies, the dependence of particle size on pressure was found to taper off between 8 and 12 atm, with little observed growth beyond 12 atm. The measurements provide additional data for one of the International Sooting Flame (ISF) workshop\\'s target pressurized flames.

  4. Incipient Soot Formation in Rich Partially Premixed Flames under High Pressure Conditions of Relevance to Compression-Ignition Engines

    Science.gov (United States)

    2017-09-09

    a Laminar Premixed Flame, Aerosol Reaction Engineering , Center for Aerosol science and Engineering (CASE) Workshop 2016, Saint Louis, Missouri, May...Publication Type: Conference Paper or Presentation Conference Name: Aerosol Reaction Engineering , Center for Aerosol science and Engineering (CASE...measurements of critical soot precursors up to 3-ring aromatics is available online to modelers to improve the chemical reaction mechanism [24]. To give a

  5. Soot and Spectral Radiation Modeling for a High-Pressure Turbulent Spray Flame

    Energy Technology Data Exchange (ETDEWEB)

    Ferreryo-Fernandez, Sebastian [Pennsylvania State Univ., University Park, PA (United States); Paul, Chandan [Pennsylvania State Univ., University Park, PA (United States); Sircar, Arpan [Pennsylvania State Univ., University Park, PA (United States); Imren, Abdurrahman [Pennsylvania State Univ., University Park, PA (United States); Haworth, Daniel C [Pennsylvania State Univ., University Park, PA (United States); Roy, Somesh P [Marquette University (United States); Modest, Michael F [University of California Merced (United States)

    2017-04-26

    Simulations are performed of a transient high-pressure turbulent n-dodecane spray flame under engine-relevant conditions. An unsteady RANS formulation is used, with detailed chemistry, a semi-empirical two-equation soot model, and a particle-based transported composition probability density function (PDF) method to account for unresolved turbulent fluctuations in composition and temperature. Results from the PDF model are compared with those from a locally well-stirred reactor (WSR) model to quantify the effects of turbulence-chemistry-soot interactions. Computed liquid and vapor penetration versus time, ignition delay, and flame lift-off height are in good agreement with experiment, and relatively small differences are seen between the WSR and PDF models for these global quantities. Computed soot levels and spatial soot distributions from the WSR and PDF models show large differences, with PDF results being in better agreement with experimental measurements. An uncoupled photon Monte Carlo method with line-by-line spectral resolution is used to compute the spectral intensity distribution of the radiation leaving the flame. This provides new insight into the relative importance of molecular gas radiation versus soot radiation, and the importance of turbulent fluctuations on radiative heat transfer.

  6. Fragmentation and bond strength of airborne diesel soot agglomerates

    Directory of Open Access Journals (Sweden)

    Messerer Armin

    2008-06-01

    Full Text Available Abstract Background The potential of diesel soot aerosol particles to break up into smaller units under mechanical stress was investigated by a direct impaction technique which measures the degree of fragmentation of individual agglomerates vs. impact energy. Diesel aerosol was generated by an idling diesel engine used for passenger vehicles. Both the aerosol emitted directly and aerosol that had undergone additional growth by Brownian coagulation ("aging" was investigated. Optionally a thermo-desoption technique at 280°C was used to remove all high-volatility and the majority of low-volatility HC adsorbates from the aerosol before aging. Results It was found that the primary soot agglomerates emitted directly from the engine could not be fragmented at all. Soot agglomerates permitted to grow additionally by Brownian coagulation of the primary emitted particles could be fragmented to a maximum of 75% and 60% respectively, depending on whether adsorbates were removed from their surface prior to aging or not. At most, these aged agglomerates could be broken down to roughly the size of the agglomerates from the primary emission. The energy required for a 50% fragmentation probability of all bonds within an agglomerate was reduced by roughly a factor of 2 when aging "dry" agglomerates. Average bond energies derived from the data were 0.52*10-16 and 1.2*10-16 J, respectively. This is about 2 orders of magnitude higher than estimates for pure van-der-Waals agglomerates, but agrees quite well with other observations. Conclusion Although direct conclusions regarding the behavior of inhaled diesel aerosol in contact with body fluids cannot be drawn from such measurements, the results imply that highly agglomerated soot aerosol particles are unlikely to break up into units smaller than roughly the size distribution emitted as tail pipe soot.

  7. Fragmentation and bond strength of airborne diesel soot agglomerates

    Science.gov (United States)

    Rothenbacher, Sonja; Messerer, Armin; Kasper, Gerhard

    2008-01-01

    Background The potential of diesel soot aerosol particles to break up into smaller units under mechanical stress was investigated by a direct impaction technique which measures the degree of fragmentation of individual agglomerates vs. impact energy. Diesel aerosol was generated by an idling diesel engine used for passenger vehicles. Both the aerosol emitted directly and aerosol that had undergone additional growth by Brownian coagulation ("aging") was investigated. Optionally a thermo-desoption technique at 280°C was used to remove all high-volatility and the majority of low-volatility HC adsorbates from the aerosol before aging. Results It was found that the primary soot agglomerates emitted directly from the engine could not be fragmented at all. Soot agglomerates permitted to grow additionally by Brownian coagulation of the primary emitted particles could be fragmented to a maximum of 75% and 60% respectively, depending on whether adsorbates were removed from their surface prior to aging or not. At most, these aged agglomerates could be broken down to roughly the size of the agglomerates from the primary emission. The energy required for a 50% fragmentation probability of all bonds within an agglomerate was reduced by roughly a factor of 2 when aging "dry" agglomerates. Average bond energies derived from the data were 0.52*10-16 and 1.2*10-16 J, respectively. This is about 2 orders of magnitude higher than estimates for pure van-der-Waals agglomerates, but agrees quite well with other observations. Conclusion Although direct conclusions regarding the behavior of inhaled diesel aerosol in contact with body fluids cannot be drawn from such measurements, the results imply that highly agglomerated soot aerosol particles are unlikely to break up into units smaller than roughly the size distribution emitted as tail pipe soot. PMID:18533015

  8. Post-depositional enrichment of black soot in snow-pack and accelerated melting of Tibetan glaciers

    International Nuclear Information System (INIS)

    Xu Baiqing; Joswiak, Daniel R; Zhao Huabiao; Cao Junji; Liu Xianqin; He Jianqiao

    2012-01-01

    The post-depositional enrichment of black soot in snow-pack was investigated by measuring the redistribution of black soot along monthly snow-pits on a Tien Shan glacier. The one-year experiment revealed that black soot was greatly enriched, defined as the ratio of concentration to original snow concentration, in the unmelted snow-pack by at least an order of magnitude. Greatest soot enrichment was observed in the surface snow and the lower firn-pack within the melt season percolation zone. Black carbon (BC) concentrations as high as 400 ng g −1 in the summer surface snow indicate that soot can significantly contribute to glacier melt. BC concentrations reaching 3000 ng g −1 in the bottom portion of the firn pit are especially concerning given the expected equilibrium-line altitude (ELA) rise associated with future climatic warming, which would expose the dirty underlying firn and ice. Since most of the accumulation area on Tibetan glaciers is within the percolation zone where snow densification is characterized by melting and refreezing, the enrichment of black soot in the snow-pack is of foremost importance. Results suggest the effect of black soot on glacier melting may currently be underestimated. (letter)

  9. Comparison of the Raman spectra of ion irradiated soot and collected extraterrestrial carbon

    Science.gov (United States)

    Brunetto, R.; Pino, T.; Dartois, E.; Cao, A.-T.; d'Hendecourt, L.; Strazzulla, G.; Bréchignac, Ph.

    2009-03-01

    We use a low pressure flame to produce soot by-products as possible analogues of the carbonaceous dust present in diverse astrophysical environments, such as circumstellar shells, diffuse interstellar medium, planetary disks, as well as in our own Solar System. Several soot samples, displaying an initial chemical diversity from aromatic to aliphatic dominated material, are irradiated with 200-400 keV H +, He +, and Ar ++ ions, with fluences comprised between 10 14 and 10 16 ions/cm 2, to simulate expected radiation induced modification on extraterrestrial carbon. The evolution of the samples is monitored using Raman spectroscopy, before, during, and after irradiation. A detailed analysis of the first- and second-order Raman spectra is performed, using a fitting combination of Lorentzian and/or Gaussian-shaped bands. Upon irradiation, the samples evolve toward an amorphous carbon phase. The results suggest that the observed variations are more related to vacancy formation than ionization processes. A comparison with Raman spectra of extraterrestrial organic matter and other irradiation experiments of astrophysically relevant carbonaceous materials is presented. The results are consistent with previous experiments showing mostly amorphization of various carbonaceous materials. Irradiated soots have Raman spectra similar to those of some meteorites, IDPs, and Comet Wild 2 grains collected by the Stardust mission. Since the early-Sun expected irradiation fluxes sufficient for amorphization are compatible with accretion timescales, our results support the idea that insoluble organic matter (IOM) observed in primitive meteorites has experienced irradiation-induced amorphization prior to the accretion of the parent bodies, emphasizing the important role played by early solar nebula processing.

  10. Soot and liquid-phase fuel distributions in a newly designed optically accessible DI diesel engine

    Science.gov (United States)

    Dec, J. E.; Espey, C.

    1993-10-01

    Two-dimensional (2-D) laser-sheet imaging has been used to examine the soot and liquid-phase fuel distributions in a newly designed, optically accessible, direct-injection diesel engine of the heavy-duty size class. The design of this engine preserves the intake port geometry and basic dimensions of a Cummins N-series production engine. It also includes several unique features to provide considerable optical access. Liquid-phase fuel and soot distribution studies were conducted at a medium speed (1,200 rpm) using a Cummins closed-nozzle fuel injector. The scattering was used to obtain planar images of the liquid-phase fuel distribution. These images show that the leading edge of the liquid-phase portion of the fuel jet reaches a maximum length of 24 mm, which is about half the combustion bowl radius for this engine. Beyond this point virtually all the fuel has vaporized. Soot distribution measurements were made at a high load condition using three imaging diagnostics: natural flame luminosity, 2-D laser-induced incandescence, and 2-D elastic scattering. This investigation showed that the soot distribution in the combusting fuel jet develops through three stages. First, just after the onset of luminous combustion, soot particles are small and nearly uniformly distributed throughout the luminous region of the fuel jet. Second, after about 2 crank angle degrees a pattern develops of a higher soot concentration of larger sized particles in the head vortex region of the jet and a lower soot concentration of smaller sized particles upstream toward the injector. Third, after fuel injection ends, both the soot concentration and soot particle size increase rapidly in the upstream portion of the fuel jet.

  11. Investigations of the long-term effects of LII on soot and bath gas

    KAUST Repository

    Cenker, Emre; Bennett, A.; Roberts, William L.

    2017-01-01

    A combination of high-repetition rate imaging, laser extinction measurements, two-colour soot pyrometry imaging, and high-resolution transmission electron microscopy of thermophoretically sampled soot is used to investigate the long

  12. Molecular modelling investigations on the possibility of phenanthrene dimers to be the primary nuclei of soot

    Science.gov (United States)

    Wei, Mingrui; Wu, Sheng; Li, Fan; Zhang, Dongju; Zhang, Tingting; Guo, Guanlun

    2017-11-01

    Pyrene dimerisation was successfully used to model the beginning of soot nucleation in some simulation models. However, the quantum mechanics (QM) calculations proved that the binding energy of a PAH dimer with three six-member rings was similar to that of a pyrene dimer. Meanwhile, the high concentration of phenanthrene at flame conditions indicated high probability of collisions among them. The small difference of the binding energy and high concentration indicated that PAHs structurally smaller than pyrene also could be involved in soot inception. Hence, binary collisions of phenanthrene were simulated to find out whether phenanthrene dimers can serve as soot primary nuclei or not by using non-equilibrium molecular dynamics (MD). Three temperatures, six collision orientations and 155 initial translational velocities (ITVs) were considered. The results indicated that the number of dimers with lifetime over 10 ps which can serve as soot nuclei decreased from 52 at 1000 K to 17 at 1600 K, and further to 6 at 2400 K, which means that low temperature was more favourable for phenanthrene to form soot nuclei. Meanwhile, no soot nuclei were formed at the high velocity region (HVR), compared to 43 and 9 at low and middle velocity regions (LVR and MVR), respectively, when temperature was 1000 K. Also, no soot nuclei were formed at HVR when the temperature was raised to 1600 K and 2400 K. This indicated that HVR was unfavourable for phenanthrene to form soot nuclei. The results computationally further illustrated that small PAHs such as phenanthrene could serve as soot primary nuclei, since they have similar mole fractions in some flames. This may be useful for future soot simulation models.

  13. Planar measurements of soot volume fraction and OH in a JP-8 pool fire

    Energy Technology Data Exchange (ETDEWEB)

    Henriksen, Tara L.; Ring, Terry A.; Eddings, Eric G. [Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Nathan, Graham J. [School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia); Alwahabi, Zeyad T.; Qamar, Nader [School of Chemical Engineering, University of Adelaide, SA 5005 (Australia)

    2009-07-15

    The simultaneous measurement of soot volume fraction by laser induced incandescence (LII) and qualitative imaging of OH by laser induced fluorescence (LIF) was performed in a JP-8 pool fire contained in a 152 mm diameter pan. Line of sight extinction was used to calibrate the LII system in a laminar flame, and to provide an independent method of measuring average soot volume fraction in the turbulent flame. The presence of soot in the turbulent flame was found to be approximately 50% probable, resulting in high levels of optical extinction, which increased slightly through the flame from approximately 30% near the base, to approximately 50% at the tip. This high soot loading pushes both techniques toward their detection limit. Nevertheless, useful accuracy was obtained, with the LII measurement of apparent extinction in the turbulent flame being approximately 21% lower than a direct measurement, consistent with the influence of signal trapping. The axial and radial distributions of soot volume fraction are presented, along with PDFs of volume fraction, and new insight into the behavior of soot sheets in pool fires are sought from the simultaneous measurements of OH and LII. (author)

  14. Estimation of the Diesel Particulate Filter Soot Load Based on an Equivalent Circuit Model

    Directory of Open Access Journals (Sweden)

    Yanting Du

    2018-02-01

    Full Text Available In order to estimate the diesel particulate filter (DPF soot load and improve the accuracy of regeneration timing, a novel method based on an equivalent circuit model is proposed based on the electric-fluid analogy. This proposed method can reduce the impact of the engine transient operation on the soot load, accurately calculate the flow resistance, and improve the estimation accuracy of the soot load. Firstly, the least square method is used to identify the flow resistance based on the World Harmonized Transient Cycle (WHTC test data, and the relationship between flow resistance, exhaust temperature and soot load is established. Secondly, the online estimation of the soot load is achieved by using the dual extended Kalman filter (DEKF. The results show that this method has good convergence and robustness with the maximal absolute error of 0.2 g/L at regeneration timing, which can meet engineering requirements. Additionally, this method can estimate the soot load under engine transient operating conditions and avoids a large number of experimental tests, extensive calibration and the analysis of complex chemical reactions required in traditional methods.

  15. Quantifying uncertainty in soot volume fraction estimates using Bayesian inference of auto-correlated laser-induced incandescence measurements

    Science.gov (United States)

    Hadwin, Paul J.; Sipkens, T. A.; Thomson, K. A.; Liu, F.; Daun, K. J.

    2016-01-01

    Auto-correlated laser-induced incandescence (AC-LII) infers the soot volume fraction (SVF) of soot particles by comparing the spectral incandescence from laser-energized particles to the pyrometrically inferred peak soot temperature. This calculation requires detailed knowledge of model parameters such as the absorption function of soot, which may vary with combustion chemistry, soot age, and the internal structure of the soot. This work presents a Bayesian methodology to quantify such uncertainties. This technique treats the additional "nuisance" model parameters, including the soot absorption function, as stochastic variables and incorporates the current state of knowledge of these parameters into the inference process through maximum entropy priors. While standard AC-LII analysis provides a point estimate of the SVF, Bayesian techniques infer the posterior probability density, which will allow scientists and engineers to better assess the reliability of AC-LII inferred SVFs in the context of environmental regulations and competing diagnostics.

  16. Effects of methyl group on aromatic hydrocarbons on the nanostructures and oxidative reactivity of combustion-generated soot

    KAUST Repository

    Guerrero Peñ a, Gerardo D.J.; Alrefaai, Mhd Maher; Yang, Seung Yeon; Raj, Abhijeet; Brito, Joaquin L.; Stephen, Samuel; Anjana, Tharalekshmy; Pillai, Vinu; Al Shoaibi, Ahmed; Chung, Suk-Ho

    2016-01-01

    The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. © 2016 The Combustion Institute

  17. Effects of methyl group on aromatic hydrocarbons on the nanostructures and oxidative reactivity of combustion-generated soot

    KAUST Repository

    Guerrero Peña, Gerardo D.J.

    2016-07-23

    The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. © 2016 The Combustion Institute

  18. Soot particles at an elevated site in eastern China during the passage of a strong cyclone

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Hongya [State Key Laboratory of Coal Resources and Safe Mining, School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan); Shao, Longyi [State Key Laboratory of Coal Resources and Safe Mining, School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); Zhang, Daizhou, E-mail: dzzhang@pu-kumamoto.ac.jp [Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan)

    2012-07-15

    Atmospheric particles larger than 0.2 {mu}m were collected at the top of Mt. Tai (36.25 Degree-Sign N, 117.10 Degree-Sign E, 1534 m a.s.l.) in eastern China in May 2008 during the passage of a strong cyclone. The particles were analyzed with electron microscopes and characterized by morphology, equivalent diameter and elemental composition. Soot particles with coating (coated soot particles) and those without apparent coating (naked soot particles) were predominant in the diameter range smaller than 0.6 {mu}m in all samples. The number-size distribution of the relative abundance of naked soot particles in the prefrontal air was similar to that in the postfrontal air and their size modes were around 0.2-0.3 {mu}m. However, the distribution of inclusions of coated soot particles showed a mode in the range of 0.1-0.3 {mu}m. The coating degree of coated soot particles, which was defined by the ratio of the diameter of inclusion to the diameter of particle body, showed a mode around 0.5 with the range of 0.3-0.6. These results indicate that the status of soot particles in the prefrontal and postfrontal air was similar although air pollution levels were dramatically different. In addition, the relative abundance of accumulation mode particles increased with the decrease of soot particles after the front passage. - Highlights: Black-Right-Pointing-Pointer Particles at an elevated site in eastern China in a strong cyclone were studied. Black-Right-Pointing-Pointer Aged status of soot particles in the prefrontal and postfrontal air was similar. Black-Right-Pointing-Pointer Soot particles in elevated layers could be considered as aged ones.

  19. Nanoparticle production by UV irradiation of combustion generated soot particles

    International Nuclear Information System (INIS)

    Stipe, Christopher B.; Choi, Jong Hyun; Lucas, Donald; Koshland, Catherine P.; Sawyer, Robert F.

    2004-01-01

    Laser ablation of surfaces normally produce high temperature plasmas that are difficult to control. By irradiating small particles in the gas phase, we can better control the size and concentration of the resulting particles when different materials are photofragmented. Here, we irradiate soot with 193 nm light from an ArF excimer laser. Irradiating the original agglomerated particles at fluences ranging from 0.07 to 0.26 J/cm 2 with repetition rates of 20 and 100 Hz produces a large number of small, unagglomerated particles, and a smaller number of spherical agglomerated particles. Mean particle diameters from 20 to 50 nm are produced from soot originally having a mean electric mobility diameter of 265nm. We use a non-dimensional parameter, called the photon/atom ratio (PAR), to aid in understanding the photofragmentation process. This parameter is the ratio of the number of photons striking the soot particles to the number of the carbon atoms contained in the soot particles, and is a better metric than the laser fluence for analyzing laser-particle interactions. These results suggest that UV photofragmentation can be effective in controlling particle size and morphology, and can be a useful diagnostic for studying elements of the laser ablation process

  20. Microwave-assisted in-situ regeneration of a perovskite coated diesel soot filter

    NARCIS (Netherlands)

    Zhang-Steenwinkel, Y.; van der Zande, L.M.; Castricum, H.L.; Bliek, A.; van den Brink, R.W.; Elzinga, G.D.

    2005-01-01

    Dielectric heating may be used as an in situ technique for the periodic regeneration of soot filters, as those used in Diesel engines. As generally the Diesel exhaust temperatures are below the soot light-off temperature, passive regeneration is not possible. Presently, we have investigated the

  1. Sources and burial fluxes of soot black carbon in sediments on the Mackenzie, Chukchi, and Bering Shelves

    Science.gov (United States)

    Yang, Weifeng; Guo, Laodong

    2018-03-01

    Black carbon (BC) has been recognized as a climate forcing and a major component in the global carbon budget. However, studies on BC in the Arctic Ocean remain scarce. We report here variations in the abundance, sources and burial fluxes of sedimentary soot black carbon (soot-BC) in the western Arctic Ocean. The soot-BC contents averaged 1.6 ± 0.3, 0.46 ± 0.04 and 0.56 ± 0.10 mg-C g-1 on the Mackenzie, Chukchi and Bering Shelves, respectively, accounting for 16.6%, 10.2% and 10.4% of the total organic carbon in surface sediment. Temporally, contents of soot-BC remained fairly stable before 1910, but increased rapidly after the 1970s on the Mackenzie Shelf, indicating enhanced source input related to warming. Comparable δ13C signatures of soot-BC (- 24.95‰ to - 24.57‰) to C3 plants pointed to a major biomass source of soot-BC to the Beaufort Sea. Soot-BC showed similar temporal patterns with large fluctuations in the Chukchi/Bering shelf regions, implying the same source terms for soot-BC in these areas. Two events with elevated soot-BC corresponded to a simultaneous increase in biomass combustion and fossil fuel (coal and oil) consumption in Asia. The similar temporal variability in sedimentary soot-BC between the Arctic shelves and Asian lakes and the comparable δ13C values manifested that anthropogenic emission from East Asia was an important source of soot-BC in the western Arctic and subarctic regions. The burial fluxes of soot-BC, estimated from both 137Cs- and 210Pb-derived sedimentation rates, were 2.43 ± 0.42 g-C m-2 yr-1 on the Mackenzie Shelf, representing an efficient soot-BC sink. Soot-BC showed an increase in buried fluxes from 0.56 ± 0.02 g-C m-2 yr-1 during 1963-1986 to 0.88 ± 0.05 g-C m-2 yr-1 after 1986 on the Chukchi Shelf, and from 1.00 ± 0.18 g-C m-2 yr-1 to 2.58 ± 1.70 g-C m-2 yr-1 on the Bering Shelf, which were consistent with recent anthropogenically enhanced BC input observed especially in Asia. Overall, the three Arctic

  2. Effects of morphology and wavelength on the measurement accuracy of soot volume fraction by laser extinction

    Science.gov (United States)

    Wang, Ya-fei; Huang, Qun-xing; Wang, Fei; Chi, Yong; Yan, Jian-hua

    2018-01-01

    A novel method to evaluate the quantitative effects of soot morphology and incident wavelength on the measurement accuracy of soot volume fraction, by the laser extinction (LE) technique is proposed in this paper. The results indicate that the traditional LE technique would overestimate soot volume fraction if the effects of morphology and wavelength are not considered. Before the agglomeration of isolated soot primary particles, the overestimation of the LE technique is in the range of 2-20%, and rises with increasing primary particle diameter and with decreasing incident wavelength. When isolated primary particles are agglomerated into fractal soot aggregates, the overestimation would exceed 30%, and rise with increasing primary particle number per soot aggregate, fractal dimension and fractal prefactor and with decreasing incident wavelength to a maximum value of 55%. Finally, based on these results above, the existing formula of the LE technique gets modified, and the modification factor is 0.65-0.77.

  3. Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII

    KAUST Repository

    Cenker, Emre

    2017-02-27

    During the rapid laser pulse heating and consecutive cooling in laser-induced incandescence (LII), soot particles may undergo thermal annealing and sublimation processes which lead to a permanent change in its optical properties and its primary particle size, respectively. Overall, effects of these two processes on soot and LII model-based particle sizing are investigated by measuring the two-color time-resolved (2C-TiRe) LII signal decay from in-flame soot after two consecutive laser pulses at 1064-nm wavelength. Experiments are carried out on a non-premixed laminar ethylene/air flame from a Santoro burner with both low and moderate laser fluences suitable for particle sizing. The probe volume is set to a radial position close to the flame axis where the soot particles are known to be immature or less graphitic. With the first pulse, soot is pre-heated, and the LII signal after the consecutive second pulse is used for analysis. The two-color incandescence emission technique is used for the pyrometric determination of the LII-heated peak soot temperature at the second pulse. A new LII simulation tool is developed which accounts for particle heating via absorption and annealing, and cooling via sublimation, conduction, and radiation with various existing sub-models from the literature. The same approach of using two laser pulses is implemented in the simulations. Measurements indicate that thermal annealing and associated absorption enhancement becomes important at laser fluences above 0.17 J/cm2 for the immature in-flame soot. After a heating pulse at 0.33 J/cm2, the increase of the soot absorption function is calculated as 35% using the temperature measured at the second pulse and an absorption model based on the Rayleigh approximation. Present annealing model, on the other hand, predicts graphitization of soot even in the absence of laser heating at typical flame temperatures. Recorded experimental LII signal decays and LII-heated peak soot temperature

  4. Single Particle Soot Photometer intercomparison at the AIDA chamber

    Directory of Open Access Journals (Sweden)

    M. Laborde

    2012-12-01

    Full Text Available Soot particles, consisting of black carbon (BC, organic carbon (OC, inorganic salts, and trace elements, are emitted into the atmosphere during incomplete combustion. Accurate measurements of atmospheric BC are important as BC particles cause adverse health effects and impact the climate.

    Unfortunately, the accurate measurement of the properties and mass concentrations of BC particles remains difficult. The Single Particle Soot Photometer (SP2 can contribute to improving this situation by measuring the mass of refractory BC in individual particles as well as its mixing state.

    Here, the results of the first detailed SP2 intercomparison, involving 6 SP2s from 6 different research groups, are presented, including the most evolved data products that can presently be calculated from SP2 measurements.

    It was shown that a detection efficiency of almost 100% down to 1 fg BC per particle can readily be achieved, and that this limit can be pushed down to ∼0.2 fg BC with optimal SP2 setup. Number and mass size distributions of BC cores agreed within ±5% and ±10%, respectively, in between the SP2s, with larger deviations in the range below 1 fg BC.

    The accuracy of the SP2's mass concentration measurement depends on the calibration material chosen. The SP2 has previously been shown to be equally sensitive to fullerene soot and ambient BC from sources where fossil fuel was dominant and less sensitive to fullerene soot than to Aquadag. Fullerene soot was therefore chosen as the standard calibration material by the SP2 user community; however, many data sets rely solely on Aquadag calibration measurements. The difference in SP2 sensitivity was found to be almost equal (fullerene soot to Aquadag response ratio of ∼0.75 at 8.9 fg BC for all SP2s. This allows the calculation of a fullerene soot equivalent calibration curve from a measured Aquadag calibration, when no fullerene soot calibration is available. It could be

  5. Two-dimensional quantification of soot and flame-soot interaction in spray combustion at elevated pressures - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, T.

    2008-07-15

    Single-pulse time-resolved laser-induced incandescence (TiRe-LII) signal transients from soot particulates were acquired during unsteady high pressure Diesel combustion in a constant volume cell near top dead centre conditions typically found in a Diesel engine. Measurements were performed for initial gas pressures between 1 MPa and 3 MPa, injection pressures between 50 MPa and 130 MPa and laser probe timings between 5 ms and 16 ms after start of fuel injection. In separate experiments and for the same cell operating conditions, gas temperatures were deduced from spectrally resolved soot pyrometry measurements. Implementing the LII model of Kock et al. ensemble mean soot particle diameters were evaluated from least-squares fitting of theoretical cooling curves to experimental TiRe-LII signal transients. Since in the experiments the environmental gas temperature and the width of an assumed particle size distribution were not known, the effects of the initial choice of these parameters on retrieved particle diameters were investigated. It is shown that evaluated mean particle diameters are only slightly biased by the choice of typical size distribution widths and gas temperatures. For a fixed combustion phase mean particle diameters are not much affected by gas pressure, however they become smaller at high fuel injection pressure. At a mean chamber pressure of 1.4 MPa evaluated mean particle diameters increased by a factor of two for probe delays between 5 ms and 16 ms after start of injection, irrespective of the choices of first-guess fitting variables, indicating a certain robustness of data analysis procedure. (author)

  6. Soot and radiation in combusting boundary layers

    Energy Technology Data Exchange (ETDEWEB)

    Beier, R.A.

    1981-12-01

    In most fires thermal radiation is the dominant mode of heat transfer. Carbon particles within the fire are responsible for most of this emitted radiation and hence warrant quantification. As a first step toward understanding thermal radiation in full scale fires, an experimental and theoretical study is presented for a laminar combusting boundary layer. Carbon particulate volume fraction profiles and approximate particle size distributions are experimentally determined in both free and forced flow for several hydrocarbon fuels and PMMA (polymethylmethacrylate). A multiwavelength laser transmission technique determines a most probable radius and a total particle concentration which are two unknown parameters in an assumed Gauss size distribution. A sooting region is observed on the fuel rich side of the main reaction zone. For free flow, all the flames are in air, but the free stream ambient oxygen mass fraction is a variable in forced flow. To study the effects of radiation heat transfer, a model is developed for a laminar combusting boundary layer over a pyrolyzing fuel surface. An optically thin approximation simplifies the calculation of the radiant energy flux at the fuel surface. For the free flames in air, the liquid fuel soot volume fractions, f/sub v/, range from f/sub v/ approx. 10/sup -7/ for n-heptane, a paraffin, to f/sub v/ approx. 10/sup -7/ for toluene, an aromatic. The PMMA soot volume fractions, f/sub v/ approx. 5 x 10/sup -7/, are approximately the same as the values previously reported for pool fires. Soot volume fraction increases monotonically with ambient oxygen mass fraction in the forced flow flames. For all fuels tested, a most probable radius between 20 nm and 80 nm is obtained which varies only slightly with oxygen mass fraction, streamwise position, or distance normal to the fuel surface. The theoretical analysis yields nine dimensionless parameters, which control the mass flux rate at the pyrolyzing fuel surface.

  7. Simultaneous measurements of acetylene and soot during the pyrolysis of ethylene and benzene in a shock tube

    KAUST Repository

    KC, Utsav

    2016-10-12

    Acetylene is one of the most important precursors of soot and contributes to soot growth by the hydrogen-abstraction acetylene-addition (HACA) mechanism. In this work, we undertake time-resolved simultaneous measurements of acetylene and soot behind reflected shock waves at temperatures of 1600-2200. K and pressures of 3-5. bar. Acetylene mole fraction time-histories are measured from the absorption of a quantum-cascade laser operating around 13.6. μm. The soot volume fraction, particle size and number densities are calculated from the extinction and scattering of a cw Nd:Yag laser at 532. nm. Acetylene and soot are generated from the pyrolysis of 1% benzene in argon, 2.35% ethylene in argon, and binary mixtures of ethylene with propane/methane in argon. We note that acetylene time-histories exhibit a two-stage growth during the pyrolysis of benzene, which can be correlated to the initial rapid increase of soot volume fraction and a later plateauing. In comparison to ethylene pyrolysis, the pyrolysis of benzene results in larger values of the soot volume fraction, particle diameter and number density. We compare the measured data against the values simulated using the method-of-moments routine in Chemkin-Pro and a detailed PAH mechanism based on KM2 [1] and AramcoMech 1.3 [2]. Large discrepancies are observed between the measured and predicted values of the soot parameters. The data obtained from our experiments may assist future validation and development of soot mechanisms.

  8. Effects of compositional heterogeneity and nanoporosity of raw and treated biomass-generated soot on adsorption and absorption of organic contaminants

    International Nuclear Information System (INIS)

    Chen Baoliang; Huang Wenhai

    2011-01-01

    A biomass-generated soot was sequentially treated by HCl-HF solution, organic solvent, and oxidative acid to remove ash, extractable native organic matter (EOM), and amorphous carbon. The compositional heterogeneity and nano-structure of the untreated and treated soot samples were characterized by elemental analysis, thermal gravimetric analysis, BET-N 2 surface area, and electron microscopic analysis. Sorption properties of polar and nonpolar organic pollutants onto the soot samples were compared, and individual contributions of adsorption and absorption were quantified. The sorption isotherms for raw sample were practically linear, while were nonlinear for the pretreated-soot. The removal of EOM enhanced adsorption and reduced absorption, indicating that EOM served as a partitioning phase and simultaneously masked the adsorptive sites. By drastic-oxidation, the outer amorphous carbon and the inner disordered core of the soot particles were completely removed, and a fullerene-like nanoporous structure (aromatic shell) was created, which promoted additional π-π interaction between phenanthrene and the soot. - Graphical abstract: The dual sorptive nature of the biomass-generated soot, i.e., the adsorptive effect of the carbonized soot fraction and the partition effect of the amorphous soot component. Research highlights: → The biomass-generated soot owns the heterogeneous compositions and nano-structures. → The soot exhibits the dual sorptive nature, i.e., adsorption and absorption. → Removal of the amorphous component weakens absorption, but strengthens adsorption. → The exposed adsorptive sites with highly aromatic nature promotes π-π interaction. → The dual sorptive nature of the soot depends on the various soot components. - The compositional heterogeneity and nano-structure play a regulating role in the adsorption and absorption of organic contaminants with the untreated and treated soot samples.

  9. Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths.

    Science.gov (United States)

    Soloviev, Sergiy O; Kapran, Andriy Y; Kurylets, Yaroslava P

    2015-02-01

    Binary oxide systems (CuCr2O4, CuCo2O4), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O2, NOx, H2O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3≫NO2>H2O>NO>O2>CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem. Copyright © 2014. Published by Elsevier B.V.

  10. Ultra-small-angle X-ray scattering characterization of diesel/gasoline soot: sizes and particle-packing conditions

    Science.gov (United States)

    Kameya, Yuki; Lee, Kyeong O.

    2013-10-01

    Regulations on particulate emissions from internal combustion engines tend to become more stringent, accordingly the importance of particulate filters in the after-treatment system has been increasing. In this work, the applicability of ultra-small-angle X-ray scattering (USAXS) to diesel soot cake and gasoline soot was investigated. Gasoline-direct-injection engine soot was collected at different fuel injection timings. The unified fits method was applied to analyze the resultant scattering curves. The validity of analysis was supported by comparing with carbon black and taking the sample images using a transmission electron microscope, which revealed that the primary particle size ranged from 20 to 55 nm. In addition, the effects of particle-packing conditions on the USAXS measurement were demonstrated by using samples suspended in acetone. Then, the investigation was extended to characterization of diesel soot cake deposited on a diesel particulate filter (DPF). Diesel soot was trapped on a small piece of DPF at different deposition conditions which were specified using the Peclet number. The dependence of scattering curve on soot-deposition conditions was demonstrated. To support the interpretation of the USAXS results, soot cake samples were observed using a scanning electron microscope and the influence of particle-packing conditions on scattering curve was discussed.

  11. Ultra-small-angle X-ray scattering characterization of diesel/gasoline soot: sizes and particle-packing conditions

    International Nuclear Information System (INIS)

    Kameya, Yuki; Lee, Kyeong O.

    2013-01-01

    Regulations on particulate emissions from internal combustion engines tend to become more stringent, accordingly the importance of particulate filters in the after-treatment system has been increasing. In this work, the applicability of ultra-small-angle X-ray scattering (USAXS) to diesel soot cake and gasoline soot was investigated. Gasoline-direct-injection engine soot was collected at different fuel injection timings. The unified fits method was applied to analyze the resultant scattering curves. The validity of analysis was supported by comparing with carbon black and taking the sample images using a transmission electron microscope, which revealed that the primary particle size ranged from 20 to 55 nm. In addition, the effects of particle-packing conditions on the USAXS measurement were demonstrated by using samples suspended in acetone. Then, the investigation was extended to characterization of diesel soot cake deposited on a diesel particulate filter (DPF). Diesel soot was trapped on a small piece of DPF at different deposition conditions which were specified using the Peclet number. The dependence of scattering curve on soot-deposition conditions was demonstrated. To support the interpretation of the USAXS results, soot cake samples were observed using a scanning electron microscope and the influence of particle-packing conditions on scattering curve was discussed

  12. Ultra-small-angle X-ray scattering characterization of diesel/gasoline soot: sizes and particle-packing conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kameya, Yuki, E-mail: ykameya@anl.gov; Lee, Kyeong O. [Argonne National Laboratory, Center for Transportation Research (United States)

    2013-10-15

    Regulations on particulate emissions from internal combustion engines tend to become more stringent, accordingly the importance of particulate filters in the after-treatment system has been increasing. In this work, the applicability of ultra-small-angle X-ray scattering (USAXS) to diesel soot cake and gasoline soot was investigated. Gasoline-direct-injection engine soot was collected at different fuel injection timings. The unified fits method was applied to analyze the resultant scattering curves. The validity of analysis was supported by comparing with carbon black and taking the sample images using a transmission electron microscope, which revealed that the primary particle size ranged from 20 to 55 nm. In addition, the effects of particle-packing conditions on the USAXS measurement were demonstrated by using samples suspended in acetone. Then, the investigation was extended to characterization of diesel soot cake deposited on a diesel particulate filter (DPF). Diesel soot was trapped on a small piece of DPF at different deposition conditions which were specified using the Peclet number. The dependence of scattering curve on soot-deposition conditions was demonstrated. To support the interpretation of the USAXS results, soot cake samples were observed using a scanning electron microscope and the influence of particle-packing conditions on scattering curve was discussed.

  13. Effect of exhaust gas recirculation (EGR) and multiple injections on diesel soot nano-structure and reactivity

    International Nuclear Information System (INIS)

    Rohani, Behzad; Bae, Choongsik

    2017-01-01

    Highlights: • EGR reduced the nano-structural order, regardless of injection strategy. • EGR reduces both VOF and reactivity, regardless of injection strategy. • Longer dwell time between pilot and main injection increases VOF and reactivity. • With EGR, VOF and reactivity are both reduced and un-affected by injection strategy. • VOF-reactivity correlation (without causality) suggests role of surface roughness. - Abstract: The physio-chemical characteristics of soot particles are of importance with regard to performance of diesel after-treatment systems. In this study, the soot particles generated in a single-cylinder heavy-duty diesel engine are examined in terms of nanostructure, oxidative reactivity and volatile organic fraction (VOF), using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman micro-spectroscopy, and high resolution transmission electron microscopy (HRTEM). Five different injection strategies including single injection and multiple injections with various pilot injection amounts and dwell times were tested with and without exhaust gas recirculation (EGR), while combustion phasing, engine speed, and fuel injection quantity was matched for all cases. Results indicate that for the soot produced under EGR condition, nano-structural order (indicated by crystallite size obtained from XRD and AD1/AG resulted from the Raman Analysis) can explain the soot reactivity. However, in the absence of EGR, the reactivity trend cannot be explained by the structural order. It is discussed that a possible reason can be a higher level of in-cylinder oxidation in non-EGR cases (indicated by higher level of surface functional groups) which roughens the soot surface, and enhances the oxidation by increasing the specific soot surface area. It is also found that in the absence of EGR, different injection strategies impact the soot reactivity and VOF content, which can be explained mainly through the level of charge premixed-ness and the in

  14. Modelling heterogeneous ice nucleation on mineral dust and soot with parameterizations based on laboratory experiments

    Science.gov (United States)

    Hoose, C.; Hande, L. B.; Mohler, O.; Niemand, M.; Paukert, M.; Reichardt, I.; Ullrich, R.

    2016-12-01

    Between 0 and -37°C, ice formation in clouds is triggered by aerosol particles acting as heterogeneous ice nuclei. At lower temperatures, heterogeneous ice nucleation on aerosols can occur at lower supersaturations than homogeneous freezing of solutes. In laboratory experiments, the ability of different aerosol species (e.g. desert dusts, soot, biological particles) has been studied in detail and quantified via various theoretical or empirical parameterization approaches. For experiments in the AIDA cloud chamber, we have quantified the ice nucleation efficiency via a temperature- and supersaturation dependent ice nucleation active site density. Here we present a new empirical parameterization scheme for immersion and deposition ice nucleation on desert dust and soot based on these experimental data. The application of this parameterization to the simulation of cirrus clouds, deep convective clouds and orographic clouds will be shown, including the extension of the scheme to the treatment of freezing of rain drops. The results are compared to other heterogeneous ice nucleation schemes. Furthermore, an aerosol-dependent parameterization of contact ice nucleation is presented.

  15. On transient climate change at the Cretaceous−Paleogene boundary due to atmospheric soot injections

    Science.gov (United States)

    Garcia, Rolando R.; Toon, Owen B.; Conley, Andrew J.

    2017-01-01

    Climate simulations that consider injection into the atmosphere of 15,000 Tg of soot, the amount estimated to be present at the Cretaceous−Paleogene boundary, produce what might have been one of the largest episodes of transient climate change in Earth history. The observed soot is believed to originate from global wildfires ignited after the impact of a 10-km-diameter asteroid on the Yucatán Peninsula 66 million y ago. Following injection into the atmosphere, the soot is heated by sunlight and lofted to great heights, resulting in a worldwide soot aerosol layer that lasts several years. As a result, little or no sunlight reaches the surface for over a year, such that photosynthesis is impossible and continents and oceans cool by as much as 28 °C and 11 °C, respectively. The absorption of light by the soot heats the upper atmosphere by hundreds of degrees. These high temperatures, together with a massive injection of water, which is a source of odd-hydrogen radicals, destroy the stratospheric ozone layer, such that Earth’s surface receives high doses of UV radiation for about a year once the soot clears, five years after the impact. Temperatures remain above freezing in the oceans, coastal areas, and parts of the Tropics, but photosynthesis is severely inhibited for the first 1 y to 2 y, and freezing temperatures persist at middle latitudes for 3 y to 4 y. Refugia from these effects would have been very limited. The transient climate perturbation ends abruptly as the stratosphere cools and becomes supersaturated, causing rapid dehydration that removes all remaining soot via wet deposition. PMID:28827324

  16. Minor and Trace Element Chemistry of Urban NS-Soot from the Central Valley of CA, USA

    Science.gov (United States)

    Kleich, S. J.; Hooper, R.

    2017-12-01

    During a recent study of metal transport in the Central Valley of California, it was noted that ns-soot (soot) occurred as complex clusters of graphene-like spheres admixed with other aerosols and were usually the dominant component of PM2.5 air particulates. These soot clusters contained a wide variety of metals of environmental concern such as As,Pb,Cr, and Ni. This study reports semi-quantitative results for 20 minor and trace elements (calibrated with Smithsonian microbeam standards) using a 200kV Transmission Electron Microscope, EDS, and SAED. This study also examined the mineralogy and crystallinity of admixed aerosols within composite soot clusters. Samples selected represent three contrasting urban settings in the Central Valley: Woodland, on the western side of the valley (Interstate highway to the east); Stockton, an inland sea-port and land transportation corridor in the center of the valley; and Roseville, a major rail-transport hub to the east. The wet/dry Mediterranean climate of California resulted in pronounced seasonal variations in total metal content. Soot cluster chemistry is highly variable however certain patterns emerged. Soot collected during the wet season is generally more aciniform, less structurally complex, and had lower sulfur (sulfate) concentrations but still had significant levels of transition metals (V,Cr,Mn,Fe,Ni,Zn and Pb) . Dry season soot was predominantly admixed with sulfate aerosols, and enriched in alkalis and alkaline earth metals. Stockton (wet-season) soot had up to 6000ppm of Pb. There is appreciable Pb (210ppm-2600ppm) in 38% of samples from Roseville but no Pb greater than 200ppm in Woodland. The highest overall total metals were found in Roseville soot with appreciable As(670ppm), V(100ppm), Pb(2600ppm), Zn(4000 ppm), Cr(90ppm), and Ni(300ppm). Heavy transport (road/rail/port) correlates with higher metal contents regardless of climate.

  17. [Secondary metabolites accumulating and geoherbs formation under enviromental stress].

    Science.gov (United States)

    Huang, Lu-Qi; Guo, Lan-Ping

    2007-02-01

    This paper analyzed how habitat affected the formation of geoherbs after summarizing the influences of environmental stress on plants growth, especially on theirs secondary metabolites accumulating, and introducing 4 kinds hypothesis about environmental stress affects plants. It was then pointed out that environmental stress may have advantage on the formation of geoherbs. The stress effect hypothesis on forming geoherbs was brought forward, and the ways and methods on study the geoherbs under environmental stress was discussed.

  18. Soot blowing methods and soot steam consumption in Swedish recovery boilers; Sotningsmetoder och sotaangfoerbrukning i svenska sodapannor

    Energy Technology Data Exchange (ETDEWEB)

    Svedin, Kristoffer; Wallin, Erik; Ahlroth, Mikael

    2008-09-15

    The aim with the report was to put together a description of the current state of the sootblowing systems at Swedish recovery boilers, and to explain differences in cleanability and sootblowing efficiency. In chapter 4 a summary of new techniques and alternative soot blowing methods is found. The report is intended for persons working in the pulp industry. To facilitate the benchmarking the recovery boilers have been divided into two groups. Group A comprises recovery boilers which only have one stop per year and the remaining recovery boilers with more than one stop are classified into group B. The following conclusions, based on the recovery boiler design specifications, are of importance to achieve high boiler availability: Low furnace load; High recovery boiler, wide furnace bottom area; Modern air ports; Small or no correlation between cross pitch division in heat surfaces and cleanability could be seen. The expectation was to identify such a relation. However there are doubts on the correctness in reported data. The amount of chlorine and potassium is assumed to affect the cleanability for a few recovery boilers, but for the majority the amounts are low and most likely do not impact the operation. Because of the large impact of the recovery boilers design data (furnace area, load etc.) on the sootblowing, it has been hard to identify the relation cleanability contra sootblowing system. The relations that could be seen are: No distinction between normally designed nozzles and 'high efficiency' nozzles could be identified. The operational conditions for the different models differ a lot and the effect of nozzle type could not be distinguished. Only a minority of the soot blowing sequences are known from the study. In the recovery boilers with problematic areas improvements can be made in the soot blowing sequence. Four recovery boilers are using intelligent soot blowing of some kind. Two of these boilers have low availability and the other two have

  19. Effects of soot by-product from the synthesis of engineered metallofullerene nanomaterials on terrestrial invertebrates.

    Science.gov (United States)

    Johnson, David R; Boyd, Robert E; Bednar, Anthony J; Weiss, Charles A; Hull, Matt S; Coleman, Jessica G; Kennedy, Alan J; Banks, Cynthia J; Steevens, Jeffery A

    2018-02-23

    The synthesis of carbon-based nanomaterials is often inefficient, generating large amounts of soot with metals as waste by-product. Currently, there are no specific regulations for disposal of engineered nanomaterials or the waste by-products resulting from their synthesis, so it is presumed that by-products are disposed of in the same way as the parent (bulk) materials. We studied the terrestrial toxicity of soot from gadolinium metallofullerene nanomanufacturing on earthworms (Eisenia fetida) and isopods (Porcellio scaber). The metallofullerene soot consisted of carbon particle agglomerates in the nanometer and submicrometer ranges (1-100 and 101-999 nm, respectively), with metals used during nanomanufacturing detectable on the particles. Despite high metal concentrations (>100 000 mg/kg) in the soot, only a relatively small amount of metals leached out of a spiked field soil, suggesting only moderate mobility. Seven- and 14-d exposures in field soil demonstrated that the soot was only toxic to earthworms at high concentrations (>10 000 mg/kg); however, earthworms avoided spiked soils at lower concentrations (as low as 500 mg/kg) and at lower soil pH. The presence of soot in food and soil did not cause isopod avoidance. These data demonstrate that metallofullerene soot from nanomanufacturing may only be toxic to earthworms at high concentrations representative of improper disposal or accidental spills. However, our results indicate that terrestrial invertebrates may avoid soils contaminated with soot at sublethal concentrations. Environ Toxicol Chem 2018;9999:1-12. Published 2018 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work, and as such, is in the public domain in the United States of America. Published 2018 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work, and as such, is in the public domain in the United States of America.

  20. A comparison of chemical structures of soot precursor nanoparticles from liquid fuel combustion in flames and engine

    International Nuclear Information System (INIS)

    Paul, Bireswar; Datta, Amitava; Datta, Aparna; Saha, Abhijit

    2013-01-01

    A comparative study of the chemical structures of soot precursor nanoparticles from the liquid fuel flame and engine exhaust has been performed in this work to establish an association between the particles from both the sources. Different ex-situ measurement techniques have been used to characterize the nanoparticles in samples collected from the laboratory petrol/air and iso-octane/air flames, as well as from a gasoline engine. The TEM images of the sampled material along with the EDS spectra corroborate the existence of carbonaceous nanoparticles. The nature of the UV absorption and fluorescence spectra of the samples from the iso-octane flame environment further confirms the sampled materials to be soot precursor nanoparticles. The DLS size distribution of the particles shows them to be below 10 nm size. FTIR spectrum of the precursor nanoparticles collected form the non-sooting zone of the flame and that of fully grown soot particles show few similarities and dissimilarities among them. The soot particles are found to be much more aromatized as compared to its precursor nanoparticles. The presence of carbonyl functional group (C=O) at around 1,720 cm −1 has been observed in soot precursor nanoparticles, while such oxygenated functional groups are not prominent in soot structure. The absorption (UV and IR) and fluorescence spectra of the carbonaceous material collected from the gasoline engine exhaust show many resemblances with those of soot precursor nanoparticles from flames. These spectroscopic resemblances of the soot precursor nanoparticles from the flame environment and engine exhaust gives the evidence that the in-cylinder combustion is the source of these particles in the engine exhaust.

  1. Structural effects on the oxidation of soot particles by O2: Experimental and theoretical study

    KAUST Repository

    Raj, Abhijeet

    2013-09-01

    Soot particles are composed of polycyclic aromatic hydrocarbons (PAHs), which have either planar or curved structures. The oxidation behaviors of soot particles differ depending on their structures, arrangement of PAHs, and the type of surface functional groups. The oxidation rate of curved PAHs in soot is thought to be higher than that of planar ones. To understand the role that PAH structure plays in soot reactivity towards O2, experimental studies are conducted on two types of commercially produced soot, Printex-U and Fullerene soot, using high resolution transmission electron microscopy, electron energy loss spectroscopy, thermo-gravimetric analysis and elemental analysis. The relative concentrations of active sites, oxygenated functional groups, aliphatics and aromatics present in soots are evaluated. The activation energies for soot oxidation at different conversion levels are determined. The average activation energies of the two soots are found to differ by 26kJ/mol. To understand the reason for this difference, quantum calculations using density functional (B3LYP) and Hartree-Fock theories are conducted to study the reaction pathways of the oxidation by O2 of planar and curved PAHs using 4-pyrenyl and 1-corannulenyl as their model molecules, respectively. The energetically preferred channels for curved PAH oxidation differ from the planar one. The addition of O2 on a radical site of a six-membered ring to form a peroxyl radical is found to be barrierless for both the model PAHs. For peroxyl decomposition, three pathways are suggested, each of which involve the activation energies of 108, 170 and 121kJ/mol to form stable molecules in the case of planar PAH, and 94, 155 and 125kJ/mol in the case of curved PAH. During the oxidation of a five-membered ring, to form stable molecules, the activation energies of 90kJ/mol for the curved PAH and 169kJ/mol for the planar PAH relative to the energy of the peroxyl radical are required. The low activation barriers of

  2. Morphological study of fluorescent carbon Nanoparticles (F-CNPs) from ground coffee waste soot oxidation by diluted acid

    Science.gov (United States)

    Gea, S.; Tjandra, S.; Joshua, J.; Wirjosentono, B.

    2018-02-01

    Coffee ground waste utilization for fluorescent carbon nanoparticles (F-CNPs) through soot oxidation with diluted HNO3 has been conducted. Soot was obtained through three different treatments to coffee ground waste; which was burned in furnaceat 550°C and 650°C and directly burned in a heat-proofcontainer. Then they were analyzed morphologically with Scanning Electron Microscope (SEM) instrument. Soot from direct burning indicated the optimum result where it has denser pores compared to other two soots. Soot obtained from direct burning was refluxed in diluted HNO3 for 12 hours to perform the oxidation. Yellowish brown supernatant was later observed which lead to green fluorescent under the UV light. F-CNPs characterization was done in Transmission Electron Microscopy, which showed that 7.4-23.4 nm of particle size were distributed.

  3. Significant Climate Changes Caused by Soot Emitted From Rockets in the Stratosphere

    Science.gov (United States)

    Mills, M. J.; Ross, M.; Toohey, D. W.

    2010-12-01

    A new type of hydrocarbon rocket engine with a larger soot emission index than current kerosene rockets is expected to power a fleet of suborbital rockets for commercial and scientific purposes in coming decades. At projected launch rates, emissions from these rockets will create a persistent soot layer in the northern middle stratosphere that would disproportionally affect the Earth’s atmosphere and cryosphere. A global climate model predicts that thermal forcing in the rocket soot layer will cause significant changes in the global atmospheric circulation and distributions of ozone and temperature. Tropical ozone columns decline as much as 1%, while polar ozone columns increase by up to 6%. Polar surface temperatures rise one Kelvin regionally and polar summer sea ice fractions shrink between 5 - 15%. After 20 years of suborbital rocket fleet operation, globally averaged radiative forcing (RF) from rocket soot exceeds the RF from rocket CO_{2} by six orders of magnitude, but remains small, comparable to the global RF from aviation. The response of the climate system is surprising given the small forcing, and should be investigated further with different climate models.

  4. Efficient low-temperature soot combustion by bimetallic Ag-Cu/SBA-15 catalysts.

    Science.gov (United States)

    Wen, Zhaojun; Duan, Xinping; Hu, Menglin; Cao, Yanning; Ye, Linmin; Jiang, Lilong; Yuan, Youzhu

    2018-02-01

    In this study, the effects of copper (Cu) additive on the catalytic performance of Ag/SBA-15 in complete soot combustion were investigated. The soot combustion performance of bimetallic Ag-Cu/SBA-15 catalysts was higher than that of monometallic Ag and Cu catalysts. The optimum catalytic performance was acquired with the 5Ag 1 -Cu 0.1 /SBA-15 catalyst, on which the soot combustion starts at T ig =225°C with a T 50 =285°C. The temperature for 50% of soot combustion was lower than that of conventional Ag-based catalysts to more than 50°C (Aneggi et al., 2009). Physicochemical characterizations of the catalysts indicated that addition of Cu into Ag could form smaller bimetallic Ag-Cu nanolloy particles, downsizing the mean particle size from 3.7nm in monometallic catalyst to 2.6nm in bimetallic Ag-Cu catalyst. Further experiments revealed that Ag and Cu species elicited synergistic effects, subsequently increasing the content of surface active oxygen species. As a result, the structure modifications of Ag by the addition of Cu strongly intensified the catalytic performance. Copyright © 2017. Published by Elsevier B.V.

  5. Mixing state of regionally transported soot particles and the coating effect on their size and shape at a mountain site in Japan

    Science.gov (United States)

    Adachi, Kouji; Zaizen, Yuji; Kajino, Mizuo; Igarashi, Yasuhito

    2014-05-01

    Soot particles influence the global climate through interactions with sunlight. A coating on soot particles increases their light absorption by increasing their absorption cross section and cloud condensation nuclei activity when mixed with other hygroscopic aerosol components. Therefore, it is important to understand how soot internally mixes with other materials to accurately simulate its effects in climate models. In this study, we used a transmission electron microscope (TEM) with an auto particle analysis system, which enables more particles to be analyzed than a conventional TEM. Using the TEM, soot particle size and shape (shape factor) were determined with and without coating from samples collected at a remote mountain site in Japan. The results indicate that ~10% of aerosol particles between 60 and 350 nm in aerodynamic diameters contain or consist of soot particles and ~75% of soot particles were internally mixed with nonvolatile ammonium sulfate or other materials. In contrast to an assumption that coatings change soot shape, both internally and externally mixed soot particles had similar shape and size distributions. Larger aerosol particles had higher soot mixing ratios, i.e., more than 40% of aerosol particles with diameters >1 µm had soot inclusions, whereas <20% of aerosol particles with diameters <1 µm included soot. Our results suggest that climate models may use the same size distributions and shapes for both internally and externally mixed soot; however, changing the soot mixing ratios in the different aerosol size bins is necessary.

  6. Characterizing germania concentration and structure in fiber soot using multiphoton microscopy and spectroscopy technology

    Science.gov (United States)

    Chen, Minghan; Li, Ming-Jun; Liu, Anping

    2015-02-01

    Germania doping is commonly used in the core of optical fiber due to its advantages compared to other materials such as superior transparency in near-infrared telecommunication wavelength region. During fiber preform manufacturing using the outside vapor deposition (OVD) process, Ge is doped into a silica soot preform by chemical vapor deposition. Since the Ge doping concentration profile is directly correlated with the fiber refractive index profile, its characterization is critical for the fiber industry. Electron probe micro-analyzer (EPMA) is a conventional analysis method for characterizing the Ge concentration profile. However, it requires extensive sample preparation and lengthy measurement. In this paper, a multiphoton microscopy technique is utilized to measure the Ge doping profile based on the multiphoton fluorescence intensity of the soot layers. Two samples, one with ramped and another with stepped Ge doping profiles were prepared for measurements. Measured results show that the technique is capable of distinguishing ramped and stepped Ge doping profiles with good accuracy. In the ramped soot sample, a sharp increment of doping level was observed in about 2 mm range from soot edge followed by a relative slow gradient doping accretion. As for the stepped doping sample, step sizes ranging from around 1 mm (at soot edge) to 3 mm (at soot center) were observed. All the measured profiles are in close agreement with that of the EPMA measurements. In addition, both multiphoton fluorescence (around 420 nm) and sharp second harmonic generations (at 532 nm) were observed, which indicates the co-existence of crystal and amorphous GeO2.

  7. SnO2 promoted by alkali metal oxides for soot combustion: The effects of surface oxygen mobility and abundance on the activity

    Science.gov (United States)

    Rao, Cheng; Shen, Jiating; Wang, Fumin; Peng, Honggen; Xu, Xianglan; Zhan, Hangping; Fang, Xiuzhong; Liu, Jianjun; Liu, Wenming; Wang, Xiang

    2018-03-01

    In this study, SnO2-based catalysts promoted by different alkali metal oxides with a Sn/M (M = Li, Na, K, Cs) molar ratio of 9/1 have been prepared for soot combustion. In comparison with the un-modified SnO2 support, the activity of the modified catalysts has been evidently enhanced, following the sequence of CsSn1-9 > KSn1-9 > NaSn1-9 > LiSn1-9 > SnO2. As testified by Raman, H2-TPR, soot-TPR-MS, XPS and O2-TPD results, the incorporation of various alkali metal oxides can induce the formation of more abundant and mobile oxygen species on the surface of the catalysts. Moreover, quantified results have proved that the amount of the surface active oxygen species is nearly proportional to the activity of the catalysts. CsSn1-9, the catalyst promoted by cesium oxide, owns the largest amount of surface mobile oxygen species, thus having the highest activity among all the studied catalysts. It is concluded that the amount of surface active and mobile oxygen species is the major factor determining the activity of the catalysts for soot combustion.

  8. Soot volume fraction fields in unsteady axis-symmetric flames by continuous laser extinction technique.

    Science.gov (United States)

    Kashif, Muhammad; Bonnety, Jérôme; Guibert, Philippe; Morin, Céline; Legros, Guillaume

    2012-12-17

    A Laser Extinction Method has been set up to provide two-dimensional soot volume fraction field time history at a tunable frequency up to 70 Hz inside an axis-symmetric diffusion flame experiencing slow unsteady phenomena preserving the symmetry. The use of a continuous wave laser as the light source enables this repetition rate, which is an incremental advance in the laser extinction technique. The technique is shown to allow a fine description of the soot volume fraction field in a flickering flame exhibiting a 12.6 Hz flickering phenomenon. Within this range of repetition rate, the technique and its subsequent post-processing require neither any method for time-domain reconstruction nor any correction for energy intrusion. Possibly complemented by such a reconstruction method, the technique should support further soot volume fraction database in oscillating flames that exhibit characteristic times relevant to the current efforts in the validation of soot processes modeling.

  9. Optics of Water Microdroplets with Soot Inclusions: Exact Versus Approximate Results

    Science.gov (United States)

    Liu, Li; Mishchenko, Michael I.

    2016-01-01

    We use the recently generalized version of the multi-sphere superposition T-matrix method (STMM) to compute the scattering and absorption properties of microscopic water droplets contaminated by black carbon. The soot material is assumed to be randomly distributed throughout the droplet interior in the form of numerous small spherical inclusions. Our numerically-exact STMM results are compared with approximate ones obtained using the Maxwell-Garnett effective-medium approximation (MGA) and the Monte Carlo ray-tracing approximation (MCRTA). We show that the popular MGA can be used to calculate the droplet optical cross sections, single-scattering albedo, and asymmetry parameter provided that the soot inclusions are quasi-uniformly distributed throughout the droplet interior, but can fail in computations of the elements of the scattering matrix depending on the volume fraction of soot inclusions. The integral radiative characteristics computed with the MCRTA can deviate more significantly from their exact STMM counterparts, while accurate MCRTA computations of the phase function require droplet size parameters substantially exceeding 60.

  10. Effect of Pore Structure on Soot Deposition in Diesel Particulate Filter

    Directory of Open Access Journals (Sweden)

    Kazuhiro Yamamoto

    2016-12-01

    Full Text Available Nowadays, in the after-treatment of diesel exhaust gas, a diesel particulate filter (DPF has been used to trap nano-particles of the diesel soot. However, as there are more particles inside the filter, the pressure which corresponds to the filter backpressure increases, which worsens the fuel consumption rate, together with the abatement of the available torque. Thus, a filter with lower backpressure would be needed. To achieve this, it is necessary to utilize the information on the phenomena including both the soot transport and its removal inside the DPF, and optimize the filter substrate structure. In this paper, to obtain useful information for optimization of the filter structure, we tested seven filters with different porosities and pore sizes. The porosity and pore size were changed systematically. To consider the soot filtration, the particle-laden flow was simulated by a lattice Boltzmann method (LBM. Then, the flow field and the pressure change were discussed during the filtration process.

  11. Effect of dust and soot on the growth of spruce trees

    Energy Technology Data Exchange (ETDEWEB)

    Rohmeder, E

    1960-07-01

    The effect of chronic exposure to road dust, calcium carbonate and soot on plant growth, was investigated in an experiment with 40 spruces of common heredity that were three years old at the start of the experiment and five years old at its conclusion. The plants were exposed for the entire 1956 growing season to the effect of a heavy coating of dust. In the following year, the growth performance and the production of shoots and needle mass in plants treated with dust were substantially below the untreated control plants. The root mass produced was also smaller in the treated plants than in those untreated. The considerable growth retardation after a heavy layering of dust lasting one growing season is primarily explained by the withdrawal of light and the resultant reduction in assimilation performance. In exposure to soot, however, the corrosive effect of the chemicals contained in the soot increased the extent of the damage to the plants.

  12. Comparison of the tribology performance of nano-diesel soot and graphite particles as lubricant additives

    International Nuclear Information System (INIS)

    Zhang, Zu-chuan; Cai, Zhen-bing; Peng, Jin-fang; Zhu, Min-hao

    2016-01-01

    The tribology behavior of exhaust diesel soot as a lubricant additive was investigated and then compared with that of a selection of commercial nano-graphite particles. Specifically, 0.01 wt% particles were dispersed in PAO4 oil with 1 wt% sorbitan monooleate (Span 80) as a dispersing agent, and wear tests based on the ball against plate mode were conducted at various temperatures. Different analytical techniques (e.g. transmission electron, scanning electron and infrared microscopy; energy dispersive x-ray and Raman spectroscopy; and charge measurement) were employed to characterize the chemistry and morphology of the additives and their tribology performance. The oil containing only 0.01 wt% diesel soot clearly improved wear resistance over 60 °C. In particular, at 100 °C the wear rate decreased by approximately 90% compared to the function of base oil. In the same test conditions, diesel soot exhibited better anti-wear performance than nano-graphite at high temperatures. The potential measure showed that the nano-graphite had positive charge and the diesel soot had negative charge. Electrochemical action may play an important role in the lubricant mechanisms of diesel soot and graphite as oil additives. (paper)

  13. Soot measurements for diesel and biodiesel spray combustion under high temperature highly diluted ambient conditions

    KAUST Repository

    Zhang, Ji; Jing, Wei; Roberts, William L.; Fang, Tiegang

    2014-01-01

    This paper presents the soot temperature and KL factor for biodiesel, namely fatty acid methyl ester (FAME) and diesel fuel combustion in a constant volume chamber using a two-color technique. The KL factor is a parameter for soot concentration

  14. Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII

    KAUST Repository

    Cenker, Emre; Roberts, William L.

    2017-01-01

    particle size, respectively. Overall, effects of these two processes on soot and LII model-based particle sizing are investigated by measuring the two-color time-resolved (2C-TiRe) LII signal decay from in-flame soot after two consecutive laser pulses

  15. Soot, organics, and ultrafine ash from air- and oxy-fired coal combustion

    KAUST Repository

    Andersen, Myrrha E.

    2016-10-19

    Pulverized bituminous coal was burned in a 10. W externally heated entrained flow furnace under air-combustion and three oxy-combustion inlet oxygen conditions (28, 32, and 36%). Experiments were designed to produce flames with practically relevant stoichiometric ratios (SR. =1.2-1.4) and constant residence times (2.3. s). Size-classified fly ash samples were collected, and measurements focused on the soot, elemental carbon (EC), and organic carbon (OC) composition of the total and ultrafine (<0.6. μm) fly ash. Results indicate that although the total fly ash carbon, as measured by loss on ignition, was always acceptably low (<2%) with all three oxy-combustion conditions lower than air-combustion, the ultrafine fly ash for both air-fired and oxy-fired combustion conditions consists primarily of carbonaceous material (50-95%). Carbonaceous components on particles <0.6. μm measured by a thermal optical method showed that large fractions (52-93%) consisted of OC rather than EC, as expected. This observation was supported by thermogravimetric analysis indicating that for the air, 28% oxy, and 32% oxy conditions, 14-71% of this material may be OC volatilizing between 100. C and 550. C with the remaining 29-86% being EC/soot. However, for the 36% oxy condition, OC may comprise over 90% of the ultrafine carbon with a much smaller EC/soot contribution. These data were interpreted by considering the effects of oxy-combustion on flame attachment, ignition delay, and soot oxidation of a bituminous coal, and the effects of these processes on OC and EC emissions. Flame aerodynamics and inlet oxidant composition may influence emissions of organic hazardous air pollutants (HAPs) from a bituminous coal. During oxy-coal combustion, judicious control of inlet oxygen concentration and placement may be used to minimize organic HAP and soot emissions.

  16. Simulation of an electrostatic soot-filter with continuous electrochemical conversion during the stages of development

    International Nuclear Information System (INIS)

    Muri, M.

    1996-04-01

    The dissertation describes the simulation of an electrostatic Diesel-Soot-Converter during its stages of development. This simulation is not only necessary for the interpretation of the experimental results, it also shows results for assumptions that cannot be received experimentally. The Diesel-Soot-Converter consists of a charging electrode, which charges the particles by a high-voltage and a ceramic monolith, where the particles are precipitated in the open channels because of an electric field created also by a high-voltage. Afterwards the particles are burned by a plasma. The filter-function of the Diesel-Soot-Converter was formulated and the efficiency for a vehicle was calculated. In the first part of the calculation the mass flow of a BMW 318tds and a BMW 325tds was determined for an US-FTP75-testcycle and for fuel load. In the second part the efficiency of different Diesel-Soot-Converter-types was calculated for the US-FTP75-testcycle and for full load. The use of the program with other testcycles is possible. The results of the calculations show the best configuration of the Diesel-Soot-Converter for the corresponding vehicle. Therefore with the help of this program time and money for the production of the ceramic can be saved. (author)

  17. A study of radiative properties of fractal soot aggregates using the superposition T-matrix method

    International Nuclear Information System (INIS)

    Li Liu; Mishchenko, Michael I.; Patrick Arnott, W.

    2008-01-01

    We employ the numerically exact superposition T-matrix method to perform extensive computations of scattering and absorption properties of soot aggregates with varying state of compactness and size. The fractal dimension, D f , is used to quantify the geometrical mass dispersion of the clusters. The optical properties of soot aggregates for a given fractal dimension are complex functions of the refractive index of the material m, the number of monomers N S , and the monomer radius a. It is shown that for smaller values of a, the absorption cross section tends to be relatively constant when D f f >2. However, a systematic reduction in light absorption with D f is observed for clusters with sufficiently large N S , m, and a. The scattering cross section and single-scattering albedo increase monotonically as fractals evolve from chain-like to more densely packed morphologies, which is a strong manifestation of the increasing importance of scattering interaction among spherules. Overall, the results for soot fractals differ profoundly from those calculated for the respective volume-equivalent soot spheres as well as for the respective external mixtures of soot monomers under the assumption that there are no electromagnetic interactions between the monomers. The climate-research implications of our results are discussed

  18. Root growth, secondary root formation and root gravitropism in carotenoid-deficient seedlings of Zea mays L

    Science.gov (United States)

    Ng, Y. K.; Moore, R.

    1985-01-01

    The effect of ABA on root growth, secondary-root formation and root gravitropism in seedlings of Zea mays was investigated by using Fluridone-treated seedlings and a viviparous mutant, both of which lack carotenoids and ABA. Primary roots of seedlings grown in the presence of Fluridone grew significantly slower than those of control (i.e. untreated) roots. Elongation of Fluridone-treated roots was inhibited significantly by the exogenous application of 1 mM ABA. Exogenous application of 1 micromole and 1 nmole ABA had either no effect or only a slight stimulatory effect on root elongation, depending on the method of application. The absence of ABA in Fluridone-treated plants was not an important factor in secondary-root formation in seedlings less than 9-10 d old. However, ABA may suppress secondary-root formation in older seedlings, since 11-d-old control seedlings had significantly fewer secondary roots than Fluridone-treated seedlings. Roots of Fluridone-treated and control seedlings were graviresponsive. Similar data were obtained for vp-9 mutants of Z. mays, which are phenotypically identical to Fluridone-treated seedlings. These results indicate that ABA is necessary for neither secondary-root formation nor for positive gravitropism by primary roots.

  19. Soot volume fraction in a piloted turbulent jet non-premixed flame of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, N.H.; Alwahabi, Z.T.; King, K.D. [Fluid Mechanics, Energy and Combustion Group, University of Adelaide, Adelaide, SA 5005 (Australia); School of Chemical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); Chan, Q.N. [Fluid Mechanics, Energy and Combustion Group, University of Adelaide, Adelaide, SA 5005 (Australia); School of Chemical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); School of Mechanical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); Nathan, G.J. [Fluid Mechanics, Energy and Combustion Group, University of Adelaide, Adelaide, SA 5005 (Australia); School of Mechanical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); Roekaerts, D. [Department of Multi-Scale Physics, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg, 1, NL-2628 CJ Delft (Netherlands)

    2009-07-15

    Planar laser-induced incandescence (LII) has been used to measure soot volume fraction in a well-characterised, piloted, turbulent non-premixed flame known as the ''Delft Flame III''. Simulated Dutch natural gas was used as the fuel to produce a flame closely matching those in which a wide range of previous investigations, both experimental and modelling, have been performed. The LII method was calibrated using a Santoro-style burner with ethylene as the fuel. Instantaneous and time-averaged data of the axial and radial soot volume fraction distributions of the flame are presented here along with the Probability Density Functions (PDFs) and intermittency. The PDFs were found to be well-characterised by a single exponential distribution function. The distribution of soot was found to be highly intermittent, with intermittency typically exceeding 97%, which increases measurement uncertainty. The instantaneous values of volume fraction are everywhere less than the values in strained laminar flames. This is consistent with the soot being found locally in strained flame sheets that are convected and distorted by the flow. (author)

  20. Co-formation and co-release of genotoxic PAHs, alkyl-PAHs and soot nanoparticles from gasoline direct injection vehicles

    Science.gov (United States)

    Muñoz, Maria; Haag, Regula; Honegger, Peter; Zeyer, Kerstin; Mohn, Joachim; Comte, Pierre; Czerwinski, Jan; Heeb, Norbert V.

    2018-04-01

    Gasoline direct injection (GDI) vehicles quickly replace traditional port-fuel injection (PFI) vehicles in Europe reaching about 50 million vehicles on roads in 2020. GDI vehicles release large numbers of soot nanoparticles similar to conventional diesel vehicles without particle filters. These exhausts will increasingly affect air quality in European cities. We hypothesized that such particles are released together with polycyclic aromatic hydrocarbons (PAHs) formed under the same combustion conditions. Emission data of a fleet of 7 GDI vehicles (1.2-1.8 L) including Euro-3,-4,-5 and -6 technologies revealed substantial particle emissions on average of 2.5 × 1012 particles km-1 in the cold worldwide harmonized light vehicle test cycle (cWLTC), the future European legislative driving cycle. Particle emissions increased 2-3 orders of magnitude during acceleration like CO, indicating that transient driving produces fuel-rich conditions with intense particle formation. For comparison, an Euro-5 diesel vehicle (1.6 L) equipped with a particle filter released 3.9 × 1010 particles km-1 (cWLTC), clearly within the Euro-5/6 limit value of 6.0 × 1011 particles km-1 and 64-fold below the GDI fleet average. PAH and alkyl-PAH emissions of the GDI vehicles also exceeded those of the diesel vehicle. Mean GDI emissions of 2-, 3-, 4-, 5- and 6-ring PAHs in the cWLTC were 240, 44, 5.8, 0.5 and 0.4 μg km-1, those of the diesel vehicle were only 8.8, 7.1, 8.6, 0.02 and 0.02 μg km-1, respectively. Thus mean PAH emissions of the GDI fleet were 2 orders of magnitude higher than the bench mark diesel vehicle. A comparison of the toxicity equivalent concentrations (TEQ) in the cWLTC of the GDI fleet and the diesel vehicle revealed that GDI vehicles released 200-1700 ng TEQ m-3 genotoxic PAHs, being 6-40 times higher than the diesel vehicle with 45 ng TEQ km-1. The co-release of genotoxic PAHs adsorbed on numerous soot nanoparticles is critical due to the Trojan horse effect

  1. Evidence that Blueberry Floral Extracts Influence Secondary Conidiation and Appressorial Formation of Colletotrichum fioriniae.

    Science.gov (United States)

    Waller, Timothy J; Vaiciunas, Jennifer; Constantelos, Christine; Oudemans, Peter V

    2018-05-01

    Blueberry anthracnose, caused by Colletotrichum fioriniae, is a pre- and postharvest disease of cultivated highbush blueberry (Vaccinium corymbosum). During disease development, the pathogen undergoes several lifestyle changes during host colonization, including epiphytic, quiescent, and necrotrophic phases. It is not clear, however, what if any host signals alter the pattern of colonization during the initial epiphytic phase and infection. This research investigated the role of blueberry floral extracts (FE) on fungal development. Results show that FE significantly increased both the quantity and rate of secondary conidiation and appressorial formation in vitro, suggesting that floral components could decrease the minimum time required for infection. Activity of FE was readily detected in water collected from field samples, where secondary conidiation and appressorial formation decreased as rainwater collections were further removed from flowers. A comparison of FE from four blueberry cultivars with different levels of field susceptibility revealed that appressorial formation but not secondary conidiation significantly increased with the FE from susceptible cultivars versus resistant cultivars. Inoculum supplemented with FE produced higher levels of disease on ripe blueberry fruit as compared with inoculum with water only. Flowers from other ericaceous species were found to also induce secondary conidiation and appressorial formation of C. fioriniae. This research provides strong evidence that flowers can contribute substantially to the infection process of C. fioriniae, signifying the importance of the bloom period for developing effective disease management strategies.

  2. TEM study of soot, organic aerosol, and sea-salt particles collected during CalNex

    Science.gov (United States)

    Adachi, K.; Buseck, P. R.

    2010-12-01

    Anthropogenic aerosol particles are emitted in abundance from megacities. Those particles can have important effects on both human health and climate. In this study, aerosol particles having aerodynamic diameters between 50 and 300 nm were collected during the CalNex campaign at the Pasadena ground site from May 15 to June 15, 2010, ~15 km northeast of downtown Los Angeles. The samples were analyzed using transmission electron microscopes (TEMs) to characterize particle shapes and compositions. Most samples are dominated by soot, organic aerosol (OA), sulfate, sea salt, or combinations thereof. Sizes and amounts of OA particles increased during the afternoons, and most soot particles were internally mixed with OA and sulfate in the afternoons. The proportion of soot to other material in individual particles increased and soot particles were more compact during the nights and early mornings. Sea-salt particles were commonly internally mixed with other materials. They have high Na contents with lesser N, Mg, S, K, and Ca and almost no Cl, suggesting that the Cl was replaced by sulfate or nitrate in the atmosphere. There is less OA and more sea salt and sulfate in the CalNex samples than in the samples from Mexico City that were collected during the MILAGRO campaign. Our study indicates that compositions of internally mixed aerosol particles and shapes of soot particles change significantly within a day. These changes probably influence the estimates of their effects on human health and climate.

  3. Carbon Nanostructure of Diesel Soot Particles Emitted from 2 and 4 Stroke Marine Engines Burning Different Fuels.

    Science.gov (United States)

    Lee, Won-Ju; Park, Seul-Hyun; Jang, Se-Hyun; Kim, Hwajin; Choi, Sung Kuk; Cho, Kwon-Hae; Cho, Ik-Soon; Lee, Sang-Min; Choi, Jae-Hyuk

    2018-03-01

    Diesel soot particles were sampled from 2-stroke and 4-stroke engines that burned two different fuels (Bunker A and C, respectively), and the effects of the engine and fuel types on the structural characteristics of the soot particle were analyzed. The carbon nanostructures of the sampled particles were characterized using various techniques. The results showed that the soot sample collected from the 4-stroke engine, which burned Bunker C, has a higher degree of order of the carbon nanostructure than the sample collected from the 2-stroke engine, which burned Bunker A. Furthermore, the difference in the exhaust gas temperatures originating from the different engine and fuel types can affect the nanostructure of the soot emitted from marine diesel engines.

  4. Prediction of soot and thermal radiation in a model gas turbine combustor burning kerosene fuel spray at different swirl levels

    Science.gov (United States)

    Ghose, Prakash; Patra, Jitendra; Datta, Amitava; Mukhopadhyay, Achintya

    2016-05-01

    Combustion of kerosene fuel spray has been numerically simulated in a laboratory scale combustor geometry to predict soot and the effects of thermal radiation at different swirl levels of primary air flow. The two-phase motion in the combustor is simulated using an Eulerian-Lagragian formulation considering the stochastic separated flow model. The Favre-averaged governing equations are solved for the gas phase with the turbulent quantities simulated by realisable k-ɛ model. The injection of the fuel is considered through a pressure swirl atomiser and the combustion is simulated by a laminar flamelet model with detailed kinetics of kerosene combustion. Soot formation in the flame is predicted using an empirical model with the model parameters adjusted for kerosene fuel. Contributions of gas phase and soot towards thermal radiation have been considered to predict the incident heat flux on the combustor wall and fuel injector. Swirl in the primary flow significantly influences the flow and flame structures in the combustor. The stronger recirculation at high swirl draws more air into the flame region, reduces the flame length and peak flame temperature and also brings the soot laden zone closer to the inlet plane. As a result, the radiative heat flux on the peripheral wall decreases at high swirl and also shifts closer to the inlet plane. However, increased swirl increases the combustor wall temperature due to radial spreading of the flame. The high incident radiative heat flux and the high surface temperature make the fuel injector a critical item in the combustor. The injector peak temperature increases with the increase in swirl flow mainly because the flame is located closer to the inlet plane. On the other hand, a more uniform temperature distribution in the exhaust gas can be attained at the combustor exit at high swirl condition.

  5. Investigating Soot Morphology in Counterflow Flames at Elevated Pressures

    KAUST Repository

    Amin, Hafiz Muhammad Fahid

    2018-01-01

    Practical combustion devices such as gas turbines and diesel engines operate at high pressures to increase their efficiency. Pressure significantly increases the overall soot yield. Morphology of these ultra-fine particles determines their airborne

  6. Oil soot measurement system of diesel engine; Diesel engine no oil sutsu sokutei sochi

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, Y; Moritsugu, M; Kato, N [Nippon Soken, Inc., Tokyo (Japan); Osaki, R [Denso Corp., Aichi (Japan)

    1997-10-01

    For use evaluate diesel engine in laboratory, we have developed a apparatus which can measure soot density in engine oil instantly and accurately. We have achieved accuracy of 0.03 wt% by employing the following; (1) utilize a ligh-reflecting oil soot sensor, (2) regurate the temperature and flow of the in-coming oil to be constant. 4 refs., 12 figs., 2 tabs.

  7. Soot and short-lived pollutants provide political opportunity

    Science.gov (United States)

    Victor, David G.; Zaelke, Durwood; Ramanathan, Veerabhadran

    2015-09-01

    Cutting levels of soot and other short-lived pollutants delivers tangible benefits and helps governments to build confidence that collective action on climate change is feasible. After the Paris climate meeting this December, actually reducing these pollutants will be essential to the credibility of the diplomatic process.

  8. Modelling and Simulation of Packed Bed Catalytic Converter for Oxidation of Soot in Diesel Powered Vehicles Flue Gas

    Directory of Open Access Journals (Sweden)

    Mohammad Nasikin

    2010-10-01

    Full Text Available Diesel vehicle is used in Indonesia in very big number. This vehicle exhausts pollutants especially diesel soot that can be reduces by using a catalytic converter to convert the soot to CO2. To obtain the optimal dimension of catalytic converter it is needed a model that can represent the profile of soot weight, temperature and pressure along the catalytic converter. In this study, a model is developed for packed bed catalytic converter in an adiabatic condition based on a kinetic study that has been  reported previously. Calculation of developed equations in this model uses Polymath 5.X solver with Range Kutta Method. The simulation result shows that temperature profile along catalytic converter increases with the decrease of soot weight,  while pressure profile decreases. The increase of soot weight in entering gas increases the needed converter length. On the other hand, the increase of catalyst diameter does not affect to soot weight along converter and temperature profile, but results a less pressure drop. For 2.500 c diesel engine, packed bed catalytic converter with ellipse's cross sectional of 14,5X7,5 cm diagonal and 0,8 cm catalyst particle diameter, needs 4,1 cm length.

  9. Light scattering and extinction measurements combined with laser-induced incandescence for the real-time determination of soot mass absorption cross section.

    Science.gov (United States)

    Wei, Yiyi; Ma, Lulu; Cao, Tingting; Zhang, Qing; Wu, Jun; Buseck, Peter R; Thompson, J E

    2013-10-01

    An aerosol albedometer was combined with laser-induced incandescence (LII) to achieve simultaneous measurements of aerosol scattering, extinction coefficient, and soot mass concentration. Frequency doubling of a Nd:YAG laser line resulted in a colinear beam of both λ = 532 and 1064 nm. The green beam was used to perform cavity ring-down spectroscopy (CRDS), with simultaneous measurements of scattering coefficient made through use of a reciprocal sphere nephelometer. The 1064 nm beam was selected and directed into a second integrating sphere and used for LII of light-absorbing kerosene lamp soot. Thermal denuder experiments showed the LII signals were not affected by the particle mixing state when laser peak power was 1.5-2.5 MW. The combined measurements of optical properties and soot mass concentration allowed determination of mass absorption cross section (M.A.C., m(2)/g) with 1 min time resolution when soot concentrations were in the low microgram per cubic meter range. Fresh kerosene nanosphere soot (ns-soot) exhibited a mean M.A.C and standard deviation of 9.3 ± 2.7 m(2)/g while limited measurements on dry ambient aerosol yielded an average of 8.2 ± 5.9 m(2)/g when soot was >0.25 μg/m(3). The method also detected increases in M.A.C. values associated with enhanced light absorption when polydisperse, laboratory-generated ns-soot particles were embedded within or coated with ammonium nitrate, ammonium sulfate, and glycerol. Glycerol coatings produced the largest fractional increase in M.A.C. (1.41-fold increase), while solid coatings of ammonium sulfate and ammonium nitrate produced increases of 1.10 and 1.06, respectively. Fresh, ns-soot did not exhibit increased M.A.C. at high relative humidity (RH); however, lab-generated soot coated with ammonium nitrate and held at 85% RH exhibited M.A.C. values nearly double the low-humidity case. The hybrid instrument for simultaneously tracking soot mass concentration and aerosol optical properties in real time is a

  10. Morphological transformation of soot: investigation of microphysical processes during the condensation of sulphuric acid and limonene ozonolysis products vapours

    Science.gov (United States)

    Pathak, R. K. P.; Pei, X.; Hallquist, M.; Pagels, J. H.

    2017-12-01

    Morphological transformation of soot particle by condensation of low volatility materials on it is a dominant atmospheric process with serious implications for its optical and hygroscopic properties, and atmospheric lifetime. In this study, the morphological transformation of soot agglomerate under the influence of condensation of vapours of sulphuric acid, and/or limonene ozonolysis products were investigated systematically using a Differential Mobility Analyser-Aerosol Particle Mass Analyser (DMA-APM) and the Tandem DMA techniques integrated with a laminar flow-tube system. We discovered that the morphology transformation of soot in general was a sequence of two-step process, i.e. (i) filling of void space within soot agglomerate; (ii) growth of particle diameter. These two steps followed and complimented each other. In the very beginning the filling was the dominant process followed by growth until it led to the accumulation of enough material that in turn exerted surface forces that eventually facilitated the further filling. The filling of void space was constrained by the initial morphology of fresh soot and the nature and amount of the material condensed. This process continued in several sequential steps until all void space within the soot agglomerate was filled completely and then growth of a spherical particle continued as long as mass was condensed on it. In this study, we developed a framework to quantify the microphysical transformation of soot upon the condensation of various materials. The framework utilized experimental data and hypothesis of ideal sphere growth and filling of voids to quantify the distribution of condensed materials in these two processes complimenting each other. Using this framework, we have quantified the percentage of material that went into processes of particle growth and void filling at each step. Using the same framework, we further estimated the fraction of internal voids and open voids and used this information to derive

  11. Impact on vehicle fuel economy of the soot loading on diesel particulate filters made of different substrate materials

    International Nuclear Information System (INIS)

    Millo, Federico; Andreata, Maurizio; Rafigh, Mahsa; Mercuri, Davide; Pozzi, Chiara

    2015-01-01

    Wall flow DPFs (Diesel Particulate Filters) are nowadays universally adopted for all European passenger cars. Since the properties of the filter substrate material play a fundamental role in determining the optimal soot loading level to be reached before DPF regeneration, three different filter material substrates (Silicon Carbide, Aluminum Titanate and Cordierite) were investigated in this work, considering different driving conditions, after treatment layouts and regeneration strategies. In the first step of the research, an experimental investigation on the three different substrates over the NEDC (New European Driving Cycle) was performed. The data obtained from experiments were then used for the calibration and the validation of a one dimensional fluid-dynamic engine and after treatment simulation model. Afterward, the model was used to predict the vehicle fuel consumption increments as a function of the exhaust back pressure due to the soot loading for different driving cycles. The results showed that appreciable fuel consumption increments could be noticed only in particular driving conditions, and, as a consequence, in most of the cases the optimal filter regeneration strategy corresponds to reach the highest soot loading that still ensures the component safety even in case of uncontrolled regeneration events. - Highlights: • Three different substrate materials for a Diesel Particulate Filter were investigated. • Fuel consumption increases due to DPF soot loading were generally not appreciable. • Optimal soot loading before regeneration was the highest safeguarding DPF integrity. • SiC substrate showed highest soot load limit and lowest fuel consumption penalties. • AT and Cd substrate properties lead to lower soot load limits than SiC

  12. Effect of A-site deficiency in LaMn_0_._9Co_0_._1O_3 perovskites on their catalytic performance for soot combustion

    International Nuclear Information System (INIS)

    Dinamarca, Robinson; Garcia, Ximena; Jimenez, Romel; Fierro, J.L.G.; Pecchi, Gina

    2016-01-01

    Highlights: • A-site defective perovskites increases the oxidation state of the B-cation. • Not always non-stoichiometric perovskites exhibit higher catalytic activity in soot combustion. • The highly symmetric cubic crystalline structure diminishes the redox properties of perovskites. - Abstract: The influence of lanthanum stoichiometry in Ag-doped (La_1_-_xAg_xMn_0_._9Co_0_._1O_3) and A-site deficient (La_1_-_xMn_0_._9Co_0_._1O_3_-_δ) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O_2-TPD and TPR. The formation of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag_2O segregated phases and the redox pair Mn"4"+/Mn"3"+. A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn"4"+/Mn"3"+, which is attributed to the cubic crystalline structure.

  13. Evaluation and optimisation of phenomenological multi-step soot model for spray combustion under diesel engine-like operating conditions

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song

    2015-01-01

    with the spray combustion solver. Prior to the soot modelling, combustion simulations are carried out. Numerical results show that the ignition delay times and lift-off lengths exhibit good agreement with the experimental measurements across a wide range of operating conditions, apart from those in the cases......, variation of spatial soot distribution and soot mass produced at oxygen molar fractions ranging from 10.0 to 21.0% for both low and high density conditions are reproduced....

  14. A new oxidation flow reactor for measuring secondary aerosol formation of rapidly changing emission sources

    Science.gov (United States)

    Simonen, Pauli; Saukko, Erkka; Karjalainen, Panu; Timonen, Hilkka; Bloss, Matthew; Aakko-Saksa, Päivi; Rönkkö, Topi; Keskinen, Jorma; Dal Maso, Miikka

    2017-04-01

    Oxidation flow reactors (OFRs) or environmental chambers can be used to estimate secondary aerosol formation potential of different emission sources. Emissions from anthropogenic sources, such as vehicles, often vary on short timescales. For example, to identify the vehicle driving conditions that lead to high potential secondary aerosol emissions, rapid oxidation of exhaust is needed. However, the residence times in environmental chambers and in most oxidation flow reactors are too long to study these transient effects ( ˜ 100 s in flow reactors and several hours in environmental chambers). Here, we present a new oxidation flow reactor, TSAR (TUT Secondary Aerosol Reactor), which has a short residence time ( ˜ 40 s) and near-laminar flow conditions. These improvements are achieved by reducing the reactor radius and volume. This allows studying, for example, the effect of vehicle driving conditions on the secondary aerosol formation potential of the exhaust. We show that the flow pattern in TSAR is nearly laminar and particle losses are negligible. The secondary organic aerosol (SOA) produced in TSAR has a similar mass spectrum to the SOA produced in the state-of-the-art reactor, PAM (potential aerosol mass). Both reactors produce the same amount of mass, but TSAR has a higher time resolution. We also show that TSAR is capable of measuring the secondary aerosol formation potential of a vehicle during a transient driving cycle and that the fast response of TSAR reveals how different driving conditions affect the amount of formed secondary aerosol. Thus, TSAR can be used to study rapidly changing emission sources, especially the vehicular emissions during transient driving.

  15. Electron spin resonance of particulate soot samples from automobiles to help environmental studies

    International Nuclear Information System (INIS)

    Yamanaka, C.; Matsuda, T.; Ikeya, M.

    2005-01-01

    The application of electron spin resonance (ESR) was studied for diesel soot samples and suspended particulate matter (SPM) from automobile engines. Soot samples or diesel exhaust particles (DEP) were recovered at various points: in the exhaust pipe of a diesel engine, at the dust sampler of a highway tunnel (standard DEP), on the soundproofing wall alongside a heavy traffic road, and on the filters of a dust sampler for SPM. The diesel soot samples apparently showed two ESR spectra: one was a broad spectrum at g=2.1 with a line width of ca. 80-120mT and the other was a sharp signal of a carbon radical at g=2.003 with a line width of 0.4mT. Annealing experiments with a DEP sample at 250 deg. C revealed drastic enhancement of the sharp ESR signal, which suggested a thermal process of carbonization of remnant organics. An oximetric study by ESR showed an enhancement of the broad signal in the diesel soot sample as well as in the sharp ESR signal. Therefore, the main part of the broad ESR signal would be attributed to carbon radicals, which form a different configuration, probably closely interacting aggregates. Enhancement of the sharp ESR signal was not observed in the standard DEP sample under vacuum condition, which suggested less adsorption sites on the surface of DEP samples

  16. In vitro induction of tuber formation for the synthesis of secondary ...

    African Journals Online (AJOL)

    In vitro induction of tuber formation for the synthesis of secondary metabolites in Chlorophytum borivilianum Sant. et Fernand. Gulab S Thakur, Rohit Sharma, Bhagwan S Sanodiya, Rakesh Baghel, Radhika Thakur, Bansh N Singh, Ashish Savita, Avinash Dubey, Latasha Sikarwar, Pallavi Jaiswal, Gunja Khatri, GBKS ...

  17. The SOA/VOC/NOx system: an explicit model of secondary organic aerosol formation

    Directory of Open Access Journals (Sweden)

    S. Madronich

    2007-11-01

    Full Text Available Our current understanding of secondary organic aerosol (SOA formation is limited by our knowledge of gaseous secondary organics involved in gas/particle partitioning. The objective of this study is to explore (i the potential for products of multiple oxidation steps contributing to SOA, and (ii the evolution of the SOA/VOC/NOx system. We developed an explicit model based on the coupling of detailed gas-phase oxidation schemes with a thermodynamic condensation module. Such a model allows prediction of SOA mass and speciation on the basis of first principles. The SOA/VOC/NOx system is studied for the oxidation of 1-octene under atmospherically relevant concentrations. In this study, gaseous oxidation of octene is simulated to lead to SOA formation. Contributors to SOA formation are shown to be formed via multiple oxidation steps of the parent hydrocarbon. The behaviour of the SOA/VOC/NOx system simulated using the explicit model agrees with general tendencies observed during laboratory chamber experiments. This explicit modelling of SOA formation appears as a useful exploratory tool to (i support interpretations of SOA formation observed in laboratory chamber experiments, (ii give some insights on SOA formation under atmospherically relevant conditions and (iii investigate implications for the regional/global lifetimes of the SOA.

  18. Secondary organic aerosol formation from biomass burning intermediates: phenol and methoxyphenols

    Directory of Open Access Journals (Sweden)

    L. D. Yee

    2013-08-01

    Full Text Available The formation of secondary organic aerosol from oxidation of phenol, guaiacol (2-methoxyphenol, and syringol (2,6-dimethoxyphenol, major components of biomass burning, is described. Photooxidation experiments were conducted in the Caltech laboratory chambers under low-NOx (2O2 as the OH source. Secondary organic aerosol (SOA yields (ratio of mass of SOA formed to mass of primary organic reacted greater than 25% are observed. Aerosol growth is rapid and linear with the primary organic conversion, consistent with the formation of essentially non-volatile products. Gas- and aerosol-phase oxidation products from the guaiacol system provide insight into the chemical mechanisms responsible for SOA formation. Syringol SOA yields are lower than those of phenol and guaiacol, likely due to novel methoxy group chemistry that leads to early fragmentation in the gas-phase photooxidation. Atomic oxygen to carbon (O : C ratios calculated from high-resolution-time-of-flight Aerodyne Aerosol Mass Spectrometer (HR-ToF-AMS measurements of the SOA in all three systems are ~ 0.9, which represent among the highest such ratios achieved in laboratory chamber experiments and are similar to that of aged atmospheric organic aerosol. The global contribution of SOA from intermediate volatility and semivolatile organic compounds has been shown to be substantial (Pye and Seinfeld, 2010. An approach to representing SOA formation from biomass burning emissions in atmospheric models could involve one or more surrogate species for which aerosol formation under well-controlled conditions has been quantified. The present work provides data for such an approach.

  19. Secondary instability in drift wave turbulence as a mechanism for avalanche and zonal flow formation

    International Nuclear Information System (INIS)

    Diamond, P.H.; Champeaux, S.; Malkov, M.

    2001-01-01

    We report on recent developments in the theory of secondary instability in drift-ITG turbulence. Specifically, we explore secondary instability as a mechanism for avalanche formation. A theory of radially extended streamer cell formation and self-regulation is presented. Aspects of streamer structure and dynamics are used to estimate the variance of the drift-wave induced flux. The relation between streamer cell structures and the avalanche concept is discussed, as are the implications of our results for transport modeling. (author)

  20. Visualizing the mobility of silver during catalytic soot oxidation

    DEFF Research Database (Denmark)

    Gardini, Diego; Christensen, Jakob M.; Damsgaard, Christian Danvad

    2016-01-01

    The catalytic activity and mobility of silver nanoparticles used as catalysts in temperature programmed oxidation of soot:silver (1:5 wt:wt) mixtures have been investigated by means of flow reactor experiments and in situ environmental transmission electron microscopy (ETEM). The carbon oxidation...

  1. Soot accumulation in diesel particulate filters using ULSD and B20 biodiesel fuel blends

    Energy Technology Data Exchange (ETDEWEB)

    Charbonneau, P.; Wallace, J.S. [Toronto Univ., ON (Canada)

    2009-07-01

    Soot accumulation in a diesel particulate filter was investigated using a newly developed dissection method that loads and dissects diesel particulate filters (DPFs). In particular, this study examined the differences in soot accumulation between ultra-low sulphur diesel (ULSD) and a B20 biodiesel blend. DPFs loaded for exposure times of 1, 2, 5 and 10 hours. Scanning electron microscopy (SEM) was used to analyze the samples of the filter substrate. The differences in particulate size and number distribution between fuels were attributed to performance differences in DPFs. ULSD loaded filters experienced increased loading and a greater pressure drop across the filters. According to SEM images, the soot cake was a relatively shallow feature increasing in density to form discrete coarse agglomerates and cakes. It was concluded that this newly developed methodology has potential for future studies in DPF loading.

  2. Soot in the atmosphere and snow surface of Antarctica

    International Nuclear Information System (INIS)

    Warren, S.G.; Clarke, A.D.

    1990-01-01

    Samples of snow collected near the south pole during January and February 1986 were analyzed for the presence of light-absorbing particles by passing the melted snow through a nuclepore filter. Transmission of light through the filter showed that snow far from the station contains the equivalent of 0.1-0.3 ng of carbon per gram of snow (ng/g). Samples of ambient air were filtered and found to contain about 1-2 ng of carbon per kilogram of air, giving a scavenging ratio of about 150. The snow downwind of the station exhibited a well-defined plume of soot due to the burning of diesel fuel, but even in the center of the plume 1 km downwind, the soot concentration was only 3 ng/g, too small to affect snow albedo significantly. Measurements of snow albedo near large inland stations are therefore probably representative of their surrounding regions

  3. Impact of morphology on the radiative properties of fractal soot aggregates

    International Nuclear Information System (INIS)

    Doner, Nimeti; Liu, Fengshan

    2017-01-01

    The impact of morphology on the radiative properties of fractal soot aggregates was investigated using the discrete dipole approximation (DDA). The optical properties of four different types of aggregates of freshly emitted soot with a fractal dimension D f =1.65 and a fractal pre-factor k f =1.76 were calculated. The four types of aggregates investigated are formed by uniform primary particles in point-touch, by uniform but overlapping primary particles, by uniform but enlarged primary particles in point-touch, and formed by point-touch and polydisperse primary particles. The radiative properties of aggregates consisting of N=20, 56 and 103 primary particles were numerically evaluated for a given refractive index at 0.532 and 1.064 μm. The radiative properties of soot aggregates vary strongly with the volume equivalent radius a eff and wavelength. The accuracy of DDA was evaluated in the first and fourth cases against the generalized multi-sphere Mie (GMM) solution in terms of the vertical–vertical differential scattering cross section (C vv ). The model predicted the average relative deviations from the base case to be within 15–25% for C vv , depending on the number of particles for the aggregate. The scattering cross sections are only slightly affected by the overlapping but more significantly influenced by primary particle polydispersity. It was also found that the enlargement of primary particles by 20% has a strong effect on soot aggregate radiative properties. - Highlights: • The radiative properties of aggregates of N=20, 56 and 103 primary particles were investigated. • Four different cases, formed by point-touch, overlapping, aggregate expansion and polydispersion, were studied. • The effects of overlapping and aggregate expansion on morphology are found to be the same.

  4. Formative assessment practices in Bhutanese secondary schools and its impact on Quality of Education

    DEFF Research Database (Denmark)

    Utha, Karma

    Using case study approach, the dissertation provides the notions and practices of formative assessment in Bhutanese Secondary Schools. It includes the teachers’ understanding of the practice of student-centered teaching and learning, which is regarded as a precondition for effective formative...... assessment. It also take account of those features of formative assessment which are much more favored by students and teachers in the case study schools....

  5. Sooting behavior of oxygenated fuels in a diffusion burner

    NARCIS (Netherlands)

    Boot, M.D.; Luijten, C.C.M.; Baert, R.S.G.; Edenhofer, R.; Dirks, H.; Lucka, K.; Köhne, H.

    2009-01-01

    Different strategies are being investigated towards reducing engine-out emission levels of soot and NOx of modern Diesel engines. A fuel-based strategy currently under investigation, entails the use of low cetane number (CN; i.e.low reactive) oxygenates. Previous research has shown that low CN

  6. Improved soot blowing, based on needs, through measurement of the natural frequency of the heat transferring tubes; Foerbaettrad behovsstyrd sotning genom maetning av oeverfoerande tubernas egenfrekvens

    Energy Technology Data Exchange (ETDEWEB)

    Blom, Elisabet; Ivarsson, Christofer

    2007-11-15

    The aim of the project is to develop a method for detecting soot on the transferring tubes by measuring the Eigen frequency of the tubes as a function of the soot deposit growth. The project is a pilot study independent of boiler type and it is applicable to all boilers where soot deposit on transferring tubes is a repeating issue. The report is supposed to answer two major questions. Is it possible to make use of Eigen frequencies in order to trace soot deposit on transferring tubes? What governing parameters are related to the Eigen frequency of transferring tubes? By today, soot blowing is executed after recommendations from the manufacturer in terms of number of soot blowing per time unit. The fuel type as well as boiler type has great influence on the soot deposit growth. The objective of the project is to investigate whether the mechanical properties of the transferring tube can be used to detect soot deposit. The project is divided into a theoretical and a practical part. The theoretical part covers the design of the probe and the change of its mechanical properties when soot deposit is present. Practical experiments were then carried out in a laboratory were the probes mechanical properties with and without soot deposit were investigated. It was shown that the Eigen frequency of the probe decreased with an increased mass due to soot deposit. A test was also made in a boiler at SAKAB but difficulties in attaching the probe to the inspection hatch. The results varied and the interpretation of the results become difficult. However, it was obvious that the mechanical properties of the probe changed with the amount of soot deposit. It was concluded that detection of soot deposit by studying the mechanical properties of the transferring tubes is possible. Yet, using a probe is no optimal solution, instead measurements should be done directly on the heat transferring tubes. In addition, a strategy for controlling the soot deposit has to be developed

  7. Mechanisms of Formation of Secondary Organic Aerosols and Implications for Global Radiative Forcing

    Energy Technology Data Exchange (ETDEWEB)

    Seinfeld, John H. [California Inst. of Technology (CalTech), Pasadena, CA (United States)

    2011-12-02

    Organic material constitutes about 50% of global atmospheric aerosol mass, and the dominant source of organic aerosol is the oxidation of volatile hydrocarbons, to produce secondary organic aerosol (SOA). Understanding the formation of SOA is crucial to predicting present and future climate effects of atmospheric aerosols. The goal of this program is to significantly increase our understanding of secondary organic aerosol (SOA) formation in the atmosphere. Ambient measurements indicate that the amount of SOA in the atmosphere exceeds that predicted in current models based on existing laboratory chamber data. This would suggest that either the SOA yields measured in laboratory chambers are understated or that all major organic precursors have not been identified. In this research program we are systematically exploring these possibilities.

  8. Candle soot nanoparticles-polydimethylsiloxane composites for laser ultrasound transducers

    Science.gov (United States)

    Chang, Wei-Yi; Huang, Wenbin; Kim, Jinwook; Li, Sibo; Jiang, Xiaoning

    2015-10-01

    Generation of high power laser ultrasound strongly demands the advanced materials with efficient laser energy absorption, fast thermal diffusion, and large thermoelastic expansion capabilities. In this study, candle soot nanoparticles-polydimethylsiloxane (CSNPs-PDMS) composite was investigated as the functional layer for an optoacoustic transducer with high-energy conversion efficiency. The mean diameter of the collected candle soot carbon nanoparticles is about 45 nm, and the light absorption ratio at 532 nm wavelength is up to 96.24%. The prototyped CSNPs-PDMS nano-composite laser ultrasound transducer was characterized and compared with transducers using Cr-PDMS, carbon black (CB)-PDMS, and carbon nano-fiber (CNFs)-PDMS composites, respectively. Energy conversion coefficient and -6 dB frequency bandwidth of the CSNPs-PDMS composite laser ultrasound transducer were measured to be 4.41 × 10-3 and 21 MHz, respectively. The unprecedented laser ultrasound transduction performance using CSNPs-PDMS nano-composites is promising for a broad range of ultrasound therapy applications.

  9. Hybrid sparse blind deconvolution: an implementation of SOOT algorithm to real data

    Science.gov (United States)

    Pakmanesh, Parvaneh; Goudarzi, Alireza; Kourki, Meisam

    2018-06-01

    Getting information of seismic data depends on deconvolution as an important processing step; it provides the reflectivity series by signal compression. This compression can be obtained by removing the wavelet effects on the traces. The recently blind deconvolution has provided reliable performance for sparse signal recovery. In this study, two deconvolution methods have been implemented to the seismic data; the convolution of these methods provides a robust spiking deconvolution approach. This hybrid deconvolution is applied using the sparse deconvolution (MM algorithm) and the Smoothed-One-Over-Two algorithm (SOOT) in a chain. The MM algorithm is based on the minimization of the cost function defined by standards l1 and l2. After applying the two algorithms to the seismic data, the SOOT algorithm provided well-compressed data with a higher resolution than the MM algorithm. The SOOT algorithm requires initial values to be applied for real data, such as the wavelet coefficients and reflectivity series that can be achieved through the MM algorithm. The computational cost of the hybrid method is high, and it is necessary to be implemented on post-stack or pre-stack seismic data of complex structure regions.

  10. Fundamental insight in soot oxidation over a Ag/Co3O4 catalyst by means of Environmental TEM

    DEFF Research Database (Denmark)

    Gardini, Diego; Christiansen, J. M.; Jensen, Anker Degn

    A novel Ag/Co3O4 catalyst for low-temperature soot oxidation has been studied by means of environmental TEM in order to get fundamental insight in the oxidation mechanism. Soot particles generated in diesel engines are responsible for respiratory diseases, lung cancer and affect the climate both...... on preparation method, degree of contact with the soot and temperature range. In order to fully understand the role of the single constituents and the influence of different operating conditions in the overall catalytic activity, flow reactor experiments have been coupled with in situ soot oxidation...

  11. Combustion and Gasification Collection of Diesel Soot by Means of Microwave Heating

    Directory of Open Access Journals (Sweden)

    Xueshi YAO

    2014-06-01

    Full Text Available The experiment of integrated purification of diesel soot was made by means of microwave heating. The experiment includes combustion and gasification collection. The catalytic effect of ceramic carrier was used in the combustion process. In order to improve the purification efficiency of PM2.5 particles, the surfactants were used in gasification collection. The model of computer control was set up so that the purification course could be controlled. The experimental principle was analyzed. Experiment result indicated that the diesel soot purifying efficiency is more than 90 %. The purification efficiency can be improved further by the optimization design of experimental device.

  12. Investigation of soot by two-color four-wave mixing

    Energy Technology Data Exchange (ETDEWEB)

    Hemmerling, B; Stampanoni-Panariello, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    A novel, non-intrusive technique has been used for the temporally resolved investigation of the interaction of laser radiation and soot in a flame. While there is a fairly good agreement between measurement and simulation remaining discrepancies indicate some shortcomings of the model employed. (author) 2 figs., 2 refs.

  13. Secondary aerosol formation from photochemical aging of aircraft exhaust in a smog chamber

    Directory of Open Access Journals (Sweden)

    M. A. Miracolo

    2011-05-01

    Full Text Available Field experiments were performed to investigate the effects of photo-oxidation on fine particle emissions from an in-use CFM56-2B gas turbine engine mounted on a KC-135 Stratotanker airframe. Emissions were sampled into a portable smog chamber from a rake inlet installed one-meter downstream of the engine exit plane of a parked and chocked aircraft. The chamber was then exposed to sunlight and/or UV lights to initiate photo-oxidation. Separate tests were performed at different engine loads (4, 7, 30, 85 %. Photo-oxidation created substantial secondary particulate matter (PM, greatly exceeding the direct PM emissions at each engine load after an hour or less of aging at typical summertime conditions. After several hours of photo-oxidation, the ratio of secondary-to-primary PM mass was on average 35 ± 4.1, 17 ± 2.5, 60 ± 2.2, and 2.7 ± 1.1 for the 4, 7, 30, and 85 % load experiments, respectively. The composition of secondary PM formed strongly depended on load. At 4 % load, secondary PM was dominated by secondary organic aerosol (SOA. At higher loads, the secondary PM was mainly secondary sulfate. A traditional SOA model that accounts for SOA formation from single-ring aromatics and other volatile organic compounds underpredicts the measured SOA formation by ~60 % at 4 % load and ~40 % at 85 % load. Large amounts of lower-volatiliy organic vapors were measured in the exhaust; they represent a significant pool of SOA precursors that are not included in traditional SOA models. These results underscore the importance of accounting for atmospheric processing when assessing the influence of aircraft emissions on ambient PM levels. Models that do not account for this processing will likely underpredict the contribution of aircraft emissions to local and regional air pollution.

  14. A review of the literature on soot production during in-situ burning of oil

    International Nuclear Information System (INIS)

    Fraser, J.; Buist, I.

    1997-01-01

    Available literature on soot production during in-situ burning of oil was reviewed to determine the range of smoke yields generated by in-situ burning of petroleum oils in water, and to determine the effects of the size of fire and the type of oil burned. For crude oil, data sets statistical analysis showed that, with a fairly high degree of confidence, smoke yield increases with fire diameter. Based on a limited number of available data sets for identifiable oil types, it appears that most oils (Arabian crude the only exception) show roughly the same correlation of smoke yield with fire diameter. Pool fires from aromatic hydrocarbons such as toluene appear to produce more soot than similar fires with crude oil. Fires of lower molecular weight non-aromatics produce an order of magnitude less soot than crude oil fires. Predictive equations with correlation coefficients are provided for specific crude oils. 50 refs., 5 tabs., 13 figs

  15. Engineering the Oryza sativa cell wall with rice NAC transcription factors regulating secondary wall formation

    Directory of Open Access Journals (Sweden)

    Kouki eYoshida

    2013-10-01

    Full Text Available Plant tissues that require structural rigidity synthesize a thick, strong secondary cell wall of lignin, cellulose and hemicelluloses in a complicated bridged structure. Master regulators of secondary wall synthesis were identified in dicots, and orthologs of these regulators have been identified in monocots, but regulation of secondary cell wall formation in monocots has not been extensively studied. Here we demonstrate that the rice transcription factors SECONDARY WALL NAC DOMAIN PROTEINs (SWNs can regulate secondary wall formation in rice (Oryza sativa and are potentially useful for engineering the monocot cell wall. The OsSWN1 promoter is highly active in sclerenchymatous cells of the leaf blade and less active in xylem cells. By contrast, the OsSWN2 promoter is highly active in xylem cells and less active in sclerenchymatous cells. OsSWN2 splicing variants encode two proteins; the shorter protein (OsSWN2S has very low transcriptional activation ability, but the longer protein (OsSWN2L and OsSWN1 have strong transcriptional activation ability. In rice, expression of an OsSWN2S chimeric repressor, driven by the OsSWN2 promoter, resulted in stunted growth and para-wilting (leaf rolling and browning under normal water conditions due to impaired vascular vessels. The same OsSWN2S chimeric repressor, driven by the OsSWN1 promoter, caused a reduction of cell wall thickening in sclerenchymatous cells, a drooping leaf phenotype, reduced lignin and xylose contents and increased digestibility as forage. These data suggest that OsSWNs regulate secondary wall formation in rice and manipulation of OsSWNs may enable improvements in monocotyledonous crops for forage or biofuel applications.

  16. Photoacoustic Soot Spectrometer (PASS) Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Dubey, M [Los Alamos National Laboratory; Springston, S [Brookhaven National Laboratory; Koontz, A [Pacific Northwest National Laboratory; Aiken, A [Los Alamos National Laboratory

    2013-01-17

    The photoacoustic soot spectrometer (PASS) measures light absorption by aerosol particles. As the particles pass through a laser beam, the absorbed energy heats the particles and in turn the surrounding air, which sets off a pressure wave that can be detected by a microphone. The PASS instruments deployed by ARM can also simultaneously measure the scattered laser light at three wavelengths and therefore provide a direct measure of the single-scattering albedo. The Operator Manual for the PASS-3100 is included here with the permission of Droplet Measurement Technologies, the instrument’s manufacturer.

  17. Measurement of Soot Volume Fraction and Temperature for Oxygen-Enriched Ethylene Combustion Based on Flame Image Processing

    Directory of Open Access Journals (Sweden)

    Weijie Yan

    2017-05-01

    Full Text Available A method for simultaneously visualizing the two-dimensional distributions of temperature and soot volume fraction in an ethylene flame was presented. A single-color charge-coupled device (CCD camera was used to capture the flame image in the visible spectrum considering the broad-response spectrum of the R and G bands of the camera. The directional emissive power of the R and G bands were calibrated and used for measurement. Slightly increased temperatures and reduced soot concentration were predicted in the central flame without self-absorption effects considered, an iterative algorithm was used for eliminating the effect of self-absorption. Nine different cases were presented in the experiment to demonstrate the effects of fuel mass flow rate and oxygen concentration on temperature and soot concentration in three different atmospheres. For ethylene combustion in pure-air atmosphere, as the fuel mass flow rate increased, the maximum temperature slightly decreased, and the maximum soot volume fraction slightly increased. For oxygen fractions of 30%, 40%, and 50% combustion in O2/N2 oxygen-enhanced atmospheres, the maximum flame temperatures were 2276, 2451, and 2678 K, whereas combustion in O2/CO2 atmospheres were 1916, 2322, and 2535 K. The maximum soot volume fractions were 4.5, 7.0, and 9.5 ppm in oxygen-enriched O2/N2 atmosphere and 13.6, 15.3, and 14.8 ppm in oxygen-enriched O2/CO2 atmosphere. Compared with the O2/CO2 atmosphere, combustion in the oxygen-enriched O2/N2 atmosphere produced higher flame temperature and larger soot volume fraction. Preliminary results indicated that this technique is reliable and can be used for combustion diagnosis.

  18. Volatile particles formation during PartEmis: a modelling study

    Directory of Open Access Journals (Sweden)

    X. Vancassel

    2004-01-01

    Full Text Available A modelling study of the formation of volatile particles in a combustor exhaust has been carried out in the frame of the PartEmis European project. A kinetic model has been used in order to investigate nucleation efficiency of the H2O-H2SO4 binary mixture in the sampling system. A value for the fraction of the fuel sulphur S(IV converted into S(VI has been indirectly deduced from comparisons between model results and measurements. In the present study, ranges between roughly 2.5% and 6%, depending on the combustor settings and on the value assumed for the parameter describing sulphuric acid wall losses. Soot particles hygroscopicity has also been investigated as their activation is a key parameter for contrail formation. Growth factors of monodisperse particles exposed to high relative humidity (95% have been calculated and compared with experimental results. The modelling study confirms that the growth factor increases as the soot particle size decreases.

  19. Intelligent soot blowing for boilers co-firing waste and biofuel; Behovsstyrd sotblaasning foer bio- och avfallseldade pannor - inventering och teknikval

    Energy Technology Data Exchange (ETDEWEB)

    Kjoerk, Anders [S.E.P. Scandinavian Energy Project AB, Goeteborg (Sweden)

    2003-11-01

    To achieve optimum boiler operation and performance it is necessary to control the cleanliness and limit the fouling of the heat transfer surfaces. Historically, the heating surfaces in boilers firing biomass and waste are cleaned by steamblowing soot blowers on scheduled time-based and/or parameter-based intervals or by mechanical methods. With the advent of fuel switching strategies and use of mixed-in industrial waste, the control of heating surface cleanliness has become even more crucial for these boilers. Scheduled and/or parameter based approaches do not easily address operational changes. As plant operators push to achieve greater efficiency and performance from their boilers, the ability to more effectively optimize cleaning cycles has become increasingly important. If soot blowing is done only when and where it is required rather than at set intervals, unit performance can be maintained with reduced blowing, which saves steam. Two philosophical approaches toward intelligent soot blowing are currently being applied in the industry. One incorporates heat flux monitors to gather real-time heat transfer data to determine which areas of the furnace need cleaning. The other uses indirect temperature and pressure data to infer locations where soot blowing is needed, and is mainly applied for controlling soot blowers in the superheater and economiser area. The heat flux monitors are so fare used for control of the furnace wall blowers. A system using temperature, pressure and flow data does not require much additional instrumentation as compared with what is available on a standard boiler. However the blower control system must be capable of operating blowers on an individual basis. For advanced options it should also be possible to adjust the speed of the soot blower and the steam pressure. The control program could be more or less advanced but the ability to model heating surfaces and determine real-time cleanliness is crucial for an intelligent soot blowing

  20. Arctic tundra shrub invasion and soot deposition: Consequences for spring snowmelt and near-surface air temperatures

    Science.gov (United States)

    Strack, John E.; Pielke, Roger A.; Liston, Glen E.

    2007-12-01

    Invasive shrubs and soot pollution both have the potential to alter the surface energy balance and timing of snow melt in the Arctic. Shrubs reduce the amount of snow lost to sublimation on the tundra during the winter leading to a deeper end-of-winter snowpack. The shrubs also enhance the absorption of energy by the snowpack during the melt season by converting incoming solar radiation to longwave radiation and sensible heat. Soot deposition lowers the albedo of the snow, allowing it to more effectively absorb incoming solar radiation and thus melt faster. This study uses the Colorado State University Regional Atmospheric Modeling System version 4.4 (CSU-RAMS 4.4), equipped with an enhanced snow model, to investigate the effects of shrub encroachment and soot deposition on the atmosphere and snowpack in the Kuparuk Basin of Alaska during the May-June melt period. The results of the simulations suggest that a complete invasion of the tundra by shrubs leads to a 2.2°C warming of 3 m air temperatures and a 108 m increase in boundary layer depth during the melt period. The snow-free date also occurred 11 d earlier despite having a larger initial snowpack. The results also show that a decrease in the snow albedo of 0.1, owing to soot pollution, caused the snow-free date to occur 5 d earlier. The soot pollution caused a 1.0°C warming of 3 m air temperatures and a 25 m average deepening of the boundary layer.

  1. MINIMIZATION OF NO EMISSIONS FROM MULTI-BURNER COAL-FIRED BOILERS

    Energy Technology Data Exchange (ETDEWEB)

    E.G. Eddings; A. Molina; D.W. Pershing; A.F. Sarofim; K.A. Davis; M.P. Heap; T.H. Fletcher; H. Zhang

    2000-04-01

    Reduction of NO{sub x} emission is an important environmental issue in pulverized coal combustion. The most cost-effective approach to NO{sub x} reduction is air-staging which can also operate with additional down-stream techniques such as reburning [1]. Air staging promotes the conversion of NO{sub x} precursors (HCN, NH{sub 3}, etc.) to N{sub 2} by delaying the oxygen supply to the greatest extent when those nitrogen species are released during devolatilization. Such a delay gives the primary volatiles a chance to undergo secondary reactions, including tar cracking and soot formation. Secondary reactions of volatiles largely determine the fate of the ultimate NO{sub x} production from pyrolysis, therefore a detailed investigation into the transformation of nitrogen species during secondary reactions and effects of soot on nitrogen release is critical for design and implementation of new pollution control strategies. Current nitrogen models (including the CPD model at BYU) only simulate the nitrogen release during primary pyrolysis, which happens at low temperatures. This project helps to build a nitrogen release model that accounts for secondary reactions and the effects of soot at temperatures relevant to industrial burners.

  2. Impact of intake CO 2 addition and exhaust gas recirculation on NO x emissions and soot reactivity in a common rail diesel engine

    KAUST Repository

    Al-Qurashi, Khalid

    2012-10-18

    The impact of intake CO 2 addition and exhaust gas recirculation (EGR) on engine combustion characteristics, NO x emissions, and soot oxidative reactivity was studied in a common rail diesel engine equipped with a cooled EGR system. The engine test results and the heat release analysis show that the reduced flame temperature, induced by the reduction of the oxygen concentration (dilution effect) is the dominant mechanism via which CO 2 and EGR lower NO x emissions in diesel engines. On the other hand, the collected soot from the engine tests was examined for its oxidative reactivity using a thermogravimetric analyzer (TGA). Results show that EGR has a significant effect on soot reactivity and results in higher initial active sites compared to the CO 2 case. We conclude that the reduced flame temperature (thermal effect) which is a consequence of the dilution effect is responsible for the observed increase in soot reactivity. These results confirm observations from our past work on flame soot, which showed that the peak adiabatic flame temperature is the governing factor affecting soot reactivity. These findings imply that driving the combustion concepts toward low temperature is favorable to effectively control engine pollutants, including soot reactivity. © 2012 American Chemical Society.

  3. Impact of intake CO 2 addition and exhaust gas recirculation on NO x emissions and soot reactivity in a common rail diesel engine

    KAUST Repository

    Al-Qurashi, Khalid; Zhang, Yu; Boehman, André Louis

    2012-01-01

    The impact of intake CO 2 addition and exhaust gas recirculation (EGR) on engine combustion characteristics, NO x emissions, and soot oxidative reactivity was studied in a common rail diesel engine equipped with a cooled EGR system. The engine test results and the heat release analysis show that the reduced flame temperature, induced by the reduction of the oxygen concentration (dilution effect) is the dominant mechanism via which CO 2 and EGR lower NO x emissions in diesel engines. On the other hand, the collected soot from the engine tests was examined for its oxidative reactivity using a thermogravimetric analyzer (TGA). Results show that EGR has a significant effect on soot reactivity and results in higher initial active sites compared to the CO 2 case. We conclude that the reduced flame temperature (thermal effect) which is a consequence of the dilution effect is responsible for the observed increase in soot reactivity. These results confirm observations from our past work on flame soot, which showed that the peak adiabatic flame temperature is the governing factor affecting soot reactivity. These findings imply that driving the combustion concepts toward low temperature is favorable to effectively control engine pollutants, including soot reactivity. © 2012 American Chemical Society.

  4. A model study of aggregates composed of spherical soot monomers with an acentric carbon shell

    Science.gov (United States)

    Luo, Jie; Zhang, Yongming; Zhang, Qixing

    2018-01-01

    Influences of morphology on the optical properties of soot particles have gained increasing attentions. However, studies on the effect of the way primary particles are coated on the optical properties is few. Aimed to understand how the primary particles are coated affect the optical properties of soot particles, the coated soot particle was simulated using the acentric core-shell monomers model (ACM), which was generated by randomly moving the cores of concentric core-shell monomers (CCM) model. Single scattering properties of the CCM model with identical fractal parameters were calculated 50 times at first to evaluate the optical diversities of different realizations of fractal aggregates with identical parameters. The results show that optical diversities of different realizations for fractal aggregates with identical parameters cannot be eliminated by averaging over ten random realizations. To preserve the fractal characteristics, 10 realizations of each model were generated based on the identical 10 parent fractal aggregates, and then the results were averaged over each 10 realizations, respectively. The single scattering properties of all models were calculated using the numerically exact multiple-sphere T-matrix (MSTM) method. It is found that the single scattering properties of randomly coated soot particles calculated using the ACM model are extremely close to those using CCM model and homogeneous aggregate (HA) model using Maxwell-Garnett effective medium theory. Our results are different from previous studies. The reason may be that the differences in previous studies were caused by fractal characteristics but not models. Our findings indicate that how the individual primary particles are coated has little effect on the single scattering properties of soot particles with acentric core-shell monomers. This work provides a suggestion for scattering model simplification and model selection.

  5. Accurate Measurements of Aircraft Engine Soot Emissions Using a CAPS PMssa Monitor

    Science.gov (United States)

    Onasch, Timothy; Thompson, Kevin; Renbaum-Wolff, Lindsay; Smallwood, Greg; Make-Lye, Richard; Freedman, Andrew

    2016-04-01

    We present results of aircraft engine soot emissions measurements during the VARIAnT2 campaign using CAPS PMssa monitors. VARIAnT2, an aircraft engine non-volatile particulate matter (nvPM) emissions field campaign, was focused on understanding the variability in nvPM mass measurements using different measurement techniques and accounting for possible nvPM sampling system losses. The CAPS PMssa monitor accurately measures both the optical extinction and scattering (and thus single scattering albedo and absorption) of an extracted sample using the same sample volume for both measurements with a time resolution of 1 second and sensitivity of better than 1 Mm-1. Absorption is obtained by subtracting the scattering signal from the total extinction. Given that the single scattering albedo of the particulates emitted from the aircraft engine measured at both 630 and 660 nm was on the order of 0.1, any inaccuracy in the scattering measurement has little impact on the accuracy of the ddetermined absorption coefficient. The absorption is converted into nvPM mass using a documented Mass Absorption Coefficient (MAC). Results of soot emission indices (mass soot emitted per mass of fuel consumed) for a turbojet engine as a function of engine power will be presented and compared to results obtained using an EC/OC monitor.

  6. Formation of secondary phases during the corrosion of vitrified nuclear waste

    International Nuclear Information System (INIS)

    Zimmer, P.

    2003-11-01

    The first aim of this work was the examination of the formation and long-term stability of secondary phases that form during an aquatic attack on simulated, vitrified nuclear waste. In the glasses used for the investigations actinides had been replaced by rare earth elements (chemical analogues), other radionuclides by inactive isotopes. For predictions about the long-term safety of nuclear waste disposals it is important to identify secondary phases that have formed during the glass corrosion process and to determine their stability. Two different saline solutions (rich in MgCl 2 and in NaCl, respectively) are relevant as a corrosion medium for waste disposals. It showed that in such an environment sulfates, silicates and molybdates represent the main new formations of minerals after 7.5 years of corrosion. However, the formation, long-term stability and sorption characteristics of those minerals regarding rare earth elements depend to a high degree on the corrosion medium as well as on changes in the geochemical environment in the course of the experiment. By means of SEM/EDX barytes of different morphology with up to 15% w/w Sr ((Ba,Sr)SO 4 ) were identified in both corrosion media; they were capable of binding long-term stable radionuclides like Sr. Furthermore, pure rare earth (RE) sulfates were observed in the saline solution rich in MgCl 2 . This formation of RE-sulfates has not been described in the literature so far. Depending on the saline solution, the secondary silicate and molybdate minerals that formed on the glass surfaces differed noticeably in their sorption characteristics and their stability. Another focus of the work was a more profound understanding of the glass corrosion mechanism in the presence of metallic iron since steel jackets are used as technical barriers for the vitrified nuclear waste in nuclear waste disposals. Another important point in connection with the mobilization and immobilization of radionuclides released during glass

  7. Secondary organic aerosol formation from road vehicle emissions

    Science.gov (United States)

    Pieber, Simone M.; Platt, Stephen M.; El Haddad, Imad; Zardini, Alessandro A.; Suarez-Bertoa, Ricardo; Slowik, Jay G.; Huang, Ru-Jin; Hellebust, Stig; Temime-Roussel, Brice; Marchand, Nicolas; Drinovec, Luca; Mocnik, Grisa; Baltensperger, Urs; Astorga, Covadogna; Prévôt, André S. H.

    2014-05-01

    Organic aerosol particles (OA) are a major fraction of the submicron particulate matter. OA consists of directly emitted primary (POA) and secondary OA (SOA). SOA is formed in-situ in the atmosphere via the reaction of volatile organic precursors. The partitioning of SOA species depends not only on the exposure to oxidants, but for instance also on temperature, relative humidity (RH), and the absorptive mass chemical composition (presence of inorganics) and concentration. Vehicle exhaust is a known source of POA and likely contributes to SOA formation in urban areas [1;2]. This has recently been estimated by (i) analyzing ambient data from urban areas combined with fuel consumption data [3], (ii) by examining the chemical composition of raw fuels [4], or (iii) smog chamber studies [5, 6]. Contradictory and thus somewhat controversial results in the relative quantity of SOA from diesel vs. gasoline vehicle exhaust were observed. In order to elucidate the impact of variable ambient conditions on the potential SOA formation of vehicle exhaust, and its relation to the emitted gas phase species, we studied SOA formed from the exhaust of passenger cars and trucks as a function of fuel and engine type (gasoline, diesel) at different temperatures (T 22 vs. -7oC) and RH (40 vs. 90%), as well as with different levels of inorganic salt concentrations. The exhaust was sampled at the tailpipe during regulatory driving cycles on chassis dynamometers, diluted (200 - 400x) and introduced into the PSI mobile smog chamber [6], where the emissions were subjected to simulated atmospheric ageing. Particle phase instruments (HR-ToF-AMS, aethalometers, CPC, SMPS) and gas phase instruments (PTR-TOF-MS, CO, CO2, CH4, THC, NH3 and other gases) were used online during the experiments. We found that gasoline emissions, because of cold starts, were generally larger than diesel, especially during cold temperatures driving cycles. Gasoline vehicles also showed the highest SOA formation

  8. The contribution of tyre and brake abrasion to soot levels in streets; Beitrag des Reifen- und Bremsenabriebs zur Russemission an Strassen

    Energy Technology Data Exchange (ETDEWEB)

    Rauterberg-Wulff, A.

    1998-09-01

    After the coming into force of the new soot emission thresholds as of July 1998, excess values are measured along many city streets. The author investigated whether tyre and brake abrasion contributes to soot emissions in addition to diesel soot. For this purpose, characteristic material and physical parameters of particles of diesel soot, tyre and brake material were investigated by thermography, AAS, and SEM. With the aid of a receptor-oriented approach, the contribution of these particles to soot levels measured in a highway tunnel and a Berlin city street could be assessed. The contribution of local traffic was calculated from the difference between soot levels along the road and in a background station. The measurements inside the tunnel served to determine emissin factors for diesel soot and abrasion particles from tyres and brakes. (orig.) [Deutsch] Mit Inkrafttreten des endgueltigen Russ-Immissionswertes der 23. Verordnung zum Bundes-Immissionsschutzgesetz im Juli 1998 ist an zahlreichen innerstaedtischen Strassen mit einer Ueberschreitung dieser Werte zu rechnen. Zur Beantwortung der Frage, inwieweit neben Dieselruss auch Reifen- und Bremsenabrieb zur verkehrsbedingten Russimmission beitragen, wurden charakteristische stoffliche und physikalische Eigenschaften von Dieselruss, Reifenabrieb und Bremsenabrieb mit der Thermographie, der AAS und der Rasterelektronenmikroskopie untersucht. Mit Hilfe dieses rezeptororientierten Ansatzes konnte der Beitrag dieser Partikel zur Russimmission in einem Autobahntunnel und an einer Hauptverkehrsstrasse in Berlin bestimmt werden, wobei zuerst der Beitrag des lokalen Verkehrs zur Russimmission aus der Differenz zwischen der Russimmission an der Strassen- und einer Hintergrundstation berechnet wurde. Mit Hilfe der Messungen im Tunnel konnten Emissionsfaktoren fuer Dieselruss und fuer Reifen- und Bremsenabriebpartikel bestimmt werden. (orig.)

  9. Soot particle size measurements in ethylene diffusion flames at elevated pressures

    KAUST Repository

    Steinmetz, Scott; Fang, Tiegang; Roberts, William L.

    2016-01-01

    for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh

  10. Atomic layer deposition of cerium oxide for potential use in diesel soot combustion

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, Tatiana V., E-mail: tatiana.ivanova@lut.fi, E-mail: ivanova.tatyana.v@gmail.com; Toivonen, Jenni; Maydannik, Philipp S.; Kääriäinen, Tommi; Sillanpää, Mika [ASTRaL Team, Laboratory of Green Chemistry, School of Engineering Science, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli (Finland); Homola, Tomáš; Cameron, David C. [R& D Centre for Low-Cost Plasma and Nanotechnology Surface Modification, Masaryk University, Kotlářská 267/2, 611 37 Brno (Czech Republic)

    2016-05-15

    The particulate soot emission from diesel motors has a severe impact on the environment and people's health. The use of catalytic convertors is one of the ways to minimize the emission and decrease the hazard level. In this paper, the activity of cerium oxide for catalytic combustion of diesel soot was studied. Thin films of cerium dioxide were synthesized by atomic layer deposition using tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)cerium [Ce(thd){sub 4}] and ozone as precursors. The characteristics of the films were studied as a function of deposition conditions within the reaction temperature range of 180–350 °C. Thickness, crystallinity, elemental composition, and morphology of the CeO{sub 2} films deposited on Si (100) were characterized by ellipsometry, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscopy, respectively. The growth rate of CeO{sub 2} was observed to be 0.30 Å/cycle at temperatures up to 250 °C with a slight increase to 0.37 Å/cycle at 300 °C. The effect of CeO{sub 2} films grown on stainless steel foil supports on soot combustion was measured with annealing tests. Based on the analysis of these, in catalytic applications, CeO{sub 2} has been shown to be effective in lowering the soot combustion temperature from 600 °C for the uncoated substrates to 370 °C for the CeO{sub 2} coated ones. It was found that the higher deposition temperatures had a positive effect on the catalyst performance.

  11. Exact calculation of loop formation probability identifies folding motifs in RNA secondary structures

    Science.gov (United States)

    Sloma, Michael F.; Mathews, David H.

    2016-01-01

    RNA secondary structure prediction is widely used to analyze RNA sequences. In an RNA partition function calculation, free energy nearest neighbor parameters are used in a dynamic programming algorithm to estimate statistical properties of the secondary structure ensemble. Previously, partition functions have largely been used to estimate the probability that a given pair of nucleotides form a base pair, the conditional stacking probability, the accessibility to binding of a continuous stretch of nucleotides, or a representative sample of RNA structures. Here it is demonstrated that an RNA partition function can also be used to calculate the exact probability of formation of hairpin loops, internal loops, bulge loops, or multibranch loops at a given position. This calculation can also be used to estimate the probability of formation of specific helices. Benchmarking on a set of RNA sequences with known secondary structures indicated that loops that were calculated to be more probable were more likely to be present in the known structure than less probable loops. Furthermore, highly probable loops are more likely to be in the known structure than the set of loops predicted in the lowest free energy structures. PMID:27852924

  12. Formation of secondary aerosols from gasoline vehicle exhaust when mixing with SO2

    Directory of Open Access Journals (Sweden)

    T. Liu

    2016-01-01

    Full Text Available Sulfur dioxide (SO2 can enhance the formation of secondary aerosols from biogenic volatile organic compounds (VOCs, but its influence on secondary aerosol formation from anthropogenic VOCs, particularly complex mixtures like vehicle exhaust, remains uncertain. Gasoline vehicle exhaust (GVE and SO2, a typical pollutant from coal burning, are directly co-introduced into a smog chamber, in this study, to investigate the formation of secondary organic aerosols (SOA and sulfate aerosols through photooxidation. New particle formation was enhanced, while substantial sulfate was formed through the oxidation of SO2 in the presence of high concentration of SO2. Homogenous oxidation by OH radicals contributed a negligible fraction to the conversion of SO2 to sulfate, and instead the oxidation by stabilized Criegee intermediates (sCIs, formed from alkenes in the exhaust reacting with ozone, dominated the conversion of SO2. After 5 h of photochemical aging, GVE's SOA production factor revealed an increase by 60–200 % in the presence of high concentration of SO2. The increase could principally be attributed to acid-catalyzed SOA formation as evidenced by the strong positive linear correlation (R2 = 0.97 between the SOA production factor and in situ particle acidity calculated by the AIM-II model. A high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS resolved OA's relatively lower oxygen-to-carbon (O : C (0.44 ± 0.02 and higher hydrogen-to-carbon (H : C (1.40 ± 0.03 molar ratios for the GVE / SO2 mixture, with a significantly lower estimated average carbon oxidation state (OSc of −0.51 ± 0.06 than −0.19 ± 0.08 for GVE alone. The relative higher mass loading of OA in the experiments with SO2 might be a significant explanation for the lower SOA oxidation degree.

  13. Extension of weighted sum of gray gas data to mathematical simulation of radiative heat transfer in a boiler with gas-soot media.

    Science.gov (United States)

    Gharehkhani, Samira; Nouri-Borujerdi, Ali; Kazi, Salim Newaz; Yarmand, Hooman

    2014-01-01

    In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site.

  14. Effect of soot on oil properties and wear of engine components

    International Nuclear Information System (INIS)

    Green, D A; Lewis, R

    2007-01-01

    The objective of the work outlined in this paper was to increase the understanding of the wear mechanisms that occur within a soot contaminated contact zone, to help in future development of a predictive wear model to assist in the automotive engine valve train design process. The paper builds on previous work by the author, through testing of different lubricants and increased levels of soot contamination. Wear testing has been carried out using specimens operating under realistic engine conditions, using a reciprocating test-rig specifically designed for this application, where a steel disc is held in a heated bath of oil and a steel ball is attached to a reciprocating arm (replicating a sliding elephant's foot valve train contact). Detailed analysis of the test specimens has been performed using scanning electron microscopy to identify wear features relating to the proposed wear mechanisms. Analysis of worn engine components from durability engine tests has also been carried out for a comparison between specimen tests and engine testing. To assist the understanding of the wear test results obtained, the physical properties of contaminated lubricants were investigated, through viscosity, traction and friction measurements. The results have revealed how varying lubrication conditions change the wear rate of engine components and determine the wear mechanism that dominates in specific situations. Testing has also shown the positive effects of advanced engine lubricants to reduce the amount of wear produced with soot present

  15. Facile synthesis of nano cauliflower and nano broccoli like hierarchical superhydrophobic composite coating using PVDF/carbon soot particles via gelation technique.

    Science.gov (United States)

    Sahoo, Bichitra Nanda; Balasubramanian, Kandasubramanian

    2014-12-15

    We have elucidated a cost effective fabrication technique to produce superhydrophobic polyvinylidene fluoride (PVDF/DMF/candle soot particle and PVDF/DMF/camphor soot particle composite) porous materials. The water repellent dry composite was formed by the interaction of non-solvent (methanol) into PVDF/carbon soot particles suspension in N,N-dimethylformamide (DMF). It is seen that longer quenching time effectively changes the surface morphology of dry composites. The nano broccoli like hierarchical microstructure with micro or nano scaled roughen surface was obtained for PVDF/DMF/camphor soot particle, which reveals water contact angle of 172° with roll off angle of 2°. However, composite coating of PVDF/DMF/candle soot particle shows nano cauliflower like hierarchical, which illustrates water contact angle of 169° with roll off angle of 3°. To elucidate the enhancement of water repellent property of PVDF composites, we further divulge the evolution mechanism of nano cauliflower and nano broccoli structure. In order to evaluate the water contact angle of PVDF composites, surface diffusion of water inside the pores is investigated. Furthermore, the addition of small amount of carbon soot particles in composite not only provides the crystallization of PVDF, but also leads to dramatical amendment of surface morphology which increases the surface texture and roughness for superhydrophobicity. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Soot measurements by two angle scattering and extinction in an N 2 -diluted ethylene/air counterflow diffusion flame from 2 to 5 atm

    KAUST Repository

    Amin, Hafiz M.F.

    2016-06-27

    The soot formed in an N-diluted ethylene/air counterflow diffusion flame at elevated pressure was investigated using two angle light scattering/extinction technique. To provide a well-controlled pressurized environment for the flame, a novel pressure vessel was built with the required optical access. The soot parameters were measured along the centerline of the counterflow flame. These properties included soot volume fraction (f ), primary particle diameter (d ), population averaged radius of gyration (R ) and number density of primary particles (n ). The Rayleigh-Debye-Gans theory for Fractal Aggregates (RDG-FA) was used to retrieve these properties from scattering and extinction measurements. Soot volume fraction was measured via light extinction from 2 to 5atm while maintaining the same global strain rate at all pressures. Scattered light from soot particles was measured at 45° and 135° and primary particle diameter was calculated using scattering/extinction ratio and the radius of gyration was determined from the dissymmetry ratio. Soot volume fraction, primary particle diameter and radius of gyration all increased with pressure while the number density of primary particles decreased with increasing pressure.

  17. Soot measurements by two angle scattering and extinction in an N 2 -diluted ethylene/air counterflow diffusion flame from 2 to 5 atm

    KAUST Repository

    Amin, Hafiz M.F.; Roberts, William L.

    2016-01-01

    The soot formed in an N-diluted ethylene/air counterflow diffusion flame at elevated pressure was investigated using two angle light scattering/extinction technique. To provide a well-controlled pressurized environment for the flame, a novel pressure vessel was built with the required optical access. The soot parameters were measured along the centerline of the counterflow flame. These properties included soot volume fraction (f ), primary particle diameter (d ), population averaged radius of gyration (R ) and number density of primary particles (n ). The Rayleigh-Debye-Gans theory for Fractal Aggregates (RDG-FA) was used to retrieve these properties from scattering and extinction measurements. Soot volume fraction was measured via light extinction from 2 to 5atm while maintaining the same global strain rate at all pressures. Scattered light from soot particles was measured at 45° and 135° and primary particle diameter was calculated using scattering/extinction ratio and the radius of gyration was determined from the dissymmetry ratio. Soot volume fraction, primary particle diameter and radius of gyration all increased with pressure while the number density of primary particles decreased with increasing pressure.

  18. Effect of ammonia on ozone-initiated formation of indoor secondary products with emissions from cleaning products

    Science.gov (United States)

    Huang, Yu; Lee, Shun Cheng; Ho, Kin Fai; Ho, Steven Sai Hang; Cao, Nanying; Cheng, Yan; Gao, Yuan

    2012-11-01

    Biogenic volatile organic compounds (BVOCs) emitted from cleaning products and air fresheners indoors are prone to oxidation resulting in the formation of secondary pollutants that can pose health risks on residents. Ammonia (NH3) is ubiquitous in ambient and indoor environments. In this study, we investigated the effect of ammonia (NH3) on secondary pollutants formation from the ozonolysis of BVOCs emitted from cleaning products including floor cleaner (FC), kitchen cleaner (KC) and dishwashing detergent (DD) in a large environmental chamber. Our results demonstrated that the presence of NH3 (maximum concentration is 240 ppb) could significantly enhance secondary organic aerosols (SOAs) formation from the ozonolysis of all the three categories of cleaning products. For example, for the FC sample, the maximum total particle concentration was up to 2.0 × 104 # cm-3 in the presence of NH3, while it was 1.3 × 104 # cm-3 which was 35% lower without NH3. However, it was found that the extent of NH3 effect on SOAs formation from the ozonolysis of BVOCs emissions was component-dependent. The presence of NH3 in the reaction systems could increase the consumptions of d-limonene that is the dominant BVOC species as identified in cleaning products. The percent yields (%) of secondary carbonyl compounds generated from the ozonolysis of BVOCs emitted from three categories of cleaning products were identified in the presence and absence of NH3, respectively. The increase in SOAs particle number concentration can be attributed to the formation of condensable salts from reactions between NH3 and organic compounds generated from the BVOCs ozonolysis processes. By investigating the NH3 effect on the ozonolysis of BVOCs mixtures in contrast to the chemistry of individual compounds, a better assessment can be made of the overall impact cleaning products have on real indoor environments.

  19. Laser-Induced Emissions Sensor for Soot Mass in Rocket Plumes, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A method is proposed to measure soot mass concentration non-intrusively from a distance in a rocket engine exhaust stream during ground tests using laser-induced...

  20. Combustion performance, flame, and soot characteristics of gasoline–diesel pre-blended fuel in an optical compression-ignition engine

    International Nuclear Information System (INIS)

    Jeon, Joonho; Lee, Jong Tae; Kwon, Sang Il; Park, Sungwook

    2016-01-01

    formation of fuel/air mixtures in the cylinder. Neat diesel fuel was tested, as well as gasoline–diesel blends of 20% and 40% gasoline mass fraction. Experiments on the mixed fuels showed that the inclusion of gasoline fuel improved fuel/air mixing, yielding more homogeneous mixtures over wider cylinder areas. The low cetane index of gasoline fuel induced long ignition delays in the mixed fuels. Compared with neat diesel combustion flame, blended fuel did not produce the soot flame, white-yellow flame. Soot intensity was calculated based on captured flame images, and its variations were investigated as a function of fuel type and injection conditions.

  1. Effect of A-site deficiency in LaMn{sub 0.9}Co{sub 0.1}O{sub 3} perovskites on their catalytic performance for soot combustion

    Energy Technology Data Exchange (ETDEWEB)

    Dinamarca, Robinson [Department of Physical Chemistry, Faculty of Chemical Sciences, University of Concepción, Concepción (Chile); Garcia, Ximena; Jimenez, Romel [Department of Chemical Engineering, Faculty of Engineering, University of Concepción, Concepción (Chile); Fierro, J.L.G. [Instituto de Catálisis y Petroleoquímica, CSIC, Cantoblanco, 28049 Madrid (Spain); Pecchi, Gina, E-mail: gpecchi@udec.cl [Department of Physical Chemistry, Faculty of Chemical Sciences, University of Concepción, Concepción (Chile)

    2016-09-15

    Highlights: • A-site defective perovskites increases the oxidation state of the B-cation. • Not always non-stoichiometric perovskites exhibit higher catalytic activity in soot combustion. • The highly symmetric cubic crystalline structure diminishes the redox properties of perovskites. - Abstract: The influence of lanthanum stoichiometry in Ag-doped (La{sub 1-x}Ag{sub x}Mn{sub 0.9}Co{sub 0.1}O{sub 3}) and A-site deficient (La{sub 1-x}Mn{sub 0.9}Co{sub 0.1}O{sub 3-δ}) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O{sub 2}-TPD and TPR. The formation of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag{sub 2}O segregated phases and the redox pair Mn{sup 4+}/Mn{sup 3+}. A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn{sup 4+}/Mn{sup 3+}, which is attributed to the cubic crystalline structure.

  2. Size-resolved measurement of the mixing state of soot in the megacity Beijing, China: diurnal cycle, aging and parameterization

    Directory of Open Access Journals (Sweden)

    Y. F. Cheng

    2012-05-01

    Full Text Available Soot particles are the most efficient light absorbing aerosol species in the atmosphere, playing an important role as a driver of global warming. Their climate effects strongly depend on their mixing state, which significantly changes their light absorbing capability and cloud condensation nuclei (CCN activity. Therefore, knowledge about the mixing state of soot and its aging mechanism becomes an important topic in the atmospheric sciences.

    The size-resolved (30–320 nm diameter mixing state of soot particles in polluted megacity air was measured at a suburban site (Yufa during the CAREBeijing 2006 campaign in Beijing, using a volatility tandem differential mobility analyzer (VTDMA. Particles in this size range with non-volatile residuals at 300 °C were considered to be soot particles. On average, the number fraction of internally mixed soot in total soot particles (Fin, decreased from 0.80 to 0.57 when initial Dp increased from 30 to 320 nm. Further analysis reveals that: (1 Fin was well correlated with the aerosol hygroscopic mixing state measured by a CCN counter. More externally mixed soot particles were observed when particles showed more heterogeneous features with regard to hygroscopicity. (2 Fin had pronounced diurnal cycles. For particles in the accumulation mode (Dp at 100–320 nm, largest Fin were observed at noon time, with "apparent" turnover rates (kex → in up to 7.8% h−1. (3 Fin was subject to competing effects of both aging and emissions. While aging increases Fin by converting externally mixed soot particles into internally mixed ones, emissions tend to reduce Fin by emitting more fresh and externally mixed soot particles. Similar competing effects were also found with air mass age indicators. (4 Under the estimated emission

  3. On the role of resonantly stabilized radicals in polycyclic aromatic hydrocarbon (PAH) formation: pyrene and fluoranthene formation from benzyl-indenyl addition.

    Science.gov (United States)

    Sinha, Sourab; Rahman, Ramees K; Raj, Abhijeet

    2017-07-26

    Resonantly stabilized radicals, such as propargyl, cyclopentadienyl, benzyl, and indenyl, play a vital role in the formation and growth of polycyclic aromatic hydrocarbons (PAHs) that are soot precursors in engines and flames. Pyrene is considered to be an important PAH, as it is thought to nucleate soot particles, but its formation pathways are not well known. This paper presents a reaction mechanism for the formation of four-ring aromatics, pyrene and fluoranthene, through the combination of benzyl and indenyl radicals. The intermediate species and transition structures involved in the elementary reactions of the mechanism were studied using density functional theory, and the reaction kinetics were evaluated using transition state theory. The barrierless addition of benzyl and indenyl to form the adduct, 1-benzyl-1H-indene, was found to be exothermic with a reaction energy of 204.2 kJ mol -1 . The decomposition of this adduct through H-abstraction and H 2 -loss was studied to determine the possible products. The rate-of-production analysis was conducted to determine the most favourable reactions for pyrene and fluoranthene formation. The premixed laminar flames of toluene, ethylbenzene, and benzene were simulated using a well-validated hydrocarbon fuel mechanism with detailed PAH chemistry after adding the proposed reactions to it. The computed and experimentally observed species profiles were compared to determine the effect of the new reactions for pyrene and fluoranthene formation on their concentration profiles. The role of benzyl and indenyl combination in PAH formation and growth is highlighted.

  4. A modelling study of the effects of different CCN on contrail formation

    Energy Technology Data Exchange (ETDEWEB)

    Gleitsmann, G; Zellner, R [Essen Univ. (Gesamthochschule) (Germany). Inst. fuer Physikalische und Theoretische Chemie

    1998-12-31

    The formation of cloud condensation nuclei (CCN) in the jet regime of a B747 airliner at cruise has been investigated by modelling calculations using the BOAT model. Both homogeneous condensation of H{sub 2}O/H{sub 2}SO{sub 4}-mixtures and heterogeneous deposition of H{sub 2}O on soot surfaces activated by H{sub 2}SO{sub 4} were taken into account. Whereas the heterogeneous condensation leads to particles with average diameters of about 1.3 {mu}m, the homogeneously condensed H{sub 2}O/H{sub 2}SO{sub 4} particles are much smaller ({<=} 7 nm) and do not contribute to visible contrail formation. Nevertheless, they contribute to the atmospheric background aerosol. Using different SO{sub 2} emission indices, it is concluded that the contrail onset is essentially independent of this quantity and depends mainly on ambient temperature and soot activation kinetics. (author) 15 refs.

  5. A modelling study of the effects of different CCN on contrail formation

    Energy Technology Data Exchange (ETDEWEB)

    Gleitsmann, G.; Zellner, R. [Essen Univ. (Gesamthochschule) (Germany). Inst. fuer Physikalische und Theoretische Chemie

    1997-12-31

    The formation of cloud condensation nuclei (CCN) in the jet regime of a B747 airliner at cruise has been investigated by modelling calculations using the BOAT model. Both homogeneous condensation of H{sub 2}O/H{sub 2}SO{sub 4}-mixtures and heterogeneous deposition of H{sub 2}O on soot surfaces activated by H{sub 2}SO{sub 4} were taken into account. Whereas the heterogeneous condensation leads to particles with average diameters of about 1.3 {mu}m, the homogeneously condensed H{sub 2}O/H{sub 2}SO{sub 4} particles are much smaller ({<=} 7 nm) and do not contribute to visible contrail formation. Nevertheless, they contribute to the atmospheric background aerosol. Using different SO{sub 2} emission indices, it is concluded that the contrail onset is essentially independent of this quantity and depends mainly on ambient temperature and soot activation kinetics. (author) 15 refs.

  6. Development of Kinetics for Soot Oxidation at High Pressures Under Fuel-Lean Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lighty, JoAnn [Univ. of Utah, Salt Lake City, UT (United States); Vander Wal, Randy [Pennsylvania State Univ., University Park, PA (United States)

    2014-04-21

    The focus of the proposed research was to develop kinetic models for soot oxidation with the hope of developing a validated, predictive, multi-­scale, combustion model to optimize the design and operation of evolving fuels in advanced engines for transportation applications. The work focused on the relatively unstudied area of the fundamental mechanism for soot oxidation. The objectives include understanding of the kinetics of soot oxidation by O2 under high pressure which require: 1) development of intrinsic kinetics for the surface oxidation, which takes into account the dependence of reactivity upon nanostructure and 2) evolution of nanostructure and its impact upon oxidation rate and 3) inclusion of internal surface area development and possible fragmentation resulting from pore development and /or surface oxidation. These objectives were explored for a variety of pure fuel components and surrogate fuels. This project was a joint effort between the University of Utah (UU) and Pennsylvania State University (Penn State). The work at the UU focuses on experimental studies using a two-­stage burner and a high- pressure thermogravimetric analyzer (TGA). Penn State provided HRTEM images and guidance in the fringe analysis algorithms and parameter quantification for the images. This report focuses on completion done under supplemental funding.

  7. Effects of S/V on secondary phase formation on waste glasses

    International Nuclear Information System (INIS)

    Feng, X.; Buck, E.C.; Bates, J.K.; Gong, M.; Dietz, N.L.; Pegg, I.L.

    1994-01-01

    Simulated West Valley high-level nuclear waste glass, WV205, was leached with and without buffered media in both deuterated and ordinary water at glass surface area to solution volumes (S/N) of 200--6000 m -1 . Examination of the glass surface after testing for 14 days indicated that the S/V-induced pH change plays a dominant role in the development of the altered surface layer and the secondary phases formed. The changes due to SN-induced pH determine the rate of surface layer formation, the element distribution in the surface layer, and possibly, the identities of the secondary phases. Changes due to SN-induced elemental concentration also influence glass reaction rate in terms of the layer thickness and the elemental distribution in the surface layers

  8. Dynamics of flow–soot interaction in wrinkled non-premixed ethylene–air flames

    KAUST Repository

    Arias, Paul G.; Lecoustre, Vivien R.; Roy, Somesh; Luo, Zhaoyu; Haworth, Daniel C.; Lu, Tianfeng; Trouvé , Arnaud; Im, Hong G.

    2015-01-01

    A two-dimensional simulation of a non-premixed ethylene–air flame was conducted by employing a detailed gas-phase reaction mechanism considering polycyclic aromatic hydrocarbons, an aerosol-dynamics-based soot model using a method of moments

  9. Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Michaels, Thomas C. T., E-mail: tctm3@cam.ac.uk; Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J., E-mail: tpjk2@cam.ac.uk [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

    2015-08-07

    The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

  10. Variability in the primary emissions and secondary gas and particle formation from vehicles using bioethanol mixtures.

    Science.gov (United States)

    Gramsch, E; Papapostolou, V; Reyes, F; Vásquez, Y; Castillo, M; Oyola, P; López, G; Cádiz, A; Ferguson, S; Wolfson, M; Lawrence, J; Koutrakis, P

    2018-04-01

    Bioethanol for use in vehicles is becoming a substantial part of global energy infrastructure because it is renewable and some emissions are reduced. Carbon monoxide (CO) emissions and total hydrocarbons (THC) are reduced, but there is still controversy regarding emissions of nitrogen oxides (NO x ), aldehydes, and ethanol; this may be a concern because all these compounds are precursors of ozone and secondary organic aerosol (SOA). The amount of emissions depends on the ethanol content, but it also may depend on the engine quality and ethanol origin. Thus, a photochemical chamber was used to study secondary gas and aerosol formation from two flex-fueled vehicles using different ethanol blends in gasoline. One vehicle and the fuel used were made in the United States, and the others were made in Brazil. Primary emissions of THC, CO, carbon dioxide (CO 2 ), and nonmethane hydrocarbons (NMHC) from both vehicles decreased as the amount of ethanol in gasoline increased. NO x emissions in the U.S. and Brazilian cars decreased with ethanol content. However, emissions of THC, CO, and NO x from the Brazilian car were markedly higher than those from the U.S. car, showing high variability between vehicle technologies. In the Brazilian car, formation of secondary nitrogen dioxide (NO 2 ) and ozone (O 3 ) was lower for higher ethanol content in the fuel. In the U.S. car, NO 2 and O 3 had a small increase. Secondary particle (particulate matter [PM]) formation in the chamber decreased for both vehicles as the fraction of ethanol in fuel increased, consistent with previous studies. Secondary to primary PM ratios for pure gasoline is 11, also consistent with previous studies. In addition, the time required to form secondary PM is longer for higher ethanol blends. These results indicate that using higher ethanol blends may have a positive impact on air quality. The use of bioethanol can significantly reduce petroleum use and greenhouse gas emissions worldwide. Given the extent of

  11. In-cylinder Combustion and Soot Evolution in the Transition from Conventional CI mode to PPC

    KAUST Repository

    An, Yanzhao

    2018-01-09

    The present study intends to explore the in-cylinder combustion and evolution of soot emission during the transition from conventional compression ignition (CI) combustion to partially premixed combustion (PPC) at low load conditions. In-cylinder combustion images and engine-out emissions were measured in an optical engine fueled with low octane heavy naphtha fuel (RON = 50). Full cycle engine simulations were performed using a three-dimensional computational fluid dynamics code CONVERGETM, coupled with gas phase chemical kinetics, turbulence, and particulate size mimic soot model. The simulations were performed under low load conditions (IMEP ~ 2 to 3 bar) at an engine speed of 1200 rpm. The start of injection (SOI) was advanced from late (-10 CAD aTDC) to early fuel injection timings (-40 CAD aTDC) to realize the combustion transition from CI combustion to PPC. The simulation results of combustion and emission are compared with the experimental results at both CI and PPC combustion modes. The results of the study show a typical low-temperature stratified lean combustion at PPC mode, while high-temperature spray-driven combustion is evident at CI mode. The in-cylinder small intermediates species such as acetylene (C2H2), propargyl (C3H3), cyclopentadienyl (C5H5) and polycyclic aromatic hydrocarbons (PAHs) were significantly suppressed at PPC mode. Nucleation reaction of PAHs collision contributed to main soot mass production. The distribution of soot mass and particle number density was consistent with the distribution of high-temperature zones at CI and PPC combustion modes.

  12. The concentration of heavy metals and PAH's in soot water - suggested methods of treatment; Halten av tungmetaller och PAH:er i sotvatten - foerslag paa behandlingsmetoder

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Bjoern (TecNet Nordic AB, Goeteborg (SE))

    2007-12-15

    What we here call 'soot water' is a contaminated water from seasonal cleaning of the furnace and heating sections with water. Earlier, it was common to discharge this type of water directly to a recipient or to the municipal sewage plant. Today, with new, more restricted regulations, this is not accepted unless the concentrations of different substances is well documented and below official limits. The objective of this project has been to increase the knowledge of soot water from different types of combustion plants and suggest ways to handle/treat this water. The project started with a literature survey of soot water in the Swedish, English and German open literature. The next step was to perform analyses on soot water from combustion of waste, wood chips, wood chips/peat, bio oil and heavy fuel oil. It is very difficult to take a representative sample of soot water. It is especially the amount of particles in the water that may change. Since particles contains high levels of heavy metals, this may severely affect the concentrations of metals in the sample, if included in the analysis. Soot water contains very low concentrations of mercury. The concentrations of PAH is also close to or below the detection limit. On the other hand, all soot water analysed, contains enough concentrations of some metal, to make it unsuitable to be discharged directly to a recipient or drain. Four methods of water treatment have been examined for its capacity to treat soot water with regard to their capacity, operational and economical performance. The result is as follows: Chemical precipitation is the method that is judged to have the highest potential as long as the chlorides and sulphates can be discharged to the recipient or municipal waste plant. Reversed osmosis is judged less suitable for soot water since the water contains calcium, sulfates and carbonates that may clog the membranes. Evaporators is also judged to be of less interest for soot water due to its

  13. Alumina supported Co-K-Mo based catalytic material for diesel soot oxidation

    Czech Academy of Sciences Publication Activity Database

    Dhakad, M.; Joshi, A.G.; Rayalu, S.; Tanwar, P.; Bassin, J.K.; Kumar, R.; Lokhande, S.; Šubrt, Jan; Mitsuhashi, T.; Labhsetwar, N.

    2009-01-01

    Roč. 52, 13-20 (2009), s. 2070-2075 ISSN 1022-5528 Institutional research plan: CEZ:AV0Z40320502 Keywords : soot oxidation * diesel particulate filter * catalyst carbon oxidation Subject RIV: CA - Inorganic Chemistry Impact factor: 2.379, year: 2009

  14. TEM and HRTEM of Soot-in-oil particles and agglomerates from internal combustion engines

    International Nuclear Information System (INIS)

    Fay, M W; Rocca, A La; Shayler, P J

    2014-01-01

    Over time, the performance of lubricating oil in a diesel engine is affected by the build-up of carbon soot produced by the combustion process. TEM and HRTEM are commonly used to investigate the characteristics of individual and agglomerated particles from diesel exhaust, to understand the structure and distribution of the carbon sheets in the primary particles and the nanostructure morphology. However, high resolution imaging of soot-in-oil is more challenging, as mineral oil is a contaminant for the electron microscope and leads to instability under the electron beam. In this work we compare solvent extraction and centrifugation techniques for removing the mineral oil contaminant, and the effect on particle size distribution

  15. Cloud processing of organic compounds: Secondary organic aerosol and nitrosamine formation

    Science.gov (United States)

    Hutchings, James W., III

    Cloud processing of atmospheric organic compounds has been investigated through field studies, laboratory experiments, and numerical modeling. Observational cloud chemistry studies were performed in northern Arizona and fog studies in central Pennsylvania. At both locations, the cloud and fogs showed low acidity due to neutralization by soil dust components (Arizona) and ammonia (Pennsylvania). The field observations showed substantial concentrations (20-5500 ng•L -1) of volatile organic compounds (VOC) in the cloud droplets. The potential generation of secondary organic aerosol mass through the processing of these anthropogenic VOCs was investigated through laboratory and modeling studies. Under simulated atmospheric conditions, in idealized solutions, benzene, toluene, ethylbenzene, and xylene (BTEX) degraded quickly in the aqueous phase with half lives of approximately three hours. The degradation process yielded less volatile products which would contribute to new aerosol mass upon cloud evaporation. However, when realistic cloud solutions containing natural organic matter were used in the experiments, the reaction kinetics decreased with increasing organic carbon content, resulting in half lives of approximately 7 hours. The secondary organic aerosol (SUA) mass formation potential of cloud processing of BTEX was evaluated. SOA mass formation by cloud processing of BTEX, while strongly dependent on the atmospheric conditions, could contribute up to 9% of the ambient atmospheric aerosol mass, although typically ˜1% appears realistic. Field observations also showed the occurrence of N-nitrosodimethylamine (NDMA), a potent carcinogen, in fogs and clouds (100-340 ng•L -1). Laboratory studies were conducted to investigate the formation of NDMA from nitrous acid and dimethylamine in the homogeneous aqueous phase within cloud droplets. While NDMA was produced in the cloud droplets, the low yields (NDMA with partitioning to droplet must be the source of aqueous

  16. Substantial secondary organic aerosol formation in a coniferous forest: observations of both day- and nighttime chemistry

    OpenAIRE

    A. K. Y. Lee; J. P. D. Abbatt; W. R. Leaitch; S.-M. Li; S. J. Sjostedt; S. J. Sjostedt; J. J. B. Wentzell; J. Liggio; A. M. Macdonald

    2016-01-01

    Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region at Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identifie...

  17. NAA of an iridium tracer to determine soot exposure of students commuting on Baltimore`s buses

    Energy Technology Data Exchange (ETDEWEB)

    Ondov, J.M.; Wu, C.C.; Lin, Zhibo; Kidwell, C.B. [Univ. of Maryland, College Park, MD (United States)

    1997-12-01

    Epidemiologic studies suggest that short-term increases in indices of particulate air pollution are associated with increased mortality and morbidity from respiratory and cardiovascular diseases. An important component of urban aerosol, diesel soot, is a known respiratory irritant and contains mutagenic and carcinogenic organic compounds. In the United States, motor vehicles are thought to be the largest single source of atmospheric soot and account for {approximately}36% of the annual anthropogenic emission of toxic polynuclear aromatic hydrocarbons (PAH). Much of the motor-vehicle-derived PAH originates from diesel-powered vehicles because their PAH emissions are up to 50-fold greater than those from gasoline engines. In Baltimore, city high school students take public buses to school and, often, must stand at bus stops while many diesel buses pass or stop before their own buses arrive. To estimate student exposures to soot emitted from public diesel buses (MTA) during commutes to city high schools, the Baltimore municipal fuel supply was tagged with an iridium tracer, and exposure was monitored during commutes with personal aerosol monitors as a part of the Baltimore Environmental Justice Project.

  18. Effects of several types of biomass fuels on the yield, nanostructure and reactivity of soot from fast pyrolysis at high temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Peter Arendt; Jensen, Anker Degn

    2016-01-01

    This study presents the effect of biomass origin on the yield, nanostructure and reactivity of soot. Soot was produced from wood and herbaceous biomass pyrolysis at high heating rates and at temperatures of 1250 and 1400 °C in a drop tube furnace. The structure of solid residues was characterized...

  19. Secondary formation of disinfection by-products by UV treatment of swimming pool water

    Energy Technology Data Exchange (ETDEWEB)

    Spiliotopoulou, Aikaterini [Water ApS, Farum Gydevej 64, 3520 Farum (Denmark); Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Kongens Lyngby (Denmark); Hansen, Kamilla M.S., E-mail: kmsh@env.dtu.dk [Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Kongens Lyngby (Denmark); Andersen, Henrik R. [Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Kongens Lyngby (Denmark)

    2015-07-01

    Formation of disinfection by-products (DBPs) during experimental UV treatment of pool water has previously been reported with little concurrence between laboratory studies, field studies and research groups. In the current study, changes in concentration of seven out of eleven investigated volatile DBPs were observed in experiments using medium pressure UV treatment, with and without chlorine and after post-UV chlorination. Results showed that post-UV chlorine consumption increased, dose-dependently, with UV treatment dose. A clear absence of trihalomethane formation by UV and UV with chlorine was observed, while small yet statistically significant increases in dichloroacetonitrile and dichloropropanone concentrations were detected. Results indicate that post-UV chlorination clearly induced secondary formation of several DBPs. However, the formation of total trihalomethanes was no greater than what could be replicated by performing the DBP formation assay with higher chlorine concentrations to simulate extended chlorination. Post-UV chlorination of water from a swimming pool that continuously uses UV treatment to control combined chlorine could not induce secondary formation for most DBPs. Concurrence for induction of trihalomethanes was identified between post-UV chlorination treatments and simulated extended chlorination time treatment. Trihalomethanes could not be induced by UV treatment of water from a continuously UV treated pool. This indicates that literature reports of experimentally induced trihalomethane formation by UV may be a result of kinetic increase in formation by UV. However, this does not imply that higher trihalomethane concentrations would occur in pools that apply continuous UV treatment. The bromine fraction of halogens in formed trihalomethanes increased with UV dose. This indicates that UV removes bromine atoms from larger molecules that participate in trihalomethane production during post-UV chlorination. Additionally, no significant

  20. Secondary formation of disinfection by-products by UV treatment of swimming pool water

    International Nuclear Information System (INIS)

    Spiliotopoulou, Aikaterini; Hansen, Kamilla M.S.; Andersen, Henrik R.

    2015-01-01

    Formation of disinfection by-products (DBPs) during experimental UV treatment of pool water has previously been reported with little concurrence between laboratory studies, field studies and research groups. In the current study, changes in concentration of seven out of eleven investigated volatile DBPs were observed in experiments using medium pressure UV treatment, with and without chlorine and after post-UV chlorination. Results showed that post-UV chlorine consumption increased, dose-dependently, with UV treatment dose. A clear absence of trihalomethane formation by UV and UV with chlorine was observed, while small yet statistically significant increases in dichloroacetonitrile and dichloropropanone concentrations were detected. Results indicate that post-UV chlorination clearly induced secondary formation of several DBPs. However, the formation of total trihalomethanes was no greater than what could be replicated by performing the DBP formation assay with higher chlorine concentrations to simulate extended chlorination. Post-UV chlorination of water from a swimming pool that continuously uses UV treatment to control combined chlorine could not induce secondary formation for most DBPs. Concurrence for induction of trihalomethanes was identified between post-UV chlorination treatments and simulated extended chlorination time treatment. Trihalomethanes could not be induced by UV treatment of water from a continuously UV treated pool. This indicates that literature reports of experimentally induced trihalomethane formation by UV may be a result of kinetic increase in formation by UV. However, this does not imply that higher trihalomethane concentrations would occur in pools that apply continuous UV treatment. The bromine fraction of halogens in formed trihalomethanes increased with UV dose. This indicates that UV removes bromine atoms from larger molecules that participate in trihalomethane production during post-UV chlorination. Additionally, no significant

  1. Time-averaged probability density functions of soot nanoparticles along the centerline of a piloted turbulent diffusion flame using a scanning mobility particle sizer

    KAUST Repository

    Chowdhury, Snehaunshu

    2017-01-23

    In this study, we demonstrate the use of a scanning mobility particle sizer (SMPS) as an effective tool to measure the probability density functions (PDFs) of soot nanoparticles in turbulent flames. Time-averaged soot PDFs necessary for validating existing soot models are reported at intervals of ∆x/D∆x/D = 5 along the centerline of turbulent, non-premixed, C2H4/N2 flames. The jet exit Reynolds numbers of the flames investigated were 10,000 and 20,000. A simplified burner geometry based on a published design was chosen to aid modelers. Soot was sampled directly from the flame using a sampling probe with a 0.5-mm diameter orifice and diluted with N2 by a two-stage dilution process. The overall dilution ratio was not evaluated. An SMPS system was used to analyze soot particle concentrations in the diluted samples. Sampling conditions were optimized over a wide range of dilution ratios to eliminate the effect of agglomeration in the sampling probe. Two differential mobility analyzers (DMAs) with different size ranges were used separately in the SMPS measurements to characterize the entire size range of particles. In both flames, the PDFs were found to be mono-modal in nature near the jet exit. Further downstream, the profiles were flatter with a fall-off at larger particle diameters. The geometric mean of the soot size distributions was less than 10 nm for all cases and increased monotonically with axial distance in both flames.

  2. The formation of science choices in secondary school

    Science.gov (United States)

    Cleaves, Anna

    2005-04-01

    In this paper I examine the formation of post-16 choices over 3 years among higher achieving students with respect to enrolment in post-compulsory science courses. Transcripts from four interviews carried out over 3 years with 72 secondary school students were qualitatively analysed. Students were found to shape their choices for science in a variety of ways across time. The situation regarding science choices hinges on far more dynamic considerations than the stereotypical image of the potential advanced science student, committed to becoming a scientist from an early age. There is an interplay of self-perception with respect to science, occupational images of working scientists, relationship with significant adults and perceptions of school science The findings are informative for science educators and for career guidance professionals who may need to take into account the complexity of young people's choices.

  3. Time-averaged probability density functions of soot nanoparticles along the centerline of a piloted turbulent diffusion flame using a scanning mobility particle sizer

    KAUST Repository

    Chowdhury, Snehaunshu; Boyette, Wesley; Roberts, William L.

    2017-01-01

    In this study, we demonstrate the use of a scanning mobility particle sizer (SMPS) as an effective tool to measure the probability density functions (PDFs) of soot nanoparticles in turbulent flames. Time-averaged soot PDFs necessary for validating

  4. High formation of secondary organic aerosol from the photo-oxidation of toluene

    OpenAIRE

    L. Hildebrandt; N. M. Donahue; S. N. Pandis

    2009-01-01

    Toluene and other aromatics have long been viewed as the dominant anthropogenic secondary organic aerosol (SOA) precursors, but the SOA mass yields from toluene reported in previous studies vary widely. Experiments conducted in the Carnegie Mellon University environmental chamber to study SOA formation from the photo-oxidation of toluene show significantly larger SOA production than parameterizations employed in current air-quality models. Aerosol mass yields depend on experimental co...

  5. Impacts of raindrop evaporative cooling on tropical cyclone secondary eyewall formation

    Science.gov (United States)

    Ge, Xuyang; Guan, Liang; Yan, Ziyu

    2018-06-01

    The impacts of raindrop evaporative cooling on secondary eyewall formation (SEF) of simulated tropical cyclones are investigated using idealized numerical experiments. The results suggest that the raindrop evaporative cooling effect is beneficial to the development of secondary eyewall through the planetary boundary layer (PBL) cold pool process. The evaporative cooling-driven downdrafts bring about the surface cold pool beneath a precipitation cloud. This cold pool dynamics act as a lifting mechanism to trigger the outer convection. The radially outward propagation of spiral rainbands broadens the TC size, by which modifies the surface heat fluxes and thus outer convection. Furthermore, the unbalanced PBL process contributes to the SEF. The radially outward surface outflows forces convection at outer region and thus favors a larger TC size. A larger TC implies an enhanced inertial stability at the outer region, which favors a higher conversion efficiency of diabatic heating to kinetic energy.

  6. A parametric study of AC electric field-induced toroidal vortex formation in laminar nonpremixed coflow flames

    KAUST Repository

    Xiong, Yuan

    2017-05-02

    This study presents an experimental work investigating the controlling parameters on the formation of an electrically-induced inner toroidal vortex (ITV) near a nozzle rim in small, laminar nonpremixed coflow flames, when an alternating current is applied to the nozzle. A systematic parametric study was conducted by varying the flow parameters of the fuel and coflowing-air velocities, and the nozzle diameter. The fuels tested were methane, ethylene, ethane, propane, n-butane, and i-butane, each representing different ion-generation characteristics and sooting tendencies. The results showed that the fluid dynamic effects on ITV formation were weak, causing only mild variation when altering flow velocities. However, increased fuel velocity resulted in increased polycyclic aromatic hydrocarbon (PAH) formation, which promoted ITV formation. When judging the ITV-formation tendency based on critical applied voltage and frequency, it was qualitatively well correlated with the PAH concentration and the relative location of PAHs to the nozzle rim. The sooting tendency of the fuels did not affect the results much. A change in the nozzle diameter highlighted the importance of the relative distance between the PAH zone and the nozzle rim, indicating the role of local electric-field intensity on ITV formation. Detailed onset conditions, characteristics of near-nozzle flow patterns, and PAH distributions are also discussed.

  7. Investigation of secondary formation of formic acid: urban environment vs. oil and gas producing region

    Science.gov (United States)

    Yuan, B.; Veres, P. R.; Warneke, C.; Roberts, J. M.; Gilman, J. B.; Koss, A.; Edwards, P. M.; Graus, M.; Kuster, W. C.; Li, S.-M.; Wild, R. J.; Brown, S. S.; Dubé, W. P.; Lerner, B. M.; Williams, E. J.; Johnson, J. E.; Quinn, P. K.; Bates, T. S.; Lefer, B.; Hayes, P. L.; Jimenez, J. L.; Weber, R. J.; Zamora, R.; Ervens, B.; Millet, D. B.; Rappenglück, B.; de Gouw, J. A.

    2015-02-01

    Formic acid (HCOOH) is one of the most abundant carboxylic acids in the atmosphere. However, current photochemical models cannot fully explain observed concentrations and in particular secondary formation of formic acid across various environments. In this work, formic acid measurements made at an urban receptor site (Pasadena) in June-July 2010 during CalNex (California Research at the Nexus of Air Quality and Climate Change) and a site in an oil and gas producing region (Uintah Basin) in January-February 2013 during UBWOS 2013 (Uintah Basin Winter Ozone Studies) will be discussed. Although the VOC (volatile organic compounds) compositions differed dramatically at the two sites, measured formic acid concentrations were comparable: 2.3 ± 1.3 in UBWOS 2013 and 2.0 ± 1.0 ppb in CalNex. We determine that concentrations of formic acid at both sites were dominated by secondary formation (> 99%). A constrained box model using the Master Chemical Mechanism (MCM v3.2) underestimates the measured formic acid concentrations drastically at both sites (by a factor of > 10). Compared to the original MCM model that includes only ozonolysis of unsaturated organic compounds and OH oxidation of acetylene, when we updated yields of ozonolysis of alkenes and included OH oxidation of isoprene, vinyl alcohol chemistry, reaction of formaldehyde with HO2, oxidation of aromatics, and reaction of CH3O2 with OH, the model predictions for formic acid were improved by a factor of 6.4 in UBWOS 2013 and 4.5 in CalNex, respectively. A comparison of measured and modeled HCOOH/acetone ratios is used to evaluate the model performance for formic acid. We conclude that the modified chemical mechanism can explain 19 and 45% of secondary formation of formic acid in UBWOS 2013 and CalNex, respectively. The contributions from aqueous reactions in aerosol and heterogeneous reactions on aerosol surface to formic acid are estimated to be 0-6 and 0-5% in UBWOS 2013 and CalNex, respectively. We observe that

  8. Experimental and detailed kinetic modeling study of PAH formation in laminar co-flow methane diffusion flames

    DEFF Research Database (Denmark)

    Cuoci, Alberto; Frassoldati, Alessio; Faravelli, Tiziano

    2013-01-01

    In the present paper, synchrotron VUV photoionization mass spectrometry is used to study the detailed chemistry of co-flow methane diffusion flames with different dilution ratios. The experimental results constitute a comprehensive characterization of species important for PAH and soot formation...

  9. Experimental and numerical study of deposit formation in secondary side SG TSP by electrokinetic approach

    International Nuclear Information System (INIS)

    Guillodo, Michael; Foucault, Marc; Ryckelynck, Natacha; Chahma, Farah; Guingo, Mathieu; Mansour, Carine; Alos-Ramos, Olga; Corredera, Geraldine

    2012-09-01

    Corrosion products deposit formation observed in PWR steam generators (SGs) - related to SG free span fouling and SG clogging - is now reported since several years. SG clogging is a localized phenomenon observed between the leading edge of the Tube Support Plate (TSP) and SG tubing materials. Based on visual inspections, it was found that the gaps between SG tubing material and TSP at the lower part of the broached holes were getting progressively blocked. Therefore, for safe operation, most affected PWRs had to be operated at reduced power. TSP blockage was mainly observed for low-pH water chemistry conditioning, which directly depends on the operating water chemistry. The TSP blockage mechanism is complex due to the localized conditions in which flow pattern change, chemistry and electrochemical conditions are not well understood. Electrokinetic considerations could be pointed out to explain the coupling of chemistry, materials and thermohydraulic (T/H) conditions. In this frame AREVA and EDF have launched a long-term R and D program in order to understand the mechanisms driving the formation of SG clogging. This study based on parametric laboratory tests aims to assess the role of secondary water chemistry, material and T/H conditions on deposit formation. The experimental approach focused on electrokinetic measurements of metallic substrates and on the assessment of oxidation properties of materials in secondary side chemistry. An overall analysis of recent results is presented to address SG deposit formation in secondary water chemistry for various conditioning amines - morpholine, ethanolamine and dimethylamine. To complete the study, the experimental results have been correlated to CFD simulations of particle deposition, by means of stochastic Lagrangian models. These calculations have in particular reproduced correctly the location of the most important particle deposit (the leading edge of the test tube), and have stressed the influence of the

  10. T-matrix modeling of linear depolarization by morphologically complex soot and soot-containing aerosols

    Science.gov (United States)

    Mishchenko, Michael I.; Liu, Li; Mackowski, Daniel W.

    2013-07-01

    We use state-of-the-art public-domain Fortran codes based on the T-matrix method to calculate orientation and ensemble averaged scattering matrix elements for a variety of morphologically complex black carbon (BC) and BC-containing aerosol particles, with a special emphasis on the linear depolarization ratio (LDR). We explain theoretically the quasi-Rayleigh LDR peak at side-scattering angles typical of low-density soot fractals and conclude that the measurement of this feature enables one to evaluate the compactness state of BC clusters and trace the evolution of low-density fluffy fractals into densely packed aggregates. We show that small backscattering LDRs measured with ground-based, airborne, and spaceborne lidars for fresh smoke generally agree with the values predicted theoretically for fluffy BC fractals and densely packed near-spheroidal BC aggregates. To reproduce higher lidar LDRs observed for aged smoke, one needs alternative particle models such as shape mixtures of BC spheroids or cylinders.

  11. Structure-reactivity correlation of diesel soot and characterization of polycyclic aromatic hydrocarbons and carbonyls in biofuel emissions; Struktur-Reaktivitaets-Korrelation von Dieselruss und Charakterisierung von PAHs und Carbonylen im Abgas von Biokraftstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Knauer, Markus

    2010-12-29

    This work reports on the determination of the structure-reactivity correlation of soot using Raman microscopy (RM) and temperature programmed oxidation (TPO), as well as on changes in the emission level of polycyclic aromatic hydrocarbons (PAH) and carbonyls at the combustion of biofuels. To characterize the reactivity of soot the combustion behaviour of model- and diesel soot has been determined by means of TPO in the presence of oxygen. In this context, spark-discharge soot and graphite powder were applied as model substances, and EURO VI and IV diesel soot as real-diesel soots. The structure of soot samples was investigated by RM and structural changes during the TPO were observed. In order to make a statement about the changes in PAH and carbonyl compound emissions during combustion of biofuels, samples were taken at different engine testbenches. Fossil fuel, biodiesel and vegetable oil were used during this study, as well as fuel mixtures with different biofuel fractions.

  12. Structure-reactivity correlation of diesel soot and characterization of polycyclic aromatic hydrocarbons and carbonyls in biofuel emissions; Struktur-Reaktivitaets-Korrelation von Dieselruss und Charakterisierung von PAHs und Carbonylen im Abgas von Biokraftstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Knauer, Markus

    2009-12-29

    This work reports on the determination of the structure-reactivity correlation of soot using Raman microscopy (RM) and temperature programmed oxidation (TPO), as well as on changes in the emission level of polycyclic aromatic hydrocarbons (PAH) and carbonyls at the combustion of biofuels. To characterize the reactivity of soot the combustion behaviour of model- and diesel soot has been determined by means of TPO in the presence of oxygen. In this context, spark-discharge soot and graphite powder were applied as model substances, and EURO VI and IV diesel soot as real-diesel soots. The structure of soot samples was investigated by RM and structural changes during the TPO were observed. In order to make a statement about the changes in PAH and carbonyl compound emissions during combustion of biofuels, samples were taken at different engine testbenches. Fossil fuel, biodiesel and vegetable oil were used during this study, as well as fuel mixtures with different biofuel fractions.

  13. Secondary ion formation during electronic and nuclear sputtering of germanium

    Science.gov (United States)

    Breuer, L.; Ernst, P.; Herder, M.; Meinerzhagen, F.; Bender, M.; Severin, D.; Wucher, A.

    2018-06-01

    Using a time-of-flight mass spectrometer attached to the UNILAC beamline located at the GSI Helmholtz Centre for Heavy Ion Research, we investigate the formation of secondary ions sputtered from a germanium surface under irradiation by swift heavy ions (SHI) such as 5 MeV/u Au by simultaneously recording the mass spectra of the ejected secondary ions and their neutral counterparts. In these experiments, the sputtered neutral material is post-ionized via single photon absorption from a pulsed, intensive VUV laser. After post-ionization, the instrument cannot distinguish between secondary ions and post-ionized neutrals, so that both signals can be directly compared in order to investigate the ionization probability of different sputtered species. In order to facilitate an in-situ comparison with typical nuclear sputtering conditions, the system is also equipped with a conventional rare gas ion source delivering a 5 keV argon ion beam. For a dynamically sputter cleaned surface, it is found that the ionization probability of Ge atoms and Gen clusters ejected under electronic sputtering conditions is by more than an order of magnitude higher than that measured for keV sputtered particles. In addition, the mass spectra obtained under SHI irradiation show prominent signals of GenOm clusters, which are predominantly detected as positive or negative secondary ions. From the m-distribution for a given Ge nuclearity n, one can deduce that the sputtered material must originate from a germanium oxide matrix with approximate GeO stoichiometry, probably due to residual native oxide patches even at the dynamically cleaned surface. The results clearly demonstrate a fundamental difference between the ejection and ionization mechanisms in both cases, which is interpreted in terms of corresponding model calculations.

  14. Diesel/biodiesel soot oxidation with ceo2 and ceo2-zro2-modified cordierites: a facile way of accounting for their catalytic ability in fuel combustion processes

    Directory of Open Access Journals (Sweden)

    Rodrigo F. Silva

    2011-01-01

    Full Text Available CeO2 and mixed CeO2-ZrO2 nanopowders were synthesized and efficiently deposited onto cordierite substrates, with the evaluation of their morphologic and structural properties through XRD, SEM, and FTIR. The modified substrates were employed as outer heterogeneous catalysts for reducing the soot originated from the diesel and diesel/biodiesel blends incomplete combustion. Their activity was evaluated in a diesel stationary motor, and a comparative analysis of the soot emission was carried out through diffuse reflectance spectroscopy. The analyses have shown that the catalyst-impregnated cordierite samples are very efficient for soot oxidation, being capable of reducing the soot emission in more than 60%.

  15. The Ångström Exponent and Turbidity of Soot Component in the ...

    African Journals Online (AJOL)

    OPAC) using FORTRAN program to model the effect of soot on optical depth, scattering coefficient, absorption coefficient, single scattering albedo, extinction coefficient and asymmetry parameter at spectral range of 0.25 to 1.00 ƒÝm for eight ...

  16. Soot and chemiluminescence in diesel combustion of bio-derived, oxygenated and reference fuels

    NARCIS (Netherlands)

    Klein-Douwel, R.J.H.; Donkerbroek, A.J.; Vliet, A.P. van; Boot, M.D.; Somers, L.M.T.; Baert, R.S.G.; Dam, N.J.; Meulen, J.J. ter

    2009-01-01

    High-speed imaging, spectroscopy and thermodynamical characterization are applied to an optically accessible, heavy-duty diesel engine in order to compare sooting and chemiluminescence behaviour of bio-derived, oxygenated fuels and various reference fuels. The fuels concerned include the bio-derived

  17. [Estimate of the formation potential of secondary organic aerosol in Beijing summertime].

    Science.gov (United States)

    Lü, Zi-Feng; Hao, Ji-Ming; Duan, Jing-Chun; Li, Jun-Hua

    2009-04-15

    Fractional aerosol coefficients (FAC) are used in conjunction with measurements of volatile organic compounds (VOC) during ozone episodes to estimate the formation potential of secondary organic aerosols (SOA) in the summertime of Beijing. The estimation is based on the actual atmospheric conditions of Beijing, and benzene and isoprene are considered as the precursors of SOA. The results show that 31 out of 70 measured VOC species are SOA precursors, and the total potential SOA formation is predicted to be 8.48 microg/m3, which accounts for 30% of fine organic particle matter. Toluene, xylene, pinene, ethylbenzene and n-undecane are the 5 largest contributors to SOA production and account for 20%, 22%, 14%, 9% and 4% of total SOA production, respectively. The anthropogenic aromatic compounds, which yield 76% of the calculated SOA, are the major source of SOA. The biogenic alkenes, alkanes and carbonyls produce 16%, 7% and 1% of SOA formation, respectively. The major components of produced SOA are expected to be aromatic compounds, aliphatic acids, carbonyls and aliphatic nitrates, which contribute to 72%, 14%, 11% and 3% of SOA mass, respectively. The SOA precursors have relatively low atmospheric concentrations and low ozone formation potential. Hence, SOA formation potential of VOC species, in addition to their atmospheric concentrations and ozone formation potential, should be considered in policy making process of VOCs control.

  18. PtrWRKY19, a novel WRKY transcription factor, contributes to the regulation of pith secondary wall formation in Populus trichocarpa

    OpenAIRE

    Li Yang; Xin Zhao; Fan Yang; Di Fan; Yuanzhong Jiang; Keming Luo

    2016-01-01

    WRKY proteins are one of the largest transcription factor families in higher plants and play diverse roles in various biological processes. Previous studies have shown that some WRKY members act as negative regulators of secondary cell wall formation in pith parenchyma cells. However, the regulatory mechanism of pith secondary wall formation in tree species remains largely unknown. In this study, PtrWRKY19 encoding a homolog of Arabidopsis WRKY12 was isolated from Populus trichocarpa. PtrWRKY...

  19. Chemical composition and heterogeneous reactivity of soot generated in the combustion of diesel and GTL (Gas-to-Liquid) fuels and amorphous carbon Printex U with NO2 and CF3COOH gases

    Science.gov (United States)

    Tapia, A.; Salgado, S.; Martín, P.; Villanueva, F.; García-Contreras, R.; Cabañas, B.

    2018-03-01

    The heterogeneous reactions of nitrogen dioxide (NO2) and trifluoroacetic acid (CF3COOH) with soot produced by diesel and GTL (gas-to-liquid) fuels were investigated using a Knudsen flow reactor with mass spectrometry as a detection system for gas phase species. Soot was generated with a 4 cylinder diesel engine working under steady-state like urban operation mode. Heterogeneous reaction of the mentioned gases with a commercial carbon, Printex U, used as reference, was also analyzed. The initial and the steady-state uptake coefficients, γ0 and γss, respectively, were measured indicating that GTL soot reacts faster than diesel soot and Printex U carbon for NO2 gas reactant. According to the number of reacted molecules on the surface, Printex U soot presents more reducing sites than diesel and GTL soot. Initial uptake coefficients for GTL and diesel soot for the reaction with CF3COOH gas reactant are very similar and no clear conclusions can be obtained related to the initial reactivity. The number of reacted molecules calculated for CF3COOH reactions shows values two orders of magnitude higher than the corresponding to NO2 reactions, indicating a greater presence of basic functionalities in the soot surfaces. More information of the surface composition has been obtained using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) before and after the reaction of soot samples with gas reactants. As conclusion, the interface of diesel and GTL soot before reaction mainly consists of polycyclic aromatic hydrocarbons (PAHs), nitro-compounds as well as ether functionalities. After reaction with gas reactant, it was observed that PAHs and nitro-compounds remain on the soot surface and new spectral bands such as carbonyl groups (carboxylic acids, aldehydes, esters and ketones) are observed. Physical properties of soot from both fuels studied such as BET surface isotherm and SEM analysis were also developed and related to the observed reactivity.

  20. Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

    Science.gov (United States)

    Alanen, Jenni; Simonen, Pauli; Saarikoski, Sanna; Timonen, Hilkka; Kangasniemi, Oskari; Saukko, Erkka; Hillamo, Risto; Lehtoranta, Kati; Murtonen, Timo; Vesala, Hannu; Keskinen, Jorma; Rönkkö, Topi

    2017-07-01

    Natural gas usage in the traffic and energy production sectors is a growing trend worldwide; thus, an assessment of its effects on air quality, human health and climate is required. Engine exhaust is a source of primary particulate emissions and secondary aerosol precursors, which both contribute to air quality and can cause adverse health effects. Technologies, such as cleaner engines or fuels, that produce less primary and secondary aerosols could potentially significantly decrease atmospheric particle concentrations and their adverse effects. In this study, we used a potential aerosol mass (PAM) chamber to investigate the secondary aerosol formation potential of natural gas engine exhaust. The PAM chamber was used with a constant UV-light voltage, which resulted in relatively long equivalent atmospheric ages of 11 days at most. The studied retro-fitted natural gas engine exhaust was observed to form secondary aerosol. The mass of the total aged particles, i.e., particle mass measured downstream of the PAM chamber, was 6-268 times as high as the mass of the emitted primary exhaust particles. The secondary organic aerosol (SOA) formation potential was measured to be 9-20 mg kgfuel-1. The total aged particles mainly consisted of organic matter, nitrate, sulfate and ammonium, with the fractions depending on exhaust after-treatment and the engine parameters used. Also, the volatility, composition and concentration of the total aged particles were found to depend on the engine operating mode, catalyst temperature and catalyst type. For example, a high catalyst temperature promoted the formation of sulfate particles, whereas a low catalyst temperature promoted nitrate formation. However, in particular, the concentration of nitrate needed a long time to stabilize - more than half an hour - which complicated the conclusions but also indicates the sensitivity of nitrate measurements on experimental parameters such as emission source and system temperatures. Sulfate was

  1. Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

    Directory of Open Access Journals (Sweden)

    J. Alanen

    2017-07-01

    Full Text Available Natural gas usage in the traffic and energy production sectors is a growing trend worldwide; thus, an assessment of its effects on air quality, human health and climate is required. Engine exhaust is a source of primary particulate emissions and secondary aerosol precursors, which both contribute to air quality and can cause adverse health effects. Technologies, such as cleaner engines or fuels, that produce less primary and secondary aerosols could potentially significantly decrease atmospheric particle concentrations and their adverse effects. In this study, we used a potential aerosol mass (PAM chamber to investigate the secondary aerosol formation potential of natural gas engine exhaust. The PAM chamber was used with a constant UV-light voltage, which resulted in relatively long equivalent atmospheric ages of 11 days at most. The studied retro-fitted natural gas engine exhaust was observed to form secondary aerosol. The mass of the total aged particles, i.e., particle mass measured downstream of the PAM chamber, was 6–268 times as high as the mass of the emitted primary exhaust particles. The secondary organic aerosol (SOA formation potential was measured to be 9–20 mg kgfuel−1. The total aged particles mainly consisted of organic matter, nitrate, sulfate and ammonium, with the fractions depending on exhaust after-treatment and the engine parameters used. Also, the volatility, composition and concentration of the total aged particles were found to depend on the engine operating mode, catalyst temperature and catalyst type. For example, a high catalyst temperature promoted the formation of sulfate particles, whereas a low catalyst temperature promoted nitrate formation. However, in particular, the concentration of nitrate needed a long time to stabilize – more than half an hour – which complicated the conclusions but also indicates the sensitivity of nitrate measurements on experimental parameters such as emission

  2. Simultaneous planar measurements of soot structure and velocity fields in a turbulent lifted jet flame at 3 kHz

    Science.gov (United States)

    Köhler, M.; Boxx, I.; Geigle, K. P.; Meier, W.

    2011-05-01

    We describe a newly developed combustion diagnostic for the simultaneous planar imaging of soot structure and velocity fields in a highly sooting, lifted turbulent jet flame at 3000 frames per second, or two orders of magnitude faster than "conventional" laser imaging systems. This diagnostic uses short pulse duration (8 ns), frequency-doubled, diode-pumped solid state (DPSS) lasers to excite laser-induced incandescence (LII) at 3 kHz, which is then imaged onto a high framerate CMOS camera. A second (dual-cavity) DPSS laser and CMOS camera form the basis of a particle image velocity (PIV) system used to acquire 2-component velocity field in the flame. The LII response curve (measured in a laminar propane diffusion flame) is presented and the combined diagnostics then applied in a heavily sooting lifted turbulent jet flame. The potential challenges and rewards of application of this combined imaging technique at high speeds are discussed.

  3. Modelling of Combustion and Pollutant Formation in a Large, Two-Stroke Marine Diesel Engine using Integrated CFD-Skeletal Chemical Mechanism

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Karvounis, Nikolas; Schramm, Jesper

    In this reported work, simulation studies of in-cylinder diesel combustion and pollutant formation processesin a two-stroke, low-speed uniflow-scavenged marine diesel engine are presented. Numerical computation is performed by integrating chemical kinetics into CFD computations. In order...... to minimize the computational runtime, an in-house skeletal n-heptane chemical mechanism is coupled with the CFD model. This surrogate fuel model comprises 89 reactions with 32 species essential to diesel ignition/combustion processes as well as the formation of soot precursors and nitrogen monoxide (NO......). Prior to the marine engine simulation,coupling of the newly developed surrogate fuel model and a revised multi-step soot model [1] is validated on the basis of optical diagnostics measurement obtained at varying ambient pressure levels [2]. It is demonstrated that the variation of ignition delay times...

  4. Formation of secondary organic aerosol from isoprene oxidation over Europe

    Directory of Open Access Journals (Sweden)

    M. Karl

    2009-09-01

    Full Text Available The role of isoprene as a precursor to secondary organic aerosol (SOA over Europe is studied with the two-way nested global chemistry transport model TM5. The inclusion of the formation of SOA from isoprene oxidation in our model almost doubles the atmospheric burden of SOA over Europe compared to SOA formation from terpenes and aromatics. The reference simulation, which considers SOA formation from isoprene, terpenes and aromatics, predicts a yearly European production rate of 1.0 Tg SOA yr−1 and an annual averaged atmospheric burden of about 50 Gg SOA over Europe. A fraction of 35% of the SOA produced in the boundary layer over Europe is transported to higher altitudes or to other world regions. Summertime measurements of organic matter (OM during the extensive EMEP OC/EC campaign 2002/2003 are better reproduced when SOA formation from isoprene is taken into account, reflecting also the strong seasonality of isoprene and other biogenic volatile organic compounds (BVOC emissions from vegetation. However, during winter, our model strongly underestimates OM, likely caused by missing wood burning in the emission inventories. Uncertainties in the parameterisation of isoprene SOA formation have been investigated. Maximum SOA production is found for irreversible sticking (non-equilibrium partitioning of condensable vapours on particles, with tropospheric SOA production over Europe increased by a factor of 4 in summer compared to the reference case. Completely neglecting SOA formation from isoprene results in the lowest estimate (0.51 Tg SOA yr−1. The amount and the nature of the absorbing matter are shown to be another key uncertainty when predicting SOA levels. Consequently, smog chamber experiments on SOA formation should be performed with different types of seed aerosols and without seed aerosols in order to derive an improved treatment of the absorption of SOA in the models. Consideration of a number of recent insights

  5. Secondary organic aerosol formation through cloud processing of aromatic VOCs

    Science.gov (United States)

    Herckes, P.; Hutchings, J. W.; Ervens, B.

    2010-12-01

    Field observations have shown substantial concentrations (20-5,500 ng L-1) of aromatic volatile organic compounds (VOC) in cloud droplets. The potential generation of secondary organic aerosol mass through the processing of these anthropogenic VOCs was investigated through laboratory and modeling studies. Under simulated atmospheric laboratory conditions, in idealized solutions, benzene, toluene, ethylbenzene, and xylene (BTEX) degraded quickly in the aqueous phase. The degradation process yielded less volatile products which would contribute to new aerosol mass upon cloud evaporation. However, when realistic cloud solutions containing natural organic matter were used in the experiments, the reaction rates decreased with increasing organic carbon content. Kinetic data derived from these experiments were used as input to a multiphase box model in order to evaluate the secondary organic aerosol (SOA) mass formation potential of cloud processing of BTEX. Model results will be presented that quantify the SOA amounts from these aqueous phase pathways. The efficiency of this multiphase SOA source will be compared to SOA yields from the same aromatics as treated in traditional SOA models that are restricted to gas phase oxidation and subsequent condensation on particles.

  6. The poplar MYB master switches bind to the SMRE site and activate the secondary wall biosynthetic program during wood formation.

    Directory of Open Access Journals (Sweden)

    Ruiqin Zhong

    Full Text Available Wood is mainly composed of secondary walls, which constitute the most abundant stored carbon produced by vascular plants. Understanding the molecular mechanisms controlling secondary wall deposition during wood formation is not only an important issue in plant biology but also critical for providing molecular tools to custom-design wood composition suited for diverse end uses. Past molecular and genetic studies have revealed a transcriptional network encompassing a group of wood-associated NAC and MYB transcription factors that are involved in the regulation of the secondary wall biosynthetic program during wood formation in poplar trees. Here, we report the functional characterization of poplar orthologs of MYB46 and MYB83 that are known to be master switches of secondary wall biosynthesis in Arabidopsis. In addition to the two previously-described PtrMYB3 and PtrMYB20, two other MYBs, PtrMYB2 and PtrMYB21, were shown to be MYB46/MYB83 orthologs by complementation and overexpression studies in Arabidopsis. The functional roles of these PtrMYBs in regulating secondary wall biosynthesis were further demonstrated in transgenic poplar plants showing an ectopic deposition of secondary walls in PtrMYB overexpressors and a reduction of secondary wall thickening in their dominant repressors. Furthermore, PtrMYB2/3/20/21 together with two other tree MYBs, the Eucalyptus EgMYB2 and the pine PtMYB4, were shown to differentially bind to and activate the eight variants of the 7-bp SMRE consensus sequence, composed of ACC(A/TA(A/C(T/C. Together, our results indicate that the tree MYBs, PtrMYB2/3/20/21, EgMYB2 and PtMYB4, are master transcriptional switches that activate the SMRE sites in the promoters of target genes and thereby regulate secondary wall biosynthesis during wood formation.

  7. Experimental study on the effect of radiation in the secondary palate formation

    Energy Technology Data Exchange (ETDEWEB)

    You, Dong Soo [Department of Dental Radiology, College of Dentistry, Seoul National University, Seoul (Korea, Republic of)

    1977-11-15

    The author observed the effect of X-ray irradiation on the secondary palate formation of the rat fetuses. The mothers were exposed to X-radiation on the 10 1/2th, 11 1/2th, and 12 1/2th day of gestation with respectively 150, 200, 250, 300, and 350 rads. The fetuses were removed from mothers on 15 1/2th, 16 1/2th, and 18 1/2th day of gestation. Morphological changes in palate formation were examined and histochemical preparations were made. 1. In control fetuses, the secondary palates were fully developed on the 15 1/2th, to 18 1/2th day of gestation. But in experimental fetuses, many cleft palates were observed in accordance with increase of X-radiation dose. 2. Frequency of incidence of horizontal position of both palatal shelves in cleft palate was highest. 3. According to the dislocation of palatal processes, the stain ability of palatal crest was varied. 4. The thickened area of palatal epithelium of palatal crest showed intense methyl green-pyronin and PAS reaction 5. Mesenchymal cell condensation was appeared under the thickened epithelium of palatal process and this mesenchymal tissue showed strong colloidal iron reaction. 6. The stain ability of alizarin red S and alkaline phosphatase reaction of tectal ridge were decreased in accordance with increase of irradiation doses.

  8. Experimental study on the effect of radiation in the secondary palate formation

    International Nuclear Information System (INIS)

    You, Dong Soo

    1977-01-01

    The author observed the effect of X-ray irradiation on the secondary palate formation of the rat fetuses. The mothers were exposed to X-radiation on the 10 1/2th, 11 1/2th, and 12 1/2th day of gestation with respectively 150, 200, 250, 300, and 350 rads. The fetuses were removed from mothers on 15 1/2th, 16 1/2th, and 18 1/2th day of gestation. Morphological changes in palate formation were examined and histochemical preparations were made. 1. In control fetuses, the secondary palates were fully developed on the 15 1/2th, to 18 1/2th day of gestation. But in experimental fetuses, many cleft palates were observed in accordance with increase of X-radiation dose. 2. Frequency of incidence of horizontal position of both palatal shelves in cleft palate was highest. 3. According to the dislocation of palatal processes, the stain ability of palatal crest was varied. 4. The thickened area of palatal epithelium of palatal crest showed intense methyl green-pyronin and PAS reaction 5. Mesenchymal cell condensation was appeared under the thickened epithelium of palatal process and this mesenchymal tissue showed strong colloidal iron reaction. 6. The stain ability of alizarin red S and alkaline phosphatase reaction of tectal ridge were decreased in accordance with increase of irradiation doses.

  9. Morphology and Chemical Composition of soot particles emitted by Wood-burning Cook-Stoves: a HRTEM, XPS and Elastic backscattering Studies.

    Science.gov (United States)

    Carabali-Sandoval, G. A., Sr.; Castro, T.; Peralta, O.; De la Cruz, W.; Días, J.; Amelines, O.; Rivera-Hernández, M.; Varela, A.; Muñoz-Muñoz, F.; Policroniades, R.; Murillo, G.; Moreno, E.

    2014-12-01

    The morphology, microstructure and the chemical composition on surface of soot particles were studied by using high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and elastic backscattering spectrometry. In order to obtain freshly soot particles emitted by home-made wood-burning cook stoves, copper grids for Transmission Electron Microscope (TEM) were placed on the last two of an 8-stages MOUDI cascade impactor. The analysis of HRTEM micrographs revealed the nanostructure and the particle size of soot particles. The XPS survey spectra show a large carbon peak around 285 eV and the oxygen signal at 533 eV. Some differences observed in the carbon/oxygen (C/O) ratio of the particles probably depend on the combustion process efficiency of each cook-stove analyzed. The C-1s XPS spectra show an asymmetric broad peak and other with low intensity that corresponds to sp2 and sp3hybridization, which were fitted with a convolution using Gaussian functions. Elastic backscattering technique allows a chemical elemental analysis of samples and confirms the presence of C, O and Si observed by XPS. Additionally, the morphological properties of soot aggregates were analyzed calculating the border-based fractal dimension (Df). Particles exhibit complex shapes with high values of Df. Also, real-time absorption (σabs) and scattering (σsct) coefficients of fine (with aerodynamic diameter < 2.5 µm) soot particles were measured. The trend in σabs and σsct indicate that the cooking process has two important combustion stages which varied in its flaming strength, being vigorous in the first stage and soft in the second one.

  10. Optimized Jasmonic Acid Production by Lasiodiplodia theobromae Reveals Formation of Valuable Plant Secondary Metabolites.

    Directory of Open Access Journals (Sweden)

    Felipe Eng

    Full Text Available Jasmonic acid is a plant hormone that can be produced by the fungus Lasiodiplodia theobromae via submerged fermentation. From a biotechnological perspective jasmonic acid is a valuable feedstock as its derivatives serve as important ingredients in different cosmetic products and in the future it may be used for pharmaceutical applications. The objective of this work was to improve the production of jasmonic acid by L. theobromae strain 2334. We observed that jasmonic acid formation is dependent on the culture volume. Moreover, cultures grown in medium containing potassium nitrate as nitrogen source produced higher amounts of jasmonic acid than analogous cultures supplemented with ammonium nitrate. When cultivated under optimal conditions for jasmonic acid production, L. theobromae secreted several secondary metabolites known from plants into the medium. Among those we found 3-oxo-2-(pent-2-enyl-cyclopentane-1-butanoic acid (OPC-4 and hydroxy-jasmonic acid derivatives, respectively, suggesting that fungal jasmonate metabolism may involve similar reaction steps as that of plants. To characterize fungal growth and jasmonic acid-formation, we established a mathematical model describing both processes. This model may form the basis of industrial upscaling attempts. Importantly, it showed that jasmonic acid-formation is not associated to fungal growth. Therefore, this finding suggests that jasmonic acid, despite its enormous amount being produced upon fungal development, serves merely as secondary metabolite.

  11. The Ångström Exponent and Turbidity of Soot Component in the ...

    African Journals Online (AJOL)

    Corresponding author: ... Origin 50 software was used to plot the graphs. SPSS 16.0 ... The α reflects the dominance of fine-mode particles while α2 at 0% RH reflects the dominance of ... 99% of the mass is carbon, but soot also contains hydrocarbons ...

  12. Density separation of combustion-derived soot and petrogenic graphitic black carbon: Quantification and isotopic characterization

    International Nuclear Information System (INIS)

    Veilleux, M-H; Gelinas, Y; Dickens, A F; Brandes, J

    2009-01-01

    The black carbon continuum is composed of a series of carbon-rich components derived from combustion or metamorphism and characterized by contrasting environmental behavior and susceptibility to oxidation. In this work, we present a micro-scale density fractionation method that allows isolating the small quantities of soot-like and graphitic material usually found in natural samples. Organic carbon and δ 13 C mass balance calculations were used to quantify the relative contributions of the two fractions to thermally-stable organic matter from a series of aquatic sediments. Varying proportions of soot-like and graphitic material were found in these samples, with large variations in δ 13 C signatures suggesting important differences in their origin and/or dynamics in the environment.

  13. Influences of the molecular fuel structure on combustion reactions towards soot precursors in selected alkane and alkene flames.

    Science.gov (United States)

    Ruwe, Lena; Moshammer, Kai; Hansen, Nils; Kohse-Höinghaus, Katharina

    2018-04-25

    In this study, we experimentally investigate the high-temperature oxidation kinetics of n-pentane, 1-pentene and 2-methyl-2-butene (2M2B) in a combustion environment using flame-sampling molecular beam mass spectrometry. The selected C5 fuels are prototypes for linear and branched, saturated and unsaturated fuel components, featuring different C-C and C-H bond structures. It is shown that the formation tendency of species, such as polycyclic aromatic hydrocarbons (PAHs), yielded through mass growth reactions increases drastically in the sequence n-pentane fuel-dependent reaction sequences of the gas-phase combustion mechanism that provide explanations for the observed difference in the PAH formation tendency. First, we investigate the fuel-structure-dependent formation of small hydrocarbon species that are yielded as intermediate species during the fuel decomposition, because these species are at the origin of the subsequent mass growth reaction pathways. Second, we review typical PAH formation reactions inspecting repetitive growth sequences in dependence of the molecular fuel structure. Third, we discuss how differences in the intermediate species pool influence the formation reactions of key aromatic ring species that are important for the PAH growth process underlying soot formation. As a main result it was found that for the fuels featuring a C[double bond, length as m-dash]C double bond, the chemistry of their allylic fuel radicals and their decomposition products strongly influences the combination reactions to the initially formed aromatic ring species and as a consequence, the PAH formation tendency.

  14. Features of formation of the individual students in secondary and high school

    Directory of Open Access Journals (Sweden)

    V.O. Sutula

    2014-03-01

    Full Text Available Purpose: Analyzed features of motivation to achievement and need to praise the students of secondary and high school. Material: In the survey took part 1634 students of secondary school in Kharkov, Vinnitsa and Lugansk regions. Carried out a comprehensive psychological testing, which allowed to find out the level of motivation of students to achievement and need for praise. Results: It is shown that during the period of study at school from fifth to eleventh classes a number of students have a low motivation to achievements, and low need for praise. Confirmed provision indicates that the modern school is still not fully realized the potential of educational pedagogy. Conclusions: It is shown that the formation personality physical education students in general education is possible only with the active and conscious of their participation in various forms of sports and recreation activities undertaken in the modern school.

  15. Secondary adult encephalocele with abscess formation of calcified frontal sinus mucocele.

    Science.gov (United States)

    Oh, Byeong Ho; Lee, Ok-Jun; Park, Young Seok

    2016-07-01

    Although encephalocele is a rare congenital abnormality, secondary encephalocele is extremely rare and can cause fatal complications. Here, we report a case of secondary encephalocele caused by frontal sinus wall defect due to chronic sinusitis, which was completely removed by cranialization with autologous bone graft. A 50-year-old man with a 10-year history of chronic sinusitis visited our hospital due to suddenly altered mentality characterized by stupor. Computerized tomography scanning and magnetic resonance imaging revealed an enlarged left frontal sinus with sinusitis. The frontal sinus cavity was calcified, and the left frontal lobe had herniated into the cavity accompanied by yellow pus. A large dural defect was also found around the frontal sinus area. After removal of the abscess and some of the frontal lobe, frontal skull base repair by cranialization was performed using autologous bone graft. Streptococcus pneumoniae was cultured from the cerebrospinal fluid (CSF), necessitating treatment with antibiotics. After the operation, the mental status of the patient improved and no CSF leakage was observed. In addition to correct diagnosis and early treatment including antibiotics, the surgical repair of defects is needed in patients with secondary encephalocele to prevent further episodes of meningitis. Surgical correction of frontal sinus encephalocele can be achieved through bifrontal craniotomy or endoscopic transnasal repair. If a patient has CSF leakage, open craniotomy may facilitate repair of the dural defect and allow for cranialization of the sinus. Removal of dysplastic herniated brain tissue and cranialization of the frontal sinus may be a good option for treating secondary encephalocele and its associated complications, including meningitis, abscess formation, and infarction of the herniated brain parenchyma.

  16. Formation of secondary aerosols from the ozonolysis of styrene: Effect of SO2 and H2O

    Science.gov (United States)

    Díaz-de-Mera, Yolanda; Aranda, Alfonso; Martínez, Ernesto; Rodríguez, Ana Angustias; Rodríguez, Diana; Rodríguez, Ana

    2017-12-01

    In this work we report the study of the ozonolysis of styrene and the reaction conditions leading to the formation of secondary aerosols. The reactions have been carried out in a Teflon chamber filled with synthetic air mixtures at atmospheric pressure and room temperature. We have found that the ozonolysis of styrene in the presence of low concentrations of SO2 readily produces new particles under concentrations of reactants lower than those required in experiments in the absence of SO2. Thus, nucleation events occur at concentrations around (5.6 ± 1.7) × 108molecule cm-3 (errors are 2σ±20%) and SO2 is consumed during the experiments. The reaction of the Criegee intermediates with SO2 to produce SO3 and then H2SO4 may explain (together with OH reactions' contribution) the high capacity of styrene to produce particulate matter in polluted atmospheres. The formation of secondary aerosols in the smog chamber is inhibited under high H2O concentrations. So, the potential formation of secondary aerosols under atmospheric conditions depends on the concentration of SO2 and relative humidity, with a water to SO2 rate constants ratio kH2O/kSO2 = (2.8 ± 0.7) × 10-5 (errors are 2σ±20%).

  17. Formation and emission of PM10 in combustion of biofuels. Final report

    International Nuclear Information System (INIS)

    Johansson, Linda; Tullin, Claes; Leckner, Bo

    2004-02-01

    .g. soot). Submicron particles (particles less than 1 μm) dominated the emission, both with respect to mass and number. Analyses with EDX (Electron Dispersive X-ray), ICP-MS (Inductively Coupled Plasma Mass-Spectrometry), and IC (Ion-Chromatography) showed that the main components in the submicron particles were potassium, sulphur, chlorine, and oxygen. TOF-SIMS (Time-of-flight Secondary Ion Mass Spectrometry) analysis showed that potassium-sulphate followed by potassium chloride were the most dominant substances among alkali -sulphates -chlorides, and -carbonates. For morphology, many spherical particles around 0.1 μm were found. In the second part of the project, the formation of particles during bio-fuel combustion is studied by first measurements on metal release during biofuel combustion. Results from the first part of the project have shown that the particle emission is dominated by inorganic particles at favourable combustion conditions, and the second part is therefore focused on inorganic particles, in which metals are a part. The release of metals is studied to investigate the possibilities to influence formation of combustion particles, and consequently the particle emission. To be able to perform as many tests as possible and to include wide variations in combustion conditions, the second part of the project is carried out using a laboratory reactor. To obtain a time-resolved signal of the release of metals, a large number of single pellets were fired in a laboratory reactor and chemically analysed afterwards using ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometry). The combustion lapse was interrupted after devolatisation, and after 25 %, 50 %, and 75 % of the char burnout. To obtain a time resolved signal of the emission of unburnt particulate matter a photoelectric aerosol sensor was used as a soot indicator. The results of the initial tests show that the main part of the metals was released during char combustion, but a certain metal

  18. An experimental study on the effects of different opening ranges of waste-gate on the exhaust soot emission of a turbo-charged DI diesel engine

    International Nuclear Information System (INIS)

    Ghazikhani, M.; Davarpanah, M.; Shaegh, S.A. Mousavi

    2008-01-01

    This experimental study was conducted to investigate the effects of different opening ranges of waste-gate of a turbo-charged DI diesel engine on improving the exhaust soot emission. Different opening ranges of waste-gate were supplied using an adjustable spring to load the actuating rod of the waste-gate in which, increasing the opening range of the waste-gate decreases the inlet manifold pressure. In this study, the maximum inlet manifold pressures which were supplied by changing the opening range of waste-gate were 0.1 bar, 0.23 bar, 0.26 bar and 0.52 bar over atmosphere and experiments were conducted under the ECE-R49, 13 mode standard test. At each mode of the test, soot emission was recorded and then brake specific soot emission was calculated. Results indicate that, soot emission decreases with increasing the maximum inlet manifold pressure from 0.1 bar to 0.23 bar. This reduction may be due to increasing the intake-air temperature which results in reduction of ignition delay that prolongs the late combustion phase. This improves the soot burnout process because enough time and sufficient in-cylinder temperature are available at the late combustion phase prior to exhaust valve opening. While for the higher maximum inlet manifold pressures from 0.23 bar to 0.52 bar, although there are enough time at the late combustion phase, but the soot emission increases which could be due to more reduction of the in-cylinder gas temperature at the end of combustion before EVO

  19. Molecular structure impacts on secondary organic aerosol formation from glycol ethers

    Science.gov (United States)

    Li, Lijie; Cocker, David R.

    2018-05-01

    Glycol ethers, a class of widely used solvents in consumer products, are often considered exempt as volatile organic compounds based on their vapor pressure or boiling points by regulatory agencies. However, recent studies found that glycol ethers volatilize at ambient conditions nearly as rapidly as the traditional high-volatility solvents indicating the potential of glycol ethers to form secondary organic aerosol (SOA). This is the first work on SOA formation from glycol ethers. The impact of molecular structure, specifically -OH, on SOA formation from glycol ethers and related ethers are investigated in the work. Ethers with and without -OH, with methyl group hindrance on -OH and with -OH at different location are studied in the presence of NOX and under "NOX free" conditions. Photooxidation experiments under different oxidation conditions confirm that the processing of ethers is a combination of carbonyl formation, cyclization and fragmentation. Bulk SOA chemical composition analysis and oxidation products identified in both gas and particle phase suggests that the presence and location of -OH in the carbon bond of ethers determine the occurrence of cyclization mechanism during ether oxidation. The cyclization is proposed as a critical SOA formation mechanism to prevent the formation of volatile compounds from fragmentation during the oxidation of ethers. Glycol ethers with -CH2-O-CH2CH2OH structure is found to readily form cyclization products, especially with the presence of NOx, which is more relevant to urban atmospheric conditions than without NOx. Glycol ethers are evaluated as dominating SOA precursors among all ethers studied. It is estimated that the contribution of glycol ethers to anthropogenic SOA is roughly 1% of the current organic aerosol from mobile sources. The contribution of glycol ethers to anthropogenic SOA is roughly 1% of the current organic aerosol from mobile sources and will play a more important role in future anthropogenic SOA

  20. Gadolinium doped cerium oxide for soot oxidation: Influence of interfacial metal–support interactions

    International Nuclear Information System (INIS)

    Durgasri, D. Naga; Vinodkumar, T.; Lin, Fangjian; Alxneit, Ivo; Reddy, Benjaram M.

    2014-01-01

    Graphical abstract: - Highlights: • Supported Ce-Gd-oxides are applied for soot oxidation for the first time. • Gd 2 O 3 doping facilitates enhanced extrinsic oxygen vacancy concentration in ceria. • The Ce-Gd/TiO 2 exhibited the highest soot oxidation activity. • Key parameters that involved in tuning the activity are discussed. - Abstract: The aim of the present investigation was to ascertain the role of Al 2 O 3 , SiO 2 , and TiO 2 supports in modulating the catalytic performance of ceria-based solid solutions. In this study, we prepared nanosized Ce-Gd/Al 2 O 3 , Ce-Gd/SiO 2 , and Ce-Gd/TiO 2 catalysts by a deposition coprecipitation method and evaluated for soot oxidation. The synthesized catalysts were calcined at two different temperatures to assess their thermal stability and extensively characterized by various techniques, namely, XRD, Raman, BET surface area, TEM, H 2 -TPR, and UV–vis DRS. XRD and TEM results indicate that Ce-Gd-oxide nanoparticles are in highly dispersed form on the surface of the supports. Raman results show a prominent sharp peak and a broad peak corresponding to the F 2g mode of ceria and the presence of oxygen vacancies, respectively. The presence of a significant number of oxygen vacancies in all samples is also confirmed from UV–vis DRS measurements. The H 2 -TPR results suggest that Gd-doping facilitates the reduction of the materials and decreases the onset temperature of reduction. Among the prepared samples, Ce-Gd/TiO 2 catalyst exhibited the highest activity, suggesting the existence of strong interfacial metal support interaction between the active metal oxide and the support

  1. Comparison of different methods for the determination of fractal characteristics of soot aggregates

    International Nuclear Information System (INIS)

    Ouf, F.X.; Coursil, C.; Vendel, J.; Coursil, C.; Gehin, E.

    2007-01-01

    Morphology of particles generated during hydrocarbons or biomass combustion is fundamental as data for characterizing the optical and aerodynamic behaviour of these particles. The fractal nature of soot particles is well known since the works of Jullien and Botet (1987). Nevertheless, the determination of the fractal morphology of these aggregates is based on direct analysis of transmission electronic microscopy (TEM) micrography (Koylo et al., 1995; Sorensen and Feke, 1996; Brasil et al., 2000) which represents a long and tiresome work. We propose in this work to use the method introduced by Kelly and McMurry (1992) and based on serial analysis of electrical mobility and aerodynamic diameters of soot aggregates. This method has been recently used by VanGulijk et al. (2004) and Park et al. (2004), and seems to bring morphological information systematically higher than the TEM analysis. In this study we will detail the TEM analysis method and the theoretical approach associated to the serial method of Kelly and McMurry (1992). We will also present the experimental setup used and the results obtained for aggregates generated during the combustion of acetylene (C 2 H 2 ), toluene (C 7 H 8 ) and Polymethyl Methacrylate (PMMA, C 5 H 8 O 2 ). These results will be compared to TEM analysis results, and discrepancies will be analysed and explained in detail. We will finally conclude on advantages and disadvantages of each method and also on potential of these approaches. The link will be thus established out with the determination of the effective density of the soot aggregates, which is presented in work of Ouf et al. (2005a). (authors)

  2. Kinetic study of diesel soot oxidation: application to simulation of diesel particulate filter regeneration; Etude cinetique de la combustion des suies diesel: application a la modelisation de la regeneration du filtre a particule

    Energy Technology Data Exchange (ETDEWEB)

    Huguet, Ch.

    2005-11-15

    Because of their toxicity, soot are considered as the most important pollutant from Diesel engines. The Diesel Particulate Filter (DPF) is widely deployed in Europe to address the significant reductions in particulate emissions required by increasingly stringent emission standards, both for heavy duty vehicles and passenger cars. Such a DPF filtrates above 99% of soot emissions and must be regularly regenerated. The use of additive allows to decrease the soot oxidation temperature to values which can be reached by appropriate engine tuning. The soot addition is a dominant parameter for the development of regeneration strategies. Its influence must be correctly represented by models. This Ph-D was performed at IFP in collaboration with ADEME and was supported by the LCSR at Orleans. The aim of the present research is to develop a kinetic mechanism characteristic of Diesel soot oxidation, which can be integrated into a DPF regeneration model and used for engine control. The oxidation study was based on soot characterisation and reaction kinetics investigations. The samples of Diesel soot were collected, without and with Cerium/Iron additive, by using two engines points representative of two normalized European cycles (ECE and EUDC). Thermal and composition analyses with techniques such as XPS, XRD or TEM were used to determine their physical and chemical properties. Their oxidation kinetics was experimentally studied on a synthetic gas bench (SGB) with a fixed bed reactor. Different tests were performed: temperature-programmed oxidation (TPO), Isothermal oxidation (IO), and sequential oxidation. The results allowed to correlate Diesel soot physical and chemical properties with their oxidation rate. A kinetic model was developed, which is based on global carbon consummation law and distinguishes the oxidation of different soot components. The simulation results agree very well with the experimental results of Diesel soot oxidation. (author)

  3. Seed regeneration potential of canopy gaps at early formation stage in temperate secondary forests, Northeast China.

    Directory of Open Access Journals (Sweden)

    Qiao-Ling Yan

    Full Text Available Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01, especially in medium and small gaps (<500 m(2. Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01. Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono, but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation.

  4. Seed Regeneration Potential of Canopy Gaps at Early Formation Stage in Temperate Secondary Forests, Northeast China

    Science.gov (United States)

    Yan, Qiao-Ling; Zhu, Jiao-Jun; Yu, Li-Zhong

    2012-01-01

    Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01), especially in medium and small gaps (<500 m2). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation. PMID:22745771

  5. Secondary aerosol formation from stress-induced biogenic emissions and possible climate feedbacks

    Directory of Open Access Journals (Sweden)

    Th. F. Mentel

    2013-09-01

    Full Text Available Atmospheric aerosols impact climate by scattering and absorbing solar radiation and by acting as ice and cloud condensation nuclei. Biogenic secondary organic aerosols (BSOAs comprise an important component of atmospheric aerosols. Biogenic volatile organic compounds (BVOCs emitted by vegetation are the source of BSOAs. Pathogens and insect attacks, heat waves and droughts can induce stress to plants that may impact their BVOC emissions, and hence the yield and type of formed BSOAs, and possibly their climatic effects. This raises questions of whether stress-induced changes in BSOA formation may attenuate or amplify effects of climate change. In this study we assess the potential impact of stress-induced BVOC emissions on BSOA formation for tree species typical for mixed deciduous and Boreal Eurasian forests. We studied the photochemical BSOA formation for plants infested by aphids in a laboratory setup under well-controlled conditions and applied in addition heat and drought stress. The results indicate that stress conditions substantially modify BSOA formation and yield. Stress-induced emissions of sesquiterpenes, methyl salicylate, and C17-BVOCs increase BSOA yields. Mixtures including these compounds exhibit BSOA yields between 17 and 33%, significantly higher than mixtures containing mainly monoterpenes (4–6% yield. Green leaf volatiles suppress SOA formation, presumably by scavenging OH, similar to isoprene. By classifying emission types, stressors and BSOA formation potential, we discuss possible climatic feedbacks regarding aerosol effects. We conclude that stress situations for plants due to climate change should be considered in climate–vegetation feedback mechanisms.

  6. Formation of secondary minerals in a lysimeter approach - A mineral-microbe interaction

    Science.gov (United States)

    Schäffner, F.; Merten, D.; De Giudici, G.; Beyer, A.; Akob, D. M.; Ricci, P. C.; Küsel, K.; Büchel, G.

    2012-04-01

    Heavy metal contamination of large areas due to uranium mining operations poses a serious long-term environmental problem. In the Ronneburg district (eastern Thuringia, Germany), leaching of low grade uranium bearing ores (uranium content metals, especially Cd, Ni, Co, Cu and Zn due to a residual contamination even after remediation efforts. To reveal the processes of secondary mineral precipitation in the field a laboratory lysimeter approach was set up under in situ-like conditions. Homogenized soil from the field site and pure quartz sand were used as substrates. In general, in situ measurements of redox potentials in the substrates showed highly oxidizing conditions (200-750 mV). Water was supplied to the lysimeter from below via a mariottés bottle containing contaminated groundwater from the field. Evaporation processes were allowed, providing a continuous flow of water. This led to precipitation of epsomite and probably aplowite on the top layer of substrate, similar to what is observed in field investigations. After 4 weeks, the first iron and manganese bearing secondary minerals became visible. Soil water samples were used to monitor the behaviour of metals within the lysimeter. Saturation indices (SI) for different secondary minerals were calculated with PHREEQC. The SI of goethite showed oversaturation with respect to the soil solution. SEM-EDX analyses and IR spectroscopy confirmed the formation of goethite. Geochemical data revealed that goethite formation was mainly dominated by Eh/pH processes and that heavy metals, e.g. Zn and U, could be enriched in this phase. Although Eh/pH data does not support formation of manganese minerals, Mn(II)-oxidizing bacteria (MOB) could be isolated from field soil samples, supporting the fact that microorganisms may influence this natural attenuation process. Laser ablation ICP-MS data reveal accumulation of manganese in MOB biomass on Mn(II)-containing agar plates. Furthermore, it was possible to show the importance

  7. Reflectance spectroscopy is an effective tool for monitoring soot pollution in an urban suburb.

    Science.gov (United States)

    Saaroni, H; Chudnovsky, A; Ben-Dor, E

    2010-02-01

    This study examines whether converting the fossil fuel of the Tel Aviv power station from oil to gas influences air pollution in the local urban environment. To this end, the spectral properties of accumulated dust on tree leaves and paper bags were assessed before (2004) and after (2006) the conversion. The sampling site was a garden in a neighborhood located 2700m downwind of the power station. In addition, air pollution concentrations and particulate matter parameters recorded by a local meteorological station were analyzed (PM(10), NO(x), NO(2), NO, and SO(2)). Although differences in the average monthly concentration of pollution parameters are mostly insignificant between the two periods, the accumulated particulate matter exhibits considerably different spectral patterns. All first period samples exhibit a distinctly concave slope in the spectral region between 400 and 1400nm, indicative of high amounts of soot, most likely due to the combustion products of fuel oil exhausted by the power plant. In contrast, the second period samples exhibit spectra that indicate reduced soot content and even appear slightly convex, evidencing the presence of dust of mineral origin, a feature likely masked by the soot in the first period. Thus, the spectral data support that the power plant conversion results in less pollution. More generally, this study corroborates that VIS-NIR-SWIR spectroscopy characterizes key properties of the particulate layer accumulating on sampled surfaces and thus, is a powerful method for monitoring the urban environment. Copyright 2009 Elsevier B.V. All rights reserved.

  8. Formation of wood secondary cell wall may involve two type cellulose synthase complexes in Populus.

    Science.gov (United States)

    Xi, Wang; Song, Dongliang; Sun, Jiayan; Shen, Junhui; Li, Laigeng

    2017-03-01

    Cellulose biosynthesis is mediated by cellulose synthases (CesAs), which constitute into rosette-like cellulose synthase complexe (CSC) on the plasma membrane. Two types of CSCs in Arabidopsis are believed to be involved in cellulose synthesis in the primary cell wall and secondary cell walls, respectively. In this work, we found that the two type CSCs participated cellulose biosynthesis in differentiating xylem cells undergoing secondary cell wall thickening in Populus. During the cell wall thickening process, expression of one type CSC genes increased while expression of the other type CSC genes decreased. Suppression of different type CSC genes both affected the wall-thickening and disrupted the multilaminar structure of the secondary cell walls. When CesA7A was suppressed, crystalline cellulose content was reduced, which, however, showed an increase when CesA3D was suppressed. The CesA suppression also affected cellulose digestibility of the wood cell walls. The results suggest that two type CSCs are involved in coordinating the cellulose biosynthesis in formation of the multilaminar structure in Populus wood secondary cell walls.

  9. Development of high fidelity soot aerosol dynamics models using method of moments with interpolative closure

    KAUST Repository

    Roy, Subrata P.; Arias, Paul G.; Lecoustre, Vivien R.; Haworth, Daniel C.; Im, Hong G.; Trouvé , Arnaud C.

    2014-01-01

    of ad hoc treatments such as clipping. The solutions proposed and demonstrated here are being applied to generate new physical insight into complex turbulence-chemistry-soot-radiation interactions in turbulent reacting flows using DNS. © 2014 Copyright

  10. Mechanism of SOA Formation Determines Magnitude of Radiative Effects

    Science.gov (United States)

    Zhu, J.; Penner, J.; Lin, G.; Zhou, C.

    2017-12-01

    Secondary organic aerosol (SOA) nearly always exists as an internal mixture and the distribution of this mixture depends on the formation mechanism of SOA. A model is developed to examine the influence of using an internal mixing states based on the mechanism of formation and to estimate the radiative forcing of SOA in the future. For the present day, 66 % of SOA is internally mixed with sulfate, while 34 % is internally mixed with primary soot. When compared with using an external mixture, the direct effect of SOA is decreased, due to the decrease of total aerosol surface area and the increase of absorption efficiency. Aerosol number concentrations are sharply reduced and this is responsible for a large decrease in the cloud albedo effect. In total, internal mixing suppresses the radiative effect of SOA by a factor of >4 compared to treating SOA as an external mixture. The future SOA burden increases by 24% due to CO2 increases and climate change, leading to a total (direct plus cloud albedo) radiative forcing of -0.05 W m-2. When the combined effects of changes in climate, anthropogenic emissions and land use are included, the SOA forcing is -0.07 W m-2, even though the SOA burden only increases by 6.8%. This is caused by the substantial increase of SOA associated with sulfate in the Aitken mode. The Aitken mode increase contributes to the enhancement of first indirect radiative forcing, which dominates the total radiative forcing.

  11. Isothermal Kinetics of Diesel Soot Oxidation over La0.7K0.3ZnOy Catalysts

    Directory of Open Access Journals (Sweden)

    Ram Prasad

    2014-10-01

    Full Text Available This paper describes the kinetics of catalytic oxidation of diesel soot with air under isothermal conditions (320-350 oC. Isothermal kinetics data were collected in a mini-semi-batch reactor. Experiments were performed over the best selected catalyst composition La0.7K0.3ZnOy prepared by sol-gel method. Characterization of the catalyst by XRD and FTIR confirmed that La1-xKxZnOy did not exhibit perovskite phase but formed mixed metal oxides. 110 mg of the catalyst-soot mixture in tight contact (10:1 ratio was taken in order to determine the kinetic model, activation energy and Arrhenius constant of the oxidation reaction under the high air flow rate assuming pseudo first order reaction. The activation energy and Arrhenius constant were found to be 138 kJ/mol and 6.46x1010 min-1, respectively. © 2014 BCREC UNDIP. All rights reservedReceived: 26th April 2014; Revised: 27th May 2014; Accepted: 28th June 2014How to Cite: Prasad, R., Kumar, A., Mishra, A. (2014. Isothermal Kinetics of Diesel Soot Oxidation over La0.7K0.3ZnOy Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 9(3: 192-200. (doi: 10.9767/bcrec.9.3.6773.192-200Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.3.6773.192-200

  12. Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation

    Directory of Open Access Journals (Sweden)

    P. O. Wennberg

    2010-08-01

    Full Text Available Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene, the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA via methacrolein (a C4-unsaturated aldehyde under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN as the important intermediate to isoprene and methacrolein SOA in this NOx regime. Here we show that as a result of this chemistry, NO2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NOx effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232 is insignificant, even under high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(OOONO2 formation is structurally unfavorable. At atmospherically relevant NO2/NO ratios (3–8, the SOA yields from isoprene high-NOx photooxidation are 3 times greater than previously measured at lower NO2/NO ratios. At sufficiently high NO2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO2 can exceed that from RO2+HO2 reactions under the same inorganic seed conditions, making RO2+NO2 an important channel for SOA formation.

  13. Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation

    Science.gov (United States)

    Chan, A. W. H.; Chan, M. N.; Surratt, J. D.; Chhabra, P. S.; Loza, C. L.; Crounse, J. D.; Yee, L. D.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H.

    2010-08-01

    Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA) via methacrolein (a C4-unsaturated aldehyde) under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN) as the important intermediate to isoprene and methacrolein SOA in this NOx regime. Here we show that as a result of this chemistry, NO2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NOx effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232) is insignificant, even under high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(O)OONO2) formation is structurally unfavorable. At atmospherically relevant NO2/NO ratios (3-8), the SOA yields from isoprene high-NOx photooxidation are 3 times greater than previously measured at lower NO2/NO ratios. At sufficiently high NO2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO2 can exceed that from RO2+HO2 reactions under the same inorganic seed conditions, making RO2+NO2 an important channel for SOA formation.

  14. Facile Fabrication and Characterization of a PDMS-Derived Candle Soot Coated Stable Biocompatible Superhydrophobic and Superhemophobic Surface.

    Science.gov (United States)

    Iqbal, R; Majhy, B; Sen, A K

    2017-09-13

    We report a simple, inexpensive, rapid, and one-step method for the fabrication of a stable and biocompatible superhydrophobic and superhemophobic surface. The proposed surface comprises candle soot particles embedded in a mixture of PDMS+n-hexane serving as the base material. The mechanism responsible for the superhydrophobic behavior of the surface is explained, and the surface is characterized based on its morphology and elemental composition, wetting properties, mechanical and chemical stability, and biocompatibility. The effect of %n-hexane in PDMS, the thickness of the PDMS+n-hexane layer (in terms of spin coating speed) and sooting time on the wetting property of the surface is studied. The proposed surface exhibits nanoscale surface asperities (average roughness of 187 nm), chemical compositions of soot particles, very high water and blood repellency along with excellent mechanical and chemical stability and excellent biocompatibility against blood sample and biological cells. The water contact angle and roll-off angle is measured as 160° ± 1° and 2°, respectively, and the blood contact angle is found to be 154° ± 1°, which indicates that the surface is superhydrophobic and superhemophobic. The proposed superhydrophobic and superhemophobic surface offers significantly improved (>40%) cell viability as compared to glass and PDMS surfaces.

  15. Gadolinium doped cerium oxide for soot oxidation: Influence of interfacial metal–support interactions

    Energy Technology Data Exchange (ETDEWEB)

    Durgasri, D. Naga; Vinodkumar, T. [Inorganic and Physical Chemistry Division, CSIR–Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007 (India); Lin, Fangjian; Alxneit, Ivo [Solar Technology Laboratory, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Reddy, Benjaram M., E-mail: bmreddy@iict.res.in [Inorganic and Physical Chemistry Division, CSIR–Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007 (India)

    2014-09-30

    Graphical abstract: - Highlights: • Supported Ce-Gd-oxides are applied for soot oxidation for the first time. • Gd{sub 2}O{sub 3} doping facilitates enhanced extrinsic oxygen vacancy concentration in ceria. • The Ce-Gd/TiO{sub 2} exhibited the highest soot oxidation activity. • Key parameters that involved in tuning the activity are discussed. - Abstract: The aim of the present investigation was to ascertain the role of Al{sub 2}O{sub 3}, SiO{sub 2}, and TiO{sub 2} supports in modulating the catalytic performance of ceria-based solid solutions. In this study, we prepared nanosized Ce-Gd/Al{sub 2}O{sub 3}, Ce-Gd/SiO{sub 2}, and Ce-Gd/TiO{sub 2} catalysts by a deposition coprecipitation method and evaluated for soot oxidation. The synthesized catalysts were calcined at two different temperatures to assess their thermal stability and extensively characterized by various techniques, namely, XRD, Raman, BET surface area, TEM, H{sub 2}-TPR, and UV–vis DRS. XRD and TEM results indicate that Ce-Gd-oxide nanoparticles are in highly dispersed form on the surface of the supports. Raman results show a prominent sharp peak and a broad peak corresponding to the F{sub 2g} mode of ceria and the presence of oxygen vacancies, respectively. The presence of a significant number of oxygen vacancies in all samples is also confirmed from UV–vis DRS measurements. The H{sub 2}-TPR results suggest that Gd-doping facilitates the reduction of the materials and decreases the onset temperature of reduction. Among the prepared samples, Ce-Gd/TiO{sub 2} catalyst exhibited the highest activity, suggesting the existence of strong interfacial metal support interaction between the active metal oxide and the support.

  16. Impacts of vehicle exhaust black soot on germination of gram seed (Cicer arietinum L.

    Directory of Open Access Journals (Sweden)

    Naba Kumar Mondal

    2014-02-01

    Full Text Available An investigation was initiated to examine the effects of carbon soot collected from exhaust tube of 15 years old petrol and diesel operated vehicles on gram seed germination and biochemical changes of seedling. In view of the widespread cultivation of gram seed in India and long-term impact of black carbon is the warming of the atmosphere as per the recommendation of IPCC (2007. Black soot were separately treated with different doses and the effects of these treatment had on seed germination, seedling vigor, chlorophyll and carotenoid content, root and shoot growth, protein, sugar, phenol and proline estimation were studied. The treatment T6 significantly affected on seed germination (84% as well as seedling vigor and chlorophyll content. But other treatment promoted both seed germination and seedling vigor along with enhancement of other biochemical constituents. On the other hand micrograph study revealed that treatments T1 and T4 both showed negative effects on stomata rather than the ultra-structure of xylem and phloem.

  17. Electron Tomography of Nanoparticle Clusters: Implications for Atmospheric Lifetimes and Radiative Forcing of Soot

    Science.gov (United States)

    vanPoppel, Laura H.; Friedrich, Heiner; Spinsby, Jacob; Chung, Serena H.; Seinfeld, John H.; Buseck, Peter R.

    2005-01-01

    Nanoparticles are ubiquitous in nature. Their large surface areas and consequent chemical reactivity typically result in their aggregation into clusters. Their chemical and physical properties depend on cluster shapes, which are commonly complex and unknown. This is the first application of electron tomography with a transmission electron microscope to quantitatively determine the three-dimensional (3D) shapes, volumes, and surface areas of nanoparticle clusters. We use soot (black carbon, BC) nanoparticles as an example because it is a major contributor to environmental degradation and global climate change. To the extent that our samples are representative, we find that quantitative measurements of soot surface areas and volumes derived from electron tomograms differ from geometrically derived values by, respectively, almost one and two orders of magnitude. Global sensitivity studies suggest that the global burden and direct radiative forcing of fractal BC are only about 60% of the value if it is assumed that BC has a spherical shape.

  18. Secondary organic aerosol formation from a large number of reactive man-made organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Derwent, Richard G., E-mail: r.derwent@btopenworld.com [rdscientific, Newbury, Berkshire (United Kingdom); Jenkin, Michael E. [Atmospheric Chemistry Services, Okehampton, Devon (United Kingdom); Utembe, Steven R.; Shallcross, Dudley E. [School of Chemistry, University of Bristol, Bristol (United Kingdom); Murrells, Tim P.; Passant, Neil R. [AEA Environment and Energy, Harwell International Business Centre, Oxon (United Kingdom)

    2010-07-15

    A photochemical trajectory model has been used to examine the relative propensities of a wide variety of volatile organic compounds (VOCs) emitted by human activities to form secondary organic aerosol (SOA) under one set of highly idealised conditions representing northwest Europe. This study applied a detailed speciated VOC emission inventory and the Master Chemical Mechanism version 3.1 (MCM v3.1) gas phase chemistry, coupled with an optimised representation of gas-aerosol absorptive partitioning of 365 oxygenated chemical reaction product species. In all, SOA formation was estimated from the atmospheric oxidation of 113 emitted VOCs. A number of aromatic compounds, together with some alkanes and terpenes, showed significant propensities to form SOA. When these propensities were folded into a detailed speciated emission inventory, 15 organic compounds together accounted for 97% of the SOA formation potential of UK man made VOC emissions and 30 emission source categories accounted for 87% of this potential. After road transport and the chemical industry, SOA formation was dominated by the solvents sector which accounted for 28% of the SOA formation potential.

  19. Different roles of water in secondary organic aerosol formation from toluene and isoprene

    Science.gov (United States)

    Jia, Long; Xu, YongFu

    2018-06-01

    Roles of water in the formation of secondary organic aerosol (SOA) from the irradiations of toluene-NO2 and isoprene-NO2 were investigated in a smog chamber. Experimental results show that the yield of SOA from toluene almost doubled as relative humidity increased from 5 to 85 %, whereas the yield of SOA from isoprene under humid conditions decreased by 2.6 times as compared to that under dry conditions. The distinct difference of RH effects on SOA formation from toluene and isoprene is well explained with our experiments and model simulations. The increased SOA from humid toluene-NO2 irradiations is mainly contributed by O-H-containing products such as polyalcohols formed from aqueous reactions. The major chemical components of SOA in isoprene-NO2 irradiations are oligomers formed from the gas phase. SOA formation from isoprene-NO2 irradiations is controlled by stable Criegee intermediates (SCIs) that are greatly influenced by water. As a result, high RH can obstruct the oligomerization reaction of SCIs to form SOA.

  20. Gasoline emissions dominate over diesel in formation of secondary organic aerosol mass

    Science.gov (United States)

    Bahreini, R.; Middlebrook, A. M.; de Gouw, J. A.; Warneke, C.; Trainer, M.; Brock, C. A.; Stark, H.; Brown, S. S.; Dube, W. P.; Gilman, J. B.; Hall, K.; Holloway, J. S.; Kuster, W. C.; Perring, A. E.; Prevot, A. S. H.; Schwarz, J. P.; Spackman, J. R.; Szidat, S.; Wagner, N. L.; Weber, R. J.; Zotter, P.; Parrish, D. D.

    2012-03-01

    Although laboratory experiments have shown that organic compounds in both gasoline fuel and diesel engine exhaust can form secondary organic aerosol (SOA), the fractional contribution from gasoline and diesel exhaust emissions to ambient SOA in urban environments is poorly known. Here we use airborne and ground-based measurements of organic aerosol (OA) in the Los Angeles (LA) Basin, California made during May and June 2010 to assess the amount of SOA formed from diesel emissions. Diesel emissions in the LA Basin vary between weekdays and weekends, with 54% lower diesel emissions on weekends. Despite this difference in source contributions, in air masses with similar degrees of photochemical processing, formation of OA is the same on weekends and weekdays, within the measurement uncertainties. This result indicates that the contribution from diesel emissions to SOA formation is zero within our uncertainties. Therefore, substantial reductions of SOA mass on local to global scales will be achieved by reducing gasoline vehicle emissions.

  1. Bacterial and iron oxide aggregates mediate secondary iron mineral formation: green rust versus magnetite.

    Science.gov (United States)

    Zegeye, A; Mustin, C; Jorand, F

    2010-06-01

    In the presence of methanoate as electron donor, Shewanella putrefaciens, a Gram-negative, facultative anaerobe, is able to transform lepidocrocite (gamma-FeOOH) to secondary Fe (II-III) minerals such as carbonated green rust (GR1) and magnetite. When bacterial cells were added to a gamma-FeOOH suspension, aggregates were produced consisting of both bacteria and gamma-FeOOH particles. Recently, we showed that the production of secondary minerals (GR1 vs. magnetite) was dependent on bacterial cell density and not only on iron reduction rates. Thus, gamma-FeOOH and S. putrefaciens aggregation pattern was suggested as the main mechanism driving mineralization. In this study, lepidocrocite bioreduction experiments, in the presence of anthraquinone disulfonate, were conducted by varying the [cell]/[lepidocrocite] ratio in order to determine whether different types of aggregate are formed, which may facilitate precipitation of GR1 as opposed to magnetite. Confocal laser scanning microscopy was used to analyze the relative cell surface area and lepidocrocite concentration within the aggregates and captured images were characterized by statistical methods for spatial data (i.e. variograms). These results suggest that the [cell]/[lepidocrocite] ratio influenced both the aggregate structure and the nature of the secondary iron mineral formed. Subsequently, a [cell]/[lepidocrocite] ratio above 1 x 10(7) cells mmol(-1) leads to densely packed aggregates and to the formation of GR1. Below this ratio, looser aggregates are formed and magnetite was systematically produced. The data presented in this study bring us closer to a more comprehensive understanding of the parameters governing the formation of minerals in dense bacterial suspensions and suggest that screening mineral-bacteria aggregate structure is critical to understanding (bio)mineralization pathways.

  2. Study of nozzle deposit formation mechanism for direct injection gasoline engines; Chokufun gasoline engine yo nozzle no deposit seisei kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, M; Saito, A [Toyota Central Research and Development Labs., Inc., Aichi (Japan); Matsushita, S [Toyota Motor Corp., Aichi (Japan); Shibata, H [Nippon Soken, Inc., Tokyo (Japan); Niwa, Y [Denso Corp., Aichi (Japan)

    1997-10-01

    Nozzles in fuel injectors for direct injection gasoline engines are exposed to high temperature combustion gases and soot. In such a rigorous environment, it is a fear that fuel flow rate changes in injectors by deposit formation on nozzles. Fundamental factors of nozzle deposit formation were investigated through injector bench tests and engine dynamometer tests. Deposit formation processes were observed by SEM through engine dynamometer tests. The investigation results reveal nozzle deposit formation mechanism and how to suppress the deposit. 4 refs., 8 figs., 3 tabs.

  3. Physical parameters effect on ozone-initiated formation of indoor secondary organic aerosols with emissions from cleaning products.

    Science.gov (United States)

    Huang, Yu; Ho, Kin Fai; Ho, Steven Sai Hang; Lee, Shun Cheng; Yau, P S; Cheng, Yan

    2011-09-15

    The effect of air exchange rate (ACH), temperature (T), and relative humidity (RH) on the formation of indoor secondary organic aerosols (SOAs) through ozonolysis of biogenic organic compounds (BVOCs) emitted from floor cleaner was investigated in this study. The total particle count (with D(p) of 6-225 nm) was up to 1.2 × 10(3)#cm(-3) with ACH of 1.08 h(-1), and it became much more significant with ACH of 0.36 h(-1) (1.1 × 10(4)#cm(-3)). This suggests that a higher ventilation rate can effectively dilute indoor BVOCs, resulting in a less ultrafine particle formation. The total particle count increased when temperature changed from 15 to 23 °C but it decreased when the temperature further increased to 30 °C. It could be explained that high temperature restrained the condensation of formed semi-volatile compounds resulting in low yields of SOAs. When the RH was at 50% and 80%, SOA formation (1.1-1.2 × 10(4)#cm(-3)) was the more efficient compared with that at RH of 30% (5.9 × 10(3)#cm(-3)), suggesting higher RH facilitating the initial nucleation processes. Oxidation generated secondary carbonyl compounds were also quantified. Acetone was the most abundant carbonyl compound. The formation mechanisms of formaldehyde and acetone were proposed. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Volatile release and particle formation characteristics of injected pulverized coal in blast furnaces

    International Nuclear Information System (INIS)

    Chen, Wei-Hsin; Du, Shan-Wen; Yang, Tsung-Han

    2007-01-01

    Volatiles release and particle formation for two kinds of pulverized coals (a high volatile bituminous coal and a low volatile bituminous coal) in a drop tube furnace are investigated to account for the reactions of pulverized coal injected in blast furnaces. Two different sizes of feed particles are considered; one is 100-200 mesh and the other is 200-325 mesh. By evaluating the R-factor, the devolatilization extent of the larger feed particles is found to be relatively poor. However, the swelling behavior of individual or two agglomerated particles is pronounced, which is conducive to gasification of the chars in blast furnaces. In contrast, for the smaller feed particles, volatiles liberated from the coal particles can be improved in a significant way as a result of the amplified R-factor. This enhancement can facilitate the performance of gas phase combustion. Nevertheless, the residual char particles are characterized by agglomeration, implying that the reaction time of the char particles will be lengthened, thereby increasing the possibility of furnace instability. Double peak distributions in char particle size are observed in some cases. This possibly results from the interaction of the plastic state and the blowing effect at the particle surface. Considering the generation of tiny aerosols composed of soot particles and tar droplets, the results indicate that their production is highly sensitive to the volatile matter and elemental oxygen contained in the coal. Comparing the reactivity of the soot to that of the unburned char, the former is always lower than the latter. Consequently, the lower is the soot formation, the better is the blast furnace stability

  5. Numerical simulations of contrail-to-cirrus transition – Part 2: Impact of initial ice crystal number, radiation, stratification, secondary nucleation and layer depth

    Directory of Open Access Journals (Sweden)

    S. Unterstrasser

    2010-02-01

    Full Text Available Simulations of contrail-to-cirrus transition were performed with an LES model. In Part 1 the impact of relative humidity, temperature and vertical wind shear was explored in a detailed parametric study. Here, we study atmospheric parameters like stratification and depth of the supersaturated layer and processes which may affect the contrail evolution. We consider contrails in various radiation scenarios herein defined by the season, time of day and the presence of lower-level cloudiness which controls the radiance incident on the contrail layer. Under suitable conditions, controlled by the radiation scenario and stratification, radiative heating lifts the contrail-cirrus and prolongs its lifetime. The potential of contrail-driven secondary nucleation is investigated. We consider homogeneous nucleation and heterogeneous nucleation of preactivated soot cores released from sublimated contrail ice crystals. In our model the contrail dynamics triggered by radiative heating does not suffice to force homogeneous freezing of ambient liquid aerosol particles. Furthermore, our model results suggest that heterogeneous nucleation of preactivated soot cores is unimportant. Contrail evolution is not controlled by the depth of the supersaturated layer as long as it exceeds roughly 500 m. Deep fallstreaks however need thicker layers. A variation of the initial ice crystal number is effective during the whole evolution of a contrail. A cut of the soot particle emission by two orders of magnitude can reduce the contrail timescale by one hour and the optical thickness by a factor of 5. Hence future engines with lower soot particle emissions could potentially lead to a reduction of the climate impact of aviation.

  6. Effects of self-absorption on simultaneous estimation of temperature distribution and concentration fields of soot and metal-oxide nanoparticles in nanofluid fuel flames using a spectrometer

    Science.gov (United States)

    Liu, Guannan; Liu, Dong

    2018-06-01

    An improved inverse reconstruction model with consideration of self-absorption effect for the temperature distribution and concentration fields of soot and metal-oxide nanoparticles in nanofluid fuel flames was proposed based on the flame emission spectrometry. The effects of self-absorption on the temperature profile and concentration fields were investigated for various measurement errors, flame optical thicknesses and detecting lines numbers. The model neglecting the self-absorption caused serious reconstruction errors especially in the nanofluid fuel flames with large optical thicknesses, while the improved model was used to successfully recover the temperature distribution and concentration fields of soot and metal-oxide nanoparticles for the flames regardless of the optical thickness. Through increasing detecting lines number, the reconstruction accuracy can be greatly improved due to more flame emission information received by the spectrometer. With the adequate detecting lines number, the estimations for the temperature distribution and concentration fields of soot and metal-oxide nanoparticles in flames with large optical thicknesses were still satisfying even from the noisy radiation intensities with signal to noise ratio (SNR) as low as 46 dB. The results showed that the improved reconstruction model was effective and robust to concurrently retrieve the temperature distribution and volume fraction fields of soot and metal-oxide nanoparticles for the exact and noisy data in nanofluid fuel sooting flames with different optical thicknesses.

  7. Comprehensive Laser-induced Incandescence (LII) modeling for soot particle sizing

    KAUST Repository

    Lisanti, Joel

    2015-03-30

    To evaluate the current state of the art in LII particle sizing, a comprehensive model for predicting the temporal incandescent response of combustion-generated soot to absorption of a pulsed laser is presented. The model incorporates particle heating through laser absorption, thermal annealing, and oxidation at the surface as well as cooling through sublimation and photodesorption, radiation, conduction and thermionic emission. Thermodynamic properties and the thermal accommodation coefficient utilized in the model are temperature dependent. In addition, where appropriate properties are also phase dependent, thereby accounting for annealing effects during laser heating and particle cooling.

  8. In-cylinder Combustion and Soot Evolution in the Transition from Conventional CI mode to PPC

    KAUST Repository

    An, Yanzhao; Jaasim, Mohammed; Raman, Vallinayagam; Im, Hong G.; Johansson, Bengt

    2018-01-01

    with gas phase chemical kinetics, turbulence, and particulate size mimic soot model. The simulations were performed under low load conditions (IMEP ~ 2 to 3 bar) at an engine speed of 1200 rpm. The start of injection (SOI) was advanced from late (-10 CAD a

  9. Observations of fine particulate nitrated phenols in four sites in northern China: concentrations, source apportionment, and secondary formation

    Science.gov (United States)

    Wang, Liwei; Wang, Xinfeng; Gu, Rongrong; Wang, Hao; Yao, Lan; Wen, Liang; Zhu, Fanping; Wang, Weihao; Xue, Likun; Yang, Lingxiao; Lu, Keding; Chen, Jianmin; Wang, Tao; Zhang, Yuanghang; Wang, Wenxing

    2018-03-01

    Filter samples of fine particulate matters were collected at four sites in northern China (urban, rural, and mountain) in summer and winter, and the contents of nine nitrated phenols were quantified in the laboratory with the use of ultra-high-performance liquid chromatography coupled with mass spectrometry. During the sampling periods, the concentrations of particulate nitrated phenols exhibited distinct temporal and spatial variation. On average, the total concentration of particulate nitrated phenols in urban Jinan in the wintertime reached 48.4 ng m-3, and those in the summertime were 9.8, 5.7, 5.9, and 2.5 ng m-3 in urban Jinan, rural Yucheng and Wangdu, and Mt. Tai, respectively. The elevated concentrations of nitrated phenols in wintertime and in urban areas demonstrate the apparent influences of anthropogenic sources. The positive matrix factorization receptor model was then applied to determine the origins of particulate nitrated phenols in northern China. The five major source factors were traffic, coal combustion, biomass burning, secondary formation, and aged coal combustion plume. Among them, coal combustion played a vital role, especially at the urban site in the wintertime, with a contribution of around 55 %. In the summertime, the observed nitrated phenols were highly influenced by aged coal combustion plumes at all of the sampling sites. Meanwhile, in remote areas, contributions from secondary formation were significant. Further correlation analysis indicates that nitrosalicylic acids were produced mostly from secondary formation that was dominated by NO2 nitration.

  10. Laboratory Studies Of Circumstellar Carbonaceous Grain Formation

    Science.gov (United States)

    Contreras, Cesar; Sciamma-O'Brien, Ella; Salama, Farid

    2014-06-01

    The study of the formation processes of dust is essential to understand the budget of extraterrestrial organic molecules. Although dust with all its components plays an important role in the evolution of interstellar (IS) chemistry and in the formation of organic molecules, little is known on the formation processes of carbonaceous dust. We report the progress that was recently achieved in this domain using NASA Ames’ COSmIC facility (Contreras & Salama 2013, ApJS, 208, 6). PAHs are important chemical building blocks of IS dust. They are detected in IDPs and in meteoritic samples. Additionally, observational, laboratory, and theoretical studies have shown that PAHs are an important, ubiquitous component of the ISM. The formation of PAHs from smaller molecules has not been extensively studied. Therefore, we have performed laboratory experiments to study the dynamic processes of carbon grain formation, starting from the smallest hydrocarbon molecules into the formation of larger PAH and further into nanograins. Studies of IS dust analogs formed from a variety of PAH and hydrocarbon precursors as well as species that include the atoms O, N, and S, have recently been performed in our laboratory using the COSmIC facility to provide conditions that simulate IS and circumstellar environments. The species formed in the COSmiC chamber through a pulsed discharge nozzle plasma source are detected and characterized with a cavity ringdown spectrometer coupled to a time-of-flight mass spectrometer, thus providing both spectroscopic and ion mass information in-situ. Analysis of solid soot particles was also conducted using scanning electron microscopy at the UCSC/NASA Ames’ MACS facility. The SEM analysis of the deposition of soot from methane and acetylene precursors seeded in argon plasmas provide examples on the types of nanoparticles and micrograins that are produced in these gas mixtures under our experimental conditions. From these measurements, we derive information on

  11. Carbon nanoparticles from corn stalk soot and its novel application as stationary phase of hydrophilic interaction chromatography and per aqueous liquid chromatography

    International Nuclear Information System (INIS)

    Li Yuanyuan; Xu Luan; Chen Tong; Liu Xiaoyan; Xu Zhigang; Zhang Haixia

    2012-01-01

    Highlights: ► Carbon nanoparticles (6–18 nm in size) were prepared from corn stalk soot. ► CNPs-based silica were used as novel chromatography stationary phase. ► The new phase shows good separation selectivity for polar compounds. ► The new phase had the similar retention for polar probes in HILIC and PALC modes. ► In contrast to PALC, under HILIC conditions high efficiencies were achieved. - Abstract: Carbon nanoparticles (CNPs) (6–18 nm in size) were prepared by refluxing corn stalk soot in nitric acid. The obtained acid-oxidized CNPs are soluble in water due to the existence of carboxylic and hydroxyl groups. 13 C NMR measurement shows the CNPs are mainly of sp 2 and sp 3 carbon structure different from CNPs obtained from candle soot and natural gas soot. Furthermore, these CNPs exhibit unique photoluminescence properties. Interestingly, the CNPs might be exploited to immobilize on the surface of porous silica particles as chromatographic stationary phase. The resultant packing material was evaluated by high-performance liquid chromatography, indicating that the new stationary phase could be used in hydrophilic interaction liquid chromatography (HILIC) and per aqueous liquid chromatography (PALC) modes. The separation of five nucleosides, four sulfa compounds and safflower injection was achieved by using the new column in the HILIC and PALC modes, respectively.

  12. NOx, Soot, and Fuel Consumption Predictions under Transient Operating Cycle for Common Rail High Power Density Diesel Engines

    Directory of Open Access Journals (Sweden)

    N. H. Walke

    2016-01-01

    Full Text Available Diesel engine is presently facing the challenge of controlling NOx and soot emissions on transient cycles, to meet stricter emission norms and to control emissions during field operations. Development of a simulation tool for NOx and soot emissions prediction on transient operating cycles has become the most important objective, which can significantly reduce the experimentation time and cost required for tuning these emissions. Hence, in this work, a 0D comprehensive predictive model has been formulated with selection and coupling of appropriate combustion and emissions models to engine cycle models. Selected combustion and emissions models are further modified to improve their prediction accuracy in the full operating zone. Responses of the combustion and emissions models have been validated for load and “start of injection” changes. Model predicted transient fuel consumption, air handling system parameters, and NOx and soot emissions are in good agreement with measured data on a turbocharged high power density common rail engine for the “nonroad transient cycle” (NRTC. It can be concluded that 0D models can be used for prediction of transient emissions on modern engines. How the formulated approach can also be extended to transient emissions prediction for other applications and fuels is also discussed.

  13. Fuel effects on illumination ignition delay and soot lift-off length in diesel combustion

    NARCIS (Netherlands)

    Frijters, P.J.M.; Vallen, R.G.M.; Somers, L.M.T.; Luijten, C.C.M.; Baert, R.S.G.; Skevis, G.

    2007-01-01

    Ignition behavior of different fuels is investigated by recording broadband soot luminosity at high speed (60 kHz).The tested fuels are regular low sulphur EN 590:2004 fuel, EN 14214:2003 (FAME), n-heptane and IDEA (2component surrogate fuel), all with a Cetane Index between 51 and 57. For this an

  14. Typical winter haze pollution in Zibo, an industrial city in China: Characteristics, secondary formation, and regional contribution.

    Science.gov (United States)

    Li, Hui; Ma, Yongliang; Duan, Fengkui; He, Kebin; Zhu, Lidan; Huang, Tao; Kimoto, Takashi; Ma, Xiaoxuan; Ma, Tao; Xu, Lili; Xu, Beiyao; Yang, Shuo; Ye, Siqi; Sun, Zhenli; An, Jiutao; Zhang, Zhaolu

    2017-10-01

    Heavy haze pollution occurs frequently in northern China, most critically in the Beijing-Tianjin-Hebei area (BTH). Zibo, an industrial city located in Shandong province, is often listed as one of the top ten most polluted cities in China, particularly in winter. However, no studies of haze in Zibo have been conducted, which limits the understanding of the source and formation of haze pollution in this area, as well as mutual effects with the BTH area. We carried out online and continuous integrated field observation of particulate matter in winter, from 11 to 25 January 2015. SO 4 2- , NO 3 - , and NH 4 + (SIA) and organics were the main constituents of PM 2.5 , contributing 59.4% and 33.6%, respectively. With the increasing severity of pollution, the contribution of SIA increased while that of organics decreased. Meteorological conditions play an important role in haze formation; high relative humidity (RH) and low wind speed increased both the accumulation of pollutants and the secondary transition from gas precursors (gas-particle phase partitioning). Since RH and the presence of O 3 can indicate heterogeneous and photochemistry processes, respectively, we carried out correlation analysis and linear regression to identify their relative importance to the three main secondary species (sulfate, nitrate, and secondary organic carbon (SOC)). We found that the impact of RH is in the order of SO 4 2-  > NO 3 -  > SOC, while the impact of O 3 is reversed, in the order of SOC > NO 3 -  > SO 4 2- , indicating different effect of these factors on the secondary formation of main species in winter. Cluster analysis of backward trajectories showed that, during the observation period, six directional sources of air masses were identified, and more than 90% came from highly industrialized areas, indicating that regional transport from industrialized areas aggravates the haze pollution in Zibo. Inter-regional joint prevention and control is necessary to prevent further

  15. Development of a photometric measuring method for soot analysis in flames. Final report; Entwicklung eines photometrischen Messverfahrens zur Russanalyse in Flammen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Weichert, R.; Niemann, J.

    1995-12-31

    The present photometric measuring method for soot analysis in flames meets the following specifications: determination of the volume concentration of soot particles from 2 x 10{sup -7} upwards by means of extinction measurement at three different wavelengths; determination of the particle size distribution of soot particles by means of nephelometry in the range betwenn 20 and 400 nm; contactless measurements on the particle collective in the flame; no need for calibration of the photometric measuring method on the basis of particles of known size and concentration. (orig./SR) [Deutsch] Es ergeben sich fuer das entwickelte photometrische Messverfahren zur Russanalyse in Flammen folgende Spezifikationen: - Bestimmung der Volumenkonzentration der Russpartikel ab 2 x 10{sup -7} mittels Extinktionsmessungen bei drei Lichtwellenlaengen, - Ermittlung der Partikelgroessenverteilung der Russpartikel aus Streulichtmessungen im Bereich von 20 bis 400 nm, - beruehrungsfreie Messung in der Flamme am Partikelkollektiv und, - keine Kalibrierung des photometrischen Messverfahrens mit Partikeln bekannter Groesse bzw. bekannter Konzentration erforderlich. (orig./SR)

  16. Study Of Soot Growth And Nucleation By A Time-Resolved Synchrotron Radiation Based X-Ray Absorption Method

    National Research Council Canada - National Science Library

    Mitchell, Judith I

    2001-01-01

    This report results from a contract tasking University of Rennes I as follows: The contractor will perform a study of soot growth and nucleation by a time-resolved synchrotron radiation based x-ray absorption method...

  17. Optimization in the design and efficiency of retractable soot blowers; Optimacion del diseno y la eficiencia de sopladores de hollin retractiles

    Energy Technology Data Exchange (ETDEWEB)

    Diego Marin, Antonio [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1988-12-31

    In this article the importance of soot blowers in the subject of design, operation and maintenance are described and the effects that its inefficient functioning causes in the steam generators. The activities and the results of a project for the evaluation of the functioning of the soot blowers in the Comision Federal de Electricidad (CFE) boilers. Finally, the scope of a new project oriented towards the retractable soot blowers efficiency optimization, and to the creation of the infra-structure to substitute the import of its components. [Espanol] En este articulo se describe la importancia de los sopladores de hollin en los aspectos de diseno, operacion y mantenimiento, y los efectos que su funcionamiento deficiente produce en los generadores de vapor. Se presentan tambien las actividades y los resultados de un proyecto para evaluar el funcionamiento de los deshollinadores de las calderas de la Comision Federal de Electricidad (CFE). Finalmente, se presenta el alcance de un nuevo proyecto que se orienta a optimar la eficiencia de los sopladores de hollin retractiles y a crear la infraestructura para sustituir las importaciones de sus componentes.

  18. Optimization in the design and efficiency of retractable soot blowers; Optimacion del diseno y la eficiencia de sopladores de hollin retractiles

    Energy Technology Data Exchange (ETDEWEB)

    Diego Marin, Antonio [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1987-12-31

    In this article the importance of soot blowers in the subject of design, operation and maintenance are described and the effects that its inefficient functioning causes in the steam generators. The activities and the results of a project for the evaluation of the functioning of the soot blowers in the Comision Federal de Electricidad (CFE) boilers. Finally, the scope of a new project oriented towards the retractable soot blowers efficiency optimization, and to the creation of the infra-structure to substitute the import of its components. [Espanol] En este articulo se describe la importancia de los sopladores de hollin en los aspectos de diseno, operacion y mantenimiento, y los efectos que su funcionamiento deficiente produce en los generadores de vapor. Se presentan tambien las actividades y los resultados de un proyecto para evaluar el funcionamiento de los deshollinadores de las calderas de la Comision Federal de Electricidad (CFE). Finalmente, se presenta el alcance de un nuevo proyecto que se orienta a optimar la eficiencia de los sopladores de hollin retractiles y a crear la infraestructura para sustituir las importaciones de sus componentes.

  19. The formation, properties and impact of secondary organic aerosol: current and emerging issues

    Directory of Open Access Journals (Sweden)

    J. Wildt

    2009-07-01

    Full Text Available Secondary organic aerosol (SOA accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

  20. Uptake of Alkylamines on Dicarboxylic Acids Relevant to Secondary Organic Aerosol Formation

    Science.gov (United States)

    Marrero-Ortiz, W.; Secrest, J.; Zhang, R.

    2017-12-01

    Aerosols play a critical role in climate directly by scattering and absorbing solar radiation, and indirectly by functioning as cloud condensation nuclei (CCN); both represent the largest uncertainties in climate predictions. New particle formation contributes significantly to CCN production; however, the mechanisms related to particle nucleation and growth processes are not well understood. Organic acids are atmospherically abundant, and their neutralization by low molecular weight amines may result in the formation of stable low volatility aminium salt products contributing to the growth of secondary organic aerosols and even the alteration of the aerosol properties. The acid-base neutralization of particle phase succinic acid and tartaric acid by low molecular weight aliphatic amines, i.e. methylamine, dimethylamine, and trimethylamine, has been investigated by employing a low-pressure fast flow reactor at 298K with an ion drift - chemical ionization mass spectrometer (ID-CIMS). The heterogeneous uptake is time dependent and influenced by organic acids functionality, alkylamines basicity, and steric effect. The implications of our results to atmospheric nanoparticle growth will be discussed.

  1. High formation of secondary organic aerosol from the photo-oxidation of toluene

    Directory of Open Access Journals (Sweden)

    L. Hildebrandt

    2009-05-01

    Full Text Available Toluene and other aromatics have long been viewed as the dominant anthropogenic secondary organic aerosol (SOA precursors, but the SOA mass yields from toluene reported in previous studies vary widely. Experiments conducted in the Carnegie Mellon University environmental chamber to study SOA formation from the photo-oxidation of toluene show significantly larger SOA production than parameterizations employed in current air-quality models. Aerosol mass yields depend on experimental conditions: yields are higher under higher UV intensity, under low-NOx conditions and at lower temperatures. The extent of oxidation of the aerosol also varies with experimental conditions, consistent with ongoing, progressive photochemical aging of the toluene SOA. Measurements using a thermodenuder system suggest that the aerosol formed under high- and low-NOx conditions is semi-volatile. These results suggest that SOA formation from toluene depends strongly on ambient conditions. An approximate parameterization is proposed for use in air-quality models until a more thorough treatment accounting for the dynamic nature of this system becomes available.

  2. Effects of diluents on soot surface temperature and volume fraction in diluted ethylene diffusion flames at pressure

    KAUST Repository

    Kailasanathan, Ranjith Kumar Abhinavam; Zhang, Ji; Fang, Tiegang; Roberts, William L.

    2014-01-01

    Soot surface temperature and volume fraction are measured in ethylene/air coflowing laminar diffusion flames at high pressures, diluted with one of four diluents (argon, helium, nitrogen, and carbon dioxide) using a two-color technique. Both

  3. Observations of fine particulate nitrated phenols in four sites in northern China: concentrations, source apportionment, and secondary formation

    Directory of Open Access Journals (Sweden)

    L. Wang

    2018-03-01

    Full Text Available Filter samples of fine particulate matters were collected at four sites in northern China (urban, rural, and mountain in summer and winter, and the contents of nine nitrated phenols were quantified in the laboratory with the use of ultra-high-performance liquid chromatography coupled with mass spectrometry. During the sampling periods, the concentrations of particulate nitrated phenols exhibited distinct temporal and spatial variation. On average, the total concentration of particulate nitrated phenols in urban Jinan in the wintertime reached 48.4 ng m−3, and those in the summertime were 9.8, 5.7, 5.9, and 2.5 ng m−3 in urban Jinan, rural Yucheng and Wangdu, and Mt. Tai, respectively. The elevated concentrations of nitrated phenols in wintertime and in urban areas demonstrate the apparent influences of anthropogenic sources. The positive matrix factorization receptor model was then applied to determine the origins of particulate nitrated phenols in northern China. The five major source factors were traffic, coal combustion, biomass burning, secondary formation, and aged coal combustion plume. Among them, coal combustion played a vital role, especially at the urban site in the wintertime, with a contribution of around 55 %. In the summertime, the observed nitrated phenols were highly influenced by aged coal combustion plumes at all of the sampling sites. Meanwhile, in remote areas, contributions from secondary formation were significant. Further correlation analysis indicates that nitrosalicylic acids were produced mostly from secondary formation that was dominated by NO2 nitration.

  4. Soot, unburned carbon and ultrafine particle emissions from air- and oxy-coal flames

    International Nuclear Information System (INIS)

    Morris, W.J.; Yu, Dunxi; Wendt, J.O.L.

    2010-01-01

    Oxy-coal combustion is one possible solution for the mitigation of greenhouse gases. In this process coal is burned in oxygen, rather than air, and the temperatures in the boiler are mitigated by recycling flue gases, so that the inlet mixture may contain either 27 % O 2 to match adiabatic flame temperatures, or 32 % O 2 to match gaseous radiation heat fluxes in the combustion chamber. However, a major issue for heat transfer from coal combustion is the radiative heat transmission from soot. For this research, air and oxy coal firing were compared regarding the emission of soot. A 100 kW down-fired laboratory combustor was used to determine effects of switching from air to oxy-firing on soot, unburned carbon and ultrafine particle emissions from practical pulverized coal flames. Of interest here were potential chemical effects of substitution of the N 2 in air by CO 2 in practical pulverized coal flames. The oxy-coal configuration investigated used once-through CO 2 , simulating cleaned flue gas recycle with all contaminants and water removed. Three coals were each burned in: a) air, b) 27 % O 2 / 73 % CO 2 , c) 32 % O 2 / 68 % CO 2 . Tests were conducted at (nominally) 3 %, 2 %, 1 % and 0 % O 2 in the exhaust (dry basis). For each condition, particulate samples were iso kinetically withdrawn far from the radiant zone, and analyzed using a photoacoustic analyzer (PA) for black carbon, a scanning mobility particle sizer (SMPS) for ultrafine particles, and a total sample loss on ignition (LOI) method for unburned carbon in ash. Data suggest that at low stoichiometric ratios, ultrafine particles consist primarily of black carbon, which, for the bituminous coal, is produced in lesser amounts under oxy-fired conditions than under the air-fired condition, even when adiabatic flame temperatures are matched. However, significant changes in mineral matter vaporization were not observed unless the flames were hotter. These and other results are interpreted in the light of

  5. The investigation of soot and temperature distributions in a visualized direct injection diesel engine using laser diagnostics

    Science.gov (United States)

    Han, Yong-taek; Kim, Ki-bum; Lee, Ki-hyung

    2008-11-01

    Based upon the method of temperature calibration using the diffusion flame, the temperature and soot concentrations of the turbulent flame in a visualized diesel engine were qualitatively measured. Two different cylinder heads were used to investigate the effect of swirl ratio within the combustion chamber. From this experiment, we find that the highest flame temperature of the non-swirl head engine is approximately 2400 K and that of the swirl head engine is 2100 K. In addition, as the pressure of fuel injection increases, the in-cylinder temperature increases due to the improved combustion of a diesel engine. This experiment represented the soot quantity in the KL factor and revealed that the KL factor was high when the fuel collided with the cylinder wall. Moreover, the KL factor was also high in the area of the chamber where the temperature dropped rapidly.

  6. RGM regulates BMP-mediated secondary axis formation in the sea anemone Nematostella vectensis.

    Science.gov (United States)

    Leclère, Lucas; Rentzsch, Fabian

    2014-12-11

    Patterning of the metazoan dorsoventral axis is mediated by a complex interplay of BMP signaling regulators. Repulsive guidance molecule (RGM) is a conserved BMP coreceptor that has not been implicated in axis specification. We show that NvRGM is a key positive regulator of BMP signaling during secondary axis establishment in the cnidarian Nematostella vectensis. NvRGM regulates first the generation and later the shape of a BMP-dependent Smad1/5/8 gradient with peak activity on the side opposite the NvBMP/NvRGM/NvChordin expression domain. Full knockdown of Smad1/5/8 signaling blocks the formation of endodermal structures, the mesenteries, and the establishment of bilateral symmetry, while altering the gradient through partial NvRGM or NvBMP knockdown shifts the boundaries of asymmetric gene expression and the positioning of the mesenteries along the secondary axis. These findings provide insight into the diversification of axis specification mechanisms and identify a previously unrecognized role for RGM in BMP-mediated axial patterning. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  7. BRITTLE CULM16 (BRITTLE NODE) is required for the formation of secondary cell walls in rice nodes

    Institute of Scientific and Technical Information of China (English)

    WANG Ying; WANG Jiu-lin; GUO Xiu-ping; ZHANG Xin; LEI Cai-lin; CHENG Zhi-jun; WAN Jian-min; REN Yu-long; CHEN Sai-hua; XU Yang; ZHOU Kun-neng; ZHANG Long; MING Ming; WU Fu-qing; LIN Qi-bing

    2017-01-01

    Plant cell walls constitute the skeletal structures of plant bodies, and thus confer lodging resistance for grain crops. While the basic cell wall synthesis machinery is relatively well established now, our understanding of how the process is regulated remains limited and fragmented. In this study, we report the identification and characterization of the novel rice (Oryza sativa L.) brittle culm16 (brittle node; bc16) mutant. The brittle node phenotype of the bc16 mutant appears exclusively at nodes, and resembles the previously reported bc5 mutant. Combined histochemical staining and electron microscopy assays revealed that in the bc16 mutant, the secondary cell wall formation and thickening of node sclerenchyma tissues are seriously affected after heading. Furthermore, cell wall composition assays revealed that the bc16 mutation led to a significant reduction in cellulose and lignin contents. Using a map-based cloning approach, the bc16 locus is mapped to an approximately 1.7-Mb region of chromosome 4. Together, our findings strengthen evidence for discretely spatial differences in the secondary cell wall formation within plant bodies.

  8. Soot concentrations along busy inland waterways in the Netherlands; Roetconcentraties langs drukke binnenvaarwegen in Nederland

    Energy Technology Data Exchange (ETDEWEB)

    Keuken, M.; Jonkers, S.; Moerman, M. [TNO Built Environment and Geosciences, Delft (Netherlands); Hoek, G. [Institute for Risk Assessment Sciences IRAS, Utrecht University, Utrecht (Netherlands)

    2013-08-15

    Exploratory research by TNO and IRAS shows that residents in the Netherlands are exposed to soot concentrations along busy inland waterways similar to living along a busy highway [Dutch] Verkennend onderzoek van TNO en IRAS laat zien dat bewoners langs drukke binnenvaarwegen worden blootgesteld aan roetconcentraties vergelijkbaar met wonen langs een drukke snelweg.

  9. Effect of NOx level on secondary organic aerosol (SOA formation from the photooxidation of terpenes

    Directory of Open Access Journals (Sweden)

    R. C. Flagan

    2007-10-01

    Full Text Available Secondary organic aerosol (SOA formation from the photooxidation of one monoterpene (α-pinene and two sesquiterpenes (longifolene and aromadendrene is investigated in the Caltech environmental chambers. The effect of NOx on SOA formation for these biogenic hydrocarbons is evaluated by performing photooxidation experiments under varying NOx conditions. The NOx dependence of α-pinene SOA formation follows the same trend as that observed previously for a number of SOA precursors, including isoprene, in which SOA yield (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted decreases as NOx level increases. The NOx dependence of SOA yield for the sesquiterpenes, longifolene and aromadendrene, however, differs from that determined for isoprene and α-pinene; the aerosol yield under high-NOx conditions substantially exceeds that under low-NOx conditions. The reversal of the NOx dependence of SOA formation for the sesquiterpenes is consistent with formation of relatively low-volatility organic nitrates, and/or the isomerization of large alkoxy radicals leading to less volatile products. Analysis of the aerosol chemical composition for longifolene confirms the presence of organic nitrates under high-NOx conditions. Consequently the formation of SOA from certain biogenic hydrocarbons such as sesquiterpenes (and possibly large anthropogenic hydrocarbons as well may be more efficient in polluted air.

  10. Formation of secondary inorganic aerosols by power plant emissions exhausted through cooling towers in Saxony.

    Science.gov (United States)

    Hinneburg, Detlef; Renner, Eberhard; Wolke, Ralf

    2009-01-01

    The fraction of ambient PM10 that is due to the formation of secondary inorganic particulate sulfate and nitrate from the emissions of two large, brown-coal-fired power stations in Saxony (East Germany) is examined. The power stations are equipped with natural-draft cooling towers. The flue gases are directly piped into the cooling towers, thereby receiving an additionally intensified uplift. The exhausted gas-steam mixture contains the gases CO, CO2, NO, NO2, and SO2, the directly emitted primary particles, and additionally, an excess of 'free' sulfate ions in water solution, which, after the desulfurization steps, remain non-neutralized by cations. The precursor gases NO2 and SO2 are capable of forming nitric and sulfuric acid by several pathways. The acids can be neutralized by ammonia and generate secondary particulate matter by heterogeneous condensation on preexisting particles. The simulations are performed by a nested and multi-scale application of the online-coupled model system LM-MUSCAT. The Local Model (LM; recently renamed as COSMO) of the German Weather Service performs the meteorological processes, while the Multi-scale Atmospheric Transport Model (MUSCAT) includes the transport, the gas phase chemistry, as well as the aerosol chemistry (thermodynamic ammonium-sulfate-nitrate-water system). The highest horizontal resolution in the inner region of Saxony is 0.7 km. One summer and one winter episode, each realizing 5 weeks of the year 2002, are simulated twice, with the cooling tower emissions switched on and off, respectively. This procedure serves to identify the direct and indirect influences of the single plumes on the formation and distribution of the secondary inorganic aerosols. Surface traces of the individual tower plumes can be located and distinguished, especially in the well-mixed boundary layer in daytime. At night, the plumes are decoupled from the surface. In no case does the resulting contribution of the cooling tower emissions to PM10

  11. Investigation of soot morphology and particle size distrib ution in a turbulent nonpremixed flame via Monte Carlo simulations

    KAUST Repository

    Abdelgadir, Ahmed; Lucchesi, Marco; Attili, Antonio; Bisetti, Fabrizio

    2015-01-01

    the soot evolution along selected Lagrangian trajectories using a Monte Carlo method. An operator splitting approach is adopted to split the deterministic processes (nucleation, surface growth and oxidation) from coagulation, which is treated stochastically

  12. Soot temperature and KL factor for biodiesel and diesel spray combustion in a constant volume combustion chamber

    KAUST Repository

    Zhang, Ji; Jing, Wei; Roberts, William L.; Fang, Tiegang

    2013-01-01

    This paper presents measurements of the soot temperature and KL factor for biodiesel and diesel combustion in a constant volume chamber using a two-color technique. This technique uses a high-speed camera coupled with two narrowband filters (550. nm

  13. Secondary cell wall formation in Cryptococcus neoformans as a rescue mechanism against acid-induced autolysis.

    Science.gov (United States)

    Farkas, Vladimír; Takeo, Kanji; Maceková, Danka; Ohkusu, Misako; Yoshida, Soichi; Sipiczki, Matthias

    2009-03-01

    Growth of the opportunistic yeast pathogen Cryptococcus neoformans in a synthetic medium containing yeast nitrogen base and 1.0-3.0% glucose is accompanied by spontaneous acidification of the medium, with its pH decreasing from the initial 5.5 to around 2.5 in the stationary phase. During the transition from the late exponential to the stationary phase of growth, many cells died as a consequence of autolytic erosion of their cell walls. Simultaneously, there was an increase in an ecto-glucanase active towards beta-1,3-glucan and having a pH optimum between pH 3.0 and 3.5. As a response to cell wall degradation, some cells developed an unusual survival strategy by forming 'secondary' cell walls underneath the original ones. Electron microscopy revealed that the secondary cell walls were thicker than the primary ones, exposing bundles of polysaccharide microfibrils only partially masked by an amorphous cell wall matrix on their surfaces. The cells bearing secondary cell walls had a three to five times higher content of the alkali-insoluble cell wall polysaccharides glucan and chitin, and their chitin/glucan ratio was about twofold higher than in cells from the logarithmic phase of growth. The cell lysis and the formation of the secondary cell walls could be suppressed by buffering the growth medium between pH 4.5 and 6.5.

  14. Reactive oxidation products promote secondary organic aerosol formation from green leaf volatiles

    Directory of Open Access Journals (Sweden)

    J. F. Hamilton

    2009-06-01

    Full Text Available Green leaf volatiles (GLVs are an important group of chemicals released by vegetation which have emission fluxes that can be significantly increased when plants are damaged or stressed. A series of simulation chamber experiments has been conducted at the European Photoreactor in Valencia, Spain, to investigate secondary organic aerosol (SOA formation from the atmospheric oxidation of the major GLVs cis-3-hexenylacetate and cis-3-hexen-1-ol. Liquid chromatography-ion trap mass spectrometry was used to identify chemical species present in the SOA. Cis-3-hexen-1-ol proved to be a more efficient SOA precursor due to the high reactivity of its first generation oxidation product, 3-hydroxypropanal, which can hydrate and undergo further reactions with other aldehydes resulting in SOA dominated by higher molecular weight oligomers. The lower SOA yields produced from cis-3-hexenylacetate are attributed to the acetate functionality, which inhibits oligomer formation in the particle phase. Based on observed SOA yields and best estimates of global emissions, these compounds may be calculated to be a substantial unidentified global source of SOA, contributing 1–5 TgC yr−1, equivalent to around a third of that predicted from isoprene. Molecular characterization of the SOA, combined with organic mechanistic information, has provided evidence that the formation of organic aerosols from GLVs is closely related to the reactivity of their first generation atmospheric oxidation products, and indicates that this may be a simple parameter that could be used in assessing the aerosol formation potential for other unstudied organic compounds in the atmosphere.

  15. Potential rare-earth modified CeO{sub 2} catalysts for soot oxidation. Part III. Effect of dopant loading and calcination temperature on catalytic activity with O{sub 2} and NO + O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, K.; Bueno-Lopez, A.; Makkee, M.; Moulijn, J.A. [Catalysis Engineering, DelftChemTech, Delft University of Technology, Julianalaan 136, NL 2628 BL Delft (Netherlands)

    2007-09-26

    CeO{sub 2} and CeReO{sub xy} catalysts are prepared by the calcination at different temperatures (y = 500-1000 C) and having a different composition (Re = La{sup 3+} or Pr{sup 3+/4+}{sub ,} 0-90 wt.%). The catalysts are characterised by XRD, H{sub 2}-TPR, Raman, and BET surface area. The soot oxidation is studied with O{sub 2} and NO + O{sub 2} in the tight and loose contact conditions, respectively. CeO{sub 2} sinters between 800-900 C due to a grain growth, leading to an increased crystallite size and a decreased BET surface area. La{sup 3+} or Pr{sup 3+/4+} hinders the grain growth of CeO{sub 2} and, thereby, improving the surface catalytic properties. Using O{sub 2} as an oxidant, an improved soot oxidation is observed over CeLaO{sub xy} and CePrO{sub xy} in the whole dopant weight loading and calcination temperature range studied, compared with CeO{sub 2}. Using NO + O{sub 2}, the soot conversion decreased over CeLaO{sub xy} catalysts calcined below 800 C compared with the soot oxidation over CeO{sub 2y}. CePrO{sub xy}, on the other hand, showed a superior soot oxidation activity in the whole composition and calcination temperature range using NO + O{sub 2}. The improvement in the soot oxidation activity over the various catalysts with O{sub 2} can be explained based on an improvement in the external surface area. The superior soot oxidation activity of CePrO{sub xy} with NO + O{sub 2} is explained by the changes in the redox properties of the catalyst as well as surface area. CePrO{sub xy}, having 50 wt.% of dopant, is found to be the best catalyst due to synergism between cerium and praseodymium compared to pure components. NO into NO{sub 2} oxidation activity, that determines soot oxidation activity, is improved over all CePrO{sub x} catalysts. (author)

  16. SECONDARY ORGANIC AEROSOL FORMATION FROM THE OXIDATION OF AROMATIC HYDROCARBONS IN THE PRESENCE OF DRY SUBMICRON AMMONIUM SULFATE AEROSOL

    Science.gov (United States)

    A laboratory study was conducted to examine formation of secondary organic aerosols. A smog chamber system was developed for studying gas-aerosol interactions in a dynamic flow reactor. These experiments were conducted to investigate the fate of gas and aerosol phase compounds ...

  17. Sensitivity of the Single Particle Soot Photometer to different black carbon types

    Science.gov (United States)

    Laborde, M.; Mertes, P.; Zieger, P.; Dommen, J.; Baltensperger, U.; Gysel, M.

    2012-05-01

    Black carbon (BC) is now mainly of anthropogenic origin. It is the dominant light absorbing component of atmospheric aerosols, playing an important role in the earth's radiative balance and therefore relevant to climate change studies. In addition, BC is known to be harmful to human beings making it relevant to policy makers. Nevertheless, the measurement of BC remains biased by the instrument-based definition of BC. The Single Particle Soot Photometer (SP2), allows the measurement of the refractory BC (rBC) mass of individual particles using laser-induced incandescence. However, the SP2 needs an empirical calibration to retrieve the rBC mass from the incandescence signal and the sensitivity of the SP2 differs between different BC types. Ideally, for atmospheric studies, the SP2 should be calibrated using ambient particles containing a known mass of ambient rBC. However, such "ambient BC" calibration particles cannot easily be obtained and thus commercially available BC particles are commonly used for SP2 calibration instead. In this study we tested the sensitivity of the SP2 to different BC types in order to characterize the potential error introduced by using non-ambient BC for calibration. The sensitivity of the SP2 was determined, using an aerosol particle mass analyzer, for rBC from thermodenuded diesel exhaust, wood burning exhaust and ambient particles as well as for commercially available products: Aquadag® and fullerene soot. Thermodenuded, fresh diesel exhaust has been found to be ideal for SP2 calibration for two reasons. First, the small amount of non-BC matter upon emission reduces the risk of bias due to incomplete removal of non-BC matter and second, it is considered to represent atmospheric rBC in urban locations where diesel exhaust is the main source of BC. The SP2 was found to be up to 16% less sensitive to rBC from thermodenuded ambient particles (≤15 fg) than rBC from diesel exhaust, however, at least part of this difference can be explained

  18. Sensitivity of the Single Particle Soot Photometer to different black carbon types

    Directory of Open Access Journals (Sweden)

    M. Laborde

    2012-05-01

    Full Text Available Black carbon (BC is now mainly of anthropogenic origin. It is the dominant light absorbing component of atmospheric aerosols, playing an important role in the earth's radiative balance and therefore relevant to climate change studies. In addition, BC is known to be harmful to human beings making it relevant to policy makers. Nevertheless, the measurement of BC remains biased by the instrument-based definition of BC. The Single Particle Soot Photometer (SP2, allows the measurement of the refractory BC (rBC mass of individual particles using laser-induced incandescence. However, the SP2 needs an empirical calibration to retrieve the rBC mass from the incandescence signal and the sensitivity of the SP2 differs between different BC types. Ideally, for atmospheric studies, the SP2 should be calibrated using ambient particles containing a known mass of ambient rBC. However, such "ambient BC" calibration particles cannot easily be obtained and thus commercially available BC particles are commonly used for SP2 calibration instead. In this study we tested the sensitivity of the SP2 to different BC types in order to characterize the potential error introduced by using non-ambient BC for calibration. The sensitivity of the SP2 was determined, using an aerosol particle mass analyzer, for rBC from thermodenuded diesel exhaust, wood burning exhaust and ambient particles as well as for commercially available products: Aquadag® and fullerene soot.

    Thermodenuded, fresh diesel exhaust has been found to be ideal for SP2 calibration for two reasons. First, the small amount of non-BC matter upon emission reduces the risk of bias due to incomplete removal of non-BC matter and second, it is considered to represent atmospheric rBC in urban locations where diesel exhaust is the main source of BC. The SP2 was found to be up to 16% less sensitive to rBC from thermodenuded ambient particles (≤15 fg than rBC from diesel exhaust, however, at least part

  19. High-aluminum-affinity silica is a nanoparticle that seeds secondary aluminosilicate formation.

    Directory of Open Access Journals (Sweden)

    Ravin Jugdaohsingh

    Full Text Available Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7 we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP. Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m(2 g(-1 and it competes effectively with transferrin for Al(III binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III species binding monomeric silica to form early phase, non-toxic aluminosilicates.

  20. High-Aluminum-Affinity Silica Is a Nanoparticle That Seeds Secondary Aluminosilicate Formation

    Science.gov (United States)

    Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J.

    2013-01-01

    Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m2 g-1 and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates. PMID:24349573

  1. Secondary circulation in river junctions even at very low flow momentum ratios : The legacy effects of point bar formation

    NARCIS (Netherlands)

    Moradi, Gelare; Rennie, Colin; Vermeulen, Bart; Cardot, Romain; Lane, Stuart

    2018-01-01

    River confluences remain a challenging subject because of their 3D geometry which leads to a complex, three-dimensional mean and turbulent velocity processes. Since secondary circulation plays an important role in flow hydrodynamics and the development of bank erosion, bed scour and bar formation,

  2. Simultaneous measurements of acetylene and soot during the pyrolysis of ethylene and benzene in a shock tube

    KAUST Repository

    KC, Utsav; Beshir, Mohamed; Farooq, Aamir

    2016-01-01

    reflected shock waves at temperatures of 1600-2200. K and pressures of 3-5. bar. Acetylene mole fraction time-histories are measured from the absorption of a quantum-cascade laser operating around 13.6. μm. The soot volume fraction, particle size and number

  3. Effects of multiple scattering on radiative properties of soot fractal aggregates

    International Nuclear Information System (INIS)

    Yon, Jérôme; Liu, Fengshan; Bescond, Alexandre; Caumont-Prim, Chloé; Rozé, Claude; Ouf, François-Xavier; Coppalle, Alexis

    2014-01-01

    The in situ optical characterization of smokes composed of soot particles relies on light extinction, angular static light scattering (SLS), or laser induced incandescence (LII). These measurements are usually interpreted by using the Rayleigh–Debye–Gans theory for Fractal Aggregates (RDG-FA). RDG-FA is simple to use but it completely neglects the impact of multiple scattering (MS) within soot aggregates. In this paper, based on a scaling approach that takes into account MS effects, an extended form of the RDG-FA theory is proposed in order to take into account these effects. The parameters of this extended theory and their dependency on the number of primary sphere inside the aggregate (1 p <1006) and on the wavelength (266nm<λ<1064nm) are evaluated thanks to rigorous calculations based on discrete dipole approximation (DDA) and generalized multi-sphere Mie-solution (GMM) calculations. This study shows that size determination by SLS is not distorted by MS effect. On the contrary, it is shown that fractal dimension can be misinterpreted by light scattering experiments, especially at short wavelengths. MS effects should be taken into account for the interpretation of absorption measurements that are involved in LII or extinction measurements. -- Highlights: • We incorporate multiple scattering effects in a scaling approach for fractal aggregates. • A generalized structure factor is introduced for implementation in RDG-FA theory. • Forward scattering is affected by multiple scattering as well as power law regime. • Absorption cross sections are affected by multiple scattering. • Absorption cross sections are 11% higher than that for forward scattering

  4. Improved soot blowing, based on needs, using the mechanical characteristics of the steam pipe - stage 2; Foerbaettrad behovsstyrd sotning med hjaelp av vaermeoeverfoerande tubens mekaniska egenskaper - etapp 2

    Energy Technology Data Exchange (ETDEWEB)

    Blom, Elisabet; Fredoe, Claes; Gabrielsson, Lars; Eriksson, Daniel

    2011-10-15

    The detection of contamination of the boiler tubes through the tube mechanical properties has been studied. The project has carried out measurements and detection of three different boilers with different conditions in terms of sooting philosophy, combustion method and sooting method. The assembly of the detecting strain gauge takes place on a clip which is screwed and glued onto the tube.

  5. Effects of Biomass Feedstock on the Yield and Reactivity of Soot from Fast Pyrolysis at High Temperatures

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Jensen, Peter A.; Glarborg, Peter

    This study investigated the effect of feedstock on the yield, nanostructure and reactivity of soot. Woody and herbaceous biomass were pyrolyzed at high heating rates and temperatures of 1250 and 1400°C in a drop tube furnace. The collected solid residues were structurally characterized by electro...

  6. New positive feedback mechanism between boundary layer meteorology and secondary aerosol formation during severe haze events.

    Science.gov (United States)

    Liu, Quan; Jia, Xingcan; Quan, Jiannong; Li, Jiayun; Li, Xia; Wu, Yongxue; Chen, Dan; Wang, Zifa; Liu, Yangang

    2018-04-17

    Severe haze events during which particulate matter (PM) increases quickly from tens to hundreds of microgram per cubic meter in 1-2 days frequently occur in China. Although it has been known that PM is influenced by complex interplays among emissions, meteorology, and physical and chemical processes, specific mechanisms remain elusive. Here, a new positive feedback mechanism between planetary boundary layer (PBL), relative humidity (RH), and secondary PM (SPM) formation is proposed based on a comprehensive field experiment and model simulation. The decreased PBL associated with increased PM increases RH by weakening the vertical transport of water vapor; the increased RH in turn enhances the SPM formation through heterogeneous aqueous reactions, which further enhances PM, weakens solar radiation, and decreases PBL height. This positive feedback, together with the PM-Radiation-PBL feedback, constitutes a key mechanism that links PM, radiation, PBL properties (e.g. PBL height and RH), and SPM formation, This mechanism is self-amplifying, leading to faster PM production, accumulation, and more severe haze pollution.

  7. A systematic review of concept mapping-based formative assessment processes in primary and secondary science education

    DEFF Research Database (Denmark)

    Hartmeyer, Rikke; Stevenson, Matt P.; Bentsen, Peter

    2017-01-01

    assessment: firstly, concept mapping should be constructed in teaching, preferably on repeated occasions. Secondly, concept mapping should be carried out individually if personal understanding is to be elicited; however, collaborative concept mapping might foster discussions valuable for developing students......’ understanding and for activating them as instructional resources and owners of their own learning. Thirdly, low-directed mapping seems most suitable for formative assessment. Fourthly, technology-based or peer assessments are useful strategies likely to reduce the load of interpretation for the educator......In this paper, we present and discuss the results of a systematic review of concept mapping-based interventions in primary and secondary science education. We identified the following recommendations for science educators on how to successfully apply concept mapping as a method for formative...

  8. Comparative Study of Different Methods for Soot Sensing and Filter Monitoring in Diesel Exhausts

    OpenAIRE

    Feulner, Markus; Hagen, Gunter; Hottner, Kathrin; Redel, Sabrina; M?ller, Andreas; Moos, Ralf

    2017-01-01

    Due to increasingly tighter emission limits for diesel and gasoline engines, especially concerning particulate matter emissions, particulate filters are becoming indispensable devices for exhaust gas after treatment. Thereby, for an efficient engine and filter control strategy and a cost-efficient filter design, reliable technologies to determine the soot load of the filters and to measure particulate matter concentrations in the exhaust gas during vehicle operation are highly needed. In this...

  9. Modeling Secondary Organic Aerosol Formation From Emissions of Combustion Sources

    Science.gov (United States)

    Jathar, Shantanu Hemant

    Atmospheric aerosols exert a large influence on the Earth's climate and cause adverse public health effects, reduced visibility and material degradation. Secondary organic aerosol (SOA), defined as the aerosol mass arising from the oxidation products of gas-phase organic species, accounts for a significant fraction of the submicron atmospheric aerosol mass. Yet, there are large uncertainties surrounding the sources, atmospheric evolution and properties of SOA. This thesis combines laboratory experiments, extensive data analysis and global modeling to investigate the contribution of semi-volatile and intermediate volatility organic compounds (SVOC and IVOC) from combustion sources to SOA formation. The goals are to quantify the contribution of these emissions to ambient PM and to evaluate and improve models to simulate its formation. To create a database for model development and evaluation, a series of smog chamber experiments were conducted on evaporated fuel, which served as surrogates for real-world combustion emissions. Diesel formed the most SOA followed by conventional jet fuel / jet fuel derived from natural gas, gasoline and jet fuel derived from coal. The variability in SOA formation from actual combustion emissions can be partially explained by the composition of the fuel. Several models were developed and tested along with existing models using SOA data from smog chamber experiments conducted using evaporated fuel (this work, gasoline, fischertropschs, jet fuel, diesels) and published data on dilute combustion emissions (aircraft, on- and off-road gasoline, on- and off-road diesel, wood burning, biomass burning). For all of the SOA data, existing models under-predicted SOA formation if SVOC/IVOC were not included. For the evaporated fuel experiments, when SVOC/IVOC were included predictions using the existing SOA model were brought to within a factor of two of measurements with minor adjustments to model parameterizations. Further, a volatility

  10. Effect of Pellet Boiler Exhaust on Secondary Organic Aerosol Formation from α-Pinene.

    Science.gov (United States)

    Kari, Eetu; Hao, Liqing; Yli-Pirilä, Pasi; Leskinen, Ari; Kortelainen, Miika; Grigonyte, Julija; Worsnop, Douglas R; Jokiniemi, Jorma; Sippula, Olli; Faiola, Celia L; Virtanen, Annele

    2017-02-07

    Interactions between anthropogenic and biogenic emissions, and implications for aerosol production, have raised particular scientific interest. Despite active research in this area, real anthropogenic emission sources have not been exploited for anthropogenic-biogenic interaction studies until now. This work examines these interactions using α-pinene and pellet boiler emissions as a model test system. The impact of pellet boiler emissions on secondary organic aerosol (SOA) formation from α-pinene photo-oxidation was studied under atmospherically relevant conditions in an environmental chamber. The aim of this study was to identify which of the major pellet exhaust components (including high nitrogen oxide (NO x ), primary particles, or a combination of the two) affected SOA formation from α-pinene. Results demonstrated that high NO x concentrations emitted by the pellet boiler reduced SOA yields from α-pinene, whereas the chemical properties of the primary particles emitted by the pellet boiler had no effect on observed SOA yields. The maximum SOA yield of α-pinene in the presence of pellet boiler exhaust (under high-NO x conditions) was 18.7% and in the absence of pellet boiler exhaust (under low-NO x conditions) was 34.1%. The reduced SOA yield under high-NO x conditions was caused by changes in gas-phase chemistry that led to the formation of organonitrate compounds.

  11. Analysis of haloforms in wastewater. Removal of haloforms during secondary and tertiary treatment and formation during disinfection

    Energy Technology Data Exchange (ETDEWEB)

    de Leer, E W.B.

    1980-01-01

    The removal of haloforms during secondary and tertiary treatment and formation during disinfection was determined with a pentane extraction method followed by gas chromatographic separation with quantification by electron capture detection, which showed good results. High chloroform and trichloroethane levels in domestic sewage were reduced in activated-sludge tanks to 0 to 2 ..mu..g/l, one order of magnitude lower than Rotterdam drinking water.

  12. Formation of secondary organic aerosol in the Paris pollution plume and its impact on surrounding regions

    Science.gov (United States)

    Zhang, Q. J.; Beekmann, M.; Freney, E.; Sellegri, K.; Pichon, J. M.; Schwarzenboeck, A.; Colomb, A.; Bourrianne, T.; Michoud, V.; Borbon, A.

    2015-12-01

    Secondary pollutants such as ozone, secondary inorganic aerosol, and secondary organic aerosol formed in the plumes of megacities can affect regional air quality. In the framework of the FP7/EU MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) project, an intensive campaign was launched in the greater Paris region in July 2009. The major objective was to quantify different sources of organic aerosol (OA) within a megacity and in its plume. In this study, we use airborne measurements aboard the French ATR-42 aircraft to evaluate the regional chemistry-transport model CHIMERE within and downwind of the Paris region. Two mechanisms of secondary OA (SOA) formation are used, both including SOA formation from oxidation and chemical aging of primary semivolatile and intermediate volatility organic compounds (SI-SOA) in the volatility basis set (VBS) framework. As for SOA formed from traditional VOC (volatile organic compound) precursors (traditional SOA), one applies chemical aging in the VBS framework adopting different SOA yields for high- and low-NOx environments, while another applies a single-step oxidation scheme without chemical aging. Two emission inventories are used for discussion of emission uncertainties. The slopes of the airborne OA levels versus Ox (i.e., O3 + NO2) show SOA formation normalized with respect to photochemical activity and are used for specific evaluation of the OA scheme in the model. The simulated slopes were overestimated slightly by factors of 1.1, 1.7 and 1.3 with respect to those observed for the three airborne measurements, when the most realistic "high-NOx" yields for traditional SOA formation in the VBS scheme are used in the model. In addition, these slopes are relatively stable from one day to another, which suggests that they are characteristic for the given megacity plume environment. The configuration with increased primary

  13. Laboratory studies of monoterpene secondary organic aerosol formation and evolution

    Science.gov (United States)

    Thornton, J. A.; D'Ambro, E.; Zhao, Y.; Lee, B. H.; Pye, H. O. T.; Schobesberger, S.; Shilling, J.; Liu, J.

    2017-12-01

    We have conducted a series of chamber experiments to study the molecular composition and properties of secondary organic aerosol (SOA) formed from monoterpenes under a range of photochemical and dark conditions. We connect variations in the SOA mass yield to molecular composition and volatility, and use a detailed Master Chemical Mechanism (MCM) based chemical box model with dynamic gas-particle partitioning to examine the importance of various peroxy radical reaction mechanisms in setting the SOA yield and properties. We compare the volatility distribution predicted by the model to that inferred from isothermal room-temperature evaporation experiments using the FIGAERO-CIMS where SOA particles collected on a filter are allowed to evaporate under humidified pure nitrogen flow stream for up to 24 hours. We show that the combination of results requires prompt formation of low volatility SOA from predominantly gas-phase mechanisms, with important differences between monoterpenes (alpha-Pinene and delta-3-Carene) followed by slower non-radical particle phase chemistry that modulates both the chemical and physical properties of the SOA. Implications for the regional evolution of atmospheric monoterpene SOA are also discussed.

  14. The Transcriptomics of Secondary Growth and Wood Formation in Conifers

    Science.gov (United States)

    Carvalho, Ana; Paiva, Jorge; Louzada, José; Lima-Brito, José

    2013-01-01

    In the last years, forestry scientists have adapted genomics and next-generation sequencing (NGS) technologies to the search for candidate genes related to the transcriptomics of secondary growth and wood formation in several tree species. Gymnosperms, in particular, the conifers, are ecologically and economically important, namely, for the production of wood and other forestry end products. Until very recently, no whole genome sequencing of a conifer genome was available. Due to the gradual improvement of the NGS technologies and inherent bioinformatics tools, two draft assemblies of the whole genomes sequence of Picea abies and Picea glauca arose in the current year. These draft genome assemblies will bring new insights about the structure, content, and evolution of the conifer genomes. Furthermore, new directions in the forestry, breeding and research of conifers will be discussed in the following. The identification of genes associated with the xylem transcriptome and the knowledge of their regulatory mechanisms will provide less time-consuming breeding cycles and a high accuracy for the selection of traits related to wood production and quality. PMID:24288610

  15. A study of a ceria-zirconia-supported manganese oxide catalyst for combustion of Diesel soot particles

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Escribano, V.; Fernandez Lopez, E.; del Hoyo Martinez, C. [Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Pa. de la Merced s/n, E-37008 Salamanca (Spain); Gallardo-Amores, J.M. [Lab. Complutense de Altas Presiones, Departamento de Quimica Inorganica I, Universidad Complutense, Ciudad Universitaria, E-28040 Madrid (Spain); Pistarino, C.; Panizza, M.; Resini, C.; Busca, G. [Dipartimento di Ingegneria Chimica e di Processo, Universita di Genova, P.le J.F. Kennedy, Pad. D, I-16129 Genoa (Italy)

    2008-04-15

    A study has been conducted on the structural and morphological characterization of a Ce-Zr mixed oxide-supported Mn oxide as well as on its catalytic activity in the oxidation of particulate matter arising from Diesel engines. X-ray powder diffraction analysis (XRD) and FT-IR and FT-Raman spectroscopy evidence that the support is a fluorite-like ceria-zirconia solid solution, whereas the supported phase corresponds to the manganese oxide denoted as bixbyite ({alpha}-Mn{sub 2}O{sub 3}). Thermal analyses and FT-IR spectra in air at varying temperatures of soot mechanically mixed with the catalyst evidence that the combustion takes place to a total extent in the range 420-720 K, carboxylic species being detected as intermediate compounds. Moreover, the soot oxidation was studied in a flow reactor and was found to be selective to CO{sub 2}, with CO as by-product in the range 420-620 K. The amount of the generated CO decreases significantly with increasing O{sub 2} concentration in the feed. (author)

  16. Increasing of prediction reliability of calcium carbonate scale formation in heat exchanger of secondary coolant circuits of thermal and nuclear power plants

    International Nuclear Information System (INIS)

    Tret'yakov, O.V.; Kritskij, V.G.; Styazhkin, P.S.

    1991-01-01

    Calcium carbonate scale formation in the secondary circuit heat exchanger of thermal and nuclear power plants is investigated. A model of calcium-carbonate scale formation providing quite reliable prediction of process running and the possibility of its control affecting the parameters of hydrochemical regime (HCR) is developed. The results can be used when designing the automatic-control system of HCR

  17. Application of a robust and efficient Lagrangian particle scheme to soot transport in turbulent flames

    KAUST Repository

    Attili, Antonio

    2013-09-01

    A Lagrangian particle scheme is applied to the solution of soot dynamics in turbulent nonpremixed flames. Soot particulate is described using a method of moments and the resulting set of continuum advection-reaction equations is solved using the Lagrangian particle scheme. The key property of the approach is the independence between advection, described by the movement of Lagrangian notional particles along pathlines, and internal aerosol processes, evolving on each notional particle via source terms. Consequently, the method overcomes the issues in Eulerian grid-based schemes for the advection of moments: errors in the advective fluxes pollute the moments compromising their realizability and the stiffness of source terms weakens the stability of the method. The proposed scheme exhibits superior properties with respect to conventional Eulerian schemes in terms of stability, accuracy, and grid convergence. Taking into account the quality of the solution, the Lagrangian approach can be computationally more economical than commonly used Eulerian schemes as it allows the resolution requirements dictated by the different physical phenomena to be independently optimized. Finally, the scheme posseses excellent scalability on massively parallel computers. © 2013 Elsevier Ltd.

  18. The effect of mineral dust and soot aerosols on ice microphysics near the foothills of the Himalayas: A numerical investigation

    Science.gov (United States)

    Hazra, Anupam; Padmakumari, B.; Maheskumar, R. S.; Chen, Jen-Ping

    2016-05-01

    This study investigates the influence of different ice nuclei (IN) species and their number concentrations on cloud ice production. The numerical simulation with different species of ice nuclei is investigated using an explicit bulk-water microphysical scheme in a Mesoscale Meteorological Model version 5 (MM5). The species dependent ice nucleation parameterization that is based on the classical nucleation theory has been implemented into the model. The IN species considered include dust and soot with two different concentrations (Low and High). The simulated cloud microphysical properties like droplet number concentration and droplet effective radii as well as macro-properties (equivalent potential temperature and relative humidity) are comparable with aircraft observations. When higher dust IN concentrations are considered, the simulation results showed good agreement with the cloud ice and cloud water mixing ratio from aircraft measurements during Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) and Modern Era Retrospective Analysis for Research and Applications (MERRA) reanalysis. Relative importance of IN species is shown as compared to the homogeneous freezing nucleation process. The tendency of cloud ice production rates is also analyzed and found that dust IN is more efficient in producing cloud ice when compared to soot IN. The dust IN with high concentration can produce more surface precipitation than soot IN at the same concentration. This study highlights the need to improve the ice nucleation parameterization in numerical models.

  19. Molecular Characterization of the Gas-Particle Interface of Soot Sampled from a Diesel Engine Using a Titration Method.

    Science.gov (United States)

    Tapia, A; Salgado, M S; Martín, María Pilar; Lapuerta, M; Rodríguez-Fernández, J; Rossi, M J; Cabañas, B

    2016-03-15

    Surface functional groups of two different types of combustion aerosols, a conventional diesel (EN 590) and a hydrotreated vegetable oil (HVO) soot, have been investigated using heterogeneous chemistry (i.e., gas-particle surface reactions). A commercial sample of amorphous carbon (Printex XE2-B) was analyzed as a reference substrate. A Knudsen flow reactor was used to carry out the experiments under molecular flow conditions. The selected gases for the titration experiments were: N(CH3)3 for the identification of acidic sites, NH2OH for the presence of carbonyl groups, CF3COOH and HCl for basic sites of different strength, and O3 and NO2 for reducing groups. Reactivity with N(CH3)3 indicates a lower density of acidic functionalities for Printex XE2-B in relation to diesel and HVO soot. Results for NH2OH experiments indicates that commercial amorphous carbon exhibits a lower abundance of available carbonyl groups at the interface compared to the results from diesel and HVO soot, the latter being the one with the largest abundance of carbonyl functions. Reactions with acids indicate the presence of weak basic oxides on the particle surface that preferentially interact with the strong acid CF3COOH. Finally, reactions with O3 and NO2 reveal that diesel and especially HVO have a significantly higher reactivity with both oxidizers compared to that of Printex XE2-B because they have more reducing sites by roughly a factor of 10 and 30, respectively. The kinetics of titration reactions have also been investigated.

  20. Detection of carbon monoxide (CO) in sooting hydrocarbon flames using femtosecond two-photon laser-induced fluorescence (fs-TPLIF)

    Science.gov (United States)

    Wang, Yejun; Kulatilaka, Waruna D.

    2018-01-01

    Ultrashort-pulse, femtosecond (fs)-duration, two-photon laser-induced fluorescence (fs-TPLIF) measurements of carbon monoxide (CO) are reported in rich, sooting hydrocarbon flames. CO-TPLIF detection using conventional nanosecond or picosecond lasers are often plagued by photochemical interferences, specifically under fuel-rich flames conditions. In the current study, we investigate the commonly used CO two-photon excitation scheme of the B1Σ+ ← X1Σ+ electronic transition, using approximately 100-fs-duration excitation pulses. Fluorescence emission was observed in the Ångström band originating from directly populated B1Σ+ upper state, as well as, in the third positive band from collisionally populated b3Σ+ upper state. The current work was focused on the Ångström band emission. Interference from nascent C2 emissions originating from hot soot particles in the flame could be reduced to a negligible level using a narrower detection gate width. In contrast, avoiding interferences from laser-generated C2 Swan-band emissions required specific narrowband spectral filtering in sooting flame conditions. The observed less than quadratic laser pulse energy dependence of the TPLIF signal suggests the presence of strong three-photon ionization and stimulated emission processes. In a range of CH4/air and C2H4/air premixed flames investigated, the measured CO fluorescence signals agree well with the calculated equilibrium CO number densities. Reduced-interference CO-TPLIF imaging in premixed C2H4/O2/N2 jet flames is also reported.