WorldWideScience

Sample records for flame effect features

  1. Annealing effect and stability of carbon nanotubes in hydrogen flame

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spectra decreased with the increase in the annealing time. The CNTs were not stable in the hydrogen flame and the etching rate of the CNTs by hydrogen flame was very high. The hydrogen flame annealing had some effects on improving the crystallinity of CNTs.

  2. Effects of Radiative and Diffusive Transport Processes on Premixed Flames near Flammability Limits

    Science.gov (United States)

    Abbud-Madrid, Angel; Ronney, Paul D.

    1991-01-01

    A study of the mechanisms of flammability limits and the dynamics of flame extinguishment in premixed gas flames is described, a novel feature of which is the use of diluent gases having a wide range of radiative and diffusive transport properties. This feature enables an assessment of the importance of volumetric heat losses and Lewis number effects on these mechanisms. Additionally, effects of flame dynamics and flame front curvature are studied by employing spherically expanding flames obtained in a microgravity environment whereby natural convection is eliminated. New diagnostics include chamber pressure measurements and the first reported species concentration measurements in a microgravity combustion experiment. The limit mechanisms and extinguishment phenomena are found to be strongly influenced by the combined effects of radiant heat loss, Lewis number and flame curvature. Two new and as yet not well understood phenomena are reported: 'double flames' in rich H2-O2-CO2 mixtures and an 'inverse flammability region' in rich C3H8-O2-CO2 mixtures.

  3. Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

    Science.gov (United States)

    Bhatia, Pramod; Singh, Ravinder

    2017-01-01

    Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

  4. Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

    Science.gov (United States)

    Bhatia, Pramod; Singh, Ravinder

    2017-06-01

    Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

  5. Effects of side walls on facade flame entrainment and flame height from opening in compartment fires

    Directory of Open Access Journals (Sweden)

    Hu L.H.

    2013-11-01

    Full Text Available This paper presents an investigation of the side wall effects on facade flames ejected from the opening (such as a window of an under-ventilated room fire. Experiments are carried out in a reduced-scale experimental setup, consisting of a cubic fire compartment having an opening with a vertical facade wall and two side walls normal to the façade wall. By changing the distance of the two side walls, the facade flame heights for different opening conditions (width, height are recorded by a CCD camera. It is found that as the distance of the two side walls decreases the behavior the flame height can be distinguished into two regimes characterized by the dimensionless excess heat release rate, $skew5dot{Q}_{ex}^{ast}$ See Formula in PDF , outside the opening: (a for the “wall fire” (skew5dot{Q}_{ex}^{ast }$See Formula in PDF ≤ 1.3 , the flame height is shown to change little with decrease of side wall distance as the dominant entrainment is from the front direction (normal to the facade wall independent of the side wall distances; (b for the “axis-symmetrical fire” (\\skew5dot{Q}_{ex}^{ast}$ > 1.3, the flame height increases significantly with a decrease in side wall distance as both the entrainment from the two side directions (parallel to the facade wall and that from the front direction (normal to the facade wall together apply. A global physically based non-dimensional factor K is then brought forward based on the side wall constraint effect on the facade flame entrainment to characterize the side wall effect on the flame height, by accounting for the dimensionless excess heat release rate, the characteristic length scales of the opening as well as the side wall separation distance. The experimental data for different opening dimensions and side wall distances collapse by using this global non-dimensional factor.

  6. Effect of Turbulence on Flame Propagation in Cornstarch Dust-Air Mixtures

    Institute of Scientific and Technical Information of China (English)

    Shuangfeng WANG; Yikang PU; Fu JIA; Artur GUTKOWSKI

    2006-01-01

    Following the quantitative determination of dust cloud parameters, this study investigated the flame propagation through cornstarch dust clouds in a vertical duct of 780 mm height and 160×160 mm square cross section, and gave particular attention to the effect of turbulence on flame characteristics. The turbulence induced by dust dispersion process was measured using a particle image velocimetry (PIV) system. Upward propagating dust flames were visualized with direct light and shadow photography. The results show that a critical value of the turbulence intensity can be specified below which laminar flame propagation would be established. This transition condition is about 10 cm/s. Themeasured propagation speed of laminar flames appears to be in the range of 0.45-0.56 m/s, consistent with the measurements reported in the literature. For the present experimental conditions, the flame speed is little sensitive to the variations in dust concentration. Some information on the flame structure was revealed from the shadow records, showing the typical heterogeneous feature of dust combustion process.

  7. Effect of Flame Conditions on Crystalline Structure of TiO2 in Liquid Flame Spraying

    Institute of Scientific and Technical Information of China (English)

    LI Chang-jiu; YANG Guan-jun; WANG Yu-yue

    2004-01-01

    Nanostructured TiO2 is a most promising functional ceramic owing to its potential utilization in photocatalytical, optical and electrical applications. Nanostructured TiO2 coating was deposited through thermal spraying with liquid feedstock. Two types of crystalline structures were present in the synthesized TiO2 coating including anatase phase and rutile phase.The effect of spray flame conditions on the crystalline structure was investigated in order to control the crystalline structure of the coating. The results showed that spray distance, flame power and precursor concentration in the liquid feedstock significantly influenced phase constitutions and grain size in the coating. Anatase phase was formed at spray distance from 150 to 250mm, while rutile phase was evidently observed in the coating deposited at 100 mm. The results suggested that anatase phase was firstly formed in the coating, and rutile phase resulted from the transformation of the deposited anatase phase. The phase transformation from anatase to rutile occurred through the annealing effect of spraying flame. The control of the phase formation can be realized through flame condition and spray distance.

  8. Effect of Electric Field on Outwardly Propagating Spherical Flame

    KAUST Repository

    Mannaa, Ossama

    2012-06-01

    The thesis comprises effects of electric fields on a fundamental study of spheri­cal premixed flame propagation.Outwardly-propagating spherical laminar premixed flames have been investigated in a constant volume combustion vessel by applying au uni-directional electric potential.Direct photography and schlieren techniques have been adopted and captured images were analyzed through image processing. Unstretched laminar burning velocities under the influence of electric fields and their associated Markstein length scales have been determined from outwardly prop­agating spherical flame at a constant pressure. Methane and propane fuels have been tested to assess the effect of electric fields on the differential diffusion of the two fuels.The effects of varying equivalence ratios and applied voltages have been in­vestigated, while the frequency of AC was fixed at 1 KHz. Directional propagating characteristics were analyzed to identify the electric filed effect. The flame morphology varied appreciably under the influence of electric fields which in turn affected the burning rate of mixtures.The flame front was found to propagate much faster toward to the electrode at which the electric fields were supplied while the flame speeds in the other direction were minimally influenced. When the voltage was above 7 KV the combustion is markedly enhanced in the downward direction since intense turbulence is generated and as a result the mixing process or rather the heat and mass transfer within the flame front will be enhanced.The com­bustion pressure for the cases with electric fields increased rapidly during the initial stage of combustion and was relatively higher since the flame front was lengthened in the downward direction.

  9. Real fuel effects on flame extinction and re-ignition

    Science.gov (United States)

    Zhao, Xinyu; Wu, Bifen; Xu, Chao; Lu, Tianfeng; Chen, Jacqueline H.

    2016-11-01

    Flame-vortex interactions have significant implications in studying combustion in practical aeronautical engines, and can be used to facilitate the model development in capturing local extinction and re-ignition. To study the interactions between the complex fuel and the intense turbulence that are commonly encountered in engines, direct numerical simulations of the interactions between a flame and a vortex pair are carried out using a recently-developed 24-species reduced chemistry for n-dodecane. Both non-premixed and premixed flames with different initial and inlet thermochemical conditions are studied. Parametric studies of different vortex strengths and orientations are carried out to induce maximum local extinction and re-ignition. Chemical-explosive-mode-analysis based flame diagnostic tools are used to identify different modes of combustion, including auto-ignition and extinction. Results obtained from the reduced chemistry are compared with those obtained from one-step chemistry to quantify the effect of fuel pyrolysis on the extinction limit. Effects of flame curvature, heat loss and unsteadiness on flame extinction are also explored. Finally, the validity of current turbulent combustion models to capture the local extinction and re-ignition will be discussed.

  10. Effect of vorticity flip-over on the premixed flame structure: First experimental observation of type I inflection flames

    CERN Document Server

    El-Rabii, Hazem

    2015-01-01

    Premixed flames propagating in horizontal tubes are observed to take on shape convex towards the fresh mixture, which is commonly explained as a buoyancy effect. A recent rigorous analysis has shown, on the contrary, that this process is driven by the balance of vorticity generated by a curved flame front with the baroclinic vorticity, and predicted existence of a regime in which the leading edge of the flame front is concave. We report first experimental realization of this regime. Our experiments on ethane and n-butane mixtures with air show that flames with an inflection point on the front are regularly produced in lean mixtures, provided that a sufficiently weak ignition is used. The observed flame shape perfectly agrees with the theoretically predicted.

  11. Feature of high velocity oxygen-fuel flame spraying; Kosoku flame yoshaho no tokucho to sono oyo

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Y.; Sakaki, K. [Shinshu University, Nagano (Japan). Faculty of Engineering

    1996-05-01

    A description is given about the high velocity flame spraying method. In this method, fuel and oxygen under high pressure are supplied to a spraying gun, a supersonic stream of flame is jetted out of a fine nozzle, and spray particles are injected into the flame to impinge on the substrate surface at a very high speed for the formation of a coating. This method is advantageous in that the spray particles are higher in flying speed than in other spraying methods, that the produced coating is dense and close and excellent in adhesion, that the flame temperature is relatively low, and that the spray material is suppressed in terms of phase transformation, oxidation, and decomposition. This spraying technique is disadvantageous in that the spray materials that it can use are limited in variety because this method meets difficulties in spraying upon high melting-point metal or ceramics. This paper also outlines the spraying devices (chamber combustion type and throat combustion type) and the characteristics of produced coatings, and spray materials and their application (centering about carbide thermit spraying) are mentioned. 23 refs., 6 figs., 2 tabs.

  12. Effects of AC Electric Field on Small Laminar Nonpremixed Flames

    KAUST Repository

    Xiong, Yuan

    2015-04-01

    Electric field can be a viable method in controlling various combustion properties. Comparing to traditional actuators, an application of electric field requires very small power consumption. Especially, alternating current (AC) has received attention recently, since it could modulate flames appreciably even for the cases when direct current (DC) has minimal effects. In this study, the effect of AC electric fields on small coflow diffusion flames is focused with applications of various laser diagnostic techniques. Flow characteristics of baseline diffusion flames, which corresponds to stationary small coflow diffusion flames when electric field is not applied, were firstly investigated with a particular focus on the flow field in near-nozzle region with the buoyancy force exerted on fuels due to density differences among fuel, ambient air, and burnt gas. The result showed that the buoyancy force exerted on the fuel as well as on burnt gas significantly distorted the near-nozzle flow-fields. In the fuels with densities heavier than air, recirculation zones were formed very close to the nozzle exit. Nozzle heating effect influenced this near-nozzle flow-field particularly among lighter fuels. Numerical simulations were also conducted and the results showed that a fuel inlet boundary condition with a fully developed velocity profile for cases with long fuel tubes should be specified inside the fuel tube to obtain satisfactory agreement in both the flow and temperature fields with those from experiment. With sub-critical AC applied to the baseline flames, particle image velocimetry (PIV), light scattering, laser-induced incandescence (LII), and laser-induced fluores- cence (LIF) techniques were adopted to identify the flow field and the structures of OH, polycyclic aromatic hydrocarbons (PAHs), soot zone. Under certain AC condi- tions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered from the

  13. Synergistic Effect of Nanosilica Aerogel with Phosphorus Flame Retardants on Improving Flame Retardancy and Leaching Resistance of Wood

    Directory of Open Access Journals (Sweden)

    Xiaodan Zhu

    2014-01-01

    Full Text Available Nanosilica (Nano-SiO2 sol fabricated by a sol-gel process was introduced into wood modification with phosphorus flame retardants to improve the flame retardancy and leaching resistance of wood. The obtained materials were characterized by scanning electron microscopy and energy dispersive spectrometer (SEM-EDS, thermogravimetric analysis (TGA, cone calorimetric (CONE, and infrared spectroscopy (FT-IR. The residual rate of flame retardants before and after leaching was determinated by a leaching resistance. The results showed that the phosphorus flame retardants and SiO2 sol could reside in the poplar wood and are widely distributed in the vessels, pits, wood timber, and the spaces between wood cells of poplar substrate. TGA and CONE results indicated that the introduction of nano-SiO2 aerogel with phosphorus flame retardants had a significantly synergistic effect on improving the flame retardancy and inhibiting the release of smoke and toxic gases. In addition, the leaching resistance test, combined with infrared analysis and EDS analysis, confirmed that the phosphorus flame retardants were able to be fixed by SiO2 aerogel in the wood.

  14. Effects of Pictographs and Quoting on Flaming in Electronic Mail.

    Science.gov (United States)

    Thompsen, Philip A.; Foulger, Davis A.

    1996-01-01

    Examines the perception of flaming (hostile verbal behavior) in electronic mail by exploring, in the context of five escalating levels of socioemotional intensity, the effects of pictographs (typographic symbols used to express emotion) and quoting. Results suggest pictographs and quoting can vary in perceived intensity and meaning, depending on…

  15. Effect of hydrogen addition on autoignited methane lifted flames

    KAUST Repository

    Choin, Byung Chul

    2012-01-01

    Autoignited lifted flames in laminar jets with hydrogen-enriched methane fuels have been investigated experimentally in heated coflow air. The results showed that the autoignited lifted flame of the methane/hydrogen mixture, which had an initial temperature over 920 K, the threshold temperature for autoignition in methane jets, exhibited features typical of either a tribrachial edge or mild combustion depending on fuel mole fraction and the liftoff height increased with jet velocity. The liftoff height in the hydrogen-assisted autoignition regime was dependent on the square of the adiabatic ignition delay time for the addition of small amounts of hydrogen, as was the case for pure methane jets. When the initial temperature was below 920 K, where the methane fuel did not show autoignition behavior, the flame was autoignited by the addition of hydrogen, which is an ignition improver. The liftoff height demonstrated a unique feature in that it decreased nonlinearly as the jet velocity increased. The differential diffusion of hydrogen is expected to play a crucial role in the decrease in the liftoff height with increasing jet velocity.

  16. Effect of CH4–Air Ratios on Gas Explosion Flame Microstructure and Propagation Behaviors

    Directory of Open Access Journals (Sweden)

    Ying Zhang

    2012-10-01

    Full Text Available To reveal the inner mechanism of gas explosion dynamic behavior affected by gas equivalent concentration, a high speed Schlieren image system and flow field measurement technology was applied to record the gas explosion flame propagation and flame structure transition. The results show that a flame front structure transition occurs, followed by a flame accelerating propagation process. The laminar to turbulence transition was the essential cause of the flame structure changes. The laminar flame propagation behavior was influenced mainly by gas expansion and fore-compressive wave effect, while the turbulent flame speed mostly depended on turbulence intensity, which also played an important role in peak value of the explosive pressure and flame speed. On the condition that the laminar-turbulent transition was easier to form, the conclusion was drawn that, the lowest CH4 concentration for maximum overpressure can be obtained, which was the essential reason why the ideal explosive concentration differs under different test conditions.

  17. Study and modeling of finite rate chemistry effects in turbulent non-premixed flames

    Science.gov (United States)

    Vervisch, Luc

    1993-01-01

    The development of numerical models that reflect some of the most important features of turbulent reacting flows requires information about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between turbulent and chemical processes is so strong that it is extremely difficult to isolate the role played by one individual physical phenomenon. Direct numerical simulation (hereafter DNS) allows us to study in detail the turbulence-chemistry interaction in some restricted but completely defined situations. Globally, non-premixed flames are controlled by two limiting regimes: the fast chemistry case, where the turbulent flame can be pictured as a random distribution of local chemical equilibrium problems; and the slow chemistry case, where the chemistry integrates in time the turbulent fluctuations. The Damkoehler number, ratio of a mechanical time scale to chemical time scale, is used to distinguish between these regimes. Today most of the industrial computer codes are able to perform predictions in the hypothesis of local equilibrium chemistry using a presumed shape for the probability density function (pdt) of the conserved scalar. However, the finite rate chemistry situation is of great interest because industrial burners usually generate regimes in which, at some points, the flame is undergoing local extinction or at least non-equilibrium situations. Moreover, this variety of situations strongly influences the production of pollutants. To quantify finite rate chemistry effect, the interaction between a non-premixed flame and a free decaying turbulence is studied using DNS. The attention is focused on the dynamic of extinction, and an attempt is made to quantify the effect of the reaction on the small scale mixing process. The unequal diffusivity effect is also addressed. Finally, a simple turbulent combustion model based on the DNS observations and tractable in real flow configurations is proposed.

  18. Releasing effects in flame photometry: Determination of calcium

    Science.gov (United States)

    Dinnin, J.I.

    1960-01-01

    Strontium, lanthanum, neodymium, samarium, and yttrium completely release the flame emission of calcium from the depressive effects of sulfate, phosphate, and aluminate. Magnesium, beryllium, barium, and scandium release most of the calcium emission. These cations, when present in high concentration, preferentially form compounds with the depressing anions when the solution is evaporated rapidly in the flame. The mechanism of the interference and releasing effects is explained on the basis of the chemical equilibria in the evaporating droplets of solution and is shown to depend upon the nature of the compounds present in the aqueous phase of the solution. The need for background correction techniques is stressed. The releasing effect is used in the determination of calcium in silicate rocks without the need for separations.

  19. The dilution effect on the extinction of wall diffusion flame

    Directory of Open Access Journals (Sweden)

    Ghiti Nadjib

    2014-12-01

    Full Text Available The dynamic process of the interaction between a turbulent jet diffusion methane flame and a lateral wall was experimentally studied. The evolution of the flame temperature field with the Nitrogen dilution of the methane jet flame was examined. The interaction between the diffusion flame and the lateral wall was investigated for different distance between the wall and the central axes of the jet flame. The dilution is found to play the central role in the flame extinction process. The flame response as the lateral wall approaches from infinity and the increasing of the dilution rate make the flame extinction more rapid than the flame without dilution, when the nitrogen dilution rate increase the flame temperature decrease.

  20. Built-up Effect of Core Material for Microencapsulated Flame Retardant Containing Dimethyl Methyl Phosphate

    Institute of Scientific and Technical Information of China (English)

    LIN Miao; DONG Kai; YANG Yong

    2008-01-01

    The flame retardants containing organophosphorus compounds have extensively been used inthe flame retarding of polymer materials.Among others,dimethyl methyl phosphate (DMMP) was applied in flame retarding of polyurethane owmg to its so much merit.However,the water-soluble property of DMMP restricted its application in textile fabric.The flame retardtag systemcontainirm DMMP will be microencapsulated to form a novel flame retardant that could be used in textiles.We have studied the builtup effect of DMMP with some inorganic compounds to improve the afterflame and afterglow suppression in the flame retarding system.The experimeatal data indicated that inorganic compounds containing various non-metal elements P,N,B and metal ions Mg2+,Al3+,Ca2+,Zn2+,Cu2+,Mn4+ could be applied in flame retarding systems as additives to effectively suppress afterflame or afterglow.

  1. Synergistic effects of sepiolite on intumescent flame retardant polypropylene

    Directory of Open Access Journals (Sweden)

    2010-12-01

    Full Text Available In this paper, the effects of sepiolite as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene (PP/IFR were studied using the limiting oxygen index (LOI, the UL-94 test, thermogravimetric analysis (TGA, laser Raman spectroscopy (LRS, cone calorimeter test (CCT and scanning electron microscopy (SEM, and the IFR system mainly consisted of the ammonium polyphosphate modified with γ-aminopropyltriethoxysilane coupling agent, melamine and dipentaerythritol. The results from the LOI and UL 94 tests show that sepiolite added to the PP/IFR system has a synergistic flame retardant effects with the IFR system. The TGA results reveal that sepiolite enhances the thermal stability of the PP/IFR composite and increases the char residue formation. The cone calorimeter results indicate that the heat release rate, mass loss rate, total heat release and average specific extinction area of the PP/IFR/sepiolite composite decrease in comparison with the PP/IFR composite. The LRS measurements provide useful information on the carbonaceous microstructures. The morphological structures observed by SEM have demonstrated that sepiolite promote the formation of the reinforced and homogeneous char barrier on the surface of the composites. Simultaneously, the Young’s modulus and flexural modulus of the PP/IFR composites are also much better improved with the increase of sepiolite added.

  2. Beam steering effects in turbulent high pressure flames

    Energy Technology Data Exchange (ETDEWEB)

    Hemmerling, B.; Kaeppeli, B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The propagation of a laser beam through a flame is influenced by variations of the optical density. Especially in turbulent high pressure flames this may seriously limit the use of laser diagnostic methods. (author) 1 fig., 2 refs.

  3. Tulip flames: changes in shape of premixed flames propagating in closed tubes

    Science.gov (United States)

    Dunn-Rankin, D.; Sawyer, R. F.

    The experimental results that are the subject of this communication provide high-speed schlieren images of the closed-tube flame shape that has come to be known as the tulip flame. The schlieren images, along with in-chamber pressure records, help demonstrate the effects of chamber length, equivalence ratio, and igniter geometry on formation of the tulip flame. The pressure/time records show distinct features which correlate with flame shape changes during the transition to tulip. The measurements indicate that the basic tulip flame formation is a robust phenomenon that depends on little except the overall geometry of the combustion vessel.

  4. Flames in vortices & tulip-flame inversion

    Science.gov (United States)

    Dold, J. W.

    This article summarises two areas of research regarding the propagation of flames in flows which involve significant fluid-dynamical motion [1]-[3]. The major difference between the two is that in the first study the fluid motion is present before the arrival of any flame and remains unaffected by the flame [1, 2] while, in the second study it is the flame that is responsible for all of the fluid dynamical effects [3]. It is currently very difficult to study flame-motion in which the medium is both highly disturbed before the arrival of a flame and is further influenced by the passage of the flame.

  5. Microgravity Flame Spread in Exploration Atmospheres: Pressure, Oxygen, and Velocity Effects on Opposed and Concurrent Flame Spread

    Science.gov (United States)

    Olson, Sandra L.; Ruff, Gary A.; Fletcher, J. Miller

    2008-01-01

    Microgravity tests of flammability and flame spread were performed in a low-speed flow tunnel to simulate spacecraft ventilation flows. Three thin fuels were tested for flammability (Ultem 1000 (General Electric Company), 10 mil film, Nomex (Dupont) HT90-40, and Mylar G (Dupont) and one fuel for flame spread testing (Kimwipes (Kimberly-Clark Worldwide, Inc.). The 1g Upward Limiting Oxygen Index (ULOI) and 1g Maximum Oxygen Concentration (MOC) are found to be greater than those in 0g, by up to 4% oxygen mole fraction, meaning that the fuels burned in 0g at lower oxygen concentrations than they did using the NASA Standard 6001 Test 1 protocol. Flame spread tests with Kimwipes were used to develop correlations that capture the effects of flow velocity, oxygen concentration, and pressure on flame spread rate. These correlations were used to determine that over virtually the entire range of spacecraft atmospheres and flow conditions, the opposed spread is faster, especially for normoxic atmospheres. The correlations were also compared with 1g MOC for various materials as a function of pressure and oxygen. The lines of constant opposed flow agreed best with the 1g MOC trends, which indicates that Test 1 limits are essentially dictated by the critical heat flux for ignition. Further evaluation of these and other materials is continuing to better understand the 0g flammability of materials and its effect on the oxygen margin of safety.

  6. 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.

  7. Mechanism of the flame ionization detector. II. Isotope effects and heteroatom effects

    DEFF Research Database (Denmark)

    Holm, Torkil

    1997-01-01

    The relative molar flame ionization detecton (FID) response (RMR) for a hydrocarbon does not change when deuterium is substituted for hydrogen. The exception is methane for which an inverse deuterium effect of 3..5% is observed for tetradeuteriomethane. [13C]Methane shows an inverse isotope effect...... of 2%. The reason for the small or non-existent isotope effects is that H/2H exchange takes place in the pre-combustion hydrogenolysis in the flame. This was shown by taking samples from the lower part of the flame by means of a fused silica capillary probe. By the same technique the hydrogenolytic...... reactions in the hydrogen flame of compounds added to the hydrogen gas in low concentrations were followed. Alcohols, ethers, ketones, and esters all produced methane and carbon monoxide, while amines produced methane and hydrogen cyanide, halogen compounds methane and hydrogen halide, etc. The FID response...

  8. Characterization of acoustic effects on flame structures by beam deflection technique

    Energy Technology Data Exchange (ETDEWEB)

    Bedat, B.; Kostiuk, L.W.; Cheng, R.K.

    1993-10-01

    This work shows that the acoustic effects are the causes of the small amplitude flame wrinkling and movements seen in all the different gravitational conditions. The comparison between the acoustic velocity and beam deflection spectra for the two conditions studied (glass beads and fiber glass) demonstrates clearly this flame/acoustic coupling. This acoustic study shows that the burner behaves like a Helmholtz resonator. The estimated resonance frequency corresponds well to the experimental measurements. The fiber glass damps the level of the resonance frequency and the flame motion. The changes shown in normalized beam deflection spectra give further support of this damping. This work demonstrates that the acoustics has a direct influence on flame structure in the laminar case and the preliminary results in turbulent case also show a strong coupling. The nature of this flame/acoustic coupling are still not well understood. Further investigation should include determining the frequency limits and the sensitivity of the flame to acoustic perturbations.

  9. Recent Advances in Understanding of Thermal Expansion Effects in Premixed Turbulent Flames

    Science.gov (United States)

    Sabelnikov, Vladimir A.; Lipatnikov, Andrei N.

    2017-01-01

    When a premixed flame propagates in a turbulent flow, not only does turbulence affect the burning rate (e.g., by wrinkling the flame and increasing its surface area), but also the heat release in the flame perturbs the pressure field, and these pressure perturbations affect the turbulent flow and scalar transport. For instance, the latter effects manifest themselves in the so-called countergradient turbulent scalar flux, which has been documented in various flames and has challenged the combustion community for approximately 35 years. Over the past decade, substantial progress has been made in investigating (a) the influence of thermal expansion in a premixed flame on the turbulent flow and turbulent scalar transport within the flame brush, as well as (b) the feedback influence of countergradient scalar transport on the turbulent burning rate. The present article reviews recent developments in this field and outlines issues to be solved in future research.

  10. Effect of applied DC electric fields in flame spread over polyethylene-coated electrical wire

    KAUST Repository

    Jin, Young Kyu

    2011-03-01

    We experimentally investigated the effect of applied DC electric fields on the flame spread over polyethylene-coated electrical wire. The flame-spread rates over electrical wire with negative and positive DC electric fields from 0 to ±7 kV were measured and analyzed. We compared the results for DC electric fields with previous results for AC electric fields. We explored whether or not various flame shapes could be obtained with DC electric fields and the main reason for the flame-spread acceleration, particularly at the end of the electrical wire, for AC electric fields. We found that DC electric fields do not significantly affect the flame-spread rates. However, the flame shape is mildly altered by the ionic wind effect even for DC electric fields. The flame-spread rate is relevant to the flame shape and the slanted direction in spite of the mild impact. A possible explanation for the flame spread is given by a thermal-balance mechanism and fuel-vapor jet. © 2011 The Korean Society of Mechanical Engineers.

  11. Potential estrogenic effects of phosphorus-containing flame retardants.

    Science.gov (United States)

    Zhang, Quan; Lu, Meiya; Dong, Xiaowu; Wang, Cui; Zhang, Chunlong; Liu, Weiping; Zhao, Meirong

    2014-06-17

    As the substitute of polybrominated diphenyl ethers (PBDEs), further assessments about the potential ecological safety and health risks of phosphorus-containing flame retardants (PFRs) are required because the worldwide demand for PFRs has been increasing every year. In this study, we examined the agonistic/antagonistic activity of a group of PFRs by three in vitro models (luciferase reporter gene assay, yeast two-hybrid assay, and E-screen assay). Molecule docking was used to further explain the interactions between ERα and PFRs. Data from luciferase reporter gene analysis showed three members of the nine tested PFRs significantly induced estrogenic effects, with the order of TPP > TCP > TDCPP, while TCEP and TEHP have remarkable antiestrogenic properties with calculated REC20 and RIC20 values of 10(-6) M or lower. Results from the luciferase reporter gene method are generally consistent with results obtained from the yeast two-hybrid assay and E-screen, except for the positive estrogenic activity of TBP in E-screen testing. Docking results showed that binding between ligands and ERα was stabilized by hydrophobic interactions. As a proposed alternative for brominated flame retardant, PFRs may have anti/estrogenic activity via ERα at the low dose typical of residue in environmental matrix or animals. PFRs with a short chain, halogen, and benzene ring in the substituent group tend to be estrogenic. Our research suggests that comprehensive evaluations, including health and ecological assessments, are required in determining whether PFRs are preferable as an emerging industrial substitute.

  12. Effect of Intense Sound Waves on a Stationary Gas Flame

    Science.gov (United States)

    Hahnemann, H; Ehret, L

    1950-01-01

    Intense sound waves with a resonant frequency of 5000 cycles per second were imposed on a stationary propane-air flame issuing from a nozzle. In addition to a slight increase of the flame velocity, a fundamental change both in the shape of the burning zone and in the flow pattern could be observed. An attempt is made to explain the origin of the variations in the flame configuration on the basis of transition at the nozzle from jet flow to potential flow.

  13. The Effect of Noise on the Propagating Speed of Pre-mixed Laminar Flame Fronts

    CERN Document Server

    Liu, Hongliang

    2016-01-01

    We study the effect of thermal noise on the propagation speed of a planar flame. We show that this out of equilibrium greatly amplifies the effect of thermal noise to yield macroscopic reductions in the flame speed over what is predicted by the noise-free model. Computations show that noise slows the flame significantly. The flame is modeled using Navier Stokes equations with appropriate diffusive transport terms and chemical kinetic mechanism of hydrogen/oxygen. Thermal noise is modeled within the continuum framework using a system of stochastic partial differential equations, with transport noise from fluctuating hydrodynamics and reaction noise from a poisson model. We use a full chemical kinetics model in order to get quantitatively meaningful results. We compute steady and dynamic flames using an operator split finite volume scheme. New characteristic boundary conditions avoid non-physical boundary layers at computational boundaries. New limiters prevent stochastic terms from introducing non-physical neg...

  14. Effects of boundary layer on flame propagation generated by forced ignition behind an incident shock wave

    Science.gov (United States)

    Ishihara, S.; Tamura, S.; Ishii, K.; Kataoka, H.

    2016-09-01

    To study the effects of the boundary layer on the deflagration to detonation transition (DDT) process, the mixture behind an incident shock wave was ignited using laser breakdown. Ignition timing was controlled so that the interaction of the resulting flame with a laminar or turbulent boundary layer could be examined. In the case of the interaction with a laminar boundary layer, wrinkling of the flame was observed after the flame reached the corner of the channel. On the other hand, interaction with the turbulent boundary layer distorted the flame front and increased the spreading rate of the flame followed by prompt DDT. The inner structure of the turbulent boundary layer plays an important role in the DDT process. The region that distorted the flame within the turbulent boundary layer was found to be the intermediate region 0.01DDT was independent of the ignition position. The effect of the boundary layer on the propagating flame, thus, became relatively small after the accelerating flame was generated.

  15. Flame Retardant Effect of Aerogel and Nanosilica on Engineered Polymers

    Science.gov (United States)

    Williams, Martha K.; Smith, Trent M.; Roberson, Luke B.; Yang, Feng; Nelson, Gordon L.

    2010-01-01

    Aerogels are typically manufactured vIa high temperature and pressure-critical-point drying of a colloidal metal oxide gel filled with solvents. Aerogel materials derived from silica materials represent a structural morphology (amorphous, open-celled nanofoams) rather than a particular chemical constituency. Aerogel is not like conventional foams in that it is a porous material with extreme microporosity and composed of individual features only a few nanometers in length with a highly porous dendriticlike structure. This unique substance has unusual properties such as low thermal conductivity, refractive index and sound suppression; in addition to its exceptional ability to capture fast moving dust. The highly porous nature of the aerogel's structure provides large amounts of surface area per unit weight. For instance, a silica aerogel material with a density of 100 kilograms per cubic meters can have surface areas of around 800 to 1500 square meters per gram depending on the precursors and process utilized to produce it. To take advantage of the unique properties of silica aerogels, especially the ultra light weight and low thermal conductivity, their composites with various engineering polymers were prepared and their flammability was investigated by Cone Calorimetry. The flammability of various polystyrene/silica aerogel nanocomposites were measured. The combination of these nanocomposites with a NASA patented flame retardant SINK were also studied. The results were compared with the base polymer to show the differences between composites with different forms of silica.

  16. The Effects of Radiation Shield and Laser Heating on the Soot Formation and Oxidation of Diffusion Flame

    Science.gov (United States)

    Lee, Chun Beom; Shin, Hyun Dong

    The effects of radiation heat transfer on the soot formation and oxidation process in laminar diffusion flames have been studied experimentally using a “radiation shield” for an ethylene flame and a laser heating technique for propylene flames. The soot volume fraction of ethylene diffusion flames was measured for two different radiation boundary conditions. One is the “radiation shield” boundary condition (AL), established by placing the flame inside a highly polished aluminum cylinder, and the other is the fully absorbing radiation boundary condition (BB), obtained with a “black body cylinder enclosure”. The soot formation and oxidation processes are enhanced under the “radiation shield” boundary condition. A second set of experiments was conducted for propylene diffusion flames around the sooting conditions. A non-sooting flame can be converted to a sooting flame when a laser light heats up a flame at a height of 7mm above the burner (HAB), where soot particles are formed. On the contrary, a sooting flame can be changed to a non-sooting flame when the flame is heated with a laser light at 13mm HAB, where soot particles are oxidized. In this study, the absorbed amounts of radiation energy, the soot volume fraction, and the increased soot temperatures were measured.

  17. Experimental study on interference effect of rarefaction wave on laminar propagating flame

    Institute of Scientific and Technical Information of China (English)

    SUN Jinhua; LIU Yi; WANG Qingsong; CHEN Peng

    2005-01-01

    In order to study the interference effect of rarefaction wave on the laminar flame propagating structure and pressure characteristics of methane-air mixture, a small scale combustion chamber has been built. The techniques of high speed Schlieren photograph, pressure measurement and so on, are used to study the influence of rarefaction wave on the laminar flame propagating through methane-air mixture. The results show that, after the rarefaction wave acts on the propagation laminar flame, the laminar combustion is fully transformed into turbulent combustion just during several milliseconds, which leads to a sharp increase in the burning surface area and the pressure rise rate.

  18. Experimental Study of Electrodes Parameters Effects on Small Diffusion Combustion Flame

    Institute of Scientific and Technical Information of China (English)

    Yiting Zhang

    2015-01-01

    To study the configuration and conductivity effects on micro⁃scale methane⁃air flames by electric field and iron wind, different electric field forces and iron winds are generated by needle, circle and plate electrodes respectively in different electrodes heights under both AC and DC fields though experiments. Experimental results showed that the flame characteristics are affected by needle electrodes mainly through the action of ion wind, by plate type electrodes mainly through the action of electric field force and by annular electrodes through both the electric field force and ion wind at the same time. Under DC field ’ s effects of all electrodes types, the flame will consequently go down while the voltage reached to a limit value, and it will breakdown under the strong effect of the ion wind by needle electrodes. The results also showed the influence by different electrodes types to the current characteristics, resistance properties and configuration of themicro⁃scale flames.

  19. Synergistic Study on the Effect of Flame Retardants on Timber

    Directory of Open Access Journals (Sweden)

    Nwajiobi, C.C

    2015-12-01

    Full Text Available the fire characteristic proportion of Halleacilliata has been carried out. The timber was treated with different concentrations of ammonium chloride (0.01, 0.05, 0.10, 0.15, 0.50, and 0.55 mol/dm3 and borax (0.01, 0.03, 0.05, 0.07, 0.10, and 0.12 mol/dm3 . Flammability tests such as ignition time, flame propagation rate and after-glow time were carried out and the results showed that the flame retardants drastically reduced the flame propagation rate and after-glow time while ignition time and percentage add-on (% increased. Synergy was observed when the two flame retardants were mixed at different concentrations which gave better retarding properties than when treated individually. These results are interpreted as arising from the fact that on heating, these flame retardants evolve molecules that interfere with the chemistry and pyrolysis of combustion of timber.

  20. Effect of water on carbon monoxide-oxygen flame velocity

    Science.gov (United States)

    Mcdonald, Glen E

    1954-01-01

    The flame velocities were measured of 20 percent oxygen and 80 percent carbon monoxide mixtures containing either light water or heavy water. The flame velocity increased from 34.5 centimeters per second with no added water to about 104 centimeters per second for a 1.8 percent addition of light water and to 84 centimeters per second for an equal addition of heavy water. The addition of heavy water caused greater increases in flame velocity with equilibrium hydrogen-atom concentration than would be predicted by the Tanford and Pease square-root relation. The ratio of the flame velocity of a mixture containing light water to that of a mixture containing heavy water was found to be 1.4. This value is the same as the ratio of the reaction rate of hydrogen to that of deuterium and oxygen. A ratio of reaction rates of 1.4 would also be required for the square-root law to give the observed ratio of flame-velocity changes.

  1. Androgens Exert a Cysticidal Effect upon Taenia crassiceps by Disrupting Flame Cell Morphology and Function.

    Directory of Open Access Journals (Sweden)

    Javier R Ambrosio

    Full Text Available The effects of testosterone (T4 and dihydrotestosterone (DHT on the survival of the helminth cestode parasite Taenia crassiceps, as well as their effects on actin, tubulin and myosin expression and their assembly into the excretory system of flame cells are described in this paper. In vitro evaluations on parasite viability, flow cytometry, confocal microscopy, video-microscopy of live flame cells, and docking experiments of androgens interacting with actin, tubulin, and myosin were conducted. Our results show that T4 and DHT reduce T. crassiceps viability in a dose- and time-dependent fashion, reaching 90% of mortality at the highest dose used (40 ng/ml and time exposed (10 days in culture. Androgen treatment does not induce differences in the specific expression pattern of actin, tubulin, and myosin isoforms as compared with control parasites. Confocal microscopy demonstrated a strong disruption of the parasite tegument, with reduced assembly, shape, and motion of flame cells. Docking experiments show that androgens are capable of affecting parasite survival and flame cell morphology by directly interacting with actin, tubulin and myosin without altering their protein expression pattern. We show that both T4 and DHT are able to bind actin, tubulin, and myosin affecting their assembly and causing parasite intoxication due to impairment of flame cell function. Live flame cell video microscopy showing a reduced motion as well changes in the shape of flame cells are also shown. In summary, T4 and DHT directly act on T. crassiceps cysticerci through altering parasite survival as well as the assembly and function of flame cells.

  2. Androgens Exert a Cysticidal Effect upon Taenia crassiceps by Disrupting Flame Cell Morphology and Function.

    Science.gov (United States)

    Ambrosio, Javier R; Valverde-Islas, Laura; Nava-Castro, Karen E; Palacios-Arreola, M Isabel; Ostoa-Saloma, Pedro; Reynoso-Ducoing, Olivia; Escobedo, Galileo; Ruíz-Rosado, Azucena; Dominguez-Ramírez, Lenin; Morales-Montor, Jorge

    2015-01-01

    The effects of testosterone (T4) and dihydrotestosterone (DHT) on the survival of the helminth cestode parasite Taenia crassiceps, as well as their effects on actin, tubulin and myosin expression and their assembly into the excretory system of flame cells are described in this paper. In vitro evaluations on parasite viability, flow cytometry, confocal microscopy, video-microscopy of live flame cells, and docking experiments of androgens interacting with actin, tubulin, and myosin were conducted. Our results show that T4 and DHT reduce T. crassiceps viability in a dose- and time-dependent fashion, reaching 90% of mortality at the highest dose used (40 ng/ml) and time exposed (10 days) in culture. Androgen treatment does not induce differences in the specific expression pattern of actin, tubulin, and myosin isoforms as compared with control parasites. Confocal microscopy demonstrated a strong disruption of the parasite tegument, with reduced assembly, shape, and motion of flame cells. Docking experiments show that androgens are capable of affecting parasite survival and flame cell morphology by directly interacting with actin, tubulin and myosin without altering their protein expression pattern. We show that both T4 and DHT are able to bind actin, tubulin, and myosin affecting their assembly and causing parasite intoxication due to impairment of flame cell function. Live flame cell video microscopy showing a reduced motion as well changes in the shape of flame cells are also shown. In summary, T4 and DHT directly act on T. crassiceps cysticerci through altering parasite survival as well as the assembly and function of flame cells.

  3. Androgens Exert a Cysticidal Effect upon Taenia crassiceps by Disrupting Flame Cell Morphology and Function

    Science.gov (United States)

    Ambrosio, Javier R.; Valverde-Islas, Laura; Nava-Castro, Karen E.; Palacios- Arreola, M. Isabel; Ostoa-Saloma, Pedro; Reynoso-Ducoing, Olivia; Escobedo, Galileo; Ruíz-Rosado, Azucena; Dominguez-Ramírez, Lenin; Morales-Montor, Jorge

    2015-01-01

    The effects of testosterone (T4) and dihydrotestosterone (DHT) on the survival of the helminth cestode parasite Taenia crassiceps, as well as their effects on actin, tubulin and myosin expression and their assembly into the excretory system of flame cells are described in this paper. In vitro evaluations on parasite viability, flow cytometry, confocal microscopy, video-microscopy of live flame cells, and docking experiments of androgens interacting with actin, tubulin, and myosin were conducted. Our results show that T4 and DHT reduce T. crassiceps viability in a dose- and time-dependent fashion, reaching 90% of mortality at the highest dose used (40 ng/ml) and time exposed (10 days) in culture. Androgen treatment does not induce differences in the specific expression pattern of actin, tubulin, and myosin isoforms as compared with control parasites. Confocal microscopy demonstrated a strong disruption of the parasite tegument, with reduced assembly, shape, and motion of flame cells. Docking experiments show that androgens are capable of affecting parasite survival and flame cell morphology by directly interacting with actin, tubulin and myosin without altering their protein expression pattern. We show that both T4 and DHT are able to bind actin, tubulin, and myosin affecting their assembly and causing parasite intoxication due to impairment of flame cell function. Live flame cell video microscopy showing a reduced motion as well changes in the shape of flame cells are also shown. In summary, T4 and DHT directly act on T. crassiceps cysticerci through altering parasite survival as well as the assembly and function of flame cells. PMID:26076446

  4. Effect of Amino alcohol functionalized polyethylene as compatibilizer for LDPE/EVA/clay/flame-retardant nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Lujan-Acosta, R. [Centro de Investigación en Química Aplicada, Blvd Enrique Reyna 140, Saltillo, Coahuila 25294 (Mexico); Sánchez-Valdes, S., E-mail: saul.sanchez@ciqa.edu.mx [Centro de Investigación en Química Aplicada, Blvd Enrique Reyna 140, Saltillo, Coahuila 25294 (Mexico); Ramírez-Vargas, E., E-mail: eduardo.ramirez@ciqa.edu.mx [Centro de Investigación en Química Aplicada, Blvd Enrique Reyna 140, Saltillo, Coahuila 25294 (Mexico); Ramos-DeValle, L.F.; Espinoza-Martinez, A.B.; Rodriguez-Fernandez, O.S. [Centro de Investigación en Química Aplicada, Blvd Enrique Reyna 140, Saltillo, Coahuila 25294 (Mexico); Lozano-Ramirez, T. [Instituto Tecnologico de Cd. Madero, Juventino Rosas Col. Los Mangos, Cd. Madero, Tamaulipas 89440 (Mexico); Lafleur, P.G. [Ecole Polytechnique de Montreal, Chemical Engineering Department, P.O. Box 6079, Stn Centre-Ville, Montreal, Quebec H3C 3A7 (Canada)

    2014-08-01

    The synergistic effect of organo-modified montmorillonite (Nanomer I28E and Cloisite 20A) and metal hydroxides (magnesium hydroxide MH and alumina trihydrate ATH) as flame retardants in LDPE/EVA nanocomposites compatibilized with amino alcohol grafted polyethylene (PEgDMAE) was studied. Morphological characterization of nanocomposites was carried out by means of X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). Flame-retardant properties of nanocomposites were evaluated by the UL-94 horizontal burning and cone calorimeter tests and limiting oxygen index (LOI). Thermal degradation behavior was analyzed with a Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR). The XRD analysis showed a displacement of the d{sub 001} plane characteristic peak of clay to lower angles, which indicates an intercalated–exfoliated morphology. From STEM images it was observed a good dispersion of flame retardants (MH and ATH) throughout the polymer matrix which was reflected in flame-retardant properties. TG-FTIR showed a better thermal stability of nanocomposites and the gases evolved during combustion showed an important reduction. Based on thermal stability and thermal degradation results, the flame-retardant mechanism of LDPE/PEgDMAE/EVA/Clay/MH nanocomposites was proposed. - Highlights: • We evaluated the synergistic effect of MMT clay and nano-metallic hydroxides for wire coating applications. • We analyzed the using of a new type of polymer-inorganic compatibilizer. • We proposed a new flame-retardant mechanism for polymer blends/Clay/MH nanocomposites.

  5. Cost Effective Approaches to Impart Flame Resistance to Cotton Nonwovens

    Science.gov (United States)

    Recent changes in the flammability laws require improvements in the flame resistance of cotton-containing consumer goods such as upholstered furniture, mattresses, and pillows. Cotton, synthetic fibers, fabrics, and foam are the basic constituents of these goods, often the first to engulf by a fire....

  6. Effects of direct-current electric fields on flame shape and combustion characteristics of ethanol in small scale

    Directory of Open Access Journals (Sweden)

    Yunhua Gan

    2016-01-01

    Full Text Available The aim of this work is to investigate the effects of direct-current electric fields on the behavior of the small-scale diffusion ethanol flame. The flow rate of liquid ethanol, the flame temperatures, and the flame shapes were measured. The results showed that the stable working ranges of a small-scale combustor became narrower under the direct-current electric field. The main reason was that the evaporation velocity of liquid ethanol limited by great heat loss effect cannot keep up with the increasing of combustion velocity by the ionic wind effect. The movements of those charged particles in flame enhanced the combustion process, resulting in higher flame temperatures under positive or negative direct-current electric field. The flame heights decreased with increasing applied voltages, due to the ionic wind effect increasing the flame temperature and the diffusivity. The flame voltage–current characteristic was also examined. Three regions can be divided: the subsaturation region, the saturation region, and the supersaturation region. Finally, the ratios of electric active power to actual burning thermal power of ethanol flame were calculated. It can be inferred that using the external direct-current electric field with little power consumption to control combustion and flame is a feasible method.

  7. Effects of gravity on structure and entropy generation of confined laminar diffusion flames

    Energy Technology Data Exchange (ETDEWEB)

    Datta, A. [Department of Power Engineering, Jadvapur University, Salt Lake Campus, Kolkata 700098 (India)

    2005-05-01

    A numerical prediction of a confined, co-flowing, laminar jet diffusion flame has been made to find the flow and scalar variables under steady state condition. These variables are used for the description of the flame structure and the evaluation of entropy generation rate and the rate of exergy loss. The exergy loss is compared against the exergy coming in, to evaluate the second law efficiency of the combustion process. The model is applied for diffusion flames in a confined geometry at various gravity levels to find the effect of gravity on the rate of entropy generation and second law efficiency. In general, the flame becomes wider in shape at reduced gravity. A correlation of the flame width against Froude number over a wide gravity range has been proposed. It is observed from the local volumetric entropy generation rate that a diffusion flame is more intense at its base than at the tip. The intensity of the flame becomes less at reduced gravity because of the lower rate of entrainment of oxygen. The entropy generation rate due to heat transfer increases considerably at normal gravity compared to that at zero gravity, because of the thermal stratification of the flow under the influence of buoyant acceleration. The rate of entropy generation due to chemical reaction and mass transfer remain almost unaltered at all gravity levels. The lowering of the total entropy generation rate and the corresponding exergy destruction increases the second law efficiency of a confined diffusion flame at reduced gravity compared to that at normal gravity. (authors)

  8. THE SYNERGISTIC EFFECT OF HYBRID FLAME RETARDANTS ON PYROLYSIS BEHAVIOUR OF HYBRID COMPOSITE MATERIALS

    Directory of Open Access Journals (Sweden)

    M. T. ALBDIRY

    2012-06-01

    Full Text Available The aim of this investigation is to comprehensively understand the polymeric composite behavior under direct fire sources. The synergistic effects of hybrid flame retardant material on inhabiting the pyrolysis of hybrid reinforced fibers, woven roving (0°- 45° carbon and kevlar (50/50 wt/wt, and an araldite resin composites were studied. The composites were synthesised and coated primarily by zinc borate (2ZnO.3B2O3.3.5H2O and modified by antimony trioxide (Sb2O3 with different amounts (10-30 wt% of flame retardant materials. In the experiments, the composite samples were exposed to a direct flame source generated by oxyacetylene flame (~3000ºC at variable exposure distances of 10-20 mm. The synergic flame retardants role of antimony trioxide and zinc borate on the composite surface noticeably improves the flame resistance of the composite which is attributed to forming a protective mass and heat barrier on the composite surface and increasing the melt viscosity.

  9. PROMOTION EFFECT OF MELAMINE ON FLAME RETARDANCY OF EPOXY RESINS CONTAINING CAGED BICYCLIC PHOSPHATE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Caged bicyclic phosphate (CBP) and its dimelamine salt (PDS) were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index (LOI) and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS,although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER < PDS30/ER < PDS15/ER < CBP15/ER, whereas that of specific extinction area is CBP15/ER > CBP30/ER > PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses (TG) and Fourier transform infrared spectroscopy (FT-IR), it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy (SEM), a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species.Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.

  10. A PAH growth mechanism and synergistic effect on PAH formation in counterflow diffusion flames

    KAUST Repository

    Wang, Yu

    2013-09-01

    A reaction mechanism having molecular growth up to benzene for hydrocarbon fuels with up to four carbon-atoms was extended to include the formation and growth of polycyclic aromatic hydrocarbons (PAHs) up to coronene (C24H12). The new mechanism was tested for ethylene premixed flames at low (20torr) and atmospheric pressures by comparing experimentally observed species concentrations with those of the computed ones for small chemical species and PAHs. As compared to several existing mechanisms in the literature, the newly developed mechanism showed an appreciable improvement in the predicted profiles of PAHs. The new mechanism was also used to simulate PAH formation in counterflow diffusion flames of ethylene to study the effects of mixing propane and benzene in the fuel stream. In the ethylene-propane flames, existing experimental results showed a synergistic effect in PAH concentrations, i.e. PAH concentrations first increased and then decreased with increasing propane mixing. This PAH behavior was successfully captured by the new mechanism. The synergistic effect was predicted to be more pronounced for larger PAH molecules as compared to the smaller ones, which is in agreement with experimental observations. In the experimental study in which the fuel stream of ethylene-propane flames was doped with benzene, a synergistic effect was mitigated for benzene, but was observed for large PAHs. This effect was also predicted in the computed PAH profiles for these flames. To explain these responses of PAHs in the flames of mixture fuels, a pathway analysis has been conducted, which show that several resonantly stabilized species as well as C4H4 and H atom contribute to the enhanced synergistic behaviors of larger PAHs as compared to the small ones in the flames of mixture fuels. © 2013 The Combustion Institute.

  11. EFFECT OF OXYGEN PLASMA PRETREATMENT AND TITANIUM DIOXIDE OVERLAY COATING ON FLAME RETARDANT FINISHED COTTON FABRICS

    Directory of Open Access Journals (Sweden)

    Yin Ling Lam

    2011-03-01

    Full Text Available Flammability properties of plasma pretreated cotton fabrics subjected to flame-retardant treatment were studied. Plasma pretreatment, using an atmospheric pressure plasma jet (APPJ, was applied to cotton fabrics to enhance material properties, while retaining inherent advantages of the substrates. An organic phosphorus compound (flame-retardant agent, FR together with a melamine resin (crosslinking agent, CL and phosphoric acid (catalyst, PA were used. Titanium dioxide (TiO2 or nano-TiO2 was used as a co-catalyst for cotton fabrics to improve treatment effectiveness and minimize side effects. Surface morphology of plasma pretreated cotton specimens subjected to flame-retardant treatment showed a roughened and wrinkled fabric surface with high deposition of the finishing agent, caused by an etching effect of plasma and attack of acidic FR. Combustibility of FR-CL-PA-TiO2 and FR-CL-PA-Nano-TiO2 treated fabrics was evaluated by a 45° flammability test. FR-CL-PA-treated specimens showed superior flame-retardancy, which was further improved by plasma pretreatment and addition of metal oxide as a co-catalyst. However, in comparison with the control sample, flame-retardant-treated cotton specimens had lower breaking load and tearing strength, resulting from side effects of the crosslinking agent used, while plasma pretreatment might compensate for the reduction in tensile strength caused by flame-retardant agents. In addition, both plasma pretreatment and metal oxide co-catalyst added in the flame-retardant finishing improved the crosslinking process between FR and cotton fabric, minimizing formation of free formaldehyde and allowing the use of FR in industry.

  12. Synergistic effects of iron powder on intumescent flame retardant polypropylene system

    Directory of Open Access Journals (Sweden)

    2009-06-01

    Full Text Available The effects of iron powder as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene composites (IFR-PP were studied. The thermogravimetric analysis (TGA and cone calorimeter (CONE were used to evaluate the synergistic effects of iron powder (Fe. The TGA data showed that Fe could enhance the thermal stability of the IFR-PP systems at high temperature and effectively increase the char residue formation. The CONE results revealed that Fe and IFR could clearly change the decomposition behavior of PP and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate (HRR, mass loss (ML, Mass loss rate (MLR, total heat release (THR, carbon monoxide and so on. Thus, a suitable amount of Fe plays a synergistic effect in the flame retardancy of IFR composites.

  13. Effects of Electric Field on the SHS Flame Propagation of the Si-C System, Examined by the Use of the Heterogeneous Theory

    Directory of Open Access Journals (Sweden)

    Atsushi Makino

    2013-01-01

    Full Text Available Relevant to the self-propagating high-temperature synthesis (SHS process, an analytical study has been conducted to investigate the effects of electric field on the combustion behavior because the electric field is indispensable for systems with weak exothermic reactions to sustain flame propagation. In the present study, use has been made of the heterogeneous theory which can satisfactorily account for the premixed mode of the bulk flame propagation supported by the nonpremixed mode of particle consumption. It has been confirmed that, even for the SHS flame propagation under electric field, being well recognized to be facilitated, there exists a limit of flammability, due to heat loss, as is the case for the usual SHS flame propagation. Since the heat loss is closely related to the representative sizes of particles and compacted specimen, this identification provides useful insight into manipulating the SHS flame propagation under electric field, by presenting appropriate combinations of those sizes. A fair degree of agreement has been demonstrated through conducting an experimental comparison, as far as the trend and the approximate magnitude are concerned, suggesting that an essential feature has been captured by the present study.

  14. Effect of Soret diffusion on lean hydrogen/air flames at normal and elevated pressure and temperature

    KAUST Repository

    Zhou, Zhen

    2017-04-12

    The influence of Soret diffusion on lean premixed flames propagating in hydrogen/air mixtures is numerically investigated with a detailed chemical and transport models at normal and elevated pressure and temperature. The Soret diffusion influence on the one-dimensional (1D) flame mass burning rate and two-dimensional (2D) flame propagating characteristics is analysed, revealing a strong dependency on flame stretch rate, pressure and temperature. For 1D flames, at normal pressure and temperature, with an increase of Karlovitz number from 0 to 0.4, the mass burning rate is first reduced and then enhanced by Soret diffusion of H2 while it is reduced by Soret diffusion of H. The influence of Soret diffusion of H2 is enhanced by pressure and reduced by temperature. On the contrary, the influence of Soret diffusion of H is reduced by pressure and enhanced by temperature. For 2D flames, at normal pressure and temperature, during the early phase of flame evolution, flames with Soret diffusion display more curved flame cells. Pressure enhances this effect, while temperature reduces it. The influence of Soret diffusion of H2 on the global consumption speed is enhanced at elevated pressure. The influence of Soret diffusion of H on the global consumption speed is enhanced at elevated temperature. The flame evolution is more affected by Soret diffusion in the early phase of propagation than in the long run due to the local enrichment of H2 caused by flame curvature effects. The present study provides new insights into the Soret diffusion effect on the characteristics of lean hydrogen/air flames at conditions that are relevant to practical applications, e.g. gas engines and turbines.

  15. Experimental study on the effects of AC electric fields on flame spreading over polyethylene-insulated electric-wire

    KAUST Repository

    Jin, Young Kyu

    2010-11-01

    In this present study, we experimentally investigated the effects of electric fields on the characteristics of flames spreading over electric-wires with AC fields. The dependence of the rate at which a flame spreads over polyethylene-insulated wires on the frequency and amplitude of the applied AC electric field was examined. The spreading of the flame can be categorized into linear spreading and non-linearly accelerated spreading of flame. This categorization is based on the axial distribution of the field strength of the applied electric field. The rate at which the flame spreads is highly dependent on the inclined direction of the wire fire. It could be possible to explain the spreading of the flame on the basis of thermal balance. © 2010 The Korean Society of Mechanical Engineers.

  16. Effect of Fuel Composition on the Response of an Acoustically Forced Flat Flame

    Science.gov (United States)

    Gorski, Jan

    Interest in alternative fuels for power generation is growing, yet these fuels bring new challenges to gas turbine design and operation. Among these challenges are combustor operability issues, highlighted by problems with combustion instabilities. For this thesis, a fundamental study of the effects of fuel composition on combustion dynamics was undertaken. An acoustically forced flat flame burner was constructed, allowing measurement of the flame transfer function (FTF) relating acoustic perturbations to heat release rate fluctuations in the flame. Tests were done using methane, along with simulated syngas and biogas fuel mixtures over a variety of operating conditions. Large variations in methane concentration had a significant impact on the FTF, while variations in the hydrogen to carbon monoxide ratio did not impact the FTF in fuel mixtures of equal parts methane and syngas. The Strouhal number was found to be an important parameter in predicting phase response independent of the fuel type. Flame liftoff distance and fuel composition were the key parameters determining the peak FTF magnitude. A hypothesis on the role of the non-adiabatic nature of the flat flame and thermal-diffusive effects on the trends in peak FTF magnitude is presented and discussed.

  17. DNS investigation of differential-diffusion effects on temporarily evolving turbulent diffusion flames

    Science.gov (United States)

    Almagro, Antonio; Garcia-Villalba, Manuel; Flores, Oscar; Sanchez, Antonio L.

    2016-11-01

    The peak temperature of nonpremixed flames is known to have a profound effect on kinetically controlled processes with a strong temperature dependence, such as strain-induced extinction and NOx production. Here, the influence of differential diffusion on the flame temperature in diffusion-controlled combustion is investigated by direct numerical simulations of a turbulent diffusion flame in a temporarily evolving mixing layer for non-unity Lewis numbers of the fuel. The problem is formulated in the limit of infinitely fast combustion in terms of Shvab-Zel'dovich conserved scalars, not changed directly by the reactions, obtained through chemistry-free linear combinations of the temperature and reactant mass fractions. A previously developed low-Mach-number code is used in the numerical integrations, which consider values of the thermochemical parameters - characterizing the exothermicity and stoichiometry of diffusion-controlled combustion - and fuel Lewis number typical of hydrogen-air and hydrocarbon-air flames. The results of the simulations are used to asses the effect of turbulence and fuel diffusivity on the flame response. This work was funded by the Spanish MCININ under project CSD2010-00011. The computational resources were provided by the XSEDE program, supported by NSF Grant Number ACI-1053575.

  18. Propagation Limits of High Pressure Cool Flames

    Science.gov (United States)

    Ju, Yiguang

    2016-11-01

    The flame speeds and propagation limits of premixed cool flames at elevated pressures with radiative heat loss are numerically modelled using dimethyl ether mixtures. The primary focus is paid on the effects of pressure, mixture dilution, flame size, and heat loss on cool flame propagation. The results showed that cool flames exist on both fuel lean and fuel rich sides and thus dramatically extend the lean and rich flammability limits. There exist three different flame regimes, hot flame, cool flame, and double flame. A new flame flammability diagram including both cool flames and hot flames is obtained at elevated pressure. The results show that pressure significantly changes cool flame propagation. It is found that the increases of pressure affects the propagation speeds of lean and rich cool flames differently due to the negative temperature coefficient effect. On the lean side, the increase of pressure accelerates the cool flame chemistry and shifts the transition limit of cool flame to hot flame to lower equivalence ratio. At lower pressure, there is an extinction transition from hot flame to cool flame. However, there exists a critical pressure above which the cool flame to hot flame transition limit merges with the lean flammability limit of the hot flame, resulting in a direct transition from hot flame to cool flame. On the other hand, the increase of dilution reduces the heat release of hot flame and promotes cool flame formation. Moreover, it is shown that a smaller flame size and a higher heat loss also extend the cool flame transition limit and promote cool flame formation.

  19. High-Speed Turbulent Reacting Flows: Intrinsic Flame Instability and its Effects on the Turbulent Cascade

    Science.gov (United States)

    Poludnenko, Alexei

    2016-11-01

    Turbulent reacting flows are pervasive both in our daily lives on Earth and in the Universe. They power modern society being at the heart of many energy generation and propulsion systems, such as gas turbines, internal combustion and jet engines. On astronomical scales, thermonuclear turbulent flames are the driver of some of the most powerful explosions in the Universe, knows as Type Ia supernovae. Despite this ubiquity in Nature, turbulent reacting flows still pose a number of fundamental questions often exhibiting surprising and unexpected behavior. In this talk, we will discuss several such phenomena observed in direct numerical simulations of high-speed, premixed, turbulent flames. We show that turbulent flames in certain regimes are intrinsically unstable even in the absence of the surrounding combustor walls or obstacles, which can support the thermoacoustic feedback. Such instability can fundamentally change the structure and dynamics of the turbulent cascade, resulting in a significant (and anisotropic) redistribution of kinetic energy from small to large scales. In particular, three effects are observed. 1) The turbulent burning velocity can develop pulsations with significant peak-to-peak amplitudes. 2) Unstable burning can result in pressure build-up and the formation of pressure waves or shocks when the flame speed approaches or exceeds the speed of a Chapman-Jouguet deflagration. 3) Coupling of pressure and density gradients across the flame can lead to the anisotropic generation of turbulence inside the flame volume and flame acceleration. We extend our earlier analysis, which relied on a simplified single-step reaction model, by demonstrating existence of these effects in realistic chemical flames (hydrogen and methane) and in thermonuclear flames in degenerate, relativistic plasmas found in stellar interiors. Finally, we discuss the implications of these results for subgrid-scale LES combustion models. This work was supported by the Air Force

  20. Experimental Observations on a Low Strain Counter-Flow Diffusion Flame: Flow and Bouyancy Effects

    Science.gov (United States)

    Sutula, J. A.; Torero, J. L.; Ezekoye, O. A.

    1999-01-01

    Diffusion flames are of great interest in fire safety and many industrial processes. The counter-flow configuration provides a constant strain flow, and therefore is ideal to study the structure of diffusion flames. Most studies have concentrated on the high velocity, high strain limit, since buoyantly induced instabilities will disintegrate the planar flame as the velocity decreases. Only recently, experimental studies in microgravity conditions have begun to explore the low strain regimes. Numerical work has shown the coupling between gas phase reaction rates, soot reaction rates, and radiation. For these programs, size, geometry and experimental conditions have been chosen to keep the flame unaffected by the physical boundaries. When the physical boundaries can not be considered infinitely far from the reaction zone discrepancies arise. A computational study that includes boundary effects and accounts for the deviations occurring when the major potential flow assumptions are relaxed was presented by Borlik et al. This development properly incorporates all heat loss terms and shows the possibility of extinction in the low strain regime. A major constraint of studying the low strain regime is buoyancy. Buoyant instabilities have been shown to have a significant effect on the nature of reactants and heat transport, and can introduce instabilities on the flow that result in phenomena such as flickering or fingering. The counter-flow configuration has been shown to provide a flame with no symmetry disrupting instabilities for inlet velocities greater than 50 mm/s. As the velocity approaches this limit, the characteristic length of the experiment has to be reduced to a few millimetres so as to keep the Rayleigh number (Ra(sub L) = (Beta)(g(sub 0))(L(exp 3) del T)/(alpha(v))) below 2000. In this work, a rectangular counter-flow burner was used to study a two-dimensional counter-flow diffusion flame. Flow visualisation and Particle Image Velocimetry served to describe

  1. 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

  2. Large Eddy Simulation Of Gravitational Effects In Transitional And Turbulent Gas-Jet Diffusion Flames

    Science.gov (United States)

    Jaberi, Farhad A.; Givi, Peyman

    2003-01-01

    The influence of gravity on the spatial and the compositional structures of transitional and turbulent hydrocarbon diffusion flames are studies via large eddy simulation (LES) and direct numerical simulation (DNS) of round and planar jets. The subgrid-scale (SGS) closures in LES are based on the filtered mass density function (FMDF) methodology. The FMDF represents the joint probability density function (PDF) of the SGS scalars, and is obtained by solving its transport equation. The fundamental advantage of LES/FMDF is that it accounts for the effects of chemical reaction and buoyancy exactly. The methodology is employed for capturing some of the fundamental influences of gravity in equilibrium flames via realistic chemical kinetic schemes. Some preliminary investigation of the gravity effects in non-equilibrium flames is also conducted, but with idealized chemical kinetics models.

  3. Effect of ac electric fields on counterflow diffusion flame of methane

    KAUST Repository

    Chul Choi, Byung

    2012-08-01

    The effect of electric fields on the response of diffusion flames in a counterflow has been investigated experimentally by varying the AC voltage and frequency. The result showed that the flame was stationary with high AC frequency above the threshold frequency, and it increased with the applied voltage and then leveled off at 35 Hz. Below the threshold frequency, however, the flame oscillated with a frequency that was synchronized with the applied AC frequency. This oscillation can be attributed to the ionic wind effect due to the generation of bulk flow, which arises from the momentum transfer by molecular collisions between neutral molecules and ions, where the ions in the reaction zone were accelerated by the Lorentz force. © 2012 The Korean Society of Mechanical Engineers.

  4. The effects of buoyancy on turbulent nonpremixed jet flames in crossflow

    Science.gov (United States)

    Boxx, Isaac G.

    An experimental research study was conducted to investigate what effect buoyancy had on the mean and instantaneous flow-field characteristics of turbulent jet-flames in crossflow (JFICF). The study used an experimental technique wherein a series of normal-gravity, hydrogen-diluted propane JFICF were compared with otherwise identical ones in low-gravity. Experiments were conducted at the University of Texas Drop Tower Facility, a new microgravity science laboratory built for this study at the University of Texas at Austin. Two different diagnostic techniques were employed, high frame-rate digital cinematographic imaging and planar laser Mie scattering (PLMS). The flame-luminosity imaging revealed significant elongation and distortion of the large-scale luminous structure of the JFICF. This was seen to affect the flametip oscillation and burnout characteristics. Mean and root-mean-square (RMS) images of flame-luminosity were computed from the flame-luminosity image sequences. These were used to compare visible flame-shapes, flame chord-lengths and jet centerline-trajectories of the normal- and low-gravity flames. In all cases the jet-centerline penetration and mean luminous flame-width were seen to increase with decreasing buoyancy. The jet-centerline trajectories for the normal-gravity flames were seen to behave differently to those of the low-gravity flames. This difference led to the conclusion that the jet transitions from a momentum-dominated forced convection limit to a buoyancy-influenced regime when it reaches xiC ≈ 3, where xiC is the Becker and Yamazaki (1978) buoyancy parameter based on local flame chord-length. The mean luminous flame-lengths showed little sensitivity to buoyancy or momentum flux ratio. Consistent with the flame-luminosity imaging experiments, comparison of the instantaneous PLMS flow-visualization images revealed substantial buoyancy-induced elongation and distortion of the large-scale shear-layer vortices in the flow. This effect

  5. Effects of electric field on micro-scale flame properties of biobutanol fuel

    Science.gov (United States)

    Xu, Tao; Chen, Qinglin; Zhang, Bingjian; Lu, Shushen; Mo, Dongchuan; Zhang, Zhengguo; Gao, Xuenong

    2016-09-01

    With the increasing need of smaller power sources for satellites, energy systems and engine equipment, microcombustion pose a potential as alternative power source to conventional batteries. As the substitute fuel source for gasoline, biobutanol shows more promising characteristics than ethanol. In this study, the diffusion microflame of liquid biobutanol under electric field have been examined through in-lab experiment and numerical simulation. It is found that traditional gas jet diffusion flame theory shows significant inconsistency with the experimental results of micro scale flame in electric field. The results suggest that with the increase of electric field intensity, the quenching flow rate decrease first and increase after it reach its minimum, while the flame height and highest flame temperature increase first and drop after its peak value. In addition, it was also observed that the flame height and highest temperature for smaller tube can reach its maximum faster. Therefore, the interaction between microscale effect and electric field plays a significant role on understanding the microcombustion of liquid fuel. Therefore, FLUENT simulation was adopted to understand and measure the impacts of microflame characteristic parameters. The final numerical results are consistent with the experimental data and show a high reliability.

  6. Effects of electric field on micro-scale flame properties of biobutanol fuel

    Science.gov (United States)

    Xu, Tao; Chen, Qinglin; Zhang, Bingjian; Lu, Shushen; Mo, Dongchuan; Zhang, Zhengguo; Gao, Xuenong

    2016-01-01

    With the increasing need of smaller power sources for satellites, energy systems and engine equipment, microcombustion pose a potential as alternative power source to conventional batteries. As the substitute fuel source for gasoline, biobutanol shows more promising characteristics than ethanol. In this study, the diffusion microflame of liquid biobutanol under electric field have been examined through in-lab experiment and numerical simulation. It is found that traditional gas jet diffusion flame theory shows significant inconsistency with the experimental results of micro scale flame in electric field. The results suggest that with the increase of electric field intensity, the quenching flow rate decrease first and increase after it reach its minimum, while the flame height and highest flame temperature increase first and drop after its peak value. In addition, it was also observed that the flame height and highest temperature for smaller tube can reach its maximum faster. Therefore, the interaction between microscale effect and electric field plays a significant role on understanding the microcombustion of liquid fuel. Therefore, FLUENT simulation was adopted to understand and measure the impacts of microflame characteristic parameters. The final numerical results are consistent with the experimental data and show a high reliability. PMID:27609428

  7. Effect of AC electric fields on the stabilization of premixed bunsen flames

    KAUST Repository

    Kim, Minkuk

    2011-01-01

    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally for stoichiometric methane-air mixture by applying AC voltage to the nozzle with the single-electrode configuration. The detachment velocity either at blowoff or partial-detachment has been measured by varying the applied voltage and frequency of AC. The result showed that the detachment velocity increased with the applied AC electric fields, such that the flame could be nozzle-attached even over five times of the blowoff velocity without having electric fields. There existed four distinct regimes depending on applied AC voltage and frequency. In the low voltage regime, the threshold condition of AC electric fields was identified, below which the effect of electric fields on the detachment velocity is minimal. In the moderate voltage regime, the flame base oscillated with the frequency synchronized to AC frequency and the detachment velocity increased linearly with the applied AC voltage and nonlinearly with the frequency. In the high voltage regime, two different sub-regimes depending on AC frequency were observed. For relatively low frequency, the flame base oscillated with the applied AC frequency together with the half frequency and the variation of the detachment velocity was insensitive to the applied voltage. For relatively high frequency, the stabilization of the flame was significantly affected by the generation of streamers and the detachment velocity decreased with the applied voltage. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  8. Effect of fuel mixture fraction and velocity perturbations on the flame transfer function of swirl stabilized flames

    Science.gov (United States)

    Wysocki, Stefan; Di-Chiaro, Giacomo; Biagioli, Fernando

    2015-11-01

    A novel methodology is developed to decompose the classic Flame Transfer Function (FTF) used in the thermo-acoustic stability analysis of lean premix combustors into contributions of different types. The approach is applied, in the context of Large Eddy Simulation (LES), to partially-premixed and fully-premixed flames, which are stabilized via a central recirculation zone as a result of the vortex breakdown phenomenon. The first type of decomposition is into contributions driven by fuel mixture fraction and dynamic velocity fluctuations. Each of these two contributions is further split into the components of turbulent flame speed and flame surface area. The flame surface area component, driven by the pure dynamic velocity fluctuation, which is shown to be a dominant contribution to the overall FTF, is also additionally decomposed over the coherent flow structures using proper orthogonal decomposition. Using a simplified model for the dynamic response of premixed flames, it is shown that the distribution of the FTF, as obtained from LES, is closely related to the characteristics of the velocity field frequency response to the inlet perturbation. Initially, the proposed method is tested and validated with a well characterized laboratory burner geometry. Subsequently, the method is applied to an industrial gas turbine burner.

  9. Effect of multiphase radiation on coal combustion in a pulverized coal jet flame

    Science.gov (United States)

    Wu, Bifen; Roy, Somesh P.; Zhao, Xinyu; Modest, Michael F.

    2017-08-01

    The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and the lift-off height of the flame increases by approximately 35%, compared to the simulation without radiation. Radiation is also found to affect the evolution of coal particles considerably as it takes over as the dominant mode of heat transfer for medium-to-large coal particles downstream of the flame. To investigate the respective effects of spectral models for the gas and solid phases, a Planck-mean-based gray gas model and a size-independent gray particle model are applied in a frozen-field analysis of a steady-state snapshot of the flame. The gray gas approximation considerably underestimates the radiative source terms for both the gas phase and the solid phase. The gray coal approximation also leads to under-prediction of the particle emission and absorption. However, the level of under-prediction is not as significant as that resulting from the employment of the gray gas model. Finally, the effect of the spectral property of ash on radiation is also investigated and found to be insignificant for the present target flame.

  10. EFFECT OF SETTING THE PARAMETERS OF FLAME WEEDER ON WEED CONTROL EFFECTIVENESS

    Directory of Open Access Journals (Sweden)

    Miroslav Mojžiš

    2013-12-01

    Full Text Available Unconventional ways of growing plants, when we return to non-chemical methods of controlling weeds, require new weed control methods. One of the few physical methods, which found wider application in practice, is a flame weeder with heat burners based on the use of gas (LPG. However, the process of practical use of this flame weeder has a number of factors that positively or negatively affect the effectiveness of weed control. A precise setting of flame weeders is influenced, for example by weed species, weed growth stage, weather, type of crop grown, but also heat transmission and heat absorption by plant. Many variables that enter into the process must be eliminated for their negative impacts on achieving the best results in fighting against weeds. In this paper, we have focused on naming these parameters, on field trials that confirm the justification of the precise setting of parameters, and recommendations for practice to achieve a higher efficiency of thermal weed control.

  11. Flame Retardant Effects of Nano-Clinoptilolite on AcrylonitrileButadiene-Styrene (ABS Nano-Composite

    Directory of Open Access Journals (Sweden)

    Aboulfazl Barati

    2012-01-01

    Full Text Available In recent years, intumescent technology has found a place in polymer science as a method of providing flame retardance to polymeric materials. On heating, fire-retardant intumescent material restricts the action of the heat flux or flame. The proposed mechanism is based on charred layer acting as physical barrier, which slows down heat and mass transfer between the gas and the condensed phases. In this paper, the flammability of intumescent fire-retardant acrylonitrile-butadiene-styrene (ABS matrix composites consisting of hydromagnesite (HMg as an acid source and blowing agent, pentaerythritol (PER as a carbonisation agent and natural zeolite (clinoptilolite rich, Kansar Shargh as a synergistic agent were examined. The flammability of composites was characterized by limiting oxygen index (LOI measurement and horizontal burning tests. A synergistic effect in flame retardancy was observed when natural zeolites were used in combination with HMg and PER.

  12. Effect of fuel type on equivalence ratio measurements using chemiluminescence in premixed flames

    Science.gov (United States)

    Orain, Mikaël; Hardalupas, Yannis

    2010-05-01

    Local temporally-resolved measurements of chemiluminescent intensity from OH ∗, CH ∗ and C ∗2 radicals were obtained in premixed counterflow flames operating with propane and prevaporised fuels (isooctane, ethanol and methanol), for different equivalence ratios and strain rates. The results quantified independently the effects of fuel type, strain rate and equivalence ratio on chemiluminescent emissions from flames. The ability of chemiluminescent intensity from OH ∗, CH ∗ and C ∗2 radicals to indicate heat release rate depends strongly on fuel type. The intensity ratio OH ∗/CH ∗ has a monotonic decrease with equivalence ratio for all fuels and can be used to measure equivalence ratio of the reacting mixture. For propane and isooctane, the OH ∗/CH ∗ ratio remains independent of flame strain rate, whereas some dependence is observed for ethanol and methanol.

  13. 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.

  14. Method for determining effective flame emissivity in a rotary kiln incinerator burning solid waste

    Institute of Scientific and Technical Information of China (English)

    Jin-cai DU; Qun-xing HUANG; Jian-hua YAN

    2012-01-01

    Temperature is the most important parameter for the improvement of combustion efficiency and the control of pollutants.In order to obtain accurate flame temperatures in a rotary kiln incinerator using non-intrusive thermographic method,the effective flame emissivity was studied.A combined narrow- and wide-band model and Mie scattering method were used to calculate the radiative properties for gases and fly-ash particles under different combustion conditions.The effects of the air/waste ratio and fly-ash particles on the effective flame emissivity were discussed.The results of numerical calculations showed that the effective emissivity decreased from 0.90 to 0.80 when the air/waste ratio increased from 1.0 to 1.8,and the effect of the fly-ash particles was ignorable under the conditions discussed in this paper.Experimental measurement results indicated that the accuracy of the thermographic temperature measurements improved significantly if the setting of the flame emissivity was adjusted according to the air/waste ratio.

  15. Tulip flames: changes in shape of premixed propagating in closed tubes

    Energy Technology Data Exchange (ETDEWEB)

    Dunn-Rankin, D. [California Univ., Irvine, CA (United States). Dept. of Mechanical and Aerospace Engineering; Sawyer, R.F. [California Univ., Berkeley, CA (United States). Dept. of Mechanical Engineering

    1998-02-01

    The experimental results that are the subject of this communication provide high-speed schlieren images of the closed-tube flame shape that has come to be known as the tulip flame. The schlieren images, along with in-chamber pressure records, help demonstrate the effects of chamber length, equivalence ratio, and igniter geometry on formation of the tulip flame. The pressure/time records show distinct features which correlate with flame shape changes during the transition to tulip. The measurements indicate that the basic tulip flame formation is a robust phenomenon that depends on little except the overall geometry of the combustion vessel. (orig.) 32 refs.

  16. Effects of Non-Equilibrium Plasmas on Low-Pressure, Premixed Flames. Part 1: CH* Chemiluminescence, Temperature, and OH

    Science.gov (United States)

    2017-08-15

    chemistry. Qualitative imaging of CH* chemiluminescence indicates that during plasma discharge, the luminous flame zone is shifted upstream towards...The same research group also has observed an increase in premixed methane/air flame blow-off velocities by more than a factor of two by the...resolution and rotational line-specific features . Due to the large number of test cases (see Table 2) and the desire for spatially-resolved

  17. Rotational effects in thermonuclear type I bursts: equatorial crossing and directionality of flame spreading

    NARCIS (Netherlands)

    Cavecchi, Y.; Watts, A.L.; Levin, Y.; Braithwaite, J.

    2015-01-01

    In a previous study on thermonuclear (type I) bursts on accreting neutron stars, we addressed and demonstrated the importance of the effects of rotation, through the Coriolis force, on the propagation of the burning flame. However, that study only analysed cases of longitudinal propagation, where

  18. 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.

  19. SYNERGISTIC EFFECTS OF NOVOLAC-BASED CHAR FORMER WITH A PHOSPHORUS/NITROGEN-CONTAINING FLAME RETARDANT IN POLYAMIDE 6

    Institute of Scientific and Technical Information of China (English)

    Wei-cheng Xiong; Li Chen; De-yi Wang; Fei Song; Yu-zhong Wang

    2012-01-01

    The synergistic effect of phosphorus oxynitride (PON) with a novolac-based char former modified by salification (NA-metal salt) on the flame retardance of polyamide 6 (PA6) was investigated.For this purpose,various flame-retardant PA6 systems were melt-compounded with PON,PON/NA,PON/NA-V2O5 and PON/NA-Fe2O3,and their flame retardance was evaluated by measuring the limiting oxygen index (LOI) values and UL-94 vertical burning ratings.The results showed that,compared with the PA6/PON/NA system,the combination of two char formers (NA-V2O5,NA-Fe2O3) with PON could obviously improve the char formation and flame retardance of PA6.The flame retardance and cone calorimetric analyses showed the stronger synergism as well as the better flame retardant performance of PON/NA-Fe2O3 flame retardant system.The effects of different char formers on the flame retardance and thermal stability of this system were also discussed.

  20. Effects of Flamelet Generated Manifolds on Turbulent Flame Structure and Pollutant Emissions

    Science.gov (United States)

    Nunno, A. Cody; Grenga, Temistocle; Mueller, Michael E.

    2016-11-01

    Heat losses substantially modify turbulent combustion processes, especially the formation of pollutant emissions such as nitrogen oxides, which are highly sensitive to temperature. To account for heat loss effects in Large Eddy Simulation (LES) with flamelet models, a priori flamelet solutions are computed at reduced enthalpy. In this work, two methods for generating flamelets of lower enthalpy are compared to determine under what conditions the different methods produce different flame structure and different pollutant emissions in order to determine their validity limits. In the first method, a variable heat loss is introduced into the flamelet solutions that mimics a real heat loss, reducing the enthalpy primarily in the post-flame region of the flamelet. In the second method, fuel and oxidizer are converted to products in the unburned gases while retaining a constant unburned temperature, reducing the enthalpy over the entire flamelet. The two methods are compared in methane-air piloted turbulent premixed planar jet flames with increasing levels of dilution with both water and carbon dioxide that maintain a constant adiabatic flame temperature. The "product conversion" method is expected to mirror some of the same effects as physical dilution.

  1. The effect of nitrogen on biogas flame propagation characteristic in premix combustion

    Science.gov (United States)

    Anggono, Willyanto; Suprianto, Fandi D.; Hartanto, Tan Ivan; Purnomo, Kenny; Wijaya, Tubagus P.

    2016-03-01

    Biogas is one of alternative energy and categorized as renewable energy. The main sources of biogas come from animal waste, garbage, and household waste that are organic waste. Primarily, over 50% of this energy contains methane (CH4). The other substances or inhibitors are nitrogen and carbon dioxide. Previously, carbon dioxide effect on biogas combustion is already experimented. The result shows that carbon dioxide reduces the flame propagation speed of biogas combustion. Then, nitrogen as an inhibitor obviously also brings some effects to the biogas combustion, flame propagation speed, and flame characteristics. Spark ignited cylinder is used for the premixed biogas combustion research. An acrylic glass is used as the material of this transparent cylinder chamber. The cylinder is filled with methane (CH4), oxygen (O2), and nitrogen (N2) with particular percentage. In this experiment, the nitrogen composition are set to 0%, 5%, 10%, 20%, 30%, 40%, and 50%. The result shows that the flame propagation speed is reduced in regard to the increased level of nitrogen. It can also be implied that nitrogen can decrease the biogas combustion rate.

  2. Assessing in-vitro estrogenic effects of currently-used flame retardants.

    Science.gov (United States)

    Krivoshiev, Boris V; Dardenne, Freddy; Covaci, Adrian; Blust, Ronny; Husson, Steven J

    2016-06-01

    Flame retardants are chemicals that are added to nearly all manufactured materials. Additionally, there has been a steady increase in diseases resulting from endocrine-disruption with an aligned increase in use of chemicals. Given the persistence, potential bioaccumulation, limited toxicological understanding, and vast use of flame retardants, there is a need to investigate potential endocrine-disruptive activity associated with these compounds in an effort for better risk assessment. We therefore used the MCF-7 flow-cytometric proliferation assay in an effort to establish potential estrogen-disrupting effects of twelve currently-used flame retardants. Triphenyl phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(butyl) phosphate, hexabromocyclododecane, and tetrabromobisphenol A showed statistically significant estrogenic activity, with hexabromocyclododecane being the most potent of the five (EC20 of 5.5 μM). Tris(2-butoxyethyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, tri(2-chloroethyl) phosphate, tris(butyl) phosphate, hexabromocyclododecane, tetrabromobisphenol A, and tris(2,3,-dibromopropyl) isocyanurate harboured anti-estrogenic activity when co-treating with 17β-estradiol, with hexabromocyclododecane showing the highest potency (IC20 of 17.6 μM). Interestingly, some compounds showed both estrogenic and anti-estrogenic effects, indicating both receptor-dependant and -independent mechanisms attributed to some of these compounds, in line with other studies. Multiple currently-used flame retardants may therefore act as xenoestrogens and anti-estrogens, or alter estrogen homeostasis, which could affect endocrine function.

  3. Investigation of the effects of quarl and initial conditions on swirling non-premixed methane flames: Flow field, temperature, and species distributions

    KAUST Repository

    Elbaz, Ayman M.

    2015-12-19

    Detailed measurements are presented of the turbulent flow field, gas species concentrations and temperature field in a non-premixed methane swirl flame. Attention is given to the effect of the quarl geometry on the flame structure and emission characteristics due to its importance in gas turbine and industrial burner applications. Two different quarls were fitted to the burner exit, one a straight quarl and the other a diverging quarl of 15° half cone angle. Stereoscopic Particle Image Velocimetry (SPIV) was applied to obtain the three components of the instantaneous velocity on a vertical plane immediately downstream of the quarl exit. Temperature and gaseous species measurements were made both inside and downstream of the quarls, using a fine wire thermocouple and sampling probe, respectively. This work provides experimental verification by complementary techniques. The results showed that although the main flame structures were governed by the swirl motion imparted to the air stream, the quarl geometry, fuel loading and air loading also had a significant effect on the flow pattern, turbulence intensity, mixture formation, temperature distribution, emissions and flame stabilization. Particularly, in the case of the straight quarl flame, the flow pattern leads to strong, rapid mixing and reduces the residence time for NO formation within the internal recirculation zone (IRZ). However, for the diverging quarl flames, the recirculation zone is shifted radially outward, and the turbulent interaction between the central fuel jet and the internal recirculation zone IRZ induces another small vortex between these two flow features. Less mixing near the diverging quarl exit is observed, with a higher concentration of NO and CO in the post-combustion zone. The instantaneous flow field for both flames showed the existence of small scale vortical structure near the shear layers which were not apparent in the time averaged flow field. These structures, along with high levels

  4. Fuel effects on the stability of turbulent flames with compositionally inhomogeneous inlets

    KAUST Repository

    Guiberti, T. F.

    2016-10-11

    This paper reports an analysis of the influence of fuels on the stabilization of turbulent piloted jet flames with inhomogeneous inlets. The burner is identical to that used earlier by the Sydney Group and employs two concentric tubes within the pilot stream. The inner tube, carrying fuel, can be recessed, leading to a varying degree of inhomogeneity in mixing with the outer air stream. Three fuels are tested: dimethyl ether (DME), liquefied petroleum gas (LPG), and compressed natural gas (CNG). It is found that improvement in flame stability at the optimal compositional inhomogeneity is highest for CNG and lowest for DME. Three possible reasons for this different enhancement in stability are investigated: mixing patterns, pilot effects, and fuel chemistry. Numerical simulations realized in the injection tube highlight similarities and differences in the mixing patterns for all three fuels and demonstrate that mixing cannot explain the different stability gains. Changing the heat release rates from the pilot affects the three fuels in similar ways and this also implies that the pilot stream is unlikely to be responsible for the observed differences. Fuel reactivity is identified as a key factor in enhancing stability at some optimal compositional inhomogeneity. This is confirmed by inference from joint images of PLIF-OH and PLIF-CHO, collected at a repetition rate of 10kHz in turbulent flames of DME, and from one-dimensional calculations of laminar flames using detailed chemistry for DME, CNG, and LPG.

  5. Effect of cavity flame holder configuration on combustion flow field performance of integrated hypersonic vehicle

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    As one of the most common methods to be used as the flame holding mechanism in the propulsion system of the integrated hypersonic vehicle,the research of cavity flame holder has drawn an ever increasing attention of many researchers. The two-dimensional coupled implicit NS equations,the standard k-ε turbulent models and the finite-rate/eddy-dissipation reaction model were employed to simulate the experimental items arranged by the orthogonal design,and the variance analysis method was used to investigate the effects of the geometric parameters of the cavity flame holder on the aero-propulsive performance of the integrated hypersonic vehicle,namely the depth,the ratio of length-to-depth and the sweepback angle. The obtained results show that the geometric parameters make only a little difference to the aero-propulsive performance of the vehicle in the range considered in this paper,and the cavity flame holder with its sweepback angle 45° can satisfy the performance requirement of the integrated hypersonic vehicle further. The hydrogen injected from the upper stream of the cavity makes the boundary layer separate on the lower wall of the engine,and a separate region appears in the upper stream and down stream of the injection slot,respectively.

  6. Blow-off characteristics of turbulent premixed flames in curved-wall Jet Burner

    KAUST Repository

    Mansour, Morkous S.

    2015-08-02

    This study concerns the flame dynamics of a curved-wall jet (CWJ) stabilized turbulent premixed flame as it approaches blow-off conditions. Time resolved OH planar laser-induced fluorescence (PLIF) delineated reaction zone contours and simultaneously stereoscopic particle image velocimetry (SPIV) quantified the turbulent flow field features. Ethylene/air flames were stabilized in CWJ burner to determine the sequence of events leading to blowoff. For stably burning flames far from blowoff, flames are characterized with a recirculation zone (RZ) upstream for flame stabilization followed by an intense turbulent interaction jet (IJ) and merged-jet regions downstream; the flame front counterparts the shear layer vortices. Near blowoff, as the velocity of reactants increases, high local stretch rates exceed the extinction stretch rates instantaneously resulting in localized flame extinction along the IJ region. As Reynolds number (Re) increases, flames become shorter and are entrained by larger amounts of cold reactants. The increased strain rates together with heat loss effects result in further fragmentation of the flame, eventually leading to the complete quenching of the flame. This is explained in terms of local turbulent Karlovitz stretch factor (K) and principal flow strain rates associated with C contours. Hydrogen addition and increasing the RZ size lessen the tendency of flames to be locally extinguished.

  7. The effect of scaling on the performance of coal flames

    Energy Technology Data Exchange (ETDEWEB)

    Lymberopoulos, N. [CINAR sa, Athens (Greece)

    1998-12-31

    In large process industries such as utility boilers used for the generation of steam to produce electricity, cement kilns, glass tanks etc. the collection of experimental data is often difficult, time consuming and expensive. Operators are reluctant to interfere with the running of a process in order to undertake the parametric exercises necessary to provide the information necessary to establish performance trends. The information that may be gathered, is not necessarily universal, applying only to the unit on which it was recorded, while the constancy of the various parameters may be suspect. One alternative is the use of scale versions of the prototype in which the physical reactions are well replicated. Such small scale units can provide total, immediate and accurate control over the inlet parameters and are easily accessible in regard to obtaining the necessary information such as gas species concentrations, temperatures and combustion efficiency data throughout the flame and the furnace. These units are also invaluable in the derivation and subsequent appraisal of novel techniques. The art is how small scale observations can be interpreted in the large scale. This is where mathematical modelling techniques are employed. What changes have to be accommodated in the model as the scale is increased? In particular what changes occur in the prediction of combustion performance of a 150 kW furnace and a 35 MW one and what justifiable modifications can be made to accommodate these nuances so that predictions at full scale can be made with added confidence. This was studied. 12 refs., 9 figs., 4 tabs.

  8. Turbulence-flame interactions in DNS of a laboratory high Karlovitz premixed turbulent jet flame

    Science.gov (United States)

    Wang, Haiou; Hawkes, Evatt R.; Chen, Jacqueline H.

    2016-09-01

    In the present work, direct numerical simulation (DNS) of a laboratory premixed turbulent jet flame was performed to study turbulence-flame interactions. The turbulent flame features moderate Reynolds number and high Karlovitz number (Ka). The orientations of the flame normal vector n, the vorticity vector ω and the principal strain rate eigenvectors ei are examined. The in-plane and out-of-plane angles are introduced to quantify the vector orientations, which also measure the flame geometry and the vortical structures. A general observation is that the distributions of these angles are more isotropic downstream as the flame and the flow become more developed. The out-of-plane angle of the flame normal vector, β, is a key parameter in developing the correction of 2D measurements to estimate the corresponding 3D quantities. The DNS results show that the correction factor is unity at the inlet and approaches its theoretical value of an isotropic distribution downstream. The alignment characteristics of n, ω and ei, which reflect the interactions of turbulence and flame, are also studied. Similar to a passive scalar gradient in non-reacting flows, the flame normal has a tendency to align with the most compressive strain rate, e3, in the flame, indicating that turbulence contributes to the production of scalar gradient. The vorticity dynamics are examined via the vortex stretching term, which was found to be the predominant source of vorticity generation balanced by dissipation, in the enstrophy transport equation. It is found that although the vorticity preferentially aligns with the intermediate strain rate, e2, the contribution of the most extensive strain rate, e1, to vortex stretching is comparable with that of the intermediate strain rate, e2. This is because the eigenvalue of the most extensive strain rate, λ1, is always large and positive. It is confirmed that the vorticity vector is preferentially positioned along the flame tangential plane, contributing

  9. Flame deposition of diamond : gas phase diagnostics and the effects of nitrogen addition

    NARCIS (Netherlands)

    Stolk, Robert Leendert

    2002-01-01

    This thesis presents research on oxyacetylene flame deposition of diamond. Two main topics are addressed, namely the development and application of laser spectroscopic techniques for flame diagnostics, and the influence of nitrogen addition on the flame and diamond layer properties. Flame diagnostic

  10. Stretch rate effects and flame surface densities in premixed turbulent combustion up to 1.25 MPa

    KAUST Repository

    Bagdanavicius, Audrius

    2015-11-01

    Independent research at two centres using a burner and an explosion bomb has revealed important aspects of turbulent premixed flame structure. Measurements at pressures and temperatures up to 1.25MPa and 673K in the two rigs were aimed at quantifying the influences of flame stretch rate and strain rate Markstein number, Masr , on both turbulent burning velocity and flame surface density. That on burning velocity is expressed through the stretch rate factor, Io , or probability of burning, Pb 0.5. These depend on Masr , but they grow in importance as the Karlovitz stretch factor, K, increases, and are evaluated from the associated burning velocity data. Planar laser tomography was employed to identify contours of reaction progress variable in both rigs. These enabled both an appropriate flame front for the measurement of the turbulent burning velocity to be identified, and flame surface densities, with the associated factors, to be evaluated. In the explosion measurements, these parameters were derived also from the flame surface area, the derived Pb 0.5 factor and the measured turbulent burning velocities. In the burner measurement they were calculated directly from the flame surface density, which was derived from the flame contours.A new overall correlation is derived for the Pb 0.5 factor, in terms of Masr at different K and this is discussed in the light of previous theoretical studies. The wrinkled flame surface area normalised by the area associated with the turbulent burning velocity measurement, and the ratio of turbulent to laminar burning velocity, ut /ul , are also evaluated. The higher the value of Pb0.5, the more effective is an increased flame wrinkling in increasing ut /ul A correlation of the product of k and the laminar flame thickness with Karlovitz stretch factor and Markstein number is explored using the present data and those

  11. Effect of pressure on high Karlovitz number lean turbulent premixed hydrogen-enriched methane-air flames using LES

    Science.gov (United States)

    Cicoria, David; Chan, C. K.

    2017-07-01

    Large eddy simulation (LES) is employed to investigate the effect of pressure on lean CH4-H2-air turbulent premixed flames at high Karlovitz number for mixtures up to 60% of hydrogen in volume. The subfilter combustion term representing the interaction between turbulence and chemistry is modelled using the PaSR model, along with complex chemistry using a skeletal mechanism based on GRI-MECH3.0. The influence of pressure at high turbulence levels is studied by means of the local flame structure, and the assessment of species formation inside the flame. Results show that the ratio of turbulent flame thickness to laminar flame thickness δt/δu increases faster with pressure, and increases with the fraction of hydrogen in the mixture, leading to higher ratio of turbulent to laminar flame speed. The flame displays smaller structures and higher degree of wrinkling at higher pressure. Final species of CO2 and H2O formation is almost independent of pressure. For intermediate species CO and OH, an increase in pressure at constant volume fraction of hydrogen β leads to a decrease of emission of these species.

  12. Flame treatment of graphene oxides: cost-effective production of nanoporous graphene electrode for Lithium-ion batteries

    Science.gov (United States)

    Jiang, Hao-Bo; Zhang, Yong-Lai; Zhang, Yi; Liu, Yan; Fu, Xiu-Yan; Liu, Yu-Qing; Wang, Chun-Dong; Sun, Hong-Bo

    2015-12-01

    A facile production of highly porous graphene foam by using flame treatment of graphene oxide (GO) is proposed. Highly porous architectures with randomly distributed micro-crack and micro-slit were produced due to the high temperature induced ruinous reduction and rapid expansion of GO. Synchronously, abundant oxygen-containing groups (OCGs) on GO sheets could be effectively removed after flame treatment, which renders significantly increased conductivity to the resultant flame reduced GO (FR-GO). The synergistic effect of micro/nanostructuring and the OCGs removal makes FR-GO a promising candidate for electrode materials. Compared with chemically reduced GO (CR-GO), FR-GO delivers much higher specific capacity. It gives us some hints that flame treatment of graphene-based material is a smart strategy for cost-effective production of anode materials for commercial application.

  13. Effect of Particle Size of Additives on the Flammability and Mechanical Properties of Intumescent Flame Retarded Polypropylene Compounds

    Directory of Open Access Journals (Sweden)

    Katalin Bocz

    2015-01-01

    Full Text Available The effect of particle size reduction of the components of a common intumescent flame retardant system, consisting of pentaerythritol (PER and ammonium polyphosphate (APP in a weight ratio of 1 to 2, was investigated on the flammability and mechanical performance of flame retarded polypropylene (PP compounds. Additives of reduced particle size were obtained by ball milling. In the case of PER, the significant reduction of particle size resulted in inferior flame retardant and mechanical performance, while the systems containing milled APP noticeably outperformed the reference intumescent system containing as-received additives. The beneficial effect of the particle size reduction of APP is explained by the better distribution of the particles in the polymer matrix and by the modified degradation mechanism which results in the formation of an effectively protecting carbonaceous foam accompanied with improved mechanical resistance. Nevertheless, 10% higher tensile strength was measured for the flame retarded PP compound when as-received APP was substituted by milled APP.

  14. Unsteady Flame Embedding (UFE) Subgrid Model for Turbulent Premixed Combustion Simulations

    KAUST Repository

    El-Asrag, Hossam

    2010-01-04

    We present a formulation for an unsteady subgrid model for premixed combustion in the flamelet regime. Since chemistry occurs at the unresolvable scales, it is necessary to introduce a subgrid model that accounts for the multi-scale nature of the problem using the information available on the resolved scales. Most of the current models are based on the laminar flamelet concept, and often neglect the unsteady effects. The proposed model\\'s primary objective is to encompass many of the flame/turbulence interactions unsteady features and history effects. In addition it provides a dynamic and accurate approach for computing the subgrid flame propagation velocity. The unsteady flame embedding approach (UFE) treats the flame as an ensemble of locally one-dimensional flames. A set of elemental one dimensional flames is used to describe the turbulent flame structure at the subgrid level. The stretched flame calculations are performed on the stagnation line of a strained flame using the unsteady filtered strain rate computed from the resolved- grid. The flame iso-surface is tracked using an accurate high-order level set formulation to propagate the flame interface at the coarse resolution with minimum numerical diffusion. In this paper the solver and the model components are introduced and used to investigate two unsteady flames with different Lewis numbers in the thin reaction zone regime. The results show that the UFE model captures the unsteady flame-turbulence interactions and the flame propagation speed reasonably well. Higher propagation speed is observed for the lower than unity Lewis number flame because of the impact of differential diffusion.

  15. Rotational effects in thermonuclear Type I Bursts: equatorial crossing and directionality of flame spreading

    CERN Document Server

    Cavecchi, Yuri; Levin, Yuri; Braithwaite, Jonathan

    2014-01-01

    In a previous study on thermonuclear (Type I) Bursts on accreting neutron stars we addressed and demonstrated the importance of the effects of rotation, through the Coriolis force, on the propagation of the burning flame. However, that study only analysed cases of longitudinal propagation, where the Coriolis force coefficient $2\\Omega\\cos\\theta$ was constant. In this paper, we study the effects of rotation on propagation in the meridional (latitudinal) direction, where the Coriolis force changes from its maximum at the poles to zero at the equator. We find that the zero Coriolis force at the equator, while affecting the structure of the flame, does not prevent its propagation from one hemisphere to another. We also observe structural differences between the flame propagating towards the equator and that propagating towards the pole, the second being faster. In the light of the recent discovery of the low spin frequency of burster IGR~J17480-2446 rotating at 11 Hz (for which Coriolis effects should be negligib...

  16. Effects of non-thermal plasmas and electric field on hydrocarbon/air flames

    Science.gov (United States)

    Ganguly, Biswa

    2009-10-01

    combustion stability The effect of applied voltage in a flame below self-sustained plasma generation is known to enhance flame holding through induced turbulence. Review of recent results will be presented to show future research opportunities in quantitative measurements and modeling of hydrocarbon/air plasma enhanced combustion.

  17. Effect of burner geometry on swirl stabilized methane/air flames: A joint LES/OH-PLIF/PIV study

    KAUST Repository

    Liu, X.

    2017-07-04

    Large eddy simulation (LES) using a transported PDF model and OH-PLIF/PIV experiments were carried out to investigate the quarl effects on the structures of swirl stabilized methane/air flames. Two different quarls were investigated, one straight cylindrical quarl and one diverging conical quarl. The experiments show that the flames are significantly different with the two quarls. With the straight cylindrical quarl a compact blue flame is observed while with the diverging conical quarl the flame appears to be long and yellow indicating a sooty flame structure. The PIV results show the formation of a stronger flow recirculation inside the diverging conical quarl than that in the straight quarl. LES results reveal further details of the flow and mixing process inside the quarl. The results show that with the diverging quarl vortex breakdown occurs much earlier towards the upstream of the quarl. As a result the fuel is convected into the air flow tube and a diffusion flame is stabilized inside the air flow tube upstream the quarl. With the straight quarl, vortex breakdown occurs at a downstream location in the quarl. The scalar dissipation rate in the shear layer of the fuel jet is high, which prevents the stabilization of a diffusion flame in the proximity of the fuel nozzle; instead, a compact partially premixed flame with two distinct heat release layers is stablized in a downstream region in the quarl, which allows for the fuel and air to mix in the quarl before combustion and a lower formation rate of soot. The results showed that the Eulerian Stochastic Fields transported PDF method can well predict the details of the swirl flame dynamics.

  18. The Effect of Water Vapor on Flame Velocity in Equivalent Carbon Monoxide and Oxygen Mixtures

    Science.gov (United States)

    Fiock, Ernest F; King, H Kendall

    1936-01-01

    This report presents the results of an investigation to study the effect of water vapor upon the spatial speed of flame in equivalent mixtures of carbon monoxide and oxygen at various total pressures from 100 to 780 mm.hg. These results show that, within this pressure range, an increase in flame speed is produced by increasing the mole fraction of water vapor at least as far as saturation at 25 degrees c., and that the rate of this increase is greater the higher the pressure. It is evident that water vapor plays an important part in the explosive oxidation of carbon monoxide; the need for further experimental evidence as to the nature of its action is indicated.

  19. Effects of Biofuel and Variant Ambient Pressure on FlameDevelopment and Emissions of Gasoline Engine.

    Science.gov (United States)

    Hashim, Akasha; Khalid, Amir; Sapit, Azwan; Samsudin, Dahrum

    2016-11-01

    There are many technologies about exhaust emissions reduction for wide variety of spark ignition (SI) engine have been considered as the improvement throughout the combustion process. The stricter on legislation of emission and demands of lower fuel consumption needs to be priority in order to satisfy the demand of emission quality. Besides, alternative fuel such as methanol-gasoline blends is used as working fluid in this study due to its higher octane number and self-sustain concept which capable to contribute positive effect to the combustion process. The purpose of this study is to investigate the effects of methanol-gasoline fuel with different blending ratio and variant ambient pressures on flame development and emission for gasoline engine. An experimental study is carried towards to the flame development of methanol-gasoline fuel in a constant volume chamber. Schlieren optical visualization technique is a visual process that used when high sensitivity is required to photograph the flow of fluids of varying density used for captured the combustion images in the constant volume chamber and analysed through image processing technique. Apart from that, the result showed combustion burn rate increased when the percentage of methanol content in gasoline increased. Thus, high percentage of methanol-gasoline blends gave greater flame development area. Moreover, the emissions of CO, NOX and HC are performed a reduction when the percentage of methanol content in gasoline is increased. Contrarily, the emission of Carbon dioxide, CO2 is increased due to the combustion process is enhanced.

  20. Effect of AC electric fields on flame spread over electrical wire

    KAUST Repository

    Kim, Minkuk

    2011-01-01

    The effect of electric fields on the characteristics of flame spread over insulated electrical wire has been investigated experimentally by varying AC voltage and frequency applied to the wire in the normal gravity condition. The polyethylene (PE) insulated electrical wire was placed horizontally on electrically non-conducting posts and one end of the wire was connected to the high voltage terminal. Thus, the electrical system is the single electrode configuration. The wire was ignited at one end and the flame spread rate along the wire has been measured from the images using a video camera. Two distinct regimes existed depending on the applied AC frequency. In the low frequency regime, the flame spread rate decreased with the frequency and voltage. While in the high frequency regime, it decreased initially with voltage and then increased. At high frequency, the spread rate was even over that without applying electric fields. This result implies that fire safety codes developed without considering the effect of electric fields may require modifications. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  1. Combination effect of melamine polyphosphate and graphene on flame retardant properties of poly(vinyl alcohol)

    Energy Technology Data Exchange (ETDEWEB)

    Huang Guobo, E-mail: huangguobo@tzc.edu.cn [School of Pharmaceutical and Chemical Engineering, Taizhou University, Linhai 317000 (China); Liang Huading; Wang Yong [School of Pharmaceutical and Chemical Engineering, Taizhou University, Linhai 317000 (China); Wang Xu; Gao Jianrong; Fei Zhengdong [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer PVA/graphene/MPP composites were prepared by solvent blending. Black-Right-Pointing-Pointer PVA/graphene systems improved the flame retardancy of the nanocomposites. Black-Right-Pointing-Pointer Flame retardation mechanism was explained by SEM, FT-IR and XPS. - Abstract: A novel flame retardant poly(vinyl alcohol) (PVA)/melamine polyphosphate (MPP)-graphene nanocomposite has been prepared by solvent blending. Results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) suggest that an excellent dispersion of exfoliated graphene and MPP in the PVA matrix was achieved. The thermal and flammability properties of the nanocomposite were investigated using thermogravimetry, cone calorimetry, and flammability tests (UL 94 and LOI). The presence of both MPP and graphene in the polymer matrix led to an enhanced thermal stability and significantly reduced flammability for the nanocomposite. PVA composites filled with 10 wt% MPP and 1 wt% graphene (PVA/G1/MPP10) achieved the LOI value of 29.6 and UL-94 V0 grade. Compared to pure PVA, the peak heat release rate (PHRR) of PVA/G1/MPP10 is reduced by about 60%. Meanwhile, the mechanical properties of PVA/G1/MPP10 composites exhibit almost no deterioration compared with pure PVA. The morphology and composition of residues generated after cone calorimeter tests were investigated by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The SEM images showed the compact and dense intumescent char jammed with graphene sheets was formed for PVA/G1/MPP10 during combustion. The results of XPS confirmed that carbon content of the char for PVA/G1/MPP10 is increased obviously by the combination effect of the flame retardant MPP and graphene.

  2. An analytical study of the effects of vaporization of twodimensional laminar droplets on a triple flame

    Directory of Open Access Journals (Sweden)

    Bidabadi Mehdi

    2011-01-01

    Full Text Available The structure of triple flame propagation in combustion systems, containing uniformly distributed volatile fuel droplet was analyzed. The analysis was established for a one-step irreversible reaction with an asymptotic limit, where the value of the Zeldovich Number is large. Here, using unit Lewis number, the analytical results for the triple flame temperature were obtained considering two sections. In the first section, a non-vaporizing fuel stream was studied and in the second section, a volatile droplet fuel stream was taken into account. It is presumed that the fuel droplets vaporize to yield a gaseous fuel of known chemical structure, which is subsequently oxidized in the gaseous phase. Here two different cases are studied. In the first case, only the velocity parallel to the reactant flow was considered; while for the latter one, the vertical velocity was considered in addition. The energy equations were solved and the temperature field equations are presented. The results are first presented for a non-vaporizing fuel and compared to the experiment results. In addition, some other results of the temperature field for a vaporizing fuel stream are demonstrated within the comparison between the abovementioned cases which revealed the effect of the considering the vertical velocity component on the flame temperature field.

  3. Investigation on Effect of Air Velocity in Turbulent Non-Premixed Flames

    Directory of Open Access Journals (Sweden)

    Namazian Zafar

    2016-09-01

    Full Text Available In this study, the turbulent non-premixed methane-air flame is simulated to determine the effect of air velocity on the length of flame, temperature distribution and mole fraction of species. The computational fluid dynamics (CFD technique is used to perform this simulation. To solve the turbulence flow, k-ε model is used. In contrast to the previous works, in this study, in each one of simulations the properties of materials are taken variable and then the results are compared. The results show that at a certain flow rate of fuel, by increasing the air velocity, similar to when the properties are constant, the width of the flame becomes thinner and the maximum temperature is higher; the penetration of oxygen into the fuel as well as fuel consumption is also increased. It is noteworthy that most of the pollutants produced are NOx, which are strongly temperature dependent. The amount of these pollutants rises when the temperature is increased. As a solution, decreasing the air velocity can decrease the amount of these pollutants. Finally, comparing the result of this study and the other work, which considers constant properties, shows that the variable properties assumption leads to obtaining more exact solution but the trends of both results are similar.

  4. Effect of Spray Cone Angle on Flame Stability in an Annular Gas Turbine Combustor

    Science.gov (United States)

    Mishra, R. K.; Kumar, S. Kishore; Chandel, Sunil

    2016-04-01

    Effect of fuel spray cone angle in an aerogas turbine combustor has been studied using computational fluid dynamics (CFD) and full-scale combustor testing. For CFD analysis, a 22.5° sector of an annular combustor is modeled and the governing equations are solved using the eddy dissipation combustion model in ANSYS CFX computational package. The analysis has been carried out at 125 kPa and 303 K inlet conditions for spray cone angles from 60° to 140°. The lean blowout limits are established by studying the behavior of combustion zone during transient engine operation from an initial steady-state condition. The computational study has been followed by testing the practical full-scale annular combustor in an aerothermal test facility. The experimental result is in a good agreement with the computational predictions. The lean blowout fuel-air ratio increases as the spray cone angle is decreased at constant operating pressure and temperature. At higher spray cone angle, the flame and high-temperature zone moves upstream close to atomizer face and a uniform flame is sustained over a wide region causing better flame stability.

  5. Dynamics and structure of stretched flames

    Energy Technology Data Exchange (ETDEWEB)

    Law, C.K. [Princeton Univ., NJ (United States)

    1993-12-01

    This program aims to gain fundamental understanding on the structure, geometry, and dynamics of laminar premixed flames, and relate these understanding to the practical issues of flame extinction and stabilization. The underlying fundamental interest here is the recent recognition that the response of premixed flames can be profoundly affected by flame stretch, as manifested by flow nonuniformity, flame curvature, and flame/flow unsteadiness. As such, many of the existing understanding on the behavior of premixed flames need to be qualitatively revised. The research program consists of three major thrusts: (1) detailed experimental and computational mapping of the structure of aerodynamically-strained planar flames, with emphasis on the effects of heat loss, nonequidiffusion, and finite residence time on the flame thickness, extent of incomplete reaction, and the state of extinction. (2) Analytical study of the geometry and dynamics of stretch-affected wrinkled flame sheets in simple configurations, as exemplified by the Bunsen flame and the spatially-periodic flame, with emphasis on the effects of nonlinear stretch, the phenomena of flame cusping, smoothing, and tip opening, and their implications on the structure and burning rate of turbulent flames. (3) Stabilization and blowoff of two-dimensional inverted premixed and stabilization and determining the criteria governing flame blowoff. The research is synergistically conducted through the use of laser-based diagnostics, computational simulation of the flame structure with detailed chemistry and transport, and mathematical analysis of the flame dynamics.

  6. Effects of buoyancy on lean premixed v-flames, Part II. VelocityStatistics in Normal and Microgravity

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, R.K.; Bedat, B.; Yegian, D.T.

    1999-07-01

    The field effects of buoyancy on laminar and turbulent premixed v-flames have been studied by the use of laser Doppler velocimetry to measure the velocity statistics in +1g, -1g and {micro}g flames. The experimental conditions covered mean velocity, Uo, of 0.4 to 2 m/s, methane/air equivalence ratio, f, of 0.62 to 0.75. The Reynolds numbers, from 625 to 3130 and the Richardson number from 0.05 to 1.34. The results show that a change from favorable (+1g) to unfavorable (-1g) mean pressure gradient in the plume create stagnating flows in the far field whose influences on the mean and fluctuating velocities persist in the near field even at the highest Re we have investigated. The use of Richardson number < 0.1 as a criterion for momentum dominance is not sufficient to prescribe an upper limit for these buoyancy effects. In {micro}g, the flows within the plumes are non-accelerating and parallel. Therefore, velocity gradients and hence mean strain rates in the plumes of laboratory flames are direct consequences of buoyancy. Furthermore, the rms fluctuations in the plumes of {micro}g flames are lower and more isotropic than in the laboratory flames to show that the unstable plumes in laboratory flames also induce velocity fluctuations. The phenomena influenced by buoyancy i.e. degree of flame wrinkling, flow acceleration, flow distribution, and turbulence production, can be subtle due to their close coupling with other flame flow interaction processes. But they cannot be ignored in fundamental studies or else the conclusions and insights would be ambiguous and not very meaningful.

  7. Influence of radiation-crosslinking on flame retarded polymer materials-How crosslinking disrupts the barrier effect

    Science.gov (United States)

    Sonnier, Rodolphe; Caro-Bretelle, Anne-Sophie; Dumazert, Loïc; Longerey, Marc; Otazaghine, Belkacem

    2015-01-01

    Fire behavior of flame retardant-free and flame retarded PP/PA6 blends was studied using pyrolysis-combustion flow calorimeter, cone calorimeter and epiradiator equipped with infrared camera and pyrometer. Blends were previously γ-irradiated in presence of crosslinking agents at various doses (up to 100 kGy) in order to assess the influence of irradiation crosslinking on flame retardancy. Crosslinked specimens exhibit a solid-like behavior under high temperature gradient in cone calorimeter and then distort considerably. The influence of such a behavior depends on the material properties. When the flame retardancy is provided by heat shielding effect, heat distortion disrupts the top protective layer leading to a substantial increase of peak of heat release rate (pHRR). The barrier layer is no longer able to prevent the heat transfer to the underlying condensed phase. In other cases (flame retardant-free blends or flame retardancy provided by other effects than heat shielding), heat distortion has negligible influence on heat release rate curves in cone calorimeter tests.

  8. Effect of Gas Phase Heat Sink on Suppression of Opposed Flow Flame Spread over Thin Solid Fuels in Microgravity Environment

    Directory of Open Access Journals (Sweden)

    Vinayak Malhotra

    2012-01-01

    Full Text Available A two-dimensional numerical model of opposed flow flame spread over thin solid fuel is formulated and modeled to study the effect of gas phase heat sink (a wire mesh placed parallel to the fuel surface on the flame-spread rate and flame extinction. The work focuses on the performance of the wire mesh in microgravity environment at an oxygen concentration 21%. The simulations were carried out for various mesh parameters (wire diameter, “” and number of wires per unit length, “” and mesh distance perpendicular to fuel surface “”. Simulations show that wire mesh is effective in reducing flame-spread rate when placed at distance less than flame width (which is about 1 cm. Mesh wire diameter is determined not to have major influence on heat transfer. However, smaller wire diameter is preferred for better aerodynamics and for increasing heat transfer surface area (here prescribed by parameter “”. Flame suppression exhibits stronger dependence on number of wires per unit length; however, it is relatively insensitive to number of wires per unit length beyond certain value (here 20 cm−1.

  9. Investigation of H2 Concentration and Combustion Instability Effects on the Kinetics of Strained Syngas Flames

    Energy Technology Data Exchange (ETDEWEB)

    Ahsan R. Choudhuri

    2006-08-07

    The flame extinction limits of syngas (H{sub 2}-CO) flames were measured using a twin-flame-counter-flow burner. Plots of Extinction limits vs. global stretch rates were generated at different mixture compositions and an extrapolation method was used to calculate the flame extinction limit corresponding to an experimentally unattainable zero-stretch condition. The zero-stretch extinction limit of H{sub 2}-CO mixtures decreases (from rich to lean) with the increase in H{sub 2} concentration in the mixture. The average difference between the measured flame extinction limit and the Le Chatelier's calculation is around {approx} 7%. The measured OH{sup -} chemiluminescent data indicates that regardless of mixture compositions the OH radical concentration reduces (within the experimental uncertainties) to an extinction value prior to the flame extinction. Flame extinction limits of H{sub 2}-CO mixtures measured in a flat-flame burner configuration also show a similar relation. Additionally, the measured laminar flame velocity close to the extinction indicates that regardless of fuel composition the premixed flame of hydrogen fuel blends extinguishes when the mixture laminar flame velocity falls below a critical value. The critical laminar flame velocity at extinction for H{sub 2}-CO premixed flames (measured in the flat flame burner configuration) is found to be 3.77({+-}0.38) cm/s. An externally perturbed H{sub 2}-CO twin flame was not experimentally achievable for the mixture conditions used in the present investigation. A slightest perturbation in the flow-field distorts the H{sub 2}-CO twin-flame. The flame becomes highly unstable with the introduction of an externally excited flow oscillation.

  10. Unsteady Flame Embedding

    KAUST Repository

    El-Asrag, Hossam A.

    2011-01-01

    Direct simulation of all the length and time scales relevant to practical combustion processes is computationally prohibitive. When combustion processes are driven by reaction and transport phenomena occurring at the unresolved scales of a numerical simulation, one must introduce a dynamic subgrid model that accounts for the multiscale nature of the problem using information available on a resolvable grid. Here, we discuss a model that captures unsteady flow-flame interactions- including extinction, re-ignition, and history effects-via embedded simulations at the subgrid level. The model efficiently accounts for subgrid flame structure and incorporates detailed chemistry and transport, allowing more accurate prediction of the stretch effect and the heat release. In this chapter we first review the work done in the past thirty years to develop the flame embedding concept. Next we present a formulation for the same concept that is compatible with Large Eddy Simulation in the flamelet regimes. The unsteady flame embedding approach (UFE) treats the flame as an ensemble of locally one-dimensional flames, similar to the flamelet approach. However, a set of elemental one-dimensional flames is used to describe the turbulent flame structure directly at the subgrid level. The calculations employ a one-dimensional unsteady flame model that incorporates unsteady strain rate, curvature, and mixture boundary conditions imposed by the resolved scales. The model is used for closure of the subgrid terms in the context of large eddy simulation. Direct numerical simulation (DNS) data from a flame-vortex interaction problem is used for comparison. © Springer Science+Business Media B.V. 2011.

  11. Effect of chemistry and turbulence on NO formation in oxygen-natural gas flames

    Science.gov (United States)

    Samaniego, J. -M.; Egolfopoulos, F. N.; Bowman, C. T.

    1996-01-01

    The effects of chemistry and turbulence on NO formation in oxygen-natural turbulent diffusion flames gas flames have been investigated. The chemistry of nitric oxides has been studied numerically in the counterflow configuration. Systematic calculations with the GRI 2.11 mechanism for combustion of methane and NO chemistry were conducted to provide a base case. It was shown that the 'simple' Zeldovich mechanism accounts for more than 75% of N2 consumption in the flame in a range of strain-rates varying between 10 and 1000 s-l. The main shortcomings of this mechanism are: 1) overestimation (15%) of the NO production rate at low strain-rates because it does not capture the reburn due to the hydrocarbon chemistry, and 2) underestimation (25%) of the NO production rate at high strainrates because it ignores NO production through the prompt mechanism. Reburn through the Zeldovich mechanism alone proves to be significant at low strain-rates. A one-step model based on the Zeldovich mechanism and including reburn has been developed. It shows good agreement with the GRI mechanism at low strain-rates but underestimates significantly N2 consumption (about 50%) at high strain-rates. The role of turbulence has been assessed by using an existing 3-D DNS data base of a diffusion flame in decaying turbulence. Two PDF closure models used in practical industrial codes for turbulent NO formation have been tested. A simpler version of the global one-step chemical scheme for NO compared to that developed in this study was used to test the closure assumptions of the PDF models, because the data base could not provide all the necessary ingredients. Despite this simplification, it was possible to demonstrate that the current PDF models for NO overestimate significantly the NO production rate due to the fact that they neglect the correlations between the fluctuations in oxygen concentration and temperature. A single scalar PDF model for temperature that accounts for such correlations based

  12. Turbulence in laminar premixed V-flames

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xiaoqian(张孝谦); LEI; Yu(雷宇); WANG; Baorui(王宝瑞); WANG; Yue(王岳); WEI; Minggang(韦明罡)

    2003-01-01

    Strong velocity fluctuations had been found in the laminar premixed V-flames. These velocity fluctuations are closely related to the chemical reaction. But the effects of the upstream combustible mixture velocity on the velocity fluctuations inside the flame are quite weak. The probability distribution function (PDF) of the velocity in the centre region of the flame appears "flat top" shaped. By analyzing the experiment results the flame-flow interactions are found to affect the flame not only at large scale in the flow field but also at small scale inside the flame. These effects will give rise to flame generated small scale turbulences.

  13. Polybrominated diphenyl ether (PBDE) flame retardants: environmental contamination, human body burden and potential adverse health effects.

    Science.gov (United States)

    Costa, Lucio G; Giordano, Gennaro; Tagliaferri, Sara; Caglieri, Andrea; Mutti, Antonio

    2008-12-01

    Polybrominated diphenyl ethers (PBDEs) are an important class of flame retardants, widely used in a variety of consumer products. In the past several years, PBDEs have become widespread environmental pollutants, and have been detected in water, soil, air, animals and human tissues. Exposure occurs in particular through the diet and the indoor environment. Infants and toddlers have the highest body burden, due to exposure via maternal milk and through house dust. Tetra-, penta- and hexa-BDEs are the congeners most commonly found in humans. Recent concerns on possible adverse health effects of PBDEs are focusing on their potential endocrine disrupting effects and on developmental neurotoxicity.

  14. Feature Selection and Effective Classifiers.

    Science.gov (United States)

    Deogun, Jitender S.; Choubey, Suresh K.; Raghavan, Vijay V.; Sever, Hayri

    1998-01-01

    Develops and analyzes four algorithms for feature selection in the context of rough set methodology. Experimental results confirm the expected relationship between the time complexity of these algorithms and the classification accuracy of the resulting upper classifiers. When compared, results of upper classifiers perform better than lower…

  15. Effective Feature Preprocessing for Time Series Forecasting

    DEFF Research Database (Denmark)

    Zhao, Junhua; Dong, Zhaoyang; Xu, Zhao

    2006-01-01

    Time series forecasting is an important area in data mining research. Feature preprocessing techniques have significant influence on forecasting accuracy, therefore are essential in a forecasting model. Although several feature preprocessing techniques have been applied in time series forecasting...... performance in time series forecasting. It is demonstrated in our experiment that, effective feature preprocessing can significantly enhance forecasting accuracy. This research can be a useful guidance for researchers on effectively selecting feature preprocessing techniques and integrating them with time...... series forecasting models....

  16. Flame Stretch Analysis in Diffusion Flames with Inert Gas

    Institute of Scientific and Technical Information of China (English)

    Ay Su; Ying-Chieh Liu

    2001-01-01

    Experimental investigations of impinging flame with fuel mixed with non-reaction gas were conducted.According to the observations of combustion test and temperature measurement, the non-reaction gas might dilute the local concentration of fuel in the diffusion process. The shape of the flame was symmetrical due to the flame stretch force. Results show that the conical flame might be de-structured by the addition of inert gas in pure methane fuel. The impinging flame became shorter and bluer as nitrogen was added to the fuel. The conditions of N2/CH4 equal to 1/2 and 1/1 show a wider plane in the YZ plane. The effect of inert gas overcomes the flame stretch and destroys the symmetrical column flame as well as the cold flow. Nitrogen addition also enhances the diffusion rate and combustion efficiency.

  17. Premixed flame propagation in vertical tubes

    CERN Document Server

    Kazakov, Kirill A

    2015-01-01

    Analytical treatment of premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations describing quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds, and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by the gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are ide...

  18. 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.

  19. A Computational and Experimental Study of Coflow Laminar Methane/Air Diffusion Flames: Effects of Fuel Dilution, Inlet Velocity, and Gravity

    Science.gov (United States)

    Cao, S.; Ma, B.; Bennett, B. A. V.; Giassi, D.; Stocker, D. P.; Takahashi, F.; Long, M. B.; Smooke, M. D.

    2014-01-01

    The influences of fuel dilution, inlet velocity, and gravity on the shape and structure of laminar coflow CH4-air diffusion flames were investigated computationally and experimentally. A series of nitrogen-diluted flames measured in the Structure and Liftoff in Combustion Experiment (SLICE) on board the International Space Station was assessed numerically under microgravity (mu g) and normal gravity (1g) conditions with CH4 mole fraction ranging from 0.4 to 1.0 and average inlet velocity ranging from 23 to 90 cm/s. Computationally, the MC-Smooth vorticity-velocity formulation was employed to describe the reactive gaseous mixture, and soot evolution was modeled by sectional aerosol equations. The governing equations and boundary conditions were discretized on a two-dimensional computational domain by finite differences, and the resulting set of fully coupled, strongly nonlinear equations was solved simultaneously at all points using a damped, modified Newton's method. Experimentally, flame shape and soot temperature were determined by flame emission images recorded by a digital color camera. Very good agreement between computation and measurement was obtained, and the conclusions were as follows. (1) Buoyant and nonbuoyant luminous flame lengths are proportional to the mass flow rate of the fuel mixture; computed and measured nonbuoyant flames are noticeably longer than their 1g counterparts; the effect of fuel dilution on flame shape (i.e., flame length and flame radius) is negligible when the flame shape is normalized by the methane flow rate. (2) Buoyancy-induced reduction of the flame radius through radially inward convection near the flame front is demonstrated. (3) Buoyant and nonbuoyant flame structure is mainly controlled by the fuel mass flow rate, and the effects from fuel dilution and inlet velocity are secondary.

  20. The effect of fuel stream mixing on the performance of pulverised coal flames

    Energy Technology Data Exchange (ETDEWEB)

    Lockwood, F.C.; Diedrichsen, J.; Kandamby, N.; Costen, P.; Abbas, T. [Imperial College of Science, Technology and Medicine, London (United Kingdom). Mechanical Engineering Dept.

    1998-12-31

    A programme of research, integrating experimental investigations undertaken in a large laboratory scale furnace with the development of mathematical modelling techniques has been performed in order to determine the effect of fuel and air stream mixing on the performance of atmospheric pulverised coal combustion, with reference to utility fired boilers. Several mixing configurations have been investigated, namely, the mixing of the fuel streams prior to injection (static blending), within the flame (dynamic blending) and in the combustion zone (reburn). During the blending exercise, in collaboration with International Combustion Limited, Derby, two world-traded coals (a Rand variety of coal from South Africa and Shamrock from the USA) have been premixed prior to being fired. A set of comparative data for flame performance and NO{sub x} emissions for identical blend ratios has been established for both in the large scale laboratory rated at 150 kW in London and at 38 MW scale in the combustion test rig at ICL, Derby. The blending exercise was continued through dynamic blending experiments in which two independent coal feeders and conduits have been incorporated into the existing system so that the initial mixing of the two fuels takes place at the burner exit. Using the same blending ratios as in the static blending trials, an assessment has been made of the effect of injection location of each of the fuels to determine the conditions which result in the lowest NO{sub x} levels while maintaining the broadest flame stability limits. 11 refs., 18 figs., 8 tabs.

  1. Assessing oestrogenic effects of brominated flame retardants hexabromocyclododecane and tetrabromobisphenol A on MCF-7 cells.

    Science.gov (United States)

    Dorosh, A; Děd, L; Elzeinová, F; Pěknicová, J

    2011-01-01

    Tetrabromobisphenol A (TBBPA) is the main flame retardant used in printed circuit boards and laminates. The human population is highly exposed to TBBPA as it is used in consumer electronics as well as office and communication equipment. The main use of hexabromocyclododecane (HBCD) is in insulation foam boards, which are widely used in the construction sector. Brominated flame retardants may possess endocrine disrupting activity and thus represent a threat to the environment, including humans and their reproduction. The aim of this work was to evaluate the oestrogenic effects of TBBPA and HBCD in vitro on MCF-7 cells. We used the proliferation test (E-screen assay) in MCF-7 breast cancer cells and reverse transcription quantitative polymerase chain reaction analysis of TFF1 gene expression to analyse oestrogenicity of the studied compounds. RT-qPCR has proved to be a fast and valuable molecular technique in gene expression quantification. HBCD but not TBBPA increased cell proliferation in MCF-7 cells and up-regulated TFF1 gene expression in a concentration-dependent manner. Anti-oestrogen ICI 182,780 inhibited up-regulation of TFF1 by HBCD. We have shown that HBCD displays oestrogen- like effects on MCF-7 cells. TBBPA, on the other hand, has not shown any oestrogenic effect mediated by the oestrogen receptor α.

  2. 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.

  3. Flame Temperature Effect on the Structure of SiC Nanoparticles Grown by Laser Pyrolysis

    Science.gov (United States)

    Herlin-Boime, N.; Vicens, J.; Dufour, C.; Ténégal, F.; Reynaud, C.; Rizk, R.

    2004-02-01

    Small SiC nanoparticles (10 nm diameter) have been grown in a flow reactor by CO2 laser pyrolysis from a C2H2 and SiH4 mixture. The laser radiation is strongly absorbed by SiH4 vibration. The energy is transferred to the reactive medium and leads to the dissociation of molecules and the subsequent growth of the nanoparticles. The reaction happens with a flame. The purpose of the experiments reported in this paper is to limit the size of the growing particles to the nanometric scale for which specific properties are expected to appear. Therefore the effects of experimental parameters on the structure and chemical composition of nanoparticles have been investigated. For a given reactive mixture and gas velocity, the flame temperature is governed by the laser power. In this study, the temperature was varied from 875°C to 1100°C. The chemical analysis of the products indicate that their composition is a function of the temperature. For the same C/Si atomic ratio in the gaseous phase, the C/Si ratio in the powder increases from 0.7 at 875°C up to 1.02 at 1100°C, indicating a growth mechanism limited by C2H2 dissociation. As expected, X-ray diffraction has shown an improved crystallisation with increasing temperature. Transmission electron microscopy observations have revealed the formation of 10 nm grains for all values of laser power (or flame temperature). These grains appear amorphous at low temperature, whereas they contain an increasing number of nanocrystals (2 nm diameter) when the temperature increases. These results pave the way to a better control of the structure and chemical composition of laser synthesised SiC nanoparticles in the 10 nm range.

  4. Numerical study of effects of the intermediates and initial conditions on flame propagation in a real homogeneous charge compression ignition engine

    Directory of Open Access Journals (Sweden)

    Zhang Meng

    2014-01-01

    Full Text Available The premixed flame speed under a small four stock homogeneous charge compression ignition engine, fueled with dimethyl ether, was investigated. The effects of intermediate species, initial temperature, initial pressure, exhaust gas recirculation, and equivalence ratio were studied and compared to the baseline condition. Results show that, under all conditions, the flame speeds calculated without intermediates are higher than those which took the intermediates in consideration. Flame speeds increase with the increase of crank angle. The increase rate is divided into three regions and the increase rate is obviously high in the event of low temperature heat release. Initial temperature and pressure only affect the crank angle of flame speed, but have little influence on its value. Equivalence ratio and exhaust gas recirculation ratio do not only distinctly decrease the flame speed, but also advance the crank angle of flame speed.

  5. Effect of borates on thermal degradation and flame retardancy of epoxy resins using polyhedral oligomeric silsesquioxane as a curing agent

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hongyu [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Department of Building and Construction, City University of Hong Kong and USTC-CityU Joint Advanced Research Centre, Suzhou (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute of University of Science and Technology of China, Suzhou (China); Wang, Xin; Yu, Bin; Song, Lei [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute of University of Science and Technology of China, Suzhou (China); Yuen, Richard K.K. [Department of Building and Construction, City University of Hong Kong and USTC-CityU Joint Advanced Research Centre, Suzhou (China)

    2012-05-10

    Highlights: Black-Right-Pointing-Pointer Flame retarded epoxy resins with borates were prepared using POSS as a curing agent. Black-Right-Pointing-Pointer Borates and POSS exhibited a synergistic effect on flame retardancy of epoxy resins. Black-Right-Pointing-Pointer Incorporation of borates and POSS significantly reduced the heat release rate. - Abstract: A series of flame-retardant epoxy resins containing boron and silicon were obtained through a crosslinking reaction, using tris (2-hydroxypropyl) borate (THPB) together with octaaminophenyl POSS (OapPOSS) as the curing agents. The limiting oxygen index (LOI) reached 30.5% when the contents of boron and silicon in the cured system were 1.5% and 0.5%, respectively, indicating that THPB and OapPOSS exhibited good flame retardant effect on epoxy resins (EP). Microscale combustion calorimetry (MCC) results indicated that the peak heat release rate (PHRR) and total heat release (THR) of the cured systems were reduced by 69% and 46%, respectively, compared to those of pure EP. Moreover, the thermal degradation process and flame retardant mechanism of the composites were investigated by TGA, real time FTIR and TG-FTIR. The chemical components of the char residues were explored by XPS.

  6. Effect of pointed and diffused air injection on premixed flame confined in a Rijke tube

    Directory of Open Access Journals (Sweden)

    Nilaj N. Deshmukh

    2016-12-01

    Full Text Available The coupling between pressure fluctuations and unsteady heat release in a combustion systems results in acoustic oscillations inside the combustion system. These acoustic oscillations, when grow sufficiently, may cause serious structural damage thereby reducing the lifespan of jet engines, gas turbines, and industrial burners. The aim of the first part of study is to define acoustically stable and unstable regions. The second part is focused on studying the effect of change in pressure field near the flame on the amplitude and frequency of the oscillations of instability. This study is carried out for three-burner positions and equivalence ratio of 0.7 by varying heat supply and total flow rate. The results show two acoustically unstable regions for 0.1 and 0.2 burner positions and only one acoustically unstable region for 0.25 burner position. The effect of pointed injection and diffused injection over a premixed flame on the sound pressure level was studied. The results show for burner position of x/L = 0.2 there is 25 dB suppression is possible using pointed injection at higher total flow rate. The experiment of diffused injection shows sound amplification more than 12 dB was observed.

  7. Effective Feature Preprocessing for Time Series Forecasting

    DEFF Research Database (Denmark)

    Zhao, Junhua; Dong, Zhaoyang; Xu, Zhao

    2006-01-01

    Time series forecasting is an important area in data mining research. Feature preprocessing techniques have significant influence on forecasting accuracy, therefore are essential in a forecasting model. Although several feature preprocessing techniques have been applied in time series forecasting......, there is so far no systematic research to study and compare their performance. How to select effective techniques of feature preprocessing in a forecasting model remains a problem. In this paper, the authors conduct a comprehensive study of existing feature preprocessing techniques to evaluate their empirical...... performance in time series forecasting. It is demonstrated in our experiment that, effective feature preprocessing can significantly enhance forecasting accuracy. This research can be a useful guidance for researchers on effectively selecting feature preprocessing techniques and integrating them with time...

  8. Irradiation and flame retardant effect of poly[bis(phenoxyphosphazene)] and magnesium hydroxide in LDPE composites

    Institute of Scientific and Technical Information of China (English)

    李建喜; 张聪; 陈涛; 李林繁; 李景烨

    2015-01-01

    Poly[bis(phenoxyphosphazene)] (PBPP) and magnesium hydroxide (MH) are used as a flame retardant blend with low-density polyethylene (LDPE) for the nuclear cable. This study aims to investigate the effects of PBPP in MH-LDPE blend composites on flame retardance and electron beam irradiation. The structure, morphology, and properties of the blend composites irradiated by an electron beam to different absorbed doses were char-acterized. The results indicated that PBPP provides lubrication during processing. As the PBPP content in the blend increases the melt flow rate at 20 phr MH, meaning the material is easier to process. The higher the PBPP content, the higher the limiting-oxygen index. The elongation at the break of the PBPP containing composites (at 50 phr MH) was evidently higher than the non-PBPP ones at different absorbed doses by electron beam irradiation. The thermogravimetric analysis results indicated that the improved mechanical property, resulting from electron-beam irradiation, could be attributed to the consumption of PBPP.

  9. Fuel density effect on near nozzle flow field in small laminar coflow diffusion flames

    KAUST Repository

    Xiong, Yuan

    2015-01-01

    Flow characteristics in small coflow diffusion flames were investigated with a particular focus on the near-nozzle region and on the buoyancy force exerted on fuels with densities lighter and heavier than air (methane, ethylene, propane, and n-butane). The flow-fields were visualized through the trajectories of seed particles. The particle image velocimetry technique was also adopted for quantitative velocity field measurements. The results showed that the buoyancy force exerted on the fuel as well as on burnt gas significantly distorted the near-nozzle flow-fields. In the fuels with densities heavier than air, recirculation zones were formed very close to the nozzle, emphasizing the importance of the relative density of the fuel to that of the air on the flow-field. Nozzle heating influenced the near-nozzle flow-field particularly among lighter fuels (methane and ethylene). Numerical simulations were also conducted, focusing specifically on the effect of specifying inlet boundary conditions for fuel. The results showed that a fuel inlet boundary with a fully developed velocity profile for cases with long tubes should be specified inside the fuel tube to permit satisfactory prediction of the flow-field. The calculated temperature fields also indicated the importance of the selection of the location of the inlet boundary, especially in testing various combustion models that include soot in small coflow diffusion flames. © 2014 The Combustion Institute.

  10. Inhibition Effect of Phosphorus Flame Retardants on the Fire Disasters Induced by Spontaneous Combustion of Coal

    Directory of Open Access Journals (Sweden)

    Yibo Tang

    2017-01-01

    Full Text Available Coal spontaneous combustion (CSC generally induces fire disasters in underground mines, thus causing serious casualties, environmental pollution, and property loss around the world. By using six P-containing additives to process three typical coal samples, this study investigated the variations of the self-ignition characteristics of the coal samples before and after treatment. The analysis was performed by combining thermogravimetric analysis/differential scanning calorimetry (TG/DSC Fourier transform infrared spectrometer (FTIR and low temperature oxidation. Experimental results showed that P-containing inhibitors could effectively restrain the heat emitted in the combustion of coal samples and therefore the ignition temperature of the coal samples was delayed at varying degrees. The combustion rate of the coal samples was reduced as well. At the temperatures ranging from 50°C to 150°C, the activation energy of the coal samples after the treatment was found to increase, which indicated that the coal samples were more difficult to be oxidized. After being treated with phosphorus flame retardants (PFRs, the content of several active groups represented by the C-O structure in the three coal samples was proved to be obviously changed. This suggested that PFRs could significantly inhibit the content of CO generated by the low temperature oxidation of coal, and the flame-retardant efficiency grew with the increasing temperature. At 200°C, the maximal inhibition efficiency reached approximately 85%.

  11. Study of the Synergistic Effect of Nanoporous Nickel Phosphates on Novel Intumescent Flame Retardant Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Shibin Nie

    2015-01-01

    Full Text Available A char forming agent (CFA and silica-gel microencapsulated ammonium polyphosphate (Si-MCAPP were selected to form novel intumescent flame retardant system to prepare flame retardant polypropylene (PP composites, and then the influences of nanoporous nickel phosphates (NiP on the thermal and flame retardant properties of flame retardant PP composites were studied by the real time FTIR (RTFTIR spectra, limited oxygen index (LOI test, and the scanning electron microscopy. RTFTIR shows the addition of NiP can improve the thermal stability of flame retardant PP composites. LOI test shows LOI value is increased with the increase of the content of NiP, and the optimized concentration of NiP is 1.0%. Furthermore, smoke toxicity of the novel flame retardant PP composites was studied by mice experiment. The upper limit of the no death smoke concentration of the composite is 12.37 mg/L.

  12. 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.

  13. Simulation analysis of within-day flow fluctuation effects on trout below flaming Gorge Dam.

    Energy Technology Data Exchange (ETDEWEB)

    Railsback, S. F.; Hayse, J. W.; LaGory, K. E.; Environmental Science Division; EPRI

    2006-01-01

    In addition to being renewable, hydropower has the advantage of allowing rapid load-following, in that the generation rate can easily be varied within a day to match the demand for power. However, the flow fluctuations that result from load-following can be controversial, in part because they may affect downstream fish populations. At Flaming Gorge Dam, located on the Green River in northeastern Utah, concern has been raised about whether flow fluctuations caused by the dam disrupt feeding at a tailwater trout fishery, as fish move in response to flow changes and as the flow changes alter the amount or timing of the invertebrate drift that trout feed on. Western Area Power Administration (Western), which controls power production on submonthly time scales, has made several operational changes to address concerns about flow fluctuation effects on fisheries. These changes include reducing the number of daily flow peaks from two to one and operating within a restricted range of flows. These changes significantly reduce the value of the power produced at Flaming Gorge Dam and put higher load-following pressure on other power plants. Consequently, Western has great interest in understanding what benefits these restrictions provide to the fishery and whether adjusting the restrictions could provide a better tradeoff between power and non-power concerns. Directly evaluating the effects of flow fluctuations on fish populations is unfortunately difficult. Effects are expected to be relatively small, so tightly controlled experiments with large sample sizes and long study durations would be needed to evaluate them. Such experiments would be extremely expensive and would be subject to the confounding effects of uncontrollable variations in factors such as runoff and weather. Computer simulation using individual-based models (IBMs) is an alternative study approach for ecological problems that are not amenable to analysis using field studies alone. An IBM simulates how a

  14. Matrix effects on the determination of manganese in geological materials by atomic-absorption spectrophotometry under different flame conditions

    Science.gov (United States)

    Sanzolone, R.F.; Chao, T.T.

    1978-01-01

    Suppression caused by five of the seven matrix elements studied (Si, Al, Fe, Ca and Mg) was observed in the atomic-absorption determination of manganese in geological materials, when synthetic solutions and the recommended oxidizing air-acetylene flame were used. The magnitude of the suppression effects depends on (1) the kind and concentration of the interfering elements, (2) the type of acid medium, and (3) the concentration of manganese to be determined. All interferences noted are removed or alleviated by using a reducing nitrous oxide-acetylene flame. The atomic-absorption method using this flame can be applied to the determination of total and extractable manganese in a wide range of geological materials without interferences. Analyses of six U.S. Geological Survey rock standards for manganese gave results in agreement with the reported values. ?? 1978.

  15. Effect of Intumescent Flame Retardants on the Properties of Polyurethanes Based on Tall Oil Fatty Acids Esters

    Directory of Open Access Journals (Sweden)

    Vladimir Yakushin

    2015-06-01

    Full Text Available Normal 0 false false false MicrosoftInternetExplorer4 The efficiency of using intumescent flame retardants in polyurethane coatings based on tall oil fatty acids esters was assessed. The influence of the content of each of the flame retardants (ammonium polyphosphate, melamine and pentaerythriol separately on the flammability parameters of wood samples with polyurethane coatings in a cone calorimeter test, as well as on the thermal and mechanical properties of the polyurethane itself, were investigated. the effect of the ratios of double and triple combinations of the mentioned flame retardants on the specified properties was studied. It has been found that, for the given type of polyester urethane, ammonium polyphosphate decreases the flammability of polyurethane to the greatest extent. Melamine, and melamine in combination with ammonium polyphosphate, decrease the smoke release upon polyurethane combustion. DOI: http://dx.doi.org/10.5755/j01.ms.21.2.5784

  16. Effect of Flame Retardant Containing Phosphorus and Silicone on Thermal Performance of PC/ABS

    Institute of Scientific and Technical Information of China (English)

    WEI Ping; WU Dan; ZHONG Hanfang; DU Jianxin

    2009-01-01

    A flame retardant (DPA-SiN) containing phosphorus, nitrogen and silicon elements was synthesized. The halogen free flame retardant was incorporated into PC/ABS to improve its flame retardancy. The flame-retardant properties of the PC/ABS/DPA-SiN blends were estimated bylimiting oxygen index (LOI) values and CONE Calorimeter, while thermal stabilities were investi-gated through thermo gravimetric analysis (TGA). The PC/ABS/DPA-SiN blends were thermally de-graded at 400 ℃ for different amounts of time and studied by Fourier transform infrared spectros-copy (FTIR) to better understand the degradation behavior of PC/ABS/DPA-SiN.

  17. The effects of burner stabilization on Fenimore NO formation in low-pressure, fuel-rich premixed CH4/O2/N2 flames

    NARCIS (Netherlands)

    van Essen, Vincent; Sepman, Alexey; Mokhov, A. V.; Levinsky, H. B.

    We investigate the effects of varying the degree of burner stabilization on Fenimore NO formation in fuel-rich low-pressure flat CH4/O-2/N-2 flames. Towards this end, axial profiles of flame temperature and OH, NO and CH mole fractions are measured using laser-induced fluorescence (LIF). The

  18. Effects of neonatal exposure to the flame retardant tetrabromobisphenol-A, aluminum diethylphosphinate or zinc stannate on long-term potentiation and synaptic protein levels in mice

    NARCIS (Netherlands)

    Hendriks, Hester S; Koolen, Lucas A E; Dingemans, Milou M L; Viberg, Henrik; Lee, Iwa; Leonards, Pim E G; Ramakers, Geert M J; Westerink, Remco H S

    2015-01-01

    Brominated flame retardants such as tetrabromobisphenol-A (TBBPA) may exert (developmental) neurotoxic effects. However, data on (neuro)toxicity of halogen-free flame retardants (HFFRs) are scarce. Recent in vitro studies indicated a high neurotoxic potential for some HFFRs, e.g., zinc stannate (ZS)

  19. Effects of neonatal exposure to the flame retardant tetrabromobisphenol-A, aluminum diethylphosphinate or zinc stannate on long-term potentiation and synaptic protein levels in mice

    NARCIS (Netherlands)

    Hendriks, Hester; Koolen, Lucas; Dingemans, Milou; Viberg, Henrik; Lee, Iwa; Leonards, P.E.G.; Ramakers, G.M.J.; Westerink, Remco

    2014-01-01

    Brominated flame retardants such as tetrabromobisphenol-A (TBBPA) may exert (developmental) neurotoxic effects. However, data on (neuro)toxicity of halogen-free flame retardants (HFFRs) are scarce. Recent in vitro studies indicated a high neurotoxic potential for some HFFRs, e.g., zinc stannate (ZS)

  20. The Effect of Velocity on the Extinction Behavior of a Diffusion Flame during Transient Depressurization

    Science.gov (United States)

    Goldmeer, Jeffrey S.; Urban, David L.; Tien, James

    1999-01-01

    Current fire suppression plans for the International Space Station include the use of venting (depressurization) as a method for extinguishing a fire. Until recently this process had only been examined as part of a material flammability experiment performed on Skylab in the early 1970's. Due to the low initial pressure (0.35 Atm) and high oxygen concentration (65%), the Skylab experimental results are not applicable for understanding the effects of venting on a fire in a space station environment (21%O2, 1 Atm). Recent research examined the extinction behavior of a diffusion flame over a polymethyl methacrylate (PMMA) cylinder during a transient depressurization in low-gravity. The numerical model was used to examine extinction limits as a function of depressurization rate, forced flow velocity, and initial solid phase temperature. The experimental and numerically predicted extinction data indicated that as the solid phase temperature increased the pressure required to extinguish the flame decreased. The numerical model was also used to examine conditions not obtainable in the low-gravity experiments. From these simulations, a series of extinction boundaries were generated that showed a region of increased flammability existed at a forced flow of 10 cm/s. Analysis of these extinction boundaries indicated that they were quasi-steady in nature, and that the final extinction conditions were independent of the transient process. The velocity range in the previous study was limited and thus the results did not examine the effects of velocities less than 1 cm/s or greater than 20 cm/s. This study utilized low-gravity experiments performed on NASA's Reduced-gravity Research Aircraft Laboratory and numerical simulations to examine conditions applicable to the Space Station environment. This paper extends the analysis of the previous study to a comprehensive examination of the effect of increased velocity on extinction behavior and extinction limits during a transient

  1. Dynamics of unconfined spherical flames

    CERN Document Server

    Leblanc, Louis; Dennis, Kadeem; Zhe,; Liang,; Radulescu, Matei I

    2012-01-01

    Using the soap bubble technique, we visualize the dynamics of unconfined hydrogen-air flames using high speed schlieren video. We show that for sufficiently weak mixtures, i.e., low flame speeds, buoyancy effects become important. Flame balls of a critical dimension begin to rise. The experiments are found in very good agreement with the scaling laws proposed by Zingale and Dursi. We report the results in a fluid dynamics video.

  2. 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.

  3. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  4. Subacute effects of the brominated flame retardants hexabromocyclododecane and tetrabromobisphenol A on hepatic cytochrome P450 levels in rats.

    NARCIS (Netherlands)

    Germer, Silke; Piersma, Aldert H; Ven, Leo T M van der; Kamyschnikow, Andreas; Fery, Yvonne; Schmitz, Hans-Joachim; Schrenk, Dieter

    2006-01-01

    The brominated flame retardants tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are found in the environment, e.g., in sediments and organisms, in food items, human blood samples and mother's milk. In this study, the effects of both compounds on rat hepatic cytochrome P450 (CYP) leve

  5. Local Limit Phenomena, Flow Compression, and Fuel Cracking Effects in High-Speed Turbulent Flames

    Science.gov (United States)

    2015-06-01

    dynamic adaptive hybrid integration, was developed for stiff chemistry. 15. SUBJECT TERMS chemical explosive mode analysis ( CEMA ...TECHNICAL DISCUSSION 1. Chemical explosive mode analysis ( CEMA ) for computational flame diagnostics The method of chemical explosive mode...analysis ( CEMA ) is a systematic approach to identify limit flame phenomena, including local ignition, extinction, and premixed and non- premixed reaction

  6. Quenching of excited alkali atoms and related effects in flames: Part I. theoretical analysis

    NARCIS (Netherlands)

    Hooymayers, H.P.; Alkemade, C.T.J.

    1966-01-01

    An a.c. photoelectric detection device has been used to determine the yield factor p of resonance fluorescence of the Na(5890/96) Å and K(7665/99) Å and (4044/47) Å resonance doublets in atmospheric flames as a function of the composition and temperature of the flame. From these measurements the val

  7. Quenching of excited alkali atoms and related effects in flames: Part II. Measurements and discussion

    NARCIS (Netherlands)

    Hooymayers, H.P.; Alkemade, C.T.J.

    1966-01-01

    An alternating current photoelectric device has been used for determining the yield factor p of resonance flourescence of the yellow sodium doublet and the infrared and blue potassium doublets in flames at atmospheric pressure as a function of the temperature and composition of the burnt flame gases

  8. Effects of Flaming Gorge Dam hydropower operations on downstream flow, stage, and sediment transport

    Energy Technology Data Exchange (ETDEWEB)

    Yin, S.C.L.; Tomasko, D.; Cho, H.E.; Williams, G. [Argonne National Lab., IL (United States); McCoy, J.; Palmer, C. [USDOE Western Area Power Administration, Salt Lake City, UT (United States)

    1996-11-01

    Hydropower operations at Flaming Gorge Dam, located on the Green River in Utah, can produce rapid downstream changes in flow and stage. These changes can in turn affect sediment transport and ecologic resources below the dam. To evaluate these effects, four hydropower operational scenarios with varying degrees of hydropower-release fluctuations were examined. This study demonstrates that the combined use of river-flow routing, water-surface profile, and sediment-transport models can provide useful information for evaluating the potential impacts of hydropower-operations on ecological and other resources downstream of the dam. Study results show that flow fluctuations may or may not persist for a long distance, depending on the initial magnitude of fluctuation and the duration of hydropower peaking. Stage fluctuations depend not only on flow fluctuations but also on river channel characteristics, such as channel width and longitudinal slope.

  9. Physical properties and flame-retardant effects of polyurethane coatings containing pyrophosphoric lactone modified polyesters

    Energy Technology Data Exchange (ETDEWEB)

    Chung, D.J.; Kim, S.R.; Park, H.J.; Park, H.S. [Myongji University, Yongin (Korea); Kim, S.J. [Korea Institute of Construction Materials, Seoul (Korea)

    2002-05-01

    Pyrophosphoric lactone modified polyester(PATT) containing two phosphorous functional groups in one unit structure was synthesized to prepare a non-toxic reactive flame-retardant coatings. Then the PATT was cured at room temperature with isocyanate, toluene diisocyanate-isocyanurate, to get a two-component polyurethane flame-retardant coatings (PIPUC). Comparing physical properties of the films of PIPUC with those of film of non-flame-retardant coating, there was no deterioration observed in physical properties by the introduction of a flame-retarding component into the resin. We found that the char lengths measured by 45 deg. Meckel burner method were 3.1{approx}4.4 cm and LOI values recorded 27{approx}30%. These results indicate that the coating prepared in this study is a good flame-retardant. The surface structure of coatings investigated with SEM does not show any defects and phase separation. (author). 23 refs., 8 tabs., 3 figs.

  10. SYNERGISTIC EFFECT OF Cu-ZSM-5 ZEOLITE ON FLAME RETARDED PP BY MELAMINE SALT OF DIPENTAERYTHRIOL PHOSPHATE

    Institute of Scientific and Technical Information of China (English)

    Jing Gu; Dao Li; Wei-wei Liao; Yuan Li; Xing-yi Wang

    2009-01-01

    A novel intumnescent flame melamine salt of dipentaerythriol phosphate (MDP),was prepared from dipentaerythritol (DPE) polyphosphoric acid,and melamine.The flammability,combustion behavior,and thermal degradation and stability of PP-MDP were characterized.When MDP loading was 20 wt%,LOI values of the composites reached up to 27%,and UL94 rating,V-2.PP-MDP containing 1 wt% Cu-ZSM-5 presented the highest LOI value of 30.5% and UL94 rating,V-0,and released lest heat during cone test.TG data showed that the thermal degradation of PP was improved by the addition of MDP.While the loading of ZSM-5 was 1 wt% or higher,the main weight loss delayed with 50℃,and 80℃,compared with PP and PP-MDP respectively.The appropriate loading Cu-ZSM-5 made PP-MDP possess higher thermal oxidative stability.By SEM,the formation of a dense and thick char layer was observed on the char layer of PP-MDP-containing Cu-ZSM-5,responsible for high flame retardancy.So,the synergistic flame retardancy effects of MDP and Cu-ZSM-5 on PP existed.The mechanism of synergistic effect of Cu-ZSM-5 zeolite on flame retarded PP by MDP was discussed.

  11. 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.

  12. Flame dynamics of a meso-scale heat recirculating combustor

    Energy Technology Data Exchange (ETDEWEB)

    Vijayan, V.; Gupta, A.K. [Department of Mechanical Engineering, University of Maryland, College Park, MD 20742 (United States)

    2010-12-15

    The dynamics of premixed propane-air flame in a meso-scale ceramic combustor has been examined here. The flame characteristics in the combustor were examined by measuring the acoustic emissions and preheat temperatures together with high-speed cinematography. For the small-scale combustor, the volume to surface area ratio is small and hence the walls have significant effect on the global flame structure, flame location and flame dynamics. In addition to the flame-wall thermal coupling there is a coupling between flame and acoustics in the case of confined flames. Flame-wall thermal interactions lead to low frequency flame fluctuations ({proportional_to}100 Hz) depending upon the thermal response of the wall. However, the flame-acoustic interactions can result in a wide range of flame fluctuations ranging from few hundred Hz to few kHz. Wall temperature distribution is one of the factors that control the amount of reactant preheating which in turn effects the location of flame stabilization. Acoustic emission signals and high-speed flame imaging confirmed that for the present case flame-acoustic interactions have more significant effect on flame dynamics. Based on the acoustic emissions, five different flame regimes have been identified; whistling/harmonic mode, rich instability mode, lean instability mode, silent mode and pulsating flame mode. (author)

  13. 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)

  14. Flame Retardancy Effects of Graphene Nanoplatelet/Carbon Nanotube Hybrid Membranes on Carbon Fiber Reinforced Epoxy Composites

    Directory of Open Access Journals (Sweden)

    Dongxian Zhuo

    2013-01-01

    Full Text Available Carbon nanotube/graphene nanoplatelet (MWCNT/GNP hybrid membranes with lower liquid permeability and better barrier effect compared to MWCNT membranes were successfully synthesized by vacuum filtering. Their morphologies, water permeability, and pore structures were characterized by a scanning electron microscope (SEM and nitrogen adsorption isotherms. Furthermore, MWCNT/GNP membranes were used to improve the flame retardancy of carbon fiber reinforced polymer (CFRP composites, and the influence of weight percentage of GNPs on the permeability and flame retardancy of MWCNT/GNP membranes was systematically investigated. Results show that incorporation of MWCNT/GNP membranes on CFRP composite plates can remarkably improve the flame retardancy of CFRP composites. Specifically, the incorporation of hierarchical MWCNT/GNP membrane with 7.5 wt% of GNP displays a 35% reduction in the peak heat release rate (PHRR for a CFRP composite plate with the epoxy as matrix and a 11% reduction in PHRR compared with the incorporation of MWCNT membrane only. A synergistic flame retarding mechanism is suggested to be attributed to these results, which includes controlling the pore size and penetrative network structure.

  15. Effects of Acoustic Modulation and Mixed Fuel on Flame Synthesis of Carbon Nanomaterials in an Atmospheric Environment

    Directory of Open Access Journals (Sweden)

    Wei-Chieh Hu

    2016-11-01

    Full Text Available In this study, methane–ethylene jet diffusion flames modulated by acoustic excitation in an atmospheric environment were used to investigate the effects of acoustic excitation frequency and mixed fuel on nanomaterial formation. Acoustic output power was maintained at a constant value of 10 W, while the acoustic excitation frequency was varied (f = 0–90 Hz. The results show that the flame could not be stabilized on the port when the ethylene volume concentration (ΩE was less than 40% at f = 10 Hz, or when ΩE = 0% (i.e., pure methane at f = 90 Hz. The reason for this is that the flame had a low intensity and was extinguished by the entrained air due to acoustic modulation. Without acoustic excitation (f = 0 Hz, the flame was comprised of a single-layer structure for all values of ΩE, and almost no carbon nanomaterials were synthesized. However, with acoustic excitation, a double-layer flame structure was generated for frequencies close to both the natural flickering frequency and the acoustically resonant frequency. This double-layer flame structure provided a favorable flame environment for the fabrication of carbon nanomaterials. Consequently, the synthesis of carbon nano-onions was significantly enhanced by acoustic excitation near both the natural flickering frequency and the acoustically resonant frequency. At f = 20 Hz (near the natural flickering frequency for 0% ≤ ΩE ≤ 100%, a quantity of carbon nano-onions (CNOs piled like bunches of grapes was obtained as a result of improved mixing of the fuel with ambient air. High-density CNOs were also produced at f = 70 Hz (close to the acoustically resonant frequency for 40% ≤ ΩE ≤ 100%. Furthermore, carbon nanotubes (CNTs were synthesized only at 80 Hz for ΩE = 0%. The suitable temperature range for the synthesis of CNTs was slightly higher than that for the formation of CNOs (about 600 °C for CNTs; 510–600 °C for CNOs.

  16. Research on flame retardation of wool fibers

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, Ichiro; Ametani, Kazuo; Sawai, Takeshi (Tokyo Metropolitan Isotope Research Center (Japan))

    1990-01-01

    Flame retardant, vinyl phosphonate oligomer, was uniformly impregnated in wool fibers, and by irradiating low energy electron beam or cobalt-60 gamma ray, the flame retardation of fabrics was attempted, as the results, the following knowledges were obtained. At the rate of sticking of flame retardant lower than that in cotton fabrics, sufficient flame retarding property can be given. The flame retarding property withstands 30 times of washing. The lowering of strength due to the processing hardly arose. For the flame retardation, gamma-ray was more effective than electron beam. Since the accidents of burning clothes have occurred frequently, their flame retardation has been demanded. So far the flame retardation of cotton fabrics has been advanced, but this time the research on the flame retardation of wool fabrics was carried out by the same method. The experimental method is explained. As for the performance of the processed fabrics, the rate of sticking of the flame retardant, the efficiency of utilization, the flame retarding property, the endurance in washing and the tensile and tearing strength were examined. As the oxygen index was higher, the flame retarding property was higher, and in the case of the index being more than 27, the flame retarding property is sufficient, that is, the rate of sticking of 6% in serge and 5% in muslin. (K.I.).

  17. Effects of thermal radiation heat transfer on flame acceleration and transition to detonation in dust cloud flames: Origins of dust explosion

    CERN Document Server

    Ivanov, Michael A Liberman M F

    2015-01-01

    We examines regimes of the hydrogen flames propagation and ignition of mixtures heated by the radiation emitted from the flame. The gaseous phase is assumed to be transparent for radiation, while the suspended particles of the dust cloud ahead of the flame absorb and reemit the radiation. The radiant heat absorbed by the particles is then lost by conduction to the surrounding unreacted gaseous phase so that the gas phase temperature lags that of the particles. The direct numerical simulations solve the full system of two phase gas dynamic time-dependent equations with a detailed chemical kinetics for a plane flames propagating through a dust cloud. Depending on the spatial distribution of the dispersed particles and on the value of radiation absorption length the consequence of the radiative preheating of the unreacted mixture can be either the increase of the flame velocity for uniformly dispersed particles or ignition deflagration or detonation ahead of the flame via the Zel'dovich gradient mechanism in the...

  18. The Effect of Hydrogen Addition on the Combustion Characteristics of RP-3 Kerosene/Air Premixed Flames

    Directory of Open Access Journals (Sweden)

    Wen Zeng

    2017-07-01

    Full Text Available Experimental studies have been performed to investigate the effects of hydrogen addition on the combustion characteristics of Chinese No.3 jet fuel (RP-3 kerosene/air premixed flames. Experiments were carried out in a constant volume chamber and the influences of the initial temperatures of 390 and 420 K, initial pressures of 0.1 and 0.3 MPa, equivalence ratios of 0.6–1.6 and hydrogen additions of 0.0–0.5 on the laminar burning velocities, and Markstein numbers of Hydrogen (H2/RP-3/air mixtures were investigated. The results show that the flame front surfaces of RP-3/air mixtures remain smooth throughout the entire flame propagation process at a temperature of 390 K, pressure of 0.3 MPa, equivalence ratio of 1.3 and without hydrogen addition, but when the hydrogen addition increases from 0.0 to 0.5 under the same conditions, flaws and protuberances occur at the flame surfaces. It was also found that with the increase of the equivalence ratio from 0.9 to 1.5, the laminar burning velocities of the mixtures increase at first and then decrease, and the highest laminar burning velocity was measured at an equivalence ratio of 1.2. Meanwhile, with the increase of hydrogen addition, laminar burning velocities of H2/RP-3/air mixtures increase. However, the Markstein numbers of H2/RP-3/air mixtures decrease with the increase of hydrogen addition, which means that the flames of H2/RP-3/air mixtures become unstable with the increase of hydrogen addition.

  19. Acute and Developmental Behavioral Effects of Flame Retardants and Related Chemicals in Zebrafish

    Science.gov (United States)

    As polybrominated diphenyl ethers are phased out, numerous compounds are emerging as potential replacement flame retardants for use in consumer and electronic products. Little is known, however, about the neurobehavioral toxicity of these replacements. This study evaluated the ne...

  20. Soot Aerosol Properties in Laminar Soot-Emitting Microgravity Nonpremixed Flames

    Science.gov (United States)

    Konsur, Bogdan; Megaridis, Constantine M.; Griffin, Devon W.

    1999-01-01

    The 0-g flame soot measurements reported in previous studies are extended by adding new 0-g data for different fuel flow rates and burner diameters. The new flame conditions allow more conclusive comparisons regarding the effect of characteristic flow residence times on soot field structure, the influence of fuel preheat on fuel pyrolysis rates near the flame centerline, and the premature cessation of soot growth along the soot annulus in 0-g when the fuel is preheated. The paper also reports on the implementation of thermophoretic soot sampling in a specific 0-g flame featuring burner exit velocities typical of buoyant flames and presents quantitative data on the radial variation of soot microstructure at a fixed height above the burner mouth.

  1. The Effects of Hydrodynamic Stretch on the Flame Propagation Enhancement of Ethylene by Addition of Ozone

    Science.gov (United States)

    2015-07-13

    the combustion of n-heptane in a HCCI engine . Proc. Combust. Inst. 34, 3005–3012. (doi:10.1016/j.proci.2012.05.042) 25. Schönborn A, Hellier P, Aliev... engineering , chemical physics, plasma physics Keywords: plasma, combustion, ozone, flame speed enhancement, Hencken flame, sub-atmospheric pressure... Engineering , University of Cincinnati, Cincinnati, OH, USA 2Aerospace Systems Directorate, US Air Force Research Laboratory, Wright-Patterson Air

  2. An analytical study of the effects of vaporization of twodimensional laminar droplets on a triple flame

    OpenAIRE

    Bidabadi Mehdi; Barari Ghazal; Azimi Milad

    2011-01-01

    The structure of triple flame propagation in combustion systems, containing uniformly distributed volatile fuel droplet was analyzed. The analysis was established for a one-step irreversible reaction with an asymptotic limit, where the value of the Zeldovich Number is large. Here, using unit Lewis number, the analytical results for the triple flame temperature were obtained considering two sections. In the first section, a non-vaporizing fuel stream was studied and in the second section...

  3. Asymptotic analysis of outwardly propagating spherical flames

    Institute of Scientific and Technical Information of China (English)

    Yun-Chao Wu; Zheng Chen

    2012-01-01

    Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy.The spherical flame structure consists of the preheat zone,reaction zone,and equilibrium zone.Analytical solutions are separately obtained in these three zones and then asymptotically matched.In the asymptotic analysis,we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius.This correlation is compared with previous results derived in the limit of infinite value of activation energy.Based on this correlation,the properties of spherical flame propagation are investigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed.Moreover,the accuracy and performance of different models used in the spherical flame method are examined.It is found that in order to get accurate laminar flame speed and Markstein length,non-linear models should be used.

  4. The Effect of Ultrafine Magnesium Hydroxide on the Tensile Properties and Flame Retardancy of Wood Plastic Composites

    Directory of Open Access Journals (Sweden)

    Zhiping Wu

    2014-01-01

    Full Text Available The effect of ultrafine magnesium hydroxide (UMH and ordinary magnesium hydroxide (OMH on the tensile properties and flame retardancy of wood plastic composites (WPC were investigated by tensile test, oxygen index tester, cone calorimeter test, and thermogravimetric analysis. The results showed that ultrafine magnesium hydroxide possesses strengthening and toughening effect of WPC. Scanning electron micrograph (SEM of fracture section of samples provided the positive evidence that the tensile properties of UMH/WPC are superior to that of WPC and OMH/WPC. The limited oxygen index (LOI and cone calorimeter test illustrated that ultrafine magnesium hydroxide has stronger flame retardancy and smoke suppression effect of WPC compared to that of ordinary magnesium hydroxide. The results of thermogravimetric analysis implied that ultrafine magnesium hydroxide can improve the char structure which plays an important role in reducing the degradation speed of the inner matrix during combustion process and increases the char residue at high temperature.

  5. Premixed flame propagation in vertical tubes

    Science.gov (United States)

    Kazakov, Kirill A.

    2016-04-01

    Analytical treatment of the premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations for a quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by a strong gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are identified. Acceleration of methane-air flames in open tubes is shown to be a combined effect of the hydrostatic pressure difference produced by the ambient cold air and the difference of dynamic gas pressure at the tube ends. On the other hand, a strong spontaneous acceleration of the fast methane-oxygen flames at the initial stage of their evolution in open-closed tubes is conditioned by metastability of the quasi-steady propagation regimes. An extensive comparison of the obtained results with the experimental data is made.

  6. N2稀释对双旋流合成气非预混燃烧特性的影响%Effect of N2 Dilution on Flame Structures of a Double-Swirled Non-Premixed Syngas Flame

    Institute of Scientific and Technical Information of China (English)

    葛冰; 臧述升; 郭培卿; 田寅申

    2012-01-01

    Experiments have been performed to investigate the effect of N2 dilution on the flame structures of a double-swirled non-premixed syngas flames. Planar laser induced fluorescence (PLIF) of OH-radical measurement is adopted to identify main reaction zones and burnt gas regions. Together with temperature and emission measurement during exhaust section, some important characteristics of the syngas flame are overall investigated. Experimental result shows that syngas flame root near the burner exit demonstrates double flame front structure. The existence of N2 expands the flame opening angle and enlarges the main reaction zone, and it may lead to lower NO emission and higher CO emission in exhaust gas.%利用平面激光诱导荧光(PLIF)、高温细丝热电偶及红外气体分析仪对不同N2稀释量下的双旋流合成气非燃烧流场进行了实验研究。实验结果表明,随着N2稀释量的增加:双旋流合成气火焰的基本结构发生变化,火焰会出现典型的推举火焰特征;火焰锋面被拉伸,主要反应区域轴向长度和径向宽度增大,喷嘴出口附近火焰锋面由M型分布逐渐转变为W型分布,轴线上未反应区域不断扩大;火焰张角与穿透深度增大,火焰推举高度减小;燃烧排气温度略有减小,NO排放明显降低。

  7. Item Feature Effects in Evolution Assessment

    Science.gov (United States)

    Nehm, Ross H.; Ha, Minsu

    2011-01-01

    Despite concerted efforts by science educators to understand patterns of evolutionary reasoning in science students and teachers, the vast majority of evolution education studies have failed to carefully consider or control for item feature effects in knowledge measurement. Our study explores whether robust contextualization patterns emerge within…

  8. Item Feature Effects in Evolution Assessment

    Science.gov (United States)

    Nehm, Ross H.; Ha, Minsu

    2011-01-01

    Despite concerted efforts by science educators to understand patterns of evolutionary reasoning in science students and teachers, the vast majority of evolution education studies have failed to carefully consider or control for item feature effects in knowledge measurement. Our study explores whether robust contextualization patterns emerge within…

  9. Direct numerical simulations of temporally developing hydrocarbon shear flames at elevated pressure: effects of the equation of state and the unity Lewis number assumption

    Science.gov (United States)

    Korucu, Ayse; Miller, Richard

    2016-11-01

    Direct numerical simulations (DNS) of temporally developing shear flames are used to investigate both equation of state (EOS) and unity-Lewis (Le) number assumption effects in hydrocarbon flames at elevated pressure. A reduced Kerosene / Air mechanism including a semi-global soot formation/oxidation model is used to study soot formation/oxidation processes in a temporarlly developing hydrocarbon shear flame operating at both atmospheric and elevated pressures for the cubic Peng-Robinson real fluid EOS. Results are compared to simulations using the ideal gas law (IGL). The results show that while the unity-Le number assumption with the IGL EOS under-predicts the flame temperature for all pressures, with the real fluid EOS it under-predicts the flame temperature for 1 and 35 atm and over-predicts the rest. The soot mass fraction, Ys, is only under-predicted for the 1 atm flame for both IGL and real gas fluid EOS models. While Ys is over-predicted for elevated pressures with IGL EOS, for the real gas EOS Ys's predictions are similar to results using a non-unity Le model derived from non-equilibrium thermodynamics and real diffusivities. Adopting the unity Le assumption is shown to cause misprediction of Ys, the flame temperature, and the mass fractions of CO, H and OH.

  10. Unsaturated polyester/expanded polystyrene composite : thermal characteristics and flame retardancy effects

    Science.gov (United States)

    Mohamed, R.; Syed Mustafa, S. A.; Norizan, Mohd N.; Amerudin, L. S.

    2017-07-01

    Panels for energy efficient buildings has to meet certain requirements such as low thermal conductivity and inherent flame retardancy characteristics, before being eligible for buildings and construction applications. Expanded Polystyrene (EPS) as waste material had been incorporated as filler in Unsaturated Polyester Resin (UPR) composites. The composite are fabricated as flat panel window or glazing to replace glass. In this study, different EPS content incorporated was found to affect flammability and thermal characteristics. Core additives such as Flame Retardant (FR) and Antioxidant (AO) were added to the composite for imparting flame retardancy and prevent aging of the composite. The result obtained via the comparison of the various composite systems studied had revealed that organic and metal oxide flame retardant (FR) additives imparts higher flame retardancy levels than others, but each type of additives had interacted with the polymeric matrixes differently. The thermal conductivity, k value, as measured from a handheld thermal probe had showed a minimum of ~0.124 W/m.K for the 1%wt zinc oxide sample, while the highest k value of ~0.280 W/m.K was exhibited by the 2%wt tin oxide sample. The first 1%wt of either metal oxide FR initially decreases both the thermal conductivity, k value; and volumetric specific heat, Cp,v of the samples. At 2%wt, increases in k value were obtained. The flammability was reduced with the use of organic Phosphate Ester FR, which had reduced the flame speed to about 37.1% of the original flame speed. With the equivalent mixture of all three organic FR system, the flammability reduced less than 30%, while the metal oxide FR additive doesn't reduces the flammability.

  11. Flame retardancy of polyamide 6 hybrid fibers: Combined effects of α-zirconium phosphate and ammonium sulfamate

    OpenAIRE

    Hengxue Xiang; Lili Li; Wei Chen; Senlong Yu; Bin Sun; Meifang Zhu

    2017-01-01

    Synergistic effect between α-zirconium phosphate (α-ZrP) and ammonium sulfamate (AS) for enhanced flame retardant properties of Polyamide 6 (PA6) was investigated by using oxygen index instrument, cone calorimeter, thermogravimetric analyzer (TGA), Instron universal test machine and scanning electron microscopy (SEM). PA6/AS/α-ZrP ternary hybrid materials with various contents of α-ZrP and AS were fabricated by melt-mixing method. The result from flammability indicated that the Limiting oxyge...

  12. Effect of ambient pressure and radiation reabsorption of atmosphere on the flame spreading over thermally thin combustibles in microgravity

    Institute of Scientific and Technical Information of China (English)

    杜文峰; 胡文瑞

    2003-01-01

    For the flame spread over thermally thin combustibles in an atmosphere, if the atmosphere cannot emit and absorb the thermal radiation (e.g. for atmosphere of O2-N2), the conductive heat transfer from the flame to the fuel surface dominates the flame spread at lower ambient atmosphere. As the ambient pressure increases, the flame spread rate increases, and the radiant heat transfer from the flame to the fuel surface gradually becomes the dominant driving force for the flame spread. In contrast, if the atmosphere is able to emit and absorb the thermal radiation (e.g. for atmosphere of O2-CO2), at lower pressure, the heat transfer from flame to the fuel surface is enhanced by the radiation reabsorption of the atmosphere at the leading edge of the flame, and both conduction and thermal radiation play important roles in the mechanism of flame spread. With the increase in ambient pressure, the oxygen diffuses more quickly from ambient atmosphere into the flame, the chemical reaction in the flame is enhanced, and the flame spread rate increases. When the ambient pressure is greater than a critical value, the thermal radiation from the flame to the solid surface is hampered by the radiation reabsorption of ambient atmosphere with the further increase in ambient pressure. As a result, with the increase in ambient pressure, the flame spread rate decreases and the heat conduction gradually dominates the flame spread over the fuel surface.

  13. An investigation of the behavior of different fuels in a co-flow flame configuration with CFD, Study on the influence of different fuels on laminar flame structures, looking more closely to more subtle effects like preferential diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Cadsand, P.G.F.

    2009-08-15

    The aim of this work is to investigate the influence of different fuels on laminar flame structures followed by an assessment on how combustion processes of these fuels can be modeled adequately, doing justice to more subtle effects like preferential diffusion. The two fuels investigated are methane and dodecane. A full detailed kinetic chemistry approach is used to compare different fuel inlet speeds for a laminar co-flow fuel air flame with a flamelet based reduction method, looking more specifically at the effect of preferential diffusion on the structure of the flame using the DRM19, GRI30 and a dodecane mechanism. This flamelet database is created with the use of the numerical code CHEM1D, assuming that the chemistry and mixture can be described by using just two variables: the mixture fraction and the progress variable. These flamelets are compiled in a manifold using the Flamelet Generated Manifold (FGM) reduction method. This results in a Flamelet Generated Manifold chemistry reduction technique. Both kinds of calculations are implemented in FLUENT to be able to compare to one and another. Results are compared with measurement on a flame using the same geometry and conditions.

  14. Flaming: More than a Necessary Evil for Academic Mailing Lists?

    Science.gov (United States)

    Wang, Hongjie

    1996-01-01

    States that although Internet "gurus" advocate that users refrain from "flaming," in fact, flaming permeates the Internet. Explores the nature of flaming in its characteristics and forms as seen in academic discussion groups. Argues that flaming educates the ignorant, tames the uncouth, and promotes effective communication. (PA)

  15. Synergistic flame retardant effects between sepiolite and magnesium hydroxide in ethylene-vinyl acetate (EVA matrix

    Directory of Open Access Journals (Sweden)

    2010-04-01

    Full Text Available Some customers are reluctant to change, because the halogen-free solutions may have higher cost. This is one of the reasons that the synergistic effect is always the subject for researchers to pursue. The synergy between sepiolite and magnesium hydroxide (MH in halogen-free flame retardant ethylene-vinyl acetate (EVA copolymer was investigated in the paper through some common facilities, such as limiting oxygen index (LOI, UL-94 test, thermogravimetric analysis (TGA, differential thermal analysis (DTA and cone calorimeter test (CCT. In the wake of the positive results from the LOI and UL-94 tests, the CCT data indicated not only the reduction of heat release rate (HRR and mass loss rates (MLR, but also prolonged ignition time (TTI and depressed smoke release (SR were observed during combustion. Simultaneously, the tensile strength and Young’s modulus of the system were also much better improved with the increase of sepiolite added due to the hydrogen bonds between silanol groups attached to the sepiolite molecules and the ester groups of EVA. The synergistic mechanism has been discussed in the paper in terms of the barrier mechanism in the condensed phase.

  16. Effect of flame conditions on abrasive wear performance of HVOF sprayed nanostructured WC-12Co coatings

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-yue; LI Chang-jiu; MA Jian; YANG Guan-jun

    2004-01-01

    Nanostructured WC-12Co coatings were deposited by high velocity oxy-fuel (HVOF) spraying with an agglomerated powder. The effect of flame conditions on the microstructure of the nanostructured coatings was investigated. The wear properties of the coatings were characterized using a dry rubber-wheel wear test. The results show that the nanostructured WC-Co coatings consist of WC, W2C, W and an amorphous binder phase. The microstructure of the coating is significantly influenced by the ratio of oxygen flow to fuel flow. Under the lower ratio of oxygen/fuel flow, the nanostructured coating presents a relative dense microstructure and severe decarburization of WC phase occurs during spraying. With increasing ratio of oxygen/fuel flow, the bonding of WC particles in the coating becomes loose resulting from the original structure of feedstock and the decarburization of WC becomes less owing to limited heating to the powder. Both the decarburization of WC particles in spraying and the bonding among WC particles in the coatings affect the wear performance. The examination of the worn surfaces of the nanostructured coatings reveals that the dominant wear mechanisms would be spalling from the interface of WCCo splats when spray particles undergo a limited melting. While the melting state of the spray particles is improved,the dominant wear mechanisms become the plastic deformation and plowing of the matrix and spalling of WC particles from the matrix.

  17. Effect of an external electric field on the propagation velocity of premixed flames

    KAUST Repository

    Sánchez-Sanz, Mario

    2015-01-01

    © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. There have been many experimental investigations into the ability of electric fields to enhance combustion by acting upon ion species present in flames [1]. In this work, we examine this phenomenon using a one-dimensional model of a lean premixed flame under the influence of a longitudinal electric field. We expand upon prior two-step chain-branching reaction laminar models with reactions to model the creation and consumption of both a positively-charged radical species and free electrons. Also included are the electromotive force in the conservation equation for ion species and the electrostatic form of the Maxwell equations in order to resolve ion transport by externally applied and internally induced electric fields. The numerical solution of these equations allows us to compute changes in flame speed due to electric fields. Further, the variation of key kinetic and transport parameters modifies the electrical sensitivity of the flame. From changes in flame speed and reactant profiles we are able to gain novel, valuable insight into how and why combustion can be controlled by electric fields.

  18. Experimental characterization of methane inverse diffusion flame

    KAUST Repository

    Elbaz, Ayman M.

    2014-06-26

    This article presents 10-kHz images of OH-PLIF simultaneously with 2-D PIV measurements in an inverse methane diffusion flame. Under a constant fuel flow rate, the central air jet Re was varied, leading to air to fuel velocity ratio, Vr, to vary from 8.3 to 66.5. Starting from Vr = 20.7, the flame is commonly characterized by three distinct zones. The length of the lower fuel entrainment region is inversely proportional to Vr. The flames investigated resemble a string shear layer confining this zone, and converging into the second distinct region, the flame neck zone. The third region is the rest of the flame, which spreads in a jet-like manner. The inverse diffusion flames exhibit varying degrees of partial premixing, depending upon on the velocity ratio Vr, and this region of partial premixing evolves into a well-mixed reaction zone along the flame centerline. The OH distribution correlated with the changes in the mean characteristics of the flow through reduction in the local Reynolds number due to heat release. The existence of a flame suppresses or laminarizes the turbulence at early axial locations and promotes fluctuations at the flame tip for flames with Vr < 49.8. In addition, the flame jet width can be correlated to the OH distribution. In upstream regions of the flames, the breaks in OH are counterbalanced by flame closures and are governed by edge flame propagation. These local extinctions were found to occur at locations where large flow structures were impinging on the flame and are associated with a locally higher strain rate or correlated to the local high strain rates at the flame hole edges without this flow impinging. Another contributor to re-ignition was found to be growing flame kernels. As the flames approach global blow-off, these kernels become the main mechanism for re-ignition further downstream of the flames. At low Vr, laminarization within the early regions of the flame provides an effective shield, preventing the jet flow from

  19. Sooting limit of a double diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    Kitano, Michio; Kobayashi, Hideaki; Nishiki, Nobuhiko (Tohoku Univ., Faculty of Engineering, Sendai, Japan Sony Corp., Tokyo (Japan))

    1989-07-25

    The soot exhaust from the flame of pot type burner for the domestic heating use was basically studied. Inside a fuel (secondary) diffusion flame in air atmosphere, which was an ordinary diffusion flame, an air (primary) diffusion flame in fuel atmosphere, which was reverse in relation between them, was formed by using propane fuel. For the sooting limit of that double diffusion flame, the effect of primary air ratio, distance between primary and secondary flames, thermal condition on wall surface and flow stretch being investigated by use of three different types of burner, the double diffusion flame method was studied in effectiveness on the soot exhaust and known to heighten the control against it, which heightening however depended in degree upon the locative relation between both the flames. The control was more heightened with a more lengthening in the secondary flame. Because the sooting limit is governed by the secondary flame temperature, the establishment of condition so as to heighten the flame temperature is necessary for the effective control against the soot exhaust. 11 refs., 11 figs.

  20. DISPERSION OF GRAPHENE OXIDE AND ITS FLAME RETARDANCY EFFECT ON EPOXY NANOCOMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Zhou Wang; Xiu-zhi Tang; Zhong-zhen Yu; Peng Guo; Huai-he Song; Xu-sheng Du

    2011-01-01

    Grraphene oxide was prepared by ultrasonication of completely oxidized graphite and used to improve the flame retardancy of epoxy. The epoxy/graphene oxide nanocomposite was studied in terms of exfoliation/dispersion, thermal stability and flame retardancy. X-ray diffraction and transmission electron microscopy confirmed the exfoliation of the graphene oxide nanosheets in epoxy matrix. Cone calorimeter measurements showed that the time to ignition of the epoxy/graphene oxide nanocomposite was longer than that of neat epoxy. The heat release rate curve of the nanocomposite was broadened compared to that of neat epoxy and the peak heat release rate decreased as well.

  1. Effect of oxygen atoms dissociated by non-equilibrium plasma on flame of methane oxygen and argon pre-mixture gas

    Science.gov (United States)

    Akashi, Haruaki; Yoshinaga, Tomokazu; Sasaki, Koichi

    2014-10-01

    For more efficient way of combustion, plasma-assisted combustion has been investigated by many researchers. But it is very difficult to clarify the effect of plasma even on the flame of methane. Because there are many complex chemical reactions in combustion system. Sasaki et al. has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power. They also measured emission from Second Positive Band System of nitrogen during the irradiation. The emission indicates existence of high energy electrons which are accelerated by the microwave. The high energy electrons also dissociate oxygen molecules easily and oxygen atom would have some effects on the flame. But the dissociation ratio of oxygen molecules by the non-equilibrium plasma is significantly low, compared to that in the combustion reaction. To clarify the effect of dissociated oxygen atoms on the flame, dependence of dissociation ratio of oxygen on the flame has been examined using CHEMKIN. It is found that in the case of low dissociation ratio of 10-6, the ignition of the flame becomes slightly earlier. It is also found that in the case of high dissociation ratio of 10-3, the ignition time becomes significantly earlier by almost half. This work was supported by KAKENHI (22340170).

  2. Flammability of Cellulose-Based Fibers and the Effect of Structure of Phosphorus Compounds on Their Flame Retardancy

    Directory of Open Access Journals (Sweden)

    Khalifah A. Salmeia

    2016-08-01

    Full Text Available Cellulose fibers are promoted for use in various textile applications due their sustainable nature. Cellulose-based fibers vary considerably in their mechanical and flammability properties depending on their chemical composition. The chemical composition of a cellulose-based fiber is further dependent on their source (i.e., seed, leaf, cane, fruit, wood, bast, and grass. Being organic in nature, cellulose fibers, and their products thereof, pose considerable fire risk. In this work we have compared the flammability properties of cellulose fibers obtained from two different sources (i.e., cotton and peat. Compared to cotton cellulose textiles, peat-based cellulose textiles burn longer with a prominent afterglow which can be attributed to the presence of lignin in its structure. A series of phosphoramidates were synthesized and applied on both cellulose textiles. From thermogravimetric and pyrolysis combustion flow analysis of the treated cellulose, we were able to relate the flame retardant efficacy of the synthesized phosphorus compounds to their chemical structure. The phosphoramidates with methyl phosphoester groups exhibited higher condensed phase flame retardant effects on both types of cellulose textiles investigated in this study. In addition, the bis-phosphoramidates exhibited higher flame retardant efficacy compared to the mono-phosphoramidates.

  3. Solvent effects on quantitative analysis of brominated flame retardants with Soxhlet extraction.

    Science.gov (United States)

    Zhong, Yin; Li, Dan; Zhu, Xifen; Huang, Weilin; Peng, Ping'an

    2017-05-18

    Reliable quantifications of brominated flame retardants (BFRs) not only ensure compliance with laws and regulations on the use of BFRs in commercial products, but also is key for accurate risk assessments of BFRs. Acetone is a common solvent widely used in the analytical procedure of BFRs, but our recent study found that acetone can react with some BFRs. It is highly likely that such reactions can negatively affect the quantifications of BFRs in environmental samples. In this study, the effects of acetone on the extraction yields of three representative BFRs [i.e., decabrominated diphenyl ether (decaBDE), hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA)] were evaluated in the Soxhlet extraction (SE) system. The results showed that acetone-based SE procedure had no measureable effect for the recovery efficiencies of decaBDE but could substantially lower the extraction yields for both TBBPA and HBCD. After 24 h of extraction, the recovery efficiencies of TBBPA and HBCD by SE were 93 and 78% with acetone, 47 and 70% with 3:1 acetone:n-hexane, and 82 and 94% with 1:1 acetone:n-hexane, respectively. After 72 h of extraction, the extraction efficiencies of TBBPA and HBCD decreased to 68 and 55% with acetone, 0 and 5% with 3:1 acetone/n-hexane mixtures, and 0 and 13% with 1:1 acetone/n-hexane mixtures, respectively. The study suggested that the use of acetone alone or acetone-based mixtures should be restricted in the quantitative analysis of HBCD and TBBPA. We further evaluated nine alternative solvents for the extraction of the three BFRs. The result showed that diethyl ether might be reactive with HBCD and may not be considered as the alternative to acetone used solvents for the extraction of HBCD.

  4. Camera calibration for multidirectional flame chemiluminescence tomography

    Science.gov (United States)

    Wang, Jia; Zhang, Weiguang; Zhang, Yuhong; Yu, Xun

    2017-04-01

    Flame chemiluminescence tomography (FCT), which combines computerized tomography theory and multidirectional chemiluminescence emission measurements, can realize instantaneous three-dimensional (3-D) diagnostics for flames with high spatial and temporal resolutions. One critical step of FCT is to record the projections by multiple cameras from different view angles. For high accuracy reconstructions, it requires that extrinsic parameters (the positions and orientations) and intrinsic parameters (especially the image distances) of cameras be accurately calibrated first. Taking the focus effect of the camera into account, a modified camera calibration method was presented for FCT, and a 3-D calibration pattern was designed to solve the parameters. The precision of the method was evaluated by reprojections of feature points to cameras with the calibration results. The maximum root mean square error of the feature points' position is 1.42 pixels and 0.0064 mm for the image distance. An FCT system with 12 cameras was calibrated by the proposed method and the 3-D CH* intensity of a propane flame was measured. The results showed that the FCT system provides reasonable reconstruction accuracy using the camera's calibration results.

  5. EFFECTS OF SIMPLIFIED CHEMICAL KINETIC MODEL ON THE MICRO-FLAME STRUCTURE AND TEMPERATURE OF THE LEAN PREMIXED METHANE-AIR MIXTURES

    Directory of Open Access Journals (Sweden)

    JUNJIE CHEN

    2015-07-01

    Full Text Available The effect of simplified chemical kinetic model on the micro-flame structure, central axis and wall temperatures were investigated with different one-step global chemical kinetic mechanisms following Mantel, Duterque and Fernández-Tarrazo models. Numerical investigations of the premixed methane-air flame in the micro-channel and lean conditions were carried out to compare and analyze the effect of the comprehensive chemical kinetic mechanisms. The results indicate that one-step global chemical kinetic mechanism affects both the micro-flame shape and the combustion temperature. Among three simulation models, Mantel model allows a stable micro-flame with a bamboo shoot form, which anchor at the inlet. Duterque model gives a stable elongated micro-flame with a considerable ignition delay, and a dead zone with fluid accumulation is observed at the entrance, which may explain the very high combustion temperature and the fast reaction rate obtained, despite the micro-flame development presents a very hot spot and causes a broadening of the combustion zone. Fernández-Tarrazo model results in a rapid extinction and doesn't seem to take all the kinetic behavior into account for the appropriate micro-combustion simulations.

  6. Toxicity of brominated flame retardants in fish, with emphasis on endocrine effects and reproduction

    NARCIS (Netherlands)

    Kuiper, R.V.

    2007-01-01

    Abstract The abundant use of brominated flame retardants (BFRs) in modern polymers has over the passed decades resulted in contamination of the environment, and BFRs are increasingly found in fish. Laboratory studies have shown that a number of BFRs and BFR-metabolites can interfere with thyroid and

  7. Electric fields effect on liftoff and blowoff of nonpremixed laminar jet flames in a coflow

    KAUST Repository

    Kim, Minkuk

    2010-01-01

    The stabilization characteristics of liftoff and blowoff in nonpremixed laminar jet flames in a coflow have been investigated experimentally for propane fuel by applying AC and DC electric fields to the fuel nozzle with a single-electrode configuration. The liftoff and blowoff velocities have been measured by varying the applied voltage and frequency of AC and the voltage and the polarity of DC. The result showed that the AC electric fields extended the stabilization regime of nozzle-attached flame in terms of jet velocity. As the applied AC voltage increased, the nozzle-attached flame was maintained even over the blowout velocity without having electric fields. In such a case, a blowoff occurred directly without experiencing a lifted flame. While for the DC cases, the influence on liftoff was minimal. There existed three different regimes depending on the applied AC voltage. In the low voltage regime, the nozzle-detachment velocity of either liftoff or blowoff increased linearly with the applied voltage, while nonlinearly with the AC frequency. In the intermediate voltage regime, the detachment velocity decreased with the applied voltage and reasonably independent of the AC frequency. At the high voltage regime, the detachment was significantly influenced by the generation of discharges. © 2009 The Combustion Institute.

  8. Effect of electric fields on the stabilization of premixed laminar bunsen flames at low AC frequency: Bi-ionic wind effect

    KAUST Repository

    Kim, Minkuk

    2012-03-01

    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally by applying AC electric fields at low frequency below 60. Hz together with DC in the single electrode configuration. The blowoff velocity has been measured for varying AC voltage and frequency. A transition frequency between low and high frequency regimes has been identified near 40-50. Hz, where AC electric fields have minimal effect on flame stabilization. In the low frequency regime, the blowoff velocity decreased linearly with AC voltage such that the flames became less stable. This was consistent with the DC result, implying the influence of the ionic wind effect. The variation of blowoff velocity with AC frequency showed a non-monotonic behavior in that the velocity decreased and then increased, exhibiting minimum blowoff velocity near 6-8. Hz. Based on the molecular kinetic theory, the developing degree of ionic wind was derived. By considering the ionic wind effects arising from both positive and negative ions in a flame zone, the bi-ionic wind effect successfully explained the non-monotonic behavior of blowoff velocity with AC frequency in the low frequency regime. © 2011 The Combustion Institute.

  9. Enhancements of Impinging Flame by Pulsation

    Institute of Scientific and Technical Information of China (English)

    AySu; Ying-ChiehLiu

    2000-01-01

    Experimental investigations on the pulsating jet-impinging diffusion flame were executed.A soleoid valve was aligned upstream of the jet orifice and the methane fuel was controlled in open-closed cycles from 0 Hz to 20Hz.Results show that the open-closed cycles,indeed increase the fluctuations of the methane fuel obviously.The evolutions of pulsating flame therefore develop faster than the continuous impinging flame.The optimized pulating frequencies are near 9 to 11 hz from the Re=170 to 283.The temperature differences between that under optimized pulsating rate and full open condition(no pulsation)are ranging from 100 to 150 degree.The pulsating effect is more singnificant at low Reynolds number.The cross section of continuous impinging flame behaves as elliptic shape with axial ratio equals to 2/3.The tip of the impinging flame obviously crosses at 42mm above the impinging point.ecause of the phenomenon of pulsation flame,the flame sheet or flame front may not be identified clearly in the averaged temperature contours.Results shows that the averaged end-contour of pulsation flame rears at 38mm above the impinging point.By observation and experiment,the pulsating flame behaves more stable and efficient than the continuous impinging flame.

  10. Numerical investigation of biogas diffusion flames characteristics under several operation conditions in counter-flow configuration with an emphasis on thermal and chemical effects of CO2 in the fuel mixture

    Science.gov (United States)

    Mameri, A.; Tabet, F.; Hadef, A.

    2017-08-01

    This study addresses the influence of several operating conditions (composition and ambient pressure) on biogas diffusion flame structure and NO emissions with particular attention on thermal and chemical effect of CO2. The biogas flame is modeled by a counter flow diffusion flame and analyzed in mixture fraction space using flamelet approach. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is adopted for the oxidation chemistry. It has been observed that flame properties are very sensitive to biogas composition and pressure. CO2 addition decreases flame temperature by both thermal and chemical effects. Added CO2 may participate in chemical reaction due to thermal dissociation (chemical effect). Excessively supplied CO2 plays the role of pure diluent (thermal effect). The ambient pressure rise increases temperature and reduces flame thickness, radiation losses and dissociation amount. At high pressure, recombination reactions coupled with chain carrier radicals reduction, diminishes NO mass fraction.

  11. Numerical investigation of biogas diffusion flames characteristics under several operation conditions in counter-flow configuration with an emphasis on thermal and chemical effects of CO2 in the fuel mixture

    Science.gov (United States)

    Mameri, A.; Tabet, F.; Hadef, A.

    2017-03-01

    This study addresses the influence of several operating conditions (composition and ambient pressure) on biogas diffusion flame structure and NO emissions with particular attention on thermal and chemical effect of CO2. The biogas flame is modeled by a counter flow diffusion flame and analyzed in mixture fraction space using flamelet approach. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is adopted for the oxidation chemistry. It has been observed that flame properties are very sensitive to biogas composition and pressure. CO2 addition decreases flame temperature by both thermal and chemical effects. Added CO2 may participate in chemical reaction due to thermal dissociation (chemical effect). Excessively supplied CO2 plays the role of pure diluent (thermal effect). The ambient pressure rise increases temperature and reduces flame thickness, radiation losses and dissociation amount. At high pressure, recombination reactions coupled with chain carrier radicals reduction, diminishes NO mass fraction.

  12. Study on the Built-up Effect of Inorganic Compounds to Flame Retardant Containing Organophosphorus in Suppression of Smoke

    Institute of Scientific and Technical Information of China (English)

    LIN Miao; XIAN Chun-ying; YANG Yong

    2006-01-01

    The built-up effect of inorganic compounds containing more active metal ions, such as Ca2+ , Al3+ , Cu2+ , and Zn2+ , as additives adding to phosphorus-containing flame retarding systems in suppression of smoke was studied. The data presented herein suggested that the amount of smoke in the burning process can be better suppressed after the cotton fabric finishing with built- up system was burnt. Some general principles were identified, and the likely causes of the observed effects were analyzed according to test data.

  13. Preparation of Flame Retardant Modified with Titanate for Asphalt Binder

    Directory of Open Access Journals (Sweden)

    Bo Li

    2014-01-01

    Full Text Available Improving the compatibility between flame retardant and asphalt is a difficult task due to the complex nature of the materials. This study explores a low dosage compound flame retardant and seeks to improve the compatibility between flame retardants and asphalt. An orthogonal experiment was designed taking magnesium hydroxide, ammonium polyphosphate, and melamine as factors. The oil absorption and activation index were tested to determine the effect of titanate on the flame retardant additive. The pavement performance test was conducted to evaluate the effect of the flame retardant additive. Oxygen index test was conducted to confirm the effect of flame retardant on flame ability of asphalt binder. The results of this study showed that the new composite flame retardant is more effective in improving the compatibility between flame retardant and asphalt and reducing the limiting oxygen index of asphalt binder tested in this study.

  14. Behaviors of tribrachial edge flames and their interactions in a triple-port burner

    KAUST Repository

    Yamamoto, Kazuhiro

    2015-05-01

    In a triple-port burner, various non-premixed flames have been observed previously. Especially for the case with two lifted flames, such configuration could be suitable in studying interaction between two tribrachial flames. In the present study, the flame characteristics have been investigated numerically by adopting a reduced kinetic mechanism in the triple-port burner. Four different types of flame configurations, including two attached flames, inner lifted/outer attached flames, inner attached/outer lifted flames, and twin lifted flames, were successfully simulated depending on the flow conditions. The representative edge propagation speed of a single lifted flame or an upstream lifted flame in the case of twin lifted flames increased as the liftoff height became higher. In the twin lifted flames, the inner lifted flame was affected appreciably when the other flame was located further upstream such that the lifted flame located further downstream encountered the axial velocity acceleration induced by the gas expansion from the lifted flame located upstream, while thermal effects were not observed since the temperature of the incoming flow toward the lifted flame was not affected. A unique flip-flop behavior between the inner and outer flames, observed experimentally previously, was successfully captured in the simulation such that the inner lifted flame became attached to the nozzle as the liftoff height of the outer lifted flame grew higher with an increase in the outer air velocity.

  15. Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV

    KAUST Repository

    Elbaz, Ayman M.

    2015-10-29

    Most previous work on inverse diffusion flames (IDFs) has focused on laminar IDF emissions and the soot formation characteristics. Here, we investigate the characteristics and structure of methane IDFs using high speed planar laser-induced fluorescence (PLIF) images of OH, particle image velocimetry (PIV), and acetone PLIF imaging for non-reacting cases. First, the flame appearance was investigated with fixed methane loading (mass flux) but with varying airflow rates, yielding a central air jet Reynolds number (Re) of 1,000 to 6,000 (when blow-off occurs). Next, it was investigated a fixed central air jet Re of 4500, but with varied methane mass flux such that the global equivalence ratio spanned 0.5 to 4. It was observed that at Re smaller than 2000, the inner air jet promotes the establishment of an inverse diffusion flame surrounded by a normal diffusion flame. However, when the Re was increased to 2500, two distinct zones became apparent in the flame, a lower entrainment zone and an upper mixing and combustion zone. 10 kHz OH-PLIF images, and 2D PIV allow the identification of the fate and spatial flame structure. Many flame features were identified and further analyzed using simple but effective image processing methods, where three types of structure in all the flames investigated here: flame holes or breaks; closures; and growing kernels. Insights about the rate of evolution of these features, the dynamics of local extinction, and the sequence of events that lead to re-ignition are reported here. In the lower entrainment zone, the occurrence of the flame break events is counterbalanced by closure events, and the edge propagation appears to control the rate at which the flame holes and closures propagate. The rate of propagation of holes was found to be statistically faster than the rate of closure. As the flames approach blow-off, flame kernels become the main mechanism for flame re-ignition further downstream. The simultaneous OH-PLIF/Stereo PIV

  16. Electrical Aspects of Impinging Flames

    Science.gov (United States)

    Chien, Yu-Chien

    from the flame to the plate can be controlled using the electric field are the two main goals of this research. Multiple diagnostic techniques are employed such as OH chemiluminescence to identify the reaction zone, OH PLIF to characterize the location of this radical species, CO released from the flame, IR imaging and OH PLIF thermometry to understand the surface and gas temperature distribution, respectively. The principal finding is that carbon monoxide release from an impinging diffusion flame results from the escape of carbon monoxide created on the fuel side of the flame along the boundary layer near the surface where it avoids oxidation by OH, which sits to the air side of the reaction sheet interface. In addition, the plate proximity to the flame has a stronger influence on the emission of toxic carbon monoxide than does the electric field strength. There is, however, a narrow region of burner to surface distance where the electric field is most effective. The results also show that heat transfer can be spatially concentrated effectively using an electric field driven ion wind, particularly at some burner to surface distances.

  17. Effect of Burning Rate Modifiers on Subatmospheric Flame Temperatures of AP/HTPB Composite Solid Propellants

    Directory of Open Access Journals (Sweden)

    S. Krishnan

    1998-04-01

    Full Text Available Using 30 um. pt and Pt 13 percent Rh thermocouples, flame temperatures of uncatalysed andcatalysed ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/lffPB composite solidpropellants were measured under subatmospheric conditions. Ferric oxide F e 2 and copper chromite(CC were the catalysts used. The study demonstrates that Fe2O3 catalysed propellant, notwithstandingits least combustion efficiency undt;r subatmospheric conditions and weak gas-phase flame, has themaximum burning rate enhancement. This is argued to be due to the increased surface and subsurfacereactions caused by Fe2O3. CC-catalysed propellant burns to the least subatmospheric pressure withminimum loss in combustion efficiency indicating that this class of propellant may be more suitablefor base-bleed applications.

  18. Kinetic Effects of Non-Equilibrium Plasma-Assisted Methane Oxidation on Diffusion Flame Extinction Limits

    Science.gov (United States)

    2011-01-01

    measured using the Two-photon Absorption Laser-Induced Fluorescence (TALIF) method (for atomic oxygen, O), Fourier Transform Infrared ( FTIR ) spectroscopy...photon Absorption Laser-Induced Fluorescence (TALIF) method (for atomic oxygen, O), Fourier Transform Infrared ( FTIR ) spectroscopy and Gas...and ozone (O3) from other plasma related species and shown that both (at concentrations of several thousand ppm) can enhance flame speeds by a few

  19. The VLT FLAMES Tarantula Survey

    NARCIS (Netherlands)

    Evans, C.; Taylor, W.; Sana, H.; Hénault-Brunet, V.; Bagnoli, T.; Bastian, N.; Bestenlehner, J.; Bonanos, A.; Bressert, E.; Brott, I.; Campbell, M.; Cantiello, M.; Carraro, G.; Clark, S.; Costa, E.; Crowther, P.; de Koter, A.; de Mink, S.; Doran, E.; Dufton, P.; Dunstall, P.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I.; Izzard, R.; Köhler, K.; Langer, N.; Lennon, D.; Maíz Apellániz, J.; Markova, N.; Najarro, P.; Puls, J.; Ramirez, O.; Sabín-Sanjulián, C.; Simón-Díaz, S.; Smartt, S.; Stroud, V.; van Loon, J.; Vink, J.S.; Walborn, N.

    2011-01-01

    We introduce the VLT FLAMES Tarantula Survey, an ESO Large Programme from which we have obtained optical spectroscopy of over 800 massive stars in the spectacular 30 Doradus region of the Large Magellanic Cloud. A key feature is the use of multi-epoch observations to provide strong constraints on

  20. Numerical simulation of tulip flame dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cloutman, L.D.

    1991-11-30

    A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a ``tulip flame`` in the literature, occurred. The ``tulip flame`` was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.

  1. Numerical simulation of tulip flame dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cloutman, L.D.

    1991-11-30

    A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a tulip flame'' in the literature, occurred. The tulip flame'' was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.

  2. Flame Retardancy, Smoke Suppression Effect and Mechanism of Aryl Phosphates in Combination with Magnesium Hydroxide in Polyamide 6

    Institute of Scientific and Technical Information of China (English)

    CHEN Jun; LIU Shumei; JIANG Zhijie; ZHAO Jianqing

    2012-01-01

    The flammability,smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis(diphenyl phosphate) (BDP) and resorcinol bis(diphenyl phosphate) (RDP)]combined with magnesium hydroxide (MH) in polyamide 6 (PA6) have been investigated.Combining 5 wt%BDP,50 wt% MH imparts a limiting oxygen index (LOI) of 40.9% and UL94 V-0 rating to PA6,meanwhile the peak rate of smoke release (pRSR),total release of smoke (TSR) and Izod notched impact strength are 41%,33% and 233% relative to the corresponding value of 55 wt% MH without BDP,respectively.Dynamic mechanical analysis (DMA) indicates that the improvement of toughness attributes to the enhanced compatibility between MH and PA6 by adding BDP.Furthermore,based on the comprehensive analysis of thermogravimetry (TG),cone calorimeter and SEM-EDX investigations,possible flame retardancy and smoke suppression mechanisms were revealed.Besides the fuel dilution and barrier effect of MH,the combination of MH and RDP shows an additional flame inhibition effect.The combination of MH and BDP results in a dominant condensed phase barrier effect which leads to obvious reduction on smoke emission and flammability.

  3. Effect of pressure on the lean limit flames of H2-CH4-air mixture in tubes

    KAUST Repository

    Zhou, Zhen

    2017-05-25

    The lean limit flames of H2-CH4-air mixtures stabilized inside tubes in a downward flow are experimentally and numerically investigated at elevated pressures ranging from 2 to 5 bar. For the shapes of lean limit flames, a change from ball-like flame to cap-like flame is experimentally observed with the increase of pressure. This experimentally observed phenomenon is qualitatively predicted by numerical simulations. The structure of ball-like and cap-like lean limit flames at all tested pressures is analysed in detail based on the numerical predictions. The results show that the lean limit flames are located inside a recirculation zone at all tested pressures. For the leading edges of the lean limit flames at all tested pressures, the fuel transport is controlled by both convection and diffusion. For the trailing edge of the ball-like lean limit flame at 2 bar, the fuel transport is dominated by diffusion. However, with increasing pressure, the transport contribution caused by convection in the trailing edges of the lean limit flames increases. Finally, the influence of transport and chemistry on the predicted ultra lean flames and lean flammability limit is analysed at elevated pressures.

  4. 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.

  5. Numerical Study on Laminar Burning Velocity and Flame Stability of Premixed Methane/Ethylene/Air Flames

    Institute of Scientific and Technical Information of China (English)

    陈珊珊; 蒋勇; 邱榕; 安江涛

    2012-01-01

    A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability under the condition of lean burning were investigated. The results show that the laminar burning velocity increases with ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to higher concentrations of H, O and OH radicals in the flame, which significantly promotes chemical reactions, and a linear correlation exists between the laminar burning velocity and the maximum H + OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is raised, while the inner layer temperature becomes lower, contributing to the enhancement of combustion. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with ethylene addition.

  6. Residence time effect on fullerene yield in butadiene-based laser pyrolysis flame

    Science.gov (United States)

    Ténégal, F.; Voicu, I.; Armand, X.; Herlin-Boime, N.; Reynaud, C.

    2003-09-01

    A new route for fullerene synthesis by CO 2-laser pyrolysis of gas phase mixture is proposed. Small hydrocarbon molecules which absorb the laser radiation, such as butadiene, are mixed with nitrous oxide (N 2O) as oxidizer. Such a mixture allows avoiding the use of a photosensitizer as SF 6 which causes contamination of the reaction zone and possibly influences the growth of fullerenic structures. This Letter also confirms the strong influence of the C/O atomic ratio in the mixture on the fullerene yield, and shows that residence time of the reactants in the pyrolysis flame and pressure influence dramatically the fullerene formation.

  7. Effect of the mixing fields on the stability and structure of turbulent partially premixed flames in a concentric flow conical nozzle burner

    KAUST Repository

    Mansour, Mohy S.

    2016-10-22

    The mixing field is known to be one of the key parameters that affect the stability and structure of partially premixed flames. Data in these flames are now available covering the effects of turbulence, combustion system geometry, level of partially premixing and fuel type. However, quantitative analyses of the flame structure based on the mixing field are not yet available. The aim of this work is to present a comprehensive study of the effects of the mixing fields on the structure and stability of partially premixed methane flames. The mixing field in a concentric flow conical nozzle (CFCN) burner with well-controlled mechanism of the mixing is investigated using Rayleigh scattering technique. The flame stability, structure and flow field of some selected cases are presented using LIF of OH and PIV. The experimental data of the mixing field cover wide ranges of Reynolds number, equivalence ratio and mixing length. The data show that the mixing field is significantly affected by the mixing length and the ratio of the air-to-fuel velocities. The Reynolds number has a minimum effect on the mixing field in high turbulent flow regime and the stability is significantly affected by the turbulence level. The temporal fluctuations of the range of mixture fraction within the mixing field correlate with the flame stability. The highest point of stability occurs at recess distances where fluid mixtures near the jet exit plane are mostly within the flammability limits. This paper provides some correlations between the stability range in mixture fraction space and the turbulence level for different equivalence ratios.

  8. 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.

  9. Direct numerical simulations of non-premixed ethylene-air flames: Local flame extinction criterion

    KAUST Repository

    Lecoustre, Vivien R.

    2014-11-01

    Direct Numerical Simulations (DNS) of ethylene/air diffusion flame extinctions in decaying two-dimensional turbulence were performed. A Damköhler-number-based flame extinction criterion as provided by classical large activation energy asymptotic (AEA) theory is assessed for its validity in predicting flame extinction and compared to one based on Chemical Explosive Mode Analysis (CEMA) of the detailed chemistry. The DNS code solves compressible flow conservation equations using high order finite difference and explicit time integration schemes. The ethylene/air chemistry is simulated with a reduced mechanism that is generated based on the directed relation graph (DRG) based methods along with stiffness removal. The numerical configuration is an ethylene fuel strip embedded in ambient air and exposed to a prescribed decaying turbulent flow field. The emphasis of this study is on the several flame extinction events observed in contrived parametric simulations. A modified viscosity and changing pressure (MVCP) scheme was adopted in order to artificially manipulate the probability of flame extinction. Using MVCP, pressure was changed from the baseline case of 1 atm to 0.1 and 10 atm. In the high pressure MVCP case, the simulated flame is extinction-free, whereas in the low pressure MVCP case, the simulated flame features frequent extinction events and is close to global extinction. Results show that, despite its relative simplicity and provided that the global flame activation temperature is correctly calibrated, the AEA-based flame extinction criterion can accurately predict the simulated flame extinction events. It is also found that the AEA-based criterion provides predictions of flame extinction that are consistent with those provided by a CEMA-based criterion. This study supports the validity of a simple Damköhler-number-based criterion to predict flame extinction in engineering-level CFD models. © 2014 The Combustion Institute.

  10. Flame Propagation Enhancement by Plasma Excitation of Oxygen. Part 1. Effects of O3

    Science.gov (United States)

    2010-01-01

    flame speed Sc Schmidt number T temperature u local flow velocity u0 initial fuel jet velocity Vco co-flow velocity x distance from fuel nozzle tip X...similarity solution in Eqs. (3) and (4), respectively. u Vco u0 Vco ¼ a 1 qa 1 q 3 32ðX XvÞ 1 1þ 3a 1 qa R 32ðXþXv Þ 2 2 ð3Þ YF ¼ að2Scþ...was used, which is for 18% O2 in 82% N2 at 101.3 kPa and 300 K). Also, Vco is the co-flow veloc- ity, a the density ratio between the fuel and oxidizer

  11. Effective Preparation Program Features: A Literature Review

    Science.gov (United States)

    Crow, Gary M.; Whiteman, Rodney S.

    2016-01-01

    This article is a summary of a report prepared for the University Council for Educational Administration Program Improvement Project for the Wallace Foundation. This explores the research base for educational leadership preparation programs, specifically examining literature on program features. The review covers context, candidates, faculty,…

  12. Effects of pressure, oxygen concentration, and forced convection on flame spread rate of Plexiglas, Nylon and Teflon

    Science.gov (United States)

    Notardonato, J. J.; Burkhardt, L. A.; Cochran, T. H.

    1974-01-01

    Experiments were conducted in which the burning of cylindrical materials in a flowing oxidant stream was studied. Plexiglas, Nylon, and Teflon fuel specimens were oriented such that the flames spread along the surface in a direction opposed to flowing gas. Correlations of flame spread rate were obtained that were power law relations in terms of pressure, oxygen concentration, and gas velocity.

  13. The effect of electron-beam irradiation and halogen-free flame retardants on properties of poly butylene terephthalate

    Science.gov (United States)

    Hooshangi, Zhila; Feghhi, Seyed Amir Hossein; Sheikh, Nasrin

    2015-03-01

    Engineering plastics like Poly (butylene terephthalate) due to their desirable properties have various industrial applications. Neat PBT is highly combustible, so it is necessary to improve significantly its fire retardancy to meet the fire safety requirements. The combustion performance of PBT can be improved by addition of appropriate flame retardant additives. In this study we have investigated the effect of halogen free flame retardants, i.e. melamine and aluminum phosphate, and instantaneously electron beam radiation-induced crosslinking in the presence of Triallyl cyanurate on various properties of PBT. The results of gel content showed that a dose range of 200-400 kGy leads to high cross linked structure in this polymer. Also mechanical experiments showed that its structure became rigid and fragile due to irradiation. Radiation crosslinking of this polymer made its dielectric loss coefficient ten times lower than non-irradiated polymer, but had no effect on its dielectric constant. Moreover the addition of the fire retardant additives as impurity decreased the dielectric loss coefficient. TGA analysis in nitrogen exhibited that irradiation increases char formation and use of the fire retardant additives leads to reduction of onset temperature and formation of higher char quantity than pure PBT. According to the results of UL-94, irradiated samples burned with lower speed and less dripping in vertical and horizontal positions than pure polymer. Finally irradiation of the polymers containing fire retardant additives with a dose of 400 kGy led to self-extinguishing and non-dripping and reach to V-0 level in the UL-94 V.

  14. Experiment and Simulation of Autoignition in Jet Flames and its Relevance to Flame Stabilization and Structure

    KAUST Repository

    Al-Noman, Saeed M.

    2016-06-01

    mainly between the fuel nozzle and the lifted flame edge. On the other hand, they were formed just prior to the flame edge for the non-autoignited lifted flames. The effect of fuel pyrolysis and partial oxidation were found to be important in explaining autoignited liftoff heights, especially in the Mild combustion regime. Flame structures of autoignited flames were investigated numerically for syngas (CO/H2) and methane fuels. The simulations of syngas fuel accounting for the differential diffusion have been performed by adopting several kinetic mechanisms to test the models ability in predicting the flame behaviors observed previously. The results agreed well with the observed nozzle-attached flame characteristics in case of non-autoignited flames. For autoignited lifted flames in high temperature regime, a unique autoignition behavior can be predicted having HO2 and H2O2 radicals in a broad region between the nozzle and stabilized lifted flame edge. Autoignition characteristics of laminar nonpremixed methane jet flames in high- temperature coflow air were studied numerically. Several flame configurations were investigated by varying the initial temperature and fuel mole fraction. Characteristics of chemical kinetics structures for autoignited lifted flames were discussed based on the kinetic structures of homogeneous autoignition and flame propagation of premixed mixtures. Results showed that for autoignited lifted flame with tribrachial structure, a transition from autoignition to flame propagation modes occurs for reasonably stoichiometric mixtures. Characteristics of Mild combustion can be treated as an autoignited lean premixed lifted flame. Transition behavior from Mild combustion to a nozzle-attached flame was also investigated by increasing the fuel mole fraction.

  15. Flame structure of methane inverse diffusion flame

    KAUST Repository

    Elbaz, Ayman M.

    2014-07-01

    This paper presents high speed images of OH-PLIF at 10. kHz simultaneously with 2D PIV (particle image velocimetry) measurements collected along the entire length of an inverse diffusion flame with circumferentially arranged methane fuel jets. For a fixed fuel flow rate, the central air jet Re was varied, leading to four air to fuel velocity ratios, namely Vr = 20.7, 29, 37.4 and 49.8. A double flame structure could be observed composed of a lower fuel entrainment region and an upper mixing and intense combustion region. The entrainment region was enveloped by an early OH layer, and then merged through a very thin OH neck to an annular OH layer located at the shear layer of the air jet. The two branches of this annular OH layer broaden as they moved downstream and eventfully merged together. Three types of events were observed common to all flames: breaks, closures and growing kernels. In upstream regions of the flames, the breaks were counterbalanced by flame closures. These breaks in OH signal were found to occur at locations where locally high velocity flows were impinging on the flame. As the Vr increased to 37.4, the OH layers became discontinuous over the downstream region of the flame, and these regions of low or no OH moved upstream. With further increases in Vr, these OH pockets act as flame kernels, growing as they moved downstream, and became the main mechanism for flame re-ignition. Along the flame length, the direction of the two dimensional principle compressive strain rate axis exhibited a preferred orientation of approximately 45° with respect to the flow direction. Moreover, the OH zones were associated with elongated regions of high vorticity. © 2013 Elsevier Inc.

  16. Pulsating instability and self-acceleration of fast turbulent flames

    CERN Document Server

    Poludnenko, A Y

    2015-01-01

    (Abridged) A series of three-dimensional numerical simulations is used to study the intrinsic stability of high-speed turbulent flames. Calculations model the interaction of a fully-resolved premixed flame with a highly subsonic, statistically steady, homogeneous, isotropic turbulence. We consider a wide range of turbulent intensities and system sizes, corresponding to the Damk\\"ohler numbers Da = 0.1-6.0. These calculations show that turbulent flames in the regimes considered are intrinsically unstable. In particular, we find three effects. 1) Turbulent flame speed develops pulsations with the observed peak-to-peak amplitude > 10 and a characteristic time scale close to a large-scale eddy turnover time. Such variability is caused by the interplay between turbulence, which continuously creates the flame surface, and highly intermittent flame collisions, which consume the flame surface. 2) Unstable burning results in the periodic pressure build-up and the formation of pressure waves or shocks, when the flame s...

  17. Visualization of ionic wind in laminar jet flames

    KAUST Repository

    Park, Daegeun

    2017-07-03

    Electric field, when it is applied to hydrocarbon flames, generates ionic wind due to the electric body force on charge carrying species. Ionic wind has been shown to influence soot emission, propagation speed, and stability of flames; however, a detailed behavior of ionic wind and its effects on flames is still not clear. Here, we investigated the dynamic behaviors of flames and ionic wind in the presence of direct current (DC) and alternating current (AC) electric fields in nonpremixed and premixed jet flames with a jet nozzle placed between two parallel electrodes. We observed a skewed flame toward a lower potential electrode with DC and lower frequency AC (e.g., 10Hz) and a steady flame with higher frequencies AC (1000Hz), while we found that the ionic wind blew toward both the anode and cathode regardless of flame type (nonpremixed or premixed) or the source of the electric field (DC and AC).

  18. Analysis of Spark Plug Gap on Flame Development using Schlieren Technique and Image Processing

    Science.gov (United States)

    Hii Shu-Yi, Paul; Khalid, Amir; Mohamad, Anuar; Manshoor, Bukhari; Sapit, Azwan; Zaman, Izzuddin; Hashim, Akasha

    2016-11-01

    Gasoline spark ignition system in cars remains one of the main consumption of fuel in the world nowadays. During combustion process, spark plug is one important key features in a gasoline engine. The incompatibility of spark plug gap width and the fuel used causing backfire and knocking in the combustion engine. Thus, the spark plug gap was studied with focussing in controlling the combustion process to improve the performance of the engine. The main purpose of this research is to investigate the effect of spark plug air gap on flame development. The parameters studied in this research include spark plug air gap width (1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm and 1.8 mm), injection pressure (0.3 MPa, 0.4 MPa, 0.5 MPa and 0.6 MPa) and flame characteristics such as flame front area and the flame intensity. The flame front area of different spark plug gap and injection pressure were investigated through Schlieren photography method. The Schlieren images taken were analysed with the time changes. The experiment results proved that the increase of spark plug gap width will led to better flame development in shorter time while increased the chance of misfire.

  19. Numerical modeling for flame dynamics and combustion processes in a two-sectional porous burner with a detailed chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Young Jun; Kim, Yong Mo [Hanyang University, Seoul (Korea, Republic of)

    2014-11-15

    A two-dimensional model with the detailed chemistry and variable transport properties has been applied to numerically investigate the combustion processes and flame dynamics in the bilayer porous burner. To account for the velocity transition and diffusion influenced by solid matrix, porosity terms are included in the governing equations. Heat transfer coefficient is calculated by Nusselt number to reflect the effect of gas velocity, pore diameter, and material properties. The detailed chemistry is based on GRI 2.11. Numerical results indicate that the present approach is capable of the essential features of the premixed combustion in the porous media in terms of the precise flame structure, pollutant formation, and stabilization characteristics. In this bilayer porous burner, the heat transferred from the downstream flame zone is conducted to the upstream flame region through the solid matrix. This heat transfer process through the solid matrix substantially influences the flame structure and stabilization characteristics in the porous media. The predicted results are compared with experimental data in terms of temperature for gaseous mixture and solid matrix, CO and NO emission level. Based on numerical results, a precise comparison has been made for the freely propagating premixed flames and the premixed flames with a porous media for various inlet velocities.

  20. Interaction Between Flames and Electric Fields Studied

    Science.gov (United States)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

  1. 氧化锌与膨胀型阻燃剂对聚丙烯的协效阻燃%Synergistic Flame Resistant Effect of Zinc Oxide and Intumescent Flame Retardant in Polypropylene

    Institute of Scientific and Technical Information of China (English)

    孙杰; 焦传梅

    2012-01-01

    A new type of intumescent flame retardant (IFR) has been synthesized using phosphorus acid, pentaerythritol and melamine. Intumescent flame retardant PP composites have been prepared based on PP as matrix resin, intumescent flame retardant as flame retardants and zinc oxide (ZnO) as synergism. The synergist effect between ZnO and IFR has been studied using limiting oxygen index test, UL-94 test and cone calorimeter. The changes of solid-phase structure in the thermal degradation process have been studied by dynamic FTIR spectroscopy. The results showed that the synergist effect obviously did exist between ZnO and a new IFR; the structures of the composites changed severely from 240 ℃ to 330 ℃ , when the sample containing 1. 6% ZnO, the char morphology got the best integrity among all samples, and the peak heat release rate was also the lowest, decreased 80% than PP without flame retardant, the UL-94 of this sample was V-0; when the content of ZnO increased to 3.2%, LOI value got to 25. 6%, and the UL-94 passed V-0.%采用磷酸、季戊四醇和三聚氰胺为原料合成了一种新型膨胀型阻燃荆(IFR).并以IFR为阻燃剂,氧化锌(ZnO)为协效阻燃剂,聚丙烯(PP)为基体树脂制备了膨胀型阻燃PP复合材料,重点研究ZnO与IFR之间的协效阻燃作用.采用氧指数测定仪、UL-94测定仪和锥形量热仪等手段研究阻燃PP复合材料的燃烧性能,用动态傅里叶变换红外光谱(FTIR)研究阻燃PP复合材料在不同温度下凝聚相的结构变化,初步揭示其热降解特性.实验结果表明:ZnO与IFR之间存在明显的协效阻燃效果;复合材料在240~330℃时,结构变化最剧烈;ZnO添加质量分数为1.6%时,炭层完整性最好,热释放速率峰值最低,降低幅度可迭80%,UL-94为V-0级;ZnO添加质量分数为3.2%时,氧指数(LOI)最大为25.6%,UL-94为V-0级.

  2. The effect of mineral fillers on the rheological, mechanical and thermal properties of halogen-free flame-retardant polypropylene/expandable graphite compounds

    Science.gov (United States)

    Mattausch, Hannelore; Laske, Stephan; Hohenwarter, Dieter; Holzer, Clemens

    2015-05-01

    In many polyolefin applications, such as electrical cables or automotive applications, the fire protection is a very important task. Unfortunately flame-retardant polymeric materials are often halogenated and form toxic substances in case of fire, which explains the general requirement to reduce the halogen content to zero. Non-halogenated, state-of-the-art flame retardants must be incorporated into the polymer in very high grades (> 40 wt%) leading to massive decrease in mechanical properties and/or processability. In this research work halogen-free flame-retardant polypropylene (PP) /expandable graphite (EG) were filled with minerals fillers such as layered silicates (MMT), magnesium hydroxide (MgOH), zeolite (Z) and expanded perlite (EP) in order to enhance the flame-retardant effect. The rheological, mechanical and thermal properties of these materials were investigated to gain more fundamental knowledge about synergistic combinations of flame-retardants and other additives. The rheological properties were characterized with a rotational rheometer with plate-plate setup. The EG/EP/PP compound exhibited the highest increase in viscosity (˜ 37 %). As representative value for the mechanical properties the Young's modulus was chosen. The final Young's modulus values of the twofold systems gained higher values than the single ones. Thermo gravimetric analysis (TGA) was utilized to investigate the material with respect to volatile substances and combustion behavior. All materials decomposed in one-step degradation. The EG filled compounds showed a significant increase in sample weight due to the expansion of EG. The combustion behavior of these materials was characterized by cone calorimeter tests. Especially combinations of expandable graphite with mineral fillers exhibit a reduction of the peak heat release rate during cone calorimeter measurements of up to 87% compared to pure PP.

  3. Candle flames in microgravity

    Science.gov (United States)

    Dietrich, D. L.; Ross, H. D.; Tien, J. S.

    1995-01-01

    The candle flame in both normal and microgravity is non-propagating. In microgravity, however, the candle flame is also non-convective where (excepting Stefan flow) pure diffusion is the only transport mode. It also shares many characteristics with another classical problem, that of isolated droplet combustion. Given their qualitatively similar flame shapes and the required heat feedback to condensed-phase fuels, the gas-phase flow and temperature fields should be relatively similar for a droplet and a candle in reduced gravity. Unless the droplet diameter is maintained somehow through non-intrusive replenishment of fuel, the quasi-steady burning characteristics of a droplet can be maintained for only a few seconds. In contrast, the candle flame in microgravity may achieve a nearly steady state over a much longer time and is therefore ideal for examining a number of combustion-related phenomena. In this paper, we examine candle flame behavior in both short-duration and long-duration, quiescent, microgravity environments. Interest in this type of flame, especially 'candle flames in weightlessness', is demonstrated by very frequent public inquiries. The question is usually posed as 'will a candle flame burn in zero gravity', or, 'will a candle burn indefinitely (or steadily) in zero gravity in a large volume of quiescent air'. Intuitive speculation suggests to some that, in the absence of buoyancy, the accumulation of products in the vicinity of the flame will cause flame extinction. The classical theory for droplet combustion with its spherically-shaped diffusion flame, however, shows that steady combustion is possible in the absence of buoyancy if the chemical kinetics are fast enough. Previous experimental studies of candle flames in reduced and microgravity environments showed the flame could survive for at least 5 seconds, but did not reach a steady state in the available test time.

  4. Industry-sponsored research on the potential health and environmental effects of selected brominated flame retardants.

    Science.gov (United States)

    Hardy, M L; Biesemeier, J; Manor, O; Gentit, W

    2003-09-01

    Modern fire-fighting techniques, equipment and fire-resistant building design has lead to less destruction than in the previous centuries. However, a high fuel load in either a residence or a commercial building can overwhelm even the best firefighters or building construction, and factors affecting the fuel load have changed in recent decades. The fire load in a typical home has doubled over the last 50 years, furnishings typically include those made of petrochemicals that can behave as if containing built-in accelerant, and modern energy-efficient buildings are less able to disperse heat in the event of a fire. Flame retardant chemicals (FRs) are one means used to reduce the risk of fire. FRs are typically added or incorporated chemically into a polymer to slow or hinder the ignition or growth of a fire in low-to-moderate cost commodity polymers. One type of FR contains bromine atoms as the active moiety. The FR industry, either as individual companies or as consortia, has conducted a broad range of studies on the commercial deca-, octa- and pentabromodiphenyl oxide/ether, tetrabromobisphenol A and hexabromocyclododecane products. These five products have data in excess of the OECD Screening Informational Data Set (SIDS) and the U.S. High Production Volume (HPV) program, and sufficient data for the performance of formal EU risk assessments. The objective of this paper is to present the range of data developed by industry consortia and to provide sources for the information. We hope to facilitate further research by assembling references to industry consortia-sponsored research here.

  5. Effects of prenatal exposure to hydoxylated PCB metabolites and some brominated flame retardants on the development of rats

    Energy Technology Data Exchange (ETDEWEB)

    Buitenhuis, C.; Cenijn, P.C.; Velzen, M. van; Gutleb, A.C.; Legler, J. [Institute for Environmental Studies (IVM), Amsterdam (Netherlands); Lilienthal, H. [Heinrich Univ., Duesseldorf (Germany). Dept. Neurobehavioural Toxicology, Medical Institute of Environmental Hygiene; Malmberg, T.; Bergman, Aa. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry; Brouwer, A.

    2004-09-15

    Possible human health effects from low-level exposure to environmental chemicals are an issue that has attracted much attention. Environmental compounds that may play a role are those that may disrupt endocrine function. Organohalogen compounds, and in particular their hydroxylated metabolites, show a striking resemblance to steroid hormones.The main objective of this research is to investigate comparative pathways of early life-stage exposure and long-term effects for several classes of organohalogens, including polychlorinated biphenyls (PCBs) and flame retardants, polybrominated bisphenols and -diphenylethers, and their hydroxylated metabolites. Due to their prevalence in human plasma, the hydroxylated PCB metabolites 4-OH-CB107 and 4-OH-CB187, as well as 6-OH-BDE47 and 2,4,6- tribromophenol, were selected as test compounds. BDE 47 has been included as a test compound due to its relatively high levels in the environment and biota, whereas tetrabromobisphenol A (TBBPA) was selected because of its high volume production. The in vivo studies involved prenatal exposure of rats to test compounds during critical stages of gonadal development and were focussed on low dose effects. Several endpoints were investigated, including endocrine (thyroid and sex steroid hormones) effects, developmental landmarks, sexual and neurobehavioural development. Blood plasma and tissue levels of test compounds were analysed to determine transplacental transfer of (hydroxylated) organohalogens.

  6. Flame retardancy of polyamide 6 hybrid fibers: Combined effects of α-zirconium phosphate and ammonium sulfamate

    Directory of Open Access Journals (Sweden)

    Hengxue Xiang

    2017-06-01

    Full Text Available Synergistic effect between α-zirconium phosphate (α-ZrP and ammonium sulfamate (AS for enhanced flame retardant properties of Polyamide 6 (PA6 was investigated by using oxygen index instrument, cone calorimeter, thermogravimetric analyzer (TGA, Instron universal test machine and scanning electron microscopy (SEM. PA6/AS/α-ZrP ternary hybrid materials with various contents of α-ZrP and AS were fabricated by melt-mixing method. The result from flammability indicated that the Limiting oxygen index (LOI and Underwriters Laboratories-94 (UL-94 rating of PA6/AS/α-ZrP were significantly accelerated under the coordinating function of α-ZrP and AS. Moreover, the thermal stability for PA6/AS/α-ZrP studied by TGA also demonstrated this synergistic effect between α-ZrP and AS on the heat resistance. The effects of the usage amount of α-ZrP and AS on mechanical properties were analyzed by using uniaxial tensile test. It was found that the addition of AS provided negative effects on the tensile strength of PA6/AS/α-ZrP, however, the adverse trends that mentioned above could be overcome by using the well dispersed α-ZrP.

  7. Study of the toxic effects of flame retardant PBDE-47 on the clam Chamelea gallina (Linnaeus, 1758

    Directory of Open Access Journals (Sweden)

    Salvatora Angela Angioni

    2013-03-01

    Full Text Available The purpose of the study is to evaluate the effects of 2,2',4,4'-tetrabromodiphenylether (PBDE-47 on the Chamelea gallina clam (according to current commercial regulations: Venus gallina. PBDEs, which are used as flame retardants in various industrial products, are classed as hazardous substances by Directive 2011/65/EU. They are bioaccumulative compounds, considered to be endocrine disruptors, genotoxic, neurotoxic and practically ubiquitous, and their concentration in the environment has considerably increased in recent years. The aim of this study is to establish the effects of PBDE-47 on Chamelea gallina: toxic power and any harmful effects on the gonads, bioaccumulation capacity in the tissues, and possible entry into the food chain. The research used 96-hour and 21-day experimental tests on clams housed in filtered seawater. The tests were preceded by a period of acclimatisation of the molluscs lasting five to seven days. The clams were fed on seaweed (Dunaliella tertiolecta. The choice of the toxic compound PBDE-47 was based on the high concentration, among the congeners of PBDE, found in some aquatic species. The study demonstrated that the concentration of the contaminant used did not alter the vital functions, cause significant levels of mortality or lead to evident alteration in the gonads of Chamelea gallina. However, the research demonstrated the bioaccumulation capacity of the bivalve mollusc, allowing PBDE-47 to enter the food chain.

  8. Flame Holder System

    Science.gov (United States)

    Haskin, Henry H. (Inventor); Vasquez, Peter (Inventor)

    2013-01-01

    A flame holder system includes a modified torch body and a ceramic flame holder. Catch pin(s) are coupled to and extend radially out from the torch body. The ceramic flame holder has groove(s) formed in its inner wall that correspond in number and positioning to the catch pin(s). Each groove starts at one end of the flame holder and can be shaped to define at least two 90.degree.turns. Each groove is sized to receive one catch pin therein when the flame holder is fitted over the end of the torch body. The flame holder is then manipulated until the catch pin(s) butt up against the end of the groove(s).

  9. Effects of alpha-zirconium phosphate on thermal degradation and flame retardancy of transparent intumescent fire protective coating

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Weiyi [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzai Road, Hefei, Anhui 230026 (China); Zhang, Ping [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, 59 Qinglong Road, Mianyang 621010 (China); Song, Lei; Wang, Xin [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzai Road, Hefei, Anhui 230026 (China)

    2014-01-01

    Graphical abstract: - Highlights: • A transparent intumescent fire protective coating was obtained by UV-cured technology. • OZrP could enhance the thermal stability and anti-oxidation of the coating. • OZrP could reduce the combustion properties of the coatings. - Abstract: Organophilic alpha-zirconium phosphate (OZrP) was used to improve the thermal and fire retardant behaviors of the phenyl di(acryloyloxyethyl)phosphate (PDHA)-triglycidyl isocyanurate acrylate (TGICA)-2-phenoxyethyl acrylate (PHEA) (PDHA-TGICA-PHEA) coating. The morphology of nanocomposite coating was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of OZrP on the flame retardancy, thermal stability, fireproofing time and char formation of the coatings was investigated by microscale combustion calorimeter (MCC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS) and scanning electric microscope (SEM). The results showed that by adding OZrP, the peak heat release rate and total heat of combustion were significantly reduced. The highest improvement was achieved with 0.5 wt% OZrP. XPS analysis indicated that the performance of anti-oxidation of the coating was improved with the addition of OZrP, and SEM images showed that a good synergistic effect was obtained through a ceramic-like layer produced by OZrP covered on the surface of char.

  10. On the dynamics of flame edges in diffusion-flame/vortex interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hermanns, Miguel; Linan, Amable [Departamento de Motopropulsion y Termofluidodinamica, Universidad Politecnica de Madrid, Pza. Cardenal Cisneros 3, 28040 Madrid (Spain); Vera, Marcos [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2007-04-15

    We analyze the local flame extinction and reignition of a counterflow diffusion flame perturbed by a laminar vortex ring. Local flame extinction leads to the appearance of flame edges separating the burning and extinguished regions of the distorted mixing layer. The dynamics of these edges is modeled based on previous numerical results, with heat release effects fully taken into account, which provide the propagation velocity of triple and edge flames in terms of the upstream unperturbed value of the scalar dissipation. The temporal evolution of the mixing layer is determined using the classical mixture fraction approach, with both unsteady and curvature effects taken into account. Although variable density effects play an important role in exothermic reacting mixing layers, in this paper the description of the mixing layer is carried out using the constant density approximation, leading to a simplified analytical description of the flow field. The mathematical model reveals the relevant nondimensional parameters governing diffusion-flame/vortex interactions and provides the parameter range for the more relevant regime of local flame extinction followed by reignition via flame edges. Despite the simplicity of the model, the results show very good agreement with previously published experimental results. (author)

  11. Selective processing of multiple features in the human brain: effects of feature type and salience.

    Science.gov (United States)

    McGinnis, E Menton; Keil, Andreas

    2011-02-09

    Identifying targets in a stream of items at a given constant spatial location relies on selection of aspects such as color, shape, or texture. Such attended (target) features of a stimulus elicit a negative-going event-related brain potential (ERP), termed Selection Negativity (SN), which has been used as an index of selective feature processing. In two experiments, participants viewed a series of Gabor patches in which targets were defined as a specific combination of color, orientation, and shape. Distracters were composed of different combinations of color, orientation, and shape of the target stimulus. This design allows comparisons of items with and without specific target features. Consistent with previous ERP research, SN deflections extended between 160-300 ms. Data from the subsequent P3 component (300-450 ms post-stimulus) were also examined, and were regarded as an index of target processing. In Experiment A, predominant effects of target color on SN and P3 amplitudes were found, along with smaller ERP differences in response to variations of orientation and shape. Manipulating color to be less salient while enhancing the saliency of the orientation of the Gabor patch (Experiment B) led to delayed color selection and enhanced orientation selection. Topographical analyses suggested that the location of SN on the scalp reliably varies with the nature of the to-be-attended feature. No interference of non-target features on the SN was observed. These results suggest that target feature selection operates by means of electrocortical facilitation of feature-specific sensory processes, and that selective electrocortical facilitation is more effective when stimulus saliency is heightened.

  12. Selective processing of multiple features in the human brain: effects of feature type and salience.

    Directory of Open Access Journals (Sweden)

    E Menton McGinnis

    Full Text Available Identifying targets in a stream of items at a given constant spatial location relies on selection of aspects such as color, shape, or texture. Such attended (target features of a stimulus elicit a negative-going event-related brain potential (ERP, termed Selection Negativity (SN, which has been used as an index of selective feature processing. In two experiments, participants viewed a series of Gabor patches in which targets were defined as a specific combination of color, orientation, and shape. Distracters were composed of different combinations of color, orientation, and shape of the target stimulus. This design allows comparisons of items with and without specific target features. Consistent with previous ERP research, SN deflections extended between 160-300 ms. Data from the subsequent P3 component (300-450 ms post-stimulus were also examined, and were regarded as an index of target processing. In Experiment A, predominant effects of target color on SN and P3 amplitudes were found, along with smaller ERP differences in response to variations of orientation and shape. Manipulating color to be less salient while enhancing the saliency of the orientation of the Gabor patch (Experiment B led to delayed color selection and enhanced orientation selection. Topographical analyses suggested that the location of SN on the scalp reliably varies with the nature of the to-be-attended feature. No interference of non-target features on the SN was observed. These results suggest that target feature selection operates by means of electrocortical facilitation of feature-specific sensory processes, and that selective electrocortical facilitation is more effective when stimulus saliency is heightened.

  13. Flame-retardancy of a Cellulosic Fabric by the Application of Synergistic Effect between Ammonium Bromide and Antimony (Ⅲ)Oxide

    Institute of Scientific and Technical Information of China (English)

    MOSTASHARI Seyed Morteza; MOAFI Hadi Fallah

    2009-01-01

    The synergistic effect between ammonium bromide and antimony(Ⅲ) oxide as a nondurable finish on the flammability of 100% woven plain cotton fabric(with a density of 144 g/m2,the number of yarns 21 per 10 mm),has been investigated in this study. The laundered totally-dried, weighed specimens were impregnated with suitable concentration individual aqueous ammonium bromide and/or antimony (Ⅲ)oxide suspension solutions and some sets weIle impregnated with appropriate admixed solutions of the both chemicals.A vertical flame spread test Was then carried-out to characterize the flammability of the samples.An acceptable synergistic effect was then experi.enced by using an admixed bath containing 0.1 molar ammonium bromide and O.05 unit formal antimony trioxide solutions for impartation of flame.retardancy to a cotton fabric.The optimum mass of the mixture required to lm.Dart flame-retardancy was about 3.64 g of anhydrous additives per 100 g of fabric.The results obtained are in favor 0f Wall Effect Theory.Moreover synergistic eflfect indicating dehydration of the treated substrate by using this combination via thermogravimetry could be deduced.

  14. Flame Quenching Dynamics of High Velocity Flames in Rectangular Cross-section Channels

    KAUST Repository

    Mahuthannan, Ariff Magdoom

    2017-01-05

    Understanding flame quenching for different conditions is necessary to develop safety devices like flame arrestors. In practical applications, the speed of a deflagration in the lab-fixed reference frame will be a strong function of the geometry through which the deflagration propagates. This study reports on the effect of the flame speed, at the entrance of a quenching section, on the quenching distance. A 2D rectangular channel joining two main spherical vessels is considered for studying this effect. Two different velocity regimes are investigated and referred to as configurations A, and B. For configuration A, the velocity of the flame is 20 m/s, while it is about 100 m/s for configuration B. Methane-air stoichiometric mixtures at 1 bar and 298 K are used. Simultaneous dynamic pressure measurements along with schlieren imaging are used to analyze the quenching of the flame. Risk assessment of re-ignition is also reported and analyzed.

  15. Effect of the Number of Injectors on the Mixing Process in a Rapidly Mixed Type Tubular Flame Burner

    Directory of Open Access Journals (Sweden)

    Y. Chouari

    2017-01-01

    Full Text Available Three-dimensional simulations are performed to study the non-reactive mixing process in a rapidly mixed type tubular flame burner (RTFB. The current work examines the effect of the number of injectors (N= 2, 4 and 6 on the mixing process by focusing on three criterions (Flow structure, local swirl intensity and mixing layer thickness. The Discrete Phase Model (DPM is used to track the particle trajectories. Validation of the numerical results is carried out by comparing the predicted particle trajectories, central recirculation zone (CRZ and tangential velocity results to the experimental data. It is concluded that the model offers a satisfactory prediction of the flow field in a RTFB. Numerical results show that, for the same geometrical swirl number (Sw and the same Reynolds number (ReT, the increasing of the number of injectors enhances the mixing process by generating a larger reverse flow and reducing the mixing layer thickness. It is also concluded that the local swirl intensity along of the RTFB can be correlated in terms of geometric swirl number and number of injectors.

  16. Effects of Obstacles on Flame Propagation Behavior and Explosion Overpressure Development During Gas Explosions in a Large Closed Tube

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-dong; BAI Chun-hua; LIU Qing-ming

    2007-01-01

    AutoReaGas was used for the simulations of premixed gas/air mixtures explosion characteristics in obstacle-filled tubes with a cross-section of 0.2 m×0.2 m and the length of 28 m. Numerical analyses provide a quantitative descripti on of dependence of flame propagation speed and explosion overpressure on obstacles number, blockage ratio and interval distance. Computational results indicate that the obstacles play a significant role in determining the flame transmission speed and explosion overpressure in gas explosions. With the increase of blockage ratio, the explosion overpressure gradually rises. Nevertheless, the flame speed does not always increase along with increasing blockage ratio, but subsequently begins to decrease as the blockage ratio increases to some extend. Also, the interval distance between obstacles strongly influences flame behavior and explosion overpressure. When the obstacle interval distance is equal to inner diameter of the tube, the average flame speed in the obstacle zone and the peak overp ressure in tube all reach maximum values.

  17. Effects of dietary exposure to brominated flame retardant BDE-47 on thyroid condition, gonadal development and growth of zebrafish

    Science.gov (United States)

    Torres, Leticia; Orazio, Carl E.; Peterman, Paul H.; Patino, Reynaldo

    2013-01-01

    Little is known about the effects of brominated flame retardants in teleosts and some of the information currently available is inconsistent. This study examined effects of dietary exposure to 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) on thyroid condition, body mass and size, and gonadal development of zebrafish. Pubertal, 49-day-old (posthatch) fish were fed diets without BDE-47 (control) or with 1, 5 or 25 μg/g BDE-47/diet. Treatments were conducted in triplicate 30-L tanks each containing 50 zebrafish, and 15 fish per treatment (5 per tank) were sampled at days 40, 80 and 120 of exposure. Measurements were taken of body mass, standard length, head depth and head length. Sex (at 40–120 days of exposure), germ cell stage (at 40 days) and thyroid condition (at 120 days; follicular cell height, colloid depletion, angiogenesis) were histologically determined. Whole-body BDE-47 levels at study completion were within the high end of levels reported in environmentally exposed (wild) fishes. Analysis of variance was used to determine differences among treatments at each sampling time. No effects were observed on thyroid condition or germ cell stage in either sex. Reduced head length was observed in females exposed to BDE-47 at 80 days but not at 40 or 120 days. In males, no apparent effects of BDE-47 were observed at 40 and 80 days, but fish exposed to 25 μg/g had lower body mass at 120 days compared to control fish. These observations suggest that BDE-47 at environmentally relevant whole-body concentrations does not affect thyroid condition or pubertal development of zebrafish but does affect growth during the juvenile-to-adult transition, especially in males.

  18. Hi-tech Flame

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Modern science plays a crucial role in lighting the Olympic flame on the world’s highest mountain when the world saw live telecasts of the Olympic flame burning onthe top of Mount Qomolangma(Mount Everest) at 9:17 on the morning of May 8, few realized the years of work and high level of technology that had

  19. Stabilization and structure of N-heptane flame on CWJ-spray burner with kHZ SPIV and OH-PLIF

    KAUST Repository

    Mansour, Morkous S.

    2015-08-31

    A curved wall-jet (CWJ) burner was employed to stabilize turbulent spray flames that utilized a Coanda effect by supplying air as annular-inward jet over a curved surface, surrounding an axisymmetric solid cone fuel spray. The stabilization characteristics and structure of n-heptane/air turbulent flames were investigated with varying fuel and air flow rates and the position of pressure atomizer (L). High-speed planar laser-induced fluorescence (PLIF) of OH radicals delineated reaction zone contours and simultaneously stereoscopic particle image velocimetry (SPIV) quantified the flow field features, involving turbulent mixing within spray, ambient air entrainment and flame-turbulence interaction. High turbulent rms velocities were generated within the recirculation zone, which improved the flame stabilization. OH fluorescence signals revealed a double flame structure near the stabilization edge of lifted flame that consisted of inner partially premixed flame and outer diffusion flame front. The inner reaction zone is highly wrinkled and folded due to significant turbulent mixing between the annular-air jet and the fuel vapor generated from droplets along the contact interface of this air jet with the fuel spray. Larger droplets, having higher momentum are able to penetrate the inner reaction zone and then vaporized in the low-speed hot region bounded by these reaction zones; this supports the outer diffusion flame. Frequent local extinctions in the inner reaction zone were observed at low air flow rate. As flow rate increases, the inner zone is more resistant to local extinction despite of its high wrinkling and corrugation degree. However, the outer reaction zone exhibits stable and mildly wrinkled features irrespective of air flow rate. The liftoff height increases with the air mass flow rate but decreases with L.

  20. Effects of radiation losses on very lean methane/air flames propagating upward in a vertical tube

    OpenAIRE

    Higuera Antón, Fco. Jose; Muntean, Victor

    2014-01-01

    The stationary upward propagation of a very lean methane/air flame in a long vertical tube open at the bottom and closed at the top is simulated numerically using a single overall chemical reaction to model combustion and assuming an optically thin gas and a transparent or non-reflecting tube wall to approximately account for radiation losses from CO2CO2 and H2OH2O. Buoyancy plays a dominant role in the propagation of these flames and causes a large region of low velocity of the burnt gas rel...

  1. Effect of the composition of the hot product stream in the quasi-steady extinction of strained premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Coriton, Bruno; Smooke, Mitchell D.; Gomez, Alessandro [Department of Mechanical Engineering, Yale Center for Combustion Studies, Yale University, New Haven, CT 06520-8286 (United States)

    2010-11-15

    The extinction of premixed CH{sub 4}/O{sub 2}/N{sub 2} flames counterflowing against a jet of combustion products in chemical equilibrium was investigated numerically using detailed chemistry and transport mechanisms. Such a problem is of relevance to combustion systems with non-homogeneous air/fuel mixtures or recirculation of the burnt gases. Contrary to similar studies that were focused on heat loss/gain, depending on the degree of non-adiabaticity of the system, the emphasis here was on the yet unexplored role of the composition of counterflowing burnt gases in the extinction of lean-to-stoichiometric premixed flames. For a given temperature of the counterflowing products of combustion, it was found that the decrease of heat release with increase in strain rate could be either monotonic or non-monotonic, depending on the equivalence ratio {phi}{sub b} of the flame feeding the hot combustion product stream. Two distinct extinction modes were observed: an abrupt one, when the hot counterflowing stream consists of either inert gas or equilibrium products of a stoichiometric premixed flame, and a smooth extinction, when there is an excess of oxidizing species in the combustion product stream. In the latter case four burning regimes can be distinguished as the strain rate is progressively increased while the heat release decreases smoothly: an adiabatic propagating flame regime, a non-adiabatic propagating flame regime, the so-called partially-extinguished flame regime, in which the location of the peak of heat release crosses the stagnation plane, and a frozen flow regime. The flame structure was analyzed in detail in the different burning regimes. Abrupt extinction was attributed to the quenching of the oxidation layer with the entire H-OH-O radical pool being comparably reduced. Under conditions of smooth extinction, the behavior is different and the concentration of the H radical decreases the most with increasing strain rate, whereas OH and O remain

  2. Combustion of Biogas Released from Palm Oil Mill Effluent and the Effects of Hydrogen Enrichment on the Characteristics of the Biogas Flame

    Directory of Open Access Journals (Sweden)

    Seyed Ehsan Hosseini

    2015-01-01

    Full Text Available Biogas released from palm oil mill effluent (POME could be a source of air pollution, which has illustrated negative effects on the global warming. To protect the environment from toxic emissions and use the energy of POME biogas, POME is conducted to the closed digestion systems and released biogas is captured. Since POME biogas upgrading is a complicated process, it is not economical and thus new combustion techniques should be examined. In this paper, POME biogas (40% CO2 and 60% CH4 has been utilized as a fuel in a lab-scale furnace. A computational approach by standard k-ε combustion and turbulence model is applied. Hydrogen is added to the biogas components and the impacts of hydrogen enrichment on the temperature distribution, flame stability, and pollutant formation are studied. The results confirm that adding hydrogen to the POME biogas content could improve low calorific value (LCV of biogas and increases the stability of the POME biogas flame. Indeed, the biogas flame length rises and distribution of the temperature within the chamber is uniform when hydrogen is added to the POME biogas composition. Compared to the pure biogas combustion, thermal NOx formation increases in hydrogen-enriched POME biogas combustion due to the enhancement of the furnace temperature.

  3. 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.

  4. The Effect of Feature Selection on Phish Website Detection

    Directory of Open Access Journals (Sweden)

    Hiba Zuhair

    2015-10-01

    Full Text Available Recently, limited anti-phishing campaigns have given phishers more possibilities to bypass through their advanced deceptions. Moreover, failure to devise appropriate classification techniques to effectively identify these deceptions has degraded the detection of phishing websites. Consequently, exploiting as new; few; predictive; and effective features as possible has emerged as a key challenge to keep the detection resilient. Thus, some prior works had been carried out to investigate and apply certain selected methods to develop their own classification techniques. However, no study had generally agreed on which feature selection method that could be employed as the best assistant to enhance the classification performance. Hence, this study empirically examined these methods and their effects on classification performance. Furthermore, it recommends some promoting criteria to assess their outcomes and offers contribution on the problem at hand. Hybrid features, low and high dimensional datasets, different feature selection methods, and classification models were examined in this study. As a result, the findings displayed notably improved detection precision with low latency, as well as noteworthy gains in robustness and prediction susceptibilities. Although selecting an ideal feature subset was a challenging task, the findings retrieved from this study had provided the most advantageous feature subset as possible for robust selection and effective classification in the phishing detection domain.

  5. Effects of Feature Extraction and Classification Methods on Cyberbully Detection

    Directory of Open Access Journals (Sweden)

    Esra SARAÇ

    2016-12-01

    Full Text Available Cyberbullying is defined as an aggressive, intentional action against a defenseless person by using the Internet, or other electronic contents. Researchers have found that many of the bullying cases have tragically ended in suicides; hence automatic detection of cyberbullying has become important. In this study we show the effects of feature extraction, feature selection, and classification methods that are used, on the performance of automatic detection of cyberbullying. To perform the experiments FormSpring.me dataset is used and the effects of preprocessing methods; several classifiers like C4.5, Naïve Bayes, kNN, and SVM; and information gain and chi square feature selection methods are investigated. Experimental results indicate that the best classification results are obtained when alphabetic tokenization, no stemming, and no stopwords removal are applied. Using feature selection also improves cyberbully detection performance. When classifiers are compared, C4.5 performs the best for the used dataset.

  6. Theory of DDT in unconfined flames

    CERN Document Server

    Khokhlov, A M; Wheeler, J C; Wheeler, J Craig

    1996-01-01

    This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames which is relevant both to problems of terrestrial combustion and to thermonuclear burning in Type Ia supernovae. Two basic assumuptions are made: 1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and 2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, the laminar flame speed, and the laminar flame thickness in the reactive gas. This approach gives a lower-bound criterion for DDT for conditions where shock preheating, wall effects, and interactions with obstacles are absent. Regions in parameter space where unconfined DDT can and cannot occur are determined. A subsequent paper will address these issues specifically in the astrophysical context.

  7. A New Type of Steady and Stable, Laminar, Premixed Flame in Ultra-Lean, Hydrogen-Air Combustion

    Energy Technology Data Exchange (ETDEWEB)

    Grcar, Joseph F; Grcar, Joseph F

    2008-06-30

    Ultra-lean, hydrogen-air mixtures are found to support another kind of laminar flame that is steady and stable beside flat flames and flame balls. Direct numerical simulations are performed of flames that develop into steadily and stably propagating cells. These cells were the original meaning of the word"flamelet'' when they were observed in lean flammability studies conducted early in the development of combustion science. Several aspects of these two-dimensional flame cells are identified and are contrasted with the properties of one-dimensional flame balls and flat flames. Although lean hydrogen-air flames are subject to thermo-diffusive effects, in this case the result is to stabilize the flame rather than to render it unstable. The flame cells may be useful as basic components of engineering models for premixed combustion when the other types of idealized flames are inapplicable.

  8. Flame spread over inclined electrical wires with AC electric fields

    KAUST Repository

    Lim, Seung J.

    2017-07-21

    Flame spread over polyethylene-insulated electrical wires was studied experimentally with applied alternating current (AC) by varying the inclination angle (θ), applied voltage (VAC), and frequency (fAC). For the baseline case with no electric field applied, the flame spread rate and the flame width of downwardly spreading flames (DSFs) decreased from the horizontal case for −20° ≤ θ < 0° and maintained near constant values for −90° ≤ θ < −20°, while the flame spread rate increased appreciably as the inclination angle of upwardly spreading flames (USFs) increased. When an AC electric field was applied, the behavior of flame spread rate in DSFs (USFs) could be classified into two (three) sub-regimes characterized by various functional dependences on VAC, fAC, and θ. In nearly all cases of DSFs, a globular molten polyethylene formed ahead of the spreading flame edge, occasionally dripping onto the ground. In these cases, an effective flame spread rate was defined to represent the burning rate by measuring the mass loss due to dripping. This effective spread rate was independent of AC frequency, while it decreased linearly with voltage and was independent of the inclination angle. In DSFs, when excessively high voltage and frequency were applied, the dripping led to flame extinction during propagation and the extinction frequency correlated well with applied voltage. In USFs, when high voltage and frequency were applied, multiple globular molten PEs formed at several locations, leading to ejections of multiple small flame segments from the main flame, thereby reducing the flame spread rate, which could be attributed to the electrospray phenomenon.

  9. Synthesis and characterization of nanosized calcium phosphates by flame spray pyrolysis, and their effect on osteogenic differentiation of stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Ataol, Sibel; Tezcaner, Ayşen [Middle East Technical University, Department of Biomedical Engineering (Turkey); Duygulu, Ozgur [TUBITAK Marmara Research Center, Materials Institute (Turkey); Keskin, Dilek [Middle East Technical University, Department of Biomedical Engineering (Turkey); Machin, Nesrin E., E-mail: nesrinmachin@gmail.com [Kocaeli University, Department of Chemical Engineering (Turkey)

    2015-02-15

    The present study evaluates the synthesis of biocompatible osteoconductive and osteoinductive nano calcium phosphate (CaP) particles by industrially applied, aerosol-derived flame spray pyrolysis method for biomedical field. Calcium phosphate nanoparticles were produced in a range of calcium-to-phosphorus ratio, (1.20–2.19) in order to analyze the morphology and crystallinity changes, and to test the bioactivity of particles. The characterization results confirmed that nanometer-sized, spherical calcium phosphate particles were produced. The average primary particle size was determined as 23 nm by counting more than 500 particles in TEM pictures. XRD patterns, HRTEM, SAED, and SEM analyses revealed the amorphous nature of the as-prepared nano calcium phosphate particles at low Ca/P ratios. Increases in the specific surface area and crystallinity were observed with the increasing Ca/P ratio. TGA–DTA analysis showed that the thermally stable crystal phases formed after 700 °C. Cell culture studies were conducted with urine-derived stem cells that possess the characteristics of mesenchymal stem cells. Synthesized amorphous nanoparticles did not have cytotoxic effect at 5–50 μg/ml concentration range. Cells treated with the as-prepared nanoparticles had higher alkaline phosphatase (ALP) enzyme activity than control cells, indicating osteogenic differentiation of cells. A slight decrease in ALP activity of cells treated with two highest Ca:P ratios at 50 μg/ml concentration was observed at day 7. The findings suggest that calcium phosphate nanoparticles produced in this work have a potential to be used as biomaterials in biomedical applications.

  10. Potential effects of four Flaming Gorge Dam hydropower operational scenarios on riparian vegetation of the Green River, Utah and Colorado

    Energy Technology Data Exchange (ETDEWEB)

    LaGory, K.E.; Van Lonkhuyzen, R.A. [Argonne National Lab., IL (United States). Ecological Sciences Section

    1995-06-01

    Four hydropower operational scenarios at Flaming Gorge Dam were evaluated to determine their potential effects on riparian vegetation along the Green River in Utah and Colorado. Data collected in June 1992 indicated that elevation above the river had the largest influence on plant distribution. A lower riparian zone occupied the area between the approximate elevations of 800 and 4,200-cfs flows--the area within the range of hydropower operational releases. The lower zone was dominated by wetland plants such as cattail, common spikerush, coyote willow, juncus, and carex. An upper riparian zone was above the elevation of historical maximum power plant releases from the dam (4,200 cfs), and it generally supported plants adapted to mesic, nonwetland conditions. Common species in the upper zone included box elder, rabbitbrush, grasses, golden aster, and scouring rush. Multispectral aerial videography of the Green River was collected in May and June 1992 to determine the relationship between flow and the areas of water and the riparian zone. From these relationships, it was estimated that the upper zone would decrease in extent by about 5% with year-round high fluctuation, seasonally adjusted high fluctuation, and seasonally adjusted moderate fluctuation, but it would increase by about 8% under seasonally adjusted steady flow. The lower zone would increase by about 13% for both year-round and seasonally adjusted high fluctuation scenarios but would decrease by about 40% and 74% for seasonally adjusted moderate fluctuation and steady flows, respectively. These changes are considered to be relatively minor and would leave pre-dam riparian vegetation unaffected. Occasional high releases above power plant capacity would be needed for long-term maintenance of this relict vegetation.

  11. 大分子溴系复合阻燃剂对PS和发泡PS的阻燃改性%Effect of Composited Macromolecular Brominated Flame Retardants on Flame Retardant Modiifcation of Polystyrene and Polystyrene Foam

    Institute of Scientific and Technical Information of China (English)

    黄朋科; 庞永艳; 张树海; 刘伟; 张利华; 郑文革

    2016-01-01

    The main objective was to study the effect of composited macromolecular flame retardants on modification of polystyrene (PS) and PS foam. Theflame retardants used were a new macromolecular brominatedflame retardant (FR–122P) and a brominated epoxy resin (2200HM). The effects of the weight ratios of FR–122P and 2200HM and the contents of the composited macromolecularflame retardants were investigated on theflame retardancy of PS,and the effects of the contents of the composited macromolecularflame retardants were investigated on the cell structure andflame retardancy of PS foam. The investigations above were carried out with TGA,SEM,LOI,UL–94 and horizontal burning. It was found that PS could pass UL–94 V–0 rating and had a LOI value of 25.8% with the composited macromolecularflame retardants at a content of 25% and a ratio of 4∶1. With 40% content of the composited macromolecularflame retardants,the PS foam showed small cell sizes,high cell density and high expansion ratio,and it could pass HF–2 grade. The composited macromolecular flame retardants showed good flame retardant performance for PS and PS foam.%将大分子溴系阻燃剂(FR–122P)与溴化环氧树脂(2200HM)组成的复合阻燃剂应用于聚苯乙烯(PS)复合材料和发泡PS中,研究了复合阻燃剂的配比和含量对PS复合材料阻燃性能以及复合阻燃剂含量对发泡PS泡孔结构和阻燃性能的影响,采用热重分析、扫描电子显微镜观察、极限氧指数(LOI)测试、垂直燃烧(UL–94)和水平燃烧试验等手段进行了表征。结果表明,当FR–122P与2200HM质量比为4∶1、总添加量为25%时,PS复合材料的LOI可达25.8%,并可通过UL–94 V–0等级;当复合阻燃剂的添加量为40%时,可得到泡孔尺寸较小、泡孔密度较大、膨胀倍率较高的发泡PS复合材料,且其可通过泡沫水平燃烧的HF–2等级。大分子溴系阻燃剂与溴化环氧树脂的复合阻燃剂对PS和发泡PS

  12. The Effectiveness of Three Serious Games Measuring Generic Learning Features

    Science.gov (United States)

    Bakhuys Roozeboom, Maartje; Visschedijk, Gillian; Oprins, Esther

    2017-01-01

    Although serious games are more and more used for learning goals, high-quality empirical studies to prove the effectiveness of serious games are relatively scarce. In this paper, three empirical studies are presented that investigate the effectiveness of serious games as opposed to traditional classroom instruction on learning features as well as…

  13. Flame Retardation Modification of Paper-Based PVC Wallcoverings

    Directory of Open Access Journals (Sweden)

    Lin Hui

    2016-01-01

    Full Text Available The flame-retarded paper-based polyvinyl chloride (PVC wallcoverings were successfully prepared, using plant fiber paper as base material and adding inorganic flame retardants and flame-retarded plasticizer as additives. Flame retardancy, thermostability, smoke suppression and mechanical properties were tested regarding to the prepared wallcoverings. The results showed that 2ZnO·3B2O3·3.5H2O could improve flame retardancy and thermostability of paper-based PVC wallcoverings; plasticizer tricresyl phosphate increased flame retardancy of the prepared materials auxiliarily. Also, flame-retarded paper-based PVC wallcoverings with higher flame retardancy, smoke suppression and mechanical property was prepared using plant fiber paper with fix quantity of 90 g/m3 as base material, using 2ZnO·3B2O3·3.5H2O as inorganic flame retardant, and using tricresyl phosphate as plasticizer. For the flame-retarded paper-based PVC wallcoverings in this study, the limit oxygen index (LOI reaches 32.3, maximal smoke density is 16.91 %, and the horizontal and longitudinal wet tensile strength reaches 1.38 kN·m−1 and 1.51 kN·m−1 respectively. Meanwhile, its flame retardancy meets the requirements about flame retardancy for material Class B1 listed in Chinese National Standards GB 8624-2012, Classification for burning behavior of building materials and products. This research creates an effective path to prepare paper-based PVC wallcoverings with high flame retardancy.

  14. Kinetic Effects of Non-Equilibrium Plasma on Partially Premixed Flame Extinction

    Science.gov (United States)

    2011-01-01

    absorption laser- induced fluorescence (TALIF) method, Fourier Transform Infrared ( FTIR ) spectrometer , and Gas Chromatography (GC). The product...workers isolated singlet oxygen (O2(a1Δg)) and ozone (O3) effects and demonstrated that both (at concentrations of several thousand ppm) enhanced...measured by Fourier Transform Infrared spectroscopy ( FTIR ) and Gas Chromatography (GC). These experimental data were used to validate our current plasma

  15. Igniting the Paralympic Flame

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Deaf-mute Jiang Xintian lights a small cauldron in the hands of wheelchairbound fencer Jin Jing at the Paralympic Flame Lighting Ceremony in Beijing’s symbolic Temple of Heaven on August 28. For nine days until September 6, when the 13th Paralympics opens in Beijing, a total of 850 torchbearers would relay the Paralympic flame along two routes through 11 Chinese provinces,

  16. The effects of overwinter flowson the spring condition of rainbow and brown trout size classes in the Green River downstream of Flaming Gorge Dam, Utah.

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, A. K.; LaGory, K. E.; Hayse, J. W.; Environmental Science Division

    2010-06-25

    Flaming Gorge Dam, a hydroelectric facility operated by the Bureau of Reclamation (Reclamation), is located on the Green River in Daggett County, northeastern Utah. Until recently, and since the early 1990s, single daily peak releases or steady flows have been the operational pattern of the dam during the winter period. However, releases from Flaming Gorge Reservoir followed a double-peak pattern (two daily flow peaks) during the winters of 2006-2007 and 2008-2009. Because there is little recent long-term history of double-peaking at Flaming Gorge Dam, the potential effects of double-peaking operations on trout body condition in the dam's tailwater are not known. A study plan was developed that identified research activities to evaluate potential effects from winter double-peaking operations (Hayse et al. 2009). Along with other tasks, the study plan identified the need to conduct a statistical analysis of historical trout condition and macroinvertebrate abundance to evaluate the potential effects of hydropower operations. The results from analyses based on the combined size classes of trout (85-630 mm) were presented in Magnusson et al. (2008). The results of this earlier analysis suggested possible relationships between trout condition and flow, but concern that some of the relationships resulted from size-based effects (e.g., apparent changes in condition may have been related to concomitant changes in size distribution, because small trout may have responded differently to flow than large trout) prompted additional analysis of within-size class relationships. This report presents the results of analyses of three different size classes of trout (small: 200-299 mm, medium: 300-399 mm, and large: {ge}400 mm body length). We analyzed historical data to (1) describe temporal patterns and relationships among flows, benthic macroinvertebrate abundance, and condition of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in the tailwaters of Flaming

  17. The research of far infrared flame retardant polyester staple fiber

    Science.gov (United States)

    Li, Qingshan; Zhang, Kaijun; Luo, Jinqong; Li, Ji’an; Jiang, Jian; Liang, Qianqian; Jin, Yongxia; Liu, Bing

    2017-01-01

    Far infrared flame retardant slices was prepared, fiber with far infrared flame retardant composite function was also prepared by the method of melt spinning. Scanning electron microscopy (SEM) was used to observe the fibrous microscopic structure. In the SEM images, functional ultrafine powder particle size and distribution in the fiber were visible. The results show that the functional ultrafine powder is evenly distributed on the fibrous surface, which is closely combined with fiber, and the far infrared emissivity is F, which is more than (8 to 14 microns) 0.88. Far infrared flame retardant polyester fiber has not only good flame retardant, but also environmental health effect: releasing negative ions and launch far-infrared, which shows wide application prospect. The fiber was processed into far-infrared flame retardant electric blanket, whose functional indicators and flame retardant properties are not reduced.

  18. New developments in the theory of flame propagation

    Energy Technology Data Exchange (ETDEWEB)

    Sivashinsky, G.I. [City College of the City Univ. of New York, NY (United States)

    1996-12-31

    Two topics in combustion fluid mechanics are discussed. The first is a theory of the outward propagating spherical flame in the regime of well-developed hydrodynamic instability. In a qualitative agreement with experimental observations it is shown that the flame assumes a fractal-like wrinkled structure resulting in the overall burning rate acceleration. In contrast to hydrodynamically unstable flames, the expanding flame subject exclusively to the effect of diffusive instability does not indicate any disposition toward acceleration. The second topic concerns the dynamics of diffusively unstable flames subjected to radiative heat losses. At high enough heat losses the flame breaks up into separate self-propagating cap-like flamelets while a significant portion of the fuel remains unconsumed.

  19. Effects of the Commercial Flame Retardant Mixture DE-71 on Cytokine Production by Human Immune Cells

    DEFF Research Database (Denmark)

    Mynster Kronborg, Thit; Frohnert Hansen, Juliana; Nielsen, Claus Henrik

    2016-01-01

    INTRODUCTION: Although production of polybrominated diphenyl ethers (PBDEs) is now banned, release from existing products will continue for many years. The PBDEs are assumed to be neurotoxic and toxic to endocrine organs at low concentrations. Their effect on the immune system has not been...... investigated thoroughly. We aimed to investigate the influence of DE-71 on cytokine production by peripheral blood mononuclear cells (PBMCs) stimulated with Escherichia Coli lipopolysaccharide (LPS) or phytohaemagglutinin-L (PHA-L). MATERIAL AND METHODS: PBMCs isolated from healthy donors were pre......-incubated with DE-71 at various concentrations and subsequently incubated with the monocyte stimulator LPS, or the T-cell activator PHA-L. Interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor (TNF)-α, IL-17A, and IL-17F were quantified in the supernatants by Luminex kits...

  20. Effects of Injector Conditions on the Flame Lift-Off Length of DI Diesel Sprays

    Energy Technology Data Exchange (ETDEWEB)

    D. L. Siebers; B. S. Higgins

    2000-07-01

    The effects of injection pressure and orifice diameter on the lift-off length of a direct-injection (DI) diesel spray (defined as the farthest upstream location of high temperature combustion) were investigated using a natural light emission imaging technique. The lift-off length experiments were conducted in a constant-volume combustion vessel under quiescent, heavy-duty DI diesel engine conditions using a Phillips research grade No.2 diesel fuel. The results show that natural light emission at 310 nm provides an excellent marker of the lift-off length. At this location, natural light emission at 310 nm is dominated by OH chemiluminescence generated by high-temperature combustion chemistry. Lift-off lengths determined from images of natural light emission at 310 nm show that as either injection pressure (i.e., injection velocity) or orifice diameter increase, the lift-off length increases. The observed lift-off length increase was linearly dependent on injection velocity, the same dependency as previously noted for gas jets. The lift-off length increase with increasing orifice diameter, however, is different than the independence of lift-off length on orifice diameter noted for gas jets An important overall observation was made by considering the lift-off length data in conjunction with data from recent investigations of liquid-phase fuel penetration and spray development. The combined data suggests that a systematic evolution of the relationship and interaction between various processes in a DI diesel spray has been occurring over time, as injection pressures have been increased and orifice diameters reduced as part of efforts to meet emissions regulations. The trends observed may eventually help explain effects of parameters such as injection pressure and orifice diameter on emissions.

  1. Effects of the Commercial Flame Retardant Mixture DE-71 on Cytokine Production by Human Immune Cells.

    Directory of Open Access Journals (Sweden)

    Thit Mynster Kronborg

    Full Text Available Although production of polybrominated diphenyl ethers (PBDEs is now banned, release from existing products will continue for many years. The PBDEs are assumed to be neurotoxic and toxic to endocrine organs at low concentrations. Their effect on the immune system has not been investigated thoroughly. We aimed to investigate the influence of DE-71 on cytokine production by peripheral blood mononuclear cells (PBMCs stimulated with Escherichia Coli lipopolysaccharide (LPS or phytohaemagglutinin-L (PHA-L.PBMCs isolated from healthy donors were pre-incubated with DE-71 at various concentrations and subsequently incubated with the monocyte stimulator LPS, or the T-cell activator PHA-L. Interferon (IFN-γ, interleukin (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor (TNF-α, IL-17A, and IL-17F were quantified in the supernatants by Luminex kits.At non-cytotoxic concentrations (0.01-10 μg/mL, DE-71 significantly enhanced secretion of IL-1β, IL-6, CXCL8, IL-10, and TNF-α (p<0.001-0.019; n = 6 from LPS-stimulated PBMCs. IFN-γ, TNF-α, IL-17A, and IL-17F (p = <0.001-0.043; n = 6 secretion were enhanced from PHA-L-stimulated PBMCs as well. Secretion of IL-1β, IL-2, IL-10, IL-8 and IL-6 was not significantly affected by DE-71.We demonstrate an enhancing effect of DE-71 on cytokine production by normal human PBMCs stimulated with LPS or PHA-L ex vivo.

  2. Effects of Palladium Loading on the Response of Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor

    OpenAIRE

    Sukon Phanichphant; Chaikarn Liewhiran

    2007-01-01

    ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in asingle step by flame spray pyrolysis (FSP) using zinc naphthenate and palladium (II)acetylacetonate dissolved in toluene-acetonitrile (80:20 vol%) as precursors. The effect ofPd loading on the ethanol gas sensing performance of the ZnO nanoparticles and thecrystalline sizes were investigated. The particle properties were analyzed by XRD, BET,AFM, SEM (EDS line scan mode), TEM, STEM, EDS, and CO-pulse chemisorptionmeasurem...

  3. Effects of Palladium Loading on the Response of a Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor

    OpenAIRE

    Liewhiran, Chaikarn; Phanichphant, Sukon

    2007-01-01

    ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in a single step by flame spray pyrolysis (FSP) using zinc naphthenate and palladium (II) acetylacetonate dissolved in toluene-acetonitrile (80:20 vol%) as precursors. The effect of Pd loading on the ethanol gas sensing performance of the ZnO nanoparticles and the crystalline sizes were investigated. The particle properties were analyzed by XRD, BET, AFM, SEM (EDS line scan mode), TEM, STEM, EDS, and CO-pulse chemisorption me...

  4. Flame Propagation Enhancement by Plasma Excitation of Oxygen. Part 2. Effects of O2(a1 Delta sub g)

    Science.gov (United States)

    2010-01-01

    ozone I0 intensity of light without the presence of ozone L absorption path length Nozone number density of ozone P pressure ppm parts per million T...temperature k reaction rate coefficient rozone absorption cross-section of ozone T. Ombrello et al. / Combustion and Flame 157 (2010) 1916–1928 1917...fluctuations in the intensity of the mercury light as a function of time during the experiments. 2.2.3. FTIR spectroscopy for NO and NO2 measurement The

  5. A Posteriori Quantification of Rate-Controlling Effects from High-Intensity Turbulence-Flame Interactions Using 4D Measurements

    Science.gov (United States)

    2016-11-22

    complete information on the thermo-chemical-fluid state available from the DNS. 9 Publications Journal Articles (Published or Accepted): 1. J. R...Tomographic PIV and OH PLIF Measurements in Turbulent Reactive Flows, Experiments in Fluids, 55:1743-62 (2014) *Two further journal articles currently are...turbulent premixed flames measured from simultaneous 10 kHz TPIV, OH PLIF, and CH2O PLIF, Com- bustion Institute Canadian Section Meeting, Waterloo ON

  6. Modeling Candle Flame Behavior In Variable Gravity

    Science.gov (United States)

    Alsairafi, A.; Tien, J. S.; Lee, S. T.; Dietrich, D. L.; Ross, H. D.

    2003-01-01

    The burning of a candle, as typical non-propagating diffusion flame, has been used by a number of researchers to study the effects of electric fields on flame, spontaneous flame oscillation and flickering phenomena, and flame extinction. In normal gravity, the heat released from combustion creates buoyant convection that draws oxygen into the flame. The strength of the buoyant flow depends on the gravitational level and it is expected that the flame shape, size and candle burning rate will vary with gravity. Experimentally, there exist studies of candle burning in enhanced gravity (i.e. higher than normal earth gravity, g(sub e)), and in microgravity in drop towers and space-based facilities. There are, however, no reported experimental data on candle burning in partial gravity (g model of the candle flame, buoyant forces were neglected. The treatment of momentum equation was simplified using a potential flow approximation. Although the predicted flame characteristics agreed well with the experimental results, the model cannot be extended to cases with buoyant flows. In addition, because of the use of potential flow, no-slip boundary condition is not satisfied on the wick surface. So there is some uncertainty on the accuracy of the predicted flow field. In the present modeling effort, the full Navier-Stokes momentum equations with body force term is included. This enables us to study the effect of gravity on candle flames (with zero gravity as the limiting case). In addition, we consider radiation effects in more detail by solving the radiation transfer equation. In the previous study, flame radiation is treated as a simple loss term in the energy equation. Emphasis of the present model is on the gas-phase processes. Therefore, the detailed heat and mass transfer phenomena inside the porous wick are not treated. Instead, it is assumed that a thin layer of liquid fuel coated the entire wick surface during the burning process. This is the limiting case that the mass

  7. Flame retardancy effect of surface-modified metal hydroxides on linear low density polyethylene

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Metal hydroxides (MAH) consisting of magnesium hydroxide and aluminum hydroxide with a mass ratio of 1:2 were surface-modified by γ-diethoxyphosphorous ester propyldiethoxymethylsilane,boric acid and diphenylsilanediol in xylene under dibutyl tin dilaurate catalyst at 140 ℃.Phosphorus,silicon and boron elements covalently bonded to metal hydroxide particles were detected by X-ray photoelectron spectroscopy.The degradation behavior of the surface-modified MAH was characterized by thermogravimetric analysis.The results show that linear low density polyethylene (LLDPE) composite,filled with 50% (mass fraction) of MAH modified by 5.0% (mass fraction) of modifiers,passes the V-O rating of UL-94 test and shows the limited oxygen index of 34%,and its heat release rate and average effective heat combustion in a cone calorimeter measurement decrease obviously;The mechanical properties of MAH can be improved by surface-modification.The uniform dispersion of particles and strong interfacial bonding between particles and matrix are obtained.

  8. POLYAMIDE 6 WITH A FLAME RETARDANT ENCAPSULATED BY POLYAMIDE 66: FLAME RETARDATION, THERMO-DECOMPOSITION AND THE POTENTIAL MECHANISM

    Institute of Scientific and Technical Information of China (English)

    Wei-cheng Xiong; Li Chen; Bin Zhao; De-yi Wang; Yu-zhong Wang

    2012-01-01

    A novel encapsulated flame retardant containing phosphorus-nitrogen (MSMM-Al-P) was prepared by encapsulating with polyamide 66 (PA66-MSMM-Al-P) for the flame retardation of polyamide 6 (PA6).The structure and thermal properties of PA66-MSMM-Al-P were characterized by Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy and thermogravimetric analysis.The flammability of PA6 containing' flame retardants (MSMMAl-P and PA66-MSMM-Al-P) was investigated by the limiting oxygen index test,vertical burning test and cone calorimeter.The flame retardancy and cone calorimetric analyses suggested a synergistic effect between PA66 and MSMM-Al-P in the flame-retardant PA6.Thermal stability of the flame-retardant PA6 was also investigated.

  9. Application of high-resolution continuum source flame atomic absorption spectrometry to reveal, evaluate and overcome certain spectral effects in Pb determination of unleaded gasoline

    Science.gov (United States)

    Kowalewska, Zofia; Laskowska, Hanna; Gzylewski, Michał

    2017-06-01

    High-resolution continuum source and line source flame atomic absorption spectrometry (HR-CS FAAS and LS FAAS, respectively) were applied for Pb determination in unleaded aviation or automotive gasoline that was dissolved in methyl-isobutyl ketone. When using HR-CS FAAS, a structured background (BG) was registered in the vicinity of both the 217.001 nm and 283.306 nm Pb lines. In the first case, the BG, which could be attributed to absorption by the OH molecule, directly overlaps with the 217 nm line, but it is of relatively low intensity. For the 283 nm line, the structured BG occurs due to uncompensated absorption by OH molecules present in the flame. BG lines of relatively high intensity are situated at a large distance from the 283 nm line, which enables accurate analysis, not only when using simple variants of HR-CS FAAS but also for LS FAAS with a bandpass of 0.1 nm. The lines of the structured spectrum at 283 nm can have ;absorption; (maxima) or ;emission; (minima) character. The intensity of the OH spectra can significantly depend on the flame character and composition of the investigated organic solution. The best detection limit for the analytical procedure, which was 0.01 mg L- 1 for Pb in the investigated solution, could be achieved using HR-CS FAAS with the 283 nm Pb line, 5 pixels for the analyte line measurement and iterative background correction (IBC). In this case, least squares background correction (LSBC) is not recommended. However, LSBC (available as the ;permanent structures; option) would be recommended when using the 217 nm Pb line. In LS FAAS, an additional phenomenon related to the nature of the organic matrix (for example, isooctane or toluene) can play an important role. The effect is of continuous character and probably due to the simultaneous efficient correction of the continuous background (IBC) it is not observed in HR-CS FAAS. The fact that the effect does not depend on the flame character indicates that it is not radiation

  10. Dynamic simulation on effect of flame arrangement on thermal process of regenerative reheating furnace

    Institute of Scientific and Technical Information of China (English)

    OU Jian-ping; MA Ai-chun; ZHAN Shu-hua; ZHOU Jie-min; XIAO Ze-qiang

    2007-01-01

    By analyzing the characteristics of combustion and billet heating process, a 3-D transient computer fluid dynamic simulation system based on commercial software CFX4.3 and some self-programmed codes were developed to simulate the thermal process in a continuous heating furnace using high temperature air combustion technology. The effects of different switching modes on injection entrancement of multi burners, combustion and billet heating process in furnace were analyzed numerically, and the computational results were compared with on-site measurement, which verified the practicability of this numerical simulation system.The results indicate that the flow pattern and distribution of temperature in regenerative reheating furnace with partial same-side-switching combustion mode are favorable to satisfy the high quality requirements of reheating, in which the terminal heating temperature of billets is more than 1 460 K and the temperature difference between two nodes is not more than 10 K. But since the surface average temperature of billets apart from heating zone is only about 1 350 K and continued heating is needed in soaking zone, the design and operation of current state are still needed to be optimized to improve the temperature schedule of billet heating. The distribution of velocity and temperature in regenerative reheating furnace with same-side-switching combustion mode cannot satisfy the even and fast heating process. The terminal heating temperature of billets is lower than that of the former case by 30 K. The distribution of flow and temperature can be improved by using cross-switching combustion mode, whose terminal temperature of billets is about 1 470 K with small temperature difference within 10 K.

  11. The Influences of Electric Fields on Soot Formation and Flame Structure of Diffusion Flames

    Institute of Scientific and Technical Information of China (English)

    LinXie; TakeyukiKishi; 等

    1993-01-01

    The influences of DC and AC electric fields,at frequencies up to 1.48 MHz and the maximum strength of about 6 kV/cm,on soot formation and flame structure were investigated using a counterflow type acetylene diffusion flame.The distributioons of flame luminosity,soot volume fraction,Flame temperature and OH concentration in flame were measured by non-invasive detection methods.Under the influence of electric fields,the changes in distribution of the soot volume fraction were confirmed.Electric fields of high frequency and high intensity reduced the soot volume fraction.whereas other electric fields increased it.The maximum values of flame temperature and OH concentration decreased.In the relationship between the maximum value of the soot volume fraction and the maximum temperature,the maximum soot volum fraction showed toth increase and decrease with maximum temperatures depending on the frequencies and intensities of the electric fields,and both of them occurred at temperatures lower than 1990 K.The production of the incipient particles seemed to be the dominant process controlling the soot volume fraction due to the electric fields.The luminosity of a sooting diffusion flame was found to depend on the volume fraction and temperature of the soot particles in the flame,As for the behavior of the flame in the electric fields.the ionic wind effect was not found to be dominant in the present work,and the result of the precious simulation based on the ionic wind theory was not consistent with the present experimental results.

  12. Effects of preprocessing Landsat MSS data on derived features

    Science.gov (United States)

    Parris, T. M.; Cicone, R. C.

    1983-01-01

    Important to the use of multitemporal Landsat MSS data for earth resources monitoring, such as agricultural inventories, is the ability to minimize the effects of varying atmospheric and satellite viewing conditions, while extracting physically meaningful features from the data. In general, the approaches to the preprocessing problem have been derived from either physical or statistical models. This paper compares three proposed algorithms; XSTAR haze correction, Color Normalization, and Multiple Acquisition Mean Level Adjustment. These techniques represent physical, statistical, and hybrid physical-statistical models, respectively. The comparisons are made in the context of three feature extraction techniques; the Tasseled Cap, the Cate Color Cube. and Normalized Difference.

  13. Analysis of lift-off height and structure of n-heptane tribrachial flames in laminar jet configuration

    KAUST Repository

    Luca, Stefano

    2015-03-30

    A set of lifted tribrachial n-heptane flames in a laminar jet configuration are simulated. The simulations are performed using finite rate chemistry and detailed transport, and aim at investigating the propagation of tribrachial flames. Varying the inlet velocity of the fuel, different stabilization heights are obtained, and the dependence of the stabilization height in the inlet velocity is compared with experimental data. A detailed analysis of the flame geometry is performed by comparingthe flame structure to that of unstretched premixed flames. Issues related to differential diffusion effects, flame stretch, and transport of heat and mass from the burnt gases to the flame front are discussed.

  14. Combustion Characteristics for Turbulent Prevaporized Premixed Flame Using Commercial Light Diesel and Kerosene Fuels

    Directory of Open Access Journals (Sweden)

    Mohamed S. Shehata

    2014-01-01

    Full Text Available Experimental study has been carried out for investigating fuel type, fuel blends, equivalence ratio, Reynolds number, inlet mixture temperature, and holes diameter of perforated plate affecting combustion process for turbulent prevaporized premixed air flames for different operating conditions. CO2, CO, H2, N2, C3H8, C2H6, C2H4, flame temperature, and gas flow velocity are measured along flame axis for different operating conditions. Gas chromatographic (GC and CO/CO2 infrared gas analyzer are used for measuring different species. Temperature is measured using thermocouple technique. Gas flow velocity is measured using pitot tube technique. The effect of kerosene percentage on concentration, flame temperature, and gas flow velocity is not linearly dependent. Correlations for adiabatic flame temperature for diesel and kerosene-air flames are obtained as function of mixture strength, fuel type, and inlet mixture temperature. Effect of equivalence ratio on combustion process for light diesel-air flame is greater than for kerosene-air flame. Flame temperature increases with increased Reynolds number for different operating conditions. Effect of Reynolds number on combustion process for light diesel flame is greater than for kerosene flame and also for rich flame is greater than for lean flame. The present work contributes to design and development of lean prevaporized premixed (LPP gas turbine combustors.

  15. Structure of low-stretch methane nonpremixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bai; Ibarreta, Alfonso F.; Sung, Chih-Jen; T' ien, James S. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States)

    2007-04-15

    The present study experimentally and numerically investigates the structure associated with extremely low-stretch ({proportional_to}2 s{sup -1}) gaseous nonpremixed flames. The study of low-stretch flames aims to improve our fundamental understanding of the flame radiation effects on flame response and extinction limits. Low-stretch flames are also relevant to fire safety in reduced-gravity environments and to large buoyant fires, where localized areas of low stretch are attainable. In this work, ultra-low-stretch flames are established in normal gravity by bottom burning of a methane/nitrogen mixture discharged from a porous spherically symmetric burner of large radius of curvature. The large thickness of the resulting nonpremixed flame allows detailed mapping of the flame structure. Several advanced nonintrusive optical diagnostics are used to study the flame structure. Gas phase temperatures are measured by Raman scattering, while the burner surface temperatures are obtained by IR imaging. In addition, OH-PLIF and chemiluminescence imaging techniques are used to help characterize the extent of the flame reaction zone. These experimental results allow direct comparison with a quasi-one-dimensional numerical model including detailed chemistry, thermodynamic/transport properties, and radiation treatment. In addition, the radiative interactions between the flame and porous burner (modeled as a gray surface) are accounted for in the present model. The numerical modeling is demonstrated to be able to simulate the low-stretch flame structure. Using the current model, the extinction limits under different conditions are also examined. The computational results are consistent with experimental observations. (author)

  16. Effect of dosage of expandable graphite, dimethyl methylphosphonate, triethanolamine, and isocyanate on fluidity, mechanical, and flame retardant properties of polyurethane materials in coal reinforcement

    Institute of Scientific and Technical Information of China (English)

    Hu Xiangming; Wang Deming; Cheng Weimin

    2016-01-01

    In this study, orthogonal experiments were conducted to investigate the influence of expandable graphite (EG), dimethyl methylphosphonate (DMMP), triethanolamine (TEA), and isocyanate content on the com-pressive and bonding strengths, oxygen index, and fluidity of rigid polyurethane foam (RPUF). The results revealed that EG significantly increased the oxygen index of RPUF, enlarged the diameter of foam cells, and decreased the cell-closed content in foam;thus, leading to a pressure drop in RPUF. However, exces-sive EG was capable of reducing the fluidity of polyurethane slurry. TEA exhibited significant influence on the compressive strength of RPUF, which dropped initially, and then increased. DMMP had a remarkable effect on the flame retardant property and compressive strength of RPUF. Compressive strength of RPUF initially displayed an increase followed by a decrease with increasing dosage of DMMP, and achieved the maximum value at DMMP dosage of 4%. DMMP could effectively reduce the diameter of RPUF cells lead-ing to an increase in the percentage of close area in foam. DMMP displayed the flame-retardation effects mainly in the gas phase leading to a significant enhancement in the oxygen index of RPUF. Moreover, the compressive strength and bonding strength of RPUF decrease significantly with the increase of isocyanate content due to the increased blowing efficiency by the CO2. The oxygen index and flowing length of foam increased with the increase in isocyanate dosage.

  17. 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.

  18. Measurements of turbulent premixed flame dynamics using cinema stereoscopic PIV

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, Adam M.; Driscoll, James F. [University of Michigan, Department of Aerospace Engineering, Ann Arbor, MI (United States); Ceccio, Steven L. [University of Michigan, Department of Mechanical Engineering, Ann Arbor, MI (United States)

    2008-06-15

    A new experimental method is described that provides high-speed movies of turbulent premixed flame wrinkling dynamics and the associated vorticity fields. This method employs cinema stereoscopic particle image velocimetry and has been applied to a turbulent slot Bunsen flame. Three-component velocity fields were measured with high temporal and spatial resolutions of 0.9 ms and 140{mu}m, respectively. The flame-front location was determined using a new multi-step method based on particle image gradients, which is described. Comparisons are made between flame fronts found with this method and simultaneous CH-PLIF images. These show that the flame contour determined corresponds well to the true location of maximum gas density gradient. Time histories of typical eddy-flame interactions are reported and several important phenomena identified. Outwardly rotating eddy pairs wrinkle the flame and are attenuated at they pass through the flamelet. Significant flame-generated vorticity is produced downstream of the wrinkled tip. Similar wrinkles are caused by larger groups of outwardly rotating eddies. Inwardly rotating pairs cause significant convex wrinkles that grow as the flame propagates. These wrinkles encounter other eddies that alter their behavior. The effects of the hydrodynamic and diffusive instabilities are observed and found to be significant contributors to the formation and propagation of wrinkles. (orig.)

  19. Nonpremixed flame in a counterflow under electric fields

    KAUST Repository

    Park, Daegeun

    2016-05-08

    Electrically assisted combustion has been studied in order to control or improve flame characteristics, and emphasizing efficiency and emission regulation. Many phenomenological observations have been reported on the positive impact of electric fields on flame, however there is a lack of detailed physical mechanisms for interpreting these. To clarify the effects of electric fields on flame, I have investigated flame structure, soot formation, and flow field with ionic wind electrical current responses in nonpremixed counterflow flames. The effects of direct current (DC) electric field on flame movement and flow field was also demonstrated in premixed Bunsen flames. When a DC electric field was applied to a lower nozzle, the flames moved toward the cathode side due to Lorentz force action on the positive ions, soot particles simultaneously disappeared completely and laser diagnostics was used to identify the results from the soot particles. To understand the effects of an electric field on flames, flow visualization was performed by Mie scattering to check the ionic wind effect, which is considered to play an important role in electric field assisted combustion. Results showed a bidirectional ionic wind, with a double-stagnant flow configuration, which blew from the flame (ionic source) toward both the cathode and the anode. This implies that the electric field affects strain rate and the axial location of stoichiometry, important factors in maintaining nonpremixed counterflow flames; thus, soot formation of the counterflow flame can also be affected by the electric field. In a test of premixed Bunsen flames having parallel electrodes, flame movement toward the cathode and bidirectional ionic wind were observed. Using PIV measurement it was found that a created radial velocity caused by positive ions (i.e. toward a cathode), was much faster than the velocity toward the anode. Even in a study of alternating current (AC) electric fields, bidirectional ionic wind could

  20. Front roughening of flames in discrete media

    Science.gov (United States)

    Lam, Fredric; Mi, XiaoCheng; Higgins, Andrew J.

    2017-07-01

    The morphology of flame fronts propagating in reactive systems composed of randomly positioned, pointlike sources is studied. The solution of the temperature field and the initiation of new sources is implemented using the superposition of the Green's function for the diffusion equation, eliminating the need to use finite-difference approximations. The heat released from triggered sources diffuses outward from each source, activating new sources and enabling a mechanism of flame propagation. Systems of 40 000 sources in a 200 ×200 two-dimensional domain were tracked using computer simulations, and statistical ensembles of 120 realizations of each system were averaged to determine the statistical properties of the flame fronts. The reactive system of sources is parameterized by two nondimensional values: the heat release time (normalized by interparticle diffusion time) and the ignition temperature (normalized by adiabatic flame temperature). These two parameters were systematically varied for different simulations to investigate their influence on front propagation. For sufficiently fast heat release and low ignition temperature, the front roughness [defined as the root mean square deviation of the ignition temperature contour from the average flame position] grew following a power-law dependence that was in excellent agreement with the Kardar-Parisi-Zhang (KPZ) universality class (β =1 /3 ). As the reaction time was increased, lower values of the roughening exponent were observed, and at a sufficiently great value of reaction time, reversion to a steady, constant-width thermal flame was observed that matched the solution from classical combustion theory. Deviation away from KPZ scaling was also observed as the ignition temperature was increased. The features of this system that permit it to exhibit both KPZ and non-KPZ scaling are discussed.

  1. Flame dynamics in a micro-channeled combustor

    Science.gov (United States)

    Hussain, Taaha; Markides, Christos N.; Balachandran, Ramanarayanan

    2015-01-01

    The increasing use of Micro-Electro-Mechanical Systems (MEMS) has generated a significant interest in combustion-based power generation technologies, as a replacement of traditional electrochemical batteries which are plagued by low energy densities, short operational lives and low power-to-size and power-to-weight ratios. Moreover, the versatility of integrated combustion-based systems provides added scope for combined heat and power generation. This paper describes a study into the dynamics of premixed flames in a micro-channeled combustor. The details of the design and the geometry of the combustor are presented in the work by Kariuki and Balachandran [1]. This work showed that there were different modes of operation (periodic, a-periodic and stable), and that in the periodic mode the flame accelerated towards the injection manifold after entering the channels. The current study investigates these flames further. We will show that the flame enters the channel and propagates towards the injection manifold as a planar flame for a short distance, after which the flame shape and propagation is found to be chaotic in the middle section of the channel. Finally, the flame quenches when it reaches the injector slots. The glow plug position in the exhaust side ignites another flame, and the process repeats. It is found that an increase in air flow rate results in a considerable increase in the length (and associated time) over which the planar flame travels once it has entered a micro-channel, and a significant decrease in the time between its conversion into a chaotic flame and its extinction. It is well known from the literature that inside small channels the flame propagation is strongly influenced by the flow conditions and thermal management. An increase of the combustor block temperature at high flow rates has little effect on the flame lengths and times, whereas at low flow rates the time over which the planar flame front can be observed decreases and the time of

  2. Flame-Vortex Interactions Imaged in Microgravity - To Assess the Theory Flame Stretch

    Science.gov (United States)

    Driscoll, James F.

    2001-01-01

    The goals of this research are to: 1) Assess the Theory of Flame Stretch by operating a unique flame-vortex experiment under microgravity conditions in the NASA Glenn 2.2 Second Drop Tower (drops to identify operating conditions have been completed); 2) Obtain high speed shadowgraph images (500-1000 frames/s) using the drop rig (images were obtained at one-g, and the NASA Kodak RO camera is being mounted on the drop rig); 3) Obtain shadowgraph and PIV images at 1-g while varying the effects of buoyancy by controlling the Froude number (completed); 4) Numerically model the inwardly-propagating spherical flame that is observed in the experiment using full chemistry and the RUN 1DL code (completed); 5) Send images of the flame shape to Dr. G. Patniak at NRL who is numerically simulating the entire flame-vortex interaction of the present experiment (data transfer completed); and 6) Assess the feasibility of obtaining PIV velocity field images in the drop rig, which would be useful (but not required) for our assessment of the Theory of Flame Stretch (PIV images were obtained at one-g using same low laser power that is available from fiber optic cable in drop tower). The motivation for the work is to obtain novel measurement needed to develop a physically accurate model of turbulent combustion that can help in the control of engine pollutants. The unique experiment allows, for the first time, the detailed study of a negatively-curved (negatively stretched) flame, which is one of the five fundamental types of premixed flames. While there have been studies of flat flames, positively-curved (outwardly-propagating) cases and positively-strained (counterflow) cases, this is the first detailed study of a negatively-curved (inwardly-propagating) flame. The first set of drops in the 2.2 Second Drop Tower showed that microgravity provides more favorable conditions for achieving inwardly-propagating flames (IPFs) than 1-g. A vortex interacts with a flame and creates a spherical

  3. Control of NO sub x emissions by combustion-air staging: the measurement of NH sub 3 , HCN, NO and N sub 2 O concentrations in fuel-oil flames

    Energy Technology Data Exchange (ETDEWEB)

    Nimmo, W.; Hampartsoumian, E.; Sedighi, K.; Williams, A. (Leeds Univ. (GB). Dept. of Fuel and Energy)

    1991-09-01

    The control of NO{sub x} formation from fuel-bound nitrogen in the combustion of coal and oil can give significant reductions in the final emission. One of the simplest and most cost-effective combustion modifications is that of staging the combustion air, whereby up to 50% is separated from the primary air and introduced into the flame further downstream. Thus the early part of the flame has a fuel-rich centre which provides a chemical environment that encourages the reaction of NO to form harmless products N{sub 2} and H{sub 2}O. The work presented here has investigated the in-flame development of NH{sub 3}, HCN, NO and N{sub 2}O for an unstaged and a staged (35%) oil flame, since they are the principal intermediates in the formation of NO. The oil spray was characterised by means of a laser particle-sizing technique over a range of oil pressures and combustion-air flows and two nozzle spray angles. The results were correlated with NO{sub x} emission measurements. The air-staging results showed that the virtually oxygen-free condition at the centre of the staged flame altered the ratio of HCN:NH{sub 3} significantly, and that in-flame development of NO was limited. Measurements of N{sub 2}O emissions from the unstaged and staged flames showed levels of typically less than 2 vpm in the exit flue, but the in-flame measurements showed that the unstaged flame exhibited a peak of circa 6 vpm at an axial position coincident with maximum NO concentrations. The staged flame did not display this feature. (author).

  4. Analysis of the Effect of the Swirl Flow Intensity on Combustion Characteristics in Liquid Fuel Powered Confined Swirling Flames

    Directory of Open Access Journals (Sweden)

    Marko Klancisar

    2016-01-01

    Full Text Available This article examines the implementation of CFD technology in the design of the industrial liquid fuel powered swirl flame burner. The coupling between the flow field and the combustion model is based on the eddy dissipation model. The choice of the LES (Large Eddy Simulation turbulence model over standard RANS (Reynolds Averaged Navier-Stokes offers a possibility to improve the quality of the combustion-flow field interaction. The Wall Adapting Local Eddy-Viscosity (WALE sub-grid model was used. The reaction chemistry is a simple infinitely fast one step global irreversible reaction. The computational model was setup with the Ansys-CFX software. Through the detailed measurements of industrial size burner, it was possible to determine the natural operational state of the burner according to the type of fuel used. For the inlet conditions, axial and radial velocity components were calculated from known physical characteristics of both the fuel and air input, with the initial tangential velocity of the fuel assumed as18% of the initial axial fuel velocity. Different swirl number (S values were studied. Addition of a surplus (in comparison to conventional flame stabilization of tangential air velocity component (W, the rotational component increases itself with a considerably high magnitude, contributing to the overall flame stabilization. The level of S especially influences the turbulent energy, its dissipation rate and turbulent (Reynolds stresses. In the case of high swirl number values (S > 0,65 it is possible to divide the flow field in three principle areas: mixing area (fuel-air, where exothermal reactions are taking place, central recirculation area and outer recirculation area, which primarily contains the flow of burnt flue gases. The described model was used to determine the flow and chemical behavior, whereas the liquid atomization was accounted for by LISA (Linear Instability Sheet Atomization model incorporating also the cavitation

  5. Stabilization and structure of n-heptane tribrachial flames in axisymmetric laminar jets

    KAUST Repository

    Bisetti, Fabrizio

    2015-01-01

    A set of tribrachial flames of n-heptane/air is simulated with finite rate chemistry and detailed transport in a realistic laminar jet configuration for which experimental data are available. The flames differ by the temperature of the unburnt mixture and stabilization height, which controls the mixture fraction gradient ahead of the flame front. The simulations reproduce the lift-off heights in the experiments, showing that the flame stabilizes further downstream as the unburnt temperature decreases. For the lowest unburnt temperature, resulting in a weak mixture fraction gradient at the tribrachial point, positive stretch along the rich premixed wing leads to an increase in the rate of chemical reaction in the whole flame. The tribrachial flame burning velocity exceeds that in the unstretched, one-dimensional flame. For the highest temperature, the flame stabilizes closest to the nozzle. Large flame tilt, large mixture fraction gradient, and small radius of curvature lead to a reduction in the heat release rate and the flame propagates slower than its one-dimensional counterpart. The observed behavior is explained with a detailed analysis of the flame geometry, differential diffusion effects, flame stretch, and transport of heat and mass from the burnt gases to the flame front. © 2014 The Combustion Institute.

  6. Flaming on YouTube

    NARCIS (Netherlands)

    Moor, Peter J.; Heuvelman, A.; Verleur, R.

    2010-01-01

    In this explorative study, flaming on YouTube was studied using surveys of YouTube users. Flaming is defined as displaying hostility by insulting, swearing or using otherwise offensive language. Three general conclusions were drawn. First, although many users said that they themselves do not flame,

  7. Flaming on YouTube

    NARCIS (Netherlands)

    Moor, Peter J.; Heuvelman, Ard; Verleur, Ria

    2010-01-01

    In this explorative study, flaming on YouTube was studied using surveys of YouTube users. Flaming is defined as displaying hostility by insulting, swearing or using otherwise offensive language. Three general conclusions were drawn. First, although many users said that they themselves do not flame,

  8. Flame retardancy and its mechanism of polymers flame retarded by DBDPE/Sb2O3

    Institute of Scientific and Technical Information of China (English)

    ZUO Jian-dong; LI Rong-xun; FENG Shao-hua; LIU Guang-ye; ZHAO Jian-qing

    2008-01-01

    The flammability characterization and thermal composition of polymers flame retarded by decabromodiphenylethane(DBDPE) and antimony trioxide (Sb2O3) were studied by cone calorimeter and thermogravimetry (TG). The results show thatABS/DBDPE/Sb2O3 has the similar flammability parameters and thermal composition curves to ABS/DBDPO/Sb3O3. It suggests thatDBDPE/Sb2O3 has the similar flame retardant behavior to DBDPO/Sb2O3. The heat release rate (HRR) and the effect heat combustion (EHC) curves of polymers flame retarded by DBDPE/Sb2O3 all decrease, but the mass loss rate (MLR) curve slightly increase. It shows that the decrease of HRR is not due to the increase of char formation ratio but the generation of incombustible gases. The major flame retardant mechanism of DBDPE/Sb2O3 is gas phase flame retardant mechanism. Increasing content of Sb2O3in DBDPE/Sb2O3 can improve the flame retardant property and thermal stability of aerylonitrile butadiene styrene. Sb203 has a good synergistic effect with DBDPE.

  9. On the influence of the gas velocity profile on the theoretically predicted opposed flow flame spread

    Energy Technology Data Exchange (ETDEWEB)

    DiBlasi, C.; Crescitelli, S.; Russo, G. (Dipartimento di Ingegneria Chimica, Universita de Napoli, Piazzale v Tecchio, Naples (IT)); FernandezPello, A.C. (California Univ., Berkeley, CA (USA). Dept. of Mechanical Engineering)

    1989-01-01

    A numerical analysis is presented of the effect on the predicted flame spread rate and flame structure of a prescribed gas velocity field opposing the direction of flame propagation. The calculations are made for two limiting cases of oxygen mass fraction and with Oseen and Hagen-Poiseuille velocity profiles. It is shown that the selected gas velocity profile has a significant influence on the flame spread predictions.

  10. Synthesis of mesoporous silica@Co-Al layered double hydroxide spheres: layer-by-layer method and their effects on the flame retardancy of epoxy resins.

    Science.gov (United States)

    Jiang, Shu-Dong; Bai, Zhi-Man; Tang, Gang; Song, Lei; Stec, Anna A; Hull, T Richard; Hu, Yuan; Hu, Wei-Zhao

    2014-08-27

    Hierarchical mesoporous silica@Co-Al layered double hydroxide (m-SiO2@Co-Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co-Al LDH, the synthetic m-SiO2@Co-Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co-Al LDH nanosheets. Subsequently, the m-SiO2@Co-Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co-Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co-Al LDH play pivotal roles in the flame retardance enhancement.

  11. Pulsed direct flame deposition and thermal annealing of transparent amorphous indium zinc oxide films as active layers in field effect transistors.

    Science.gov (United States)

    Kilian, Daniel; Polster, Sebastian; Vogeler, Isabell; Jank, Michael P M; Frey, Lothar; Peukert, Wolfgang

    2014-08-13

    Indium-zinc oxide (IZO) films were deposited via flame spray pyrolysis (FSP) by pulsewise shooting a Si/SiO2 substrate directly into the combustion area of the flame. Based on UV-vis measurements of thin-films deposited on glass substrates, the optimal deposition parameters with respect to low haze values and film thicknesses of around 100 nm were determined. Thermal annealing of the deposited films at temperatures between 300 and 700 °C was carried out and staggered bottom gate thin-film transistors (TFT) were fabricated. The thin films were investigated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy, and room-temperature photoluminescence measurements. The outcome of these investigations lead to two major requirements in order to implement a working TFT: (i) organic residues from the deposition process need to be removed and (ii) the net free charge carrier concentration has to be minimized by controlling the trap states in the semiconductor. The optimal annealing temperature was 300 °C as both requirements are fulfilled best in this case. This leads to field effect transistors with a low hysteresis, a saturation mobility of μSat = 0.1 cm(2)/(V s), a threshold voltage of Vth = -18.9 V, and an Ion/Ioff ratio on the order of 10(7). Depending on thermal treatment, the defect density changes significantly strongly influencing the transfer characteristics of the device.

  12. Modeling flame structure in wildland fires using the one-dimensional turbulence model

    Science.gov (United States)

    David O. Lignell; Elizabeth I. Monson; Mark A. Finney

    2010-01-01

    The mechanism of flame propagation in wildland fire fuel beds is of critical importance for understanding and quantifying fire spread rates. Recent observations and experiments have indicated the dominance of flame propagation by direct contact between flames and unburnt fuel, as opposed to propagation via radiative heating alone. It is postulated that effects of...

  13. Investigations of two-phase flame propagation under microgravity conditions

    Science.gov (United States)

    Gokalp, Iskender

    2016-07-01

    Investigations of two-phase flame propagation under microgravity conditions R. Thimothée, C. Chauveau, F. Halter, I Gökalp Institut de Combustion, Aérothermique, Réactivité et Environnement (ICARE), CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France This paper presents and discusses recent results on two-phase flame propagation experiments we carried out with mono-sized ethanol droplet aerosols under microgravity conditions. Fundamental studies on the flame propagation in fuel droplet clouds or sprays are essential for a better understanding of the combustion processes in many practical applications including internal combustion engines for cars, modern aircraft and liquid rocket engines. Compared to homogeneous gas phase combustion, the presence of a liquid phase considerably complicates the physico-chemical processes that make up combustion phenomena by coupling liquid atomization, droplet vaporization, mixing and heterogeneous combustion processes giving rise to various combustion regimes where ignition problems and flame instabilities become crucial to understand and control. Almost all applications of spray combustion occur under high pressure conditions. When a high pressure two-phase flame propagation is investigated under normal gravity conditions, sedimentation effects and strong buoyancy flows complicate the picture by inducing additional phenomena and obscuring the proper effect of the presence of the liquid droplets on flame propagation compared to gas phase flame propagation. Conducting such experiments under reduced gravity conditions is therefore helpful for the fundamental understanding of two-phase combustion. We are considering spherically propagating two-phase flames where the fuel aerosol is generated from a gaseous air-fuel mixture using the condensation technique of expansion cooling, based on the Wilson cloud chamber principle. This technique is widely recognized to create well-defined mono-size droplets

  14. In vitro effects of selected brominated flame retardants on the adreno cortical enzyme (CYP17). A novel endocrine mechanism of action?

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Canton, R.; Sanderson, T.; Nijmeijer, S.; Berg, M. van den [Utrecht Univ. (NL). Inst. for Risk Assessment Sciences (IRAS); Berkman, Aa. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry and Analytical Chemistry

    2004-09-15

    Fire incidents have decreased over the last 20 years partly due to regulations requiring addition of flame retardants (FRs) to materials. These compounds can be divided into different chemical classes: inorganic, nitrogen, phosphorus and halogen containing flame retardants (usually brominated or chlorinated). Not surprisingly, the use of brominated flame retardants (BFRs) in a variety of commercial and household products has increased over the years due to their low cost and high effectiveness. Consequence of the high production of BFRs is that these compounds are now readily detectable in air, water, birds, fish, marine mammals, and in human adipose tissue and blood. The five major BFRs are hexabromocyclododecane (HBCD), tetrabromobisphenol-A (TBBPA) and three commercial mixtures of polybrominated diphenyl ethers (PBDEs) (penta, octa, deca), which are extensively used as FRs at high production volume levels. In addition, concentrations of PBDEs concentration have been rapidly increasing during the last 10 years in human breast milk from European and American women and a number of endocrine (in vitro) effects have been reported. Consequently, the concern about BFRs and their metabolites with respect to their potential as endocrine disruptors (EDs) has been growing. Studies in our laboratory are focused on potential interactions of a wide range of BFRs with sex hormone synthesis and metabolism. Previous results from our research group, showed inhibitory and inductive effects on aromatase (CYP19) (the key enzyme that converts androgens to estrogens) by certain BFRs, in particular the hydroxylated PBDEs and several bromophenols. In the present study, the effects of ten of these BFRs on CYP17 activity were investigated. This enzyme also catalyzes an important step in the sex steroidogenesis and is responsible for the biosynthesis of dehydroepiandrosterone (DHEA). DHEA, produced in the adrenal gland, is the most abundant sex steroid hormone in human blood and has been

  15. Effects of the brominated flame retardant TBCO on fecundity and profiles of transcripts of the HPGL-axis in Japanese medaka.

    Science.gov (United States)

    Saunders, David M V; Podaima, Michelle; Wiseman, Steve; Giesy, John P

    2015-03-01

    The novel brominated flame retardant, 1,2,5,6-tetrabromocyclooctane (TBCO) is an additive flame retardant which is marketed under the trade name Saytex BCL-48. TBCO has recently been investigated as a potential alternative to the major use brominated flame retardant, hexabromocyclododecane (HBCD), which could have major implications for significant increases in amounts of TBCO used. Yet there is a lack of information regarding potential toxicities of TBCO. Recently, results of in vitro experiments have demonstrated the potential of TBCO to modulate endocrine function through interaction with estrogen and androgen receptors and via alterations to the synthesis of 17-β-estradiol and testosterone. Further research is required to determine potential endocrine disrupting effects of TBCO in vivo. In this experiment a 21-day fecundity assay with Japanese medaka (Oryzias latipes) was conducted to examine endocrine disrupting effects of TBCO in vivo. Medaka were fed a diet containing either 607 or 58μg TBCO/g food, wet mass (wm). Fecundity, measured as cumulative deposition of eggs and fertilization of eggs, as well as abundances of transcripts of 34 genes along the hypothalamus-pituitary-gonadal-liver (HPGL) axis were measured as indicators of holistic endocrine disruption and to determine mechanisms of effects, respectively. Cumulative fecundity was 18% lesser by medaka exposed to 58μg TBCO/g, wm food. However, fecundity of medaka exposed to 607μg TBCO/g, wm food was not significantly different from that of controls. Organ-specific and dose-dependent alterations to abundances of transcripts were observed in male and female medaka. A pattern of down-regulation of expression of genes involved in steroidogenesis, metabolism of cholesterol, and regulatory feedback mechanisms was observed in gonads from male and female medaka which had been exposed to the greater concentration of TBCO. However, these effects on expression of genes were not manifested in effects on

  16. Analysis of Reaction-Diffusion Systems for Flame Capturing in Type Ia Supernova Simulations

    CERN Document Server

    Zhiglo, Andrey V

    2009-01-01

    We present a study of numerical behavior of a thickened flame used in Flame Capturing (FC, Khokhlov (1995)) for tracking thin unresolved physical flames in deflagration simulations. We develop a steady-state procedure for calibrating the flame model used, and test it against analytical results. We observe numerical noises generated by original realization of the technique. Alternative artificial burning rates are discussed, which produce acceptably quiet flames. Two new quiet models are calibrated to yield required "flame" speed and width, and further studied in 2D and 3D setting. Landau-Darrieus type instabilities of the flames are observed. One model also shows significantly anisotropic propagation speed on the grid, both effects increasingly pronounced at larger matter expansion as a result of burning; this makes the model unacceptable for use in type Ia supernova simulations. Another model looks promising for use in flame capturing at fuel to ash density ratio of order 3 and below. That "Model B" yields f...

  17. Effects of hydropower operations on recreational use and nonuse values at Glen Canyon and Flaming Gorge Dams

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, J.L.

    1995-03-01

    Increases in streamflows are generally positively related to the use values of angling and white-water boating, and constant flows tend to increase the use values more than fluctuating flows. In most instances, however, increases in streamflows beyond some threshold level cause the use values to decrease. Expenditures related to angling and white-water boating account for about $24 million of activity in the local economy around Glen Canyon Dam and $24.8 million in the local economy around flaming Gorge Dam. The range of operational scenarios being considered in the Western Area Power Administration`s Electric Power Marketing Environmental Impact Statement, when use rates are held constant, could change the combined use value of angling and white-water boating below Glen Canyon Dam, increasing it by as much as 50%, depending on prevailing hydrological conditions. Changes in the combined use value below Flaming Gorge Dam could range from a decrease of 9% to an increase of 26%. Nonuse values, such as existence and bequest values, could also make a significant contribution to the total value of each site included in this study; however, methodological and data limitations prevented estimating how each operational scenario could change nonuse values.

  18. Effects of Flaming Gorge Dam hydropower operations on flow and stage in the Green River, Utah and Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Yin, S.C.L.; Cho, H.E. [Argonne National Lab., IL (United States). Environmental Assessment Div.; McCoy, J.J.; Palmer, S.C. [Western Area Power Administration, Salt Lake City, UT (United States)

    1995-05-01

    This report presents the development of Flaming Gorge Reservoir release patterns and resulting downstream flows and stages for four potential hydropower operational scenarios. The release patterns were developed for three representative hydrologic years: moderate, dry, and wet. Computer models were used to estimate flows and stages in the Green River resulting from these release patterns for the moderate water year. The four hydropower operational scenarios for Flaming Gorge Dam were year-round high fluctuating flows, seasonally adjusted high fluctuating flows, seasonally adjusted moderate fluctuating flows, and seasonally adjusted steady flows. The year-round high fluctuating flow scenario assumes that the monthly total reservoir releases would be the same as historical releases. The remaining seasonally adjusted flow scenarios would comply with the 1992 Biological Opinion of the US Fish and Wildlife Service, which requires high flows in the spring and limited hourly fluctuations, especially in summer and autumn releases, to protect endangered fish. Within one year, the maximum daily river stage fluctuations resulting from hydropower operations under the seasonally adjusted high fluctuating flow scenario would be similar to the maximum daily fluctuations under the year-round high fluctuating flow scenario. However, reduced or no fluctuations would occur in some time periods under the former scenario. The maximum daily river stage fluctuations under the seasonally adjusted moderate fluctuating flow scenario would be about half of those under the seasonally adjusted high fluctuating flow scenario.

  19. Weakly Bound Free Radicals in Combustion: "Prompt" Dissociation of Formyl Radicals and Its Effect on Laminar Flame Speeds

    Energy Technology Data Exchange (ETDEWEB)

    Labbe, Nicole J.; Sivaramakrishnan, Raghu; Goldsmith, C. Franklin; Georgievskii, Yuri; Miller, James A.; Klippenstein, Stephen J.

    2016-01-07

    Weakly bound free radicals have low-dissociation thresholds such that at high temperatures, timescales for dissociation and collisional relaxation become comparable, leading to significant dissociation during the vibrational-rotational relaxation process. Here we characterize this “prompt” dissociation of formyl (HCO), an important combustion radical, using direct dynamics calculations for OH + CH2O and H + CH2O (key HCO-forming reactions). For all other HCO-forming reactions, presumption of a thermal incipient HCO distribution was used to derive prompt dissociation fractions. Inclusion of these theoretically derived HCO prompt dissociation fractions into combustion kinetics models provides an additional source for H-atoms that feeds chain branching reactions. Simulations using these updated combustion models are therefore shown to enhance flame propagation in 1,3,5-trioxane and acetylene. The present results suggest that HCO prompt dissociation should be included when simulating flames of hydrocarbons and oxygenated molecules and that prompt dissociations of other weakly bound radicals may also impact combustion simulations

  20. Weakly Bound Free Radicals in Combustion: "Prompt" Dissociation of Formyl Radicals and Its Effect on Laminar Flame Speeds.

    Science.gov (United States)

    Labbe, Nicole J; Sivaramakrishnan, Raghu; Goldsmith, C Franklin; Georgievskii, Yuri; Miller, James A; Klippenstein, Stephen J

    2016-01-01

    Weakly bound free radicals have low-dissociation thresholds such that at high temperatures, time scales for dissociation and collisional relaxation become comparable, leading to significant dissociation during the vibrational-rotational relaxation process. Here we characterize this "prompt" dissociation of formyl (HCO), an important combustion radical, using direct dynamics calculations for OH + CH2O and H + CH2O (key HCO-forming reactions). For all other HCO-forming reactions, presumption of a thermal incipient HCO distribution was used to derive prompt dissociation fractions. Inclusion of these theoretically derived HCO prompt dissociation fractions into combustion kinetics models provides an additional source for H-atoms that feeds chain-branching reactions. Simulations using these updated combustion models are therefore shown to enhance flame propagation in 1,3,5-trioxane and acetylene. The present results suggest that HCO prompt dissociation should be included when simulating flames of hydrocarbons and oxygenated molecules and that prompt dissociations of other weakly bound radicals may also impact combustion simulations.

  1. Hydrogen-oxygen flame acceleration and transition to detonation in channels with no-slip walls for a detailed chemical reaction model.

    Science.gov (United States)

    Ivanov, M F; Kiverin, A D; Liberman, M A

    2011-05-01

    The features of flame acceleration in channels with wall friction and the deflagration to detonation transition (DDT) are investigated theoretically and using high resolution numerical simulations of two-dimensional reactive Navier-Stokes equations, including the effects of viscosity, thermal conduction, molecular diffusion, and a detailed chemical reaction mechanism for hydrogen-oxygen gaseous mixture. It is shown that in a wide channel, from the beginning, the flame velocity increases exponentially for a short time and then flame acceleration decreases, ending up with the abrupt increase of the combustion wave velocity and the actual transition to detonation. In a thin channel with a width smaller than the critical value, the exponential increase of the flame velocity is not bounded and ends up with the transition to detonation. The transition to detonation occurs due to the pressure pulse, which is formed at the tip of the accelerating flame. The amplitude of the pressure pulse grows exponentially due to a positive feedback coupling between the pressure pulse and the heat released in the reaction. Finally, large amplitude pressure pulse steepens into a strong shock coupled with the reaction zone forming the overdriven detonation. The evolution from a temperature gradient to a detonation via the Zeldovich gradient mechanism and its applicability to the deflagration-to-detonation transition is investigated for combustible materials whose chemistry is governed by chain-branching kinetics. The results of the high resolution simulations are fully consistent with experimental observations of the flame acceleration and DDT.

  2. Effects of Hydrogen Enhancement in LPG/Air Premixed Flame%添加氢气对LPG/空气预混火焰结构的影响

    Institute of Scientific and Technical Information of China (English)

    王彬彬; 邱榕; 蒋勇

    2008-01-01

    针对氢气添加的LPG(液化石油气)+空气预混火焰结构进行了数值研究,详细计算了在含氢比a为O%到45%、稀释引子D为21%到16%条件下的自由蔓延火焰,得到了不同燃烧条件(φ=0.7-1.4)下的绝热燃烧速率变化规律.由于LPG中的主要成分为丙烷和丁烷,作者针对C3和C4物质提出了详细化学反应动力学系统,并针对氢气添加的丁烷燃烧过程进行了数值计算,得到了与实验相一致的结果,验证了改进的详细化学机理的有效性.此外,进一步计算了对撞双火焰的加氢LPG火焰,更加深入地探讨了火焰拉伸对燃烧稳定性和温度的影响,重点研究了φ在0.5到0.7的稀薄燃烧,验证了氢气添加可以有效提高稀薄燃烧条件下熄火拉伸率,扩大稀薄燃烧的极限,增加火焰的稳定性.%A numerical study of hydrogen-enhanced liquefied petroleum gas (LPG)+air flames was presented.The variations of the adiabatic burning velocity in different conditions of combustion(φ=0.7-1.4)were studied extensively.The hydrogen content in the fuel was varied from 0% to 45% and the dilution factor was from 21% to 16%.Since the major components of LPG are butane and propane.an appropriate chemical kinetic model must be chosen to solve the chemical reaction of C3 and C4 species.Validation of the chemical kinetic model against the fundamental combustion data was performed to insure accuracy.In addition,independem simulations were conducted in the opposed-jet,symmetric,twin-flame configuration.The effects of fluid mechanics,as manifested by the induced strain rate,were also considered.The effects of extinction strain rate on flame temperature and the fiammability limits were calculated and the results showed that hydrogen-enhanced LPG/air premixed flames were more stable at high flame strain.The lean flammability limits were extended by the H2 addition.

  3. Numerical modelling of ion transport in flames

    KAUST Repository

    Han, Jie

    2015-10-20

    This paper presents a modelling framework to compute the diffusivity and mobility of ions in flames. The (n, 6, 4) interaction potential is adopted to model collisions between neutral and charged species. All required parameters in the potential are related to the polarizability of the species pair via semi-empirical formulas, which are derived using the most recently published data or best estimates. The resulting framework permits computation of the transport coefficients of any ion found in a hydrocarbon flame. The accuracy of the proposed method is evaluated by comparing its predictions with experimental data on the mobility of selected ions in single-component neutral gases. Based on this analysis, the value of a model constant available in the literature is modified in order to improve the model\\'s predictions. The newly determined ion transport coefficients are used as part of a previously developed numerical approach to compute the distribution of charged species in a freely propagating premixed lean CH4/O2 flame. Since a significant scatter of polarizability data exists in the literature, the effects of changes in polarizability on ion transport properties and the spatial distribution of ions in flames are explored. Our analysis shows that changes in polarizability propagate with decreasing effect from binary transport coefficients to species number densities. We conclude that the chosen polarizability value has a limited effect on the ion distribution in freely propagating flames. We expect that the modelling framework proposed here will benefit future efforts in modelling the effect of external voltages on flames. Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/13647830.2015.1090018. © 2015 Taylor & Francis.

  4. Propagation and Extinction of a Cylindrical Premixed Flame Undergoing Equivalence Ratio Fluctuation Near the Lean Limit

    Science.gov (United States)

    Suenaga, Yosuke; Kitano, Michio; Takahashi, Yoichi

    Experimental study was made to investigate the propagation and extinction characteristics of a stretched cylindrical flame undergoing periodic fluctuation of equivalence ratio near the lean limit. With a lean methane-air and a lean propane-air mixture, burning velocity, flame luminosity and flame stretch rate were measured or evaluated for the fluctuation frequencies of 5Hz and 20Hz. The results were summarized as follows: (1) In some part of a period, burning velocity and flame luminosity of the dynamic flame near the lean limit were possible to become lower than those at the lean flammability limit of the static flame. (2) At the high frequency of 20Hz, the burning velocity took a negative value in a certain time range. In spite of this loss of propagation ability, the flame was not extinguished but sustained, indicating the recovery of the flame intensity due to the dynamic effect of fluctuating flame. (3) Flame recovery phenomenon could occur more easily for the methane flame which was strengthened by the Lewis number effect than the propane flame which was weakened by that effect.

  5. Simulations of flame generated particles

    KAUST Repository

    Patterson, Robert

    2016-01-05

    The nonlinear structure of the equations describing the evolution of a population of coagulating particles in a flame make the use of stochastic particle methods attractive for numerical purposes. I will present an analysis of the stochastic fluctuations inherent in these numerical methods leading to an efficient sampling technique for steady-state problems. I will also give some examples where stochastic particle methods have been used to explore the effect of uncertain parameters in soot formation models. In conclusion I will try to indicate some of the issues in optimising these methods for the study of uncertain model parameters.

  6. Launch Pad Flame Trench Refractory Materials

    Science.gov (United States)

    Calle, Luz M.; Hintze, Paul E.; Parlier, Christopher R.; Bucherl, Cori; Sampson, Jeffrey W.; Curran, Jerome P.; Kolody, Mark; Perusich, Steve; Whitten, Mary

    2010-01-01

    The launch complexes at NASA's John F. Kennedy Space Center (KSC) are critical support facilities for the successful launch of space-based vehicles. These facilities include a flame trench that bisects the pad at ground level. This trench includes a flame deflector system that consists of an inverted, V-shaped steel structure covered with a high temperature concrete material five inches thick that extends across the center of the flame trench. One side of the "V11 receives and deflects the flames from the orbiter main engines; the opposite side deflects the flames from the solid rocket boosters. There are also two movable deflectors at the top of the trench to provide additional protection to shuttle hardware from the solid rocket booster flames. These facilities are over 40 years old and are experiencing constant deterioration from launch heat/blast effects and environmental exposure. The refractory material currently used in launch pad flame deflectors has become susceptible to failure, resulting in large sections of the material breaking away from the steel base structure and creating high-speed projectiles during launch. These projectiles jeopardize the safety of the launch complex, crew, and vehicle. Post launch inspections have revealed that the number and frequency of repairs, as well as the area and size of the damage, is increasing with the number of launches. The Space Shuttle Program has accepted the extensive ground processing costs for post launch repair of damaged areas and investigations of future launch related failures for the remainder of the program. There currently are no long term solutions available for Constellation Program ground operations to address the poor performance and subsequent failures of the refractory materials. Over the last three years, significant liberation of refractory material in the flame trench and fire bricks along the adjacent trench walls following Space Shuttle launches have resulted in extensive investigations of

  7. "Magic Eraser" Flame Tests

    Science.gov (United States)

    Landis, Arthur M.; Davies, Malonne I.; Landis, Linda

    2009-01-01

    Cleaning erasers are used to support methanol-fueled flame tests. This safe demonstration technique requires only small quantities of materials, provides clean colors for up to 45 seconds, and can be used in the classroom or the auditorium. (Contains 1 note.)

  8. Effects of the brominated flame retardants hexabromocyclododecane (HBCDD), and tetrabromobisphenol A (TBBPA), on hepatic enzymes and other biomarkers in juvenile rainbow trout and feral eelpout

    Energy Technology Data Exchange (ETDEWEB)

    Ronisz, D.; Farmen Finne, E.; Karlsson, H.; Foerlin, L

    2004-08-25

    Brominated flame retardants (BFRs) leak out in the environment, including the aquatic one. Despite this, sublethal effects of these chemicals are poorly investigated in fish. In this study, a screening of selected biomarkers in juvenile rainbow trout (Oncorhynchus mykiss) and feral eelpout (Zoarces viviparus) was performed after exposure to hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA). Rainbow trout was injected intraperitoneally (i.p.) with HBCDD or TBBPA. Two out of four short-term experiments with HBCDD showed an increase in the activity of catalase. A 40% increase in liver somatic index (LSI) could be observed after 28 days. HBCDD did also seem to have an inhibitory effect on CYP1A's activity (ethoxyresorufin-O-deethylase (EROD)). A putative peroxisome proliferating activity of the compound was investigated without giving a definite answer. HBCDD did not seem to be estrogenic or genotoxic. TBBPA increased the activity of glutathione reductase (GR) after 4, 14 and 28 days in rainbow trout suggesting a possible role of this compound in inducing oxidative stress. The compound did not seem to be estrogenic. TBBPA seemed to compete with the artificial substrate ethoxyresorufin in vitro, during the EROD assay. In eelpout, only one 5 days in vivo experiment was performed. Neither of the compounds gave rise to any effect in this fish. This was the first screening of sublethal effects of the two chemicals in fish, using high doses. Our results indicate that there is a need for further studies of long-term, low-dose effects of these two widely used flame retardants.

  9. 氢氧化镁阻燃剂的改性效果研究%The Modification Effect of Magnesium Hydroxide Flame Retardants

    Institute of Scientific and Technical Information of China (English)

    贾静娴

    2014-01-01

    探讨硬脂酸锌对氢氧化镁阻燃剂的改性效果。考察了工艺条件对氢氧化镁阻燃剂表面改性效果的影响,确定了最佳改性工艺条件:改性时间30 min,改性温度85℃,改性剂用量4%。%The modification effect of zinc stearate on magnesium hydroxide flame retardants is studied and the surface modification effect of technological conditions on magnesium hydroxide is analyzed. The experimental result shows that the optimum technical condition of modification is 30 min in time, 85℃in temperature and 4%in dosage.

  10. Structure and stabilization of cryogenic spray flames; Structure et stabilisation des flammes cryotechniques

    Energy Technology Data Exchange (ETDEWEB)

    Juniper, M.

    2001-11-01

    Cryogenic rocket motors are fueled by liquid oxygen and gaseous hydrogen. The development of design methods is based on reliable numerical simulations, which rely on detailed knowledge of the flame structure and well-defined entry conditions. This research project concerns the region near the fuel injectors. We examine here: (1) The flame structure and injector geometry, (2) The flame stabilization. Tests have been performed on an injector which is similar to those in real motors. Models are developed and their results compared with experimental results in order to study the effect of the injector geometry. A new result of scientific interest is that a wake is more unstable when the outer flow is confined. This mechanism might explain the effect of recess on a cryogenic spray flame. The base of the flame is divided into two parts and a counter-flow flame analysis is applied to the first part. The second part is considered first as a flame in a corner (cross-flow flame). The flame above a porous plate with fuel injection is considered next and we envisage then a flame above a vaporizing fuel. Finally, the flame behind a step over a vaporizing fuel is envisaged. With this progression, the dimensionless parameters which control flame stabilization are identified. (author)

  11. Computational Flame Diagnostics for Direct Numerical Simulations with Detailed Chemistry of Transportation Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Tianfeng [Univ. of Connecticut, Storrs, CT (United States)

    2017-02-16

    The goal of the proposed research is to create computational flame diagnostics (CFLD) that are rigorous numerical algorithms for systematic detection of critical flame features, such as ignition, extinction, and premixed and non-premixed flamelets, and to understand the underlying physicochemical processes controlling limit flame phenomena, flame stabilization, turbulence-chemistry interactions and pollutant emissions etc. The goal has been accomplished through an integrated effort on mechanism reduction, direct numerical simulations (DNS) of flames at engine conditions and a variety of turbulent flames with transport fuels, computational diagnostics, turbulence modeling, and DNS data mining and data reduction. The computational diagnostics are primarily based on the chemical explosive mode analysis (CEMA) and a recently developed bifurcation analysis using datasets from first-principle simulations of 0-D reactors, 1-D laminar flames, and 2-D and 3-D DNS (collaboration with J.H. Chen and S. Som at Argonne, and C.S. Yoo at UNIST). Non-stiff reduced mechanisms for transportation fuels amenable for 3-D DNS are developed through graph-based methods and timescale analysis. The flame structures, stabilization mechanisms, local ignition and extinction etc., and the rate controlling chemical processes are unambiguously identified through CFLD. CEMA is further employed to segment complex turbulent flames based on the critical flame features, such as premixed reaction fronts, and to enable zone-adaptive turbulent combustion modeling.

  12. Computatonal and experimental study of laminar flames

    Energy Technology Data Exchange (ETDEWEB)

    Smooke, M.D.; Long, M.B. [Yale Univ., New Haven, CT (United States)

    1993-12-01

    This research has centered on an investigation of the effects of complex chemistry and detailed transport on the structure and extinction of hydrocarbon flames in counterflow, cylindrical and coflowing axisymmetric configurations. The authors have pursued both computational and experimental aspects of the research in parallel. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the one and two-dimensional nonlinear boundary value problems describing the various reacting systems. Detailed experimental measurements were performed on axisymmetric coflow flames using two-dimensional imaging techniques. In particular, spontaneous Raman scattering and laser induced fluorescence were used to measure the temperature, major and minor species profiles.

  13. Effects of landscape features on waterbird use of rice fields

    Science.gov (United States)

    King, S.; Elphick, C.S.; Guadagnin, D.; Taft, O.; Amano, T.

    2010-01-01

    Literature is reviewed to determine the effects of landscape features on waterbird use of fields in regions where rice (Oryza sativa) is grown. Rice-growing landscapes often consist of diverse land uses and land cover, including rice fields, irrigation ditches, other agricultural fields, grasslands, forests and natural wetlands. Numerous studies indicate that local management practices, such as water depth and timing of flooding and drawdown, can strongly influence waterbird use of a given rice field. However, the effects of size and distribution of rice fields and associated habitats at a landscape scale have received less attention. Even fewer studies have focused on local and landscape effects simultaneously. Habitat connectivity, area of rice, distance to natural wetlands, and presence and distance to unsuitable habitat can be important parameters influencing bird use of rice fields. However, responses to a given landscape vary with landscape structure, scale of analysis, among taxa and within taxa among seasons. A lack of multi-scale studies, particularly those extending beyond simple presence and abundance of a given species, and a lack of direct tests comparing the relative importance of landscape features with in-field management activities limits understanding of the importance of landscape in these systems and hampers waterbird conservation and management.

  14. An investigation of streaklike instabilities in laminar boundary layer flames

    Science.gov (United States)

    Miller, Colin; Finney, Mark; Forthofer, Jason; McAllister, Sara; Gollner, Michael

    2016-11-01

    Observations of coherent structures in boundary layer flames, particularly wildland fires, motivated an investigation on flame instabilities within a boundary layer. This experimental study examined streaklike structures in a stationary diffusion flame stabilized within a laminar boundary layer. Flame streaks were found to align with pre-existing velocity perturbations, enabling stabilization of these coherent structures. Thermocouple measurements were used to quantify streamwise amplification of flame streaks. Temperature mapping indicated a temperature rise in the flame streaks, while the region in between these streaks, the trough, decreased in temperature. The heat flux to the surface was measured with a total heat flux gauge, and the heat flux below the troughs was found to be higher at all measurement locations. This was likely a function of the flame standoff distance, and indicated that the flame streaks were acting to modify the spanwise distribution of heat flux. Instabilities in boundary layer combustion can have an effect on the spanwise distribution of heat transfer. This finding has significant implications for boundary layer combustion, indicating that instantaneous properties can vary significantly in a three-dimensional flow field.

  15. Biochar from "Kon Tiki" flame curtain and other kilns: Effects of nutrient enrichment and kiln type on crop yield and soil chemistry.

    Science.gov (United States)

    Pandit, Naba Raj; Mulder, Jan; Hale, Sarah Elisabeth; Schmidt, Hans Peter; Cornelissen, Gerard

    2017-01-01

    Biochar application to soils has been investigated as a means of improving soil fertility and mitigating climate change through soil carbon sequestration. In the present work, the invasive shrub "Eupatorium adenophorum" was utilized as a sustainable feedstock for making biochar under different pyrolysis conditions in Nepal. Biochar was produced using several different types of kilns; four sub types of flame curtain kilns (deep-cone metal kiln, steel shielded soil pit, conical soil pit and steel small cone), brick-made traditional kiln, traditional earth-mound kiln and top lift up draft (TLUD). The resultant biochars showed consistent pH (9.1 ± 0.3), cation exchange capacities (133 ± 37 cmolc kg-1), organic carbon contents (73.9 ± 6.4%) and surface areas (35 to 215 m2/g) for all kiln types. A pot trial with maize was carried out to investigate the effect on maize biomass production of the biochars made with various kilns, applied at 1% and 4% dosages. Biochars were either pretreated with hot or cold mineral nutrient enrichment (mixing with a nutrient solution before or after cooling down, respectively), or added separately from the same nutrient dosages to the soil. Significantly higher CEC (Pbiochar as compared to non-amended control soils. Importantly, the study showed that biochar made by flame curtain kilns resulted in the same agronomic effect as biochar made by the other kilns (P > 0.05). At a dosage of 1% biochar, the hot nutrient-enriched biochar led to significant increases of 153% in above ground biomass production compared to cold nutrient-enriched biochar and 209% compared to biochar added separately from the nutrients. Liquid nutrient enhancement of biochar thus improved fertilizer effectiveness compared to separate application of biochar and fertilizer.

  16. The Synergistic Effect of Bismuth Oxide on Flame Retardancy and Smoke Suppression of the Cotton Fabric Flame-retarded with Cyclic Phosphonate%氧化铋对环状膦酸酯阻燃棉织物的协效阻燃抑烟作用

    Institute of Scientific and Technical Information of China (English)

    孙才英; 王红; 董春梅

    2011-01-01

    The synergistic effect of bismuth oxide on flame retardancy and smoke suppression of the cotton fabric flame-retarded with cyclic phosphonate ester MCPPE was discussed in this paper. The results show that the LOI of the cotton fabric flame-retarded with MCPPE increased from 43% to 52% when 0.4 g/L bismuth oxide was added in MCPPE flame retardant finishing agent. Damaged carbon length shortened to 5 cm,and vertical flame reached B, level. Yet for breaking strength the influence was not so significant. Thermogravimetrie analysis shows that bismuth oxide further reduced the initial decomposition temperature and maximum pyrolysis temperature. SEM shows that the char of the burned cotton was denser after adding bismuth oxide and bismuth oxide had obvious resistance to deformation. Cone test shows that bismuth oxide not only reduced the total heat release rate of flame retarded cotton fabrics but also lowered the total smoke yield by 60%.%通过阻燃性能测试、热重分析、锥形量热分析等研究手段,考察了氧化铋对环状膦酸酯阻燃棉织物的阻燃抑烟协效作用.结果发现,在阻燃整理剂中添加0.4 g/L的氧化铋,可以使阻燃棉布的极限氧指数从43%提高到52%;损毁炭长缩短到5 cm,垂直燃烧达到B1级;而对断裂强度影响不大.热重分析表明,氧化铋的加入进一步降低了阻燃棉织物的初始分解温度和最大热解速率,500℃时的成炭量有所增加;扫描电镜显示,添加氧化铋后,棉织物燃烧成炭更致密;氧化铋具有明显的抗燃烧变形能力;锥形量热测试表明,氧化铋的添加不仅降低了阻燃棉织物的总热释放速率,而且使阻燃棉织物的总烟释放量降低了60%.

  17. Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

    KAUST Repository

    Kedia, Kushal S.

    2012-03-01

    The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly adiabatic conditions. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. Results show a bell-shaped flame stabilizing above the burner plate hole, with a U-shaped section anchored between neighboring holes. The base of the positively curved U-shaped section of the flame is positioned near the stagnation point, at a location where the flame displacement speed is equal to the flow speed. This location is determined by the combined effect of heat loss and flame stretch on the flame displacement speed. As the mass flow rate of the reactants is increased, the flame displacement speed at this location varies non-monotonically. As the inlet velocity is increased, the recirculation zone grows slowly, the flame moves downstream, and the heat loss to the burner decreases, strengthening the flame and increasing its displacement speed. As the inlet velocity is raised, the stagnation point moves downstream, and the flame length grows to accommodate the reactants mass flow. Concomitantly, the radius of curvature of the flame base decreases until it reaches an almost constant value, comparable to the flame thickness. While the heat loss decreases, the higher flame curvature dominates thereby reducing the displacement speed of the flame base. For a stable flame, the gradient of the flame base displacement speed normal to the flame is higher than the gradient of the flow speed along the same direction, leading to dynamic stability. As inlet velocity is raised further, the former decreases while the latter increases until the stability condition is violated, leading to blowoff. The flame speed during blow off is determined by the feedback between the

  18. Turbulence-Flame Interactions in Type Ia Supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (Authors 1, 2& 3); Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (Author 4); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (Author 5); Aspden, Andrew J; Aspden, Andrew J.; Bell, John B.; Day, Marc S.; Woosley, Stan E.; Zingale, Mike

    2008-05-27

    The large range of time and length scales involved in type Ia supernovae (SN Ia) requires the use of flame models. As a prelude to exploring various options for flame models, we consider, in this paper, high-resolution three-dimensional simulations of the small-scale dynamics of nuclear flames in the supernova environment in which the details of the flame structure are fully resolved. The range of densities examined, 1 to 8 x 107 g cm-3, spans the transition from the laminar flamelet regime to the distributed burning regime where small scale turbulence disrupts the flame. The use of a low Mach number algorithm facilitates the accurate resolution of the thermal structure of the flame and the inviscid turbulent kinetic energy cascade, while implicitly incorporating kinetic energy dissipation at the grid-scale cutoff. For an assumed background of isotropic Kolmogorov turbulence with an energy characteristic of SN Ia, we find a transition density between 1 and 3 x 107 g cm-3 where the nature of the burning changes ualitatively. By 1 x 107 g cm-3, energy diffusion by conduction and radiation is exceeded, on the flame scale, by turbulent advection. As a result, the effective Lewis Number approaches unity. That is, the flame resembles a laminar flame, but is turbulently broadened with an effective diffusion coefficient, D_T \\sim u' l, where u' is the turbulent intensity and l is the integral scale. For the larger integral scales characteristic of a real supernova, the flame structure is predicted to become complex and unsteady. Implications for a possible transition to detonation are discussed.

  19. Synergistic effects of zirconia-coated carbon nanotube on crystalline structure of polyvinylidene fluoride nanocomposites: electrical properties and flame-retardant behavior.

    Science.gov (United States)

    Pal, Kaushik; Kang, Dong Jin; Zhang, Zhen Xiu; Kim, Jin Kuk

    2010-03-02

    Pristine multiwalled carbon nanotubes (MWNTs) and zirconia-coated multiwalled carbon nanotubes (ZrO(2)/MWNTs) by isothermal hydrolysis and the traditional chemical precipitation method have been dispersed into polyvinylidene fluoride (PVDF) copolymer by solution mixing in N,N-dimethylformamide (DMF). The effect of ZrO(2)-coated MWNTs on morphological properties, electrical properties, and flame-retardant behavior has been studied in comparison with virgin PVDF and PVDF/MWNTs nanocomposites. Due to the improved dispersion of the coated nanotubes, the incorporation of 3 wt % of ZrO(2)-coated MWNTs leads to an increase of the thermal stability and dielectric properties and a decrease of the peak heat-release rate.

  20. Effect of single flame retardant aluminum tri-hydroxide and boric acid against inflammability and biodegradability of recycled PP/KF composites

    Science.gov (United States)

    Suharty, Neng Sri; Dihardjo, Kuncoro; Handayani, Desi Suci; Firdaus, Maulidan

    2016-03-01

    Composites rPP/DVB/AA/KF had been reactively synthesized in melt using starting material: recycled polypropylene (rPP), kenaf fiber (KF), multifunctional compound acrylic acid (AA), compatibilizer divinyl benzene (DVB). To improve the inflammability of composites, single flame retardant aluminum tri-hydroxide (ATH) and boric acid (BA) as an additive was added. The inflammability of the composites was tested according to ASTM D635. By using 20% ATH and 5% BA additive in the composites it is effectively inhibiting its time to ignition (TTI). Its burning rate (BR) can be reduced and its heat realease (%HR) decreases. The biodegradability of composites was quantified by its losing weight (LW) of composites after buried for 4 months in the media with rich cellulolytic bacteria. The result shows that the LW of composites in the presence 20% ATH and 5% BA is 6.3%.

  1. Statistical evaluation of the effects of fall and winter flows on the spring condition of rainbow and brown trout in the green river downstream of Flaming Gorge Dam.

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, A. K.; LaGory, K. E.; Hayse, J. W.; Environmental Science Division

    2009-01-09

    Flaming Gorge Dam, a hydroelectric facility operated by the Bureau of Reclamation (Reclamation), is located on the Green River in Daggett County, northeastern Utah. In recent years, single peak releases each day or steady flows have been the operational pattern during the winter period. A double-peak pattern (two flow peaks each day) was implemented during the winter of 2006-2007 by Reclamation. Because there is no recent history of double-peaking at Flaming Gorge Dam, the potential effects of double-peaking operations on the body condition of trout in the dam's tailwater are not known. A study plan was developed that identified research activities to evaluate potential effects from double-peaking operations during winter months. Along with other tasks, the study plan identified the need to conduct a statistical analysis of existing data on trout condition and macroinvertebrate abundance to evaluate potential effects of hydropower operations. This report presents the results of this analysis. We analyzed historical data to (1) describe temporal patterns and relationships among flows, benthic macroinvertebrate abundance, and condition of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in the tailwaters of Flaming Gorge Dam and (2) to evaluate the degree to which flow characteristics (i.e., flow volumes and flow variability) and benthic macroinvertebrate abundance affect the condition of trout in this area. This information, together with further analyses of size-stratified trout data, may also serve as baseline data to which the effects of potential future double-peaking flows can be compared. The condition (length, weight and/or relative weight) of rainbow trout (Oncorhynchus mykiss) at two sites in the Green River downstream of Flaming Gorge Dam (Tailrace and Little Hole) and weight of brown trout (Salmo trutta) at the Little Hole site has been decreasing since 1990 while the abundance of brown trout has been increasing at the two sites. At

  2. Large Scale Flame Spread Environmental Characterization Testing

    Science.gov (United States)

    Clayman, Lauren K.; Olson, Sandra L.; Gokoghi, Suleyman A.; Brooker, John E.; Ferkul, Paul V.; Kacher, Henry F.

    2013-01-01

    Under the Advanced Exploration Systems (AES) Spacecraft Fire Safety Demonstration Project (SFSDP), as a risk mitigation activity in support of the development of a large-scale fire demonstration experiment in microgravity, flame-spread tests were conducted in normal gravity on thin, cellulose-based fuels in a sealed chamber. The primary objective of the tests was to measure pressure rise in a chamber as sample material, burning direction (upward/downward), total heat release, heat release rate, and heat loss mechanisms were varied between tests. A Design of Experiments (DOE) method was imposed to produce an array of tests from a fixed set of constraints and a coupled response model was developed. Supplementary tests were run without experimental design to additionally vary select parameters such as initial chamber pressure. The starting chamber pressure for each test was set below atmospheric to prevent chamber overpressure. Bottom ignition, or upward propagating burns, produced rapid acceleratory turbulent flame spread. Pressure rise in the chamber increases as the amount of fuel burned increases mainly because of the larger amount of heat generation and, to a much smaller extent, due to the increase in gaseous number of moles. Top ignition, or downward propagating burns, produced a steady flame spread with a very small flat flame across the burning edge. Steady-state pressure is achieved during downward flame spread as the pressure rises and plateaus. This indicates that the heat generation by the flame matches the heat loss to surroundings during the longer, slower downward burns. One heat loss mechanism included mounting a heat exchanger directly above the burning sample in the path of the plume to act as a heat sink and more efficiently dissipate the heat due to the combustion event. This proved an effective means for chamber overpressure mitigation for those tests producing the most total heat release and thusly was determined to be a feasible mitigation

  3. Experimental study of limit lean methane/air flame in a standard flammability tube using particle image velocimetry method

    Energy Technology Data Exchange (ETDEWEB)

    Shoshin, Yuriy; Gorecki, Grzegorz; Jarosinski, Jozef; Fodemski, Tadeusz [Department of Heat Technology and Refrigeration, Technical University of Lodz, Lodz 90-924 (Poland)

    2010-05-15

    Lean limit methane/air flame propagating upward in a standard 50 mm diameter and 1.8 m length tube was studied experimentally using particle image velocimetry method. Local stretch rate along the flame front was determined by measured gas velocity distributions. It was found that local stretch rate is maximum at the flame leading point, which is in agreement with earlier theoretical results. Similar to earlier observations, extinction of upward propagating limit flame was observed to start from the flame top. It is stated that the observed behavior of the extinction of the lean limit methane/air flame can not be explained in terms of the coupled effect of flame stretch and preferential diffusion. To qualitatively explain the observed extinction behavior, it is suggested that the positive strain-induced flame stretch increases local radiation heat losses from the flame front. An experimental methodology for PIV measurements in a round tube is described. (author)

  4. FLARE FLAME INSTABILITY AND BURNER COMBUSTION CONTROL

    OpenAIRE

    БОНДАРЕНКО А.В.; В. Э. Волков; Максимов, М. В.

    2014-01-01

    Research of the flare instability development and the laminar-to-turbulent transition for the flares was executed. It was proved that the effects of viscosity and compressibility have the stabilizing influence on the gas flame. The study of the individual flare stability makes the theoretical basis of the fuel burning technology in combustion chambers and for the burner combustion control.

  5. 带侧边微孔射流扰动火焰结构特性%Flame Structure of a Jet Flame with Penetration of Side Micro-jets

    Institute of Scientific and Technical Information of China (English)

    曹玉春; 吴金星; 米建春; 周钰

    2008-01-01

    In this paper, an innovative jet lifted flame with side micro-jets has been proposed and its effects on the flame structure have also been investigated. Due to the changes of the initial combustion conditions, mixing and aerodynamics which resulted from the perturbation of the side micro-jets, such a lifted jet flame has different flame structure compared with the common premixed flame. Results demonstrate that use of the micro-jets can control, to a certain extent, the flame structure, including the flame length, lift-off distance and blow-off limit. With the same fuel and air flow rate, the flame length with the side micro-jets will decrease about 5% 40% as the air volume ratio a increases from 58%-76%. Compared with the common diffusion flame, the jet flame with the side micro-jets demonstrates to be easier to be a momentum-dominated flame. The flame length with 2 micro-jets is about 5% less than with 6 micro-jets under the same fuel and air flow rate. With the same α, the fewer number of the controlled jets lead to the flame with relatively shorter length, not easier to be blown off and higher NOx emission. With certain fuel flow rate, the critical air volume ratio is largest for the flame with 3 micro-jets, which is more difficult to be blown off than the cases with 2,4 or 6 micro-jets.

  6. Flame kernel generation and propagation in turbulent partially premixed hydrocarbon jet

    KAUST Repository

    Mansour, Mohy S.

    2014-04-23

    Flame development, propagation, stability, combustion efficiency, pollution formation, and overall system efficiency are affected by the early stage of flame generation defined as flame kernel. Studying the effects of turbulence and chemistry on the flame kernel propagation is the main aim of this work for natural gas (NG) and liquid petroleum gas (LPG). In addition the minimum ignition laser energy (MILE) has been investigated for both fuels. Moreover, the flame stability maps for both fuels are also investigated and analyzed. The flame kernels are generated using Nd:YAG pulsed laser and propagated in a partially premixed turbulent jet. The flow field is measured using 2-D PIV technique. Five cases have been selected for each fuel covering different values of Reynolds number within a range of 6100-14400, at a mean equivalence ratio of 2 and a certain level of partial premixing. The MILE increases by increasing the equivalence ratio. Near stoichiometric the energy density is independent on the jet velocity while in rich conditions it increases by increasing the jet velocity. The stability curves show four distinct regions as lifted, attached, blowout, and a fourth region either an attached flame if ignition occurs near the nozzle or lifted if ignition occurs downstream. LPG flames are more stable than NG flames. This is consistent with the higher values of the laminar flame speed of LPG. The flame kernel propagation speed is affected by both turbulence and chemistry. However, at low turbulence level chemistry effects are more pronounced while at high turbulence level the turbulence becomes dominant. LPG flame kernels propagate faster than those for NG flame. In addition, flame kernel extinguished faster in LPG fuel as compared to NG fuel. The propagation speed is likely to be consistent with the local mean equivalence ratio and its corresponding laminar flame speed. Copyright © Taylor & Francis Group, LLC.

  7. Selecting Testlet Features With Predictive Value for the Testlet Effect

    Directory of Open Access Journals (Sweden)

    Muirne C. S. Paap

    2015-04-01

    Full Text Available High-stakes tests often consist of sets of questions (i.e., items grouped around a common stimulus. Such groupings of items are often called testlets. A basic assumption of item response theory (IRT, the mathematical model commonly used in the analysis of test data, is that individual items are independent of one another. The potential dependency among items within a testlet is often ignored in practice. In this study, a technique called tree-based regression (TBR was applied to identify key features of stimuli that could properly predict the dependence structure of testlet data for the Analytical Reasoning section of a high-stakes test. Relevant features identified included Percentage of “If” Clauses, Number of Entities, Theme/Topic, and Predicate Propositional Density; the testlet effect was smallest for stimuli that contained 31% or fewer “if” clauses, contained 9.8% or fewer verbs, and had Media or Animals as the main theme. This study illustrates the merits of TBR in the analysis of test data.

  8. Recognizing and predicting movement effects: identifying critical movement features.

    Science.gov (United States)

    Cañal-Bruland, Rouwen; Williams, A Mark

    2010-01-01

    It is not clear whether the critical features used to discriminate movements are identical to those involved in predicting the same movement's effects and consequently, whether the mechanisms underlying recognition and anticipation differ. We examined whether people rely on different kinematic information when required to recognize differences in the movement pattern in comparison to when they have to anticipate the outcome of these same movements. Naïve participants were presented with paired presentations of point-light animated tennis shots that ended at racket-ball contact. We instructed them either to judge whether the movements observed were the same or different or to predict shot direction (left vs. right). In addition, we locally manipulated the kinematics of point-light figures in an effort to identify the critical features used when making recognition and anticipation judgments. It appears that observers rely on different sources of information when required to recognize movement differences compared to when they need to anticipate the outcome of the same observed movements. Findings are discussed with reference to recent ideas focusing on the role of perceptual and motor resonance in perceptual judgments.

  9. Flame Retardant Epoxy Resins

    Science.gov (United States)

    Thompson, C. M.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; Lyon, R. E.

    2004-01-01

    As part of a program to develop fire resistant exterior composite structures for future subsonic commercial aircraft, flame retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured epoxies were characterized by thermogravimetric analysis, propane torch test, elemental analysis and microscale combustion calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness of plaques of several cured formulations was determined on single-edge notched bend specimens. The chemistry and properties of these new epoxy formulations are discussed.

  10. Antimony: a flame fighter

    Science.gov (United States)

    Wintzer, Niki E.; Guberman, David E.

    2015-01-01

    Antimony is a brittle, silvery-white semimetal that conducts heat poorly. The chemical compound antimony trioxide (Sb2O3) is widely used in plastics, rubbers, paints, and textiles, including industrial safety suits and some children’s clothing, to make them resistant to the spread of flames. Also, sodium antimonate (NaSbO3) is used during manufacturing of high-quality glass, which is found in cellular phones.

  11. Effects of Normal Aging on Memory for Multiple Contextual Features

    Science.gov (United States)

    Gagnon, Sylvain; Soulard, Kathleen; Brasgold, Melissa; Kreller, Joshua

    2007-01-01

    Twenty-four younger (18-35 years) and 24 older adult participants (65 or older) were exposed to three experimental conditions involving the memorization words and their associated contextual features, with contextual feature complexity increasing from Conditions 1 to 3. In Condition 1, words presented varied only on one binary feature (color,…

  12. Effect of Feature Dimensionality on Object-based Land Cover ...

    African Journals Online (AJOL)

    Myburgh, G, Mnr

    Object features were considered in the order of their obtained rank. The ... stable results as the feature-set size was increased towards the maximum (22 features). ..... considerably over classified their Urban class (which would be similar to the ...

  13. Influence of Pilot Flame Parameters on the Stability of Turbulent Jet Flames

    KAUST Repository

    Guiberti, Thibault F.

    2016-11-08

    This paper presents a comprehensive study of the effects of pilot parameters on flame stability in a turbulent jet flame. The Sydney inhomogeneous piloted burner is employed as the experimental platform with two main fuels, namely, compressed natural gas and liquefied petroleum gas. Various concentrations of five gases are used in the pilot stream, hydrogen, acetylene, oxygen, nitrogen, and argon, to enable a sufficient range in exploring the following parameters: pilot heat release, temperature, burnt gas velocity, equivalence ratio, and H/C ratio. The experimental results are mainly presented in the form of blow-off limits and supported by simple calculations, which simulate various conditions of the pilot–mixture interface. It is found that increasing the pilot adiabatic flame temperature benefits the flame stability and has an even greater influence than the heat release, which is also known to enhance the blow-off limits. Conversely, increasing the pilot burnt gas velocity reduces the blow-off velocity, except for the limiting case when the jet is fully non-premixed. The H/C ratio has negligible effects, while resorting to lean pilots significantly increases the stability of globally rich partially premixed and premixed jets. Such findings are consistent with trends obtained from laminar flame calculations for rich fuel/air mixtures issuing against hot combustion products to simulate the pilot stream.

  14. New trichoscopy findings in trichotillomania: flame hairs, V-sign, hook hairs, hair powder, tulip hairs.

    Science.gov (United States)

    Rakowska, Adriana; Slowinska, Monika; Olszewska, Malgorzata; Rudnicka, Lidia

    2014-05-01

    Differential diagnosis of trichotillomania is often difficult in clinical practice. Trichoscopy (hair and scalp dermoscopy) effectively supports differential diagnosis of various hair and scalp diseases. The aim of this study was to assess the usefulness of trichoscopy in diagnosing trichotillomania. The study included 370 patients (44 with trichotillomania, 314 with alopecia areata and 12 with tinea capitis). Statistical analysis revealed that the main and most characteristic trichoscopic findings of trichotillomania are: irregularly broken hairs (44/44; 100% of patients), v-sign (24/44; 57%), flame hairs (11/44; 25%), hair powder (7/44; 16%) and coiled hairs (17/44; 39%). Flame hairs, v-sign, tulip hairs, and hair powder were newly identified in this study. In conclusion, we describe here specific trichoscopy features, which may be applied in quick, non-invasive, in-office differential diagnosis of trichotillomania.

  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. The effect of stratification on premixed swirl-flame flashback by using porous center-body injection

    Science.gov (United States)

    McCaslin, Andrew; Ranjan, Rakesh; Clemens, Noel

    2016-11-01

    Boundary layer flashback must be prevented in order to stably operate stationary gas turbines. One strategy to avoid flashback is to create equivalence-ratio stratification, such as by reducing the fuel/air ratio in the boundary layer below the flammability limit. Typically, stratification is achieved by using radially non-uniform fuel injection. The goal of the current study is to reduce the propensity of flashback in a premixed annular swirl combustor that uses a premix section with center-body. A porous metal center-body (10 micron pore size) is used to bleed air directly into the boundary layer and thus locally reduce the equivalence ratio. Planar laser-induced fluorescence imaging of anisole-seeded flow is carried out to assess the stratification in the flow. Time-resolved PIV and chemiluminescence imaging are used to investigate flashback at atmospheric pressure conditions. A comparative study between fully premixed and stratified flame flashback is conducted to determine how stratification influences flashback physics. This work was sponsored by the DOE NETL under Grant DEFC2611-FE0007107. This source of funding is gratefully acknowledged.

  17. Influence of the radiation absorbed by micro particles on the flame propagation and combustion regimes

    CERN Document Server

    Ivanov, M F; Liberman, M A

    2015-01-01

    Thermal radiation of the hot combustion products usually does not influence noticeably the flame propagating through gaseous mixture. the situation is changed drastically in the presence even small concentration of particles, which absorb radiation, transfer the heat to the surrounding unburned gaseous mixture by means of heat conduction, so that the gas phase temperature in front of the advancing flame lags that of the particles. It is shown that radiative preheating of unreacted mixture ahead of the flame results in a modest increase of the advancing flame velocity for a highly reactive gaseous fuel, or to considerable increase of the flame velocity in the case of a slow reactive mixture. The effects of radiation preheating as stronger as smaller the normal flame velocity. The radiation heat transfer can become a dominant mechanism compared with molecular heat conduction, determining the structure and the speed of combustion wave in the case of a small enough velocity of the advancing flame. It is shown tha...

  18. Highly Turbulent Counterflow Flames: A Laboratory Scale Benchmark for Practical Combustion Systems

    Science.gov (United States)

    Gomez, Alessandro

    2013-11-01

    Since the pioneering work of Weinberg's group at Imperial College in the `60s, the counterflow system has been the workhorse of laminar flame studies. Recent developments have shown that it is also a promising benchmark for highly turbulent (Ret ~ 1000) nonpremixed and premixed flames of direct relevance to gasturbine combustion. Case studies will demonstrate the versatility of the system in mimicking real flame effects, such as heat loss and flame stratification in premixed flames, and the compactness of the combustion region. The system may offer significant advantages from a computational viewpoint, including: a) aerodynamic flame stabilization near the interface between the two opposed jets, with ensuing simplifications in the prescription of boundary conditions; b) a fiftyfold reduction of the domain of interest as compared to conventional nonpremixed jet flames at the same Reynolds number; and c) millisecond mean residence times, which is particularly useful for DNS/LES computational modeling, and for soot suppression in the combustion of practical fuels.

  19. Nitric Oxide and Oxygen Air-Contamination Effects on Extinction Limits of Non-Premixed Hydrocarbon-Air Flames for a HIFiRE Scramjet

    Science.gov (United States)

    Pellett, Gerald L.; Dawson, Lucy C.; Vaden, Sarah N.; Wilson, Lloyd G.

    2009-01-01

    Unique nitric oxide (NO) and oxygen air-contamination effects on the extinction Flame Strength (FS) of non-premixed hydrocarbon (HC) vs. air flames are characterized for 7 gaseous HCs, using a new idealized 9.3 mm straight-tube Opposed Jet Burner (OJB) at 1 atm. FS represents a laminar strain-induced extinction limit based on cross-section-average air jet velocity, Uair, that sustains combustion of a counter jet of gaseous fuel just before extinction. Besides ethane, propane, butane, and propylene, the HCs include ethylene, methane, and a 64 mole-% ethylene / 36 % methane mixture, the writer s previously recommended gaseous surrogate fuel for HIFiRE scramjet tests. The HC vs. clean air part of the work is an extension of a May 2008 JANNAF paper that characterized surrogates for the HIFiRE project that should mimic the flameholding of reformed (thermally- or catalytically-cracked) endothermic JP-like fuels. The new FS data for 7 HCs vs. clean air are thus consolidated with the previously validated data, normalized to absolute (local) axial-input strain rates, and co-plotted on a dual kinetically dominated reactivity scale. Excellent agreement with the prior data is obtained for all 7 fuels. Detailed comparisons are also made with recently published (Univ. Va) numerical results for ethylene extinction. A 2009-revised ethylene kinetic model (Univ. Southern Cal) led to predicted limits within approx. 5 % (compared to 45 %, earlier) of this writer s 2008 (and present) ethylene FSs, and also with recent independent data (Univ. Va) obtained on a new OJB system. These +/- 5 % agreements, and a hoped-for "near-identically-performing" reduced kinetics model, would greatly enhance the capability for accurate numerical simulations of surrogate HC flameholding in scramjets. The measured air-contamination effects on normalized FS extinction limits are projected to assess ongoing Arc-Heater-induced "facility test effects" of NO production (e.g., 3 mole-%) and resultant oxygen

  20. Flame Retardant Polyamide Fibres: The Challenge of Minimising Flame Retardant Additive Contents with Added Nanoclays

    Directory of Open Access Journals (Sweden)

    Richard Horrocks

    2016-08-01

    Full Text Available This work shows that halogen-free, flame retarded polyamide 6 (PA6, fabrics may be produced in which component fibres still have acceptable tensile properties and low levels (preferably ≤10 wt % of additives by incorporating a nanoclay along with two types of flame retardant formulations. The latter include (i aluminium diethyl phosphinate (AlPi at 10 wt %, known to work principally in the vapour phase and (ii ammonium sulphamate (AS/dipentaerythritol (DP system present at 2.5 and 1 wt % respectively, believed to be condense phase active. The nanoclay chosen is an organically modified montmorillonite clay, Cloisite 25A. The effect of each additive system is analysed in terms of its ability to maximise both filament tensile properties relative to 100% PA6 and flame retardant behaviour of knitted fabrics in a vertical orientation. None of the AlPi-containing formulations achieved self-extinguishability, although the presence of nanoclay promoted lower burning and melt dripping rates. The AS/DP-containing formulations with total flame retardant levels of 5.5 wt % or less showed far superior properties and with nanoclay, showed fabric extinction times ≤ 39 s and reduced melt dripping. The tensile and flammability results, supported by thermogravimetric analysis, have been interpreted in terms of the mechanism of action of each flame retardant/nanoclay type.

  1. Radiative Transport Based Flame Volume Reconstruction from Videos.

    Science.gov (United States)

    Shen, Liang; Zhu, Dengming; Nadeem, Saad; Wang, Zhaoqi; Kaufman, Arie E

    2017-06-06

    We introduce a novel approach for flame volume reconstruction from videos using inexpensive charge-coupled device (CCD) consumer cameras. The approach includes an economical data capture technique using inexpensive CCD cameras. Leveraging the smear feature of the CCD chip, we present a technique for synchronizing CCD cameras while capturing flame videos from different views. Our reconstruction is based on the radiative transport equation which enables complex phenomena such as emission, extinction, and scattering to be used in the rendering process. Both the color intensity and temperature reconstructions are implemented using the CUDA parallel computing framework, which provides real-time performance and allows visualization of reconstruction results after every iteration. We present the results of our approach using real captured data and physically-based simulated data. Finally, we also compare our approach against the other state-of-the-art flame volume reconstruction methods and demonstrate the efficacy and efficiency of our approach in four different applications: (1) rendering of reconstructed flames in virtual environments, (2) rendering of reconstructed flames in augmented reality, (3) flame stylization, and (4) reconstruction of other semitransparent phenomena.

  2. The Effects of Brominated Epoxy Resin on the Flame-Retardant Properties of PBT/EPDM Alloy%溴化环氧树脂对PBT/EPDM合金阻燃性能的影响

    Institute of Scientific and Technical Information of China (English)

    田维春; 郭建兵; 于磊; 范全保; 王峰; 胡晓玉

    2012-01-01

    PBT was modified with the brominated epoxy resin, and effects of contents of flame retardant on mechanical properties,flame-resistant properties and thermal stabilities of PBT/EPDM alloy were researched. The result showed that the flame retardant grades and the limiting oxygen index values of PBT/EPDM alloy were improved obviously with the increasing of flame retardant. In the TGA cure, the addition of flame retardant not only decreased the thermal stabilities of PBT/EPDM alloy, but also reduced its initial weight loss temperature and maximum weight loss velocity temperature. The contents of residual carbon in the end were also increased. At the same time,the tensile strength and bending strength were improved, while the impact strength was reduced.%采用阻燃剂溴化环氧树脂对PBT/EPDM合金进行改性,研究阻燃剂含量对PBT/EPDM合金力学、阻燃性能和热稳定性的影响.研究结果表明:随着阻燃剂含量的增加,PBT/EPDM合金的阻燃等级、极限氧指数均有显著提高.TGA曲线显示,阻燃剂的加入,起始失重温度和最大热失重速率温度均向低温移动,且最终的残留率均明显增多.同时,随着阻燃剂的增加,PBT/EPDM合金的拉伸强度和弯曲性能呈上升趋势,冲击强度呈下降趋势.

  3. Demonstration of new frequency-based flame monitoring system

    Energy Technology Data Exchange (ETDEWEB)

    Khesin, M. [MK Engineering Inc., North Andover, MA (United States)

    1996-11-01

    Methods of flame monitoring and combustion diagnostics based on analysis of temporal frequency spectra of flame radiation are attracting growing attention. It has been demonstrated that valuable flame quality information can be extracted from the chaos of burner flames by applying advanced signal analysis. A new flame diagnostics system (Flamenco), based on the application of new signal processing algorithms, have been developed and tested. The system generates an array of statistical values correlating with main combustion parameters of individual burner flames. Along with the main system, several derivative software systems were developed to enhance the testing and analysis capabilities. This paper presents preliminary results of pilot-scale testing of the new system, conducted at a single-burner combustion test facility, with support of Forney Corporation. Pilot-scale testing was conducted on a 1.0 Mbtu/hr single-burner gas-fired boiler, equipped with analytical instrumentation to measure NOx, O{sub 2}, CO{sub 2} and CO. The tests were conducted for the full range of air flow changes at different loads. The results have proven that the new system generates output signals correlated with measured burner parameters, such as NOx and airflow. The new system offers an effective and economical new method of flame monitoring and combustion diagnostics, to facilitate balancing and adjustment of individual burners and it is applicable to both single and multi-burner installations.

  4. Flame Retardant Applications in Camping Tents and Potential Exposure.

    Science.gov (United States)

    Keller, Alexander S; Raju, Nikhilesh P; Webster, Thomas F; Stapleton, Heather M

    2014-02-11

    Concern has mounted over health effects caused by exposure to flame retardant additives used in consumer products. Significant research efforts have focused particularly on exposure to polybrominated diphenyl ethers (PBDEs) used in furniture and electronic applications. However, little attention has focused on applications in textiles, particularly textiles meeting a flammability standard known as CPAI-84. In this study, we investigated flame retardant applications in camping tents that met CPAI-84 standards by analyzing 11 samples of tent fabrics for chemical flame retardant additives. Furthermore, we investigated potential exposure by collecting paired samples of tent wipes and hand wipes from 27 individuals after tent setup. Of the 11 fabric samples analyzed, 10 contained flame retardant additives, which included tris(1,3-dichloroisopropyl) phosphate (TDCPP), decabromodiphenyl ether (BDE-209), triphenyl phosphate, and tetrabromobisphenol-A. Flame retardant concentrations were discovered to be as high as 37.5 mg/g (3.8% by weight) in the tent fabric samples, and TDCPP and BDE-209 were the most frequently detected in these samples. We also observed a significant association between TDCPP levels in tent wipes and those in paired hand wipes, suggesting that human contact with the tent fabric material leads to the transfer of the flame retardant to the skin surface and human exposure. These results suggest that direct contact with flame retardant-treated textiles may be a source of exposure. Future studies will be needed to better characterize exposure, including via inhalation and dermal sorption from air.

  5. Numerical Simulation of Microgravity Flame Spread Over Solid Combustibles

    Institute of Scientific and Technical Information of China (English)

    JIANGXi; FANWeicheng

    1995-01-01

    A computational model of three-dimensional,time-dependent flame spread in microgravity environment is presented.THe solid is assumed to be a thermally-thin,pyrolysing cellulosic sheet.The gas phase model includes the full Navier-Stokes equations with density and pressure variations and six-flus model of radiation heat transfer,The solid phase model consists of continuity and energy equations whose solution provides boundary conditions for the gas phase equatons.In the numerical procedure,the gas-and solid -phase equations are solved separately and iteratively at each time step.Predictions have been made of flame spreas in slow forced flow under gravitational acceleration normal to fuel surface and flame spread in a quiescent environment in an enclosed chamber under gravitational acceleration parallel to fuel surface.Numerical simulations show that,under microgravity,slow-flow conditions,flame spread process is highly unsteady with the upstream flame spreads faster than the downstream flame after a period of ignition,It has also been shown that the level of microgravity has a significant effect on the flame spread process.

  6. Potential effects of four Flaming Gorge Dam hydropower operational scenarios on the fishes of the Green River, Utah and Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Hlohowskyj, I.; Hayse, J.W.

    1995-09-01

    Aerial videography and modeling were used to evaluate the impacts of four hydropower operational scenarios at Flaming Gorge Dam, Utah, on trout and native fishes in the Green River, Utah and Colorado. The four operational scenarios studied were year-round high fluctuations, seasonally adjusted high fluctuations, seasonally adjusted moderate fluctuations, and seasonally adjusted steady flows. Impacts on trout were evaluated by examining differences among scenarios in the areas of inundated substrates that serve as spawning and feeding habitat. All scenarios would provide at least 23 acres per mile of habitat for spawning and food production; seasonally adjusted operations would provide additional areas during periods of sustained high release. Seasonally adjusted high fluctuations would increase inundated areas by 12 to 26% for a short period in winter and spring, but food production and reproduction would not be expected to increase. Seasonally adjusted moderate fluctuations and steady flows would produce similar increases in area, but the longer period of inundation could also result in increased food production and provide additional spawning sites for trout. Impacts on native fishes were assessed by examining daily changes in backwater nursery areas. Compared with year-round high fluctuations, the daily changes in backwater area would decrease by about 47, 89, and 100% under the seasonally adjusted high fluctuation, moderate fluctuation, and steady flow scenarios, respectively. Similarly, daily stage fluctuations during the nursery period would decrease by 72, 89, and 100% under the seasonally adjusted high fluctuation, moderate fluctuation, and steady flow scenarios, respectively. These reductions in daily fluctuations in backwater area and stage would improve conditions in nursery habitats and could in turn improve recruitment and overwinter survival. Introduced fish species could also benefit from the seasonally adjusted operational scenarios.

  7. Seasonal Effect of Geomorphological Chronosequence Features on Soil Biota Dynamics

    Institute of Scientific and Technical Information of China (English)

    S.PEN-MOURATOV; N.GENZER; N.SHUKUROV; J.PLAKHT; Y.STEINBERGER

    2010-01-01

    Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity.However,the extent to which unique geomorphic formations influence soil biotic seasonal variation is not clear.Our aim was to define seasonal variations of soil biota in soils of different-aged terraces of the Makhtesh Ramon anticline erosional cirque in southern Israel.The strong effect of Makhtesh Ramon(Ramon crater)erosional fluvial terrace age initiated by climatic changes during the Late Pleistocene-Early Holocene period on seasonal variations in both soil properties and the abundance and composition of soil biota were demonstrated.However,age dependence was not constant and values for observed soil properties and microbial activity were negligible between younger and older terraces for certain seasons,while free-living nematodes along with bacterial-feeding group were strongly dependent on the geomorphic features of the ages throughout the study period.

  8. Solid Propellant Flame Spectroscopy

    Science.gov (United States)

    1988-08-01

    400 jm to reach the maximum flame temperature, a distance that can be reduced by replacing the HTPB binder with a polyester or CMDB binder. The...the dark zone for propellants similar to HIX2 is 2-2.5 mm at 1.8 MPa (18 atm, 265 psia) (Ref. 22,187). In contrast, the dark zone for HMX CMDB ...propellants eliminates the dark zone is not surprising, since TMETN is a nitrate ester as was the double-base matrix of Kubota’s HMX CMDB propellant. A

  9. Combining cone calorimeter and PCFC to determine the mode of action of flame retardant additives

    OpenAIRE

    LOPEZ CUESTA, José-Marie; Sonnier, Rodolphe; Ferry, Laurent; Longuet, Claire; Laoutid, Fouad; Friedrich, Blandine; Laachachi, Abdelghani

    2011-01-01

    Abstract The flammability of various flame retarded formulations containing different hydrated mineral fillers and/or phosphorous compounds and/or carbon nanotubes has been investigated using both cone calorimeter and PCFC. A method was proposed to evaluate the barrier effect of the flame retardant additives. This method is based on the fact that PCFC is non sensitive to physical flame retardant effects while both chemical and physical phenomena have a great effect on cone calorime...

  10. Quantification of extinction mechanism in counterflow premixed flames

    KAUST Repository

    Choi, Sangkyu

    2014-09-01

    The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH4, C3H8, H2, CO and for the mixture fuels of CH4+H2 and CO+H2 by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H2, CH4, CH4+H2, CO+H2, and rich C3H8 premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H2, CH4, CH4+H2, CO+H2, and lean C3H8 premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H2 mixing to CO is found to be quite significant as compared to CH4+H2 cases, which can alter the flame behavior of CO flames to that of H2.

  11. 无机复合阻燃剂及催化剂对PIR硬泡阻燃性能的影响%The Effect of Composite Inorganic Flame Retardant and Catalysts on the Properties of Flame Retardant Rigid PIR Foam

    Institute of Scientific and Technical Information of China (English)

    李慧; 吴建龙; 李景庆

    2016-01-01

    在聚酯多元醇中加入复合无机阻燃剂和复合催化剂,与多异氰酸酯反应制备硬质聚异氰脲酸酯( PIR)泡沫塑料。研究了无机阻燃剂和复合催化剂对泡沫的氧指数、尺寸稳定性等硬泡性能的影响。结果表明,当聚酯多元醇为100份,复合催化剂总量4�5份,且叔胺类催化剂与有机金属催化剂质量比为4∶1,复合阻燃剂总量20份,且SiO2与膨胀石墨质量比为1∶2,制得的PIR硬泡氧指数达到30%,导热系数0�019 W/( m·K ),密度48 kg/m3,线性收缩率0�20%,压缩强度185 kP a。%The polyisocyanurate foam was prepared by polyester polyols, polyisocyanate, combined catalysts and composite inorganic flame retardants, etc. The influences of combined catalysts and combined inorganic flame retardants on the oxygen index and other properties of the PIR foam were investigated. The results showed that, when the dosage of all catalysts and all flame retardants were 4�5 and 20 parts respectively ( based on 100 parts poly⁃ester polyols) , the mass ratio of tertiary amine catalyst and organometallic catalyst was 4∶1, and mass ratio of sili⁃con dioxide and expansible graphite was 1∶2, the limited oxygen index of PIR foam would be reached to 30%, and the coefficient of thermal conductivity was about 0�019 W/(m·K), while the density was 48 kg/m3,the linear shrinkage was 0�20%, compression strength was 185 kPa.

  12. Effective Feature Selection for 5G IM Applications Traffic Classification

    Directory of Open Access Journals (Sweden)

    Muhammad Shafiq

    2017-01-01

    Full Text Available Recently, machine learning (ML algorithms have widely been applied in Internet traffic classification. However, due to the inappropriate features selection, ML-based classifiers are prone to misclassify Internet flows as that traffic occupies majority of traffic flows. To address this problem, a novel feature selection metric named weighted mutual information (WMI is proposed. We develop a hybrid feature selection algorithm named WMI_ACC, which filters most of the features with WMI metric. It further uses a wrapper method to select features for ML classifiers with accuracy (ACC metric. We evaluate our approach using five ML classifiers on the two different network environment traces captured. Furthermore, we also apply Wilcoxon pairwise statistical test on the results of our proposed algorithm to find out the robust features from the selected set of features. Experimental results show that our algorithm gives promising results in terms of classification accuracy, recall, and precision. Our proposed algorithm can achieve 99% flow accuracy results, which is very promising.

  13. Effect of Brazilian Propolis on Exacerbation of Respiratory Syncytial Virus Infection in Mice Exposed to Tetrabromobisphenol A, a Brominated Flame Retardant

    Science.gov (United States)

    Takeshita, Tomomi; Toyama, Satomi; Hayashi, Yuya; Honda, Shiori; Sakamoto, Shuichi; Matsuoka, Sayuri; Hidaka, Muneaki; Tsutsumi, Shigetoshi; Yasukawa, Ken; Park, Yong Kun

    2013-01-01

    Tetrabromobisphenol A (TBBPA), a brominated flame retardant, has been found to exacerbate pneumonia in respiratory syncytial virus- (RSV-) infected mice. We examined the effect of Brazilian propolis (AF-08) on the exacerbation of RSV infection by TBBPA exposure in mice. Mice were fed a powdered diet mixed with 1% TBBPA alone, 0.02% AF-08 alone, or 1% TBBPA and 0.02% AF-08 for four weeks and then intranasally infected with RSV. TBBPA exposure increased the pulmonary virus titer and level of IFN-γ, a representative marker of pneumonia due to RSV infection, in the lungs of infected mice without toxicity. AF-08 was significantly effective in reducing the virus titers and IFN-γ level increased by TBBPA exposure. Also, AF-08 significantly reduced proinflammatory cytokine (TNF-α and IL-6) levels in the lungs of RSV-infected mice with TBBPA exposure, but Th2 cytokine (IL-4 and IL-10) levels were not evidently increased. Neither TBBPA exposure nor AF-08 treatment affected the anti-RSV antibody production in RSV-infected mice. In flow cytometry analysis, AF-08 seemed to be effective in reducing the ratio of pulmonary CD8a+ cells in RSV-infected mice with TBBPA exposure. TBBPA and AF-08 did not exhibit anti-RSV activity in vitro. Thus, AF-08 probably ameliorated pneumonia exacerbated by TBBPA exposure in RSV-infected mice by limiting excess cellular immune responses. PMID:24250719

  14. Effect of surface topological structure and chemical modification of flame sprayed aluminum coatings on the colonization of Cylindrotheca closterium on their surfaces

    Science.gov (United States)

    Chen, Xiuyong; He, Xiaoyan; Suo, Xinkun; Huang, Jing; Gong, Yongfeng; Liu, Yi; Li, Hua

    2016-12-01

    Biofouling is one of the major problems for the coatings used for protecting marine infrastructures during their long-term services. Regulation in surface structure and local chemistry is usually the key for adjusting antifouling performances of the coatings. In this study, flame sprayed multi-layered aluminum coatings with micropatterned surfaces were constructed and the effects of their surface structure and chemistry on the settlement of typical marine diatoms were investigated. Micropatterned topographical morphology of the coatings was constructed by employing steel mesh as a shielding plate during the coating deposition. A silicone elastomer layer for sealing and interconnection was further brush-coated on the micropatterned coatings. Additional surface modification was made using zwitterionic molecules via DOPA linkage. The surface-modified coatings resist effectively colonization of Cylindrotheca closterium. This is explained by the quantitative examination of a simplified conditioning layer that deteriorated adsorption of bovine calf serum proteins on the zwitterionic molecule-treated samples is revealed. The colonization behaviors of the marine diatoms are markedly influenced by the micropatterned topographical morphology. Either the surface micropatterning or the surface modification by zwitterionic molecules enhances antimicrobial ability of the coatings. However, the combined micropatterned structure and zwitterionic modification do not show synergistic effect. The results give insight into anti-corrosion/fouling applications of the modified aluminum coatings in the marine environment.

  15. The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars

    CERN Document Server

    Apellániz, J Maíz; Barbá, R H; Gräfener, G; Bestenlehner, J M; Crowther, P A; García, M; Herrero, A; Sana, H; Simón-Díaz, S; Taylor, W D; van Loon, J Th; Vink, J S; Walborn, N R

    2014-01-01

    Context: The commonly used extinction laws of Cardelli et al. (1989) have limitations that, among other issues, hamper the determination of the effective temperatures of O and early B stars from optical+NIR photometry. Aims: We aim to develop a new family of extinction laws for 30 Doradus, check their general applicability within that region and elsewhere, and apply them to test the feasibility of using optical+NIR photometry to determine the effective temperature of OB stars. Methods: We use spectroscopy and NIR photometry from the VLT-FLAMES Tarantula Survey and optical photometry from HST/WFC3 of 30 Doradus and we analyze them with the software code CHORIZOS using different assumptions such as the family of extinction laws. Results: We derive a new family of optical+NIR extinction laws for 30 Doradus and confirm its applicability to extinguished Galactic O-type systems. We conclude that by using the new extinction laws it is possible to measure the effective temperatures of OB stars with moderate uncertain...

  16. Lean flammability limit of downward propagating hydrogen-air flames

    Science.gov (United States)

    Patnaik, G.; Kailasanath, K.

    1992-01-01

    Detailed multidimensional numerical simulations that include the effects of wall heat losses have been performed to study the dynamics of downward flame propagation and extinguishment in lean hydrogen-air mixtures. The computational results show that a downward propagating flame in an isothermal channel has a flammability limit of around 9.75 percent. This is in excellent agreement with experimental results. Also in excellent agreement are the detailed observations of the flame behavior at the point of extinguishment. The primary conclusion of this work is that detailed numerical simulations that include wall heat losses and the effect of gravity can adequately simulate the dynamics of the extinguishment process in downward-propagating hydrogen-air flames. These simulations can be examined in detail to gain understanding of the actual extinction process.

  17. Augmenting the Structures in a Swirling Flame via Diffusive Injection

    Directory of Open Access Journals (Sweden)

    Jonathan Lewis

    2014-01-01

    Full Text Available Small scale experimentation using particle image velocimetry investigated the effect of the diffusive injection of methane, air, and carbon dioxide on the coherent structures in a swirling flame. The interaction between the high momentum flow region (HMFR and central recirculation zone (CRZ of the flame is a potential cause of combustion induced vortex breakdown (CIVB and occurs when the HMFR squeezes the CRZ, resulting in upstream propagation. The diffusive introduction of methane or carbon dioxide through a central injector increased the size and velocity of the CRZ relative to the HMFR whilst maintaining flame stability, reducing the likelihood of CIVB occurring. The diffusive injection of air had an opposing effect, reducing the size and velocity of the CRZ prior to eradicating it completely. This would also prevent combustion induced vortex breakdown CIVB occurring as a CRZ is fundamental to the process; however, without recirculation it would create an inherently unstable flame.

  18. Effect of processing on structural features of anodic aluminum oxides

    Science.gov (United States)

    Erdogan, Pembe; Birol, Yucel

    2012-09-01

    Morphological features of the anodic aluminum oxide (AAO) templates fabricated by electrochemical oxidation under different processing conditions were investigated. The selection of the polishing parameters does not appear to be critical as long as the aluminum substrate is polished adequately prior to the anodization process. AAO layers with a highly ordered pore distribution are obtained after anodizing in 0.6 M oxalic acid at 20 °C under 40 V for 5 minutes suggesting that the desired pore features are attained once an oxide layer develops on the surface. While the pore features are not affected much, the thickness of the AAO template increases with increasing anodization treatment time. Pore features are better and the AAO growth rate is higher at 20 °C than at 5 °C; higher under 45 V than under 40 V; higher with 0.6 M than with 0.3 M oxalic acid.

  19. The advanced flame quality indicator system

    Energy Technology Data Exchange (ETDEWEB)

    Oman, R.; Rossi, M.J.; Calia, V.S.; Davis, F.L.; Rudin, A. [Insight Technologies, Inc., Bohemia, NY (United States)

    1997-09-01

    By combining oil tank monitoring, systems diagnostics and flame quality monitoring in an affordable system that communicates directly with dealers by telephone modem, Insight Technologies offers new revenue opportunities and the capability for a new order of customer relations to oil dealers. With co-sponsorship from New York State Energy Research and Development Authority, we have incorporated several valuable functions to a new product based on the original Flame Quality Indicator concept licensed from the US DOE`s Brookhaven National Laboratory. The new system is the Advanced Flame Quality Indicator, or AFQI. As before, the AFQI monitors and reports the intensity of the burner flame relative to a calibration established when the burner is set up at AFQI installation. Repairs or adjustments are summoned by late-night outgoing telephone calls when limits are exceeded in either direction, indicating an impending contamination or other malfunction. A independently, a pressure transducer for monitoring oil tank level and filter condition, safety lockout alarms and a temperature monitor; all reporting automatically at instructed intervals via an on-board modem to a central station PC computer (CSC). Firmware on each AFQI unit and Insight-supplied software on the CSC automatically interact to maintain a customer database for an oil dealer, an OEM, or a regional service contractor. In addition to ensuring continuously clean and efficient operation, the AFQI offers the oil industry a new set of immediate payoffs, among which are reduced outages and emergency service calls, shorter service calls from cleaner operation, larger oil delivery drops, the opportunity to stretch service intervals to as along as three years in some cases, new selling features to keep and attract customers, and greatly enhanced customer contact, quality and reliability.

  20. Lean histogram of oriented gradients features for effective eye detection

    Science.gov (United States)

    Sharma, Riti; Savakis, Andreas

    2015-11-01

    Reliable object detection is very important in computer vision and robotics applications. The histogram of oriented gradients (HOG) is established as one of the most popular hand-crafted features, which along with support vector machine (SVM) classification provides excellent performance for object recognition. We investigate dimensionality deduction on HOG features in combination with SVM classifiers to obtain efficient feature representation and improved classification performance. In addition to lean HOG features, we explore descriptors resulting from dimensionality reduction on histograms of binary descriptors. We consider three-dimensionality reduction techniques: standard principal component analysis, random projections, a computationally efficient linear mapping that is data independent, and locality preserving projections (LPP), which learns the manifold structure of the data. Our methods focus on the application of eye detection and were tested on an eye database created using the BioID and FERET face databases. Our results indicate that manifold learning is beneficial to classification utilizing HOG features. To demonstrate the broader usefulness of lean HOG features for object class recognition, we evaluated our system's classification performance on the CalTech-101 dataset with favorable outcomes.

  1. Turbulent Flame Propagation Characteristics of High Hydrogen Content Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Seitzman, Jerry [Georgia Inst. of Technology, Atlanta, GA (United States); Lieuwen, Timothy [Georgia Inst. of Technology, Atlanta, GA (United States)

    2014-09-30

    This final report describes the results of an effort to better understand turbulent flame propagation, especially at conditions relevant to gas turbines employing fuels with syngas or hydrogen mixtures. Turbulent flame speeds were measured for a variety of hydrogen/carbon monoxide (H2/CO) and hydrogen/methane (H2/CH4) fuel mixtures with air as the oxidizer. The measurements include global consumption speeds (ST,GC) acquired in a turbulent jet flame at pressures of 1-10 atm and local displacement speeds (ST,LD) acquired in a low-swirl burner at atmospheric pressure. The results verify the importance of fuel composition in determining turbulent flame speeds. For example, different fuel-air mixtures having the same unstretched laminar flame speed (SL,0) but different fuel compositions resulted in significantly different ST,GC for the same turbulence levels (u'). This demonstrates the weakness of turbulent flame speed correlations based simply on u'/SL,0. The results were analyzed using a steady-steady leading points concept to explain the sensitivity of turbulent burning rates to fuel (and oxidizer) composition. Leading point theories suggest that the premixed turbulent flame speed is controlled by the flame front characteristics at the flame brush leading edge, or, in other words, by the flamelets that advance farthest into the unburned mixture (the so-called leading points). For negative Markstein length mixtures, this is assumed to be close to the maximum stretched laminar flame speed (SL,max) for the given fuel-oxidizer mixture. For the ST,GC measurements, the data at a given pressure were well-correlated with an SL,max scaling. However the variation with pressure was not captured, which may be due to non-quasi-steady effects that are not included in the current model. For the ST,LD data, the leading points model again faithfully captured the variation of turbulent flame speed over a wide range of fuel-compositions and turbulence intensities. These

  2. Flame Retardant Applications in Camping Tents and Potential Exposure

    OpenAIRE

    Keller, Alexander S.; Raju, Nikhilesh P.; Webster, Thomas F.; Stapleton, Heather M.

    2014-01-01

    Concern has mounted over health effects caused by exposure to flame retardant additives used in consumer products. Significant research efforts have focused particularly on exposure to polybrominated diphenyl ethers (PBDEs) used in furniture and electronic applications. However, little attention has focused on applications in textiles, particularly textiles meeting a flammability standard known as CPAI-84. In this study, we investigated flame retardant applications in camping tents that met C...

  3. Effects of Flaming Gorge Dam hydropower operations on sediment transport in the Browns Park reach of the Green River, Utah and Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Williams, G.P.; Tomasko, D.; Cho, H.E.; Yin, S.C.L. [Argonne National Lab., IL (United States). Environmental Assessment Div.

    1995-05-01

    Three methods for comparing sediment transport were applied to four proposed hydropower operational scenarios under study for Flaming Gorge Dam on the Green River in Utah. These methods were effective discharge, equilibrium potential, and cumulative sediment load with flow exceedance plots. Sediment loads transported by the Green River in the Browns Park reach were calculated with the Engelund-Hansen equation for three historical water years and four hydropower operational scenarios. A model based on the Engelund-Hansen equation was developed using site-specific information and validated by comparing predictions for a moderate water year with measured historical values. The three methods were used to assess the impacts of hydropower operational scenarios on sediment resources. The cumulative sediment load method provided the most useful information for impact evaluation. Effective discharge was not a useful tool because of the limited number of discrete flows associated with synthetic hydrographs for the hydropower operational scenarios. The equilibrium potential method was relatively insensitive to the variations in operating conditions, rendering it comparatively ineffective for impact evaluation.

  4. Influence of sulfur in fuel on the properties of diffusion flame soot

    Science.gov (United States)

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

    2016-10-01

    Previous studies indicate that sulfur in fuel affects the hygroscopicity of soot. However, the issue of the effect of sulfur in fuel on soot properties is not fully understood. Here, the properties of soot prepared from fuel with a variable sulfur content were investigated under lean and rich flame conditions. Lean flame soot was influenced more by sulfur in fuel than rich flame soot. The majority of sulfur in fuel in lean flame was converted to gaseous SO2, while a small fraction appeared as sulfate and bisulfate (referred to as sulfate species) in soot. As the sulfur content in fuel increased, sulfate species in lean flame soot increased nonlinearly, while sulfate species on the surface of lean flame soot increased linearly. The hygroscopicity of lean flame soot from sulfur-containing fuel was enhanced mainly due to sulfate species. Meanwhile, more alkynes were formed in lean flame. The diameter of primary lean flame soot particles increased and accumulation mode particle number concentrations of lean flame soot from sulfur-containing fuel increased as a result of more alkynes. Because the potential effects of soot particles on air pollution development greatly depend on the soot properties, which are related to both chemical aging and combustion conditions, this work will aid in understanding the impacts of soot on air quality and climate.

  5. The effect of Pt nanoparticles loading on H{sub 2} sensing properties of flame-spray-made SnO{sub 2} sensing films

    Energy Technology Data Exchange (ETDEWEB)

    Liewhiran, Chaikarn, E-mail: chaikarn_l@yahoo.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50202 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50202 (Thailand); Tamaekong, Nittaya [Program in Materials Science, Faculty of Science, Maejo University, Chiang Mai 50290 (Thailand); Tuantranont, Adisorn; Wisitsoraat, Anurat [Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology Center, Klong Luang, Pathumthani 12120 (Thailand); Phanichphant, Sukon [Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50202 (Thailand)

    2014-10-15

    SnO{sub 2} nanoparticles loaded with 0.2–2 wt% Pt have successfully been synthesized in a single step by flame spray pyrolysis (FSP) and investigated for gas sensing towards hydrogen (H{sub 2}). According to characterization results by X-ray diffraction, nitrogen adsorption, scanning/high resolution-transmission electron microscopy and analyses based on Hume-Rothery rules using atomic radii, crystal structure, electronegativities, and valency/oxidation states of Pt and Sn, it is conclusive that Pt is not solute in SnO{sub 2} crystal but forms nanoparticles loaded on SnO{sub 2} surface. H{sub 2} gas sensing was studied at 200–10,000 ppm and 150–350 °C in dry air. It was found that H{sub 2} response was enhanced by more than one order of magnitude with a small Pt loading concentration of 0.2 wt% but further increase of Pt loading amount resulted in deteriorated H{sub 2}-sensing performance. The optimal SnO{sub 2} sensing film (0.2 wt% Pt-loaded SnO{sub 2}, 20 μm in thickness) showed an optimum H{sub 2} response of ∼150.2 at 10,000 ppm and very short response time in a few seconds at a low optimal operating temperature of 200 °C. In addition, the response tended to increase linearly and the response times decreased drastically with increasing H{sub 2} concentration. Moreover, the selectivity against carbon monoxide (CO) and acetylene (C{sub 2}H{sub 2}) gases was also found to be considerably improved with the small amount of Pt loading. The H{sub 2} response dependence on Pt concentration can be explained based on the spillover mechanism, which is highly effective only when Pt catalyst is well-dispersed at the low Pt loading concentration of 0.2 wt%. - Highlights: • Pt/SnO{sub 2} nanoparticles were prepared in a single step by flame spray pyrolysis. • Pt loading on SnO{sub 2} nanoparticles at low level of 0.2 wt% gives optimal H{sub 2} response. • 0.2 wt% Pt/SnO{sub 2} sensor exhibits a low optimum operating temperature of 200 °C. • H

  6. Subwoofer and nanotube butterfly acoustic flame extinction

    Science.gov (United States)

    Aliev, Ali E.; Mayo, Nathanael K.; Baughman, Ray H.; Mills, Brent T.; Habtour, Ed

    2017-07-01

    Nonchemical flame control using acoustic waves from a subwoofer and a lightweight carbon nanotube thermoacoustic projector was demonstrated. The intent was to manipulate flame intensity, direction and propagation. The mechanisms of flame suppression using low frequency acoustic waves were discussed. Laminar flame control and extinction were achieved using a thermoacoustic ‘butterfly’ projector based on freestanding carbon nanotube sheets.

  7. Interactions between soil biota and the effects on geomorphological features

    Science.gov (United States)

    Zaitlin, Beryl; Hayashi, Masaki

    2012-07-01

    The interaction of animals with abiotic features of their environment has long been known to cause alterations to geomorphic features, and these interactions may cause feedback loops that further alter geomorphic features and animal communities. This paper samples the literature on selected burrowing animals in western North America, and discusses the interactions of animals with abiotic features of the environment and with each other, and the resulting impacts on geomorphic features and each other. As expected, burrowing characteristics of animals influence geomorphological processes. For example, pocket gophers and certain ground squirrels that burrow horizontal tunnels on sloping grounds seem to have significant impacts on horizontal movement of soils, whereas prairie dogs and harvester ants have more impact on vertical movement of soils. Burrowing animals, in general, increase the patchiness of the environment, which creates localized patch habitat for other plants and animals, thereby increasing biodiversity at the landscape scale. Burrowing animals influence and are influenced by microbes: sylvatic plague wiped out large populations of prairie dogs, earthworms cause major changes in soil microflora, pocket gophers and harvester ants cause changes in mycorrhizal communities, which in turn impact plant communities.

  8. THERMAL DEGRADATION AND FLAME RETARDANCY OF CALCIUM ALGINATE FIBERS

    Institute of Scientific and Technical Information of China (English)

    Qing-shan Kong; Bing-bing Wang; Quan Ji; Yan-zhi Xia; Zhao-xia Guo; Jian Yu

    2009-01-01

    Calcium alginate fibers were prepared by wet spinning of sodium alginate into a coagulating bath containing calcium chloride. The thermal degradation and flame retardancy of calcium alginate fibers were investigated with thermal gravimetry (TG), X-ray diffraction (XRD), limiting oxygen index (LOI) and cone calorimeter (CONE). The results show that calcium alginate fibers are inherently flame retardant with a LOI value of 34, and the heat release rate (HRR), total heat release (THR), CO and CO_2 concentrations during combustion are much lower compared with those of viscose fibers. Calcium carbonate and calcium oxide were formed during thermal degradation of calcium alginate fibers at different temperatures. The shape of calcium alginate fibers is well kept after LOI test. The rigid combustion residue char acts as an effective barrier to the outward diffusion of flame and heat. The combustion process and flame retardant mechanism of calcium alginate fibers are also discussed.

  9. Aryl Polyphosphonates: Useful Halogen-Free Flame Retardants for Polymers

    Directory of Open Access Journals (Sweden)

    Li Chen

    2010-10-01

    Full Text Available Aryl polyphosphonates (ArPPN have been demonstrated to function in wide applications as flame retardants for different polymer materials, including thermosets, polycarbonate, polyesters and polyamides, particularly due to their satisfactory thermal stability compared to aliphatic flame retardants, and to their desirable flow behavior observed during the processing of polymeric materials. This paper provides a brief overview of the main developments in ArPPN and their derivatives for flame-retarding polymeric materials, primarily based on the authors’ research work and the literature published over the last two decades. The synthetic chemistry of these compounds is discussed along with their thermal stabilities and flame-retardant properties. The possible mechanisms of ArPPN and their derivatives containing hetero elements, which exhibit a synergistic effect with phosphorus, are also discussed.

  10. Recent Advances in Flame Tomographyt

    Institute of Scientific and Technical Information of China (English)

    闫勇; 邱天; 卢钢; M.M.Hossain; G.Gilabert; 刘石

    2012-01-01

    To reduce greenhouse gas emissions from fossil fuel fired power plants,a range of new combustion technologies are being developed or refined,including oxy-fuel combustion,co-firing biomass with coal and fluidized bed combustion.Flame characteristics under such combustion conditions are expected to be different from those in normal air fired combustion processes.Quantified flame characteristics such as temperature distribution,oscillation frequency,and ignition volume play an important part in the optimized design and operation of the environmentally friendly power generation systems.However,it is challenging to obtain such flame characteristics particularly through a three-dimensional and non-intrusive means.Various tomography methods have been proposed to visualize and characterize flames,including passive optical tomography,laser based tomography,and electrical tomography.This paper identifies the challenges in flame tomography and reviews existing techniques for the quantitative characterization of flames.Future trends in flame tomography for industrial applications are discussed.

  11. Parametric Erosion Investigation: Propellant Adiabatic Flame Temperature

    Directory of Open Access Journals (Sweden)

    P. J. Conroy

    2002-01-01

    Full Text Available The influence of quasi-independent parameters and their potential influence on erosion in guns have been investigated. Specifically, the effects of flame temperature and the effect of assuming that the Lewis number (ratio of mass-to-heat transport to the surface, Le = 1, has been examined. The adiabatic flame temperature for a propellant was reduced by the addition of a diluent from a high temperature of 3843 K (similar to that of M9 down to 3004 K, which is near the value for M30A1 propellant. Mass fractions of critical species at the surface with and without the assumption of Le = 1 are presented, demonstrating that certain species preferentially reach the surface providing varied conditions for the surface reactions. The results for gun tube bore surface regression qualitatively agree with previous studies and with current experimental data.

  12. Statistical evaluation of the effects of fall and winter flows on the spring condition of rainbow and brown trout in the green river downstream of Flaming Gorge Dam.

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, A. K.; LaGory, K. E.; Hayse, J. W.; Environmental Science Division

    2009-01-09

    Flaming Gorge Dam, a hydroelectric facility operated by the Bureau of Reclamation (Reclamation), is located on the Green River in Daggett County, northeastern Utah. In recent years, single peak releases each day or steady flows have been the operational pattern during the winter period. A double-peak pattern (two flow peaks each day) was implemented during the winter of 2006-2007 by Reclamation. Because there is no recent history of double-peaking at Flaming Gorge Dam, the potential effects of double-peaking operations on the body condition of trout in the dam's tailwater are not known. A study plan was developed that identified research activities to evaluate potential effects from double-peaking operations during winter months. Along with other tasks, the study plan identified the need to conduct a statistical analysis of existing data on trout condition and macroinvertebrate abundance to evaluate potential effects of hydropower operations. This report presents the results of this analysis. We analyzed historical data to (1) describe temporal patterns and relationships among flows, benthic macroinvertebrate abundance, and condition of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in the tailwaters of Flaming Gorge Dam and (2) to evaluate the degree to which flow characteristics (i.e., flow volumes and flow variability) and benthic macroinvertebrate abundance affect the condition of trout in this area. This information, together with further analyses of size-stratified trout data, may also serve as baseline data to which the effects of potential future double-peaking flows can be compared. The condition (length, weight and/or relative weight) of rainbow trout (Oncorhynchus mykiss) at two sites in the Green River downstream of Flaming Gorge Dam (Tailrace and Little Hole) and weight of brown trout (Salmo trutta) at the Little Hole site has been decreasing since 1990 while the abundance of brown trout has been increasing at the two sites. At

  13. 甲烷火焰中氢气对着火与燃尽的影响%Effect of H2 on Ignition and Burnout in Methane Flame

    Institute of Scientific and Technical Information of China (English)

    钟北京; 傅维标

    2001-01-01

    This paper studied ignition and burnout characteristics of methane-air premixed flame with H2 added,using chemical reaction mechanism.The effect of hydrogen on methane combustion and ignition temperature,burning rate and burnout time are discussed through analyzing the calculated results.Results show that the hydrog en in methane/air mixture not only decreases the ignition temperature greatly,bu t increases the burning rate and shortens the burnout time notably.These calcula ted results are identical with the experimental results.%利用化学反应动力学机理研究了甲烷-空气预混火焰添加H2的着火和燃尽特性。通过分析计算,讨论了氢气对甲烷燃烧过程及着火温度、燃烧速率、燃尽时间的影响。结果表明,甲烷火焰中少量氢气的存在不仅可以降低甲烷的着火温度,而且可以显著增大燃烧速率,缩短燃尽时间。这些结果与已有的实验结果吻合。

  14. Effect of electron beam irradiation and microencapsulation on the flame retardancy of ethylene-vinyl acetate copolymer materials during hot water ageing test

    Science.gov (United States)

    Sheng, Haibo; Zhang, Yan; Wang, Bibo; Yu, Bin; Shi, Yongqian; Song, Lei; Kundu, Chanchal Kumar; Tao, Youji; Jie, Ganxin; Feng, Hao; Hu, Yuan

    2017-04-01

    Microencapsulated ammonium polyphosphate (MCAPP) in combination with polyester polyurethane (TPU) was used to flame retardant ethylene-vinyl acetate copolymer (EVA). The EVA composites with different irradiation doses were immersed in hot water (80 °C) to accelerate ageing process. The microencapsulation and irradiation dose ensured positive impacts on the properties of the EVA composites in terms of better dimensional stability and flame retardant performance. The microencapsulation of APP could lower its solubility in water and the higher irradiation dose led to the more MCAPP immobilized in three dimensional crosslinked structure of the EVA matrix which could jointly enhance the flame retardant and electrical insulation properties of the EVA composites. So, the EVA composites with 180 kGy irradiation dose exhibited better dimensional stability than the EVA composites with 120 kGy due to the higher crosslinking degree. Moreover, the higher irradiation dose lead to the more MCAPP immobilizated in crosslinked three-dimensional structure of EVA, enhancing the flame retardancy and electrical insulation properties of the EVA composites. After ageing test in hot water at 80 °C for 2 weeks, the EVA/TPU/MCAPP composite with 180 kGy could still maintain the UL-94 V-0 rating and the limiting oxygen index (LOI) value was as high as 30%. This investigation indicated the flame retardant EVA cable containing MCAPP could achieve stable properties and lower electrical fire hazard risk during long-term hot water ageing test.

  15. Propagating nonpremixed edge-flames in a counterflow, annular slot burner under DC electric fields

    KAUST Repository

    Tran, Vu Manh

    2016-09-11

    Characteristics of propagating nonpremixed edge-flames were investigated in a counterflow, annular slot burner. A high-voltage direct current (DC) was applied to the lower part of the burner and the upper part was grounded, creating electric field lines perpendicular to the direction of edge-flame propagation. Upon application of an electric field, an ionic wind is caused by the migration of positive and negative ions to lower and higher electrical potential sides of a flame, respectively. Under an applied DC, we found a significant decrease in edge-flame displacement speeds unlike several previous studies, which showed an increase in displacement speed. Within a moderate range of field intensity, we found effects on flame propagation speeds to be negligible after correcting the flame displacement speed with respect to the unburned flow velocity ahead of the flame edge. This indicates that the displacement speed of an edge-flame strongly depends on ionic wind and that an electric field has little or no impact on propagation speed. The ionic wind also influenced the location of the stoichiometric contour in front of the propagating edge in a given configuration such that a propagating edge was relocated to the higher potential side due to an imbalance between ionic winds originating from positive and negative ions. In addition, we observed a steadily wrinkled flame following transient propagation of the edge-flame, a topic for future research. © 2016 The Combustion Institute

  16. The experimental of methane-air flame propagation in the tube with quadrate cross section

    Institute of Scientific and Technical Information of China (English)

    GUO Zi-ru; SHEN Zhao-wu; LU Shou-xiang; ZHOU Ning

    2005-01-01

    The flame propagation of methane-air mixture with various methane concentrations was experimentally investigated at venting flame acceleration tube with quadrate cross section under different obstacles presented. The flame shape and propagation speed was observed by high-speed color video camera. The explosion pressure was determined by piezoelectricity pressure transducers. The results are: The flame propagates in the shape of a hemisphere before the flame reaches the first baffle and flame propagation speed is not more than 15 m/s. When the flame propagates across the baffle, the flame begins to accelerate due to turbulence induced by obstacle.Blockage ratio has relatively greater effect on the flame propagation speed than repeated baffle number does. The flame propagation speed and the pressure at different location along the tube are maximum when methane-air mixture is near the chemical stoichoimetric ratio. The pressure increases with the distance from ignition end at first and the maximum pressure was obtained at the middle of tube, but the pressure decreases and again increases at venting end.

  17. Application of computer vision in studying fire plume behavior of tilting flames

    Science.gov (United States)

    Aminfar, Amirhessam; Cobian Iñiguez, Jeanette; Pham, Stephanie; Chong, Joey; Burke, Gloria; Weise, David; Princevac, Marko

    2016-11-01

    With the development in computer sciences especially in the field of computer vision, image processing has become an inevitable part of flow visualization. Computer vision can be used to visualize flow structure and to quantify its properties. We used a computer vision algorithm to study fire plume tilting when the fire is interacting with a solid wall. As the fire propagates to the wall the amount of air available for the fire to consume will decrease on the wall side. Therefore, the fire will start tilting towards the wall. Aspen wood was used for the fuel source and various configurations of the fuel were investigated. The plume behavior was captured using a digital camera. In the post processing, the flames were isolated from the image by using edge detection technics, making it possible to develop an algorithm to calculate flame height and flame orientation. Moreover, by using an optical flow algorithm we were able to calculate the speed associated with the edges of the flame which is related to the flame propagation speed and effective vertical velocity of the flame. The results demonstrated that as the size of the flame was increasing, the flames started tilting towards the wall. Leading to the conclusion that there should be a critical area of fire in which the flames start to tilt. Also, the algorithm made it possible to calculate a critical distance in which the flame will start orienting towards the wall

  18. The Effect of Resolution on Detecting Visually Salient Preattentive Features

    Science.gov (United States)

    2015-06-01

    distinguish a dull yellow daffodil among a field of dull yellow dandelions versus finding a bright red rose in that same field. The human eye is directed...to particular regions in a scene by highly salient 2 features, for example, the color of the flower discussed in the previous example. These

  19. Flame front detection by active contour method from OH-PLIF images under microgravity

    Institute of Scientific and Technical Information of China (English)

    Yandong Tang; Yue Wang; Christian Eigenbrod

    2006-01-01

    @@ It is difficult and high-cost to detect flame fronts by laser-sheet diagnostics under microgravity (μg),thus image processing is critical to obtain valuable information from the raw data. In the present study,premixed V-flames were detected under μg by OH planar laser-induced fluorescence (PLIF) and an effective method based on active contour model (ACM) is presented for automatic detecting and tracking flame fronts in the PLIF images. ACM can effectively detect the flame front in the images with low contrast and noises. Compared with other methods of flame front detection, the advantage of this method is that the image smoothing and image enhancement are not necessary for the correct detection of flame fronts in raw PLIF images.

  20. Synthesis,Characterization and Flame-retardant Properties of Epoxy Resins and AACHH Composites

    Institute of Scientific and Technical Information of China (English)

    QIN Linqing; ZHANG Lianmeng; HUANG Zhixiong; HUANG Zhiliang; WANG Yanbing

    2009-01-01

    Flame retardant epoxy resins were prepared by a simple mixed method using am-monium aluminum carbonate hydroxy hydrate(AACHH)as a halogen-free flame retardant.The pre-pared samples were characterized by X-ray diffraction,thermogravimetric and differential scanning calorimetry,scanning electron microscope and limiting oxygen index(LOI)experiments.Effects of AACHH content on LOI of epoxy resins/AACHH composite and flame retardant mechanism were investigated and discussed.Results show that AACHH exhibites excellent flame-retardant properties in epoxy resin(EP).When the content of AACHH was 47.4%,the LOI of EP reached 32.2%.Moreover, the initial and terminal decomposition temperature of EP increased by 48 ℃and 40℃,respectively. The flame retarded mechanism of AACHH is due to the synergic flame retardant effects of diluting, cooling,decomposition resisting and obstructing.

  1. The Mechanisms of Flame Stabilization and Low NOx Emission in an Eccentric Jet Pulverized Coal Combustor

    Institute of Scientific and Technical Information of China (English)

    SunWenchao; SunYezhu; 等

    1992-01-01

    The mechanisms of flame stabilization and low NOx emission features of an accentric jet pulverzed coal combustor were studied through numerical modelling and experimental investigation.The results show that the formation of the unique flowfield structure is closely related to the interaction among combustor configuration.the primary jet and the control Jet.and that certain rules should be follwed in orber to obtain the optimum condition for flame stabilization.The distributions of temperature and concentration of NO,O2,CO and CO2 inside the combustor were experimentally measured.The effects of strustural and operational parameters on combustion and NO formation were studied.It was found that reduction of primary air,suitable use of control jet and reasonable uptilt angle of the primary jet all contributed to the reduction of NOx at the combustor exit.A new hypothesis,that reasonable separation of oxygen and fuel within the fuel-rich zone is beneficial to further reduction of NOx emission,is given,The study showed that good compatibility existed between the capability of flame stabilization and low NOX emission for this type of combustor.

  2. Liftoff and blowoff of a diffusion flame between parallel streams of fuel and air

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Tarrazo, Eduardo [I.N.T.A. Area de Propulsion-Edificio R02, Ctra. Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid (Spain); Vera, Marcos [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Linan, Amable [Departamento de Motopropulsion y Termofluidodinamica, Universidad Politecnica de Madrid, Pza. Cardenal Cisneros 3, 28040 Madrid (Spain)

    2006-01-01

    A numerical analysis is presented to describe the liftoff and blowoff of a diffusion flame in the mixing layer between two parallel streams of fuel (mainly methane diluted with nitrogen) and air emerging from porous walls. The analysis, which takes into account the effects of thermal expansion, assumes a one-step overall Arrhenius reaction, where the activation energy E is allowed to vary to reproduce the variations of the planar flame propagation velocity with the equivalence ratio. First, we describe the steady flame-front structure when stabilized close to the porous wall (attached flame regime). Then, we analyze the case where the flame front is located far away from the porous wall, at a distance x{sub f}' such that, upstream of the flame front, the mixing layer has a self-similar structure (lifted flame regime). For steady lifted flames, the results, given here in the case when the fuel and air streams are injected with the same velocity, relate U{sub f}'/S{sub L}, the front velocity (relative to the upstream flow) measured with the planar stoichiometric flame velocity, with the Damkohler number D{sub m}=({delta}{sub m}/{delta}{sub L}){sup 2}, based on the thickness, {delta}{sub m}, of the nonreacting mixing layer at the flame-front position and the laminar flame thickness, {delta}{sub L}. For large values of D{sub m}, the results, presented here for a wide range of dilutions of the fuel stream, provide values of the front propagation velocity that are in good agreement with previous experimental results, yielding well-defined conditions for blowoff. The calculated flame-front velocity can also be used to describe the transient flame-front dynamics after ignition by an external energy source.

  3. Laminar oxy-fuel diffusion flame supported by an oxygen-permeable-ion-transport membrane

    KAUST Repository

    Hong, Jongsup

    2013-03-01

    A numerical model with detailed gas-phase chemistry and transport was used to predict homogeneous fuel conversion processes and to capture the important features (e.g., the location, temperature, thickness and structure of a flame) of laminar oxy-fuel diffusion flames stabilized on the sweep side of an oxygen permeable ion transport membrane (ITM). We assume that the membrane surface is not catalytic to hydrocarbon or syngas oxidation. It has been demonstrated that an ITM can be used for hydrocarbon conversion with enhanced reaction selectivity such as oxy-fuel combustion for carbon capture technologies and syngas production. Within an ITM unit, the oxidizer flow rate, i.e., the oxygen permeation flux, is not a pre-determined quantity, since it depends on the oxygen partial pressures on the feed and sweep sides and the membrane temperature. Instead, it is influenced by the oxidation reactions that are also dependent on the oxygen permeation rate, the initial conditions of the sweep gas, i.e., the fuel concentration, flow rate and temperature, and the diluent. In oxy-fuel combustion applications, the sweep side is fuel-diluted with CO2, and the entire unit is preheated to achieve a high oxygen permeation flux. This study focuses on the flame structure under these conditions and specifically on the chemical effect of CO2 dilution. Results show that, when the fuel diluent is CO2, a diffusion flame with a lower temperature and a larger thickness is established in the vicinity of the membrane, in comparison with the case in which N2 is used as a diluent. Enhanced OH-driven reactions and suppressed H radical chemistry result in the formation of products with larger CO and H2O and smaller H2 concentrations. Moreover, radical concentrations are reduced due to the high CO2 fraction in the sweep gas. CO2 dilution reduces CH3 formation and slows down the formation of soot precursors, C2H2 and C2H4. The flame location impacts the species diffusion and heat transfer from the

  4. Dynamics of Diffusion Flames in von Karman Swirling Flows Studied

    Science.gov (United States)

    Nayagam, Vedha; Williams, Forman A.

    2002-01-01

    Von Karman swirling flow is generated by the viscous pumping action of a solid disk spinning in a quiescent fluid media. When this spinning disk is ignited in an oxidizing environment, a flat diffusion flame is established adjacent to the disk, embedded in the boundary layer (see the preceding illustration). For this geometry, the conservation equations reduce to a system of ordinary differential equations, enabling researchers to carry out detailed theoretical models to study the effects of varying strain on the dynamics of diffusion flames. Experimentally, the spinning disk burner provides an ideal configuration to precisely control the strain rates over a wide range. Our original motivation at the NASA Glenn Research Center to study these flames arose from a need to understand the flammability characteristics of solid fuels in microgravity where slow, subbuoyant flows can exist, producing very small strain rates. In a recent work (ref. 1), we showed that the flammability boundaries are wider and the minimum oxygen index (below which flames cannot be sustained) is lower for the von Karman flow configuration in comparison to a stagnation-point flow. Adding a small forced convection to the swirling flow pushes the flame into regions of higher strain and, thereby, decreases the range of flammable strain rates. Experiments using downward facing, polymethylmethacrylate (PMMA) disks spinning in air revealed that, close to the extinction boundaries, the flat diffusion flame breaks up into rotating spiral flames (refs. 2 and 3). Remarkably, the dynamics of these spiral flame edges exhibit a number of similarities to spirals observed in biological systems, such as the electric pulses in cardiac muscles and the aggregation of slime-mold amoeba. The tail of the spiral rotates rigidly while the tip executes a compound, meandering motion sometimes observed in Belousov-Zhabotinskii reactions.

  5. Flame image monitoring and analysis in combustion management

    Energy Technology Data Exchange (ETDEWEB)

    Popovic, D. [CEZ, a.s. Elektrarna Detmarovice, Detmarovice (Czech Republic); Huttunen, A.J.; Nihtinen, J.J. [Imatran Voima Oy, IVO Technology Centre, Vantaa (Finland)

    1997-12-31

    When NO{sub x} emissions are reduced with new low-NO{sub x} burners and infurnace modifications in old pulverised fuel boilers, many changes in the firing conditions may occur. Depending on coal quality and the original furnace design, low-NO{sub x} burners, overtire air, low-excess-air firing and other primary modifications in various combinations may cause flame instability, increased slagging, increased minimum load and other difficulties in controlling the burning process. To find and solve these problems quicker, a new type of burner management system for pulverised fuel and oil-fired boilers was developed by Imatran Voima Oy. The DIMAC combustion management system monitors and analyses individually each burner or burner level. There are special software for wall and corner fired boilers. The DIMAC system is comprised of two functional subsystems: flame monitoring and flame analysis. The DIMAC enables the power plant operators to minimise NO{sub x} emissions and optimise the burning efficiency with varying coal qualities and boiler loads at the same time so that slagging, unburnt carbon in fly ash and flame stability stay in acceptable limits. It also guarantees that burners operate in good safety conditions in each burner level. The DIMAC system monitors perpendicularly each individual burner and evaluates flame parameters. Real-time flame monitoring and analysis allows the operator to directly see the effect of changing fuel distribution on flame pattern and flame stability. Based on data from the DIMAC references the system can improve boiler efficiency by 0.2 - 0.5 per cent unit as a result of more efficient control of the burning process. At the same time, the NO{sub x} formation can be reduced by 10 - 20 % 2 refs.

  6. Smoke suppression properties of ferrite yellow on flame retardant thermoplastic polyurethane based on ammonium polyphosphate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xilei; Jiang, Yufeng; Jiao, Chuanmei, E-mail: jiaochm@qust.edu.cn

    2014-02-15

    Highlights: • Smoke suppression of FeOOH on flame retardant TPU composites has been investigated. • FeOOH has excellent smoke suppression abilities for flame retardant TPU composites. • FeOOH has good ability of char formation, hence improved smoke suppression property. -- Abstract: This article mainly studies smoke suppression properties and synergistic flame retardant effect of ferrite yellow (FeOOH) on flame retardant thermoplastic polyurethane (TPU) composites using ammonium polyphosphate (APP) as a flame retardant agent. Smoke suppression properties and synergistic flame retardant effect of FeOOH on flame retardant TPU composites were intensively investigated by smoke density test (SDT), cone calorimeter test (CCT), scanning electron microscopy (SEM), and thermal-gravimetric analysis (TGA). Remarkably, the SDT results show that FeOOH can effectively decrease the amount of smoke production with or without flame. On the other hand, the CCT data reveal that the addition of FeOOH can apparently reduce heat release rate (HRR), total heat release (THR), and total smoke release (TSR), etc. Here, FeOOH is considered to be an effective smoke suppression agent and a good synergism with APP in flame retardant TPU composites, which can greatly improve the structure of char residue realized by TGA and SEM results.

  7. Turbulent Chemical Diffusion in Convectively Bounded Carbon Flames

    CERN Document Server

    Lecoanet, Daniel; Quataert, Eliot; Bildsten, Lars; Timmes, F X; Burns, Keaton J; Vasil, Geoffrey M; Oishi, Jeffrey S; Brown, Benjamin P

    2016-01-01

    It has been proposed that mixing induced by convective overshoot can disrupt the inward propagation of carbon deflagrations in super-asymptotic giant branch stars. To test this theory, we study an idealized model of convectively bounded carbon flames with 3D hydrodynamic simulations of the Boussinesq equations using the pseudospectral code Dedalus. Because the flame propagation timescale is $\\sim 10^5$ times longer than the convection timescale, we approximate the flame as fixed in space, and only consider its effects on the buoyancy of the fluid. By evolving a passive scalar field, we derive a turbulent chemical diffusivity produced by the convection as a function of height, $D_t(z)$. Convection can stall a flame if the chemical mixing timescale, set by the turbulent chemical diffusivity, $D_t$, is shorter than the flame propagation timescale, set by the thermal diffusivity, $\\kappa$, i.e., when $D_t>\\kappa$. However, we find $D_t<\\kappa$ for most of the flame because convective plumes are not dense enoug...

  8. Conditional moment closure modeling of a lifted turbulent flame

    Institute of Scientific and Technical Information of China (English)

    JIANG Yong; QIU Rong; ZHOU Wei; FAN Weicheng

    2005-01-01

    Results obtained using conditional moment closure (CMC) approach to modeling a lifted turbulent hydrogen flame are presented. Predictions are based on k-ε-g turbulent closure, a 23-step chemical mechanism and a radially averaged CMC model. The objectives are to find out how radially averaged CMC can represent a lifted flame and which mechanism of flame stabilization can be described by this modeling method. As a first stage of the study of multi-dimensional CMC for large eddy simulation (LES) of the lifted turbulent flames, the effect of turbulence upon combustion is included, the high-order compact finite- difference scheme (Padé) is used and previously developed characteristic-wave-based boundary conditions for multi- component perfect gas mixtures are here extended to their conditional forms but the heat release due to combustion is not part of the turbulent calculations. Attention is focused to the lift-off region of the flame which is commonly considered as a cold flow. Comparison with published experimental data and the computational results shows that the lift-off height can be accurately determined, and Favre averaged radial profiles of temperature and species mole fractions are also reasonably well predicted. Some of the current flame stabilization mechanisms are discussed.

  9. Ion measurements in premixed methane-oxygen flames

    KAUST Repository

    Alquaity, Awad

    2014-07-25

    Ions are formed as a result of chemi-ionization processes in combustion systems. Recently, there has been an increasing interest in understanding flame ion chemistry due to the possible application of external electric fields to reduce emissions and improve combustion efficiency by active control of combustion process. In order to predict the effect of external electric fields on combustion plasma, it is critical to gain a good understanding of the flame ion chemistry. In this work, a Molecular Beam Mass Spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane-oxygen-argon burner-stabilized flames. Lean, stoichiometric and rich flames at atmospheric pressure are used to study the dependence of ion chemistry on equivalence ratio of premixed flames. The relative ion concentration profiles are compared qualitatively with previous methane-oxygen studies and show good agreement. The relative ion concentration data obtained in the present study can be used to validate and improve ion chemistry models for methane-oxygen flames.

  10. 纳米阻燃剂对饰面型防火涂料性能影响研究%Effect of Nano Flame Retardant on the Performance of Decorated Fire-retardant Coating

    Institute of Scientific and Technical Information of China (English)

    方璐; 张佳璐; 王美琴; 张华文

    2015-01-01

    Decorated fire-retardant coating is an important method to avoid building fire accidents.Now the research finded that nanometre fire-retardant could solve the problems existing in the application of decorated fire-retardant coating and improved the performance.In order to research the effect of nano flame retardant on the performance of decorated fire-retardant coating, based on the nanometer aluminum hydroxide flame retardant.The method of tunnel ignition was adopted to test the fire performance of ordinary decorating fire-retardant coatings and the fire performance of the decorating fire-retardant coatings adding nanometer aluminum hydroxide. Comparative analysis of experimental results was used to obtained the inference rule of nanometer aluminum hydroxide flame retardant and to have a more intuitive understanding of the inference of nano flame retardant.Fire retardant coatings for nano future trends were forecasted.%饰面型防火涂料是建筑物防火的一种重要方法。现研究发现纳米阻燃剂可改善饰面型防火涂料存在问题,提高防火性能。为研究纳米阻燃剂对饰面型防火涂料的性能影响,本文以纳米氢氧化铝阻燃剂为例,通过隧道燃烧法测量火焰传播比值来对普通饰面型防火涂料和纳米改性涂料的耐火性能进行分析,得出纳米氢氧化铝的影响规律,对纳米阻燃剂的作用有一个更直观的认识,并对纳米防火涂料的未来发展进行展望。

  11. Terahertz time-domain spectroscopy of high-pressure flames

    Institute of Scientific and Technical Information of China (English)

    Jason BASSI; Mark STRINGER; Bob MILES; Yang ZHANG

    2009-01-01

    Laser spectroscopy in the visible and near infrared is widely used as a diagnostic tool for combustion devices, but this approach is difficult at high pressures within a sooty flame itself. High soot concentrations render flames opaque to visible light, but they remain transparent to far-infrared or terahertz (THz) radiation. The first far-infrared absorption spectra, to the best of our knowledge, of sooty, non-premixed, ethylene high-pressure flames covering the region of 0.2-2.5 THz is presented. A specially designed high-pressure burner which is optically accessible to THz radiation has been built allowing flame transmission measurements up to pressures of 1.6 MPa. Calculations of the theoretical combustion species absorption spectra in the 0.2-3 THz range have shown that almost all the observable features arise from H2O. A few OH (1.84 and 2.51 THz), CH (2.58 THz), and NH3 (1.77 and 2.95 THz) absorption lines are also observable in principle. A large number of H2O absorption lines are observed in the ground vibrational in a laminar non-premixed, sooty flame (ethylene) at pressures up to 1.6 MPa.

  12. Computational and experimental study of laminar flames

    Energy Technology Data Exchange (ETDEWEB)

    Smooke, Mitchell [Yale Univ., New Haven, CT (United States)

    2015-05-29

    During the past three years, our research has centered on an investigation of the effects of complex chemistry and detailed transport on the structure and extinction of hydrocarbon flames in coflowing axisymmetric configurations. We have pursued both computational and experimental aspects of the research in parallel on both steady-state and time-dependent systems. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the steady-state and time-dependent boundary value problems describing the various reacting systems. Detailed experimental measurements were performed on axisymmetric coflow flames using two-dimensional imaging techniques. Previously, spontaneous Raman scattering, chemiluminescence, and laser-induced fluorescence were used to measure the temperature, major and minor species profiles. Particle image velocimetry (PIV) has been used to investigate velocity distributions and for calibration of time-varying flames. Laser-induced incandescence (LII) with an extinction calibration was used to determine soot volume fractions, while soot surface temperatures were measured with three-color optical pyrometry using a color digital camera. A blackbody calibration of the camera allows for determination of soot volume fraction as well, which can be compared with the LII measurements. More recently, we have concentrated on a detailed characterization of soot using a variety of techniques including time-resolved LII (TiRe-LII) for soot primary particles sizes, multi-angle light scattering (MALS) for soot radius of gyration, and spectrally-resolved line of sight attenuation (spec-LOSA). Combining the information from all of these soot measurements can be used to determine the soot optical properties, which are observed to vary significantly depending on spatial location and fuel dilution. Our goal has been to obtain a more fundamental understanding of the important fluid dynamic and chemical interactions in

  13. Role of flame generated flow in the formation of tulip flame

    Energy Technology Data Exchange (ETDEWEB)

    Jeung, I.S.; Cho, K.K.; Jeong, K.S.

    1989-01-01

    The role of flame generated flow during the laminar 'tulip' flame formation in a long rectangular combustion vessel was examined by laser Doppler velocimeter measurement, high speed schlieren photographic flame visualization, and combustion vessel pressure measurement. Results of these investigations showed the transition of convex-shaped flame to concave-shaped tulip flame and interactions between the flame shape and flame generated flow in a confined geometry, and gave physical understanding of flow field formation of tulip flame. 15 references.

  14. Explosive-driven shock wave and vortex ring interaction with a propane flame

    Science.gov (United States)

    Giannuzzi, P. M.; Hargather, M. J.; Doig, G. C.

    2016-11-01

    Experiments were performed to analyze the interaction of an explosively driven shock wave and a propane flame. A 30 g explosive charge was detonated at one end of a 3-m-long, 0.6-m-diameter shock tube to produce a shock wave which propagated into the atmosphere. A propane flame source was positioned at various locations outside of the shock tube to investigate the effect of different strength shock waves. High-speed retroreflective shadowgraph imaging visualized the shock wave motion and flame response, while a synchronized color camera imaged the flame directly. The explosively driven shock tube was shown to produce a repeatable shock wave and vortex ring. Digital streak images show the shock wave and vortex ring propagation and expansion. The shadowgrams show that the shock wave extinguishes the propane flame by pushing it off of the fuel source. Even a weak shock wave was found to be capable of extinguishing the flame.

  15. Analysis of flame acceleration induced by wall friction in open tubes

    CERN Document Server

    Akkerman, V'yacheslav; Bychkov, Vitaly; Eriksson, Lars-Erik; 10.1063/1.3425646

    2012-01-01

    Spontaneous flame acceleration leading to explosion triggering in open tubes/channels due to wall friction was analytically and computationally studied. It was first demonstrated that the acceleration is effected when the thermal expansion across the flame exceeds a critical value depending on the combustion configuration. For the axisymmetric flame propagation in cylindrical tubes with both ends open, a theory of the initial (exponential) stage of flame acceleration in the quasi-isobaric limit was developed and substantiated by extensive numerical simulation of the hydrodynamics and combustion with an Arrhenius reaction. The dynamics of the flame shape, velocity, and acceleration rate, as well as the velocity profile ahead and behind the flame, have been determined.

  16. A Rational Model of the Effects of Distributional Information on Feature Learning

    Science.gov (United States)

    Austerweil, Joseph L.; Griffiths, Thomas L.

    2011-01-01

    Most psychological theories treat the features of objects as being fixed and immediately available to observers. However, novel objects have an infinite array of properties that could potentially be encoded as features, raising the question of how people learn which features to use in representing those objects. We focus on the effects of…

  17. 氧化亚镍在RTB-IFR膨胀阻燃体系中的协效作用%Synergistic Effect of NiO on RTB-IFR Intumescent Flame Retardant System

    Institute of Scientific and Technical Information of China (English)

    鲍文波; 季洋; 张惠; 司广博; 佟丽梅; 高苏亮

    2011-01-01

    In this paper, NiO was used as an effective synergist for RTB-IFR intumescent flame retard-ant that was produced ( RTB-IFR was trademark). The synergistic flame retardant effects of NiO in application in PP composite was studied. The flame retardance, mechanical properties and thermal degradation behavior of NiO on PP system were investigated. Results showed adding 20% RTB-IFR, the 3. 2 mm RTB-IFR/ PP sample can pass UL94 V-0 rating with LOI of 31. 8% and had well flame retardance. By addition of 5% NiO, the 1. 6 mm sample can pass UL94 V-0 rating with LOI value of 33. 6% and the flame retardance improved significantly. Moreover, further tests demonstrated that the addition of NiO did not have a significant effect on mechanical properties of PP system. The addition of NiO changed the thermal degradation process of RTB-IFR or RTB-IFR/PP system which lead to a lower evolution burning rate and improved the carbon residual at high temperature materials and thermal stability of composite.%将氧化亚镍(NiO)与膨胀阻燃剂(RTB-IFR,未添加协效剂成分)复配,应用在聚丙烯(PP)复合材料中以研究NiO的阻燃协效作用.探讨了NiO对膨胀阻燃PP复合材料的阻燃性能、力学性能及热降解行为的影响.结果表明,在PP中单独添加20% RTB-IFR阻燃剂,PP复合材料具有较好的阻燃性能,氧指数为31.8%,3.2 mm样条能通过UL94 V-0级.当RTB-IFR阻燃剂中加入5% NiO时,PP复合材料的阻燃性能明显得到提高,氧指数达到33.6%,1.6 mm样条即能通过UL94 Ⅴ-0级.同时,NiO对PP复合材料的力学性能影响较小.NiO的引入改变了RTB-IFR及RTB-IFR/PP体系的热降解过程,降低了PP复合材料的热分解速率,提高了复合材料高温时的残炭量和热稳定性.

  18. A, a Brominated Flame Retardant

    Directory of Open Access Journals (Sweden)

    Tomomi Takeshita

    2013-01-01

    Full Text Available Tetrabromobisphenol A (TBBPA, a brominated flame retardant, has been found to exacerbate pneumonia in respiratory syncytial virus- (RSV- infected mice. We examined the effect of Brazilian propolis (AF-08 on the exacerbation of RSV infection by TBBPA exposure in mice. Mice were fed a powdered diet mixed with 1% TBBPA alone, 0.02% AF-08 alone, or 1% TBBPA and 0.02% AF-08 for four weeks and then intranasally infected with RSV. TBBPA exposure increased the pulmonary virus titer and level of IFN-γ, a representative marker of pneumonia due to RSV infection, in the lungs of infected mice without toxicity. AF-08 was significantly effective in reducing the virus titers and IFN-γ level increased by TBBPA exposure. Also, AF-08 significantly reduced proinflammatory cytokine (TNF-α and IL-6 levels in the lungs of RSV-infected mice with TBBPA exposure, but Th2 cytokine (IL-4 and IL-10 levels were not evidently increased. Neither TBBPA exposure nor AF-08 treatment affected the anti-RSV antibody production in RSV-infected mice. In flow cytometry analysis, AF-08 seemed to be effective in reducing the ratio of pulmonary CD8a+ cells in RSV-infected mice with TBBPA exposure. TBBPA and AF-08 did not exhibit anti-RSV activity in vitro. Thus, AF-08 probably ameliorated pneumonia exacerbated by TBBPA exposure in RSV-infected mice by limiting excess cellular immune responses.

  19. Soot Deposit Properties in Practical Flames

    Energy Technology Data Exchange (ETDEWEB)

    Preciado, Ignacio [University of Utah; Eddings, Eric G. [University of Utah; Sarofim, Adel F. [University of Utah; Dinwiddie, Ralph Barton [ORNL; Porter, Wallace D [ORNL; Lance, Michael J [ORNL

    2009-01-01

    Soot deposition from hydrocarbon flames was investigated in order to evaluate the evolution of the deposits during the transient process of heating an object that starts with a cold metal surface that is exposed to a flame. The study focused on the fire/metal surface interface and the critical issues associated with the specification of the thermal boundaries at this interface, which include the deposition of soot on the metal surface, the chemical and physical properties of the soot deposits and their subsequent effect on heat transfer to the metal surface. A laboratory-scale device (metallic plates attached to a water-cooled sampling probe) was designed for studying soot deposition in a laminar ethylene-air premixed flame. The metallic plates facilitate the evaluation of the deposition rates and deposit characteristics such as deposit thickness, bulk density, PAH content, deposit morphology, and thermal properties, under both water-cooled and uncooled conditions. Additionally, a non-intrusive Laser Flash Technique (in which the morphology of the deposit is not modified) was used to estimate experimental thermal conductivity values for soot deposits as a function of deposition temperature (water-cooled and uncooled experiments), location within the flame and chemical characteristics of the deposits. Important differences between water-cooled and uncooled surfaces were observed. Thermophoresis dominated the soot deposition process and enhanced higher deposition rates for the water-cooled experiments. Cooler surface temperatures resulted in the inclusion of increased amounts of condensable hydrocarbons in the soot deposit. The greater presence of condensable material promoted decreased deposit thicknesses, larger deposit densities, different deposit morphologies, and higher thermal conductivities.

  20. 无机色粉对阻燃ABS性能影响%Effect of Inorganic Color Toners on Properties of Flame-Retardant ABS

    Institute of Scientific and Technical Information of China (English)

    田雪梅

    2012-01-01

    主要研究了在TBBPA(四溴双酚-A)阻燃丙烯腈-丁二烯-苯乙烯共聚物(ABS)中分别填充钛白、铁红和炭黑3种无机色粉后的性能,结果表明,填充3种色粉均可以使ABS的密度升高,铁红和炭黑的加入使ABS弯曲强度和弯曲模量升高,炭黑和钛白粉降低了ABS熔体流动速率,3种无机色粉填充阻燃ABS的阻燃性能均达到UL94V-0级,综合性能优异.%The performance of the TBBPA flame retarded ABS filled by three kinds of inorganic color toners of TiO2, Fe2O3, and carbon black (C), was mainly studied. The results show that all the three kinds of inorganic color toners increase the flame-re-tardant ABS density. Fe2 O3 and C increase the flexural strength and modulus of ABS. C and TiO2 decrease the melt index of ABS. The flame retardancy of flame-retardant ABS filled by three kinds of inorganic color toners reaches UL94V-0 level, and the comprehensive properties are excellent.

  1. Effects of salt-alkali stress on active oxygen metabolism in roots of Spiraea × bumalda ‘Gold Mound' and Spiraea × bumalda ‘Gold Flame'

    Institute of Scientific and Technical Information of China (English)

    YAN Yong-qing; CHE Dai-di; SHI Xi-chan; LIU Xing-liang

    2011-01-01

    Under artificially-simulated complex salt-alkali stress, the levels of active oxygen metabolism in roots were studied using three-year-old cutting seedlings of Spiraea × bumalda ‘Gold Mound' and Spiraea × bumalda ‘Gold Flame'. The present study aimed at exploring the antioxidant capacity in roots of spiraeas and revealing their adaptability to salt-alkali stress. Results indicate that the oxygen free radicals contents, electrolyte leakage rates and MDA contents in roots of Spiraea × buralda ‘Gold Mound' and Spiraea × bumalda ‘Gold Flame' show an increasing tendency with the increases of the salinity and pH value,whereas the activities of superoxide dismutase (SOD), peroxidase (POD)and catalase (CAT) all increased firstly and then decreased. With the increase in intensity of salt-alkali stress, the CAT activity in roots of Spiraea × bumalda ‘Gold Flame' is higher and the increasing extents in the oxygen free radicals contents, electrolyte leakage rates as well as MDA contents are lower compared with Spiraea × bumalda ‘Gold Mound', indicating that Spiraea × bumalda ‘Gold Flame' has a stronger antioxidant capacity.

  2. Bidirectional ionic wind in nonpremixed counterflow flames with DC electric fields

    KAUST Repository

    Park, Daegeun

    2016-05-05

    Under an electric field, ions in the reaction zone of a flame generate a bulk flow motion called ionic wind. Because the majority of ions are positive, ionic wind is commonly considered to be unidirectional toward the cathode. A more thorough understanding of the effects of electric fields on flames could be obtained by clarifying the role of minor negative ions in the ionic wind. Here, we report on the effects of direct current on nonpremixed counterflow flames by visualizing the ionic wind. We found that the original flow field separates near the flame when it locates at a flow stagnation plane, resulting in a double-stagnant flow configuration. This evidences a bidirectional ionic wind blowing from the flame to both the cathode and the anode due to the positive and the negative ions, respectively. Meanwhile, an electric body force pulls the flame toward the cathode. Thus, the electric field affects the strain rate and the axial location of the stoichiometry, which are important for characterizing nonpremixed counterflow flames. In addition, measurement of the electric current density roughly showed a nearly saturated current when these flames restabilized under relatively high voltage. Detailed explanations of flame behavior, electric currents, and flow characteristics of various fuels are discussed in this study.

  3. Mechanistic aspects of ionic reactions in flames

    DEFF Research Database (Denmark)

    Egsgaard, H.; Carlsen, L.

    1993-01-01

    Some fundamentals of the ion chemistry of flames are summarized. Mechanistic aspects of ionic reactions in flames have been studied using a VG PlasmaQuad, the ICP-system being substituted by a simple quartz burner. Simple hydrocarbon flames as well as sulfur-containing flames have been investigated....... The simple hydrocarbon flames are dominated by a series of hydrocarbonic ions and, to a minor extent, protonated oxo-compounds. The introduction of sulfur to the flames leads to significant changes in the ion composition, as sulfur-containing species become dominant. The ability of the technique to study...

  4. The effect of roundabout design features on cyclist accident rate

    DEFF Research Database (Denmark)

    Hels, Tove; Orozova-Bekkevold, Ivanka

    2007-01-01

    yearly rate of cyclist accidents on one hand and roundabout geometry, age and traffic volume (vehicles and cyclists) on the other. We related all roundabout cyclist accidents recorded by the hospital emergency department of the town of Odense, Denmark, through the years 1999-2003 (N = 171) to various...... geometric features, age and traffic volume of all roundabouts on the Danish island of Funen (N = 88). Cyclist and vehicle volumes turned out to be significant predictors in most of our models-the higher the volumes, the more accidents. Moreover, potential vehicle speed was a significant predictor, and so...... was age of the roundabout-older roundabouts related to more accidents and higher accident probability. Excluding 48 single cyclist accidents strengthened the relationship between accidents on one hand and vehicle and cyclist volume and potential vehicle speed on the other. This stresses the significance...

  5. Effects of metals on the transformation of hexabromocyclododecane (HBCD) in solvents: implications for solvent-based recycling of brominated flame retardants.

    Science.gov (United States)

    Zhong, Yin; Peng, Ping'an; Yu, Zhiqiang; Deng, Haopeng

    2010-09-01

    The management of electronic wastes (e-wastes) has become a global issue as it may release large quantities of hazardous materials such as heavy metals and brominated flame retardants (BFRs) to the environment. Solvent-based recycling is a newly developed, efficient and environmentally beneficial technology for the removal or recovery of BFRs from e-wastes. However, little is known about the behavior of BFRs in the solvents and to what extent they may be affected by co-existing heavy metals. This study quantified the rates of transformation of hexabromocyclododecane (HBCD), a widely used BFR, in the presence of different solvents (i.e. acetone, methanol or toluene) and metals (i.e. Ni, Cu, Zn, Fe or Al). Our experimental results showed that less than 20% of HBCD was transformed in all pure solvent systems within 24h at 50 degrees C. The presence of Ni greatly increased the transformation of HBCD (45-99%) in these solvent systems, whereas other metals had little or no effect on extraction process. The kinetics study showed that transformation of HBCD in Ni-containing systems followed pseudo-first-order kinetics and that the highest transformation rate constant (1.2+/-0.1h(-1)) of HBCD was recorded in the Ni+acetone system. The formation of HBr and pentabromocyclododecene in the acetone+Ni system suggested that transformation of HBCD proceeded via dehydrobromination. Collectively, these results indicated that acetone should not be applied in the recycling or extraction of HBCD from Ni-rich e-wastes, as debromination of HBCD may occur during these processes, even at mild extraction temperatures.

  6. Effects of Palladium Loading on the Response of Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor

    Directory of Open Access Journals (Sweden)

    Sukon Phanichphant

    2007-07-01

    Full Text Available ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in asingle step by flame spray pyrolysis (FSP using zinc naphthenate and palladium (IIacetylacetonate dissolved in toluene-acetonitrile (80:20 vol% as precursors. The effect ofPd loading on the ethanol gas sensing performance of the ZnO nanoparticles and thecrystalline sizes were investigated. The particle properties were analyzed by XRD, BET,AFM, SEM (EDS line scan mode, TEM, STEM, EDS, and CO-pulse chemisorptionmeasurements. A trend of an increase in specific surface area of samples and a decrease inthe dBET with increasing Pd concentrations was noted. ZnO nanoparticles were observed asparticles presenting clear spheroidal, hexagonal and rod-like morphologies. The sizes ofZnO spheroidal and hexagonal particle crystallites were in the 10-20 nm range. ZnOnanorods were in the range of 10-20 nm in width and 20-50 nm in length. The size of Pdnanoparticles increased and Pd-dispersion% decreased with increasing Pd concentrations.The sensing films were produced by mixing the particles into an organic paste composedof terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed ontoAl2O3 substrates interdigitated with Au electrodes. The film morphology was analyzed bySEM and EDS analyses. The gas sensing of ethanol (25-250 ppm was studied in dry air at400°C. The oxidation of ethanol on the sensing surface of the semiconductor wasconfirmed by MS. A well-dispersed of 1 mol%Pd/ZnO films showed the highest sensitivityand the fastest response time (within seconds.

  7. The Effects of Feature Optimization on High-Dimensional Essay Data

    Directory of Open Access Journals (Sweden)

    Bong-Jun Yi

    2015-01-01

    Full Text Available Current machine learning (ML based automated essay scoring (AES systems have employed various and vast numbers of features, which have been proven to be useful, in improving the performance of the AES. However, the high-dimensional feature space is not properly represented, due to the large volume of features extracted from the limited training data. As a result, this problem gives rise to poor performance and increased training time for the system. In this paper, we experiment and analyze the effects of feature optimization, including normalization, discretization, and feature selection techniques for different ML algorithms, while taking into consideration the size of the feature space and the performance of the AES. Accordingly, we show that the appropriate feature optimization techniques can reduce the dimensions of features, thus, contributing to the efficient training and performance improvement of AES.

  8. Experimental Study on Downwardly Spreading Flame over Inclined Polyethylene-insulated Electrical Wire with Applied AC Electric Fields

    KAUST Repository

    Lim, Seung Jae

    2014-12-30

    An experimental study on downwardly spreading flame over slanted electrical wire, which is insulated by Polyethylene (PE), was conducted with applied AC electric fields. The result showed that the flame spread rate decreased initially with increase in inclination angle of wire and then became nearly constant. The flame shape was modified significantly with applied AC electric field due to the effect of ionic wind. Such a variation in flame spread rate could be explained by a thermal balance mechanism, depending on flame shape and slanted direction of flame. Extinction of the spreading flame was not related to angle of inclination, and was described well by a functional dependency upon the frequency and voltage at extinction.

  9. Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

    Science.gov (United States)

    Sun, Z.; Huertas, J. I.; Axelbaum, R. L.

    1999-01-01

    Gas-phase combustion (flame) synthesis has been an essential industrial process for producing large quantities of powder materials such as carbon black, titanium dioxide, and silicon dioxide. Flames typically produce simple oxides, with carbon black being the noted exception because the oxides of carbon are gaseous and are easily separated from the particulate matter that is formed during fuel pyrolysis. Furthermore, the powders produced in flames are usually agglomerated, nanometer-sized particles (nanoparticles). This composition and morphology is acceptable for many applications. However, the present interest in nanoparticles for advanced materials application has led to efforts to employ flames for the synthesis of unagglomerated nanoparticles (2 to 100 nm) of metals and non-oxide ceramics. Sodium-halide chemistry has proven to be viable for producing metals and non-oxide ceramics in flames. Materials that have been produced to date include Si (Calcote and Felder, 1993), TiN, TiB2, TiC, TiSi2, SiC, B4C (Glassman et al, 1993) Al, W, Ti, TiB2, AlN, and W-Ti and Al-AlN composites (DuFaux and Axelbaum, 1995, Axelbaum et al 1996,1997). Many more materials are possible. The main challenge that faces application of flame synthesis for advanced materials is overcoming formation of agglomerates in flames (Brezinsky, 1997). The high temperatures and high number densities in the flame environment favor the formation of agglomerates. Agglomerates must be avoided for many reasons. For example, when nanopowders are consolidated, agglomerates have a deleterious effect on compaction density, leading to voids in the final part. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Another critical challenge that faces all synthesis routes for nanopowders is ensuring that the powders are high purity and that the process is scaleable. Though the containerless, high temperature

  10. Measurements of Positively Charged Ions in Premixed Methane-Oxygen Atmospheric Flames

    KAUST Repository

    Alquaity, Awad B. S.

    2016-08-22

    Cations and anions are formed as a result of chemi-ionization processes in combustion systems. Electric fields can be applied to reduce emissions and improve combustion efficiency by active control of the combustion process. Detailed flame ion chemistry models are needed to understand and predict the effect of external electric fields on combustion plasmas. In this work, a molecular beam mass spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane–oxygen argon burner-stabilized atmospheric flames. Lean and stoichiometric flames are considered to assess the dependence of ion chemistry on flame stoichiometry. Relative ion concentration profiles are compared with numerical simulations using various temperature profiles, and good qualitative agreement was observed for the stoichiometric flame. However, for the lean flame, numerical simulations misrepresent the spatial distribution of selected ions greatly. Three modifications are suggested to enhance the ion mechanism and improve the agreement between experiments and simulations. The first two modifications comprise the addition of anion detachment reactions to increase anion recombination at low temperatures. The third modification involves restoring a detachment reaction to its original irreversible form. To our knowledge, this work presents the first detailed measurements of cations and flame temperature in canonical methane–oxygen-argon atmospheric flat flames. The positive ion profiles reported here may be useful to validate and improve ion chemistry models for methane-oxygen flames.

  11. Spherical Ethylene/Air Diffusion Flames Subject to Concentric DC Electric Field in Microgravity

    Science.gov (United States)

    Yuan, Z. -G.; Hegde, U.; Faeth, G. M.

    2001-01-01

    It is well known that microgravity conditions, by eliminating buoyant flow, enable many combustion phenomena to be observed that are not possible to observe at normal gravity. One example is the spherical diffusion flame surrounding a porous spherical burner. The present paper demonstrates that by superimposing a spherical electrical field on such a flame, the flame remains spherical so that we can study the interaction between the electric field and flame in a one-dimensional fashion. Flames are susceptible to electric fields that are much weaker than the breakdown field of the flame gases owing to the presence of ions generated in the high temperature flame reaction zone. These ions and the electric current of the moving ions, in turn, significantly change the distribution of the electric field. Thus, to understand the interplay between the electric field and the flame is challenging. Numerous experimental studies of the effect of electric fields on flames have been reported. Unfortunately, they were all involved in complex geometries of both the flow field and the electric field, which hinders detailed study of the phenomena. In a one-dimensional domain, however, the electric field, the flow field, the thermal field and the chemical species field are all co-linear. Thus the problem is greatly simplified and becomes more tractable.

  12. Supplementary Material for: Measurements of Positively Charged Ions in Premixed Methane-Oxygen Atmospheric Flames

    KAUST Repository

    Alquaity, Awad B. S.

    2017-01-01

    Cations and anions are formed as a result of chemi-ionization processes in combustion systems. Electric fields can be applied to reduce emissions and improve combustion efficiency by active control of the combustion process. Detailed flame ion chemistry models are needed to understand and predict the effect of external electric fields on combustion plasmas. In this work, a molecular beam mass spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane–oxygen argon burner-stabilized atmospheric flames. Lean and stoichiometric flames are considered to assess the dependence of ion chemistry on flame stoichiometry. Relative ion concentration profiles are compared with numerical simulations using various temperature profiles, and good qualitative agreement was observed for the stoichiometric flame. However, for the lean flame, numerical simulations misrepresent the spatial distribution of selected ions greatly. Three modifications are suggested to enhance the ion mechanism and improve the agreement between experiments and simulations. The first two modifications comprise the addition of anion detachment reactions to increase anion recombination at low temperatures. The third modification involves restoring a detachment reaction to its original irreversible form. To our knowledge, this work presents the first detailed measurements of cations and flame temperature in canonical methane–oxygen-argon atmospheric flat flames. The positive ion profiles reported here may be useful to validate and improve ion chemistry models for methane-oxygen flames.

  13. Turbulent Flame Speeds and NOx Kinetics of HHC Fuels with Contaminants and High Dilution Levels

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Eric [Texas A & M Univ., College Station, TX (United States); Krejci, Michael [Texas A & M Univ., College Station, TX (United States); Mathieu, Olivier [Texas A & M Univ., College Station, TX (United States); Vissotski, Andrew [Texas A & M Univ., College Station, TX (United States); Ravi, Sankat [Texas A & M Univ., College Station, TX (United States); Plichta, Drew [Texas A & M Univ., College Station, TX (United States); Sikes, Travis [Texas A & M Univ., College Station, TX (United States); Levacque, Anthony [Texas A & M Univ., College Station, TX (United States); Camou, Alejandro [Texas A & M Univ., College Station, TX (United States); Aul, Christopher [Texas A & M Univ., College Station, TX (United States)

    2014-01-24

    This final report documents the technical results of the 3-year project entitled, “Turbulent Flame Speeds and NOx Kinetics of HHC Fuels with Contaminants and High Dilution Levels,” funded under the NETL of DOE. The research was conducted under six main tasks: 1) program management and planning; 2) turbulent flame speed measurements of syngas mixtures; 3) laminar flame speed measurements with diluents; 4) NOx mechanism validation experiments; 5) fundamental NOx kinetics; and 6) the effect of impurities on NOx kinetics. Experiments were performed using primary constant-volume vessels for laminar and turbulent flame speeds and shock tubes for ignition delay times and species concentrations. In addition to the existing shock- tube and flame speed facilities, a new capability in measuring turbulent flame speeds was developed under this grant. Other highlights include an improved NOx kinetics mechanism; a database on syngas blends for real fuel mixtures with and without impurities; an improved hydrogen sulfide mechanism; an improved ammonia kintics mechanism; laminar flame speed data at high pressures with water addition; and the development of an inexpensive absorption spectroscopy diagnostic for shock-tube measurements of OH time histories. The Project Results for this work can be divided into 13 major sections, which form the basis of this report. These 13 topics are divided into the five areas: 1) laminar flame speeds; 2) Nitrogen Oxide and Ammonia chemical kinetics; 3) syngas impurities chemical kinetics; 4) turbulent flame speeds; and 5) OH absorption measurements for chemical kinetics.

  14. The effect of roundabout design features on cyclist accident rate.

    Science.gov (United States)

    Hels, Tove; Orozova-Bekkevold, Ivanka

    2007-03-01

    Roundabouts are known to result in fewer traffic accidents than traditional intersections. However, this is to a lesser degree true for bicycles than for vehicles. In this paper, we aimed at establishing statistical relationships through Poisson regression and logistic regression analyses between yearly rate of cyclist accidents on one hand and roundabout geometry, age and traffic volume (vehicles and cyclists) on the other. We related all roundabout cyclist accidents recorded by the hospital emergency department of the town of Odense, Denmark, through the years 1999-2003 (N=171) to various geometric features, age and traffic volume of all roundabouts on the Danish island of Funen (N=88). Cyclist and vehicle volumes turned out to be significant predictors in most of our models-the higher the volumes, the more accidents. Moreover, potential vehicle speed was a significant predictor, and so was age of the roundabout-older roundabouts related to more accidents and higher accident probability. Excluding 48 single cyclist accidents strengthened the relationship between accidents on one hand and vehicle and cyclist volume and potential vehicle speed on the other. This stresses the significance of speed and traffic volume for traffic accidents with more than one partner involved. The 48 single cyclist accidents were significantly related to the traffic volume of cyclists only. Due to our limited number of observations, the models should be regarded as indicative.

  15. Effect of zooming on texture features of ultrasonic images

    Directory of Open Access Journals (Sweden)

    Kyriacou Efthyvoulos

    2006-01-01

    Full Text Available Abstract Background Unstable carotid plaques on subjective, visual, assessment using B-mode ultrasound scanning appear as echolucent and heterogeneous. Although previous studies on computer assisted plaque characterisation have standardised B-mode images for brightness, improving the objective assessment of echolucency, little progress has been made towards standardisation of texture analysis methods, which assess plaque heterogeneity. The aim of the present study was to investigate the influence of image zooming during ultrasound scanning on textural features and to test whether or not resolution standardisation decreases the variability introduced. Methods Eighteen still B-mode images of carotid plaques were zoomed during carotid scanning (zoom factor 1.3 and both images were transferred to a PC and normalised. Using bilinear and bicubic interpolation, the original images were interpolated in a process of simulating off-line zoom using the same interpolation factor. With the aid of the colour-coded image, carotid plaques of the original, zoomed and two resampled images for each case were outlined and histogram, first order and second order statistics were subsequently calculated. Results Most second order statistics (21/25, 84% were significantly (p Conclusion Texture analysis of ultrasonic plaques should be performed under standardised resolution settings; otherwise a resolution normalisation algorithm should be applied.

  16. The Effect of Dynamic Acoustical Features on Musical Timbre

    Science.gov (United States)

    Hajda, John M.

    Timbre has been an important concept for scientific exploration of music at least since the time of Helmholtz ([1877] 1954). Since Helmholtz's time, a number of studies have defined and investigated acoustical features of musical instrument tones to determine their perceptual importance, or salience (e.g., Grey, 1975, 1977; Kendall, 1986; Kendall et al., 1999; Luce and Clark, 1965; McAdams et al., 1995, 1999; Saldanha and Corso, 1964; Wedin and Goude, 1972). Most of these studies have considered only nonpercussive, or continuant, tones of Western orchestral instruments (or emulations thereof). In the past few years, advances in computing power and programming have made possible and affordable the definition and control of new acoustical variables. This chapter gives an overview of past and current research, with a special emphasis on the time-variant aspects of musical timbre. According to common observation, "music is made of tones in time" (Spaeth, 1933). We will also consider the fact that music is made of "time in tones."

  17. Effectiveness of Statistical Features for Human Emotions Classification using EEG Biosensors

    Directory of Open Access Journals (Sweden)

    Chai Tong Yuen

    2013-05-01

    Full Text Available This study proposes a statistical features-based classification system for human emotions by using Electroencephalogram (EEG bio-sensors. A total of six statistical features are computed from the EEG data and Artificial Neural Network is applied for the classification of emotions. The system is trained and tested with the statistical features extracted from the psychological signals acquired under emotions stimulation experiments. The effectiveness of each statistical feature and combinations of statistical features in classifying different types of emotions has been studied and evaluated. In the experiment of classifying four main types of emotions: Anger, Sad, Happy and Neutral, the overall classification rate as high as 90% is achieved.

  18. Role of the outer-edge flame on flame extinction in nitrogen-diluted non-premixed counterflow flames with finite burner diameters

    KAUST Repository

    Chung, Yong Ho

    2013-03-01

    This study of nitrogen-diluted non-premixed counterflow flames with finite burner diameters investigates the important role of the outer-edge flame on flame extinction through experimental and numerical analyses. It explores flame stability diagrams mapping the flame extinction response of nitrogen-diluted non-premixed counterflow flames to varying global strain rates in terms of burner diameter, burner gap, and velocity ratio. A critical nitrogen mole fraction exists beyond which the flame cannot be sustained; the critical nitrogen mole fraction versus global strain rate curves have C-shapes for various burner diameters, burner gaps, and velocity ratios. At sufficiently high strain-rate flames, these curves collapse into one curve; therefore, the flames follow the one-dimensional flame response of a typical diffusion flame. Low strain-rate flames are significantly affected by radial conductive heat loss, and therefore flame length. Three flame extinction modes are identified: flame extinction through shrinkage of the outer-edge flame with or without oscillations at the outer-edge flame prior to the extinction, and flame extinction through a flame hole at the flame center. The extinction modes are significantly affected by the behavior of the outer-edge flame. Detailed explanations are provided based on the measured flame-surface temperature and numerical evaluation of the fractional contribution of each term in the energy equation. Radial conductive heat loss at the flame edge to ambience is the main mechanism of extinction through shrinkage of the outer-edge flame in low strain-rate flames. Reduction of the burner diameter can extend the flame extinction mode by shrinking the outer-edge flame in higher strain-rate flames. © 2012 Elsevier Ltd. All rights reserved.

  19. Engineering Flame Retardant Biodegradable Nanocomposites

    Science.gov (United States)

    He, Shan; Yang, Kai; Guo, Yichen; Zhang, Linxi; Pack, Seongchan; Davis, Rachel; Lewin, Menahem; Ade, Harald; Korach, Chad; Kashiwagi, Takashi; Rafailovich, Miriam

    2013-03-01

    Cellulose-based PLA/PBAT polymer blends can potentially be a promising class of biodegradable nanocomposites. Adding cellulose fiber reinforcement can improve mechanical properties of biodegradable plastics, but homogeneously dispersing hydrophilic cellulose in the hydrophobic polymer matrix poses a significant challenge. We here show that resorcinol diphenyl phosphates (RDP) can be used to modify the surface energy, not only reducing phase separation between two polymer kinds but also allowing the cellulose particles and the Halloysite clay to be easily dispersed within polymer matrices to achieve synergy effect using melt blending. Here in this study we describe the use of cellulose fiber and Halloysite clay, coated with RDP surfactant, in producing the flame retardant polymer blends of PBAT(Ecoflex) and PLA which can pass the stringent UL-94 V0 test. We also utilized FTIR, SEM and AFM nanoindentation to elucidate the role RDP plays in improving the compatibility of biodegradable polymers, and to determine structure property of chars that resulted in composites that could have optimized mechanical and thermal properties. Supported by Garcia Polymer Center and NSF Foundation.

  20. Enhancement of turbulent flame speed of V-shaped flames in fractal-grid-generated turbulence

    NARCIS (Netherlands)

    Verbeek, A.A.; Willems, P.A.; Stoffels, G.G.M.; Geurts, B.J.; Meer, van der T.H.

    2016-01-01

    A variety of fractal grids is used to investigate how fractal-grid-generated turbulence affects the turbulent flame speed for premixed flames. The grids are placed inside a rectangular duct and a V-shaped flame is stabilized downstream of the duct, using a metal wire. This flame is characterized usi

  1. 33 CFR 154.822 - Detonation arresters, flame arresters, and flame screens.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Detonation arresters, flame arresters, and flame screens. 154.822 Section 154.822 Navigation and Navigable Waters COAST GUARD... BULK Vapor Control Systems § 154.822 Detonation arresters, flame arresters, and flame screens. (a)...

  2. Flame Retardants Used in Flexible Polyurethane Foam

    Science.gov (United States)

    The partnership project on flame retardants in furniture seeks to update the health and environmental profiles of flame-retardant chemicals that meet fire safety standards for upholstered consumer products with polyurethane foam

  3. Some features of irradiated chitosan and its biological effect

    Energy Technology Data Exchange (ETDEWEB)

    Hai, Le; Hien, Nguyen Quoc; Luan, Le Quang; Hanh, Truong Thi; Man, Nguyen Tan; Ha, Pham Thi Le; Thuy, Tran Thi [Nuclear Research Institute, VAEC, Dalat (Viet Nam); Yoshii, Fumio; Kume, Tamikazu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    2001-03-01

    Preparation of chitosan oligomer by radiation degradation was carried out on the gamma Co-60 source. The radiation degradation yield (G{sub d}) of the chitosan was found to be of 1.03. The oligochitosan with 50% of dp>8 fraction was obtained by irradiating the 10% (w/v) chitosan solution in 5% acetic acid at 45 kGy for the chitosan having the initial viscometric average molecular weight, Mv=60,000. Irradiated chitosan showed higher antifungal effect than that of unirradiated one. Furthermore, the irradiated chitosan also showed the growth-promotion effect for plants. (author)

  4. On-line tracking of pulverized coal and biomass fuels through flame spectrum analysis

    Institute of Scientific and Technical Information of China (English)

    迟天阳; 张宏建

    2007-01-01

    This paper presents a new approach to the on-line tracking of pulverized coal and biomass fuels through flame spectrum analysis. A flame detector containing four photodiodes is used to derive multiple signals covering a wide spectrum of the flame from visible, near-infrared and mid-infrared spectral bands as well as a part of far-infrared band. Different features are extracted in time and frequency domains to identify the dynamic "fingerprints" of the flame. Fuzzy logic inference techniques are employed to combine typical features together and infer the type of fuel being burnt. Four types of pulverized coal and five types of biomass are burnt on a laboratory-scale combustion test rig. Results obtained demonstrate that this approach is capable of tracking the type of fuel under steady combustion conditions.

  5. Microencapsulated Starter Culture During Yoghurt Manufacturing, Effect on Technological Features

    NARCIS (Netherlands)

    Prisco, de Annachiara; Valenberg, van Hein J.F.; Fogliano, Vincenzo; Mauriello, Gianluigi

    2017-01-01

    The potential of living cell microencapsulation in sustaining cells’ viability, functionality and targeted release in gastrointestinal tract is relatively well documented. Differently, the effects exerted by the capsules on cell metabolic activities during fermentation of a food matrix as well as

  6. Orientation effects on spectral emission features of quasars

    CERN Document Server

    Bisogni, Susanna; Risaliti, Guido

    2016-01-01

    We present an analysis of the orientation effects in SDSS quasar composite spectra. In a previous work we have shown that the equivalent width EW of the [OIII] {\\lambda}5008{\\AA} line is a reliable indicator of the inclination of the accretion disk. Here, we have selected a sample of ~15,000 quasars from the SDSS 7th Data Release and divided it in sub-samples with different values of EW([OIII]). We find inclination effects both on broad and narrow quasars emission lines, among which an increasing broadening from low to high EW for the broad lines and a decreasing importance of the blue component for the narrow lines. These effects are naturally explained with a variation of source inclination from nearly face-on to edge-on, confirming the goodness of EW([OIII]) as an orientation indicator. Moreover, we suggest that orientation effects could explain, at least partially, the origin of the anticorrelation between [OIII] and FeII intensities, i.e. the well known Eigenvector 1.

  7. Orientation effects on spectral emission features of quasars

    Science.gov (United States)

    Bisogni, Susanna; Marconi, Alessandro; Risaliti, Guido

    2017-01-01

    We present an analysis of the orientation effects in Sloan Digital Sky Survey (SDSS) quasar composite spectra. In a previous work, we have shown that the equivalent width (EW) of the [O III] λ5007 Å (vacuum rest wavelength 5008.24 Å) line is a reliable indicator of the inclination of the accretion disc. Here, we have selected a sample of ˜12 000 quasars from the SDSS 7th Data Release and divided it in subsamples with different values of EW_{[{O {III}]}}. We find inclination effects both on broad and narrow quasars emission lines, among which an increasing broadening from low to high EW for the broad lines and a decreasing importance of the blue component for the narrow lines. These effects are naturally explained with a variation of source inclination from nearly face-on to edge-on, confirming the goodness of EW_{[{O {III}]}} as an orientation indicator. Moreover, we suggest that orientation effects could explain, at least partially, the origin of the anticorrelation between [O III] and Fe II intensities, i.e. the well-known eigenvector 1.

  8. Synergistic effect of silicone and MFAPP on flame retardancy in epoxy resin%有机硅与聚磷酸铵在环氧树脂基体中的协效阻燃性

    Institute of Scientific and Technical Information of China (English)

    吴唯; 阮明珠; 王铮; 姜晨晨

    2015-01-01

    The flame retarding synergism of silicone FCA-117 with melamine-coated ammonium polyphosphate(MFAPP)was investigated in epoxy resin.Results show that FCA-117 exhibites synergistic flame-retarding effect with MFAPP.By adding 1% FCA-117,the flame retarding system reaches UL94-V0 rank with only 10% MFAPP;moreover,the side effect on mechanical properties caused by MFAPP reduces.According to thermo-gravimetric analysis(TGA),Fourier transform infrared spectroscopy(FT-IR)and scanning electron microscope( SEM) ,FCA-117 improves the mass and properties of charred layer because of the synergistic effect of silicone and MFAPP during combustion.They degrade to generate ceramic compounds containing phosphorus and silicon elements, which improves the flame-retarding effect by reinforcing mechanical properties and insulating effect of charred layer.%通过将复配阻燃剂有机硅FCA-117引入聚磷酸铵阻燃环氧树脂体系制备了无卤阻燃环氧树脂,研究了有机硅与密胺包覆聚磷酸铵(MFAPP)的协效性对环氧树脂(EP)阻燃性能的影响。研究表明, FCA-117与MFAPP具有明显的协效阻燃作用。添加1%有机硅阻燃剂FCA-117,能够在减少5%MFAPP使用量的同时达到UL94-V0级,并能够降低MFAPP对环氧树脂力学性能带来的负面影响。热重分析( TGA)、傅里叶红外光谱( FT-IR)及扫描电镜( SEM)结果表明,FCA-117的加入可提高残炭量及炭层的性能。这主要是由于有机硅与MFAPP共同作用,在燃烧过程中生成了含有磷、硅元素的复合无机炭层,这种炭层强度更高、阻隔性更好,从而提升了材料的阻燃性能。

  9. Pressure dependence of NO formation in laminar fuel-rich premixed CH4/air flames

    NARCIS (Netherlands)

    van Essen, V. M.; Sepman, A. V.; Mokhov, A. V.; Levinsky, H. B.

    Effects of pressure on NO formation in CH4/air flames at a fixed equivalence ratio of 1.3 are investigated. The axial profiles of temperature, OH, CH, and NO mole fractions are measured using laser-induced fluorescence and compared with one-dimensional flame calculations. The measured and calculated

  10. Piperazine-phosphonate derivatives: their flame retardant and thermal degradation properties on cotton fibers

    Science.gov (United States)

    It has been known that phosphorus-nitrogen system shows greater flame resistance in cotton textiles at a lower level than phosphorus used alone. This research aims to compare the effectiveness of Tetraethyl piperazine-1,4-diyldiphosphonate (TEPP) as a flame retardant (FR) for cotton fabric to a prev...

  11. Firefighters and flame retardant activism.

    Science.gov (United States)

    Cordner, Alissa; Rodgers, Kathryn M; Brown, Phil; Morello-Frosch, Rachel

    2015-02-01

    In the past decade, exposure to flame retardant chemicals has become a pressing health concern and widely discussed topic of public safety for firefighters in the United States. Working through local, state, and national unions and independent health and advocacy organizations, firefighters have made important contributions to efforts to restrict the use of certain flame retardants. Firefighters are key members in advocacy coalitions dedicated to developing new environmental health regulations and reforming flammability standards to reflect the best available fire science. Their involvement has been motivated by substantiated health concerns and critiques of deceptive lobbying practices by the chemical industry. Drawing on observations and interviews with firefighters, fire safety experts, and other involved stakeholders, this article describes why firefighters are increasingly concerned about their exposure to flame retardant chemicals in consumer products, and analyzes their involvement in state and national environmental health coalitions.

  12. New optical method for heat flux measurements in stagnation point laminar methane/air flames and hydrogen/methane/air flames using thermographic phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Elmnefi, Mohamed Salem

    2010-11-24

    In the present study, a new optical method was implemented to study the heat transfer from flat stagnation point flames which can be regarded as one-dimensional in the central part. Premixed methane-air flames and hydrogen-methane-air flames were investigated. The effects of burner-to-plate distance and the fresh gas mixture velocity on heat transfer were examined. Experiments were performed using light induced phosphorescence from thermographic phosphors to study the wall temperatures and heat fluxes of nearly one-dimensional flat premixed flames impinging upward normally on a horizontal water cooled circular flat plate. The investigated flames were stoichiometric, lean and rich laminar methane/air flames with different equivalence ratios of {phi} =1, {phi} = 0.75 and {phi} = 1.25 and stoichiometric laminar hydrogen/methane/air flames. Mixtures of air with 10, 25, 50 and 75 % hydrogen in methane (CH{sub 4}) as well as a pure hydrogen flames at ambient pressure were investigated. The central part of this plate was an alumina ceramic plate coated from both sides with chromium doped alumina (ruby) and excited with a Nd:YAG laser or a green light emitting diode (LED) array to measure the wall temperature from both sides and thus the heat flux rate from the flame. The outlet velocity of the gases was varied from 0.1 m/s to 1.2 m/s. The burner to plate distance ranged from 0.5 to 2 times the burner exit diameter (d = 30 mm).The accuracy of the method was evaluated. The measured heat flux indicate the change of the flame stabilization mechanism from a burner stabilized to a stagnation plate stabilized flame. The results were compared to modeling results of a one dimensional stagnation point flow, with a detailed reaction mechanism. In order to prove the model, also measured gas phase temperatures by OH LIF for a stoichiometric stagnation point flame were discussed. It turns out that the flame stabilization mechanism and with it the heat fluxes change from low to high

  13. Droplet and Supercritical Flame Dynamics in Propulsion

    Science.gov (United States)

    2010-03-26

    In order to study the stability of a lifted jet flame by nozzle-generated vortexes, we have developed a chemical explosive mode analysis ( CEMA ) to...runaway can consequently be distinguished. CEMA of the lifted flame shows the existence of two premixed flame fronts, which are difficult to detect

  14. 30 CFR 14.20 - Flame resistance.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Flame resistance. 14.20 Section 14.20 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING, EVALUATION, AND APPROVAL OF... § 14.20 Flame resistance. Conveyor belts for use in underground coal mines must be flame-resistant...

  15. Acoustic power measurements of oscillating flames

    NARCIS (Netherlands)

    Valk, M.

    1981-01-01

    The acoustic power of an oscillating flame is measured. A turbulent premixed propane/air flame is situated near a pressure antinode of a standing wave in a laboratory combustion chamber. This standing wave is generated by a piston. The fluctuating heat release of the flame will supply acoustic power

  16. Hysteresis and transition in swirling nonpremixed flames

    NARCIS (Netherlands)

    Tummers, M.J.; Hübner, A.W.; Veen, van E.H.; Hanjalic, K.; Meer, van der Th.H.

    2009-01-01

    Strongly swirling nonpremixed flames are known to exhibit a hysteresis when transiting from an attached long, sooty, yellow flame to a short lifted blue flame, and vice versa. The upward transition (by increasing the air and fuel flow rates) corresponds to a vortex breakdown, i.e. an abrupt change f

  17. Acoustic power measurements of oscillating flames

    NARCIS (Netherlands)

    Valk, M.

    1981-01-01

    The acoustic power of an oscillating flame is measured. A turbulent premixed propane/air flame is situated near a pressure antinode of a standing wave in a laboratory combustion chamber. This standing wave is generated by a piston. The fluctuating heat release of the flame will supply acoustic power

  18. Environmental Considerations for Flame Resistant Textiles

    Science.gov (United States)

    Virtually all common textiles will ignite and burn. There are mandatory and voluntary cigarette and open-flame ignition regulations to address unreasonable fire risks associated with textile products that require them to be treated with and/or contain flame retardant chemicals to make them flame res...

  19. The i-V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

    KAUST Repository

    Han, Jie

    2016-07-17

    The i-V curve describes the current drawn from a flame as a function of the voltage difference applied across the reaction zone. Since combustion diagnostics and flame control strategies based on electric fields depend on the amount of current drawn from flames, there is significant interest in modeling and understanding i-V curves. We implement and apply a detailed model for the simulation of the production and transport of ions and electrons in one-dimensional premixed flames. An analytical reduced model is developed based on the detailed one, and analytical expressions are used to gain insight into the characteristics of the i-Vcurve for various flame configurations. In order for the reduced model to capture the spatial distribution of the electric field accurately, the concept of a dead zone region, where voltage is constant, is introduced, and a suitable closure for the spatial extent of the dead zone is proposed and validated. The results from the reduced modeling framework are found to be in good agreement with those from the detailed simulations. The saturation voltage is found to depend significantly on the flame location relative to the electrodes, and on the sign of the voltage difference applied. Furthermore, at sub-saturation conditions, the current is shown to increase linearly or quadratically with the applied voltage, depending on the flame location. These limiting behaviors exhibited by the reduced model elucidate the features of i-V curves observed experimentally. The reduced model relies on the existence of a thin layer where charges are produced, corresponding to the reaction zone of a flame. Consequently, the analytical model we propose is not limited to the study of premixed flames, and may be applied easily to others configurations, e.g.~nonpremixed counterflow flames.

  20. Microgravity experiments and numerical studies on ethanol/air spray flames

    Science.gov (United States)

    Thimothée, Romain; Chauveau, Christian; Halter, Fabien; Nicoli, Colette; Haldenwang, Pierre; Denet, Bruno

    2017-01-01

    Spray flames are known to exhibit amazing features in comparison with single-phase flames. The weightless situation offers the conditions in which the spray characteristics can be well controlled before and during combustion. The article reports on a joint experimental/numerical work that concerns ethanol/air spray flames observed in a spherical chamber using the condensation technique of expansion cooling (based on the Wilson cloud chamber principle), under microgravity. We describe the experimental set-up and give details on the creation of a homogeneous and nearly monosized aerosol. Different optical diagnostics are employed successfully to measure the relevant parameters of two-phase combustion. A classical shadowgraphy system is used to track the flame speed propagation and allow us to observe the flame front instability. The complete characterization of the aerosol is performed with a laser diffraction particle size analyser by measuring the droplet diameter and the droplet density number, just before ignition. A laser tomography device allows us to measure the temporal evolution of the droplet displacement during flame propagation, as well as to identify the presence of droplets in the burnt gases. The numerical modelling is briefly recalled. In particular, spray-flame propagation is schematized by the combustion spread in a 2-D lattice of fuel droplets surrounded by an initial gaseous mixture of fuel vapour and air. In its spherical expansion, the spray flame presents a corrugated front pattern, while the equivalent single-phase flame does not. From a numerical point of view, the same phenomena of wrinkles are also observed in the simulations. The front pattern pointed out by the numerical approach is identified as of Darrieus-Landau (DL) type. The droplets are found to trigger the instability. Then, we quantitatively compare experimental data with numerical predictions on spray-flame speed. The experimental results show that the spray-flame speed is of the

  1. Effect of the methyl substitution on the combustion of two methylheptane isomers: Flame chemistry using vacuum-ultraviolet (VUV) photoionization mass spectrometry

    KAUST Repository

    Selim, Hatem

    2015-04-16

    Alkanes with one or more methyl substitutions are commonly found in liquid transportation fuels, so a fundamental investigation of their combustion chemistry is warranted. In the present work, stoichiometric low-pressure (20 Torr) burner-stabilized flat flames of 2-methylheptane and 3-methylheptane were investigated. Flame species were measured via time-of-flight molecular-beam mass spectrometry, with vacuum-ultraviolet (VUV) synchrotron radiation as the ionization source. Mole fractions of major end-products and intermediate species (e.g., alkanes, alkenes, alkynes, aldehydes, and dienes) were quantified axially above the burner surface. Mole fractions of several free radicals were also measured (e.g., CH3, HCO, C2H3, C3H3, and C3H5). Isomers of different species were identified within the reaction pool by an energy scan between 8 and 12 eV at a distance of 2.5 mm away from the burner surface. The role of methyl substitution location on the alkane chain was determined via comparisons of similar species trends obtained from both flames. The results revealed that the change in CH3 position imposed major differences on the combustion of both fuels. Comparison with numerical simulations was performed for kinetic model testing. The results provide a comprehensive set of data about the combustion of both flames, which can enhance the erudition of both fuels combustion chemistry and also improve their chemical kinetic reaction mechanisms. © 2015 American Chemical Society.

  2. Cars Spectroscopy of Propellant Flames

    Science.gov (United States)

    1983-11-01

    Harris, K. Aron, and J. Fendell "N2 and 00 Vibrational CARS and H2 Rotational CARS Spectroscopy of CHI/N20 Flames," Proceedings of the Nineteenth...JANNAF Combustion Meeting, CIIA Publication No. 366, 1982, p 123. 21. K. Aron, L. E. Harris, and J. Fendell , "N and CO Vibrational CARS and H2 Rotational...9 6 5 . p 3 8 4 . . . . . 23. J. Fendell , L. E, Harris, and K. Aron, "Theoretical Calculation of 11 CARS S-Branches for Propellant Flames

  3. Effects of soot absorption coefficient-Planck function correlation on radiative heat transfer in oxygen-enriched propane turbulent diffusion flame

    Science.gov (United States)

    Consalvi, J. L.; Nmira, F.

    2016-03-01

    The main objective of this article is to quantify the influence of the soot absorption coefficient-Planck function correlation on radiative loss and flame structure in an oxygen-enhanced propane turbulent diffusion flame. Calculations were run with and without accounting for this correlation by using a standard k-ε model and the steady laminar flamelet model (SLF) coupled to a joint Probability Density Function (PDF) of mixture fraction, enthalpy defect, scalar dissipation rate, and soot quantities. The PDF transport equation is solved by using a Stochastic Eulerian Field (SEF) method. The modeling of soot production is carried out by using a flamelet-based semi-empirical acetylene/benzene soot model. Radiative heat transfer is modeled by using a wide band correlated-k model and turbulent radiation interactions (TRI) are accounted for by using the Optically-Thin Fluctuation Approximation (OTFA). Predicted soot volume fraction, radiant wall heat flux distribution and radiant fraction are in good agreement with the available experimental data. Model results show that soot absorption coefficient and Planck function are negatively correlated in the region of intense soot emission. Neglecting this correlation is found to increase significantly the radiative loss leading to a substantial impact on flame structure in terms of mean and rms values of temperature. In addition mean and rms values of soot volume fraction are found to be less sensitive to the correlation than temperature since soot formation occurs mainly in a region where its influence is low.

  4. Brominated flame retardant: environmental and exposed individuals' health impact.

    Science.gov (United States)

    Dufour, Patrice; Charlier, Corinne

    2017-04-01

    Since Antiquity, men have used chemicals to protect their goods against fire. Effective and easy to use, brominated flame retardants are used since decades massively in plastic industry. Such like other organohalogenated compounds, brominated flame retardants are very persistent in the environment and able to accumulate along the food chain. Many authors highlight their presence in the environment, in many animal species and in the human serum. Worryingly, man is exposed as soon as the pregnancy and then by the breastfeeding. This exposition may have consequence on our health. Many studies (in vitro, in vivo or epidemiologic) highlight brominated flame retardant negative effects on the endocrine system, mainly on the thyroid function but also on the reproduction, the neurodevelopment in the children and on the metabolism with increasing diabetes risk. If authorities and some big enterprises are aware about the problematic, new studies are needed to confirm previous results, elucidate endocrine disrupting mechanisms and highlight hypothetical synergies with other pollutants such like PCBs.

  5. Jet flow and premixed jet flame control by plasma swirler

    Science.gov (United States)

    Li, Gang; Jiang, Xi; Zhao, Yujun; Liu, Cunxi; Chen, Qi; Xu, Gang; Liu, Fuqiang

    2017-04-01

    A swirler based on dielectric barrier discharge plasma actuators is designed and its effectiveness in both jet flow and premixed jet flame control is demonstrated. In contrast to traditional spanwise-oriented actuators, plasma actuators are placed along the axial direction of the injector to induce a circumferential velocity to the main flow and create a swirl flow without any insertion or moving part. In the DBD plasma swirl injector, the discharge does not ignite the mixture nor does it induce flashback. Flame visualization is obtained by cameras while velocity profiles are obtained by Laser Doppler Anemometry measurements. The results obtained indicate the effectiveness of the new design.

  6. Markstein Numbers of Negatively-Stretched Premixed Flames: Microgravity Measurements and Computations

    Science.gov (United States)

    Ibarreta, Alfonso F.; Driscoll, James F.; Feikema, Douglas A.; Salzman, Jack (Technical Monitor)

    2001-01-01

    The effect of flame stretch, composed of strain and curvature, plays a major role in the propagation of turbulent premixed flames. Although all forms of stretch (positive and negative) are present in turbulent conditions, little research has been focused on the stretch due to curvature. The present study quantifies the Markstein number (which characterizes the sensitivity of the flame propagation speed to the imposed stretch rate) for an inwardly-propagating flame (IPF). This flame is of interest because it is negatively stretched, and is subjected to curvature effects alone, without the competing effects of strain. In an extension of our previous work, microgravity experiments were run using a vortex-flame interaction to create a pocket of reactants surrounded by an IPF. Computations using the RUN-1DL code of Rogg were also performed in order to explain the measurements. It was found that the Markstein number of an inwardly-propagating flame, for both the microgravity experiment and the computations, is significantly larger than that of an outwardly-propagating flame. Further insight was gained by running the computations for the simplified (hypothetical) cases of one step chemistry, unity Lewis number, and negligible heat release. Results provide additional evidence that the Markstein numbers associated with strain and curvature have different values.

  7. Effects of OMMT-halogen-antimony Flame Retardant on the PA6/LGF Composites%OMMT -卤-锑阻燃体系对 PA6/LGF 复合材料的影响

    Institute of Scientific and Technical Information of China (English)

    单辰杰; 左晓玲; 江来; 郝智; 郭建兵

    2014-01-01

    利用有机蒙脱土( OMMT)协同溴代环氧树脂( BER)、三氧化二锑( Sb2 O3)通过熔融插层法制备OMMT-卤-锑阻燃长玻纤增强尼龙6复合材料(OMMT/FR/PA6/LGF),通过极限氧指数(LOI)、垂直燃烧(UL-94)、锥形量热分析(CONE)、热失重分析( TGA)、扫描电镜( SEM)等方法研究了不同质量比的OMMT-卤-锑阻燃体系对OMMT/FR/PA6/LGF复合材料成炭、阻燃、燃烧、力学性能以及热稳定性的影响。结果表明,当OMMT添加量为2%, BER/Sb2 O3添加量为10%时,二者表现出优异的协同阻燃效应,不仅能促使OMMT/FR/PA6/LGF复合材料生成的炭层结构最为致密、均匀、连续,氧指数值最高且能保持FV-0级,还对复合材料的力学性能影响相对最小。%Long-glass -fiber reinforced polyamide 6 composites were flame -retarded with OMMT -halogen -antimony flame retardant containing organic montmorillonite (OMMT) synchronized with brominated epoxy resins (BER) and antimony trioxide ( Sb2 O3 ) were prepared via melting processing.The effects of different mass ratio of OMMT -halogen -antimony on char formation , flame retardant , combustion , mechanical properties of OMMT/FR/PA6/LGF composites were studied by limited oxygen index measurements (LOI), vertical burning test (UL-94), cone calorimeter test (CONE), thermogravimetric analysis (TGA) and scanning electronic microscopy (SEM).The results demonstrated that both OMMT and BER/Sb2 O3 exhibited excellent effect of synchronized flame retardant , for the samples containing 2wt%OMMT synchronized with 10wt%BER/Sb2 O3 , which not only promoted OMMT/FR/PA6/LGF composites to form a more compacted, homogeneous and continuous chars layer structure and owned the highest LOI value and FV -0 rating, but also had the least effect on composites'mechanical property relatively.

  8. Cool flames at terrestrial, partial, and near-zero gravity

    Energy Technology Data Exchange (ETDEWEB)

    Foster, Michael; Pearlman, Howard [Department of Mechanical Engineering and Mechanics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States)

    2006-10-15

    Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra<600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; and reduced gravity, {approx}10{sup -2}g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350? deg C (593-623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive-diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results. (author)

  9. Metallic iron nanoparticles: Flame synthesis, characterization and magnetic properties

    Institute of Scientific and Technical Information of China (English)

    Yunfeng Li; Yanjie Hu; Guangjian Huang; Chunzhong Li

    2013-01-01

    Metallic iron (Fe) nanoparticles (NPs) with a typical core-shell structure have been prepared by a simple and continuous flame spray pyrolysis (FSP) method,which are stabilized by the corresponding Fe3O4 shell with a thickness of 4-6 nm.The size of metallic Fe cores is about 30-80 nm.The core-shell structured iron NPs show an air stability as long as one month as a result of the protection of oxide shell.Through the control of the residence time of materials in flame and flame atmosphere,metallic Fe and iron oxides are obtained,showing a better external magnetic field responsibility.It is concluded that the evolution of morphology and composition of flame-made magnetic NPs could be attributed to the competition mechanism between reduction and oxidation reactions of in situ flame combustion,which offers more choices and better effective design strategy for the synthesis of advanced functional materials via FSP techniques.

  10. Effect of feature-selective attention on neuronal responses in macaque area MT.

    Science.gov (United States)

    Chen, X; Hoffmann, K-P; Albright, T D; Thiele, A

    2012-03-01

    Attention influences visual processing in striate and extrastriate cortex, which has been extensively studied for spatial-, object-, and feature-based attention. Most studies exploring neural signatures of feature-based attention have trained animals to attend to an object identified by a certain feature and ignore objects/displays identified by a different feature. Little is known about the effects of feature-selective attention, where subjects attend to one stimulus feature domain (e.g., color) of an object while features from different domains (e.g., direction of motion) of the same object are ignored. To study this type of feature-selective attention in area MT in the middle temporal sulcus, we trained macaque monkeys to either attend to and report the direction of motion of a moving sine wave grating (a feature for which MT neurons display strong selectivity) or attend to and report its color (a feature for which MT neurons have very limited selectivity). We hypothesized that neurons would upregulate their firing rate during attend-direction conditions compared with attend-color conditions. We found that feature-selective attention significantly affected 22% of MT neurons. Contrary to our hypothesis, these neurons did not necessarily increase firing rate when animals attended to direction of motion but fell into one of two classes. In one class, attention to color increased the gain of stimulus-induced responses compared with attend-direction conditions. The other class displayed the opposite effects. Feature-selective activity modulations occurred earlier in neurons modulated by attention to color compared with neurons modulated by attention to motion direction. Thus feature-selective attention influences neuronal processing in macaque area MT but often exhibited a mismatch between the preferred stimulus dimension (direction of motion) and the preferred attention dimension (attention to color).

  11. Application of validated radiation model in flame spread rate over solid fuels

    Science.gov (United States)

    Ivisic, Ivan

    In this thesis the radiative effects of opposed flow flames spreading over solid fuels are discussed as well as the coupling of a radiation and CFD program. The coupled programs are used to show the radiative heat transfer mechanisms and how they affect the flame globally. A radiation program is used to calculate radiation properties of the flame such as the heat flux distribution, net heat flow, and mean Plank absorptivity constant for a particular flame. The radiation program imports the temperature fields from a CFD program. Trends in the mean Plank absorptivity constant with varying ambient conditions are analyzed and an application of the radiation program to simulate a physical radiometer is demonstrated for a test case. The CFD program can import radiation results to help improve the accuracy of the simulation. A script was written to automate the update process to produce more accurate results for flame simulations. Flux distributions, stability and relative error are analyzed to show the coupled programs are producing results within an acceptable error. Trends in error and stability are discussed and stable regions with low enough error are determined. The coupled programs are used to gather data on flame spread rate and find differences in flame structure and properties of neglecting certain radiation mechanisms. No radiation included produced the hottest fastest moving flame, while no gas to surface radiation produced the coolest flame. Including the gas to surface radiation produced a slightly hotter faster moving flame. This trend was studied across different opposed flow velocities and sample widths. The radiative heat fluxes are analyzed for the cases as well. All the flame simulations in this thesis were run for a microgravity, 21% oxygen, and PMMA fuel.

  12. Straining and wrinkling processes during turbulence-premixed flame interaction measured using temporally-resolved diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, Adam M.; Driscoll, James F. [Department of Aerospace Engineering, The University of Michigan, Ann Arbor, MI 48109 (United States)

    2009-12-15

    The dynamical processes of flame surface straining and wrinkling that occur as turbulence interacts with a premixed flame were measured using cinema-stereoscopic PIV (CS-PIV) and orthogonal-plane cinema-stereoscopic PIV (OPCS-PIV). These diagnostics provided temporally resolved measurements of turbulence-flame interaction at frame rates of up to 3 kHz and spatial resolutions as small as 280{mu} m. Previous descriptions of flame straining and wrinkling have typically been derived based on a canonical interaction between a pair of counter-rotating vortices and a planar flame surface. However, it was found that this configuration did not properly represent real turbulence-flame interaction. Interactions resembling the canonical configuration were observed in less than 10% of the recorded frames. Instead, straining and wrinkling were generally caused more geometrically complex turbulence, consisting of large groups of structures that could be multiply curved and intertwined. The effect of the interaction was highly dependent on the interaction geometry. Furthermore, even when the turbulence did exist in the canonical geometry, the straining and wrinkling of the flame surface were not well characterized by the vortical structures. A new mechanistic description of the turbulence-flame interaction was therefore identified and confirmed by the measurements. In this description, flame surface straining is caused by coherent structures of fluid-dynamic strain-rate (strain-rate structures). The role of vortical structures is to curve existing flame surface, creating wrinkles. By simultaneously considering both forms of turbulent structure, turbulence-flame interactions in both the canonical configuration and more complex geometries could be understood. (author)

  13. New Flexible Flame Retardant Coatings Based on Siloxane Resin and Ethylene-Vinyl Chloride Copolymer

    Directory of Open Access Journals (Sweden)

    Dorota Wesolek

    2016-12-01

    Full Text Available This work presents the effectiveness of a phosphorus-containing flame retardant based on siloxane resin and ethylene-vinyl chloride copolymer as a back-coating of fabrics. The possibility of improving flame retardant efficiency of this composition by introducing fumed silica, montmorillonite, carbon nanotubes, and graphite was evaluated. The effect of each additive on the efficiency of the composition was examined separately. Flammability tests of flame retardant-coated fabrics (natural and synthetic were carried out using pyrolysis combustion flow calorimetry (PCFC, cone calorimetry, and limiting oxygen index determination. An assessment of the ignitability of upholstered furniture containing flame retardant fabric, resistance to washing, antifungal activity, and some of the utility properties of the final newly-developed flame-retardant coating was conducted.

  14. FLAME MONITORING IN POWER STATION BOILERS USING IMAGE PROCESSING

    Directory of Open Access Journals (Sweden)

    K. Sujatha

    2012-05-01

    Full Text Available Combustion quality in power station boilers plays an important role in minimizing the flue gas emissions. In the present work various intelligent schemes to infer the flue gas emissions by monitoring the flame colour at the furnace of the boiler are proposed here. Flame image monitoring involves capturing the flame video over a period of time with the measurement of various parameters like Carbon dioxide (CO2, excess oxygen (O2, Nitrogen dioxide (NOx, Sulphur dioxide (SOx and Carbon monoxide (CO emissions plus the flame temperature at the core of the fire ball, air/fuel ratio and the combustion quality. Higher the quality of combustion less will be the flue gases at the exhaust. The flame video was captured using an infrared camera. The flame video is then split up into the frames for further analysis. The video splitter is used for progressive extraction of the flame images from the video. The images of the flame are then pre-processed to reduce noise. The conventional classification and clustering techniques include the Euclidean distance classifier (L2 norm classifier. The intelligent classifier includes the Radial Basis Function Network (RBF, Back Propagation Algorithm (BPA and parallel architecture with RBF and BPA (PRBFBPA. The results of the validation are supported with the above mentioned performance measures whose values are in the optimal range. The values of the temperatures, combustion quality, SOx, NOx, CO, CO2 concentrations, air and fuel supplied corresponding to the images were obtained thereby indicating the necessary control action taken to increase or decrease the air supply so as to ensure complete combustion. In this work, by continuously monitoring the flame images, combustion quality was inferred (complete/partial/incomplete combustion and the air/fuel ratio can be automatically varied. Moreover in the existing set-up, measurements like NOx, CO and CO2 are inferred from the samples that are collected periodically or by

  15. Effect of sow history features on growth and feed intake in grow-finish pigs

    NARCIS (Netherlands)

    Sell-Kubiak, E.B.; Knol, E.F.; Bijma, P.

    2012-01-01

    The sow provides a specific environment to her offspring during gestation and lactation. Certain features in the early life of the sow (sow history features) may affect her ability to deliver and feed a healthy litter. In genetic analyses of grow-finish traits, these effects are estimated as common

  16. Featuring Old/New Recognition: The Two Faces of the Pseudoword Effect

    Science.gov (United States)

    Joordens, Steve; Ozubko, Jason D.; Niewiadomski, Marty W.

    2008-01-01

    In his analysis of the pseudoword effect, [Greene, R.L. (2004). Recognition memory for pseudowords. "Journal of Memory and Language," 50, 259-267.] suggests nonwords can feel more familiar that words in a recognition context if the orthographic features of the nonword match well with the features of the items presented at study. One possible…

  17. Effect of sow history features on growth and feed intake in grow-finish pigs

    NARCIS (Netherlands)

    Sell-Kubiak, E.B.; Knol, E.F.; Bijma, P.

    2012-01-01

    The sow provides a specific environment to her offspring during gestation and lactation. Certain features in the early life of the sow (sow history features) may affect her ability to deliver and feed a healthy litter. In genetic analyses of grow-finish traits, these effects are estimated as common

  18. Advanced monitoring of industrial burners based on fluctuating flame signals

    Energy Technology Data Exchange (ETDEWEB)

    A. Sanz; J. Ballester; R. Hernandez; L.M. Cerecedo [University of Zaragoza, Zaragoza (Spain). Fluid Mechanics Group/LITEC

    2008-06-15

    The present work explores the potential of pressure and radiation sensors for the advanced monitoring/control of industrial flames. These instruments are rugged, non-intrusive and non-expensive and might be used in routine plant operation to obtain direct information from the flame. However, further research is needed to assess the existence of relationships among their outputs and operating conditions as well as to define suitable methods for signal processing. Those aspects have been addressed by means of a thorough experimental programme in a model industrial burner. Parametric analysis of flame signals recorded for a broad range of operating conditions revealed that they varied widely with the actual combustion state. In order to perform a systematic study, different correlation techniques were tried. Multiple regression methods provided some insight into mutual influences among different variables, although only in case of linear dependences. Artificial neural networks have been used as a more versatile type of algorithms, suitable for complex functional forms between input and output variables. Remarkably good results were obtained when NOx emissions or some burner settings were estimated from selected features of the flame signals, supporting their applicability for the development of advanced diagnostic methods in combustion processes. 40 refs., 13 figs., 3 tabs.

  19. Nanotechnology finding its way into flame retardancy

    Energy Technology Data Exchange (ETDEWEB)

    Schartel, Bernhard, E-mail: bernhard.schartel@bam.de [BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin (Germany)

    2014-05-15

    Nanotechnology is one of the key technologies of the 21{sup st} century. The exploitation of 'new' effects that arise from materials structured on the nano-scale has also been proposed successfully for flame retardancy of polymers since the end of the 90s. Of all of the approaches these include, at this time the use of nanocomposites offers the best potential for industrial application, also some other ideas are sketched, such as using electrospun nanofibers mats or layer-by-layer deposits as protection coatings, as well as sub-micrometer multilayer coatings as effective IR-mirrors. The general phenomena, inducing a flow limit in the pyrolysing melt and changing the fire residue, are identified in nanocomposites. Key experiments are performed such as quasi online investigation of the protection layer formation to understand what is going on in detail. The flame retardancy mechanisms are discussed and their impact on fire behaviour quantified. With the latter, the presentation pushes forward the state of the art. For instance, the heat shielding is experimentally quantified for a layered silicate epoxy resin nanocomposite proving that it is the only import mechanism controlling the reduction in peak heat release rate in the investigated system for different irradiations. The flame retardancy performance is assessed comprehensively illuminating not only the strengths but also the weak points of the concepts. Guidelines for materials development are deduced and discussed. Apart from inorganic fillers (layered silicate, boehmite, etc.) not only carbon nanoobjects such as multiwall carbon nanotubes, multilayer graphene and graphene are investigated, but also nanoparticles that are more reactive and harbor the potential for more beneficial interactions with the polymer matrix.

  20. Analysis of flame acceleration in open or vented obstructed pipes

    Science.gov (United States)

    Bychkov, Vitaly; Sadek, Jad; Akkerman, V'yacheslav

    2017-01-01

    While flame propagation through obstacles is often associated with turbulence and/or shocks, Bychkov et al. [V. Bychkov et al., Phys. Rev. Lett. 101, 164501 (2008), 10.1103/PhysRevLett.101.164501] have revealed a shockless, conceptually laminar mechanism of extremely fast flame acceleration in semiopen obstructed pipes (one end of a pipe is closed; a flame is ignited at the closed end and propagates towards the open one). The acceleration is devoted to a powerful jet flow produced by delayed combustion in the spaces between the obstacles, with turbulence playing only a supplementary role in this process. In the present work, this formulation is extended to pipes with both ends open in order to describe the recent experiments and modeling by Yanez et al. [J. Yanez et al., arXiv:1208.6453] as well as the simulations by Middha and Hansen [P. Middha and O. R. Hansen, Process Safety Prog. 27, 192 (2008) 10.1002/prs.10242]. It is demonstrated that flames accelerate strongly in open or vented obstructed pipes and the acceleration mechanism is similar to that in semiopen ones (shockless and laminar), although acceleration is weaker in open pipes. Starting with an inviscid approximation, we subsequently incorporate hydraulic resistance (viscous forces) into the analysis for the sake of comparing its role to that of a jet flow driving acceleration. It is shown that hydraulic resistance is actually not required to drive flame acceleration. In contrast, this is a supplementary effect, which moderates acceleration. On the other hand, viscous forces are nevertheless an important effect because they are responsible for the initial delay occurring before the flame acceleration onset, which is observed in the experiments and simulations. Accounting for this effect provides good agreement between the experiments, modeling, and the present theory.

  1. Discriminative feature representation: an effective postprocessing solution to low dose CT imaging

    Science.gov (United States)

    Chen, Yang; Liu, Jin; Hu, Yining; Yang, Jian; Shi, Luyao; Shu, Huazhong; Gui, Zhiguo; Coatrieux, Gouenou; Luo, Limin

    2017-03-01

    This paper proposes a concise and effective approach termed discriminative feature representation (DFR) for low dose computerized tomography (LDCT) image processing, which is currently a challenging problem in medical imaging field. This DFR method assumes LDCT images as the superposition of desirable high dose CT (HDCT) 3D features and undesirable noise-artifact 3D features (the combined term of noise and artifact features induced by low dose scan protocols), and the decomposed HDCT features are used to provide the processed LDCT images with higher quality. The target HDCT features are solved via the DFR algorithm using a featured dictionary composed by atoms representing HDCT features and noise-artifact features. In this study, the featured dictionary is efficiently built using physical phantom images collected from the same CT scanner as the target clinical LDCT images to process. The proposed DFR method also has good robustness in parameter setting for different CT scanner types. This DFR method can be directly applied to process DICOM formatted LDCT images, and has good applicability to current CT systems. Comparative experiments with abdomen LDCT data validate the good performance of the proposed approach. This research was supported by National Natural Science Foundation under grants (81370040, 81530060), the Fundamental Research Funds for the Central Universities, and the Qing Lan Project in Jiangsu Province.

  2. Imaging Invisible Flames Without Additives

    Science.gov (United States)

    Weiland, Karen J.

    1996-01-01

    Image intensifiers, video cameras, and image-data-processing computers used to study combustion. Possible to view and analyze methane, hydrogen, and other flames dim or invisible to human eye and difficult to image by use of conventional photographic and video cameras.

  3. Olympic Flame Burning In Athens

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正>At 6:00pm March 25 (Beijing time), 2004 Athens Olympic flame was lit in Greece’s ancient sanctuary, indicating that the torch relay started.The torch relay, established at the Berlin Games in 1936, will for the first time visit all five continents

  4. Flame monitoring enhances burner management

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, T.; Bailey, R.; Fuller, T.; Daw, S.; Finney, C.; Stallings, J. [Babcock & Wilcox Research Center (USA)

    2003-02-01

    A new burner monitoring and diagnostic system called Flame Doctor offers users a more precise and discriminating understanding of burner conditions. Alpha testing on Unit 4 at AmerenUE's Meramec power plant in St. Louis, MO, USA and Beta testing is underway at plants owned by Dynegy and Allegheny Energy. 6 refs., 3 figs.

  5. Turbulent Oxygen Flames in Type Ia Supernovae

    CERN Document Server

    Aspden, A J; Woosley, S E; 10.1088/0004-637X/730/2/144

    2011-01-01

    In previous studies, we examined turbulence-flame interactions in carbon-burning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damk\\"ohler numbers ($\\Da_{16}$) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when $\\Da_{16}1$, turbulence enhances heat transfer and drives the propagation of a flame that is {\\em narrower} than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen turbulent flame with complex compound structure. The simulations do not ...

  6. Flame Reconstruction Using Synthetic Aperture Imaging

    CERN Document Server

    Murray, Preston; Tree, Dale; Truscott, Tadd

    2011-01-01

    Flames can be formed by burning methane (CH4). When oxygen is scarce, carbon particles nucleate into solid particles called soot. These particles emit photons, making the flame yellow. Later, methane is pre-mixed with air forming a blue flame; burning more efficiently, providing less soot and light. Imaging flames and knowing their temperature are vital to maximizing efficiency and validating numerical models. Most temperature probes disrupt the flame and create differences leading to an inaccurate measurement of the flame temperature. We seek to image the flame in three dimensions using synthetic aperture imaging. This technique has already successfully measured velocity fields of a vortex ring [1]. Synthetic aperture imaging is a technique that views one scene from multiple cameras set at different angles, allowing some cameras to view objects that are obscured by others. As the resulting images are overlapped different depths of the scene come into and out of focus, known as focal planes, similar to tomogr...

  7. Flex-flame burner and combustion method

    Science.gov (United States)

    Soupos, Vasilios; Zelepouga, Serguei; Rue, David M.; Abbasi, Hamid A.

    2010-08-24

    A combustion method and apparatus which produce a hybrid flame for heating metals and metal alloys, which hybrid flame has the characteristic of having an oxidant-lean portion proximate the metal or metal alloy and having an oxidant-rich portion disposed above the oxidant lean portion. This hybrid flame is produced by introducing fuel and primary combustion oxidant into the furnace chamber containing the metal or metal alloy in a substoichiometric ratio to produce a fuel-rich flame and by introducing a secondary combustion oxidant into the furnace chamber above the fuel-rich flame in a manner whereby mixing of the secondary combustion oxidant with the fuel-rich flame is delayed for a portion of the length of the flame.

  8. An evolution equation modeling inversion of tulip flames

    Energy Technology Data Exchange (ETDEWEB)

    Dold, J.W. [Univ. of Bristol (United Kingdom). School of Mathematics; Joulin, G. [E.N.S.M.A., Poitiers (France). Lab. d`Energetique et de Detonique

    1995-02-01

    The authors attempt to reduce the number of physical ingredients needed to model the phenomenon of tulip-flame inversion to a bare minimum. This is achieved by synthesizing the nonlinear, first-order Michelson-Sivashinsky (MS) equation with the second order linear dispersion relation of Landau and Darrieus, which adds only one extra term to the MS equation without changing any of its stationary behavior and without changing its dynamics in the limit of small density change when the MS equation is asymptotically valid. However, as demonstrated by spectral numerical solutions, the resulting second-order nonlinear evolution equation is found to describe the inversion of tulip flames in good qualitative agreement with classical experiments on the phenomenon. This shows that the combined influences of front curvature, geometric nonlinearity and hydrodynamic instability (including its second-order, or inertial effects, which are an essential result of vorticity production at the flame front) are sufficient to reproduce the inversion process.

  9. A turbulent premixed flame on fractal-grid generated turbulence

    CERN Document Server

    Soulopoulos, Nikos; Beyrau, Frank; Hardalupas, Yannis; Taylor, A M K P; Vassilicos, J Christos

    2010-01-01

    A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent combustion experiment. In contrast to the power law decay of a standard turbulence grid, the downstream turbulence intensity of the fractal grid increases until it reaches a peak at some distance from the grid before it finally decays. The effective mesh size and the solidity are the same as those of a standard square mesh grid with which it is compared. It is found that, for the same flow rate and stoichiometry, the fractal generated turbulence enhances the burning rate and causes the flame to further increase its area. Using a flame fractal model, an attempt is made to highlight differences between the flames established at the two different turbulent fields.

  10. Effect of sow history features on growth and feed intake in grow-finish pigs.

    Science.gov (United States)

    Sell-Kubiak, E; Knol, E F; Bijma, P

    2012-01-01

    The sow provides a specific environment to her offspring during gestation and lactation. Certain features in the early life of the sow (sow history features) may affect her ability to deliver and feed a healthy litter. In genetic analyses of grow-finish traits, these effects are estimated as common litter or permanent sow effects. The objective of this research was to identify sow history features that affect the growth rate (GR) and feed intake (FI) of her offspring during the grow-finish stage. Data from 17,743 grow-finish pigs, coming from 604 sires and 681 crossbred sows, were recorded between May 2001 and February 2010 at the experimental farm of the Institute for Pig Genetics (Beilen, the Netherlands). The grow-finish stage was divided into 2 phases (phase 1: 26 to 75 kg; phase 2: 75 to 115 kg). The sow history features were birth litter size, birth year and season, birth farm, weaning age, age of transfer to the experimental farm, and age at first insemination. The sow features were added to the basic model one at a time to study their effect on the grow-finish traits of the pigs. Subsequently, significant sow features (P finish pigs by 0.1 g/d. The heritability estimates for GR and FI (only in phase 2 of the grow-finish stage) decreased after adding the sow features to the model. No differences were found in estimates of the common litter effects between the basic model and the model with all significant sow features. The estimates of the permanent sow effect changed for FI from 0.03 (basic model) to 0.00 (model with sow features), and for FI in phase 1, the permanent sow effect decreased from 0.03 (basic model) to 0.01 (model with sow features). In conclusion, selected sow features do affect the grow-finish traits of the pigs, but their estimates are small and explain only a small proportion of the differences in the GR and FI of grow-finish pigs. The sow features partially explained the permanent sow effect of FI-related traits and did not explain the

  11. The discrete regime of flame propagation

    Science.gov (United States)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew

    The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment

  12. EPDM-g-MAH对PP膨胀阻燃材料性能的影响%Effect of maleic anhydride grafted EPDM on properties of intumescent flame retardant PP materials

    Institute of Scientific and Technical Information of China (English)

    闫怀文; 危加丽; 尹波; 杨鸣波

    2012-01-01

    采用氮磷膨胀型阻燃剂制备了无卤阻燃聚丙烯(PP)材料,研究了马来酸酐(MAH)接枝三元乙丙橡胶(EPDM)(EPDM-g-MAH)对PP无卤阻燃材料性能的影响.结果表明:加入EPDM-g-MAH可提高阻燃剂和PP基体间的界面作用,降低试样在燃烧过程中的熔融滴落现象,且加入EPDM-g-MAH提高了阻燃PP的力学性能.此外,加入EPDM-g-MAH可提高PP无卤阻燃材料在高温(600~800℃)下的炭层热稳定性以及材料的最大热分解速率,但会降低材料的最大热分解温度.因此,少量的EPDM-g-MAH可以提高PP无卤阻燃材料的极限氧指数(LOI),但当w(EPDM-g-MAH)超过10%时,PP无卤阻燃材料的LOI下降,阻燃性能降低.%The authors prepared halogen-free flame retardant polypropylene (PP) by introducing intumescent flame retardant made from nitrogen phosphorus compound, and studied the effect of content of maleic anhydride grafted ethylene propylene diene monomer(EPDM-g-MAH) on properties of the PP materials. The results show that adding EPDM-g-MAH can enhance interfacial interaction between PP matrix and the flame retardant, reduce melt dripping of the specimens during combustion process and improve mechanical properties of the PP materials. The addition of EPDM-g-MAH can raise thermal stability of the carbon layer at high temperature (600-800 ℃) and the maximum thermal decomposition rate but lowers the maximum thermal decomposition temperature of the PP materials. As a result, adding a small quantity of EPDM-g-MAH can make the limited oxygen index (LOF) of the PP materials augment However, the LOI decreases and the flame retardancy of the PP material declines when the mass content of EPDM-g-MAH exceeds 10%.

  13. 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

  14. A flame particle tracking analysis of turbulence–chemistry interaction in hydrogen–air premixed flames

    KAUST Repository

    Uranakara, Harshavardhana A.

    2015-11-21

    Interactions of turbulence, molecular transport, and energy transport, coupled with chemistry play a crucial role in the evolution of flame surface geometry, propagation, annihilation, and local extinction/re-ignition characteristics of intensely turbulent premixed flames. This study seeks to understand how these interactions affect flame surface annihilation of lean hydrogen–air premixed turbulent flames. Direct numerical simulations (DNSs) are conducted at different parametric conditions with a detailed reaction mechanism and transport properties for hydrogen–air flames. Flame particle tracking (FPT) technique is used to follow specific flame surface segments. An analytical expression for the local displacement flame speed (Sd) of a temperature isosurface is considered, and the contributions of transport, chemistry, and kinematics on the displacement flame speed at different turbulence-flame interaction conditions are identified. In general, the displacement flame speed for the flame particles is found to increase with time for all conditions considered. This is because, eventually all flame surfaces and their resident flame particles approach annihilation by reactant island formation at the end of stretching and folding processes induced by turbulence. Statistics of principal curvature evolving in time, obtained using FPT, suggest that these islands are ellipsoidal on average enclosing fresh reactants. Further examinations show that the increase in Sd is caused by the increased negative curvature of the flame surface and eventual homogenization of temperature gradients as these reactant islands shrink due to flame propagation and turbulent mixing. Finally, the evolution of the normalized, averaged, displacement flame speed vs. stretch Karlovitz number are found to collapse on a narrow band, suggesting that a unified description of flame speed dependence on stretch rate may be possible in the Lagrangian description.

  15. Acoustic excitation of diffusion flames with coherent structure in a plane shear layer.; Effects of acoustic excitation on combustion properties; Soshiki kozo wo tomonau sendan kakusan kaen no onkyo reiki.; Onkyo reiki ni yoru nensho tokusei no henka

    Energy Technology Data Exchange (ETDEWEB)

    Ishino, Y.; Kojima, T.; Oiwa, N.; Yamaguchi, S. [Nagoya Institute of Technology, Nagoya (Japan)

    1993-10-25

    This paper reports on experiments for acoustic excitation of plane shear structured flame. Flows of air separated into the higher velocity side and the lower velocity side by a partition on the center of a flow path merge at the measuring point to form a mixed layer with coherent structure. Fuel is supplied to this mixed layer with the flows so adjusted that the generated flame will attach to the partition on the lower velocity side. Acoustic excitation (at a sound pressure level of 100 dB to 120 dB) is performed in a speaker fitted on a wall on the higher velocity side. The paper mentions the results of the experiments as follows: the acoustic excitation produces such changes to diffusion flame in the plane shear layer as shorter flame and blue flame combustion and clarification of flame structures; as seen from spectral characteristics of temperature change in the flames, a flame acoustically excited strongly presents remarkable improvements in periodicity of the structure; as seen from sound pressure distribution in the flow direction at the measuring point, the flame zone of the flame acoustically excited strongly is positioned at the middle of the node and loop of a standing wave. 6 refs., 9 figs., 1 tab.

  16. Combustion characteristics of natural gas-hydrogen hybrid fuel turbulent diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    El-Ghafour, S.A.A.; El-dein, A.H.E.; Aref, A.A.R. [Mechanical Power Engineering Department, Faculty of Engineering, Suez Canal University, Port-Said (Egypt)

    2010-03-15

    Combustion characteristics of natural gas - hydrogen hybrid fuel were investigated experimentally in a free jet turbulent diffusion flame flowing into a slow co-flowing air stream. Experiments were carried out at a constant jet exit Reynolds number of 4000 and with a wide range of NG-H{sub 2} mixture concentrations, varied from 100%NG to 50%NG-50% H{sub 2} by volume. The effect of hydrogen addition on flame stability, flame length, flame structure, exhaust species concentration and pollutant emissions was conducted. Results showed that, hydrogen addition sustains a progressive improvement in flame stability and reduction in flame length, especially for relatively high hydrogen concentrations. Hydrogen-enriched flames found to have a higher combustion temperatures and reactivity than natural gas flame. Also, it was found that hydrogen addition to natural gas is an ineffective strategy for NO and CO reduction in the studied range, while a significant reduction in the %CO{sub 2} molar concentration by about 30% was achieved. (author)

  17. Flame retardant wool using zirconium oxychloride in various acidic media optimized by RSM

    Energy Technology Data Exchange (ETDEWEB)

    Forouharshad, M., E-mail: Forouharmahdi@gmail.com [Textile Department, Islamic Azad University South Tehran Branch, Tehran (Iran, Islamic Republic of); Montazer, M., E-mail: tex5mm@aut.ac.ir [Textile Department, Center of Excellence, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Moghadam, M.B. [Department of Statistics, Allameh-Tabataba' i University, Tehran (Iran, Islamic Republic of); Saligheh, O. [Textile Department, Islamic Azad University South Tehran Branch, Young Researchers Club, Tehran (Iran, Islamic Republic of)

    2011-03-20

    Research highlights: {yields} We investigate effect of ZrOCl{sub 2} and HCl on the flame retardancy of wool fabric. {yields} The response surface methodology uses for the experimental plan with. {yields} The thermal degradation studies by thermal analysis, LOI and vertical flame test. {yields} The fabric surfaces observe by SEM. {yields} Results show an increase in the decomposition temperature, residual mass and LOI. - Abstract: The flame retardant wool was prepared using zirconium oxychloride with various acids. The thermal degradation of wool treated with the flame retardant synergistic system, zirconium oxychloride, citric acid and hydrochloric acid, was studied by thermal analysis, mass loss, limiting oxygen index (LOI) and vertical flame test. The fabric surfaces were also observed by SEM. The wool treated with the flame-retardant shows an increase in the decomposition temperature, residual mass and LOI. Also the wool treated with hydrochloric acid showed improved flame retardant properties compared to the use of formic acid. The response surface methodology (RSM) was also used for the experimental plan with four variables on the results of flame retardancy. The statistical analysis confirms the optimum conditions obtained by the experimental results.

  18. Experimental study on velocity characteristics of recirculation zone in humid air non-premixed flame

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To examine the effect of the flow field within the recirculation zone on flame structure,the characteristic velocity fields of methane/humid air flame in nonpremixed combustion behind a disc bluff-body burner were experimentally studied by particle image velocimeter (PIV).The results show that two stagnation points exist on the centerline in the recirculation zone flame.However,the distance of the two stagnation points in humid air combustion shortens,and the minimal dimensionless velocity increases compared with the conventional nonhumid air combustion.In addition,the positional curves of the minimal velocities can be partitioned into three phases representing three different flame patterns.The analysis of axial minimal velocities on the centerline and their positions under different co-flow air velocity conditions reveals that fuel-to-air velocity ratio is the crucial parameter that governs humid air combustion flame characteristics.

  19. Unsupervised analysis of experiments of laminar flame propagation in a spherical enclosure

    Science.gov (United States)

    Barone, Mario; Chaumeix, Nabiha; Comandini, Andrea; Continillo, Gaetano; Lombardi, Simone; Nativel, Damien

    2016-12-01

    The paper illustrates the methodology developed for unsupervised analysis to be conducted on high-definition, high sampling rate image sequences collected in experiments with a single spark ignition optically accessible spherical bomb. Images recorded along the line-of-sight were first processed to identify the reaction front, and then analyzed by means of a two-dimensional numerical estimation technique. The laminar flame front is detected by making use of the concept of "scalar dissipation rate" basing on flame luminosity data, i.e. the square of the gradient of flame luminosity. The new scalar field is then tracked to derive the time history of the flame radius. In order to extract the Region Of Interest from the images, masking techniques are employed, whereas signal-to-noise ratio is improved by means of data binning. The proposed automatic, non-intrusive method proves effective in providing a fast characterization of the flame propagation phenomenon in terms of apparent velocity.

  20. Dynamics of autoignitive DME/air coflow flames in oscillating flows

    Science.gov (United States)

    Deng, Sili; Zhao, Peng; Mueller, Michael; Law, Chung

    2016-11-01

    The structure and dynamics of laminar nonpremixed dimethyl ether (DME)/air coflow flames were investigated at elevated temperatures and pressures, conditions at which autoignition times become competitive with flame times. Computations with detailed chemistry were performed for DME and heated coflow air at 30 atm with uniform but sinusoidally oscillating inlet velocities. These unsteady cases were compared with steady flames to elucidate the effect of oscillation frequency on the flame dynamics. In the oscillating reacting flow, periodic but hysteretic transition occurs between a multibrachial autoignition front that locates downstream at high inlet velocity and a tribrachial flame that locates upstream at low inlet velocity. The finite induction time for autoignition results in this hysteretic behavior, which diminishes at lower oscillation frequency as there is more time for chemistry to respond to the hydrodynamic changes and consequently approach steady state.