High temperature combustion facility: present capabilities and future prospects

International Nuclear Information System (INIS)

Boccio, J.L.; Ginsberg, T.; Ciccarelli, G.

1995-01-01

The high-temperature combustion facility constructed and operated by the Department of Advanced Technology of Brookhaven National Laboratory to support and promote research in the area of hydrogen combustion phenomena in mixtures prototypical to light-water reactor containment atmospheres under potential severe accident conditions is reported. The facility can accommodate combustion research activities encompassing the fields of detonation physics, flame acceleration, and low-speed deflagration in a wide range of combustible gas mixtures at initial temperatures up to 700 K and post-combustion pressures up to 100 atmospheres. Some preliminary test results are presented that provide further evidence that the effect of temperature is to increase the sensitivity of hydrogen-air-steam mixtures to undergo detonation [ru

Development of High Efficiency and Low Emission Low Temperature Combustion Diesel Engine with Direct EGR Injection

Science.gov (United States)

Ho, R. J.; Kumaran, P.; Yusoff, M. Z.

2016-03-01

Focus on energy and environmental sustainability policy has put automotive research & development directed to developing high efficiency and low pollutant power train. Diffused flame controlled diesel combustion has reach its limitation and has driven R&D to explore other modes of combustions. Known effective mode of combustion to reduce emission are Low temperature combustion (LTC) and homogeneous charge combustion ignition by suppressing Nitrogen Oxide(NOx) and Particulate Matter (PM) formation. The key control to meet this requirement are chemical composition and distribution of fuel and gas during a combustion process. Most research to accomplish this goal is done by manipulating injected mass flow rate and varying indirect EGR through intake manifold. This research paper shows viable alternative direct combustion control via co-axial direct EGR injection with fuel injection process. A simulation study with OpenFOAM is conducted by varying EGR injection velocity and direct EGR injector diameter performed with under two conditions with non-combustion and combustion. n-heptane (C7H16) is used as surrogate fuel together with 57 species 290 semi-detailed chemical kinetic model developed by Chalmers University is used for combustion simulation. Simulation result indicates viability of co-axial EGR injection as a method for low temperature combustion control.

Large Eddy Simulation of High-Speed, Premixed Ethylene Combustion

Science.gov (United States)

Ramesh, Kiran; Edwards, Jack R.; Chelliah, Harsha; Goyne, Christopher; McDaniel, James; Rockwell, Robert; Kirik, Justin; Cutler, Andrew; Danehy, Paul

2015-01-01

A large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) methodology is used to simulate premixed ethylene-air combustion in a model scramjet designed for dual mode operation and equipped with a cavity for flameholding. A 22-species reduced mechanism for ethylene-air combustion is employed, and the calculations are performed on a mesh containing 93 million cells. Fuel plumes injected at the isolator entrance are processed by the isolator shock train, yielding a premixed fuel-air mixture at an equivalence ratio of 0.42 at the cavity entrance plane. A premixed flame is anchored within the cavity and propagates toward the opposite wall. Near complete combustion of ethylene is obtained. The combustor is highly dynamic, exhibiting a large-scale oscillation in global heat release and mass flow rate with a period of about 2.8 ms. Maximum heat release occurs when the flame front reaches its most downstream extent, as the flame surface area is larger. Minimum heat release is associated with flame propagation toward the cavity and occurs through a reduction in core flow velocity that is correlated with an upstream movement of the shock train. Reasonable agreement between simulation results and available wall pressure, particle image velocimetry, and OH-PLIF data is obtained, but it is not yet clear whether the system-level oscillations seen in the calculations are actually present in the experiment.

High Frequency Combustion Instabilities of LOx/CH4 Spray Flames in Rocket Engine Combustion Chambers

NARCIS (Netherlands)

Sliphorst, M.

2011-01-01

Ever since the early stages of space transportation in the 1940’s, and the related liquid propellant rocket engine development, combustion instability has been a major issue. High frequency combustion instability (HFCI) is the interaction between combustion and the acoustic field in the combustion

Straw combustion on slow-moving grates

DEFF Research Database (Denmark)

Kær, Søren Knudsen

2005-01-01

Combustion of straw in grate-based boilers is often associated with high emission levels and relatively poor fuel burnout. A numerical grate combustion model was developed to assist in improving the combustion performance of these boilers. The model is based on a one-dimensional ‘‘walking......-column’’ approach and includes the energy equations for both the fuel and the gas accounting for heat transfer between the two phases. The model gives important insight into the combustion process and provides inlet conditions for a computational fluid dynamics analysis of the freeboard. The model predictions...... indicate the existence of two distinct combustion modes. Combustion air temperature and mass flow-rate are the two parameters determining the mode. There is a significant difference in reaction rates (ignition velocity) and temperature levels between the two modes. Model predictions were compared...

Performance of a Compression-ignition Engine with a Precombustion Chamber Having High-Velocity Air Flow

Science.gov (United States)

Spanogle, J A; Moore, C S

1931-01-01

Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.

Study on Combustion Oscillation of Premixed Flame with Pilot Fuel at Elevated Pressures

Science.gov (United States)

Ohtsuka, Masaya; Yoshida, Shohei; Hirata, Yoshitaka; Kobayashi, Nariyoshi

Acoustically-coupled combustion oscillation is studied for premixed flame with pilot fuel to be used in gas turbine combustors. Premixed gas is passed through swirl vanes and burnt with the centrally injected pilot fuel. The dependencies of pressure, fuel to air ratio, premixed fuel rate, inlet velocity and air temperature on the combustion oscillation are investigated. Two kinds of oscillation modes of ˜100Hz and ˜350Hz are activated according to inlet velocities. Fluctuating pressures are amplified when the premixed fuel rate is over ˜80% at elevated pressures. The fluctuating pressure peak moves to a higher premixed fuel ratio region with increased pressure or fuel to air ratio for the Helmholz type mode. Combustion oscillation occurs when the pilot fuel velocity is changed proportionally with the flame length.

Laminar Burning Velocities of Fuels for Advanced Combustion Engines (FACE) Gasoline and Gasoline Surrogates with and without Ethanol Blending Associated with Octane Rating

KAUST Repository

Mannaa, Ossama

2016-05-04

Laminar burning velocities of fuels for advanced combustion engines (FACE) C gasoline and of several blends of surrogate toluene reference fuels (TRFs) (n-heptane, iso-octane, and toluene mixtures) of the same research octane number are presented. Effects of ethanol addition on laminar flame speed of FACE-C and its surrogate are addressed. Measurements were conducted using a constant volume spherical combustion vessel in the constant pressure, stable flame regime at an initial temperature of 358 K and initial pressures up to 0.6 MPa with the equivalence ratios ranging from 0.8 to 1.6. Comparable values in the laminar burning velocities were measured for the FACE-C gasoline and the proposed surrogate fuel (17.60% n-heptane + 77.40% iso-octane + 5% toluene) over the range of experimental conditions. Sensitivity of flame propagation to total stretch rate effects and thermo-diffusive instability was quantified by determining Markstein length. Two percentages of an oxygenated fuel of ethanol as an additive, namely, 60 vol% and 85 vol% were investigated. The addition of ethanol to FACE-C and its surrogate TRF-1 (17.60% n-heptane + 77.40% iso-octane + 5% toluene) resulted in a relatively similar increase in the laminar burning velocities. The high-pressure measured values of Markstein length for the studied fuels blended with ethanol showed minimal influence of ethanol addition on the flame’s response to stretch rate and thermo-diffusive instability. © 2016 Taylor & Francis.

Laminar Burning Velocities of Fuels for Advanced Combustion Engines (FACE) Gasoline and Gasoline Surrogates with and without Ethanol Blending Associated with Octane Rating

KAUST Repository

Mannaa, Ossama; Mansour, Morkous S.; Roberts, William L.; Chung, Suk-Ho

2016-01-01

Laminar burning velocities of fuels for advanced combustion engines (FACE) C gasoline and of several blends of surrogate toluene reference fuels (TRFs) (n-heptane, iso-octane, and toluene mixtures) of the same research octane number are presented. Effects of ethanol addition on laminar flame speed of FACE-C and its surrogate are addressed. Measurements were conducted using a constant volume spherical combustion vessel in the constant pressure, stable flame regime at an initial temperature of 358 K and initial pressures up to 0.6 MPa with the equivalence ratios ranging from 0.8 to 1.6. Comparable values in the laminar burning velocities were measured for the FACE-C gasoline and the proposed surrogate fuel (17.60% n-heptane + 77.40% iso-octane + 5% toluene) over the range of experimental conditions. Sensitivity of flame propagation to total stretch rate effects and thermo-diffusive instability was quantified by determining Markstein length. Two percentages of an oxygenated fuel of ethanol as an additive, namely, 60 vol% and 85 vol% were investigated. The addition of ethanol to FACE-C and its surrogate TRF-1 (17.60% n-heptane + 77.40% iso-octane + 5% toluene) resulted in a relatively similar increase in the laminar burning velocities. The high-pressure measured values of Markstein length for the studied fuels blended with ethanol showed minimal influence of ethanol addition on the flame’s response to stretch rate and thermo-diffusive instability. © 2016 Taylor & Francis.

Fluidized-bed calciner with combustion nozzle and shroud

International Nuclear Information System (INIS)

Wielang, J.A.; Palmer, W.B.; Kerr, W.B.

1977-01-01

A nozzle employed as a burner within a fluidized bed is coaxially enclosed within a tubular shroud that extends beyond the nozzle length into the fluidized bed. The open-ended shroud portion beyond the nozzle end provides an antechamber for mixture and combustion of atomized fuel with an oxygen-containing gas. The arrangement provides improved combustion efficiency and excludes bed particles from the high-velocity, high-temperature portions of the flame to reduce particle attrition. 4 claims, 2 figures

Internal and surface phenomena in metal combustion

Science.gov (United States)

Dreizin, Edward L.; Molodetsky, Irina E.; Law, Chung K.

1995-01-01

Combustion of metals has been widely studied in the past, primarily because of their high oxidation enthalpies. A general understanding of metal combustion has been developed based on the recognition of the existence of both vapor-phase and surface reactions and involvement of the reaction products in the ensuing heterogeneous combustion. However, distinct features often observed in metal particle combustion, such as brightness oscillations and jumps (spearpoints), disruptive burning, and non-symmetric flames are not currently understood. Recent metal combustion experiments using uniform high-temperature metal droplets produced by a novel micro-arc technique have indicated that oxygen dissolves in the interior of burning particles of certain metals and that the subsequent transformations of the metal-oxygen solutions into stoichiometric oxides are accompanied with sufficient heat release to cause observed brightness and temperature jumps. Similar oxygen dissolution has been observed in recent experiments on bulk iron combustion but has not been associated with such dramatic effects. This research addresses heterogeneous metal droplet combustion, specifically focusing on oxygen penetration into the burning metal droplets, and its influence on the metal combustion rate, temperature history, and disruptive burning. A unique feature of the experimental approach is the combination of the microgravity environment with a novel micro-arc Generator of Monodispersed Metal Droplets (GEMMED), ensuring repeatable formation and ignition of uniform metal droplets with controllable initial temperature and velocity. The droplet initial temperatures can be adjusted within a wide range from just above the metal melting point, which provides means to ignite droplets instantly upon entering an oxygen containing environment. Initial droplet velocity will be set equal to zero allowing one to organize metal combustion microgravity experiments in a fashion similar to usual microgravity

Photographic investigation into the mechanism of combustion in irregular detonation waves

Science.gov (United States)

Kiyanda, C. B.; Higgins, A. J.

2013-03-01

Irregular detonations are supersonic combustion waves in which the inherent multi-dimensional structure is highly variable. In such waves, it is questionable whether auto-ignition induced by shock compression is the only combustion mechanism present. Through the use of high-speed schlieren and self-emitted light photography, the velocity of the different components of detonation waves in a {{ CH}}_4+2{ O}_2 mixture is analyzed. The observed burn-out of unreacted pockets is hypothesized to be due to turbulent combustion.

Auditory velocity discrimination in the horizontal plane at very high velocities.

Science.gov (United States)

Frissen, Ilja; Féron, François-Xavier; Guastavino, Catherine

2014-10-01

We determined velocity discrimination thresholds and Weber fractions for sounds revolving around the listener at very high velocities. Sounds used were a broadband white noise and two harmonic sounds with fundamental frequencies of 330 Hz and 1760 Hz. Experiment 1 used velocities ranging between 288°/s and 720°/s in an acoustically treated room and Experiment 2 used velocities between 288°/s and 576°/s in a highly reverberant hall. A third experiment addressed potential confounds in the first two experiments. The results show that people can reliably discriminate velocity at very high velocities and that both thresholds and Weber fractions decrease as velocity increases. These results violate Weber's law but are consistent with the empirical trend observed in the literature. While thresholds for the noise and 330 Hz harmonic stimulus were similar, those for the 1760 Hz harmonic stimulus were substantially higher. There were no reliable differences in velocity discrimination between the two acoustical environments, suggesting that auditory motion perception at high velocities is robust against the effects of reverberation. Copyright © 2014 Elsevier B.V. All rights reserved.

Novel Active Combustion Control Concept for High-Frequency Modulation of Atomized Fuel Flow, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This proposal by Jansen's Aircraft Systems Controls, Inc presents an innovative solution for Active Combustion Control. Relative to the state of the art, this...

Staged, High-Pressure Oxy-Combustion Technology: Development and Scale-Up

Energy Technology Data Exchange (ETDEWEB)

Axelbaum, Richard; Xia, Fei; Gopan, Akshay; Kumfer, Benjamin

2014-09-30

Washington University in St. Louis and its project partners are developing a unique pressurized oxy-combustion process that aims to improve efficiency and costs by reducing the recycling of flue gas to near zero. Normally, in the absence of recycled flue gas or another inert gas, combustion of fuel and oxygen results in a dramatic increase in temperature of the combustion products and radiant energy, as compared to combustion in air. High heat flux to the boiler tubes may result in a tube surface temperatures that exceed safe operating limits. In the Staged Pressurized Oxy-Combustion (SPOC) process, this problem is addressed by staging the delivery of fuel and by novel combustion design that allows control of heat flux. In addition, the main mode of heat transfer to the steam cycle is by radiation, as opposed to convection. Therefore, the requirement for recycling large amounts of flue gas, for temperature control or to improve convective heat transfer, is eliminated, resulting in a reduction in auxiliary loads. The following report contains a detailed summary of scientific findings and accomplishments for the period of Oct. 1, 2013 to Sept 30, 2014. Results of ASPEN process and CFD modelling activities aimed at improving the SPOC process and boiler design are presented. The effects of combustion pressure and fuel moisture on the plant efficiency are discussed. Combustor pressure is found to have only a minor impact beyond 16 bar. For fuels with moisture content greater than approx 30%, e.g. coal/water slurries, the amount of latent heat of condensation exceeds that which can be utilized in the steam cycle and plant efficiency is reduced significantly. An improved boiler design is presented that achieves a more uniform heat flux profile. In addition, a fundamental study of radiation in high-temperature, high-pressure, particle-laden flows is summarized which provides a more complete understanding of heat transfer in these unusual conditions and to allow for

Modeling internal ballistics of gas combustion guns.

Science.gov (United States)

Schorge, Volker; Grossjohann, Rico; Schönekess, Holger C; Herbst, Jörg; Bockholdt, Britta; Ekkernkamp, Axel; Frank, Matthias

2016-05-01

Potato guns are popular homemade guns which work on the principle of gas combustion. They are usually constructed for recreational rather than criminal purposes. Yet some serious injuries and fatalities due to these guns are reported. As information on the internal ballistics of homemade gas combustion-powered guns is scarce, it is the aim of this work to provide an experimental model of the internal ballistics of these devices and to investigate their basic physical parameters. A gas combustion gun was constructed with a steel tube as the main component. Gas/air mixtures of acetylene, hydrogen, and ethylene were used as propellants for discharging a 46-mm caliber test projectile. Gas pressure in the combustion chamber was captured with a piezoelectric pressure sensor. Projectile velocity was measured with a ballistic speed measurement system. The maximum gas pressure, the maximum rate of pressure rise, the time parameters of the pressure curve, and the velocity and path of the projectile through the barrel as a function of time were determined according to the pressure-time curve. The maximum gas pressure was measured to be between 1.4 bar (ethylene) and 4.5 bar (acetylene). The highest maximum rate of pressure rise was determined for hydrogen at (dp/dt)max = 607 bar/s. The muzzle energy was calculated to be between 67 J (ethylene) and 204 J (acetylene). To conclude, this work provides basic information on the internal ballistics of homemade gas combustion guns. The risk of injury to the operator or bystanders is high, because accidental explosions of the gun due to the high-pressure rise during combustion of the gas/air mixture may occur.

Electron-beam-induced acoustic-wave enhancement of gaseous combustion

International Nuclear Information System (INIS)

Bidwell, S.W.; Bosch, R.A.; Gilgenbach, R.M.

1989-01-01

The combustion rate of premixed gases in a closed vessel was increased by injecting a high-current electron beam into the gas mixture within about 20 ms of spark ignition. This effect was observed with the fuels ethylene, methane, ethane, propane, and n-butane. Experimental results provide strong evidence that e-beam excitation of the fundamental longitudinal-acoustic mode of the cylindrical chamber is the mechanism of combustion enhancement. An observable combustion enhancement required that the amplitude of the fluid velocity oscillation in this acoustic mode be greater than or approximately equal to the flame propagation speed and was associated with a wrinkled or cellular flame structure with dimensions on the order of 1/2 cm. These results are in good agreement with values for the threshold acoustic velocity amplitude and dimension of cellular structure predicted for a periodically accelerated flame

Fast Slip Velocity in a High-Entropy Alloy

Science.gov (United States)

Rizzardi, Q.; Sparks, G.; Maaß, R.

2018-04-01

Due to fluctuations in nearest-neighbor distances and chemistry within the unit cell, high-entropy alloys are believed to have a much higher resistance to dislocation motion than pure crystals. Here, we investigate the coarse-grained dynamics of a number of dislocations being active during a slip event. We found that the time-resolved dynamics of slip is practically identical in Au and an Al0.3CoCrFeNi high-entropy alloy, but much faster than in Nb. Differences between the FCC-crystals are seen in the spatiotemporal velocity profile, with faster acceleration and slower velocity relaxation in the high-entropy alloy. Assessing distributions that characterize the intermittently evolving plastic flow reveals material-dependent scaling exponents for size, duration, and velocity-size distributions. The results are discussed in view of the underlying dislocation mobility.

Combustion in a High-Speed Compression-Ignition Engine

Science.gov (United States)

Rothrock, A M

1933-01-01

An investigation conducted to determine the factors which control the combustion in a high-speed compression-ignition engine is presented. Indicator cards were taken with the Farnboro indicator and analyzed according to the tangent method devised by Schweitzer. The analysis show that in a quiescent combustion chamber increasing the time lag of auto-ignition increases the maximum rate of combustion. Increasing the maximum rate of combustion increases the tendency for detonation to occur. The results show that by increasing the air temperature during injection the start of combustion can be forced to take place during injection and so prevent detonation from occurring. It is shown that the rate of fuel injection does not in itself control the rate of combustion.

High speed analysis of high pressure combustion in a constant volume cell

NARCIS (Netherlands)

Frijters, P.J.M.; Klein-Douwel, R.J.H.; Manski, S.S.; Somers, L.M.T.; Baert, R.S.G.; Dias, V.

2005-01-01

A combustion process with N2, O2 and C2H4 as fuel used in an opticallyaccessible, high pressure, high temperature, constant volume cell forresearch on diesel fuel spray formation, is studied. The flame frontspeed Vf,HS is determined using high speed imaging. The pressure traceof the combustion

Numerical simulations of turbulent jet ignition and combustion

Science.gov (United States)

Validi, Abdoulahad; Irannejad, Abolfazl; Jaberi, Farhad

2013-11-01

The ignition and combustion of a homogeneous lean hydrogen-air mixture by a turbulent jet flow of hot combustion products injected into a colder gas mixture are studied by a high fidelity numerical model. Turbulent jet ignition can be considered as an efficient method for starting and controlling the reaction in homogeneously charged combustion systems used in advanced internal combustion and gas turbine engines. In this work, we study in details the physics of turbulent jet ignition in a fundamental flow configuration. The flow and combustion are modeled with the hybrid large eddy simulation/filtered mass density function (LES/FMDF) approach, in which the filtered form the compressible Navier-Stokes equations are solved with a high-order finite difference scheme for the turbulent velocity and the FMDF transport equations are solved with a Lagrangian stochastic method to obtain the scalar (temperature and species mass fractions) field. The hydrogen oxidation is described by a detailed reaction mechanism with 37 elementary reactions and 9 species.

Optimal combustor dimensions for the catalytic combustion of methane-air mixtures in micro-channels

International Nuclear Information System (INIS)

Chen, Junjie; Song, Wenya; Xu, Deguang

2017-01-01

Highlights: • The effect of combustor dimensions on the combustion stability was elucidated. • Wall thermal properties are important for optimizing combustor dimensions. • The optimal wall thickness increases with flow velocity. • The optimal combustor length depends on the wall thermal conductivity. • Stability diagrams were constructed and design recommendations were made. - Abstract: This paper addresses the question of choosing appropriate combustor dimensions for the self-sustained catalytic combustion in parallel plate micro-channels. The combustion characteristics and stability of methane-air mixtures over platinum in catalytic micro-combustors were studied, using a two-dimensional computational fluid dynamics (CFD) model with detailed chemistry and transport. The effects of gap size, wall thickness, and combustor length on the combustion stability and combustor performance were explored to provide guidelines for optimal design of combustor dimensions. Combustion stability diagrams were constructed, and design recommendations were made. The effect of wall thermal conductivity on the mechanisms of extinction and blowout, and its implications on optimal combustor geometry were studied. It was shown that combustor dimensions are vital in determining the combustion stability of the system. The choice of appropriate combustor dimensions is crucial in achieving stable combustion, due to a rather narrow operating space determined by stability, material, and conversion constraints. The optimal gap size depends on whether the flow velocity or flow rate is kept constant. For most practical wall materials in the range of metals to highly conductive ceramics, larger combustors are more stable at a fixed flow velocity, whereas smaller combustors are recommended for a fixed flow rate at the expense of hot spots. The optimal wall thickness increases with flow velocity. Higher flow velocities can be sustained in combustors with low-conductivity materials using

The Brief Introduction of Different Laser Diagnostics Methods Used in Aeroengine Combustion Research

Directory of Open Access Journals (Sweden)

Fei Xing

2016-01-01

Full Text Available Combustion test diagnosis has always been one of the most important technologies for the development of aerospace engineering. The traditional methods of measurement have been unable to meet the requirements of accurate capture of the flow field in the development process of the aeroengine combustor. Therefore, the development of high-precision measurement and diagnostic techniques to meet the needs of the aeroengine combustor design is imperative. Laser diagnostics techniques developed quickly in the past several years. They are used to measure the parameters of the combustion flow field such as velocity, temperature, and components concentration with high space and time resolution and brought no disturbance. Planar laser-induced fluorescence, coherent anti-Stokes Raman scattering, tunable diode laser absorption spectroscopy, and Raman scattering were introduced systemically in this paper. After analysis of their own advantages and disadvantages, the authors considered validated Raman scattering system and Tunable Diode Laser Absorption Tomography are more suitable for research activities on aeroengine combustion systems.

Combustion of environmentally altered molybdenum trioxide nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Moore, Kevin; Pantoya, Michelle L. [Mechanical Engineering Department, Texas Tech University, 2500 Broadway, Lubbock, TX 79409 (United States)

2006-06-15

Nanocomposite thermite mixtures are currently under development for many primer applications due to their high energy densities, high ignition sensitivity, and low release of toxins into the environment. However, variability and inconsistencies in combustion performance have not been sufficiently investigated. Environmental interactions with the reactants are thought to be a contributing factor to these variabilities. Combustion velocity experiments were conducted on aluminum (Al) and molybdenum trioxide (MoO{sub 3}) mixtures to investigate the role of environmental interactions such as light exposure and humidity. While the Al particles were maintained in an ambient, constant environment, the MoO{sub 3} particles were exposed to UV or fluorescent light, and highly humid environments. Results show that UV and fluorescent lighting over a period of days does not significantly contribute to performance deterioration. However, a humid environment severely decreases combustion performance if the oxidizer particles are not heat-treated. Heat treatment of the MoO{sub 3} greatly increases the material's ability to resist water absorption, yielding more repeatable combustion performance. This work further quantifies the role of the environment in the decrease of combustion performance of nanocomposites over time. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

NEDO project reports. High performance industrial furnace development project - High temperature air combustion

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-21

For the purpose of reducing energy consumption, a NEDO project 'Developmental research on high efficiency industrial furnaces' was carried out from FY 1993 to FY 1999 by The Japan Industrial Furnaces Manufacturers Association, and the paper outlined the details of the project. Industrial furnaces handled in this R and D can bring 30% reduction of the energy consumption and approximately 50% NOx reduction, and were given the 9th Nikkei global environmental technology prize. In the study of combustion phenomena of high temperature air combustion, the paper arranged characteristics of flame, the base of gaseous fuel flame, the base of liquid fuel flame, the base of solid fuel flame, etc. Concerning high temperature air combustion models for simulation, fluid dynamics and heat transfer models, and reaction and NOx models, etc. As to impacts of high temperature air combustion on performance of industrial furnaces, energy conservation, lowering of pollution, etc. In relation to a guide for the design of high efficiency industrial furnaces, flow charts, conceptual design, evaluation method for heat balance and efficiency using charts, combustion control system, applicability of high efficiency industrial furnaces, etc. (NEDO)

NEDO project reports. High performance industrial furnace development project - High temperature air combustion

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-21

For the purpose of reducing energy consumption, a NEDO project 'Developmental research on high efficiency industrial furnaces' was carried out from FY 1993 to FY 1999 by The Japan Industrial Furnaces Manufacturers Association, and the paper outlined the details of the project. Industrial furnaces handled in this R and D can bring 30% reduction of the energy consumption and approximately 50% NOx reduction, and were given the 9th Nikkei global environmental technology prize. In the study of combustion phenomena of high temperature air combustion, the paper arranged characteristics of flame, the base of gaseous fuel flame, the base of liquid fuel flame, the base of solid fuel flame, etc. Concerning high temperature air combustion models for simulation, fluid dynamics and heat transfer models, and reaction and NOx models, etc. As to impacts of high temperature air combustion on performance of industrial furnaces, energy conservation, lowering of pollution, etc. In relation to a guide for the design of high efficiency industrial furnaces, flow charts, conceptual design, evaluation method for heat balance and efficiency using charts, combustion control system, applicability of high efficiency industrial furnaces, etc. (NEDO)

Effects of Port Shape on Steady Flow Characteristics in an SI Engine with Semi-Wedge Combustion Chamber (2) - Velocity Distribution (2)

Energy Technology Data Exchange (ETDEWEB)

Yoon, Inkyoung; Ohm, Inyong [Seoul Nat’l Univ. of Science and Technology, Seoul (Korea, Republic of)

2017-02-15

This study is the second investigation on the steady flow characteristics of an SI engine with a semi-edge combustion chamber as a function of the port shape with varying evaluation positions. For this purpose, the planar velocity profiles were measured from 1.75B, 1.75 times of bore position apart from the bottom of head, to 6.00B positions using particle – image velocimetry. The flow patterns were examined with both a straight and a helical port. The velocity profiles, streamlines, and centers of swirl were almost the same at the same valve lift regardless of the measuring position, which is quite different from the case of the pent-roof combustion chamber. All the eccentricity values of the straight port were out of distortion criterion 0.15 through the lifts and the position. However, the values of the helical port exceeded the distortion criterion by up to 4 mm lift, but decreased rapidly above the 3.00B position and the 5 mm lift. There always existed a relative offset effect in the evaluation of the swirl coefficient using the PIV method due to the difference of the ideal impulse swirl meter velocity profile assumption, except for the cylinder-center-base estimation that was below 4 mm of the straight port. Finally, it was concluded that taking the center as an evaluation basis and the assumption about the axial velocity profile did not have any qualitative effect on swirl evaluation, but affected the value owing to the detailed profile.

Modelling of NOx emissions from pressurized fluidized bed combustion - A parameter study

DEFF Research Database (Denmark)

Jensen, Anker; Johnsson, Jan Erik

1997-01-01

velocity, the bubble size, the bubble rise velocity and the gas interchange coefficient between bubble and dense phase. The most important combustion parameters are the rates of CO and CH4 combustion and the CO/(CO + CO2) ratio from char combustion. (C) 1997 Elsevier Science Ltd....

Study on the effect of distance between the two nozzle holes on interaction of high pressure combustion-gas jets with liquid

International Nuclear Information System (INIS)

Xue, Xiaochun; Yu, Yonggang; Zhang, Qi

2014-01-01

Highlights: • We design a five-stage cylindrical stepped-wall chamber to study twin combustion-gas jets. • We observe mixing processes of twin combustion-gases and liquid by high speed photographic system. • We discuss the influence of multiple parameters on expansion shape of the Taylor cavities. • The three-dimensional mathematics model is established to simulate the energy release process. • We obtain distribution characteristics of parameters under different nozzle distances. - Abstract: The combustion-gas generator and cylindrical stepped-wall observation chambers with five stages are designed to study the expansion characteristic of twin combustion-gas jets in liquid working medium under high temperature and high pressure. The expansion processes of Taylor cavities formed by combustion-gas jets and the mixing characteristics of gas–liquid are studied by means of high-speed digital camera system. The effects of the distance between the two nozzle holes, injection pressure and nozzle diameter on jet expansion processes are discussed. The experimental results indicate that, the velocity differences exist on the gas–liquid interface during expansion processes of twin combustion-gas jets, and the effect of Taylor–Helmholtz instability is intense, so interfaces between gas and liquid show turbulent folds and randomness. The strong turbulent mixing of gas and liquid leads to release of combustion-gas energy with the temperature decreasing. Moreover, the mixing effectiveness is obviously enhanced on the corners of each step of the cylindrical stepped-wall structure, forming radial expansion phenomenon. The reasonable matching of multi-parameter can restrain the jet instability and make the combustion-gas energy orderly release. Based on the experiments, the three-dimensional unsteady mathematical model of interaction of twin combustion-gas jets and liquid working medium is established to obtain the density, pressure, velocity and temperature

Evaluation of catalytic combustion of actual coal-derived gas

Science.gov (United States)

Blanton, J. C.; Shisler, R. A.

1982-01-01

The combustion characteristics of a Pt-Pl catalytic reactor burning coal-derived, low-Btu gas were investigated. A large matrix of test conditions was explored involving variations in fuel/air inlet temperature and velocity, reactor pressure, and combustor exit temperature. Other data recorded included fuel gas composition, reactor temperatures, and exhaust emissions. Operating experience with the reactor was satisfactory. Combustion efficiencies were quite high (over 95 percent) over most of the operating range. Emissions of NOx were quite high (up to 500 ppm V and greater), owing to the high ammonia content of the fuel gas.

Separating Direct and Indirect Turbofan Engine Combustion Noise While Estimating Post-Combustion (Post-Flame) Residence Time Using the Correlation Function

Science.gov (United States)

Miles, Jeffrey Hilton

2011-01-01

A previous investigation on the presence of direct and indirect combustion noise for a full-scale turbofan engine using a far-field microphone at 130 is extended by also examining signals obtained at two additional downstream directions using far-field microphones at 110 deg and 160 deg. A generalized cross-correlation function technique is used to study the change in propagation time to the far field of the combined direct and indirect combustion noise signal as a sequence of low-pass filters are applied. The filtering procedure used produces no phase distortion. As the low-pass filter frequency is decreased, the travel time increases because the relative amount of direct combustion noise is reduced. The indirect combustion noise signal travels more slowly because in the combustor entropy fluctuations move with the flow velocity, which is slow compared to the local speed of sound. The indirect combustion noise signal travels at acoustic velocities after reaching the turbine and being converted into an acoustic signal. The direct combustion noise is always propagating at acoustic velocities. The results show that the estimated indirect combustion noise time delay values (post-combustion residence times) measured at each angle are fairly consistent with one another for a relevant range of operating conditions and demonstrate source separation of a mixture of direct and indirect combustion noise. The results may lead to a better idea about the acoustics in the combustor and may help develop and validate improved reduced-order physics-based methods for predicting turbofan engine core noise.

Diffusion Driven Combustion Waves in Porous Media

Science.gov (United States)

Aldushin, A. P.; Matkowsky, B. J.

2000-01-01

Filtration of gas containing oxidizer, to the reaction zone in a porous medium, due, e.g., to a buoyancy force or to an external pressure gradient, leads to the propagation of Filtration combustion (FC) waves. The exothermic reaction occurs between the fuel component of the solid matrix and the oxidizer. In this paper, we analyze the ability of a reaction wave to propagate in a porous medium without the aid of filtration. We find that one possible mechanism of propagation is that the wave is driven by diffusion of oxidizer from the environment. The solution of the combustion problem describing diffusion driven waves is similar to the solution of the Stefan problem describing the propagation of phase transition waves, in that the temperature on the interface between the burned and unburned regions is constant, the combustion wave is described by a similarity solution which is a function of the similarity variable x/square root of(t) and the wave velocity decays as 1/square root of(t). The difference between the two problems is that in the combustion problem the temperature is not prescribed, but rather, is determined as part of the solution. We will show that the length of samples in which such self-sustained combustion waves can occur, must exceed a critical value which strongly depends on the combustion temperature T(sub b). Smaller values of T(sub b) require longer sample lengths for diffusion driven combustion waves to exist. Because of their relatively small velocity, diffusion driven waves are considered to be relevant for the case of low heat losses, which occur for large diameter samples or in microgravity conditions, Another possible mechanism of porous medium combustion describes waves which propagate by consuming the oxidizer initially stored in the pores of the sample. This occurs for abnormally high pressure and gas density. In this case, uniformly propagating planar waves, which are kinetically controlled, can propagate, Diffusion of oxidizer decreases

Effect of pre-combustion characteristics in pulse detonation engine using shchelkin spiral

Directory of Open Access Journals (Sweden)

C. T. Dheeraj Kumar Singh

2016-09-01

Full Text Available Pulse detonation engines are the modern propulsive device which provides high thrust. They are unsteady propulsive devices which has multi cycle operations in it. In this multi cycle process for every cycle fuel and air are initiated and a shock wave is generated in combustion chamber in form of deflagration. Combustion chamber is maintained with high pressure and high temperature which leads to combustion of reactants. This deflagration transmits to detonation with high velocity and increasing Mach number. Deflagration propagates forward by taking all unburned species and products formed after combustion. Propagation of Deflagration – Detonation Transition (DDT shock wave studies is a pioneering research concept. In the present study, simulation of PDE with Shchelkin spiral geometry is considered with two mass flow inlets has been used in which one is for fuel inlet and other for oxidizer. Geometry and meshing has been done in Gambit. Fuel used is gaseous fuel hydrogen and oxidizer is air mixture of O2, N2 work has been performed for different mass flow rates of fuel and oxidizer. Energy equation, Species transport equation to be solved in Fluent. Comparison results of DDT in parameters of mach number, velocity, pressure and temperatures depending on different time steps have been observed

Comparison of Combustion properties of simulated biogas and methane

International Nuclear Information System (INIS)

Diaz Gonzalez, Carlos; Arrieta, Andres Amell; Suarez, Jose Luis

2009-01-01

The utilization of new renewable energy sources has been of special interest during the past years, seeking to decrease our dependence on fossil fuels and the corresponding environmental impact derived from their use. The combustion properties of a simulated gas composed of 60% methane and 40% carbon dioxide in volume are determined in this paper by means of calculation algorithms developed by the GASURE team, comparing them to pure methane properties. Furthermore, the effect of these properties on premixed flame characteristic phenomena is demonstrated. These properties were determined by theoretical estimations. The characteristic phenomena (laminar deflagration velocity, flame structure, radiation pattern) are determined experimentally. Results show a high effect of carbon dioxide in the combustion properties and characteristic parameters of a biogas premixed flame such as laminar deflagration velocity, flame structure and gas-methane exchangeability problems. The difference regarding flame structure and combustion properties lead to a difference in radiation pattern of the gases studied.

Comparison of combustion properties of simulated biogas and methane

International Nuclear Information System (INIS)

Diaz G, Carlos; Amell, Andres; Suarez, Jose

2010-01-01

The utilization of new renewable energy sources has been of special interest during the past years, seeking to decrease our dependence on fossil fuels and the corresponding environmental impact derived from their use. The combustion properties of a simulated gas composed of 60% methane and 40% carbon dioxide in volume are determined in this paper by means of calculation algorithms developed by the GASURE team, comparing them to pure methane properties. Furthermore, the effect of these properties on premixed flame characteristic phenomena is demonstrated. These properties were determined by theoretical estimations. The characteristic phenomena (laminar deflagration velocity, flame structure, radiation pattern) are determined experimentally. Results show a high effect of carbon dioxide in the combustion properties and characteristic parameters of a biogas premixed flame such as laminar deflagration velocity, flame structure and gas-methane exchangeability problems. The difference regarding flame structure and combustion properties lead to a difference in radiation pattern of the gases studied.

Staged, High-Pressure Oxy-Combustion Technology: Development and Scale-Up

Energy Technology Data Exchange (ETDEWEB)

Axelbaum, Richard [Washington Univ., St. Louis, MO (United States); Kumfer, Benjamin [Washington Univ., St. Louis, MO (United States); Gopan, Akshay [Washington Univ., St. Louis, MO (United States); Yang, Zhiwei [Washington Univ., St. Louis, MO (United States); Phillips, Jeff [Electric Power Research Inst. (EPRI), Palo Alto, CA (United States); Pint, Bruce [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-12-29

The immediate need for a high efficiency, low cost carbon capture process has prompted the recent development of pressurized oxy-combustion. With a greater combustion pressure the dew point of the flue gas is increased, allowing for effective integration of the latent heat of flue gas moisture into the Rankine cycle. This increases the net plant efficiency and reduces costs. A novel, transformational process, named Staged, Pressurized Oxy-Combustion (SPOC), achieves additional step changes in efficiency and cost reduction by significantly reducing the recycle of flue gas. The research and development activities conducted under Phases I and II of this project (FE0009702) include: SPOC power plant cost and performance modeling, CFD-assisted design of pressurized SPOC boilers, theoretical analysis of radiant heat transfer and ash deposition, boiler materials corrosion testing, construction of a 100 kWth POC test facility, and experimental testing. The results of this project have advanced the technology readiness level (TRL) of the SPOC technology from 1 to 5.

Active Brownian particles with velocity-alignment and active fluctuations

International Nuclear Information System (INIS)

Großmann, R; Schimansky-Geier, L; Romanczuk, P

2012-01-01

We consider a model of active Brownian particles (ABPs) with velocity alignment in two spatial dimensions with passive and active fluctuations. Here, active fluctuations refers to purely non-equilibrium stochastic forces correlated with the heading of an individual active particle. In the simplest case studied here, they are assumed to be independent stochastic forces parallel (speed noise) and perpendicular (angular noise) to the velocity of the particle. On the other hand, passive fluctuations are defined by a noise vector independent of the direction of motion of a particle, and may account, for example, for thermal fluctuations. We derive a macroscopic description of the ABP gas with velocity-alignment interaction. Here, we start from the individual-based description in terms of stochastic differential equations (Langevin equations) and derive equations of motion for the coarse-grained kinetic variables (density, velocity and temperature) via a moment expansion of the corresponding probability density function. We focus here on the different impact of active and passive fluctuations on onset of collective motion and show how active fluctuations in the active Brownian dynamics can change the phase-transition behaviour of the system. In particular, we show that active angular fluctuations lead to an earlier breakdown of collective motion and to the emergence of a new bistable regime in the mean-field case. (paper)

High Pressure Combustion Experimental Facility(HPCEF) for Studies on Combustion in Reactive Flows

Science.gov (United States)

2017-12-13

SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6...Report: High Pressure Combustion Experimental Facility (HPCEF) for Studies on Combustion in Reactive Flows The views, opinions and/or findings... contained in this report are those of the author(s) and should not contrued as an official Department of the Army position, policy or decision, unless so

Low Temperature Combustion Demonstrator for High Efficiency Clean Combustion

Energy Technology Data Exchange (ETDEWEB)

Ojeda, William de

2010-07-31

The project which extended from November 2005 to May of 2010 demonstrated the application of Low Temperature Combustion (LTC) with engine out NOx levels of 0.2 g/bhp-hr throughout the program target load of 12.6bar BMEP. The project showed that the range of loads could be extended to 16.5bar BMEP, therefore matching the reference lug line of the base 2007 MY Navistar 6.4L V8 engine. Results showed that the application of LTC provided a dramatic improvement over engine out emissions when compared to the base engine. Furthermore LTC improved thermal efficiency by over 5% from the base production engine when using the steady state 13 mode composite test as a benchmark. The key enablers included improvements in the air, fuel injection, and cooling systems made in Phases I and II. The outcome was the product of a careful integration of each component under an intelligent control system. The engine hardware provided the conditions to support LTC and the controller provided the necessary robustness for a stable combustion. Phase III provided a detailed account on the injection strategy used to meet the high load requirements. During this phase, the control strategy was implemented in a production automotive grade ECU to perform cycle-by-cycle combustion feedback on each of the engine cylinders. The control interacted on a cycle base with the injection system and with the Turbo-EGR systems according to their respective time constants. The result was a unique system that could, first, help optimize the combustion system and maintain high efficiency, and secondly, extend the steady state results to the transient mode of operation. The engine was upgraded in Phase IV with a Variable Valve Actuation system and a hybrid EGR loop. The impact of the more versatile EGR loop did not provide significant advantages, however the application of VVA proved to be an enabler to further extend the operation of LTC and gain considerable benefits in fuel economy and soot reduction. Finally

High-velocity frictional properties of gabbro

Science.gov (United States)

Tsutsumi, Akito; Shimamoto, Toshihiko

High-velocity friction experiments have been performed on a pair of hollow-cylindrical specimens of gabbro initially at room temperature, at slip rates from 7.5 mm/s to 1.8 m/s, with total circumferential displacements of 125 to 174 m, and at normal stresses to 5 MPa, using a rotary-shear high-speed friction testing machine. Steady-state friction increases slightly with increasing slip rate at slip rates to about 100 mm/s (velocity strengthening) and it decreases markedly with increasing slip rate at higher velocities (velocity weakening). Steady-state friction in the velocity weakening regime is lower for the non-melting case than the frictional melting case, due perhaps to severe thermal fracturing. A very large peak friction is always recognized upon the initiation of visible frictional melting, presumably owing to the welding of fault surfaces upon the solidification of melt patches. Frictional properties thus change dramatically with increasing displacement at high velocities, and such a non-linear effect must be incorporated into the analysis of earthquake initiation processes.

Microemulsions in the Preparation of Highly Active Combustion Catalysts

Czech Academy of Sciences Publication Activity Database

Rymeš, Jan; Ehret, G.; Hilaire, L.; Boutonnet, M.; Jirátová, Květa

2002-01-01

Roč. 75, 1-4 (2002), s. 297-303 ISSN 0920-5861 R&D Projects: GA ČR GA106/02/0523 Institutional research plan: CEZ:AV0Z4072921 Keywords : microemulsion s * catalytic combustion * VOC Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.146, year: 2002

Decomposition of water into highly combustible hydroxyl gas used in ...

African Journals Online (AJOL)

The method proposed involves the decomposition of water into highly combustible hydroxyl gas via electrolysis, which is used in internal combustion engines of electrical generators for electricity generation. The by-product obtained from combustion of this gas is water vapour and oxygen to replenish the atmosphere.

Combustion Sensors: Gas Turbine Applications

Science.gov (United States)

Human, Mel

2002-01-01

This report documents efforts to survey the current research directions in sensor technology for gas turbine systems. The work is driven by the current and future requirements on system performance and optimization. Accurate real time measurements of velocities, pressure, temperatures, and species concentrations will be required for objectives such as combustion instability attenuation, pollutant reduction, engine health management, exhaust profile control via active control, etc. Changing combustor conditions - engine aging, flow path slagging, or rapid maneuvering - will require adaptive responses; the effectiveness of such will be only as good as the dynamic information available for processing. All of these issues point toward the importance of continued sensor development. For adequate control of the combustion process, sensor data must include information about the above mentioned quantities along with equivalence ratios and radical concentrations, and also include both temporal and spatial velocity resolution. Ultimately these devices must transfer from the laboratory to field installations, and thus must become low weight and cost, reliable and maintainable. A primary conclusion from this study is that the optics-based sensor science will be the primary diagnostic in future gas turbine technologies.

Southern high-velocity stars

International Nuclear Information System (INIS)

Augensen, H.J.; Buscombe, W.

1978-01-01

Using the model of the Galaxy presented by Eggen, Lynden-Bell and Sandage (1962), plane galactic orbits have been calculated for 800 southern high-velocity stars which possess parallax, proper motion, and radial velocity data. The stars with trigonometric parallaxes were selected from Buscombe and Morris (1958), supplemented by more recent spectroscopic data. Photometric parallaxes from infrared color indices were used for bright red giants studied by Eggen (1970), and for red dwarfs for which Rodgers and Eggen (1974) determined radial velocities. A color-color diagram based on published values of (U-B) and (B-V) for most of these stars is shown. (Auth.)

Active Combustion Control for Aircraft Gas-Turbine Engines-Experimental Results for an Advanced, Low-Emissions Combustor Prototype

Science.gov (United States)

DeLaat, John C.; Kopasakis, George; Saus, Joseph R.; Chang, Clarence T.; Wey, Changlie

2012-01-01

Lean combustion concepts for aircraft engine combustors are prone to combustion instabilities. Mitigation of instabilities is an enabling technology for these low-emissions combustors. NASA Glenn Research Center s prior activity has demonstrated active control to suppress a high-frequency combustion instability in a combustor rig designed to emulate an actual aircraft engine instability experience with a conventional, rich-front-end combustor. The current effort is developing further understanding of the problem specifically as applied to future lean-burning, very low-emissions combustors. A prototype advanced, low-emissions aircraft engine combustor with a combustion instability has been identified and previous work has characterized the dynamic behavior of that combustor prototype. The combustor exhibits thermoacoustic instabilities that are related to increasing fuel flow and that potentially prevent full-power operation. A simplified, non-linear oscillator model and a more physics-based sectored 1-D dynamic model have been developed to capture the combustor prototype s instability behavior. Utilizing these models, the NASA Adaptive Sliding Phasor Average Control (ASPAC) instability control method has been updated for the low-emissions combustor prototype. Active combustion instability suppression using the ASPAC control method has been demonstrated experimentally with this combustor prototype in a NASA combustion test cell operating at engine pressures, temperatures, and flows. A high-frequency fuel valve was utilized to perturb the combustor fuel flow. Successful instability suppression was shown using a dynamic pressure sensor in the combustor for controller feedback. Instability control was also shown with a pressure feedback sensor in the lower temperature region upstream of the combustor. It was also demonstrated that the controller can prevent the instability from occurring while combustor operation was transitioning from a stable, low-power condition to

Combustion response to acoustic perturbation in liquid rocket engines

Science.gov (United States)

Ghafourian, Akbar

An experimental study of the effect of acoustic perturbations on combustion behavior of a model liquid propellant rocket engine has been carried out. A pair of compression drivers were used to excite transverse and longitudinal acoustic fields at strengths of up to 156.6 dB and 159.5 dB respectively in the combustion chamber of the experimental rocket engine. Propellant simulants were injected into the combustion chamber through a single element shear coaxial injector. Water and air were used in cold flow studies and ethanol and oxygen-enriched air were used as fuel and oxidizer in reacting hot flow studies. In cold flow studies an imposed transverse acoustic field had a more pronounced effect on the spray pattern than a longitudinal acoustic fields. A transverse acoustic field widened the spray by as much as 33 percent and the plane of impingement of the spray with chamber walls moved up closer to the injection plane. The behavior was strongly influenced by the gas phase velocity but was less sensitive to changes in the liquid phase velocity. In reacting hot flow studies the effects of changes in equivalence ratio, excitation amplitude, excitation frequency, liquid and gas phase velocity and chamber pressure on the response of the injector to imposed high frequency transverse acoustic excitation were measured. Reducing the equivalence ratio from 7.4 to 3.8 increased the chamber pressure response to the imposed excitation at 3000 Hz. Increasing the excitation amplitude from 147 dB to 155.6 dB at 3000 Hz increased the chamber pressure response to the excitation. In the frequency range of 1240 Hz to 3220 Hz, an excitation frequency of 3000 Hz resulted in the largest response of the chamber pressure indicating the importance of fluid dynamic coupling. Increasing the liquid phase velocity from 9.2 m/sec to 22.7 m/sec, did not change the amplitude of the chamber pressure response to excitation. This implied the importance of local equivalence ratio and not the overall

Effect of combustion condition on cytotoxic and inflammatory activity of residential wood combustion particles

Science.gov (United States)

Jalava, Pasi I.; Salonen, Raimo O.; Nuutinen, Kati; Pennanen, Arto S.; Happo, Mikko S.; Tissari, Jarkko; Frey, Anna; Hillamo, Risto; Jokiniemi, Jorma; Hirvonen, Maija-Riitta

2010-05-01

Residential heating is an important local source of fine particles and may cause significant exposure and health effects in populations. We investigated the cytotoxic and inflammatory activity of particulate emissions from normal (NC) and smouldering (SC) combustion in one masonry heater. The PM 1-0.2 and PM 0.2 samples were collected from the dilution tunnel with a high-volume cascade impactor (HVCI). Mouse RAW 264.7 macrophages were exposed to the PM-samples for 24 h. Inflammatory mediators, (IL-6, TNFα and MIP-2), and cytotoxicity (MTT-test), were measured. Furthermore, apoptosis and cell cycle of macrophages were analyzed. The HVCI particulate samples were characterized for ions, elements and PAH compounds. Assays of elemental and organic carbon were conducted from parallel low volume samples. All the samples displayed mostly dose-dependent inflammatory and cytotoxic activity. SC samples were more potent than NC samples at inducing cytotoxicity and MIP-2 production, while the order of potency was reversed in TNFα production. SC-PM 1-0.2 sample was a significantly more potent inducer of apoptosis than the respective NC sample. After adjustment for the relative toxicity with emission factor (mg MJ -1), the SC-PM emissions had clearly higher inflammatory and cytotoxic potential than the NC-PM emissions. Thus, operational practice in batch burning of wood and the resultant combustion condition clearly affect the toxic potential of particulate emissions.

On the effects of organic matter and sulphur-containing compounds on the CCN activation of combustion particles

Directory of Open Access Journals (Sweden)

A. Petzold

2005-01-01

Full Text Available The European PartEmis project (Measurement and prediction of emissions of aerosols and gaseous precursors from gas turbine engines was focussed on the characterisation and quantification of exhaust emissions from a gas turbine engine. The combustion aerosol characterisation included on-line measurements of mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, cloud condensation nuclei (CCN activation potential, and off-line analysis of chemical composition. Based on this extensive data set, the role of sulphuric acid coating and of the organic fraction of the combustion particles for the CCN activation was investigated. Modelling of CCN activation was conducted using microphysical and chemical properties obtained from the measurements as input data. Coating the combustion particles with water-soluble sulphuric acid, increases the potential CCN activation, or lowers the activation diameter, respectively. The adaptation of a Köhler model to the experimental data yielded coatings from 0.1 to 3 vol-% of water-soluble matter, which corresponds to an increase in the fraction of CCN-activated combustion particles from ≤10−4 to ≌10−2 at a water vapour saturation ratio Sw=1.006. Additional particle coating by coagulation of combustion particles and aqueous sulphuric acid particles formed by nucleation further reduces the CCN activation diameter. In contrast, particles containing a large fraction of non-volatile organic compounds grow significantly less at high relative humidity than particles with a lower content of non-volatile OC. The resulting reduction in the potential CCN activation with an increasing fraction of non-volatile OC becomes visible as a trend in the experimental data. While a coating of water-soluble sulphuric acid increases the potential CCN activation, or lowers the activation diameter, respectively, the non-volatile organic compounds, mainly found at

Combustion phasing for maximum efficiency for conventional and high efficiency engines

International Nuclear Information System (INIS)

Caton, Jerald A.

2014-01-01

Highlights: • Combustion phasing for max efficiency is a function of engine parameters. • Combustion phasing is most affected by heat transfer, compression ratio, burn duration. • Combustion phasing is less affected by speed, load, equivalence ratio and EGR. • Combustion phasing for a high efficiency engine was more advanced. • Exergy destruction during combustion as functions of combustion phasing is reported. - Abstract: The importance of the phasing of the combustion event for internal-combustion engines is well appreciated, but quantitative details are sparse. The objective of the current work was to examine the optimum combustion phasing (based on maximum bmep) as functions of engine design and operating variables. A thermodynamic, engine cycle simulation was used to complete this assessment. As metrics for the combustion phasing, both the crank angle for 50% fuel mass burned (CA 50 ) and the crank angle for peak pressure (CA pp ) are reported as functions of the engine variables. In contrast to common statements in the literature, the optimum CA 50 and CA pp vary depending on the design and operating variables. Optimum, as used in this paper, refers to the combustion timing that provides the maximum bmep and brake thermal efficiency (MBT timing). For this work, the variables with the greatest influence on the optimum CA 50 and CA pp were the heat transfer level, the burn duration and the compression ratio. Other variables such as equivalence ratio, EGR level, engine speed and engine load had a much smaller impact on the optimum CA 50 and CA pp . For the conventional engine, for the conditions examined, the optimum CA 50 varied between about 5 and 11°aTDC, and the optimum CA pp varied between about 9 and 16°aTDC. For a high efficiency engine (high dilution, high compression ratio), the optimum CA 50 was 2.5°aTDC, and the optimum CA pp was 7.8°aTDC. These more advanced values for the optimum CA 50 and CA pp for the high efficiency engine were

Internal and Surface Phenomena in Heterogenous Metal Combustion

Science.gov (United States)

Dreizin, Edward L.

1997-01-01

The phenomenon of gas dissolution in burning metals was observed in recent metal combustion studies, but it could not be adequately explained by the traditional metal combustion models. The research reported here addresses heterogeneous metal combustion with emphasis on the processes of oxygen penetration inside burning metal and its influence on the metal combustion rate, temperature history, and disruptive burning. The unique feature of this work is the combination of the microgravity environment with a novel micro-arc generator of monodispersed metal droplets, ensuring repeatable formation and ignition of uniform metal droplets with a controllable initial temperature and velocity. Burning droplet temperature is measured in real time with a three wavelength pyrometer. In addition, particles are rapidly quenched at different combustion times, cross-sectioned, and examined using SEM-based techniques to retrieve the internal composition history of burning metal particles. When the initial velocity of a spherical particle is nearly zero, the microgravity environment makes it possible to study the flame structure, the development of flame nonsymmetry, and correlation of the flame shape with the heterogeneous combustion processes.

Steady state HNG combustion modeling

Energy Technology Data Exchange (ETDEWEB)

Louwers, J.; Gadiot, G.M.H.J.L. [TNO Prins Maurits Lab., Rijswijk (Netherlands); Brewster, M.Q. [Univ. of Illinois, Urbana, IL (United States); Son, S.F. [Los Alamos National Lab., NM (United States); Parr, T.; Hanson-Parr, D. [Naval Air Warfare Center, China Lake, CA (United States)

1998-04-01

Two simplified modeling approaches are used to model the combustion of Hydrazinium Nitroformate (HNF, N{sub 2}H{sub 5}-C(NO{sub 2}){sub 3}). The condensed phase is treated by high activation energy asymptotics. The gas phase is treated by two limit cases: the classical high activation energy, and the recently introduced low activation energy approach. This results in simplification of the gas phase energy equation, making an (approximate) analytical solution possible. The results of both models are compared with experimental results of HNF combustion. It is shown that the low activation energy approach yields better agreement with experimental observations (e.g. regression rate and temperature sensitivity), than the high activation energy approach.

The rheodynamics and combustion of coal-water mixtures

Energy Technology Data Exchange (ETDEWEB)

Burdukov, A.P.; Popov, V.I.; Tomilov, V.G.; Fedosenko, V.D. [Russian Academy of Science, Novosibirsk (Russian Federation). Inst. of Thermophysics (Siberian Branch, Russian Academy of Science)

2002-05-01

Investigation methods for characteristics of movement along the tubes, combustion dynamics and gasification of separate drops were developed for the coal-water mixtures (CWM). The following parameters were determined on the basis of laser heating: thermometric, pyrometric and concentration dynamics of single-drop combustion, complete combustion times, duration of temperature phases of combustion, as well as the moment and temperature of ignition. Information on the combustion mass velocity and gasification products was also obtained using laser heating. 6 refs., 13 figs., 1 tab.

Experimental study of slight temperature rise combustion in trapped vortex combustors for gas turbines

International Nuclear Information System (INIS)

Zhang, R.C.; Fan, W.J.; Xing, F.; Song, S.W.; Shi, Q.; Tian, G.H.; Tan, W.L.

2015-01-01

Interstage turbine combustion used for improving efficiency of gas turbine was a new type of combustion mode. Operating conditions and technical requirements for this type of combustor were different from those of traditional combustor. It was expected to achieve engineering application in both ground-based and aviation gas turbine in the near future. In this study, a number of modifications in a base design were applied and examined experimentally. The trapped-vortex combustion technology was adopted for flame stability under high velocity conditions, and the preheating-fuel injection technology was used to improve the atomization and evaporation performance of liquid fuel. The experimental results indicated that stable and efficient combustion with slight temperature-rise can be achieved under the high velocity conditions of combustor inlet. Under all experimental conditions, the excess air coefficients of ignition and lean blow-out were larger than 7 and 20, respectively; pollutant emission index of NO x and the maximum wall temperature were below 2.5 g/(kg fuel) and 1050 K, respectively. Moreover, the effects of fuel injection and overall configuration on the combustion characteristics were analyzed in detail. The number increase, area increase and depth increase of fuel injectors had different influences on the stability, combustion characteristic and temperature distribution. - Highlights: • The combustion mode of slight temperature-rise (200 K) was achieved. • Effect of fuel and air injection on stability characteristic was investigated. • Impact of overall configuration on combustion performance was analyzed. • The feasibility of scheme was determined.

Straw combustion on slow-moving grates - a comparison of model predictions with experimental data

Energy Technology Data Exchange (ETDEWEB)

Kaer, S.K. [Aalborg Univ. (Denmark). Inst. of Energy Technology

2005-03-01

Combustion of straw in grate-based boilers is often associated with high emission levels and relatively poor fuel burnout. A numerical grate combustion model was developed to assist in improving the combustion performance of these boilers. The model is based on a one-dimensional ''walking-column'' approach and includes the energy equations for both the fuel and the gas accounting for heat transfer between the two phases. The model gives important insight into the combustion process and provides inlet conditions for a computational fluid dynamics analysis of the freeboard. The model predictions indicate the existence of two distinct combustion modes. Combustion air temperature and mass flow-rate are the two parameters determining the mode. There is a significant difference in reaction rates (ignition velocity) and temperature levels between the two modes. Model predictions were compared to measurements in terms of ignition velocity and temperatures for five different combinations of air mass flow and temperature. In general, the degree of correspondence with the experimental data is favorable. The largest difference between measurements and predictions occurs when the combustion mode changes. The applicability to full-scale is demonstrated by predictions made for an existing straw-fired boiler located in Denmark. (author)

Motion of water droplets in the counter flow of high-temperature combustion products

Science.gov (United States)

Volkov, R. S.; Strizhak, P. A.

2018-01-01

This paper presents the experimental studies of the deceleration, reversal, and entrainment of water droplets sprayed in counter current flow to a rising stream of high-temperature (1100 K) combustion gases. The initial droplets velocities 0.5-2.5 m/s, radii 10-230 μm, relative volume concentrations 0.2·10-4-1.8·10-4 (m3 of water)/(m3 of gas) vary in the ranges corresponding to promising high-temperature (over 1000 K) gas-vapor-droplet applications (for example, polydisperse fire extinguishing using water mist, fog, or appropriate water vapor-droplet veils, thermal or flame treatment of liquids in the flow of combustion products or high-temperature air; creating coolants based on flue gas, vapor and water droplets; unfreezing of granular media and processing of the drossed surfaces of thermal-power equipment; ignition of liquid and slurry fuel droplets). A hardware-software cross-correlation complex, high-speed (up to 105 fps) video recording tools, panoramic optical techniques (Particle Image Velocimetry, Particle Tracking Velocimetry, Interferometric Particle Imagine, Shadow Photography), and the Tema Automotive software with the function of continuous monitoring have been applied to examine the characteristics of the processes under study. The scale of the influence of initial droplets concentration in the gas flow on the conditions and features of their entrainment by high-temperature gases has been specified. The dependencies Red = f(Reg) and Red' = f(Reg) have been obtained to predict the characteristics of the deceleration of droplets by gases at different droplets concentrations.

DNS and LES/FMDF of turbulent jet ignition and combustion

Science.gov (United States)

Validi, Abdoulahad; Jaberi, Farhad

2014-11-01

The ignition and combustion of lean fuel-air mixtures by a turbulent jet flow of hot combustion products injected into various geometries are studied by high fidelity numerical models. Turbulent jet ignition (TJI) is an efficient method for starting and controlling the combustion in complex propulsion systems and engines. The TJI and combustion of hydrogen and propane in various flow configurations are simulated with the direct numerical simulation (DNS) and the hybrid large eddy simulation/filtered mass density function (LES/FMDF) models. In the LES/FMDF model, the filtered form of the compressible Navier-Stokes equations are solved with a high-order finite difference scheme for the turbulent velocity and the FMDF transport equation is solved with a Lagrangian stochastic method to obtain the scalar field. The DNS and LES/FMDF data are used to study the physics of TJI and combustion for different turbulent jet igniter and gas mixture conditions. The results show the very complex and different behavior of the turbulence and the flame structure at different jet equivalence ratios.

Effects of Injection Timing on Fluid Flow Characteristics of Partially Premixed Combustion Based on High-Speed Particle Image Velocimetry

KAUST Repository

Izadi Najafabadi, Mohammad

2017-03-28

Partially Premixed Combustion (PPC) is a promising combustion concept ,based on judicious tuning of the charge stratification, to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delays of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NO emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with the Homogeneous Charge Compression Ignition (HCCI) concept. Injection timing is the major parameter with which to affect the level of fuel and combustion stratification and to control the combustion phasing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To this end, high-speed Particle Image Velocimetry (PIV) is implemented in a light-duty optical engine to measure fluid flow characteristics, including the flow fields, mean velocity and cycle-resolved turbulence, inside the piston bowl as well as the squish region with a temporal resolution of 1 crank angle degree at 800 rpm. Two injectors, having 5 and 7 holes, were compared to see their effects on fluid flow and heat release behavior for different injection timings. Reactive and non-reactive measurements were performed to distinguish injection-driven and combustion-driven turbulence. Formation of vortices and higher turbulence levels enhance the air/fuel interaction, changing the level of fuel stratification and combustion duration. Results demonstrate clearly how turbulence level correlates with heat release behavior, and provide a quantitative dataset for validation of numerical simulations.

Combustion and smoke formation following exposure of actinide metals to explosions

International Nuclear Information System (INIS)

Luna, R.E.; Church, H.W.; Elrick, R.M.; Parker, D.R.; Nelson, L.S.

1976-01-01

Results from the plutonium aerosol generation experiment (PAGE) program studies indicate that: (1) Significant quantities of metal-bearing aerosols are likely to be formed in an accidental high explosive detonation of a nuclear weapon. Although the explosive charge-to-metal ratio has been reduced in modern weapons, considerable inhalation hazard is still expected due to increased shrapnel formation and streamer combustion. (2) Close-in shrapnel particle sizes and velocities can be estimated by impact sampling techniques. (3) Uranium droplets are a very accurate simulant of plutonium droplets from the standpoint of combustion-related phenomena but do not seem to simulate either the total quantity of aerosol formed from plutonium droplets or its time-dependent generation pattern very well. This is due primarily to the large effect of the explosion of the burning uranium droplets on total aerosol formation which is not observed in the case of plutonium, even though more aerosol is produced per unit time during the actual combustion itself. (4) The formation of chain-like plutonium aerosols from the droplets produced during streamer combustion is expected to produce an unusually active material from the standpoint of inhalation into the lung and ultimate translocation in the body. 16 figures

A model for steady-state HNF combustion

Energy Technology Data Exchange (ETDEWEB)

Louwers, J.; Gadiot, G.M.H.J.L. [TNO Prins Maurits Lab., Rijswijk (Netherlands); Brewster, M.Q. [Univ. of Illinois, Urbana, IL (United States); Son, S.F. [Los Alamos National Lab., NM (United States)

1997-09-01

A simple model for the combustion of solid monopropellants is presented. The condensed phase is treated by high activation energy asymptotics. The gas phase is treated by two limit cases: high activation energy, and low activation energy. This results in simplification of the gas phase energy equation, making an (approximate) analytical solution possible. The results of the model are compared with experimental results of Hydrazinium Nitroformate (HNF) combustion.

Optimization of combustion process for radiation-treated solid fuels in dust state

International Nuclear Information System (INIS)

Askarova, A.S.; Bajdullaeva, G.E.

1997-01-01

Computation experiment on combustion of solid radiation-treated fuel in burning chamber of boiler at Pavlodar thermal electric plant is carried out. Velocity, temperature distribution and concentration of combustion products by height of chamber are received. Analysis of received results shows that radiation treatment of fuels exerts substantial effect on egress parameters of thermal electric plant. It is shown, that radiation treatment allows to improve effectiveness of boiler device and reduce of harmful substances discharge in atmosphere. Results of conducted numerical experiments allow to create complete methods of solid fuel combustion with high moisture and ashiness

Charging conditions research to increase the initial projected velocity at different initial charge temperatures

Science.gov (United States)

Ishchenko, Aleksandr; Burkin, Viktor; Kasimov, Vladimir; Samorokova, Nina; Zykova, Angelica; Diachkovskii, Alexei

2017-11-01

The problems of the defense industry occupy the most important place in the constantly developing modern world. The daily development of defense technology does not stop, nor do studies on internal ballistics. The scientists of the whole world are faced with the task of managing the main characteristics of a ballistic experiment. The main characteristics of the ballistic experiment are the maximum pressure in the combustion chamber Pmax and the projected velocity at the time of barrel leaving UM. During the work the combustion law of the new high-energy fuel was determined in a ballistic experiment for different initial temperatures. This combustion law was used for a parametric study of depending Pmax and UM from a powder charge mass and a traveling charge was carried out. The optimal conditions for loading were obtained for improving the initial velocity at pressures up to 600 MPa for different initial temperatures. In this paper, one of the most promising schemes of throwing is considered, as well as a method for increasing the muzzle velocity of a projected element to 3317 m/s.

Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

Science.gov (United States)

Paxson, Daniel E. (Inventor)

2014-01-01

An apparatus and method for thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such as Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air, and a spark. Metal is inserted continuously in a high volume of metal into a combustion chamber of the pulsejet. The combustion is thereafter controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tailpipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

Prediction of Combustion Stability and Flashback in Turbines with High-Hydrogen Fuel

Energy Technology Data Exchange (ETDEWEB)

Lieuwen, Tim [Georgia Inst. of Technology, Atlanta, GA (United States); Santavicca, Dom [Georgia Inst. of Technology, Atlanta, GA (United States); Yang, Vigor [Georgia Inst. of Technology, Atlanta, GA (United States)

2012-03-31

During the duration of this sponsorship, we broadened our understanding of combustion instabilities through both analytical and experimental work. Predictive models were developed for flame response to transverse acoustic instabilities and for quantifying how a turbulent flame responds to velocity and fuel/air ratio forcing. Analysis was performed on the key instability mechanisms controlling heat release response for flames over a wide range of instability frequencies. Importantly, work was done closely with industrial partners to transition existing models into internal instability prediction codes. Experimentally, the forced response of hydrogen-enriched natural gas/air premixed and partially premixed flames were measured. The response of a lean premixed flame was investigated, subjected to velocity, equivalence ratio, and both forcing mechanisms simultaneously. In addition, important physical mechanisms controlling the response of partially premixed flames to inlet velocity and equivalence ratio oscillations were analyzed. This final technical report summarizes our findings and major publications stemming from this program.

Fuel Flexible Combustion Systems for High-Efficiency Utilization of Opportunity Fuels in Gas Turbines

Energy Technology Data Exchange (ETDEWEB)

Venkatesan, Krishna

2011-11-30

The purpose of this program was to develop low-emissions, efficient fuel-flexible combustion technology which enables operation of a given gas turbine on a wider range of opportunity fuels that lie outside of current natural gas-centered fuel specifications. The program encompasses a selection of important, representative fuels of opportunity for gas turbines with widely varying fundamental properties of combustion. The research program covers conceptual and detailed combustor design, fabrication, and testing of retrofitable and/or novel fuel-flexible gas turbine combustor hardware, specifically advanced fuel nozzle technology, at full-scale gas turbine combustor conditions. This project was performed over the period of October 2008 through September 2011 under Cooperative Agreement DE-FC26-08NT05868 for the U.S. Department of Energy/National Energy Technology Laboratory (USDOE/NETL) entitled "Fuel Flexible Combustion Systems for High-Efficiency Utilization of Opportunity Fuels in Gas Turbines". The overall objective of this program was met with great success. GE was able to successfully demonstrate the operability of two fuel-flexible combustion nozzles over a wide range of opportunity fuels at heavy-duty gas turbine conditions while meeting emissions goals. The GE MS6000B ("6B") gas turbine engine was chosen as the target platform for new fuel-flexible premixer development. Comprehensive conceptual design and analysis of new fuel-flexible premixing nozzles were undertaken. Gas turbine cycle models and detailed flow network models of the combustor provide the premixer conditions (temperature, pressure, pressure drops, velocities, and air flow splits) and illustrate the impact of widely varying fuel flow rates on the combustor. Detailed chemical kinetic mechanisms were employed to compare some fundamental combustion characteristics of the target fuels, including flame speeds and lean blow-out behavior. Perfectly premixed combustion experiments were conducted to

Highly time-resolved imaging of combustion and pyrolysis product concentrations in solid fuel combustion: NO formation in a burning cigarette.

Science.gov (United States)

Zimmermann, Ralf; Hertz-Schünemann, Romy; Ehlert, Sven; Liu, Chuan; McAdam, Kevin; Baker, Richard; Streibel, Thorsten

2015-02-03

The highly dynamic, heterogeneous combustion process within a burning cigarette was investigated by a miniaturized extractive sampling probe (microprobe) coupled to photoionization mass spectrometry using soft laser single photon ionization (SPI) for online real-time detection of molecular ions of combustion and pyrolysis products. Research cigarettes smoked by a smoking machine are used as a reproducible model system for solid-state biomass combustion, which up to now is not addressable by current combustion-diagnostic tools. By combining repetitively recorded online measurement sequences from different sampling locations in an imaging approach, highly time- and space-resolved quantitative distribution maps of, e.g., nitrogen monoxide, benzene, and oxygen concentrations were obtained at a near microscopic level. The obtained quantitative distribution maps represent a time-resolved, movie-like imaging of the respective compound's formation and destruction zones in the various combustion and pyrolysis regions of a cigarette during puffing. Furthermore, spatially resolved kinetic data were ascertainable. The here demonstrated methodology can also be applied to various heterogenic combustion/pyrolysis or reaction model systems, such as fossil- or biomass-fuel pellet combustion or to a positional resolved analysis of heterogenic catalytic reactions.

CATALYTIC COMBUSTION OF METHANE OVER Pt/γ-Al2O3 IN MICRO-COMBUSTOR WITH DETAILED CHEMICAL KINETIC MECHANISMS

Directory of Open Access Journals (Sweden)

JUNJIE CHEN

2014-11-01

Full Text Available Micro-scale catalytic combustion characteristics and heat transfer processes of preheated methane-air mixtures (φ = 0.4 in the plane channel were investigated numerically with detailed chemical kinetic mechanisms. The plane channel of length L = 10.0 mm, height H =1.0 mm and wall thickness δ = 0.1 mm, which inner horizontal surfaces contained Pt/γ-Al2O3 catalyst washcoat. The computational results indicate that the presence of the gas phase reactions extends mildly the micro-combustion stability limits at low and moderate inlet velocities due to the strong flames establishment, and have a more profound effect on extending the high-velocity blowout limits by allowing for additional heat release originating mainly from the incomplete CH4 gas phase oxidation in the plane channel. When the same mass flow rate (ρin × Vin is considered, the micro-combustion stability limits at p: 0.1 MPa are much narrower than at p: 0.6 MPa due to both gas phase and catalytic reaction activities decline with decreasing pressure. Catalytic micro-combustor can achieve stable combustion at low solid thermal conductivity ks < 0.1 W∙m-1•K-1, while the micro-combustion extinction limits reach their larger extent for the higher thermal conductivity ks = 20.0-100.0 W∙m-1•K-1. The existence of surface radiation heat transfers significantly effects on the micro-combustion stability limits and micro-combustors energy balance. Finally, gas phase combustion in catalytic micro-combustors can be sustained at the sub-millimeter scale (plane channel height of 0.25 mm.

An experimental study on suspended sodium droplet combustion

International Nuclear Information System (INIS)

Sato, Kenji

2003-03-01

As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies, ignition process and succeeding combustion of suspended single sodium droplet had been investigated by using high speed movie camera, and a temperature measurement system feasible for the experiment had been developed. In the present study, by using 4 mm diam. suspended sodium droplet, combustion experiments were performed for the free-stream velocity of dry air flow of 20 to 60 cm/s, and for the initial droplet temperature of 280 to 400degC, and the effects of the free-stream velocity and initial droplet temperature on the ignition behavior and droplet temperature variation with time were examined by using high speed movie camera and sheath-type fine thermocouple. The experimental results are as follows: (1) When the initial droplet temperature is less than 290degC, before ignition the oxide film accompanied with vertical streak appeared and the droplet turned to teardrop shape. (2) The ignition delay time defined as the time to evolution of orange color light emission zone or flame zone decreases with the increase o the free-stream velocity or of initial droplet temperature. Examples of typical ignition time are 1.4 s at the free-stream velocity 20 cm/s and initial droplet temperature 300degC, and 0.65 s at 60 cm/s and 400degC. (3) the dependence of the ignition delay time on the free-stream velocity decreases as the free stream velocity increases. (4) The droplet temperatures at the moment of melting extending all over the surface and at the moment of ignition are around 460degC and 500 to 600degC (mostly around 575degC), respectively. These values are essentially independent of the free-stream velocity and initial droplet temperature. (5) The rate of temperature rise does not change through the moment of ignition. (6) The asymptotic droplet temperature at approaching to quasi-steady combustion state following ignition is independent of

Mechanisms and kinetics of granulated sewage sludge combustion.

Science.gov (United States)

Kijo-Kleczkowska, Agnieszka; Środa, Katarzyna; Kosowska-Golachowska, Monika; Musiał, Tomasz; Wolski, Krzysztof

2015-12-01

This paper investigates sewage sludge disposal methods with particular emphasis on combustion as the priority disposal method. Sewage sludge incineration is an attractive option because it minimizes odour, significantly reduces the volume of the starting material and thermally destroys organic and toxic components of the off pads. Additionally, it is possible that ashes could be used. Currently, as many as 11 plants use sewage sludge as fuel in Poland; thus, this technology must be further developed in Poland while considering the benefits of co-combustion with other fuels. This paper presents the results of experimental studies aimed at determining the mechanisms (defining the fuel combustion region by studying the effects of process parameters, including the size of the fuel sample, temperature in the combustion chamber and air velocity, on combustion) and kinetics (measurement of fuel temperature and mass changes) of fuel combustion in an air stream under different thermal conditions and flow rates. The combustion of the sludge samples during air flow between temperatures of 800 and 900°C is a kinetic-diffusion process. This process determines the sample size, temperature of its environment, and air velocity. The adopted process parameters, the time and ignition temperature of the fuel by volatiles, combustion time of the volatiles, time to reach the maximum temperature of the fuel surface, maximum temperature of the fuel surface, char combustion time, and the total process time, had significant impacts. Copyright © 2015 Elsevier Ltd. All rights reserved.

Experimental Investigation and High Resolution Simulation of In-Situ Combustion Processes

Energy Technology Data Exchange (ETDEWEB)

Margot Gerritsen; Tony Kovscek

2008-04-30

This final technical report describes work performed for the project 'Experimental Investigation and High Resolution Numerical Simulator of In-Situ Combustion Processes', DE-FC26-03NT15405. In summary, this work improved our understanding of in-situ combustion (ISC) process physics and oil recovery. This understanding was translated into improved conceptual models and a suite of software algorithms that extended predictive capabilities. We pursued experimental, theoretical, and numerical tasks during the performance period. The specific project objectives were (i) identification, experimentally, of chemical additives/injectants that improve combustion performance and delineation of the physics of improved performance, (ii) establishment of a benchmark one-dimensional, experimental data set for verification of in-situ combustion dynamics computed by simulators, (iii) develop improved numerical methods that can be used to describe in-situ combustion more accurately, and (iv) to lay the underpinnings of a highly efficient, 3D, in-situ combustion simulator using adaptive mesh refinement techniques and parallelization. We believe that project goals were met and exceeded as discussed.

Spectroscopy and kinetics of combustion gases at high temperatures

Energy Technology Data Exchange (ETDEWEB)

Hanson, R.K.; Bowman, C.T. [Stanford Univ., CA (United States)

1993-12-01

This program involves two complementary activities: (1) development and application of cw ring dye laser absorption methods for sensitive detection of radical species and measurement of fundamental spectroscopic parameters at high temperatures; and (2) shock tube studies of reaction kinetics relevant to combustion. Species currently under investigation in the spectroscopic portion of the research include NO and CH{sub 3}; this has necessitated the continued operated at wavelengths in the range 210-230 nm. Shock tube studies of reaction kinetics currently are focussed on reactions involving CH{sub 3} radicals.

Effects of boron addition on the formation of MoSi2 by combustion synthesis mode

International Nuclear Information System (INIS)

Feng Peizhong; Wu Jie; Islam, S.H.; Liu Weisheng; Niu Jinan; Wang Xiaohong; Qiang Yinghuai

2010-01-01

The combustion synthesis behavior of Mo-Si-B powder was investigated. Test specimens with nominal compositions including MoSi 2 , Mo(Si 0.975 B 0.025 ) 2 , Mo(Si 0.95 B 0.05 ) 2 , Mo(Si 0.925 B 0.075 ) 2 and Mo(Si 0.9 B 0.1 ) 2 were employed. The combustion mode, propagation velocity of combustion wave, combustion temperature and combustion product structure were studied. The results showed that the combustion wave propagated along a spiral trajectory till reaching the bottom of the compacts. The combustion temperature was increased by the addition of boron, to as high as 1922 K in the case of the Mo(Si 0.95 B 0.05 ) 2 sample. However, the flame-front propagation velocity decreased as a result of the addition of boron. The X-ray diffraction results showed that the combustion products of the Mo(Si 0.975 B 0.025 ) 2 and Mo(Si 0.9 B 0.1 ) 2 samples were composed of MoSi 2 with minor MoB. Those of the Mo(Si 0.95 B 0.05 ) 2 and Mo(Si 0.925 B 0.075 ) 2 samples were composed of MoSi 2 with minor MoB and MoB 2 . And traces of Mo 2 B 5 were identified in the Mo(Si 0.95 B 0.05 ) 2 sample.

Modelling the average velocity of propagation of the flame front in a gasoline engine with hydrogen additives

Science.gov (United States)

Smolenskaya, N. M.; Smolenskii, V. V.

2018-01-01

The paper presents models for calculating the average velocity of propagation of the flame front, obtained from the results of experimental studies. Experimental studies were carried out on a single-cylinder gasoline engine UIT-85 with hydrogen additives up to 6% of the mass of fuel. The article shows the influence of hydrogen addition on the average velocity propagation of the flame front in the main combustion phase. The dependences of the turbulent propagation velocity of the flame front in the second combustion phase on the composition of the mixture and operating modes. The article shows the influence of the normal combustion rate on the average flame propagation velocity in the third combustion phase.

Elemental analysis of combustion products by neutron activation

International Nuclear Information System (INIS)

Heft, R.E.; Koszykowski, R.F.

1980-01-01

This paper gives a brief description of the neutron activation analysis method, which is being used to determine the elemental profile of combustion products from coal-fired power plants, oil shale retorting, and underground coal gasification

Combustion synthesis of TiC-based materials: Mechanisms, densification, and properties

International Nuclear Information System (INIS)

LaSalvia, J.C.; Meyers, M.A.

1995-01-01

The micromechanisms involved in the combustion synthesis of a Ti-C-Ni-Mo mixture resulting in the formation of a TiC-based composite were examined using the combustion wave quenching technique developed by Rogachev et al. At the micron level, the main reaction occurs at the interface between a Ti-Ni-C melt and C particles, resulting in the formation of a solid TiC x layer on the C particles. This layer undergoes a successive process of rapid growth and decomposition into TiC x spherules until all of the C particle is consumed. This mechanism is consistent with the apparent activation energy (E = 100 kJ/mol) for the process obtained from a macrokinetic investigation of the system. The apparent uniformity in size (d = 1 μm) of the TiC x spherules upon formation indicates a critical condition in the stability of the energetics involved in the process. These TiC x spherules undergo growth due to Ostwald ripening and coalescence mechanisms resulting in a final apparent size of 2.5 μm. For the compositions investigated, the addition of Mo did not affect either the micromechanisms or macrokinetics of the combustion synthesis process. Densification of the porous body after the combustion synthesis process can be carried out while it is still in a easily deformable state. The highly porous body is densified by a combination of fracture (communition), plastic deformation, and sintering. The mechanisms are identified for the case of combustion synthesized TiC. Mechanical properties and microstructures of a number of materials (e.g. TiC, TiB 2 , Al 2 O 3 -TiB 2 , TiB 2 -SiC, TiC-Ni-Mo) produced by combustion synthesis combined with a high-velocity forging step are reviewed

Impact of oxy-fuel combustion gases on mercury retention in activated carbons from a macroalgae waste: effect of water.

Science.gov (United States)

Lopez-Anton, M A; Ferrera-Lorenzo, N; Fuente, E; Díaz-Somoano, M; Suarez-Ruíz, I; Martínez-Tarazona, M R; Ruiz, B

2015-04-01

The aim of this study is to understand the different sorption behaviors of mercury species on activated carbons in the oxy-fuel combustion of coal and the effect of high quantities of water vapor on the retention process. The work evaluates the interactions between the mercury species and a series of activated carbons prepared from a macroalgae waste (algae meal) from the agar-agar industry in oxy-combustion atmospheres, focussing on the role that the high concentration of water in the flue gases plays in mercury retention. Two novel aspects are considered in this work (i) the impact of oxy-combustion gases on the retention of mercury by activated carbons and (ii) the performance of activated carbons prepared from biomass algae wastes for this application. The results obtained at laboratory scale indicate that the effect of the chemical and textural characteristics of the activated carbons on mercury capture is not as important as that of reactive gases, such as the SOx and water vapor present in the flue gas. Mercury retention was found to be much lower in the oxy-combustion atmosphere than in the O2+N2 (12.6% O2) atmosphere. However, the oxidation of elemental mercury (Hg0) to form oxidized mercury (Hg2+) amounted to 60%, resulting in an enhancement of mercury retention in the flue gas desulfurization units and a reduction in the amalgamation of Hg0 in the CO2 compression unit. This result is of considerable importance for the development of technologies based on activated carbon sorbents for mercury control in oxy-combustion processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

High Velocity Gas Gun

Science.gov (United States)

1988-01-01

A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

Energy Technology Data Exchange (ETDEWEB)

Rader, D.J.; Benson, D.A.

1995-05-01

This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 {mu}m and a geometric standard deviation, {sigma}{sub g} of about 2; the CMD was found to increase and {sigma}{sub g} decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 {mu}m and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented.

Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

International Nuclear Information System (INIS)

Rader, D.J.; Benson, D.A.

1995-05-01

This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 μm and a geometric standard deviation, σ g of about 2; the CMD was found to increase and σ g decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 μm and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented

Transient flow combustion

Science.gov (United States)

Tacina, R. R.

1984-01-01

Non-steady combustion problems can result from engine sources such as accelerations, decelerations, nozzle adjustments, augmentor ignition, and air perturbations into and out of the compressor. Also non-steady combustion can be generated internally from combustion instability or self-induced oscillations. A premixed-prevaporized combustor would be particularly sensitive to flow transients because of its susceptability to flashback-autoignition and blowout. An experimental program, the Transient Flow Combustion Study is in progress to study the effects of air and fuel flow transients on a premixed-prevaporized combustor. Preliminary tests performed at an inlet air temperature of 600 K, a reference velocity of 30 m/s, and a pressure of 700 kPa. The airflow was reduced to 1/3 of its original value in a 40 ms ramp before flashback occurred. Ramping the airflow up has shown that blowout is more sensitive than flashback to flow transients. Blowout occurred with a 25 percent increase in airflow (at a constant fuel-air ratio) in a 20 ms ramp. Combustion resonance was found at some conditions and may be important in determining the effects of flow transients.

Enhanced activity and stability of La-doped CeO2 monolithic catalysts for lean-oxygen methane combustion.

Science.gov (United States)

Zhu, Wenjun; Jin, Jianhui; Chen, Xiao; Li, Chuang; Wang, Tonghua; Tsang, Chi-Wing; Liang, Changhai

2018-02-01

Effective utilization of coal bed methane is very significant for energy utilization and environment protection. Catalytic combustion of methane is a promising way to eliminate trace amounts of oxygen in the coal bed methane and the key to this technology is the development of high-efficiency catalysts. Herein, we report a series of Ce 1-x La x O 2-δ (x = 0-0.8) monolithic catalysts for the catalytic combustion of methane, which are prepared by citric acid method. The structural characterization shows that the substitution of La enhance the oxygen vacancy concentration and reducibility of the supports and promote the migration of the surface oxygen, as a result improve the catalytic activity of CeO 2 . M-Ce 0.8 La 0.2 O 2-δ (monolithic catalyst, Ce 0.8 La 0.2 O 2-δ coated on cordierite honeycomb) exhibits outstanding activity for methane combustion, and the temperature for 10 and 90% methane conversion are 495 and 580 °C, respectively. Additionally, Ce 0.8 La 0.2 O 2-δ monolithic catalyst presents excellent stability at high temperature. These Ce 1-x La x O 2-δ monolithic materials with a small amount of La incorporation therefore show promises as highly efficient solid solution catalysts for lean-oxygen methane combustion. Graphical abstract ᅟ.

Quenching Combustible Dust Mixtures Using Electric Particulate Suspensions (EPS): A New Testing Method For Microgravity

Science.gov (United States)

Colver, Gerald M.; Greene, Nathanael; Shoemaker, David; Xu, Hua

2003-01-01

The Electric Particulate Suspension (EPS) is a combustion ignition system being developed at Iowa State University for evaluating quenching effects of powders in microgravity (quenching distance, ignition energy, flammability limits). Because of the high cloud uniformity possible and its simplicity, the EPS method has potential for "benchmark" design of quenching flames that would provide NASA and the scientific community with a new fire standard. Microgravity is expected to increase suspension uniformity even further and extend combustion testing to higher concentrations (rich fuel limit) than is possible at normal gravity. Two new combustion parameters are being investigated with this new method: (1) the particle velocity distribution and (2) particle-oxidant slip velocity. Both walls and (inert) particles can be tested as quenching media. The EPS method supports combustion modeling by providing accurate measurement of flame-quenching distance as a parameter in laminar flame theory as it closely relates to characteristic flame thickness and flame structure. Because of its design simplicity, EPS is suitable for testing on the International Space Station (ISS). Laser scans showing stratification effects at 1-g have been studied for different materials, aluminum, glass, and copper. PTV/PIV and a leak hole sampling rig give particle velocity distribution with particle slip velocity evaluated using LDA. Sample quenching and ignition energy curves are given for aluminum powder. Testing is planned for the KC-135 and NASA s two second drop tower. Only 1-g ground-based data have been reported to date.

Mixing and combustion enhancement of Turbocharged Solid Propellant Ramjet

Science.gov (United States)

Liu, Shichang; Li, Jiang; Zhu, Gen; Wang, Wei; Liu, Yang

2018-02-01

Turbocharged Solid Propellant Ramjet is a new concept engine that combines the advantages of both solid rocket ramjet and Air Turbo Rocket, with a wide operation envelope and high performance. There are three streams of the air, turbine-driving gas and augment gas to mix and combust in the afterburner, and the coaxial intake mode of the afterburner is disadvantageous to the mixing and combustion. Therefore, it is necessary to carry out mixing and combustion enhancement research. In this study, the numerical model of Turbocharged Solid Propellant Ramjet three-dimensional combustion flow field is established, and the numerical simulation of the mixing and combustion enhancement scheme is conducted from the aspects of head region intake mode to injection method in afterburner. The results show that by driving the compressed air to deflect inward and the turbine-driving gas to maintain strong rotation, radial and tangential momentum exchange of the two streams can be enhanced, thereby improving the efficiency of mixing and combustion in the afterburner. The method of injecting augment gas in the transverse direction and making sure the injection location is as close as possible to the head region is beneficial to improve the combustion efficiency. The outer combustion flow field of the afterburner is an oxidizer-rich environment, while the inner is a fuel-rich environment. To improve the efficiency of mixing and combustion, it is necessary to control the injection velocity of the augment gas to keep it in the oxygen-rich zone of the outer region. The numerical simulation for different flight conditions shows that the optimal mixing and combustion enhancement scheme can obtain high combustion efficiency and have excellent applicability in a wide working range.

The Influence of Particle Size, Fluidization Velocity, and Fuel Type on Ash-Induced Agglomeration in Biomass Combustion

Energy Technology Data Exchange (ETDEWEB)

Gatternig, Bernhard, E-mail: bernhard.gatternig@cbi.uni-erlangen.de; Karl, Jürgen [Chair of Energy Process Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Nuremberg (Germany)

2014-11-19

Agglomeration of the bed material is one of the main obstacles for biomass utilization in fluidized bed combustors. Especially, high-potential fuels such as fast growing energy crops or biogeneous residues are affected because of their high content of alkaline metals. Despite ongoing research efforts, the knowledge base on what fuels are affected is still limited. This paper describes the design and installation of two lab-scale reactors for the experimental determination of agglomeration temperatures. The reactor concept and measurement method were developed under consideration of experiences from existing test rigs published in literature. Preliminary tests confirmed a reproducibility of ±5°C for both new reactors. The results of an extended measurement campaign (156 test runs of 25 fuel species at a wide range of the operational parameters “bed particle size,” “gas velocity,” and “bed ash accumulation”), based on “design of experiment” (DoE) criteria, showed high-agglomeration tendencies for residues (e.g., dried distillery grains, corn cobs) while woody energy crops (e.g., willow, alder) exhibited very stable combustion behavior. The operating parameters influenced the agglomeration behavior to a lesser degree than different ash compositions of fuel species tested. An interpolation within the DoE factor space allowed for a subsequent comparison of our results with experiments reported in literature. Good agreement was reached for fuels of comparable ash composition considering the interpolation errors of ±32°C on average.

Tailoring a High Temperature Corrosion Resistant FeNiCrAl for Oxy-Combustion Application by Thermal Spray Coating and HIP

Directory of Open Access Journals (Sweden)

Jarkko Metsäjoki

2015-10-01

Full Text Available Oxy-fuel combustion combined with CCS (carbon capture and storage aims to decrease CO2 emissions in energy production using fossil fuels. Oxygen firing changes power plant boiler conditions compared to conventional firing. Higher material temperatures and harsher and more variable environmental conditions cause new degradation processes that are inadequately understood at the moment. In this study, an Fe-Ni-Cr-Al alloy was developed based on thermodynamic simulations. The chosen composition was manufactured as powder by gas atomization. The powder was sieved into two fractions: The finer was used to produce thermal spray coatings by high velocity oxy-fuel (HVOF and the coarser to manufacture bulk specimens by hot isostatic pressing (HIP. The high temperature corrosion properties of the manufactured FeNiCrAl coating and bulk material were tested in laboratory conditions simulating oxy-combustion. The manufacturing methods and the results of high temperature corrosion performance are presented. The corrosion performance of the coating was on average between the bulk steel references Sanicro 25 and TP347HFG.

Combustion Mode Design with High Efficiency and Low Emissions Controlled by Mixtures Stratification and Fuel Reactivity

Directory of Open Access Journals (Sweden)

Hu eWang

2015-08-01

Full Text Available This paper presents a review on the combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixture stratification that have been conducted in the authors’ group, including the charge reactivity controlled homogeneous charge compression ignition (HCCI combustion, stratification controlled premixed charge compression ignition (PCCI combustion, and dual-fuel combustion concepts controlled by both fuel reactivity and mixture stratification. The review starts with the charge reactivity controlled HCCI combustion, and the works on HCCI fuelled with both high cetane number fuels, such as DME and n-heptane, and high octane number fuels, such as methanol, natural gas, gasoline and mixtures of gasoline/alcohols, are reviewed and discussed. Since single fuel cannot meet the reactivity requirements under different loads to control the combustion process, the studies related to concentration stratification and dual-fuel charge reactivity controlled HCCI combustion are then presented, which have been shown to have the potential to achieve effective combustion control. The efforts of using both mixture and thermal stratifications to achieve the auto-ignition and combustion control are also discussed. Thereafter, both charge reactivity and mixture stratification are then applied to control the combustion process. The potential and capability of thermal-atmosphere controlled compound combustion mode and dual-fuel reactivity controlled compression ignition (RCCI/highly premixed charge combustion (HPCC mode to achieve clean and high efficiency combustion are then presented and discussed. Based on these results and discussions, combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixtures stratification in the whole operating range is proposed.

Sludge combustion in fluidized bed reactors at laboratory scale

International Nuclear Information System (INIS)

Chirone, R.; Cammarota, A.

2001-01-01

The combustion of a dried sewage sludge in laboratory scale fluidized bed has been studied in Naples by the Istituto di ricerche sulla combustione (Irc) in the framework of a National project named Thermal Process with Energy Recovery to be used in laboratory and pre-pilot scale apparatus. The attention has been focused on emissions of unreacted carbon as elutriated fines, on the emissions of pollutant gases and on the assessment of the inventory of fly- and bottom ashes. The combustion behaviour of sewage sludge has been compared with those of a market available Tyre Derived Fuel (TDF) and a biomass from Mediterranean area (Robinia Pseudoacacia) and with that of a South African bituminous coal. Stationary combustion tests were carried out at 850 0 C by feeding particles in the size range 0-1 mm into a bed of silica sand without any sorbent addition. The fluidized bed combustor has been operated, at a superficial gas velocity of 0.4 m/s and different excesses of air ranging between 14 and 98%. Relatively high combustion efficiency, larger than 98.9% has been obtained in experiments carried out with sewage sludge and excess of air larger than 20%. These values, are comparable with those obtained in previously experimental activity carried out under similar operative conditions with a South Africa Bituminous coal (97-98%). It is larger than those obtained by using a Tyre Derived Fuel (89-90%) and the Robinia Pseudoacacia Biomass (93-93%). The relative importance of carbon fines elutriation, CO emissions and volatile bypassing the bed in determining the loss of combustion efficiency has been evaluated for the different fuels tested [it

The thermodynamic characteristics of high efficiency, internal-combustion engines

International Nuclear Information System (INIS)

Caton, Jerald A.

2012-01-01

Highlights: ► The thermodynamics of an automotive engine are determined using a cycle simulation. ► The net indicated thermal efficiency increased from 37.0% to 53.9%. ► High compression ratio, lean mixtures and high EGR were the important features. ► Efficiency increased due to lower heat losses, and increased work conversion. ► The nitric oxides were essentially zero due to the low combustion temperatures. - Abstract: Recent advancements have demonstrated new combustion modes for internal combustion engines that exhibit low nitric oxide emissions and high thermal efficiencies. These new combustion modes involve various combinations of stratification, lean mixtures, high levels of EGR, multiple injections, variable valve timings, two fuels, and other such features. Although the exact combination of these features that provides the best design is not yet clear, the results (low emissions with high efficiencies) are of major interest. The current work is directed at determining some of the fundamental thermodynamic reasons for the relatively high efficiencies and to quantify these factors. Both the first and second laws are used in this assessment. An automotive engine (5.7 l) which included some of the features mentioned above (e.g., high compression ratios, lean mixtures, and high EGR) was evaluated using a thermodynamic cycle simulation. These features were examined for a moderate load (bmep = 900 kPa), moderate speed (2000 rpm) condition. By the use of lean operation, high EGR levels, high compression ratio and other features, the net indicated thermal efficiency increased from 37.0% to 53.9%. These increases are explained in a step-by-step fashion. The major reasons for these improvements include the higher compression ratio and the dilute charge (lean mixture, high EGR). The dilute charge resulted in lower temperatures which in turn resulted in lower heat loss. In addition, the lower temperatures resulted in higher ratios of the specific heats which

Influence of the altitude on the burning velocity of the natural gas

International Nuclear Information System (INIS)

Arrieta, Andres Amell; Garcia Posada, Jorge Mario; Quilindo Valencia, Arvey; Henao Vallejo, Diego Alberto

2004-01-01

By the increasing use of natural gas in cities of Latin America located to high altitude, is necessary to study the effect of the altitude on the combustion, for example the burning velocity. This work is an experimental study of as it changes to the burning velocity with the altitude, being made test in sites with altitude of 40, 550, 1.020, 1.550, 2.040 and 2.550 meters. The result was that the variations are slight

Effect of Metal Additives on the Combustion Characteristics of High-Energy Materials

OpenAIRE

Korotkikh, Aleksandr Gennadievich; Glotov, Oleg; Sorokin, Ivan

2016-01-01

Thermodynamic calculation of combustion parameters and equilibrium composition of HEMs combustion products showed, that at the increase of aluminum powder dispersity the specific impulse and combustion temperature of solid propellants are reduced due to the decrease of the mass fraction of active aluminum in particles. Partial or complete replacement of aluminum by metal powder (B, Mg, AlB[2], Al\\Mg alloy, Fe, Ti and Zr) in HEMs composition leads to the reduce of the specific impulse and comb...

In situ high-temperature gas sensors: continuous monitoring of the combustion quality of different wood combustion systems and optimization of combustion process

Directory of Open Access Journals (Sweden)

H. Kohler

2018-03-01

Full Text Available The sensing characteristics and long-term stability of different kinds of CO ∕ HC gas sensors (non-Nernstian mixed potential type during in situ operation in flue gas from different types of low-power combustion systems (wood-log- and wood-chip-fuelled were investigated. The sensors showed representative but individual sensing behaviour with respect to characteristically varying flue gas composition over the combustion process. The long-term sensor signal stability evaluated by repeated exposure to CO ∕ H2 ∕ N2 ∕ synthetic air mixtures showed no sensitivity loss after operation in the flue gas. Particularly for one of the sensors (Heraeus GmbH, this high signal stability was observed in a field test experiment even during continuous operation in the flue gas of the wood-chip firing system over 4 months. Furthermore, it was experimentally shown that the signals of these CO ∕ HC sensing elements yield important additional information about the wood combustion process. This was demonstrated by the adaptation of an advanced combustion airstream control algorithm on a wood-log-fed fireplace and by the development of a combustion quality monitoring system for wood-chip-fed central heaters.

Effects of air jet duration and timing on the combustion characteristics of high-pressure air jet controlled compression ignition combustion mode in a hybrid pneumatic engine

International Nuclear Information System (INIS)

Long, Wuqiang; Meng, Xiangyu; Tian, Jiangping; Tian, Hua; Cui, Jingchen; Feng, Liyan

2016-01-01

Highlights: • A 3-D CFD model of the power cylinder in HPE was developed. • High-pressure air JCCI combustion mode includes two-stage high-temperature reaction. • The combustion phasing of the pre-mixture is controllable via the SOJ timing. • There exists an optimum SOJ timing for obtaining the highest combustion efficiency and shortest burning duration. - Abstract: The high-pressure air jet controlled compression ignition (JCCI) combustion mode was employed to control the premixed diesel compression ignition combustion phasing by using the compound thermodynamic cycle under all operating conditions, which is accomplished in a hybrid pneumatic engine (HPE). A three-dimensional computational fluid dynamics (CFD) numerical simulation coupled with reduced n-heptane chemical kinetics mechanism has been applied to investigate the effects of high-pressure air jet duration and the start of jet (SOJ) timing on the combustion characteristics in the power cylinder of HPE. By sweeping the high-pressure air jet durations from 6 to 14 °CA and SOJ timings from −12 °CA ATDC to the top dead center (TDC) under the air jet temperatures of 400 and 500 K, respectively, the low- and high-temperature reactions, combustion efficiency, as well as the combustion phasing and burning duration have been analyzed in detail. The results illustrated that a longer air jet duration results in a higher peak in the first-stage high-temperature reaction, and the short air jet duration of 6 °CA can lead to a higher combustion efficiency. The SOJ timing sweep results showed that there exists an optimum timing for obtaining the highest combustion efficiency and shortest burning duration.

Superconducting spoke cavities for high-velocity applications

Energy Technology Data Exchange (ETDEWEB)

Hopper, Christopher S. [Old Dominion U.; Delayen, Jean R. [Old Dominion U., JLAB

2013-10-01

To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.

High Gravity (g) Combustion

Science.gov (United States)

2006-02-01

UNICORN (Unsteady Ignition and Combustion with Reactions) code10. Flame propagation in a tube that is 50-mm wide and 1000-mm long (similar to that...turbine engine manufacturers, estimating the primary zone space heating rate. Both combustion systems, from Company A and Company B, required a much...MBTU/atm-hr-ft3) Te m pe ra tu re R is e (K ) dP/P = 2% dP/P = 2.5% dP/P = 3% dP/P = 3.5% dP/P = 4% Company A Company B Figure 13: Heat Release Rate

Study on Combustion Characteristics and Propelling Projectile Motion Process of Bulk-Loaded Liquid Propellant

Science.gov (United States)

Xue, Xiaochun; Yu, Yonggang; Mang, Shanshan

2017-07-01

Data are presented showing that the problem of gas-liquid interaction instability is an important subject in the combustion and the propellant projectile motion process of a bulk-loaded liquid propellant gun (BLPG). The instabilities themselves arise from the sources, including fluid motion, to form a combustion gas cavity called Taylor cavity, fluid turbulence and breakup caused by liquid motion relative to the combustion chamber walls, and liquid surface breakup arising from a velocity mismatch on the gas-liquid interface. Typically, small disturbances that arise early in the BLPG combustion interior ballistic cycle can become amplified in the absence of burn rate limiting characteristics. Herein, significant attention has been given to developing and emphasizing the need for better combustion repeatability in the BLPG. Based on this goal, the concept of using different geometries of the combustion chamber is introduced and the concept of using a stepped-wall structure on the combustion chamber itself as a useful means of exerting boundary control on the combustion evolution to thus restrain the combustion instability has been verified experimentally in this work. Moreover, based on this background, the numerical simulation is devoted to a special combustion issue under transient high-pressure and high-temperature conditions, namely, studying the combustion mechanism in a stepped-wall combustion chamber with full monopropellant on one end that is stationary and the other end can move at high speed. The numerical results also show that the burning surface of the liquid propellant can be defined geometrically and combustion is well behaved as ignition and combustion progressivity are in a suitable range during each stage in this combustion chamber with a stepped-wall structure.

SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS

International Nuclear Information System (INIS)

Kwak, Kyujin; Henley, David B.; Shelton, Robin L.

2011-01-01

We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass ∼ 120 M sun ) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass ∼ 4 x 10 5 M sun ) remained largely intact, although deformed, during its simulation period (240 Myr).

Development of a high-pressure compaction system for non-combustible solid waste

International Nuclear Information System (INIS)

Yogo, S.; Hata, T.; Torita, K.; Yamamoto, K.; Karita, Y.

1989-01-01

In recent years, nuclear power plants in Japan have been in search of a means to reduce the volume of non-combustible solid wastes and therefore the application of a high-pressure compaction system has been in demand. Most non-combustible solid wastes have been packed in 200-litre drums for storage and the situation requires a high-pressure compaction system designed exclusively for 200-litre drums. The authors have developed a high-pressure compaction system which compresses 200-litre drums filled with non-combustible solid wastes and packs them into new woo-litre drums efficiently. This paper reports the outline of this high-pressure compaction system and the results of the full-scale verification tests

Verification of Conditions for use of Combustion Products‘ Heat

Directory of Open Access Journals (Sweden)

Kažimírová Viera

2015-06-01

Full Text Available Presented contribution deals with the verification of conditions for use of combustion products‘ heat, generated by combustion of wood in a fireplace used in a household. It is necessary to know the temperature behaviour of the fireplace to determine the adequacy of the technical solution for using combustion products‘ heat. The combustion products‘ temperature at the upper part of the chimney is 80-120 °C. The dew point value was established to be below 51 °C. The average observed value of combustion product velocity is 1.6 m s-1. The volume flow rate of combustion products is 12 m3 h-1. Measured values allow for effective solution of the use of combustion products‘ heat.

High-velocity runaway stars from three-body encounters

Science.gov (United States)

Gvaramadze, V. V.; Gualandris, A.; Portegies Zwart, S.

2010-01-01

We performed numerical simulations of dynamical encounters between hard, massive binaries and a very massive star (VMS; formed through runaway mergers of ordinary stars in the dense core of a young massive star cluster) to explore the hypothesis that this dynamical process could be responsible for the origin of high-velocity (≥ 200 - 400 km s-1) early or late B-type stars. We estimated the typical velocities produced in encounters between very tight massive binaries and VMSs (of mass of ≥ 200 M⊙) and found that about 3 - 4% of all encounters produce velocities ≥ 400 km s-1, while in about 2% of encounters the escapers attain velocities exceeding the Milky Ways's escape velocity. We therefore argue that the origin of high-velocity (≥ 200 - 400 km s-1) runaway stars and at least some so-called hypervelocity stars could be associated with dynamical encounters between the tightest massive binaries and VMSs formed in the cores of star clusters. We also simulated dynamical encounters between tight massive binaries and single ordinary 50 - 100 M⊙ stars. We found that from 1 to ≃ 4% of these encounters can produce runaway stars with velocities of ≥ 300 - 400 km s-1 (typical of the bound population of high-velocity halo B-type stars) and occasionally (in less than 1% of encounters) produce hypervelocity (≥ 700 km s-1) late B-type escapers.

Fuel oil-water emulsions combustion and application perspectives in Mexico; Combustion de emulsiones de agua en combustoleo y perspectivas de aplicacion en Mexico

Energy Technology Data Exchange (ETDEWEB)

Ocampo Barrera, Rene [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1998-09-01

Fuel drops with a content of 16% by weight were burned in three emulsions prepared with 5%, 15% and 25% water. The combustion of the drops was carried out in an spherical furnace utilizing the technique of a drop suspended in a filament. The combustion process was registered by a high velocity video system. It was found that the surface of the particles produced by the combustion of the emulsions, had larger holes than the ones of the fuel, therefore it is expected that emulsifying the fuel can help in reducing the unburned particles emission. [Espanol] Se quemaron gotas de un combustoleo, con un contenido de asfaltenos del 16% en peso, y de tres emulsiones preparadas con 5%, 15% y 25% de agua. La combustion de las gotas se llevo a cabo en un horno esferico empleando la tecnica de gota suspendida en un filamento. El proceso de combustion se registro mediante un sistema de video de alta velocidad. Se encontro que la superficie de las particulas de coque, producidas por la combustion de emulsiones, tuvo hoyos mas grandes que la del combustoleo, por lo que es de esperarse que emulsionar el combustoleo puede ayudar a reducir las emisiones de particulas inquemadas.

On the origin of high-velocity runaway stars

Science.gov (United States)

Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

2009-06-01

We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary 50-100Msolar star or a more massive one, formed through runaway mergers of ordinary stars in the core of a young massive star cluster). In this process, one of the binary components becomes gravitationally bound to the very massive star, while the second one is ejected, sometimes with a high speed. We performed three-body scattering experiments and found that early B-type stars (the progenitors of the majority of neutron stars) can be ejected with velocities of >~200-400kms-1 (typical of pulsars), while 3-4Msolar stars can attain velocities of >~300-400kms-1 (typical of the bound population of halo late B-type stars). We also found that the ejected stars can occasionally attain velocities exceeding the Milky Ways's escape velocity.

GOTHIC-3D applicability to hydrogen combustion analysis

International Nuclear Information System (INIS)

Lee, Jung Jae; Lee, Jin Yong; Park, Goon Cherl; Yoo, Ho Jong; Kim, Hyeong Taek; Lee, Byung Chul; Oh, Seung Jong

2005-01-01

Severe accidents in nuclear power plants can cause hydrogen-generating chemical reactions, which create the danger of hydrogen combustion and thus threaten containment integrity. For containment analyses, a three-dimensional mechanistic code, GOTHIC-3D has been applied near source compartments to predict whether or not highly reactive gas mixtures can form during an accident with the hydrogen mitigation system working. To assess the code applicability to hydrogen combustion analysis, this paper presents the numerical calculation results of GOTHIC-3D for various hydrogen combustion experiments, including FLAME, LSVCTF, and SNU-2D. In this study, a technical base for the modeling of large- and small-scale facilities was introduced through sensitivity studies on cell size and burn modeling parameters. Use of a turbulent burn option of the eddy dissipation concept enabled scale-free applications. Lowering the burn parameter values for the flame thickness and the burn temperature limit resulted in a larger flame velocity. When applied to hydrogen combustion analysis, this study revealed that the GOTHIC-3D code is generally able to predict the combustion phenomena with its default burn modeling parameters for large-scale facilities. However, the code needs further modifications of its burn modeling parameters to be applied to either small-scale facilities or extremely fast transients

Gasoline Engine HCCI Combustion - Extending the high load limit

Energy Technology Data Exchange (ETDEWEB)

Dahl, Daniel

2012-07-01

There is an increasing global focus on reducing emissions of greenhouse gases. For the automotive industry this means reducing CO2 emissions of the vehicles manufactured, which is synonymous with reducing their fuel consumption or adapting them for using renewable fuels. This thesis is based on a project aimed at improving the efficiency of gasoline engines in the lower load/speed region. The focus was mainly on a combustion strategy called homogeneous charge compression ignition (HCCI), but also on homogeneous lean and stratified lean spark-ignited combustion. In contrast to traditional stoichiometric spark-ignited combustion, HCCI can operate with diluted mixtures, which leads to better cycle efficiency, smaller pumping losses and smaller heat losses. However, at relatively high loads, HCCI combustion becomes excessively rapid, generating in-cylinder pressure oscillations (ringing), which are perceived as noise by the human ear. The main objective of the project was to identify ways to avoid this ringing behaviour in order to increase the upper load limit of HCCI. This is vital to avoid the need for mode switches to spark-ignited combustion at higher loads and to operate the engine as much as possible in the more effective HCCI mode. The strategy for reducing ringing investigated most extensively in the project was charge stratification, achieved by injecting part of the fuel late in the compression stroke. Available literature on effects of this strategy gave conflicting indications, both positive and negative effects have been reported, depending on the type of fuel and engine used. It was soon found that the strategy is effective for reducing ringing, but with resulting increases of NOX emissions. Further, in order for the strategy to be effective, global air/fuel ratios must not be much leaner than stoichiometric. The increases in NOX emissions were countered by shifting the ratio towards stoichiometric using exhaust gas recirculation (EGR), allowing a three

Numerical simulation of altitude impact on pulverized coal combustion

Energy Technology Data Exchange (ETDEWEB)

Pei, Xiaohui; He, Boshu; Ling, Ling; Wang, Lei [Beijing Jiaotong Univ., Beijing (China). Inst. of Mechanical, Electronic and Control Engineering

2013-07-01

A drop-tube Furnace simulation model has been developed to investigate the pulverized coal combustion characteristics under different altitudes using the commercially available software Fluent. The altitude conditions of 0, 500, 1,000, 1,500 m have been discussed. The results included the fields of temperature, pressure, velocity, the coal burnout, CO burnout and NO emission in the tube furnace. The variation of these parameters with altitude has been analyzed. The coal combustion characteristics were affected by the altitude. The time and space for coal burnout should be increased with the rise of altitude. The valuable results could be referenced in the design of coal- fired furnaces for the high altitude areas.

Concept for premixed combustion of hydrogen-containing fuels in gas turbines; Konzept zur vorgemischten Verbrennung wasserstoffhaltiger Brennstoffe in Gasturbinen

Energy Technology Data Exchange (ETDEWEB)

Mayer, Christoph

2012-07-19

One of the main challenges for future gas turbines and their combustion systems is to provide fuel flexibility. The fuel range is expected to reach from the lowly reactive natural gas to highly reactive hydrogen-containing syngases. The objective of the project in which this work was pursued is to develop such a combustion system. The burner has to ensure premixed operation with an aerodynamically stabilized flame. The focus of this work is on characterizing and optimizing the operational safety of the system, but also on ensuring sufficientmixing and lowemissions. A burner and fuel injection design is achieved that leads not only to emissions far below the permissible values, but also to flashback safety for hydrogen combustion that comes close to the theoretically achievable maximum at atmospheric pressure conditions. In this design flashback due to combustion-induced vortex breakdown and wall boundary layer flashback is avoided. Flashback only takes place when the flow velocity reaches the flame velocity.

The Effects of Combustion Parameters on Pollutant Emissions in a Porous Burner

Directory of Open Access Journals (Sweden)

Negin Moallemi Khiavi

2014-06-01

Full Text Available This paper reports a two-dimensional numerical prediction of premixed methane/air combustion in inert porous media. The two dimensional Navier-stokes equations, the two separate energy equations for solid and gas and conservation equations for chemical species are solved using finite volume method based on SIMPLE algorithm. The burner under study is a rectangular one with two different regions. First region is a preheating zone (low porosity matrix that followed by the actual combustion region (high porosity matrix. For simulating the chemical reactions, skeletal mechanism (26 species and 77 reactions is used. For studying the pollutant emissions in this porous burner, the effects of porous matrix properties, excess air ratio and inlet velocity are studied. The predicted gas temperature contour and pollutant formations are in good agreement with the available experimental data. The results indicate that the downstream of the burner should be constructed from materials with high conductivity, high convective heat transfer coefficient and high porosity in order to decrease the CO and NO emissions. Also, with increasing the inlet velocity of gas mixture and the excess air ratio, the pollutant emissions are decreased.

Experimental investigation of flash pyrolysis oil droplet combustion

DEFF Research Database (Denmark)

Ibrahim, Norazana; Jensen, Peter A.; Dam-Johansen, Kim

2013-01-01

at a temperature ranging between 1000 and 1400°C with an initial gas velocity of 1.6 m/s and oxygen concentration of 3%. The evolution of combustion of bio-oil droplets was recorded by a digital video camera. It was observed that the combustion behaviour of pyrolysis oil droplet differ from the heavy oil in terms......The aim of this work is to investigate and compare the combustion behaviour of a single droplet of pyrolysis oil derived from wheat straw and heavy fossil oil in a single droplet combustion chamber. The initial oil droplet diameters were in between 500 μm to 2500 μm. The experiments were performed...

Characterization of biomass combustion at high temperatures based on an upgraded single particle model

International Nuclear Information System (INIS)

Li, Jun; Paul, Manosh C.; Younger, Paul L.; Watson, Ian; Hossain, Mamdud; Welch, Stephen

2015-01-01

Highlights: • High temperature rapid biomass combustion is studied based on single particle model. • Particle size changes in devolatilization and char oxidation models are addressed. • Time scales of various thermal sub-processes are compared and discussed. • Potential solutions are suggested to achieve better biomass co-firing performances. - Abstract: Biomass co-firing is becoming a promising solution to reduce CO 2 emissions, due to its renewability and carbon neutrality. Biomass normally has high moisture and volatile contents, complicating its combustion behavior, which is significantly different from that of coal. A computational fluid dynamics (CFD) combustion model of a single biomass particle is employed to study high-temperature rapid biomass combustion. The two-competing-rate model and kinetics/diffusion model are used to model biomass devolatilization reaction and char burnout process, respectively, in which the apparent kinetics used for those two models were from high temperatures and high heating rates tests. The particle size changes during the devolatilization and char burnout are also considered. The mass loss properties and temperature profile during the biomass devolatilization and combustion processes are predicted; and the timescales of particle heating up, drying, devolatilization, and char burnout are compared and discussed. Finally, the results shed light on the effects of particle size on the combustion behavior of biomass particle

Image processing analysis of combustion for D. I. diesel engine with high pressure fuel injection. ; Effects of air swirl and injection pressure. Nensho shashin no gazo shori ni yoru koatsu funsha diesel kikan no nensho kaiseki. ; Swirl oyobi funsha atsuryoku no eikyo

Energy Technology Data Exchange (ETDEWEB)

Yamaguchi, I. (Japan Automobile Research Institute, Inc., Tsukuba (Japan)); Tsujimura, K.

1994-02-25

This paper reports an image processing analysis of combustion for a high-pressure direct injection diesel engine on the effects of air swirl and injection pressure upon combustion in the diesel engine. The paper summarizes a method to derive gas flow and turbulence strengths, and turbulent flow mixing velocity. The method derives these parameters by detecting movement of brightness unevenness on two flame photographs through utilizing the mutual correlative coefficients of image concentrations. Five types of combustion systems having different injection pressures, injection devices, and swirl ratios were used for the experiment. The result may be summarized as follows: variation in the average value of the turbulent flow mixing velocities due to difference in the swirl ratio is small in the initial phase of diffusion combustion; the difference is smaller in the case of high swirl ratio than in the case of low swirl ratio after the latter stage of the injection; the average value is larger with the higher the injection pressure during the initial stage of the combustion; after termination of the injection, the value is larger in the low pressure injection; and these trends agree with the trend in the time-based change in heat generation rates measured simultaneously. 6 refs., 14 figs., 2 tabs.

Spectroscopy and Kinetics of Combustion Gases at High Temperatures

Energy Technology Data Exchange (ETDEWEB)

Hanson, Ronald [Stanford Univ., CA (United States); Bowman, Craig [Stanford Univ., CA (United States)

2016-02-01

This report describes our research program that involves two complementary activities: (1) development and application of cw laser absorption methods for the measurement of concentration time-histories and fundamental spectroscopic parameters for species of interest in combustion; and (2) shock tube studies of reaction kinetics relevant to combustion. This first part of this report covers research during the final three-year support period, i.e. March 2012 – November 2015. The later part of this report summarizes research conducted over multiple-year periods between March 1988 to March 2012. Publications supported by DOE for each period are summarized at the end of that report section.

Some Applications of Fast Neutron Activation Analysis of Oxygen

Energy Technology Data Exchange (ETDEWEB)

Owrang, Farshid

2003-07-01

In this thesis we focus on applications of neutron activation of oxygen for several purposes: A) measuring the water level in a laboratory tank, B) measuring the water flow in a pipe system set-up, C) analysing the oxygen in combustion products formed in a modern gasoline SI engine, and D) measuring on-line the amount of oxygen in bulk liquids. A) Water level measurements. The purpose of this work was to perform radiation based water level measurements, aimed at nuclear reactor vessels, on a laboratory scale. A laboratory water tank was irradiated by fast neutrons from a neutron generator. The water was activated at different water levels and the water level was decreased. The produced gamma radiation was measured using two detectors at different heights. The results showed that the method is suitable for measurement of water level and that a relatively small experimental set-up can be used for developing methods for water level measurements in real boiling water reactors based on activated oxygen in the water. B) Water flows in pipe. The goal in this work was to investigate the asymmetric distribution of activity in flow measurements with pulsed neutron activation (PNA) in a laboratory piping system. Earlier investigations had shown a discrepancy between the measured velocity of the activated water by PNA and the true mean velocity in the pipe. This discrepancy decreased with larger distances from the activation point. It was speculated that the induced activity in the pipe did not distribute homogeneously. With inhomogeneous radial distribution of activity in combination with a velocity profile in the pipe, the activated water may not have the same velocity as the mean velocity of water in the pipe. To study this phenomenon, a water-soluble colour was injected into a transparent pipe for simulation of the transport of the activated water. The radial concentration of the colour, at different distances from the activation point, was determined. The result

Some Applications of Fast Neutron Activation Analysis of Oxygen

International Nuclear Information System (INIS)

Owrang, Farshid

2003-01-01

In this thesis we focus on applications of neutron activation of oxygen for several purposes: A) measuring the water level in a laboratory tank, B) measuring the water flow in a pipe system set-up, C) analysing the oxygen in combustion products formed in a modern gasoline SI engine, and D) measuring on-line the amount of oxygen in bulk liquids. A) Water level measurements. The purpose of this work was to perform radiation based water level measurements, aimed at nuclear reactor vessels, on a laboratory scale. A laboratory water tank was irradiated by fast neutrons from a neutron generator. The water was activated at different water levels and the water level was decreased. The produced gamma radiation was measured using two detectors at different heights. The results showed that the method is suitable for measurement of water level and that a relatively small experimental set-up can be used for developing methods for water level measurements in real boiling water reactors based on activated oxygen in the water. B) Water flows in pipe. The goal in this work was to investigate the asymmetric distribution of activity in flow measurements with pulsed neutron activation (PNA) in a laboratory piping system. Earlier investigations had shown a discrepancy between the measured velocity of the activated water by PNA and the true mean velocity in the pipe. This discrepancy decreased with larger distances from the activation point. It was speculated that the induced activity in the pipe did not distribute homogeneously. With inhomogeneous radial distribution of activity in combination with a velocity profile in the pipe, the activated water may not have the same velocity as the mean velocity of water in the pipe. To study this phenomenon, a water-soluble colour was injected into a transparent pipe for simulation of the transport of the activated water. The radial concentration of the colour, at different distances from the activation point, was determined. The result

Low-Temperature Combustion of High Octane Fuels in a Gasoline Compression Ignition Engine

Directory of Open Access Journals (Sweden)

Khanh Duc Cung

2017-12-01

Full Text Available Gasoline compression ignition (GCI has been shown as one of the advanced combustion concepts that could potentially provide a pathway to achieve cleaner and more efficient combustion engines. Fuel and air in GCI are not fully premixed compared to homogeneous charge compression ignition (HCCI, which is a completely kinetic-controlled combustion system. Therefore, the combustion phasing can be controlled by the time of injection, usually postinjection in a multiple-injection scheme, to mitigate combustion noise. Gasoline usually has longer ignition delay than diesel. The autoignition quality of gasoline can be indicated by research octane number (RON. Fuels with high octane tend to have more resistance to autoignition, hence more time for fuel-air mixing. In this study, three fuels, namely, aromatic, alkylate, and E30, with similar RON value of 98 but different hydrocarbon compositions were tested in a multicylinder engine under GCI combustion mode. Considerations of exhaust gas recirculating (EGR, start of injection, and boost were investigated to study the sensitivity of dilution, local stratification, and reactivity of the charge, respectively, for each fuel. Combustion phasing (location of 50% of fuel mass burned was kept constant during the experiments. This provides similar thermodynamic conditions to study the effect of fuels on emissions. Emission characteristics at different levels of EGR and lambda were revealed for all fuels with E30 having the lowest filter smoke number and was also most sensitive to the change in dilution. Reasonably low combustion noise (<90 dB and stable combustion (coefficient of variance of indicated mean effective pressure <3% were maintained during the experiments. The second part of this article contains visualization of the combustion process obtained from endoscope imaging for each fuel at selected conditions. Soot radiation signal from GCI combustion were strong during late injection and also more intense

Determination of the propellant combustion law under ballistic experiment conditions

Science.gov (United States)

Ishchenko, A. N.; Diachkovskii, A. S.; Zykova, A. I.; Kasimov, VZ; Samorokova, N. M.

2017-11-01

The main characteristics of ballistic experiment are the maximum pressure in the combustion chamber P max and the projectile velocity at the time of barrel leaving U M. During the work the burning law of the new high-energy fuel was determined in a ballistic experiment. This burning law was used for a parametric study of depending P max and U M from a powder charge mass and a traveling charge at initial temperature of + 20 °C was carried out. The optimal conditions for loading were obtained for improving the muzzle velocity by 14.9 %. Under optimal loading, there is defined the conditions, which is possible to get the greatest value muzzle velocity projectile at pressures up to 600 MPa.

Upscaling Self-Sustaining Treatment for Active Remediation (STAR): Experimental Study of Scaling Relationships for Smouldering Combustion to Remediate Soil

Science.gov (United States)

Kinsman, L.; Gerhard, J.; Torero, J.; Scholes, G.; Murray, C.

2013-12-01

Self-sustaining Treatment for Active Remediation (STAR) is a relatively new remediation approach for soil contaminated with organic industrial liquids. This technology uses smouldering combustion, a controlled, self-sustaining burning reaction, to destroy nonaqueous phase liquids (NAPLs) and thereby render soil clean. While STAR has been proven at the bench scale, success at industrial scales requires the process to be scaled-up significantly. The objective of this study was to conduct an experimental investigation into how liquid smouldering combustion phenomena scale. A suite of detailed forward smouldering experiments were conducted in short (16 cm dia. x 22 cm high), intermediate (16 cm dia. x 127 cm high), and large (97 cm dia. x 300 cm high; a prototype ex-situ reactor) columns; this represents scaling of up to 530 times based on the volume treated. A range of fuels were investigated, with the majority of experiments conducted using crude oil sludge as well as canola oil as a non-toxic surrogate for hazardous contaminants. To provide directly comparable data sets and to isolate changes in the smouldering reaction which occurred solely due to scaling effects, sand grain size, contaminant type, contaminant concentration and air injection rates were controlled between the experimental scales. Several processes could not be controlled and were identified to be susceptible to changes in scale, including: mobility of the contaminant, heat losses, and buoyant flow effects. For each experiment, the propagation of the smouldering front was recorded using thermocouples and analyzed by way of temperature-time and temperature-distance plots. In combination with the measurement of continuous mass loss and gaseous emissions, these results were used to evaluate the fundamental differences in the way the reaction front propagates through the mixture of sand and fuel across the various scales. Key governing parameters were compared between the small, intermediate, and large

Experimental and Numerical Studies on Self-Propagating High-Temperature Synthesis of Ta5Si3 Intermetallics

Directory of Open Access Journals (Sweden)

Chun-Liang Yeh

2015-09-01

Full Text Available Formation of Ta5Si3 by self-propagating high-temperature synthesis (SHS from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion wave velocity and reaction temperature. The apparent activation energy, Ea ≈ 108 kJ/mol, was determined for the synthesis reaction. Based upon numerical simulation, the Arrhenius factor of the rate function, K0 = 2.5 × 107 s−1, was obtained for the 5Ta + 3Si combustion system. In addition, the influence of sample density on combustion wave kinetics was correlated with the effective thermal conductivity (keff of the powder compact. By adopting 0.005 ≤ keff/kbulk ≤ 0.016 in the computation model, the calculated combustion velocity and temperature were in good agreement with experimental data of the samples with compaction densities between 35% and 45% theoretical maximum density (TMD.

Carbohydrate-Assisted Combustion Synthesis To Realize High-Performance Oxide Transistors.

Science.gov (United States)

Wang, Binghao; Zeng, Li; Huang, Wei; Melkonyan, Ferdinand S; Sheets, William C; Chi, Lifeng; Bedzyk, Michael J; Marks, Tobin J; Facchetti, Antonio

2016-06-08

Owing to high carrier mobilities, good environmental/thermal stability, excellent optical transparency, and compatibility with solution processing, thin-film transistors (TFTs) based on amorphous metal oxide semiconductors (AOSs) are promising alternatives to those based on amorphous silicon (a-Si:H) and low-temperature (IGZO) TFTs suffer from low carrier mobilities and/or inferior bias-stress stability versus their sputtered counterparts. Here we report that three types of environmentally benign carbohydrates (sorbitol, sucrose, and glucose) serve as especially efficient fuels for IGZO film combustion synthesis to yield high-performance TFTs. The results indicate that these carbohydrates assist the combustion process by lowering the ignition threshold temperature and, for optimal stoichiometries, enhancing the reaction enthalpy. IGZO TFT mobilities are increased to >8 cm(2) V(-1) s(-1) on SiO2/Si gate dielectrics with significantly improved bias-stress stability. The first correlations between precursor combustion enthalpy and a-MO densification/charge transport are established.

High-magnification velocity field measurements on high-frequency, supersonic microactuators

Science.gov (United States)

Kreth, Phil; Fernandez, Erik; Ali, Mohd; Alvi, Farrukh

2014-11-01

The Resonance-Enhanced Microjet (REM) actuator developed at our laboratory produces pulsed, supersonic microjets by utilizing a number of microscale, flow-acoustic resonance phenomena. The microactuator used in this study consists of an underexpanded source jet flowing into a cylindrical cavity with a single orifice through which an unsteady, supersonic jet issues at a resonant frequency of 7 kHz. The flowfields of a 1 mm underexpanded free jet and the microactuator are studied in detail using high-magnification, phase-locked flow visualizations (microschlieren) and 2-component particle image velocimetry. The challenges of these measurements at such small scales and supersonic velocities are discussed. The results clearly show that the microactuator produces supersonic pulsed jets with velocities exceeding 400 m/s. This is the first direct measurement of the velocity field and its temporal evolution produced by such actuators. Comparisons are made between the flow visualizations, velocity field measurements, and simulations using Implicit LES for a similar microactuator. With high, unsteady momentum output, this type of microactuator has potential in a range of flow control applications.

Determination of burning velocity of methane-air mixtures using soap bubbles and a hot-wire anemometer

Energy Technology Data Exchange (ETDEWEB)

Sakai, Yukio

1987-12-25

The rate of combustion of the mixture of methane and air under a constant atmospheric pressure was determined using a soap bubble and a hot-wire anemometer. The flame propagation velocity, Ss, of the specified ratio of mixed gas confined in a soap bubble regarded as a transparent vessel was recorded using the multi-exposurement schlieren method by igniting the gas at the centre of bubble. The velocity of mixed gas, Sg, in front of the flame was measured by the hot-wire anemometer installed in the soap bubble to obtain the rate of combustion Su (Ss-Sg). The maximum Su was 45 cm/s obtained at the ratio of equivalent amounts of 1.08, which agreed with the theoretical value of one-dimensional flame. This is because the measuring method accords with the definition of rate of combustion. Su was 12.5 and 11.0 cm/s at the ratio of equivalent amounts of 0.6 and 1.6, respectively. The measurements by this method considerably agreed with those by conventional similar methods and other high-accuracy methods. The method is applicable accurately to various combustible mixed gas. (6 figs, 1 tab, 18 refs)

High velocity properties of the dynamic frictional force between ductile metals

International Nuclear Information System (INIS)

Hammerberg, James Edward; Hollan, Brad L.; Germann, Timothy C.; Ravelo, Ramon J.

2010-01-01

The high velocity properties of the tangential frictional force between ductile metal interfaces seen in large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations are characterized by interesting scaling behavior. In many cases a power law decrease in the frictional force with increasing velocity is observed at high velocities. We discuss the velocity dependence of the high velocity branch of the tangential force in terms of structural transformation and ultimate transition, at the highest velocities, to confined fluid behavior characterized by a critical strain rate. The particular case of an Al/Al interface is discussed.

Pulsating combustion - Combustion characteristics and reduction of emissions

Energy Technology Data Exchange (ETDEWEB)

Lindholm, Annika

1999-11-01

In the search for high efficiency combustion systems pulsating combustion has been identified as one of the technologies that potentially can meet the objectives of clean combustion and good fuel economy. Pulsating combustion offers low emissions of pollutants, high heat transfer and efficient combustion. Although it is an old technology, the interest in pulsating combustion has been renewed in recent years, due to its unique features. Various applications of pulsating combustion can be found, mainly as drying and heating devices, of which the latter also have had commercial success. It is, however, in the design process of a pulse combustor, difficult to predict the operating frequency, the heat release etc., due to the lack of a well founded theory of the phenomenon. Research concerning control over the combustion process is essential for developing high efficiency pulse combustors with low emissions. Natural gas fired Helmholtz type pulse combustors have been the experimental objects of this study. In order to investigate the interaction between the fluid dynamics and the chemistry in pulse combustors, laser based measuring techniques as well as other conventional measuring techniques have been used. The experimental results shows the possibilities to control the combustion characteristics of pulsating combustion. It is shown that the time scales in the large vortices created at the inlet to the combustion chamber are very important for the operation of the pulse combustor. By increasing/decreasing the time scale for the large scale mixing the timing of the heat release is changed and the operating characteristics of the pulse combustor changes. Three different means for NO{sub x} reduction in Helmholtz type pulse combustors have been investigated. These include exhaust gas recirculation, alteration of air/fuel ratio and changed inlet geometry in the combustion chamber. All used methods achieved less than 10 ppm NO{sub x} emitted (referred to stoichiometric

Combustion

CERN Document Server

Glassman, Irvin

2008-01-01

Combustion Engineering, a topic generally taught at the upper undergraduate and graduate level in most mechanical engineering programs, and many chemical engineering programs, is the study of rapid energy and mass transfer usually through the common physical phenomena of flame oxidation. It covers the physics and chemistry of this process and the engineering applications-from the generation of power such as the internal combustion automobile engine to the gas turbine engine. Renewed concerns about energy efficiency and fuel costs, along with continued concerns over toxic and particulate emissions have kept the interest in this vital area of engineering high and brought about new developments in both fundamental knowledge of flame and combustion physics as well as new technologies for flame and fuel control. *New chapter on new combustion concepts and technologies, including discussion on nanotechnology as related to combustion, as well as microgravity combustion, microcombustion, and catalytic combustion-all ...

Manifold methods for methane combustion

Energy Technology Data Exchange (ETDEWEB)

Yang, B.; Pope, S.B. [Cornell Univ., Ithaca, NY (United States)

1995-10-01

Great progresses have been made in combustion research, especially, the computation of laminar flames and the probability density function (PDF) method in turbulent combustion. For one-dimensional laminar flames, by considering the transport mechanism, the detailed chemical kinetic mechanism and the interactions between these two basic processes, today it is a routine matter to calculate flame velocities, extinction, ignition, temperature, and species distributions from the governing equations. Results are in good agreement with those obtained for experiments. However, for turbulent combustion, because of the complexities of turbulent flow, chemical reactions, and the interaction between them, in the foreseeable future, it is impossible to calculate the combustion flow field by directly integrating the basic governing equations. So averaging and modeling are necessary in turbulent combustion studies. Averaging, on one hand, simplifies turbulent combustion calculations, on the other hand, it introduces the infamous closure problems, especially the closure problem with chemical reaction terms. Since in PDF calculations of turbulent combustion, the averages of the chemical reaction terms can be calculated, PDF methods overcome the closure problem with the reaction terms. It has been shown that the PDF method is a most promising method to calculate turbulent combustion. PDF methods have been successfully employed to calculate laboratory turbulent flames: they can predict phenomena such as super equilibrium radical levels, and local extinction. Because of these advantages, PDF methods are becoming used increasingly in industry combustor codes.

A comprehensive review of oil spill combustion studies

International Nuclear Information System (INIS)

Walavalkar, A.Y.; Kulkarni, A.K.

1996-01-01

The complex process of in-situ burning of oil or a water-in-oil emulsion floating on top of a water-base, such as the ocean, was discussed. The process was examined before, during and after actual combustion. In general, the success of oil spill combustion is measured in terms of the fraction of the spilled oil or emulsion that is burned away. However, the air and aquatic pollution caused by the combustion should also be considered. The physical conditions such as wind velocity, waves and the presence or absence of a containment device, such as a fire boom, could determine the continuation of the combustion process. An overview of the oil spill combustion techniques was provided. There still remains a need for fundamental studies, especially in mathematical modeling, to understand the basic mechanisms and predict the applicability of the in-situ combustion. 74 refs., 7 tabs., 3 figs

Improvement of a combustion model in MELCOR code

International Nuclear Information System (INIS)

Ogino, Masao; Hashimoto, Takashi

1999-01-01

NUPEC has been improving a hydrogen combustion model in MELCOR code for severe accident analysis. In the proposed combustion model, the flame velocity in a node was predicted using five different flame front shapes of fireball, prism, bubble, spherical jet, and plane jet. For validation of the proposed model, the results of the Battelle multi-compartment hydrogen combustion test were used. The selected test cases for the study were Hx-6, 13, 14, 20 and Ix-2 which had two, three or four compartments under homogeneous hydrogen concentration of 5 to 10 vol%. The proposed model could predict well the combustion behavior in multi-compartment containment geometry on the whole. MELCOR code, incorporating the present combustion model, can simulate combustion behavior during severe accident with acceptable computing time and some degree of accuracy. The applicability study of the improved MELCOR code to the actual reactor plants will be further continued. (author)

Activity-induced radial velocity variation of M dwarf stars

DEFF Research Database (Denmark)

Andersen, Jan Marie; Korhonen, Heidi Helena

2012-01-01

that can drown out a planetary signature. Cool, low-mass M dwarf stars can be highly active, which can make detection of potentially habitable planets around these stars difficult. We investigate radial velocity variations caused by different activity (spot) patterns on M dwarf stars in order to determine...... the limits of detectability for small planets orbiting active M dwarfs. We report on our progress toward the aim of answering the following questions: What types of spot patterns are realistic for M dwarf stars? What effect will spots have on M dwarf RV measurements? Can jitter from M dwarf spots mimic...... planetary signals? What is the ideal observing wavelength to reduce M dwarf jitter?...

Effect of Metal Additives on the Combustion Characteristics of High-Energy Materials

Directory of Open Access Journals (Sweden)

Korotkikh Alexander

2016-01-01

Full Text Available Thermodynamic calculation of combustion parameters and equilibrium composition of HEMs combustion products showed, that at the increase of aluminum powder dispersity the specific impulse and combustion temperature of solid propellants are reduced due to the decrease of the mass fraction of active aluminum in particles. Partial or complete replacement of aluminum by metal powder (B, Mg, AlB2, Al\\Mg alloy, Fe, Ti and Zr in HEMs composition leads to the reduce of the specific impulse and combustion temperature. Replacement of aluminum powder by boron and magnesium in HEM reduces the mass fraction of condensed products in the combustion chamber of solid rocket motor. So, for compositions HEMs with boron and aluminum boride the mass fraction in chamber is reduced by 24 and 36 %, respectively, with respect to the composition HEMs with Al powder. But the mass fraction of CCPs in the nozzle exit increases by 13 % for HEMs with aluminum boride due to the formation of boron oxide in the condensed combustion products. Partial replacement of 2 wt. % aluminum powder by iron and copper additives in HEM leads to the reduce of CCPs mass fraction in chamber by 4–10 % depending on the aluminum powder dispersity duo to these metals are not formed condensed products at the HEMs combustion in chamber.

Removing Activity-Related Radial Velocity Noise to Improve Extrasolar Planet Searches

Science.gov (United States)

Saar, Steven; Lindstrom, David M. (Technical Monitor)

2004-01-01

We have made significant progress towards the proposal goals of understanding the causes and effects of magnetic activity-induced radial velocity (v_r) jitter and developing methods for correcting it. In the process, we have also made some significant discoveries in the fields of planet-induced stellar activity, planet detection methods, M dwarf convection, starspot properties, and magnetic dynamo cycles. We have obtained super high resolution (R approximately 200,000), high S / N (greater than 300) echelle study of joint line bisector and radial velocity variations using the McDonald 2-D coude. A long observing run in October 2002 in particular was quite successful (8 clear nights). We now have close to three years of data, which begins to sample a good fraction of the magnetic cycle timescales for some of our targets (e.g., kappa Ceti; P_cyc = 5.6 yrs). This will be very helpful in unraveling the complex relationships between plage and radial velocity (v-r) changes which we have uncovered. Preliminary analysis (Saar et al. 2003) of the data in hand, reveals correlations between median line bisector displacement and v_r. The correlation appears to be specific the the particular star being considered, probably since it is a function of both spectral type and rotation rate. Further analysis and interpretation will be in the context of evolving plage models and is in progress.

Comparison of high group velocity accelerating structures

International Nuclear Information System (INIS)

Farkas, Z.D.; Wilson, P.B.

1987-02-01

It is well known that waveguides with no perturbations have phase velocities greater than the velocity of light c. If the waveguide dimensions are chosen so that the phase velocity is only moderately greater than c, only small perturbations are required to reduce the phase velocity to be synchronous with a high energy particle bunch. Such a lightly loaded accelerator structure will have smaller longitudinal and transverse wake potentials and hence will lead to lower emittance growth in an accelerated beam. Since these structures are lightly loaded, their group velocities are only slightly less than c and not in the order of 0.01c, as is the case for the standard disk-loaded structures. To ascertain that the peak and average power requirements for these structures are not prohibitive, we examine the elastance and the Q for several traveling wave structures: phase slip structures, bellows-like structures, and lightly loaded disk-loaded structures

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

KAUST Repository

Zhang, Ji

2014-11-01

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

Oxy-combustion of high water content fuels

Science.gov (United States)

Yi, Fei

As the issues of global warming and the energy crisis arouse extensive concern, more and more research is focused on maximizing energy efficiency and capturing CO2 in power generation. To achieve this, in this research, we propose an unconventional concept of combustion - direct combustion of high water content fuels. Due to the high water content in the fuels, they may not burn under air-fired conditions. Therefore, oxy-combustion is applied. Three applications of this concept in power generation are proposed - direct steam generation for the turbine cycle, staged oxy-combustion with zero flue gas recycle, and oxy-combustion in a low speed diesel-type engine. The proposed processes could provide alternative approaches to directly utilize fuels which intrinsically have high water content. A large amount of energy to remove the water, when the fuels are utilized in a conventional approach, is saved. The properties and difficulty in dewatering high water content fuels (e.g. bioethanol, microalgae and fine coal) are summarized. These fuels include both renewable and fossil fuels. In addition, the technique can also allow for low-cost carbon capture due to oxy-combustion. When renewable fuel is utilized, the whole process can be carbon negative. To validate and evaluate this concept, the research focused on the investigation of the flame stability and characteristics for high water content fuels. My study has demonstrated the feasibility of burning fuels that have been heavily diluted with water in a swirl-stabilized burner. Ethanol and 1-propanol were first tested as the fuels and the flame stability maps were obtained. Flame stability, as characterized by the blow-off limit -- the lowest O2 concentration when a flame could exist under a given oxidizer flow rate, was determined as a function of total oxidizer flow rate, fuel concentration and nozzle type. Furthermore, both the gas temperature contour and the overall ethanol concentration in the droplets along the

Methane combustion over lanthanum-based perovskite mixed oxides

Energy Technology Data Exchange (ETDEWEB)

Arandiyan, Hamidreza [New South Wales Univ., Sydney (Australia). School of Chemical Engineering

2015-11-01

This book presents current research into the catalytic combustion of methane using perovskite-type oxides (ABO{sub 3}). Catalytic combustion has been developed as a method of promoting efficient combustion with minimum pollutant formation as compared to conventional catalytic combustion. Recent theoretical and experimental studies have recommended that noble metals supported on (ABO{sub 3}) with well-ordered porous networks show promising redox properties. Three-dimensionally ordered macroporous (3DOM) materials with interpenetrated and regular mesoporous systems have recently triggered enormous research activity due to their high surface areas, large pore volumes, uniform pore sizes, low cost, environmental benignity, and good chemical stability. These are all highly relevant in terms of the utilization of natural gas in light of recent catalytic innovations and technological advances. The book is of interest to all researchers active in utilization of natural gas with novel catalysts. The research covered comes from the most important industries and research centers in the field. The book serves not only as a text for researcher into catalytic combustion of methane, 3DOM perovskite mixed oxide, but also explores the field of green technologies by experts in academia and industry. This book will appeal to those interested in research on the environmental impact of combustion, materials and catalysis.

Method and apparatus for active control of combustion rate through modulation of heat transfer from the combustion chamber wall

Science.gov (United States)

Roberts, Jr., Charles E.; Chadwell, Christopher J.

2004-09-21

The flame propagation rate resulting from a combustion event in the combustion chamber of an internal combustion engine is controlled by modulation of the heat transfer from the combustion flame to the combustion chamber walls. In one embodiment, heat transfer from the combustion flame to the combustion chamber walls is mechanically modulated by a movable member that is inserted into, or withdrawn from, the combustion chamber thereby changing the shape of the combustion chamber and the combustion chamber wall surface area. In another embodiment, heat transfer from the combustion flame to the combustion chamber walls is modulated by cooling the surface of a portion of the combustion chamber wall that is in close proximity to the area of the combustion chamber where flame speed control is desired.

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

Energy Technology Data Exchange (ETDEWEB)

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2003-09-30

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons. The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor. LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygen In addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m{sup 2}/g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be

Internal combustion engine using premixed combustion of stratified charges

Science.gov (United States)

Marriott, Craig D [Rochester Hills, MI; Reitz, Rolf D [Madison, WI

2003-12-30

During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

Combustion modelling of a fuel oil flame; Modelisation de la combustion d`une flamme de fuel

Energy Technology Data Exchange (ETDEWEB)

Flour, I.; Mechitouan, N.

1996-10-01

The combustion modelling of a fuel oil flame has been realised in the scope of the R and D `Combustion Turbines`. This report presents the results of the 2D simulation of a fuel oil flame (n-octane), at atmospherical pressure, without swirl, realised using the Eulerian two-phase flow software Melodif. This calculation has been defined in collaboration with IFP, using experimental data from the IFRP. The hollow cone spray of liquid fuel is injected in the middle of the combustion chamber, with a co-flowing annular air. The furnace diameter is 2 meter and its length is 6,25 meter. A large recirculation zone is induced by the air flow, and leads to take into account the whole furnace, in order to avoid some problems with the limit conditions at the outlet. This calculation deals with droplets evaporation, gaseous phase combustion and radiation heat transfer. Predictions concerning gaseous axial mean velocity and mean temperature gradient in the flame, are in good agreement with measurements. However the temperature is too low in the peripheral zone of the flow. This is probably due to the fact that heat exchanges at the wall furnace are not correctly represented, because of a lack of detailed limit conditions for the walls. The mean radial velocity is not so well predicted, but this measurement is also quite difficult in a strongly longitudinal flow. The results concerning the dispersed phase will not be compared, because no measurements on the liquid fuel were available. As it has been experimentally observed, the simulation shows that the fuel oil spray quickly evaporates as it enters the combustion chamber. This result allows to propose to use an homogeneous approach (hypothesis of no-slipping between the two phases) in an Eulerian one-phase flow code, in case of a 3D simulation of liquid fuel turbine. (authors)

Combustion Stratification for Naphtha from CI Combustion to PPC

KAUST Repository

Vallinayagam, R.

2017-03-28

This study demonstrates the combustion stratification from conventional compression ignition (CI) combustion to partially premixed combustion (PPC). Experiments are performed in an optical CI engine at a speed of 1200 rpm for diesel and naphtha (RON = 46). The motored pressure at TDC is maintained at 35 bar and fuelMEP is kept constant at 5.1 bar to account for the difference in fuel properties between naphtha and diesel. Single injection strategy is employed and the fuel is injected at a pressure of 800 bar. Photron FASTCAM SA4 that captures in-cylinder combustion at the rate of 10000 frames per second is employed. The captured high speed video is processed to study the combustion homogeneity based on an algorithm reported in previous studies. Starting from late fuel injection timings, combustion stratification is investigated by advancing the fuel injection timings. For late start of injection (SOI), a direct link between SOI and combustion phasing is noticed. At early SOI, combustion phasing depends on both intake air temperature and SOI. In order to match the combustion phasing (CA50) of diesel, the intake air temperature is increased to 90°C for naphtha. The combustion stratification from CI to PPC is also investigated for various level of dilution by displacing oxygen with nitrogen in the intake. The start of combustion (SOC) was delayed with the increase in dilution and to compensate for this, the intake air temperature is increased. The mixture homogeneity is enhanced for higher dilution due to longer ignition delay. The results show that high speed image is initially blue and then turned yellow, indicating soot formation and oxidation. The luminosity of combustion images decreases with early SOI and increased dilution. The images are processed to generate the level of stratification based on the image intensity. The level of stratification is same for diesel and naphtha at various SOI. When O concentration in the intake is decreased to 17.7% and 14

Numerical analysis on the combustion and emission characteristics of forced swirl combustion system for DI diesel engines

International Nuclear Information System (INIS)

Su, LiWang; Li, XiangRong; Zhang, Zheng; Liu, FuShui

2014-01-01

Highlights: • A new combustion system named FSCS for DI diesel engines was proposed. • Fuel/air mixture formation was improved for the application of FSCS. • The FSCS showed a good performance on emission characteristics. - Abstract: To optimize the fuel/air mixture formation and improve the environmental effect of direct injection (DI) diesel engines, a new forced swirl combustion system (FSCS) was proposed concerned on unique design of the geometric shape of the combustion chamber. Numerical simulation was conducted to verify the combustion and emission characteristics of the engines with FSCS. The fuel/air diffusion, in-cylinder velocity distribution, turbulent kinetic energy and in-cylinder temperature distribution were analyzed and the results shown that the FSCS can increase the area of fuel/air diffusion and improve the combustion. The diesel engine with FSCS also shown excellent performance on emission. At full load condition, the soot emission was significantly reduced for the improved fuel/air mixture formation. There are slightly difference for the soot and NO emission between the FSCS and the traditional omega combustion system at lower load for the short penetration of the fuel spray

Design and experimental investigation of an oxy-fuel combustion system for magnetohydrodynamic power extraction

Science.gov (United States)

Hernandez, Manuel Johannes

A general consensus in the scientific and research community is the need to restrict carbon emissions in energy systems. Therefore, extensive research efforts are underway to develop the next generation of energy systems. In the field of power generation, researchers are actively investigating novel methods to produce electricity in a cleaner, efficient form. Recently, Oxy-Combustion for magnetohydrodynamic power extraction has generated significant interest, since the idea was proposed as a method for clean power generation in coal and natural gas power plants. Oxy-combustion technologies have been proposed to provide high enthalpy, electrically conductive flows for direct conversion of electricity. Direct power extraction via magnetohydrodynamics (MHD) can occur as a consequence of the motion of "seeded" combustion products in the presence of magnetic fields. However, oxy-combustion technologies for MHD power extraction has not been demonstrated in the available literature. Furthermore, there are still fundamental unexplored questions remaining, associated with this technology, for MHD power extraction. In this present study, previous magnetohydrodynamic combustion technologies and technical issues in this field were assessed to develop a new combustion system for electrically conductive flows. The research aims were to fully understand the current-state-of-the-art of open-cycle magnetohydrodynamic technologies and present new future directions and concepts. The design criteria, methodology, and technical specifications of an advanced cooled oxy-combustion technology are presented in this dissertation. The design was based on a combined analytical, empirical, and numerical approach. Analytical one-dimensional (1D) design tools initiated design construction. Design variants were analyzed and vetted against performance criteria through the application of computational fluid dynamics modeling. CFD-generated flow fields permitted insightful visualization of the

A review of active control approaches in stabilizing combustion systems in aerospace industry

Science.gov (United States)

Zhao, Dan; Lu, Zhengli; Zhao, He; Li, X. Y.; Wang, Bing; Liu, Peijin

2018-02-01

Self-sustained combustion instabilities are one of the most plaguing challenges and problems in lean-conditioned propulsion and land-based engine systems, such as rocket motors, gas turbines, industrial furnace and boilers, and turbo-jet thrust augmenters. Either passive or active control in open- or closed-loop configurations can be implemented to mitigate such instabilities. One of the classical disadvantages of passive control is that it is only implementable to a designed combustor over a limited frequency range and can not respond to the changes in operating conditions. Compared with passive control approaches, active control, especially in closed-loop configuration is more adaptive and has inherent capacity to be implemented in practice. The key components in closed-loop active control are 1) sensor, 2) controller (optimization algorithm) and 3) dynamic actuator. The present work is to outline the current status, technical challenges and development progress of the active control approaches (in open- or closed-loop configurations). A brief description of feedback control, adaptive control, model-based control and sliding mode control are provided first by introducing a simplified Rijke-type combustion system. The modelled combustion system provides an invaluable platform to evaluate the performance of these feedback controllers and a transient growth controller. The performance of these controllers are compared and discussed. An outline of theoretical, numerical and experimental investigations are then provided to overview the research and development progress made during the last 4 decades. Finally, potential, challenges and issues involved with the design, application and implementation of active combustion control strategies on a practical engine system are highlighted.

Combustion chemistry - activities in the CHEK research programme

Energy Technology Data Exchange (ETDEWEB)

Dam-Johansen, K.; Johnsson, J.E.; Glarborg, P.; Frandsen, F.; Jensen, A.; Oestberg, M. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Chemical Engineering

1997-10-01

The combustion chemistry in the oxidation of fossil fuels and biofuels determines together with mixing and heat transfer the required size of a furnace, the emission of gaseous pollutants, and the formation of ash and deposits on surfaces. This presentation describes technologies for solid fuels combustion and gives a summary of the fuels, the pollutant chemistry and the inorganic chemistry in combustion processes. Emphasis is put on the work carried out in the CHEC (Combustion and Harmful Emission Control) Research Programme. (orig.)

Combustion chemistry. Activities in the CHEC research programme

Energy Technology Data Exchange (ETDEWEB)

Dam-Johansen, K; Johnsson, J E; Glarborg, P; Frandsen, F; Jensen, A; Oestberg, M [Technical Univ. of Denmark, Dept. of Chemical Engineering, Lyngby (Denmark)

1996-12-01

The combustion chemistry in the oxidation of fossil fuels and biofuels determines together with mixing and heat transfer the required size of a furnace, the emission of gaseous pollutants, and the formation of ash and deposits on surfaces. This paper describes technologies for solid fuels combustion and gives a summary of the fuels, the pollutant chemistry and the inorganic chemistry in combustion processes. Emphasis is put on the work carried out in the CHEC (Combustion and Harmful Emission Control Research Programme). (au) 173 refs.

Simple Motor Control Concept Results High Efficiency at High Velocities

Science.gov (United States)

Starin, Scott; Engel, Chris

2013-09-01

The need for high velocity motors in space applications for reaction wheels and detectors has stressed the limits of Brushless Permanent Magnet Motors (BPMM). Due to inherent hysteresis core losses, conventional BPMMs try to balance the need for torque verses hysteresis losses. Cong-less motors have significantly less hysteresis losses but suffer from lower efficiencies. Additionally, the inherent low inductance in cog-less motors result in high ripple currents or high switching frequencies, which lowers overall efficiency and increases performance demands on the control electronics.However, using a somewhat forgotten but fully qualified technology of Isotropic Magnet Motors (IMM), extremely high velocities may be achieved at low power input using conventional drive electronics. This paper will discuss the trade study efforts and empirical test data on a 34,000 RPM IMM.

Fuel and combustion stratification study of Partially Premixed Combustion

OpenAIRE

Izadi Najafabadi, M.; Dam, N.; Somers, B.; Johansson, B.

2016-01-01

Relatively high levels of stratification is one of the main advantages of Partially Premixed Combustion (PPC) over the Homogeneous Charge Compression Ignition (HCCI) concept. Fuel stratification smoothens heat release and improves controllability of this kind of combustion. However, the lack of a clear definition of “fuel and combustion stratifications” is obvious in literature. Hence, it is difficult to compare stratification levels of different PPC strategies or other combustion concepts. T...

An experimental study on suspended sodium droplet combustion (2)

International Nuclear Information System (INIS)

Sato, Kenji

2004-03-01

As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies for suspended single sodium droplet, behavior of ignition process and succeeding combustion, ignition delay time, and droplet temperature history had been investigated. In the present study, by using 4 mm diam. suspended sodium droplet, combustion experiments were performed for extended free-stream velocity range of dry air up to 200 cm/s, and for the initial droplet temperature T i =300degC and 400degC, and the effects of the free-stream velocity and initial droplet temperature on the ignition/burning behavior and ignition delay time were examined by using high speed video camera. The obtained experimental results are as follows: (1) Ignition phenomena of suspended spherical shape droplet were observed for all examined experimental conductions except the case of free-stream velocity U=200 cm/s at 300degC, where detachment of droplet from the support due to strained oxide film occurred. (2) The ignition delay time defined as the time to evolution of orange-light emitting zone or flame zone decreases with the increase of the free-stream velocity or of initial droplet temperature. Examples of typical ignition delay time are 0.68 s at U=20 cm/s, 0.52 s at U=100 cm/s, and 0.37 s at 200 cm/s for T i =400degC. (3) The orange-light emission at the moment of ignition occurs simultaneously over whole surface except the top region of the droplet. The intensity of the emission at the moment of ignition takes its maximum at the bottom region or upstream region of the droplet, and the emission intensity during the stable burning period increases with the increase of U. (4) When T i is 300degC, formation of temporal multiple short projections are observed before ignition for all examined free-stream velocities. The projections often do not disappear before ignition when the velocity is relatively high. (5) The layer or cloud composed of aerosol is formed

Modelling of plume chemistry of high flying aircraft with H2 combustion engines

International Nuclear Information System (INIS)

Weibring, G.; Zellner, R.

1993-01-01

Emissions from hydrogen fueled aircraft engines include large concentrations of radicals such as NO, OH, O and H. We describe the result of modelling studies in which the evolution of the radical chemistry in an expanding and cooling plume for three different mixing velocities is evaluated. The simulations were made for hydrogen combustion engines at an altitude of 26 km. For the fastest mixing conditions, the radical concentrations decrease only because of dilution with the ambient air, since the time for chemical reaction is too short. With lower mixing velocities, however, larger chemical conversions were determined. For the slowest mixing conditions the unburned hydrogen is converted into water. As a consequence the radicals O and OH increase considerably around 1400 K. The only exception being NO, for which no chemical change during the expansion is found. The concentrations of the reservoir molecules like H 2 O 2 , N 2 O 5 or HNO 3 have been calculated to remain relatively small. (orig.)

IEA combustion agreement : a collaborative task on alternative fuels in combustion

International Nuclear Information System (INIS)

Larmi, M.

2009-01-01

The focus of the alternative fuels in combustion task of the International Energy Agency is on high efficiency engine combustion, furnace combustion, and combustion chemistry. The objectives of the task are to develop optimum combustion for dedicated fuels by fully utilizing the physical and chemical properties of synthetic and renewable fuels; a significant reduction in carbon dioxide, NOx and particulate matter emissions; determine the minimum emission levels for dedicated fuels; and meet future emission standards of engines without or with minimum after-treatment. This presentation discussed the alternative fuels task and addressed issues such as synthetic fuel properties and benefits. The anticipated future roadmap was presented along with a list of the synthetic and renewable engine fuels to be studied, such as neat oxygenates like alcohols and ethers, biogas/methane and gas combustion, fuel blends, dual fuel combustion, high cetane number diesel fuels like synthetic Fischer-Tropsch diesel fuel and hydrogenated vegetable oil, and low CN number fuels. Implementation examples were also discussed, such as fuel spray studies in optical spray bombs; combustion research in optical engines and combustion chambers; studies on reaction kinetics of combustion and emission formation; studies on fuel properties and ignition behaviour; combustion studies on research engines; combustion optimization; implementing the optimum combustion in research engines; and emission measurements. Overall milestone examples and the overall schedule of participating countries were also presented. figs.

Experimental and CFD investigation of gas phase freeboard combustion

DEFF Research Database (Denmark)

Andersen, Jimmy

Reliable and accurate modeling capabilities for combustion systems are valuable tools for optimization of the combustion process. This work concerns primary precautions for reducing NO emissions, thereby abating the detrimental effects known as “acid rain”, and minimizing cost for flue gas...... treatment. The aim of this project is to provide validation data for Computational Fluid Dynamic (CFD) models relevant for grate firing combustion conditions. CFD modeling is a mathematical tool capable of predicting fluid flow, mixing and chemical reaction with thermal conversion and transport. Prediction......, but under well-defined conditions. Comprehensive experimental data for velocity field, temperatures, and gas composition are obtained from a 50 kW axisymmetric non-swirling natural gas fired combustion setup under two different settings. Ammonia is added to the combustion setup in order to simulate fuel...

Diesel oil combustion in fluidized bed; Combustion de aceite diesel en lecho fluidizado

Energy Technology Data Exchange (ETDEWEB)

Rodriguez Cazares, Mario [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1992-07-01

The effect of the fluidized bed depth in the combustion in burning diesel oil in a fluidized bed, was analyzed. A self sustained combustion was achieved injecting the oil with an injector that utilized a principle similar to an automobile carburetor venturi. Three different depths were studied and it was found that the deeper the bed, the greater the combustion efficiency. Combustion efficiencies were attained from 82% for a 100mm bed depth, up to 96% for a 200mm bed depth. The diminution in the efficiency was mainly attributed to unburned hydrocarbons and to the carbon carried over, which was observed in the black smoke at the stack outlet. Other phenomena registered were the temperature gradient between the lower part of the bed and the upper part, caused by the fluidization velocity; additionally it was observed that the air employed for the oil injection (carbureting air) is the most important parameter to attain a complete combustion. [Espanol] Se analizo el efecto de la profundidad del lecho en la combustion al quemar aceite diesel en un lecho fluidizado experimental. Se logro combustion autosostenida inyectando el aceite con un inyector que utilizo un principio similar al venturi del carburador de automovil. Se estudiaron tres diferentes profundidades del lecho y se encontro que a mayor profundidad del lecho, mayor eficiencia de la combustion. Se lograron eficiencias de la combustion desde 82% para el lecho de 100 mm de profundidad hasta 96% para el de 200 mm. La disminucion de la eficiencia se atribuyo, principalmente, a los hidrocarburos no quemados y al carbon arrastrado, lo cual se observo en el humo negro a la salida de la chimenea. Otros fenomenos registrados fueron el gradiente de temperatura entre la parte baja del lecho y la parte superior causado por la velocidad de fluidizacion; ademas, se observo que el aire utilizado para inyectar el aceite (aire de carburacion) es el parametro mas importante para lograr una combustion completa.

Structure of a swirling jet with vortex breakdown and combustion

Science.gov (United States)

Sharaborin, D. K.; Dulin, V. M.; Markovich, D. M.

2018-03-01

An experimental investigation is performed in order to compare the time-averaged spatial structure of low- and high-swirl turbulent premixed lean flames by using the particle image velocimetry and spontaneous Raman scattering techniques. Distributions of the time-average velocity, density and concentration of the main components of the gas mixture are measured for turbulent premixed swirling propane/air flames at atmospheric pressure for the equivalence ratio Φ = 0.7 and Reynolds number Re = 5000 for low- and high-swirl reacting jets. For the low-swirl jet (S = 0.41), the local minimum of the axial mean velocity is observed within the jet center. The positive value of the mean axial velocity indicates the absence of a permanent recirculation zone, and no clear vortex breakdown could be determined from the average velocity field. For the high-swirl jet (S = 1.0), a pronounced vortex breakdown took place with a bubble-type central recirculation zone. In both cases, the flames are stabilized in the inner mixing layer of the jet around the central wake, containing hot combustion products. O2 and CO2 concentrations in the wake of the low-swirl jet are found to be approximately two times smaller and greater than those in the recirculation zone of the high-swirl jet, respectively.

Appraisal of possible combustion hazards associated with a high-temperature gas-cooled reactor

International Nuclear Information System (INIS)

Palmer, H.B.; Sibulkin, M.; Strehlow, R.A.; Yang, C.H.

1978-03-01

The report presents a study of combustion hazards that may be associated with the High Temperature Gas Cooled Reactor (HTGR) in the event of a primary coolant circuit depressurization followed by water or air ingress into the prestressed concrete reactor vessel (PCRV). Reactions between graphite and steam or air produce the combustible gases H 2 and/or CO. When these gases are mixed with air in the containment vessel (CV), flammable mixtures may be formed. Various modes of combustion including diffusion or premixed flames and possibly detonation may be exhibited by these mixtures. These combustion processes may create high over-pressure, pressure waves, and very hot gases within the CV and hence may threaten the structural integrity of the CV or damage the instrumentation and control system installations within it. Possible circumstances leading to these hazards and the physical characteristics related to them are delineated and studied in the report

Experimental study on the combustion characteristics of liquid fuel in the straight tubes

Energy Technology Data Exchange (ETDEWEB)

Yang, Fei; Li, JunWei; Zhou, ZhaoQiu; Zhang, Xin; Wang, NingFei [Beijing Institute of Technology, Beijing (China). School of Aerospace Engineering

2013-07-01

This study investigates combustion characteristics of liquid hydrocarbon fuel (n-heptane, c7h16) under different operating conditions. In the paper we designed a burner consisting of a stainless steel capillary which is used to dump the fuel and a larger stainless steel tube (or quartz tube) used as a combustion chamber. The inner diameter (ID) of the capillary is 0.24 mm, the inner and external diameter of the larger tube is 4 and 6 mm, respectively. According to the experimental results, the combustion process reaches a stable status after about 100 s. Wall temperature distribution and combustion products are analyzed under conditions with different equivalence ratios, gas flow velocities and materials. As equivalence ratio (ER) whose range is in 0.56-1.08 increases, the wall temperature declines, and wall temperature gradient increases slightly. The range of gas flow velocity is in 0.6-1 m/s, the overall trend of wall temperature distribution is the second point from left boundary as a line, the wall temperature distribution of the four points in the right side increases with the flow velocity increasing, but the left point is rapidly declining. When the burner made of stainless steel, the wall temperature distribution varies slightly due to the larger thermal conductivity of stainless steel than that of quartz, which makes the heat transfer in stainless steel faster and the temperature distribution is more uniform. The thermodynamic calculation software is also used to study the compositions of combustion products. In a word, this structure of the burner shows poor combustion characteristics, we should change the structure and the experimental conditions to achieve better combustion characteristics in the future.

Carbon monoxide - hydrogen combustion characteristics in severe accident containment conditions. Final report

International Nuclear Information System (INIS)

2000-03-01

production from a study for French reactors. For limestone-sand concrete, CO could be present in significant quantities (6% to 8%). For siliceous concrete, on the other hand, the CO concentration is generally small, of the order of 1%. Combustible gas generation (carbon monoxide and ex-vessel hydrogen) from core-concrete interactions is predicted in available codes (i.e., CORCON, WECHSL) but results are also highly plant specific. For this reason, the generation of CO is not examined in detail in this report, beyond defining a relevant range of compositions that bound the possible cases. This report reviews the knowledge base on CO/H 2 combustion from the perspective of assessing the potential combustion threat in containment during a severe reactor accident. Most aspects of classical combustion behaviour are discussed, including flammability limits, burning velocities, pressure development and detonability. Since CO and H 2 co-exist with copious quantities of CO 2 and steam in containment, diluent effects of CO 2 and steam on H 2 /CO combustion properties are also examined, where known. Where evident gaps in knowledge exist, they are identified and the safety implications of the resulting uncertainties are discussed: - Flammability limits for CO-H 2 -H 2 O-CO 2 -air mixtures can be determined accurately from Le Chatelier's rule or from empirical curve-fits to the experimental data. The presence of CO widens the flammability limits of hydrogen. - Burning velocities in CO 2 , H 2 , steam, and air mixtures can be determined reasonably accurately at low CO concentrations using available codes. However, available codes are not reliable at low hydrogen concentrations. There is a need for experimental determination of burning velocities for CO in the range of 0 to 10% and H2 in the range of 9 to 20%, and diluent (steam-CO 2 ) concentrations of up to 50%. Because burning velocity is a basic input parameter in the calculation of combustion pressure development, and since the

Combustion of methane-oxygen and methane-oxygen-CFC mixtures initiated by a high-current slipping surface discharge

International Nuclear Information System (INIS)

Kossyi, I.A.; Silakov, V.P.; Tarasova, N.M.

2001-01-01

Results are presented from experimental studies of the destruction of chlorofluorocarbon (CF 2 Cl 2 ) molecules in a methane-oxygen (air) gas mixture whose combustion is initiated by a high-current slipping surface discharge. It is found that a three-component CH 4 + O 2 (air)+ CF 2 Cl 2 gas mixture (even with a considerable amount of the third component) demonstrates properties of explosive combustion involving chain reactions that are typical of two-component CH 4 + O 2 mixtures. Experiments show the high degree of destruction (almost complete decomposition) of chlorofluorocarbons contained in the mixture during one combustion event. The combustion dynamics is studied. It is shown that the combustion initiated by a slipping surface discharge has a number of characteristic features that make it impossible to identify the combustion dynamics with the formation of a combustion or detonation wave. The features of the effects observed can be related to intense UV radiation produced by a pulsed high-current surface discharge

Combustion characteristics and air pollutant formation during oxy-fuel co-combustion of microalgae and lignite.

Science.gov (United States)

Gao, Yuan; Tahmasebi, Arash; Dou, Jinxiao; Yu, Jianglong

2016-05-01

Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species. Copyright © 2016 Elsevier Ltd. All rights reserved.

High pressure combustion of liquid fuels. [alcohol and n-paraffin fuels

Science.gov (United States)

Canada, G. S.

1974-01-01

Measurements were made of the burning rates and liquid surface temperatures for a number of alcohol and n-paraffin fuels under natural and forced convection conditions. Porous spheres ranging in size from 0.64-1.9 cm O.D. were emloyed to simulate the fuel droplets. The natural convection cold gas tests considered the combustion in air of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane droplets at pressures up to 78 atmospheres. The pressure levels of the natural convection tests were high enough so that near critical combustion was observed for methanol and ethanol vaporization rates and liquid surface temperature measurements were made of droplets burning in a simulated combustion chamber environment. Ambient oxygen molar concentrations included 13%, 9.5% and pure evaporation. Fuels used in the forced convection atmospheric tests included those listed above for the natural convection tests. The ambient gas temperature ranged from 600 to 1500 K and the Reynolds number varied from 30 to 300. The high pressure forced convection tests employed ethanol and n-heptane as fuels over a pressure range of one to 40 atmospheres. The ambient gas temperature was 1145 K for the two combustion cases and 1255 K for the evaporation case.

HIGH VELOCITY THERMAL GUN FOR SURFACE PREPARATION AND TREATMENT

Directory of Open Access Journals (Sweden)

I.A. Gorlach

2012-01-01

Full Text Available Many surface preparation and treatment processes utilise compressed air to propel particles against surfaces in order to clean and treat them. The effectiveness of the processes depends on the velocity of the particles, which in turn depends on the pressure of the compressed air. This paper describes a thermal gun built on the principles of High Velocity Air Fuel (HVAF and High Velocity Oxy Fuel (HVOF processes. The designed apparatus can be used for abrasive blasting, coating of surfaces, cutting of rocks, removing rubber from mining equipment, cleaning of contaminations etc.

On the origin of high-velocity runaway stars

NARCIS (Netherlands)

Gvaramadze, V.V.; Gualandris, A.; Portegies Zwart, S.

2009-01-01

We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary 50-100 M-circle dot star or a more massive one, formed through runaway mergers of ordinary

AuRu/meso-Mn2O3: A Highly Active and Stable Catalyst for Methane Combustion

Science.gov (United States)

Han, Z.; Fang, J. Y.; Xie, S. H.; Deng, J. G.; Liu, Y. X.; Dai, H. X.

2018-05-01

Three-dimensionally ordered mesoporous Mn2O3 (meso-Mn2O3) and its supported Au, Ru, and AuRu alloy (0.49 wt% Au/meso-Mn2O3, 0.48 wt% Ru/meso-Mn2O3, and 0.97 wt% AuRu/meso-Mn2O3 (Au/Ru molar ratio = 0.98)) nanocatalysts were prepared using the KIT-6-templating and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for the combustion of methane. It is found that among all of the samples, 0.48 wt% Ru/meso-Mn 2O3 and 0.97 wt% AuRu/meso-Mn2O3 performed the best (the reaction temperature (T90% ) at 90% methane conversion was 530-540°C), but the latter showed a better thermal stability than the former. The partial deactivation of 0.97 wt% AuRu/meso-Mn2O3 due to H2O or CO2 introduction was reversible. It is concluded that the good catalytic activity and thermal stability of 0.97 wt% AuRu/meso-Mn2O3 was associated with the high dispersion of AuRu alloy NPs (2-5 nm) on the surface of meso-Mn2O3 and good low-temperature reducibility.

Treatment Protocol for High Velocity/High Energy Gunshot Injuries to the Face

Science.gov (United States)

Peled, Micha; Leiser, Yoav; Emodi, Omri; Krausz, Amir

2011-01-01

Major causes of facial combat injuries include blasts, high-velocity/high-energy missiles, and low-velocity missiles. High-velocity bullets fired from assault rifles encompass special ballistic properties, creating a transient cavitation space with a small entrance wound and a much larger exit wound. There is no dispute regarding the fact that primary emergency treatment of ballistic injuries to the face commences in accordance with the current advanced trauma life support (ATLS) recommendations; the main areas in which disputes do exist concern the question of the timing, sequence, and modes of surgical treatment. The aim of the present study is to present the treatment outcome of high-velocity/high-energy gunshot injuries to the face, using a protocol based on the experience of a single level I trauma center. A group of 23 injured combat soldiers who sustained bullet and shrapnel injuries to the maxillofacial region during a 3-week regional military conflict were evaluated in this study. Nine patients met the inclusion criteria (high-velocity/high-energy injuries) and were included in the study. According to our protocol, upon arrival patients underwent endotracheal intubation and were hemodynamically stabilized in the shock-trauma unit and underwent total-body computed tomography with 3-D reconstruction of the head and neck and computed tomography angiography. All patients underwent maxillofacial surgery upon the day of arrival according to the protocol we present. In view of our treatment outcomes, results, and low complication rates, we conclude that strict adherence to a well-founded and structured treatment protocol based on clinical experience is mandatory in providing efficient, appropriate, and successful treatment to a relatively large group of patients who sustain various degrees of maxillofacial injuries during a short period of time. PMID:23449809

Combustion measurements in an industrial gas-fired flat-glass furnace

Energy Technology Data Exchange (ETDEWEB)

Newbold, J; Webb, B W; McQuay, M Q [Brigham Young Univ., Provo, UT (United States). Mechanical Engineering Dept.; Huber, A M [Ford Motor Co., Glass Div., Dearborn, MI (United States)

1997-06-01

Profiles of velocity, species concentration (O{sub 2}, CO and CO{sub 2}), wall incident radiative heat flux and temperature are reported in the combustion space of a regenerative, side-port, 550t/day, gas-fired flat-glass furnace. A region exists of fast-moving gases near the glass, with axial velocity components exceeding 20 m s{sup -1}, and a large recirculation zone near the crown. Temperatures as high as 1985 K in the flame and as low as 1750 K in the recirculation zone are reported. A region of intense reaction is observed near the glass, with large concentration gradients and incomplete combustion even in the tail of the flame. Local incident radiant fluxes on the crown were nearly uniform spatially at a level of 680 kW m{sup -2}. In the portnecks, flat inlet velocity profiles were measured with a magnitude of approximately 11 m s{sup -1}. Significant variations were observed in the exhaust profiles of most measured variables. Large errors in exhaust mass balance suggest a complex, three-dimensional flow with recirculation zones along the side walls of the portnecks. A nominal preheat air temperature of 1420 k and a variation of exhaust temperatures between 1630 K and 1835 K were noted. O{sub 2} concentrations as high as 8.4% were measured at the exit, suggesting a bypass of oxygen-rich flow around the flame. CO{sub 2} concentrations were the highest near the batch, where the glass reactions are the most intense. (Author)

A new wall function boundary condition including heat release effect for supersonic combustion flows

International Nuclear Information System (INIS)

Gao, Zhen-Xun; Jiang, Chong-Wen; Lee, Chun-Hian

2016-01-01

Highlights: • A new wall function including heat release effect is theoretically derived. • The new wall function is a unified form holding for flows with/without combustion. • The new wall function shows good results for a supersonic combustion case. - Abstract: A new wall function boundary condition considering combustion heat release effect (denoted as CWFBC) is proposed, for efficient predictions of skin friction and heat transfer in supersonic combustion flows. Based on a standard flow model including boundary-layer combustion, the Shvab–Zeldovich coupling parameters are introduced to derive a new velocity law-of-the-wall including the influence of combustion. For the temperature law-of-the-wall, it is proposed to use the enthalpy–velocity relation, instead of the Crocco–Busemann equation, to eliminate explicit influence of chemical reactions. The obtained velocity and temperature law-of-the-walls constitute the CWFBC, which is a unified form simultaneously holding for single-species, multi-species mixing and multi-species reactive flows. The subsequent numerical simulations using this CWFBC on an experimental case indicate that the CWFBC could accurately reflect the influences on the skin friction and heat transfer by the chemical reactions and heat release, and show large improvements compared to previous WFBC. Moreover, the CWFBC can give accurate skin friction and heat flux for a coarse mesh with y"+ up to 200 for the experimental case, except for slightly larger discrepancy of the wall heat flux around ignition position.

MAGNETIZED GAS IN THE SMITH HIGH VELOCITY CLOUD

International Nuclear Information System (INIS)

Hill, Alex S.; McClure-Griffiths, Naomi M.; Mao, S. A.; Benjamin, Robert A.; Lockman, Felix J.

2013-01-01

We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures toward extragalactic radio sources behind the Smith Cloud, new H I observations from the Robert C. Byrd Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure (RM) of ≈100 rad m –2 which are generally well correlated with decelerated Hα emission. We estimate a lower limit on the line-of-sight component of the field of ≈8 μG along a decelerated filament; this is a lower limit due to our assumptions about the geometry. No RM excess is evident in sightlines dominated by H I or Hα at the velocity of the Smith Cloud. The smooth Hα morphology of the emission at the Smith Cloud velocity suggests photoionization by the Galactic ionizing radiation field as the dominant ionization mechanism, while the filamentary morphology and high (≈1 Rayleigh) Hα intensity of the lower-velocity magnetized ionized gas suggests an ionization process associated with shocks due to interaction with the Galactic interstellar medium. The presence of the magnetic field may contribute to the survival of high velocity clouds like the Smith Cloud as they move from the Galactic halo to the disk. We expect these data to provide a test for magnetohydrodynamic simulations of infalling gas

Mechanically Activated Combustion Synthesis of MoSi₂-Based Composites

Energy Technology Data Exchange (ETDEWEB)

Shafirovich, Evgeny [Univ. of Texas, El Paso, TX (United States)

2015-09-30

The thermal efficiency of gas-turbine power plants could be dramatically increased by the development of new structural materials based on molybdenum silicides and borosilicides, which can operate at temperatures higher than 1300 °C with no need for cooling. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. One approach is based on the fabrication of MoSi2-Mo5Si3 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of Mo5Si3. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, materials based on Mo5SiB2 phase are promising materials that offer favorable combinations of high temperature mechanical properties and oxidation resistance. However, the synthesis of Mo-Si-B multi-phase alloys is difficult because of their extremely high melting temperatures. Mechanical alloying has been considered as a promising method, but it requires long milling times, leading to large energy consumption and contamination of the product by grinding media. In the reported work, MoSi2-Mo5Si3 composites and several materials based on Mo5SiB2 phase have been obtained by mechanically activated self-propagating high-temperature synthesis (MASHS). Short-term milling of Mo/Si mixture in a planetary mill has enabled a self-sustained propagation of the combustion front over the mixture pellet, leading to the formation of MoSi2-T1 composites. Combustion of Mo/Si/B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of MoB, TiC, or TiB2. Upon ignition, Mo/Si/B and Mo/Si/B/Ti mixtures exhibited spin combustion, but the products were porous, contained undesired secondary phases, and had low oxidation resistance. It has been shown that use of

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry

Energy Technology Data Exchange (ETDEWEB)

Hong G. Im; Arnaud Trouve; Christopher J. Rutland; Jacqueline H. Chen

2009-02-02

The TSTC project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of our approach is direct numerical simulation (DNS) featuring highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. The code named S3D, developed and shared with Chen and coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for spray dynamics, combustion, and pollutant formation processes in turbulent combustion. Major accomplishments include improved characteristic boundary conditions, fundamental studies of auto-ignition in turbulent stratified reactant mixtures, flame-wall interaction, and turbulent flame extinction by water spray. The overarching scientific issue in our recent investigations is to characterize criticality phenomena (ignition/extinction) in turbulent combustion, thereby developing unified criteria to identify ignition and extinction conditions. The computational development under TSTC has enabled the recent large-scale 3D turbulent combustion simulations conducted at Sandia National Laboratories.

Terascale High-Fidelity Simulations of Turbulent Combustion with Detailed Chemistry

Energy Technology Data Exchange (ETDEWEB)

Im, Hong G [University of Michigan; Trouve, Arnaud [University of Maryland; Rutland, Christopher J [University of Wisconsin; Chen, Jacqueline H [Sandia National Laboratories

2012-08-13

The TSTC project is a multi-university collaborative effort to develop a high-fidelity turbulent reacting flow simulation capability utilizing terascale, massively parallel computer technology. The main paradigm of our approach is direct numerical simulation (DNS) featuring highest temporal and spatial accuracy, allowing quantitative observations of the fine-scale physics found in turbulent reacting flows as well as providing a useful tool for development of sub-models needed in device-level simulations. The code named S3D, developed and shared with Chen and coworkers at Sandia National Laboratories, has been enhanced with new numerical algorithms and physical models to provide predictive capabilities for spray dynamics, combustion, and pollutant formation processes in turbulent combustion. Major accomplishments include improved characteristic boundary conditions, fundamental studies of auto-ignition in turbulent stratified reactant mixtures, flame-wall interaction, and turbulent flame extinction by water spray. The overarching scientific issue in our recent investigations is to characterize criticality phenomena (ignition/extinction) in turbulent combustion, thereby developing unified criteria to identify ignition and extinction conditions. The computational development under TSTC has enabled the recent large-scale 3D turbulent combustion simulations conducted at Sandia National Laboratories.

Hydrogen detonation and detonation transition data from the High-Temperature Combustion Facility

International Nuclear Information System (INIS)

Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.; Finfrock, C.; Gerlach, L.; Malliakos, A.

1995-01-01

The BNL High-Temperature Combustion Facility (HTCF) is an experimental research tool capable of investigating the effects of initial thermodynamic state on the high-speed combustion characteristic of reactive gas mixtures. The overall experimental program has been designed to provide data to help characterize the influence of elevated gas-mixture temperature (and pressure) on the inherent sensitivity of hydrogen-air-steam mixtures to undergo detonation, on the potential for flames accelerating in these mixtures to transition into detonations, on the effects of gas venting on the flame-accelerating process, on the phenomena of initiation of detonations in these mixtures by jets of hot reactant product,s and on the capability of detonations within a confined space to transmit into another, larger confined space. This paper presents results obtained from the completion of two of the overall test series that was designed to characterize high-speed combustion phenomena in initially high-temperature gas mixtures. These two test series are the intrinsic detonability test series and the deflagration-to-detonation (DDT) test series. A brief description of the facility is provided below

Hydrogen detonation and detonation transition data from the High-Temperature Combustion Facility

International Nuclear Information System (INIS)

Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.; Finfrock, C.

1996-01-01

The BNL High-Temperature Combustion Facility (HTCF) is an experimental research tool capable of investigating the effects of initial thermodynamic state on the high-speed combustion characteristic of reactive gas mixtures. The overall experimental program has been designed to provide data to help characterize the influence of elevated gas-mixture temperature (and pressure) on the inherent sensitivity of hydrogen-air-steam mixtures to undergo detonation, on the potential for flames accelerating in these mixtures to transition into detonations, on the effects of gas venting on the flame-accelerating process, on the phenomena of initiation of detonations in these mixtures by jets of hot reactant products, and on the capability of detonations within a confined space to transmit into another, larger confined space. This paper presents results obtained from the completion of two of the overall test series that was designed to characterize high-speed combustion phenomena in initially high-temperature gas mixtures. These two test series are the intrinsic detonability test series and the deflagration-to-detonation (DDT) test series. A brief description of the facility is provided below

Metastable structure formation during high velocity grinding

International Nuclear Information System (INIS)

Samarin, A.N.; Klyuev, M.M.

1984-01-01

Metastable structures in surface layers of samples are; investigated during force high-velocity abrasive grinding. Samples of martensitic (40Kh13), austenitic (12Kh18N10T), ferritic (05Kh23Yu5) steels and some alloys, in particular KhN77TYuR (EhI437B), were grinded for one pass at treatment depth from 0.17 up to 2.6 mm. It is established that processes of homogenizing, recrystallization and coagulation are; developed during force high-velocity grinding along with polymorphic transformations in the zone of thermomechanical effect, that leads to changes of physical and mechanical properties of the surface

Consideration of wear rates at high velocity

Science.gov (United States)

Hale, Chad S.

The development of the research presented here is one in which high velocity relative sliding motion between two bodies in contact has been considered. Overall, the wear environment is truly three-dimensional. The attempt to characterize three-dimensional wear was not economically feasible because it must be analyzed at the micro-mechanical level to get results. Thus, an engineering approximation was carried out. This approximation was based on a metallographic study identifying the need to include viscoplasticity constitutive material models, coefficient of friction, relationships between the normal load and velocity, and the need to understand wave propagation. A sled test run at the Holloman High Speed Test Track (HHSTT) was considered for the determination of high velocity wear rates. In order to adequately characterize high velocity wear, it was necessary to formulate a numerical model that contained all of the physical events present. The experimental results of a VascoMax 300 maraging steel slipper sliding on an AISI 1080 steel rail during a January 2008 sled test mission were analyzed. During this rocket sled test, the slipper traveled 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s. This type of environment was never considered previously in terms of wear evaluation. Each of the features of the metallography were obtained through micro-mechanical experimental techniques. The byproduct of this analysis is that it is now possible to formulate a model that contains viscoplasticity, asperity collisions, temperature and frictional features. Based on the observations of the metallographic analysis, these necessary features have been included in the numerical model, which makes use of a time-dynamic program which follows the movement of a slipper during its experimental test run. The resulting velocity and pressure functions of time have been implemented in the explicit finite element code, ABAQUS. Two-dimensional, plane strain models

Mechanically activated combustion synthesis of molybdenum borosilicides for ultrahigh-temperature structural applications

Energy Technology Data Exchange (ETDEWEB)

Esparza, Alan A.; Shafirovich, Evgeny, E-mail: eshafirovich2@utep.edu

2016-06-15

The thermal efficiency of gas-turbine power plants could be dramatically increased by the development of new structural materials based on molybdenum silicides and borosilicides, which can operate at temperatures higher than 1300 °C with no need for cooling. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. Materials based on Mo{sub 5}SiB{sub 2} (called T{sub 2}) phase are promising materials that offer favorable combinations of high temperature mechanical properties and oxidation resistance. In the present paper, T{sub 2} phase based materials have been obtained using mechanically activated self-propagating high-temperature synthesis (MASHS). Upon ignition, Mo/Si/B/Ti mixtures exhibited a self-sustained propagation of a spinning combustion wave, but the products were porous, contained undesired secondary phases, and had low oxidation resistance. The “chemical oven” technique has been successfully employed to fabricate denser and stronger Mo{sub 5}SiB{sub 2}–TiC, Mo{sub 5}SiB{sub 2}–TiB{sub 2}, and Mo–Mo{sub 5}SiB{sub 2}–Mo{sub 3}Si materials. Among them, Mo{sub 5}SiB{sub 2}–TiB{sub 2} material exhibits the best oxidation resistance at temperatures up to 1500 °C. - Highlights: • Mechanical activation has enabled combustion synthesis of Mo{sub 5}SiB{sub 2} based materials. • For the first time, the fabrication of Mo{sub 5}SiB{sub 2}–TiB{sub 2} material has been reported. • Among the obtained materials, Mo{sub 5}SiB{sub 2}–TiB{sub 2} exhibits the best oxidation resistance.

Experimental and numerical investigation of gas phase freeboard combustion

DEFF Research Database (Denmark)

Andersen, J.; Jensen, Peter Arendt; Meyer, K.E.

2009-01-01

Experimental data for velocity field, temperatures, and gas composition have been obtained from a 50 kW axisymmetric non-swirling natural gas fired combustion setup under two different settings. The reactor was constructed to simulate the conditions in the freeboard of a grate-fired boiler...... but under well-defined conditions. The experimental results are compared to computational fluid dynamics (CFD) modeling predictions, using the eddy dissipation model (EDM) its well as the eddy dissipation concept (EDC). The use of EDC allows for implementation of more advanced combustion schemes; we have...... tested the four-step global mechanism by Jones and Lindstedt (Combust. Flame 1988, 73, 233-249), and the 16 species and 41 reaction skeletal mechanism by Yang and Pope (Combust. Flame 1998, 112 16-32). The CFD model captured the main features of the combustion process and flow patterns. The application...

Selected parameters of maize straw briquettes combustion

Directory of Open Access Journals (Sweden)

Kraszkiewicz Artur

2018-01-01

Full Text Available An analysis of the process of burning briquettes made of maize straw was performed. A number of traits have been evaluated, including physical characteristics of the fuel through parameters describing combustion kinetics as well as products and combustion efficiency. The study was conducted in a grate boiler, during which the differentiating factor was the air velocity flowing to the boiler. It was observed that the obtained values of the considered parameters were different, particularly temperature of the flue gas and the amount of CO and SO2 in the flue gas.

Combustion of Jordanian oil shale using circulating fluidized bed

International Nuclear Information System (INIS)

Hamdan, M.; Al-Azzam, S.

1998-11-01

this study re[resents design and manufacturing of a lab-scale circulating fluidized bed (C.F.B) to burn low grade fuel such as Jordanian oil shale. Hydrodynamic properties of C.F.B. were studied like minimum fluidization velocity, circulation flux and carryover rate. a hot run was firstly conducted by the combustion of L.P.G. to start up the combustion process. It proceeds until reaching the minimum burning temperature of oil shale particles, at which time the LPG supply was gradually reduced and oil shale feeding started. soon after reaching a self sustainable condition of oil shale particles, the LPG supply was cut off. The main combustion variables were investigated such as air to fuel ratios, temperature profiles across the bed, exhaust gas analysis and combustion efficiency. a combustion intensity of 859 kg/hr.m 2 and combustion efficiency of 96% were achieved. (authors). 19 refs., 9 tab., 18 fig

Uncertainties in hydrogen combustion

International Nuclear Information System (INIS)

Stamps, D.W.; Wong, C.C.; Nelson, L.S.

1988-01-01

Three important areas of hydrogen combustion with uncertainties are identified: high-temperature combustion, flame acceleration and deflagration-to-detonation transition, and aerosol resuspension during hydrogen combustion. The uncertainties associated with high-temperature combustion may affect at least three different accident scenarios: the in-cavity oxidation of combustible gases produced by core-concrete interactions, the direct containment heating hydrogen problem, and the possibility of local detonations. How these uncertainties may affect the sequence of various accident scenarios is discussed and recommendations are made to reduce these uncertainties. 40 references

Velocity bunching of high-brightness electron beams

Directory of Open Access Journals (Sweden)

S. G. Anderson

2005-01-01

Full Text Available Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly

40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?

Science.gov (United States)

2010-07-01

... waste combustion unit at your plant. Include supporting calculations. (b) Records of low carbon feed... waste combustion units that use activated carbon? 60.1370 Section 60.1370 Protection of Environment... SOURCES Standards of Performance for Small Municipal Waste Combustion Units for Which Construction is...

Study of the behaviour of P-oxides produced in the combustion of phosphorus-bearing organic compounds and their absorption on suitable substances by means of compounds labelled with 32P. I

International Nuclear Information System (INIS)

Binkowski, J.; Gizinski, S.; Kaminski, R.; Reimschuessel, W.

1976-01-01

During the pyrolytic reaction of phosphorus-bearing compounds in an atmosphere of oxygen, there are produced P-oxides, which interfere in the determination of carbon and hydrogen. The behaviour of these P-oxides was studied intensively in the empty combustion tube in dependence on temperature, velocity of the carrier gas, the nature of the combustion and the positioning of the tube. The P-oxides were determined by the employment of 32 P-labelled aniline phosphate and by activation measurement of the 32 P directly through the tube walls as well as in the finely divided material. In conventional combustions the P-oxides separate abundantly on the walls of the tube provided that the gas velocity is low, especially in those zones of the tube where there is marked temperature lowering, or where very high temperature prevail. Deposited P-oxides are swept out of the tube only in the course of a very long time. Consequently a tube in which the P-bearing compounds have been burned will interfere because of the eluted P-oxides and hence will interfere also if P-free compounds are burned in this same tube

Dilute Oxygen Combustion Phase I Final Report

Energy Technology Data Exchange (ETDEWEB)

Ryan, H.M.; Riley, M.F.; Kobayashi, H.

1997-10-31

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions

Some comments on combusting flows and instrumentation for two-phase flows

International Nuclear Information System (INIS)

Whitelaw, J.H.

1985-01-01

Measurements of the velocity characteristics of combusting flows have been reported over the past 15 years and have Encompassed an extensive range of flows configurations. Difficulties in applying instrumentation and interpreting results are, however, still experienced and this presentation describes two experiments which are useful examples of successful applications. The first is concerned with a gas-turbine combustion chamber which involves limited optical access with high heat release but does not require measurement accuracy such as that of, for example, external aerodynamic flows. The second combines laser velocimetry with digitally compensated thermocouples to provide detailed information of a premixed, bluff-body stabilized flame and involves conditionally sampled results so as to determine the separate flow characteristics of products and reactants

Comparison of Diesel Spray Combustion in Different High-temperature, High-pressure Facilities

DEFF Research Database (Denmark)

Pickett, Lyle M.; Genzale, Caroline L.; Bruneaux, Gilles

2010-01-01

Diesel spray experimentation at controlled high-temperature and high-pressure conditions is intended to provide a more fundamental understanding of diesel combustion than can be achieved in engine experiments. This level of understanding is needed to develop the high-fidelity multi-scale CFD models...... participants in the ECN. Thus, in addition to the presentation of a comparative study, this paper demonstrates steps that are needed for other interested groups to participate in ECN spray research. We expect that this collaborative effort will generate a high-quality dataset to be used for advanced...

Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering.

Science.gov (United States)

Ehn, Andreas; Zhu, Jiajian; Li, Xuesong; Kiefer, Johannes

2017-03-01

Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.

Dilute oxygen combustion. Phase I report

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-10-01

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NO{sub x}) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NO{sub x} through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NO{sub x} production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature ({approximately}1366 K) oxidant (7-27% O{sub 2} vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d{sup +} scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d{sup +} scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW ({approximately}0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric

Prediction of flame formation in highly preheated air combustion

International Nuclear Information System (INIS)

Yang, Jang Sik; Choi, Gyung Min; Kim, Duck Jool; Katsuki, Masashi

2008-01-01

Fundamental information about the ignition position and shape of a flame in highly preheated air combustion was obtained, and the suitability of the suggested reduced kinetic mechanism that reflects the characteristics of the highly preheated air combustion was demonstrated. Flame lift height and flame length with variations of premixed air temperature and oxygen concentration were measured by CH chemiluminescence intensity, and were computed with a reduced kinetic mechanism. Flame attached near a fuel nozzle started to lift when preheated air temperature became close to auto-ignition temperature and/or oxygen concentration reduced. The flame lift height increased but the flame length decreased with decreasing preheated air temperature and flame length reversed after a minimum value. Calculated results showed good agreement with those of experiment within tolerable error. Flame shape shifted from diffusion flame shape to partial premixed flame shape with increasing lift height and this tendency was also observed in the computation results

Prediction of flame formation in highly preheated air combustion

Energy Technology Data Exchange (ETDEWEB)

Yang, Jang Sik; Choi, Gyung Min; Kim, Duck Jool [Pusan National University, Busan (Korea, Republic of); Katsuki, Masashi [Osaka University, Osaka (Japan)

2008-11-15

Fundamental information about the ignition position and shape of a flame in highly preheated air combustion was obtained, and the suitability of the suggested reduced kinetic mechanism that reflects the characteristics of the highly preheated air combustion was demonstrated. Flame lift height and flame length with variations of premixed air temperature and oxygen concentration were measured by CH chemiluminescence intensity, and were computed with a reduced kinetic mechanism. Flame attached near a fuel nozzle started to lift when preheated air temperature became close to auto-ignition temperature and/or oxygen concentration reduced. The flame lift height increased but the flame length decreased with decreasing preheated air temperature and flame length reversed after a minimum value. Calculated results showed good agreement with those of experiment within tolerable error. Flame shape shifted from diffusion flame shape to partial premixed flame shape with increasing lift height and this tendency was also observed in the computation results

A survey of high-velocity H I in the Cetus region

International Nuclear Information System (INIS)

Cohen, R.J.

1982-01-01

The region 02sup(h) 16sup(m) 0 0 surrounding the Cohen and Davies complex of high-velocity clouds has been surveyed in the 21-cm line of H I using the Jodrell Bank MK II radio telescope (beamwidth 31 x 34 arcmin). The high-velocity cloud complex was sampled every 2sup(m) in right ascension and every 0 0 .5 in declination. The observations cover a velocity range of 2100 km s -1 with a resolution of 7.3 km s -1 and an rms noise level of 0.025 K. No HVCs were found outside the velocity range -400 to +100 km s -1 . The data are presented on microfiche as a set of contour maps showing 21-cm line temperature as a function of declination and radial velocity at constant values of right ascension. Discussion is centred on the very-high-velocity clouds at velocities of -360 to -190 km s -1 . It is concluded that they are probably debris from the tidal interaction between our Galaxy and the Magellanic Clouds. (author)

Optical diagnostics of diesel spray injections and combustion in a high-pressure high-temperature cell

NARCIS (Netherlands)

Bougie, H.J.T.; Tulej, M.; Dreier, T.; Dam, N.J.; Meulen, J.J. ter; Gerber, T.

2005-01-01

We report on spatially and temporally resolved optical diagnostic measurements of propagation and combustion of diesel sprays introduced through a single-hole fuel injector into a constant volume, high-temperature, high-pressure cell. From shadowgraphy images in non-reacting environments of pure

Effects of Noise and Time Delay Upon Active Control of Combustion Instabilities

National Research Council Canada - National Science Library

Zinn, Ben

2001-01-01

To improve the performance of practical active control system (ACS) for unstable combustors, the effects of system noise and ACS time delay upon combustion instabilities and the ACS performance were studied...

The effect of low ceiling on the external combustion of the cabin fire

Science.gov (United States)

Su, Shichuan; Chen, Changyun; Wang, Liang; Wei, Chengyin; Cui, Haibing; Guo, Chengyu

2018-06-01

External combustion is a phenomenon where the flame flares out of the window and burns outside. Because of the particularity of the ship's cabin structure, there is a great danger in the external combustion. In this paper, the numerical calculation and analysis of three kinds of low ceiling ship cabin fire are analyzed based on the large eddy numerical simulation technique. Through the analysis of temperature, flue gas velocity, heat flux density and so on, the external combustion phenomenon of fire development is calculated. The results show that when external combustion occurs, the amount of fuel escaping decreases with the roof height. The temperature above the window increases with the height of the ceiling. The heat flux density in the external combustion flame is mainly provided by radiation, and convection is only a small part; In the plume area there is a time period, in this time period, the convective heat flux density is greater than the radiation heat flux, this time with the ceiling height increases. No matter which ceiling height, the external combustion will seriously damage the structure of the ship after a certain period of time. The velocity distribution of the three roof is similar, but with the height of the ceiling, the area size is also increasing.

Comparative sinterability of combustion synthesized and commercial titanium carbides

International Nuclear Information System (INIS)

Manley, B.W.

1984-11-01

The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600 0 C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables

High-gravity combustion synthesis and in situ melt infiltration: A new method for preparing cemented carbides

International Nuclear Information System (INIS)

Liu, Guanghua; Li, Jiangtao; Yang, Zengchao; Guo, Shibin; Chen, Yixiang

2013-01-01

A new method of high-gravity combustion synthesis and in situ melt infiltration is reported for preparing cemented carbides, where hot nickel melt is in situ synthesized from a highly exothermic combustion reaction and then infiltrated into tungsten carbide powder compacts. The as-prepared sample showed a homogeneous microstructure, and its relative density, hardness and flexural strength were 94.4%, 84 HRA and 1.49 GPa, respectively. Compared with conventional powder metallurgy approaches, high-gravity combustion synthesis offers a fast and furnace-free way to produce cemented carbides

Reliability of force-velocity relationships during deadlift high pull.

Science.gov (United States)

Lu, Wei; Boyas, Sébastien; Jubeau, Marc; Rahmani, Abderrahmane

2017-11-13

This study aimed to evaluate the within- and between-session reliability of force, velocity and power performances and to assess the force-velocity relationship during the deadlift high pull (DHP). Nine participants performed two identical sessions of DHP with loads ranging from 30 to 70% of body mass. The force was measured by a force plate under the participants' feet. The velocity of the 'body + lifted mass' system was calculated by integrating the acceleration and the power was calculated as the product of force and velocity. The force-velocity relationships were obtained from linear regression of both mean and peak values of force and velocity. The within- and between-session reliability was evaluated by using coefficients of variation (CV) and intraclass correlation coefficients (ICC). Results showed that DHP force-velocity relationships were significantly linear (R² > 0.90, p  0.94), mean and peak velocities showed a good agreement (CV reliable and can therefore be utilised as a tool to characterise individuals' muscular profiles.

CFD analysis of combustion of natural gas and syngas from biomass pyrolysis in the combustion chamber of a micro gas turbine

Energy Technology Data Exchange (ETDEWEB)

Fantozzi, Francesco; Laranci, Paolo; D' Alessandro, Bruno [University of Perugia (DII/UNIPG) (Italy). Dept. of Industrial Engineering], Emails: fanto@unipg.it, paolo.laranci@unipg.it, dalessandro@bio-net.it

2009-07-01

Micro gas turbines (MGT) can be profitably used for the production of distributed energy (DE), with the possibility to use gaseous fuels with low BTU derived from biomass or waste through the pyrolysis or gasification processes. These synthesis gases (SG) show significant differences with respect to natural gas (NG), in terms of composition, calorific value, content of hydrogen, tar and particulate matter content; such differences can be turn into problems of ignition, instability burning, difficulties in controlling the emissions and fouling. CFD analysis of the combustion process is an essential tool for identifying the main critical arising in using these gases, in order to modify existing geometries and to develop new generation of combustor for use with low BTU gases. This paper describes the activities of experimental and numerical analysis carried out to study the combustion process occurring inside an existing annular Rich-Quench-Lean (RQL) Combustion Chamber (CC) of a 80 kW MGT. In the paper some results of a CFD study of the combustion process performed with an original developed chemical models are reported in terms of temperature and velocity distributions inside the CC and in terms of compositions of turbine inlet gas and of its thermodynamic parameters (mass flow, temperature, pressure). An evaluation of pollutant emissions of CO, CO{sub 2} and NOx and a comparison with the available experimental data relating to the case of combustion of NG is also provided in the paper. Moreover, the carried out investigation concerns the case of operation with a SG fuel derived from biomass in an Integrated Pyrolysis Regenerated Plant (IPRP). (author)

Magnetic and Velocity Field Variations in the Active Regions NOAA ...

Indian Academy of Sciences (India)

Abstract. We study the magnetic and velocity field evolution in the two magnetically complex active regions NOAA 10486 and NOAA 10488 observed during October–November 2003. We have used the available data to examine net flux and Doppler velocity time profiles to identify changes associated with evolutionary and ...

Spray structure of a pressure-swirl atomizer for combustion applications

Directory of Open Access Journals (Sweden)

Jicha Miroslav

2012-04-01

Full Text Available In the present work, global as well as spatially resolved parameters of a spray produced by a pressure-swirl atomizer are obtained. Small pressure-swirl atomizer for aircraft combustion chambers was run on a newly designed test bench with Jet A-1 kerosene type aviation fuel. The atomizer was tested in four regimes based on typical operation conditions of the engine. Spray characteristics were studied using two optical measurement systems, Particle Image velocimetry (PIV and Phase-Doppler Particle Analyzer (P/DPA. The results obtained with P/DPA include information about Sauter Mean Diameter of droplets and spray velocity profiles in one plane perpendicular to the spray axis. Velocity magnitudes of droplets in an axial section of the spray were obtained using PIV. The experimental outputs also show a good confirmation of velocity profiles obtained with both instruments in the test plane. These data together will elucidate impact of the spray quality on the whole combustion process, its efficiency and exhaust gas emissions.

Spray structure of a pressure-swirl atomizer for combustion applications

Science.gov (United States)

Durdina, Lukas; Jedelsky, Jan; Jicha, Miroslav

2012-04-01

In the present work, global as well as spatially resolved parameters of a spray produced by a pressure-swirl atomizer are obtained. Small pressure-swirl atomizer for aircraft combustion chambers was run on a newly designed test bench with Jet A-1 kerosene type aviation fuel. The atomizer was tested in four regimes based on typical operation conditions of the engine. Spray characteristics were studied using two optical measurement systems, Particle Image velocimetry (PIV) and Phase-Doppler Particle Analyzer (P/DPA). The results obtained with P/DPA include information about Sauter Mean Diameter of droplets and spray velocity profiles in one plane perpendicular to the spray axis. Velocity magnitudes of droplets in an axial section of the spray were obtained using PIV. The experimental outputs also show a good confirmation of velocity profiles obtained with both instruments in the test plane. These data together will elucidate impact of the spray quality on the whole combustion process, its efficiency and exhaust gas emissions.

PIV measurements of the turbulence integral length scale on cold combustion flow field of tangential firing boiler

Energy Technology Data Exchange (ETDEWEB)

Wu, Wen-fei; Xie, Jing-xing; Gong, Zhi-jun; Li, Bao-wei [Inner Mongolia Univ. of Science and Technology, Baotou (China). Inner Mongolia Key Lab. for Utilization of Bayan Obo Multi-Metallic Resources: Elected State Key Lab.

2013-07-01

The process of the pulverized coal combustion in tangential firing boiler has prominent significance on improving boiler operation efficiency and reducing NO{sub X} emission. This paper aims at researching complex turbulent vortex coherent structure formed by the four corners jets in the burner zone, a cold experimental model of tangential firing boiler has been built. And by employing spatial correlation analysis method and PIV (Particle Image Velocimetry) technique, the law of Vortex scale distribution on the three typical horizontal layers of the model based on the turbulent Integral Length Scale (ILS) has been researched. According to the correlation analysis of ILS and the temporal average velocity, it can be seen that the turbulent vortex scale distribution in the burner zone of the model is affected by both jet velocity and the position of wind layers, and is not linear with the variation of jet velocity. The vortex scale distribution of the upper primary air is significantly different from the others. Therefore, studying the ILS of turbulent vortex integral scale is instructive to high efficiency cleaning combustion of pulverized coal in theory.

Combustion instabilities in sudden expansion oxy-fuel flames

Energy Technology Data Exchange (ETDEWEB)

Ditaranto, Mario; Hals, Joergen [Department of Energy Processes, SINTEF Energy Research, 7465 Trondheim (Norway)

2006-08-15

An experimental study on combustion instability is presented with focus on oxy-fuel type combustion. Oxidants composed of CO{sub 2}/O{sub 2} and methane are the reactants flowing through a premixer-combustor system. The reaction starts downstream a symmetric sudden expansion and is at the origin of different instability patterns depending on oxygen concentration and Reynolds number. The analysis has been conducted through measurement of pressure, CH* chemiluminescence, and velocity. As far as stability is concerned, oxy-fuel combustion with oxygen concentration similar to that found in air combustion cannot be sustained, but requires at least 30% oxygen to perform in a comparable manner. Under these conditions and for the sudden expansion configuration used in this study, the instability is at low frequency and low amplitude, controlled by the flame length inside the combustion chamber. Above a threshold concentration in oxygen dependent on equivalence ratio, the flame becomes organized and concentrated in the near field. Strong thermoacoustic instability is then triggered at characteristic acoustic modes of the system. Different modes can be triggered depending on the ratio of flame speed to inlet velocity, but for all types of instability encountered, the heat release and pressure fluctuations are linked by a variation in mass-flow rate. An acoustic model of the system coupled with a time-lag-based flame model made it possible to elucidate the acoustic mode selection in the system as a function of laminar flame speed and Reynolds number. The overall work brings elements of reflection concerning the potential risk of strong pressure oscillations in future gas turbine combustors for oxy-fuel gas cycles. (author)

Non-combustible nuclear radiation shields with high hydrogen content

International Nuclear Information System (INIS)

Hall, W.C.; Peterson, J.M.

1978-01-01

The invention relates to compositions, methods of production, and uses of non-combustible nuclear radiation shields, with particular emphasis on those containing a high concentration of hydrogen atoms, especially effective for moderating neutron energy by elastic scatter, dispersed as a discontinuous phase in a continuous phase of a fire resistant matrix

Numerical Modeling of MILD Combustion at High Pressure to Predict the Optimal Operating Conditions

KAUST Repository

Vanteru, Mahendra Reddy

2017-02-01

This Chapter presents numerical simulation on MILD combustion operating at high pressure. Influence of preheat and dilution of oxidizer and operating pressure on stabilization of MILD combustion are presented. Three different preheat temperatures (1100, 1300 and 1500 K) and three different dilution levels (3, 6 and 9% O2) are simulated over an operating pressure variation from 1 atm to 16 atm. A classical jet in hot coflow burner is considered for this study. Total of 45 cases are simulated and analyzed. Essential characteristics of MILD combustion, i.e., maximum temperature (Tmax), temperature rise (ΔT) and temperature distributions, are analyzed. The distribution of emissions OH and CO are also studied and presented. Well-stabilized MILD combustion is observed for all cases except for two cases with high preheated (1500 K). Peak temperature is observed to decrease with increasing operating pressure for a given level of preheat and dilution. OH mass faction is reduced with increasing pressure. The CO emissions show little sensitivity to operating pressure. However, CO mass fraction is slightly higher at 1 atm operating pressure as compared to 4 to 16 atm. Since the residence time of reactants increases as the operating pressure increases, well-stabilized MILD combustion is observed for all highly diluted and low temperature preheat cases (3% O2 and 1100 K).

Numerical Modeling of MILD Combustion at High Pressure to Predict the Optimal Operating Conditions

KAUST Repository

Vanteru, Mahendra Reddy; Roberts, William L.

2017-01-01

This Chapter presents numerical simulation on MILD combustion operating at high pressure. Influence of preheat and dilution of oxidizer and operating pressure on stabilization of MILD combustion are presented. Three different preheat temperatures (1100, 1300 and 1500 K) and three different dilution levels (3, 6 and 9% O2) are simulated over an operating pressure variation from 1 atm to 16 atm. A classical jet in hot coflow burner is considered for this study. Total of 45 cases are simulated and analyzed. Essential characteristics of MILD combustion, i.e., maximum temperature (Tmax), temperature rise (ΔT) and temperature distributions, are analyzed. The distribution of emissions OH and CO are also studied and presented. Well-stabilized MILD combustion is observed for all cases except for two cases with high preheated (1500 K). Peak temperature is observed to decrease with increasing operating pressure for a given level of preheat and dilution. OH mass faction is reduced with increasing pressure. The CO emissions show little sensitivity to operating pressure. However, CO mass fraction is slightly higher at 1 atm operating pressure as compared to 4 to 16 atm. Since the residence time of reactants increases as the operating pressure increases, well-stabilized MILD combustion is observed for all highly diluted and low temperature preheat cases (3% O2 and 1100 K).

Hydrodynamic and thermal mechanisms of filtration combustion inclinational instability based on non-uniform distribution of initial preheating temperature

Science.gov (United States)

Xia, Yongfang; Shi, Junrui; Xu, Youning; Ma, Rui

2018-03-01

Filtration combustion (FC) is one style of porous media combustion with inert matrix, in which the combustion wave front propagates, only downstream or reciprocally. In this paper, we investigate the FC flame front inclinational instability of lean methane/air mixtures flowing through a packed bed as a combustion wave front perturbation of the initial preheating temperature non-uniformity is assumed. The predicted results show that the growth rate of the flame front inclinational angle is proportional to the magnitude of the initial preheating temperature difference. Additionally, depending on gas inlet gas velocity and equivalence ratio, it is demonstrated that increase of gas inlet gas velocity accelerates the FC wave front deformation, and the inclinational instability evolves faster at lower equivalence ratio. The development of the flame front inclinational angle may be regarded as a two-staged evolution, which includes rapid increase, and approaching maximum value of inclinational angle due to the quasi-steady condition of the combustion system. The hydrodynamic and thermal mechanisms of the FC inclinational instability are analyzed. Consequently, the local propagation velocity of the FC wave front is non-uniform to result in the development of inclinational angle at the first stage of rapid increase.

Indirect Combustion Noise: Noise Generation by Accelerated Vorticity in a Nozzle Flow

Directory of Open Access Journals (Sweden)

Nancy Kings

2010-09-01

Full Text Available The noise generation by accelerated vorticity waves in a nozzle flow was investigated in a model experiment. This noise generation mechanism belongs, besides entropy noise, to the indirect combustion noise phenomena. Vorticity as well as entropy fluctuations, originating from the highly turbulent combustion zone, are convected with the flow and produce noise during their acceleration in the outlet nozzle of the combustion chamber. In the model experiment, noise generation of accelerated vorticity fluctuations was achieved. The vorticity fluctuations in the tube flow were produced by injecting temporally additional air into the mean flow. As the next step, a parametric study was conducted to determine the major dependencies of the so called vortex noise. A quadratic dependency of the vortex noise on the injected air amount was found. In order to visualise and classify the artificially generated vorticity structures, planar velocity measurements have been conducted applying Particle Image Velocimetry (PIV.

HERCULES Advanced Combustion Concepts Test Facility: Spray/Combustion Chamber

Energy Technology Data Exchange (ETDEWEB)

Herrmann, K. [Eidgenoessische Technische Hochschule (ETH), Labor fuer Aerothermochemie und Verbrennungssysteme, Zuerich (Switzerland)

2004-07-01

This yearly report for 2004 on behalf of the Swiss Federal Office of Energy (SFOE) at the Laboratory for Aero-thermochemistry and Combustion Systems at the Federal Institute of Technology ETH in Zurich, Switzerland, presents a review of work being done within the framework of HERCULES (High Efficiency R and D on Combustion with Ultra Low Emissions for Ships) - the international R and D project concerning new technologies for ships' diesels. The work involves the use and augmentation of simulation models. These are to be validated using experimental data. The report deals with the development of an experimental set-up that will simulate combustion in large two-stroke diesel engines and allow the generation of reference data. The main element of the test apparatus is a spray / combustion chamber with extensive possibilities for optical observation under variable flow conditions. The results of first simulations confirm concepts and shall help in further work on the project. The potential offered by high-speed camera systems was tested using the institute's existing HTDZ combustion chamber. Further work to be done is reviewed.

Engine combustion network (Ecn) : characterization and comparison of boundary conditions for different combustion vessels

NARCIS (Netherlands)

Meijer, M.; Somers, L.M.T.; Johnson, J.; Naber, J.; Lee, S.Y.; Malbec, L.M.; Bruneaux, G.; Pickett, L.M.; Bardi, M.; Payri, R.; Bazyn, T.

2012-01-01

The Engine Combustion Network (ECN) is a worldwide group of institutions using combustion vessels and/or performing computational fluid dynamics (CFD) simulation, whose aim is to advance the state of spray and combustion knowledge at engine-relevant conditions. A key activity is the use of spray

Nitrogen Chemistry in Fluidized Bed Combustion of Coal

DEFF Research Database (Denmark)

Jensen, Anker Degn

and reduction by homogeneous and heterogeneous reactions. The data for the estimation of kinetics of the heterogeneous reactions were measured by one of the partners in the project for char and bed material sampled from a pressurized FBC pilot plant burning Kiveton Park coal. Experimental data from the pilot...... plant were used for model verification. The simulations of the NO emission during staged combustion and NH3 injection for NO reduction were in qualitative agreement with the experimental data. A parametric study of the influence of operating conditions on the conversion of fuel-N to NO showed......, the gas interchange coefficient, the bubble size and the bubble rise velocity. The most important combustion parameters were the rate of CO and CH4 combustion and the fraction of CO produced from char combustion. By using a rate of production analysis, the important reactions in the NO model were...

Holographic aids for internal combustion engine flow studies

Science.gov (United States)

Regan, C.

1984-01-01

Worldwide interest in improving the fuel efficiency of internal combustion (I.C.) engines has sparked research efforts designed to learn more about the flow processes of these engines. The flow fields must be understood prior to fuel injection in order to design efficient valves, piston geometries, and fuel injectors. Knowledge of the flow field is also necessary to determine the heat transfer to combustion chamber surfaces. Computational codes can predict velocity and turbulence patterns, but experimental verification is mandatory to justify their basic assumptions. Due to their nonintrusive nature, optical methods are ideally suited to provide the necessary velocity verification data. Optical sytems such as Schlieren photography, laser velocimetry, and illuminated particle visualization are used in I.C. engines, and now their versatility is improved by employing holography. These holographically enhanced optical techniques are described with emphasis on their applications in I.C. engines.

Some results of WNRE experiments on hydrogen combustion

International Nuclear Information System (INIS)

Liu, D.D.S.; MacFarlane, R.; Clegg, L.J.

1981-01-01

This paper describes some experimental results on hydrogen combustion related to the safety of nuclear reactor containment during a postulated loss-of-coolant accident and simultaneous loss-of-emergency-cooling accident. The following subjects are described: measurement of the burning velocity of hydrogen-air-steam mixtures; steam effect on the combustion of hydrogen-air mixtures near the lower flammability limit; and the effect of plasma, induced by laser breakdown at a wavelength of 1064 nm, on ignition behaviour in hydrogen-air mixtures with a view to understanding radiation effects on flammability limits

Combustion and agglomeration of aluminized high-energy compositions

International Nuclear Information System (INIS)

Korotkikh, A G; Slyusarskiy, K V; Arkhipov, V A; Glotov, O G

2015-01-01

The results of combustion study for high-energy compositions (HECs) based on ammonium perchlorate (AP), butadiene rubber and ultrafine powder (UFP) aluminum Alex, and agglomeration of metal particles on the burning surface and composition of condensed combustion products (CCPs) are presented. It was found that partial replacement 2 wt. % of Alex by iron UFP in HEC increases the burning rate 1.3—1.4 times at the range of nitrogen pressure 2.0-7.5 MPa and reduces the mean diameter of CCPs particles d 43 from 37.4 μm to 33.5 μm at pressure ∼ 4 MPa. Upon partial replacement 2 wt. % of Alex by boron UFP in HEC the recoil force of gasification products outflow from burning surface is increased by 9 % and the burning rate of HEC does not change in the above pressure range, while the mean diameter of CCPs particles is reduced to 32.6 μm at p ∼ 4 MPa. (paper)

Thermo-acoustic instabilities of high-frequency combustion in rocket engines; Instabilites thermo-acoustiques de combustion haute-frequence dans les moteurs fusees

Energy Technology Data Exchange (ETDEWEB)

Cheuret, F

2005-10-15

Rocket motors are confined environments where combustion occurs in extreme conditions. Combustion instabilities can occur at high frequencies; they are tied to the acoustic modes of the combustion chamber. A common research chamber, CRC, allows us to study the response of a turbulent two-phase flame to acoustic oscillations of low or high amplitudes. The chamber is characterised under cold conditions to obtain, in particular, the relative damping coefficient of acoustic oscillations. The structure and frequency of the modes are determined in the case where the chamber is coupled to a lateral cavity. We have used a powder gun to study the response to a forced acoustic excitation at high amplitude. The results guide us towards shorter flames. The injectors were then modified to study the combustion noise level as a function of injection conditions. The speed of the gas determines whether the flames are attached or lifted. The noise level of lifted flames is higher. That of attached flames is proportional to the Weber number. The shorter flames whose length is less than the radius of the CRC, necessary condition to obtain an effective coupling, are the most sensitive to acoustic perturbations. The use of a toothed wheel at different positions in the chamber allowed us to obtain informations on the origin of the thermo-acoustic coupling, main objective of this thesis. The flame is sensitive to pressure acoustic oscillations, with a quasi-zero response time. These observations suggest that under the conditions of the CRC, we observe essentially the response of chemical kinetics to pressure oscillations. (author)

Robust active combustion control for the optimization of environmental performance and energy efficiency

Science.gov (United States)

Demayo, Trevor Nat

Criteria pollutant regulations, climate change concerns, and energy conservation efforts are placing strict constraints in the design and operation of advanced, stationary combustion systems. To ensure minimal pollutant emissions and maximal efficiency at every instant of operation while preventing reaction blowout, combustion systems need to react and adapt in real-time to external changes. This study describes the development, demonstration, and evaluation of a multivariable feedback control system, designed to maximize the performance of natural gas-fired combustion systems. A feedback sensor array was developed to monitor reaction stability and measure combustion performance as a function of NOx, CO, and O, emissions. Acoustic and UV chemiluminescent emissions were investigated for use as stability indicators. Modulated signals of CH* and CO2* chemiluminescence were found to correlate well with the onset of lean blowout. A variety of emissions sensors were tested and evaluated, including conventional CEMS', micro-fuel cells, a zirconia NOx transducer, and a rapid response predictive NOx sensor based on UV flame chemiluminescence. A dual time-scale controller was designed to actively optimize operating conditions by maximizing a multivariable performance function J using a linear direction set search algorithm. The controller evaluated J under slow, quasi steady-state conditions, while dynamically monitoring the reaction zone at high speed for pre-blowout instabilities or boundary condition violations. To establish the input control parameters, two burner systems were selected: a 30 kW air-swirl, generic research burner, and a 120 kW scaled, fuel-staged, industrial boiler burner. The parameters, chosen to most affect burner performance, consisted of air swirl intensity and excess air for the generic burner, and fuel-staging and excess air for the boiler burner. A set of optimization parameters was also established to ensure efficient and deterministic

Thermal stability in a newly designed columnar-conical fluidized bed for combustion of rice husk

Energy Technology Data Exchange (ETDEWEB)

Rozainee, M.; Salema, A.A.; Ngo, S.P.; Chye, G.B. [Malaysian Technological Univ., Johor Bahru (Malaysia). Dept. of Chemical Engineering

2006-07-01

The effects of fluidizing and liquid propane gas (LPG) flow rates on thermal stability of a fluidized bed were examined. The aim of the study was to hybridize a columnar and conical fluidized bed (CCFB) in order to encourage the combustion of low-calorific fuels such as rice husks. Experiments were conducted to examine the thermal stability of the CCFB. Premixed primary air and liquid propane gas (LPG) was fed into the bed in order to verify its thermal stability. Temperature profiles of the combustor and bed were measured. The impact of the fluidizing velocity and LPG flow rate on the temperature profile was examined in order to analyze the influence of the fluidizing velocity and LPG rate on combustion rates. Results of the study showed that the combustion of the CCFB was sustained at a fluidizing velocity of 1.5 U{sub mf} and at an LPG flow rate of 8 liters per minute. Results of the study showed that fluidizing velocity played an important role on the thermal stability of the bed. It was concluded that the thermal stability of the combustor is sufficient for the CCFB. 13 refs., 2 tabs., 5 figs.

Improved hydrogen combustion model for multi-compartment analysis

International Nuclear Information System (INIS)

Ogino, Masao; Hashimoto, Takashi

2000-01-01

NUPEC has been improving a hydrogen combustion model in MELCOR code for severe accident analysis. In the proposed combustion model, the flame velocity in a node was predicted using six different flame front shapes of fireball, prism, bubble, spherical jet, plane jet, and parallelepiped. A verification study of the proposed model was carried out using the NUPEC large-scale combustion test results following the previous work in which the GRS/Battelle multi-compartment combustion test results had been used. The selected test cases for the study were the premixed test and the scenario-oriented test which simulated the severe accident sequences of an actual plant. The improved MELCOR code replaced by the proposed model could predict sufficiently both results of the premixed test and the scenario-oriented test of NUPEC large-scale test. The improved MELCOR code was confirmed to simulate the combustion behavior in the multi-compartment containment vessel during a severe accident with acceptable degree of accuracy. Application of the new model to the LWR severe accident analysis will be continued. (author)

Experimental study of a single fuel jet in conditions of highly preheated air combustion

Energy Technology Data Exchange (ETDEWEB)

Lille, Simon; Blasiak, W. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Metallurgy

2000-04-01

Highly Preheated Air Combustion (HPAC) is a technique to reduce consumption of fuel and decrease NO{sub x} formation in furnaces. The main change that occur in the furnace chamber is that the flow pattern of flue gases changes dramatically resulting in a more uniform heat transfer. The usefulness of regenerative combustion is very clear, but the advantages have so far been accompanied by high levels of pollutants, such as NO{sub x}. The combination of the regeneration technique and internal flue gas recirculation, thus decreasing NO{sub x} and keeping the other advantages, has made HPAC a very attractive combustion technology with application to heat treatment reheating and melting processes. This work gives an introduction to regenerative combustion with diluted air, including theory on flame stabilization. Furthermore, a description of a new test furnace is given with results from a parametric study and from tests using schlieren color visualization, direct photography, and laser Doppler anemometry. In the parametric study NO{sub x}-emission, CO-emission, lift-off, fluctuations, and some flame characteristics are related to nozzle diameter, oxygen concentration, and preheat temperature. For the schlieren technique and direct photography, both still and high-speed cameras were used.

High-velocity winds from a dwarf nova during outburst

Science.gov (United States)

Cordova, F. A.; Mason, K. O.

1982-01-01

An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km/s, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (more than about 10 solar luminosities) and low inclination angles with respect to the observer's line of sight. The mass loss rate for cataclysmic variables is of order 10 to the -11th solar mass per yr; this is from 0.01 to 0.001 of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed.

Fuel and combustion stratification study of Partially Premixed Combustion

NARCIS (Netherlands)

Izadi Najafabadi, M.; Dam, N.; Somers, B.; Johansson, B.

2016-01-01

Relatively high levels of stratification is one of the main advantages of Partially Premixed Combustion (PPC) over the Homogeneous Charge Compression Ignition (HCCI) concept. Fuel stratification smoothens heat release and improves controllability of this kind of combustion. However, the lack of a

Evidence for mass loss at moderate to high velocity in Be stars

International Nuclear Information System (INIS)

Snow, T.P. Jr.; Marlborough, J.M.

1976-01-01

Ultraviolet spectra of intermediate resolution have been obtained with Copernicus of 12 objects classified as Be or shell stars, and 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si iv doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km s -1 . Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotation effects reduce the effective gravity near the equator. The mass loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be 10 -10 --10 -9 M/sub sun/ yr -1 . The data are suggestive that the extended atmospheres associated with Be star phenomena may be formed by mass ejection

Diesel Combustion and Emission Using High Boost and High Injection Pressure in a Single Cylinder Engine

Science.gov (United States)

Aoyagi, Yuzo; Kunishima, Eiji; Asaumi, Yasuo; Aihara, Yoshiaki; Odaka, Matsuo; Goto, Yuichi

Heavy-duty diesel engines have adopted numerous technologies for clean emissions and low fuel consumption. Some are direct fuel injection combined with high injection pressure and adequate in-cylinder air motion, turbo-intercooler systems, and strong steel pistons. Using these technologies, diesel engines have achieved an extremely low CO2 emission as a prime mover. However, heavy-duty diesel engines with even lower NOx and PM emission levels are anticipated. This study achieved high-boost and lean diesel combustion using a single cylinder engine that provides good engine performance and clean exhaust emission. The experiment was done under conditions of intake air quantity up to five times that of a naturally aspirated (NA) engine and 200MPa injection pressure. The adopted pressure booster is an external supercharger that can control intake air temperature. In this engine, the maximum cylinder pressure was increased and new technologies were adopted, including a monotherm piston for endurance of Pmax =30MPa. Moreover, every engine part is newly designed. As the boost pressure increases, the rate of heat release resembles the injection rate and becomes sharper. The combustion and brake thermal efficiency are improved. This high boost and lean diesel combustion creates little smoke; ISCO and ISTHC without the ISNOx increase. It also yields good thermal efficiency.

Investigation on the Potential of High Efficiency for Internal Combustion Engines

Directory of Open Access Journals (Sweden)

Haifeng Liu

2018-02-01

Full Text Available The current brake thermal efficiency of advanced internal combustion engines is limited to 50%, and how to further improve the efficiency is a challenge. In this study, a theoretical investigation on engine thermal efficiency was carried out using one-dimension simulations based on the first law of thermodynamics. The energy balance was evaluated by varying parameters such as compression ratio (CR; heat transfer coefficient; intake charge properties; and combustion phasing etc.—their influences on the efficiency limits were demonstrated. Results show that for a given heat transfer coefficient, an optimal CR exists to obtain the peak efficiency. The optimal CR decreases with the increase of heat transfer coefficient, and high CR with a low heat-transfer coefficient can achieve a significantly high efficiency. A higher density and specific heat ratio of intake charge, as well as a shorter combustion duration with a proper CA50 (crank angle at 50% of total heat release, can increase efficiency significantly. Methanol shows an excellent ability in decreasing the peak in-cylinder temperature; and the peak indicated efficiency is relatively higher than other tested fuels. The displacement has few effects on the indicated efficiency, while it shows a strong effect on the energy distribution between heat transfer and exhaust energy. All these strategies with high CR result in high in-cylinder pressure and temperature; which means a breakthrough of material is needed in the future.

Aluminum metal combustion in water revealed by high-speed microphotography

Science.gov (United States)

Tao, William C.; Frank, Alan M.; Clements, Rochelle E.; Shepherd, Joseph E.

1991-01-01

In high explosives designed for air blast cratering fragmentation and underwater applications metallic additives chemically react with the oxidizer and are used to tailor the rate of energy delivery by the expansion medium. Although the specific mechanism for sustained metal combustion in the dense detonation medium remains in question it is generally accepted that the fragmentation of the molten particle and disruption of its oxide layer are a necessity. In this study we use high speed microphotography to examine the ignition and combustion of small 25-76 jim diameter and 23 mm long aluminum wires rapidly heated by a capacitor discharge system in water. Streak and framing photographs detailing the combustion phenomenon and the fragmentation of the molten aluminum were obtained over periods of 100 nsec - 100 j. tsec with a spatial resolution of 2 . im. The wire temperature was determined as a function of time by integrating the circuit equation together with the energy equation for an adiabatic wire and incorporating known aluminum electrical resistivity and temperature functions of energy density in the integration. In order for the aluminum to sustain a rapid chemical reaction with the water we found that the wire temperature has to be raised above the melting temperature of aluminum oxide. The triggering mechanism for this rapid reaction appears to be the fragmentation of the molten aluminum from the collapse of a vapor blanket about

PM From the Combustion of heavy fuel oils

KAUST Repository

Elbaz, Ayman M.

2018-03-30

This work presents an experimental study investigating the formation and oxidation of particulate matter from the combustion of heavy fuel oil, HFO, droplets. The study includes results from both a falling droplet in a drop tube furnace and a suspended droplet in a heated convective flow. The falling droplets in a heated coflow air with variable temperature path and velocity were combusted and the resulting particles, cenospheres, were collected. To characterize the microstructure of these particles, scanning electron microscopy (SEM), and energy dispersive X-Ray (EDX) analysis were used. The particles were found to have either a porous or a skeleton/membrane morphology. The percentage of particles of either type appears to be related to the thermal history, which was controlled by the heated co-flow velocity. In the suspended droplet experiments, by suspending the droplet on a thermocouple, the temperature inside the droplet was measured while simultaneously imaging the various burning phases. A number of specific phases were identified, from liquid to solid phase combustion are presented and discussed. The droplet ignition temperature was seen to be independent of the droplet size. However, the liquid phase ignition delay time and the droplet lifetime were directly proportional to the initial droplet diameter.

Combustion Dynamics and Control for Ultra Low Emissions in Aircraft Gas-Turbine Engines

Science.gov (United States)

DeLaat, John C.

2011-01-01

Future aircraft engines must provide ultra-low emissions and high efficiency at low cost while maintaining the reliability and operability of present day engines. The demands for increased performance and decreased emissions have resulted in advanced combustor designs that are critically dependent on efficient fuel/air mixing and lean operation. However, all combustors, but most notably lean-burning low-emissions combustors, are susceptible to combustion instabilities. These instabilities are typically caused by the interaction of the fluctuating heat release of the combustion process with naturally occurring acoustic resonances. These interactions can produce large pressure oscillations within the combustor and can reduce component life and potentially lead to premature mechanical failures. Active Combustion Control which consists of feedback-based control of the fuel-air mixing process can provide an approach to achieving acceptable combustor dynamic behavior while minimizing emissions, and thus can provide flexibility during the combustor design process. The NASA Glenn Active Combustion Control Technology activity aims to demonstrate active control in a realistic environment relevant to aircraft engines by providing experiments tied to aircraft gas turbine combustors. The intent is to allow the technology maturity of active combustion control to advance to eventual demonstration in an engine environment. Work at NASA Glenn has shown that active combustion control, utilizing advanced algorithms working through high frequency fuel actuation, can effectively suppress instabilities in a combustor which emulates the instabilities found in an aircraft gas turbine engine. Current efforts are aimed at extending these active control technologies to advanced ultra-low-emissions combustors such as those employing multi-point lean direct injection.

Experimental investigation of the fluid dynamic efficiency of a high performance multi-valve internal combustion engine during the intake phase: Influence of valve-valve interference phenomena

Directory of Open Access Journals (Sweden)

Algieri Angelo

2013-01-01

Full Text Available The purpose of the present work is the analysis of the fluid dynamic behavior of a high performance internal combustion engine during the intake phase. In particular, a four-valve spark-ignition engine has been characterized at the steady flow rig. Dimensionless discharge coefficients have been used to define the global fluid dynamic efficiency of the intake system, while the Laser Doppler Anemometry (LDA technique has been employed to evaluate the mean flow in the valve curtain area and to characterise the interference phenomena between the two intake valves. The investigation has shown the significant influence of the valve lift on the volumetric efficiency of the intake apparatus. Moreover, the experimental analysis has highlighted that the valve-valve interference phenomena have a relevant impact on the head breathability, on the flow development within the combustion chamber and on the velocity standard deviations.

GOTHIC 3D applicability to fast hydrogen combustions

International Nuclear Information System (INIS)

Lee, Jung Jae; Park, Goon Cherl; Lee, Byung Chul; Yoo, Ho Jong; Kim, Hyeong Taek; Oh, Seung Jong

2004-01-01

Under severe accidents in nuclear power plant (NPP), the hydrogen can be generated by chemical reactions and may threaten the containment integrity via hydrogen combustion. For containment analyses, three-dimensional mechanistic code, GOTHIC had to be applied near source compartments in order to predict whether highly reactive gas mixture can be formed or not under hydrogen mitigation system (HMS) working. For its applicability, this paper presents numerical calculation results of GOTHIC 3D on some hydrogen combustion experiments, which are the FLAME (Sandia National Lab.) experiments, the LSVCTF (AECL Whiteshell Lab.) experiments and the SNU-2D (Seoul National Univ.) experiments. A technical basis for the modeling of the large- and small-scale facilities was developed through sensitivity studies on cell size and combustion modeling parameters. It was found that for large-scale facilities, there were no significant differences in the results with different turbulent burn options, while for small-scale facility, the option using the eddy dissipation concept showed the faster flame propagations. The flame velocity became larger with smaller burn parameters such as the flame thickness δ f and the burn temperature limit T lim . The best estimate modeling parameters found from this study would be applied to real plant simulation of GOTHIC 3D later

High-definition velocity-space tomography of fast-ion dynamics

DEFF Research Database (Denmark)

Salewski, Mirko; Geiger, B.; Jacobsen, A.S.

2016-01-01

Velocity-space tomography of the fast-ion distribution function in a fusion plasma is usually a photon-starved tomography method due to limited optical access and signal-to-noise ratio of fast-ion Dα (FIDA) spectroscopy as well as the strive for high-resolution images. In high-definition tomography...... information to reconstruct where in velocity space the measurements and the simulation disagree. This alternative approach is demonstrated for four-view as well as for two-view FIDA measurements. The high-definition tomography tools allow us to study fast ions in sawtoothing plasmas and the formation of NBI...

New class of combustion processes

International Nuclear Information System (INIS)

Merzhanov, A.G.; Borovinskaya, I.P.

1975-01-01

A short review is given of the results of work carried out since 1967 on studying the combustion processes caused by the interaction of chemical elements in the condensed phase and leading to the formation of refractory compounds. New phenomena and processes are described which are revealed when investigating the combustion of the systems of this class, viz solid-phase combustion, fast combustion in the condensed phase, filtering combustion, combustion in liquid nitrogen, spinning combustion, self-oscillating combustion, and repeated combustion. A new direction in employment of combustion processes is discussed, viz. a self-propagating high-temperature synthesis of refractory nitrides, carbides, borides, silicides and other compounds

Fire, Climate, and Human Activity: A Combustive Combination

Science.gov (United States)

Kehrwald, N. M.; Battistel, D.; Argiriadis, E.; Barbante, C.; Barber, L. B.; Fortner, S. K.; Jasmann, J.; Kirchgeorg, T.; Zennaro, P.

2017-12-01

Ice and lake core records demonstrate that fires caused by human activity can dominate regional biomass burning records in the Common Era. These major increases in fires are often associated with extensive land use change such as an expansion in agriculture. Regions with few humans, relatively stable human populations and/or unvarying land use often have fire histories that are dominated by climate parameters such as temperature and precipitation. Here, we examine biomass burning recorded in ice cores from northern Greenland (NEEM, (77°27'N; 51°3.6'W), Alaska (Juneau Icefield, 58° 35' N; 134° 29'W) and East Antarctica (EPICA DOME C; 75°06'S; 123°21'E), along with New Zealand lake cores to investigate interactions between climate, fire and human activity. Biomarkers such as levoglucosan, and its isomers mannosan and galactosan, can only be produced by cellulose combustion and therefore are specific indicators of past fire activity archived in ice and lake cores. These fire histories add another factor to climate proxies from the same core, and provide a comparison to regional fire syntheses from charcoal records and climate models. For example, fire data from the JSBACH-Spitfire model for the past 2000 years demonstrates that a climate-only scenario would not increase biomass burning in high northern latitudes for the past 2000 years, while NEEM ice core and regional pollen records demonstrate both increased fire activity and land use change that may be ascribed to human activity. Additional biomarkers such as fecal sterols in lake sediments can determine when people were in an area, and can help establish if an increased human presence in an area corresponds with intensified fire activity. This combination of specific biomarkers, other proxy data, and model output can help determine the relative impact of humans versus climate factors on regional fire activity.

Extended lattice Boltzmann scheme for droplet combustion.

Science.gov (United States)

Ashna, Mostafa; Rahimian, Mohammad Hassan; Fakhari, Abbas

2017-05-01

The available lattice Boltzmann (LB) models for combustion or phase change are focused on either single-phase flow combustion or two-phase flow with evaporation assuming a constant density for both liquid and gas phases. To pave the way towards simulation of spray combustion, we propose a two-phase LB method for modeling combustion of liquid fuel droplets. We develop an LB scheme to model phase change and combustion by taking into account the density variation in the gas phase and accounting for the chemical reaction based on the Cahn-Hilliard free-energy approach. Evaporation of liquid fuel is modeled by adding a source term, which is due to the divergence of the velocity field being nontrivial, in the continuity equation. The low-Mach-number approximation in the governing Navier-Stokes and energy equations is used to incorporate source terms due to heat release from chemical reactions, density variation, and nonluminous radiative heat loss. Additionally, the conservation equation for chemical species is formulated by including a source term due to chemical reaction. To validate the model, we consider the combustion of n-heptane and n-butanol droplets in stagnant air using overall single-step reactions. The diameter history and flame standoff ratio obtained from the proposed LB method are found to be in good agreement with available numerical and experimental data. The present LB scheme is believed to be a promising approach for modeling spray combustion.

Unsupervised Learning Through Randomized Algorithms for High-Volume High-Velocity Data (ULTRA-HV).

Energy Technology Data Exchange (ETDEWEB)

Pinar, Ali [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kolda, Tamara G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carlberg, Kevin Thomas [Wake Forest Univ., Winston-Salem, MA (United States); Ballard, Grey [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mahoney, Michael [Univ. of California, Berkeley, CA (United States)

2018-01-01

Through long-term investments in computing, algorithms, facilities, and instrumentation, DOE is an established leader in massive-scale, high-fidelity simulations, as well as science-leading experimentation. In both cases, DOE is generating more data than it can analyze and the problem is intensifying quickly. The need for advanced algorithms that can automatically convert the abundance of data into a wealth of useful information by discovering hidden structures is well recognized. Such efforts however, are hindered by the massive volume of the data and its high velocity. Here, the challenge is developing unsupervised learning methods to discover hidden structure in high-volume, high-velocity data.

An experimental study on suspended sodium droplet combustion (3)

International Nuclear Information System (INIS)

Sato, Kenji

2005-03-01

As part of studies for phenomenological investigation of sodium droplet burning behavior, in our previous experimental studies for suspended single sodium droplet, behavior of ignition process and succeeding combustion, ignition delay time, and droplet temperature history had been investigated. In this study, combustion experiments of suspended sodium droplet were performed in upward dry air flow by expanding the range of free-stream velocity U of air flow into 400 cm/s with initial droplet temperature Ti=300, 350, and 400degC and initial droplet diameter 4 mm at first. Then, the combustion experiments were also performed by changing the initial droplet diameter from 2.3 to 4.4 mm with Ti=350 and 400degC and U=100 cm/s. From the experimental results, the effects of free-stream velocity, initial droplet temperature, and initial droplet diameter on the ignition/burning behavior and ignition delay time were examined. The obtained results are as follows: (1) Ignition phenomena of suspended droplet were observed for all examined experimental conditions up to 400 cm/s. The orange emission observed at the moment of ignition occurs simultaneously over whole droplet surface except the top region of it. (2) The feature of the dependence of ignition delay time on the free-stream velocity is independent of the initial droplet temperature. With the increase of the free-stream velocity, up to 300 cm/s the ignition delay time decreases with decreasing dependency, and then the dependency increases more. (3) The ignition delay time increases with the increase of initial droplet diameter. The dependency increases as the initial droplet diameter increases. The ignition delay time extrapolated toward zero diameters from the obtained results becomes to be essentially zero. (author)

Investigation of bluff-body micro-flameless combustion

International Nuclear Information System (INIS)

Hosseini, Seyed Ehsan; Wahid, Mazlan Abdul

2014-01-01

Highlights: • The temperature uniformity of the micro-flameless combustion increases when a triangular bluff-body is applied. • The velocity and temperature of exhaust gases are higher in micro-flameless combustion compared to the conventional mode. • The rate of fuel–oxidizer consumption in micro-flameless mode is lower than conventional micro-combustion. - Abstract: Characteristics of lean premixed conventional micro-combustion and lean non-premixed flameless regime of methane/air are investigated in this paper by solving three-dimensional governing equations. At moderate equivalence ratio (∅ = 0.5), standard k–ε and the eddy-dissipation concept are employed to simulate temperature distribution and combustion stability of these models. The effect of bluff-body on the temperature distribution of both conventional and flameless mode is developed. The results show that in the premixed conventional micro-combustion the stability of the flame is increased when a triangular bluff-body is applied. Moreover, micro-flameless combustion is more stable when bluff-body is used. Micro-flameless mode with bluff-body and 7% O 2 concentration (when N 2 is used as diluent) illustrated better performance than other cases. The maximum temperature in premixed conventional micro-combustion and micro-flameless combustion was recorded 2200 K and 1520 K respectively. Indeed, the flue gas temperature of conventional mode and flameless combustion was 1300 K and 1500 K respectively. The fluctuation of temperature in the conventional micro-combustor wall has negative effects on the combustor and reduces the lifetime of micro-combustor. However, in the micro-flameless mode, the wall temperature is moderate and uniform. The rate of fuel–oxidizer consumption in micro-flameless mode takes longer time and the period of cylinders recharging is prolonged

Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

Energy Technology Data Exchange (ETDEWEB)

Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J; Tsujimura, T; Osswald, P; Kohse-Hoinghaus, K

2010-12-12

Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temperature and low temperature reaction pathways. In this study, the primary experimental validation target for the model is premixed flat low-pressure flame species profiles obtained using molecular beam mass spectrometry (MBMS). The model is also validated against previously published data for premixed flame velocity and n-butanol rapid compression machine and shock tube ignition delay. The agreement with these data sets is reasonably good. The dominant reaction pathways at the various pressures and temperatures studied are elucidated. At low temperature conditions, we found that the reaction of alphahydroxybutyl with O{sub 2} was important in controlling the reactivity of the system, and for correctly predicting C{sub 4} aldehyde profiles in low pressure premixed flames. Enol-keto isomerization reactions assisted by HO{sub 2} were also found to be important in converting enols to aldehydes and ketones in the low pressure premixed flames. In the paper, we describe how the structural features of the four different butanol isomers lead to differences in the combustion properties of each isomer.

Some Factors Affecting Combustion in an Internal-Combustion Engine

Science.gov (United States)

Rothrock, A M; Cohn, Mildred

1936-01-01

An investigation of the combustion of gasoline, safety, and diesel fuels was made in the NACA combustion apparatus under conditions of temperature that permitted ignition by spark with direct fuel injection, in spite of the compression ratio of 12.7 employed. The influence of such variables as injection advance angle, jacket temperature, engine speed, and spark position was studied. The most pronounced effect was that an increase in the injection advance angle (beyond a certain minimum value) caused a decrease in the extent and rate of combustion. In almost all cases combustion improved with increased temperature. The results show that at low air temperatures the rates of combustion vary with the volatility of the fuel, but that at high temperatures this relationship does not exist and the rates depend to a greater extent on the chemical nature of the fuel.

Combustion/particle sizing experiments at the Naval Postgraduate School Combustion Research Laboratory

Science.gov (United States)

Powers, John; Netzer, David

1987-01-01

Particle behavior in combustion processes is an active research area at NPS. Currently, four research efforts are being conducted: (1) There is a long standing need to better understand the soot production and combustion processes in gas turbine combustors, both from a concern for improved engine life and to minimize exhaust particulates. Soot emissions are strongly effected by fuel composition and additives; (2) A more recent need for particle sizing/behavior measurements is in the combustor of a solid fuel ramjet which uses a metallized fuel. High speed motion pictures are being used to study rather large burning particles; (3) In solid propellant rocket motors, metals are used to improve specific impulse and/or to provide damping for combustion pressure oscillations. Particle sizing experiments are being conducted using diode arrays to measure the light intensity as a function of scattering angle; (4) Once a good quality hologram is attained, a need exists for obtaining the particle distributions from hologram in a short period of time. A Quantimet 720 Image Analyzer is being used to reconstruct images.

An Investigation on Flame Shape and Size for a High-Pressure Turbulent Non-Premixed Swirl Combustion

Directory of Open Access Journals (Sweden)

Zhongya Xi

2018-04-01

Full Text Available Flame shape and size for a high-pressure turbulent non-premixed swirl combustion were experimentally investigated over a wide range of varying parameters including fuel mass flow rate, combustor pressure, primary-air mass flow rate, and nozzle exit velocity. A CFD simulation was conducted to predict the flame profile. Meanwhile, a theoretical calculation was also performed to estimate flame length. It was observed that flame length increased linearly with increasing fuel mass flow rate but decreased with the increment of combustor pressure in the power function. The flame diminished at a larger primary-air mass flow rate but remained unaffected by the increasing nozzle exit velocity. Considering the global effect of all parameters at a particular pressure, the flame length generally decreased as the primary-air to fuel ratio increased. This was attributed to the reduced air entrainment required to dilute the fuel to stoichiometric proportions. The CFD simulation offered a good prediction of the variation trends of flame length, although some deviations from experimental values were observed. The theoretical calculation estimated the trends of flame length variation particularly well. Nevertheless the difference between the theoretical and experimental results was found to be due to the swirl influence. Hence, a swirl factor was proposed to be added to the original equation for swirl flames.

Numerical investigation of spray combustion in jet mixing type combustor for low NOx emission

International Nuclear Information System (INIS)

Watanabe, Hirotatsu; Suwa, Yoshikazu; Matsushita, Yohsuke; Morozumi, Yoshio; Aoki, Hideyuki; Tanno, Shoji; Miura, Takatoshi

2008-01-01

The present paper describes a numerical investigation of spray combustion in a jet mixing type combustor. In this combustor, kerosene spray was injected with a pressure atomizer, and high speed combustion air was introduced towards the spray flow through some inlet air nozzles to improve mixing of the spray and the air. In the numerical simulation, the conservative equations of mass, momentum and energy in the turbulent flow field were solved in conjunction with the k-ε two equation turbulence model. The effects of the diameter and the number of air inlet nozzles on the combustion behavior and NO emission were numerically investigated. When the diameter of the inlet air nozzle decreased from 8 to 4 mm, the calculated NO mole fraction in the exhaust gas was drastically decreased by about 80%. An increase in the inlet velocity resulted in improvement of the mixing of the spray and the air, and hence, the high temperature region where thermal NO was formed became narrow. As a result, the exhaust NO mole fraction decreased. Furthermore, a decrease in exhaust NO mole fraction was explained by a decrease in the residence time in the high temperature region above 1800 K

Study on the Enhancement Effect of Dielectric Barrier Discharge on the Premixed Methane/Oxygen/Helium Flame Velocity

International Nuclear Information System (INIS)

Mu Haibao; Yu Lin; Li Ping; Zhang Guanjun; Tang Chenglong; Wang Jinhua

2015-01-01

Recently, plasma-assisted combustion has become a potentially applicable technology in many combustion scenarios. In this paper, a dielectric barrier discharge (DBD) plasma generator is designed to explore the effect of plasma on the CH4 oxidation process, and several properties of combustion are considered. First, in the presence or absence of plasma discharge, physical appearance of the flame is examined and analyzed. Second, the flame propagation velocity is calculated by the flame front extracted from the imaging data with the Bunsen burner method. Finally, the main molecular components and their intensity variation in the flame and the plasma zones are identified with an emission spectrograph to analyze the effect of active species on the combustion process. We also discuss the possible kinetic regime of plasma-assisted combustion. Experimental results imply that plasma discharge applied to the premixed CH4/O2/He mixture significantly raises the flame speed with equivalence ratios ranging from 0.85 to 1.10, with the flame speed improved by 17% to 35%. It can be seen that plasma can improve methane oxidation efficiency in the premixed fuel/oxidizer, especially at a low equivalence ratio. (paper)

Combustion instability control in the model of combustion chamber

International Nuclear Information System (INIS)

Akhmadullin, A N; Ahmethanov, E N; Iovleva, O V; Mitrofanov, G A

2013-01-01

An experimental study of the influence of external periodic perturbations on the instability of the combustion chamber in a pulsating combustion. As an external periodic disturbances were used sound waves emitted by the electrodynamics. The purpose of the study was to determine the possibility of using the method of external periodic perturbation to control the combustion instability. The study was conducted on a specially created model of the combustion chamber with a swirl burner in the frequency range from 100 to 1400 Hz. The study found that the method of external periodic perturbations may be used to control combustion instability. Depending on the frequency of the external periodic perturbation is observed as an increase and decrease in the amplitude of the oscillations in the combustion chamber. These effects are due to the mechanisms of synchronous and asynchronous action. External periodic disturbance generated in the path feeding the gaseous fuel, showing the high efficiency of the method of management in terms of energy costs. Power required to initiate periodic disturbances (50 W) is significantly smaller than the thermal capacity of the combustion chamber (100 kW)

Velocity field measurements on high-frequency, supersonic microactuators

Science.gov (United States)

Kreth, Phillip A.; Ali, Mohd Y.; Fernandez, Erik J.; Alvi, Farrukh S.

2016-05-01

The resonance-enhanced microjet actuator which was developed at the Advanced Aero-Propulsion Laboratory at Florida State University is a fluidic-based device that produces pulsed, supersonic microjets by utilizing a number of microscale, flow-acoustic resonance phenomena. The microactuator used in this study consists of an underexpanded source jet that flows into a cylindrical cavity with a single, 1-mm-diameter exhaust orifice through which an unsteady, supersonic jet issues at a resonant frequency of 7 kHz. The flowfields of a 1-mm underexpanded free jet and the microactuator are studied in detail using high-magnification, phase-locked flow visualizations (microschlieren) and two-component particle image velocimetry. These are the first direct measurements of the velocity fields produced by such actuators. Comparisons are made between the flow visualizations and the velocity field measurements. The results clearly show that the microactuator produces pulsed, supersonic jets with velocities exceeding 400 m/s for roughly 60 % of their cycles. With high unsteady momentum output, this type of microactuator has potential in a range of ow control applications.

Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol.

Science.gov (United States)

Martinsson, J; Eriksson, A C; Nielsen, I Elbæk; Malmborg, V Berg; Ahlberg, E; Andersen, C; Lindgren, R; Nyström, R; Nordin, E Z; Brune, W H; Svenningsson, B; Swietlicki, E; Boman, C; Pagels, J H

2015-12-15

The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Ångström exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.

Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines

International Nuclear Information System (INIS)

Zheng Ming; Reader, Graham T.

2004-01-01

The use of three way catalytic converters in stoichiometric burn reciprocating internal combustion engine systems has proved to be an effective and efficient method for reducing the level of criteria pollutants. However, such passive systems have not been as successful in emission amelioration when combined with lean burn engines. This is because of the thermochemical nature of the exhaust gases generated by such engines. The high content of exhaust oxygen largely negates the effectiveness of three way catalytic converters, and the comparatively low temperature of the combusted gases means that supplemental energy has to be added to these gases to enable the converter to function correctly. This requirement severely reduces the energy efficiency of conventional passive aftertreatment systems. However, initial empirical studies have indicated that a possible means of improving the performance of aftertreatment devices when used with lean burn engine systems is to use active flow control of the exhaust gases. These results are reported in this paper. This concept has been further investigated by developing an energy efficiency analysis that enables the effects on aftertreatment performance of different gas flow rates, flow reversal frequencies and monolith solid properties to be investigated. Simulation results indicate that through active thermal management, the supplemental energy consumption can be drastically reduced

Low emission turbulent technology for fuel combustion

International Nuclear Information System (INIS)

Finker, F. Z.; Kubyshkin, I. B.; Zakharov, B. Yu.; Akhmedov, D. B.; Sobchuk, Ch.

1997-01-01

The company 'POLITEKHENERGO' in co-operation and the Russian-Poland firm 'EnergoVIR' have performed investigations for modernization of the current existing boilers. A low emission turbulent technology has been used for the modernization of 10 industrial boilers. The reduction of NO x emissions is based on the following processes: 1) multistage combustion assured by two counter-deviated fluxes; 2) Some of the combustion facilities have an abrupt slope and a reduced air supply which leads to an intense separation of the fuel in the bottom part and a creation of a low-temperature combustion zone where the active restoration of the NO x takes part; 3) The influence of the top high-temperature zone on the NO x formation is small. Thus the 'sandwich' consisting of 'cold' and'hot' combustion layers provides a full rate combustion. This technique permits to: decrease of the NO x and CO x down to the European standard values;increase of the efficiency in 1-2%; obtain a stable coal combustion up to 97-98%; assure the large loading range (30 -100%); modernize and use the old boilers

Carotid near-occlusion frequently has high peak systolic velocity on Doppler ultrasound

Energy Technology Data Exchange (ETDEWEB)

Khangure, Simon R.; Machnowska, Matylda; Fox, Allan J.; Hojjat, Seyed-Parsa; Aviv, Richard I. [Sunnybrook Health Sciences Centre, Department of Medical Imaging, Neuroradiology Division, Toronto, ON (Canada); University of Toronto, Department of Medical Imaging, Division of Neuroimaging, Toronto (Canada); Benhabib, Hadas [Sunnybrook Health Sciences Centre, Department of Medical Imaging, Neuroradiology Division, Toronto, ON (Canada); Groenlund, Christer [Umeaa University, Department of Radiation Sciences, Biomedical Engineering, Umeaa (Sweden); Herod, Wendy [Department of Surgery, Sunnybrook Health Sciences Centre, Toronto (Canada); Maggisano, Robert [Department of Surgery, Sunnybrook Health Sciences Centre, Toronto (Canada); University of Toronto, Division of Vascular Surgery, Department of Surgery, Toronto (Canada); Sjoeberg, Anders [Umeaa University, Department of Radiation Sciences, Biomedical Engineering, Umeaa (Sweden); Umeaa University, Department of Pharmacology and Clinical Neuroscience, Umeaa (Sweden); Wester, Per [Umeaa University, Department of Public Health and Clinical Medicine, Umeaa (Sweden); Karolinska Institutet Danderyds Hospital, Department of Clinical Sciences, Stockholm (Sweden); Hopyan, Julia [University of Toronto, Division of Neurology, Department of Medicine, Toronto (Canada); Johansson, Elias [Umeaa University, Department of Pharmacology and Clinical Neuroscience, Umeaa (Sweden); Umeaa University, Department of Public Health and Clinical Medicine, Umeaa (Sweden)

2018-01-15

Carotid near-occlusion is a tight atherosclerotic stenosis of the internal carotid artery (ICA) resulting in decrease in diameter of the vessel lumen distal to the stenosis. Near-occlusions can be classified as with or without full collapse, and may have high peak systolic velocity (PSV) across the stenosis, mimicking conventional > 50% carotid artery stenosis. We aimed to determine how frequently near-occlusions have high PSV in the stenosis and determine how accurately carotid Doppler ultrasound can distinguish high-velocity near-occlusion from conventional stenosis. Included patients had near-occlusion or conventional stenosis with carotid ultrasound and CT angiogram (CTA) performed within 30 days of each other. CTA examinations were analyzed by two blinded expert readers. Velocities in the internal and common carotid arteries were recorded. Mean velocity, pulsatility index, and ratios were calculated, giving 12 Doppler parameters for analysis. Of 136 patients, 82 had conventional stenosis and 54 had near-occlusion on CTA. Of near-occlusions, 40 (74%) had high PSV (≥ 125 cm/s) across the stenosis. Ten Doppler parameters significantly differed between conventional stenosis and high-velocity near-occlusion groups. However, no parameter was highly sensitive and specific to separate the groups. Near-occlusions frequently have high PSV across the stenosis, particularly those without full collapse. Carotid Doppler ultrasound does not seem able to distinguish conventional stenosis from high-velocity near-occlusion. These findings question the use of ultrasound alone for preoperative imaging evaluation. (orig.)

Numerical Simulation of In Situ Combustion of Oil Shale

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Huan Zheng

2017-01-01

Full Text Available This paper analyzes the process of in situ combustion of oil shale, taking into account the transport and chemical reaction of various components in porous reservoirs. The physical model is presented, including the mass and energy conservation equations and Darcy’s law. The oxidation reactions of oil shale combustion are expressed by adding source terms in the conservation equations. The reaction rate of oxidation satisfies the Arrhenius law. A numerical method is established for calculating in situ combustion, which is simulated numerically, and the results are compared with the available experiment. The profiles of temperature and volume fraction of a few components are presented. The temperature contours show the temperature variation in the combustion tube. It is found that as combustion reaction occurs in the tube, the concentration of oxygen decreases rapidly, while the concentration of carbon dioxide and carbon monoxide increases contrarily. Besides, the combustion front velocity is consistent with the experimental value. Effects of gas injection rate, permeability of the reservoir, initial oil content, and injected oxygen content on the ISC process were investigated in this study. Varying gas injection rate and oxygen content is important in the field test of ISC.

Spray-combustion synthesis: efficient solution route to high-performance oxide transistors.

Science.gov (United States)

Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P H; Bedzyk, Michael J; Ferragut, Rafael; Marks, Tobin J; Facchetti, Antonio

2015-03-17

Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations.

Recent progress in the joint velocity-scalar PDF method

Science.gov (United States)

Anand, M. S.

1995-01-01

This viewgraph presentation discusses joint velocity-scalar PDF method; turbulent combustion modeling issues for gas turbine combustors; PDF calculations for a recirculating flow; stochastic dissipation model; joint PDF calculations for swirling flows; spray calculations; reduced kinetics/manifold methods; parallel processing; and joint PDF focus areas.

Effect of energetic electrons on combustion of premixed burner flame

Science.gov (United States)

Sasaki, Koichi

2011-10-01

In many studies of plasma-assisted combustion, authors superpose discharges onto flames to control combustion reactions. This work is motivated by more fundamental point of view. The standpoint of this work is that flames themselves are already plasmas. We irradiated microwave power onto premixed burner flame with the intention of heating electrons in it. The microwave power was limited below the threshold for a discharge. We obtained the enhancement of burning velocity by the irradiation of the microwave power, which was understood by the shortening of the flame length. At the same time, we observed the increases in the optical emission intensities of OH and CH radicals. Despite the increases in the optical emission intensities, the optical emission spectra of OH and CH were not affected by the microwave irradiation, indicating that the enhancement of the burning velocity was not attributed to the increase in the gas temperature. On the other hand, we observed significant increase in the optical emission intensity of the second positive system of molecular nitrogen, which is a clear evidence for electron heating in the premixed burner flame. Therefore, it is considered that the enhancement of the burning velocity is obtained by nonequilibrium combustion chemistry which is driven by energetic electrons. By irradiating pulsed microwave power, we examined the time constants for the increases and decreases in the optical emission intensities of N2, OH, CH, and continuum radiation.

Evidence for mass loss at moderate to high velocity in Be stars

Science.gov (United States)

Snow, T. P., Jr.; Marlborough, J. M.

1976-01-01

Ultraviolet spectra of intermediate resolution have been obtained with Copernicus for 12 objects classified as Be or shell stars and for 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km/s. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered, there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotational effects reduce the effective gravity near the equator. The mass-loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be one billionth or one ten-billionth of a solar mass per year. The data suggest that the extended atmospheres associated with Be-star phenomena may be formed by mass ejection.

Determination of iodine in diverse botanical and dietary matrices by pre-irradiation combustion followed by neutron activation analysis

International Nuclear Information System (INIS)

Norman, B.R.; Iyengar, G.V.

1994-01-01

The method chosen for determination of iodine in this investigation is an extension of an existing analytical technique to food samples which was developed for environmental samples. The method is based on pre-irradiation combustion of the sample to liberate iodine, trapping the iodine on charcoal, and quantitating the element by neutron activation analysis (NAA). Existing botanical and dietary reference materials were used to check the validity of the method. Several mixed diet samples with high fat content from the U.S. Total Diet Study and composites of cereals with both low and high iodine content were analyzed. This method of pre-irradiation combustion followed by NAA has been shown to be a viable technique for the determination of iodine in dietary samples. However, with a detection limit of about 50 ng of iodine, large amounts of sample (> 1 g) are typically required for each determination. (orig.)

High-temperature CO / HC gas sensors to optimize firewood combustion in low-power fireplaces

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B. Ojha

2017-06-01

Full Text Available In order to optimize firewood combustion in low-power firewood-fuelled fireplaces, a novel combustion airstream control concept based on the signals of in situ sensors for combustion temperature, residual oxygen concentration and residual un-combusted or partly combusted pyrolysis gas components (CO and HC has been introduced. A comparison of firing experiments with hand-driven and automated airstream-controlled furnaces of the same type showed that the average CO emissions in the high-temperature phase of the batch combustion can be reduced by about 80 % with the new control concept. Further, the performance of different types of high-temperature CO / HC sensors (mixed-potential and metal oxide types, with reference to simultaneous exhaust gas analysis by a high-temperature FTIR analysis system, was investigated over 20 batch firing experiments (∼ 80 h. The distinctive sensing behaviour with respect to the characteristically varying flue gas composition over a batch firing process is discussed. The calculation of the Pearson correlation coefficients reveals that mixed-potential sensor signals correlate more with CO and CH4; however, different metal oxide sensitive layers correlate with different gas species: 1 % Pt / SnO2 designates the presence of CO and 2 % ZnO / SnO2 designates the presence of hydrocarbons. In the case of a TGS823 sensor element, there was no specific correlation with one of the flue gas components observed. The stability of the sensor signals was evaluated through repeated exposure to mixtures of CO, N2 and synthetic air after certain numbers of firing experiments and exhibited diverse long-term signal instabilities.

Effect of Fe on the phases and microstructure of TiC-Fe cermets by combustion synthesis/quasi-isostatic pressing

International Nuclear Information System (INIS)

Zhang Weifang; Zhang Xinghong; Wang Jianli; Hong Changqing

2004-01-01

Fully dense TiC-Fe cermets (x = 10, 20, 30, and 40 wt.%) were produced from Ti-C-Fe powder mixtures by combustion synthesis with quasi-isostatic pressing. The effect of Fe content on combustion temperature, combustion wave velocity, and final product density was investigated. The final product was characterized by XRD, SEM, and TEM. The combustion temperature and wave velocity decreased with increasing Fe content. Product density increased with increasing Fe content (96% at 30 wt.%). X-ray diffraction and transmission electron microscopy (TEM) revealed the final product to contain TiC, Fe phases, lath martensite, and Fe 2 Ti. The TiC particle size decreased with increasing Fe content. In addition, a low density of dislocations was observed in both the TiC particles and Fe binder, indicative of annealing and recrystallization, respectively

Burning Questions in Gravity-Dependent Combustion Science

Science.gov (United States)

Urban, David; Chiaramonte, Francis P.

2012-01-01

Building upon a long history of spaceflight and ground based research, NASA's Combustion Science program has accumulated a significant body of accomplishments on the ISS. Historically, NASAs low-gravity combustion research program has sought: to provide a more complete understanding of the fundamental controlling processes in combustion by identifying simpler one-dimensional systems to eliminate the complex interactions between the buoyant flow and the energy feedback to the reaction zone to provide realistic simulation of the fire risk in manned spacecraft and to enable practical simulation of the gravitational environment experienced by reacting systems in future spacecraft. Over the past two decades, low-gravity combustion research has focused primarily on increasing our understanding of fundamental combustion processes (e.g. droplet combustion, soot, flame spread, smoldering, and gas-jet flames). This research program was highly successful and was aided by synergistic programs in Europe and in Japan. Overall improvements were made in our ability to model droplet combustion in spray combustors (e.g. jet engines), predict flame spread, predict soot production, and detect and prevent spacecraft fires. These results provided a unique dataset that supports both an active research discipline and also spacecraft fire safety for current and future spacecraft. These experiments have been conducted using the Combustion Integrated Rack (CIR), the Microgravity Science Glovebox and the Express Rack. In this paper, we provide an overview of the earlier space shuttle experiments, the recent ISS combustion experiments in addition to the studies planned for the future. Experiments in combustion include topics such as droplet combustion, gaseous diffusion flames, solid fuels, premixed flame studies, fire safety, and super critical oxidation processes.

Study of combustion properties of a solid propellant by highly time-resolved passive FTIR

Energy Technology Data Exchange (ETDEWEB)

Zhang, Liming; Zhang, Lin; Li, Yan; Liu, Bingping; Wang, Junde [Laboratory of Advanced Spectroscopy, Nanjing University of Science and Technology, Nanjing 210014 (China)

2006-10-15

With a time resolution of 0.125 s and a spectral resolution of 4 cm{sup -1}, emission spectra of the combustion process of a solid propellant were recorded by highly time-resolved passive FTIR. Some gaseous combustion products, such as H{sub 2}O, CO, CO{sub 2}, NO and HCl, were distinguished by the characteristic emission band of each molecule. The equation for flame temperature calculation based on the diatomic molecule emission fine structure theory was improved through judicious utilization of the spectral running number 'm' which makes the temperature measurement simpler and faster. Some combustion information of the solid propellant had been given including the characteristic spectral profile, the distribution of the absolute spectral energy, the distribution of the combustion flame temperature, and the concentration distributions of HCl and NO versus burning time. The results will provide theoretical and experimental bases for improving the formula and raising combustion efficiency of solid propellant, and developing the design of rocket motor, infrared guidance and antiguidance systems. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Manufacturing of Porous Al-Cr Preforms for Composite Reinforcing Using Microwave Activated Combustion Synthesis

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Naplocha K.

2014-10-01

Full Text Available The combustion synthesis of porous skeletons (preforms of intermetallic Al–Cr compounds intended for metal matrix composite MMC reinforcing was developed. Mixture of Al and Cr powders with granularity of −10, −44, −74mm were cold isostatic pressed and next ignited and synthetized in a microwave reactor under argon atmosphere (microwave-activated combustion synthesis MACS. In order to ignite the synthesis, microwave energy was focused by a tuner on the specimen. The analysis of reaction temperature diagrams revealed that the synthesis proceeded through the following peritectic transformations: L(liquidus+Al7Cr→L+Al11Cr2→L+Al4Cr. Moreover, EDS and XRD examinations showed that the reaction proceeded between a solid Cr and a liquid Al to create a distinct envelope of Al9Cr4 on Cr particle which next extended and spreaded over the entire structure. The produced preforms with uniform structure and interconnected porosity were infiltrated with liquid Cu and Al alloy. The obtained composite materials exhibited high hardness, wear and distinct temperature oxidation resistance.

Holey graphene frameworks for highly selective post-combustion carbon capture

Science.gov (United States)

Chowdhury, Shamik; Balasubramanian, Rajasekhar

2016-02-01

Atmospheric CO2 concentrations continue to rise rapidly in response to increased combustion of fossil fuels, contributing to global climate change. In order to mitigate the effects of global warming, development of new materials for cost-effective and energy-efficient CO2 capture is critically important. Graphene-based porous materials are an emerging class of solid adsorbents for selectively removing CO2 from flue gases. Herein, we report a simple and scalable approach to produce three-dimensional holey graphene frameworks with tunable porosity and pore geometry, and demonstrate their application as high-performance CO2 adsorbents. These holey graphene macrostructures exhibit a significantly improved specific surface area and pore volume compared to their pristine counterparts, and can be effectively used in post-combustion CO2 adsorption systems because of their intrinsic hydrophobicity together with good gravimetric storage capacities, rapid removal capabilities, superior cycling stabilities, and moderate initial isosteric heats. In addition, an exceptionally high CO2 over N2 selectivity can be achieved under conditions relevant to capture from the dry exhaust gas stream of a coal burning power plant, suggesting the possibility of recovering highly pure CO2 for long-term sequestration and/or utilization for downstream applications.

Rheology of serpentinite in high-temperature and low-slip-velocity regime

Science.gov (United States)

Takahashi, M.; Uehara, S.; Mizoguchi, K.; Takeda, N.; Masuda, K.

2009-12-01

This study was designed to clarify the rheology of serpentinite experimentally, related both the sliding velocity and the temperature. The frictional behavior of serpentinite is of particular interest in the study of earthquake generation processes along subducting plates and transform faults. Previous studies [Reinen et al., 1991-93] revealed that the serpentinites indicated two-mechanical behaviors at velocity-step test: ‘state-variable dominated behavior’ at relatively higher velocity (0.1-10 μm/sec) and ‘flow-dominated behavior’ at lower velocity (less than 0.1 μm/sec). Such complexity on the frictional behavior could make it complicated to forecast on the slip acceleration process from the plate motion velocity to the earthquake. Even under the room-temperature condition, those multiple behavior could be observed, thus, serpentinite can be a model substance to present a new constitutive law at the brittle-ductile transition regime. We, therefore, focus to discuss the transient behaviors of serpentinite at the velocity-step test. We used a gas-medium, high-pressure, and high-temperature triaxial testing machine belonging to the National Institute of Advanced Industrial Science and Technology (AIST), Japan. Sliding deformation was applied on the thin zone of the serpentinite gouge (1.0 g of almost pure antigorite powder) sandwiched between two alumina blocks with oblique surfaces at 30° to the axis. All experiments were carried out under a set of constant conditions, 100 MPa of the confining pressure (Ar-gas) and 30 MPa of the pore pressure (distilled water). The temperature conditions were varied from the room-temperature to 500° C, and three sliding velocity-regimes were adopted: low (0.0115 - 0.115 μm/sec), middle (0.115 - 1.15 μm/sec) and high (1.15 - 11.5 μm/sec) velocity regimes. In each velocity regime, the sliding velocity was increased or decreased in a stepwise fashion, and then we observed the transient behaviors until it reached the

New Metamaterials with Combined Subnano - and Mesoscale Topology for High-efficiency Catalytic Combustion Chambers of Innovative Gas Turbine Engines

Science.gov (United States)

Knysh, Yu A.; Xanthopoulou, G. G.

2018-01-01

The object of the study is a catalytic combustion chamber that provides a highly efficient combustion process through the use of effects: heat recovery from combustion, microvortex heat transfer, catalytic reaction and acoustic resonance. High efficiency is provided by a complex of related technologies: technologies for combustion products heat transfer (recuperation) to initial mixture, catalytic processes technology, technology for calculating effective combustion processes based on microvortex matrices, technology for designing metamaterials structures and technology for obtaining the required topology product by laser fusion of metal powder compositions. The mesoscale level structure provides combustion process with the use of a microvortex effect with a high intensity of heat and mass transfer. High surface area (extremely high area-to-volume ratio) created due to nanoscale periodic structure and ensures catalytic reactions efficiency. Produced metamaterial is the first multiscale product of new concept which due to combination of different scale level periodic topologies provides qualitatively new set of product properties. This research is aimed at solving simultaneously two global problems of the present: ensure environmental safety of transport systems and power industry, as well as the economy and rational use of energy resources, providing humanity with energy now and in the foreseeable future.

Thermogravimetric analysis of biowastes during combustion

International Nuclear Information System (INIS)

Otero, M.; Sanchez, M.E.; Gomez, X.; Moran, A.

2010-01-01

The combustion of sewage sludge (SS), animal manure (AM) and the organic fraction of municipal solid waste (OFMSW) was assessed and compared with that of a semianthracite coal (SC) and of a PET waste by thermogravimetric (TG) analysis. Differences were found in the TG curves obtained for the combustion of these materials accordingly to their respective proximate analysis. Non-isothermal thermogravimetric data were used to assess the kinetics of the combustion of these biowastes. The present paper reports on the application of the Vyazovkin model-free isoconversional method for the evaluation of the activation energy necessary for the combustion of these biowastes. The activation energy related to SS combustion (129.1 kJ/mol) was similar to that corresponding to AM (132.5 kJ/mol) while the OFMSW showed a higher value (159.3 kJ/mol). These values are quite higher than the one determined in the same way for the combustion of SC (49.2 kJ/mol) but lower than that for the combustion of a PET waste (165.6 kJ/mol).

Establishment of Combustion Model for Isooctane HCCI Marine Diesel Engine and Research on the Combustion Characteristic

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Li Biao

2016-01-01

Full Text Available The homogeneous charge compression ignition (HCCI combustion mode applied in marine diesel engine is expected to be one of alternative technologies to decrease nitrogen oxide (NOX emission and improve energy utilization rate. Applying the chemical-looping combustion (CLC mechanism inside the cylinder, a numerical study on the HCCI combustion process is performed taking a marine diesel engine as application object. The characteristic feature of combustion process is displayed. On this basis, the formation and emission of NOX are analyzed and discussed. The results indicate that the HCCI combustion mode always exhibit two combustion releasing heats: low-temperature reaction and high-temperature reaction. The combustion phase is divided into low-temperature reaction zone, high-temperature reaction zone and negative temperature coefficient (NTC zone. The operating conditions of the high compression ratio, high intake air temperature, low inlet pressure and small excess air coefficient would cause the high in-cylinder pressure which often leads engine detonation. The low compression ratio, low intake air temperature and big excess air coefficient would cause the low combustor temperature which is conducive to reduce NOX emissions. These technological means and operating conditions are expected to meet the NOX emissions limits in MARPOL73/78 Convention-Annex VI Amendment.

Effect of density on forward and upward smoldering combustion of cellulosic material

Science.gov (United States)

Veronica, Sherly; Putri, R. H.; Fitriani, F.; Ramadhan, M. L.; Riki, M.; Reynaldo, S.; Imran, F. A.; Nugroho, Yulianto S.

2017-03-01

Smoldering is a slow, flameless and the most persistent type of combustion. Wildland fire or ground fire is an example of smoldering combustion which has become one of the most important issue in Indonesia and no effective solution has been found to solve this phenomenon yet. The organic materials contained in peatland can potentially become a flammable fuel with the presence of a trigger for wildland fire. In this experimental work tobacco material was used to study smoldering phenomenon. The relation between material density with temperature distribution and mass loss rate are conducted in the experiment. The transmissivity of the smoke produced by the smoldering combustion will also be analyzed. Experiments are carried out for the material density ranging from 0.12 - 0.2 g/cm3. The result showed that smoldering combustion are affected by density, due to the allowance of airflow and heat propagation. The result showed that material bed with the lowest density of 0.12 g/cm3 has the slowest smoldering velocity and mass loss rate while the material bed with the highest density of 0.2 g/cm3 has the fastest smoldering velocity and mass loss rate. The smoke took a longer period time to reach the bed surface at higher bed density.

Theoretical Research Progress in High-Velocity/Hypervelocity Impact on Semi-Infinite Targets

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Yunhou Sun

2015-01-01

Full Text Available With the hypervelocity kinetic weapon and hypersonic cruise missiles research projects being carried out, the damage mechanism for high-velocity/hypervelocity projectile impact on semi-infinite targets has become the research keystone in impact dynamics. Theoretical research progress in high-velocity/hypervelocity impact on semi-infinite targets was reviewed in this paper. The evaluation methods for critical velocity of high-velocity and hypervelocity impact were summarized. The crater shape, crater scaling laws and empirical formulae, and simplified analysis models of crater parameters for spherical projectiles impact on semi-infinite targets were reviewed, so were the long rod penetration state differentiation, penetration depth calculation models for the semifluid, and deformed long rod projectiles. Finally, some research proposals were given for further study.

Effect of secondary air injection on the combustion efficiency of sawdust in a fluidized bed combustor

Directory of Open Access Journals (Sweden)

K. V. N. Srinivasa Rao

2008-03-01

Full Text Available Agricultural wastes like bagasse, paddy husks, sawdust and groundnut shells can be effectively used as fuels for fluidized bed combustion; otherwise these biomass fuels are difficult to handle due to high moisture and fines content. In the present work the possibility of using sawdust in the fluidized bed combustor, related combustion efficiencies and problems encountered in the combustion process are discussed. The temperature profiles for sawdust with an increase in fluidizing velocity along the vertical height above the distributor plate indicate that considerable burning of fuel particles is taking place in the freeboard zone rather than complete burning within the bed. Therefore, an enlarged disengagement section is provided to improve the combustion of fines. The temperature profiles along the bed height are observed at different feed rates. The feed rate of sawdust corresponding to the maximum possible temperature was observed to be 10.2 kg/h. It is observed that 50-60% excess air is optimal for reducing carbon loss during the burning of sawdust. The maximum possible combustion efficiency with sawdust is 99.2% and is observed with 65% excess air.

Management of High-Velocity Injuries of the Head and Neck.

Science.gov (United States)

Majors, Jacob S; Brennan, Joseph; Holt, G Richard

2017-11-01

Trauma centers must prepare to manage high-velocity injuries resulting from a mass casualty incidents as global terrorism becomes a greater concern and an increasing risk. The most recent conflicts in Iraq and Afghanistan have significantly improved understanding of battlefield trauma and how to appropriately address these injures. This article applies combat surgery experience to civilian situations, outlines the physiology and kinetics of high-velocity injuries, and reviews applicable triage and management strategies. Published by Elsevier Inc.

Combustion behaviors and kinetics of sewage sludge blended with pulverized coal: With and without catalysts.

Science.gov (United States)

Wang, Zhiqiang; Hong, Chen; Xing, Yi; Li, Yifei; Feng, Lihui; Jia, Mengmeng

2018-04-01

The combustion behaviors of sewage sludge (SS), pulverized coal (PC), and their blends were studied using a thermogravimetric analyzer. The effect of the mass ratio of SS to PC on the co-combustion characteristics was analyzed. The experiments showed that the ignition performance of the blends improved significantly as the mass percentage of SS increased, but its combustion intensity decreased. The burnout temperature (T b ) and comprehensive combustibility index (S) of the blends were almost unchanged when the mass percentage of SS was less than 10%. However, a high mass percentage of SS (>10%) resulted in a great increase in T b and a notable decrease in S. Subsequently, the effects of different catalysts (CaO, CeO 2 , MnO 2 , and Fe 2 O 3 ) on the combustion characteristics and activation energy of the SS/PC blend were investigated. The four catalysts promoted the release and combustion of volatile matters in the blended fuels and shifted their combustion profiles to a low temperature. In addition, their peak separating tendencies were obvious at 350-550 C, resulting in high peak widths. All the catalysts improved combustion activity of the blended fuel and accelerated fixed carbon combustion, which decreased the ignition temperature and burnout temperature of the fuels. CeO 2 had the best catalytic effects in terms of the comprehensive combustion performance and activation energy, followed closely by Fe 2 O 3 . However, the rare-earth compounds are expensive to be applied in the catalytic combustion process of SS/PC blend at present. Based on both catalytic effects and economy, Fe 2 O 3 was potentially an optimal option for catalytic combustion among the tested catalysts. Copyright © 2018 Elsevier Ltd. All rights reserved.

Emission and combustion characteristics of multiple stage diesel combustion; Nidan nensho ni yoru diesel kikan no nensho to haishutsubutsu tokusei

Energy Technology Data Exchange (ETDEWEB)

Hashizume, T; Miyamoto, T; Tsujimura, K [New A.C.E. Institute Co. Ltd., Tokyo (Japan); Kobayashi, S; Shimizu, K [Japan Automobile Research Institute, Tsukuba (Japan)

1997-10-01

A new concept of multiple stage diesel combustion was studied by means of engine test, combustion observation and numerical simulation, in order to reduce NOx emissions at high load conditions. With this concept, the premixed combustion occurs under the fuel lean conditions and the diffusion combustion occurs under the high temperature conditions. As seen in the result of combustion observation, a first stage combustion occurs with no luminous flame. A second stage combustion occurs with a luminous flame after very short ignition delay period. However the luminous flame is disappeared immediately. Because cylinder temperature is high, and hence soot oxidizes immediately. 5 refs., 11 figs., 1 tab.

Correlation Water Velocity and TSS with Natural Radionuclides Activity

International Nuclear Information System (INIS)

Tri Harningsih; Muzakky; Agus Taftazani

2007-01-01

Correlation water velocity and TSS with natural radionuclides activity has been studied. For that purpose, the study is to correlation water velocity and TSS with radionuclides on water and sediment samples in alongside river Code Yogyakarta. This research selected radionuclides, for examples Ra-226, Pb-212, Ac- 228, and K-40. Election of this radionuclides to spread over gamma gross composition alongside river of Code. Gamma gross influenced by water velocity and TSS, so that require to correct between water velocity and TSS to radionuclides. Sampling water and sediment conducted when dry season of August, 2006 at 11 locations, start from Boyong Bridge until Pacar Bridge. Result of analysis showed that water velocity range from 8-1070 L/dt and TSS range from 2.81 E-06 - 8.02 E-04 mg/L. The accumulation of radionuclides in water samples non correction water velocity for Ra-226: 0.302-2.861 Bq/L, Pb-212: 0.400-3.390 Bq/L, Ac- 228: 0.0029-0.0047 Bq/L and K-40: 0.780-9.178 Bq/L. The accumulation of radionuclide in water samples correction water velocity for Ra-226: 1.112-70.454 Bq/L, Pb-212: 0.850-77.113 Bq/L, Ac-228: 0.7187- 60.859 Bq/L and K-40: 2.420-208.8 Bq/L. While distribution of radionuclide in sediment for the Ra-226: 0.0012-0.0211 Bq/kg, Pb-212: 0.0017-0.0371 Bq/kg, Ac-228: 0.0021-0.0073 Bq/kg and K-40: 0.0006-0.0084 Bq/kg. (author)

Development of a high velocity rain erosion test method

Energy Technology Data Exchange (ETDEWEB)

Chung, Dong Teak; Jin, Doo Han [Korea University of Technology and Education, Cheonan (Korea, Republic of); Kang, Hyung [Agency for Defense Development, Daejeon (Korea, Republic of)

2009-07-01

The nose of a missile, flying through raining region with a supersonic speed, is subjected to the rain erosion because the nose is made of a brittle ceramic material. A simple yet very effective rain erosion test method is developed. The sabot assembly similar to the hypodermic syringe carries specific amount of water is launched by a low pressure air gun. After the stopper stop the sabot assembly by impact, the steel plunger continues moving toward to squeeze the silicon rubber in front. The pressurized silicon rubber then is squeezed through the orifice in front of the sabot at high velocity, thus, accelerates the water droplet to higher velocity. The droplet velocity up to 800m/s is successfully attained using a low pressure air gun. The ceramic specimen assembly is placed in front of the high speed water droplet and the rain erosion damage on the surface of the specimen is observed.

A simple one-step chemistry model for partially premixed hydrocarbon combustion

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Tarrazo, Eduardo [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Sanchez, Antonio L. [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, Leganes 28911 (Spain); Linan, Amable [ETSI Aeronauticos, Pl. Cardenal Cisneros 3, Madrid 28040 (Spain); Williams, Forman A. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093-0411 (United States)

2006-10-15

This work explores the applicability of one-step irreversible Arrhenius kinetics with unity reaction order to the numerical description of partially premixed hydrocarbon combustion. Computations of planar premixed flames are used in the selection of the three model parameters: the heat of reaction q, the activation temperature T{sub a}, and the preexponential factor B. It is seen that changes in q with equivalence ratio f need to be introduced in fuel-rich combustion to describe the effect of partial fuel oxidation on the amount of heat released, leading to a universal linear variation q(f) for f>1 for all hydrocarbons. The model also employs a variable activation temperature T{sub a}(f) to mimic changes in the underlying chemistry in rich and very lean flames. The resulting chemistry description is able to reproduce propagation velocities of diluted and undiluted flames accurately over the whole flammability limit. Furthermore, computations of methane-air counterflow diffusion flames are used to test the proposed chemistry under nonpremixed conditions. The model not only predicts the critical strain rate at extinction accurately but also gives near-extinction flames with oxygen leakage, thereby overcoming known predictive limitations of one-step Arrhenius kinetics. (author)

Strong Velocity-Weakening of Nanograins at High Slip-Rates

Science.gov (United States)

Han, R.; Hirose, T.; Ando, J.

2008-12-01

It has been observed that slip localization zones in some experimental and natural faults consist of crystalline or amorphous nanograins of different minerals. Prolonged grinding of silicate rocks (e.g., quartz rock and granite) is known to produce amorphous silica nanograins and mechanical properties of the material (especially under wet condition) have been attributed to a mechanism of fault weakening. Also, recent high- velocity friction tests on carbonate rocks showed that faults can be weakened by thermal decomposition of calcite into nanograins of lime and carbon dioxide and the lubrication effect of the nanograins would be critical for the fault weakening. However, mechanical behavior(s) and friction mechanism(s) of fault slip zones with nanograins, especially at high slip-rates, are still poorly understood, despite their potential importance to the understanding of seismic faulting. In this contribution, we show you our experimental results indicating velocity-weakening of nanograins (probably caused by still unknown mechanical behaviors of nanograins) rather than by temperature-related weakening behavior. In our high-velocity friction tests on Carrara marble at seismic slip-rates, we have tried to "cool" the simulated fault with liquid nitrogen and compressed air during frictional sliding, and found, in the simulated fault coated with nanopowders of lime (CaO) formed by thermal decomposition, no correlation between friction and temperature measured with thermocouples (i.e., no temperature-related weakening behavior), although strong "velocity-weakening" behavior appeared. The observation was confirmed by another experiment: from (1) the calculated "maximum" sliding surface temperature [Carslaw and Jaeger, 1959] using the mechanical data, with an assumption of strong slip localization into a very thin layer, and (2) the measured temperature with thermocouples at a place just below the sliding surface and close to the periphery of the specimen, it was found

Measurement of laminar burning velocities and Markstein lengths of diluted hydrogen-enriched natural gas

Energy Technology Data Exchange (ETDEWEB)

Miao, Haiyan; Jiao, Qi; Huang, Zuohua; Jiang, Deming [State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Eng., Xi' an Jiaotong University (China)

2009-01-15

The laminar flame characteristics of natural gas-hydrogen-air-diluent gas (nitrogen/CO{sub 2}) mixtures were studied in a constant volume combustion bomb at various diluent ratios, hydrogen fractions and equivalence ratios. Both unstretched laminar burning velocity and Markstein length were obtained. The results showed that hydrogen fraction, diluent ratio and equivalence ratio have combined influence on laminar burning velocity and flame instability. The unstretched laminar burning velocity is reduced at a rate that is increased with the increase of the diluent ratio. The reduction effect of CO{sub 2} diluent gas is stronger than that of nitrogen diluent gas. Hydrogen-enriched natural gas with high hydrogen fraction can tolerate more diluent gas than that with low hydrogen fraction. Markstein length can either increase or decrease with the increase of the diluent ratio, depending on the hydrogen fraction of the fuel. (author)

Study on mechanism of combustion instability in a dump gas turbine combustor

International Nuclear Information System (INIS)

Lee, Yeon Joo; Lee, Jong Ho; Jeon, Chong Hwan; Chang, Yonng June

2002-01-01

Combustion instabilities are an important concern associated with lean premixed combustion. Laboratory-scale dump combustor was used to understand the underlying mechanisms causing combustion instabilities. Experiments were conducted at atmospheric pressure and sound level meter was used to track the pressure fluctuations inside the combustor. Instability maps and phase-resolved OH chemiluminescence images were obtained at several conditions to investigate the mechanism of combustion instability and relations between pressure wave and heat release rate. It showed that combustion instability was susceptible to occur at higher value of equivalence ratio (>0.6) as the mean velocity was decreased. Instabilities exhibited a longitudinal mode with a dominant frequency of ∼341.8 Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instabilities occurred. Rayleigh index distribution gave a hint about the location where the strong coherence of pressure and heat release existed. These results also give an insight to the control scheme of combustion instabilities. Emission test revealed that NO x emissions were affected by not only equivalence but also combustion instability

Modeling the effects of auxiliary gas injection and fuel injection rate shape on diesel engine combustion and emissions

Science.gov (United States)

Mather, Daniel Kelly

1998-11-01

The effect of auxiliary gas injection and fuel injection rate-shaping on diesel engine combustion and emissions was studied using KIVA a multidimensional computational fluid dynamics code. Auxiliary gas injection (AGI) is the injection of a gas, in addition to the fuel injection, directly into the combustion chamber of a diesel engine. The objective of AGI is to influence the diesel combustion via mixing to reduce emissions of pollutants (soot and NO x). In this study, the accuracy of modeling high speed gas jets on very coarse computational grids was addressed. KIVA was found to inaccurately resolve the jet flows near walls. The cause of this inaccuracy was traced to the RNG k - ɛ turbulence model with the law-of-the-wall boundary condition used by KIVA. By prescribing the lengthscale near the nozzle exit, excellent agreement between computed and theoretical jet penetration was attained for a transient gas jet into a quiescent chamber at various operating conditions. The effect of AGI on diesel engine combustion and emissions was studied by incorporating the coarse grid gas jet model into a detailed multidimensional simulation of a Caterpillar 3401 heavy-duty diesel engine. The effects of AGI timing, composition, amount, orientation, and location were investigated. The effects of AGI and split fuel injection were also investigated. AGI was found to be effective at reducing soot emissions by increasing mixing within the combustion chamber. AGI of inert gas was found to be effective at reducing emissions of NOx by depressing the peak combustion temperatures. Finally, comparison of AGI simulations with experiments were conducted for a TACOM-LABECO engine. The results showed that AGI improved soot oxidation throughout the engine cycle. Simulation of fuel injection rate-shaping investigated the effects of three injection velocity profiles typical of unit-injector type, high-pressure common-rail type, and accumulator-type fuel injectors in the Caterpillar 3401 heavy

Online Wavelet Complementary velocity Estimator.

Science.gov (United States)

Righettini, Paolo; Strada, Roberto; KhademOlama, Ehsan; Valilou, Shirin

2018-02-01

In this paper, we have proposed a new online Wavelet Complementary velocity Estimator (WCE) over position and acceleration data gathered from an electro hydraulic servo shaking table. This is a batch estimator type that is based on the wavelet filter banks which extract the high and low resolution of data. The proposed complementary estimator combines these two resolutions of velocities which acquired from numerical differentiation and integration of the position and acceleration sensors by considering a fixed moving horizon window as input to wavelet filter. Because of using wavelet filters, it can be implemented in a parallel procedure. By this method the numerical velocity is estimated without having high noise of differentiators, integration drifting bias and with less delay which is suitable for active vibration control in high precision Mechatronics systems by Direct Velocity Feedback (DVF) methods. This method allows us to make velocity sensors with less mechanically moving parts which makes it suitable for fast miniature structures. We have compared this method with Kalman and Butterworth filters over stability, delay and benchmarked them by their long time velocity integration for getting back the initial position data. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Introduction to Analytical Methods for Internal Combustion Engine Cam Mechanisms

CERN Document Server

Williams, J J

2013-01-01

Modern design methods of Automotive Cam Design require the computation of a range of parameters. This book provides a logical sequence of steps for the derivation of the relevant equations from first principles, for the more widely used cam mechanisms. Although originally derived for use in high performance engines, this work is equally applicable to the design of mass produced automotive and other internal combustion engines.   Introduction to Analytical Methods for Internal Combustion Engine Cam Mechanisms provides the equations necessary for the design of cam lift curves with an associated smooth acceleration curve. The equations are derived for the kinematics and kinetics of all the mechanisms considered, together with those for cam curvature and oil entrainment velocity. This permits the cam shape, all loads, and contact stresses to be evaluated, and the relevant tribology to be assessed. The effects of asymmetry on the manufacture of cams for finger follower and offset translating curved followers is ...

Lab-scale investigation of Middle-Bosnia coals to achieve high-efficient and clean combustion technology

Directory of Open Access Journals (Sweden)

Smajevic Izet

2014-01-01

Full Text Available This paper describes full lab-scale investigation of Middle-Bosnia coals launched to support selection an appropriate combustion technology and to support optimization of the boiler design. Tested mix of Middle-Bosnia brown coals is projected coal for new co-generation power plant Kakanj Unit 8 (300-450 MWe, EP B&H electricity utility. The basic coal blend consisting of the coals Kakanj: Breza: Zenica at approximate mass ratio of 70:20:10 is low grade brown coal with very high percentage of ash - over 40%. Testing that coal in circulated fluidized bed combustion technique, performed at Ruhr-University Bohum and Doosan Lentjes GmbH, has shown its inconveniency for fluidized bed combustion technology, primarily due to the agglomeration problems. Tests of these coals in PFC (pulverized fuel combustion technology have been performed in referent laboratory at Faculty of Mechanical Engineering of Sarajevo University, on a lab-scale PFC furnace, to provide reliable data for further analysis. The PFC tests results are fitted well with previously obtained results of the burning similar Bosnian coal blends in the PFC dry bottom furnace technique. Combination of the coals shares, the process temperature and the air combustion distribution for the lowest NOx and SO2 emissions was found in this work, provided that combustion efficiency and CO emissions are within very strict criteria, considering specific settlement of lab-scale furnace. Sustainability assessment based on calculation economic and environmental indicators, in combination with Low Cost Planning method, is used for optimization the power plant design. The results of the full lab-scale investigation will help in selection optimal Boiler design, to achieve sustainable energy system with high-efficient and clean combustion technology applied for given coals.

Modelling of turbulence and combustion for simulation of gas explosions in complex geometries

Energy Technology Data Exchange (ETDEWEB)

Arntzen, Bjoern Johan

1998-12-31

This thesis analyses and presents new models for turbulent reactive flows for CFD (Computational Fluid Dynamics) simulation of gas explosions in complex geometries like offshore modules. The course of a gas explosion in a complex geometry is largely determined by the development of turbulence and the accompanying increased combustion rate. To be able to model the process it is necessary to use a CFD code as a starting point, provided with a suitable turbulence and combustion model. The modelling and calculations are done in a three-dimensional finite volume CFD code, where complex geometries are represented by a porosity concept, which gives porosity on the grid cell faces, depending on what is inside the cell. The turbulent flow field is modelled with a k-{epsilon} turbulence model. Subgrid models are used for production of turbulence from geometry not fully resolved on the grid. Results from laser doppler anemometry measurements around obstructions in steady and transient flows have been analysed and the turbulence models have been improved to handle transient, subgrid and reactive flows. The combustion is modelled with a burning velocity model and a flame model which incorporates the burning velocity into the code. Two different flame models have been developed: SIF (Simple Interface Flame model), which treats the flame as an interface between reactants and products, and the {beta}-model where the reaction zone is resolved with about three grid cells. The flame normally starts with a quasi laminar burning velocity, due to flame instabilities, modelled as a function of flame radius and laminar burning velocity. As the flow field becomes turbulent, the flame uses a turbulent burning velocity model based on experimental data and dependent on turbulence parameters and laminar burning velocity. The laminar burning velocity is modelled as a function of gas mixture, equivalence ratio, pressure and temperature in reactant. Simulations agree well with experiments. 139

Emission characteristics of multiple stage diesel combustion. Effect of exhaust gas recirculation; Nidan nensho diesel kikan no haishutsubutsu tokusei. EGR no eikyo

Energy Technology Data Exchange (ETDEWEB)

Hashizume, T.; Miyamoto, T.; Akagawa, H.; Tsujimura, K. [New A.C.E. Institute Co. Ltd., Tokyo (Japan)

1998-05-01

For an aim to reduce NOx emission from diesel engines, it has become possible to realize it with smoke emission maintained at low levels by taking the following steps: initial combustion is carried out as lean pre-mixed combustion by adopting early fuel injection; the fuel is injected again after completion of this combustion; and EGR is combined with two-stage combustion which performs diffusion combustion under high temperature atmosphere. When a large quantity of EGR is used, cylinder temperature drops to have ignition timing delayed in the first stage, serving for improving fuel consumption. The problem of increase in smoke generation is solved by optimizing the injection timing at the second stage to suppress smoke generation increase, resulting in realization of lower NOx emission. By completing the second-stage fuel injection before ignition of the first-stage injection, it was possible to realize further lower NOx emission. Smoke increase due to higher EGR ratio was suppressed by pre-mixing both fuels injected in the first and second stages, although this is a high load operation. In addition, oxygen concentration and cylinder temperature were reduced, the gas pre-mixture was homogenized, and combustion velocity was suppressed by delaying the angle of ignition timing. This made low smoke combustion at {lambda} = 1 possible even in compressed ignition combustion. 8 refs., 12 figs., 1 tab.

Hydrogen combustion issues and containment integrity

International Nuclear Information System (INIS)

Tennankore, K.N.; Koroll, G.W.; Kumar, R.K.; Lam, A.H.T.; Chan, C.K.; Wren, D.J.

1987-01-01

This report reviews recent results from the research program at the Whiteshell Nuclear Research Establishment aimed at resolving hydrogen combustion issues relevant to reactor containment integrity. The areas considered are hydrogen mixing behaviour, flame propagation, pressure transients caused by deflagration, flame acceleration and transition to detonation. Small-scale tests carried out with helium/CO 2 systems indicate that the presence of a recirculation path will enhance buoyancy-driven mixing of hydrogen-steam jets with air in the containment. An extensive database has been assembled for the laminar burning velocity of hydrogen-air-steam mixtures. Work is now beginning on obtaining burning velocities under turbulent conditions likely to prevail in containments. Turbulent and vented combustion data obtained in a 2.3-m-diameter spherical vessel have been analyzed. The results indicate that the pressure predictions of a one-dimensional model can be matched with the data if different effective burning velocities are used. Obstacle-induced flame acceleration and transition to detonation have been studied in a small-scale test facility to determine conditions required for transition to detonation in containments. For a repeated obstacle configuration, the obstacle blockage ratio required to cause transition (deflagation to detonation or detonation to deflagration) can be correlated well with detonation cell size. Cell sizes for mixtures of interest are being determined in our laboratory to complement available data. The transition-to-detonation process has been visualized in the above tests by Schlieren photography. The eventual objective of this work is to identify the local conditions controlling the transition process

Enhanced RAMAC performance in subdetonative propulsion mode with semi-combustible projectile

Energy Technology Data Exchange (ETDEWEB)

Legendre, J.F.; Giraud, M. [French-German Res. Inst., Saint-Louis (France)

2000-11-01

Investigations are carried out at ISL to determine the experimental conditions required to accelerate a projectile in the mass range from 1.5 to 2 kg up to a muzzle velocity of 3 km/s while keeping the maximum acceleration below 40,000 g. Therefore, two smooth-bore ram-accelerators denoted RAMAC 30-II and RAMAC 90, in caliber 30 and 90 mm respectively, are being operated in the thermally choked propulsion mode. Different material configurations for the projectile afterbody have been investigated, while keeping an aluminum nose cone. Besides afterbodies made of aluminum or magnesium alloy only, a third configuration is presented relying on a short magnesium part fitted to the base of an aluminum afterbody. This configuration denoted as ''semi-combustible'' is designed so that magnesium particles are steadily injected and burnt-out within the combustion zone at the base, therefore providing an additional heat release and consequently a significantly greater forward thrust. Experimental results achieved in both 30 and 90 mm along a 300-caliber-long ram-section and using up to three different gaseous mixtures are presented. To date, for a given semi-combustible projectile and an injection velocity into the ram-section of 1380 m/s, a maximum muzzle velocity of 2380 m/s has been achieved in RAMAC 30-II and 2180 m/s in RAMAC 90, the initial projectile mass being 69 g and 1608 g respectively. (orig.)

Fuel Combustion and Engine Performance | Transportation Research | NREL

Science.gov (United States)

Fuel Combustion and Engine Performance Fuel Combustion and Engine Performance Photo of a gasoline emissions in advanced engine technologies. Photo by Dennis Schroeder, NREL NREL's combustion research and combustion and engine research activities include: Developing experimental and simulation research platforms

Atomic collision experiments utilizing low-velocity, highly-charged ion beams

International Nuclear Information System (INIS)

Johnson, B.M.; Jones, K.W.; Meron, M.

1983-01-01

Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandems in a unique four-stage accel/decel mode. This mode of operation combines three stages of acceleration, stripping at high energy, and one stage of deceleration to near-zero velocity. To date, experiments have used 10-100 nA beams of bare and few-electron heavy ions at energies as low as 0.2 MeV/amu, and upgrades of the facility should push the lower limit below 0.1 MeV/amu. Recent experiments, such as measurements of charge transfer and x-ray production for S 6 - 16 + on He and Ar at 6-20 MeV and P(b) measurements for MO x-rays produced in Cl 16 + + Ar collisions at 20, 10 and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed

Atomic collision experiments utilizing low-velocity, highly-charged ion beams

International Nuclear Information System (INIS)

Johnson, B.M.; Jones, K.W.; Meron, M.

1982-01-01

Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandens in a unique four-stage accel/decel mode. This mode of operation combines three stages of acceleration, stripping at high energy, and one stage of deceleration to near-zero velocity. To date, experiments have used 10-100 nA beams of bare and few-electron heavy ions at energies as low as 0.2 MeV/amu, and upgrades of the facility should push the lower limit below 0.1 MeV/amu. Recent experiments, such as measurements of charge transfer and x-ray production for S/sup 6-16+/ on He and Ar at 6 to 20 MeV and P(b) measurements for MO x-rays produced in Cl 16 + + Ar collisions at 20, 10, and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed

Stratified charge rotary engine combustion studies

Science.gov (United States)

Shock, H.; Hamady, F.; Somerton, C.; Stuecken, T.; Chouinard, E.; Rachal, T.; Kosterman, J.; Lambeth, M.; Olbrich, C.

1989-07-01

Analytical and experimental studies of the combustion process in a stratified charge rotary engine (SCRE) continue to be the subject of active research in recent years. Specifically to meet the demand for more sophisticated products, a detailed understanding of the engine system of interest is warranted. With this in mind the objective of this work is to develop an understanding of the controlling factors that affect the SCRE combustion process so that an efficient power dense rotary engine can be designed. The influence of the induction-exhaust systems and the rotor geometry are believed to have a significant effect on combustion chamber flow characteristics. In this report, emphasis is centered on Laser Doppler Velocimetry (LDV) measurements and on qualitative flow visualizations in the combustion chamber of the motored rotary engine assembly. This will provide a basic understanding of the flow process in the RCE and serve as a data base for verification of numerical simulations. Understanding fuel injection provisions is also important to the successful operation of the stratified charge rotary engine. Toward this end, flow visualizations depicting the development of high speed, high pressure fuel jets are described. Friction is an important consideration in an engine from the standpoint of lost work, durability and reliability. MSU Engine Research Laboratory efforts in accessing the frictional losses associated with the rotary engine are described. This includes work which describes losses in bearing, seal and auxillary components. Finally, a computer controlled mapping system under development is described. This system can be used to map shapes such as combustion chamber, intake manifolds or turbine blades accurately.

High-speed combustion diagnostics in a rapid compression machine by broadband supercontinuum absorption spectroscopy.

Science.gov (United States)

Werblinski, Thomas; Fendt, Peter; Zigan, Lars; Will, Stefan

2017-05-20

The first results under fired internal combustion engine conditions based on a supercontinuum absorption spectrometer are presented and discussed. Temperature, pressure, and water mole fraction are inferred simultaneously from broadband H 2 O absorbance spectra ranging from 1340 nm to 1440 nm. The auto-ignition combustion process is monitored for two premixed n-heptane/air mixtures with 10 kHz in a rapid compression machine. Pressure and temperature levels during combustion exceed 65 bar and 1900 K, respectively. To allow for combustion measurements, the robustness of the spectrometer against beam steering has been improved compared to its previous version. Additionally, the detectable wavelength range has been extended further into the infrared region to allow for the acquisition of distinct high-temperature water transitions located in the P-branch above 1410 nm. Based on a theoretical study, line-of-sight (LOS) effects introduced by temperature stratification on the broadband fitting algorithm in the complete range from 1340 nm to 1440 nm are discussed. In this context, the recorded spectra during combustion were evaluated only within a narrower spectral region exhibiting almost no interference from low-temperature molecules (here, P-branch from 1410 nm to 1440 nm). It is shown that this strategy mitigates almost all of the LOS effects introduced by cold molecules and the evaluation of the spectrum in the entirely recorded wavelength range at engine combustion conditions.

Vortex combustor for low NOX emissions when burning lean premixed high hydrogen content fuel

Science.gov (United States)

Steele, Robert C; Edmonds, Ryan G; Williams, Joseph T; Baldwin, Stephen P

2012-11-20

A trapped vortex combustor. The trapped vortex combustor is configured for receiving a lean premixed gaseous fuel and oxidant stream, where the fuel includes hydrogen gas. The trapped vortex combustor is configured to receive the lean premixed fuel and oxidant stream at a velocity which significantly exceeds combustion flame speed in a selected lean premixed fuel and oxidant mixture. The combustor is configured to operate at relatively high bulk fluid velocities while maintaining stable combustion, and low NOx emissions. The combustor is useful in gas turbines in a process of burning synfuels, as it offers the opportunity to avoid use of diluent gas to reduce combustion temperatures. The combustor also offers the possibility of avoiding the use of selected catalytic reaction units for removal of oxides of nitrogen from combustion gases exiting a gas turbine.

Investigation on Flame Characteristics and Burner Operability Issues of Oxy-Fuel Combustion

Energy Technology Data Exchange (ETDEWEB)

Choudhuri, Ahsan [Univ. Of Texas, El Paso, TX (United States)

2013-09-30

Oxy-fuel combustion has been used previously in a wide range of industrial applications. Oxy- combustion is carried out by burning a hydrocarbon fuel with oxygen instead of air. Flames burning in this configuration achieve higher flame temperatures which present opportunities for significant efficiency improvements and direct capture of CO₂ from the exhaust stream. In an effort to better understand and characterize the fundamental flame characteristics of oxy-fuel combustion this research presents the experimental measurements of flame stability of various oxyfuel flames. Effects of H₂ concentration, fuel composition, exhaust gas recirculation ratio, firing inputs, and burner diameters on the flame stability of these fuels are discussed. Effects of exhaust gas recirculation i.e. CO₂ and H₂O (steam) acting as diluents on burner operability are also presented. The roles of firing input on flame stability are then analyzed. For this study it was observed that many oxy-flames did not stabilize without exhaust gas recirculation due to their higher burning velocities. In addition, the stability regime of all compositions was observed to decrease as the burner diameter increased. A flashback model is also presented, using the critical velocity gradient g_F) values for CH₄-O₂-CO₂ flames. The second part of the study focuses on the experimental measurements of the flow field characteristics of premixed CH₄/21%O₂/79%N₂ and CH₄/38%O₂/72%CO₂ mixtures at constant firing input of 7.5 kW, constant, equivalence ratio of 0.8, constant swirl number of 0.92 and constant Reynolds Numbers. These measurements were taken in a swirl stabilized combustor at atmospheric pressure. The flow field visualization using Particle Imaging Velocimetry (PIV) technique is implemented to make a better understanding of the turbulence characteristics of

Experimental and numerical studies of high-velocity impact fragmentation

Energy Technology Data Exchange (ETDEWEB)

Kipp, M.E.; Grady, D.E.; Swegle, J.W.

1993-08-01

Developments are reported in both experimental and numerical capabilities for characterizing the debris spray produced in penetration events. We have performed a series of high-velocity experiments specifically designed to examine the fragmentation of the projectile during impact. High-strength, well-characterized steel spheres (6.35 mm diameter) were launched with a two-stage light-gas gun to velocities in the range of 3 to 5 km/s. Normal impact with PMMA plates, thicknesses of 0.6 to 11 mm, applied impulsive loads of various amplitudes and durations to the steel sphere. Multiple flash radiography diagnostics and recovery techniques were used to assess size, velocity, trajectory and statistics of the impact-induced fragment debris. Damage modes to the primary target plate (plastic) and to a secondary target plate (aluminum) were also evaluated. Dynamic fragmentation theories, based on energy-balance principles, were used to evaluate local material deformation and fracture state information from CTH, a three-dimensional Eulerian solid dynamics shock wave propagation code. The local fragment characterization of the material defines a weighted fragment size distribution, and the sum of these distributions provides a composite particle size distribution for the steel sphere. The calculated axial and radial velocity changes agree well with experimental data, and the calculated fragment sizes are in qualitative agreement with the radiographic data. A secondary effort involved the experimental and computational analyses of normal and oblique copper ball impacts on steel target plates. High-resolution radiography and witness plate diagnostics provided impact motion and statistical fragment size data. CTH simulations were performed to test computational models and numerical methods.

High-velocity two-phase flow two-dimensional modeling

International Nuclear Information System (INIS)

Mathes, R.; Alemany, A.; Thilbault, J.P.

1995-01-01

The two-phase flow in the nozzle of a LMMHD (liquid metal magnetohydrodynamic) converter has been studied numerically and experimentally. A two-dimensional model for two-phase flow has been developed including the viscous terms (dragging and turbulence) and the interfacial mass, momentum and energy transfer between the phases. The numerical results were obtained by a finite volume method based on the SIMPLE algorithm. They have been verified by an experimental facility using air-water as a simulation pair and a phase Doppler particle analyzer for velocity and droplet size measurement. The numerical simulation of a lithium-cesium high-temperature pair showed that a nearly homogeneous and isothermal expansion of the two phases is possible with small pressure losses and high kinetic efficiencies. In the throat region a careful profiling is necessary to reduce the inertial effects on the liquid velocity field

Multi-stage combustion using nitrogen-enriched air

Science.gov (United States)

Fischer, Larry E.; Anderson, Brian L.

2004-09-14

Multi-stage combustion technology combined with nitrogen-enriched air technology for controlling the combustion temperature and products to extend the maintenance and lifetime cycles of materials in contact with combustion products and to reduce pollutants while maintaining relatively high combustion and thermal cycle efficiencies. The first stage of combustion operates fuel rich where most of the heat of combustion is released by burning it with nitrogen-enriched air. Part of the energy in the combustion gases is used to perform work or to provide heat. The cooled combustion gases are reheated by additional stages of combustion until the last stage is at or near stoichiometric conditions. Additional energy is extracted from each stage to result in relatively high thermal cycle efficiency. The air is enriched with nitrogen using air separation technologies such as diffusion, permeable membrane, absorption, and cryogenics. The combustion method is applicable to many types of combustion equipment, including: boilers, burners, turbines, internal combustion engines, and many types of fuel including hydrogen and carbon-based fuels including methane and coal.

Mode Selection in Flame-Vortex driven Combustion Instabilities

KAUST Repository

Speth, Ray

2011-01-04

In this paper, we investigate flame-vortex interaction in a lean premixed, laboratory scale, backward-facing step combustor. Two series of tests were conducted, using propane/hydrogen mixtures and carbon monoxide/hydrogen mixtures as fuels, respectively. Pressure measurements and high speed particle imaging velocimetry (PIV) were employed to generate pressure response curves as well as the images of the velocity field and the flame brush. We demonstrate that the step combustor exhibits several operating modes depending on the inlet conditions and fuel composition, characterized by the amplitude and frequency of pressure oscillations along with distinct dynamic flame shapes. We propose a model in which the combustor\\'s selection of the acoustic mode is governed by a combustion-related time delay inversely proportional to the flame speed. Our model predicts the transition between distinct operating modes. We introduce non-dimensional parameters characterizing the flame speed and stretch rate, and develop a relationship between these quantities at the operating conditions corresponding to each mode transition. Based on this relationship, we show that numerically-calculated density-weighted strained flame speed can be used to collapse the combustion dynamics data over the full range of conditions (inlet temperature, fuel composition, and equivalence ratio). Finally, we validate our strain flame based model by measuring the strain rate using the flame image and the velocity field from the PIV measurement. Our results show that the measured strain rates lie in the same range as the critical values at the transitions among distinct modes as those predicted by our model.

Acoustic and streaming velocity components in a resonant waveguide at high acoustic levels.

Science.gov (United States)

Daru, Virginie; Reyt, Ida; Bailliet, Hélène; Weisman, Catherine; Baltean-Carlès, Diana

2017-01-01

Rayleigh streaming is a steady flow generated by the interaction between an acoustic wave and a solid wall, generally assumed to be second order in a Mach number expansion. Acoustic streaming is well known in the case of a stationary plane wave at low amplitude: it has a half-wavelength spatial periodicity and the maximum axial streaming velocity is a quadratic function of the acoustic velocity amplitude at antinode. For higher acoustic levels, additional streaming cells have been observed. Results of laser Doppler velocimetry measurements are here compared to direct numerical simulations. The evolution of axial and radial velocity components for both acoustic and streaming velocities is studied from low to high acoustic amplitudes. Two streaming flow regimes are pointed out, the axial streaming dependency on acoustics going from quadratic to linear. The evolution of streaming flow is different for outer cells and for inner cells. Also, the hypothesis of radial streaming velocity being of second order in a Mach number expansion, is not valid at high amplitudes. The change of regime occurs when the radial streaming velocity amplitude becomes larger than the radial acoustic velocity amplitude, high levels being therefore characterized by nonlinear interaction of the different velocity components.

Thermal Behavior of Coal Used in Rotary Kiln and Its Combustion Intensification

Directory of Open Access Journals (Sweden)

Qiang Zhong

2018-04-01

Full Text Available Pyrolysis and combustion behaviors of three coals (A, B, and C coals were investigated and their combustion kinetics were calculated by the Freeman–Carroll method to obtain quantitative insight into their combustion behaviors. Moreover, the effects of coal size, air flow, oxygen content, and heating rate on coal combustion behaviors were analyzed. Results showed that the three coals have a similar trend of pyrolysis that occurs at about 670 K and this process continuously proceeds along with their combustion. Combustion characteristics and kinetic parameters can be applied to analyze coal combustion behaviors. Three coals having combustion characteristics of suitable ignition temperature (745–761 K, DTGmax (14.20–15.72%/min, and burnout time (7.45–8.10 min were analyzed in a rotary kiln. Combustion kinetic parameters provide quantitative insights into coal combustion behavior. The suitable particle size for coal combustion in a kiln is that the content of less than 74 μm is 60% to 80%. Low activation energy and reaction order make coal, especially C coal, have a simple combustion mechanism, great reactivity, be easily ignited, and a low peak temperature in the combustion state. Oxygen-enrichment and high heating rates enhance coal combustion, increasing combustion intensity and peak value, thus shortening burnout time.

Catalytic reduction of emissions from small scale wood combustion. State of the art

Energy Technology Data Exchange (ETDEWEB)

Hargitai, T.; Silversand, F.A. [Katator AB, Lund (Sweden)

1998-12-31

Small-scale combustion of big-fuel often results in excessive emissions of volatile organic compounds (VOC), polyaromatic compounds (PAM) and carbon monoxide (CO). These compounds have a negative impact on human health and urban air quality. The predominant volatile organic compounds present in flue gases from big-fuel combustion are propylene, ethylene, butadiene, methanol, ethanol, methane, phenol and benzene. The poor combustion performance of some wood stoves has in certain cases led to legislation against small-scale combustion of big-fuel in urban areas. Catalytic cleaning is one very efficient way of decreasing the environmental impacts of big-fuel combustion. Several studies concerning catalytic purification of flue gases from big-fuel combustion have been presented over the years. Several problems must be addressed when designing a catalyst for this application: Clogging problems from deposition of ashes and particulates in the catalyst; Catalyst poisoning by sulphur, phosphorus, alkali metals etc.; Catalyst fouling due to deposition of ashes and particulates; Catalyst overheating at high flue-gas temperatures and Poor catalyst performance during start-up Most studies have been focused on monolith-type catalysts and- the conversion of CO, VOC and PAH typically is above 80 %. The observed problems are associated with increased pressure drop due to catalyst clogging and decreased catalyst performance due to fouling and poisoning. In most cases precious metals, preferably Pt. have been used as active combustion catalyst. Precious metals have a high activity for the combustion of CO and hydrocarbons and a fair stability against poisoning with compounds present in flue gases from big-fuel, e.g. sulphur and alkali metals. The majority of the studies on precious metals have been focused on Pt. Rh and Pd, which are especially active in catalytic combustion. Some metal oxides are used in catalytic combustion, especially at low temperatures (e.g. in VOC abatement

Simultaneous planar measurements of soot structure and velocity fields in a turbulent lifted jet flame at 3 kHz

Science.gov (United States)

Köhler, M.; Boxx, I.; Geigle, K. P.; Meier, W.

2011-05-01

We describe a newly developed combustion diagnostic for the simultaneous planar imaging of soot structure and velocity fields in a highly sooting, lifted turbulent jet flame at 3000 frames per second, or two orders of magnitude faster than "conventional" laser imaging systems. This diagnostic uses short pulse duration (8 ns), frequency-doubled, diode-pumped solid state (DPSS) lasers to excite laser-induced incandescence (LII) at 3 kHz, which is then imaged onto a high framerate CMOS camera. A second (dual-cavity) DPSS laser and CMOS camera form the basis of a particle image velocity (PIV) system used to acquire 2-component velocity field in the flame. The LII response curve (measured in a laminar propane diffusion flame) is presented and the combined diagnostics then applied in a heavily sooting lifted turbulent jet flame. The potential challenges and rewards of application of this combined imaging technique at high speeds are discussed.

Entropy Analyses of Droplet Combustion in Convective Environment with Small Reynolds Number

Institute of Scientific and Technical Information of China (English)

ZHANG Xiaobin; ZHANG Wei; ZHANG Xuejun

2013-01-01

This paper analyzes the entropy generation rate of simple pure droplet combustion in a temperature-elevated air convective environment based on the solutions of flow,and heat and mass transfer between the two phases.The flow-field calculations are carried out by solving the respective conservation equations for each phase,accounting for the droplet deformation with the axisymmetric model.The effects of the temperature,velocity and oxygen fraction of the free stream air on the total entropy generation rate in the process of the droplet combustion are investigated.Special attention is given to analyze the quantitative effects of droplet deformation.The results reveal that the entropy generation rate due to chemical reaction occupies a large fraction of the total entropy generated,as a result of the large areas covered by the flame.Although,the magnitude of the entropy generation rate per volume due to heat transfer and combined mass and heat transfer has a magnitude of one order greater than that due to chemical reaction,they cover a very limited area,leading to a small fraction of the total entropy generated.The entropy generation rate due to mass transfer is negligible.High temperature and high velocity of the free stream are advantageous to increase the exergy efficiency in the range of small Reynolds number (＜1) from the viewpoint of the second-law analysis over the droplet lifetime.The effect of droplet deformation on the total entropy generation is the modest.

Trend and future of diesel engine: Development of high efficiency and low emission low temperature combustion diesel engine

International Nuclear Information System (INIS)

Ho, R J; Yusoff, M Z; Palanisamy, K

2013-01-01

Stringent emission policy has put automotive research and development on developing high efficiency and low pollutant power train. Conventional direct injection diesel engine with diffused flame has reached its limitation and has driven R and D to explore other field of combustion. Low temperature combustion (LTC) and homogeneous charge combustion ignition has been proven to be effective methods in decreasing combustion pollutant emission. Nitrogen Oxide (NO x ) and Particulate Matter (PM) formation from combustion can be greatly suppressed. A review on each of method is covered to identify the condition and processes that result in these reductions. The critical parameters that allow such combustion to take place will be highlighted and serves as emphasis to the direction of developing future diesel engine system. This paper is written to explore potential of present numerical and experimental methods in optimizing diesel engine design through adoption of the new combustion technology.

Trend and future of diesel engine: Development of high efficiency and low emission low temperature combustion diesel engine

Science.gov (United States)

Ho, R. J.; Yusoff, M. Z.; Palanisamy, K.

2013-06-01

Stringent emission policy has put automotive research & development on developing high efficiency and low pollutant power train. Conventional direct injection diesel engine with diffused flame has reached its limitation and has driven R&D to explore other field of combustion. Low temperature combustion (LTC) and homogeneous charge combustion ignition has been proven to be effective methods in decreasing combustion pollutant emission. Nitrogen Oxide (NOx) and Particulate Matter (PM) formation from combustion can be greatly suppressed. A review on each of method is covered to identify the condition and processes that result in these reductions. The critical parameters that allow such combustion to take place will be highlighted and serves as emphasis to the direction of developing future diesel engine system. This paper is written to explore potential of present numerical and experimental methods in optimizing diesel engine design through adoption of the new combustion technology.

Highly-controlled, reproducible measurements of aerosol emissions from African biomass combustion

Science.gov (United States)

Haslett, Sophie; Thomas, J. Chris; Morgan, William; Hadden, Rory; Liu, Dantong; Allan, James; Williams, Paul; Sekou, Keïta; Liousse, Catherine; Coe, Hugh

2017-04-01

Particulate emissions from biomass burning can alter the atmosphere's radiative balance and cause significant harm to human health. However, the relationship between these emissions and fundamental combustion processes is, to date, poorly characterised. In atmospheric models, aerosol emissions are represented by emission factors based on mass loss, which are averaged over an entire combustion event for each particulate species. This approach, however, masks huge variability in emissions during different phases of the combustion period. Laboratory tests have shown that even small changes to the burning environment can lead to huge variation in observed aerosol emission factors (Akagi et al., 2011). In order to address this gap in understanding, in this study, small wood samples sourced from Côte D'Ivoire were burned in a highly-controlled laboratory environment. The shape and mass of samples, available airflow and surrounding heat were carefully regulated. Organic aerosol and refractory black carbon emissions were measured in real-time using an Aerosol Mass Spectrometer and a Single Particle Soot Photometer, respectively. Both of these instruments are used regularly to measure aerosol concentrations in the field. This methodology produced remarkably repeatable results, allowing three different phases of combustion to be identified by their emissions. Black carbon was emitted predominantly during flaming combustion; organic aerosols were emitted during pyrolysis before ignition and from smouldering-dominated behaviour near the end of combustion. During the flaming period, there was a strong correlation between the emission of black carbon and the rate of mass loss, which suggests there is value in employing a mass-based emission factor for this species. However, very little correlation was seen between organic aerosol and mass loss throughout the tests. As such, results here suggest that emission factors averaged over an entire combustion event are unlikely to be

Elastic Wave Velocity Measurements on Mantle Peridotite at High Pressure and Temperature

Science.gov (United States)

Mistler, G. W.; Ishikawa, M.; Li, B.

2002-12-01

With the success of conducting ultrasonic measurements at high pressure and high temperature in large volume high pressure apparatus with in-situ measurement of the sample length by X-ray imaging, it is now possible to measure elastic wave velocities on aggregate samples with candidate compositions of the mantle to the conditions of the Earth's transition zone in the laboratory. These data can be directly compared with seismic data to distinguish the compositional models in debate. In this work, we carried out velocity measurements on natural peridotite KLB-1 at the conditions of the Earth's upper mantle. Fine powered sample of natural KLB-1 was used as starting material. Specimens for ultrasonic measurements were hot-pressed and equilibrated at various pressure and temperature conditions along geotherm up to the transition zone. The recovered samples were characterized with density measurement, X-ray diffraction and microprobe analysis. Bench top P and S wave velocities of KLB-1 sample sintered at 3-4 GPa and 1400 degree centigrade showed a very good agreement with the VRH average of pyrolite. High pressure and high temperature measurements was conducted up to 7 GPa and 800 degree centigrade using ultrasonic interferometric method in a DIA-type high pressure apparatus in conjunction with X-ray diffraction and X-ray imaging. The utilization of X-ray imaging technique provides direct measurements of sample lengths at high pressure and high temperature, ensuring a precise determination of velocities. The results of P and S wave velocities at high pressure and high temperature as well as their comparison with calculated pyrolite model will be presented.

Unified approach to the study of solid fuel combustion characteristics at high airflow speeds

Science.gov (United States)

Vnuchkov, D. A.; Lukashevich, S. V.; Nalivaychenko, D. G.; Zvegintsev, V. I.

2017-10-01

The main objective of the research is the development of guidelines for a unified approach to testing the combustion of different solid fuels in gaseous oxidant high-speed flow, so that research outcomes could be presented in a standardized and cohesive form. All the experiments were performed on a special experimental installation designed for quantification of the burning characteristics of different fuels in a wide range of the airflow parameters at the same geometry of the combustion chamber.

Characteristics of fundamental combustion and NOx emission using various rank coals.

Science.gov (United States)

Kim, Sung Su; Kang, Youn Suk; Lee, Hyun Dong; Kim, Jae-Kwan; Hong, Sung Chang

2011-03-01

Eight types of coals of different rank were selected and their fundamental combustion characteristics were examined along with the conversion of volatile nitrogen (N) to nitrogen oxides (NOx)/fuel N to NOx. The activation energy, onset temperature, and burnout temperature were obtained from the differential thermogravimetry curve and Arrhenius plot, which were derived through thermo-gravimetric analysis. In addition, to derive the combustion of volatile N to NOx/fuel N to NOx, the coal sample, which was pretreated at various temperatures, was burned, and the results were compared with previously derived fundamental combustion characteristics. The authors' experimental results confirmed that coal rank was highly correlated with the combustion of volatile N to NOx/fuel N to NOx.

Numerical studies of the integration of a trapped vortex combustor into traditional combustion chambers

Energy Technology Data Exchange (ETDEWEB)

Patrignani, L.; Losurdo, M.; Bruno, C. [Sapienza Univ. de Roma, Rome (Italy)

2010-09-15

Exhaust emissions from furnace burners can be reduced by premixing reactants with combustion products. This paper discussed the use of a trapped vortex combustor (TVC) as a very promising technology for gas turbines. The TVC can reduce emissions and ensure that the temperature is uniform in the exhaust products, which is a key aspect for certain types of heat treatments, such as in steel rolling mills. The TVC for gas turbines is configured to mix air, fuel and hot products at turbulent scales fine enough to render the combustion mode flameless, or close to flameless. The vortex ensures a high recirculation factor between hot combustion products and reactants, and ultimately flame stability. In this study, the TVC configuration for an existing gas turbine was numerically investigated by means of RANS and LES. According to preliminary results of the fast-flameless combustion (FFC) strategy, the proposed TVC is a suitable candidate to reduce nitrogen oxide (NOx) emissions while keeping the pressure drop below 1 per cent. Both RANS and LES show that too much fuel burns along the main duct. Better fuel splitting or a different position for the injectors may enhance combustion inside the recirculation zone. Behaviour of the main vortices showed that a more accurate design of the internal shape of the combustor is needed to prevent excessive velocity fluctuation or vortex instabilities and therefore emissions. 13 refs., 9 figs.

Ash deposition and high temperature corrosion at combustion of aggressive fuels

Energy Technology Data Exchange (ETDEWEB)

Hede Larsen, O [I/S Fynsvaerket, Faelleskemikerne, Odense (Denmark); Henriksen, N [Elsamprojekt A/S, Faelleskemikerne, Fredericia (Denmark)

1996-12-01

In order to reduce CO{sub 2} emission, ELSAM is investigating the possibilities of using biomass - mainly straw - for combustion in high efficiency power plants. As straw has very high contents of chlorine and potassium, a fuel with high corrosion and ash deposition propensities has been introduced. ELSAM has investigated 3 ultra supercritical boiler concepts for combustion of straw alone or together with coal: (1) PF boilers with a relatively low share of straw, (2) CFB boilers with low to high share of straw and (3) vibrating grate boilers with 100% straw. These investigations has mainly been full-scale tests with straw fed into existing boilers. Corrosion tests have been performed in these boilers using temperature regulated probes and in-plant test tubes in existing superheaters. The corrosion has been determined by detailed measurements of wall thickness reduction and light optical microscopic measurements of the material degradation due to high temperature corrosion. Corrosion mechanisms have been evaluated using SEM/EDX together with thermodynamical considerations based on measurements of the chemical environment in the flue gas. Ash deposition is problematic in CFB boilers and in straw fired boilers, especially in years with high potassium and chlorine content of the straw. This ash deposition also is related to condensation of KCl and can probably only be handled by improved cleaning devices. (EG)

Numerical investigation of biogas flameless combustion

International Nuclear Information System (INIS)

Hosseini, Seyed Ehsan; Bagheri, Ghobad; Wahid, Mazlan Abdul

2014-01-01

Highlights: • Fuel consumption decreases from 3.24 g/s in biogas conventional combustion to 1.07 g/s in flameless mode. • The differences between reactants and products temperature intensifies irreversibility in traditional combustion. • The temperature inside the chamber is uniform in biogas flameless mode and exergy loss decreases in this technique. • Low O 2 concentration in the flameless mode confirms a complete and quick combustion process in flameless regime. - Abstract: The purpose of this investigation is to analyze combustion characteristics of biogas flameless mode based on clean technology development strategies. A three dimensional (3D) computational fluid dynamic (CFD) study has been performed to illustrate various priorities of biogas flameless combustion compared to the conventional mode. The effects of preheated temperature and wall temperature, reaction zone and pollutant formation are observed and the impacts of combustion and turbulence models on numerical results are discussed. Although preheated conventional combustion could be effective in terms of fuel consumption reduction, NO x formation increases. It has been found that biogas is not eligible to be applied in furnace heat up due to its low calorific value (LCV) and it is necessary to utilize a high calorific value fuel to preheat the furnace. The required enthalpy for biogas auto-ignition temperature is supplied by enthalpy of preheated oxidizer. In biogas flameless combustion, the mean temperature of the furnace is lower than traditional combustion throughout the chamber. Compared to the biogas flameless combustion with uniform temperature, very high and fluctuated temperatures are recorded in conventional combustion. Since high entropy generation intensifies irreversibility, exergy loss is higher in biogas conventional combustion compared to the biogas flameless regime. Entropy generation minimization in flameless mode is attributed to the uniform temperature inside the chamber

The Multi-User Droplet Combustion Apparatus: the Development and Integration Concept for Droplet Combustion Payloads in the Fluids and Combustion Facility Combustion Integrated Rack

Science.gov (United States)

Myhre, C. A.

2002-01-01

using liquid combustibles on Earth and in space. As a result of the concurrent design process of MDCA and CIR, the MDCA team continues to work closely with the CIR team, developing Integration Agreements and an Interface Control Document during preliminary integration activities. Integrated testing of hardware and software systems will occur at the Engineering Model and Flight Model phases. Because the engineering model is a high fidelity unit, it will be upgraded to a flight equivalent Ground Integration Unit (GIU) when the engineering model phase is completed. The GIU will be available on the ground for troubleshooting of any on-orbit problems. Integrated verification testing will be conducted with the MDCA flight unit and the CIR flight unit. Upon successful testing, the MDCA will be shipped to the Kennedy Space Center for a post-shipment checkout and final turn-over to CIR for final processing and launch to the International Space Station. Once on-orbit, the MDCA is managed from the GRC Telescience Support Center (TSC). The MDCA operations team resides at the TSC. Data is transmitted to the PI's at their home sites by means of TREK workstations, allowing direct interaction between the PI and operations staff to maximum science. Upon completion of a PI's experiment, the MDCA is reconfigured for the next of the three follow-on experiments or ultimately removed from the CIR, placed into stowage, and returned to Earth.

The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

Science.gov (United States)

Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

2011-12-01

Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism

Modeling random combustion of lycopodium particles and gas

Directory of Open Access Journals (Sweden)

M Bidabadi

2016-06-01

Full Text Available The random modeling combustion of lycopodium particles has been researched by many authors. In this paper, we extend this model and we also generate a different method by analyzing the effect of random distributed sources of combustible mixture. The flame structure is assumed to consist of a preheat-vaporization zone, a reaction zone and finally a post flame zone. We divide the preheat zone to different parts. We assumed that there is different distribution of particles in sections which are really random. Meanwhile, it is presumed that the fuel particles vaporize first to yield gaseous fuel. In other words, most of the fuel particles are vaporized at the end of the preheat zone. It is assumed that the Zel’dovich number is large; therefore, the reaction term in preheat zone is negligible. In this work, the effect of random distribution of particles in the preheat zone on combustion characteristics such as burning velocity, flame temperature for different particle radius is obtained.

Large-Eddy Simulations of Motored Flow and Combustion in a Homogeneous-Charge Spark-Ignition Engine

Science.gov (United States)

Shekhawat, Yajuvendra Singh

Cycle-to-cycle variations (CCV) of flow and combustion in internal combustion engines (ICE) limit their fuel efficiency and emissions potential. Large-eddy simulation (LES) is the most practical simulation tool to understand the nature of these CCV. In this research, multi-cycle LES of a two-valve, four-stroke, spark-ignition optical engine has been performed for motored and fired operations. The LES mesh quality is assessed using a length scale resolution parameter and a energy resolution parameter. For the motored operation, two 50-consecutive-cycle LES with different turbulence models (Smagorinsky model and dynamic structure model) are compared with the experiment. The pressure comparison shows that the LES is able to capture the wave-dynamics in the intake and exhaust ports. The LES velocity fields are compared with particle-image velocimetry (PIV) measurements at three cutting planes. Based on the structure and magnitude indices, the dynamic structure model is somewhat better than the Smagorinsky model as far as the ensemble-averaged velocity fields are concerned. The CCV in the velocity fields is assessed by proper-orthogonal decomposition (POD). The POD analysis shows that LES is able to capture the level of CCV seen in the experiment. For the fired operation, two 60-cycle LES with different combustion models (thickened frame model and coherent frame model) are compared with experiment. The in-cylinder pressure and the apparent heat release rate comparison shows higher CCV for LES compared to the experiment, with the thickened frame model showing higher CCV than the coherent frame model. The correlation analysis for the LES using thickened frame model shows that the CCV in combustion/pressure is correlated with: the tumble at the intake valve closing, the resolved and subfilter-scale kinetic energy just before spark time, and the second POD mode (shear flow near spark gap) of the velocity fields just before spark time.

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

KAUST Repository

An, Yanzhao

2017-09-23

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

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

KAUST Repository

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

2017-01-01

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

Fuels and Combustion

KAUST Repository

Johansson, Bengt

2016-08-17

This chapter discusses the combustion processes and the link to the fuel properties that are suitable for them. It describes the basic three concepts, including spark ignition (SI) and compression ignition (CI), and homogeneous charge compression ignition (HCCI). The fuel used in a CI engine is vastly different from that in an SI engine. In an SI engine, the fuel should sustain high pressure and temperature without autoignition. Apart from the dominating SI and CI engines, it is also possible to operate with a type of combustion: autoignition. With HCCI, the fuel and air are fully premixed before combustion as in the SI engine, but combustion is started by the increased pressure and temperature during the compression stroke. Apart from the three combustion processes, there are also a few combined or intermediate concepts, such as Spark-Assisted Compression Ignition (SACI). Those concepts are discussed in terms of the requirements of fuel properties.

Fuels and Combustion

KAUST Repository

Johansson, Bengt

2016-01-01

This chapter discusses the combustion processes and the link to the fuel properties that are suitable for them. It describes the basic three concepts, including spark ignition (SI) and compression ignition (CI), and homogeneous charge compression ignition (HCCI). The fuel used in a CI engine is vastly different from that in an SI engine. In an SI engine, the fuel should sustain high pressure and temperature without autoignition. Apart from the dominating SI and CI engines, it is also possible to operate with a type of combustion: autoignition. With HCCI, the fuel and air are fully premixed before combustion as in the SI engine, but combustion is started by the increased pressure and temperature during the compression stroke. Apart from the three combustion processes, there are also a few combined or intermediate concepts, such as Spark-Assisted Compression Ignition (SACI). Those concepts are discussed in terms of the requirements of fuel properties.

Preparation of molybdenum borides by combustion synthesis involving solid-phase displacement reactions

International Nuclear Information System (INIS)

Yeh, C.L.; Hsu, W.S.

2008-01-01

Preparation of molybdenum borides of five different phases in the Mo-B binary system (including Mo 2 B, MoB, MoB 2 , Mo 2 B 5 , and MoB 4 ) was performed by self-propagating high-temperature synthesis (SHS) with two kinds of the reactant samples. When elemental powder compacts with an exact stoichiometry corresponding to the boride phase were employed, self-sustaining reaction was only achieved in the sample with Mo:B = 1:1 and nearly single-phase MoB was yielded. Therefore, the other four boride compounds were prepared from the reactant compacts composed of MoO 3 , Mo, and B powders, within which the displacement reaction of MoO 3 with boron was involved in combustion synthesis. Experimental evidence shows that the extent of displacement reaction in the overall reaction has a significant impact on sustainability of the synthesis reaction, combustion temperature, reaction front velocity, and composition of the end product. An increase in the solid-phase displacement reaction taking place during the SHS process contributes more heat flux to the synthesis reaction, thus resulting in the increase of combustion temperature and enhancement of the reaction front velocity. Based upon the XRD analysis, formation of Mo 2 B, MoB 2 , and Mo 2 B 5 as the dominant boride phase in the end product was successful through the SHS reaction with powder compacts under appropriate stoichiometries between MoO 3 , Mo, and B. However, a poor conversion was observed in the synthesis of MoB 4 . The powder compact prepared for the production of MoB 4 yielded mostly Mo 2 B 5

Combustion Characteristics in a Non-Premixed Cool-Flame Regime of n-Heptane in Microgravity

Science.gov (United States)

Takahashi, Fumiaki; Katta, Viswanath R.; Hicks, Michael C.

2015-01-01

A series of distinct phenomena have recently been observed in single-fuel-droplet combustion tests performed on the International Space Station (ISS). This study attempts to simulate the observed flame behavior numerically using a gaseous n-heptane fuel source in zero gravity and a time-dependent axisymmetric (2D) code, which includes a detailed reaction mechanism (127 species and 1130 reactions), diffusive transport, and a radiation model (for CH4, CO, CO2, H2O, and soot). The calculated combustion characteristics depend strongly on the air velocity around the fuel source. In a near-quiescent air environment (combustion experiments.

Combustion of drops of Mexican fuel oils with high asphaltenes content; Combustion de gotas de combustoleos mexicanos con alto contenido de asfaltenos

Energy Technology Data Exchange (ETDEWEB)

Garcia Rodriguez, Jose Francisco [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1998-09-01

In this work the combustion of fuel drops with a content of 18% of asphaltenes has been studied . The results obtained for this fuel were compared with the ones obtained for another with a content of 12% asphaltenes. The drops were suspended in a platinum filament and burned in an spherical radiant furnace. The drop size varied between 600 and 800 microns. The fuel drops with 12% asphaltenes showed shorter combustion times, a smaller diameter increment of the smaller diameter during the combustion stages and also a shorter burning time of the carbonaceous residue than the fuel drops with a content of 18% asphaltenes. [Espanol] En el presente trabajo se ha estudiado la combustion de gotas de combustible con 18% de contenido de asfaltenos. Los resultados obtenidos para este combustible se compararon con los obtenidos para otro con 12% de contenido de asfaltenos. Las gotas fueron suspendidas en un filamento de platino y quemadas en un horno radiante esferico. El tamano de las gotas vario entre 600 y 800 micras. Las gotas de combustible con 12% de asfaltenos mostraron tiempos de combustion mas cortos, un incremento del diametro menor durante las etapas de combustion y un tiempo de quemado del residuo carbonoso tambien mas corto que las gotas del combustible con 18% de contenido de asfaltenos.

Evaluation of coal combustion byproducts as soil liming materials - their influence on soil pH and enzyme activities

Energy Technology Data Exchange (ETDEWEB)

McCarty, G W; Siddaramappa, R; Wright, R J; Codling, E E; Gao, G

1994-03-01

To evaluate coal combustion byproducts as liming materials and address issues related to soil quality, the authors compared the influence of different amounts of four combustion byproducts (fly ash and bed ash from a fluidized bed combustion furnace, lime-injected multistage burner residue, and spray dryer residue) and CaCO[sub 3] on soil pH and activities of urease, phosphatase, arylsulfatase, and dehydrogenase in an acidic soil. Studies comparing the influence of the combustion byproducts and CaCO[sub 3] on soil pH showed that on weight basis of application, substantial differences were observed in the ability of these materials to influence soil pH but that such differences decreased markedly after the data were transformed to a CaCO[sub 3] equivalent basis of application. Analysis of covariance for these transformed data indicated that whereas the liming abilities of fly ash and CaCO[sub 3] were not significantly different when compared on the CaCO[sub 3] equivalent basis, those of bed ash, multistage burner residue, and spray dryer residue were less than that of CaCO[sub 3]. Studies comparing the influence of the byproducts and CaCO[sub 3] on soil enzyme activities showed that the effect of these liming materials on the enzyme activities studied was largely due to their influence on soil pH. These studies showed that the combustion byproducts tested functioned as soil liming materials in a manner similar to that of CaCO[sub 3] and seemed to have little adverse effect on soil quality.

Jet plume injection and combustion system for internal combustion engines

Science.gov (United States)

Oppenheim, Antoni K.; Maxson, James A.; Hensinger, David M.

1993-01-01

An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.

Development of a Premixed Combustion Capability for Scramjet Combustion Experiments

Science.gov (United States)

Rockwell, Robert D.; Goyne, Christopher P.; Rice, Brian E.; Chelliah, Harsha; McDaniel, James C.; Edwards, Jack R.; Cantu, Luca M. L.; Gallo, Emanuela C. A.; Cutler, Andrew D.; Danehy, Paul M.

2015-01-01

Hypersonic air-breathing engines rely on scramjet combustion processes, which involve high speed, compressible, and highly turbulent flows. The combustion environment and the turbulent flames at the heart of these engines are difficult to simulate and study in the laboratory under well controlled conditions. Typically, wind-tunnel testing is performed that more closely approximates engine testing rather than a careful investigation of the underlying physics that drives the combustion process. The experiments described in this paper, along with companion data sets being developed separately, aim to isolate the chemical kinetic effects from the fuel-air mixing process in a dual-mode scramjet combustion environment. A unique fuel injection approach is taken that produces a nearly uniform fuel-air mixture at the entrance to the combustor. This approach relies on the precombustion shock train upstream of the dual-mode scramjet combustor. A stable ethylene flame anchored on a cavity flameholder with a uniformly mixed combustor inflow has been achieved in these experiments allowing numerous companion studies involving coherent anti-Stokes Raman scattering (CARS), particle image velocimetry (PIV), and planar laser induced fluorescence (PLIF) to be performed.

The efficiency of ceramic-faced metal targets at high-velocity impact

Science.gov (United States)

Tolkachev, V. F.; Konyaev, A. A.; Pakhnutova, N. V.

2017-11-01

The paper represents experimental results and engineering evaluation concerning the efficiency of composite materials to be used as an additional protection during the high- velocity interaction of a tungsten rod with a target in the velocity range of 1...5 km/s. The main parameter that characterizes the high-velocity interaction of a projectile with a layered target is the penetration depth. Experimental data, numerical simulation and engineering evaluation by modified models are used to determine the penetration depth. Boron carbide, aluminum oxide, and aluminum nickelide are applied as a front surface of targets. Based on experimental data and numerical simulation, the main characteristics of ceramics are determined, which allows composite materials to be effectively used as additional elements of protection.

Analysis of Chemical Reaction Kinetics Behavior of Nitrogen Oxide During Air-staged Combustion in Pulverized Boiler

Directory of Open Access Journals (Sweden)

Jun-Xia Zhang

2016-03-01

Full Text Available Because the air-staged combustion technology is one of the key technologies with low investment running costs and high emission reduction efficiency for the pulverized boiler, it is important to reveal the chemical reaction kinetics mechanism for developing various technologies of nitrogen oxide reduction emissions. At the present work, a three-dimensional mesh model of the large-scale four corner tangentially fired boiler furnace is established with the GAMBIT pre-processing of the FLUENT software. The partial turbulent premixed and diffusion flame was simulated for the air-staged combustion processing. Parameters distributions for the air-staged and no the air-staged were obtained, including in-furnace flow field, temperature field and nitrogen oxide concentration field. The results show that the air-staged has more regular velocity field, higher velocity of flue gas, higher turbulence intensity and more uniform temperature of flue gas. In addition, a lower negative pressure zone and lower O2 concentration zone is formed in the main combustion zone, which is conducive to the NO of fuel type reduced to N2, enhanced the effect of NOx reduction. Copyright © 2016 BCREC GROUP. All rights reserved Received: 5th November 2015; Revised: 14th January 2016; Accepted: 16th January 2016  How to Cite: Zhang, J.X., Zhang, J.F. (2016. Analysis of Chemical Reaction Kinetics Behavior of Nitrogen Oxide During Air-staged Combustion in Pulverized Boiler. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 100-108. (doi:10.9767/bcrec.11.1.431.100-108 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.431.100-108

Research into three-component biodiesel fuels combustion process using a single droplet technique

Directory of Open Access Journals (Sweden)

L. Raslavičius

2007-12-01

Full Text Available In order to reduce the engine emission while at same time improving engine efficiency, it is very important to clarify the combustion mechanism. Even if, there are many researches into investigating the mechanism of engine combustion, so that to clarify the relationship between complicated phenomena, it is very difficult to investigate due to the complicated process of both physical and chemical reaction from the start of fuel injection to the end of combustion event. The numerical simulations are based on a detailed vaporization model and detailed chemical kinetics. The influence of different physical parameters like droplet temperature, gas phase temperature, ambient gas pressure and droplet burning velocity on the ignition delay process is investigated using fuel droplet combustion stand. Experimental results about their influence on ignition delay time were presented.

A method for determining the completeness of fuel combustion

Energy Technology Data Exchange (ETDEWEB)

Tavger, M.D.; Chepkin, V.M.; Gruzdev, V.N.; Talantov, A.V.

1982-01-01

The current of conductivity (ionization) of gaseous combustion products, which forms with feeding of electric voltage to a special probe, is proposed for determining the completeness of fuel combustion. Here, the charged particles are formed from substances which form in the intermediate stages of the combustion reaction. The volume of charged particles is proportional to the volume of the intermediate substances, whose presence attests to the incompleteness of the combustion reaction. The fullness of fuel combustion is determined from a formula which includes the stoichiometric coefficient, a gas constant, the energy of activation, the characteristics of the chemical activity of the intermediate substances, the coefficient of air excess, the temperature of the combustion products and the conductivity current.

AUTOMATIC CONTROL SYSTEM FOR REGULATED HIGH TEMPERATURE MAIN COMBUSTION CHAMBER OF MANEUVERABLE AIRCRAFT MULTIMODE GAS TURBINE ENGINE

Directory of Open Access Journals (Sweden)

T. V. Gras’Ko

2014-01-01

Full Text Available The paper describes choosing and substantiating the control laws, forming the appearance the automatic control system for regulated high temperature main combustion chamber of maneuverable aircraft multimode gas turbine engine aimed at sustainable and effective functioning of main combustion chamber within a broad operation range.

Influence of the microwave irradiation dewatering on the combustion characteristics of Chinese brown coals

Science.gov (United States)

Ge, Lichao; Feng, Hongcui; Xu, Chang; Zhang, Yanwei; Wang, Zhihua

2018-02-01

This study investigates the influence of microwave irradiation on coal composition, pore structure, coal rank, and combustion characteristics of typical brown coals in China. Results show that the upgrading process significantly decreased the inherent moisture, and increased calorific value and fixed carbon content. After upgrading, pore distribution extended to micropore region, oxygen functional groups were reduced and destroyed, and the apparent aromaticity increased suggesting an improvement in the coal rank. Based on thermogravimetric analysis, the combustion processes of upgraded coals were delayed toward the high temperature region, and the temperatures of ignition, peak and burnout increased. Based on the average combustion rate and comprehensive combustion parameter, the upgraded coals performed better compared with raw brown coals and a high rank coal. In ignition and burnout segments, the activation energy increased but exhibited a decrease in the combustion stage.

Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net

Science.gov (United States)

Poggi, V.; Burjanek, J.; Michel, C.; Fäh, D.

2017-08-01

The Swiss Seismological Service (SED) has recently finalised the installation of ten new seismological broadband stations in northern Switzerland. The project was led in cooperation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) and Swissnuclear to monitor micro seismicity at potential locations of nuclear-waste repositories. To further improve the quality and usability of the seismic recordings, an extensive characterization of the sites surrounding the installation area was performed following a standardised investigation protocol. State-of-the-art geophysical techniques have been used, including advanced active and passive seismic methods. The results of all analyses converged to the definition of a set of best-representative 1-D velocity profiles for each site, which are the input for the computation of engineering soil proxies (traveltime averaged velocity and quarter-wavelength parameters) and numerical amplification models. Computed site response is then validated through comparison with empirical site amplification, which is currently available for any station connected to the Swiss seismic networks. With the goal of a high-sensitivity network, most of the NAGRA stations have been installed on stiff-soil sites of rather high seismic velocity. Seismic characterization of such sites has always been considered challenging, due to lack of relevant velocity contrast and the large wavelengths required to investigate the frequency range of engineering interest. We describe how ambient vibration techniques can successfully be applied in these particular conditions, providing practical recommendations for best practice in seismic site characterization of high-velocity sites.

A preliminary high-pressure thermogravimetric study of combustion reactivity of a Collie coal char

Energy Technology Data Exchange (ETDEWEB)

Chan, Yii Leng; Zhang, Zhezi; Zhu, Mingming; Zhang, Dongke [Western Australia Univ., Crawley, WA (Australia). Centre for Energy (M473); Luan, Chao [Western Australia Univ., Crawley, WA (Australia). Centre for Energy (M473); Tsinghua Univ., Beijing (China). Inst. of Thermal Engineering; You, Changfu [Tsinghua Univ., Beijing (China). Inst. of Thermal Engineering

2013-07-01

The effect of pressure(up to 20 bar)on the reactivity of a char(150-160 {mu}m) produced from Western Australian Collie coal has been studied using a high-pressure thermogravimetric analyser (HP TGA). The pressure demonstrated a positive effect in enhancing char combustion reactivities.Kinetic parameters have been determined from the experimental data.The apparent reaction order was found to be approximately 0.7 and the apparent activation energies were 91.0 kJ/mol at atmospheric pressure and 1.5 kJ/mol at an elevated pressure(10 bar),indicating a shift in the control regimes of the reaction at elevated pressures.The lumped effect of the sample size, bulk diffusion,interparticle and intraparticle diffusion at the elevated pressures played an important role in reducing the mass transfer during the HP-TGA experimentation.Thus the activation energy calculated at elevated pressures may not represent the intrinsic activation energy of the char particles but the apparent values of the bulk of the samples.

Study of the catalytic activity of ceramic nano fibers in the methane combustion

International Nuclear Information System (INIS)

Reolon, R.P.; Berutti, F.A.; Alves, A.K.; Bergmann, C.P.

2009-01-01

In this work titanium oxide fibers, doped with cerium and copper, were synthesized using the electro spinning process. Titanium propoxide was used as a precursor in the electro spinning synthesis. The obtained fibers were heat treated after receive a spray with an alcoholic solution of cerium acetate and copper nitrate. The non-tissue material obtained was characterized by X-ray diffraction to determine the phase and crystallite size, X-ray photoelectron spectroscopy (XPS), BET method to determine the surface and SEM to analyze the microstructure of the fibers. The catalytic activity was evaluated by methane and air combustion under different temperatures. The amount of combustion gases such as NO x , C x H y , CO e CO 2 , were analyzed. (author)

Temporal evolution of ultrafine particles and of alveolar deposited surface area from main indoor combustion and non-combustion sources in a model room.

Science.gov (United States)

Manigrasso, Maurizio; Vitali, Matteo; Protano, Carmela; Avino, Pasquale

2017-11-15

Aerosol number size distributions, PM mass concentrations, alveolar deposited surface areas (ADSAs) and VOC concentrations were measured in a model room when aerosol was emitted by sources frequently encountered in indoor environments. Both combustion and non-combustion sources were considered. The most intense aerosol emission occurred when combustion sources were active (as high as 4.1×10 7 particlescm -3 for two meat grilling sessions; the first with exhaust ventilation, the second without). An intense spike generation of nucleation particles occurred when appliances equipped with brush electric motors were operating (as high as 10 6 particlescm -3 on switching on an electric drill). Average UFP increments over the background value were highest for electric appliances (5-12%) and lowest for combustion sources (as low as -24% for tobacco cigarette smoke). In contrast, average increments in ADSA were highest for combustion sources (as high as 3.2×10 3 μm 2 cm -3 for meat grilling without exhaust ventilation) and lowest for electric appliances (20-90μm 2 cm -3 ). The health relevance of such particles is associated to their ability to penetrate cellular structures and elicit inflammatory effects mediated through oxidative stress in a way dependent on their surface area. The highest VOC concentrations were measured (PID probe) for cigarette smoke (8ppm) and spray air freshener (10ppm). The highest PM mass concentration (PM 1 ) was measured for citronella candle burning (as high as 7.6mgm -3 ). Copyright © 2017 Elsevier B.V. All rights reserved.

Pressurized Fluidized Bed Combustion of Sewage Sludge

Science.gov (United States)

Suzuki, Yoshizo; Nojima, Tomoyuki; Kakuta, Akihiko; Moritomi, Hiroshi

A conceptual design of an energy recovering system from sewage sludge was proposed. This system consists of a pressurized fluidized bed combustor, a gas turbine, and a heat exchanger for preheating of combustion air. Thermal efficiency was estimated roughly as 10-25%. In order to know the combustion characteristics of the sewage sludge under the elevated pressure condition, combustion tests of the dry and wet sewage sludge were carried out by using laboratory scale pressurized fluidized bed combustors. Combustibility of the sewage sludge was good enough and almost complete combustion was achieved in the combustion of the actual wet sludge. CO emission and NOx emission were marvelously low especially during the combustion of wet sewage sludge regardless of high volatile and nitrogen content of the sewage sludge. However, nitrous oxide (N2O) emission was very high. Hence, almost all nitrogen oxides were emitted as the form of N2O. From these combustion tests, we judged combustion of the sewage sludge with the pressurized fluidized bed combustor is suitable, and the conceptual design of the power generation system is available.

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.

Improved Modeling of Finite-Rate Turbulent Combustion Processes in Research Combustors

Science.gov (United States)

VanOverbeke, Thomas J.

1998-01-01

The objective of this thesis is to further develop and test a stochastic model of turbulent combustion in recirculating flows. There is a requirement to increase the accuracy of multi-dimensional combustion predictions. As turbulence affects reaction rates, this interaction must be more accurately evaluated. In this work a more physically correct way of handling the interaction of turbulence on combustion is further developed and tested. As turbulence involves randomness, stochastic modeling is used. Averaged values such as temperature and species concentration are found by integrating the probability density function (pdf) over the range of the scalar. The model in this work does not assume the pdf type, but solves for the evolution of the pdf using the Monte Carlo solution technique. The model is further developed by including a more robust reaction solver, by using accurate thermodynamics and by more accurate transport elements. The stochastic method is used with Semi-Implicit Method for Pressure-Linked Equations. The SIMPLE method is used to solve for velocity, pressure, turbulent kinetic energy and dissipation. The pdf solver solves for temperature and species concentration. Thus, the method is partially familiar to combustor engineers. The method is compared to benchmark experimental data and baseline calculations. The baseline method was tested on isothermal flows, evaporating sprays and combusting sprays. Pdf and baseline predictions were performed for three diffusion flames and one premixed flame. The pdf method predicted lower combustion rates than the baseline method in agreement with the data, except for the premixed flame. The baseline and stochastic predictions bounded the experimental data for the premixed flame. The use of a continuous mixing model or relax to mean mixing model had little effect on the prediction of average temperature. Two grids were used in a hydrogen diffusion flame simulation. Grid density did not effect the predictions except

Test Plan for Measuring Ventilation Rates and Combustible Gas Levels in TWRS Active Catch Tanks

Energy Technology Data Exchange (ETDEWEB)

NGUYEN, D.M.

1999-10-25

The purpose of this sampling activity is to obtain data to support an initial evaluation of potential hazards due to the presence of combustible gas in catch tanks that are currently operated by the River Protection Project (RPP). Results of the hazard analysis will be used to support closure of the flammable gas unreviewed safety question for these facilities. The data collection will be conducted in accordance with the Tank Safety Screening Data Quality Objective (Dukelow et al. 1995). Combustible gas, ammonia, and organic vapor levels in the headspace of the catch tanks will be field-measured using hand-held instruments. If a combustible gas level measurement in a tank exceeds an established threshold, gas samples will he collected in SUMMA' canisters for more extensive laboratory analysis. In addition, ventilation rates of some catch tanks will be measured to evaluate removal of flammable gas by air flowing through the tanks. This test plan identifies the sample collection, laboratory analysis, quality assurance, and reporting objectives for this data collection effort. The plan also provides the procedures for field measurement of combustible gas concentrations and ventilation rates.

Distances, metallicities and origins of high-velocity clouds

NARCIS (Netherlands)

van Woerden, H; Wakker, BP; Peletier, RF; Schwarz, UJ; KraanKorteweg, RC; Henning, PA; Andernach, H

2000-01-01

A review is given of distances of high-velocity clouds (HVCs) derived from absorption-line measurements, and of the metallicities of HVCs. Chain A definitely lies in the Galactic halo, between 2.5 and 7 kpc above the plane. The distance limits available for other HVCs allow a variety of locations:

Combustion driven NF3 chemical laser

International Nuclear Information System (INIS)

1975-01-01

Stable, inert, non-corrosive nitrogen trifluoride gas and an inorganic source of hydrogen or deuterium gas are used as reactants in a compact combustion driven chemical laser. Nitrogen trifluoride is introduced into the combustion chamber of a chemical laser together with a hydrogen source selected from hydrogen, hydrazine, ammonia, acetylene, or benzene and the deuterated isotopes thereof and an optional inert diluent gas wherein the nitrogen trifluoride and the hydrogen- or deuterium-source gas hypergolically reacted upon heating to initiation temperature. Dissociated products from the reaction pass into a laser cavity at supersonic velocities where they are reacted with a source gas which is the isotopic opposite of the gas introduced into the combustor and which has been heated by regenerative cooling. Excited molecules of hydrogen fluoride or deuterium fluoride produce laser radiation which leaves the optical resonator cavity transversely to the flow of gases

Velocity measurements in a rigid ceramic filter in a parallel-flow arrangement

International Nuclear Information System (INIS)

Al-Hajeri, M.H.; Aroussi, A.; Witry, A.

2002-01-01

Rigid ceramic filters have been developed for cleaning the hot combustion gas streams upstream of the turbine in a combined cycle power plant. To obtain continues operation a periodic cleaning is necessary and the cleaning efficiency depends on the distribution of the filtration cake. Consequently uniform particle deposition on the filter element surface is desired. The flow around three filter elements in cross flow is investigated computationally using the commercial code FLUENT. Three filter elements are placed in a two-dimensional rectangle duct with fixed face velocity and varying the velocity ratio between the approach and face velocity. Particle trajectories are obtained for a number of particle diameters and different inlet (approach) velocity to face filtration velocity ratios to investigate the behavior of particles around the filter element. (author)

Shale oil combustion

International Nuclear Information System (INIS)

Al-dabbas, M.A.

1992-05-01

A 'coutant' carbon steel combustion chamber cooled by water jacket was conslructed to burn diesel fuel and mixlure of shale oil and diesel fuels. During experimental work nir fuel ratio was determined, temperaturces were measured using Chromel/ Almel thermocouple, finally the gasous combustion product analysis was carricd out using gas chromatograph technique. The constructed combustion chamber was operating salisfactory for several hours of continous work. According to the measurements it was found that: the flame temperature of a mixture of diesel and shale oil fuels was greater than the flame temperature of diesel fuel. and the sulfer emissious of a mixture of diesel and shale oil fuels was higher than that of diesel fuel. Calculation indicated that the dry gas energy loss was very high and the incomplete combustion energy loss very small. (author). 23 refs., 35 figs

Shale oil combustion

Energy Technology Data Exchange (ETDEWEB)

Al-dabbas, M A

1992-05-01

A `coutant` carbon steel combustion chamber cooled by water jacket was conslructed to burn diesel fuel and mixlure of shale oil and diesel fuels. During experimental work nir fuel ratio was determined, temperaturces were measured using Chromel/ Almel thermocouple, finally the gasous combustion product analysis was carricd out using gas chromatograph technique. The constructed combustion chamber was operating salisfactory for several hours of continous work. According to the measurements it was found that: the flame temperature of a mixture of diesel and shale oil fuels was greater than the flame temperature of diesel fuel. and the sulfer emissious of a mixture of diesel and shale oil fuels was higher than that of diesel fuel. Calculation indicated that the dry gas energy loss was very high and the incomplete combustion energy loss very small. (author). 23 refs., 35 figs.

New technologies reducing emissions from combustion of biofuels

International Nuclear Information System (INIS)

Oravainen, H.

1997-01-01

In reducing CO 2 emissions, bioenergy will be the most important source of renewable energy in the next few decades. In principle, combustion of biomass is friendly to the environment because CO 2 released during combustion is recycled back into natural circulation. Biofuels normally contain little nitrogen and sulphur. However, depending on the combustion technology used, emissions may be quite high. This is true of combustion of biomass fuels in small appliances like wood stoves, fireplaces, small boilers etc. When fuels having high content of volatile matter are burnt in appliances using batch type combustion, the process is rather an unsteady-state combustion. Emissions of carbon monoxide, other combustible gases and particulates are quite difficult to avoid. With continuous combustion processes this is not normally a problem. This conference paper presents some means of reducing emissions from combustion of biofuels. 5 refs., 4 figs

Mathematical Modeling in Combustion Science

CERN Document Server

Takeno, Tadao

1988-01-01

An important new area of current research in combustion science is reviewed in the contributions to this volume. The complicated phenomena of combustion, such as chemical reactions, heat and mass transfer, and gaseous flows, have so far been studied predominantly by experiment and by phenomenological approaches. But asymptotic analysis and other recent developments are rapidly changing this situation. The contributions in this volume are devoted to mathematical modeling in three areas: high Mach number combustion, complex chemistry and physics, and flame modeling in small scale turbulent flow combustion.

Flow velocity change in the cortical vein during motor activation and its effect on functional brain MRI

Energy Technology Data Exchange (ETDEWEB)

Nakajima, Kazuhiro [Kyoto Prefectural Univ. of Medicine (Japan)

1998-06-01

On the brain functional magnetic resonance imaging (fMRI) using the gradient-recalled echo technique with clinical MR scanner, the activated areas nearly correspond with the cortical veins. This suggests that the fMRI signal mainly originates from the cortical veins. In this study, we analyzed the flow velocity in the cortical vein quantitatively during brain activation and resting status using 2 dimensional time-of-flight cine MR venography (2D-TOF-cine-MRV) and 2 dimensional phase contrast MRV (2D-PC-MRV) techniques, and demonstrated that the flow velocity increased in the cortical vein corresponding to the activated area during activation status. The increase of flow velocity was calculated to be about 20%. The reason for the increased flow velocity is probably due to the increased regional cerebral blood flow and volume in the activated area. We should be careful to analyze the data of the fMRI because the flow velocity affects the fMRI signal such as the inflow effect and the oblique flow effect. When using the gradient echo method, the effect of the flow velocity is one of the important factors of the fMRI signal. (author)

Low temperature combustion of organic coal-water fuel droplets containing petrochemicals while soaring in a combustion chamber model

Directory of Open Access Journals (Sweden)

Valiullin Timur R.

2017-01-01

Full Text Available The paper examines the integral characteristics (minimum temperature, ignition delay times of stable combustion initiation of organic coal-water fuel droplets (initial radius is 0.3-1.5 mm in the oxidizer flow (the temperature and velocity varied in ranges 500-900 K, 0.5-3 m/s. The main components of organic coal-water fuel were: brown coal particles, filter-cakes obtained in coal processing, waste engine, and turbine oils. The different modes of soaring and ignition of organic coal-water fuel have been established. The conditions have been set under which it is possible to implement the sustainable soaring and ignition of organic coal-water fuel droplets. We have compared the ignition characteristics with those defined in the traditional approach (based on placing the droplets on a low-inertia thermocouple junction into the combustion chamber. The paper shows the scale of the influence of heat sink over the thermocouple junction on ignition inertia. An original technique for releasing organic coal-water fuel droplets to the combustion chamber was proposed and tested. The limitations of this technique and the prospects of experimental results for the optimization of energy equipment operation were also formulated.

Mechanical and chemical responses of low-velocity impacted RDX and HMX explosive powders

Science.gov (United States)

Wu, Yanqing; Guo, Hongfu; Huang, Fenglei; Bao, Xiaowei; Explosion; damage Team

2017-06-01

The experimental analyses of mechanical and chemical responses of RDX and HMX particles were performed based on the optimized drop-weight experimental system equipped with the High-Speed Camera (HSC). It has been found that Jetting phenomenon observed by HSC is the result of the energy released by gaseous products, which push the pulverized or melted explosives to splash radially. Jetting is the only and the most obvious difference between reactive and inert particles prior to combustion so that jetting can be regarded as the sign of ignition. Area expansion velocity, jetting velocity, and flame propagation velocity have been estimated via image processing, making it possible to characterize mechanical deformation and violence of reaction of each stage. Hot-spots coalescence promotes flame propagation whose velocity reflects the violence of deflagration reaction. Jetting appearance time can be used to determine time-to-ignition more accurately than other ways. For RDX, molten phase plays an important role to the formation of the hot-spots. Multiple particles experienced more severe burning reactions than an individual particle. China National Nature Science Foundation (11572045), ``Science Challenging Program'' (JCKY2016212A501),opening fund from Safety ammunition research and Development Center (RMC2015B03).

Numerical simulation of a high velocity impact on fiber reinforced materials

International Nuclear Information System (INIS)

Thoma, Klaus; Vinckier, David

1994-01-01

Whereas the calculation of a high velocity impact on isotropical materials can be done on a routine basis, the simulation of the impact and penetration process into nonisotropical materials such as reinforced concrete or fiber reinforced materials still is a research task.We present the calculation of an impact of a metallic fragment on a modern protective wall structure. Such lightweight protective walls typically consist of two layers, a first outer layer made out of a material with high hardness and a backing layer. The materials for the backing layer are preferably fiber reinforced materials. Such types of walls offer a protection against fragments in a wide velocity range.For our calculations we used a non-linear finite element Lagrange code with explicit time integration. To be able to simulate the high velocity penetration process with a continuous erosion of the impacting metallic fragment, we used our newly developed contact algorithm with eroding surfaces. This contact algorithm is vectorized to a high degree and especially robust as it was developed to work for a wide range of contact-impact problems. To model the behavior of the fiber reinforced material under the highly dynamic loads, we present a material model which initially was developed to calculate the crash behavior (automotive applications) of modern high strength fiber-matrix systems. The model can describe the failure and the postfailure behavior up to complete material crushing.A detailed simulation shows the impact of a metallic fragment with a velocity of 750ms -1 on a protective wall with two layers, the deformation and erosion of fragment and wall material and the failure of the fiber reinforced material. ((orig.))

Control issues in oxy-fuel combustion

Energy Technology Data Exchange (ETDEWEB)

Snarheim, Dagfinn

2009-08-15

Combustion of fossil fuels is the major energy source in todays society. While the use of fossil fuels is a necessity for our society to function, there has been an increasing concern on the emissions of CO{sub 2} resulting from human activities. Emissions of CO{sub 2} are considered to be the main cause for the global warming and climate changes we have experienced in recent years. To fight the climate changes, the emissions of CO{sub 2} must be reduced in a timely fashion. Strategies to achieve this include switching to less carbon intensive fuels, renewable energy sources, nuclear energy and combustion with CO{sub 2} capture. The use of oxy-fuel combustion is among the alternative post- and pre combustion capture concepts, a strategy to achieve power production from fossil fuels with CO{sub 2} capture. In an oxy-fuel process, the fuel is burned in a mixture of oxygen and CO{sub 2} (or steam), leaving the exhaust consisting mainly of CO{sub 2} and steam. The steam can be removed by use of a condenser, leaving (almost) pure CO{sub 2} ready to be captured. The downside to CO{sub 2} capture is that it is expensive, both in capital cost of extra equipment, and in operation as it costs energy to capture the CO{sub 2}. Thus it is important to maximize the efficiency in such plants. One attractive concept to achieve CO{sub 2} capture by use of oxy-fuel, is a semi-closed oxy-fuel gas turbine cycle. The dynamics of such a plant are highly integrated, involving energy and mass recycle, and optimizing efficiency might lead to operational (control) challenges. In these thesis we investigate how such a power cycle should be controlled. By looking at control at such an early stage in the design phase, it is possible to find control solutions otherwise not feasible, that leads to better overall performance. Optimization is used on a nonlinear model based on first principles, to compare different control structures. Then, closed loop simulations using MPC, are used to validate

Experimental study of biogas combustion using a gas turbine configuration

Energy Technology Data Exchange (ETDEWEB)

Lafay, Y.; Taupin, B.; Martins, G.; Cabot, G.; Renou, B.; Boukhalfa, A. [CNRS UMR 6614, Universite et INSA de ROUEN, Site universitaire du Madrillet, Saint Etienne du Rouvray (France)

2007-08-15

The aim of the present work is to compare stability combustion domains, flame structures and dynamics between CH{sub 4}/air flames and a biogas/air flames (issued from waste methanisation) in a lean gas turbine premixed combustion conditions. Velocity profiles are obtained by Laser Doppler Anemometry measurements. CH* chemiluminescence measurements and temporal acquisition of chamber pressure are performed in order to describe flame structure and instabilities. Changes in flame structure and dynamics when fuel composition is varying are found to strongly depend on laminar flame speed. No clear correlation between the unstable flame and the reaction zone penetration in the corner recirculation can be found. (orig.)

Large-eddy simulation of ethanol spray combustion using a finite-rate combustion model

Energy Technology Data Exchange (ETDEWEB)

Li, K.; Zhou, L.X. [Tsinghua Univ., Beijing (China). Dept. of Engineering Mechanics; Chan, C.K. [Hong Kong Polytechnic Univ. (China). Dept. of Applied Mathematics

2013-07-01

Large-eddy simulation of spray combustion is under its rapid development, but the combustion models are less validated by detailed experimental data. In this paper, large-eddy simulation of ethanol-air spray combustion was made using an Eulerian-Lagrangian approach, a subgrid-scale kinetic energy stress model, and a finite-rate combustion model. The simulation results are validated in detail by experiments. The LES obtained statistically averaged temperature is in agreement with the experimental results in most regions. The instantaneous LES results show the coherent structures of the shear region near the high-temperature flame zone and the fuel vapor concentration map, indicating the droplets are concentrated in this shear region. The droplet sizes are found to be in the range of 20-100{mu}m. The instantaneous temperature map shows the close interaction between the coherent structures and the combustion reaction.

Numerical simulation code for combustion of sodium liquid droplet and its verification

International Nuclear Information System (INIS)

Okano, Yasushi

1997-11-01

The computer programs for sodium leak and burning phenomena had been developed based on mechanistic approach. Direct numerical simulation code for sodium liquid droplet burning had been developed for numerical analysis of droplet combustion in forced convection air flow. Distributions of heat generation and temperature and reaction rate of chemical productions, such as sodium oxide and hydroxide, are calculated and evaluated with using this numerical code. Extended MAC method coupled with a higher-order upwind scheme had been used for combustion simulation of methane-air mixture. In the numerical simulation code for combustion of sodium liquid droplet, chemical reaction model of sodium was connected with the extended MAC method. Combustion of single sodium liquid droplet was simulated in this report for the verification of developed numerical simulation code. The changes of burning rate and reaction product with droplet diameter and inlet wind velocity were investigated. These calculation results were qualitatively and quantitatively conformed to the experimental and calculation observations in combustion engineering. It was confirmed that the numerical simulation code was available for the calculation of sodium liquid droplet burning. (author)

An Assessment of Combustion Dynamics in a Low-Nox, Second-Generation Swirl-Venturi Lean Direct Injection Combustion Concept

Science.gov (United States)

Tacina, K. M.; Chang, C. T.; Lee, P.; Mongia, H.; Podboy, D. P.; Dam, B.

2015-01-01

Dynamic pressure measurements were taken during flame-tube emissions testing of three second-generation swirl-venturi lean direct injection (SV-LDI) combustor configurations. These measurements show that combustion dynamics were typically small. However, a small number of points showed high combustion dynamics, with peak-to-peak dynamic pressure fluctuations above 0.5 psi. High combustion dynamics occurred at low inlet temperatures in all three SV-LDI configurations, so combustion dynamics were explored further at low temperature conditions. A point with greater than 1.5 psi peak-to-peak dynamic pressure fluctuations was identified at an inlet temperature of 450!F, a pressure of 100 psia, an air pressure drop of 3%, and an overall equivalence ratio of 0.35. This is an off design condition: the temperature and pressure are typical of 7% power conditions, but the equivalence ratio is high. At this condition, the combustion dynamics depended strongly on the fuel staging. Combustion dynamics could be reduced significantly without changing the overall equivalence ratio by shifting the fuel distribution between stages. Shifting the fuel distribution also decreased NOx emissions.

Numerical investigation of spray combustion towards HITAC conditions

NARCIS (Netherlands)

Zhu, Shanglong

2017-01-01

The features of High Temperature Air Combustion (HiTAC), i.e. high-efficiency combustion processes creating a uniform temperature distribution with low NOX and CO emissions, lend itself ideally for the combustion of all sorts of "difficult” fuels, ranging from low-calorific gases such as

Pressure evolution of the high-frequency sound velocity in liquid water

International Nuclear Information System (INIS)

Krisch, M.; Sette, F.; D'Astuto, M.; Lorenzen, M.; Mermet, A.; Monaco, G.; Verbeni, R.; Loubeyre, P.; Le Toullec, R.; Ruocco, G.; Cunsolo, A.

2002-01-01

The high-frequency sound velocity v ∞ of liquid water has been determined to densities of 1.37 g/cm 3 by inelastic x-ray scattering. In comparison to the hydrodynamic sound velocity v 0 , the increase of v ∞ with density is substantially less pronounced, indicating that, at high density, the hydrogen-bond network is decreasingly relevant to the physical properties of liquid water. Furthermore, we observe an anomaly in v ∞ at densities around 1.12 g/cm 3 , contrasting the smooth density evolution of v 0

Moessbauer spectroscopy with a high velocity resolution: advances in biomedical, pharmaceutical, cosmochemical and nano technological research

International Nuclear Information System (INIS)

Oshtrakha, M.I.; Semionkina, V.A.

2011-01-01

Full text: Velocity resolution is a term denoted the smallest velocity step (2V/2 n ) in velocity driving system of Moessbauer spectrometer and velocity step for the one point in Moessbauer spectrum. Velocity resolution coefficient 1/2 n in velocity driving system is constant and velocity resolution value depends on velocity range (2V) only while velocity resolution in Moessbauer spectrum may be the same or less. Moessbauer spectroscopy with a high velocity resolution is a new method to measure precision high quality spectra. It is well known that one of the main parts of Moessbauer spectrometer is velocity driving system. Usual spectrometers are used sinusoidal or triangular velocity reference signal and 256 or 512 channels to form velocity signal. Such velocity driving system provides spectra measurement with a low velocity resolution (2 n =256 or 512 channels) with possibility to decrease measurement time and reach needed signal/noise ratio by spectra folding on the direct and reverse motion. However, these driving systems do not provide a low systematic error for velocity signal while folding increases integral velocity error due to different velocity errors on the direct and reverse motions. These problems can be neglected if a high precision is not required for spectra measurement. Nevertheless, further development of Moessbauer spectroscopy may be related to increase in precision and quality of spectra measurement with less instrumental (systematic) velocity error and to increase in velocity resolution for both spectrometer and spectrum. A new velocity driving system was developed for Moessbauer spectrometer SM- 2201. This system uses saw-tooth shape velocity reference signal and 2 n =4096 channels to form velocity signal. On the basis of SM-2201 and liquid nitrogen cryostat with moving absorber and temperature variation in the range of 295-85 K a new automated precision Moessbauer spectrometric system with a high velocity resolution was created

Reducing emissions from diesel combustion

International Nuclear Information System (INIS)

Anon.

1992-01-01

This paper contains information dealing with engine design to reduce emissions and improve or maintain fuel economy. Topics include: Observation of High Pressure Fuel Spray with Laser Light Sheet Method; Determination of Engine Cylinder Pressures from Crankshaft Speed Fluctuations; Combustion Similarity for Different Size Diesel Engines: Theoretical Prediction and Experimental Results; Prediction of Diesel Engine Particulate Emission During Transient Cycles; Characteristics and Combustibility of Particulate Matter; Dual-Fuel Diesel Engine Using Butane; Measurement of Flame Temperature Distribution in D.I. Diesel Engine with High Pressure Fuel Injection: and Combustion in a Small DI Diesel Engine at Starting

Large-eddy simulations of turbulent flows in internal combustion engines

Science.gov (United States)

Banaeizadeh, Araz

The two-phase compressible scalar filtered mass density function (FMDF) model is further developed and employed for large-eddy simulations (LES) of turbulent spray combustion in internal combustion (IC) engines. In this model, the filtered compressible Navier-Stokes equations are solved in a generalized curvilinear coordinate system with high-order, multi-block, compact differencing schemes for the turbulent velocity and pressure. However, turbulent mixing and combustion are computed with a new two-phase compressible scalar FMDF model. The spray and droplet dispersion/evaporation are modeled with a Lagrangian method. A new Lagrangian-Eulerian-Lagrangian computational method is employed for solving the flow, spray and scalar equation. The pressure effect in the energy equation, as needed in compressible flows, is included in the FMDF formulation. The performance of the new compressible LES/FMDF model is assessed by simulating the flow field and scalar mixing in a rapid compression machine (RCM), in a shock tube and in a supersonic co-axial jet. Consistency of temperatures predicted by the Eulerian finite-difference (FD) and Lagrangian Monte Carlo (MC) parts of the LES/FMDF model are established by including the pressure on the FMDF. It is shown that the LES/FMDF model is able to correctly capture the scalar mixing in both compressible subsonic and supersonic flows. Using the new two-phase LES/FMDF model, fluid dynamics, heat transfer, spray and combustion in the RCM with flat and crevice piston are studied. It is shown that the temperature distribution in the RCM with crevice piston is more uniform than the RCM with flat piston. The fuel spray characteristics and the spray parameters affecting the fuel mixing inside the RCM in reacting and non-reacting flows are also studied. The predicted liquid penetration and flame lift-off lengths for respectively non-reacting and reacting sprays are found to compare well with the available experimental data. Temperatures and

Sandia Combustion Research Program

Energy Technology Data Exchange (ETDEWEB)

Johnston, S.C.; Palmer, R.E.; Montana, C.A. (eds.)

1988-01-01

During the late 1970s, in response to a national energy crisis, Sandia proposed to the US Department of Energy (DOE) a new, ambitious program in combustion research. Shortly thereafter, the Combustion Research Facility (CRF) was established at Sandia's Livermore location. Designated a ''user facility,'' the charter of the CRF was to develop and maintain special-purpose resources to support a nationwide initiative-involving US inventories, industry, and national laboratories--to improve our understanding and control of combustion. This report includes descriptions several research projects which have been simulated by working groups and involve the on-site participation of industry scientists. DOE's Industry Technology Fellowship program, supported through the Office of Energy Research, has been instrumental in the success of some of these joint efforts. The remainder of this report presents results of calendar year 1988, separated thematically into eleven categories. Referred journal articles appearing in print during 1988 and selected other publications are included at the end of Section 11. Our traditional'' research activities--combustion chemistry, reacting flows, diagnostics, engine and coal combustion--have been supplemented by a new effort aimed at understanding combustion-related issues in the management of toxic and hazardous materials.

A basic experimental study on combustion of suspended sodium droplet. 2

International Nuclear Information System (INIS)

Sato, Kenji

1999-10-01

For appropriate understanding and/or prediction of the combustion behavior of sodium, working as liquid coolant in fast breeder reactors, in case of leakage accident, phenomenological analyses of the behavior must be also important along with conventional engineering approach. Following our previous study in the last year, the major objective of this experimental research is to elucidate the effects of the initial temperature and diameter of droplet, and of the air flow velocity on ignition process of a sodium droplet, by exposing a suspended droplet to the air flow at room-temperature. In the experiments, a high-temperature droplet suspended from the end of a fine stainless steel nozzle of the liquid sodium supply system was exposed to an upward air flow, and the ignition and succeeding combustion phenomena were observed by using high-speed color video recording system. In the preliminary study, the effects of lighting and image data processing on obtaining pictures suitable to analyses were investigated with the apparatus used in the previous study. After the experimental apparatus was modified partially in order to expose the unreacted droplet to the air flow more quickly, main experiments were performed in synthetic dry air or oxygen-nitrogen mixture of 21% oxygen. Good quality pictures of the phenomena achieved under good conditions were recorded even for a few cases. The details of the ignition process of a sodium droplet, including the aspects of the surface and light emission, were examined, and the effects of the air flow velocity were discussed. Since number of performed experimental runs was small, the effects of the initial droplet temperature were not examined. (author)

Computational fluid dynamics (CFD) analysis of an industrial gas turbine combustion chamber

Energy Technology Data Exchange (ETDEWEB)

Anzai, Thiago Koichi; Fontes, Carlo Eduardo; Ropelato, Karolline [Engineering Simulation and Scientic Software Ltda. (ESSS), Rio de Janeiro, RJ (Brazil)], E-mails: anzai, carlos.fontes, ropelato@esss.com.br; Silva, Luis Fernando Figueira da; Huapaya, Luis Enrique Alva [Pontificia Universidade Catolica do Rio de Janeiro (PUC-Rio), RJ (Brazil). Dept. of Mechanical Engineering], E-mail: luisfer.luisalva@esp.puc-rio.br

2010-07-01

The accurate determination of pollutant emission from gas turbine combustors is a crucial problem in situations when such equipment is subject to long periods of operation away from the design point. In such operating conditions, the flow field structure may also drastically differ from the design point one, leading to the presence of undesirable hot spots or combustion instabilities, for instance. A priori experiments on all possible operation conditions is economically unfeasible, therefore, models that allow for the prediction of combustion behavior in the full operation range could be used to instruct power plant operators on the best strategies to be adopted. Since the direct numerical simulation of industrial combustors is beyond reach of the foreseeable computational resources, simplified models should be used for such purpose. This works presents the results of the application to an industrial gas turbine combustion chamber of the CFD technique to the prediction of the reactive flow field. This is the first step on the coupling of reactive CFD results with detailed chemical kinetics modeling using chemical reactor networks, toward the goal of accurately predicting pollutant emissions. The CFD model considers the detailed geometrical information of such a combustion chamber and uses actual operating conditions, calibrated via an overall gas turbine thermodynamical simulation, as boundary conditions. This model retains the basic information on combustion staging, which occurs both in diffusion and lean premixed modes. The turbulence has been modeled using the SST-CC model, which is characterized by a well established regime of accurate predictive capability. Combustion and turbulence interaction is accounted for by using the Zimont et al. model, which makes use of on empirical expression for the turbulent combustion velocity for the closure of the progress variable transport equation. A high resolution scheme is used to solve the advection terms of the

Peach and apricot stone combustion in a bubbling fluidized bed

Energy Technology Data Exchange (ETDEWEB)

Kaynak, B.; Atimtay, Aysel T. [Department of Environmental Engineering, Middle East Technical University, Ankara 06531 (Turkey); Topal, H. [Department of Mechanical Engineering, Engineering and Architecture Faculty, Gazi University, Ankara 06570 (Turkey)

2005-07-25

In this study, a bubbling fluidized bed combustor (BFBC) of 102 mm inside diameter and 900 mm height was used to investigate the combustion characteristics of peach and apricot stones produced as a waste from the fruit juice industry. A lignite coal was also burned in the same combustor. The combustion characteristics of the wastes were compared with that of a lignite coal that is most widely used in Turkey. On-line concentrations of O{sub 2}, CO, CO{sub 2}, SO{sub 2}, NO{sub X} and total hydrocarbons (C{sub m}H{sub n}) were measured in the flue gas during combustion experiments. By changing the operating parameters (excess air ratio, fluidization velocity, and fuel feed rate), the variation of emissions of various pollutants was studied. Temperature distribution along the bed was measured with thermocouples. During the combustion tests, it was observed that the volatile matter from peach and apricot stones quickly volatilizes and mostly burn in the freeboard. The temperature profiles along the bed and the freeboard also confirmed this phenomenon. It was found that as the volatile matter of fruit stones increases, the combustion takes place more in the freeboard region. The results of this study have shown that the combustion efficiencies ranged between 98.8% and 99.1% for coal, 96.0% and 97.5% for peach stone and 93.4% and 96.3% for apricot stones. The coal has zero CO emission, but biomass fuels have very high CO emission which indicates that a secondary air addition is required for the system. SO{sub 2} emission of the coal is around 2400-2800 mg/Nm{sup 3}, whereas the biomass fuels have zero SO{sub 2} emission. NO{sub x} emissions are all below the limits set by the Turkish Air Quality Control Regulation of 1986 (TAQCR) for all tests. As the results of combustion of two biomass fuels are compared with each other, peach stones gave lower CO and NO{sub x} emissions but the SO{sub 2} emissions are a little higher than for apricot stones. These results suggest that

Carbon Shale Combustion in the Fluidized Bed Reactor

Directory of Open Access Journals (Sweden)

Olek Małgorzata

2014-06-01

Full Text Available The purpose of this article is to present the possibilities of coal shale combustion in furnaces with bubbling fluidized bed. Coal shale can be autothermally combusted in the fluidized bed, despite the low calorie value and high ash content of fuel. Established concentrations of CO (500 ppm and VOC (30 mg/m3 have indicated a high conversion degree of combustible material during combustion process. Average concentrations of SO2 and NOx in the flue gas were higher than this received from the combustion of high quality hard coal, 600 ppm and 500 ppm, respectively. Optional reduction of SO2 and NOx emission may require the installation of flue gas desulphurization and de-NOx systems.

Atomic beam formed by the vaporization of a high velocity pellet

International Nuclear Information System (INIS)

Foster, C.A.; Hendricks, C.D.

1974-01-01

A description of an atomic beam formed by vaporizing an electrostatically accelerated high velocity pellet is given. Uniformly sized droplets of neon will be formed by the mechanical disintegration of liquid jet and frozen by adiabatic vaporization in vacuum. The pellets produced will be charged and accelerated by contacting a needle held at high potential. The accelerated pellets will be vaporized forming a pulse of mono-energetic atoms. The advantages are that a wide range of energies will be possible. The beam will be mono-energetic. The beam is inheretly pulsed, allowing a detailed time of flight velocity distribution measurement. The beam will have a high instantaneous intensity. The beam will be able to operate into an ultra high vacuum chamber

Three-dimensional time-lapse velocity tomography of an underground longwall panel

Energy Technology Data Exchange (ETDEWEB)

Luxbacher, K.; Westman, E.; Swanson, P.; Karfakis, M. [Virginia Tech., Blacksburg, VA (United States). Dept. of Mining & Minerals Engineering

2008-06-15

Three-dimensional velocity tomograms were generated to image the stress redistribution around an underground coal longwall panel to produce a better understanding of the mechanisms that lead to ground failure, especially rockbursts. Mining-induced microseismic events provided passive sources for the three-dimensional velocity tomography. Surface-mounted geophones monitored microseismic activity for 18 days. Eighteen tomograms were generated and high-velocity regions correlated with high abutment stresses predicted by numerical modeling. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated, indicating that velocity tomography may be an appropriate technology for monitoring stress redistribution in underground mines.

Combustion

CERN Document Server

Glassman, Irvin

1997-01-01

This Third Edition of Glassman's classic text clearly defines the role of chemistry, physics, and fluid mechanics as applied to the complex topic of combustion. Glassman's insightful introductory text emphasizes underlying physical and chemical principles, and encompasses engine technology, fire safety, materials synthesis, detonation phenomena, hydrocarbon fuel oxidation mechanisms, and environmental considerations. Combustion has been rewritten to integrate the text, figures, and appendixes, detailing available combustion codes, making it not only an excellent introductory text but also an important reference source for professionals in the field. Key Features * Explains complex combustion phenomena with physical insight rather than extensive mathematics * Clarifies postulates in the text using extensive computational results in figures * Lists modern combustion programs indicating usage and availability * Relates combustion concepts to practical applications.

Combustion from basics to applications

CERN Document Server

Lackner, Maximilian; Winter, Franz

2013-01-01

Combustion, the process of burning, is defined as a chemical reaction between a combustible reactant (the fuel) and an oxidizing agent (such as air) in order to produce heat and in most cases light while new chemical species (e.g., flue gas components) are formed. This book covers a gap on the market by providing a concise introduction to combustion. Most of the other books currently available are targeted towards the experienced users and contain too many details and/or contain knowledge at a fairly high level. This book provides a brief and clear overview of the combustion basics, suitable f

Combustion synthesized hierarchically porous WO{sub 3} for selective acetone sensing

Energy Technology Data Exchange (ETDEWEB)

Dong, Chengjun; Liu, Xu; Guan, Hongtao; Chen, Gang; Xiao, Xuechun [Department of Materials Science and Engineering, Yunnan University, 650091, Kunming (China); Djerdj, Igor [Ruđer Bošković Institute, Bijenička 54, 10000, Zagreb (Croatia); Wang, Yude, E-mail: ydwang@ynu.edu.cn [Department of Materials Science and Engineering, Yunnan University, 650091, Kunming (China); Yunnan Province Key Lab of Mico-Nano Materials and Technology, Yunnan University, 650091, Kunming (China)

2016-12-01

An easy, inexpensive combustion route was designed to synthesize hierarchically porous WO{sub 3}. The tungsten source was fresh peroxiotungstic acid by dissolving tungsten powder into hydrogen peroxide. To promote the combustion reaction, a combined fuel of both glycine and hydrazine hydrate was used. The microstructure was well-connected pores comprised of subunit nanoparticles. Upon exposing towards acetone gas, the porous WO{sub 3} based sensor exhibits high gas response, rapid response and recovery, and good selectivity in the range of 5–1000 ppm under working temperature of 300 °C. This excellent sensing performance was plausibly attributed to the porous morphology, which hence provides more active sites for the gas molecules' reaction. - Graphical abstract: Hierarchically porous WO{sub 3} synthesized by combustion process exhibits high gas response, rapid response and recovery, and excellent selectivity for acetone, making it to be promising candidates for practical detectors for acetone. - Highlights: • Hierarchically porous WO{sub 3} synthesized by combustion process. • Hierarchically porous WO{sub 3} exhibits high gas response and excellent selectivity for acetone. • The excellent sensing property was plausibly attributed to the porous morphology.

Carbon Dioxide Dispersion in the Combustion Integrated Rack Simulated Numerically

Science.gov (United States)

Wu, Ming-Shin; Ruff, Gary A.

2004-01-01

When discharged into an International Space Station (ISS) payload rack, a carbon dioxide (CO2) portable fire extinguisher (PFE) must extinguish a fire by decreasing the oxygen in the rack by 50 percent within 60 sec. The length of time needed for this oxygen reduction throughout the rack and the length of time that the CO2 concentration remains high enough to prevent the fire from reigniting is important when determining the effectiveness of the response and postfire procedures. Furthermore, in the absence of gravity, the local flow velocity can make the difference between a fire that spreads rapidly and one that self-extinguishes after ignition. A numerical simulation of the discharge of CO2 from PFE into the Combustion Integrated Rack (CIR) in microgravity was performed to obtain the local velocity and CO2 concentration. The complicated flow field around the PFE nozzle exits was modeled by sources of equivalent mass and momentum flux at a location downstream of the nozzle. The time for the concentration of CO2 to reach a level that would extinguish a fire anywhere in the rack was determined using the Fire Dynamics Simulator (FDS), a computational fluid dynamics code developed by the National Institute of Standards and Technology specifically to evaluate the development of a fire and smoke transport. The simulation shows that CO2, as well as any smoke and combustion gases produced by a fire, would be discharged into the ISS cabin through the resource utility panel at the bottom of the rack. These simulations will be validated by comparing the results with velocity and CO2 concentration measurements obtained during the fire suppression system verification tests conducted on the CIR in March 2003. Once these numerical simulations are validated, portions of the ISS labs and living areas will be modeled to determine the local flow conditions before, during, and after a fire event. These simulations can yield specific information about how long it takes for smoke and

N-Acetyl-2-Aminofluorene (AAF) Processing in Adult Rat Hepatocytes in Primary Culture Occurs by High-Affinity Low-Velocity and Low-Affinity High-Velocity AAF Metabolite-Forming Systems.

Science.gov (United States)

Koch, Katherine S; Moran, Tom; Shier, W Thomas; Leffert, Hyam L

2018-05-01

N-acetyl-2-aminofluorene (AAF) is a procarcinogen used widely in physiological investigations of chemical hepatocarcinogenesis. Its metabolic pathways have been described extensively, yet little is known about its biochemical processing, growth cycle expression, and pharmacological properties inside living hepatocytes-the principal cellular targets of this hepatocarcinogen. In this report, primary monolayer adult rat hepatocyte cultures and high specific-activity [ring G-3 H]-N-acetyl-2-aminofluorene were used to extend previous observations of metabolic activation of AAF by highly differentiated, proliferation-competent hepatocytes in long-term cultures. AAF metabolism proceeded by zero-order kinetics. Hepatocytes processed significant amounts of procarcinogen (≈12 μg AAF/106 cells/day). Five ring-hydroxylated and one deacetylated species of AAF were secreted into the culture media. Extracellular metabolite levels varied during the growth cycle (days 0-13), but their rank quantitative order was time invariant: 5-OH-AAF > 7-OH-AAF > 3-OH-AAF > N-OH-AAF > aminofluorene (AF) > 1-OH-AAF. Lineweaver-Burk analyses revealed two principal classes of metabolism: System I (high-affinity and low-velocity), Km[APPARENT] = 1.64 × 10-7  M and VMAX[APPARENT] = 0.1 nmol/106 cells/day and System II (low-affinity and high-velocity), Km[APPARENT] = 3.25 × 10-5  M and VMAX[APPARENT] = 1000 nmol/106 cells/day. A third system of metabolism of AAF to AF, with Km[APPARENT] and VMAX[APPARENT] constants of 9.6 × 10-5  M and 4.7 nmol/106 cells/day, was also observed. Evidence provided in this report and its companion paper suggests selective roles and intracellular locations for System I- and System II-mediated AAF metabolite formation during hepatocarcinogenesis, although some of the molecules and mechanisms responsible for multi-system processing remain to be fully defined.

High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

Science.gov (United States)

Bhat, Biliyar N.; Ellis, David; Singh, Jogender

2014-01-01

Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion

Combustion of Solid Fuel in a Vortex Furnace with Counter-swirling Flows

Directory of Open Access Journals (Sweden)

Redko A.A.

2017-12-01

Full Text Available The results of computer simulation of the processes of incineration of low-grade solid fuel-pulverized peat with a moisture content of 40%, an ash content of 6% are given. It has been determined the fields of distribution of temperature, velocity of gases and particles in the volume and at the outlet from the furnace. The three-dimensional temperature distribution in the combustion chamber indicates high-temperature combustion of peat particles at temperatures above 1700°C with liquid ash removal in the lower part of the furnace. It has been determined that when the furnace is cooled, it is not ensured combustion of the fuel completely. The value of the swirling flow rate at the outlet from the furnace (up to 370 m/s ensures the efficiency of separation of fuel particles, reducing heat losses from mechanical underburning. It is determined that the concentration of oxygen is close to zero over the entire height of the furnace, at an outlet from the furnace the oxygen concentration is 5...6%, since oxygen is supplied with excess (αв=1,2. The results of a numerical study showed that the diameter of peat particles affects the process of their combustion: coke particles with an initial diameter of 25 mkm to 250 mkm burn out by 96%. With an increase in particle diameter up to 1000 mkm, the degree of burn-out of coke decreases, but at the same time their removal decreases. It is shown that the furnace ensures the completeness of combustion of peat particles of peat 99.8%, volatiles is 100%.

Zero-velocity solitons in high-index photonic crystal fibers

DEFF Research Database (Denmark)

Lægsgaard, Jesper

2011-01-01

Nonlinear propagation in slow-light states of high-index photonic crystal fibers (PCFs) is studied numerically. To avoid divergencies in dispersion and nonlinear parameters around the zero-velocity mode, a time-propagating generalized nonlinear Schrödinger equation is formulated. Calculated slow-...

Burning velocity of the heterogeneous flame propagation in the SHS process expressed in explicit form

International Nuclear Information System (INIS)

Makino, A.; Law, C.K.

1995-01-01

The combustion behavior of the self-propagating high-temperature synthesis (SHS) process has been the subject of many analytical and experimental investigations. Recently, a theory based on spray combustion was proposed for the SHS flame structure and propagation. In contrast to previous studies based on the homogeneous premixed flame, this theory accounts for the premixed-mode of propagation of the bulk flame and the non-premixed reaction of the dispersed nonmetal (or higher melting-point metal) particles which supports the bulk flame. Finite-rate reaction at the particle surface and the temperature-dependent, Arrhenius nature of mass diffusion are both incorporated. The heterogeneous nature of the theory has satisfactorily captured the effects of particle size on the flame propagation speed. The final solution of Makino and Law was obtained numerically and hence presented parametrically. The authors have since then derived an approximate analytical expression for the burning velocity, which explicitly displays the functional dependence of the burning velocity on the various system parameters. This result is presented herein. Applicability of this expression is examined by comparing it with the numerical results for Ti-C, Ti-B, Zr-B, Hf-B, and Co-Ti systems. A fair degree of agreement has been shown as far as the general trend and approximate magnitude are concerned

Development of reduced kinetic schemes for the description of pollutants formation in combustion; Mise au point de schemas cinetiques reduits pour decrire la formation des polluants dans la combustion

Energy Technology Data Exchange (ETDEWEB)

Ferrendier, M.

1998-12-17

The typical dimensions of details chemical-kinetic mechanisms proposed to describe combustion systems are too large for multi-dimensional computations applications. The objective of reduction methods is to construct low-dimensional schemes that can be incorporated in industrial codes. We consider here a new class of methods based on a mathematical analysis of the detailed chemical-kinetic mechanisms, and the identification of a low-dimensional manifold that describes the slow dynamics of the chemical system. The mathematical reduction methods considered in this work are the Intrinsic Low Dimensional Manifold (ILDM) method proposed by Maas and Pope (1992), and the Singular Perturbation (PS) method proposed by Duchene and Rouchon (1996). The domain of validity of the ILDM or PS reduced schemes is limited to a high temperature domain T {>=} T{sub c}. This result suggests that ignition is out of the domain of application of reduced mechanisms. In the case of a CO/H{sub 2}/N{sub 2}-air combustion system, and using a two-dimensional slow manifold, we find T{sub c} {approx} 750 K. We also find that for that particular system, 2 progress variables are sufficient for an accurate description of the structure and the velocity of a laminar premixed flame. In the case of a CH{sub 4}-air combustion system, and using a two-dimensional slow manifold, we find T{sub c}{approx}1500 K. We also find that 2 progress variables are insufficient for an accurate description of the structure and the velocity of a laminar premixed flame. The study of the different NO formation mechanisms show that the thermal NO mechanism (the Zeldovich mechanism) is dominant for premixed configurations with lean or stoichiometric conditions ({phi}){>=}1.2), and for non-premixed configurations at high temperatures and high pressures (T{sub air}{>=}1000 K, P {>=} 10 bars). Under these conditions, the MPKIVA sub model used to describe NO formation in the IFP version of the KIVA code performs reasonably well. An

Combustion stratification study of partially premixed combustion using Fourier transform analysis of OH* chemiluminescence images

KAUST Repository

Izadi Najafabadi, Mohammad

2017-11-06

A relatively high level of stratification (qualitatively: lack of homogeneity) is one of the main advantages of partially premixed combustion over the homogeneous charge compression ignition concept. Stratification can smooth the heat release rate and improve the controllability of combustion. In order to compare stratification levels of different partially premixed combustion strategies or other combustion concepts, an objective and meaningful definition of “stratification level” is required. Such a definition is currently lacking; qualitative/quantitative definitions in the literature cannot properly distinguish various levels of stratification. The main purpose of this study is to objectively define combustion stratification (not to be confused with fuel stratification) based on high-speed OH* chemiluminescence imaging, which is assumed to provide spatial information regarding heat release. Stratification essentially being equivalent to spatial structure, we base our definition on two-dimensional Fourier transforms of photographs of OH* chemiluminescence. A light-duty optical diesel engine has been used to perform the OH* bandpass imaging on. Four experimental points are evaluated, with injection timings in the homogeneous regime as well as in the stratified partially premixed combustion regime. Two-dimensional Fourier transforms translate these chemiluminescence images into a range of spatial frequencies. The frequency information is used to define combustion stratification, using a novel normalization procedure. The results indicate that this new definition, based on Fourier analysis of OH* bandpass images, overcomes the drawbacks of previous definitions used in the literature and is a promising method to compare the level of combustion stratification between different experiments.

Studies in combustion dynamics

Energy Technology Data Exchange (ETDEWEB)

Koszykowski, M.L. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

The goal of this program is to develop a fundamental understanding and a quantitative predictive capability in combustion modeling. A large part of the understanding of the chemistry of combustion processes comes from {open_quotes}chemical kinetic modeling.{close_quotes} However, successful modeling is not an isolated activity. It necessarily involves the integration of methods and results from several diverse disciplines and activities including theoretical chemistry, elementary reaction kinetics, fluid mechanics and computational science. Recently the authors have developed and utilized new tools for parallel processing to implement the first numerical model of a turbulent diffusion flame including a {open_quotes}full{close_quotes} chemical mechanism.

High-resolution vertical velocities and their power spectrum observed with the MAARSY radar - Part 1: frequency spectrum

Science.gov (United States)

Li, Qiang; Rapp, Markus; Stober, Gunter; Latteck, Ralph

2018-04-01

The Middle Atmosphere Alomar Radar System (MAARSY) installed at the island of Andøya has been run for continuous probing of atmospheric winds in the upper troposphere and lower stratosphere (UTLS) region. In the current study, we present high-resolution wind measurements during the period between 2010 and 2013 with MAARSY. The spectral analysis applying the Lomb-Scargle periodogram method has been carried out to determine the frequency spectra of vertical wind velocity. From a total of 522 days of observations, the statistics of the spectral slope have been derived and show a dependence on the background wind conditions. It is a general feature that the observed spectra of vertical velocity during active periods (with wind velocity > 10 m s-1) are much steeper than during quiet periods (with wind velocity wind conditions considered together the general spectra are obtained and their slopes are compared with the background horizontal winds. The comparisons show that the observed spectra become steeper with increasing wind velocities under quiet conditions, approach a spectral slope of -5/3 at a wind velocity of 10 m s-1 and then roughly maintain this slope (-5/3) for even stronger winds. Our findings show an overall agreement with previous studies; furthermore, they provide a more complete climatology of frequency spectra of vertical wind velocities under different wind conditions.

Ultra-High Efficiency and Low-Emissions Combustion Technology for Manufacturing Industries

Energy Technology Data Exchange (ETDEWEB)

Atreya, Arvind

2013-04-15

The purpose of this research was to develop and test a transformational combustion technology for high temperature furnaces to reduce the energy intensity and carbon footprint of U.S. manufacturing industries such as steel, aluminum, glass, metal casting, and petroleum refining. A new technology based on internal and/or external Flue Gas Recirculation (FGR) along with significant enhancement in flame radiation was developed. It produces "Radiative Flameless Combustion (RFC)" and offers tremendous energy efficiency and pollutant reduction benefits over and above the now popular "flameless combustion." It will reduce the energy intensity (or fuel consumption per unit system output) by more than 50% and double the furnace productivity while significantly reducing pollutants and greenhouse gas emissions (10^3 times reduction in NOx and 10 times reduction in CO & hydrocarbons and 3 times reduction in CO2). Product quality improvements are also expected due to uniform radiation, as well as, reduction in scale/dross formation is expected because of non-oxidative atmosphere. RFC is inexpensive, easy to implement, and it was successfully tested in a laboratory-scale furnace at the University of Michigan during the course of this work. A first-ever theory with gas and particulate radiation was also developed. Numerical programs were also written to design an industrial-scale furnace. Nine papers were published (or are in the process of publication). We believe that this early stage research adequately proves the concept through laboratory experiments, modeling and computational models. All this work is presented in the published papers. Important conclusions of this work are: (1) It was proved through experimental measurements that RFC is not only feasible but a very beneficial technology. (2) Theoretical analysis of RFC was done in (a) spatially uniform strain field and (b) a planar momentum jet where the strain rate is neither prescribed nor uniform. Four important non

Large-eddy simulation of swirling pulverized-coal combustion

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Hu, L.Y.; Luo, Y.H. [Shanghai Jiaotong Univ. (China). School of Mechanical Engineering; Zhou, L.X.; Xu, C.S. [Tsinghua Univ., Beijing (China). Dept. of Engineering Mechanics

2013-07-01

A Eulerian-Lagrangian large-eddy simulation (LES) with a Smagorinsky-Lilly sub-grid scale stress model, presumed-PDF fast chemistry and EBU gas combustion models, particle devolatilization and particle combustion models are used to study the turbulence and flame structures of swirling pulverized-coal combustion. The LES statistical results are validated by the measurement results. The instantaneous LES results show that the coherent structures for pulverized coal combustion is stronger than that for swirling gas combustion. The particles are concentrated in the periphery of the coherent structures. The flame is located at the high vorticity and high particle concentration zone.

Combustion of agro-waste with coal in a fluidized bed

Energy Technology Data Exchange (ETDEWEB)

Atimtay, Aysel T. [Middle East Technical University, Department of Environmental Engineering, Ankara (Turkey)

2010-02-15

In this study, a review of the studies done on the co-combustion of some agro-waste in a bubbling fluidized bed combustor (BFBC) having an inside diameter of 102 mm and a height of 900 mm is given. The agro-waste used to investigate the co-combustion characteristics were peach and apricot stones produced as a waste from the fruit juice industry, and olive cake produced as a waste from the olive oil industry. These are typical wastes for a Mediterranean country. A lignite coal was used for co-combustion. On-line concentrations of O{sub 2}, CO, CO{sub 2}, SO{sub 2}, NO{sub x} and total hydrocarbons (C{sub m} H{sub n}) were measured in the flue gas during combustion experiments. Variations of emissions of various pollutants were studied by changing the operating parameters (excess air ratio, fluidization velocity and fuel feed rate). Temperature distribution along the bed was measured with thermocouples. Emissions were also monitored from the exhaust. Various combinations of coal and biomass mixtures were tested. During the combustion tests, it was observed that the volatile matter from the biomass quickly volatilizes and mostly burns in the freeboard. The temperature profiles along the bed and the freeboard also confirmed this phenomenon. It was found that as the volatile matter of the biomass increases, combustion takes place more in the freeboard region. Better combustion conditions occur at higher excess air ratios. The results showed that co-combustion with these three proposed biomasses lowers the SO{sub 2} and NO{sub x} emissions considerably. CO and hydrocarbon emissions are lower at the higher excess air ratios. (orig.)

DETERMINING THE COMPOSITION OF HIGH TEMPERATURE COMBUSTION PRODUCTS OF FOSSIL FUEL BASED ON VARIATIONAL PRINCIPLES AND GEOMETRIC PROGRAMMING

Directory of Open Access Journals (Sweden)

Velibor V Vujović

2011-01-01

Full Text Available This paper presents the algorithm and results of a computer program for calculation of complex equilibrium composition for the high temperature fossil fuel combustion products. The method of determining the composition of high temperatures combustion products at the temperatures appearing in the open cycle MHD power generation is given. The determination of combustion product composition is based on minimization of the Gibbs free energy. The number of equations to be solved is reduced by using variational principles and a method of geometric programming and is equal to the sum of the numbers of elements and phases. A short description of the computer program for the calculation of the composition and an example of the results are also given.

Direct numerical simulation of combustion at high Reynolds numbers; Direkte Numerische Simulation der Verbrennung bei hoeheren Reynoldszahlen

Energy Technology Data Exchange (ETDEWEB)

Frouzakis, C. E.; Boulouchos, K.

2005-12-15

This comprehensive illustrated final report for the Swiss Federal Office of Energy (SFOE) reports on the work done at the Swiss Federal Institute of Technology in Zurich on the numerical simulation of combustion processes at high Reynolds numbers. The authors note that with appropriate extensive calculation effort, results can be obtained that demonstrate a high degree of accuracy. It is noted that a large part of the project work was devoted to the development of algorithms for the simulation of the combustion processes. Application work is also discussed with research on combustion stability being carried on. The direct numerical simulation (DNS) methods used are described and co-operation with other institutes is noted. The results of experimental work are compared with those provided by simulation and are discussed in detail. Conclusions and an outlook round off the report.

Kinematics of Local, High-Velocity K dwarfs in the SUPERBLINK Proper Motion Catalog

Science.gov (United States)

Kim, Bokyoung; Lepine, Sebastien

2018-01-01

We present a study of the kinematics of 345,480 K stars within 2 kpc of the Sun, based on data from the SUPERBLINK catalog of stars with high proper motions (> 40 mas/yr), combined with data from the 2MASS survey and from the first GAIA release, which together yields proper motions accurate to ~2 mas/yr. All K dwarfs were selected based on their G-K colors, and photometric distances were estimated from a re-calibrated color-magnitude relationship for K dwarfs. We plot transverse velocities VT in various directions on the sky, to examine the local distribution of K dwarfs in velocity space. We have also obtained radial velocity information for a subsample of 10,128 stars, from RAVE and SDSS DR12, which we use to construct spatial velocity (U, V, W) plots. About a third (123,350) of the stars are high-velocity K dwarfs, with motions consistent with the local Galactic halo population. Our kinematic analysis suggests that their velocity-space distribution is very uniform, and we find no evidence of substructure that might arise, e.g., from local streams or moving groups.

High Precision UTDR Measurements by Sonic Velocity Compensation with Reference Transducer

Directory of Open Access Journals (Sweden)

Sam Stade

2014-07-01

Full Text Available An ultrasonic sensor design with sonic velocity compensation is developed to improve the accuracy of distance measurement in membrane modules. High accuracy real-time distance measurements are needed in membrane fouling and compaction studies. The benefits of the sonic velocity compensation with a reference transducer are compared to the sonic velocity calculated with the measured temperature and pressure using the model by Belogol’skii, Sekoyan et al. In the experiments the temperature was changed from 25 to 60 °C at pressures of 0.1, 0.3 and 0.5 MPa. The set measurement distance was 17.8 mm. Distance measurements with sonic velocity compensation were over ten times more accurate than the ones calculated based on the model. Using the reference transducer measured sonic velocity, the standard deviations for the distance measurements varied from 0.6 to 2.0 µm, while using the calculated sonic velocity the standard deviations were 21–39 µm. In industrial liquors, not only the temperature and the pressure, which were studied in this paper, but also the properties of the filtered solution, such as solute concentration, density, viscosity, etc., may vary greatly, leading to inaccuracy in the use of the Belogol’skii, Sekoyan et al. model. Therefore, calibration of the sonic velocity with reference transducers is needed for accurate distance measurements.

Simulation of low temperature combustion mechanism of different combustion-supporting agents in close-coupled DOC and DPF system.

Science.gov (United States)

Jiao, Penghao; Li, Zhijun; Li, Qiang; Zhang, Wen; He, Li; Wu, Yue

2018-07-01

In the coupled Diesel Oxidation Catalyst (DOC) and Diesel Particular Filter (DPF) system, soot cannot be completely removed by only using the passive regeneration. And DPF active regeneration is necessary. The research method in this paper is to spray different kinds of combustion-supporting agents to the DOC in the front of the DPF. Therefore, the low temperature combustion mechanism of different kinds of combustion-supporting agents in DOC was studied, in order to grasp the law of combustion in DOC, and the influence of follow-up emission on DPF removal of soot. During the study, CH 4 H 2 mixture and diesel (n-heptane + toluene) were used as combustion-supporting agents respectively. The simplified mechanisms of two kinds of gas mixtures used as the combustion-supporting agents in DPF have been constructed and testified in the paper. In this paper, the combustion and emission conditions of the two combustion-supporting agents were analyzed so as to meet the practical requirements of different working conditions. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.