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Modeling of extinction in turbulent diffusion flames by the velocity-disalpation-compositon PDF method
09
Combustion
(burners,
combustion
systems)
A light acatterlng study of coal combustion In a 95102888 drop tube furnace
Card, J. B. and Jones, A. R. Purr. Sysr. Charact, 1994, 11, (3), 258-265. Describes a light scattering method which has been devised to discriminate between coal and fly ash and measure particle size. Sizing was performed by the measurement of forward scattered intensity, and discrimination was displayed by the ratio of the intensities of crossed to parallel polarization at a scattering angle of 160”. The technique has been applied to a study of coal combustion in a variable length drop tube furnace.
Mixing characterlatlca of compressor vortex rlnga lnteractlng wlth normal shock wavea
95102889
Cetegen, B. M. and Hermanson, J. C. Comburrion & Flame, Jan. 1995, 100, (l), 232-240. The instability mechanisms and mixing enhancement arising from the interaction of a compressible vortex rin with a normal shock wave were studied in a colinear, dual-shock tube. #his flow geometry simulates features of the interaction of a shock wave with a jet containing streamwise vorticity, a configuration of significant interest for supersonic combustion applications. Flow visualization and quantitative concentration measurements were performed by planar laser Rayleigh scattering.
Modellng of coal pyrolyale klnetlca 95/02890 Liliedahl, T. and Sjostrom, K. AI&!? J., 1994, 40, (9), 1515-1523. The paper describes how four coals were instantaneously introduced into a laboratory-scale pyrolysis chamber and their devolatilization kinetics were analyzed using an empirical model based on the assumption that only the magnitude and not the shape of the devolatilization profile will be influenced by the total amounts of volatile matter. 95102891
Modellng of combuatlon of coal partlclea In a turbulent stream
Aslanyan, G. S. er al., Fir. Goreniya Vzryva, 1994, 30, (4), 46-52. (In Russian) Describes a model which has been developed for the combustion of coal particles in a 2-dimensional stream of gaseous oxidant. It accounts for the effect of gas turbulence on coal particle velocity. 95102892
Modeling of extlnctlon In turbulent dlffuslon flames by the velocity-dlaalpatlon-compoaltlon PDF method
~lolrrr.oA. T. and Pope, S. B.
Combustion & Flame, Jan. 1995, 100, (1)
The velocity-dissipation-composition probability density function (pdf) method is used to model turbulent CO/H&-air-piloted jet diffusion flame in the regime of extinction. The thermochemistry is modelled by a threescalar simplified formulation obtained by the intrinsic low-dimensional manifold method. Calculations are performed for five different jet velocities, and the scalar ndfs are comoared with exnerimental data. Overall good aerkement is obtamed between the calculations and the exnerimental results with the only significant difference being the high level of scatter in the experimental data compared with the pdf results: reasons for this difference are discussed.
NO and N,O In lean-premlxed Jet-atlrred flames 95102893 Steele, R. C. et a/!, Combusrion & Flame, Feb. 1995, 100, (3), 440-449. The study examines NO&O formation mechanisms that are relevant to lean-premixed combustion in practical high-intensity wmbustors. Both experiments and kinetic modelling are presented. 95102894
Numerlcal modeling of combustion PrOCeaaea Induced by a auperaonlc conlcal Blunt body _
Lefebvre. M. H. and Fuiiwara, T. Combusrion & Flame, Jan. 1995, 100, (l), 85-93. . The structure of standing oblique detonations around a blunt conical body is numerically studied. A large range of incoming flow velocities and tip radii are compared. The mixture studied is a stoichiometric hydrogen-air at 0.1 atm. The physical model includes a detailed full-chemistry mechanism for the reaction rates. The numerical model is based on a TVD upwind algorithm including a point-implicit finite difference scheme for the wupling between the flow equations and the chemical reactions equations. 95102895
Obsetvatlon of laser lgnltlon and combustion of Dulverlzed COsl
Chen, J. C. et al., Fuel, Mar. 1995, 74, (3), 323-330. Direct observation of pulsed-laser ignition and combustion of pulverized coals with a high speed video has been made. A dilute stream of particles was dropped into a laminar, upward-flow wind tunnel with a quartz test section. The gas stream was not preheated. A single pulse from a Nd:YAG laser was focused through the tunnel and ignited several particles. The transparent test section and cool walls allowed for optical detection of the reaction sequence. The ignition and combustion behaviours of amorphous carbon spheres and an anthracite were as expected for heterogeneous ignition and reaction. Surprisingly, the reaction of a high volatile bituminous and a subbituminous coal exhibited two broad emissions, as detected with a photomultiplier tube.
208
Fuel and Energy Abstracts May 1995
95102898
On the structure of a atretched/compreaaed lamlnar flamelet-lnfluence of preferential dlffualon
Katta, V. R. and Roquemore, W. M. Combustion & Flame, Jan. 1995, 100., II‘). \ 61-70. The local Lewis number on the field side of a Hz/air diffusion flame is known to be lower than unity. When a high-Damkohler-number hydrogen flame is stretched, the flame temperature changesnot because of incomplete chemical reactions, but due to the preferential diffusion resulting from the nonunity Lewis number. These changes are examined using a computational fluid dynamics with chemical reactions code that is thudorder accurate. Detailed chemical kinetics including NO reactions is used to investigate the effects of stretch on the flame structure. I,
95102897
The partltlonlng of Iron durlng the combuatlon of pulverized coal
Bool, L. E. et al., Combustion & F&me, Jan. 1995, 100, (l), 262-270. The partitioning of iron during pulverized coal combustion was investigated both experimentally and theoretically. Emphasis was on determining how coal variables and combustion conditions influenced the formation of slagging precursors.
Phaa averaglng of the preceaalng vortex core In a 95102898 awlrl burner under plloted and premlxed combuatlon condltlona Froud, D. et a& Combusrion & Flame, Feb. 1995, 100, (3), 407-413. The flow patterns produced in and past the exhaust of a lOO-KW swirl burner have been investigated experimentally under piloted premixed wmbustion conditions. The well-known three-dimensional time-dependent instability called the processing vortex wre (PVC) dominates the flow and mixing patterns. The PVC and its associated cycle time were used to trigger a three-component laser anemometry system. Successive cycles were overlaid and phase averaged to give a three-dimensional picture of the rotating flow fields. Measurements were obtained over successive slices of the flow, extending to X/De = 2.5 past the burner exit. A description of the flow was thus obtained in terms of phase averaged tangential, axial and radial velocities in taneentiaVradia1 and axial/radial manes. Results confirm previously reported w&k on the same burner operated isothermally.
95102899
Predlctlona of wlnd-opposed flame spread rates and energy feedback analyala for charrlng aollda In a mlcrogravlty envlronment Di Blasi, C. Combustion & Flame, Jan. 1995, 100, (1). 332-340. Discusses the changes in the mechanisms controlling ‘microgravity flame spread over cellulosic fuels, as the forced as flow opposing the flame spread and the solid thickness are varied. b e analysis is based on the numerical simulation of the problem by means of a two-dimensional, nonconstant spread rate, quasi steady mathematical model.
Propertlea of carbon In fly ash dlacharged from pulverlred coal combustion boller
95102900
Chen, Y. and Mori, S. Nippon Enerugi Gakkaishi, 1994,73, (8), 748-752. fin Jaoanesel Fly ashes E and G, discharged from the same pulverized coal boiler, were classified into two components, i.e. fly ash ~38 microns and >125 microns. The carbon contained in both fractions were separated from fly ash by using the ultrasonic oil agglomeration method. The carbon remains in the warser fly ash as unburned char, and that contained in finer fly ash are carbon black and rock carbon. The properties of carbon contained in fly ash present significant information for rational operation and control of pulverized coal combustion.
Response of counterflow dlffuslon flames to osclllatlng strain rates
95102901
Im, H. G. er al., Combustion & Flame, Jan. 1995, 100, (l), 21-30. The response of counterflow flames to oscillating strain rates is analyzed by using large activation energy asymptotics, as a potential application to turbulent combustion and acoustic instabilitv of rocket engines. The characteristic oscillation time of practical interest is found to-be of the same order as the characteristic diffusion time of the flame, so that the flame structure consists of a quasi-steady reactive-diffusive layer embedded in the outer unsteadv-diffusive-convective zone. A linear analvsis is wnducted by assuming that the amplitude of the strain rate oscillaiion is small relative to the mean strain rate.
Slntered metal burner: A burner wlth perapectlve 95102902 Polman, E. et al., Gas (Netherlands), Feb. 1995, 115, (2), 30-33. (In Flemish) Sintered metal can very well be used as a burner material because of its low CO and NO, emissions and high modularity. The use of a hole pattern leads to a pressure fall over the burner and also results in lower NO, emissions. Further studies have to be conducted into the optimisation of the hole pattern with regard to pressure fall and CO and NO, emissions and into the high-temperature properties of sintered metal. Smtered metal is particularly suitable for compact modulating burners.
Combustion
(burners,
combustion
systems)
A light acatterlng study of coal combustion In a 95102888 drop tube furnace
Card, J. B. and Jones, A. R. Purr. Sysr. Charact, 1994, 11, (3), 258-265. Describes a light scattering method which has been devised to discriminate between coal and fly ash and measure particle size. Sizing was performed by the measurement of forward scattered intensity, and discrimination was displayed by the ratio of the intensities of crossed to parallel polarization at a scattering angle of 160”. The technique has been applied to a study of coal combustion in a variable length drop tube furnace.
Mixing characterlatlca of compressor vortex rlnga lnteractlng wlth normal shock wavea
95102889
Cetegen, B. M. and Hermanson, J. C. Comburrion & Flame, Jan. 1995, 100, (l), 232-240. The instability mechanisms and mixing enhancement arising from the interaction of a compressible vortex rin with a normal shock wave were studied in a colinear, dual-shock tube. #his flow geometry simulates features of the interaction of a shock wave with a jet containing streamwise vorticity, a configuration of significant interest for supersonic combustion applications. Flow visualization and quantitative concentration measurements were performed by planar laser Rayleigh scattering.
Modellng of coal pyrolyale klnetlca 95/02890 Liliedahl, T. and Sjostrom, K. AI&!? J., 1994, 40, (9), 1515-1523. The paper describes how four coals were instantaneously introduced into a laboratory-scale pyrolysis chamber and their devolatilization kinetics were analyzed using an empirical model based on the assumption that only the magnitude and not the shape of the devolatilization profile will be influenced by the total amounts of volatile matter. 95102891
Modellng of combuatlon of coal partlclea In a turbulent stream
Aslanyan, G. S. er al., Fir. Goreniya Vzryva, 1994, 30, (4), 46-52. (In Russian) Describes a model which has been developed for the combustion of coal particles in a 2-dimensional stream of gaseous oxidant. It accounts for the effect of gas turbulence on coal particle velocity. 95102892
Modeling of extlnctlon In turbulent dlffuslon flames by the velocity-dlaalpatlon-compoaltlon PDF method
~lolrrr.oA. T. and Pope, S. B.
Combustion & Flame, Jan. 1995, 100, (1)
The velocity-dissipation-composition probability density function (pdf) method is used to model turbulent CO/H&-air-piloted jet diffusion flame in the regime of extinction. The thermochemistry is modelled by a threescalar simplified formulation obtained by the intrinsic low-dimensional manifold method. Calculations are performed for five different jet velocities, and the scalar ndfs are comoared with exnerimental data. Overall good aerkement is obtamed between the calculations and the exnerimental results with the only significant difference being the high level of scatter in the experimental data compared with the pdf results: reasons for this difference are discussed.
NO and N,O In lean-premlxed Jet-atlrred flames 95102893 Steele, R. C. et a/!, Combusrion & Flame, Feb. 1995, 100, (3), 440-449. The study examines NO&O formation mechanisms that are relevant to lean-premixed combustion in practical high-intensity wmbustors. Both experiments and kinetic modelling are presented. 95102894
Numerlcal modeling of combustion PrOCeaaea Induced by a auperaonlc conlcal Blunt body _
Lefebvre. M. H. and Fuiiwara, T. Combusrion & Flame, Jan. 1995, 100, (l), 85-93. . The structure of standing oblique detonations around a blunt conical body is numerically studied. A large range of incoming flow velocities and tip radii are compared. The mixture studied is a stoichiometric hydrogen-air at 0.1 atm. The physical model includes a detailed full-chemistry mechanism for the reaction rates. The numerical model is based on a TVD upwind algorithm including a point-implicit finite difference scheme for the wupling between the flow equations and the chemical reactions equations. 95102895
Obsetvatlon of laser lgnltlon and combustion of Dulverlzed COsl
Chen, J. C. et al., Fuel, Mar. 1995, 74, (3), 323-330. Direct observation of pulsed-laser ignition and combustion of pulverized coals with a high speed video has been made. A dilute stream of particles was dropped into a laminar, upward-flow wind tunnel with a quartz test section. The gas stream was not preheated. A single pulse from a Nd:YAG laser was focused through the tunnel and ignited several particles. The transparent test section and cool walls allowed for optical detection of the reaction sequence. The ignition and combustion behaviours of amorphous carbon spheres and an anthracite were as expected for heterogeneous ignition and reaction. Surprisingly, the reaction of a high volatile bituminous and a subbituminous coal exhibited two broad emissions, as detected with a photomultiplier tube.
208
Fuel and Energy Abstracts May 1995
95102898
On the structure of a atretched/compreaaed lamlnar flamelet-lnfluence of preferential dlffualon
Katta, V. R. and Roquemore, W. M. Combustion & Flame, Jan. 1995, 100., II‘). \ 61-70. The local Lewis number on the field side of a Hz/air diffusion flame is known to be lower than unity. When a high-Damkohler-number hydrogen flame is stretched, the flame temperature changesnot because of incomplete chemical reactions, but due to the preferential diffusion resulting from the nonunity Lewis number. These changes are examined using a computational fluid dynamics with chemical reactions code that is thudorder accurate. Detailed chemical kinetics including NO reactions is used to investigate the effects of stretch on the flame structure. I,
95102897
The partltlonlng of Iron durlng the combuatlon of pulverized coal
Bool, L. E. et al., Combustion & F&me, Jan. 1995, 100, (l), 262-270. The partitioning of iron during pulverized coal combustion was investigated both experimentally and theoretically. Emphasis was on determining how coal variables and combustion conditions influenced the formation of slagging precursors.
Phaa averaglng of the preceaalng vortex core In a 95102898 awlrl burner under plloted and premlxed combuatlon condltlona Froud, D. et a& Combusrion & Flame, Feb. 1995, 100, (3), 407-413. The flow patterns produced in and past the exhaust of a lOO-KW swirl burner have been investigated experimentally under piloted premixed wmbustion conditions. The well-known three-dimensional time-dependent instability called the processing vortex wre (PVC) dominates the flow and mixing patterns. The PVC and its associated cycle time were used to trigger a three-component laser anemometry system. Successive cycles were overlaid and phase averaged to give a three-dimensional picture of the rotating flow fields. Measurements were obtained over successive slices of the flow, extending to X/De = 2.5 past the burner exit. A description of the flow was thus obtained in terms of phase averaged tangential, axial and radial velocities in taneentiaVradia1 and axial/radial manes. Results confirm previously reported w&k on the same burner operated isothermally.
95102899
Predlctlona of wlnd-opposed flame spread rates and energy feedback analyala for charrlng aollda In a mlcrogravlty envlronment Di Blasi, C. Combustion & Flame, Jan. 1995, 100, (1). 332-340. Discusses the changes in the mechanisms controlling ‘microgravity flame spread over cellulosic fuels, as the forced as flow opposing the flame spread and the solid thickness are varied. b e analysis is based on the numerical simulation of the problem by means of a two-dimensional, nonconstant spread rate, quasi steady mathematical model.
Propertlea of carbon In fly ash dlacharged from pulverlred coal combustion boller
95102900
Chen, Y. and Mori, S. Nippon Enerugi Gakkaishi, 1994,73, (8), 748-752. fin Jaoanesel Fly ashes E and G, discharged from the same pulverized coal boiler, were classified into two components, i.e. fly ash ~38 microns and >125 microns. The carbon contained in both fractions were separated from fly ash by using the ultrasonic oil agglomeration method. The carbon remains in the warser fly ash as unburned char, and that contained in finer fly ash are carbon black and rock carbon. The properties of carbon contained in fly ash present significant information for rational operation and control of pulverized coal combustion.
Response of counterflow dlffuslon flames to osclllatlng strain rates
95102901
Im, H. G. er al., Combustion & Flame, Jan. 1995, 100, (l), 21-30. The response of counterflow flames to oscillating strain rates is analyzed by using large activation energy asymptotics, as a potential application to turbulent combustion and acoustic instabilitv of rocket engines. The characteristic oscillation time of practical interest is found to-be of the same order as the characteristic diffusion time of the flame, so that the flame structure consists of a quasi-steady reactive-diffusive layer embedded in the outer unsteadv-diffusive-convective zone. A linear analvsis is wnducted by assuming that the amplitude of the strain rate oscillaiion is small relative to the mean strain rate.
Slntered metal burner: A burner wlth perapectlve 95102902 Polman, E. et al., Gas (Netherlands), Feb. 1995, 115, (2), 30-33. (In Flemish) Sintered metal can very well be used as a burner material because of its low CO and NO, emissions and high modularity. The use of a hole pattern leads to a pressure fall over the burner and also results in lower NO, emissions. Further studies have to be conducted into the optimisation of the hole pattern with regard to pressure fall and CO and NO, emissions and into the high-temperature properties of sintered metal. Smtered metal is particularly suitable for compact modulating burners.