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00974 Combustion mechanism of an RDX-based composite propellant
09
Combustion
00100974 composite
(burners, combustion
Combustion propellant
systems)
mechanism
of an RDX-based
De Luca, L. <‘I rrl. Coi,ih~\/r~,,~ & Nrr,?rc, IYO’), I IS. ( I-?). 114%261. The combustion mechanism of a composite propellant having the nominal composition 84% RDX + 16% HTPB has been investigated experimentally. The following steady combustion parameters were collected over the pressure range 0.1 to 8.21 MPa: burn rates, burn surface temperatures, thermal gradients, heat release in the condensed phase, heat feedback from the gas phase, first and second (or final) flame temperatures. In general, for the tested RDX.HTPB mixture. values smaller than the corresponding AP.HTPB parameters are found, while the burning rate pressure exponent is larger. Likewise. the measured values are smaller than the corresponding pure RDX parameters when HTPB binder is added: a notable exception is the heat release in the condensed phase, which is larger. The ohtained dependence of burn rate on hum surface temperature fits the unified gasification law for nitramincs. Thus. RDX seems to dictate it\ macrokinetics law upon the HTPB gasification. The main processes taking place simultaneously at the burn surface arc: gasification and thermal dccomposition of RDX, as well as oxidation of part of the HTPB binder, probably due to liquid-phase mixing between molten ingredients.
00/00975
Combustion
method and apparatus
Components, formulations, solutions, evaluation, 00100976 and application of comprehensive combustion models Eaton. A. M. el al. Progress in Enerfiy & Comhuslior~ Science, 1999. 25, (4). 387-436. Development and application of comprehensive multidimensional computational combustion models are increasing at a significant pace across the world. While once confined to specialized research computer codes, these combustion models are becoming more readily accessible as features in commercially available computational fluid dynamics (CFD) computer codes, Simulations made with such computer codes offer great potential for use in analysing, designing. retrofitting and optimizing the performance of fossil-fuel combustion and conversion systems. The purpose of this paper is to provide an overview of comprehensive combustion modelling technology as applied to fossil-fuel combustion processes. This overview is divided into three main parts. First, a brief review of the state-of-the-art of the various components or submodels that are required in a comprehensive combustion model is presented. A summary of the submodels that are available in representative computer codes is also presented. Second. the kinds of data required to evaluate and validate the predictions of comprehensive combustion codes are considered. To be viewed with confidence, code simulations must have been rigorously evaluated and validated by comparison with appropriate experimental data, preferahly from a variety at various geometric scales. Three sets of of combustor geometric5 validation data are discussed in detail. Third, representative applications of comprehensive combustion models are summarized. and three sets of model simulations are compared with experimental data.
Conditional
moment
closure for turbulent
Klimenko, A. Y. and Bilger. R. W. Progress in Ener~ & Combustion Science, 1999, 25, (6), 595-687. This paper reviews the fundamentals of conditional moment closure (CMC) methods for the prediction of turbulent reacting flows with particular emphasis on combustion. It also surveys several of the applications that have been made. CMC methods predict the conditional averages and higher moments of quantities such as species mass fractions and enthalpy, conditional on the mixture fraction or reaction progress variable having a particular value. A brief introduction is given to generalized functions and probability density function (pdf) methods. This is followed by an exposition on the various methods of derivation for the CMC equation and the general characteristics of this equation and its boundary conditions. Simplifications that can be made in slender layer flows such as jets and plumes are outlined and examples of application of the technique to such flows are given. The method allows the definition of a new class of simplified reactors related to the well known perfectly stirred reactor and plug flow reactor: these are outlined. CMC predictions are compared to experimental and direct numerical simulations for flows with homogeneous turbulence. Derivation and modelling of the equations for conditional variances and covariances are outlined and their use in second-order CMC illustrated. Brief review is made of progress on application of the method to problems involving differential diffusion, multiple conditioning, sprays and premixed combustion.
108
Fuel and Energy Abstracts
March 2000
This paper deals with the control of soot emission from acetylene diffusion flames by applying an electric field. The effects of applied voltage, polarity and spacing of electrodes on soot emissions were investigated experimentally. The results showed that the shape of the flame changed remarkably with increasing applied voltage. The polarity of the applied voltage influenced the shape of the flame and the soot emissions. When a positive voltage was applied to the nozzle electrode. the flame length became shorter and the width at the flame tip was spread at high voltages. More than 90% of the soot emission was suppressed at over 200 kV!m of electric field intensity. Also, the flame temperature increased with increasing applied voltage. In particular, in the case of voltages above ZlO kV/m, the temperatures at the flame tip were about SOO’C higher than in the absence of an electric field. The rise of flame temperature was caused hy the air entrainmenl promoted by an ionic wind. It was concluded that the Soot reduction by applying an electric field was due to the oxidation of soot particles. In contrast, when negative voltages were applied to the nozzle electrode. the efficiency of soot control was limited to about 70% because the flame temperature, even at high applied voltages. was comparable to that in the absence of the electric field.
for fossil fuels
Miyoshi, T. Jpn. Kokai Tokkyo Koho JP 11 21,572 [99 21,572] (Cl. CIOL3I IO), 26 Jan 1999, Appl. 971190,492, 30 Jun 1997, 4 pp. (In Japanese) A method for combustion of fossil fuels, especially kerosene. gas oils and fuel oils, is presented. It involves generating a gas from the decomposition of water containing hydrogen and oxygen by an electrolytic cell; vaporizing a hydrocarbon fuel by heating to obtain a hydrocarbon gas: mixing the two gases to give a combustion gas; and comhusting the gas by a combustion apparatus such as a boiler gas reactor, a furnace or a hurrier.
00/00977 combustion
00100978 Control of soot emitted from acetylene diffusion flames by applying an electric field LG F/ame, 1999, I 19. (3), 35f>-366. Saito, M. er al. Comhurtion
00100979
Development
of pressurized
coal partial combustor
optical Suds, M. ef al. Proc. Annu. Int. Pittsburgh Coal Conf.. [computer disk], 1998. 15, 713-726. Coal partial combustor (CPC) techniques were applied to a pressurized CPC as a gasifier for the integrated gasification combined cycle (IGCC) system. Systematic experiments were conducted on an air-hlown process with a two-stage dry feed system, using a 7 t/d-coal element test facility and a 25 t/d-coal pilot plant. The purpose of this was to clarify the influence of coal feed ratio, oxygen enrichment and coal types on coal gasification performance.
00100980 Dynamic light scattering in sooting premixed atmospheric-pressure methane-, propane-, ethene-, and propene-oxygen flames Combustion & Name, 1999. 118. (l-2). 140-150. Lamprecht, A. et al. In a systematic investigation under well-defined flame conditions, dynamic light scattering (DLS) was applied to the determination of soot particle radii with the aim of examining the suitability of this technique for accurate soot particle sizing. In particular, flat premixed methane-. propane-. etheneand propene-oxygen flames at atmospheric pressure were investigated, and particle sizes were ohtained as a function of stoichiometry and height above the burner surface. In combination with absorption measurements, soot volume fraction and particle number density were determined: also, the temperature was measured at each flame condition. In comparison to absorption techniques. attractive features of DLS are its independence of the particle refractive index and its insensitivity to fluorescence interference; also, it offers spatial resolution. In principle, additional information on the particle size distribution as well as on the global shape of the particles may be obtained from DLS experiments. This study is therefore an evaluation of the potential of DLS as a complement to other soot diagnostic techniques.
00/00981 pyrolysis
Effect of some factors on pressurized
coal
Ma, 2. ef al. Sekitan Kagaku Kagr Happy0 Ronhunshu, 1997, 34, 373-376. (In Japanese) Taiheiyo coal was pyrolysed using a continuous feeding reactor in a wide range of operating conditions. The experiments were carried out for a series of temperatures ranging from 6OO” to 800”, under He, H2 and CO? atmosphere at pressures of 1.0 and 3.0 MPa. The results indicate that the distribution of pyrolysis products is significantly effected hy pyrolysis temperature, gas pressure and carrier gas type.
00100982 temperature
Effect of volatile retention on the products from low pyrolysis in a fixed bed batch reactor
Cloke, M. et al. Fuel, 1999. 78, (14). 1719-1728. This study looks at the effect of volatile retention, within a batch reactor, on the products from fixed bed coal pyrolysis. It has been found that increased retention of volatiles within the reactor can increase the specific calorific value of the solid product. Increased confinement can also increase the specific calorific value of the gas, by increasing the production of methane and ethane from the reactor. The oxygen content of the coal is also shown to be an important parameter in determining the degree of upgrading that can be achieved. The reactivity of the chars from the fixed bed has also been tested in a drop tube furnace. Increasing treatment temperature and increased confinement have been shown to decrease the reactivity of the solid, as measured by combustibles remaining from the drop tube. It is concluded that increased confinement during pyrolysis in a fixed bed batch reactor may improve both the gas and solid products in terms of heat content, although problems may he encountered in burning the solid. in conventional pulverized fuel boilers.
Combustion
00100974 composite
(burners, combustion
Combustion propellant
systems)
mechanism
of an RDX-based
De Luca, L. <‘I rrl. Coi,ih~\/r~,,~ & Nrr,?rc, IYO’), I IS. ( I-?). 114%261. The combustion mechanism of a composite propellant having the nominal composition 84% RDX + 16% HTPB has been investigated experimentally. The following steady combustion parameters were collected over the pressure range 0.1 to 8.21 MPa: burn rates, burn surface temperatures, thermal gradients, heat release in the condensed phase, heat feedback from the gas phase, first and second (or final) flame temperatures. In general, for the tested RDX.HTPB mixture. values smaller than the corresponding AP.HTPB parameters are found, while the burning rate pressure exponent is larger. Likewise. the measured values are smaller than the corresponding pure RDX parameters when HTPB binder is added: a notable exception is the heat release in the condensed phase, which is larger. The ohtained dependence of burn rate on hum surface temperature fits the unified gasification law for nitramincs. Thus. RDX seems to dictate it\ macrokinetics law upon the HTPB gasification. The main processes taking place simultaneously at the burn surface arc: gasification and thermal dccomposition of RDX, as well as oxidation of part of the HTPB binder, probably due to liquid-phase mixing between molten ingredients.
00/00975
Combustion
method and apparatus
Components, formulations, solutions, evaluation, 00100976 and application of comprehensive combustion models Eaton. A. M. el al. Progress in Enerfiy & Comhuslior~ Science, 1999. 25, (4). 387-436. Development and application of comprehensive multidimensional computational combustion models are increasing at a significant pace across the world. While once confined to specialized research computer codes, these combustion models are becoming more readily accessible as features in commercially available computational fluid dynamics (CFD) computer codes, Simulations made with such computer codes offer great potential for use in analysing, designing. retrofitting and optimizing the performance of fossil-fuel combustion and conversion systems. The purpose of this paper is to provide an overview of comprehensive combustion modelling technology as applied to fossil-fuel combustion processes. This overview is divided into three main parts. First, a brief review of the state-of-the-art of the various components or submodels that are required in a comprehensive combustion model is presented. A summary of the submodels that are available in representative computer codes is also presented. Second. the kinds of data required to evaluate and validate the predictions of comprehensive combustion codes are considered. To be viewed with confidence, code simulations must have been rigorously evaluated and validated by comparison with appropriate experimental data, preferahly from a variety at various geometric scales. Three sets of of combustor geometric5 validation data are discussed in detail. Third, representative applications of comprehensive combustion models are summarized. and three sets of model simulations are compared with experimental data.
Conditional
moment
closure for turbulent
Klimenko, A. Y. and Bilger. R. W. Progress in Ener~ & Combustion Science, 1999, 25, (6), 595-687. This paper reviews the fundamentals of conditional moment closure (CMC) methods for the prediction of turbulent reacting flows with particular emphasis on combustion. It also surveys several of the applications that have been made. CMC methods predict the conditional averages and higher moments of quantities such as species mass fractions and enthalpy, conditional on the mixture fraction or reaction progress variable having a particular value. A brief introduction is given to generalized functions and probability density function (pdf) methods. This is followed by an exposition on the various methods of derivation for the CMC equation and the general characteristics of this equation and its boundary conditions. Simplifications that can be made in slender layer flows such as jets and plumes are outlined and examples of application of the technique to such flows are given. The method allows the definition of a new class of simplified reactors related to the well known perfectly stirred reactor and plug flow reactor: these are outlined. CMC predictions are compared to experimental and direct numerical simulations for flows with homogeneous turbulence. Derivation and modelling of the equations for conditional variances and covariances are outlined and their use in second-order CMC illustrated. Brief review is made of progress on application of the method to problems involving differential diffusion, multiple conditioning, sprays and premixed combustion.
108
Fuel and Energy Abstracts
March 2000
This paper deals with the control of soot emission from acetylene diffusion flames by applying an electric field. The effects of applied voltage, polarity and spacing of electrodes on soot emissions were investigated experimentally. The results showed that the shape of the flame changed remarkably with increasing applied voltage. The polarity of the applied voltage influenced the shape of the flame and the soot emissions. When a positive voltage was applied to the nozzle electrode. the flame length became shorter and the width at the flame tip was spread at high voltages. More than 90% of the soot emission was suppressed at over 200 kV!m of electric field intensity. Also, the flame temperature increased with increasing applied voltage. In particular, in the case of voltages above ZlO kV/m, the temperatures at the flame tip were about SOO’C higher than in the absence of an electric field. The rise of flame temperature was caused hy the air entrainmenl promoted by an ionic wind. It was concluded that the Soot reduction by applying an electric field was due to the oxidation of soot particles. In contrast, when negative voltages were applied to the nozzle electrode. the efficiency of soot control was limited to about 70% because the flame temperature, even at high applied voltages. was comparable to that in the absence of the electric field.
for fossil fuels
Miyoshi, T. Jpn. Kokai Tokkyo Koho JP 11 21,572 [99 21,572] (Cl. CIOL3I IO), 26 Jan 1999, Appl. 971190,492, 30 Jun 1997, 4 pp. (In Japanese) A method for combustion of fossil fuels, especially kerosene. gas oils and fuel oils, is presented. It involves generating a gas from the decomposition of water containing hydrogen and oxygen by an electrolytic cell; vaporizing a hydrocarbon fuel by heating to obtain a hydrocarbon gas: mixing the two gases to give a combustion gas; and comhusting the gas by a combustion apparatus such as a boiler gas reactor, a furnace or a hurrier.
00/00977 combustion
00100978 Control of soot emitted from acetylene diffusion flames by applying an electric field LG F/ame, 1999, I 19. (3), 35f>-366. Saito, M. er al. Comhurtion
00100979
Development
of pressurized
coal partial combustor
optical Suds, M. ef al. Proc. Annu. Int. Pittsburgh Coal Conf.. [computer disk], 1998. 15, 713-726. Coal partial combustor (CPC) techniques were applied to a pressurized CPC as a gasifier for the integrated gasification combined cycle (IGCC) system. Systematic experiments were conducted on an air-hlown process with a two-stage dry feed system, using a 7 t/d-coal element test facility and a 25 t/d-coal pilot plant. The purpose of this was to clarify the influence of coal feed ratio, oxygen enrichment and coal types on coal gasification performance.
00100980 Dynamic light scattering in sooting premixed atmospheric-pressure methane-, propane-, ethene-, and propene-oxygen flames Combustion & Name, 1999. 118. (l-2). 140-150. Lamprecht, A. et al. In a systematic investigation under well-defined flame conditions, dynamic light scattering (DLS) was applied to the determination of soot particle radii with the aim of examining the suitability of this technique for accurate soot particle sizing. In particular, flat premixed methane-. propane-. etheneand propene-oxygen flames at atmospheric pressure were investigated, and particle sizes were ohtained as a function of stoichiometry and height above the burner surface. In combination with absorption measurements, soot volume fraction and particle number density were determined: also, the temperature was measured at each flame condition. In comparison to absorption techniques. attractive features of DLS are its independence of the particle refractive index and its insensitivity to fluorescence interference; also, it offers spatial resolution. In principle, additional information on the particle size distribution as well as on the global shape of the particles may be obtained from DLS experiments. This study is therefore an evaluation of the potential of DLS as a complement to other soot diagnostic techniques.
00/00981 pyrolysis
Effect of some factors on pressurized
coal
Ma, 2. ef al. Sekitan Kagaku Kagr Happy0 Ronhunshu, 1997, 34, 373-376. (In Japanese) Taiheiyo coal was pyrolysed using a continuous feeding reactor in a wide range of operating conditions. The experiments were carried out for a series of temperatures ranging from 6OO” to 800”, under He, H2 and CO? atmosphere at pressures of 1.0 and 3.0 MPa. The results indicate that the distribution of pyrolysis products is significantly effected hy pyrolysis temperature, gas pressure and carrier gas type.
00100982 temperature
Effect of volatile retention on the products from low pyrolysis in a fixed bed batch reactor
Cloke, M. et al. Fuel, 1999. 78, (14). 1719-1728. This study looks at the effect of volatile retention, within a batch reactor, on the products from fixed bed coal pyrolysis. It has been found that increased retention of volatiles within the reactor can increase the specific calorific value of the solid product. Increased confinement can also increase the specific calorific value of the gas, by increasing the production of methane and ethane from the reactor. The oxygen content of the coal is also shown to be an important parameter in determining the degree of upgrading that can be achieved. The reactivity of the chars from the fixed bed has also been tested in a drop tube furnace. Increasing treatment temperature and increased confinement have been shown to decrease the reactivity of the solid, as measured by combustibles remaining from the drop tube. It is concluded that increased confinement during pyrolysis in a fixed bed batch reactor may improve both the gas and solid products in terms of heat content, although problems may he encountered in burning the solid. in conventional pulverized fuel boilers.