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06359 A rapid compression machine investigation of oxidation and auto-ignition of n-heptane: Measurements and modeling
09 Oxidation of carbon black partlclea In a premixed 95106350 flame under pressure Rybak, W. et al., Carbon, 1995, 33, (3), 259-264. There is a need for more information about the soot formation and oxidation in a flame at high tern erature under pressure. Such data are important for model development oP many real combustion systems that operate at high pressure to improve their fuel economy,, increase the thermal efficiency of the system, and reduce the air lluoon. They are also important for testing basic theoretical models for K” ames. The lack of information is partially due to the difficulties in simultaneous generation of soot particles and the study of their combustion at high temperature under pressure. A way to overcome this difficulty is to introduce into a remixed flame a dilute stream of carbon black and measure the rate oP oxidation of the aggregates. The objective of the present work is to determine the influence of pressure on the oxidation rate of carbon black particles. Oxidation rates of lnduetrlsl cokes with CO, and alr 95lO6351 Zamalloa, M. et al., ISIJ Int., 1995, 35, (S), 458-463. The reaction rates of different sizes of commercial cokes with CO, and air were measured using a combined thermogravimetric and differenaal thermal analysis technique. The temperature range for air oxidation was 873 to 1073 K, and for the reactions with CO, it was 1173 to 1573 K. Perturbatlon analysis of a catalytic combustor 95106352 Correa, S. M. Combusrion & Flame, Jul. 1995, 102, (l), ?05-208. Predlctlon of scattering effect b ash polydlsper95106353 slon on spectral emlsslon from coal-fired MHl! combustion gas Onda, K. J. Quant Speclrosc. Radiat. Transfer, 1995, 53, (4), 381-395. Scattering effects by ash polydispersion on spectral emission from the coal-fired MHD combustion gas are predicted numerically by tht 1st (P,) and 3rd (P,) spherical harmonics approximations of a ridiative tran;&r eouation in a rectancmlar cross section of the MHD uower generation channil, with consideratTon of variation in optical properties a&oss a boundary layer, particle diameter distribution of ash polydispersion and wavelength chang; of ash complex refractive indexes. Predlctlons of turbulent, premixed flame propaga95lO6354 tlon In explosion tubes Catlin, C. A. el al., Combustion & Flame, Jul. 1995, 102, (l), 115-128. A mathematical model capable of predicting the overpressures generated by gaseous explosions is decribed. The model is based on solutions of the fluid flow equations obtained using a second-order accurate, finite-volume integration scheme coupled to an adaptive grid algorithm. Turbulence generated ahead of a propagating flame is modelled using a k-e approach, whilst the premixed combustion process is described using a semiempirical method which admits both chemical kinetic and flow field influences on the burning velocity of a flame, while also maintaining realistic flame thicknesses throughout the course of a flame’s propagation. Premlxed and dlffuslon flames In a centrifuge 95106355 Durox, D. er al., Combuslion & Flame, Sep. 1995, 102, (4), 501-511. Combustion experiments conducted in a centrifuge a/e rare, and the authors uresent results obtained durinn different tests camoaiens. For oremixed iames or for diffusion flames,-two cases are distin‘guilhed-in bne, small flames are steady, and in the other, tall flames may be sensitive to a natural instability created by buoyancy in burned gases..The results show that for premixed stationary flames, the flame shape is almost insensitive to buoyancy, except for a very li ht modification of the streamlines in burned and fresh gases due to the hy$rodynamic effects. The physicochemistry of the flame front is not modified in the range of ravity levels studied. On the other hand, the morphology of stationary dlf fusion flames is strongly changed. Both flame height and surface area are reduced as gravity increases. A correlation with a theoretical model gives good agreement. Premlxed flame effects on turbulence and pres95/06356 sure-related terms Zhang, S. and Rutland, C. J. Combustion & Flame, Sep. 1995, 102, (4), 447-461. Direct numerical simulations (DNS) were carried out for premi\r ed, planar, turbulent flames. Heat release effects are accounted for by inclusion of variable density. The simulated flames are thin in the sense that the reaction progress variable is bi-modal and consistent with BL theory. The DNS data were used for detailed studv of flame effects on turbulence within the turbulent flame brush by examining the turbulent kinetic energy budget. The flame effects on turbulent lcmetic energy were found to depend strongly on the heat release. Both mean and-fluctuating pressure terms were found to be the main factors responsible for increases ir turbulent kinetic energy. The main sinks for turbulence are dissipation and mean dilatation. Pressure diffusion was found to dominate the other turbulent kinetic energy diffusion terms.
Combustion (burners, combustion systems)
95106357 Quenching of reverse smolder Lozinski, D. and Buckmaster, J. Combustion & Flame, Jul. 1995, 102, (l), 87-100. A simple model of reverse smolder in a porous medium is analyzed using asymptotic methods. When the only chemical reaction is exothermic oxidation, the burning rate is a single-valued function of the blowing rate, increasing from zero to a maximum, and then returning to zero. When endothermic pyrolysis is added to the description, the burning rate is double-valued for blowing rates less than some maximum. Beyond this maximum there are no solutions. The upper branch of the double-valued solution is the physically relevant one. On it, for certain choices of parameters, the burning rate increases from zero to a maximum, and then decreases until quenching occurs at the maximum blowing rate. This behaviour mimics experimental observations by Torero, Femandez-Pello and Kitano. 95lO5359 Radlatlon heat transfer In dust-loaded systems Stappcr, B. and Koneke, D. Chemical Engineering & Processing, Apr. 1995, 34, (2), 105-113. The design of radiation heat exchangers in the high-temperature range is influenced by the solid loading of the participating media. In order to obtain data and criteria for a more sophisticated design, emission measurements of different gas-dispersed solids (quartz sand, ash from fluidized bed combustion, corundum) has been carried out in an experimental plant specially designed for this purpose. An equation is derived to describe the particle emission coefficient in a geometry with surrounding grey walls. The experimental data fit this model well. An examination of the composition of the solids has shown the considerable influence of the quartz content on the radiation behaviour. 95lO5359 A rapid compression machine Investigation of oxldatlon and auto-lgnltlon of n-heptane: Measurements and modeling Minetti, R. er al., Combusrion & Flame, Aug. 1995, 102, (3), 298-309. n-Heptane oxidation and auto-ignition in a rapid compression mat ine is studied in low and intermediate temperature regimes at high pre! sures. Experimental ignition delay times and some phenomenological aspects related to knock in engines are presented, providing additional information at lower temperatures on previously published delays from shock tube experiments. The products of oxidation are identified and time profiles are measured during a two-stage ignition process. Eight C, heterocycles, heptanes, lower I-alkenes, aldehydes, and carbon monoxide are the main species. The origin is discussed in relation to the isomerization and decomposition of heptylperoxy radicals. Rapld heating of coals: Ways of lm lementatlon, 95lQ5360 effect on structure and properties of products, an8 dlrectlons of use Skripchenko, G. B. et al., Khim. Tverd. Topl. (Moscow), 1995, (2), 12-17. (In Russian) Reactlvlty of coke with particle size of 6-10 mm at 95105361 temcerature ranae 600-l OOO’C We&el, J. and Srzc&icka, E. Karbo-Energochem.-Ekol., 1994, 39, (ll), 279-280, 282-283. (In Polish) Describes the reactivity of several cokes with particle size 6-10 mm for CO, which has been determined at 600-1000°. Reduction of a phosphorus oxlde and acid reactlon 95106362 set Twarowski, A. Combustion & Flame, Jul. 1995, 102, (l), 41-54. The addition of small amounts of phosphine combustion products (phosphorus oxides and acids) to water va.f our has been found to result in a faster relaxation rate of OH to its eqm lbrmm density following H,O photolysis. The article describes the systematic construction of a reaction model of 162 phosphorus reactions among 17 phosphorus-containing species. Those reactions that contribute to the reestablishment of equilibrium followine the oerturbation of the svstem bv H,O ohotolvsis or bv an increase.% temberature are identified: A the&odyna&ic fre; energy iunction is used to quantify the rate of system relaxation back to equilibrium for a series of 36 reaction conditions coverinq a tern 3000 K. a pas density range of 5 X lo‘ to 5 ~$re;~;~m?f~;~u; equival&ceratio of d.9 to i.2. Relatlon between functlonal forms of coal nitrogen 95106363 and NO,, emlsslons from pulverized coal combustion Kambara, S. er al., Fuel, Sep. 1995, 74, (9), 1247-1253. NO, emissions during ulverized coal combustio?, the thermal decom osition behaviour of fuel-YJ ound nitrogen during rapId pyrolysis and the Punctional forms of coal nitrogen were investigated to develop the eneral index estimating NO, levels for coals covering a wide ran f e of raf. NO, levels under excess air and two-stage combustion strong y depended on coal type. The effect of nitrogen content in the parent coal on NO, levels was not a continuous relationship, seemingly because of the yields of volatile nitro en species which evolve during the early stage of combustion. An imorove %model of NO. formation was urooosed to exolain the influence of ‘coal typ. The domiiant factors for go,-reduction were derived on the basis of the improved model.
Fuel and Energy Abstracts November 1995 449
Combustion (burners, combustion systems)
95106357 Quenching of reverse smolder Lozinski, D. and Buckmaster, J. Combustion & Flame, Jul. 1995, 102, (l), 87-100. A simple model of reverse smolder in a porous medium is analyzed using asymptotic methods. When the only chemical reaction is exothermic oxidation, the burning rate is a single-valued function of the blowing rate, increasing from zero to a maximum, and then returning to zero. When endothermic pyrolysis is added to the description, the burning rate is double-valued for blowing rates less than some maximum. Beyond this maximum there are no solutions. The upper branch of the double-valued solution is the physically relevant one. On it, for certain choices of parameters, the burning rate increases from zero to a maximum, and then decreases until quenching occurs at the maximum blowing rate. This behaviour mimics experimental observations by Torero, Femandez-Pello and Kitano. 95lO5359 Radlatlon heat transfer In dust-loaded systems Stappcr, B. and Koneke, D. Chemical Engineering & Processing, Apr. 1995, 34, (2), 105-113. The design of radiation heat exchangers in the high-temperature range is influenced by the solid loading of the participating media. In order to obtain data and criteria for a more sophisticated design, emission measurements of different gas-dispersed solids (quartz sand, ash from fluidized bed combustion, corundum) has been carried out in an experimental plant specially designed for this purpose. An equation is derived to describe the particle emission coefficient in a geometry with surrounding grey walls. The experimental data fit this model well. An examination of the composition of the solids has shown the considerable influence of the quartz content on the radiation behaviour. 95lO5359 A rapid compression machine Investigation of oxldatlon and auto-lgnltlon of n-heptane: Measurements and modeling Minetti, R. er al., Combusrion & Flame, Aug. 1995, 102, (3), 298-309. n-Heptane oxidation and auto-ignition in a rapid compression mat ine is studied in low and intermediate temperature regimes at high pre! sures. Experimental ignition delay times and some phenomenological aspects related to knock in engines are presented, providing additional information at lower temperatures on previously published delays from shock tube experiments. The products of oxidation are identified and time profiles are measured during a two-stage ignition process. Eight C, heterocycles, heptanes, lower I-alkenes, aldehydes, and carbon monoxide are the main species. The origin is discussed in relation to the isomerization and decomposition of heptylperoxy radicals. Rapld heating of coals: Ways of lm lementatlon, 95lQ5360 effect on structure and properties of products, an8 dlrectlons of use Skripchenko, G. B. et al., Khim. Tverd. Topl. (Moscow), 1995, (2), 12-17. (In Russian) Reactlvlty of coke with particle size of 6-10 mm at 95105361 temcerature ranae 600-l OOO’C We&el, J. and Srzc&icka, E. Karbo-Energochem.-Ekol., 1994, 39, (ll), 279-280, 282-283. (In Polish) Describes the reactivity of several cokes with particle size 6-10 mm for CO, which has been determined at 600-1000°. Reduction of a phosphorus oxlde and acid reactlon 95106362 set Twarowski, A. Combustion & Flame, Jul. 1995, 102, (l), 41-54. The addition of small amounts of phosphine combustion products (phosphorus oxides and acids) to water va.f our has been found to result in a faster relaxation rate of OH to its eqm lbrmm density following H,O photolysis. The article describes the systematic construction of a reaction model of 162 phosphorus reactions among 17 phosphorus-containing species. Those reactions that contribute to the reestablishment of equilibrium followine the oerturbation of the svstem bv H,O ohotolvsis or bv an increase.% temberature are identified: A the&odyna&ic fre; energy iunction is used to quantify the rate of system relaxation back to equilibrium for a series of 36 reaction conditions coverinq a tern 3000 K. a pas density range of 5 X lo‘ to 5 ~$re;~;~m?f~;~u; equival&ceratio of d.9 to i.2. Relatlon between functlonal forms of coal nitrogen 95106363 and NO,, emlsslons from pulverized coal combustion Kambara, S. er al., Fuel, Sep. 1995, 74, (9), 1247-1253. NO, emissions during ulverized coal combustio?, the thermal decom osition behaviour of fuel-YJ ound nitrogen during rapId pyrolysis and the Punctional forms of coal nitrogen were investigated to develop the eneral index estimating NO, levels for coals covering a wide ran f e of raf. NO, levels under excess air and two-stage combustion strong y depended on coal type. The effect of nitrogen content in the parent coal on NO, levels was not a continuous relationship, seemingly because of the yields of volatile nitro en species which evolve during the early stage of combustion. An imorove %model of NO. formation was urooosed to exolain the influence of ‘coal typ. The domiiant factors for go,-reduction were derived on the basis of the improved model.
Fuel and Energy Abstracts November 1995 449