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01696 Creeping flame spread: Some new results and interpretation for material flammability characterization
00
Combustion (burners, wmbustion
systems)
%iOW%
Creeping flame spread: Some now reoulte and Intorpretatlon for materlrl flammablllty ohrrrctorizmtlon C&&ysd Deli&a&s, M. A. Combustion & Flame, Dec. 1994,99, k important component for material flammability is the propnsi t&of flames to spread in horixontal or downward orientation, a situation w ch is usually called creeping or lateral 5ame spread. Interpretation of test methods for creepin flame spread is difficult because it involves heat transfer at the time 0f the flame, aucnching of the flame, the formation of a triole-oremixed-d flame. & well &solid ovrolv&s kinetics. Seoaratioit or these effects theoretic& numerically or ‘e;pe;imentally is @tired for deducing relevant flammability properties. New results presented in thii paper on this subject are related to a modification of the initial formulation of the creeping flame spread problems. Demonstmtlon of mlcronlzed coal roburnlng for %I01 607 NO, control on a 176 MW unlt Butler, T. F. et al., Prepr. Pap.-Am. Chem. Sot., Div. Fuel Chem., 1994, 39, (2), 365374. Reports that the Tennessee Valley Authority has been selected for the US Department of Energy’s Clean Coal Technology IV rogram to demonstrate micronized coal reburn technology for control of K 0 emissions on a 175 MW, wall-fd steam generator at its Shawnee Fossil Plant. The paper includes plans for a full-scale demonstration unit at the Shawnee plant. 05/01%8 Detallrd klnetlc modeling of prrmlxrd benzene flame8 L&dstlge;lt, R. P. and Sk&s, G. Combusfion % Flame, Dec. 1994,99, (3), -
.
unccrtainities on the main reaction path is small to moderate. Development and demonotratlon of 2D-UF for %I01690 otudlea of mixture orroaratlon In 81 malnro . . Neij, H. et al., Combusrion % Flame, Nov. 1994, 99, (2), 449-457. Describes how laser-induced fluorescence (LIF) has been developed for visualization of fuel distribution fields in an operating spark-@ion engine. Since the standard research fuel &octane. does not yield a useful LIF signal a fluorescent additive was used. None of the commonly used seeds were found ad uate. A seed not commonly used in this context, 3pentanonc, GH &COC, “t4, was chosen due to favourable vaporization characteristics and uomsccnt properties. Results from pre aratory investigations in the actual engine environment are presented an B related laboratory data are discussed. %I01 7% Dew10 ment of carbon monoxide ?? enoom for the efflclent control of Bumem qe+gan, M. D: et aL, Proc. 2nil Int. Co$ Ceramics ln Energy no?22y Instuute of Energy, 18 Devon&we St., London WIN 2.4 . Discusses why then is a continuing need to product low cost, high sensitivity, gas specific sensors. One major requirement is for an efficient low cost carbon monoxide specific sensor for use in burner controls to ensure optimum efficiency of combustion. A method of fabricating semiconducting SnO&O, sensors using the sol-gel route has been developed and has been shown to have a number of advantages. The method of preparation accurately controls the chemistry of the sol and ensures mixing at the moleculai levels. The direct detiition of the sol onto a se-nsor subitrate to form a gel results in exccllerit adhesion and thickness control. Precise control of the surface area, porosity and particle size of the sensor films can be achieved by subsequent sintering of the gel to product a mixed metal oxide. %I01 701 The development of Inotabllltlw In lamlnar oxplo8lon flame0 Bradle , D. and Harper, C. M. Combustion &Flame, Dec. 1994,99, (3), 562-S&.
Theoretical and experimental studies are presented of the growth of flame instabilities arising from peturbations of spherically pro agating laminar flames in an explosion bomb. High-speed cme schlieren p1 otographs show flame instability to be associated with the propagation of cracks, originating from disturbances due to flame movement over the spark electrodes, along the flame surface.
11s
Fuel and Energy Abstract8 March 1995
%I01 702 Devolatlllzatlon of pulverized coal durlng combustlon and reactivity of thr rerldual char Chen, H. d al., Huazhong Ligong Daxuc Xuebao, 1994, 22, (3), 47-51. (In Chinese) Reports on a study of the evolving mechanism of volatile materials during combustion of Heshan (China) coal and compares the results &om pyrolysis of the same coal in an inert atmosphere. The mechanisms were different. Experiments were carried out in a drop tube. furnace and the reactivity of the residual semicoke was calculated. Effect of gravlty on the structure of an unatordy %m1703 spray dlffuslon flame Park, T. W. and Agganval, S. K. Combustion & Flame, Dec. 1994,99, (31. . ,, 767-774 774. The authors present time-dependent axisymmctric numerical simulation of an unsteady n-heptanc spray flame, and examine the effect of gravity on the flame structure. The effect of hydro en and propane rddltlon on the %/Oi 704 operatlon of a natuml gao-fire8 pul8ed comburtor JE;~$. R. and Lcng, J. Combustion & Flame, Nov. 1994, 99, (2), A coAercially available nonpremixed pulsed combustion room heater designed to bum natural gas has been used to study the effect of gas composition on the operational characteristics of the combustor. Three parameters have been monitored as fuel flowrates and gas composition were varied, viz, the amplitude of the pressure oscillatioiis, the operating frequency and the phase difference between the pressure and heat release oscillations. When burning methane only, an increase in fuel flowrate caused a decrease in the phase difference which led to an increase. in chamber pressure. This is attributed to an increase in the ignition delay time as the fuel flowrate increases. Addition of hydrogen, however, caused a sharp dropin pressure, and increases in the operating frequency and in the phase difference. %iOl7% Effect of the occurmnce and comporltlon of rlllcatr and alumlnorlllcate compound. on aah formatlon In pllotscale combustion of pulverlred coal and coal-water 8lurry furlr Miller, S. F. and Schobert, H. H. Energy& Fuels, Nov.-De.. 1994,8, (6), 1197-1207. Beulah (North Dakota) lignite and Elk Creek (west Virginia) high-volatile A bituminous coal were burned in both pulverized coal and coal-water slurry fuel forms to study the effct of the modes of occurrence and composition of aluminosilicates and silicates on the particle size distriiution and composition of ash. The dominant mechanisin for ash formation in the Beulah pulverized coal was fragmentation of mineral particles, such as quartz and pyrite, during combustion. By contrast, the main mechanism for determining the Beulah CWSF ash particle sixe distribution was coalescence and agglomeration of inherent aluminosilicates and silicates during combustion. _-----__ -Effect of the occurmnce and modea of Incorpora%/OI 7% tlon of alkallr, alkaline earth element& and rulfur on arh formatlon In pllot-ocals combuatlon of Beulrh pulverlzad coal and coal-water rlurrv fuel M-IY&ri&? and &hobert, H. H. Energy & Fue4 Nov.-Dec. 1994,8, (6),
.
Bculah(I&h Dakota)lignite was fired in both pulverized and coal-water slurry form to study the effed of fuel form and rank on ash formation mccsses. The fuels were burned in a down-fired pilot-scale combustor at 16 MJ/h. In both the Beulah fuels, organically bound sodium was important in the formation of micrometer and submicrometer sodium sulphate particles and coatings on larger silicate and aluminosilicate particles. The resence of sulphates indicates the importance of sulplmr fixation by alkaI&e elements during combustion. Organically bound calcium is hi@ly reactive within the char particle, participating in the formation of mtxed aluminosilicates during char burnout; calcium is not associated with sulphur and does not appear to react outside of the char particle. Effect8 of unconverted pulverhed coal on the %I01 707 dogma d gnphltlzatlon of coke aZheg) et aL, Chongqing Daxue Xuebao, 1994, 17, (3), 112-116. (In
Ensrg efflclent hl h trmperatum rppllcatlon of %I01 7% crramlcr through tK??beat pmct& e progmmmo Ahmad, J. Proc. 2nd Inr. Con& Ceramics in Institute of Enerw. 18 Dewnshlre St., London WIN
The apci de&&es the aims of the Best prncticc programme and the colla go rative wrok of the Department of Envtronment s Energy Efficiency Office and ETSU, in gathermg and disseminating information on energy efficiency projects. The latter part of the paper looks at recent advances in the application of ceramics, for the develo ment of energy efficient burner technologies which have been supported gy the EEO.
Combustion (burners, wmbustion
systems)
%iOW%
Creeping flame spread: Some now reoulte and Intorpretatlon for materlrl flammablllty ohrrrctorizmtlon C&&ysd Deli&a&s, M. A. Combustion & Flame, Dec. 1994,99, k important component for material flammability is the propnsi t&of flames to spread in horixontal or downward orientation, a situation w ch is usually called creeping or lateral 5ame spread. Interpretation of test methods for creepin flame spread is difficult because it involves heat transfer at the time 0f the flame, aucnching of the flame, the formation of a triole-oremixed-d flame. & well &solid ovrolv&s kinetics. Seoaratioit or these effects theoretic& numerically or ‘e;pe;imentally is @tired for deducing relevant flammability properties. New results presented in thii paper on this subject are related to a modification of the initial formulation of the creeping flame spread problems. Demonstmtlon of mlcronlzed coal roburnlng for %I01 607 NO, control on a 176 MW unlt Butler, T. F. et al., Prepr. Pap.-Am. Chem. Sot., Div. Fuel Chem., 1994, 39, (2), 365374. Reports that the Tennessee Valley Authority has been selected for the US Department of Energy’s Clean Coal Technology IV rogram to demonstrate micronized coal reburn technology for control of K 0 emissions on a 175 MW, wall-fd steam generator at its Shawnee Fossil Plant. The paper includes plans for a full-scale demonstration unit at the Shawnee plant. 05/01%8 Detallrd klnetlc modeling of prrmlxrd benzene flame8 L&dstlge;lt, R. P. and Sk&s, G. Combusfion % Flame, Dec. 1994,99, (3), -
.
unccrtainities on the main reaction path is small to moderate. Development and demonotratlon of 2D-UF for %I01690 otudlea of mixture orroaratlon In 81 malnro . . Neij, H. et al., Combusrion % Flame, Nov. 1994, 99, (2), 449-457. Describes how laser-induced fluorescence (LIF) has been developed for visualization of fuel distribution fields in an operating spark-@ion engine. Since the standard research fuel &octane. does not yield a useful LIF signal a fluorescent additive was used. None of the commonly used seeds were found ad uate. A seed not commonly used in this context, 3pentanonc, GH &COC, “t4, was chosen due to favourable vaporization characteristics and uomsccnt properties. Results from pre aratory investigations in the actual engine environment are presented an B related laboratory data are discussed. %I01 7% Dew10 ment of carbon monoxide ?? enoom for the efflclent control of Bumem qe+gan, M. D: et aL, Proc. 2nil Int. Co$ Ceramics ln Energy no?22y Instuute of Energy, 18 Devon&we St., London WIN 2.4 . Discusses why then is a continuing need to product low cost, high sensitivity, gas specific sensors. One major requirement is for an efficient low cost carbon monoxide specific sensor for use in burner controls to ensure optimum efficiency of combustion. A method of fabricating semiconducting SnO&O, sensors using the sol-gel route has been developed and has been shown to have a number of advantages. The method of preparation accurately controls the chemistry of the sol and ensures mixing at the moleculai levels. The direct detiition of the sol onto a se-nsor subitrate to form a gel results in exccllerit adhesion and thickness control. Precise control of the surface area, porosity and particle size of the sensor films can be achieved by subsequent sintering of the gel to product a mixed metal oxide. %I01 701 The development of Inotabllltlw In lamlnar oxplo8lon flame0 Bradle , D. and Harper, C. M. Combustion &Flame, Dec. 1994,99, (3), 562-S&.
Theoretical and experimental studies are presented of the growth of flame instabilities arising from peturbations of spherically pro agating laminar flames in an explosion bomb. High-speed cme schlieren p1 otographs show flame instability to be associated with the propagation of cracks, originating from disturbances due to flame movement over the spark electrodes, along the flame surface.
11s
Fuel and Energy Abstract8 March 1995
%I01 702 Devolatlllzatlon of pulverized coal durlng combustlon and reactivity of thr rerldual char Chen, H. d al., Huazhong Ligong Daxuc Xuebao, 1994, 22, (3), 47-51. (In Chinese) Reports on a study of the evolving mechanism of volatile materials during combustion of Heshan (China) coal and compares the results &om pyrolysis of the same coal in an inert atmosphere. The mechanisms were different. Experiments were carried out in a drop tube. furnace and the reactivity of the residual semicoke was calculated. Effect of gravlty on the structure of an unatordy %m1703 spray dlffuslon flame Park, T. W. and Agganval, S. K. Combustion & Flame, Dec. 1994,99, (31. . ,, 767-774 774. The authors present time-dependent axisymmctric numerical simulation of an unsteady n-heptanc spray flame, and examine the effect of gravity on the flame structure. The effect of hydro en and propane rddltlon on the %/Oi 704 operatlon of a natuml gao-fire8 pul8ed comburtor JE;~$. R. and Lcng, J. Combustion & Flame, Nov. 1994, 99, (2), A coAercially available nonpremixed pulsed combustion room heater designed to bum natural gas has been used to study the effect of gas composition on the operational characteristics of the combustor. Three parameters have been monitored as fuel flowrates and gas composition were varied, viz, the amplitude of the pressure oscillatioiis, the operating frequency and the phase difference between the pressure and heat release oscillations. When burning methane only, an increase in fuel flowrate caused a decrease in the phase difference which led to an increase. in chamber pressure. This is attributed to an increase in the ignition delay time as the fuel flowrate increases. Addition of hydrogen, however, caused a sharp dropin pressure, and increases in the operating frequency and in the phase difference. %iOl7% Effect of the occurmnce and comporltlon of rlllcatr and alumlnorlllcate compound. on aah formatlon In pllotscale combustion of pulverlred coal and coal-water 8lurry furlr Miller, S. F. and Schobert, H. H. Energy& Fuels, Nov.-De.. 1994,8, (6), 1197-1207. Beulah (North Dakota) lignite and Elk Creek (west Virginia) high-volatile A bituminous coal were burned in both pulverized coal and coal-water slurry fuel forms to study the effct of the modes of occurrence and composition of aluminosilicates and silicates on the particle size distriiution and composition of ash. The dominant mechanisin for ash formation in the Beulah pulverized coal was fragmentation of mineral particles, such as quartz and pyrite, during combustion. By contrast, the main mechanism for determining the Beulah CWSF ash particle sixe distribution was coalescence and agglomeration of inherent aluminosilicates and silicates during combustion. _-----__ -Effect of the occurmnce and modea of Incorpora%/OI 7% tlon of alkallr, alkaline earth element& and rulfur on arh formatlon In pllot-ocals combuatlon of Beulrh pulverlzad coal and coal-water rlurrv fuel M-IY&ri&? and &hobert, H. H. Energy & Fue4 Nov.-Dec. 1994,8, (6),
.
Bculah(I&h Dakota)lignite was fired in both pulverized and coal-water slurry form to study the effed of fuel form and rank on ash formation mccsses. The fuels were burned in a down-fired pilot-scale combustor at 16 MJ/h. In both the Beulah fuels, organically bound sodium was important in the formation of micrometer and submicrometer sodium sulphate particles and coatings on larger silicate and aluminosilicate particles. The resence of sulphates indicates the importance of sulplmr fixation by alkaI&e elements during combustion. Organically bound calcium is hi@ly reactive within the char particle, participating in the formation of mtxed aluminosilicates during char burnout; calcium is not associated with sulphur and does not appear to react outside of the char particle. Effect8 of unconverted pulverhed coal on the %I01 707 dogma d gnphltlzatlon of coke aZheg) et aL, Chongqing Daxue Xuebao, 1994, 17, (3), 112-116. (In
Ensrg efflclent hl h trmperatum rppllcatlon of %I01 7% crramlcr through tK??beat pmct& e progmmmo Ahmad, J. Proc. 2nd Inr. Con& Ceramics in Institute of Enerw. 18 Dewnshlre St., London WIN
The apci de&&es the aims of the Best prncticc programme and the colla go rative wrok of the Department of Envtronment s Energy Efficiency Office and ETSU, in gathermg and disseminating information on energy efficiency projects. The latter part of the paper looks at recent advances in the application of ceramics, for the develo ment of energy efficient burner technologies which have been supported gy the EEO.