基于混合分数模型的层流扩散火焰碳黑生成模拟
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摘要
烟点高度是表征燃料碳黑生成能力的重要参数,基于烟点高度的碳黑生成模型能够与混合分数燃烧模型耦合使用,使得计算成本降低;该模型仅包含一个与燃料相关的模型参数(烟点高度),使其容易扩展至其它燃料。因此基于烟点高度的碳黑生成模型是复杂火灾场景模拟的理想碳黑模型之一。但是,该模型还需要相应的适用于混合分数的碳黑氧化模型,因此本文通过假设氧气浓度在化学当量比附近的分布,对碳黑表面氧化模型中氧气摩尔浓度的计算进行了一定的修正。运用修正后的碳黑模型,结合混合分数燃烧模型对三种不同种类的层流扩散火焰进行数值模拟,结果表明,三种层流火焰的碳黑体积分数计算值和实验测量值基本吻合,表明碳黑氧化模型中氧气摩尔浓度的修正是基本合理的。
The laminar smoke point height is the characterization of sooting propensity of fuels. And the soot formation model based on laminar smoke point height can be combined with the mixture fraction combustion model, which requires relatively lower computational cost. Besides, this soot model has only one model parameter related to fuel type(the smoke point height) which makes it easier to apply to other fuels. Hence, the global soot formation model based on laminar smoke point is quite appropriate for fires simulation. However, the corresponding soot oxidation model, which is applicable for the mixture fraction, is required. Therefore, the oxygen molar fraction calculation in the surface-area dependent soot oxidation model was modified based on the distribution assumption of oxygen concentration near the stoichiometric mixture fraction. Combined with mixture fraction,the modified soot model was validated in three laminar diffusion flames, and good agreement was achieved between the prediction of soot volume fraction and the experimental data, which proves the validity of the modification of oxygen molar concentration.
The laminar smoke point height is the characterization of sooting propensity of fuels. And the soot formation model based on laminar smoke point height can be combined with the mixture fraction combustion model, which requires relatively lower computational cost. Besides, this soot model has only one model parameter related to fuel type(the smoke point height) which makes it easier to apply to other fuels. Hence, the global soot formation model based on laminar smoke point is quite appropriate for fires simulation. However, the corresponding soot oxidation model, which is applicable for the mixture fraction, is required. Therefore, the oxygen molar fraction calculation in the surface-area dependent soot oxidation model was modified based on the distribution assumption of oxygen concentration near the stoichiometric mixture fraction. Combined with mixture fraction,the modified soot model was validated in three laminar diffusion flames, and good agreement was achieved between the prediction of soot volume fraction and the experimental data, which proves the validity of the modification of oxygen molar concentration.
引文
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[2]Lee Y P,Delichatsios M A,Silcock G W H.Heat Fluxes and Flame Heights in Facades From Fires in Enclosures of Varying Geometry[J].Proceedings of the Combustion Institute,2007,31(2):2521-2528
[3]Pierce J B M,Moss J B.Smoke Production.Radiation Heat Transfer and Fire Growth in a Liquid-fuelled Compartment Fire[J].Fire Safety Journal,2007,42(4):310-320
[4]Wu J S,Krishnan S S,Faeth G M.Refractive Indices at Visible Wavelengths of Soot Emitted From Buoyant Turbulent Diffusion Flames[J].Journal of Heat Transfer,1997,119(2):230-237
[5]Koylii U O,Faeth G M.Carbon Monoxide and Soot Emissions From Liquid-fueled Buoyant Turbulent Diffusion Flames[J].Combustion and Flame,1991,87(1):61-76
[6]Skaggs R R,Miller J H.A Study of Carbon Monoxide in a Series of Laminar Ethylene/air Diffusion Flames Using Tunable Diode Laser Absorption Spectroscopy[J].Combustion and Flame,1995,100(3):430-439
[7]Kennedy I M.Models of soot Formation and Oxidation[J].Progress in Energy and Combustion Science,1997(23),95-132
[8]Lautenberger C W,Ris J L D,Dembsey N A,et al.A Simplified Model for Soot Formation and Oxidation in CFD Simulation of Non-premixed Hydrocarbon Flames[J].Fire Safety Journal,2005,40(2):141-176
[9]Delichatsios M.A Phenomenological Model for Smokepoint and Soot Formation in Laminar Flames[J].Com-bustion Science and Technology.1994,100(1-6):283-298
[10]Beji T,Zhang J P,Yao W,et al.A Novel Soot Model for Fires:Validation in a Laminar Non-premixed Flame[J].Combustion and Flame,2011,158(2):281-290
[11]Yao W,Zhang J,Nadjai A.et al.A Global Soot Model Developed for Fires:Validation in Laminar Flames and Application in Turbulent Pool Fires[J].Fire Safety Journal,2011,46(7):371-387
[12]Li L,Sunderland P B.An Improved Method of Smoke Point Normalization[J].Combustion Science and Technology,2012,184(6):829-841
[13]Lee K B,Thring M W,Beer J M.On the Rate of Combustion of Soot in a Laminar Soot Flame[J].Combustion and Flame,1962,6(62):137-145
[14]Leung K M,Lindstedt R P,Jones W P.A Simplified Reaction Mechanism for Soot Formation in Nonpremixed Flames[J].Combustion and Flame,1991,87(3/4):289-305
[15]McGrattan K,Hostikka S,and Floyd J,et al.Fire Dynamics Simulator(Version 5)Technical Reference Guide[M].Washington:National Institute of Standards and Technology,2009
[16]Kent J H,Honnery D R.A Soot Formation Rate Map for a Laminar Ethylene Diffusion Flame[J].Combustion and Flame,1990,79(3/4):287-298
[17]Smyth K C,Diffusion Flame Measurements of Species Concentrations,Soot Concentrations,Temperature,and Velocity[J/OL].[2017-06-17].http://www.fire.nist.gov/fire/flamedata/
[2]Lee Y P,Delichatsios M A,Silcock G W H.Heat Fluxes and Flame Heights in Facades From Fires in Enclosures of Varying Geometry[J].Proceedings of the Combustion Institute,2007,31(2):2521-2528
[3]Pierce J B M,Moss J B.Smoke Production.Radiation Heat Transfer and Fire Growth in a Liquid-fuelled Compartment Fire[J].Fire Safety Journal,2007,42(4):310-320
[4]Wu J S,Krishnan S S,Faeth G M.Refractive Indices at Visible Wavelengths of Soot Emitted From Buoyant Turbulent Diffusion Flames[J].Journal of Heat Transfer,1997,119(2):230-237
[5]Koylii U O,Faeth G M.Carbon Monoxide and Soot Emissions From Liquid-fueled Buoyant Turbulent Diffusion Flames[J].Combustion and Flame,1991,87(1):61-76
[6]Skaggs R R,Miller J H.A Study of Carbon Monoxide in a Series of Laminar Ethylene/air Diffusion Flames Using Tunable Diode Laser Absorption Spectroscopy[J].Combustion and Flame,1995,100(3):430-439
[7]Kennedy I M.Models of soot Formation and Oxidation[J].Progress in Energy and Combustion Science,1997(23),95-132
[8]Lautenberger C W,Ris J L D,Dembsey N A,et al.A Simplified Model for Soot Formation and Oxidation in CFD Simulation of Non-premixed Hydrocarbon Flames[J].Fire Safety Journal,2005,40(2):141-176
[9]Delichatsios M.A Phenomenological Model for Smokepoint and Soot Formation in Laminar Flames[J].Com-bustion Science and Technology.1994,100(1-6):283-298
[10]Beji T,Zhang J P,Yao W,et al.A Novel Soot Model for Fires:Validation in a Laminar Non-premixed Flame[J].Combustion and Flame,2011,158(2):281-290
[11]Yao W,Zhang J,Nadjai A.et al.A Global Soot Model Developed for Fires:Validation in Laminar Flames and Application in Turbulent Pool Fires[J].Fire Safety Journal,2011,46(7):371-387
[12]Li L,Sunderland P B.An Improved Method of Smoke Point Normalization[J].Combustion Science and Technology,2012,184(6):829-841
[13]Lee K B,Thring M W,Beer J M.On the Rate of Combustion of Soot in a Laminar Soot Flame[J].Combustion and Flame,1962,6(62):137-145
[14]Leung K M,Lindstedt R P,Jones W P.A Simplified Reaction Mechanism for Soot Formation in Nonpremixed Flames[J].Combustion and Flame,1991,87(3/4):289-305
[15]McGrattan K,Hostikka S,and Floyd J,et al.Fire Dynamics Simulator(Version 5)Technical Reference Guide[M].Washington:National Institute of Standards and Technology,2009
[16]Kent J H,Honnery D R.A Soot Formation Rate Map for a Laminar Ethylene Diffusion Flame[J].Combustion and Flame,1990,79(3/4):287-298
[17]Smyth K C,Diffusion Flame Measurements of Species Concentrations,Soot Concentrations,Temperature,and Velocity[J/OL].[2017-06-17].http://www.fire.nist.gov/fire/flamedata/