book-chapt7——Turbulent Combustion Modeling.pdf

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1、Chapter7TurbulentCombustionModeling7.1RegimesofturbulentcombustionNumerousphysicalphenomenaareinvolvedinturbulent(premixedandnon-premixed)combustionanddifferenthavebeendevelopedtocapturetheminthemodelingdependingonthecombustionregimes.Thepremixedcombustio

2、nregimesareidentiedaccordingtokeypa-rameterdiagramproposedin[32].Inthecaseofhighintensityturbulence,thedispersionofFigure7.1:Diagramofturbulentcombustionregimes.uidelementsbecomessufcientlylargetocausedifferentportionsofwrinkledamesheetstoapproacheach

3、other.Laminaramepropagationmaycausethereactionfrontstointersectandcutoffpocketsofunburntgas.Theamefrontreconnectioncanbeinterpretedasaturbulentamepropagation,andformationofanarchipelagoofunburnedgaspocketssurroundedbycombustionproductscouldbeamainconse

4、quencesofchemistry-turbulenceinteraction.Thetransitionfromoneregimeofturbulentcombustiontoanotherisresponsibletoameaccel-erationphenomenonbecauseoftheincreaseinamesurfaceareaoftheameletsinsidetheturbulentstructure.Forsufcientlyhighlevelofturbulence,th

5、eameletstructuremaybedestroyedandreplacedbya”distributed”reactionzone.Thus,undertheseconditions,turbu-lenceexertsthemaininuenceonthemotionofthereactionzone,butchemicalkineticsandmoleculartransporteffectsarenevernegligible.387.2Multi-componentgasphaseche

6、mistryTheaveragedgasphaseequationsforachemicallyreactingmixtureofidealgaseswithembeddedcondensedliquiddropletscanbewrittenas@Yktcs+r[Yk~urYk]=_k+_k;k=1;:::;Ns(7.1)@tSckwhere_ckisthechemicalsourcetermdenedbycombustionmechanism.TheNrelementarychemic

7、alreactionsinvolvingNsspeciesXsarerepresentedintheformNkrXsfXNs0X*)00X;r=1;N:(7.2)srssrsrs=1krs=1bHereXsstandsforonemoleofs-species,and0srand00srarestoichiometriccoefcientsforther-threaction.Formalkineticsrequires0sr
00sr=0,i.e.species”s”isformedon

8、lyfromtheotherspecies.Thechemicalmassproductiontermsinthemassbalanceeqs(4)areXNr_=M(000)!_;(7.3)sssrsrrr=1andthechemicalheatreleasetermintheinternalenergyequationisgivenbyXNrQ_c=qr!_r;(7.4)r=1whereqristheheatofr