资源描述：
《FLUENT中NOX模型.doc》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、17.1.1OverviewandLimitationsNOxemissionconsistsofmostlynitricoxide(NO).Lesssignificantarenitrogenoxide(NO2)andnitrousoxide(N2O).NOxisaprecursorforphotochemicalsmog,contributestoacidrain,andcausesozonedepletion.Thus,NOxisapollutant.TheFLUENTNOxmodelprovidesatooltounderstandthesourcesofNOxprodu
2、ctionandtoaidinthedesignofNOxcontrolmeasures.NOxModelinginFLUENTTheFLUENTNOxmodelprovidesthecapabilitytomodelthermal,prompt,andfuelNOxformationaswellasNOxconsumptionduetoreburningincombustionsystems.ItusesratemodelsdevelopedattheDepartmentofFuelandEnergy,TheUniversityofLeeds,Englandaswellasfr
3、omtheopenliterature.TopredictNOxemission,FLUENTsolvesatransportequationfornitricoxide(NO)concentration.WithfuelNOxsources,FLUENTsolvesanadditionaltransportequationforanintermediatespecies(HCNorNH3).TheNOxtransportequationsaresolvedbasedonagivenflowfieldandcombustionsolution.Inotherwords,NOxis
4、postprocessedfromacombustionsimulation.ItisthusevidentthatanaccuratecombustionsolutionbecomesaprerequisiteofNOxprediction.Forexample,thermalNOxproductiondoublesforevery90 Ktemperatureincreasewhentheflametemperatureisabout2200 K.Greatcaremustbeexercisedtoprovideaccuratethermophysicaldataandbou
5、ndaryconditioninputsforthecombustionmodel.Appropriateturbulence,chemistry,radiationandothersubmodelsmustbeapplied.Toberealistic,onecanonlyexpectresultstobeasaccurateastheinputdataandtheselectedphysicalmodels.Undermostcircumstances,NOxvariationtrendscanbeaccuratelypredictedbuttheNOxquantityits
6、elfcannotbepinpointed.AccuratepredictionofNOxparametrictrendscancutdownonthenumberoflaboratorytests,allowmoredesignvariationstobestudied,shortenthedesigncycle,andreduceproductdevelopmentcost.ThatistrulythepoweroftheFLUENTNOxmodeland,infact,thepowerofCFDingeneral.TheFormationofNOxinFlamesInlam
7、inarflames,andatthemolecularlevelwithinturbulentflames,theformationofNOxcanbeattributedtofourdistinctchemicalkineticprocesses:thermalNOxformation,promptNOxformation,fuelNOxformation,andreburning.ThermalNOxisformedbytheoxidationofatmosphericni
