Modeling turbulent transport effects on kernel formation and ?ame propagation in an ignition process

作者:LinghanKONG;ZhuyinREN;LingyunHOU 刊名:中国航空学报:英文版 上传者:常玉芬

【摘要】Reliablerelightingiscrucialforadvancedlow-emissionaero-enginecombustors.Forforcedignitionunderhighly-turbulentconditions;eddiesofsizesbeingsmallerthantheflamekernelcanaffectitsformationthroughpenetratingandmodifyingthekernelstructure.Inthisstudy;aone-dimensionalmodelforsmall-scaleturbulenceonkernelformationisdevelopedthroughtheincorporationofturbulence-induceddiffusioningoverningequations.Withgivenflowconditions;thespatialandtime-dependentturbulentdiffusivityismodeledusingtheideaofresidualeddyviscosity.One-dimensionalsphericalflamesofpremixedpre-vaporizedn-dodecane/airmixturesunderhigh-altitudeconditionsaresimulatedtoinvestigatetheeffectsofturbulence.Itisrevealedthattherangeoftheequivalenceratioforsuccessfulturbulentignitionismuchnarrowerthanthatforlaminarignition.Therangedecreaseswithanincreasedturbulentintensity;andthiseffectismorepronouncedforalowsparkenergy.Inaddition;turbulenttransporthasmorepronouncedeffectsonrichmixtures.Ananalysisonenergybudgetandspeciesprofilesshowsthatturbulence-induceddiffusionenhancestheheatlossattheverybeginningofthekernelformationprocessthatcouldleadtoignitionfailure.Aftertheflamekernelisestablished;turbulenttransportbroadenstheflamefront;enhancestheheatreleaserate;andthereafterincreasestheflamepropagationspeed.

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