How fast can we burn2.0.docx

Howfastcanweburn,2.0SimoneHochgrebUniversityofCambridge.TrunipingtonSt,CambridgeCB2IPZ,UKReceived31January2023:accepted21June2023Avai1ab1eon1inexxxAbstractWereviewthes1ateoftheartinmeasurementsandsimu1ationsofthebehaviorofpremixed1aminarandturbu1entf1ames,subjecttodifferentia1diffusion,stretchandcurvature.Thefirstpartofthepaperreviewsthebehaviorofpremixed1aminarf1amessubjecttof1owstretch,andhowitaffectstheaccuracyofmeasurementsofunstrained1aminarf1amespeedsinstretchedandspherica11ypropagatingf1ames.Wethenexaminehowf1owfie1dstretchanddifferentia1diffusioninteractwithf1amepropagation,promotingorsuppressingtheonsetofthermodiffusiveinstabi1ities.Second1y,wesurveythemethodo1ogyforandresu1tsofmeasurementsofturbu1entf1amespeedsinthe1ightoftheory,andidentifyissuesofconsistencyinthedefinitionofmeanf1amespeeds,andtheircorrespondingmeanareas.Dataformethaneatasing1eoperatingconditionarecomparedforarangeofturbu1entconditions,showing(hatfundamenta1issuesthathaveyettobereso1vedforBunsenandspherica11ypropagatingames.Fina11y,weconsiderhowthe1aminarf1amesca1eresponseoff1amestof1owperturbationsintectingwithdifferentia1diffusion1eadstoverydifferentoutcomestotheovera11sensitivityoftheburningratetoturbu1ence,accordingtonumerica1simu1ations(DNS).Thepaperconc1udeswithopportunitiesforfuturemeasurementsandmode1deve1opment,inc1udingtheperennia1recommendationforrobustarchiva1databasesofexperimenta1andDNSresu1tsforfuturetestingofmode1s.©2023TheAuthor.Pub1ishedbyE1sevierInc.onbeha1fofTheCombustionInstitute.Thisisanopenaccessartic1eundertheCCBY1icense(hup:CreaIiVeCOmmOnS.orgIiCenSCSZby/4.0/)Keywords:Premixedf1ames:Turbu1entf1ames;1ewisnumbers;MeasurementE-nuii1Midresses:sinione.hochgrebeng.cam.ac.uk,sh372cam.ac.ukhttps:/doi.org/10.1016/j.proci.2023.06.0291540-7489>2023TheAuthor.Pub1ishedbyE1sevierInc.onbeha1fofTheCombustionInstitute.Thisisanopenaccessartic1eundertheCCBY1icense(http,rcaiivecommons.org1icensesby4.0)1.IntroductionIn1992,DerekBrad1eygavea1ectureattheInternationa1Symposium,entit1ed,HowFastCanWeBum,(1,inwhichheattemptedtosummarizewhatwasthenknownaboutthero1eofturbu1enceontheburningrateofmixtures,andhowmo1ecu-IarditTusionp1ayedaro1einthemicrostructureofturbu1entf1ames.Thepresentreviewwasinspiredbythesameneedtounderstandfromthebottomupbothhowf1owfie1ds,reactionanddiffusioninteracttoaffect1aminarf1ames,andhowtheseef-fectsgoontogeneratesomewhatpecu1iarbehaviorobservedinturbu1entf1ames.Thetaskofmeasurementandva1idationofmode1sforavarietyofmixtureswithdifferentthermo-diffusivepropertieshasbecomeparticu1ar1yimportantaswearetransition-ingfromcarbon-basedfue1s,forwhichmo1ecu1ardiffusivityanddifferentreactivityregimesmaybequitedifferentfromusua1hydrocarbons.Theevo1utionofpremixed1aminarandIurbu-1entpremixedandstratifiedcombustionisre1evanttoa1argec1assofsituationsconvertingchemica1totherma1energy.Turbu1entf1owsforcombustiondevicesaregenera11ydesignedtomaximizeentrain-mentandpromotef1amestabi1ization,producinghighratesofburningperunitvo1ume.1argetur-bu1entsca1esoriginatingfromtheincominggeom-etrydirectthef1ow,forexamp1ebygeneratingswir1,shearortumb1e,whichcontro1entrainmentandof-tencoup1ewithacousticstogeneratecombustioninstabi1ities.Hea1re1easetakesp1acea1thef1amesca1es,governedbytherateofmixingandreaction,whichareingenera1enhancedbyturbu1entf1uctuations.Theovera11reactionra1eperunitvo1-umeisu1timate1ygovernedbytheextenttowhichturbu1entve1ocityf1uctuationsincreasemixingofproductsandreactantsinsuchawayastoenhancetherateofreaction.Ve1ocityandsca1arf1uctua-tionsarecoup1edtotheprocessofcombustion,de-mandingpredictionsthatmustspanawiderangeofspatia1andtimesca1esforaccuratepredictions,asdiscussedinbks(2-41andreviews5-91overthepastdecade.Experimentsandmode1storepresentthebehav-iorofpremixedf1ameshaveco-evo1vedthrough-outhistorj,sincethefirstexperimentsin1aminarf1amesbyMa11ardand1eChate1ierand1ewisandvonE1be110,111andtheear1iestexperimentsofDamkdh1erinturbu1entf1ames12.Theorigina1findingsandtheoriescontinuetoformtheback-boneofOurthinkingonthesubject,butincreasing1ysophisticatedmethodshavebecomeavai1ab1eintheformofoptica1diagnostics,theoretica1understanding.andsheercomputationa1powerfordetai1edsimu1ations,a11owingamuchc1oserexp1o-rationoftheunder1yingphysica1phenomena.Understandingofthebehaviorof1aminarf1ameshasadvancedtoaveryhigh1eve1offide1ityformixturesforwhichdetai1edandverifiedchem-ica1kineticmode1sexist.Directnumerica1Simu1a-tions(DNS)ofthesteadyandunsteadybehaviorof1amin<rf1amesabound113-16.However,nota11predictionshavebeenorcanbeexperimenta11yver-ifiedorverifiab1e.Insomecases,itisdifficu1ttoex-perimenta11yrecreateanidea1izedsimu1ationcon-dition.Moregenera11y,simu1ationsarere1ative1yin-expensivere1ative1yoexperiments,sotheformeraresignificant1ymoreabundant.Yetitisimportanttocontinuetotestmode1sagainstexperiments.Eventhoughdirectnumerica1simu1ationswithwe11estab1ishedchemica1kineticmode1saretrusted,itisnotuncommonthatprevious1yneg1ectedphenom-enaarefoundtobere1eva