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「 -三Iこ二三合さでご三三ア'竺--土:七百七三宝 二三三コl Simulation of the Heat Transfer Mechanism ofFlame Spread over Liquids
G.Tashtoush¥A.Narumi，A.Ito，K.SaitoandC.CrenlerS
Combustion，Fireresearch& Leanmanufacturing(CFL)Laborat01ア DepartmentofMechanicalEngineering UniversityofKentucky
Lexington，K Y40506
Flamespreadoverliquidsisofcurentinterestbecauseofitsimportancetofresafetyandthecuriosityofcombustion researchersstudyingthe加 damentalheattransfermechanismofthisphenomenon.Themajorheat-仕ansferproces betwentheflame'sleadingedgeandtheliquidisahighlytransientphenomenoninvolvingbothliquidandgasphases. Theseinteractwitheachotherthroughtheexchangesofmomentum，heat，andmas. Theliquidconvectionaheadofthe flameisunique，complexandplaysanimportantroleinthespreadingproces. I~ ourpaststudieswefocusedon obtaining acurate and detai!ed'measurements offlow and temperature forboth liquid and gas phases and fuel concentrationsgeneratedbytheflame. Toenhanceourunderstandingoftheheat-transfermechanism，thispaperfocuses onsimulatingtheliquid-convectionflowexperimentalybysudenlymixingtwoiIquidseachhavingdiferents町 face- tensionproperties. Thefrstliquidsimulatedtheheatedliquidbeneaththeflameathightempera旬reandlowsurface tension.Thesecondonesimulatedtheunbumedups仕切mliquidatroomtempera加reandhighersurfacetension. Both liquidsweremixedsudenlythroughthesurfaceonly. Thevelocityprofileswere visualizedexperim~ntally usingthe 2-DLaser-ShetParticle-Tracking(LSPT)technique.Thepreliminaryresultsshowedthat，ifwecanchosesucesfuly thetwoliquidsthatmatchthepropertiesoftheliquidsundemeathandaheadoftheflame，agoodsimilaritybetwenthe velocityprofi1esofmixingoftwoliquidsandofthose合omrealflamespreadingexperimentcanbeobtained. Asaresult theliquidflowpa仕emsaheadofthef1amecanbesimulatedacuratelyinordertoaplythe3-Dholographicimaging techniquewhichislimitedbecauseofthedistortionofthereferencebeambytemperatureanddensitygradient，tobeter understandthemechanismofheattransferaheadoftheflame.
Introduction
The fundamentalheat-transfermechanisms offlame
spreadoverliquidswilbeourfocusinthisresearch. The spreadingphenomenonishighlytransientinvolvingboth liquidandgasphasesthatinteractwitheachotherthrough theexchangesofmomentum，heat，andmas. Thecritical transportofthosequantitiesocuringingasandliquid phases within several mil limeters 丘 o m its interface and withinafewcentimeters丘omtheflame'sleadingedge. Intheflamespreadoverliquids，liquidconvectionahead of a flame is unique and plays an important role in the spreadingproces. Becauseoftheape町 anceoftheliquid convection，the flame spreading proces s is complex in comparisontotheflamespreadoversolids [13]. The convectivemotionoftheliquidphaseandthesensitivity of liquid properties to contamination，increase the complexity ofthe phenomenon. In our past studies [ 1 ム 3 人 5 ] w e f o c u s e d o n o b t a i n i n g a c c u r a t e a n d d e t a i! e d measurementsofflow(bothliquidandgas)，tempera旬re (both liquid and gas) and gaseous fuel concentrations generated by the spreading flame. Researchers have apliedopticalmeasurementtechniquestorevealf1ow， tempera加 reandfuelconcentrationstructures[4，6，7].
Flamespreadingoveraliquid fuelattemperature below its flash point involves surface tension driven flows. Itdependsonthefact.thatsurfacetensiondecreases asthetempera伽 reincreases;thiswilcausehotfueltobe
-expeledfrombeneaththeflame，therebydisplacingthe colersurfacelayer.
To date，lit tle work has be en done to simulate the flame-spread-heat-transfermechanism. ThisresearchwilI sektoimproveourunderstandingoftheheat凶 nsfer mechanismoftheflamespreadoverliquids. Thispap町 focuses on simulating the liquid convection experimentaly by sudenly mixing two liquids (1- butanolorl-propanolaIcohol)withiso-octaneusing a smalaboratory-scaleopenpoo.1Suchlaboratorystudies wil provideuseful informatiqn for aproximating the characteristicsoflargerscalefresandwil beauseful educationalto.1
ExperimentalApparatusandProcedure AschematiciIlustrationoftheexperimentalapara加 s
and印 刷pisshowninfigure1. Fueltraysof5and10 m mwidex20m mdepx300m mlongwereused;the twolongsidesofthefueltraysweremadeofPyrexglas
ホCorespondingAuthor:Tel(606)257-936/Fax(606)257-304，Email:gmtashOO@pop.uky.edu. Procedingofthe198TechnicalMetingoftheCentralStatesSectionoftheCombustionInstitute
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