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Concen住ation[vol%]
Concentration[vol%]
Step(b) Fig.6(con't)
Step(a)
Fig.6 DW-holograms(top)andverticalconcentrationprofiles(bo仕om)
inthepulsatingsteps(a，b，andd1)
shownin.Figure4(α)，wherethefiamespreadrateis1.2cmJs， showsnoliquidconvectiveandsurfacetensionfiowandthereare sma)1flamesinducedairfiowthatwasc1earvisualy，butnotc1ears in也eSTTphotograph.Figure4(b)，wherethefi釦 lespreadrateis 2.0cmls，showsbothasmal lcirculation5m minlengthand2m m in height and its circulation center is located ap proximately 5 m m from血efiameleadingedge)andsurface-tensionfiow.Figure4(c)， wherethe宜amespreadrateis4.6cmJs，showsafulydeveloped circu1ationinthegasandliquidphases.Thecenterof出egas- phasecirculation(15.7rnminlength(4.1m minheight)islocated 8.5m mups仕eamfromthefiameleadingedge.Figure4(dj) shows thefiame-spreadrateωbe14.1crnJs.Note出atboththeliquidand gas-phasecirculationdecreasetheirdiameter.
DWHIResults. High-spedvideoandIRphotographstak:en 企omabovethe仕ayrevea1ed血atforthe0.5-cmwideなay，boththe surface-temperaturedistributionandtheshapeofthefi叩 le企ont 紅 ep紅 abolicinna回re，whileforthe1，2and4-cmwide仕ays， smaltwinvorticesaregeneratedonthefuelsurface(Rosand Miler，196)sugesting出atthecharl!cterofthefiowprofileofthe gas-phasefiowprofileischanged在omtwodimensionsto出re dimensionsbyincreasing由ewidthof血etray.Arecentstudyby Garcia-Y bar ra (Garcia-Y bar ra et al.， 19 96) also sug gested the 也 re e-dimensional nature qf 也 e gas-ph.ase fiow induced by a spreadingfiameoveralcoho.lToincreasetheacuracyofthe DWHI，thethre-dimensiona1efectnedstobeminirnized.We tokaseriesofvideopicturesandD Whologramssimultaneously andidentifiedthebesttwo-dimensionalfiameshapewith80per- centacuracy.
Weuseda40-mmwidetrayandconductedfiamespreadtests 418IVo.l121，MAY1999
overn-propanolatits泊itialtemperature100C sincethespatial resolutionofourDWHIisbeterforthewidertraywidth(Narurni， etal.).However，w号confumed出atthefiame-spreadrateoverthe
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Fig.6(top).Figure6(botom)shows出at也epropanolconcen- 仕ation出 theareabelowthesolidlinesatisfies也.ele自 白 むnma- bilitylirnit;thus，thefi釘 neisabletospreadthroughaprernixed prop臼 ol-airmixture(GlassmanandDryer，1981).
SummaryandConclusions
1 WedevelopedauniqueLSPTsystemformeasuringve- locityprofilesfor回 nsientfiowinave可 lirnitedspace叩 d confirmedtheexistenceofagas-phasecirculationinthepulsating spreadregiontoge白erwithaliquid-phaseconvection，bothof whichwerepredictedbyotherresearchers.
2 Weobtainedaseriesoftwo-dimensionalD Wholbgrams and confirmed 白 at the fiame spread oc curs only when 血 e prop担 01-白elconcen凶 tionover出efuelsurfClceishigher白 血 血e lean 自 ammabi1ity lirni.t Thus the ac curacy of the D W I丑 ne eds to beimprovedifitistobeapliedto由re-dimensiona1problems.' Toovercomethislirnitation，weareinprogresinthedevelopment ofanadvanced吐re-dimensiona1DWHIsystem，whichisbeyond 出~ scopeofthispaper.
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rnmwide凶 ysisapproximate~y thesameand thefiamestructureoverbothtraysisverysimilarinnature.Figure 6showsD Whologramsandverticalprofilesofpropanolfuel concen凶 tionforsteps(a，b，anddj). 百lelean自白nmab出句， lirnit forn-prop佃 01位 (2.2mol~ percent)isshownasasolid胎lein
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