Page 79 - konishipaper

Step(a)
Step (b)
Step(c)
Step(d，)
gasphaseandiIquidphase.Thecenterofthegl，lsphasecirculation (15.7mminlengthx4.1mminheight)islocated8.5mmupstream fromtheflameleadingedge.Figure4(d1)showstheflamespread ratetobe14.1cmJsandboththeliquidandg，asphasecirculations decreasedtheirdiameter.
DWHIResuIts HighspedvideoandIRphotographst<ycenfromabovethetray
revealedthatforthe0.5cmwidetray，both:thesurface-temperature distributionandtheshapeoftheflamefront;areparabolicinnature， whi1eforthe1，2and4cmwidetrays，smaltwincirculationswere generatedonthefuelsurface[RosandMilIer，196]sugestingthat thecharacteroftheflowprofileofthegasphaseflowprofileis chang凶 from2・Dto3-Dbyincreasingthewidthofthetray. A recentstudybyGarcia-Ybara[Garcia-Ybara，eta，.1 196]also
the3・D natureofthegas-phaseflowinducedbya spreadingflameoveralcohols. Toincreasetheacuracyofthe DWHI，the3・Defectnedstobeminimized.Weexperimentalydid thisbytakingaseriesofvid巴opic加 restogetherwithD Wholograms andidenti今ingthebest2-D-flameshapefromthevideofilmandthe cor responding D W hologram.
SincethespatialresolutionofourDWHIisbet巴rforthewider traywidth[Narumi，etal.，] weuseda40mmwidetrayand conducted flame spread tests over n-propanol at its initial temperature10oC. However，weconfirmedthattheflamespread rateoverthe20mmwideand40mmwidetraysisaproximatelythe sameandtheflamestructureoverbothtraysisverysimilarinnature. Fi思lre6showsD Whologramsandv巴rticalprofilesofpropanolfuel concentrationforsteps(a，b，anddl). 官 1eleanflam mabiJitylimitfor n・propanol-air(2.2molepercent)isshownina'soiIdlineinFig.6 (top).Figure6(botom)showsthepropanolconcentrationinthe 釘 eabelowthesolidlinesatisfiestheleanflamabilitylimit，thus， theflameisableωspreadthroughapremixedpropanol-airmix旬re.
SUMMARYANDCONCLUSIONS
(1) Previously，wedevelopedauniquePTLSsystemformeasuring ve1.opityprofilesfortransientflowinaverylimitedspace. We apliedthisP1LSsystemtostuclythemechanismofth巴 pulsating flamespreadoverpropanolandsucesfulyobtainedaseriesof PTLSflowdiagrams. 百lesePTLSflowdiagramsrevealedagas- phase circulation in the puIsating spread region together with a liquid-phase convection，both of which were predicted by other researchers. (2)WeapliedtheDWHIsystemtomeasuretransientprofilesofthe gas-phasepropanolconcentrationovertheJiquid-propanoLsurface.
WeobtainedaseriesofD Whologramsandconfirmedthattheflame spreadocuredonlywhenthepropanolfuelconcentrationoverthe fuelsurfaceishigherthantheleanflamabilitylimi.t Ourcurent DWHIasumesa2・Dmodel，thustheacuracyoftheDWHIneds tobeimprov巴dwhenitisapiIedto3・Dproblems.
ACKNO司札EDGEMENTS ThisstudywassuportedinpartbytheNationalInstituteof
StandardsandTechnologyunderGrant#60NANB4D1674，inpartby theNASA-KentuckyEPSCoRProgram，inpartbytheJapanese Ministry of Education under U ふ Japan Col laborative Agre ement
Figure4 Fourdiferentflowvisualzationphotographs obtainedforsteps(a，b，c，andd1).
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