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276 1T
t句
~ 0.1 A
0.01 0.01
K.Takahashieta.l/Procedings01theCombustionIlstitute30(205)2271-2277
data,andf=15(We)-1
with(Fr川laう-1.). ThisstudyalsoidentifiedI1.T (the temperature dif ference between fiash point andliquidbulktemperature)tobeanimportant parametertodescribeseparationbetweenpulsat- inganduniformspreadintheI1Tasafunction of(Ma)-Jplot(Fig.7).Pulsatingfrequencywas cor related with (We)-l for both thin liquid and thickliquidpols(Fig.8).
〆-ThickliquidpolH>5mm
Fr/一 一 /.JMa
10.0
出1.0 「、
0.1
Fig.8.PulsationfrequencyasafunctionofWe-1for1- propanolwithH = 1-20m mand1-butanolwith'H = 1- 20mm.
4.Conclusions
Weconductedstabilityandscalinganalyseson
丑amespreadexperimentaldataoverliquidfuels
obtained by other researchers as wel1 as our
group. As a result,we found thre important
(Ma,Fr,andWe)pi-numbersandacriticalength
scaleratioconsistingoftwocharacteristiclengths
(oneisforthehorizontalthermal-fiuiddynamic
length,andtheotherisliquidconvectiondepth)
asociatedwithfiamespreadoverliquids.Finaly,
wecorelatedfiamespreadrateoverfourdiferent
alcoholfuelsandtheinitialfu己1thicknesranging
from1to20m mwithFr/Mdω(Fig.6).Thereare
twodistinctivelydiferentregions:spreadra~~ for
thin liquid pols corelates with (Fr/MaU.)-l,
Fig.6.Flamespreadrateasafunctionof(FげMaO.5)for four dif ferent alcohols (methanol-O: H = 1-10mm; ethanol一口 H=1-5mm; l-propanolーム H=l- 20mm;and1-butanol-0:H =1-20mm).
traywereused,thedatapoint[1]isexpectedto movetowardthetinliquidpolline,because thevalueofFr/Mαωdecreaseswithanincrease inh.
Figure7showsthetemperaturediferencebe- tween fiash point and liquid bulk temperature: I1Tasafunctionof(Ma)-lforfourdi百erenttype liquidfuels,andthefuelthicknesrangesfrom1 to 20mm..There are two lines in the figure: I1T=4(Mα)-u.コ corelateswith_thethinliquid p o o l d a t a , a n d I1. T = O .l 5 ( M a ) - J c o r r e l a t e s w i t h thethickliquidpoldata.Pulsatingfiamespread ocursintheregionaboveeachline,whi1euni- formspreadocursintheregionbeloweachline. Fig.8showspulsationfrequencyasafunctionof (We)-l. There are two lines in the figure:
f= 35(We)-l cor relates_with the thin liquid po ol
liquidtemperaturetowardfiashpoint.
whilespreadJ?-te(orthickliquidpolscorelates u
corelateswiththethick liquidpoldata.Frequencyofpulsationincreases withadecreaseintheliquidthicknes.Fig.8also explainsageneralyobservedtrendthatpulsation frequencyincreaseswithanincreaseintheinitial
10
ど10 P
Thick1iquidpol 0.01 0.01
1/Ma
Thinliquidpool 0.1 1
Acknowledgments
WethankF.Mi1erandK.Kuwanafortheir valuablediscusionsoninstabilityanalysis.
References
[1] H. Ros s,F. M il1er,Proc. Combust. Inst.26 (19 96) 1327-134.
ロ]P.L.Garcia-Ybara,J.C.Antoranz,V.Sankovitch, J.L.Castil1o,Phys.Rev.E49(194)525-529. [3]P.L.Garcia-Ybara,J.L.Casti1o,J.C.Antoranz,
V.Sankovitch,J.SanMartin,Proc.Combust.IlSt.
26(196)1469-1475. [4]H.D.Ros,Prog.EnergyCombust.Sci. 20(194)
17-63.
1
・;)
Fig.7.Thetemperaturediferencebetwenflashpoint andliquidbu1ktemperature:ATasafunctionofMa-J forfourdiferentalcohols(methanol:H =1-10mm; ethanol: H =1-5mm; propanol: H =1-20mm; and butanol: H = 1-20 m m).
10
、急¥
1 10 10
l/We
hh
AV