Page 142 - konishipaper

270 FIRE-IgnitionandFlameSpread 25 oMain-pulsation(lg) I
・
15 10 5
Oo 5 10 15 20 25
Initialbutanolayerthicknesh(mm)
FIG.3.Thefrequencyofthem山 pulsationifM)，sub- pulsation(ん)， surfacewave，andliquidsurfacetempera- ture，alasafunctionoftheinitialbutanolthicmes(h). ThesurfacewavefrequencywasmeasuredbyHI，andthe surfacetemperaturewasmeasuredbyIRthermograph.
(a)
へ FIG.5.Aザpicalhigh-speddigitalimageoftheFig.4 目立meshowingasurfacewavecreatedduringapulsating flamespread.Thelocationsoftheflamefrontandsurface wavearerespectivelyindicatedbylines.
gasphase，whilethemainpulsationisasociatedwith andcontroledbytheliquidphase.Thatisbecause liquidbutanolhashigherdensi句Tandhigherthermal inertia 也 an 出 e air and butanol vapor，so 也 at it is noteasyfortheliquidbutanoltocreatetheobserved 6-12Hzfrequencypulsationintheliquidphase.
FormationofSuφceWave
Figure4(a)showsahologramtakenattheinitial butanoltemperatureof20oC，andFig.4(b)isasche- maticilustrationofthehologramofFig.4(a).加 1 interesting observation was made: when the first smal-scalesurfacewavewasgeneratedin出eliquid phasewi出 adistancedfromtheflameleadingedge， thesecondwaveappearedbetweenthefirstwave crestandtheflameleadingedge，traveledtowardthe crestof也efirstwave，anddisapeared.Thecrest heightofthesecondwave，whichislikelycontroled bysurfacetensionandviscousforces，isshorter也an 也efirstwave，whichislikeヤcontrolIedbygravity andviscousforces.Afterthesecondwavedisap- peared，thethirdwave，similartothesecondwave type，appearedandrepeatedthesamepa枕emofbe- havior.Duringonemainpulsationsequence，weob- servedthecreationanddisapearanceoftwoor threoftheseccmdザpewave.Thisliquidwavemo- 世onwasrecordedbyahigh-speddigitalcameraand wasreviewedinmagnifiedimages(Fig.5showsa typicalflamespreadingimagethatweobtained).N0 obviouscorelationwasmadebetweensubpulsa世on andtheaboveliquidsurfacemotion，indicatingthe subpulsation to be the gas-phase contro.l Fig. 5 shows aphotographofasurfacewavespreading aheadofflameleadingedge.
Figure6showstherela甘vehorizontaldistance-be- tweentheflameleadingedgeandthecrestofthe
S曲 -pulsation(lg) よ 20 ムWavefrequency肝1) 十 A Temperaturefrequency(IR1).
(b)
供服 Liqiud
Suifucewave
Gas
le叩 伊
FIG.4.(a)Agas-phasehologramandaliquid-phaseho- logram，bothtakenfromthetopatthesametime.The directionofflamespreadisfromlefttoright.(b)A sche- maticofthehologramsin(a).Theinitialbutanoltempera- turewas20oC，andtheinitialbutanoldepthwas1mm.
Fueltray
(N工)JRJhocDコωσ」比