Page 141 - konishipaper

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SUB圃 PULSATION
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0.05 0.1 0.15 0.2
Timre(sec)
FIG.2.Top:Thespreadingdistanceoftheflameleading edge，広 measuredfrom出e宜ameleadingedge.loca世on(此 t=0)，whichisfixedtothecontainer.Botlom:Themag- nificationofthetopresultfor0.2stimeperiod.Theinitial n-butanoltemperatureis16oC，andtheinitialbutanol layerdepthis20mm.
0.2stimeperiod.InFig.2(top)，step[a]core- spondsto0.7sand[e]to1.7s，resultingin1Hz cycle.InFig.2(botom)，theini世alstepinsubpul- sationisat0s，andthefinalstepisatabout0.85Hz， resul世ngina12Hzcycle.
Figure3，obtainedbychangingtheinitialbutanol depthinthe廿ayandrepeating吐leflame-spreadex- periments，showsthefrequencyofthemainpulsa- 世on，subpulsation，surfacewave(measuredbyHI)， andsurfacetemperature(measuredbyIRcamera)， alasafunc世onoftheini世albutanolayerthiclmes. NASA'smicrogravityflame-spreadexperimentdata overn-butanol[18-20]wereoriginalyaddedtoFig. 3，butlaterdeletedduetoexperimentaluncertainty. Notethatthefrequencyofthemainpulsationas- sociatedwiththecrawlingproceshasasystematic decreasewithanincreaseofthefueldepth，while 吐lefrequencyofthesubpulsationhasalargescat目 teringtrend.Thisindicatesthatthesubpulsation maywelbeasociatedwithandcontroledbythe
SURFACEWAVEONPULSATINGFLAMESPREAD 269
(Sideview)
εE ×
Recirculationcel Flammablevapor|
FIG.1.Topandsideviewschematicsoftemperature， flow，andfuelvaporconcentrationstructurescreateddur- ingthepulsatingflamespread抗 step[b]overbutanol poledinarectangu1artraywith2cmwidth.Thesche- maticswereconstructedbasedonourcurentandprevious measurements[8-10].Ahigh-speddigitalimageshowing asurfacewaveisalsoprovidedinFig.5.
seriesofexperimentalstudiesonflamespreadover liquids，anaproximatelocationandaschematicof someoftheabovemeasuredparametersareshown inFig.1.Thefive-stepspreadingprocesesdetailed 泊 ourpreviouspaper[8，9]areasfolows.Step[a]is theonsetofpulsation;step[b]istheformationofa smalliquidsurfacewave出atisanewobservation madein出isstudy;step[c]issubpulsationproces， anewlyobservedproces;step[d]is出eprocesof fuelvaporbuildup;andstep[e]isaflamejumping proces.Theaboveprocesesaredetailedinourpre- viouspaper[8，9].Herewefocusonthenewlyob- servedsmal-scaleliquidsurfacewaveand.itsrolein flamepulsation，particularlyonsteps[b]，[c]，and[d].
MainPulsationandSubpulsation
Figure2(top)showsspreadinghorizontaldistance fromafi.xedflameleadingedgeattime= O.Fig.2 (botom)showsmagnificationofthetopresultfor
MAIN-PULSATION
Time(sec)