Page 122 - konishipaper

reproducibilityinspreadratemeasurements. A 4-W Ar-ionlaserwasusedaslightsourceto forma1-mmthicklasershetbypasingthebeamthroughcylindricalenses. Threpositionsof thelasershetwerechosenundertheliquidsurfaceat2，4and6m mandtwopositionsoverthe liquidsurfaceinthegasphaseat1and2m m，aswil lbese en. Velocityprofilesofthe'liquidand thegasconvectionweremeasuredindependentlyusingthesameLSPTtechnique.
FIGUREl(b)A schematicdiagramofthefuel仕aysystem.(c)Aphotographofaspreading flameovertheflamespreadaparatus.
Talcparticlesweredisperseduniformlyoverthefuelsurfaceforthemeasurementofgasphase convection. Aluminumparticlesof15土:( 5)戸ndiameterweremixedwiththeliquidforthe
measurementofliquidconvection. Somealuminumparticlesfloatedontheliquidsurfaceand othersenteredintotheliquid. Thetotalmassofaluminump訂 ticlesusedwerelesthan0.1 gramssothattheparticleshadlit1eefectonthefuelproperties. Ahigh-spedcamerasystem Wl也 anul仕avioletlensandanimageintensifierhavingasped'of500企ames/swasusedto obtainthevelocityprofiles. The廿ajectoriesoftheseparticleswererecordedby，thehigh-sped videocamera，whichwasconectedtoavideosystemandaTVmonitorfortherealtime observationofboththeflow五eldandspreadingflame.
RESULTSANDDISCUSSION
Thetestsectionwidthplaysanimportantroleintheflamespreadmechanismbecauseofthe efectofthewalontheheat-仕 組sferproces. Inordertostudythisefectweusedthre-test sectionwidths:5，10，and20m mandkepttheotherdimensionsthesame. Astheflamebeganto propagate，thepreheatedregionextendedaheadoftheflame. 立也endevelopedtwosymme仕lC vortices也atroleduptowardthesidewa1swhilethepreheat，edliquidatthecentercontinuedto proce edupstreamoftheflame. Later，whenthegaseous白 el-airmixtureovertheliquidsurface reaches吐leleanflamm~bil
-'、" 、-