Page 145 - konishipaper

ELSEVIER
...d
ProcedingsoftheCombustionInstitute30(205)271-27
JP>roce<l1IlIlgs ofthe ComblUlstI1olIl
:n:lI1lstit1lte w.elsevier.com/locate/proci
...叩
Scalingandinstabilityanalysesonflame spreadoverliquids
KozueTakahashia AkihikoItoa，YujiKudoa TadashiKonishib ララヲ
KozoSaitoc，*
aFaculty01ScienceandTechnology，HirosakiUniversity，Hirosala036-8561，Japan
b Department01MechanicalEngine ering，OuaNationalCol lege01Technology，Oitα879-0152，Japαn cDepartment01MechanicalEnginering，University01Kentucky，Lexington，KY40506-0503，USA
Abstract
Stabilityandscalinganalyseswereapliedtoexperimentaldataobtainedbythisgroupandother researchersonpulsatingflamespreadoverliquids.Datatobe叩ana叫ly戸ze吋dinc1uderecent自ndi泊ng伊sぱ0fcyclic apearanceofacoldtemperaturevaleyattheli同q叫u吋1idsu江rf:白ac印e-crea抗tedsu江rf:白acωe
f臼lam，e久 andmain-p卯Iu山ls剖ationぱ0fO.5子一2Hzandsub-pulsationof5-10Hz.Ourstabilityanalysisisperformedto understandthemechanismofinstabilityontheliquidsurfaceaheadofaflame'sleadingedge，whichis thoughtofasthemajorcauseforpulsatingflamespread.Thescalinganalysisisperformedtoexplore theroleoffourindependent(gravity，surface-tension，viscose，andinertia)forcesonthemechanismsof flalnespread.Thesefourforcesformthreindependentpi-numbers:Marangoni(Ma)number，Weber (We)number，andFroude(Fr)number，alofwhichinc1udethecriticallengthscaleratio:(heightof sub-surfacecirculation)j(horizontalengthofpreheatedliquidsurface).Wecombinedthewaveequation obtainedfromthestabilityanalysis，thethrepi-numbers，.andthecriticalengthscaleratio，andusedthem asauniversalformulatodescribeflamespreadoverliquids.Usingthisformula，flamespreadmechanism overfourdi百erenttypesofalcoholswasdividedintotwoseparateregimes:thethinliquidp~)Ol二 号nd the thick-liquidpoo.1Forthethinliquidpol，theflamesp~e?-d .r~te wascorelatedwith(Fr/Mau.;)-lぺwhile
uniformtothepulsatingcanbedescribedwithtemperaturediferencebetwentheflashpoint~~d bulk
liquidtemperature.ForthethinliquidpolthistemperaturediferenceiscorelatedwithMa一ω ，while
forthethick-liquidpolitwas~orreîated with(Fr/MaO5 .)一1.5.Changeofflamespreadpaternfromthe
。forthethick-liquidpolitiscorelatedwithMaーへ Thef:reguencyofpulsationiscorelatedwith We- U 1コ・
l. forthethinliquidpol，whileitiscorelatedwithWe- forthethick-liquidpoo.1 204TheCombustionInstitute.PublishedbyElsevierInc.Alrightsreserved.
Keywords:Flamespread;Liquidfuels;Scalingandinstabilityanalyses
1.Introduction Overthepast10years，aseriesofexperimental
studiesonflamespreadoverliquidshaveben *Corespondirigauthor.Fax:+1859257304.
E-mailadres:saito@engr.uky.edu(K.Saito).
conducted [1-8]，creating a rich experimental databasetobeanalyzed.Withsixdiferentexper- imental(lasershetpartic1etracking，snioketrac- ing，single and dual wavelength holographic interferometer，infraredthermograph，andhigh- spedphotography)techniques，wemeasuredthe detai1ed thermal，日uid dynamic，and chemical structuresofbothgasandliquidphasesnearthe
1540-7489/$-sefrontmater@ 204TheCombustionInstitute.PublishedbyElsevierInc.Alrightsreserved. doi:10.1016/j.proci.204.08.246