Page 189 - konishipaper

indexofaliquidisastrongfunctionofdensity，ap- proximately100interferencefringes/mmareformed， andthe.gapbetweentheinterferencefringesfora given wavelength dif fe.rence can be observed. O n theotherhand，aproximately10fringes/mmare formedforgaseousmeasurementsandamicroscope is needed to ac curately measure the interference fringesforagivenwavelengthdiference.Forthis reason，.whiletheDWHImethodisfrequentlyused forthesimultaneousmeasurementofconcentration andtemperatureinaliquid，itisseldomusedto measurethetemper叫 ureandconcentrationchange
simultaneouslyinagas. AnIRcamerahasbeenusedpreviouslytomeasure
thetemperatureofasolidandliquidfuelsurface duringcombustion.9-13Inthesestudies，theIRcam- erawasplacedovertheburningfueltoprovideob- servationthroughtheflame.AnIRcamerahasalso beenusedtomeasuretheconcentrationofafuelva- poroveraquiescentliquidsurface.14Thiswasacom- plishedbycorelatingtheabsorptionofIRthermal radiationbythefuelvaporwiththeconcentr叫 ioi1 variationsofthefu.elvapor.However，usingthispro- ceduredoesnotalowforthesimultaneousmeasure- mentoftemperatureandconcentration.Toovercome thislimitation，anewopticalsystemwasdeveloped thatcombinestheIRabsorptionmethodwiththe holographicinterferometrymethod. Theresulting in企ared-holographicinterferOlnetry(IR-HI)system canmeasuretransient2Dtemperatureandconcen- trationsjmultaneously.Thisisacomplishedbynot- ingthattheIRsourceandtheHe-Nelaseraretwo
，thermalradiationsourceswithalargediferencein dispersion.TheIRthermalradiationemited企 om thehotisothermalsurfaceiscombinedwiththether- malradiationemitedfro，m: theHe-Nelaserbya half-miror.Afterthecombinedraysareabsorbedby thefuelvaporlayerthroughthesameopticalpath， theIRimageisrecordedonthein企 aredcameraand theHe-Nelaserisusedtogenerateaholographic interferogram.Asmentionedabovetheconcentration oftemperatureandspeciescanbedeterminedbyan examinationoftheIRabsorptionandthefringeshifts ontheholographyinterferogram.W henaplyingthe IR-HImethodtothen-propanolfuelvapor，themea- surementerorwasconsiderablysmalerthanthat asociatedwiththeconventionalDWHImethod.
Theprimaryobjectiveofthisinvestigationwasto dev
2. MeasurementPrinciples
A. DualWavelengthHolographicInterferometry
Assumethatliquidfuelformsa2Ddistributionof temperature，Tr(s)，andconcentration，pパ:z)，overits surface.Theobjectivewastomeasuretheunsteady temperature and concentration behavior simulta- neously.Thispurposewasachievedbytheoptical combinationofholographicinterferometryandanIR absorptionthermographymethod.
Holographicinterferometryisbasedonre仕 active indexchangesinthegasphaseduetovariationsin bothtemperatureandspeciesconcentration.Aquan- titativeevaluationofinterferogramsanddetailsof interferogramanalysiscanbefoundinVest8 and Konishietal.15Therefractiveindexofagasisrelated to density by the Gladston←Dale equation. The Gladstone-Daleequationforanisothermalmixture ofairandfuelvaporcanbegivenby
M sn(z)=n-no=¥Kr- M~
5726 APPLlEDOPTICS1Vo.l45，No.21August206
wherenisthere企activeindexofthefuelvaporand air mixture，no is the re合 active index at the atmo- sphericconditibn，K istheGladstone-Daleconstant， M isthemolecularweight，andsubscriptsαandf denoteairandfuelvapor，respectively.Ifthetemper- atureofabinaryidealgasmixturechangesfromits initialvalueTotoT，(z)，Eq.(1)canbereplacedbythe folowingexpresion:
~(Kf-~".)pr(z)+竿(合一え)，
wherePistotalpresureandRisthegasconstantofr themixture.Thechangeinre合 activeindexisrelated tothenumberoffringesintheinterferogram'bythe relation
sn(z)L=Ni(z)λ. (3)
BycombiningEqs.(2)and(3)，theresultinginterfero- metric企ingepaterncanbeinterpretedtodetermine thetemperaturedistributionofthefuelvaporby
1 1，Ni(z)λRRpt(z)(Ma¥
号約九 LMα .1(4)
，¥
，
Ka)Pr(Z)， (1)
KaP MaKaP¥'t Mr"a)
一一一=~+一一一一一一一一一一|時一一iKa
，
，
Equation4hastwounknowns，Tr位)andpパz).Itis posible to aply DWHI to obtain both values sincetheGladstone-Daleconstantsdependonwave- length.IntheDWHImethod，interferogramsaTere- cordedattwodif ferentwavelengths，入 1 and入2' Ifwe denotetheTesultingnumberof仕ingeshiftsineach wavelengthbyN1 andN2，then