Designation:E2872−14StandardGuideforDeterminingCross-SectionAveragedCharacteristicsofaSprayUsingLaser-DiffractionInstrumentsinaWindTunnelApparatus1ThisstandardisissuedunderthefixeddesignationE2872;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONInthisguide,testmethodologiesaredescribedspecificallyrelatingtotheuseoflaserdiffraction(LD)instrumentationtoestimatethedroplet-sizedistributionforliquidspraysreleasedintomovingairstreams.Thisguidepresentedisprimarilyapplicabletoaerialagriculturalspraying,aerialforestsprays,orair-blastspraying.Casesinwhichthesprayisejectedintoaquiescentgasenvironmentthatlackstheunifyingeffectofawell-definedgasco-flowmayrequiredifferenttechniquesorinstrumentationorboth.Inthisguide,anaveragedropletsizedistributionfortheentiresprayisdetermined.Itrequiresthatthespraybestatisticallysteadyintime,butitmaybepolydisperseandspatiallynon-uniform.Thedroplet-sizedistributionusedforcharacterizationofamovingspraysourcemustbedeterminedfroma“flux-sensitivesample”orequivalent.Thisisbecauseaflux-sensitivesampleprovidesthefractionofthetotalliquidflowratecontributedbyeachsizeclassofdropletsand,therefore,isdirectlyrelatedtothespraycoverage.Incontrast,theLDinstrumentderivesitsdroplet-sizedistributionfroma“spatialsample,”andtherefore,itsuseforspraycharacterizationislimitedtotestconditionsunderwhichequivalencebetweenflux-sensitivesamplesandspatialsamplescanbeestablished.Suchequivalenceexistswhenthevelocityofalldropletsofthesprayisequalandcreatingtheseconditionsisthebasisofthisguide.Alltestsrelatingtothisguiderequireawindtunnelwithatestsectionofsufficientsizethatitcontainstheentiresprayplumeuptotheplaneofmeasurementwithoutdropletsimpactingthetestsectionwallsundertheprescribedoperatingconditions.Theunobstructedwindtunnelairstreamshallbeuniforman...
