英文原文EnginepartsleakdetectiontechnologyandapplicationFirst,anoverviewofthevoiceLeakdetectiontechniques,sometimesreferredtoasthetesttechnologyorsealingleakagedetectiontechnology.Inrecentyearshasbeenwidelyusedinautomobilemanufacturingindustry,suchasthecylinderblockwaterjacket,watersetofcylinderhead,crankshaftoilholes,etc.,inaddition,thereareclearancevolumemeasurementandengineassemblytesting,etc.Withtheapplicationanddevelopmentofleakdetectiontechnology,alsohasformedaprofessionalmanufacturers,moreprestigiousmanufacturerssuchasGermany,FrenchATEQJWFROEHLICHcompany,inc.,UnitedStatesoftheU-SONcompany,COSMIntertechcorporation,inadditiontoJapan,TokyoMicroctrolvantypestrainscommune,Italy,etc.Leakingtestmachineismadeupofleakdetectioninstrument,mechanicalsealingclamp,up-downmaterialmechanicalpartsandelectriccontrolsystemcompositionandsoon.SomemanufacturerssuchasGermany,aFloridacompany,notonlycanprovideallkindsofleakdetectionequipment,andcanprovidetryleakageorleakageautomaticline.Intheleakdetectiontechnology,thefirsttopointoutisleakingandnotleakisjustarelativeconcept,isnoleakageintheory,onlywhentheleakagequantitydoesnotexceedcertainlimits,wethinkthatisnotleak,orqualified.Second,fundamentalknowledgeofleakage1.1theflowofthefluidAleakiscontentbyalimitedspacetoruntotheexternalorothersubstancesbyspaceoutsideintotheinside.Contentscanbegas,liquidorsolid.Limitedspacecanmakeallkindsofexplanation,suchasenginecylinderbodywassealedchannelisalimitedspace.Leak,inshort,isakindoffluidflowphenomenon.Ingeneral,isfluidflowsthroughtheholesontheobjectorthe.Fluidflow,liketheflowoftheelectric,electronicmobilebecauseapotentialofhighandlow,aslongasthepotentialdifferencebetweentheconductors,therewillbeaflowofelectriccharge.Movementofmaterialmusthavemotivepower,theelectricpotentialdifferenceisthedrivingforce.Leakage,leakageamountdependsonthesizeoftheprimemover,availableundertypesaid:Q=f(delta),whereQsaidleakage,deltasaidimpulsion,fisthefunction.Fisacomplexfunctionnormally,itisverydifficulttodeterminethesizeofthe,ifweseeitonlyasakindofextremelypureproportionalrelationship,andalsoonlytoapressuredifference-delta,typeontheQ=C(P1,P2),theproportionalityconstantCtype,P1,P2,saidthespacebothinsideandoutsidepressure,leakageoftheprimemoverislikecurrentelectromotiveforce,Cislikeconductance,socanbeCsaidasconduction.Aleakageisreferstothefluidthroughtheholesthroughthephenomenon,throughthequantityisrelatedtopressuredifferenceonbothsidesofthehole,alsowiththeeaseofflowthrough,namely,conduction.1.2fluidmotionAccordingtofluidmechanicstheory,theflowofthefluidaretwokindsofstate,thelaminarflowandturbulentflow.Whenlaminarviscousforceplaysaleadingrole,theparticleisgovernedbyviscousfluid,notvoluntarymovement,theinertialforceplaysaleadingrolewhenturbulentflow,fluidparticleinhigh-speedmotionviscositynolongerbindit.Inthevacuumtechnology,canbedividedintolaminar(viscousflow)andmolecularflow.Accordingtothetheoryofgasmolecularmotion,forthroughthegascylinder,whenthegaswhenthemeanfreepathislargerthanthediameterofthecylinder,asmolecularflow.Ontheotherhand,themeanfreepathofgashours,thanthediameterofthecylinderisviscousflow.1.3thepipelineresistanceandconductionWiththeconductionofelectricityneedsaconductor,theconductoristhepipeline.Fortheleakitself,whetheritisasmallholeorcrack,canberegardedasakindofpipe.Inthetype,Q=C(P1,P2),conductionCasthereciprocalofresistance.Therefore,canbecalculatedinthepipelinetransmissionpipelineresistance.Fluidflowisfarmorecomplicatedthantheelectricconduction,whencalculatingtheCvalue,shouldbeaccordingtothesize,shape,pressurepipe,fluidcharacteristics,suchasspecificconditionstocalculate.Ifacontainerunderacertainpressureleak,butitdoesnotleak.Couldget,fromwehavetalkedabouttheformulasofgasandliquidinthesamepipelinetransmissionisnotthesame.2.1leakageofformContainerleakphenomenon,suchaswaterleakageoftheenginecylinder,usuallyismainlyduetothelocaltissuelooseontheblankcastingquality,castingormachiningerrorcausetheholewallistoothinandprocesscausedbyunequalsealantpluggingplacedaubreason.Infact,forleakagetechnology,thereisnoneedforaccurateunderstandingoftheleakageofvariousforms,butitisalsoimpossible.Leakdetectionbelongstoakindofnon-destructivetesting,metallographicanalysisofitisdifferentfromthematerial.Therefore,wecandoisdetermineleakage.Inordertobetterunderstandtheleakagephenomenon,itisnecessarytoknowsomesimilardiffusionandthroughthephenomenontoleakphenomenon.Thesephenomenainthegasflowthroughsolidthispoint,andtheleakageoftheresultisthesame.Diffusionphenomenonreferstobothsidesofthegasinavehiclewithadifferentialpressure,orpressuredifference.Gasfromhighpressureorhighpressuretolowinthedirectionoftheflowdirection.Thisphenomenonissimilartoleak.Whenthevehicleissolid,gasfrommediumflowsthroughtheholes,orspreadtothevehicle(vehiclenoleakhole)flowafterthepast.Inbothcasesisbelongtowhichkindof,sometimesitisdifficulttojudge.Throughreferstogasfromasolidpasseddissolvedthematerialfirst,increasingconcentration,finallyintheweehours.2.2theleakageTherearethreekindsofleakageofrepresentation:(1)insize,suchasroundandstraightshape,innerdiameterandlengthishowmuchforeachpleaseindicateassaid.Actuallythissizemeasurementisverydifficulttodoit,evencantdo.So,thismethodisnotpractical.(2)usingleak,saidtothedifficultyofthetransmissionbox.Thiswayisnotsaidleakageshapeitself,butsaidthesizeofthegaspathway.(3)expressedingasflow.Thismethodhasbeenwidelyused,becauseitiseasytouseinstrumenttomeasuretheflowofgas,orgasflowmeasurementwithacollectionofbubblesmethod.3.1theclassificationoftestmethodToonedevicetoknowtheleaks,andwillknowhowmuchitsleakage,mustexertaprimemover,i.e.letthedeviceproducesapressuredifferencebetweeninsideandoutside,socanthedevicecompressionordecompressiontwoways.Inaddition,canalsobeclassifiedaccordingtotheleakdetectionprocess,onekindisplaced,anotherfordynamicmethod.Alsohaveaccordingtothedeterminationofobjectclassification,canbedividedintotheamountofgasorliquidquantitymeasurementandpressuremeasurementdirectlyorpartialpressuremeasurement.Intheabovedetectionmethod,pressuremethodisusedforthedetectionofcommonlyusedmethods.Pressuremethodisusedforthedetectionofcommonlyusedmethods.Placepressuremethodandpressuremethodandpressuredynamicmethod.Decompressionmethodiscommonlyreferredtoasvacuummethod,thismethodisnocompressionmethodusedwidely,butithashighdetectionaccuracy,andeasyintheworkpiecetobemeasuredhavetoseal.Vacuumprocess,likepressure,vacuumandvacuumdynamicplacement.Suchasvacuumdifferentialpressuremethod,liquidcoatingmethod,etc.Andmethodsusedinthevacuumconditionsthanthekindsofpressureundertheconditionofthekindsofdetectionmethods.3.2selectionofleaktestInnumerousdetectionmethods,eachmethodhasitsdifferentfeatures.Choicesshouldconsiderwhoissuitablefor,thosewhodontfit.Accordingtothedifferentfeaturesofvariousdetectionmethodstochoosefromthefollowingaspectsintoconsideration:Principle:(1)irrespectiveoftheapproach,dontfullyunderstandtheprincipleofthemethod,willnotgetgoodresult.(2)thesensitivity(theminimumleakagecanbemeasured)shouldconsiderwhichmethodisusedtomeasureoftheleveltowhichtheleakage.(3)detectiontimeirrespectiveofthedetectionmethod,ittakesacertaintime.Forplacementtesting,fromRichardwillextendtheplacedtimewillimprovethesensitivityandthedetectionofanartifactoftheleakagetakesalongtime,obviouslycannotbeusedforon-linedetectionofengineparts.(4)testenvironmentofvarioustestmethodsisdifferenttotherequirementoftestenvironment.Ifadoptthemethodofmeasuringpressurevalue,itisfollowtheidealgasequationofstate,sothetemperature,humidityandotherfactorsonthemeasuringresultsislarger,theinfluenceofthechoiceismustbetakenintoaccount.(5)leakagepositionjudgmentinallkindsofdetectionmethods,somecanonlygivetotheleakage,leakagecandeterminewhetherartifacts,butitcantleak,somecanreflecttheworkpieceisleaking,anddetermineleak,butthespecificleakageitisdifficulttoget,andcangiveleakage,candeterminethespecificleakagain.Ifwanttorepairtheleakageoftheworkpiece,theleakofthejudgmentisnecessary.6reliabilityleakdetectionbelongstoameasuringtechnique,themeasurementmustbecredibleandreliable.Allkindsofmethodisusuallyaccompaniedbyhumaneyedetection,duetothefactorsthat,itsconsistencyispoor,butisstableandreliable.Andvariousinstrumentmethod,althoughbetterconsistency,butitsstabilityandreliabilityoftheinstrument,andmanyotherfactorsinfluence.Alllandownerseconomydetectionefficiencywhenchoosingmethodofmeasurementisalsoafactortoconsider.Theaboveitemsisourstartingpointofhowtochoosewhatkindoftestmethod.Inspecificchoices,theyshouldbeandotherfactors,suchastests,theinfluenceofworkpiecetosealtheeaseofcombinationofconsideration,andchoosethebestmethodforleakdetection.4severalmajorleakdetectorandthedetectionmethodIntheleakdetectiontechnology,atpresentthemainleakagedetectorandthedetectionmethodhasa)absolutepressuretypeleakagedetectorb)differentialpressuretypeleakagedetectorc)massflowleakdetector4.1theabsolutepressuretypeleakdetectorandthedetectionmethodCommonlyusedisthestep-downmethod,alsocanuseboosterandthevacuumismeasured.Thetestprocedurecanberoughlydividedinto:preinflatable,inflatable,voltageregulator,measurement-exhaustfivestages；1openthevalve,airinflatedtothepressureP,fillingstageandcanbebrokendownintopreaerationandaerationsteportwo.Stablestage:1valveclosed,thisphaseistoprovidethestablegasandheatexchangeoftime,itisnecessaryforprecisemeasurement,thestablephaseovertheinstantaneouspressurevalueasareferencepressurestorage.Phases:measurementsystemformeasuring.Tomonitorthefinalpressure,andcomparingwithreferencevalue,measurethePvalues,Pvaluesinexcessoftheprescribedthresholdforunqualified,leakratecanbeobtainedbyPvalueV；Exhaustphase:theartifactsinthegasfromtheatmosphere,usuallyadoptslooseblockingartifactstoexhaust.4.2thedifferentialpressuretypeleakdetectorandthedetectionmethodIntheabsolutepressuretypetestinginstrument,sensitiveelementUSESthepressuresensor,differentialpressuretypeleakagedetectorisusedinthedifferentialpressuresensor.Differentialpressuretypeofleakdetectormeasurementprocessbasicallyisdividedintofivestages.Thedifferenceisinflatablestage1,2valveareopened.Bygasphaseintothestable(balance),1offvalve,thevalveopen2,sothebalanceattheendofthestage,backpressurechamberHandLpressureequaltothepressureroom,P=0.Whenenteredthemeasurementphase,valveshutoff.IfleaksartifactshaveLcavitypressureisreduced,producingpressuredifferentialP,inthesameway,andcanbedeterminedfromPVleakrate.AbsolutepressureanddifferentialpressuretypeleakdetectordetectorismeasuredbyusingthepressurevaluetoindirectlymeasurethechangeoftheleakrateofV.4.3themassflowtypeleakdetectorandthedetectionmethodMassflowtypeleakdetectorisdirectlymeasuredworkpieceleakflowinstrument,thesensitiveelementistheflowsensor(usuallyusingthemodulecomponent).Inflowsensorwithaconstanttemperatureheatingsystem,whentheairflow(flow)change,takeawaytheheatchangemaketemperaturet,sothatthetemperatureoftheclosed-loopsystemheatingcurrent(orvoltage)changes,whichcanmeasuretheflowchanges,duetothezeromethodisusedtomeasure,soitcanobtainhigherprecision.Thisk