关于二级液压节流锥阀的低汽蚀研究论文外文翻译中英文文献对照翻译.docx

关于二级液压节流锥阀的低汽蚀研究论文外文翻译中英文文献对照翻译.docx

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关于二级液压节流锥阀的低汽蚀研究论文外文翻译中英文文献对照翻译

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关于二级液压节流锥阀的低汽蚀研究

Researchonlowcavitationinwaterhydraulictwo-stagethrottlepoppetvalve

Abstract:

Cavitationhasimportanteffectsontheperformancesandlifespanofwaterhydrauliccontrolvalve,suchasdegradingefficiency,intensenoise,andseverevibration.Two-stagethrottlevalveisapracticableconfigurationtomitigatecavitation,whichisextensivelyusedinwaterhydraulicpressurereliefvalvesandthrottlevalves.Thepressuredistributioninsideamediumchamberlocatedbetweentwothrottlesofatwo-stagethrottlevalveisinvestigatedthroughnumericalsimulations.Theeffectsofthepassagearearatioofthetwothrottlesandtheinletandoutletpressuresonthepressureinsidethemediumchamberareexamined.Thesimulationresultsindicatethat（a）thepressureinsidethemediumchamberisnotconstant,（b）thelocationsofmaximumandminimumpressuresinsidethemediumchamberarebothfixed,whichwillnotvarywiththepassagearearatioortheinletandoutletpressures,and（c）theratioofthepressuredropacrossthefrontthrottletothetotalpressuredropacrossthetwo-stagethrottlevalveisnearlyconstant.Thecriticalcavitationindexofthetwo-stagethrottlevalveisthenestablished.Asemiempiricaldesigncriterionisobtainedforthewaterhydraulictwo-stagethrottlevalve.Thecorrelationbetweenthecriticalcavitationindexandthepassagearearatioofthetwothrottlesisinvestigated.Relevantvalidationexperimentsareconductedatacustom-manufacturedtestingapparatus.Theexperimentalresultsareconsistentwiththesimulatedones.Furtheranalysesindicatethat（a）thelargebackpressurecanimprovenotonlytheanti-cavitationcapabilitybutalsothetotalloadrigidityofthewaterhydraulictwo-stagethrottlevalve,（b）anappropriatepassagearearatiowillbebeneficialforimprovingtheanti-cavitationcapabilityofthewaterhydraulictwo-stagethrottlevalve,and（c）thewaterhydraulictwo-stagethrottlevalvewithapassagearearatioof0.6wouldhavethebestanti-cavitationperformancewiththelowestriskofcavitation.Keywords:

computationalfluiddynamicssimulationcavitationloadrigiditypassagearearatiotwo-stagethrottlevalvewaterhydraulics

1INTRODUCTION

Waterhydraulicsystemsareoperatedwithrawwater（puretapwater）substitutingformineraloil.Theyhaveadvantagesintermsofdurability,reliability,safety,andcleanness.Suchsystemsarebecomingmoreandmorepopular,especiallyinfieldsofsteelandglassproduction,coalandgoldmining,foodandmedicineprocessing,nuclearpowergeneration,oceanexploration,andunderwaterrobotics[1–5].

Becausetheopeningofawaterhydrauliccontrolvalveisverysmallcomparedwiththatofoilvalve,thewaterflowvelocitythroughthewaterhydrauliccontrolvalveislargerunderthesamepressurecondition;thuscavitationerosionmayoccurduetothehighvapourpressureofwater.Cavitationhasanimportanteffectontheperformanceandlifespanofwaterhydrauliccontrolvalve,suchasdegradingefficiency,intensenoise,andseverevibration.Previously,anumberofstudiesontherelationshipsbetweencavitationanddischargecoefficient,thrustforceandpressuredistributionsinthevalves,andmitigationofcavitationdamagewerecarriedoutthroughincreasingoutletpressureofvalves,modifyingshapesofthrottles,addingstagesofvalves,selectinganti-corrosionmaterialsforparts,andcontrollingmaximumfluidtemperatureandflowvelocity.Tsukijietal.[6]investigatedcavitationbyflowvisualizationinhydraulicpoppet-typeholdingvalvestoreducecavitation.Somemeasureswereemployedtodiminishnoiseandcavitationthroughcontrollingflowrate,upstreampressure,downstreampressure,andvalveliftincaseofconvergingflow.

Aoyamaetal.[7]studiedexperimentallytheunsteadycavitationperformanceinanoilhydraulicpoppetvalve.Itwasfoundthat,asabsolutevaluesofthevariationratesofinletandoutletpressureincreased,theincipientcavitationindexexhibitedatendencytodecrease,whereasthefinalcavitationindexatendencytoincreaseunderallgeometricalparameters.Astheabsolutevaluesofthevariationratesofinletandoutletpressurefurtherincreased,thehysteresisbetweentheincipientandfinalcavitationindiceswouldbecomelargerthaneverforeachcombinationofthevalveandvalveseat.

Ishiharaetal.[8]studiedoilflowunsteadinesseffectoncavitationphenomenaatsharp-edgedorifices.Therateofpressuredropacrosstheorificewaskeptconstant,andcavitationincipienceandfinalewererecordedbyusingscatteredlaserbeamsshowingthat（a）thereexistedtwotypesofcavitation,namely,gaseouscavitationandvapourouscavitation,and（b）cavitationincipienceandfinalevariedwiththeinitialcondition,thetemperatureofhydraulicoil,andtherateofpressuredrop.

Johnstonetal.[9]carriedoutanexperimentalinvestigationofflowandforcecharacteristicsofhydraulicpoppetanddiscvalvesusingwaterastheworkingfluid.Theaxisymmetricvalvehousingwasconstructedfromclearperspextofacilitateflowvisualization;testswereperformedonarangeofdifferentpoppetanddiscvalvesoperatingundersteadyandnon-cavitatingconditions,forReynoldsnumbersgreaterthan2500.Measuredflowcoefficientsandforcecharacteristicsshowedobviousdifferencesdependingonvalvegeometryandopening.

Vaughanetal.[10]conductedcomputationalfluiddynamics（CFD）analysisonflowthroughpoppetvalves.Simulationswerecomparedwithexperimentalmeasurementsandvisualizedflowpatterns.Aqualitativeagreementbetweensimulatedandvisualizedflowpatternswasidentified.However,errorsinthepredictionofjetseparationandreattachmentresultedinquantitativeinaccuracies.Theseerrorswereduetothelimitationsoftheupwinddifferencingschemeemployedandtherepresentationofturbulencebythek–1model,whichwasknowntobeinaccuratewhenappliedtorecirculatingflow.

Uenoetal.[11]investigatedexperimentallyandnumericallytheoilflowinapressurecontrolvalveunderanassumptionofnon-cavitatingconditionsforvariousconfigurationsofthevalvesonthebasicsofafinitedifferencemethod.Theyconcludedthatthemainnoiseofthetestingvalveswasgeneratedfromcavitation,andthenoisewasaffectedbythevalveconfiguration.Pressuremeasurementsandflowvisualizationattwolocationsinavalvechamberwerealsoperformedonthebasisoftwo-dimensionalmodels.Throughcomparisonsofthemeasuredandcalculatedresults,severaldesigncriteriaweresetupforlow-noisevalves.

Martinetal.[12]investigatedcavitationinspoolvalvesinordertoidentifydamagemechanismsoftherelatedcomponents.Testswereconductedinarepresentativemetalspoolvalveaswellasamodelbeingthreetimeslarger.Datatakenundernon-cavitatingconditionswithbothofthesevalvesshowedthattheorientationofhigh-velocityangularjetswouldbeshiftedduetovariationsinvalveopeningandReynoldsnumber.Bymeansofhigh-frequencyresponsepressuretransducersstrategicallyplacedinthevalvechamber,thecavitationcouldbesensedthroughthecorrelationofnoisewithacavitationindex.Theonsetofcavitationcouldbedetectedbycomparingenergyspectraforafixedvalveopeningwithaconstantdischarge.Theincipientcavitationindex,asdefinedinthisinvestigation,wascorrelatedwiththeReynoldsnumberforbothvalves.

Gaoetal.[13]performedasimulationofcavitatingflowsinhydraulicpoppetvalvesbymeansofanrenormalizationgroup（RNG）k–1turbulencemodel,whichwasderivedfromthenstantaneousNavier–StokesequationsbasedontheRNGtheory.Experimentswereconductedtocatchcavitationimagesaroundtheseatofapoppetvalvefromperpendiculardirections,usingapairofindustrialfibrescopesandahigh-speedvisualizationsystem.Thebinarycavitatingflowfielddistributionsobtainedthroughdigitalprocessingoftheoriginalcavitationimageshowedsatisfactoryagreementwithnumericalresults;thevibrationsofvalvebodyandpoppetinducedbythecavitatingflowweredetectedusingavortexdisplacementtransducer,alaserdisplacementmetreandadigitalstraindevice.Itwasconcludedthattheopeningandconeofaconicalvalvehadsignificanteffectsontheintensityofcavitation.However,inthisstudy,onlydownstreamcavitationinceptionvolumewasanalysedinestimatingtheanti-cavitationcapability,whereastheeffectsofoutletpressurewerenotconsidered.

Oshimaetal.[14]experimentallyinvestigatedtheinfluencesof（a）chamferlengthinthevalveseat,（b）thepoppetangle,and（c）theoiltemperatureontheflowcharacteristicsandthecavitationphenomena,usingwaterinsteadofoilastheworkingmediuminwaterpoppetthrottles.Thecavitationphenomenaweredirectlyobservedandthepressuredistributionbetweenthevalveseatandpoppetsurfacewasmeasuredinwaterpoppetthrottles.Comparisonanalysesontheconditionofcriticalcavitationwereconductedbetweenoilandwater.Itwasfoundthatthedischargecoefficientandthecriticalcavitationnumberforwaterpoppetthrottleswereconsiderablydifferentfromthoseofoilones,duetothehighdensityandlowviscosityofwater.Recently,Liuetal.[15,16]investigatedexperimentallytheflowandcavitationcharacteristicsofatwo-stagethrottleinwaterhydraulicsystem;theyconcludedthatthetwo-stagethrottlehadstrongeranti-cavitationcapabilitythanthesingle-stageone,andthattheshapeofseatsalsoaffectedtheanti-cavitationcapabilityofthethrottles.Thecavitationchokingappearedonlywhencavitationindexwaslessthan0.4.Theyalsoconductedsevera