外文翻译关于二级液压节流锥阀的低汽蚀研究Word文档下载推荐.docx

外文翻译关于二级液压节流锥阀的低汽蚀研究Word文档下载推荐.docx

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外文翻译

学生姓名

学院名称

机电工程学院

专业名称

指导教师

2011年

05月

27日

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）cavitationincipienceandfinalevarie