油压泵简介--中英文翻译.docx

外文翻译原文标题Oilpressurepumpcover油压泵简介机械工程系译文标题作者所在系别作者所在专业机械设计制造及其自动化完成时间译文标题油压泵原文标题Oilpressurepumpcover作者译名国籍原文出处原义Ahydraulicpumpisamechanicaldevicewhichconvertsmechanicalenergyintohydraulicenergy.Morespecifically,apumpconvertsthekinetic(moving)energyofarotatingshaftintothekineticenergyoffluidflow.Thefluidflowalsohaspotentialenergythatallowsittoovercometheresistanceofthesystemtofluidflow.Rememberthatapumpprovidestheforceproduceflowandtransmitpower.Hydraulicpressureiscausedbytheloadonthesystemandbytheresistanceofthehydraulicsystemtofluidflow.Whenoperating,ahydraulicpumpperformstwofunctions.First,itcreatesapartialvacuumatitsinlet,permittingtheatmosphericpressureinthefluidreservoirtopushthehydraulicfluidthroughtheinletstrainerandlineintothepump.Second,itsmechanicalactiondeliversthefluidtoitsoutletandintothehydraulicsystems,asshowninFig.5-1.Asthefluidleavesthepump,itencounterstheworkingpressureinthesystem.Thispressureisproducedbythepressureregulatingvalve,thesystemworkload,andflowlossesinthehydraulictubingpumpisclassifiedonthebasisofthephysicalarrangementofitspumpingmechanismanditsbasicprincipleofoperating.Pumpsclassifiedbyprincipleofoperationincludepositivedisplacementandnonpositive-diSplacementtypes.Positive-displacementpumpsareequippedwithamechanicalseparation(gears,vanes,orimpellers)betweentheinletandoutlet,whichminimizesinternalleakageorslippage.Therefore,theoutputofpositive-displacementpumpsisalmostunaffectedbyvariationsinsystempressureNopositive-displacementpumps(suchascentrifugalpumps)donothaveapositiveinternalseparationagainstleakageorslippage.Becauseofthisslippage,thedeliveryofthesepumpisreducedastheworkingpressureofasystemisincreased.However,nonpositive-displacementpumpsdeliveracontinuousflow,whilepositive-displacementpumpsdeliveranintermittent(pulsating)flow.Thesepulsationsaresmallandcanbesmoothoutbytheaccumulatororthesystempiping.Mosthydraulicpumpsarepositivedisp1acementpumpsoftherotarytype.Positive-displacementpumpshaveeitherafixedorvariabledisplacement.Thevolumeofdelivery,orgpm,ofafixed-displacementpumpcanbechangedonlybychangingthespeedofthepump,becausethephysicalarrangementofthepumpingmechanismcannotbechanged,(Thisdoesnotmeanthattheflowinotherportionsofthesystemcannotbeadjustedbyvalves.)Theflowofavariable-disp1acementpumpcanbechangedbychangingthephysicalarrangementofthepumpingmechanismwithabuilt-incontrollingdevice.Thisdeviceoftenfunctionsinresponsetosystempressureorothersignals.Variable-displacementpumpsaremorecomplexthanfixed-displacementpumpsand,therefore,costmore.Inaddition,theefficiencyofavariable-displacementpumpislowerthanthatofafixed-displacementpump.Thisisoffsetsomewhatbythehigheroverallefficiencyofasystempoweredbyavariable-displacementpump.Mostpositive-displacementpumpsareclassifiedasrotarypumps.Thisisbecausetheassemblythattransfersthefluidfromthepumpinlettothepumpoutlethasarotatingmotion.Rotarypumpsarefurtherclassifiedaccordingtothemechanismthattransfersthefluid-suchasgears,vanes,orscrews.differentkindofpositive-dispIacementpumpispistonpump.Thispumpusesareciprocating(back-and-forth)motionofthepiston,alternatelytoreceivefluidontheinletside,andtodischargefluidontheoutletside.Aradial-pistonpumphasarevolvingassemblywithseveralpistonassembliesbuiltintoit,andcanbeclassifiedasarotarypump.Severaltypesofpistonpumpswillbediscussedlaterinthischapter.Theperformanceofdifferentpumpsisevaluatedonthebasisofmanyfactors,inculdingphysicalcharacteristics,operatingcharacteristics,andcost.Whenselectingapump,thefollowpumpratingandselectionfactorsareconsidered;CapacityPressureEnergyconsumptionDrivespeedEfficiencyReliabilityFluidcharacteristicsSizeandweightControladaptabilityServicelifeInstallationandmaintenancecostsSomeoftheperformancecharacteristicsofdifferentpumpsaregiveninTable5-1.Eachoftheseselectionfactorsisdescribedbrieflyinthefollowingparagraph.Theprimaryratingofapumpisitscapacity.Thisisalsocalledthedeliveryrate,flowrate,orvolumetricoutput.ThecapacityusualIyisgiven3/ingallonsperminute(gpm),cubicinchesperminute("'rnn),orcubicinchesperrevolutionatspecifiedoperatingconditions.Pumpcapacityratingsusuallyaregivenatstandardatmosphericinletpressureandvariousoutputpressures,aswellasatapproximatefluidservicetemperatures.Thepressureratingofapumpgenerallyisbasedontheabilityofthepumptowithstandpressurewithoutanundesirableincreaseinitsinternalleakage(orslippage)ordamagetopumpparts.Pumpsarepressure-ratedunderthesameconditions(speed,temperrature,andinletpressure)atwhichtheyarecapacity-rated.Mostpumpsarepressure-ratedat100,500,1000,1500,2000,3500,or5000psi.Energyconsumptionisanimportantconsiderationnotonlyintheselectionofapump,butalsointheoperatingperformanceofthepumpafterthesystemisinstalled.Theenergyrequirementforpumpingdependsonthepumpingpressure,andonthemassoffluidpumpedinagiventime.Thefluidpumpinghorsepowerisdeterminedasf