油压泵简介--中英文翻译.docx

外文翻译原文标题Oilpressurepumpcover译文标题油压泵简介译文标题油压泵原文标题Oilpressurepumpcover作者译名国籍原文出处原文Ahydraulicpumpisamechanicaldevicewhichconvertsmechanicalenergyintohydraulicenergy.MorespecificalIy,apumpconvertsthekinetic(moving)energyofarotatingshaftintothekineticenergyoffluidflow.Thefluidflowalsohaspotentialenergythatallowsittoovercometheresistanceofthesystemtofluidflow.Rememberthatapumpprovidestheforceproduceflowandtransmitpower.Hydraulicpressureiscausedbytheloadonthesystemandbytheresistanceofthehydraulicsystemtofluidflow.Whenoperating,ahydraulicpumpperformstwofunctions.First,itcreatesapartialvacuumatitsinlet,permittingtheatmosphericpressureinthefluidreservoirtopushthehydraulicfluidthroughtheinletstrainerandlineintothepump.Second,itsmechanicalactiondeliversthefluidtoitsoutletandintothehydraulicsystems,asshowninFig.5-1.Asthefluidleavesthepump,itencounterstheworkingpressureinthesystem.Thispressureisproducedbythepressureregulatingvalve,thesystemworkload,andflowlossesinthehydraulictubingApumpisclassifiedonthebasisofthephysicalarrangementofitspumpingmechanismanditsbasicprincipleofoperating.Pumpsclassifiedbyprincipleofoperationincludepositivedisplacementandnonpositive-diSplacementtypes.Positive-displacementpumpsareequippedwithamechanicalseparation(gears,vanes,orimpellers)betweentheinletandoutlet,whichminimizesinternalleakageorslippage.Therefore,theoutputofpositive-displacementpumpsisalmostunaffectedbyvariationsinsystempressureNopositive-displacementpumps(suchascentrifugalpumps)donothaveapositiveinternalseparationagainstleakageorslippage.Becauseofthissiippage,thedeliveryofthesepumpisreducedastheworkingpressureofasystemisincreased.However,nonpositive-displacementpumpsdeliveracontinuousflow,whilepositive-displacementpumpsdeliveranintermittent(pulsating)flow.Thesepulsationsaresmal1andcanbesmoothoutbytheaccumulatororthesystempiping.Mosthydraulicpumpsarepositive-displacementpumpsoftherotarytype.Positive-dispIacementpumpshaveeitherafixedorvariabledisplacement.Thevolumeofdelivery,orgpm,ofafixed-displacementpumpcanbechangedonlybychangingthespeedofthepump,becausethephysicalarrangementofthepumpingmechanismcannotbechanged,(Thisdoesnotmeanthattheflowinotherportionsofthesystemcannotbeadjustedbyvalves.)Theflowofavariable-displacementpumpcanbechangedbychangingthephysicalarrangementofthepumpingmechanismwithabuilt-incontrollingdevice.Thisdeviceoftenfunctionsinresponsetosystempressureorothersignals.Variable-displacementpumpsaremorecomplexthanfixed-diSplacementpumpsand,therefore,costmore.Inaddition,theefficiencyofavariable-displacementpumpislowerthanthatofafixed-displacementpump.Thisisoffsetsomewhatbythehigheroverallefficiencyofasystempoweredbyavariable-displacementpump.Mostpositive-displacementpumpsareclassifiedasrotarypumps.Thisisbecausetheassemblythattransfersthefluidfromthepumpinlettothepumpoutlethasarotatingmotion.Rotarypumpsarefurtherclassifiedaccordingtothemechanismthattransfersthefluid-suchasgears,vanes,orscrews.Adifferentkindofpositive-displacementpumpispistonpump.Thispumpusesareciprocating(back-and-forth)motionofthepiston,alternatelytoreceivefluidontheinletside,andtodischargefluidontheoutletside.Aradial-pistonpumphasarevolvingassemblywithseveralpistonassembliesbuiItintoit,andcanbeclassifiedasarotarypump.Severaltypesofpistonpumpswillbediscussedlaterinthischapter.Theperformanceofdifferentpumpsisevaluatedonthebasisofmanyfactors,InculdingPhySiCalcharacteristics,operatingcharacteristics,andcost.Whenselectingapump,thefollowpumpratingandselectionfactorsareconsidered;CapacityPressureEnergyconsumptionDrivespeedEfficiencyReliabilityFluidcharacteristicsSizeandweightControladaptabilityServicelifeInstalIationandmaintenancecostsSomeoftheperformancecharacteristicsofdifferentpumpsaregiveninTable5-1.Eachoftheseselectionfactorsisdescribedbrieflyinthefollowingparagraph.Theprimaryratingofapumpisitscapacity.Thisisalsocalledthedeliveryrate,flowrate,orvolumetricoutput.Thecapacityusuallyisgiven3/ingallonsperminute(gpm),cubicinchesperminute(m/min)jorcubicinchesperrevolutionatspecifiedoperatingconditions.Pumpcapacityratingsusuallyaregivenatstandardatmosphericinletpressureandvariousoutputpressures,aswel1asatapproximatefluidservicetemperatures.Thepressureratingofapumpgenerallyisbasedontheabilityofthepumptowithstandpressurewithoutanundesirableincreaseinitsinternal1eakage(orslippage)ordamagetopumpparts.Pumpsarepressure-ratedunderthesameconditions(speed,temperrature,andinletpressure)atwhichtheyarecapacity-rated.Mostpumpsarepressure-ratedat100,500,1000,1500,2000,3500,or5000psi.Energyconsumptionisanimportantconsiderationnotonlyintheselectionofapump,butalsointheoperatingperformanceofthepumpafterthesystemisinstalled.Theenergyrequirementforpumpingdependsonthepumpingpressure,andonthemassoffluidpumpedinagiventime.Thefluidpumpinghorsepowerisdeterminedasfollow:Hp=(gpm*1/.*psi)/(14286*n)Wherenistheoveralleffciencyofthepump,motor,anddr