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1、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.Thefluidflowalsohaspotentialenergyth
2、atallowsittoovercometheresistanceofthesystemtofluidflow.Rememberthatapumpprovidestheforceproduceflowandtransmitpower.Hydraulicpressureiscausedbytheloadonthesystemandbytheresistanceofthehydraulicsystemtofluidflow.Whenoperating,ahydraulicpumpperformstwofunctions.First,itcreatesapartialvacuumatitsinlet
3、,permittingtheatmosphericpressureinthefluidreservoirtopushthehydraulicfluidthroughtheinletstrainerandlineintothepump.Second,itsmechanicalactiondeliversthefluidtoitsoutletandintothehydraulicsystems,asshowninFig.5-1.Asthefluidleavesthepump,itencounterstheworkingpressureinthesystem.Thispressureisproduc
4、edbythepressureregulatingvalve,thesystemworkload,andflowlossesinthehydraulictubingApumpisclassifiedonthebasisofthephysicalarrangementofitspumpingmechanismanditsbasicprincipleofoperating.Pumpsclassifiedbyprincipleofoperationincludepositivedisplacementandnonpositive-diSplacementtypes.Positive-displace
5、mentpumpsareequippedwithamechanicalseparation(gears,vanes,orimpellers)betweentheinletandoutlet,whichminimizesinternalleakageorslippage.Therefore,theoutputofpositive-displacementpumpsisalmostunaffectedbyvariationsinsystempressureNopositive-displacementpumps(suchascentrifugalpumps)donothaveapositivein
6、ternalseparationagainstleakageorslippage.Becauseofthissiippage,thedeliveryofthesepumpisreducedastheworkingpressureofasystemisincreased.However,nonpositive-displacementpumpsdeliveracontinuousflow,whilepositive-displacementpumpsdeliveranintermittent(pulsating)flow.Thesepulsationsaresmal1andcanbesmooth
7、outbytheaccumulatororthesystempiping.Mosthydraulicpumpsarepositive-displacementpumpsoftherotarytype.Positive-dispIacementpumpshaveeitherafixedorvariabledisplacement.Thevolumeofdelivery,orgpm,ofafixed-displacementpumpcanbechangedonlybychangingthespeedofthepump,becausethephysicalarrangementofthepumpin
8、gmechanismcannotbechanged,(Thisdoesnotmeanthattheflowinotherportionsofthesystemcannotbeadjustedbyvalves.)Theflowofavariable-displacementpumpcanbechangedbychangingthephysicalarrangementofthepumpingmechanismwithabuilt-incontrollingdevice.Thisdeviceoftenfunctionsinresponsetosystempressureorothersignals
9、.Variable-displacementpumpsaremorecomplexthanfixed-diSplacementpumpsand,therefore,costmore.Inaddition,theefficiencyofavariable-displacementpumpislowerthanthatofafixed-displacementpump.Thisisoffsetsomewhatbythehigheroverallefficiencyofasystempoweredbyavariable-displacementpump.Mostpositive-displaceme
10、ntpumpsareclassifiedasrotarypumps.Thisisbecausetheassemblythattransfersthefluidfromthepumpinlettothepumpoutlethasarotatingmotion.Rotarypumpsarefurtherclassifiedaccordingtothemechanismthattransfersthefluid-suchasgears,vanes,orscrews.Adifferentkindofpositive-displacementpumpispistonpump.Thispumpusesar
11、eciprocating(back-and-forth)motionofthepiston,alternatelytoreceivefluidontheinletside,andtodischargefluidontheoutletside.Aradial-pistonpumphasarevolvingassemblywithseveralpistonassembliesbuiItintoit,andcanbeclassifiedasarotarypump.Severaltypesofpistonpumpswillbediscussedlaterinthischapter.Theperform
12、anceofdifferentpumpsisevaluatedonthebasisofmanyfactors,InculdingPhySiCalcharacteristics,operatingcharacteristics,andcost.Whenselectingapump,thefollowpumpratingandselectionfactorsareconsidered;CapacityPressureEnergyconsumptionDrivespeedEfficiencyReliabilityFluidcharacteristicsSizeandweightControladap
13、tabilityServicelifeInstalIationandmaintenancecostsSomeoftheperformancecharacteristicsofdifferentpumpsaregiveninTable5-1.Eachoftheseselectionfactorsisdescribedbrieflyinthefollowingparagraph.Theprimaryratingofapumpisitscapacity.Thisisalsocalledthedeliveryrate,flowrate,orvolumetricoutput.Thecapacityusu
14、allyisgiven3/ingallonsperminute(gpm),cubicinchesperminute(m/min)jorcubicinchesperrevolutionatspecifiedoperatingconditions.Pumpcapacityratingsusuallyaregivenatstandardatmosphericinletpressureandvariousoutputpressures,aswel1asatapproximatefluidservicetemperatures.Thepressureratingofapumpgenerallyisbas
15、edontheabilityofthepumptowithstandpressurewithoutanundesirableincreaseinitsinternal1eakage(orslippage)ordamagetopumpparts.Pumpsarepressure-ratedunderthesameconditions(speed,temperrature,andinletpressure)atwhichtheyarecapacity-rated.Mostpumpsarepressure-ratedat100,500,1000,1500,2000,3500,or5000psi.En
16、ergyconsumptionisanimportantconsiderationnotonlyintheselectionofapump,butalsointheoperatingperformanceofthepumpafterthesystemisinstalled.Theenergyrequirementforpumpingdependsonthepumpingpressure,andonthemassoffluidpumpedinagiventime.Thefluidpumpinghorsepowerisdeterminedasfollow:Hp=(gpm*1/.*psi)/(14286*n)Wherenistheoveralleffciencyofthepump,motor,anddr
