液压专业毕业设计外文翻译

TheAnalysisofCavitationProblemsintheAxialPistonPumpshuWangEatonCorporation,14615LoneOakRoad,EdenPrairie,Thispaperdiscussesandanalyzesthecontrolvolumeofapistonboreconstrainedbythevalveplateinaxialpistonpumps.Thevacuumwithinthepistonborecausedbytherisevolumeneedstobecompensatedbytheflow;otherwise,thelowpressuremaycausethecavitationsandaerations.Intheresearch,thevalveplategeometrycanbeoptimizedbysomeanalyticallimitationstopreventthepistonpressurebelowthevaporpressure.Thelimitationsprovidethedesignguideofthetimingsandoverlapareasbetweenvalveplateportsandbarrelkidneystoconsiderthecavitationsandaerations.__Keywords:cavitation,optimization,valveplate,pressureundershoots1IntroductionInhydrostaticmachines,cavitationsmeanthatcavitiesorbubblesforminthehydraulicliquidatthelowpressureandcollapseatthehighpressureregion,whichcausesnoise,vibration,andlessefficiency.Cavitationsareundesirableinthepumpsincetheshockwavesformedbycollapsedmaybestrongenoughtodamagecomponents.Thehydraulicfluidwillvaporizewhenitspressurebecomestooloworwhenthetemperatureistoohigh.Inpractice,anumberofapproachesaremostlyusedtodealwiththeproblems:(1)raisetheliquidlevelinthetank,(2)pressurizethetank,(3)boostertheinletpressureofthepump,(4)lowerthepumpingfluidtemperature,and(5)designdeliberatelythepumpitself.Manyresearcheffortshavebeenmadeoncavitationphenomenainhydraulicmachinedesigns.Thecavitationisclassifiedintotwotypesinpistonpumps:trappingphenomenonrelatedone(whichcanbepreventedbytheproperdesignofthevalveplate)andtheoneobservedonthelayersafterthecontractionorenlargementofflowpassages(causedbyrotatinggroupdesigns)inRef.(1).Therelationshipbetweenthecavitationandthemeasuredcylinderpressureisaddressedinthisstudy.EdgeandDarling(2)reportedanexperimentalstudyofthecylinderpressurewithinanaxialpistonpump.Theinclusionoffluidmomentumeffectsandcavitationswithinthecylinderborearepredictedatbothhighspeedandhighloadconditions.AnotherstudyinRef.(3)providesanoverviewofhydraulicfluidimpactingontheinletconditionandcavitationpotential.Itindicatesthatphysicalproperties(suchasvaporpressure,viscosity,density,andbulkmodulus)arevitaltoproperlyevaluatetheeffectsonlubricationandcavitation.Ahomogeneouscavitationmodelbasedonthethermodynamicpropertiesoftheliquidandsteamisusedtounderstandthebasicphysicalphenomenaofmassflowreductionandwavemotioninfluencesinthehydraulictoolsandinjectionsystems(4).Dularetal.(5,6)developedanexpertsystemformonitoringandcontrolofcavitationsinhydraulicmachinesandinvestigatedthepossibilityofcavitationerosionbyusingthecomputationalfluiddynamics(CFD)tools.Theerosioneffectsofcavitationshavebeenmeasuredandvalidatedbyasimplesinglehydrofoilconfigurationinacavitationtunnel.ItisassumedthatthesevereerosionisoftenduetotherepeatedcollapseofthetravelingvortexgeneratedbyaleadingedgecavityinRef.(7).Then,thecavitationerosionintensitymaybescaledbyasimplesetofflowparameters:theupstreamvelocity,theStrouhalnumber,thecavitylength,andthepressure.Anewcavitationerosiondevice,calledvortexcavitationgenerator,isintroducedtocomparativelystudyvariouserosionsituations(8).Morepreviousresearchhasbeenconcentratedonthevalveplatedesigns,piston,andpumppressuredynamicsthatcanbeassociatedwithcavitationsinaxialpistonpumps.Thecontrolvolumeapproachandinstantaneousflows(leakage)areprofoundlystudiedinRef.[9].Bertaetal.[10]usedthefinitevolumeconcepttodevelopamathematicalmodelinwhichtheeffectsofportplatereliefgrooveshavebeenmodeledandthegaseouscavitationisconsideredinasimplifiedmanner.AnimprovedmodelisproposedinRef.[11]andvalidatedbyexperimentalresults.Themodelmayanalyzethecylinderpressureandflowripplesinfluencedbyportplateandreliefgroovedesign.Manringcomparedprincipaladvantagesofvariousvalveplateslots(i.e.,theslotswithconstant,linearlyvarying,andquadraticvaryingareas)inaxialpistonpumps[12].Fourdifferentnumericalmodelsarefocusedonthecharacteristicsofhydraulicfluid,andcavitationsaretakenintoaccountindifferentwaystoassistthereductioninflowoscillations[13].Theexperiencesofpistonpumpdevelopmentsshowthattheoptimizationofthecavitations/aerationsshallincludethefollowingissues:occurringcavitationandairrelease,pumpacousticscausedbytheinducednoises,maximalamplitudesofpressurefluctuations,rotationaltorqueprogression,etc.However,theaimofthisstudyistomodifythevalveplatedesigntopreventcavitationerosionscausedbycollapsingsteamorairbubblesonthewallsofaxialpumpcomponents.Incontrasttoliteraturestudies,theresearchfocusesonthedevelopmentofanalyticalrelationshipbetweenthevalveplategeometricsandcavitations.Theoptimizationmethodisappliedtoanalyzethepressureundershootscomparedwiththesaturatedvaporpressurewithinthepistonbore.Theappropriatedesignofinstantaneousflowareasbetweenthevalveplateandbarrelkidneycanbedecidedconsequently.2TheAxialPistonPumpandValvePlateThetypicalschematicofthedesignoftheaxispistonpumpisshowninFig.1.Theshaftoffseteisdesignedinthiscasetogeneratestrokingcontainmentmomentsforreducingcostpurposes.Thevariationbetweenthepivotcenteroftheslipperandswashrotatingcenterisshownasa.Theswashangleisthevariablethatdeterminestheamountoffluidpumpedpershaftrevolution.InFig.1,thenthpiston-slipperassemblyislocatedattheangleof.Thedisplacementofthenthpiston-slipperassemblyalongthex-axiscanbewrittenasxn=Rtan（）sin（）+asec（）+etan()(1)whereRisthepitchradiusoftherotatinggroup.Then,theinstantaneousvelocityofthenthpistonisx˙n=Rsin（）+Rtan（）cos（）+Rsin（）+e(2)wheretheshaftrotatingspeedofthepumpis=ddt.Thevalveplateisthemostsignificantdevicetoconstraintflowinpistonpumps.Thegeometryofintake/dischargeportsonthevalveplateanditsinstantaneousrelativepositionswithrespecttobarrelkidneysareusuallyreferredtothevalveplatetiming.Theportsofthevalveplateoverlapwitheachbarrelkidneystoconstructaflowareaorpassage,whichconfinesthefluiddynamicsofthepump.InFig.2,thetiminganglesofthedischargeandintakeportsonthevalveplatearelistedasand.Theopeningangleofthebarrelkidneyisreferredtoas.Insomedesigns,thereexistsasimultaneousoverlapbetweenthebarrelkidneyandintake/dischargeslotsatthelocationsofthetopdeadcenter(TDC)orbottomdeadcenter(BDC)onthevalveplateonwhichtheoverlapareaappearstogetherreferredtoas“cross-porting”inthepumpdesignengineering.Thecross-portingcommunicatesthedischargeandintakeports,whichmayusuallylowerthevolumetricefficiency.Thetrapped-volumedesigniscomparedwiththedesignofthecross-porting,anditcanachievebetterefficiency14].However,thecross-portingisFig.1Thetypicalaxispistonpumpcommonlyusedtobenefitthenoiseissueandpumpstabilityinpractice.3TheControlVolumeofaPistonBoreInthepistonpump,thefluidwithinonepistonisembracedbythepistonbore,cylinderbarrel,slipper,valveplate,andswashplateshowninFig.3.ThereexistsometypesofslipflowbyvirtueofrelativeFig.2Timingofthevalveplatemotionsandclearancesbetweenthosecomponents.Withinthecontrolvolumeofeachpistonbore,theinstantaneousmassiscalculatedas=(3)whereandaretheinstantaneousdensityandvolumesuchthatthemasstimerateofchangecanbegivenasFig.3Thecontrolvolumeofthepistonbore(4)wheredisthevaryingofthevolume.Basedontheconservationequation,themassrateinthecontrolvolumeis(5)whereistheinstantaneousflowrateinandoutofonepiston.Fromthedefinitionofthebulkmodulus,(6)wherePnistheinstantaneouspressurewithinthepistonbore.SubstitutingEqs.(5)and(6)intoEq.(4)yields(7)wheretheshaftspeedofthepumpis.TheinstantaneousvolumeofonepistonborecanbecalculatedbyusingEq.(1)as=+[Rtan（）sin（）+asec（）+etan()](8)whereisthepistonsectionalareaandisthevolumeofeachpiston,whichhaszerodisplacementalongthex-axis(when=0,).Thevolumerateofchangecanbecalculatedatthecertainswashangle,i.e.,=0,suchthat(9)inwhichitisnotedthatthepistonborevolumeincreasesordecreaseswithrespecttotherotatingangleof.SubstitutingEqs.(8)and(9)intoEq.(7)yields(10)4OptimalDesignsTofindtheextremaofpressureovershootsandundershootsinthecontrolvolumeofpistonbores,theoptimizationmethodcanbeusedinEq.(10).Inanonlinearfunction,reachingglobalmaximaandminimaisusuallythegoalofoptimization.Ifthefunctioniscontinuousonaclosedinterval,globalmaximaandminimaexist.Furthermore,theglobalmaximum(orminimum)eithermustbealocalmaximum(orminimum)intheinteriorofthedomainormustlieontheboundaryofthedomain.So,themethodoffindingaglobalmaximum(orminimum)istodetectallthelocalmaxima(orminima)intheinterior,evaluatethemaxima(orminima)pointsontheboundary,andselectthebiggest(orsmallest)one.Localmaximumorlocalminimumcanbesearchedbyusingthefirstderivativetestthatthepotentialextremaofafunctionf(·),withderivative,cansolvetheequationatthecriticalpointsof=0[15].ThepressureofcontrolvolumesinthepistonboremaybefoundaseitheraminimumormaximumvalueasdP/dt=0.Thus,lettingtheleftsideofEq.(10)beequaltozeroyields(11)Inapistonbore,thequantityofoffsetsthevolumevaryingandthendecreasestheovershootsandundershootsofthepistonpressure.Inthisstudy,themostinterestingareundershootsofthepressure,whichmayfallbelowthevaporpressureorgasdesorptionpressuretocausecavitations.ThetermofinEq.(11)hasthepositivevalueintherangeofintakeports(),showninFig.2,whichmeansthatthepistonvolumearises.Therefore,thepistonneedsthesufficientflowin;otherwise,thepressuremaydrop.Inthepiston,theflowofmaygetthroughinafewscenariosshowninFig.3:(I)theclearancebetweenthevalveplateandcylinderbarrel,(II)theclearancebetweenthecylinderboreandpiston,(III)theclearancebetweenthepistonandslipper,(IV)theclearancebetweentheslipperandswashplate,and(V)theoverlappingareabetweenthebarrelkidneyandvalveplateports.Aspumpsoperatestably,theflowsintheaslaminarflows,whichcanbecalculatedas[16](12)whereistheheightoftheclearance,isthepassagelength,scenariosI–IVmostlyhavelowReynoldsnumbersandcanberegardedisthewidthoftheclearance(notethatinthescenarioII,=2·r,inwhichristhepistonradius),andisthepressuredropdefinedintheintakeportsas=-(13)whereisthecasepressureofthepump.Thefluidfilmsthroughtheaboveclearanceswereextensivelyinvestigatedinpreviousresearch.TheeffectsofthemainrelateddimensionsofpumpandtheoperatingconditionsonthefilmarenumericallyclarifiedinRefs.[17,18].ThedynamicbehaviorofslipperpadsandtheclearancebetweentheslipperandswashplatecanbereferredtoRefs.[19,20].Manringetal.[21,22]investigatedtheflowrateandloadcarryingcapacityoftheslipperbearingintheoreticalandexperimentalmethodsunderdifferentdeformationconditions.AsimulationtoolcalledCASPARisusedtoestimatethenonisothermalgapflowbetweenthecylinderbarrelandthevalveplatebyHuangandIvantysynova[23].Thesimulationprogramalsoconsidersthesurfacedeformationstopredictgapheights,frictions,etc.,betweenthepistonandbarrelandbetweentheswashplateandslipper.AlltheseclearancegeometricsinEq.(12)arenonlinearandoperationbased,whichisacomplicatedissue.Inthisstudy,theexperimentalmeasurementsofthegapflowsarepreferred.Ifitisnotpossible,theworstcasesofthegeometricsortoleranceswithempiricaladjustmentsmaybeusedtoconsiderthecavitationissue,i.e.,minimumgapflows.ForscenarioV,theflowismostlyinhighvelocityandcanbedescribedbyusingtheturbulentorificeequationas(14)wherePiandPdaretheintakeanddischargepressureofthepumpandandaretheinstantaneousoverlapareabetweenbarrelkidneysandinlet/dischargeportsofthevalveplateindividually.Theareasarenonlinearfunctionsoftherotatingangle,whichisdefinedbythegeometricsofthebarrelkidney,valveplateports,silencinggrooves,decompressionholes,andsoforth.CombiningEqs.(11)–(14),theareacanbeobtainedas(15)whereisthetotaloverlapareaof=,and

isdefinedasInthepistonbore,thepressurevariesfromlowtohighwhilepassingovertheintakeanddischargeportsofthevalveplates.Itispossiblethattheinstantaneouspressureachievesextremelylowvaluesduringtheintakearea(showninFig.2)thatmaybelocatedbelowthevaporpressure,i.e.,;thencavitationscanhappen.Topreventthephenomena,thetotaloverlapareaofmightbedesignedtobesatisfiedwith(16)whereistheminimumareaof=andisaconstantthatis

Vaporpressureisthepressureunderwhichtheliquidevaporatesintoagaseousform.ThevaporpressureofanysubstanceincreasesnonlinearlywithtemperatureaccordingtotheClausius–Clapeyronrelation.Withtheincrementalincreaseintemperature,thevaporpressurebecomessufficienttoovercomeparticleattractionandmaketheliquidformbubblesinsidethesubstance.Forpurecomponents,thevaporpressurecanbedeterminedbythetemperatureusingtheAntoineequationas,whereTisthetemperature,andA,B,andCareconstants[24].Asapistontraversetheintakeport,thepressurevariesdependentonthecosinefunctioninEq.(10).Itisnotedthattherearesometypicalpositionsofthepistonwithrespecttotheintakeport,thebeginningandendingofoverlap,i.e.,TDCandBDC()andthezerodisplacementposition(=0).Thetwosituationswillbediscussedasfollows:(1)When,itisnotalwaysnecessarytomaintaintheoverlapareaofbecauseslipflowsmayprovidefillingupforthevacuum.FromEq.(16),letting=0,thetiminganglesattheTDCandBDCmaybedesignedas(17)inwhichtheopenangleofthebarrelkidneyis.Thereisnocross-portingflowwiththetimingintheintakeport.(2)When=0,thefunctionofcoshasthemaximumvalue,whichcanprovideanotherlimitationoftheoverlapareatopreventthelowpressureundershootssuchthat(18)whereistheminimumoverlapareaof.Topreventthelowpistonpressurebuildingbubbles,thevaporpressureisconsideredasthelowerlimitationforthepressuresettingsinEq.(16).Theoverallofoverlapareasthencanbederivedtohaveadesignlimitation.Thelimitationisdeterminedbytheleakageconditions,vaporpressure,rotatingspeed,etc.Itindicatesthatthehigherthepumpingspeed,themoreseverecavitationmayhappen,andthenthedesignsneedmoreoverlapareatoletflowinthepistonbore.Ontheotherside,thelowvaporpressureofthehydraulicfluidispreferredtoreducetheopportunitiestoreachthecavitationconditions.Asaresult,onlythevaporpressureofthepurefluidisconsideredinEqs.(16)–(18).Infact,airreleasestartsinthehigherpressurethanthepurecavitationprocessmainlyinturbulentshearlayers,whichoccurinscenarioV.Therefore,thevaporpressuremightbeadjustedtodesigntheoverlapareabyEq.(16)ifthereexistssubstantialtrappedanddissolvedairinthefluid.Thelaminarleakagesthroughtheclearancesaforementionedareatradeoffinthedesign.Itisdemonstratedthatthemoreleakagefromthepumpcasetopistonmayrelievecavitationproblems.However,themoreleakagemaydegradethepumpefficiencyinthedischargeports.Insomedesigncases,themaximumtiminganglescanbedeterminedbyEq.(17)tonothavebothsimultaneousoverlappingandhighlylowpressureattheTDCandBDC.Whilethepistonrotatestohavethezerodisplacement,theminimumoverlapareacanbedeterminedbyEq.18,whichmayassistthepistonnottohavethelargepressureundershootsduringflowintake.6ConclusionsThevalveplatedesignisacriticalissueinaddressingthecavitationoraerationphenomenainthepistonpump.Thisstudyusesthecontrolvolumemethodtoanalyzetheflow,pressure,andleakageswithinonepistonborerelatedtothevalveplatetimings.Iftheoverlapareadevelopedbybarrelkidneysandvalveplateportsisnotproperlydesigned,nosufficientflowreplenishestherisevolumebytherotatingmovement.Therefore,thepistonpressuremaydropbelowthesaturatedvaporpressureoftheliquidandairingresstoformthevaporbubbles.Tocontrolthedamagingcavitations,theoptimizationapproachisusedtodetectthelowestpressureconstrictedbyvalveplatetimings.Theanalyticallimitationoftheoverlapareaneedstobesatisfiedtoremainthepressuretonothavelargeundershootssothatthesystemcanbelargelyenhancedoncavitation/aerationissues.Inthisstudy,thedynamicsofthepistoncontrolvolumeisdevelopedbyusingseveralassumptionssuchasconstantdischargecoefficientsandlaminarleakages.Thedischargecoefficientispracticallynonlinearbasedonthegeometrics,flownumber,etc.Leakageclearancesofthecontrolvolumemaynotkeeptheconstantheightandwidthaswellinpracticeduetovibrationsanddynamicalripples.Alltheseissuesarecomplicatedandveryempiricalandneedfurtherconsiderationinthefuture.Theresultspresentedinthispapercanbemoreaccurateinestimatingthecavitationswiththeseextensivestudies.NomenclaturethetotaloverlapareabetweenvalveplateportsandbarrelkidneysAp=pistonsectionareaA,B,C=constantsA=offsetbetweenthepiston-slipperjointandsurfaceoftheswashplate=orificedischargecoefficiente=offsetbetweentheswashplatepivotandtheshaftcenterlineofthepump=theheightoftheclearance=thepassagelengthoftheclearanceM=massofthefluidwithinasinglepiston(kg)N=numberofpistonsn=pistonandslippercounter=fluidpressureandpressuredrop(bar)Pc=thecasepressureofthepump(bar)Pd=pumpdischargepressure(bar)Pi=pumpintakepressure(bar)Pn=fluidpressurewithinthenthpistonbore(bar)Pvp=thevaporpressureofthehydraulicfluid(bar)qn,qLn,qTn=theinstantaneousflowrateofeachpiston(l/min)R=pistonpitchradiusr=pistonradius(mm)t=time(s)V=volumewk=thewidthoftheclearance(mm)x,x˙=pistondisplacementandvelocityalongtheshaftaxis(m,m/s)=Cartesiancoordinateswithanoriginontheshaftcenterline=Cartesiancoordinateswithanoriginonswashplatepivot=swashplateangleandvelocity(rad,rad/s)=fluidbulkmodulus(bar)=timingangleofvalveplatesattheBDCandTDC(rad)=theopenangleofthebarrelkidney(rad)=fluiddensity(kgm3)=angularpositionandvelocityoftherotatingkit(rad,rad/s)=absoluteviscosity(Cp)=coefficientsrelatedtothepressuredrop外文中文翻译：在轴向柱塞泵气蚀问题的分析本论文讨论和分析了一个柱塞孔与配流盘限制在轴向柱塞泵的控制量设计。真空是由柱塞的运动量引起的，需要由流动补偿，否则，低气压可能导致的气蚀和曝气。配流盘几何的研究，可以优化一些分析性的限制，以防止蒸气压以下的柱塞压力。配流盘的端口和缸体腰形窗口之间重叠的地方，设计时要考虑的空蚀和曝气。关键词：空蚀，优化，配流盘，负脉冲压力1介绍在水压机等液压元件中，空穴或气穴意味着，在低压区液压液体会出有空腔或气泡形成以及崩溃在高压地区，这将导致噪声，振动，这将会降低效率。空蚀对泵的使用是极为不利的，这是因为倒塌形成的冲击波可能像炸弹一样足以损坏元件。当其压力过低或温度过高时，液压油会蒸发。在实践中，许多方法大多用于处理这些问题，比如：（1）提高油箱中的液位高度，（2油箱加压，（3）提高泵的进口压力，（4）降低泵内流体的温度，（5）特意设计的柱塞泵本身，对其结构进行优化设计。在液压机设计中的气蚀现象，许多研究成果已取得一定的成果。在柱塞泵中，气蚀主要可以分为两种类型：一是与困油现象有关（这种现象可通过适当的设计配流盘来阻止困油现象的发生）和所观察到的层上收缩或扩大后的流动通道(由于旋转设计所造成的)。在这项研究中处理气蚀和测量气缸压力之间的关系。EdgeandDarling报道了关于轴向柱塞泵内的气缸压力的实验研究。其中包括流体势效应和气蚀在气缸内高速度和高负荷条件的预测。另一项研究概述了液压流体影响进气条件和汽蚀潜力的观点。它表明,物理属性(如蒸汽压力、粘度、密度和体积弹性模量)对适当地评估影响润滑和气蚀是至关重要的。一个相似的气蚀模型在热力学性质液体和蒸汽基础上的用来理解了基本的物理现象的质量流量减少和波动产生影响的液压工具和喷射系统。Dularetal开发了一套专业系统用它来监测和控制的液压机械和调查气蚀的可能性通过使用运用计算流体动力学(CFD)工具。通过一个简单的单翼配置在一个空化隧道，气蚀侵蚀作用已经被测量和验证。它假定了严重侵蚀经常是由于一个主要的空穴飞转的漩涡重复的崩溃所产生的。然后,在汽蚀强度通过一套简单流参数可能扩大: 上游速度,空腔长度和压力。一个新的空蚀装置,称为漩涡汽蚀生成器,介绍了各种侵蚀情况。更多的先前的研究已经被集中在阀板的设计,在轴向柱塞泵中活塞和泵压动力学与空穴现象相关联。控制体积的方法和瞬时流(泄漏)正在深刻地研究中。Bertaetal采用有限体积的概念发展了一个数学模型，压力平衡槽的形式已经被效仿和气态的汽蚀被认为是在一个简化的方式。一种改进的模型已经被提出且实验验证了其结果。该模型可以分析气缸压力和流量的涟漪影响压力平衡槽的设计。四种不同的数值模型的重点是液压液体的特点,考虑到空穴以不同的方法协助减少流量振荡。柱塞泵发展的经验表明,优化的空穴现象应当包括下列问题: 发生气蚀和空气释放、泵声学引起的噪声诱导、最大振幅的压力波动,转动力矩进展等。然而,这项研究的目的是修改配流盘的设计来防止气蚀造成侵蚀蒸汽或空气泡沫崩溃的墙壁上的轴向泵组件。与文学研究相反，这项研究主要集中在配流盘的几何形状和气蚀分析之间的关系的发展。此优化方法应用于分析的压力脉冲与活塞孔内饱和蒸汽压。2轴向柱塞泵,配流盘典型轴向柱塞泵的原理如图1所示。在这种情况下，轴偏移e的设计对降低成本是十分重要的。柱塞泵斜盘倾角度是可变的，决定每转的排量即决定柱塞泵的流量。如图一所示，第N个柱塞滑靴组件转过的转角为在第n个柱塞滑靴组件沿x轴的位移可以写成xn=Rtan（）sin（）+asec（）+etan()(1)其中R为柱塞滑靴组件的分布圆半径。此刻，在第n个柱塞的瞬时速度是x˙n=Rsin（）+Rtan（）cos（）+Rsin（）+e(2)其中轴泵的旋转速度=ddt.配流盘是约束柱塞泵流量的最重要的设备。配流盘吸排油窗口的几何形状以及瞬时相对缸体腰形窗口的位置通常被称为配流盘的时间效应。配流盘开口与缸体底部的腰形窗口的重叠构建流程区域或通道,它限制了柱塞泵的流体动力学，影响着其力学性能。在图2中，在配流盘上吸排油窗口的角度分别为，.缸体配流腰形窗口的开启角度为。在某些设计,在缸体腰形窗口和吸排油窗口的相对位置在上死点或下死点出现叠区域被称为“cross-porting“在泵设计工程。正是由