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外文翻译--化工工业离心泵.doc

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外文翻译--化工工业离心泵.doc

1CENTRIFUGALPUMPSINTHECHEMICALINDUSTRYABSTRACTACENTRIFUGALPUMPCONVERTSTHEINPUTPOWERTOKINETICENERGYINTHELIQUIDBYACCELERATINGTHELIQUIDBYAREVOLVINGDEVICEANIMPELLERTHEMOSTCOMMONTYPEISTHEVOLUTEPUMPFLUIDENTERSTHEPUMPTHROUGHTHEEYEOFTHEIMPELLERWHICHROTATESATHIGHSPEEDTHEFLUIDISACCELERATEDRADIALLYOUTWARDFROMTHEPUMPCHASINGAVACUUMISCREATEDATTHEIMPELLERSEYETHATCONTINUOUSLYDRAWSMOREFLUIDINTOTHEPUMPTHISARTICLESTRESSESONASERIESOFCENTRIFUGALPUMPS,FROMABRIEFINTRODUCTIONTOTHEPRINCIPLESKEYWORDSCENTRIFUGALPUMP,INTRODUCTION,WORKINGPRINCIPLE,CAVITATION,MECHANISMOFCAVITATION,SOLUTIONANDREMEDIES1INTRODUCTIONPUMP,DEVICEUSEDTORAISE,TRANSFER,ORCOMPRESSLIQUIDSANDGASESFOURGENERALCLASSESOFPUMPSFORLIQUIDSAREDESCRIBEDBELOWINALLOFTHEM,STEPSARETAKENTOPREVENTCAVITATIONTHEFORMATIONOFAVACUUM,WHICHWOULDREDUCETHEFLOWANDDAMAGETHESTRUCTUREOFTHEPUMPPUMPSUSEDFORGASESANDVAPORSAREUSUALLYKNOWNASCOMPRESSORSTHESTUDYOFFLUIDSINMOTIONISCALLEDFLUIDDYNAMICSWATERPUMP,DEVICEFORMOVINGWATERFROMONELOCATIONTOANOTHER,USINGTUBESOROTHERMACHINERYWATERPUMPSOPERATEUNDERPRESSURESRANGINGFROMAFRACTIONOFAPOUNDTOMORETHAN10,000POUNDSPERSQUAREINCHEVERYDAYEXAMPLESOFWATERPUMPSRANGEFROMSMALLELECTRICPUMPSTHATCIRCULATEANDAERATEWATERINAQUARIUMSANDFOUNTAINSTOSUMPPUMPSTHATREMOVEWATERFROMBENEATHTHEFOUNDATIONSOFHOMESONETYPEOFMODERNPUMPSUSEDTOMOVEWATERISTHECENTRIFUGALPUMPEARLYVERSIONOFTHECENTRIFUGALPUMP,THESCREWPUMP,CONSISTSOFACORKSCREWSHAPEDMECHANISMINAPIPETHAT,WHENROTATED,PULLSWATERUPWARDSCREWPUMPSAREOFTENUSEDINWASTEWATERTREATMENTPLANTSBECAUSETHEYCANMOVELARGEAMOUNTSOFWATERWITHOUTBECOMINGCLOGGEDWITHDEBRISINTHEANCIENTMIDDLEEASTTHENEEDFORIRRIGATIONOFFARMLANDWASASTRONGINDUCEMENTTODEVELOPAWATERPUMPEARLYPUMPSINTHISREGIONWERESIMPLEDEVICESFORLIFTINGBUCKETSOFWATERFROMASOURCETOACONTAINERORATRENCHGREEKMATHEMATICIANANDINVENTORARCHIMEDESISTHOUGHTTOHAVEDEVISEDTHEFIRSTSCREWPUMPINTHETHIRDCENTURYBCLATERGREEKINVENTORCTESIBIUSDEVELOPTHEFIRSTLIFTPUMPDURINGTHELATE17THANDEARLY18THCENTURIESAD,BRITISHENGINEERTHOMASSAVERY,FRENCHPHYSICISTDENISPAPIN,ANDBRITISHBLACKSMITHANDINVENTORTHOMASNEWCOMENCONTRIBUTEDTOTHEDEVELOPMENTOFAWATERPUMPTHATUSEDSTEAMTOPOWERTHEPUMP’PISTONTHESTEAMPOWEREDWATERPUMP’SFIRSTWIDEUSEWASINPUMPINGWATEROUTOFMINESMODERNDAYEXAMPLESOFCENTRIFUGALPUMPSARETHOSEUSEDATTHEGRANDCOULEEDAMONTHECOLUMBIARIVERTHISPUMPSYSTEMHASTHEPOTENTIALTOIRRIGATEOVERONEMILLIONACRESOFLANDALSOKNOWNASROTARYPUMPS,CENTRIFUGALPUMPSHAVEAROTATINGIMPELLER,ALSOKNOWNASABLADE,THATISIMMERSEDINTHELIQUIDLIQUIDENTERSTHEPUMPNEARTHEAXISOFTHEIMPELLER,ANDTHEROTATINGIMPELLERSWEEPSTHELIQUIDOUTTOWARDTHEENDSOFTHEIMPELLERBLADESATHIGHPRESSURETHEIMPELLERALSOGIVESTHELIQUIDARELATIVELYHIGHVELOCITYTHATCANBECONVERTEDINTOPRESSUREINASTATIONARYPARTOFTHEPUMP,KNOWNASTHEDIFFUSERINHIGHPRESSUREPUMPS,ANUMBEROFIMPELLERMAYBEUSEDINSERIES,ANDTHEDIFFUSERSFOLLOWINGEACHIMPELLERMAYCONTAINGUIDEVANESTOGRADUALLYREDUCETHELIQUIDVELOCITYFORLOWERPRESSUREPUMPS,THEDIFFUSERISGENERALLYASPIRALPASSAGE,KNOWNASAVOLUTE,WITHITSCROSSSECTIONALAREAINCREASINGGRADUALLYTOREDUCETHEVELOCITYEFFICIENTLYTHEIMPELLERMUSTBEPRIMEDBEFOREITCANBEGINOPERATION,THATIS,THEIMPELLERMUSTBESURROUNDEDBYLIQUIDWHENTHEPUMPISSTARTEDTHISCANBEDONEBYPLACINGACHECKVALVEINTHESUCTIONLINE,WHICHHOLDSTHELIQUIDINTHEPUMPWHENTHEIMPELLERISNOTROTATINGIFTHISVALVELEAKS,THEPUMPMAYNEEDTOBEPRIMEDBYTHEINTRODUCTIONOFLIQUIDFROMANOUTSIDESOURCESUCHASTHEDISCHARGERESERVOIRACENTRIFUGALPUMPGENERALLYHASAVALVEINTHEDISCHARGELINETOCONTROLTHEFLOWAND2PRESSUREFORLOWFLOWSANDHIGHPRESSURES,THEACTIONOFTHEIMPELLERISLARGELYRADIALFORHIGHERFLOWSANDLOWERDISCHARGEPRESSURE,THEDIRECTIONOFTHEFLOWWITHINTHEPUMPISMORENEARLYPARALLELTOTHEAXISOFTHESHAFT,ANDTHEPUMPISSAIDTOHAVEANAXIALFLOWTHEIMPELLERINTHISCASEACTSASAPROPELLERTHETRANSITIONFROMONESETOFFLOECONDITIONSTOTHEOTHERISGRADUAL,ANDFORINTERMEDIATECONDITION,THEDEVICEISCALLEDAMIXEDFLOWPUMP2THECENTRIFUGALPUMPTHECENTRIFUGALPUMPISBYFARTHEMOSTWIDELYUSEDTYPEINTHECHEMICALANDPETROLEUMINDUSTRIESITWILLPUMPLIQUIDSWITHVERYWIDERANGINGPROPERTIESANDSUSPENSIONSWITHAHIGHSOLIDSCONTENTINCLUDING,FOREXAMPLE,CEMENTSLURRIES,ANDMAYBECONSTRUCTEDFROMAVERYWIDERANGOFCORROSIONRESISTANTMATERIALSTHEWHOLEPUMPCASINGMAYBECONSTRUCTEDFROMPLASTICSUCHASPOLYPROPYLENEORITMAYBEFITTEDWITHACORROSIONRESISTANTLININGBECAUSEITOPERATESATHIGHSPEED,ITMAYBEDIRECTLYCOUPLEDTOANELECTRICMOTORANDITWILLGIVEAHIGHFLOWRATEFORITSSIZEINTHISTYPEOFPUMP,THEFLUIDISFEDTOTHECENTREOFAROTATINGIMPELLERANDISTHROWNOUTWARDBYCENTRIFUGALACTIONASARESULTOFTHEHIGHSPEEDOFROTATIONTHELIQUIDACQUIRESAHIGHKINETICENERGYANDTHEPRESSUREDIFFERENCEBETWEENTHESUCTIONANDDELIVERYSIDESARISESFROMTHECONVERSIONOFKINETICENERGYINTOPRESSUREENERGYTHEIMPELLERCONSISTSOFASERIESOFCURVEDVANESSOSHAPEDTHATTHEFLOWWITHINTHEPUMPISASSMOOTHASPOSSIBLETHEGREATERTHENUMBEROFVANESONTHEIMPELLER,THEGREATERISTHECONTROLOVERTHEDIRECTIONOFTHELIQUIDANDHENCETHESMALLERARETHELOSSESDUETOTURBULENCEANDCIRCULATIONBETWEENTHEVANESINTHEOPENIMPELLER,THEVANESAREFIXEDTOACENTRALHUB,WHEREASINTHECLOSEDTYPETHEVANESAREHELDBETWEENTWOSUPPORTINGPLATESANDLEAKAGEACROSSTHEIMPELLERISREDUCEDASWILLBESEENLATER,THEANGLEOFTHETIPSOFTHEBLADESVERYLARGELYDETERMINESTHEOPERATINGCHARACT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