外文翻译--润滑和摩擦学在海水水力活塞泵中的应用.doc外文翻译--润滑和摩擦学在海水水力活塞泵中的应用.doc

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附录二外文翻译英文文献lubricationandtribologyinseawaterhydraulicpistonpumpAbstract:Waterhydraulicsystemshaveprovokedmajorinterestbecauseofthehumanfriendlyandenvironmentalsafetyaspects.Pistonpumpisoneofthemostfrequentlyusedhydraulicunitsinrecentengineeringtechnique.Inwaterhydraulicpistonpump,poorlubricationismorelikelytohappenthaninoilhydrauliconebecauseofdifferenceinpropertiesbetweenwaterandoil.Sotherearesomekeyproblemssuchascorrosivewearanderosion,whichareinvestigatedbriefly.Manynewmaterialshavebeendeveloped,whichgivelongerlifeexpectancieswithwaterwithoutcorrosionanderosion.AnewtypeofseawaterhydraulicpistonpumpswithbettersuctioncharacteristicshadbeendevelopedatHUST.Muchofthisresearchhasconcentratedonnewmaterials,structureandexperiments,whicharealsospeciallyintroduced.Keywords:waterhydraulics;pistonpump;lubrication;test;materialINTRODUCTIONTheearliesthydraulicsystemsusedwaterasthehydraulicfluid.Thisrestrictedtheworkingtemperaturerangeandcausedcorrosionaswellaslubricatingproblems.Itwasnotuntilthelate1920'sthatmineralhydraulicoilswereintroduced.Consequently,theoilbecamethemainpressuremediumofhydraulicapplications.Recently,thedemandforusingpuretapwater(excludingseawater)asapressuremediuminhydraulicapplicationshasincreasedduetoitsavailability,easymaintenance,itslowcostandhighsafetylevelsagainstpollutionandfirehazard.So,waterhydraulicscanbeusedinnewapplicationareassuchasfoodprocessing,pulpandpaperindustry,medicine,glassmaking,coalminingandnuclearindustry.Waterischaracterizedbyverylowviscosityincomparisonwithmineralhydraulicoils.Forexample,thekinematicsviscosityofwaterat40isabout0.72m/sandoftypicalmineraloilis322m/s.Keyproblemsshouldbeconsideredinwaterhydraulicsystem.Firstly,theverylowviscositymustincreasethedifficultyofdevelopinghydrodynamicfilmbetweenfrictionalpairs,andtheverysmallchangeofwater'sviscositywithpressuremeansthatelastohydrodynamiclubricationwithhardmaterialsisunlikelytooccur.So,thelowviscosityisaccompaniedwithpoorlubricityofwater.Poorlubricitycancausecorrosivewearanderosionproblems.Secondly,itistobenotedthatwater(especiallyseawater)iselectricallyconductiveandmayactasanelectrolytewhenimpuritiesorcertainadditivesarepresent.Insuchcasestheelectrolyticcorrosionmayoccur.Thereforemetallicmaterialstobeusedinconnectionwiththewaterpressuremediumshouldcomplywiththeelectrochemicalseries.Fromthepresentpointofview,oilhasanadvantageagainstwaterintheaspectoflubricationbuttherecenttechnologyofmaterials,designsandtribologyhasbroughtthepossibilityofusingwaterasapressuremediumagain.Anumberofnewmaterials,suchasstainlesssteel,corrosionresistantalloy,ceramics,polymers,bronze,brass,anodizedaluminaandcomposites,etc.,havegoodcompatibilitywithwater,alongwithmoderndesignandmanufacturingtechniques,waterhydraulicsbecomemoreandmorepractical.Modernscienceandtechnologiescanprovideessentialtechnicalguaranteeforthereemergenceanddevelopmentofwaterhydraulics.Pistonpumpisoneofthemostfrequentlyusedhydraulicunitsinrecentengineeringtechniques.Inwaterhydraulicpistonpump,poorlubricationismorelikelytohappenthanthatinoilhydrauliconeInwaterhydraulicsystem,thefirstobjectiveistodeveloppistonpumpandmotorusingrawwateraspressuremedium.Todealwithproblemsofusingrawwateraslubricant,threecriticalslidingpairs,suchasthecylinderblock/portplate,piston/cylinderbore,swashplate/slipperpadhavebeenfocused.Waterpistonpump(motor)hasbeendevelopedinsomedevelopedcountries,suchasUSA,UK,Japan,Denmark,GermanyandFinland,etc.Pumpsandmotorsarevirtuallyidentical.TheFennercompanyintheUnitedKingdomhasdevelopedanaxialpumpforrawwaterwithfixeddisplacement.Thepumpsandmotorsareoftheswashplatetype.Bearingcentersaredesignedtobeinlinewiththetorquecentersoftheunitsinordertominimizetiltforcesonthevalveplate.Allrubbingsurfacesusepolymer-stainlessinterfaces.Anadaptationofthepumpusingceramicpistonshasoperatedsuccessfullyupto14MPa.Thecasingaremadeofstainlesssteel.TheHauhincoradialpistonpumpinGermanyhasfixeddisplacement.Thepumpdesignisbaseduponusingnewandnon-traditionalmaterialssothataseparatelubricationsystemisavoided.Themedium,industrialwater,tobepumpedalsoactsasalubricant.Typicallypumpratingsare:flowrateupto242L/min,pressureupto32MPa.TheDanfossNessiepumpoftypePHA(pumpaxialhigh-pressure)inDenmarkisdesignedasanintegralunitbasedupontheswashplateprinciple.Allfrictionsurfaces,suchascylinders,thrustplateandpistonshoes,aremadesolelyofreinforcedplasticorovermoldedstainlesssteel.Theouterhousingandendflangesaremadeofchronite-castedspecialbrassinordertopreventcorrosion.Thepumpisdesignedsothatthelubricationofthemovingpartsinthepumpismaintainedbythewateritself.Allthepartsinthepumparemadeofnon-corrosivematerials,ensuringalonglifeofthepump.Thepressurelevelofthepumpis16MPa.TheaxialpistonpumpintheFinnishcompanyHytarcanalsoactasamotoranditcanbeoperatedinnormaltapwaterandseawater.Thepressurelevelofthepumpis21Mpaandthelifespanisabout8000hAftertenyearsofresearchanddevelopmentonhighwaterbasedfluidhydraulics,anewresearchanddevelopmentprogramfortapwaterandseawaterhydraulicssupportedbyNationalScienceFoundationofChinawerecarriedoutatHuazhongUniversityofScience&Technology(HUST)from1990totoday.Recently,anewtypeofseawaterhydraulicpistonpumpswithbettersuctioncharacteristicshadbeendevelopedatHUST[4].Muchofthisresearchhasconcentratedonnewmaterials,structureandexperiments,whicharespeciallyintroducedinthispaper.Meanwhile,theapplicationsonsomeaspectsforwaterhydraulicsarealsodescribed.1SEAWATERHYDRAULICAXIALPISTONPUMPATHUSTFigure1showstheschematicdiagramoftheseawaterhydraulicaxialpistonpumpatHUST.Itisaswashplateaxialseven-pistonpumpwithfixeddisplacement,whichcanworkwitheitherseawaterorrawwater.Thispump'sratingsare:flowrateupto40L/min,pressureupto14MPa.Thespecifiedpressureis10MPa.Theinletandoutletcheckvalveswithsoftsealsarerespectivelyassociatedwitheachpiston,onthepistonsuctionstroke,waterisdrawnbyvacuumfromtheinletportthroughtheinletcheckvalves,fillingthespaceattheleftsideofthepistons.Onthepistondischargestroke,thewaterisforcedtotheoutletportthroughtheoutletvalves.Togetbetterlubricationforthebearings,thedrivemechanismofthepumpislubricatedwithoilandtheoilchamberattherightsideofthepistonsiskeptseparatefromthedisplacementsidebyusingdoublepackingsealsaroundeachofthesevenpistons.Therefore,bearingsandtheswashplate/slipperpadfrictionpairsarelubricatedwithoil.Thepiston/cylinderborefrictionpairsarelubricatedwithrawwater.Fig.1SchematicDiagramoftheSeawaterAxialPistonPumpWhenusingrawwateraslubricant,duetorawwater'schemicallyactivenature,lowviscosity,poorlubricationandhighvaporpressure,theselectionofmaterialsused,playakeyroleindetermininglonglifespanforawaterhydraulicpump.Thefrontandrearcasings,cylinderblockaremadeofaluminum-alloywithanodizingtreatment,pistonsandcylinderlinersaremadeofstainlesssteel(1Cr18Ni9Ti)andreinforcedpolymerorreinforcedpolymer-eterketon(PEEK),respectively.Thesealsofinletandoutletvalvesaremadeofpolytetrafluoroethylene(PTEF)andthepoppetswithsoftsealsaremadeofbronzedstainlesssteel.Inordertoreducethewearonasurface,materialswithlowfrictioncoefficientmustbeused.relativelynewpolymer,PEEKshowsaverylowfrictioncoefficient,about0.02,incontacttosteelwithawaterfilm[4].Thisfrictioncoefficientiscomparablewith0.05~0.07forsteeltosteelwithmineraloil.Recently,PEEK,hasturnedtobecommonlyusedforslidingpartsinwaterhydraulicpumpandmotor.Inordertoreducethewearonasurface,materialswithlowfrictioncoefficientmustbeused.Arelativelynewpolymer,PEEKshowsaverylowfrictioncoefficient,about0.02,incontacttosteelwithawaterfilm[4].Thisfrictioncoefficientiscomparablewith0.05~0.07forsteeltosteelwithmineraloil.Recently,PEEK,hasturnedtobecommonlyusedforslidingpartsinwaterhydraulicpumpandmotor.1EXPERIMENTAL2.1TestapparatusInordertoexaminethefunctionsofthispump,anexperimentalstudyisinprogress.Thetestpumpisdrivenbyanelectricmotor.Tostudythefunctionsofthispumpatdifferentpumprotation,whichwascontrolledbyadjustmentsinelectriccabinet.Thereliefvalvecanbeusedtoprotectthesystem.Thethrottleisusedasloadingunitforthetestpump.Thecoolercontrolsthetemperatureofthesystem.Allhydrauliccomponentsweredesignedbyourselves.2.2ExperimentalmethodThetestmethodisdescribedasfollows.Eitherrawwater(puretapwater)orseawater(imitationseawater)canbeusedaspressuremedium.Theimitationseawatercanbemadeupaccordingtothestandard(ASTMD21142252)oftheUnitedStatesofAmericaThatthemainfeaturesofthetestsweredecidedasfollows:(a)Theloadingpressureshouldbeadjustedupto14MPa.(b)Thespeedofrotationshouldbefullyvariableupto1000r/min.(c)Afterspeedreachesasteadystate,waterpressureandtheflowrateshouldberecorded.(d)Thetemperatureoffluidmediumiscontrolledintherangeof20~40e.2.3TestprocedureTheaimofthetestwastodeterminethevariationofvolumetricefficiency,forthepump,withpressureandspeed,aswellasthecurvesofthepumpinletvacuumversusflowrate.UsuallyVolumetricefficiencycanbeusedtodescribetheperformancesofapump.Itisdefinedas:=0QQ100℅Whereisvolumetricdfficiency;Qisthedffective,averagedpumpdeliveryperunittime,L/min;Q0isthetheoretical,averagedpumpdeliveryperunit
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