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外文翻译--研究一个离心泵内的震动压力—利用数字表示的方法来支持工业实验.doc

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外文翻译--研究一个离心泵内的震动压力—利用数字表示的方法来支持工业实验.doc

英文文献InvestigationintopressurepulsationsinacentrifugalpumpusingnumericalmethodssupportedbyindustrialtestsR.SpenceandJ.AmaralTeixeiraABSTRACTTheoperationofcentrifugalpumpscangenerateinstabilitiesandpressurepulsationsthatmaybedetrimentaltotheintegrityandperformanceofthepump.Inthepresentstudyanumericalinvestigationofthetimevariationofpressurewithinacompletepumpwasundertaken.Arangeofparametersandthreeflowrateswereinvestigatedandthepulsationswereextractedat15differentlocationscoveringimportantpumplocationsexperiencingthelargestpulsationlevels.Itwasalsonotethatmonitoringpulsationsatthetopdeadcentreofthepumpvolutecasingwouldprovideabetterindicationofinternalpumppulsationsthanmonitoringatthedischarge.1、IntroductionCentrifugalpumpshavebeendevelopedandrefinedovermanyyears.Inpracticethedesignofboththeimpellerandvolutearecomplex,withnumerousgeometricalparametersbeingrequiredtoidentifyadesignthatwillformahydraulicallyefficientpump.Evenwithtrieddesignsitiswellknownthattheoperationofrotodynamicpumpcanresultinthegenerationofthedesignprocessusedthefinaldecisionregardingthesuitabilityofanysignificantlynewpumpdesignisusuallymadefollowingphysicaltesting.Thesetestsareoftenexpensiveintermoftimeandresources,forexampleduetothemanufacturingofpatternequipment,theprototypepumpitselfaswellastheassemblyandtheuseoftestfacilities.Gradually,pumpmanufacturersareturningtocomputationaltechniquestostudydesignfeatures.Typicallytheseinvestigationsareconductedwithaviewtoreducing,oreliminatingthenumberoftestsconductedandtohighlightanyundesirabledesigncharacteristicsatanearlystage.AlthoughcommercialCFDpackageshavebeenusedtopredicttimedependentpressurepulsations,computationalfacilitiesseemtohavelimitedmostofthatworktosimulatingthevoluteandimpellerinteractionsonly,withoutthesuctioninletbranchandleakageflowpathsbeingconsidered.Thecurrentworkaimstoimprovethequalityandscopeofpreviousworkrelatedtopressurepulsationsbyperformingsimulationsinvolvingthecompletehydraulicpumpgeometry.Thenumericalmodelincorporatesallofthemajorflowpathsinapumpencompassingthesuctioninlet,impeller,leakagepathwaysandthevolutecasing.Theworkfocusesonareducedscaleversionofahighenergyimpellerinadoubleentry,singlestagepumparrangement.Theunderstandingofpressurepulsationsbypumpmanufacturersseemssurprisinglylimited.Noofficialstandardsexistforsafelevelsofpressurepulsationsinpumpstheonlyindustryadoptedguidelineisaguaranteeoflessthan3variationinthepumpoutletpressure.Yet,itisnotknownwhetheralimitationof3variationinthedischargecorrespondstoasafelimitatotherlocationswithinapump.Thereforeadetailedassessmentofpreesurepulsationsinboththeimpellerandvolutehasbeenperformedtoguaranteeforothercriticalpartsofthepump.Theanalysiscoversthreeflowratesoveraflowrangeextendingfromthepumpdutycondition1.00oQntoacommonpumpminimumoperatingpointof25ofthedutycondition0.25oQnTheanalysespresentedherearepartofalargeparametricstudyinvestigatingtheeffectofinternalgeometryonpressurepulsationswithinthepump.Duetotheconstrainsinvolvedinsuchalargestudy,oneadditionalaimofthisworkwastoshowthatareasonableestimateofpressurepulsationsandtrendsinpressurepulsationscanbeachieved,fordifferingpumpgeometries,inareasonabletimeframebynumericalmeans.2、ExperimentalInvestigationSomeexperimentalresultswereavailabletooneoftheauthorsfromindustrialtestsperformedtoexaminepressurepulsationsinareducedscalecontractpump.Thisexperimentalworkperformedanumberofyearsbeforethenumericalanalyses.Thepumpreceivedfluidfromaclosedsystem,suchthatthepumpwassituatedwithabend3.5diametersupstreamandasecondbend4diametersdownstream.Directlyfollowingtheupstreambend,flowstraightenerswerefitteninordertoreducethefloweffectscausedbythebendontheinflowtothepump.TenZtypeKistlerpressuretappingsweremountedonthepump.Pressuretappingswereusedtocollectdataatvariousstationarylocationsaroundthepump.Holesweredrilledatspecificlocationsaroundthepumpandtubeswereusedtoconnectthepressuretransducerstoeachlocation.Thepathdistancefromthetappingpointtothetransducerwaskeptasshortaspossible1015ommtoensurethatanyresonantfrequenciescausedbythepathdistanceareabovethemeasuredrange.OneZtypeEntranpressuretransducerwasutilizedintheexperimentaltests.Thistransducerwasmountedintheimpellershroud15ommbehindthesuctionfaceofanimpellerblade.Theelectricalsignalsfromthetransducersweretransferredfromtherotatingelementthestationarydatarecorderviaaslipringarrangementatthenondriveendofthepump.Thetestringwasrunataninitialspeedof1400RPMovertheflowrange25125ofdutywith5mintaperecordingsofthetransducersbeingtakenateach25flowincrement.The1.00oQndutyconditionequatedtoaflowrateof500om3/handanominalheadof33.8omfortheinlineimpellerwhenthepumpwasrunat1400RPM.Theflowchangewasachievedbyadjustingaflowvalveasslowlyandassmoothlyaspossible.Arangeoftestswasperformedforanumberofpumpgeometricalarrangements,howeveronlytwoareofparticularinterestheretermedAandBasdetailedabove.Atimehistoryofthepressurevariationateachoftheabovelocationsisrecorded.AspectralanalysiswasthenconductedonthisdatawiththepressurepulsationsbeingoutputastherootmeansquareRMSpressurepulsation.Duetothetimeconstraintsinvolvedintheexperimentaltests,detailedperformancedatawasnottaken.Thetestworkwasconductedinaccordancewithnormalindustrialpracticesanditisconsideredthatthepressureswereaccuratewithin1.5.3、NumericalInvestigationCFXTASCflowisacommercial3DCFDcodethatafiniteelementbasedfinitevolumemethodtothetransportequations.Thismethodprovidesthebenefitofretainingthegeometricflexibilityoffiniteelementmethodswhileretainingtheconservationpropertiesofthefinitevolumemethod,I,elownumericalerroronnonsmoothgirds.Thecodeemployscolocatedstructuredgridsandacoupiedalgebraicmultigridschemetosolvethesystemofequations.Itisafullyimplicitsolver,thusitcreatesnotimesteplimitationandisconsideredeasytoimplement.Thisdoesnothaveanybearingonthesteadystatesolution.Butdoeslimittransientcalculationstobeingonlyfirstorderaccurateintime.TheCFXTASCflowsolverisalsoacoupledsolvermeaningthatthemomentumandcontinuityequationsaresolvedsimultaneously.Thisapproachreducesthenumberofiterationsrequiredtoobtainconvergenceandnopressurecorrectionstermisrequiredtoretainmassconservation,leadingtoamorerobustandaccuratesolver.Theprogramalsoincludessomepreandpostprocessingcapabilitiesthatarespecificallygearedtowardsturbomachinerycomponents,thesefacilitatethesetupofthemodelandtheexaminationoftheresultsCFXTASCflowhasaproventrackrecordinturbomachineryapplications,withnumerousitemsofliteraturebeingpublished.3、1ModelgenerationTheimpellergeometrywascreatedusingCFXBladehenastwomirroredhalves,usingthemaximumdiameterof366omm.ThebullnoseaspectoftheinlineimpellerdesignproveddifficulttocapturewithinCFXBladegen,astheprogramisnotdesignedtomodeldoubleentryimpelleranddoesnotallowforhubprofilesthatterminateinthebullnosearrangement.Toavoidthisproblem,althoughthetruehubeffectivelyfinishedatthepointofsymmetry,afictitioushubwasextendedfromthemidpointofthebullnosetotheimpelleroutletalongtheimpellerlineofsymmetry.Thereforewithonlyslightmodificationstothemeridionalhubprofileasatisfactorymodelwasproducedfortheinlineimpeller.Thestaggeredimpellercouldbeusedwithoutanymodification,asthemeridionalflowpathsforeithersideoftheimpellerdonotconnect.CFXTurbogridwasusedtogenerategridaroundthebladesoneithersideoftheimpeller,withthegridonbothsidesoftheimpellersbeingidentical.Fortheinlineimpeller,carewastakentoensurethatthegridwasradialatthepositionofthebullnose.ThisisessentialtoaidthecreationofaninterfacebetweentheimpellersinCFXTASCflow,howeveritalsolimitedthequalityofthegrid.Withaninitialimpellergridestimateofaround500,000modes,itisimmediatelyapparentthatsplittingthisgridbetween12impellerpassagewaysandtheleakageflowwillresultinimpellerpassagewaygridsoflessthanidealsize.Someefforthasbeenmadetofocusonthelessergridsizes,whileincludinggridsaslargeas86,499nodes.AdecisionwastakentoconductthegridindependencecheckusingsteadystateanalysesincorporatingamodelconsistingofhalfapumpIesiximpellerpassagesandhalfpumpvoluteusingsymmetry,astheimpellerinteractionwiththevoluteisextremelyimportant.Thevolutemodelwasidenticalineachofthegridindependenceanalyses,withadistributionsimilartothatusedinthefinalpumpmodel.Itisexpectedthatthisinteractionwillcauselargerdifferencestobeevidentbetweenthegirdsthanisusuallydisplayedingridindependenceforimpelleronlycomparisonsduetotheincreasedcomplexityoftheflowpatterns.Theanalyseswererunatthedutyflowcondition1.00oQn,boundaryconditionsbeingmassflowatinletandaveragestaticpressureatoutlet,withthemaximumresidualconvergencecriteriabeingsetto1e4max.thepressuredatareportedbelowrelatestothevariationinasingleimpellerpassagewayfrommidpassagetomidpassageatasinglepositionwithinthevolute.4、2SolutionparametersAsthemotionoftheimpellerbladesrelativetothestationaryvoluteiscentraltotheinvestigation,theanalysismustinvolvemultipleframesofreference.Inordertopreventtworotor/statorinterfacesbeingperpendiculartoeachotherattheompelleroutlet,theleakageflowpathsandtheimpellergridsweresetintherotationalframeofreference.Thesuctioninletandvolutegridswereinthestationaryframeofreference.ThegridinterfacesusedinthestudycanbesummarizedasfollowsInternalcomponentconnectiongeneralgridinterfaceGGIBetweentwostationarycomponentsgeneralgridinterfaceBetweentworotationalcomponentsgeneralgridinterfaceBetweenrotationalandstationarycomponentsFrozenrotorinterfacesteadystateanalysisRotor/statorinterfacetransientanalysisThefrozenrotorinterfaceachievesframechangewithoutrelativepositionchangeovertimeandwithoutinterfacialaveraging.Localflowfeaturesareallowedtopropagate.Aphysicalanalogyistoimagineobservingtheflowbetweenastationaryandrotatingcomponentunderstroboscopiclighting.Therotor/statorinterfaceisaslidingframechangeinterfacethatcanaccountfortransientinteractioneffects.Themeshoneithersideofarotor/statorinterfaceisalwaysinrelativemotionwithrespecttooneanother.TherearethreecommoncombinationsofboundaryconditionsthatareoftenusedforanalyzingpumpflowInlettotalpressureOutletmassflowInletmassflowOutletstaticpressureInlettotalpressureOutletstaticptessureThetransientanalysiswasconductedforthreeflowrates.Thesearedefinedasbeingthedutyflowcondition1.00oQn,0.50oQnand0.25oQn.Turbulencehasbeensimulatedusingthestandatdkepsilonmodel.Aninvestigationwasconductedintovariousturbulencemodelsandthestandardkepsilonmodelwasfoundtobemorestableandproducebetterresultsthanothermodelsovertheflowrangebeingconsidered.Thegridsizeusedintheanalysisisnotcapableofmodelinglocal

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