涡轮增压器的压力测量PPT格式课件下载.pptx

涡轮增压器的压力测量PPT格式课件下载.pptx

《涡轮增压器的压力测量PPT格式课件下载.pptx》由会员分享，可在线阅读，更多相关《涡轮增压器的压力测量PPT格式课件下载.pptx（33页珍藏版）》请在冰豆网上搜索。

ConceptsNREC,PressureMeasurement,NickBainesConceptsNREC,Probesareusedformeasurementsoftotalpressure,staticpressure,andflowanglewithintheflowitself.Awiderangeofprobesisavailable,andprobesareoftenmanufacturedforspecialpurposes.Dynamic（time-varying）pressuremeasurementrequiresspecialconsideration.Conventionalpneumatictapsandprobesdonothaveanadequateresponsetimetocaptureanybuttheslowestoftime-varyingevents,butmanyspecialtransducersandmeasuringsystemsareavailableforthispurpose.,ConceptsNREC2003,Pressuremeasurement,PrinciplesWallstatictapsTotalpressureprobesTotal-staticprobesDirectionalpressureprobesPressuretransducersDynamicpressuremeasurementPressurescanners,Pressuremeasurement,ThedifferencebetweentotalandstaticpressurecanbeseenbysolvingtheEulerequationalongastreamline.Thisissimplytheforce-momentumequation,inwhichwebalancetheforces（pressureforcesandgravitationalforce）againstthechangeofmomentumthatoccursasthefluidmovesalongastreamline.Thisgivesadifferentialequationthatcanbesolvediftheflowisincompressibletogiveanequationwithpressure,kineticenergy,andpotentialenergyterms.Formostpracticalpurposeswecanneglectthepotentialenergy.Wethendefinethetotalpressurep0asthesumofthestaticpressurepandthedynamicpressurerC2.Iftheflowiscompressible（densityisnotconstant）thenwehavetotakeaslightlydifferentapproach,butwecanstillobtainanequation,thistimeincludingtheMachnumberM,thatexpressestherelationbetweenthetotalandstaticpressures.,ConceptsNREC2003,Totalandstaticpressures,Compressibleflow:

@#@,Pressuremeasurement,Asinglesensorlocatedinthe“wrong”positionmaygivemisleadingmeasurements.Ideallyseveralsensorscircumferentiallyspacedshouldbeusedateachlocation.Ifmeasurementsarebeingmadeadjacenttoarowoffixedbladesorvanes,thesensorlocationsshouldbephasedrelativetothebladespacinginordertocoveracompletepassage.Sidewallstatictapsshouldbelocatedonboththehubandshroudsurfacesifatallpossible.Oneshouldneverassume（withoutgoodevidence）thatthestaticpressureisconstantacrossapassage,particularlyifthereisanycurvature.,ConceptsNREC2003,Singleandmultiplepointmeasurements,SinglepointmeasurementsWherefinespatialdefinitionisrequired,orWhereweareverysuretheflowisaxisymmetric,orWhereaccessisverydifficultMulti-pointmeasurementsarealmostalwayspreferredwherepossible,Pressuremeasurement,Pressureand/ortemperaturerakesmeasureacross-sectionoftotalpressure,staticpressureand/ortotaltemperatureofamovingfluid.Rakesoffertheadvantageofprovidingmanyseparatereadingssimultaneouslyorasimpleaverageofmanyreadings.Rakesarecustomdesignedandconstructedtomatchtheflowconditionsofaparticularapplication.Rakesmayincorporatefromtwotoseveraldozenindividualmeasuringelements.Thedesignofagivenrakeisdeterminedbymanyfactors,includingfluidvelocityandtemperature,flowanglevariation,thetypeofmeasurementrequiredandthephysicaldimensionsoftheflowpassage.Manyflowortemperatureprobesmaybeincorporatedintoarake.,ConceptsNREC2003,Traversingversusproberake,TraverseprobeGoodspatialresolutionLessblockageRequiresactuation（usuallyremote）andcontrolProberakeSimpleMoreblockage,Pressuremeasurement,Todeterminetheerrorduetotapdiameter,testscanbedonecomparingtheresponseofdifferentsizetapstothesamepressure,andtheresultingcurveofpressureagainstdiameterextrapolatedtozerodiameter.Thiscanthenformacorrectiontothepressuresmeasuredwithfinitediametertaps.,ConceptsNREC2003,Wallstatictaps1,Maketapsassmallaspossible,consistentwithtimeresponseandmanufacturinglimits,Pressuremeasurement,ConceptsNREC2003,Wallstatictaps2,Manufactureandfinishareimportanttoobtainingaccuratemeasurements,Pressuremeasurement,Wallstatictaps3,Whereholesizeisalimitingfactor,itisbestdeterminedbyexperiment:

@#@carefullymeasurethepressureatseveralholesizesandextrapolatetoConceptsNREC2003zero,Pressuremeasurement,Foraccuratemeasurementitisessentialthatprobesarealignedwiththeflowdirection.Staticpressureprobescanbeusedintransonicandsupersonicflows,butmustbeindividuallycalibratedforthepurpose.,ConceptsNREC20,03,Staticpressureprobes,AccuracydependsonthelocationofstaticholesrelativetonoseNotusefulinrestrictedspaces,Pressuremeasurement,Totalpressureprobes,PitotprobeConceptsNREC2003,Stagnationprobes,Pressuremeasurement,ConceptsNREC20,03,Effectofflowangle,Pressuremeasurement,MachnumberrangeTruetotalpressureisindicateduptoaMachnumberof1.0.ThereisaslightdropinyawinsensingrangeaboveM=0.3.Thisdecreasesaveragesabout4%foralltypesataMachnumberof1.0.Reynolds