C-6-Centrifugals-离心压气机设计

MichaelCaseyCompressorsC_6_CentrifugalsPage1Version:August2015Compressors(C)C_6:CentrifugalcompressorsProf.MichaelCaseyMA,DPhil,FIMechE,CEng,FASMERetiredProfessorofThermalTurbomachineryintheUniversityofStuttgartAneducationalcourseoncompressorsbasedonlecturesgivenbytheauthorintheUniversityofStuttgartCompressorsC_6_CentrifugalsPage2MichaelCaseyVersion:August2015ContentsC_6.1:IntroductionanddefinitionsC_6.2:VelocitytrianglesandenergytransferC_6.3:LossesincentrifugalcompressorsC_6.4:DesignofimpellerinletC_6.5:DesignofimpellerexitC_6.6:ImpellerbladegeometryC_6.7:DesignofdiffuserC_6.8:VoluteC_6.9:ReturnchannelC_6.10:CentrifugalcompressorperformancecharacteristicsCompressorsC_6_CentrifugalsPage3MichaelCaseyVersion:August2015Centrifugalcompressors•Alsoknownasradialcompressors–butusuallyhaveaxialinletflowandradialoutletflowsoarereallymixedflowcompressors•Allopenimpellers(noshroud)appearverysimilar(atfirstsight)–Back-sweepatoutletof-30to-50°–Inletbladeanglesattipof–60°–Splittervanes–everysecondbladecutbackattheinlet–Inletdiameterattiparound0.7ofoutletdiameter•Pressureratiosbetween1.5and10•Comparisonwithaxialcompressors–Lessflowforgivenoverallsizeduetosmallerinletarea–Lowerefficiencythananaxialcompressor(complexflowpassages)–Higherworkandpressureratioforsamerotationalspeed(centrifugaleffect)•Asingleradialstagecantypicallyreplace3axialstages–Centrifugalshaveflatterspeed-lineperformancecurvesthanaxialsC_6.1.1CompressorsC_6_CentrifugalsPage4MichaelCaseyVersion:August2015Whatdistinguishesacentrifugalcompressor?•Axial•Diagonal•Radial•MixedTheflowexperiencesamarkedradiuschangeasitpassesthroughtherotorC_6.1.2CentrifugalsCompressorsC_6_CentrifugalsPage5MichaelCaseyVersion:August2015Wherearecentrifugalcompressorsused?•Radialcompressorapplications–Turbochargers–Gasturbines•APU’sandsmallandmicrosizedgasturbine•Largergasturbines–Laststageofaxial-centrifugalcompressor•Multistagecompressorsforindustrialgases–gastransportinpipelines–air-liquefactionplants–largerefrigerationplant–Centrifugalfansforairconditioning–Blowers•processgases•miningventilationC_6.1.3CompressorsC_6_CentrifugalsPage6MichaelCaseyVersion:August2015SomeexamplesTurbocharger(ABB)Singlestagecompressor(MANTurbo)Multistagecompressor(MANTurbo)Ventilatorfan(EBMPapst)C_6.1.4CompressorsC_6_CentrifugalsPage7MichaelCaseyVersion:August2015Rotatingimpeller(rotor)Statorvane,diffuser.(vanedorvaneless)CasingImpellerbladeImpellerinlet(inducer)1ImpellerInlet2Impellerexit/diffuserinlet3DiffuserexitCollector/housing/voluteHubsurfaceInletguidevanes(optional)0IGVInletCompressorstagecomponentsSource:AtlasCopcoC_6.1.5CompressorsC_6_CentrifugalsPage8MichaelCaseyVersion:August2015Impellergeometry•Themostimportantgeometricparameters–Impelleroutletwidthratio•0.04b2/D20.10–Tipclearancegap•j0.5mm–Bladenumber(atoutlet)•12z32–Splittervanesandbladethickness(t)–Axiallength•L/D2~0.35–Inletdiameterratios•D1s/D2,~0.7,D1h/D2~0.25–Bladeangles•Inlettipb1s,=-60°,Outletb2,~-40°D2D1sD1nLb2jD2D1sD1nLb2j-b2C_6.1.6CompressorsC_6_CentrifugalsPage9MichaelCaseyVersion:August2015Centrifugalcompressorperformancemap•Workinputandpressureratioincreasesroughlywiththesquareofthespeedandthevolumeflowincreasesroughlylinearlywithspeed(~parabola)–Lowspeedhasverylowboostpressurewithlowvolumeflows•Alongaspeedlinethepressureratioincreasesasthevolumeflowdecreasesbutclosetothepeakpressurerisebecomesflatterbeforetheflowbecomesunstable(surgeorrotatingstall)•Themapsplitsintothreeregions–Lowflow-unstableregion(left)–Normalflow-stableregion(middle)–Highflow-maximumflowlimitedbychoke•Thedesignpointshouldlieinthestableregionclosetopeakefficiency•Operationinunstableregionnotallowed:–Pressureandflowfluctuations–Mechanicalbladevibrations–Noise•SeealsochapterC_8Surgeline=konst.ChokeUnstableregionnV100%60%1080%40%~ParabolaSpeedlinesSurgeline=konst.ChokeUnstableregionnV100%60%1080%40%~ParabolaSpeedlinesC_6.1.7CompressorsC_6_CentrifugalsPage10MichaelCaseyVersion:August2015DiffuserImpellerReferenceplanenotation•Notationforstagereferenceplanes–0upstreamofstator(inletguidevane,ifpresent)–1impellerinlet,downstreamofIGV–2impelleroutlet,diffuserinlet–3diffuseroutletStage1to3Impeller1to2Diffuser2to3RS213RS213C_6.1.8CompressorsC_6_CentrifugalsPage11MichaelCaseyVersion:August2015Velocitytrianglenotation•Notation–Meridionaldirectionusedinsteadofaxialorradialdirection–cuandwupositiveinrotationaldirection–cuandapositiveasshownbelow–wuandbnegativeasshownbelowuummmuumummuumumwucc,/tan,sin,cos)(/tan,sin,cos)(2222bbbaaacrczcmrzcrczcmrz)(22rzmccccwub(-)awu(-)cucm=wmC_6.1.9CompressorsC_6_CentrifugalsPage12MichaelCaseyVersion:August2015VelocitytrianglesRS213RS213c1baw1u1c2baw2u2c3a132c1baw1u1c2baw2u2c3a132C_6.2.1CompressorsC_6_CentrifugalsPage13MichaelCaseyVersion:August2015h-sDiagram•Note–About55%ofstaticpressureriseproducedinimpellerorrotor(degreeofreaction)–Veryhighabsolutekineticenergyatrotorexitrequiresaneffectivediffuserp1p212hsp33½c32½c12hSThLA½c22p1p212hsp33½c32½c12hSThLA½c22c1baw1u1c