Centrifugal Compressor Design and Rerating in Turbochargers

download Centrifugal Compressor Design and Rerating in Turbochargers

of 8

  • date post

    13-Dec-2015
  • Category

    Documents

  • view

    12
  • download

    1

Embed Size (px)

description

Design

Transcript of Centrifugal Compressor Design and Rerating in Turbochargers

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 1/8

    CentrifugalCompressorDesignandReratinginTurbochargersWrittenbyLeonidMoroz

    Monday,05April201008:17

    LeonidMoroz

    SoftInWay,Inc.Burlington,MA01803,USA

    SergeyGnezdilovJSCSKBTPenza,440034,Russia

    Contactauthor:LeonidMoroz,L.Moroz@SoftInWay.com

    Abstract

    Specialnumericalresearchiscarriedouttostudytheeffectsofdifferentcentrifugalcompressordesignandreratingstrategiesneededforflowpathcomponentsstandardizationduringmanufacturingandretrofittingprocessesinturbochargers.

    Experimentaldatavscalculationresultscomparisonsforseveralcentrifugalcompressordesignsareusedtoconfirmthevalidityofcalculationsinpredictingperformanceandoperatingrange.

    Numericalcalculationsallowedtoestimatetheinfluenceofimpellerandvaneddiffusergeometrymodificationsacceptablewithinselectedconstraints.

    Thestrategygivespossibilitytodesignhighlyefficientcentrifugalcompressorsoruseexistingcentrifugalcompressorflowpathsinsteadofnewonesthatcanbecreatedby

    trimmingtheimpellerwheelattrailingedgevaryingimpellerbladeheightsatleadingandtrailingedgesmodifyingvaneddiffuserheightanditsstaggerangle

    Accurateoffdesignflowpredictionsaremadetofindstableoperationrangesofupgradedcentrifugalcompressorflowpaths.

    Thedescribedstudyiscarriedoutincollaborationwithlargeturbochargersmanufacturerengagedinlocomotive,marine,heavydutytrucks,drillingrigs,power,andpipelinestationsappliances.

    Nomenclature

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 2/8

    D1,D2 Impellerinlet/outletdiameter

    l1,l2 Impellerinlet/outletbladeheight

    Compressorefficiency

    Rotationalspeed

    C Compressorpressureratio

    Figure1.Centrifugalcompressorinturbocharger

    Introduction

    Centrifugalcompressorsareusedinturbochargersextensivelybecauseoftheirsmoothoperation,theircapabilityforwideoperatingrange,andtheirhighreliability.

    Properselectionofthecentrifugalcompressorisanimportantdecisioninfluencingthesuccessfuloperationoftheturbocharger.Thus,completedesignworkflowshouldbeusedtotakeintoaccountallengineeringaspectsinvolvingsequenceofseveralsteps:

    Preliminarydesign(sizing)MeanlinecalculationsPerformancemapsanalysisFlowpathoptimizationProfilingand3DbladedesignStructuralandmodalanalysis3Dflowanalysis

    Preliminarydesignofcentrifugalcompressorrequiresminimalinputofgeometricalandoperationalconstraintstofindacceptablesizesoftheflowpath.

    Meanlinecalculationsandperformancemapsanalysisisthenextsteptorefinethesolution.Somegeometrymodificationscanbemadeduringthissteptooptimizetheefficiencyandmeetrequiredlevelofstableoperatingrange.

    3Dbladedesignandprofilingincombinationwithstructural,modaland3Dflowanalysesgivethefinalanswertothequestionwhatkindofflowpathismostsuitableforspecificneeds.

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 3/8

    Centrifugalcompressorreratingisoftenrequiredtomeetnewdesignflowrateorhead.Thesechanges,inmanycases,needthecompressortobe"redesigned".

    Itincludesanythingfromasimplespeedchangetotrimmingofimpellers.Inthecaseofvaneddiffuserbeingusedinthecompressor,thecompressorsurgemarginisgreatlyreducedbecauseofchangesinsuctionpressures[1].Thisisduetotheflowangleattheexitoftheimpellerhavingalargeincidenceangleonthediffuserblade.

    Inthisarticlesomewaystochangetheheadandflowofexistingcompressorsarediscussedandinvestigated.Compressorreratingrequiresanindepthknowledgeofthecompressoranditscomponents.

    Therequirementsforadifferentheadatapproximatelyjustthesameflowwouldrequirechangesinmachinespeedand,insomecases,thetrimmingofthewheels.

    Itisalsoknownthattrimmingthecompressorwheelswouldalsoreduceheadproduced.Aspeedincreaseafterthewheelshavebeentrimmedwouldthenincreasetheheaddeliveredatahigherflow[2].

    ExperimentalTestFacility

    Centrifugalcompressorperformancewasevaluatedusinganexperimentaltestfacility.Centrifugalcompressorwasdrivenbytheaxialturbinestageutilizingthepowerofexhaustgasessuppliedbyconvertedaeroderivativecombustionchamber.Thismethodwasusedbecauseofhighpowerinputlevelthathasbeenneededfordrivingthecentrifugalcompressorinselectedturbocharger.

    Thelocationsofpressure,temperature,andflowmeasuringsystemsareschematicallyshownonfig.2.

    Inletanddischargepipingwasselectedinthatwaytopreserveflowconditionsthatminimizemeasuringuncertainties.

    Dataacquisitionmethodswereusedduringexperimentaldataprocessing.Pressure,temperature,flowmeasuringandrotationalspeedmeasuringinstrumentationwascalibratedbeforecarryingouttheexperimentalstudiestomeetallmeasurementrequirements.

    Figure2.Experimentaltestfacility

    ProblemFormulation

    Currentstudywasintendedtofindquickandreliableapproachtopredictoffdesignperformanceandstableoperatingrangeofnewandupgradedcentrifugalcompressorflowpathsusedinturbochargers.Thestudywasdividedinto

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 4/8

    severalphases:

    ValidationofcentrifugalcompressorflowpredictiontoolusingperformancedataobtainedduringexperimentalstudiesofseveralcompressorflowpathsPerformanceandstableoperatingrangepredictionsfordifferentalternativecentrifugalcompressorflowpathmodifications

    PreliminaryDesign

    Thefirststepofthestudywastocarryoutthepreliminarydesignfromthegroundandfindoptimalsolutionusinggeometricalconstraintsandoperationalboundaryconditionsclosetovaluesofdesignparametersusedincentrifugalcompressor(TK23series)manufacturedbyJSCSKBT.

    Preliminarydesignin1Dinverseproblemformulationwasusedtofindthesolutiontakingintoaccountspecifieddesignconditions(=32000rpm,C=3.5).

    Arandomsearchmethodisallowedtofindacloudofsolutionpointswithintheselectedranges(fig.3).Themaximumefficiencyistakenascriteriontodefinetheoptimalsolutionpoint.

    Figure3.Cloudofsolutionpoints

    Figure4.Bestcentrifugalcompressorflowpathselectedafterpreliminarydesign

    Resultsfromthepreliminarydesignstudyshowedthatgeometricalandoperationalparametersofanewlydesigned

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 5/8

    flowpathareveryclosetotheoriginalone(fig.4).Thismeansthattheflowpathoftheoriginalcentrifugalcompressorisatitsoptimallevel.

    ComparisonofExperimentalandCalculationalResults

    Theexperimentalperformancesofseveralcentrifugalcompressorswereevaluatedandcomparedtonumericalcalculations.Comparisonofexperimentalandflowpredictionsforonecasestudyisshownonfig.5.Analysisofperformancemapsshowsgoodagreementofnumericalcalculationswithexperiment.

    Figure5.Performancemapscomparisonofexperimentalandcalculationresults

    Figure6.Centrifugalcompressor3Dflowpath

    Accurateoffdesignflowpredictionsallowedtousethecalculationapproachinfurtherstudiesofupgradedcentrifugalcompressorflowpaths.Numericalstudiestestplanincludesperformanceevaluationoforiginalcompressorflowpathmodificationsdueto

    trimmingofimpellertrailingedgediametervaryingimpellerbladeheightsatleadingandtrailingedgesmodifyingvaneddiffuserheightandstaggerangle

    EffectofImpellerWheelTrimmingatTrailingEdge

    Flowpredictionsweremadeforseveralmodificationstostudytheeffectofimpellerwheeltrimming.Fig.7depictscalculatedperformancemapsforcasestudiesdescribedbellow:

    initialflowpathgeometry:impelleroutletdiameterD2=275mm

    modification1:wheeltrimming(3.5mm)modification2:wheeltrimming(7mm)

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 6/8

    Figure7.Effectofimpellerwheeltrimmingattrailingedge

    EffectofImpellerInletHeightVariation

    Flowpredictionsweremadeforseveralmodificationstostudytheeffectofimpellerinletheightvariation.Fig.8depictscalculatedperformancemapsforcasestudiesdescribedbellow:

    initialflowpathgeometry:impellerinletheightl1=47.5mm

    modification3:impellerinletheightreducing(2.5mm)modification4:impellerinletheightreducing(5mm)

    Itisevidentthatchokeinvaneddiffusercausesthecoincidenceofspeedlineswhenperformanceisbeingestimatedonlowerrotationalspeeds.

    Figure8.Effectofimpellerinletheightvariation

    EffectofImpellerOutletHeightVariation

    Flowpredictionsweremadeforseveralmodificationstostudytheeffectofimpelleroutletheightvariationincombinationwithreducingofvaneddiffuserheight.Fig.9depictscalculatedperformancemapsforcasestudiesdescribedbellow:

    2=11.4mmmodification5:impelleroutletheightreducing(1mm)modification6:impelleroutletheight

    reducing(2mm)

  • 8/31/2015 CentrifugalCompressorDesignandReratinginTurbochargers

    http://articles.compressionjobs.com/articles/engineering/3458centrifugalcompressordesignreratingturbochargers?tmpl=component&print=1&page= 7/8

    Figure9.Effectofimpelleroutletheightvariation

    EffectofVanedDiffuserStagerAngleVariation

    Flowpredictionsweremadeforseveralmodificationstostudytheeffectofvaneddiffuserstaggeranglevariation.Fig.10depictscalculatedperformancemapsforcasestudiesdescribedbellow:

    initialflowpathgeometry:defaultvaneddiffuserstaggerangl