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外文翻译--离心式和往复式压缩机的工作效率特性.doc

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外文翻译--离心式和往复式压缩机的工作效率特性.doc

英文原文EFFICIENCYANDOPERATINGCHARACTERISTICSOFCENTRIFUGALANDRECIPROCATINGCOMPRESSORSBYRAINERKURZ,BERNHARDWINKELMANN,ANDSAEIDIVIOKHATABRECIPROCATINGCOMPRESSORSANDCENTRIFUGALCOMPRESSORSHAVEDIFFERENTOPERATINGCHARACTERISTICSANDUSEDIFFERENTEIFICIENCYDEFINITIONSTHISARTICLEPROVIDESGUIDELINESFORANEQUITABLECOMPARISON,RESULTINGINAUNIVERSALEFFICIENCYDEFINITIONFORBOTHTYPESOFMACHINESTHECOMPARISONISBASEDONTHEREQUIREMENTSINWHICHAUSERISULTIMATELYINTERESTEDFURTHER,THEIMPACTOFACTUALPIPELINEOPERATINGCONDITIONSANDTHEIMPACTONEFFICIENCYATDIFFERENTLOADLEVELSISEVALUATEDATFIRSTGLANCE,CALCULATINGTHEEFFICIENCYFORANYTYPEOFCOMPRESSIONSEEMSTOBESTRAIGHTFORWARDCOMPARINGTHEWORKREQUIREDOFANIDEALCOMPRESSIONPROCESSWITHTHEWORKREQUIREDOFANACTUALCOMPRESSIONPROCESSTHEDIFFICULTYISCORRECTLYDEFININGAPPROPRIATESYSTEMBOUNDARIESTHATINCLUDELOSSESASSOCIATEDWITHTHECOMPRESSIONPROCESSUNLESSTHESEBOUNDARIESAREAPPROPRIATELYDEFINED,COMPARISONSBETWEENCENTRIFUGALANDRECIPROCATINGCOMPRESSORSBECOMEFLAWEDWEALSONEEDTOACKNOWLEDGETHATTHEEFFICIENCYDEFINITIONS,EVENWHENEVALUATEDEQUITABLY,STILLDONTCOMPLETELYANSWERONEOFTHEOPERATORSMAINCONCERNSWHATISTHEDRIVERPOWERREQUIREDFORTHECOMPRESSIONPROCESSTOACCOMPLISHTHIS,MECHANICALLOSSESINTHECOMPRESSIONSYSTEMSNEEDTOBEDISCUSSEDTRENDSINEFFICIENCYSHOULDALSOBECONSIDEREDOVERTIME,SUCHASOFFDESIGNCONDITIONSASTHEYAREIMPOSEDBYTYPICALPIPELINEOPERATIONS,ORTHEIMPACTOFOPERATINGHOURSANDASSOCIATEDDEGRADATIONONTHECOMPRESSORSTHECOMPRESSIONEQUIPMENTUSEDFORPIPELINESINVOLVESEITHERRECIPROCATINGCOMPRESSORSORCENTRIFUGALCOMPRESSORSCENTRIFUGALCOMPRESSORSAREDRIVENBYGASTURBINES,ORBYELECTRICMOTORSTHEGASTURBINESUSEDARE,INGENERAL,TWOSHAFTENGINESANDTHEELECTRICMOTORDRIVESUSEEITHERVARIABLESPEEDMOTORS,ORVARIABLESPEEDGEARBOXESRECIPROCATINGCOMPRESSORSAREEITHERLOWSPEEDINTEGRALUNITS,WHICHCOMBINETHEGASENGINEANDTHECOMPRESSORINONECRANKCASING,ORSEPARABLEHIGHSPEEDUNITSTHELATTERUNITSOPERATEINTHE7501,200RPMRANGE1,800RPMFORSMALLERUNITSANDAREGENERALLYDRIVENBYELECTRICMOTORS,ORFOURSTROKEGASENGINESEFFICIENCYTODETERMINETHEISENTROPICEFFICIENCYOFANYCOMPRESSIONPROCESSBASEDONTOTALENTHALPIESH,TOTALPRESSURESP,TEMPERATURESTANDENTROPIESSATSUCTIONANDDISCHARGEOFTHECOMPRESSORAREMEASURED,ANDTHEISENTROPICEFFICIENCYR\THENBECOMES,,,,SUCTSUCTDISCHDISCHSUCTSUCTSUCTDISCHSTPHTPHTPHSPHEQ1AND,WITHMEASURINGTHESTEADYSTATEMASSFLOWM,THEABSORBEDSHAFTPOWERIS,,SUCTSUCTDISCHDISCHMTPHTPHMPEQ2CONSIDERINGTHEMECHANICALEFFICIENCYR\THETHEORETICALISENTROPICPOWERCONSUMPTIONWHICHISTHELOWESTPOSSIBLEPOWERCONSUMPTIONFORANADIABATICSYSTEMFOLLOWSFROM,,SUCTSUCTSUCTDISCHTHEORTPHSPHMPEQ3THEFLOWINTOANDOUTOFACENTRIFUGALCOMPRESSORCANBECONSIDEREDASSTEADYSTATEHEATEXCHANGEWITHTHEENVIRONMENTISUSUALLYNEGLIGIBLESYSTEMBOUNDARIESFORTHEEFFICIENCYCALCULATIONSAREUSUALLYTHESUCTIONANDDISCHARGENOZZLESITNEEDSTOBEASSUREDTHATTHESYSTEMBOUNDARIESENVELOPEALLINTERNALLEAKAGEPATHS,INPARTICULARRECIRCULATIONPATHSFROMBALANCEPISTONORDIVISIONWALLLEAKAGESTHEMECHANICALEFFICIENCYR,,DESCRIBINGTHEFRICTIONLOSSESINBEARINGSANDSEALS,ASWELLASWINDAGELOSSES,ISTYPICALLYBETWEEN98AND99FORRECIPROCATINGCOMPRESSORS,THEORETICALGASHORSEPOWERISALSOGIVENBYEQ3,GIVENTHESUCTIONANDDISCHARGEPRESSUREAREUPSTREAMOFTHESUCTIONPULSATIONDAMPENERSANDDOWNSTREAMOFTHEDISCHARGEPULSATIONDAMPENERSRECIPROCATINGCOMPRESSORS,BYTHEIRVERYNATURE,REQUIREMANIFOLDSYSTEMSTOCONTROLPULSATIONSANDPROVIDEISOLATIONFROMNEIGHBORINGUNITSBOTHRECIPROCATINGANDCENTRIFUGAL,ASWELLASFROMPIPELINEFLOWMETERSANDYARDPIPINGANDCANBEEXTENSIVEINNATURETHEDESIGNOFMANIFOLDSYSTEMSFOREITHERSLOWSPEEDORHIGHSPEEDUNITSUSESACOMBINATIONOFVOLUMES,PIPINGLENGTHSANDPRESSUREDROPELEMENTSTOCREATEPULSATIONACOUSTICFILTERSTHESEMANIFOLDSYSTEMSFILTERSCAUSEAPRESSUREDROP,ANDTHUSMUSTBECONSIDEREDINEFFICIENCYCALCULATIONSPOTENTIALLY,ADDITIONALPRESSUREDEDUCTIONSFROMTHESUCTIONPRESSUREWOULDHAVETOMADETOINCLUDETHEEFFECTSOFRESIDUALPULSATIONSLIKECENTRIFUGALCOMPRESSORS,HEATTRANSFERISUSUALLYNEGLECTEDFORINTEGRALMACHINES,MECHANICALEFFICIENCYISGENERALLYTAKENAS95FORSEPARABLEMACHINESA97MECHANICALEFFICIENCYISOFTENUSEDTHESENUMBERSSEEMTOBESOMEWHATOPTIMISTIC,GIVENTHEFACTTHATANUMBEROFSOURCESSTATETHATRECIPROCATINGENGINESINCURBETWEEN815MECHANICALLOSSESANDRECIPROCATINGCOMPRESSORSBETWEEN612REF1KURZ,R,KBUN,2007OPERATINGCONDITIONSFORASITUATIONWHEREACOMPRESSOROPERATESINASYSTEMWITHPIPEOFTHELENGTHLUUPSTREAMANDAPIPEOFTHELENGTHLDDOWNSTREAM,ANDFURTHERWHERETHEPRESSUREATTHEBEGINNINGOFTHEUPSTREAMPIPEPUANDTHEENDOFTHEDOWNSTREAMPIPEPEAREKNOWNANDCONSTANT,WEHAVEASIMPLEMODELOFACOMPRESSORSTATIONOPERATINGINAPIPELINESYSTEMFIGURE1FIGURE1CONCEPTUALMODELOFAPIPELINESEGMENTREF2KURZ,R,MLUBOMIRSKY2006FORAGIVEN,CONSTANTFLOWCAPACITYQSTDTHEPIPELINEWILLTHENIMPOSEAPRESSUREPSATTHESUCTIONANDPDATTHEDISCHARGESIDEOFTHECOMPRESSORFORAGIVENPIPELINE,THEHEADHSFLOWQRELATIONSHIPATTHECOMPRESSORSTATIONCANBEAPPROXIMATEDBY11112243SKKDSPPQCCTCH(EQ4)WHEREC3ANDC4ARECONSTANTSFORAGIVENPIPELINEGEOMETRYDESCRIBINGTHEPRESSUREATEITHERENDSOFTHEPIPELINE,ANDTHEFRICTIONLOSSES,RESPECTIVELYREF2KURZ,R,MLUBOMIRSKY,2006AMONGOTHERISSUES,THISMEANSTHATFORACOMPRESSORSTATIONWITHINAPIPELINESYSTEM,THEHEADFORAREQUIREDFLOWISPRESCRIBEDBYTHEPIPELINESYSTEMFIGURE2INPARTICULAR,THISCHARACTERISTICREQUIRESTHECAPABILITYFORTHECOMPRESSORSTOALLOWAREDUCTIONINHEADWITHREDUCEDFLOW,ANDVICEVERSA,INAPRESCRIBEDFASHIONTHEPIPELINEWILLTHEREFORENOTREQUIREACHANGEINFLOWATCONSTANTHEADORPRESSURERATIOFIGURE2STAFIONHEADFLOWRELATIONSHIPBASEDONEQ4INTRANSIENTSITUATIONSFOREXAMPLEDURINGLINEPACKING,THEOPERATINGCONDITIONSFOLLOWINITIALLYACONSTANTPOWERDISTRIBUTION,IETHEHEADFLOWRELATIONSHIPFOLLOWSCONSTHPSSM(EQ5)QCONSTHSS1ANDWILLASYMPTOTICALLYAPPROACHTHESTEADYSTATERELATIONSHIPREF3OHANIAN,S,RKURZ,2002BASEDONTHEREQUIREMENTSABOVE,THECOMPRESSOROUTPUTMUSTBECONTROLLEDTOMATCHTHESYSTEMDEMANDTHISSYSTEMDEMANDISCHARACTERIZEDBYASTRONGRELATIONSHIPBETWEENSYSTEMFLOWANDSYSTEMHEADORPRESSURERATIOGIVENTHELARGEVARIATIONSINOPERATINGCONDITIONSEXPERIENCEDBYPIPELINECOMPRESSORS,ANIMPORTANTQUESTIONISHOWTOADJUSTTHECOMPRESSORTOTHEVARYINGCONDITIONS,AND,INPARTICULAR,HOWDOESTHISINFLUENCETHEEFFICIENCYCENTRINAGALCOMPRESSORSTENDTOHAVERATHERFLATHEADVSFLOWCHARACTERISTICTHISMEANSTHATCHANGESINPRESSURERATIOHAVEASIGNIFICANTEFFECTONTHEACTUALFLOWTHROUGHTHEMACHINEREF4KURZ,R,2004FORACENTRIFUGALCOMPRESSOROPERATINGATACONSTANTSPEED,THEHEADORPRESSURERATIOISREDUCEDWITHINCREASINGFLOWCONTROLLINGTHEFLOWTHROUGHTHECOMPRESSORCANBEACCOMPLISHEDBYVARYINGTHEOPERATINGSPEEDOFTHECOMPRESSORTHISISTHEPREFERREDMETHODOFCONTROLLINGCENTRIFUGALCOMPRESSORSTWOSHAFTGASTURBINESANDVARIABLESPEEDELECTRICMOTORSALLOWFORSPEEDVARIATIONSOVERAWIDERANGEUSUALLYFROM4050TO100OFMAXIMUMSPEEDORMOREITSHOULDBENOTED,THATTHECONTROLLEDVALUEISUSUALLYNOTSPEED,BUTTHESPEEDISINDIRECTLYTHERESULTOFBALANCINGTHEPOWERGENERATEDBYTHEPOWERTURBINEWHICHISCONTROLLEDBYTHEFUELFLOWINTOTHEGASTURBINEANDTHEABSORBEDPOWEROFTHECOMPRESSORVIRTUALLYANYCENTRIFUGALCOMPRESSORINSTALLEDINTHEPAST15YEARSINPIPELINESERVICEISDRIVENBYAVARIABLESPEEDDRIVER,USUALLYATWOSHAFTGASTURBINEOLDERINSTALLATIONSANDINSTALLATIONSINOTHERTHANPIPELINESERVICESOMETIMESUSESINGLESHAFTGASTURBINESWHICHALLOWASPEEDVARIATIONFROMABOUT90100SPEEDANDCONSTANTSPEEDELECTRICMOTORSINTHESEINSTALLATIONS,SUCTIONTHROTTLINGORVARIABLEINLETGUIDEVANESAREUSEDTODROVIDEMEANSOFCONTROLFIGURE3TYPICALPIPELINEOPERATINGPOINTSPLOTTEDINTOATYPICALCENTRIFUGALCOMPRESSORPERFORMANCEMAPTHEOPERATINGENVELOPEOFACENTRIFUGALCOMPRESSORISLIMITEDBYTHEMAXIMUMALLOWABLESPEED,THEMINIMUMFLOWSURGEFLOW,ANDTHEMAXIMUMFLOWCHOKEORSTONEWALLFIGURE3ANOTHERLIMITINGFACTORMAYBETHEAVAILABLEDRIVERPOWERONLYTHEMINIMUMFLOWREQUIRESSPECIALATTENTION,BECAUSEITISDEFINEDBYANAERODYNAMICSTABILITYLIMITOFTHECOMPRESSORCROSSINGTHISLIMITTOLOWERFLOWSWILLCAUSEAFLOWREVERSALINTHECOMPRESSOR,WHICHCANDAMAGETHECOMPRESSORMODEMCONTROLSYSTEMSPREVENTTHISSITUATIONBYAUTOMATICALLYOPENINGARECYCLEVALVEFORTHISREASON,VIRTUALLYALLMODERNCOMPRESSORINSTALLATIONSUSEARECYCLELINEWITHCONTROLVALVETHATALLOWSTHEINCREASEOFTHEFLOWTHROUGHTHECOMPRESSORIFITCOMESNEARTHESTABILITYLIMITTHECONTROLSYSTEMSCONSTANTLYMONITORTHEOPERATINGPOINTOFTHECOMPRESSORINRELATIONTOITSSURGELINE,ANDAUTOMATICALLYOPENORCLOSETHERECYCLEVALVEIFNECESSARYFORMOSTAPPLICATIONS,THEOPERATINGMODEWITHANOPEN,ORPARTIALLYOPENRECYCLEVALVEISONLYUSEDFORSTARTUPANDSHUTDOWN,ORFORBRIEFPERIODSDURINGUPSETOPERATINGCONDITIONSASSUMINGTHEPIPELINECHARACTERISTICDERIVEDINEQ4,THECOMPRESSORIMPELLERSWILLBESELECTEDTOOPERATEATORNEARITSBESTEFFICIENCYFORTHEENTIRERANGEOFHEADANDFLOWCONDITIONSIMPOSEDBYTHEPIPELINETHISISPOSSIBLEWITHASPEEDNCONTROLLEDCOMPRESSOR,BECAUSETHEBESTEFFICIENCYPOINTSOFACOMPRESSORARECONNECTEDBYARELATIONSHIPTHATREQUIRESAPPROXIMATELYFANLAWEQUATION525CNH6CNQ26525CCQHEQ6FOROPERATINGPOINTSTHATMEETTHEABOVERELATIONSHIP,THEABSORBEDGASPOWERPGISDUETOTHEFACTTHATTHEEFFICIENCYSTAYSAPPROXIMATELYCONSTANT37653726557GNCCCQCCCQHCPEQ7ASITIS,THISPOWERSPEEDRELATIONSHIPALLOWSTHEPOWERTURBINETOOPERATEAT,ORVERYCLOSETOITSOPTIMUMSPEEDFORTHEENTIRERANGETHETYPICALOPERATINGSCENARIOSINPIPELINESTHEREFOREALLOWTHECOMPRESSORANDTHEPOWERTURBINETOOPERATEATITSBESTEFLICIENCYFORMOSTOFTHETIMETHEGASPRODUCEROFTHEGASTURBINEWILL,HOWEVER,LOSESOMETHERMALEFFICIENCYWHENOPERATEDINPARTLOADFIGURE3SHOWSATYPICALREALWORLDEXAMPLEPIPELINEOPERATINGPOINTSFORDIFFERENTFLOWREQUIREMENTSAREPLOTTEDINTOTHEPERFORMANCEMAPOFTHESPEEDCONTROLLEDCENTRIFUGALCOMPRESSORUSEDINTHECOMPRESSORSTATIONRECIPROCATINGCOMPRESSORSWILLAUTOMATICALLYCOMPLYWITHTHESYSTEMPRESSURERATIODEMANDS,ASLONGASNOMECHANICALLIMITSRODLOADPOWERAREEXCEEDEDCHANGESINSYSTEMSUCTIONORDISCHARGEPRESSUREWILLSIMPLYCAUSETHEVALVESTOOPENEARLIERORLATERTHEHEADISLOWERED

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