《轮机英语（二三管轮）》-Lesson 8 Compressed Air／Starting Air System

NewWordsandExpressionshydraulically[haɪˈdrɔːlɪk(ə)li]ad.液压地pneumatically[nju(ː)ˈmætɪk(ə)li]ad.气动地governor[ˈɡʌvənə(r)]n.调速器distributor[dɪˈstrɪbjətə(r)]n.分配器maneuverability[məˌnuːvərəˈbɪlɪti]n.机动性consecutive[kənˈsekjətɪv]a.连续不断的pinion[ˈpɪnjən]n.齿轮clutch[klʌtʃ]n.离合器NewWordsandExpressionsscrewdownnon-returnvalve

截止止回阀pilotair

控制空气，先导空气fusibleplug

易熔塞unidirectionalengine

单转向发动机，不可倒转发动机interlock[ˌɪntəˈlɒk]n.连锁装置flametrap

阻焰器burstingdisk

防爆盘screwdownnon-returnvalve

截止止回阀8.1Compressed

airsystemAtypicalcompressedairsystemisillustratedinFig.8-1.Thethreesegmentsofthesystemprovideairforenginestarting,forinstrumentationandcontrol,andformiscellaneousship’sservices.Someengines,mostlysmallerauxiliaryengines,arestartedbycrankingmotors,whichmaybebattery,hydraulically,pneumatically,ormechanicallydriven.Mostlargerauxiliaryengines,however,aswellasmostpropulsionengines,arestartedbythetimedintroductionofcompressedairdirectlyintothosecylindersthatwerestoppedinpositionscorrespondingtothebeginningoftheirpowerstrokesintheselecteddirectionofrotation.大多数大型副机，当然也包括大多数推进主机都由压缩空气定时地直接进入某些气缸来起动的，这些缸（的活塞）的停止位置位于它们所选转向的做功冲程的始点。8.1Compressed

airsystemThecompressedairdrivesthosepistonsdown,infiringordersequence,therebycompressingairtrappedinothercylinders.Asoneormorerevolutionsarecompleted,fuelisintroducedinthenormalmannerintothosecylinderswhosepistonsarecompletingacompressionstroke,whichthenfire.Thestartingairiscutoffandtheengineacceleratestoitsidlespeed,undercontrolofthegovernor.Typically,eachcylinderofanin-lineengineisfittedwithastartingairvalve,butcommonlyonlythecylindersofonebankofaVenginearesofitted.通常，直列机发动机的每缸都安装一个起动空气阀，但是V型机通常只有一排气缸才这样安装。8.1Compressed

airsystemThevalvesareusuallyopenedbypilotairsuppliedviaacamshaft-drivenstartingairdistributor.Indirect-reversingenginesthedistributortimingisshiftedforreverserotation(togetherwiththetimingoftheinletandexhaustvalvesandthefuelinjectionpumps),directingpilotairtothosecylinderswhosepistonshavestoppedjustshortofTDContheupstrokes,sothattheengineisrotatedintheoppositedirectionforstarting.8.1Compressed

airsystemBecausethemaneuverabilityofashipistiedtotheavailabilityofstartingair,theminimumnumberandsizeofstartingairreceiversmustcomplywithregulatorybodyrequirements.Typically,sufficientairmustbestoredtoenableatleastsixconsecutivestartsofanon-reversingengine,ortwelveofadirect-reversingengine,withoutrecharging,inatleasttworeceivers.Althoughthepressuremaybereducedforadmissiontothecylinders,thepressureatwhichtheairisstoredwillbetwenty-fivetothirtybarsormore,withthishigherpressureallowingsmallerreceivers.8.1Compressed

airsystemItisusuallynecessarytoprovideanindependentmeansofstartingtheship’sservicedieselgenerators.Inthesystemshown,asmall(andthereforerapidlyrecharged)receiverfloatsonthestartingairmain.Intheabsenceofanothersourceofcompressedair,thisemergencyreceivercaninturnbechargedbyanemergencyaircompressor,whichmaybedrivenby,forexample,ahand-starteddieselengineoramotorsuppliedpowerfromtheemergencyswitchboard.在没有其他压缩空气来源的情况下，应急空气瓶可以用一台应急空压机充气，该应急空压机可以由应急配电板提供的动力驱动，例如手动启动的柴油发动机或电动机。8.1Compressed

airsystemShip’sserviceairsupplymaybetakenfromthestartingairreceiversaslongasdemandislimited.Wheredemandishigh,aseparate,lowpressurecompressorshouldbeusedinordertolimitrunninghoursonthelargestartingaircompressors.Compressedairsystemsonmodernshipstendtobecompletelyauto-matedeveninplantswithattendedmachinery.Automaticdraintrapsarefittedatreceiversandmoistureseparators,andcompressorsmaybestartedandstoppedautomaticallybypressureswitchesonthereceivers,ortheymaystartautomatically,afterwhichtheyruncontinuouslyuntilmanuallysecured,beingunloadedandloadedautomaticallyasreceiverpressurerisesorfalls.Thepressureswitchesaresettostartcompressorssuccessively,ratherthansimultaneously,aspressurefallsinresponsetodemand(当空气压力降低到响应需求时，压力开关设定为逐个启动空压机，而不是同时启动).8.1Compressed

airsystem8.2StartingairsystemLargemarinedieselenginesusehighpressurecompressedairtostartthem.Theairflowsintothecylinderwhenthepistonismovingdownthecylinderonthepowerstroke.Tominimizetheriskofanairstartexplosion,fuelisnotinjectedintothecylinderwhilsttheairisbeingadmitted.Airstartsystemsvaryintheirdesignandcanbequitecomplex.Therewillbeameanstostarttheenginelocallyaswellasfromaremotelocation(TheBridgeortheenginecontrolroom).ThissystemshowninFig.8-2isnotrepresentativeofonetypeofenginebutissimplifiedtogiveabasicunderstanding.8.2StartingairsystemCompressedairisproducedbyaircompressorstotheairreceiversthroughthescrewdownnon-returnvalves(SDNRv/v).Thecompressedairisthensuppliedbyalargeborepipetoaremoteoperatingnon-returnorautomaticvalveandthentothecylinderairstartvalve.Openingofthecylinderairstartvalvewilladmitcompressedairintothecylinder.8.2StartingairsystemWhenthestartsignalissent,asupplyofpilotairenablestheremotevalvetoopen.Pilotairfortheappropriatedirectionofoperationisalsosuppliedtoanairdistributor.Thisdeviceisusuallydrivenbytheenginecamshaftandsuppliespilotairtothecontrolcylindersofthecylinderairstartvalves.Thepilotairisthensuppliedintheappropriatesequenceforthedirectionofoperationrequired.Thecylinderairstartvalvesareheldclosedbyspringswhennotinuseandopenedbythepilotairenablingthecompressedairdirectfromthereceiverstoentertheenginecylinder.8.2StartingairsystemTwoairstartcompressorsarenormallysuppliedwhichmustbecapableofchargingtheairreceiversfromemptytofullinonehour.Theyareusuallytwostagereciprocatingwithinterandafter-stagecooling.Reliefvalveswillbefittedtoeachstagewhichwilllimitthepressureriseto10%ofdesignpressure,andahightemperaturecutoutorfusibleplugtolimittheHPdischargeto121°C(每一级都安装了安全阀，限制压力上升在设计压力的10%以内，安装一个高温切断装置或者易熔塞来限制输出的高压气体温度在121°C以内).Intercoolersarealsofittedwithburstingdisksorreliefvalvesonthewaterside.8.2StartingairsystemTwoairstartreceiversarefitted.Thetotalcapacityofthereceiversmustbesufficienttostarttheengine12timesalternatingbetweenaheadandasternwithoutrechargingthereceivers.Inthecaseofaunidirectionalengine,thenthecapacitymustbesufficientfor6starts.Apressuregaugeandadrainmustalsobefitted.Amanholegivesaccesstothereceiverforinspectionpurposes.8.2StartingairsystemTheautomaticvalveisonlyopenwhilstanairstartistakingplace.Itincorporatesanonreturnvalvetopreventanyexplosionintheairstartsystemgettingbacktotheairreceivers.Aslowturnvalveisincorporatedinthesmallerborepipeworktothesideofthevalve.Thisisusedtoturntheengineslowlybeforestarting,topreventdamagewhichcouldbecausedifliquidhadfounditswayintothecylinder.一个慢转阀安装在阀侧的小管径管系上，这用于启动前慢转发动机，防止缸内有液体时可能造成的损坏。8.2StartingairsystemTheairstartvalveislocatedinthecylinderhead.Whenitisopenedbytheairsignalfromthedistributor,compressedairat30barflowsintothecylinder,forcingthepistondown.Theturninggearinterlockisacontrolvalvewhichwillnotallowstartingairtooperatethesystemwhentheturninggearisengaged.8.2StartingairsystemTheairdistributornormallyconsistsofaseriesofpilotvalves,oneforeachcylinderarrangedradiallyaroundacam(空气分配器一般包括一系列控制阀，每缸一个围绕凸轮径向布置).Timedtotheengineanddrivenfromthecamshaft,thedistributoropensthemainairstartvalvesinthecorrectsequence.Theconnectiontoeachairstartvalveisfittedwithaprotectiondevice.Thiscanbeeitheraflametraporaburstingdisk.Theflametrapwillpreventanycombustioninthecylinderpassingtotheairstartlineandcausinganexplosion,whereasaburstingdiskwilllimitanypressurerisebybursting.8.2Startingairsystem

Exercises1.Theairreservoirsmusthave

fittedtopreventruptureintheeventoffire.A.highpressurealarm B.firealarmC.extinguishers

D.fusibleplugs2.Dieselenginesarestartedbysupply

ingintothecylindersintheappropriatesequencefortherequireddirection.A.coolingwater B.compressedairC.compressingair D.cylinderoilDB

Exercises3.Byfarthegreatestuseisfordieselenginestartingusingairpressureof2.5MPaormoreprovidedby

.A.rotarycompressors B.reciprocatingcompressorsC.centrifugalcompressors D.screwcompressors4.

deviceisprovidedtopreventstartingairfrombeingadmittedtothecylindersbeforethereversingiscompleted.A.Anautom