轮机英语（轮机长大管轮）

Lesson3PerformanceparametersofmarinedieselengineNewWordsandExpressionselectricity[ɪ'lɛk'trɪsəti]n.电力；电流；强烈的紧张情绪kilowatt['kɪlə'wɑt]n.[电]千瓦（功率单位）cylinder['sɪlɪndɚ]n.圆筒；汽缸；[数]柱面；圆柱状物indicator['ɪndɪketɚ]n.指标，标志，迹象；指示器crankshaft['kræŋk'ʃæft]n.曲轴；机轴flange[flændʒ]n.[机]法兰；[机][古生]凸缘；轮缘；边缘

vt.给…装凸缘brake[brek]v.刹车NewWordsandExpressionsdynamometer[,daɪnə'mɑmətɚ]n.测力计；功率计；动力计torsionmeter['tɔ:ʃən,mi:tə]n.扭矩测量仪；扭力计entail[ɪn'tel]vt.使需要，必需；承担；遗传给；蕴含

n.引起；需要；继承discard[dɪsˈkɑːrd]v.放弃

n.抛弃；被丢弃的东西或人shorthand['ʃɔrthænd]n.速记；速记法denote[dɪ'not]vt.表示，指示NewWordsandExpressionsresonant['rɛznənt]adj.洪亮的，共振的；共鸣的damp[dæmp]vt.使潮湿；使阻尼；使沮丧，抑制

vi.减幅，阻尼；变潮湿elastically[ɪ'læstɪkli]adv.有弹性地；伸缩自如地amplitude['æmplə'tʊd]n.振幅；丰富，充足；广阔elastic[ɪ'læstɪk]adj.有弹性的；灵活的；易伸缩的

n.松紧带；橡皮圈sinusoidal[,sɪnə'sɔɪdl]adj.正弦曲线的stiffness['stɪfnɪs]n.僵硬；坚硬；不自然；顽固Theonlyreasonapracticalengineerwantstorunanengineeratallistoachieveadesiredoutputofusefulwork,whichis,forourpresentpurposes,todriveashipatprescribedspeed,and/ortoprovideelectricityataprescribedkilowatt.

驱动现场工程师的唯一理由是让其完成一个有输出效果有用的工作，就目前的实际意义来看，让船舶在既定的航速航行或者让电力在既定的功率运转是我们的目的。

THERMALEFFICIENCYThermalefficiency（）istheoverallmeasureofperformance.Inabsolutetermsitisequalto:

Aslongastheunitsusedagreeitdoesnotmatterwhethertheheatorworkisexpressedinpounds-feet,kilograms-meters.But，calories,kWhorjoules.TherecommendedunitstousearenowthoseoftheSIsystem. Heatconvertedintoworkperhour=Nkwh=3600NkJ

THERMALEFFICIENCYWhereN=thepoweroutputinKWHeatsupplied=M×KWhereM=massoffuelusedperhourinkgandK=calorificvalueofthefuelinkJ/kgthereforeItisnownecessarytodecidewheretheworkistobemeasured.Ifitistobemeasuredinthecylinders,asitusuallydoneinslow-runningmachinery,bymeansofanindicator,theworkmeasured(thehencepower)isthatindicatedwithinthecylinder,andthecalculationleadstotheindicatedthermalefficiency.

THERMALEFFICIENCYIftheworkismeasuredatthecrankshaftoutputflange,itisnetoffriction,auxiliarydrives,etc.,andiswhatwouldbemeasuredbyabrake,whenthetermbrakethermalefficiency(如果功是在曲轴输出法兰上测量的，那么它是净摩擦，辅助驱动等，如果是用制动器来测量的，就是制动热效率).Additionally,thefuelisreckonedtohaveahigher(orgross)andalower(ornet)calorificvalue,accordingtowhetheronecalculatestheheatrecoverableiftheexhaustproductsarecooledbacktostandardatmosphericconditions,orassessedattheexhaustoutlet.Theessentialdifferenceisthatinthelatercasethewaterproducedincombustionisreleasedassteamandretainsitslatentheatofvaporization.Thisisthemorerepresentativecase-andmoredesirableaswaterintheexhaustflowislikelytobecorrosive.Todaythenetorlowercalorificvalue(LCV)ismorewidelyused.

THERMALEFFICIENCYReturningtoourformula,ifwetakethecaseofanengineerproducinga(brake)outputof10000KWforanhourusing2000kgoffuelperhourhavinganLCVof42000KJ/kg

=42.9%(basedonLCV)

MechanicalefficiencyThereasonsforthedifferencearelistedabove.Thebrakepowerisnormallymeasuredwithahighaccuracy(98percentorso)bycouplingtheenginetoadynamometeratthebuilder’sworks.Ifitismeasuredintheshipbytorsionmeteritisdifficulttomatchthisaccuracyand,ifthetorsionmetercannotbeinstalledbetweentheoutputflangeandthethrustblockorthegearboxinput,additionallosseshavetobereckonedduetothefrictionentailedbythesecomponents.Theindicatedpowercanonlybemeasuredfromdiagramwherethesearefeasibleandtheyarealsosubjecttosignificantmeasurementerrors.=42.9%(basedonLCV)

MechanicalefficiencyFortunatelyforourattemptstoreckononthemechanicalefficiency,testbedexperienceshowsthatthefrictiontorque(thatis,infact,allthelossesreckonedtoinfluencethedifferencebetweenindicatedandbraketorque)isnotverygreatlyaffectedbytheengine’storqueoutput,notbythespeed.Thismeansthatthefrictionpowerlossisroughlyproportionaltospeed,andfairlyconstantatfixedspeedovertheoutputrange.Mechanicalefficiencythereforefallsmoreandmorerapidlyasbrakeoutputfalls.Itisoneofthereasonswhyitisundesirabletoletanenginerunforprolongedperiodsatlessthan30percenttorque.

WorkingcyclesAdieselenginemaybedesignedtoworkonthetwo-strokeoronthefour-strokecycle;bothoftheseareexplainedbelow.Theyshouldnotbeconfusedwiththeterms‘single-acting’or‘double-acting’,whichrelatetowhethertheworkingfluid(thecombustiongases)actsononeorbothsidesofthepiston.

HorsepowerMeaneffectivepressureismainlyusefulasadesignshorthandfortheseverityoftheloadingimposedontheworkingpartsbycombustion.Inthatcontextitisusuallyderivedfromthehorsepower.Ifthelatteris‘brake’horsepower(bhp),themepderivedisthebrakemeaneffectivepressure(bmep);butitshouldberememberedthatitthenhasnodirectphysicalsignificanceofitsown.Toobtainthetotalforcethemepmustbemultipliedbytheareaonwhichitacts.Thisinreturncomprisestheareaofonepiston,a=πd²/4,multipliedbythenumberofcylindersintheengine,denotedbyN.thedistancemovedpercyclebytheforceistheworkingstokesinonecylinderinthespecifiedtime.Gatheringallthesefactorsgivesthewell-known‘plan’formula:

HorsepowerDespitetheintroductionoftheSIsystem,inwhichpowerismeasuredinkilowatts(kW),horsepowercannotyetbediscardedaltogether.Poweristherateofdoingwork.Inlinearmeasureitisthemeanforceactingonapistonmultipliedbythedistanceitmovesinagiventime.Theforcehereisthemeanpressureactingonthepiston.Thisisobtainedbyaveragingthedifferenceinpressureinthecylinderbetweencorrespondingpointsduringthecompressionandexpansionstrokes(可以通过平均压缩和膨胀冲程中对气缸内相应点的压力差得到).Itcanbederivedbymeasuringtheareaofanindicatordiagramanddividingitbyitslength.Thisgivesnaturallytheindicatedmeaneffectivepressure(imep),alsoknownasmeanindicatedpressure(mip).Letthisbedenotedby‘p’.

HorsepowerThevalueoftheconstantkdependsontheunitsused.Theunitsmustbeconsistentasregardsforce,lengthandtime.If,forinstance,SIunitsareusedkwillbe1000andthepowerwillbegiveninKW.Ifimperialunitsareusedkwillbe33000andtheresultisinimperialhorsepower.Onboardshipthemarineengineer’sinterestintheaboveformulawillusuallybetorelatemepandpowerfortheenginewithwhichheisdirectlyconcerned.Inthatcase,，a,nbecomeconstantsaswellaskand

MeanpistonspeedThisparameterissometimesusedasanindicationofhowhighlyratedanengineis.However,althoughinprincipleahigherpistonspeedcanimplyagreaterdegreeofstress,aswellaswear,etc,inmodernpracticethelubricationofpistonringsandliner,aswellasofotherrubbingsurfaces,hasbecomemuchmorescientific(然而，理论上，更快的活塞速度意味着更大的压力，以及磨损等，但在实际过程中，润滑活塞环和衬套，以及其他摩擦表面，已变得更加科学).Itnolongerfollowsthata‘high’pistonspeedisofitselfmoredetrimentalthanaloweroneinawell-designedengine.Thisisgiveninmeters/secif=strokeinmetersandn=revolutionsperminute.

Fuelconsumptionin24hoursInSIunits:Wherew=fuelconsumptionrate,kg/kWhW=totalfuelconsumedperdayintones.（1tonne=1000kg）

VibrationManyproblemshavetheirrootsin,ormanifestthemselvesas,vibration.Vibrationmaybeinanylineardirection,anditmayberotational.Vibrationmayberesonant,atoneofitsnaturalfrequencyuptothosewhicharemorecommonlycallednoise.Thatvibrationfailuresarelessdramaticnowthanformerlyisduetotheadvancesinourunderstandingofitduringthelast80years.Itcanbecontrolled,onceitisrecognized,bydesignandbycorrectmaintenance,byminimizingitatsource,bydamping,andbyarrangingtoavoidexcitingresonance.Vibrationisaverycomplexsubjectandallthatwillbeattemptedhereisabriefoutline.）

VibrationAnyelasticallycoupledshaftorothersystemwillhaveoneormorenaturalfrequencieswhich,ifexcited,canbuilduptoanamplitudewhichisperfectlycapableofbreakingcrankshafts(任何弹性联轴节或其他系统将有一个或多个固有频率，如果被激活，建立的振幅完全能够折断曲轴).‘Elastic’inthissensemeansthatadisplacementoratwistfromrestcreatesaforceortorquetendingtoreturnthesystemtoitspositionofrest,andwhichisproportionaltothedisplacement.Anelasticsystem,oncesetinmotioninthisway,willgoonswinging,orvibrating,aboutitsequilibriumpositionforever,inthetheoreticalabsenceofanydampinginfluence.Theresultingtime/amplitudecurveisexactlyrepresentedbyasinewave,i.e.itissinusoidal.

VibrationIngeneral,therefore,thefrequencyoftorsionalvibrationofasinglemasswillbe:

cyclepersecondWhereqisthestiffnessinnewtonmetersperradianandIisthemomentofinertialoftheattachedmassinkgmeters2.Foratransverseoraxialvibrationwheresisthestiffnessinnewtonspermetreofdeflectionandmisthemassattachedinkg.Lesson4WorkingPrincipleofMarineDieselEngineNewWordsandExpressionssparkplug

火花塞gasolineengine

汽油机cylinder['sɪlɪndə]n.汽缸；柱面；圆柱状物piston['pɪst(ə)n]n.活塞evaporates[ɪ'væpəreɪts]n.蒸发；蒸发岩；蒸发盐auto-ignition['ɔːtəʊ-ɪg'nɪʃ(ə)n]n.自燃；自动点火release[rɪ'liːs]vt.释放；发射downwards['daʊnwɚdz]adv.向下，往下NewWordsandExpressionscrankshaft['kræŋkʃɑːft]n.曲轴；机轴two-stroke['tu:strəuk]adj.两冲程的（内燃机）revolution[revə'luːʃ(ə)n]n.革命；运行；循环suction['sʌkʃ(ə)n]n.吸；吸力；抽吸compression[kəm'preʃ(ə)n]n.压缩，浓缩；压迫expansion[ɪk'spænʃ(ə)n]n.膨胀；阐述；扩张物exhaust[ɪg'zɔːst;eg-]n.排气；废气；排气装置descend[dɪ'send]vi.下降；下来；遗传NewWordsandExpressionstachometer[tæˈkɑmɪtə(r)]n.转速计；流速计valve[vælv]n.阀；瓣膜；真空管；活门rockerarm

摇臂，[机]摇杆progressively[prəˈgresɪvli]adv.渐进地；日益增多地ascend[ə'send]vi.上升；登高；追溯instantly['ɪnst(ə)ntlɪ]adv.立即地；马上地；即刻地TopDeadCenter

上止点spray[spreɪ]n.喷雾；喷雾器；水沫tachometer[tæˈkɑmɪtə(r)]n.转速计；流速计NewWordsandExpressionsconsecutive[kənˈsɛkjətɪv]adj连续的，连贯的BottomDeadCenter

下止点nitrogen['naɪtrədʒ(ə)n]n.氮；氮气rotary[rotary]adj.旋转的，转动的；轮流的rod[rɒd]n.棒；惩罚；枝条；权力bearing['beərɪŋ]adj.轴承；关系；方位；举止crankcase['kræŋkkeɪs]n.曲轴箱；曲柄箱smoothen['smuðən]vt.使平滑，使平和consecutive[kənˈsɛkjətɪv]adj连续的，连贯的NewWordsandExpressionsuneventorque

不平衡力矩reciprocating[rɪ'sɪprəˌkeɪtɪŋ]adj.往复的；交互的；摆动的intake['ɪnteɪk]n.摄取量；通风口；引入口scavenging['skævɪndʒɪŋ]n.清除；净化；除气法port[pɔːt]n.港口；端口；左舷；舱门adjacent[ə'dʒeɪs(ə)nt]adj.邻近的，毗连的uniflow['ju:nifləu]adj.单向流动的manifold['mænɪfəʊld]n.多种；复印本uneventorque

不平衡力矩Thedieselengineisatypeofinternalcombustionengine,morespecifically,itisacompressionignitionheatengine,inwhichthefuelisignitedbybeingsuddenlyexposedtothehightemperatureandpressureofacompressedgas,ratherthanbyaseparatesourceofignition,suchasasparkplug,asisthecaseinthegasolineengine(柴油机是内燃机的一种。更准确的来讲，作为压缩发火的热机，在柴油机中，柴油是通过突然暴露在高温高压的被压缩气体中被点燃的，而不是像汽油机那样需要额外的能源（火花塞）来引燃).Thisisknownasthedieselcycle,afterGermanengineerRudolfDiesel,whoinventeditin1892basedonthehotbulbengineandreceivedthepatentonFebruary23,1893.

WorkingcycleDieselaimstoproducemechanicalenergyfromchemicalenergystoredinfuels.Theengineusesaconventionalarrangementofcylindersandpistonsfoundinothertypesofinternalcombustionengines,asgasolineengines.Conceptually,thedieselengineachieveshighperformanceandexcellentfuelconsumptionbycompressingtheaircontainedwithinthecylinderathighpressureandinjectingasmallamountoffuelintohighlycompressedair(从概念上讲，柴油发动机在高压下压缩气缸内的空气并将少量燃料喷射到高压空气中，从而实现了高性能和优异的燃料消耗).Thetemperaturegeneratedduringthecompressionoftheairmakesthissmallamountofatomizedfuelevaporates.

WorkingcycleMixtureofatomizedfueltotheexistinghotairintothecombustionchambercausesthevaporizedfueltoreachitsauto-ignitiontemperatureandburn.Thusfreeingtheenergystoredbefore.Withtheburningoffuel,energyintheformofheatisreleasedincreasingthepressureinsidethecylinder.Thisenergyreleasedraisesthepressureinthecylinderthatisappliedtothesurfaceofthepiston,whichmakesthepistondownwardsanddoworkonthecrankshaft.Adieselenginemaybedesignedtoworkonthetwo-strokeoronthefour-strokecycle.Bothofthemareexplainedbelow.

FourstrokedieselengineInfour-strokecycleengines,therearefourstrokescompletingtworevolutionsofthecrankshaft.Thesearerespectively,thesuction,compression,power(expansion)andexhauststrokes(在四冲程循环发动机中，有四个冲程完成曲轴的两次旋转。四个冲程分别是吸气，压缩，做功（膨胀）和排气).InFig.1(I),thepistonisshowndescendingonitssuctionstroke.Onlypureairisdrawnorpushedbytheturbochargerintothecylinderduringthisstrokethroughtheinletvalve,whereas,theexhaustvalveisclosed.Thesevalvescanbeoperatedbythecam,pushrodandrockerarm.Thenextstrokeisthecompressionstroke(II)inwhichthepistonmovesupwithboththevalvesremainingclosed.Theair,whichhasbeendrawnintothecylinderduringthesuctionstroke,isprogressivelycompressedasthepistonascends.Thepressureattheendofthecompressionstrokerangesfrom30to60bar,evento150bar.

FourstrokedieselengineAstheairisprogressivelycompressedinthecylinder,itstemperatureincreasestoabout600-700℃,untilwhenneartheendofthecompressionstroke,itbecomessufficientlyhightoinstantlyigniteanyfuelthatisinjectedintothecylinder(随着气缸内的空气逐渐被压缩，其温度会上升到600-700℃左右，直到接近压缩行程结束时，它会变得足够高，以便立即点燃注入气缸内的燃料).Whenthepistonisnearthetopofthecylinder(knownasTopDeadCenterorTDC),dieseloilissprayedintothecombustionchamberthroughfueloilinjectorunderhighpressure,higherthanthatexistinginthecylinderitself.Thisfuelthenignites,beingburntwiththeoxygenofthehighlycompressedair.

FourstrokedieselengineDuringthefuelinjectionperiod,thepistonreachestheendofitscompressionstrokeandcommencestoreturnonitsthirdconsecutivestroke,powerstroke(III).Duringthisstroke,thehotproductsofcombustionconsistingchieflyofcarbondioxide,togetherwiththenitrogenleftfromthecompressedairexpand,thusforcingthepistondownward(在该行程中，主要由二氧化碳组成的热燃烧产物与从压缩空气中排出的氮气一起膨胀，因此迫使活塞向下运动).Thisisonlytheworkingstrokeofthecylinder.Duringthepowerstroke,thepressurefallsfromitsmaximumcombustionvalue(50-80bar,evenhigherthan150bar),whichisusuallyhigherthanthegreatervalueofthecompressionpressure,toabout3.5-5barnearthebottomofthecylinder(knownasBottomDeadCenterorBDC).

FourstrokedieselengineTheexhaustvalvethenopens,usuallyalittleearlierthanwhenthepistonreachesBDC.Theexhaustgasesaresweptoutonthefollowingupwardstrokeofthepiston.Theexhaustvalveremainsopenthroughoutthewholeexhauststroke(IV)andclosesatthetopofthestroke.Thereciprocatingmotionofthepistonisconvertedintotherotarymotionofthecrankshaftbymeansofaconnectingrodandcrankshaft.Thecrankshaftrotatesinthemainbearings,whicharesetinthecrankcase.Theflywheelisfittedonthecrankshaftinordertosmoothenouttheuneventorquethatisgeneratedinthereciprocatingengine.

FourstrokedieselengineFig.1WorkingCycleoffour-strokeengine

TwostrokedieselengineThetwostrokedieselengineperformsthesamecycleofeventsasthefourstrokedieselengine.Themaindifferenceisthatintake,compression,power,andexhaustfunctionstakeplaceduringonlytwostrokesofthepiston.Thetwostrokesoccurduringeachrevolutionofthecrankshaft.Therefore,ittakesonlyonerevolutionoftheshafttocompleteatwo-strokecycle.Inthetwostrokedieselengine,thefirststrokeiscompressionstroke,thesecondoneconsistsofignition,combustion,expansion,exhaustandscavenging.

TwostrokedieselengineTwo-strokeenginesinvariablyhaveportstoadmitairwhenuncoveredbythedescendingpiston.Theexhaustmaybeviaportsadjacenttotheairportsandcontrolledbythesamepiston(loopscavenge)orviaexhaustvalvesattheotherendofthecylinder(uniflowscavenge)(弯流扫气中，废气是通过与进气相邻近的气口排出，排气口的打开是通过活塞控制的；直流扫气中，废气是通过布置在气缸另一端的排气阀排出的).Themostwidelyusedtwostrokedieselengineonboardshipistheuniflowscavengetype.Fig.2showsthesequenceofeventsinatypicaltwo-strokecycle.

TwostrokedieselengineFig.2WorkingCycleoftwo-strokeengine

TwostrokedieselengineFirststroke(Compression):–ThepistonisatBDC.–Thescavengeportsandexhaustvalveopen.–Scavengeairflowsintothecylinderandpushestheexhaustgasesthroughtheexhaustvalveintotheexhaustgasmanifoldandthentotheturbocharger.–Thepistonmovesup.–AtthepointES,thepistoncoversthescavengeports.–AtthepointAS,theexhaustvalveclosesandcompressionstarts,whichheatstheair.

TwostrokedieselengineSecondStroke(Ignition−Combustion−Expansion−Exhaust−Scavenging):–WhenthepistonisalmostatTopDeadCenter(TDC),fuelisinjectedintothe–cylinder.–Thefuelignitesinthecompressed,heatedairandthencombustionstarts.–Thegasesexpandandpushthepistondown(workingstroke).–AtthepointAO,theexhaustvalveopens,exhaustgasflowsoutofthecylinderintotheexhaustgasmanifold.–AtthepointEO,thepistoncontinuestomovedowntoletairinthroughthescavengeports.Scavengeairflowsintothecylinderandpushestheexhaustgasthroughtheexhaustvalveintotheexhaustgasmanifoldandthentotheturbocharger.Lesson5DesignFeaturesofMCEnginesNewWordsandExpressionsoverhaul[ˈoʊvərhɔ:l]n.大修，检查，彻底检修，详细检查topland[tɑ:plænd]n.(活塞的）顶岸高度combustion[kəmˈbʌstʃən]n.燃烧mating[ˈmeɪtɪŋ]n.接触，结合greycastiron[ɡrekæstˈaɪərn]n.灰口铸铁biannual[baɪˈænjuəl]adj.一年二次的component[kəmˈpoʊnənt]n.成分，组分，零件uppermost[ˈʌpərmoʊst]adj.最重要的，最高的，至高的NewWordsandExpressionspatent[ˈpætnt]n.专利，执照，专利品adoublelapjoint

n.重叠搭口groove[ɡruv]n.凹槽，环槽

vt.开槽于Al-bronze[brɑ:nz]n.铝青铜，铜铝合金coating[ˈkoʊtɪŋ]n.涂层，覆盖层ash[æʃ]n.灰，灰烬hypothesis[haɪˈpɑ:θəsɪs]n.灰，灰烬NewWordsandExpressionsdecisive[dɪˈsaɪsɪv]adj.决定性的，坚定的，果断的，决断的deterioration[dɪˌtɪrɪəˈreʃən]n.恶化，退化，堕落byvirtueof

adv.依靠，由于chambergeometry

n.燃烧室几何形状weld[wɛld]vt.焊接

n.焊接，焊缝inconel[ɪn'koʊnl]n.铬镍铁合金heatresistance

n.耐热性decisive[dɪˈsaɪsɪv]adj.决定性的，坚定的，果断的，决断的NewWordsandExpressionsmargin[ˈmɑ:rdʒən]n.边缘，范围，空白shakercooling

n.晃动冷却，振荡冷却pronounced[prəˈnaʊnst]adj.明显的，显著的，被说出来的Inrecentyears,anumberoffeatureshavebeensuccessfullyintroduced,primarilywiththeaimoffurtherimprovingthecylinderconditionandincreasingthetimebetweenoverhauls.Inthiscontext,weareinparticularaddressingfeaturessuchasthehightoplandpistonwhichprotectsthepistonringsagainstthethermalloadfromthecombustiongases.Thisimprovestheperformanceofthepistonringpacksignificantly,andthegraduallossoftensioninthepistonringsisreduced,resultinginhigherTBOsforthepiston.Afurtherbenefitisthatthehightoplandhasmadeitpossibletolowerthematingsurfacesbetweencylinderlinerandcylindercover,thusreducingthethermalloadonthecylinderlinerandthusimprovingtheconditionsforthelubeoilfilm(提高活塞顶岸高度的好处还有：使降低气缸套和气缸盖的结合面的高度成为了可能，这降低了气缸套的热负荷并大大改善了润滑油膜的工作条件).Thehighheatinputisabsorbedbythesteelcylindercover,whichhasahigherthermalstabilitythanthegreycastironusedforcylinderliners.Asaconsequence,thereliabilityofthecylinderlinerisfurtherenhancedbytheintroductionofthehigh-toplandpiston.Testswithhigh-toplandpistonswerestartedaboutfouryearsagoonanS80MCengineandshowedasignificantimprovementinthegeneralcombustionchamberconditionandanincreaseinthetimebetweenoverhaulsbyafactorof3,makingbiannualoverhaulssufficient.Ofotherimportantfeatures,thepistonringpackshouldbementioned.Thereliabilityofthecombustionchambercomponentsandthecylinderconditiondependsverymuchontheperformanceofthepistonringpackwhich,accordingly,iscontinuouslybeingoptimized(燃烧室部件的稳定性和气缸的工作状况取决于活塞环组件的工作状况，因此人们一直致力于优化活塞环组件的工作性能).Thetwouppermostpistonringsarehigher,givingtheseringsgreaterstrengthandthermalstability.Thepistonringmaterialhasbeenoptimizedtocopewiththeincreasedthermalloadthatresultsfromthehigherratingoftheengines.Someyearsago,aspecialpatentedCPR(ControlledPressureRelief)pistonringasthetoppistonringwastestedandsubsequentlyintroduced.Thisringhasadoublelapjoint,andanoptimalpressuredropacrossthetoppistonringisensuredbyreliefgrooves.Foreaseofrunning-in,anAl-bronzecoatingisappliedonthelowerrings.AthirdfeatureintroducedisthePistonCleaning(PC)ring.Thepurposeofthisringistocontrolashandcarbondepositsonthepistontoplandandthuspreventcontactbetweenthecylinderlinerandthesedeposits,whichwouldremovepartofthecylinderoilfromthelinerwall(这种活塞环的主要目的是控制活塞顶部的灰尘和积碳，并阻止气缸套和这些积碳之间的接触，气缸套和积碳之间的摩擦会破坏气缸壁的润滑膜).Long-termtestsonanS80MCenginesince1994haveshownpositiveresults,verifyingthehypothesisthat“borepolish”maybeadecisivefactorinthedeteriorationofthecylindercondition,especiallyinhigh-ratedlargeengines.PCringsarethereforenowstandardonthemostrecentlargeboreMCengines.Protectingandcontrollingtheheatexposedpartsinthecombustionchamberhavealwaysbeendesignpriorities.Byvirtueofmodifiedcombustionchambergeometry,thishasbeenfurtherenhanced.ThisdevelopmentwaspromptedinparticularbytheK-MC(-C)engineswiththenarrowcombustionspace.Overtheyears,thepistonsintheseengineshavebeenprovidedwithawelded-onlayerofinconeltoincreasetheheatresistance.Evenso,heatexposureeffectshavebeenexperiencedontheK-MC(-C)enginesincertaincases,indicatingthatthemarginsshouldpreferablybehigher.Withthenewgeometry,wehaveobtainedmorespacearoundthefuelnozzles,andthusagreaterdistancefromthenozzlestothepistontop.Thismeansthatthefuelinjectionandcombustiongiverisetosmallerheatinputtothepistontopandunchangedheatinputtocylindercoverandexhaustvalve(通过这种型的燃烧室结构，我们可以在喷油器附近获得更多的空间，因此燃油喷嘴和活塞头顶部之间的距离更大。这意味着燃油喷射和燃烧会产生更少的热量传至活塞顶部，而传至气缸盖和排气阀的热量则保持不变).Measurementshaveconfirmedatemperaturereductionofthepistontopofsome100°Caswellasunchangedtemperaturesonothercombustionchambercomponents.Thesimpleshakercoolingprincipletraditionallyappliedforthepistoncantherebybemaintained.ThisnewcombustionchamberdesignhasalreadybeenintroducedonanumberofMCenginesbeingproducedforcontainervesselsandisthepresentstandardonlarge-boreMCengines,includingMC/MC-CenginesapplicableforVLCC,i.e.S80MC,S80MC-C,S90MC-CandL90MC-C.Eventhoughtheheatexposureofthepistonislesspronouncedintheseengines,theadditionalmarginhasbeenintroducedalsoontheseengines.Lesson6DieselEngineConstruction(1)NewWordsandExpressionsbedplate['bɛd,plet]n.机座rigid['rɪdʒɪd]adj.坚硬的；精确的crankshaft['kræŋk'ʃæft]n.曲轴；机轴transversegirders

横梁alignment[ə'laɪnmənt]n.队列，成直线，对中，对齐longitudinalgirders

纵梁crankshaftthrow

曲轴行程thrustcollar

止推环，推力环，止推套环NewWordsandExpressionsbore[bɔr]n.孔，孔径castiron

铸铁weld[wɛld]v.焊接，使结合，使成整体ClassificationSociety

船级社frame[frem]n.机架，结构crosshead['krɔːs,hed]n.十字头entablature[ɛn'tæblətʃɚ]n.气缸体crankcase['kræŋk,kes]n.曲轴箱，曲柄箱NewWordsandExpressionsmisalignment[mɪsə'laɪnmənt]n.不重合，未对准，不对中strengtheningstringers

加强纵梁grind[ɡraɪnd]vt.打磨，磨碎scavenge['skævɪndʒ]vt.扫气，打扫matingsurface

配合面，啮合面cylinderbeam

缸梁multi-cylinder

多缸的fittedbolts

连接螺栓NewWordsandExpressionstiebolt

系紧螺栓，枕木螺栓，连接螺栓tierod

贯穿螺栓compressionstroke

压缩冲程jackbolt

定位螺栓compressionstroke

压缩冲程stud[stʌd]n.螺柱nut[nʌt]n.螺母，螺帽cylinderliner

气缸套NewWordsandExpressionsreciprocate[rɪ'sɪprəket]n.往复'O'ring

O型圈telltalepassage

漏泄通道borecooling

孔冷却flange[flændʒ]n.法兰tangent['tændʒənt]n.切线exhaustvalve

排气阀pushrod

制动缸推杆，推棒，顶杆reliefvalve

安全阀，减压阀Thebedplateisthefoundationonwhichthetwostrokeengineisbuilt.Itmustberigidenoughtosupporttheweightoftherestoftheengine,andmaintainthecrankshaft,whichsitsinthebearinghousingsinthetransversegirders,inalignment.Atthesametimeitmustbeflexibleenoughtohogandsagwiththefoundationplatetowhichitisattachedandwhichformspartoftheshipsstructure.Basicallythebedplateconsistsoftwolongitudinalgirderswhichrunthelengthoftheengine.Connectingtheselongitudinalgirdersarethetransversegirderswhicharepositionedbetweeneachcrankshaftthrowandeithersideofthethrustcollar.Builtintothetransversegirdersarethemainbearingpocketsforthecrankshafttorunin.TheBedplateOnthesmallboreengines,thebedplatecanbemadefromcastironasasinglecasting.Largerengineshaveafabricatedbedplate.Thismeansitisweldedtogetherfromsteelsections,steelcastingsandplate.ThesteelistoClassificationSocietyspecificationsandisalowcarbonsteelwithamaximumcarboncontentof0.23%.Earlierfabricatedbedplateshadboxsectionlongitudinalgirdersandboxsectionfabricatedtransversegirders.Problemswereencounteredwithcrackingofthetransversegirders,whichincreasedasenginepowersandcrankshaftthrowsgotlarger(随着发动机功率和曲轴抛出量增大，横梁发生开裂问题也随之增加).TheBedplateThemodernbedplateisconstructedfromfabricatedlongitudinalgirderswithcaststeeltransversesectionscontainingthebearingpocketsandtieboltholesweldedintoplace.Aftermanufacture,thebedplateisstressrelieved,thebearingpocketsarelineboredandlandingsurfacesmachined.TheBedplateTheframesareotherwiseknownastheAframes.Thesecarrythecrossheadguidesandsupporttheengineentablature(thecylinderblock).Onolderengines,theAframeswereind