輪機英語閱讀1-22

IV.Readingcomprehension:

Thedieselengineisaformofinternalcombustionenginesimilartothatusedinabus.Its

powerisexpressedasbrakehorsepower(bhp).Thisisthepowerputoutbytheengine.Elective

horsepoweristhepowerdevelopedbythepistoninthecylinder,butsomeofthisislostbyfriction

withintheengine.Thepoweroutputofamodemmarinedieselengineisabout40.000brake

horsepower.Thisisnowexpressedinkilowatts.Bycomparisontheengineofasmallfamilycar

hasanoutputofabout80bhp.Largedieselengines,whichhavecylindersnearly3ftindiameter,

turnattherelativelyslowspeedofabout108rpm.Theseareknownasslow-speeddieselengines.

Theycanbeconnecteddirectlytothepropellerwithoutgearing.Althoughhigherpowercouldbe

producedbyhigherrevolutions,thiswouldreducetheefficiencyofthepropeller,becausethe

propellerismoreefficientthelargeritisandthesloweritturns.Theselargeslowrunningengines

areusedinthelargermerchantships,particularlyintankersandbulkcarriers.Themainreasonis

theirlowfuelconsumption.Moreandmoreofthelargermerchantvesselsarebeingpoweredby

medium-speeddieselengines.Theseoperatebetween150and450rpm,thereforetheyare

connectedtothepropellerbygearing.Thistypeofenginewasoncerestrictedtosmallercargo

ships,butnowtheyareusedinfastcargolinersaswellasintankersandbulkcarriers.Theyare

cheaperthanslow-speeddieselengines,andtheirsmallersizeandweightcanresultinasmaller,

cheapership.

1.Whydolargermerchantvesselsuseslow-speeddieselengines?

A.Becausetheyturnatabout108rpm.B.Becausetheirpropellersaremoreefficient.

C.Becausetheycanbeconnecteddirectlytothepropellerwithoutgearing.

D.Becausetheyarefuel-saving.

2.Accordingtotheauthor'sstandpoint,whatdoestheefficiencyofslow-speeddieselengine

propellersdependon?

A.PropellerpowerB.Bothpropellersizeandrevolutions

C.PropellersizeD.Propellerrevolutions

3.Whydomedium-speeddieselengineshavegearing?

A.InviewofpropellerefficiencyB.Inviewofenginerevolution

C.InviewoffuelconsumptionD.Inviewofmerchantshipsize

4.Whatisprobablythemainreasonwhymedium-speeddieselengineswereoncerestricted受限

制tosmallercargoships?

A.Theyarecheaperthanslow-speeddieselengines.

B.Thefuelconsumptionofthemediumspeedengineismorethanthatoftheslowspeedengine.

C.Theyoperatebetween150and450rpm.

D.Smallercargoshipsrequiremoreefficientpropellers.

答案DBAB

2

IV.Readingcomprehension:

Thissequenceofeventsismadepossiblebysubstitutingportsinthebottomofthecylinderwall

fortheinletandexhaustvalves.Therearetwogroupsoftheseports,oneforexhaustandtheother

fbrscavengingair,usuallyontheoppositesidesofthecylinder,butinsomedesignsbothgroups

arearrangedonthesameside.Theexhaustportsconnectwiththeexhaustmanifold,whilethe

scavengingportscommunicatewiththescavengingairreceiverinwhichlow-pressureairisstored.

Theexhaustportsarcslightlyhigherthanthescavengingports,sothattheyareuncoveredbythe

pistonwhilethescavengingportsarestillclosed.

(Thefollowing2questionsarebasedonthepassageabove)

1.Fromtheparagraphabove,weknowthat.

A.Ingeneral,bothexhaustportsandscavengingairportsareontheoppositesidesofthecylinder

B.Theexhaustportsareontheoppositesides,butthescavengingairportsareonthesamesides

C.Thescavengingairportsareontheoppositesides,buttheexhaustportsareonthesamesides

D.Twogroupsofpartsareneverarrangedonthesamesides

2.Accordingtotheaboveparagraphtheexhaustportslinkwith.

A.theexhaustvalvesB.thescavengingairreceivers

C.theexhaustmanifoldD.thescavengingports

答案AC

3

IV.Readingcomprehension:

Passage1

Crankshaftisbuiltup,theforgedmainbearingjournalsbeingshrunkintocaststeelcrank

throws.Thecrankthrowsaredisplacedfromeachothertoobtainthesamenumberofdegrees

betweenthedifferentcrankthrows.Thealignmentofthecrankshaftinthebedplateshouldbe

checkedatintervalstoensurethattheshaftisnotsubjectedtoadditionalbendingstresses,which,

underextremeconditions,maycausecrankshaftfailure.

(Thefollowing3questionsarebasedonthepassageabove)

1.Whatdoestheword“alignment"meaninthispassage?

A.thebedplateischeckedatintervals

B.toensurethattheshaftisnotsubjectedtoadditionalbendingstresses

C.toobtainthesamenumberofdegreesbetweenthedifferentcrankthrows

D.arrangementinastraightline

2.Thenumberofdegreesbetweenthedifferentcrankthrowsshouldbe

A.allthesameB.alittlebitdifferentC.smallerD.larger

3.Thepurposeofalignmentofthecrankshaftis

A.fortheforgedmainbearingjournalsbeingshrunkintocaststeelcrankthrows

B.todecreasetheadditionalbendingstresses

C.toensurethattheshaftisnotsubjectedtoadditionalbendingstresses

D.toobtainthesamenumberofdegreesbetweenthedifferentcrankthrows

答案DAC

Passage2

Theengine,ssupportingelementconsistsofabedplateandframe.Thebedplatecanbeof

weldedoreastdesign.Theframeismadeofcastiron.Theturbochargermounting,thehousingfor

theaircoolerandthechargingairreceiverarecastasanintegralpartoftheframe.Theunderslung

crankshaftsmainbearingsaremountedinboresintheframeandsecuredwithmainbearingcaps

ofsteel.Thecapsareguidedsidewaysandaresecuredbymeansofthreadedstudsandnutsthat

aretightenedhydraulically.Thecapsarealsosecuredwithhorizontalbracingscrewsintheframe.

Thebearingshellsareproducedwithatolerancethatmakesitpossibletochangethemasetat

atimewithoutanyscraping-in.

Thetopflangesofthecylinderlinersareforcedagainstthetopfaceoftheframebythe

cylindercovers,whereasatthebottomtheyareguidedbyabottomflangethroughwhichtheyare

freetoexpandundertheeffectsofheat.Tightnessbetweenthewaterchamberandthecrankcaseis

achievedwithtworubberringsinsertedinslotsintheguidesurfaceofthecylinderliner.

Thecamshaftisdrivenfromthecrankshaftthroughagearing,whichismountedonthe

engine'sflywheelendandcoveredbya2-partshield.Thecamshaftrunsinsteelbusheslinedwith

whitemetal.

Ineachsideoftheframe,largeopeningsareprovidedforinspectionofrollerguides,camsand

themainandcrankbearings.Theopeningshavecovers,someofwhichareprovidedwith

crankcaseexplosionreliefvalvesthatequalizethepressureiftheoilvaporsinthecrankcaseare

ignited,fbrexampleasaresultofhotrunning.

Thebedplatecanbeusedasalubricatingoilreservoirandisthereforeprovidedwithadipstick.

Theoilcan,however,bedrainedofftoaspecialbottomtank,sothattheenginerunswithadry

sump.

Afueloilpumpofthegeartypeisdrivenfromthecamshaftthroughaclutch.Alubricatingoil

pump,whichisofthesametype,isdrivenbyaclutchmountedontheendofthecrankshaftor,for

propulsionplant,throughaflexiblegearwheeldrive.

(Thefollowingquestionsarebasedonthepassageabove)

1.Thispassageismainlyabout

A.theconstructionofanengineB.howtheengineworks

C.thelubeandcoolingsystemofanengineD.whenthecrankcaseexplosionoccurs

2.WhichofthefollowingisNOTmentionedasanintegralpartoftheframe?

A.TurbochargermountingB.Bearingcaps

C.AircoolerhousingD.Scavengingairreservoir

3.Thecamshaft.

A.issupportedbybearingsB.maynotdrivethefueloilpumpinsomecases

C.willnotdrivealubeoilpumpD.Alloftheabovearetrue.

4.WhichofthefollowingisNOTtrue?

A.Theframeismadeofcastiron.B.Thereareunderslungbearingsinthisengine.

C.Fourrubberringsensurethetightnessbetweenthecrankcaseandthewaterchamber.

D.Reliefvalvesareprovidedontheframe.

5.Whichofthefollowingwordcanbeusedinsteadoftheword''equalize"(underlinedinthefifth

paragraph)?

A.EquivalentB.InterferenceC.ReleaseD.Fix

答案ABDCC

Passage3

Thecylindercoverismadeofcastironandisprovidedwithtwoinletvalves,twoexhaust

valves,acentralmountedfuelinjectionvalveandanindicatorvalve.Theinletvalvesaremounted

withseparateseatingringsmadeofspecialheat-resistantcastiron.Theseringsarepressedintothe

cylindercoverincooledconditions.Theexhaustvalveseatingsarespecial,water-cooledseating

rings.Theseringsarealsopressedintothecylindercoverincooledconditions.

Eachcylindercoverisprovidedwithcoolingwaterfromascrewed-ontubularcoolingwater

jacketthroughradialboresinthethickbottomofthecover.Eachoftheradialboresisconnected

totwosidebores.Thecoverhasfurtherseparateboresthatleadtothecoolingwaterjacketandthe

boresinthecylindercovertoacommonoutletchamber.Thecylindercoverandcylinderlinerare

assembledbymeansoffourthreadedstudsscrewedintotheframe.Tighteningiseffectedby

meansofhydraulictools,andsealingbymeansofathinringmountedbetweenthecylindercover

andthecylinderliner.Astartingvalveismountedonthesideofthecylindercover.

Theenginehasoil-cooledpistonsofcastiron.Thepistonsareprovidedwiththree

compressionringsandaspring-loadedscraperring.Aspaceforcoolingoilisprovidedatthetop

ofthepiston.Thescraperringpreventslubricatingoilfrombeing&awnupintothecombustion

chamber.

Oilfbrcoolingthepistoncrownisledfromaboreinthecrankshaftthroughachannelinthe

connectingrodandtheconnectingrodjournal,tothebushingfbrthegudgeonpin.Thisbushingis

providedwithanannulargroovefromwhichpartoftheoilisledfbrlubricatingthegudgeonpin.

Theremainingoilcontinuesthroughboresinthegudgeonpinandthepistontopistoncooling

chamber.

(Thefollowingquestionsarebasedonthepassageabove)

1.Thispassageismainlyabout.

A.cylindersandcylindercoversB.cylindersandpistons

C.cylindercoversandpistonsD.cylindersandoil

2.Whichofthefollowingmaybeprovidedontopofthecylindercover?

A.TwoexhaustvalvesB.Astartingvalve

C.AnindicatorD.Alloftheabove

3.Whichofthefollowingistrue?

A.Theinletvalveseatingringsareofheat-resistantcaststeel.

B.Therearesixstudsbywhichthecylindercoverandlineraretightened.

C.Theexhaustvalveseatingsarecooledbywater.

D.Acopperringismountedbetweenthecylindercoverandtheline匚

4.WhichofthefollowingisNOTtree?

A.Thepistonsarecooledbyoil.

B.Fourpistonringsarefittedtoeachpiston.

C.Thescraperringscrapestheoildownwards.

D.Thepistoncoolingisofsplashtype.

5.The"fourthreadedstuds”(underlinedinthesecondparagraph)means.

A.studswhichhavefourthreadsB.fourthreadsstuds

C.fourstudsthathavethreadD.threadsfbrstuds

答案CACDC

Passage4

Thecylinderlinerisofalloycastiron,itsupperflangelandsontopoftheframeandhasbore

cooling.Itissecuredbyaforgedsteelcylindercoverwhichisalsoborecooledandisshaped

internallytoaccommodatemostofthecombustionspace.Cylinderlubricatingoilisinjectedat

onelevelintheliner.Pistonshaveachrome-molybdenumalloysteelcrownwithhard

chrome-surfacedringgroovesinwhichfourcompressiontingsarefitted.Inthisparticularmodela

protectivelayerofInconelisweldedtopartofthecrownsurfacetopreventhightemperature

corrosion.Thepistonisoilcooled,oilbeingsuppliedbyatelescopicglandtothecrossheadand

thenthroughthepistonrod.Itisreturnedfromthecrossheadtoaslottedpipeinthecrankcase.A

shorteastironskirtisadded.Thecrownisboltedtothepistonrodataninnersupportring.

Surfacehardeningreduceswearonthepistonrodatthediaphragmgland.Therodisboltedat

thetopofacylindricalcrossheadwhichisoflargediameterandincorporatesafull-lengthbottom

ballbearingshell.Floatingguideshoesareattachedateachend.

Thecrankshaftmaybeeithersemi-builtuporofweldedconstruction,withlargejournalsand

pins.Allcrankcasebeatingsareofwhitemetal.Mainbearingshavethickshells,crankpin(bottom

end)andcrosshead(topend)bearinghavethin-wallshells.Whitemetalisusedfortheguide

surfaces.Theexhaustvalvesareoperatedhydraulicallyunderoilpressurefromcam-timed

actuatedpistons.Theyhaveaircompressedspringswhichallowsthemtoberotatedbyvanes.The

valvespindlesareusuallymanufacturedbythehotisostaticpressure(HIP)method,acompound

Nimonicandausteniticsteelpartconstruction.Valvehousingiscooledatitsseatandspindle

guidebushbutitupperductisuncooledtoavoidlowtemperaturecorrosion.

1.Whichofthefollowingfeaturesisnotmentionedaboutthecylindercover?

A.MadeofforgedsteelB.Specialshaped

C.BorecooledD.Intensivelycooled

2.Inordertopreventhightemperaturecorrosiononthepistoncrown,whatkindofspecial

measuresistaken?

A.Madeofchrome-molybdenumalloysteelB.Hardchrome-surfaced

C.InconelweldedD.Surfacehardened

3.Whichoneisnotbolt-connected?

A.ThepistoncrownandthepistonskirtB.Thepistoncrownandthepistonrod

C.ThepistoncrownandthecrossheadD.Theguideshoesandtheguide

4.Theexhaustvalvesarerotatedby.

A.camB.compressedair

C.vanesD.hydraulicoil

5.Whichoneisnottrue?

A.Mainbearing,crankpinbearing,crossheadbearingandguidesurfaceareallwhite

metaled.

B.Thecylinderlinerismadeofalloycastiron.

C.Thecrownisboltedtothepistonrodatanoutersupportring.

D.Theexhaustvalvehousingiscooledpartly.

答案DCDBC

Passage5

Afterensuringthatthe"nip"iscorrectthebeatingclearanceshouldbechecked.Thebearing

cupanditsassociatedhalfshellsareremovedleavingtheotherhalfinposition.Twopiecesof

pureleadwireareplacedacrossthejournalatpositionsone-thirdandtwo-thirdsalongitslength.

Thecapandshellarereplacedandtightenedupuntilthe"nip”iszero.Thecapandshellarethen

removedandthethicknessoftheleadwiremeasuredbyamicrometer.Itisimportanttouseonly

purelead,whichisverysoft,andtochooseathicknessofwire,whichisgreaterthanthenormal

allowableclearancesbutnotgreaterthantwicethisamount.Theclearanceshouldbewithinthe

manufacture*slimits.Asaguidethesewillbeapproximately0.1to0.2mmfbrwhitemetal

bearingsandapproximately0.25to0.4mmfbrcopper-leadortin-aluminumbearingswith

crankshaftjournaldiametersintherangefromabout200to400m.

1.Theleadwireshouldbeputontheuppersurfaceofthejournal.

A.longitudinallyB.verticallyC.transverselyD.angularity

2.Whichofthefollowingstatementsistree?

A.Thecapandshellbegintobetightenedwhenthennip"iszero.

B.Thecapandshellaretobetighteneduntilthe"nip"iszero.

C.Thecapandshellarenottobetighteneduntilthe"nip”iszero.

D.Thecapandshellhaven'tbeentightenedwhenthe"nip*iszero.

3.Accordingtopassage,thethicknessoftheleadwireshouldbemeasured.

A.beforethecapandshellareremoved

B.whenthecapandshellarebeingremoved

C.afterthecapandshellhavebeenremovedsecondtime

D.untilthecapandshellarcremoved

4.Accordingtothepassage,theclearanceforwhitemetalbearingshouldbe.

A.lessthan0.1mmB.largerthan0.2mm

C.withinabout0.25to0.4D.intherangefromabout0.1to0.2mm

答案CBCD

Passage6

Thealignmentofthecrankshaftinthebcd-plateshouldbecheckedatregularintervalsto

ensurethattheshaftisnotsubjectedtoadditionalbendingstresseswhich,underextreme

conditions,maycausecrankshaftfailure.Asimplemeansofcheckingthealignmentistomeasure

thechangeinthedistancebetweenapairofwebsateachquarterofonecycleasdistancefrom

webtowebmeasuredattheopenend,moreorlessincreasesanddecreasesduringonecycle,

dependinguponthemisalignmentoftheshaft.Moreinformationcanbeobtainedbythemethod

thanmeasuringthesaggingofthejournalinthemainbearing.

Crank-webdimensions,i.e.thedistancebetweenasetofwebs,arereferencevalueswhichare

detenninedduringerectionandarerecordedintheAcceptanceRecords.Measurementsaretaken

withadialgauge,thepointsatwhichitistobetakenforonecylinderinTDC,BDCpositionsand

atexhaustandcontrolsides,twotimesforeach.Theaveragevalueistobeusedandcompared,

andthevaluedifferenceisthecrankshaftdeflection.

Apositivedififerenceisanindicationofadeflectionoftheparticularthrowindownward

directionwhereasanegativevalueindicatesadeflectioninupwarddirection.Themeasurement

takeninashipthatisreadyforacceptancewillnotagreewiththemeasurementstakenatthe

manufacturer'sworks,buttheymustnot,underanycircumstances,exceedthespecifiedlimitsfor

arealignedcrankshaft.

Thevaluesobtainedwhentheshipisunderballastwilldifferfromthoseoftheloadedship

andthemagnitudeofthedifferencedependsonthepositionofengineintheship,thestiffnessof

thefoundationandtheshipproper.Moreover,themeasurementstakenfromthewarmenginewill

notagreewiththemeasurementstakenwhentheengineiscold.Onboardmeasurementsshouldbe

takenasearlyaspossibleincoldandwarmconditionoftheengineandundervariousshiploads.

Thesemeasurementsaretoserveasreferencebasisfortheevaluationofthemeasurementswhich

aresubsequentlytobetakenatregularintervals.Allreadingsandconditionsunderwhichtheyare

takenaretobeenteredintheservicerecordstogetherwiththedata.Suchdatacouldsupplyuseful

informationtofurtherinvestigation.

I.Thepurposeofalignmentofthecrankshaftis.

A.todecreasetheadditionalbendingstresses

B.toincreasetheadditionalbendingstresses

C.toensurethattheshaftdoesnotstandadditionalbendingstresses

D.toensurethatitshouldbecheckedatregularintervals

2.Crank-webdimensionsaretakenwithadialgauge.Foranenginewithsixcylinders,howmany

suchmeasurementsarctobetaken?

A.TwotimesB.EighttimesC.36timesD.48times

3.Whichofthefollowingstatementsistrue?

A.Thevaluesobtainedwhentheshipisunderballastshouldbeasequalasthoseoftheloaded

ship.

B.Themeasurementstakenfromthewarmenginewilldifferfromthosetakenfromtheengineis

cold.

C.Themeasurementstakeninashipwillbenotdifferentfromthosetakenatthe

manufacturersworks.

D.Anegativevalueindicatesadeflectionindownwarddirectionwhileapositiveoneindicatesa

deflectioninupwarddirection.

4.Theword"alignment**inthispassagemeans.

A.misalignmentB.Realignment

C.arrangementinacircularlineD.arrangementinastraightline

答案CDBD

4

IV.Readingcomprehension:

Passage1

Fueloilisthoughttobeoneofthemainfactors,havingmuchtodowiththeoperationand

maintenanceofanengine.Thefueloilsystemforadieselenginecanbeconsideredintwoparts:

thefuelsupplyandthefuelinjectionsystem.Whentheatomizedfuelisinjectedintothe

combustionspace,ignitionisnotaltogetherinstantaneous,adefinitetimelagbeingmeasurable

betweenthetimeofinjectionandignition.Theperiodofignitionlagdepends,amongotherfactors,

ontheignitionqualityofthefuelandthetemperatureofthecompressedair.

(Thefollowing2questionsarebasedonthepassageabove.)

1.Thisparagraphtellsusthat.

A.ignitiontakesplacebeforetheinjectionoftheatomizedfuel

B.ignitiontakesplacesimultaneouslywiththeinjectionoftheatomizedfuel

C.theperiodofignitionlagdependsonlyonthequalityofthefuelandthetemperatureofthe

compressedair

D.theignitionqualityofthefuelandthetemperatureofthecompressedairarethetwomain

factorsdeterminingtheperiodofignitionlag

2.^instantaneous"inthepassageprobablymeans.

A.simultaneousB.afterC.beforeD.when

答案DA

Passage2

Highsulphurcontentincreasestheriskforcorrosionandwear,particularlyatlowloads,and

maycontributetohigh-temperaturedepositfbnnation.Thelubricatingoilspecificationmustbe

matchedtothis.

Highvanadiumcontentcauseshotcorrosiononexhaustvalvesparticularlyincombination

withhighsodiumcontent.Thecorrosionincreaseswithincreasedtemperatures(increasedengine

output).

HighConradsoncarbonmaycausedepositformationincombustionchamberandexhaust

system,particularlyatlowengineoutput.

Highcontentofasphaltenesmaycontributetodepositformationincombustionchamberand

exhaustsystems(atlowloads).Asphaltenesmayundercertaincircumstances,precipitatefrom

thefuelandblockfiltersand/orcausedepositsinthefuelsystem.Precipitatingasphaltenesmay

alsocauseexcessivecentrifugesludge.

Heavyfuelsmaycontainupto1%wateratdelivery.Watermayalsooriginatefromthe

installationbunkertanks.Toavoiddifficultiesintheenginefuelinjectionsystemwatermustbe

removed.

Althoughlowignitionqualityproduceslongignitiondelay,advancingtheignitiontiming

makesthingsonlyworse;fuelisinjectedatalowercompressiontemperatureandthiswillproduce

evenlongerignitiondelay.

Aluminum+Silicon.Fuelsmaycontainhighlyabrasiveparticlescomposedofaluminumand

siliconoxidesknownas"catalyticfines"fromcertainrefiningprocesses.Ifnotremovedby

efficientfueltreatment,weardownofhighpressurefuelpumps,nozzlesandcylinderlinersina

fewhoursmayexpected.

1.Whentheengineoutputisincreased,whichcomponentmaycausecorrosiononexhaustvalves?

A.SulphurcontentB.Highwatercontent

C.HighvanadiumcontentD.HighConradsoncarbon

2.Whichcomponentmayresultinlowtemperaturecorrosion?

A.SulphurcontentB.Vanadium-sodiumcontent

C.ConradsoncarboncontentD.Asphaltenecontent

3.Whichcomponentmayresultinseriouswear-downofthecylinderliners?

A.Vanadium-sodiumcontentB.Conradsoncarbon

C.AsphaltenecontentD.Aluminum&silicon

4.Whichofthefollowingcomponentsmaymakeitnecessarytoshortenthedischargingintervals

whenfueloilispurified?

A.HighashcontentB.Highwatercontents

C.HighasphahenecontentD.Highaluminum&silicon

5.Toimproveignitionquality,thefueloilshavinglowignitionqualityshouldbe.

A.injectedproperlyinadvanceB.injectedatlowloads

C.injectedathighloadsD.injectedatalatertime

答案CADCD

Passage3

Acommontroublewiththefuelpumpplungersorfuelvalvespindlesisoilleakage.Good

strainersandfinefiltersshouldbeprovidedinthefueloilsystemandtheyshouldbecleanedat

intervals,soastopreventdirtfromgettingunderafuelinjectionpumpvalveandcausingitto

leak.

Itisnotuncommonforthelubricatingoilpumpsuctiontobecloggedwiththedirtleftinthe

crankcaseafterworkhasbeendoneontheengine.Excessiveclearancesinthemainorcrankpin

bearingswillsometimesbeindicatedbylossofpressureinthelubricatingsystembeforeany

bearingknockisheard.

Theenginemaylosepowerorslowdownwhenrunning.Whenthisoccurs,thefirstcause

possiblemaybehotbeatingsandseizureofthepistonsinthecylinders.Failureofthefuelsupply

tooneormorecylindersmaybeanothercause.

Cracksinthecylindersandcylindercoversmayresultfromunequalheating.

Bearingknocksarelikelytooccurfrombearingwear.Valvegearknocksatemoreeasily

locatedwhiletheengineisrunning.Knockingthatoccursbetweencamsandrollersmaybe

causedbytroublessuchasexcessiveclearancesandwornorbrokenrollers,orthe

troublemaybeinthevalves.

1.Oilleakageisacommontroublewith.

A.thefuelpumpsB.fuelvalves

C.fuelvalvespindlesorthefuelpumpplungersD.strainersandfilters

2.Whichofthefollowingstatementsistrue?

A.Itisrathercommonforthelubricatingoilpumpsuctiontobecloggedwithdirtleftinthe

crankcaseafterworkhasbeendoneontheengine

B.Excessiveclearancesinthecrankpinbearingsarealwaysindicatedbylossofpressureinthe

lubricatingsystem.

C.Bearingknockisheardbeforelossofpressureisobserved.

D.Dirtisneverfoundinthecrankcaseafterworkhasbeendoneontheengine.

3.Allofthefollowingtroublesmaycausetheenginetolosepowerorslowdownwhenrunning

except.

A.hotbearingsB.seizureofthepistonsinthecylinders

C.unequalheatingD.failureofthefuelsupplytooneormorecylinders

4.Bearingknocksarelikelytooccurwhen.

A.rollersarebrokenB.thebearingiswornout

C.thecamsarenotproperlysetD.thereareexcessiveclearancesbetweencamsandrollers

5.Unequalheatingmayresultin.

A.cracksinthecylindercoversB.cracksinthecylinders

C.constantbearingknocksD.cracksinthecylindersandthecylindercovers

答案CACBD

Passage4

EachoftheenginecylindersisprovidedwithaBosch,typePF,fuelpump.Thefuelpumpis

asingle-actingplungerpumpwithnon-adjustablestroke.Theplungerissoaccuratelygroundand

lappedthatitsclearanceinsidethebarrelisonly0.002-0.003mm.Thisprovidessufficient

tightnessbetweenplungerandbarrel,evenatpressuresashighas200?400bar,withouttheneed

forsealingmaterials.Neithertheplungernorthebarre