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．Theengineroomistheheartofaship.Itisgenerallylocatedatthesternneartheshipbottom.Intheengineroom,therearealotofmachineryandsystems,suchasthemainengine,thegeneraterengine,boilers,pumps,therefrigeratingsystem,andtheairconditioningsystem.Themainengine,alsocalledthemainpropulsionplant，isthelargestandmostimportantone.Themodernimprovementofcontrolsystemsresultsinmachineryspaceremainingunattendedforlongperiods.ThatisUMS.第二章口述1.Themaindifferencebetweenthedieselengineandthegasolineengineinclude:1)thecombustionmediumofadieselengineisdieseloilorfueloil,whilethatforagasolineengineisgasoil.2)thedieselengineisignitedthroughcompressionofhot,highpressureoil/airmixture,butthegasolineengineisignitedbyelectricalsparkplug.3)fordieselengine,theairandoilismixedinsidethecylinder,whileforgasolineengine,theyaremixedoutsidethecylinder.2.First,Iwilltellthecadettheimportancetheengineroom.Second,Ishouldintroducethevariousmachineryandsystemsintheengineroom,suchasthemainengine,thegeneraterengine,boilers,pumps,therefrigeratingsystem,andtheairconditioningsystem.Third,Iwillshowhimhowtooperatethevariousequipmentanddevicessafely,andintroduceasmuchsafetyknowledgeasIcan.3.sameasquestionNo2.4.Thepowerofthedieselengineistransmittedtothepropellerthroughthetransmissionsystem.Theitemsoftransmissionsystemincludevariousshafts,suchasthethrustshaft,oneormoreintermediateshaftsandtailshaft.Theseshaftsaresupportedbythethrustblock,intermediatebearingsandthesterntubebearing.Thepropellerconsistofabosswithseveralblades,.Thethrustistransmittedalongtheshaftingtothethrustblockandfinallytoshipstructure.5.Whentheshipissailingatfullspeed,itneedfourenginesrunning.Whentheshipissailingathalfspeed,itrequiretwoenginesrunning.Whiletheshipisoperatingatabout30%offullspeed,oneengineisenoughtomeetitspowerrequiement.Thatis,theshipcanbeoperatedwithsingleengine,doubleengines,orfourenginesaccordingtheloadcondition.Generally,whentheshipissailingatseaspeed,ithasfourenginserunning,whieitapproachesthewharf,ithastwo.6.Thestructureofthemainengineisasfollows:theconstructionmainlyincludebedplate,frame,cylinders,pistons,connectingrod,mainbearingandcrankshaft.Thecrankshaftrestsinmainbearingsbuiltintocrossgirdersofthebedplate.OnthetopofAframesthereisascavengingairbox.Thebedplate,framesandcylinderblocksaresecuredtogetherbylongtie-rods.Apistonconsistsofalowerpartcalledpistonskirtandanupperpartcalledpistoncrown.7.Themovingpartsshownintheillustrationmainlyincludethepiston,theconnectingrod,andthecrankshaft.Theseareallcriticalpartsoftheengine.Accordingtothespecificconditionshowninthepicture,thepistonisundercompressionforce,theconnectingrodisundertensionstressandcompressionforce,whilethecrankshaftisunderthetorsionforces.8.Pistonscanbedividedintotwomainclasses:thecrossheadtypepistonsandthetrunktypepistons.Thetopsurfaceofthecrossheadpistoncanbeflat,sunkenorconvex.Thepistonshownintheillustrationisthecrossheadtypepistonwithasunkensurface.Ithastheadvantageofincreasingtheairturbulanceandimporvingtheoil/airmixingquality.Itsdisadvantageisthatthecylindervolumetricclearancewillbelarger.9.Thepistonringsshownintheillustrationhastheshapeofrectangleortrapezoid.Someofthemare:atotallylosssystemfeedingthecylindersandacirculatingsystemlubricatingtherunninggearandcoolingthepistons.Oilissuppliedtothecylinderlinerwallandpistonringsbymeansofmechanicallubricators.Thelubeoiltothevaroiusmovingpartsenabletheformationofanoilfilmwhichreducesfrictionandwear.三．A1Inordertoensurethesafenavigationoftheship,frequentcommunicationbetweentheengineersandofficersisnecessary.Theusualmeansofcommunicationisbytelephoneandtelegraph.Ifthecommunicationbetweentheengineroomandthebridgefails,theshipwillbeendangered.Therecordsofcommunicationshouldbemaintainedwhichwillprovideevidenceintheeventofanaccidentatsea.Noonreportisalsoagoodmeansofcommunicationbetweentheengineroomandthebridge.4Atthecompletionofthewatch,eachmemberofwatchkeepingshouldhandovertohisrelief,ensuringthatthereliefiscompetenttotakeoverandcarryouthisdutieseffectively.Beforegoingoffduty,theengineerinchargeofthewatchshallensurethatalleventsrelatedtothemainandauxiliarymachineryaresuitalbyrecorded.Heshouldtelltherelievingengineerthestandingorders,specialintructionsandunfinishedwork,ifany.Ifhehasanyreasontobelievethattherelievingengineerisnotcapableofcarryingoutthewatchkeepingdutieseffectively,heshallnothandoverthewatchandthechiefengineershallbenotified.四1LastyearwhenIworkedonabulkcarrier,Ifoundtheexhausttemperatureofthemainengineisrisingquickly.Therewasafireinthescavengeairbox.Theenginewassloweddown.Thefuelwasshutofffromtheaffectedcylinders.Iopenedwidetheinletvalveofthecoolingwater.Thedutymotormanincreasedthecylinderlubrication.Thefirequicklyb