Lesson1TypesofDieselEngine

Lesson1TypesofDieselEngine第1课柴油机的种类1.Theinventionofthedieselenginein1892hasbeenattributedtoRudolfDiesel,aGermanmechanicalengineerandinventor.Sincethendieselengineshaveplayedanimportantroleintheshippingindustrybecauseoftheirimprovedengineefficienciesanddesignscomparedtootherformsofpropulsionsuchassteamorgasturbines.Dieselenginesareknownbythenameofcompressionignitionenginesduetotechnicalreasons.Thereareseveralwaysofclassificationofdieselenginesbasedonvariousparameters.Accordingtotheirspeeds,dieselenginesmaybedividedintothreetypes:slowspeed,mediumspeedandhighspeeddieselengines.1.1892年柴油机的问世归功于德国机械工程师、发明家鲁道夫·狄塞尔。自此，由于与其他形式的推进装置比如蒸汽机或燃气轮机相比，柴油机在效率和设计上更具优势，在航运业发挥了很重要的作用。川出于技术原因，柴油机也叫压燃机。基于不同的参数柴油机有若干种分类方法。柴油机根据速度可分三类:低速、中速和高速柴油机。SlowSpeedDieselEngines低速柴油机2.Slowspeeddieselenginesarelarge,especiallytall,andheavyandoperateonthetwo-strokecycle.Theyarethelargestdieselengineseverbuilt.Enginepowerupto100,000kWisavailablefromasingleengine.Theyaretalltoallowforlongstrokeswhichimproveengineefficiency.Thelargephysicalsizeoftheengineandcomponentsleadstoslowrotationalspeedwithspeedsupto300r/minconsideredtobeslow.Forequivalentpoweroutput,thetwo-strokedieselengineissignificantlylighterthanthefour-strokeone.Thisismostapparentforlargepowerrequirementswherethetwo-strokeengineproducesmuchmorepowerforthesameweight.2.低速柴油机体积大，高度特别高，而且重量大，以二冲程循环运转。这是迄今为止建造出的最大型的柴油机。单独一台发动机就能提供高达100000kW的功率。这类柴油机之所以高是为了容许长冲程，从而提高发动机的效率。大体积的柴油机和部件使得转速较慢，为300r/min，这被视为低速。对于相同的输出功率，二冲程柴油机明显轻于四冲程柴油机。这一点对于满足大功率的需求是非常明显的，相同重量时二冲程柴油机能产生更大的功率。3.Large,slowspeed,two-strokemarinedieselenginesoffertheadvantagesof•burningpoorerquality,cheaperfuel;•providinglargepowerfromasingle,lesscomplicatedmachinecomprisingfewerindividualcylindersandmovingparts•havingalowrotationalspeedallowingthemtobedirectlycoupledtothepropellerandremovingtheneedforgearboxes;and•beingreversibleandthuseliminatingtheneedforreversinggearorcontrollablepitchpropellers.3.大型低速二冲程船用柴油机有以下优点:·燃烧质量较差、价格低廉的燃料;··由单台不太复杂的发动机提供大功率，分段气缸和运动部件数量较少;·具有低转速，能够直接连接螺旋桨，不需要变速箱;以及·可倒转，从而无需换向装置或可调螺距螺旋桨。4.Merchantshipsdrivenbyslowspeeddieselenginewillusuallyhaveasinglelargemainenginedirectlycoupledtoasinglefixedpitchpropeller.Thethrustforcesfromthepropellerwillbetransferredtothehulloftheshipthroughathrustbearing.4.由低速柴油机驱动的商船通常有一台大型主机直接连接到一个固定螺距螺旋桨。来自螺旋桨的推力通过推力轴承传送到船体。MediumSpeed,Four-StrokeDieselEngines中速四冲程柴油机5.Mediumspeedenginesoperateinspeedrangesfrom300to1,000r/min.Themajorityofmediumspeedenginesoperateonthefour-strokecycle.Theyaremostcommonasthepropulsionenginesinsmallerships,ro-roandpassengerships.Theyareusedwidelyastheelectricalpowergenerationenginesinmostmerchantcargoships5.中速柴油机的速度范围是300至1000r/min。大多数中速柴油机以四冲程循环运行。它们是小型船舶、滚装船和客船上常见的推进发动机。在大多数商用货船上，它们被广泛用作发电机。6.Four-strokeengineshavemoremovingparts,aremorecomplexandproducelesspowerforequivalentweightcomparedtotwo-strokeslowspeedengines.Mediumspeedenginesdo,however,offerseveraladvantages.Fig.1-1Afour-strokedieselengine图1-1四冲程柴油机•Theenginesarecompact-theyarenotlongorhigh,thisallowsthemtofitinengineroomswithlowheadspacesuchasthoseinro-roships.•Mediumspeedenginesuselessoilthanslowspeedengines.•Recentdevelopmentshaveproducedmediumspeedenginescapableofburninglowqualityheavyfueloil.•Enginesofconsiderablepower,to25,000kWandmore,havebeendeveloped,allowingalargepowersystemtobeachievedwithcompactenginesandengineroom.Thismakesthemsuitableforpassengershipapplicationswherethesmallerthespaceprovidedforenginesandmachinerythemorespaceisavailableforpayingpassengers.6.与同等重量的二冲程低速柴油机相比，四冲程柴油机(见图1-1)的运动部件更多，结构更复杂，产生的功率更低。但是，中速柴油机有以下几个方面的优势。·发动机结构紧凑-其长度或高度不大，能够安装在净空高度较低的机舱内，如滚装船的机舱。·中速柴油机比低速柴油机油耗低。·最近研制生产出了能够燃烧低质量重油的中速柴油机。·已开发了功率大于等于25000kW的大功率发动机，这使得结构紧凑的发动机和狭小的机舱都能实现大功率系统。这也使得这些发动机适用于客船，在客船上发动机和机器占的空间越小，可容纳乘客的空间就越大。7.Mostmedium-speeddieselenginesarenon-reversiblemeaningthatacontrollablepitchpropellerisusuallyemployedtocaterforasternthrust.7.大多数中速柴油机是不可倒转的，这意味着，通常要使用可调螺距螺旋桨来实现倒车推进。HighSpeedDieselEngines高速柴油机8.themostcommondieselenginethroughouttheworldisthehigh-speedengine.Themajorityoftheseenginesoperateonthefour-strokecyclebutasignificantproportionutilizethetwo-strokecycle.Theseengineshaverunningspeedsover1,000r/minandareideallysuitedtodrivingland-basedvehiclessuchasbusesandtrucks.Theapplicationofhigh-speeddieselenginesaspropulsionenginesatseaislimitedtosmallervesselssuchastugs,ferriesandbargesetc.Theyareregularlyusedforelectricalpowergenerationinsupportofamedium-speedpropulsionenginesandonlargeshipstheiruseislimitedtoemergencypowergenerationtosmallapplicationssuchasdieseldrivenemergencypumpsandcompressors8.全世界最常见的柴油机是高速柴油机。这类发动机大多数以四冲程循环运行，但也有相当大的比例利用二冲程循环。这些发动机运行速度在1000r/min以上，适于驱动陆地上的车辆，如公共汽车和卡车。应用高速柴油机在海上作为推进发动机只限于较小的船只，如拖船、渡船和驳船等。这类柴油机经常用于发电，以支持中速推进发动机，而在大型船舶上的应用仅限于小型装置的应急发电，如柴油驱动的应急泵和压缩机。Task1ReadingComprehension任务1阅读理解A.TopicsforDiscussion讨论话题1.Whatadvantagesdolarge,slowspeed,two-strokemarinedieselenginesoffer?1.大型低速二冲程船用柴油机有哪些优点?Large，slow-speed，two-strokemarinedieselenginesoffertheadvantagesofburningpoorerquality,cheaperfuel;providinglargepowerfromasingle，lesscomplicat