Automobile English Unit Two.docx
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Automobile English Unit Two.docx
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AutomobileEnglishUnitTwo
UnitTwo
AutomobileEngines
Thereciprocatingpistoninternalcombustionsystemhasbeenthemostsuccessfulforautomobiles,whiledieselenginesarewidelyusedfortrucksandbuses.Thegasolineenginewasoriginallyselectedfortheautomobileduetoitsflexibilityoverawiderangeofspeeds.Also,thepowerdevelopedforagivenweightenginewasreasonable;itcouldbeproducedbyeconomicalmassproductionmethods;anditusedareadilyavailable,moderatelypricedfuel-gasoline.Reliability,compactsize,andrangeofoperationlaterbecameimportantfactors.
Almostallcarscurrentlyusewhatiscalledthefourstrokecycleenginetoconvertgasolineintomotion.Thefour-strokeapproachisalsoknownastheOttocycle,inhonorofNikolausOtto,whoinventeditin1867.Thefourstrokesareintakestroke,compressionstroke,powerstroke,exhauststroke.
Thepistonisconnectedtothecrankshaftbyaconnectingrod.Ontheintakestroke,thepistonmovesdownfromthetopdeadcentertothebottomdeadcenterasthecrankshaftrevolves.Theintakevalveopensandthefreshvaporizedair-fuelmixtureentersthecylinder.Themixtureofairandvaporizedgasolineisdeliveredtothecylinderbythefuelsystemandcarburetor.Thenthepistonmovesbackuptocompressthiscombustiblemixturewithinthecombustionchamberandtheintakevalveandtheexhaustvalveareallclosed.Whenthemixtureiscompressed,notonlydoesthepressureinthecylindergoup,butalsothetemperatureincreases.BeforethepistonreachesTDConthecompressionstroke,thesparkplugemitsasparktoignitethemixture.Thegasolinechargeinthecylinderexplodes,drivingthepistondown.Atthesametime,thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.Finally,oncethepistonhitsneartheBDC,theexhaustvalveopens.Thenthepistonagainmovesupinthecylinderandtheburnedgasarepushout.Theintakevalveusuallyopensbeforetheendofexhauststroke.WhenthepistonagainmovesdownwardtoBDC,thefreshcombustiblemixturewillbeintroducedintothecylinder.Theabovefourstrokesarecontinuouslyrepeatedaslongastheengineremainsrunning.Noticethatthelinearmotionofthepistonsinanengineisconvertedintorotationalmotionbythecrankshaft.Therotationalmotionisnicebecauseweplantorotatethecar'swheelswithitanyway.
Thecoreoftheengineisthecylinder,withthepistonmovingupanddowninsidethecylinder.Theenginedescribedabovehasonecylinder.Thatistypicalofmostlawnmowers,butmostcarshavemorethanonecylinder(four,sixandeightcylindersarecommon).Inamulti-cylinderengine,thecylindersusuallyarearrangedinoneofthreeways:
in-line,Vorflat(alsoknownashorizontallyopposed).Asthein-lineengine,cylindersmaybearrangedinastraightlineonebehindtheother.Themostautomotivein-linedesignshavethefour-andsix-cylinderengines.TheVtypeenginehastwobanksofcylinderswhichhaveaninclinationof60to90degrees.Thecylindersofeachbankarearrangedonebehindtheother.Themostcommonexampleshavesixoreightcylinders.Theflatenginehastwobanksofcylindersopposedeachotherhorizontally.Differentconfigurationshavedifferentadvantagesanddisadvantagesintermsofsmoothness,manufacturingcostandshapecharacteristics.Theseadvantagesanddisadvantagesmakethemmoresuitableforcertainvehicles.
Thecombustionchamberistheareawherecompressionandcombustiontakeplace.AsthepistonmovesfromBDCtoTDC,youcanseethatthesizeofthecombustionchamberchanges.Ithassomemaximumvolumeaswellasaminimumvolume.ThedifferencebetweenthemaximumandminimumiscalledthedisplacementandismeasuredinlitersorCCs(CubicCentimeters,where1,000cubiccentimetersequalsaliter).Itvarieswithcylinderboresize,lengthofpistonstroke,andnumberofcylinders.Enginedisplacementiscalculatedbymultiplyingthenumberofcylindersintheenginebythepistondisplacementofonecylinder.Mostnormalcarenginesfallsomewherebetween1.5liter(1,500cc)and4.0liters(4,000cc).Ifyouhavea4-cylinderengineandeachcylinderdisplaceshalfaliter,thentheentireengineisa"2.0literengine."IfeachcylinderdisplaceshalfaliterandtherearesixcylindersarrangedinaVconfiguration,youhavea"3.0literV-6."
Generally,thedisplacementtellsyousomethingabouthowmuchpoweranenginecanproduce.Acylinderthatdisplaceshalfalitercanholdtwiceasmuchfuel/airmixtureasacylinderthatdisplacesaquarterofaliter,andthereforeyouwouldexpectabouttwiceasmuchpowerfromthelargercylinder(ifeverythingelseisequal).Soa2.0literengineisroughlyhalfaspowerfulasa4.0literengine.Youcangetmoredisplacementinanengineeitherbyincreasingthenumberofcylindersorbymakingthecombustionchambersofallthecylindersbigger(orboth).
Thepistondisplacementseemstobethesameasthetotalcylindervolume,butitisnot.Totalcylindervolumeisthesumofthepistondisplacementandtheclearancevolume.TheclearancevolumeisthecombustionchambervolumewiththepistonatTDC.Compressionratioisthetotalvolumeofacylinderdividedbyitsclearancevolume.Intheory,thehigherthecompressionratio,thegreatertheefficiencyoftheengine,andthemorepoweranenginewillproduceonconditionthatitholdsagivenquantityoffuel.However,therearepracticallimitstohowhighacompressionratiocanbe.Thehighratioleadstohighcombustionchambertemperature.Itinsultsintheformationofoxidesofnitrogen,aprimaryairpollutant.Intheearly1970’s,thecompressionratioisloweredtoabout8andlowoctane,lowleadorunleadedfuelisused.Now,EFIenginecanraisecompressionratiotothe9and10to1rangeforgoodperformanceandeconomy.
Intoday’sworld,therehasbeenagrowingemphasisonthepollutionduetoexhaustemissionsofengines.Thishascreatednewinterestinalternatepowersourcesandinternalcombustionenginerefinementsthatwerenoteconomicallyfeasibleinprioryears.Althoughafewlimited-productionbattery-poweredelectricvehicleshaveappearedfromtimetotime,theyhavenotprovedtobecompetitiveowingtocostsandoperatingcharacteristics.However,thegasolineengine,withitsnewemission-controldevicestoimproveemissionperformance,hasnotyetbeenchallengedsignificantly.
NewWords
1.reciprocating[]a.往复的,来回的
2.originally[]ad.原来,最初
3.flexibility[]n.灵活性,适应性,机动性
4.stroke[]n.行程,冲程
5.cycle[]n.循环
6.intake[]n.入口,进口
7.exhaust[]n.排气,排气装置
8.figure[]n.图形,画像
9.revolve[]v.旋转
10.valve[]n.阀门
11.vaporize[]vt.vi.(使)蒸发
12.carburetor[]n.化油器
13.explode[]v.爆炸
14.introduce[]vt.引进,引导
15.linear[]adj.线的,成直线的
16.anyway[]ad.不管怎样
17.core[]n.核心
18.lawn[]n.草坪
19.mower[]n.割草机
20.arrange[]v.排列,安排
21.horizontal[]a.水平的
22.oppose[]v.反对,使对立
23.bank[]n.一系列;一排
24.inclination[]n.倾斜,倾度
25.degree[]n.度
26.configuration[]n.轮廓,结构
27.smoothness[]n.平滑,平坦
28.cubic[]a.立方的
29.centimeter[]n.厘米
30.liter[]n.升(容量单位)
31.displacement[]n.位移,排量
32.multiply[]v.乘,增加
33.quarter[]n.一刻钟,四分之一
34.calculate[]v.计算
35.clearance[]n.间隔,距离
36.quantity[]n.数量
37.lead[]n.铅
38.oxide[]n.氧化物
39.nitrogen[]n.[化]氮
40.lower[]v.降低,减弱
41.performance[]n.性能
42.significantly[]ad.意味深长地,值得注目地
PhrasesandExpressions
1.massproduction大规模生产
2.fourstrokecycleengine四冲程发动机
3.Ottocycle奥托循环
NikolausOtto尼古拉斯·奥托(德国物理学家,1832—1891,奥托循环理论的提出者)
4.intakestroke进气行程
5.compressionstroke压缩行程
6.compressionstroke作功行程
7.exhauststroke排气行程
8.topdeadcenter(TDC)上止点
9.bottomdeadcenter(BDC)下止点
10.intakevalve进气门
11.exhaustvalve排气门
12.combustionchamber燃烧室
13.goup上升,增长
14.sparkplug火花塞
15.in-lineengine直列式发动机
16.flatengine对置式发动机
17.cylinderbore汽缸内径
18.enginedisplacement发动机排量
19.intheory理论上
20.compressionratio压缩比
NotestoText
1.Reliability,compactsize,andrangeofoperationlaterbecameimportantfactors.
后来,汽油机的可靠性、紧凑的尺寸以及宽泛的工作范围成为选用汽油机的重要因素。
2.Thefour-strokeapproachisalsoknownastheOttocycle,inhonorofNikolausOtto,whoinventeditin1867.
为了纪念尼古拉斯·奥托,发动机的四冲程循环方式也被称为奥托循环,尼古拉斯·奥托在1867发明了这种循环方式。
inhonorof为向…表示敬意,为纪念…,
例如:
Hewritesanarticleinhonorofhisteacher。
为了纪念他的老师他写了一篇文章。
beknownas以…知名,被认为是。
3.Whenthemixtureiscompressed,notonlydoesthepressureinthecylindergoup,butalsothetemperatureincreases.
当可燃混合物被压缩时,不但汽缸内的压力上升,而且温度也升高。
notonly…butalso不但…而且…,
4.Thatistypicalofmostlawnmowers,butmostcarshavemorethanonecylinder(four,sixandeightcylindersarecommon).
大多数草坪割草机用的是发动机是典型的单缸发动机,但是,大多数汽车的发动机不止一个汽缸(四缸、六缸和八缸是常见的)。
5.TheVtypeenginehastwobanksofcylinderswhichhaveaninclinationof60to90degrees.
V型发动机有两排汽缸相互倾斜成60°到90°角。
6.Enginedisplacementiscalculatedbymultiplyingthenumberofcylindersintheenginebythepistondisplacementofonecylinder.
发动机的排量是用汽缸数乘以一个汽缸的活塞位移(汽缸的工作容积)的乘积计算而得到的。
7.Thecompressionratiosofmostgasolineenginesarerestrictedwithinthelimitsof11.5to1.
大多数发动机的压缩比被限制在了11.5﹕1的范围内。
Exercises
1.Questionstothetext
(1)Listthefourstrokesofafour-strokeengineinproperorder,please.
(2)Howmanywaysthecylindersarearrangedininamulti-cylinderengine?
Whatarethey?
(3)Howi
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- Automobile English Unit Two