哈工程輪機(jī)英語(yǔ)--lesson 1

1、Harbin Engineering University2007-11-1Lesson one How does a Marine Diesel engine Work?Prof. Song ZhouHarbin Engineering University2007-11-1New Words and Expressions in Text marine 海運(yùn)的，船用的 diesel 柴油，柴油機(jī) internal 內(nèi)部的 combustion 燃燒 ignite 點(diǎn)燃 inject 噴射 chamber 腔，室 principle 原理，原則 operation 工作，操作，運(yùn)轉(zhuǎn)，進(jìn)程 c

2、harge 裝，充；充填物 fresh 新鮮的，淡(水)的 draw 抽吸 cylinder 氣缸 compression 壓縮 piston 活塞 fine 細(xì)小的，好的 spray 噴霧，(水，油)霧 burn 燃燒Harbin Engineering University2007-11-1 rotate 旋轉(zhuǎn)，回轉(zhuǎn) medium 中間的，介質(zhì) alternator 交流發(fā)電機(jī) in turn 依次，輪流變成 turn into 變成 event 事件，過(guò)程 stroke 沖程，行程 separate (from) 分離，分開(kāi) exhaust 排出，耗盡；排氣 combine (with)

3、 結(jié)合，聯(lián)合 inlet 進(jìn)口，入口 scavenge 掃除；吹除 blow 吹，鼓風(fēng) residual 剩余的，殘留的 value 價(jià)值，數(shù)值 injector 噴射器，噴油器 continue 繼續(xù)(進(jìn)行) revolution 轉(zhuǎn) theoretically 理論上地 inefficient 效率低的，無(wú)效的Harbin Engineering University2007-11-1 advantage 優(yōu)勢(shì)，優(yōu)點(diǎn)，長(zhǎng)處 application 應(yīng)用 propulsion 推進(jìn)(裝置) cause 引起；原因 force 迫使 crankshaft 曲鈾 propeller 螺旋槳，推進(jìn)

4、器 cycle 循環(huán) consist (of) 由組成 fix 固定 sequence 順序，系列 bottom dead centre (BDC) 下止點(diǎn) top dead centre (TDC) 上止點(diǎn) on board ship 在船上 r/min 轉(zhuǎn)分 reduction gear box 減速齒輪箱Harbin Engineering University2007-11-1*The diesel engine is a type of internal combustion engine which ignites(點(diǎn)燃點(diǎn)燃) the fuel by injecting(噴射噴射)

5、 it into hot, high pressure air in a combustion chamber(燃燒室燃燒室). Harbin Engineering University2007-11-1The marine diesel engine is a type of diesel engine used on ships. The principle of its operation is as follows:Harbin Engineering University2007-11-1A charge of fresh air is drawn or pumped into t

6、he engine cylinder(氣缸氣缸) and then compressed by the moving piston(活塞活塞) to very high pressure.Harbin Engineering University2007-11-1When the air is compressed, its temperature rises so that it ignites the fine spray(噴霧、噴霧、油霧油霧) of fuel injected into the cylinder.Harbin Engineering University2007-11-

7、1The burning of the fuel adds more heat to the air charge, causing it to expand and force the engine piston to do work on the crankshaft which in turn drives the ships propeller(螺旋槳螺旋槳).Harbin Engineering University2007-11-1Exhaust valveInlet valveFuel injectorCylinderPistonPiston ringConnecting rod

8、Four-stroke diesel engineCombustion chamberPiston pincrankshaftCrank webHarbin Engineering University2007-11-1Fuel injectorFuel injectorExhaust valve掃氣口掃氣口Scavenge portExhaust portTwo-strokeEngineCross scavenge systemUniflow scavenge systemPiston rodConnecting rodPiston pinCrossheadHarbin Engineerin

9、g University2007-11-1The operation between two fuel injections is called a working cycle, which consists of a fixed sequence of events. Harbin Engineering University2007-11-1This cycle may be achieved either in four strokes(沖程、沖程、行程行程) or two.Harbin Engineering University2007-11-1In a four-stroke di

10、esel engine, the cycle requires four separate strokes of the piston, i . e . s u c t i o n ( 吸 氣吸 氣 ) , c o m p r e s s i o n ( 壓 縮壓 縮 ) , e x p a n s i o n ( 膨 脹膨 脹 ) a n d exhaust(排氣排氣). * Note: i.e. (拉拉=id est)即；就是即；就是Harbin Engineering University2007-11-1If we combine the suction and exhaust ope

11、rations with the compression and expansion strokes, the four-stroke engine will be turned into a two-stroke one, as is shown in Figures 1-a)d). Harbin Engineering University2007-11-1Scavenge(a)Compression(b)Injection(c)Exhaust(d)ScavengeportExhaustportFuel injectorCylinderPistonConnecting rodCrankHa

12、rbin Engineering University2007-11-1The two-stroke cycle begins with the piston coming up from the bottom of its stroke, i.e. bottom dead center (BDC), with the air inlet ports or scavenge ports(掃氣口掃氣口) in the sides of the cylinder being opened (Fig. 1-a). Harbin Engineering University2007-11-1The e

13、xhaust ports are uncovered also. Pressurized fresh air charges into the cylinder, blowing out any residual exhaust gases from the last stroke through the exhaust ports. Harbin Engineering University2007-11-1As the piston moves about one fifth of the way up, it closes the inlet ports and the exhaust

14、p o r t s . T h e a i r i s t h e n compressed as the piston moves up. (Fig. 1-b). Harbin Engineering University2007-11-1When the piston reaches the top of its stroke, i.e. the top dead center (TDC), both the pressure and the temperature of the air rise to very high values. Harbin Engineering Univer

15、sity2007-11-1The fuel injector injects a fine spray of fuel into the hot air and combustion take place, producing much higher pressure in the gases. Harbin Engineering University2007-11-1The piston is forced(迫使迫使) downward as the high pressure gases expand until it uncovers the exhaust ports. Harbin

16、 Engineering University2007-11-1The burning gases begin to exhaust (Fig. 1-d) and the piston continues down until it opens the inlet ports. Then another cycle begins.Harbin Engineering University2007-11-1In the two-stroke engine, each revolution of the crankshaft (曲軸曲軸) makes one power or working st

17、roke, while in the four-stroke engine, it takes two revolutions to make one power stroke. Harbin Engineering University2007-11-1That is why a two-stroke cycle engine will theoretically develop twice (two times) the power of a four-stroke engine of the same size.Harbin Engineering University2007-11-1

18、Inefficient scavenging and other losses, however, reduce the power advantage to about 1.8.Harbin Engineering University2007-11-1Each type of engine has its application on board ship. The slow speed (i.e. 90 to 120 rev/min) main propulsion diesel operates on the two-stroke cycle. Harbin Engineering U

19、niversity2007-11-1At this low speed the engine requires no reduction gearbox between it and propeller. Harbin Engineering University2007-11-1The four-stroke engine (usually rotating at medium speed, between 250 to 750 rev/min) is used for alternators and sometimes for main propulsion with a gearbox

20、to provide a propeller speed of between 90 to 120 rev/min. Harbin Engineering University2007-11-1Reading Material Working cyclesA diesel engine may be designed to work on the two-stroke or on the four-stroke cycle: both of these are explained below.Harbin Engineering University2007-11-1The four-stro

21、ke cycleF i g u r e 2 s h o w s d i a g r a m m a t i c a l l y t h e sequence of events throughout the typical four-stroke cycle of two revolutions. Harbin Engineering University2007-11-1It is usual to draw such diagrams starting at TDC (firing), but the explanation will start at TDC (scavenge ). T

22、op dead center is sometimes referred to as inner dead center (IDC).Harbin Engineering University2007-11-1Proceeding clockwise round the diagram, both inlet (or suction) and exhaust valves are initially open. (All modern four-stroke engines have poppet valves (提升閥提升閥).)Harbin Engineering University20

23、07-11-1I f t h e e n g i n e i s n a t u r a l l y aspirated(自然吸氣自然吸氣), or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap(重疊重疊), i.e. when both valves are open, will be short, and the exhaust valve will close some 10after top dead center (ATDC). Harbin Engine

24、ering University2007-11-1TDC（firing)Fuel valve closed(full load)Injection commences10-20BTDCExhaust valve opens120-150ATDCExhaust valve closes 50-60ATDCInlet valve open70-80 BTDCInlet valve close146-155BTDCFig 2四沖程定時(shí)圖BDCHarbin Engineering University2007-11-1Propulsion engines and the vast majority o

25、f auxiliary generator engines running at speeds below 1000 rev/min will a l m o s t c e r t a i n l y b e turbocharged andHarbin Engineering University2007-11-1will be designed to allow a generous throughflow of scavenge air at this point in order to control the turbine blade temperature.Harbin Engi

26、neering University2007-11-1In this case the exhaust valve will remain open until exhaust valve closure (EVC) at 50-60ATDC. As the piston descends to outer or bottom dead center (BDC) on the suction stroke, it will inhale(吸吸入入) a fresh charge of air. Harbin Engineering University2007-11-1To maximize

27、this, balancing the reduced opening as the valve seats against the slight ram(進(jìn)氣進(jìn)氣閥座閥座) or inertia effect of the incoming charge, the inlet (suction) valve will normally be held open until about 25- 35 ABDC (145-155BTDC). Harbin Engineering University2007-11-1This event is called inlet valve closure

28、 (IVC). The charge is then compressed by the rising piston until it has attained a temperature of some 550. Harbin Engineering University2007-11-1At about 10-20BTDC(firing), depending on the type and speed of the engine, the injector admits finely atomized(霧化的霧化的) fuel which ignites within 2-7(depen

29、ding on type again) andHarbin Engineering University2007-11-1the fuel burns over a period of 30-50while the piston begins to descend on the expansion stroke, the piston movement usually helping to induce air m o v e m e n t t o a s s i s t combustion.Harbin Engineering University2007-11-1At about 12

30、0-150ATDC the exhaust valve opens (EVO), the timing being chosen to promote(促進(jìn)促進(jìn)) a very rapid blow-down(排出排出) of the cylinder gases to exhaust. Harbin Engineering University2007-11-1T h i s i s d o n e : ( a ) t o preserve(保留保留) as much energy as is practicable to drive the turbocharger, and (b) to

31、 reduce the cylinder pressure to a minimum by BDC to reduce pumping work on the “exhaust” stroke.Harbin Engineering University2007-11-1The rising piston expels(排出排出) the remaining exhaust gas and at about 70-80 BTDC the inlet valve opens (IVO) so that the inertia of the outflowing gas, Harbin Engine

32、ering University2007-11-1plus the positive pressure difference, which usually exists across the cylinder by now, produces a through flow of air to the exhaust to scavenge the cylinder.Harbin Engineering University2007-11-1If the engine is naturally aspirated the IVO is about 10BTDC. The cycle now re

33、peats. Harbin Engineering University2007-11-1The two-stroke cycleFigure 3 shows the sequence of events in a typical two-stroke cycle, which, as the name implies, is accomplished in one complete revolution of the crank. Harbin Engineering University2007-11-1Exhaust closes110-150BTDCExhaust opens110-1

34、20ATDCInlet opens130-150ATDCInlet closes130-150BTDCTDCFuel valve closes (full load )Injection commences10-20BTDCFig.3二沖程定時(shí)圖The two-stroke cycleHarbin Engineering University2007-11-1Two-stroke engines invariably have ports to admit air when uncovered by the descending piston.Harbin Engineering Univer

35、sity2007-11-1The exhaust may be via ports adjacent to the air ports and controlled by same piston (loop scavenge回流掃氣回流掃氣) or via poppet exhaust valves at the other end of the cylinder (uniflow scavenge直流掃氣直流掃氣). Harbin Engineering University2007-11-1Starting at TDC combustion is already under the wa

36、y and the exhaust opens (EO) at 110-120ATDC to promote a rapid blow-down before the inlet opens (IO) about 20-30later (130-150ATDC). Harbin Engineering University2007-11-1In this way the inertia of the exhaust gasesmoving at about the speed of soundis contrived(設(shè)計(jì)、設(shè)法設(shè)計(jì)、設(shè)法) to encourage the incoming

37、air to flow quickly through the cylinder with a minimum of mixing, Harbin Engineering University2007-11-1because any unexpelled (未排未排出 的 ）出 的 ） e x h a u s t g a s e s detracts(減損，降低減損，降低) from the weight of air entrained for the next stroke. Harbin Engineering University2007-11-1The exhaust should

38、close before the inlet on the compression stroke to maximize the charge, but the geometry of the engine may prevent this if the two events are piston controlled. Harbin Engineering University2007-11-1It can be done in an engine with exhaust valves. Harbin Engineering University2007-11-1At all events

39、 the inlet ports will be closed as many degrees ABDC as opened before it (i.e.again 130150 BTDC) and the exhaust in the same region. Harbin Engineering University2007-11-1Injection commences at about 10-20BTDC depending on speed, and combustion lasts 30-50as with the four-stroke. Harbin Engineering

40、University2007-11-11. More than 50 / above 50 / over 50 50多2. Less than 50 / under 50 / below 50 不到50 或50 以下 The temperature is below 20.3. 50 more 再加50 ten more days 再10天 Please add 50 more grams of salt to the water.Harbin Engineering University2007-11-14. a kilometer or more 一公里或一公里多些 a long kilo

41、meter 一公里多 a long hour 足足一小時(shí) a dozen 一打，dozens 幾十、幾打5. 數(shù)字+ odd twenty odd / twenty-odd / twenty and odd / 20多Harbin Engineering University2007-11-16. from twenty to thirty / twenty to thirty / 從20 到307. some thirty feet / about thirty feet / thirty feet or so / 30英尺左右 a hundred more or less / 100上下

42、more or less twenty pages / 20頁(yè)左右8. n time(s) / 增加到n倍，n倍于 The output has increased (by) threetimes as compared with that of last year.Harbin Engineering University2007-11-1Water conducts heat about 20 times better than air does. 8. 增加多少量， 常用by引出。The coke used has been increased by 18% as compared wi

43、th last year.This pipe is 2 inches longer than that one.Harbin Engineering University2007-11-19. 降低多少倍：減少n times，譯為降低到幾分之幾，或降低了幾分之幾。The new motor is ten times as light asthe old one.新馬達(dá)的重量是舊馬達(dá)的十分之一.The switching time of the new-type transistor is reduced 3 times.新晶體管的開(kāi)關(guān)時(shí)間減縮了三分之二.Harbin Engineering University2007-11-110. 減少多少量，常以by引出，為絕對(duì)數(shù)量。The prime cost decreased by 40%.主要成本下降了百分之四十。This pipe is shorter than that one by 3 me