輪機(jī)英語(yǔ)教學(xué)課件

1、New 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 charge 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2007-11-1 rotate 旋轉(zhuǎn)，回轉(zhuǎn) medium

2、 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，過程 stroke 沖程，行程 separate (from) 分離，分開 exhaust 排出，耗盡；排氣 combine (with) 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，無效的2007-11-1

3、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)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2007-11-1*The diesel engine is a type of

4、internal combustion engine which ignites(點(diǎn)燃) the fuel by injecting(噴射) it into hot, high pressure air in a combustion chamber(燃燒室). 2007-11-1The marine diesel engine is a type of diesel engine used on ships. The principle of its operation is as follows:2007-11-1A charge of fresh air is drawn or pump

5、ed into the engine cylinder(氣缸) and then compressed by the moving piston(活塞) to very high pressure.2007-11-1When the air is compressed, its temperature rises so that it ignites the fine spray(噴霧、油霧) of fuel injected into the cylinder.2007-11-1The burning of the fuel adds more heat to the air charge,

6、 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).2007-11-1Exhaust valveInlet valveFuel injectorCylinderPistonPiston ringConnecting rodFour-stroke diesel engineCombustion chamberPiston pincrankshaftCrank web2007-11-1Fuel inje

7、ctorFuel injectorExhaust valve掃氣口Scavenge portExhaust portTwo-strokeEngineCross scavenge systemUniflow scavenge systemPiston rodConnecting rodPiston pinCrosshead2007-11-1The operation between two fuel injections is called a working cycle, which consists of a fixed sequence of events. 2007-11-1This c

8、ycle may be achieved either in four strokes(沖程、行程) or two.2007-11-1In a four-stroke diesel engine, the cycle requires four separate strokes of the piston, i.e. suction(吸氣), compression(壓縮), expansion(膨脹) and exhaust(排氣). * Note: i.e. (拉=id est)即；就是2007-11-1If we combine the suction and exhaust opera

9、tions 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). 2007-11-1Scavenge(a)Compression(b)Injection(c)Exhaust(d)ScavengeportExhaustportFuel injectorCylinderPistonConnecting rodCrank2007-11-1The two-stroke cycle beg

10、ins 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) in the sides of the cylinder being opened (Fig. 1-a). 2007-11-1The exhaust ports are uncovered also. Pressurized fresh air charges into the cylinder, blowing ou

11、t any residual exhaust gases from the last stroke through the exhaust ports. 2007-11-1As the piston moves about one fifth of the way up, it closes the inlet ports and the exhaust ports. The air is then compressed as the piston moves up. (Fig. 1-b). 2007-11-1When the piston reaches the top of its str

12、oke, i.e. the top dead center (TDC), both the pressure and the temperature of the air rise to very high values. 2007-11-1The fuel injector injects a fine spray of fuel into the hot air and combustion take place, producing much higher pressure in the gases. 2007-11-1The piston is forced(迫使) downward

13、as the high pressure gases expand until it uncovers the exhaust ports. 2007-11-1The burning gases begin to exhaust (Fig. 1-d) and the piston continues down until it opens the inlet ports. Then another cycle begins.2007-11-1In the two-stroke engine, each revolution of the crankshaft (曲軸) makes one po

14、wer or working stroke, while in the four-stroke engine, it takes two revolutions to make one power stroke. 2007-11-1That is why a two-stroke cycle engine will theoretically develop twice (two times) the power of a four-stroke engine of the same size.2007-11-1Inefficient scavenging and other losses,

15、however, reduce the power advantage to about 1.8.2007-11-1Each 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. 2007-11-1At this low speed the engine requires no reduction gearbox between it and propell

16、er. 2007-11-1The 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 to provide a propeller speed of between 90 to 120 rev/min. 2007-11-1Reading Material Working cyclesA diesel engine may be design

17、ed to work on the two-stroke or on the four-stroke cycle: both of these are explained below.2007-11-1The four-stroke cycleFigure 2 shows diagrammatically the sequence of events throughout the typical four-stroke cycle of two revolutions. 2007-11-1It is usual to draw such diagrams starting at TDC (fi

18、ring), but the explanation will start at TDC (scavenge ). Top dead center is sometimes referred to as inner dead center (IDC).2007-11-1Proceeding 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).)2007

19、-11-1If the engine is naturally aspirated(自然吸氣), or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap(重疊), i.e. when both valves are open, will be short, and the exhaust valve will close some 10after top dead center (ATDC). 2007-11-1TDC（firing)Fuel valve closed(

20、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BDC2007-11-1Propulsion engines and the vast majority of auxiliary generator engines running at speeds below 1000 rev/min will almost cert

21、ainly be turbocharged and2007-11-1will be designed to allow a generous throughflow of scavenge air at this point in order to control the turbine blade temperature.2007-11-1In this case the exhaust valve will remain open until exhaust valve closure (EVC) at 50-60ATDC. As the piston descends to outer

22、or bottom dead center (BDC) on the suction stroke, it will inhale(吸入) a fresh charge of air. 2007-11-1To maximize this, balancing the reduced opening as the valve seats against the slight ram(進(jìn)氣閥座) or inertia effect of the incoming charge, the inlet (suction) valve will normally be held open until a

23、bout 25- 35 ABDC (145-155BTDC). 2007-11-1This event is called inlet valve closure (IVC). The charge is then compressed by the rising piston until it has attained a temperature of some 550. 2007-11-1At about 10-20BTDC(firing), depending on the type and speed of the engine, the injector admits finely

24、atomized(霧化的) fuel which ignites within 2-7(depending on type again) and2007-11-1the 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 movement to assist combustion.2007-11-1At about 120-150ATDC the exhaust

25、valve opens (EVO), the timing being chosen to promote(促進(jìn)) a very rapid blow-down(排出) of the cylinder gases to exhaust. 2007-11-1This is done: (a) to preserve(保留) as much energy as is practicable to drive the turbocharger, and (b) to reduce the cylinder pressure to a minimum by BDC to reduce pumping

26、work on the “exhaust” stroke.2007-11-1The rising piston expels(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, 2007-11-1plus the positive pressure difference, which usually exists across the cylinder by now, produces a thro

27、ugh flow of air to the exhaust to scavenge the cylinder.2007-11-1If the engine is naturally aspirated the IVO is about 10BTDC. The cycle now repeats. 2007-11-1The two-stroke cycleFigure 3 shows the sequence of events in a typical two-stroke cycle, which, as the name implies, is accomplished in one c

28、omplete revolution of the crank. 2007-11-1Exhaust closes110-150BTDCExhaust opens110-120ATDCInlet opens130-150ATDCInlet closes130-150BTDCTDCFuel valve closes (full load )Injection commences10-20BTDCFig.3二沖程定時(shí)圖The two-stroke cycle2007-11-1Two-stroke engines invariably have ports to admit air when unco

29、vered by the descending piston.2007-11-1The exhaust may be via ports adjacent to the air ports and controlled by same piston (loop scavenge回流掃氣) or via poppet exhaust valves at the other end of the cylinder (uniflow scavenge直流掃氣). 2007-11-1Starting at TDC combustion is already under the way and the

30、exhaust opens (EO) at 110-120ATDC to promote a rapid blow-down before the inlet opens (IO) about 20-30later (130-150ATDC). 2007-11-1In this way the inertia of the exhaust gasesmoving at about the speed of soundis contrived(設(shè)計(jì)、設(shè)法) to encourage the incoming air to flow quickly through the cylinder wit

31、h a minimum of mixing, 2007-11-1because any unexpelled (未排出的）exhaust gases detracts(減損，降低) from the weight of air entrained for the next stroke. 2007-11-1The exhaust should close before the inlet on the compression stroke to maximize the charge, but the geometry of the engine may prevent this if the

32、 two events are piston controlled. 2007-11-1It can be done in an engine with exhaust valves. 2007-11-1At all events 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. 2007-11-1Injection commences at about 10-20BTDC depe

33、nding on speed, and combustion lasts 30-50as with the four-stroke. 2007-11-11. 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.2007-11-14. a kilometer o

34、r more 一公里或一公里多些 a long kilometer 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2007-11-16. 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 m

35、ore 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.2007-11-1Water 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 with last year.This pipe is 2 in

36、ches longer than that one.2007-11-19. 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.新晶體管的開關(guān)時(shí)間減縮了三分之二.2007-11-110. 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 meters.這根管子比那根短3米。2007-11-11、主語(yǔ)如果是用連詞and, both