汽車(chē)專(zhuān)業(yè)英語(yǔ)-2-AUTOMOTIVEENGINE講解課件

1、Chapter 2 AUTOMOTIVE ENGINE 背景知識(shí) 發(fā)動(dòng)機(jī)最早誕生在英國(guó)，所以，發(fā)動(dòng)機(jī)的概念也源于英語(yǔ)，它的本義是指那種“產(chǎn)生動(dòng)力的機(jī)械裝置”。隨著科技的進(jìn)步，人們不斷地研制出不同用途多種類(lèi)型的發(fā)動(dòng)機(jī)，如：活塞式，轉(zhuǎn)子式，渦輪噴氣式，渦輪風(fēng)扇式等。但是，不管哪種發(fā)動(dòng)機(jī)，它的基本前提都是要以某種燃料燃燒來(lái)產(chǎn)生動(dòng)力。所以，以電為能量來(lái)源的電動(dòng)機(jī)，不屬于發(fā)動(dòng)機(jī)的范疇?；仡櫚l(fā)動(dòng)機(jī)產(chǎn)生和發(fā)展的歷史，它經(jīng)歷了外燃機(jī)和內(nèi)燃機(jī)兩個(gè)發(fā)展階段。 Chapter 2 AUTOMOTIVE ENGINE 背景知識(shí) 外燃機(jī)，就是說(shuō)它的燃料在發(fā)動(dòng)機(jī)的外部燃燒，發(fā)動(dòng)機(jī)將這種燃燒產(chǎn)生的熱能轉(zhuǎn)化成動(dòng)能，瓦特發(fā)明的

2、蒸汽機(jī)就是一種典型的外燃機(jī)，當(dāng)大量的煤燃燒產(chǎn)生熱能把水加熱成大量的水蒸汽時(shí)，高壓便產(chǎn)生了，然后這種高壓又推動(dòng)機(jī)械做功，從而完成了熱能向動(dòng)能的轉(zhuǎn)變。 蒸汽機(jī) steam engine（steamer）Watt invented the steam engine. 瓦特發(fā)明了蒸汽機(jī)。 Chapter 2 AUTOMOTIVE ENGINE 背景知識(shí) 內(nèi)燃機(jī)與外燃機(jī)的最大不同在于它的燃料在其內(nèi)部燃燒。內(nèi)燃機(jī)的種類(lèi)十分繁多，我們常見(jiàn)的汽油機(jī)、柴油機(jī)是典型的內(nèi)燃機(jī)。我們不常見(jiàn)的火箭發(fā)動(dòng)機(jī)和飛機(jī)上裝配的噴氣式發(fā)動(dòng)機(jī)也屬于內(nèi)燃機(jī)。不過(guò)，由于動(dòng)力輸出方式不同，前兩者和后兩者又存在著巨大的差異。一般地，在地面上

3、使用的多是前者，在空中使用的多是后者。 當(dāng)然有些汽車(chē)制造者出于創(chuàng)造世界汽車(chē)車(chē)速新紀(jì)錄的目的，也在汽車(chē)上裝用過(guò)噴氣式發(fā)動(dòng)機(jī)，但這總是很特殊的例子，并不存在批量生產(chǎn)的適用性。 Internal combustion內(nèi)燃機(jī)作為汽車(chē).拖拉機(jī).摩托車(chē).工程機(jī)械.船舶.航空.農(nóng)業(yè).林業(yè).軍隊(duì).等各行各業(yè)的動(dòng)力裝置，應(yīng)用極為廣泛， Chapter 2 AUTOMOTIVE ENGINE New Wordslongitudinal lnditju:dinl adj. 縱向的，經(jīng)度的transverse trnsv:s adj. 橫向的，橫斷的reciprocate rsprket v. 往復(fù)，來(lái)回spin s

4、pin v. 旋轉(zhuǎn)；n旋轉(zhuǎn)piston pistn n. 活塞 ignite inait v. 點(diǎn)火，點(diǎn)燃rub rb v. 摩擦，擦quart kw:t n. 夸脫(容量單位)reservoir rezvw: n. 油箱mechanical miknikl adj. 機(jī)械的，機(jī)械制的，機(jī)械似的，呆板的enclosed inkluzd adj. 被附上的gallon ln n. 加侖stroke struk n. 沖程，行程Chapter 2 AUTOMOTIVE ENGINE New Wordsrub rb v. 摩擦，擦camshaft km:ft n. 凸輪軸combustion kmb

5、stn n. 燃燒，著火disengaged dsn ged d adj. 脫開(kāi)的，脫離嚙合的flywheel flaiwi:l n. 飛輪，慣性輪，儲(chǔ)能輪 PHRASES AND EXPRESSIONSinternal-combustion engine 內(nèi)燃機(jī)diesel-fuel 柴油機(jī)燃料，柴油LPG = Liquefied Petroleum Gas 液化石油氣體CNG = Compressed natural gas 壓縮天然氣spark ignition 火花點(diǎn)火 PHRASES AND EXPRESSIONScompression ignition 壓縮點(diǎn)火spark plug

6、 火花塞gas-turbine engine 燃?xì)鉁u輪發(fā)動(dòng)機(jī)steam engine 蒸汽機(jī)Stirling engine 斯特靈發(fā)動(dòng)機(jī)lubricating system 潤(rùn)滑系統(tǒng)oil pan 油底殼oil pump 機(jī)油泵exhaust system 排氣系統(tǒng)emission-control system 排放控制系統(tǒng)Chapter 2 AUTOMOTIVE ENGINE PHRASES AND EXPRESSIONSenergy conversion 能量轉(zhuǎn)換air/fuel ratio 空燃比connecting rod 連桿TDC = Top Dead Center 上止點(diǎn)BDC

7、= Bottom Dead Center 下止點(diǎn)intake stroke 進(jìn)氣沖程compression stroke 壓縮沖程power stroke 作功沖程exhaust stroke 排氣沖程compression ratio 壓縮率，壓縮比Chapter 2 AUTOMOTIVE ENGINE The purpose of an automotive engine is to supply the power needed to move the vehicle. The engine produces this power by burning fuel inside it. B

8、ecause the engine burns fuel inside, or internally, the engine is known as an internal combustion engine (ICE) .Chapter 2 AUTOMOTIVE ENGINE2.1 Purpose and Locations of Engines譯文：汽車(chē)發(fā)動(dòng)機(jī)的功用是汽車(chē)行駛提供必需的動(dòng)力。發(fā)動(dòng)機(jī)通過(guò)它內(nèi)部的燃料燃燒來(lái)產(chǎn)生動(dòng)力。由于發(fā)動(dòng)機(jī)在其內(nèi)部燃燒燃料，所以發(fā)動(dòng)機(jī)被稱(chēng)作內(nèi)燃機(jī)。Engines may be fueled by gasoline, propane （LPG-liquefie

9、d petroleum gas） , or diesel fuel. Compressed natural gas （CNG） may also be used in some vehicles.譯文：發(fā)動(dòng)機(jī)燃料可以是汽油、丙烷（液化石油汽體）或柴油。壓縮天燃?xì)庖部梢杂迷谝恍┸?chē)輛上。be fueled by 通過(guò)得到燃料Most automotive engines are located at the front of the vehicle. Many engines drive the rear wheels. This requires a long drive shaft exten

10、ding form the front wheels to the rear wheels. Other engines drive the front wheels. In the rear-wheel-drive arrangement, the engine sits longitudinally. Its long dimension is from front to back.譯文：大多數(shù)汽車(chē)發(fā)動(dòng)機(jī)位于汽車(chē)前方。許多發(fā)動(dòng)機(jī)由后輪驅(qū)動(dòng)。這需要一根長(zhǎng)傳動(dòng)軸從前輪延伸到后輪。其它發(fā)動(dòng)機(jī)由前輪驅(qū)動(dòng)。在后輪驅(qū)動(dòng)布置中，發(fā)動(dòng)機(jī)縱向放置。它前后尺寸最長(zhǎng)。In the front-wheel-dri

11、ve arrangement, the engine sits crosswise, transversely. With either arrangement, the power is carried to the drive wheels （rear or front）by gears and shafts.譯文：在前輪驅(qū)動(dòng)布置中，發(fā)動(dòng)機(jī)橫向放置。不管哪種放置方式，動(dòng)力都是通過(guò)齒輪和軸傳遞到驅(qū)動(dòng)輪。Some cars have the engine mounted in back of the front seat. This is called a mid-engine arrange

12、ment. Other cars have been built with the engine mounted at the rear, in back of rear seat. The Volkswagen beetle is an example of rear.譯文：一些轎車(chē)把發(fā)動(dòng)機(jī)安裝在前排座位的后面，這稱(chēng)為中置發(fā)動(dòng)機(jī)布置。其它轎車(chē)發(fā)動(dòng)機(jī)安裝在車(chē)的尾部，也就是后排座的后面。比如：大眾汽車(chē)甲殼蟲(chóng)就是采用這種發(fā)動(dòng)機(jī)后置布置。 Various kinds of engines are used in automotive vehicles. The two major types are

13、:1. The piston engine in which pistons move up and down, or reciprocate, in the engine cylinders. This is the engine used in all cars today, except for some models of Mazda.Chapter 2 AUTOMOTIVE ENGINE2.2 Engine Types譯文：機(jī)動(dòng)車(chē)輛上采用各種各樣的發(fā)動(dòng)機(jī)，其兩種主要類(lèi)型為：1、活塞發(fā)動(dòng)機(jī)，活塞在其氣缸內(nèi)上下或往復(fù)運(yùn)動(dòng)。這就是現(xiàn)今轎車(chē)所采用的發(fā)動(dòng)機(jī)形式，除了馬自達(dá)的一些型號(hào)發(fā)動(dòng)機(jī)。cy

14、linderpistonPiston pinConnecting rodcrankshaftOil pipeIntake valveExhaust valve Timing gearOil pump2. The Wankel rotary engine in which rotors rotate, or spin. The Mazda Motor Corporation of Japan is the major manufacturer of this engine.譯文：汪克爾轉(zhuǎn)子發(fā)動(dòng)機(jī)，由其轉(zhuǎn)子回轉(zhuǎn)。日本馬自達(dá)發(fā)動(dòng)機(jī)公司是這類(lèi)發(fā)動(dòng)機(jī)的主要生產(chǎn)商。There are two types

15、of piston engines-spark ignition （SI） and compression ignition（CI） . Spark-ignition engines use an electric ignition system with spark plugs. Electric sparks at the spark plugs ignite, or set fire, the fuel in the engine cylinders. 譯文：有兩種類(lèi)型的活塞發(fā)動(dòng)機(jī)：火花點(diǎn)火和壓縮點(diǎn)火?；鸹c(diǎn)火發(fā)動(dòng)機(jī)采用帶有火花塞的電子點(diǎn)火系統(tǒng)?；鸹ㄈ碾娀鸹c(diǎn)燃發(fā)動(dòng)機(jī)氣缸中的燃料。Th

16、e combustion of the fuel makes the engine run and produce power. This is the type of engine used in most produce power. This is the type of engine used in most automotive vehicles.譯文：燃料燃燒使發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)并產(chǎn)生動(dòng)力。這是在大多數(shù)產(chǎn)生動(dòng)力的發(fā)動(dòng)機(jī)所采用的形式，這種類(lèi)型的發(fā)動(dòng)機(jī)在大部分機(jī)動(dòng)車(chē)輛上使用。The compression-ignition engine the diesel uses the heat of

17、compression to ignite the fuel. When air is compressed, it gets very hot. In the diesel engine, the air is compressed so much that its temperature goes up to 1,000 degrees Fahrenheit （538 degrees Celsius） or higher. 譯文：壓縮點(diǎn)火發(fā)動(dòng)機(jī)，柴油機(jī)使用壓縮產(chǎn)生的熱量來(lái)點(diǎn)燃燃料。當(dāng)空氣被壓縮時(shí)，會(huì)變得非常熱。柴油機(jī)內(nèi)空氣壓縮溫度可過(guò)1000華氏以上（538攝氏度）。一般情況下,柴油的燃點(diǎn)

18、220 汽油的燃點(diǎn)427The diesel fuel is sprayed into this very hot air and is ignited by the heat. Some automobiles have diesel engines. Many heavy-duty trucks and buses are powered by diesel engines.譯文：然后柴油被噴射到這種熱空氣中，并被這種熱度點(diǎn)燃。一些汽車(chē)上采用柴油機(jī)。大多重型卡車(chē)和客車(chē)由柴油機(jī)提供動(dòng)力。There are other engines still in the experimental sta

19、ge that might someday become important. These include gas-turbine engines, steam engines, Stirling engines, and electric motors.譯文：還有一些其它的發(fā)動(dòng)機(jī)仍處于實(shí)驗(yàn)階段，總有一天會(huì)變得重要。它們包括燃?xì)鉁u輪發(fā)動(dòng)機(jī)、蒸汽機(jī)、斯特林（熱氣體）發(fā)動(dòng)機(jī)和電動(dòng)機(jī)。 A spark-ignition engine requires four basic systems to run. Diesel engines require three of these systems. T

20、hey are fuel system, ignition system（except diesel） , lubricating system and cooling system. Each performs a basic job in making the engine run. These are described briefly below.Chapter 2 AUTOMOTIVE ENGINE2.3 Basic Engine Systems譯文：火花點(diǎn)火發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)需要4個(gè)基本系統(tǒng)。柴油發(fā)動(dòng)機(jī)需要其中的3個(gè)。它們是燃料系統(tǒng)，點(diǎn)火系統(tǒng)（除了柴油機(jī)），潤(rùn)滑系統(tǒng)和冷卻系統(tǒng)。其每個(gè)系統(tǒng)在

21、使發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)時(shí)完成一個(gè)基本工作。簡(jiǎn)要介紹如下：2.3.1 Fuel SystemsThe fuel system supplies gasoline or diesel fuel to the engine. This fuel is mixed with air to make a combustible mixture （a mixture that will burn）. Each cylinder is repeatedly filled with the mixture. 譯文：燃料系統(tǒng)給發(fā)動(dòng)機(jī)提供汽油或柴油燃料。燃料與空氣混合形成可燃混合氣（一種會(huì)燃燒的混合物）。氣缸被反復(fù)填充這種

22、混合氣體。Then, the mixture is ignited and burned, producing high pressure. The high pressure makes the pistons move （or rotors spin） . This turns shafts that rotate the wheels, causing the vehicle to move.譯文：然后被點(diǎn)燃、燃燒，產(chǎn)生高壓，推動(dòng)活塞運(yùn)動(dòng)（或轉(zhuǎn)子旋轉(zhuǎn)）。這使車(chē)軸帶到車(chē)輪旋轉(zhuǎn)，從而使車(chē)輛移動(dòng)。2.3.2 Ignition systemEvery time the fuel system d

23、elivers air/fuel mixture to a cylinder, the ignition system follows up by delivering an electric spark. This ignites the mixture which creates the high pressure that moves the pistons and turns the car wheels. The action is repeated many times each second while the engine is running.譯文：每當(dāng)燃料系統(tǒng)傳送可燃混合氣

24、給氣缸，點(diǎn)火系統(tǒng)隨后會(huì)產(chǎn)生電火花來(lái)點(diǎn)燃混合氣，從而產(chǎn)生高壓，使活塞運(yùn)動(dòng)和車(chē)輪運(yùn)轉(zhuǎn)。當(dāng)發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)時(shí)，每秒鐘這個(gè)動(dòng)作重復(fù)多次。The ignition system takes the low voltage, of the battery and builds it up to a very high voltage: as high as 47,000 volts in some systems. This high voltage jumps the gaps in the spark plugs, producing the sparks that ignite the air/fuel

25、mixture in the engine cylinders.譯文：點(diǎn)火系統(tǒng)把蓄電池的低壓增到高壓，在一些系統(tǒng)中可達(dá)到47000伏。高壓擊穿火花塞（兩電極之間）間隙，產(chǎn)生電火花，點(diǎn)燃發(fā)動(dòng)機(jī)氣缸內(nèi)的可燃混合氣。2.3.3 Lubricating systemThe engine has many moving metal parts. If metal parts rub against each other, they will wear rapidly. To prevent this, engines have lubricating oil. The oil gets between

26、the metal parts so they slide on the oil, and not on each other.譯文：發(fā)動(dòng)機(jī)有許多運(yùn)動(dòng)金屬部件。如果金屬部件之間相互磨擦，會(huì)加速磨損。為防止這樣，發(fā)動(dòng)機(jī)帶有潤(rùn)滑油。潤(rùn)滑油充斥在金屬部件之間，從而使它們?cè)谟兔嫔匣瑒?dòng)，而不是在其表面。The lubricating system has an oil pan at the bottom of the engine which holds several quarts （liters）of oil. An oil pump, driven by the engine, sends oil

27、 from this reservoir through the engine. After circulating through the engine, the oil drops back down into the oil pan. The oil pump continues to circulate the oil as long as the engine is running.譯文：潤(rùn)滑系統(tǒng)油底殼位于發(fā)動(dòng)機(jī)的底部，它可保存幾夸脫（升）的潤(rùn)滑油。油泵由發(fā)動(dòng)機(jī)驅(qū)動(dòng)把潤(rùn)滑油從油底殼送到發(fā)動(dòng)機(jī)各個(gè)部件，潤(rùn)滑油在發(fā)動(dòng)機(jī)內(nèi)循環(huán)后，回落到油底殼中。只要發(fā)動(dòng)機(jī)不斷運(yùn)轉(zhuǎn)，油泵就會(huì)連續(xù)循環(huán)潤(rùn)滑油。

28、夸脫(容量單位=1/4 加侖, 約1.14升)2.3.4 Cooling systemWhere there is fire（combustion）, there is heat. Burning of the air/fuel mixture raises the temperature inside the engine cylinders several thousand degrees. 譯文：有火（燃燒）的地方，就會(huì)有熱?？扇蓟旌蠚獾娜紵龝?huì)把發(fā)動(dòng)機(jī)氣缸內(nèi)的溫度提升到幾千攝氏度。Some of this heat produces the high pressure that move

29、s the pistons to produce power. Some of the heat leaves the cylinders with the exhaust gas. The exhaust gas is what is left after the air/fuel mixture burns. It is cleared out of the cylinders after combustion is complete.譯文：其中一部分熱量產(chǎn)生高壓推動(dòng)活塞運(yùn)動(dòng)來(lái)產(chǎn)生動(dòng)力。另外一部分熱量隨著廢氣排出氣缸。廢氣是指可燃混合氣燃燒后殘留的氣體。它在燃燒完成后被排出氣缸。 Some

30、 of the heat is removed by the circulating oil. After the hot oil drops down into the oil pan, the oil gives up some of this heat to the air passing under the oil pan. The rest of the heat is removed by the cooling system.譯文：還有一部分熱量由循環(huán)潤(rùn)滑油帶走。灼熱的潤(rùn)滑油落到油底殼后，會(huì)把部分熱量傳給通過(guò)油底殼下方的空氣。其余熱量由冷卻系散發(fā)。2.3.5 Other engi

31、ne systemsAn engine will run with the four basic systems described abovefuel, ignition, lubricating, and cooling. However, three other related systems are also necessary. These are the exhaust system, the emission-control system, and the starting system.譯文：發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)需要上述4個(gè)基本系統(tǒng)燃料、點(diǎn)火、潤(rùn)滑和冷卻。但是，還有另外三個(gè)相關(guān)系統(tǒng)也是必

32、需的。它們是排放系統(tǒng)、廢氣處理（排氣凈化）系統(tǒng)和起動(dòng)系統(tǒng)。The exhaust system reduces the noise of the burned gases leaving the engine cylinders and carries these exhaust gases safely away from the people in the car. The emission-control system is required by law to reduce the air pollution the engine could produce. 譯文：排放系統(tǒng)功能，一方

33、面減小燃燒廢氣排出氣缸時(shí)所產(chǎn)生的噪聲，另一方面把這些廢氣從車(chē)中乘客身邊安全帶走。廢氣處理（排放控制）系統(tǒng)是法規(guī)所要求的用來(lái)降低發(fā)動(dòng)機(jī)所產(chǎn)生的空氣污染。The starting system is needed to crank the engine. A battery provides the electric power to operate the starting motor and the ignition system during cranking.譯文：起動(dòng)系統(tǒng)用來(lái)轉(zhuǎn)動(dòng)發(fā)動(dòng)機(jī)曲軸。蓄電池在起動(dòng)時(shí)為開(kāi)動(dòng)起動(dòng)機(jī)和點(diǎn)火系統(tǒng)提供電力。 The internal combustion e

34、ngine is a device used to convert the chemical energy of the fuel （gasoline or diesel fuel） into heat energy, and then to convert this heat energy into usable mechanical energy. Chapter 2 AUTOMOTIVE ENGINE2.4 Energy Conversion譯文：內(nèi)燃機(jī)是一種把（汽油或柴油）燃料的化學(xué)能轉(zhuǎn)變成熱能，再轉(zhuǎn)換成可利用的機(jī)械能的裝置。This is achieved by combining

35、the appropriate amounts of air and fuel, and burning the mixture in an enclosed cylinder at a controlled rate. A movable piston in the cylinder is forced down by the expanding gases of combustion.譯文：這通過(guò)混合適量的空氣和燃料，并在密閉的汽缸中按照控制速度燃燒來(lái)實(shí)現(xiàn)。氣缸中活塞由燃燒氣體膨脹作功來(lái)壓下。An average air/fuel ratio for good combustion is

36、about 15 parts of air to 1 part of fuel by weight. This means that for every gallon of gasoline burned, the oxygen is about 9,000 to 10,000 gallons of air is required. Air is about 21% oxygen and 78% nitrogen.譯文：燃燒良好的空燃比，按質(zhì)量平均大約是15：1。這意味著每加侖汽油完全燃燒所需的空氣質(zhì)量大約在9000到10000加侖?？諝庵醒鯕獬煞蔹c(diǎn)21%，氮?dú)庹?8%。Diesel engi

37、nes operate on a much wider air/fuel ratio, since air intake is not regulated on most diesels. Ratios may range from about 20:1 to about 100:1. The fact, plus the high compression of the diesel, makes it a very fuel efficient engine.譯文：因?yàn)檫M(jìn)氣量在大多數(shù)內(nèi)柴油機(jī)上不規(guī)則的，柴油機(jī)有更寬的空燃比。其范圍大約在20：1到100：1之間。實(shí)際上，加上柴油機(jī)的高壓縮比，

38、使其成為極其節(jié)約燃油的發(fā)動(dòng)機(jī)。fuel efficient節(jié)約燃油的，燃油經(jīng)濟(jì)性高的The movable piston in the cylinder is connected to the top of a connecting rod. The bottom of the connecting rod is attached to the offset portion of a crankshaft. As the piston is force down, this force is transferred to the crankshaft, causing the cranksha

39、ft to rotate. 譯文：氣缸活塞與連桿上端相連。連桿底部則連到曲軸的偏心部。當(dāng)活塞被壓下時(shí)，驅(qū)動(dòng)力被傳遞到曲軸，并帶動(dòng)曲軸旋轉(zhuǎn)。The reciprocating （back and forth or up and down） movement of the piston is converted to rotary （turning） motion of the crankshaft, which supplies the power to drive the vehicle.譯文：活塞的往復(fù)運(yùn)動(dòng)轉(zhuǎn)化成曲軸的旋轉(zhuǎn)運(yùn)動(dòng)，從而為驅(qū)動(dòng)車(chē)輛提供動(dòng)力。The efficiency of th

40、e internal combustion, reciprocating piston engine in converting the potential energy in fuel into mechanical energy is only about 33 %. Of the available heat energy in the fuel, about one-third is lost through the exhaust system and one-third is absorbed and dissipated by the cooling system. Of the

41、 remaining one-third, about one-half is lost through available at the vehicles drive wheels.譯文：活塞發(fā)動(dòng)機(jī)在轉(zhuǎn)化燃料的勢(shì)能為機(jī)械能時(shí)的效率大約只有33%。對(duì)于燃料的可用熱能，大概有1/3損失在排放系統(tǒng)中，另外1/3被冷卻系統(tǒng)吸收和散發(fā)。在剩余的1/3中，約有一半完全利用在車(chē)輛的驅(qū)動(dòng)輪上。The overall efficiency of the diesel engine is considerably higher than that of the gasoline engine. The reas

42、ons for this are: the higher compression ratio, the higher air/fuel ratio, and the higher heat value of the fuel. The useful power developed at the drive wheels by a diesel engine is about 25% as compared to 15% by a gasoline engine.譯文：柴油機(jī)的總效率明顯高于汽油機(jī)。原因在于柴油機(jī)的高壓縮比，高空燃比和柴油的高熱值。柴油機(jī)傳遞到車(chē)輪的有效功率大約在25%，而汽油機(jī)

43、只有15%。 The movement of the piston from its uppermost position （TDC, top dead center）to its lowest position （BDC, bottom dead center） is called a stroke. Most automobile engines operate on the four stroke-cycle principle. Chapter 2 AUTOMOTIVE ENGINE2.4 Four-Stroke-Cycle Gasoline Engine Operation譯文：從活

44、塞的最上端（上止點(diǎn)）到它的最下端（下止點(diǎn)）的運(yùn)動(dòng)過(guò)程稱(chēng)為一個(gè)行程。大多數(shù)汽車(chē)發(fā)動(dòng)機(jī)根據(jù)四沖程原理工作。A series of events involving four strokes of the piston completes one cycle. Figure 2-1. These events are: （1） the intake stroke, （2） the compression stroke, （3） the power stroke, and （4） the exhaust stroke. Two revolutions of the crankshaft and one

45、 revolution of the camshaft are required to complete one cycle.譯文：四個(gè)活塞行程完成一個(gè)工作周期。這4個(gè)行程是進(jìn)氣行程，壓縮行程，作功行程和排氣行程。同時(shí)，需要曲軸轉(zhuǎn)動(dòng)兩圈，凸輪軸轉(zhuǎn)動(dòng)一圈。On the intake stroke the piston is pulled down in the cylinder by the crankshaft and connecting rod. During this time the intake valve is held open by the camshaft. Since th

46、e piston has moved down in the cylinder, creating a low-pressure area（vacuum）, atmospheric pressure forces a mixture of air and fuel past the intake valve into the cylinder. 譯文：在進(jìn)氣行程中，活塞在氣缸中被曲軸和連桿拉下。這時(shí)，進(jìn)氣門(mén)被凸輪軸開(kāi)啟。因?yàn)榛钊跉飧字邢蛳乱苿?dòng)，產(chǎn)生一個(gè)低壓區(qū)（真空），大氣壓將可燃混合氣通過(guò)進(jìn)氣門(mén)壓入氣缸。Atmospheric pressure is approximately 14.7 p

47、ounds per square inch （about 101.35 kilopascals） at sea level. Pressure in the cylinder during the intake stroke is considerably less than this. The pressure difference is the force that causes the air/fuel mixture to flow into the cylinder, since a liquid or a gas （vapor） will always flow from a hi

48、gh-pressure to a low-pressure area.譯文：大氣壓在海平面上大約為14.7磅/平方英寸(101.35千帕)。進(jìn)氣行程中氣缸內(nèi)壓力遠(yuǎn)小于大氣壓力。因?yàn)橐后w或氣體（蒸汽）總是從高壓區(qū)流向低壓區(qū)，所以這個(gè)壓力差促使可燃混合氣注入汽缸。As the piston is moved up by the crankshaft from BDC, the intake valve closes. The air/fuel mixture is trapped in the cylinder above the piston. Further piston travel com

49、presses the air/fuel mixture to approximately one-eighth of its original volume （approximately 8: 1 compression ratio） when the piston has reached TDC. This completes the compression stroke.譯文：當(dāng)活塞曲軸帶動(dòng)從下止點(diǎn)向上移時(shí)，進(jìn)氣門(mén)關(guān)閉?？扇蓟旌蠚夥庠跉飧變?nèi)活塞的上方。當(dāng)活塞到達(dá)上止點(diǎn)時(shí)，可燃混合氣體積由活塞運(yùn)動(dòng)壓縮至其原來(lái)體積的約1/8（8:1的壓縮比）。這就完成了壓縮行程。When the pisto

50、n is at or near TDC, the air/fuel mixture is ignited. The burning of the air/fuel mixture （combustion） takes place at a controlled rate. Expansion of the burning mixture causes a rapid rise in pressure. This increased pressure forces the piston down on the power stroke, causing the crankshaft to rot

51、ate.譯文：當(dāng)活塞移動(dòng)到上止點(diǎn)附近時(shí)，可燃混合氣被點(diǎn)燃?；旌衔锏娜紵凑湛刂扑俣冗M(jìn)行。燃燒氣體體積膨脹使（氣缸內(nèi)）壓力迅速上升。在此作功行程中，氣體增壓推動(dòng)活塞向下移動(dòng)，帶動(dòng)曲軸旋轉(zhuǎn)。At the end of the power stroke the camshaft opens the exhaust valve, and the exhaust stroke begins. Remaining pressure in the cylinder, and upward movement of piston, force the exhaust gases out of the cylin

52、der. At the end of the exhaust stroke, the exhaust valve closes and the intake valve opens, repeating the entire cycle of events over and over again.譯文：在作功行程結(jié)束時(shí)，凸輪軸打開(kāi)排氣門(mén)，進(jìn)入排氣行程。氣缸中剩余壓力和活塞的向上移動(dòng)把廢氣排出氣缸。排氣行程結(jié)束時(shí)，排氣門(mén)關(guān)閉，進(jìn)氣門(mén)打開(kāi)，反復(fù)不斷重復(fù)整個(gè)沖程循環(huán)周期。To start the engine, some method of cranking the engine is requir

53、ed to turn the crankshaft and cause piston movement. This is done by the starter motor when the ignition key is in the start position. 譯文：為了起動(dòng)發(fā)動(dòng)機(jī)，需要一些起動(dòng)方法來(lái)轉(zhuǎn)動(dòng)發(fā)動(dòng)機(jī)曲軸，使活塞（上下）運(yùn)動(dòng)。這在點(diǎn)火開(kāi)關(guān)處于起動(dòng)位置時(shí)由起動(dòng)機(jī)來(lái)實(shí)現(xiàn)。When sufficient air/fuel mixture has entered the cylinders and is ignited, the power strokes create enough

54、 energy to continue crankshaft rotation. At the point, the ignition key is released to the run position and the starter is disengaged.譯文：當(dāng)足量的可燃混合氣進(jìn)入氣缸并且被點(diǎn)燃，作功行程能產(chǎn)生足夠的熱量來(lái)繼續(xù)曲軸旋轉(zhuǎn)，此時(shí)點(diǎn)火開(kāi)關(guān)釋放至運(yùn)行位置，起動(dòng)機(jī)解除。Sufficient energy is stored in the flywheel and other rotating parts on the power stroke to move the piston and related parts through the other three strokes （exhaust, intake, and compression）. The amount of air/fuel mixture allowed to enter the cylinder determines the power and speed developed by the engine.