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附錄A 外文文獻
Engine operating principls
Most automobile dngines are internal combustion, reciprocating4-stroke gasoline engines, but other types have been used, including the diesel, the rotary (wankel),the 2-stroke ,and stratifild charge.
Recipprocating means up and down or banck and forth, it is the up an down action of a piston in the cylinder blick ,or engine block . the blick is an iron or aluminum casting that contains engine cylinders and passage called water jackets for coolant circulation .the top of the block is covered with the cylinder head. Which forms the combustion chanber. The bottom of the block is covered with an oil pan or oil sump.
Power is produced by the linear motion of a piston in a cylinder.however, this linear motion must be changed into rotary motion to turn the wheels of cars of trucks. The pistion is attached to the top of a connecting rod by a pin, called a pistion pin or wrist pin the bottom of the connecting rod is attached to the crankshaft . the connecting rod transmits the up-and-down motion of the piston to the crankshaft , which changes it into rotarymotion.
The connecting rod is mounted on the crankshaft with large beaings called rod bearings. Similar bearings, called main bearings, are used to mount the crankshaft in the block .shown in fig ,1-1.
The diameter of the cylinder is called the engine bore. Displacement and compression ratio are two frequently used engine specifications. Displacement indicates engine size , and compression ratio compares the total cylinder volume to compression chamber volume.
The term stroke is uesd to describe the movement of the iston within the cylinder, as well as the distance of pistion travel. Depending on the type of engine the operating cycle may require either two or four strokes to complete. The 4-strokes engine is also called otto cycle engine ,in honor of the german enginner , Dr. Nikolaus otto , who first applied the principle in 1876 . In the 4-stroke engine ,four strokes of the piston in the cylinder are required to complete one full operating cycle .Each stroke is named after the action it performes instake , compression ,power, and exhaust in that order, shown in Fig1-2.
1、 Instake stroke
As the piston moves down , the vaporized mixture of fuel and air enters the cylinder through open instake vavle. To obtain the maximum filling of the cylinder the instake valve opens about 10° before t.b.c ,giving 20° overlap. The inlet valve remains open until some 50° after b.d.c to take advantage of incoming mixture.
2、Compression stroke
The pieton turns up , the instake valve closes, the mixture is compressed within the combustion chamber, while the pressure rise to ahout 1 Mpa, depending on various factors inclouding the compression ratio, throttle opening and engine speed. Near the top of the stroke the mixture is ignited by a spark which bridge the gap of the spark plug.
3、Power stroke
The expanding gases of combution produces a rise in pressure of the gas to some 3.5Mpa, and the piston is forced down in the cylinder. The exhaust valve opens near the bottom of the stroke.
4、Exhust stroke
The piston moves back up with the exhause valve open some 50°before b.d.d.,allowing the pressure within the cylinder to fall and to reduce ‘back’ pressure on the piston during the exhaust stroke, and the burned gases are pushed out to prepare for the next instake stroke. The instake valve usually opens just before the exhaust stroke.
This 4-stroke cycle is continuously repared in every as long as the engineremains running
A-2-stroke engine also goes through four actions to complete one operating cycle.
However , the instake and the compression actions are combined in one seroke,and the power and exhaust actions are combined in the other stroke. The term2-stroke cycle or 2-stroke cycle or 2-stroke is preferred to the term 2-cycle, which is really not accurate.
In automobile engines, all pistons are attached to a single crankshaft. The more cylinders an engine has ,the more power strokes produced for cach revolusion. This means that means that an 8-cylinder engine runs more smoothly because the power atrokes are closer together in time and in degrees of engine rotation.
The cylinder of multi-cyclinder automotive engines arranged in one of three ways.
1、 Inline engine use a single block of cylinder. Most 4-cylinder and 6-cylinder engines are of this design. The cylinder do not have to be vertical. They can be inclined either side.
2、 V-type engine use two equal bands of cylinder , usually inclined 60degrees or 90degrees from the cach other. Most V-type engines have 6 or 8 cylinders, although V-4 and V-12 engine have been built.
3、 Horizontally opposed or pancake engine have two equal banks of cylinders 180degrees apart . these space saving engine designs are often air-cooled,and are found in the chevrolet carvair porsches, Subaus,and Volkswagens. Subaus design is liquid cooled.Later –model Volkswagen vans use a liquil-cooled VWhorizontally opposed engine.
附錄B 中文翻譯
發(fā)動機工作原理
大多數(shù)汽車的發(fā)動機是內(nèi)燃機，往復(fù)四沖程汽油機，但是也有使用其他類型的發(fā)動機，包括柴油機，轉(zhuǎn)子發(fā)動機二沖程發(fā)動機和分程燃燒發(fā)動機。往復(fù)的意思就是上下或前后運動，在往復(fù)發(fā)動機中，氣缸中活塞的上下運動產(chǎn)生發(fā)動機的動力，這種類型幾乎所有的發(fā)動機都是依賴氣缸體即發(fā)動機缸體，缸體是鑄鐵或鑄鋁制的，它包括發(fā)動機氣缸和冷卻液循環(huán)用的水套，缸體的頂部是氣缸蓋，它組成了燃燒室，缸體底部是油底殼。
氣缸內(nèi)活塞的運動產(chǎn)生動力，然而，必須將直線運動轉(zhuǎn)化為旋轉(zhuǎn)運動，使汽車車輪轉(zhuǎn)動，活塞銷將活塞連接在連桿頂部，連桿底部與曲軸連接，使汽車車輪轉(zhuǎn)動，活塞銷將活塞連桿頂部、連桿底部與曲軸連接，連桿將活塞的往復(fù)運動傳遞給曲軸，曲軸將其轉(zhuǎn)化為旋轉(zhuǎn)動力，連桿是用連桿曲軸安裝在曲軸上的，用類似的軸承即主軸承將曲軸固定在缸體內(nèi)。
氣缸的直徑成為發(fā)動機的內(nèi)徑，排量和壓縮比是兩個常用的發(fā)動機參數(shù)，排量是指發(fā)動機的大小，壓縮比是氣缸總?cè)莘e與燃燒室壓縮容積之比。
術(shù)語：沖程是用來說明活塞在氣缸內(nèi)的運動，也就是活塞行程的距離根據(jù)發(fā)動機類型的需要二沖程或四沖程來完成一個完整的工作循環(huán)，每個在沖程根據(jù)其行為命名分別為：進氣沖程、壓縮沖程、作功行沖程和排氣行沖程。
1、進氣沖程
當活塞下移時，霧化后的可燃混合氣通過打開的進氣門進入氣缸，為了達到最大的進氣量，進氣門在活塞到達上止點前10°打開，使進、排氣有20°打開重疊角，進氣門一直打開到活塞到達下止點充分進入混合氣之后50°左右。
2、壓縮沖程
活塞開始向上移動時，進氣門關(guān)閉，混合氣在燃燒室中壓縮，根據(jù)不同因素包括壓縮比，節(jié)氣門開度，發(fā)動機轉(zhuǎn)速壓力上升到約1兆帕，接近沖程頂部時，火花塞產(chǎn)生的電火花擊穿點火間隙點燃可燃混合氣。
3、作功沖程
燃燒膨脹的氣體產(chǎn)生的壓力上升到3.5個兆帕?xí)r，推動活塞下移，接近氣缸底時，排氣門打開。
4、排氣行程
隨著排氣門開啟約下止點前50°，活塞回升，使氣缸內(nèi)壓力下降在排氣沖程，減少對活塞回壓，排除廢氣，為下一個進氣沖程做準備，通常情況下，進氣門在排氣沖程完成前打開。
只要發(fā)動機保持運轉(zhuǎn)，每個氣缸內(nèi)四個沖程循環(huán)連續(xù)不斷的重復(fù)下去。
兩沖程的發(fā)動機也同樣通過四行程來完成，一個工作循環(huán)既是進氣沖程、壓縮沖程合為一個沖程，作功沖程行程另一個沖程，術(shù)語兩行程循環(huán)和兩行程就是所謂的術(shù)語雙循環(huán)，但實際上并不準確。
在所有的汽車發(fā)動機中，所有的活塞都是固定在一個曲軸上，氣缸中發(fā)動機越多，每轉(zhuǎn)為發(fā)動機的作功沖程產(chǎn)生越多的動力，這就意味著八缸發(fā)動機運轉(zhuǎn)的越平順，因為發(fā)動機在作功沖程中運轉(zhuǎn)時間和旋轉(zhuǎn)角度緊密。
多缸發(fā)動機有三種排列形式，任其一種
1、 直列式發(fā)動機用一個氣缸體，大多數(shù)四缸發(fā)動機和一些六缸發(fā)動機都采用這種形式，這種氣缸不必垂直分布，它們可以向任一方向傾斜。
2、 V-型發(fā)動機用兩排同樣的氣缸，通常夾角為60°或90°，大多數(shù)有六缸或八缸，盡
管四缸和十二缸也有采用V型的。
3、臥式或者對置式發(fā)動機有兩排互為180°的氣缸，這些發(fā)動機通常采用風冷式，在雪弗蘭、富士、大眾車采用這種形式、富士采用水冷式，在頂置式風冷發(fā)動機中，大眾的新型廂式汽車采用水冷式。
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