汽車專業(yè)外文文獻(xiàn)英文翻譯(編輯修改稿)
2024-12-07 00:25 本頁面
【文章內(nèi)容簡介】 nded) to the possibilities of an ecological disaster on the horizon, maybe it’s time that we got over our need to drive huge SUVs and start moderating our fuel consumption. Then again, as gas prices hovering around $ and with no ceiling in sight, we may have little choice in the matter. Engine Operating Principles Most automobile dngines are internal bustion, reciprocating 4stroke gasoline engines, but other types have been used, including the diesel, the rotary ( Wankel ) , the 2srtoke, and stratified charge. Reciprocating means up and down or banck and forth, It is the up and 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 passges called water jackets for coolant circulation. The top of the block is covered with the cylinder head. Which forms the bustion 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 piston is attached to the top of a connecting rod by a pin, called a piston pin or wrist pin. The bottom of the connecting rod is attached to the crankshaft. The connecting rod transmits the upanddown motion of the piston to the crankshaft, which changes it into rotary motion. The connecting rod is mounted on the crankshaft with large beaings called rod 北京化工大學(xué)北方學(xué)院汽車服務(wù)工程 —— 外文文獻(xiàn)原稿和譯文 bearings. Similar bearings, called main bearings, are used to mount the crankshaft in the block. Shown in Fig. 11 The diameter of the cylinder is called the engine bore. Displacement and pression ratio are two frequently used engine specifications. Displacement indicates engine size, and pression ratio pares the total cylinder volume to pression chamber volume. The term stroke is used to describe the movement of the iston within the cylinder, as well as the distance of piston travel. Depending on the type of engine the operating cycle may require either two or four strokes to plete. The 4stroke engine is also called Otto cycle engine, in honor of the German engineer, Dr. Nikolaus Otto, who first applied the principle in 1876. In the 4stroke engine, four strokes of the piston in the cylinder are required to plete one full operating cycle. Each stroke is named after the action it performs intake, pression, power, and exhaust in that order, shown in Fig12. Intake stroke As the piston moves down, the vaporized mixture of fuel and air enters the cylinder through open intake valve. To obtain the maximum filling of the cylinder the intake valve opens about 10176。before ., giving 20176。overlap. The inlet valve remains open until some 50176。after . to take advantage of ining mixture. Compression stroke The piston turns up, the intake valve closes, the mixture is pressed within the bustion chamber, while the pressure rise to about 1Mpa, depending on various factors including the pression ratio, throttle opening and engine speed. Near the top of the stroke the mixture is ignited by a spark which bridges the gap of the spark plug. Power stroke The expanding gases of bustion produces a rise in pressure of the gas to some , and the piston is forced down in the cylinder. The exhaust valve opens near the bottom of the stroke. Exhust stroke The piston moves back up with the exhaust valve open some 50176。before ., 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
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