Unit 6 Engine

1、Unit 6 Engine Operation ContentsnI. New words & phrases nII. Text analysis nIII. Exercises I. New words & phrases nengine endin 发动机npiston pistn 活塞ncylinder silind 气缸ncrankshaft krkft 曲轴nflywheel flawil 飞轮nstroke struk 冲程nsuction skn 吸入，吸收ncompression kmpren 压缩nexhaust iz:st 排气，废气nvalve vlv

2、阀门nignition gn()n 点火，点燃nlubrication ,lubrken 润滑nconnecting rod 连杆nfour-stroke-cycle engine 四冲程循环发动机nintake valve 进气口nexhaust valve 排气口 II. Text analysis nInternal combustion engines are those that burn their fuel inside the engine. 内燃机：燃料在发动机气缸内燃烧，所产生的燃气直接推动活塞运动 External combustion engine 外燃机 e.g :

3、steam engine (uses a fire in a boiler rather than inside the engine) 在锅炉燃烧而不是发动机Engine classification 发动机分类nNumber of cylinders 汽缸数 single cylinder engine 单汽缸发动机 multicylinder engine 多汽缸发动机 ：双缸，三缸，四缸。nArrangement of cylinders 气缸排列顺序 in-line engine 直列式发动机 V-type engine V 型发动机 Flat engine 水平对置式发动机nArr

4、angement of valves 进气方式 1）naturally aspirated engine (NA engine) 自然吸气式发动机：空气靠活塞的抽吸作用进入气缸内。汽油机常采用自然吸气式。 2）supercharged engine 增压式发动机：为增大功率，在发动机上装有增压器（supercharger)，使进入气缸的气体预先经过压气机压缩后再进入气缸。柴油机为了提高功率常采用增压式。nType of cooling 冷却方式 1) liquid/coolant cooling engine ：以冷却液（coolant)作为冷却介质 2)air cooling engine

5、:以空气作为冷却介质 nNumber of cycles 实现循环的行程数 two-stroke engine 二冲程发动机：活塞移动四个行程或曲轴转两圈气缸内完成一个工作循环 four-stroke engine 四冲程发动机：活塞移动两个行程或曲轴转一圈气缸内完成一个工作循环n Type of fuel burned 所用燃料 gasoline engine 汽油机 diesel engine 柴油机nType of ignition 点火方式 spark-ignition engine 点燃式发动机:利用火花塞发出的电火花强制点燃燃料，使燃料强行着火燃烧。如汽油机。 compressio

6、n-ignition engine 压燃式发动机：利用气缸内空气被压缩后产生的高温，使燃油自燃。如柴油机。The main parts of engines发动机的主要组成部分n1）the engine block 发动机体n2) the cylinder n3) cylinder head 汽缸盖n4) the piston n5) the connecting rod n6) crankshaft n7) camshaft 凸轮轴n8) the fuel pump 燃油泵Five systems of the engines 发动机的五大系统nThe engines required ma

7、ny systems for their performance. These are： A. fuel system 燃油供给系 B. ignition system 点火系 C. lubricating (lubrication) system 润滑系 D. cooling system 冷却系 E. starting system 启动系Four-stroke-cycle-engine nThe piston in cylinder makes four movements (two up and two down ) or two revolutions of the cranksha

8、ft for each combustion . ( 每一次燃烧活塞在气缸内往返4个行程，即曲轴转2转）n Stroke refers to piston movement. A stroke occurs when the piston moves from one extreme position to the other inside the cylinder. 活塞在气缸里从一头运行到另一头完成 一个冲程。nFour strokes: suction stroke (intake stroke): 进气冲程 fresh mixture is sucked into the cylind

9、er through the open inlet valve 进气门打开，排气门关闭，活塞位于最高点，向下移动，然后混合气体进入气缸。 n compression stroke 压缩冲程 the air-fuel mixture is squeezed into smaller and smaller volume 活塞向上运动，压缩可燃混合气，混合气体温度升高，为点火做准备nPower stroke 做功冲程 the mixture under pressure is ignited. The air-fuel mixture is burning and the expanding ga

10、ses push the piston down creating a power stroke. 高压可燃混合气被点燃，气体膨胀推动活塞向下移动，完成做功冲程。nExhaust stroke 排气冲程 the piston moves upward. Forcing the burned gases from the combustion chamber （燃烧室） through the exhaust valve. 活塞向上运动，排气阀打开，废气被排出燃烧室。Necessary components of the four-stroke engine (四冲程发动机的必须部件）nFlyw

11、heel: since only the third stroke produces work, the piston needs help over the other strokes. This is given by a flywheel attached to the crankshaft , which stores up energy from power stroke; this energy then carries the piston through the three strokes until the next stroke caused by the combusti

12、on is repeated. 因为只有第三冲程做功，活塞在其他冲程需要帮助。由安装在曲轴端部的飞轮提供这种帮助。飞轮在做功冲程吸收能量，这些能量可以带动活塞通过三个冲程直到下一次燃烧nCamshaft (凸轮轴）： controls the cams that open or close valves to let gases in and out of the cylinder 控制着打开或关闭阀门使气体进入或排出气缸的凸轮补充nTDC：top-dead-center 上止点 the highest position that the piston reaches inside the c

13、ylinder nBDC： bottom-dead-center 下止点 the lowest position that the piston reaches inside the cylinder Homeworkn1. According to the type of cooling, engines can be divided into _ engines and air cooling engines. A. liquid cooling B. fan cooing C. oil cooling D. fuel cooling 2. The first stroke of the engine is_. A. intake stroke B. compr