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1、Unit4 Piston and PowerPart1 TextFig 4.1Engine Sectional ViewPart1 Text Engine is the heart of the automobile. There are some main parts in the engine. Take off the oil filler cap then refill engine oil when necessary. The inlet valve opens to let fuel-air-mixture into the cylinder . The exhaust valv
2、e opens to let the exhaust gases out of the cylinder. The crankshaft converts the up-and-down movement of the piston into a rotary movement. The camshaft opens and closes the valves. It is driven by the crankshaft. The piston compresses the fuel-air-mixture. The connecting rods are the moving links
3、between the crankshafts and the pistons. The flywheel picks up the power and helps the crankshaft to rotate between power strokes. The combustion chamber is the place where the fuelair-mixture is ignited and where the power is produced. The oil pan contains the oil needed to lubricate the engine. Oi
4、l has to be changed every 10,000 km. The V-belt drives the alternator of the car. It has to be checked at every service.flywheel (飞轮)cylinder (汽缸)Crankshaft(曲轴)Fill in the blanks. The piston_compresses_the fuel-air-mixture. The crankshaft _converts_ the up-and-down movement. The camshaft opens and c
5、loses_ the valves. The V-bel _drives_ the alternator. The flywheel _picks up_ the power. The oil pan _contains_ the oil.True or false（1）The connecting rods are the fixed links between the crankshaft and the pistons.(T)（2） Fuel-air-mixture is produced in the cylinder. (F)（3）Camshaft is driven by the
6、crankshaft. (T)（4） The function of piston is to compresses the fuel-air-mixture. (T)Connect the following phrasescombustion chamber 燃烧室up-and-down movement 做功冲程rotary movement 旋转运动power stroke 往复运动Part 2 Dialogue: What Kind of Engine Is This?Jack ：May I help you?Customer ： Will you do the service fo
7、r my car?Jack ：I am sorry, sir, but I can ask the senior mechanic（高级工） to do it.Customer ： Do you know what kind of engine this is?Jack ： Yes, its a four-cylinder engine. Look, it has four spark plugs, one for each cylinder.The spark plug cables are connected to the distributor（分电器）.Customer ：Oh! An
8、d whats that thing in front of engine?Jack ：Thats the radiator（散热器）. Do you see this big cooling fan?Customer ：Yes.Jack ：It forces air through the radiator when the car moves slowly.Customer ：Hmm, I see. Thank you!Jack ： You are welcome!1Read the dialogue again and complete the following sentences.（
9、1）The_has four spark plugs.（2）The _ air through the radiator.（3）The _ cables are connected to the distributor.2Write down the main idea of the dialogue.Part 3 Practice MaterialA:Intake Stroke Part 3 Practice MaterialB:Four-Stroke Spark-Ignition Engine The cycle of operation for a four-stroke spark-i
10、gnition engine includes intake stroke，compression stroke，power stroke and exhaust stroke. Here we introduce intake stroke ： This stroke introduces a mixture of atomized（雾状的） gasoline and air into the cylinder. The stroke starts when the piston moves downward from a position near the top of the cylin
11、der. As the piston moves downward，a vacuum，or low-pressure area，is created.During the intake stroke，one of the ports is opened by moving the inlet valve. The exhaust valve remains tightly closed. Look at the following drawings of the four strokes of an engine and put them in correct order.Fig 4.4The Operation of a Four-Stroke Cycle Engine
