概念汽车实用英语毛矛概念汽车实用英语U8章节.pptVIP

PPT研究院 POWERPOINT ACADEMY * * CAR ENGINE (4) Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. Now the engine is ready for the next cycle, so it intakes another charge of air and gasoline. * CAR ENGINE Notice that the motion that comes out of an internal combustion engine is rotational. In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is nice because we plan to turn the cars wheels with it anyway. * CAR ENGINE The core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder, but most cars have more than one cylinder. In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: in-line, V or flat. * CAR ENGINE Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles. * CAR ENGINE 2. Engine Parts The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly. * CAR ENGINE The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed. A piston is a cylindrical piece of metal that moves up and down inside the cylinder. * CAR ENGINE Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes: 1) They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion. 2) They keep oil in the sump from leaking into the combustion area, where it wou