Unit汽车专业英语(发动机)资料.ppt

Compression stroke. After the piston reaches BDC, or the lower limit of its travel. It begins to move upwards. As this happens, the intake valve closes. The exhaust valve is also closed, so that the cylinder is sealed. As the piston moves upward (pushed now by the revolving crankshaft and connecting rod), the air-fuel mixture is compressed to as little as one-tenth of its original volume, or even less. When the air-fuel mixture is compressed, not only does the pressure in the cylinder to up, but the temperature of the mixture also increases. revolving [r?‘v?lv??] adj. 旋转的 volume???[‘v?lju?m] n. 量 After the piston reaches BDC, or the lower limit of its travel. It begins to move upwards. As this happens, the intake valve closes. The exhaust valve is also closed, so that the cylinder is sealed. 在活塞到达下止点时或者是活塞下限时，活塞开始向上运动。同时，进气门关闭，排气门也关闭，所以这时的汽缸是封闭的。 As the piston moves upward (pushed now by the revolving crankshaft and connecting rod), the air-fuel mixture is compressed to as little as one-tenth of its original volume, or even less. 当活塞向上运动时(这时是由转动的曲轴和连杆推动活塞)，可燃混合气被压缩。当活塞到达上止点时，可燃混合气被压缩到有原体积的十分之下甚至更少。 When the air-fuel mixture is compressed, not only does the pressure in the cylinder to up, but the temperature of the mixture also increases. 当油气混合燃料被压缩时，不仅汽缸里的压力上升，可燃混合气的温度也随之增加了。 Power stroke. As the piston reaches TDC on the compression stroke, and electric spark is produced at the spark plug. The ignition system delivers a high-voltage surge of electricity to the spark plug to produce the spark. The spark ignites the air-fuel mixture. It now begins to burn very rapidly, and the cylinder pressure increased to as much as 3-5MPa or even more. This terrific push against the piston forces it downward, and a power impulse is transmitted through the connecting rod to the crankpin on the crankshaft. The crankshaft is rotated as the piston is pushed down by the pressure above it. As the piston reaches TDC on the compression stroke, and electric spark is produced