发动机的气密性是保证其正常工作的重要条件之一。气密性越好的发动机,气缸压力就愈高,发动机工作行程产生的瞬时有效压力就愈大,混合气燃烧迅速,冷却水及废气热损失少,其动力性和经济性就好。 Engine air tightness is one of the important conditions to ensure its normal work. The more airtight engine, the higher the cylinder pressure, the greater the instantaneous effective pressure generated by the working stroke of the engine, the rapid combustion of the mixture, the less heat loss of the cooling water and the exhaust gas, and the better dynamic performance and economy.