英汉练习（3）发动机

Now let us compare the diesel engine with the gasoline engine. Firstly, the explosive mixture of the gasoline engine is provided by a carburettor, but in the case of the diesel engine the supply is effected by an injection or "jerk" pump which forces a "shot" of fuel into each cylinder in turn according to the correct firing sequence.

Secondly, the fundamental difference between gasoline and diesel engines is that in the gasoline engine the source of the heat for igniting the charge, namely, an electric spark, is generated outside the engine, and is taken, as it were, into the waiting charge at the required instant. In the diesel engine the source of heat for igniting the charge is created within the engine by compressing pure air to a degree that will initiate combustion and then injecting the fuel at the right time in relation to the movement of the crankshaft.

现在我们来比较一下柴油发动机和汽油机。首先，汽油发动机的爆炸性混合物是由化油器提供的，而柴油发动机的爆炸性混合物则是由喷油泵(脉动泵)提供的，由喷油泵根据正确的点火顺序依次将燃油“射”入各气缸。

其次，汽油发动机和柴油发动机的根本区别在于：在汽油发动机中，用于点燃混合气的热源（即电火花），是在发动机外产生的，而且可以说是在需要的那一瞬间才被摄入待燃的混合气中。而在柴油发动机中，用于点燃混合气的热源是在发动机内产生的，是通过将纯净空气压缩至混合气可以燃烧的程度，然后随着曲轴的运动适时喷入燃油。