Atmospheric pressure then pushes the piston back down the cylinder, and if anything (such as a pump) is attached to the piston, some useful work can be done.

于是，气压就会再次将活塞推至汽缸底部。而假如有诸如水泵这样的物体与活塞连接，就可以在活塞的带动下完成一些工作。

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This pressure then forces the piston back down producing mechanical work.

这种压力迫使活塞则回落生产机械工作。

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In a HFPE, the free piston assembly is driven back and forth between two outer dead centers by fuel energy, and at the same time hydraulic oil is pumped out for energy.

在左、右动力腔的交替驱动下，HFPE的活塞组件在腔体中作往复直线运动，同时泵出液压油驱动负载工作。

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This drives the piston back and forth so that it acts as an alternator, generating electricity.

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The piston then moves back up to sustain the reaction in the upper reactor, and so on.

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