The engine is used for pumping water out of the mine.
这台发动机是用来从矿井中抽水的。
《牛津词典》
2
Remember this engine is running backward, and we're pumping heat up.
记住这个热机是反向运行的，我们把热量向上传输。
3
It also minimises the pumping losses caused by no longer having to "throttle" (ie, strangle) the air flowing into the cylinders in order to control the engine speed.