A locomotive going in advance of a train to make sure that the way is clear.

An aeolipile.

plural of Hero engine

(thermodynamics) A theoretical engine that converts information into energy for use in work, decreasing heat entropy in the process. / (data processing) A data processor.

A standalone machine that combines an electrical generator with an engine.

plural of rocket engine

plural of Otto engine

An engine using the Otto cycle.

A generator having its revolving part carried on the shaft of the driving engine.

plural of engine generator