Vertical Triple Expansion Engine
The Vertical Triple Expansion Engine was the zenith of steam-powered piston-based marine engine design in the late 1800s and early twentieth century.
As a form of compound steam engine, the V.T.E. design used a series of three cylinders and pistons of progressively larger volume to convert the steam's energy into motive force, with each piston operating on the lower-energy steam output by the preceding cylinder.
V.T.E. engines were generally displaced, first in small vessels and soon enough in larger ones, by the more efficient and reliable Turbine Steam Engine, in which the passage of high pressure steam over a vaned turbine provided the transition from thermal energy to rotational energy.