Prime mover

Article By:

Baumeister, Theodore Formerly, Department of Mechanical Engineering, Columbia University, New York, New York; Editor in Chief, "Standard Handbook for Mechanical Engineers"

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.544700

The component of a power plant that transforms energy from the thermal or the pressure form to the mechanical form. Mechanical energy may be in the form of a rotating or a reciprocating shaft, or a jet for thrust or propulsion. The prime mover is frequently called an engine or turbine and is represented by such machines as waterwheels, hydraulic turbines, steam engines, steam turbines, windmills, gas turbines, internal combustion engines, and jet engines. These prime movers operate by either of two principles (Fig. 1): (1) balanced expansion, positive displacement, intermittent flow of a working fluid into and out of a piston and cylinder mechanism so that by pressure difference on the opposite sides of the piston, or its equivalent, there is relative motion of the machine parts; or (2) free continuous flow through a nozzle where fluid acceleration in a jet (and vane) mechanism gives relative motion to the machine parts by impulse, reaction, or both. See also: Impulse turbine; Internal combustion engine; Reaction turbine; Steam engine

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