A steam turbine is a heat engine in which the potential energy of a steam is changed into useful work into two distinct steps:

  1. The available energy is converted into energy of motion, kinetic energy, by steam expansion in a nozzle or suitable passage, from which the steam emerges at a high velocity.
  2. This kinetic energy is converted into mechanical energy or useful work by directing the steam jet against blades mounted on a revolving rotor, or by the reaction of the jet itself in the expanding passage if the passage revolves.

A steam turbine consists of a motor wheel with blades secured to the shaft. A high velocity jet of superheated steam is directly to the nozzles in impulse turbine or by stationary blades in reaction turbine, against the blade row to produce rotational motion of the shaft which is connected to reduce reduction gear leading to propeller. It is mounted by apparatus and steam seals in order to prevent leakage of high-pressure steam to the atmosphere and air into the low pressure side.

Related Terms


A steam turbine, consisting of a high-pressure turbine, a crossover pipe, and a low-pressure turbine.


A steam turbine in which the steam is directed tangentially and radially inward by nozzles against buckets milled in the wheel rim; the steam flows in a helical path, reentering the buckets one or more times. Also known as tangential helical-flow turbine.


The steam rate is the pounds of steam that must be supplied per kilowatt-hour of generator output at the steam turbine inlet.


An oil used to lubricate bearings in a steam or gas turbine.


A type of flexible coupling used to join a steam turbine to a reduction-gear pinion shaft; consists of a short piece of shaft with gear teeth at each end, and mates with internal gears in a flange at the ends of the two shafts to be joined.

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