The turbine is a machine for generating mechanical power from the energy of the stream of fluid. Steam, hot air or gaseous products of combustion, and water are the most widely used working fluids.
A steam turbine may be defined as a form of heat engine in which the energy of the steam is transformed into kinectic energy. It consists of the following fundamental parts: a) a casing or shell containing stationary blades: c) a set of bearings; d) a governor and valve system for regulating the speed and power of the turbine. The main types of steam turbines are axialflow turbines and radial-stage turbines.
The reciprocating steam engine came into its own during the nineteenth century, when it found greatest use in mills, locomotives and pumping systems. The modern steam turbine, developed last century, is rapidly replacing the reciprocating engine for large installations. Gas is used as the working fluid in gas turbines. The basic theory underlying their design and their operating characteristics is identical with that for steam turbines. The energy of water is converted into mechanical energy of a rotating shaft in hydraulic turbines. Power may be developed from water by three fundamental processes: by action of its weight, of its pressure or of its velocity; or by a combination of any or all three.