impulse turbine

impulse turbine

[′im‚pəls ¦tər‚bən]

(mechanical engineering)

A prime mover in which fluid under pressure enters a stationary nozzle where its pressure (potential) energy is converted to velocity (kinetic) energy and absorbed by the rotor.

Impulse turbine

A turbine in which fluid is deflected without a pressure drop in the blade passages. A turbine is a power-producing machine fitted with shaft-mounted wheels. Turbine blades, attached to the wheels' periphery, are driven by the through-flow of water, steam, or gas. The rotary motion of the wheel is maintained by forces imparted to the blades by the impingement against them of high-speed fluid streams. Before the stream of fluid reaches the moving turbine blades, it is accelerated in stationary passages called nozzles. The nozzles are shaped to convert mechanical or thermal energy of the fluid into kinetic energy; that is, the nozzles increase the fluid's velocity while decreasing its pressure and temperature. Upon leaving the nozzles the high-speed fluid strikes the moving blades, and a force is imparted to the blades as the fluid is deflected by them. If the fluid's deflection in the blade passage is accompanied by a pressure drop and a relative velocity rise, the turbine is called a reaction turbine; if the fluid is deflected without a pressure drop in the blade passages, it is called an impulse turbine. See Nozzle, Reaction turbine

impulse turbine

Variation of pressure and velocity through an impulse turbine.

A type of turbine in which the stator vane and rotor blades are arranged in such a way that the pressure drop occurs in the converging nozzle guide vane passages along with a corresponding increase in velocity while the blades form straight ducts. The turbine rotor is then turned by the impulse as gases impinge on the blades—hence, the nomenclature.