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reaction turbine[rē′ak·shən ‚tər·bən]
a turbine in which a substantial part of the potential energy in the working fluid (the fluid head or the thermal gradient of a gas or steam) is converted into mechanical work in the blade passages of a runner that have the configuration of a jet nozzle.
In modern turbines the peripheral force that turns the runner is created by the total effect of two forces: the force that develops when the direction of flow of the working fluid is changed in the blade passages (the impulse principle) and the reactive force that develops when the velocity of the working fluid is increased (the reaction principle). The ratio of the amount of energy that is converted in the rotating blades of a turbine to the total amount of energy used is called the degree of reaction p. When ρ = 1, a turbine is said to be completely reactive, and when ρ = 0, the turbine is called an impulse turbine. In practice, all turbines operate with some degree of reaction, but only those in which not less than 50 percent of the total potential energy in the working fluid is converted by the reaction principle, that is, in which ρ ≥ ½, are conventionally called reaction turbines.
A power-generation prime mover utilizing the steady-flow principle of fluid acceleration, where nozzles are mounted on the moving element. The rotor is turned by the reaction of the issuing fluid jet and is utilized in varying degrees in steam, gas, and hydraulic turbines. All turbines contain nozzles; the distinction between the impulse and reaction principles rests in the fact that impulse turbines use only stationary nozzles, while reaction turbines must incorporate moving nozzles. See Impulse turbine, Prime mover