Two major types of centrifugal hydraulic power recovery turbines are used.
1. Reaction—Single or multistage Francis-type rotor with fixed or variable guide vanes.
2. Impulse—Pelton Wheel, usually specified for relatively high differential pressures.
HPRTs with Francis-type rotors are similar to centrifugal pumps. In fact, a good centrifugal pump can be expected to operate with high efficiency as an HPRT when the direction of flow is reversed.
The Pelton Wheel or impulse runner type HPRT is used in high head applications. The impulse type turbine has a nozzle which directs the high pressure fluid against bowl-shaped buckets on the impulse wheel.
This type of turbines’ performance is dependent upon back pressure, while the reaction type is less dependent upon back pressure.
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