This paper described a reverse running double suction centrifugal pump turbine, which was newly designed and developed in order to adopt at a high fixed rotational speed 2980 [min−1] with high head H=245.6 [m]. New turbine model was developed by using CFD and its performance was validated by model test. There were a few studies about a reverse running pump turbine. However, a method of “Q-H performance adjustment” for the pump turbine is not clear. In order to reveal a method of Q-H performance adjustment of a turbine, CFD simulation and model test was carried out.
The model test results showed that the performance of new turbine model fully satisfied Q-H requirement. And the results of steady CFD simulation were in good agreements with the model test results.
Two possible methods to adjust the Q-H performance curve of a reverse running double suction centrifugal pump turbine were confirmed by model tests and CFD. The first method was modifying a throat sectional area of inlet spiral casing by cutting off a casing tongue. The model test result showed that this method moves the Q-H performance curve of turbine from high head to lower head at a constant capacity with very small efficiency drop at rated operating point. The result of CFD showed that, the Q-H performance change was obtained by the change in absolute tangential velocity at the runner inlet, which represents the inlet angular momentum, by the modification of throat sectional area.
The second method was adjusting the runner outlet velocity triangle by modifying the runner blade trailing edge profile by under-filing or over-filing. The model test result proved that, the above modification of runner blade trailing edge profile is effective to control the Q-H performance curve of a reverse running pump turbine.