Numerical study on the energy evaluation characteristics in a pump turbine based on the thermodynamic entropy theory

Abstract

Pumped storage power stations have attracted more and more attention in recent years. As the core component, the performance of pump-turbine has a strong connection with the station's economic effectiveness. The energy evaluation characteristics in a pump turbine are deeply investigated based on the entropy generation theory which has a great advantage to the traditional pressure drop method. The multiphase flow in the pump-turbine under several classical operating conditions are simulated using a modified turbulence model. Cavitation's contribution in energy loss is also considered in the entropy generation theory. Compared with the traditional differential pressure method, the accuracy of entropy generation method is verified. Then, the internal energy loss distribution along the pump-turbine passage at different flow rates are obtained. According to the result, the hydraulic loss mainly occurs in the runner, followed by guide vanes and stay vanes. In the runner, most of the energy loss is distributed in the channel near the lower ring, and the pressure surface is lower than that of the suction surface. The results also show that the stable attached cavity can wrap the blade and reduce friction resistance, and then reduce the wall entropy production value.