Entropy Production Analysis for S-Characteristics of a Pump Turbine

Due to the S-shape characteristics and the complicated flow in pump turbine, there may be serious instability when the pump-storage power plant starts. In order to conduct further study on the energy dissipation in hydraulic turbine, three dimensional incompressible steady state simulations were applied using SST k-omega turbulence model in this paper. It can be seen that the simulation results are consistent with experimental results well by the comparison of characteristic curves, and further analyses were made based on the entropy production theory. It is shown that the entropy production of spiral casing accounts for the minimum proportion in all components. The entropy production of cascades and runner differs a lot at different guide vane openings, and it features "S" characteristics with the increase of discharge. Then, the analysis of entropy production distribution on runner, blade cascades and draft tube was carried out at the 10mm guide vane opening. It was found that the losses in guide vane space is much higher than that of stay vane space and the losses are mainly in the tail area of stay vanes and vaneless space. The losses mainly occurs in the leading edges and the trailing edges of blades. The largest losses mainly lie at the wall of straight cone near the inlet in draft tube. The losses at the inner surface of elbow are also very high. The results indicate that the method based on the entropy production theory is very helpful to analyze and locate the losses in hydraulic turbine.