Suppression of hump characteristic for a pump-turbine using leading-edge protuberance

The application of wave guide vanes with bio-inspired leading-edge protuberances to the hump characteristic of a pump-turbine is examined in this study. Numerical simulation with a shear-stress transport turbulence model is used to calculate the three-dimensional flow in a pump-turbine in pumping mode. Three tubercle amplitudes of 0.02c, 0.04c, and 0.08c (c is chord length), and three spanwise wavenumbers (2/s, 4/s and 8/s, s is the length of span) for guide vanes are especially considered. The results obtained show that the simulated performances of original guide vanes are found to be in good qualitative agreement with experimental data, supporting the validation of the computational fluid dynamics method. For different wave guide vanes with leading-edge protuberances, it is shown that the hump characteristic of the pump-turbine in pumping mode is effectively improved. This is due to improved flow fields below the tongue in view of entropy production and vector field. The energy loss can be clearly compared through the entropy distribution for different locations of the guide vanes, and it is improved for the wave guide vanes with bio-inspired leading-edge protuberances. For current pump-turbine, the optimal amplitude and wavenumber are found to be around 0.04c and 4/s.