Study on the motion characteristics of sediment particles in the hump region of a pump–turbine in a pump model

Pumped storage power stations on sediment-laden rivers are highly susceptible to erosion damage on the surfaces of major flow-passing components due to sediment particles. In this study, an Euler–Lagrange model is employed to numerically investigate the sand–water flow characteristics and erosion prediction of a pump–turbine under hump-region conditions, focusing on crest, trough, and high-flow operating points. The results show that the internal flow of the pump–turbine undergoes significant changes in the hump region. Under low-flow conditions, flow separation, backflow, and local vortex phenomena occur inside the runner. Vortices in the runner passages tend to entrain sediment particles, resulting in a reduction in particle velocity. With increasing sand–water flow rate, a pronounced velocity difference develops on both sides of the blades, with the maximum difference reaching 20 m/s. The average erosion rates on the runner blades and the end faces of the guide vanes are 4.2 × 10−8 and 3.5 × 10−8 kg/(s·m2), respectively. The cutting erosion patterns on the blade surfaces coincide with the trajectories of the water flow vortices, and the erosion rate distribution on the guide vane end faces shows a high degree of consistency with the distribution of sand–water vortices.