Investigation of solid–liquid two-phase flow dynamics and resulting wear patterns in a mixed flow pump as turbine under pumping condition

Mixed-flow pump as turbine (PAT), combining pumping and power generation capabilities, is applied in low-head tidal power stations and bidirectional river water transfer projects. However, solid particles inevitably ingested during pumping condition cause wear and deformation that threatens equipment life and safety. This paper employs the Eulerian–Lagrangian multiphase model and the Tabakoff wear model to numerically simulate the pump mode, with results agreeing with experimental data. With increasing flow rate, the flow direction mismatches the impeller inlet angle, deflecting particles toward the suction surface of impeller blades. This reduces wear area on the pressure surface of impeller blades but intensifies wear at the leading edges of both the impeller and guide vane suction surfaces, extending toward the trailing edge. As particle diameter increases, greater inertia deflects trajectories toward the impeller pressure surface, increasing wear area and rate across all surfaces of the impeller and guide vanes. With rising particle volume fraction, increased collision frequency shifts trajectories toward the impeller pressure surface and elevates wear rates. Compared to pure water operation, solid–liquid flow significantly reduces efficiency and head, with particle volume fraction exerting the strongest negative effect. This research offers valuable insights for refining PAT designs to improve the wear resistance.