Study on the dominant mechanism of sediment characteristics in the erosion difference between the pumping and generating modes of a reversible pump turbine

The operational stability and service life of a pump turbine under sediment conditions are influenced by multiple factors and are critically linked to power grid stability. This study integrates SST k-ω , Oka and DPM models to simulate hydraulic and erosion characteristics of pump turbine in generating and pumping modes (T and P). Pearson correlation analysis was conducted to establish a comprehensive model linking sediment properties, hydraulic performance and erosion behavior under bidirectional operation. Results indicate hydraulic efficiency ( η ), head ( H ) and output power ( N ) decrease with increasing sediment concentration ( α ) and particle size ( d ): α significantly affects η and N , while d dominates H . Erosion zones differ by mode: trailing edge of runner blade suction surface and guide vane leading edge in P mode; leading edge of blade pressure surface and large-diameter volute wall in T mode (average erosion rate E r-ave = 53% higher than P mode). For runner blades, small d (0.01 mm) causes extensive cutting erosion (42% of blade area), while large d (0.25 mm) induces localized impact erosion, the maximum erosion rate ( E r-max ) is 1.43 times that for the 0.01 mm particle size. With similar d , α increases pressure surface erosion area ( E r-area ) by 17.9% (T) and 12.7% (P) at maximum. The E r-area on the pressure surface increases linearly with flow rate ( T = 0.00085/ Q BEP and P = 0.0015/ Q BEP , where Q BEP refers to the Best Efficiency Point), while the E r-area on the suction surface decreases nonlinearly ( T = 0.0014/ Q BEP 2 and P = 0.002/ Q BEP 2 ). These findings provide a theoretical basis for sediment erosion assessment and anti-erosion design of pump turbine. • The relationships among sediment, hydraulics, and erosion in a pump turbine are built. • The spatial evolution mechanism of sediment erosion in the pump turbine is revealed. • The influence of flow rate on the solid-phase erosion in the pump turbine is elucidated.