关键词: 水泵水轮机, 过渡过程, 固液两相流, 泥沙磨损, 数值模拟

Abstract: A pumped storage station constructed at a water dam on a sediment-rich river is susceptible to damage caused by the abrasion of sediment particles passing over the surfaces of its primary flow components. This study adopts the Euler-Lagrange approach to numerically simulate the sediment-laden flow behaviors and predict the wear in a pump turbine under the operating conditions of transient flows, using the standard k-ε turbulence model, the particle motion equation, and the McLaury wear model. The findings reveal that in the hump operating range, the internal flow field in the pump turbine undergoes substantial alterations, marked by the occurrence of prominent vortex structures in the non-blade zones and within blade passages. A reduction in the sediment-laden flow leads to a significant increase in the spatial extent of the zones with high turbulent energy fluctuation (TEF > 1800 s–1), from an volume ratio of 5% or lower to 30% or higher; The direct and indirect entropy production rates increase by 22.4% and 34.6% respectively. Unstable blade passage vortices and other flow instability leads to disorder in particle motion trajectories, and complicated particle-vortex coupling raises the uncertainty of particle migrating paths. The Reynolds number of the particles increases by 3-5 times in the runner and the guide vane section. Under three operating conditions, average differences in particle and water flow velocities under low-flow conditions are nearly 0.7 m/s, 6.4 m/s, and 3.3 m/s respectively. Under low-flow conditions, particle momentum enrichment zones are mostly distributed in Channels No. 2 to No. 4 and near the runner channel outlet, and the area of high-momentum regions inside the runner exceeds 30%. The maximum wear rates on the suction and pressure sides of the runner blades are 8.3×10-8 and 5.6×10-8 kg/(m2·s) respectively; Differences in the average wear rates of different blades reaches 1 to 3 times. Spatial variations are relatively small in the wear of the moving vanes’ surfaces. And the blade passage vortices have a significant impact on the enrichment of particles, while relative weak impact on the particles in the non-blade section of the flow passage.

Key words: pump turbine, transition process, solid-liquid two-phase flow, sediment erosion, numerical simulation