Numerical analysis of hydro-abrasive erosion in a five-jet Pelton turbine distributor

Abstract

In high-head hydropower plants, the Pelton injector is prone to erosion even for low sediment concentration and smaller size particles due to high flow velocities. Here, the effect of complex flow in a five-jet Pelton distributor is considered for analysing the erosion in the injector and distributor numerically. The discrete phase model based on an Eulerian-Lagrangian approach is used for tracking sediment particles. In this study, a good agreement of the obtained results with the experiments and field observations in a high-head hydropower plant validated the numerical methods selected. For larger-sized particles, a significant difference in the erosion among nozzles of the distributor was found. However, the difference in the erosion was reduced for smaller-sized particles. Further, erosion observed in the fifth nozzle was four times higher than the second nozzle considering 200 μm size particles during part-load conditions. Variation of sediment impact velocity due to change in sediment size has a similar trend for both the nozzle and needle surfaces. In contrast, variation in sediment concentration in the nozzle and needle resulted in an inverse relation with sediment size. The asymmetrical erosion pattern obtained for the nozzle is consistent with the erosion pattern from the prototype plant. Asymmetricity was also observed in the distribution of sediments in the jet, substantially for the fifth injector. The head loss at the third bifurcation is two times more at the full-load condition compared to the part-load condition.