Research on sediment erosion and jet flow characteristics of Pelton turbine's injector

The Pelton turbine frequently operates in environments characterized by high head and heavy sedimentation, where the flow containing sediments can cause erosion on the surfaces of flow components, affecting the stability and safety of the unit. To investigate this phenomenon, present study applies the standard k-ε turbulence model and the Discrete Phase Model to conduct a three-phase unsteady numerical simulation of flow with sediment. The straight pipe erosion simulation results align with previous experimental findings, verifying the accuracy of the methods employed herein. The main conclusions are as follows: (1) Severe erosion predominantly occurs at the spray needle and nozzle outlet. The maximum velocity is achieved at the nozzle outlet. There is a “velocity deficit zone” at the needle tip, which can somewhat protect the tip from erosion. (2) Increasing opening (ΔS) reduces internal flow velocity, decreasing sediment transport capacity and erosion severity. The erosion rate at ΔS = 0.62 decreased by about 95% compared to ΔS = 0.07. (3) An increase in sediment concentration CV enhances the interaction between particles and the surface, leading to severe erosion at both the needle and nozzle. The erosion rate at CV = 5% is about 2.5 times that at CV = 1%. Additionally, sediments with smaller diameters and lower densities exhibit better flowability, resulting in more severe erosion on the injector. (4) Analysis results from machine learning (XGBoost) reveal that sediment concentration, diameter, and nozzle opening affect erosion more significantly than sediment density. The results can provide some guidance for the safety maintenance and erosion prediction of Pelton turbine.