Numerical Analysis of Sand Erosion for a Pelton Turbine injector at High Concentration

Abstract

Hydro-abrasive erosion due to sediment flow often leads to the efficiency loss, seriously vibration, and sometimes even failure for Pelton turbines. This kind of erosion can be greatly intensified when the concentration of sand increases. It is of paramount importance to study the erosion mechanism for such machines, especially in Asia, where the sand concentration in many rivers is relatively higher due to some geologically young mountains like the Himalayas. In this study, the erosion patterns of the injector have been predicted at high sand concentration. The simulated scenario was based on continuous measurement of sediment flow during the flood season in an power plant. Firstly, the three-dimensional modeling for the whole flow domain of the injector with jet has been carried out by ANSYS Fluent. The free air-water flow from the injector has been simulated with the SST k-ω turbulence model, where the VOF (volume of fluid) model was implemented to capture the air-water interface. Then after tracking the particle movement in the air-water flow by the Lagrangian method, the Mansouri model was adopted to predict the erosion patterns. The erosion mechanism was explained by detailed analysis of particle impact properties like the average hits, the impact velocity, and the impact angle. The results show that the "velocity deficit region" will reduce erosion on the needle tip. In addition, abrupt geometry change can be designed at low-velocity regions to reduce erosion. This paper can provide a better understanding of the erosion mechanism, which can help to reduce wear in future designs.