Numerical prediction of sediment erosion in reference Francis turbine for complete operating range

Abstract

Erosive and abrasive wear affect the overall performance of hydro-turbines. Hard and excessive sediment particles are unavoidable in power plants of Himalayan basins. However, modifying the design of turbine components to have a minimum impact of the sediments could be one of the viable solutions. Past studies have shown possibilities of minimizing the erosion in turbine components by changing the blade angle distribution of the runner. The optimizations were based on the designed condition, i.e. at the Best Efficiency Point (BEP) of the turbine. The turbines are however, operated in various conditions, which might produce a different erosion scenario compared to BEP. Hence, the optimization process should also take these off-designed points under consideration. This paper presents a case study of Jhimruk hydropower plant of Nepal, whose turbine components get severely eroded due to sediments. Steady state numerical simulations for 4 guide vanes and 3 runner blade passages are done for the predictions of efficiency and percentile sediment erosion rate density (PSERD) on runner blades for 11 operating conditions including BEP. Apart from the conventional efficiency hill chart diagram, this paper focuses on the development of a hill diagram of PSERD, such that the prediction of the erosion in turbines can be done similar to the efficiency. Introduction of such PSERD hill diagrams could be a standard mean for the design optimization of turbines in sediment laden water.