Method of erosion prediction hill diagram to investigate the performance of Francis turbine operated in sediment laden water

Abstract

Sediment erosion problem in hydropower plants located under Himalayan regions of Nepal is inevitable. Reliance to the performance curves from model test data in terms of hydraulic efficiency cannot predict the actual performance in context of sediment laden hydropower projects in Nepal. This paper presents novel technique to predict the erosion affecting regions in various operating points in terms of sediment erosion hill diagram. A 2-D representation of erosion rate in several operational points is presented in this paper. This representation is compared with the efficiency characteristics of the same turbine that will be useful for considering the compromise between efficiency and erosion wear for erosion affected hydropower projects. A reference hydropower projects severely affected with sediment erosion is chosen for this study. Using suitable numerical modelling technique, performance of the turbine is calculated in terms of efficiency. Similarly, area averaged erosion rate in the walls of the numerical model was computed at various operating condition. It gives the idea that the turbine can be operated in variable speed operation that in one hand improves the efficiency and minimizes the erosion effects as well.