Numerical Analysis of Cavitation Characteristics of Francis Turbine at Different Runner Blade Numbers

Abstract The main objective of this study is to evaluate the hydraulic performance and cavitation characteristics of Francis turbine at different operating conditions by varying the number of runner blades 13, 15, and 17 using commercially available CFX code. The runner blade numbers have a significant impact on both the turbine’s hydraulic efficiency and cavitation characteristic performance. The turbine efficiency and cavitation characteristic of turbine has been analysed under the best efficiency point (BEP) condition in order to achieve the optimum number of runner blades for Francis turbine. The turbulent nature of water flow through the turbine passages is accurately captured by SST turbulent model. The numerical results obtained from the CFD analysis were validated by comparing them with turbine manufacturer data available in the literature. Based on the simulation results, the hydraulic efficiency of turbine has been found to be maximum with 15 runner blades as compared to 13 and 17 runner blades. However, the predicted zone of water vapour volume fraction becomes less on trailing edge suction side of blades with an increase in number of runner blades. The results of the suggested research could prove highly valuable to hydro turbine manufacturers.