Selection of guide vane profile for erosion handling in Francis turbines

In guide vane cascade of Francis turbine, highest acceleration occurs, which generates equivalent amount of force for work done and erosion due to instantaneous change in flow dynamics. Hence in addition to runner vane, suitable selection of guide vane profile has equal importance. Usually, NACA defined hydrofoils are used for guide vanes. Numerous options are available, but selection of best one for optimum energy harness is important. Primarily, guide vane torque and turbine efficiency is prioritized. For the turbines operating in sediment laden water, pressure difference between two sides of guide vane and erosion resistivity are additional factors to be considered. This work was performed in the vicinity of guide vane profile selection for Francis turbines operating in sediment laden water. Computational analysis on turbine flow passage and experimental study with Rotating Disc Apparatus were performed in order to identify suitable profile. Unsymmetrical profiles were found to be better handling erosion maintaining consistency in turbine performance.