Numerical Investigation of Sediment Erosion in Guide Vanes of Francis Turbine with Experimental Validations

Abstract

Abstract Serving as crucial elements within the distributor of Francis turbines, guide vanes aid in converting pressure energy into velocity energy. Additionally, they are responsible for directing water into the runner at the appropriate angle and quantity. The existence of a clearance gap in the guide vanes leads to the development of a leakage flow due to the pressure variation between the two sides. This leakage flow develops into a vortex, which interacts with sediment-laden flow and causes erosion of the guide vane as well as the runner. This study conducts a comprehensive analysis of erosion patterns in the guide vanes of a 2-kW model Francis turbine. Employing a dual approach that combines both experimental and computational methods, the investigation focuses on the impact of clearance gaps on erosion. The numerical study focuses on two cases, one incorporating a 2 mm clearance gap on the hub side of the guide vane and the other without the clearance gap. Both studies report erosion initiating from the mid-section and extending to the trailing edge at the suction side of the guide vane. Noteworthy is the leakage flow from the pressure side to the suction side of the blade, which, when converging with the main flow, disturbs the primary flow pattern and forms vortices, leading to erosion. This research also shows that the results from both the experimental and numerical analyses are in agreement.