Numerical study of sediment erosion in guide vanes of a high head Francis turbine

Abstract

Abstract Erosion in guide vanes (GVs) has been reported from several power plants in Himalayan and Andes basins which affects the efficiency of turbine. Wear in clearance gaps (CGs) increases with the sediments passing through them resulting in increased gap size, which disturbs the flow into the runner inducing more losses. This paper investigates the flow and erosion pattern around GVs along with the leakage flow. Simulations are carried out in full GV and runner model with varying CGs with the inclusion of sediment. 3 types of clearance gaps viz., 0.5 mm, 1 mm and 1.5 mm are included and numerical results obtained are compared with the photograph of the erosion affected guide vanes. Result shows that erosion was prevalent in regions downstream of the mid-chord position inside the CG due to high pressure difference between two sides of GVs and the leakage flow induced from the pressure difference mixes with the main flow forming a vortex filament, which is driven towards the runner inlet.