Experimental Investigations of Sediment Erosion in Guide Vanes of Francis Turbine

Abstract Guide vanes are the cascade of hydrofoil like structures surrounding the Francis turbine runner which guides the water from spiral casing and controls the flow to the turbine. A large portion of hydraulic energy of incoming flow is converted to kinetic energy within guide vanes. Sediment erosion causes deterioration of turbine components. Guide vanes are generally eroded due to sediments at the outlet region, facing plates, and clearance gap region. This research encompasses the study of erosion in guide vanes of a 2 kW capacity Francis turbine. The guide vanes were coated with four different coats of colour. The test rig was operated in maintaining erosive environment with an average concentration of sediment particles of 1400 ppm. The total time of operation was 36 hours and the observations were made at interval of each 4 hours. Observable patterns of erosion were seen at different location of guide vanes showing the areas prone to the effect of sediment erosion. The erosion was mostly observed at the trailing edge of the suction side of the guide vanes near to the top and bottom face. The pressure side of the guide vanes experienced a uniformly distributed erosion throughout the width at the leading edge. The causes of erosion were identified as high velocity and acceleration of sediment particles, vortex due to leakage flow and horse shoe vortices. The eroded weight of the guide vanes was recorded for 45 hours of rig operation in erosive environment. Cumulative erosion rate of 0.039 mg gm −1 hr −1 was quantified with an average percentage weight loss of 0.058% was observed in guide vanes.