Influence of guide vane skirt structure on sediment erosion of high-head turbine in high hardness and sandy river

Due to the high sand content and hardness in the Kezilesu River Basin, the high-head Francis turbines operating in this basin experience significant issues of guide vane erosion. By altering the skirt structure through varying guide vane height to skirt maximum diameter ratio Δ, the anti-abrasion design of turbine guide vane can be improved. The sand-water velocity, local sediment concentration distribution, and sediment erosion at the surface of a 250 m turbine in a power station within this basin were numerically analyzed under different Δ and operating conditions. The study investigated the influence of different Δ on the wear of the turbine guide vane. The numerical calculations of sand-water flow and sediment erosion in the turbine revealed that under rated working conditions, an optimal Δ = 1.511 was obtained. The sand and water flow remained stable, with low sediment concentration near the skirt. The maximum velocity of sand and water at the skirt wall was lower compared to other Δ conditions, i.e., approximately 45 m/s, and the weighted wear area was only 1057 mm2. Under low flow conditions, an optimal Δ = 1.511 was obtained, with the sediment concentration near the skirt gradually increasing with an increase in Δ. Additionally, the maximum velocity at the skirt wall was about 60 m/s under both conditions. The ratio Δ and the erosion resistance of guide vanes initially increased and then decreased. The research results offer a technical basis for the anti-abrasion design of the guide vane in high-head Francis turbines operating in high hardness, sandy waters.