Numerical analysis of solid-liquid turbulent flow in Francis turbine spiral case

Abstract

Based on the hydrological conditions of a hydropower station, the three-dimensional turbulent flow in a Francis turbine with splitter blades was numerically simulated in sandy water. The solid-liquid two-phase turbulent flow in the spiral case at different loads was numerically analyzed in emphasis, including the distribution of pressure, sand volume and velocity on different sections of the spiral case. The movement pattern of sandy water in the turbine spiral case was studied. The results show that the pressure distribution in the spiral case varies uniformly at different loads, a high pressure zone will be generated at the bottom of the spiral case and a low pressure zone at the outlet; the spiral case bottom and the nose has the largest area of sand and the highest sand volume fraction; with the increasing of the load, the high pressure zone moves from the bottom to the exterior margin, the sand volume fraction decreases, and the sediment-carrying capacity increases. At off-design conditions, the joint effect of sand abrasion and cavitation will worsen the erosion of the spiral case.