Numerical Investigation of Flow Behaviour and Erosion Potential in the Side-Wall Clearance Between Guide Vane and Runner

Abstract

In the hydropower plants exposed to excessive sediment concentration, the components of Francis turbines, especially the regions of Guide Vanes (GVs) and Runner Vanes (RVs) are severely eroded. The side-wall clearance between GV and runner is present in these turbines to separate the rotating and stationary components. The height difference between the runner inlet and GV outlet covers, introduced during the fabrication or assembly process might play a crucial role in accelerating the erosion process in these components. This study is focused on numerical analysis of simplified geometries that replicate different scenarios of the height difference and consequent flow behaviour in the side-wall clearance of Francis turbines. The numerical analysis is done in OpenFOAM using the available solver adopting the finite volume method (FVM). The numerical study is compared with the experimental results obtained from Rotating Disc Apparatus (RDA). The numerical analysis shows the vortex formation in the side-wall clearance region which traps the sediment particles. Such vortex formation causes erosion in the region. The vortex formation and flow behaviour in different height difference scenarios vary with each other and so does the erosion pattern in the experimental results.