Leakage Vortex Progression through a Guide Vane’s Clearance Gap and the Resulting Pressure Fluctuation in a Francis Turbine

A clearance gap (CG) between guide vanes (GVs) and facing plates exists at both ends of a Francis turbine allows the opening angle to be adjusted for varying operating conditions. Leakage flow is induced through this due pressure difference two sides vanes. While some research works have used qualitative approaches visualize predict strength leakage vortex (LV), paper presents method quantifying vortices along trajectory. In paper, prototype high-head runner with specific speed 85.4 considered as reference case. systematic investigation across space time carried out, i.e., analysis spatial temporal progression LV three travelling from CG leading edge, evolution trajectory data are observed values vorticity turbulent kinetic energy calculated Frequency spectrum analyses oscillations in vaneless space, blade, draft tube also performed observe peak pulsation its harmonics. Unsteady fluctuations output torque finally studied identify patterns magnitudes oscillations.