Numerical Investigation on Hydraulic Performance of Reversible Pump Turbines with Various Wrap Angles in Turbine Mode of Operation

Abstract

Abstract Reversible Pump Turbines (RPTs) are radial turbines, used in Pumped Storage Hydropower (PHS) plants. They have two modes of operation: generating and pumping. Despite of their uniqueness and importance, RPTs have typical range of operation at both modes and are prone to undesirable instabilities. The shape of the geometry plays a crucial role on reducing these characteristics and even the minor changes to the geometry can have a significant impact on its performance. In this paper, the effect of blade wrap angles on the hydraulic performance of runner was studied in an attempt to mitigate instabilities at turbine mode of operation. For that, two dimensionally similar RPT runners were designed using CFTurbo software by only varying wrap angle. The wrap angle considered for the runners are 150° and 180°. Steady state simulation was done in ANSYS-CFX for both the designs under same boundary conditions. It was found that the hydrodynamic performance of the runner gradually decreases in both cases when the operating condition deviates from normal operating range, causing flow instabilities within the runner. The study also found that varying blade wrap angles had no significant impact on the reduction of instabilities on RPTs, however it is an important parameter that comes into play while designing turbines at different head and flow conditions.