Numerical study of pressure fluctuation in vaneless space of variable speed reversible pump-turbine in turbine mode at maximum head

Abstract Efficiency and grid stability of pumped storage plants with significant head variations can be enhanced by the implementation of variable speed operation. The reversible pump-turbine (RPT) operating in turbine mode is particularly prone to fatigue and vibrations when operating at maximum head conditions, primarily due to hydraulic instabilities caused by pressure fluctuations in vaneless space and thus, the performance of the RPT becomes increasingly critical under such operating conditions. It is, therefore, important to examine the pressure fluctuations in vaneless space of RPTs operating at higher heads. The findings indicate that the main source of pressure fluctuations across all operating conditions is rotor-stator interaction (RSI), where the dominant frequency is blade passing frequency (9 f n ) and its harmonics.