ROTOR-STATOR INTERACTION AND VORTEX ROPE IN THE REVERSIBLE PUMP-TURBINE AT OFF-DESIGN CONDITIONS IN TURBINE MODE

The reversible pump-turbine (RPT) operates at off-design operating conditions to balance the electricity grid due to the high penetration of variable and intermittent solar and wind energy. During these operating conditions, hydraulic instabilities such as rotor-stator interaction (RSI) and vortex rope in the draft tube give rise to pressure fluctuations in the vaneless space (VS) between the guide vanes and runner, and the draft tube, respectively. Therefore, the RPT may experience fatigue and vibration, further causing the vibration in the local components of the powerhouse. A reduced-scale high-head RPT model, and the SST k-.turbulence model was used to carry out numerical calculations under the present study. The guide vane opening of 10 degrees, 14 degrees, 18.06 degrees (best efficiency point), and 24 degrees were performed and analyzed. The RSI phenomenon occurs in the VS due to the interaction of guide vane and runner. The vortex rope in the draft tube, due to the flow separation in the runner channels, was observed.