Numerical analysis of unsteady flow behaviour and pressure pulsation in pump turbine with misaligned guide vanes

The unsteady flow within the entire flow passage of a pump-turbine with misaligned guide vanes (MGV) device under the rated speed was simulated using the Reynolds-averaged Navier-Stokes equations together with the k-ω based SST turbulence model. Three kinds of MGV arrangement of different opening angles were chosen to analyse the influence of MGV on the pressure pulsation in the flow passages of spiral case, stay vanes, guide vanes, rotating runner blades and draft tube. The characteristics of the dominant frequency of the unsteady flows in different flow parts under different misaligned guide vane arrangement/openings and the hydraulic performance of the pump-turbine were investigated at the turbine operating condition. The computation result shows that the MGV can decrease the peak-to-peak amplitude of the pressure fluctuation in the whole flow passage except the rotating runner blades. The low frequencies and the influence of Rotor Stator Interaction (RSI) in the entire flow passage vary with the arrangement/ openings of MGV.