Vibration and noise of a high head pump turbine: analysis and improvement

Abstract In a high head pumped storage power plant with 9 blades and 20 guide vanes, vibration and noise problems occurred with characteristic frequency of 2 times the blade passing frequency (BPF). It is found that the first main frequency of pressure pulsation in the vaneless zone is also 2BPF with a two-nodal diameter mode by using three dimensional unsteady numerical method, which indicates that the main cause of vibration and noise is rotor stator interaction (RSI). By increasing the radial gap of the vaneless zone, the amplitude of pressure pulsation in the vaneless zone is reduced by 40%-50% according numerical results. One unit in the power station was refurbished. It was shown that the pressure pulsation in the vaneless zone was reduced by 40%, and the head cover vibration was also reduced, and the noise in the turbine pit was reduced by 6 dB according the field test results. So the numerical analysis and prediction here are very accurate, and the vibration and noise problems of this power station are caused by RSI.