Study of the phase resonance phenomenon in Francis turbine

Abstract

In hydraulic machinery, the phenomenon of rotor-stator interaction will produce periodic pressure waves in the stationary cascade. These pressure waves have the same phase, and will spread and superimpose in the volute. When the pressure waves propagate and superpose, the pressure pulsation with large amplitude will be formed. This phenomenon is called phase resonance, which will threaten the safe and stable operation of the machinery. Therefore, it is necessary to study the rotor-stator interference phenomenon and analyze the risk of phase resonance. In this paper, a high head Francis turbine with phase resonance in engineering is analyzed, which is also verified by the existing theoretical analysis. The phase resonance in the turbine is analyzed by using one-dimensional hydro acoustic model and three-dimensional compressible flow CFD simulation method, and the results are consistent with the actual engineering phenomenon. In order to study the measures to improve the phase resonance phenomenon, this paper carries out the simulation calculation from changing the rotation speed, wave speed and guide vane-runner blade number combination. The results show that adjusting the above parameters can reduce the amplitude of large pressure pulsation caused by the phase resonance in different degrees, and changing the number combination of guide vanes and runner blades is the most effective and feasible measure.