Redesign of Adjustable Guide Vane Cascades of Pump Turbine and Its Effect on Self-Excited Vibrations at Slight Opening During Pump Mode’s Starting Up Process

Abnormal sounds and vibrations have occurred at several pumped storage power stations, when the guide vanes are at a slight opening during the pump mode’s starting up process. This paper proposes a modification method for active guide vanes to reduce the probability of abnormal vibration caused by self-excited vibration. A set of real machine guide vanes was selected to investigate the influence of different geometric parameters on self-excited vibration. Comprehensive analyses were conducted on the modified blades by the unsteady Reynolds-averaged Navier-Stokes solver and the 1DOF oscillator model (URANS-1DOF) coupling simulations. The results indicate that the probability of self-excited vibration divergence of the guide vanes is closely related to the degree of contraction and diffusion of the narrow gap flow channel. The self-excited vibration of the guide vane can be effectively suppressed by selecting appropriate overlapping length, contraction coefficient and diffusion coefficient. In addition, model tests have verified that the modification method has a slight impact on hydraulic performance.