Effect of outer edge modification on dynamic characteristics of pump turbine runner

It is currently in the period of high-speed construction of pumped storage projects. However, the problems caused by vibration of pump turbine units, especially the runners, are very serious. It is of great significance to study the dynamic characteristics of pump turbine runner for the safety and stability of power station. In this paper, the natural modes of a pump turbine runner in the air and in the flow channels are calculated by numerical method. The influence and mechanism of the outer edge modification on the natural frequencies of the runner are studied. The results show that, for the object studied in this paper, the frequency of most modes will be decreased by thickening the outer edge. The frequency change can be attributed to two aspects, one is the change of the mass and the stiffness of the runner, and the other is the change of added mass of the water. Furthermore, the main mechanism of outer edge modification affecting the added mass coefficient is that the height of the radial clearance is changed.