Modal Calculation and Vibration Characteristics Analysis of Francis Turbine Runner

In order to further investigate the causes of cracks and even breaks in the turbine runner during the operation, a Francis turbine used in a domestic power station was adopted as the research object.Based on the one-way fluid-structure interaction theory, ANSYS CFX and workbench platform were employed to simulate the full flow passage and modal analysis in this paper.The natural frequency and mode shapes of the first six-order of the free mode and prestressed mode of the turbine runner were obtained.And the frequency is compared with the excitation frequency to comprehensively analyze its deformation and vibration characteristics.The results show that the maximum deformation of the turbine runner is mainly located in the upper crown of the runner, the lower ring and the middle of the blade outlet.The runner mode shape is mainly presented as four categories, namely, swing, pivoting, bend and the up and down vibrating in the axial direction. When the turbine is operated at the speed 272.7 r/min, the excitation frequency is close to the low-order natural frequency and the unit is prone to resonance.