混流式水轮机转轮模态计算及振动特性分析

为深入探究水轮机转轮在运行过程中出现裂纹甚至断裂的原因，以国内某电站所使用的混流式水轮机为研究对象，基于单向流固耦合理论，采用ANSYS CFX和workbench平台对水轮机全流道进行数值计算，得到水轮机转轮自由模态和预应力模态前6阶的固有频率和振型，并将转轮的固有频率与各水力激振力频率进行比较，分析其变形及振动特性。研究结果表明:水轮机转轮最大变形主要位于转轮上冠、下环以及叶片出水边中部；转轮的振型主要表现为摆动、绕轴旋转、弯曲及沿轴向方向上下振动；水轮机在转速n=272.7 r/min下运行时，激振频率与低阶固有频率相近，机组易发生共振。

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.