偏负荷工况混流式水轮机转轮结构稳定性研究

为探究偏负荷运行工况下混流式水轮机转轮结构稳定性，本文基于单向流固耦合方法，对三种典型偏负荷工况下转轮结构进行了静力学分析和模态分析。结果表明：受不稳定水流影响，80%、60%和40%负荷工况下，较大变形分别位于转轮下环、叶片出水边中部以及叶片迎水刃处中部。预应力对转轮结构影响较少，其导致固有频率增加1 Hz左右；而水介质对转轮结构影响较大，导致固有频率降低15% ~ 36%，且得到转轮固有频率更符合工程实际。受导叶出口处水流扰动影响，转轮结构极有可能发生共振，其振型主要表现为径向、弯曲、弯扭及绕轴旋转变形，其中弯扭变形影响最大，极可能导致叶片断裂。该研究成果可为混流式水轮机柔性运行稳定性，提供一定理论参考。

Study on structural stability of Francis turbine impellers under partial load conditions

For flexible operation of hydro-generator sets,structural stability of Francis turbine impellers under partial load operation is extremely important.This paper presents a static analysis and a modal analysis of the impeller under three typical partial load conditions,based on the one-way fluid-structure coupling method.The results show that under load conditions of 80%,60%and 40%,large deformation is located at the impeller lower ring,the middle of the tail edge,and the middle of the head edge of the impeller blades respectively.Prestressing has small influence on the runner structure such as an increase of only about 1Hz in its natural frequency,while water mass has a great impact including a frequency reduction of 15%to 36%but the reduced natural frequencies agree better with the real values.Under the influence of flow disturbance at the outlet of guide blades,the impeller will resonate under these three partial loads,largely in the modes of radial,bending,bending and torsion,and axial rotation deformation.Of all the modes,bending and torsion deformation has the greatest influence likely causing blade fracture.The results are significant to theoretical stability analysis of the flexible operation of Francis turbines.