大型混流式水轮机转轮叶片结构动力特性分析

DYNAMIC CHARACTERISTIC ANALYSIS FOR THE BLADES OF FRANCIS TURBINE

转轮是水轮机结构中重要部件之一。比较不同单元类型对转轮叶片振动计算精度的影响 ,从推导的转轮叶片液固耦合运动方程出发 ,分别计算混流式水轮机转轮叶片在空气中和在工作流道中振动的主频与主振型。结果表明 ,叶片在水中的频率较空气中的频率有所降低 。

The Francis turbine is widely applied. It is of value to study dynamic characteristic of the Francis turbine revolver's blade, which is subjected to a variety of vibration excitations. The influence of the water environment on natural frequencies of a Francis turbine runner's blade is analyzed. The finite element method (FEM) model includes the complete blade structure and the fluid region. The results of numerical analysis are compared with experimentally obtained data. The eigenfrequencies and mode shapes of the blade vibrating in operating flow path are compared with those in the air. The results show that the frequency in the water is smaller than the one with same order in the air, with different reduction to different order. The average reduction amounts to 40%. They also show the mesh density greatly affects the precision of computation and the element with mid node is much more accurate than the one without mid node.