混流式转轮静强度和振动特性分析

Strength and vibration analysis of a Francis turbine

为大型水轮机组的安全、稳定运行,研究了转轮在水介质中的动力特性。运用顺序耦合的方法,分析了在三维旋转流动所产生的水压力作用下转轮体的静强度特性;运用全流固耦合的三维有限元方法进行了转轮在水介质中的模态分析。强度分析结果表明,应力集中的部位与裂纹实际产生的位置完全吻合,但最大等效应力远小于材料的极限破坏应力;模态分析得到转轮在水中的自振频率和振型等振动特性,指出了发生共振的可能性。结果证实了导致裂纹产生的原因不是静应力而是动载荷的作用。

This paper studies the underwater dynamic characteristics of Francis turbines to enhance the safety and stability of hydroelectric power stations. The 3-D flow field and stresses in a rotating Francis turbine were studied numerically using the sequential coupling method. The fluid-structure interactions were studied using modal analysis. The calculated results showed that stress concentrations occurred on the blade root near the crown, which corresponds with cracks observed in operating units. The maximum equivalent stress was found to be much smaller than the failure stress. The underwater vibrations occurred at frequencies and modes which suggest the occurrence of resonance vibrations. Therefore, the results suggest that the cracks are not due to the static stresses but due to the dynamic loads.