【摘要】 为防止水轮机转轮发生共振,导致叶片产生共振裂纹,需要对水轮机的固有频率进行计算,使转轮的固有频率避开外界的激振频率。本文基于流固耦合方法,将CFD软件CFX与有限元软件ANSYS Workbench相结合,对某水电站混流式水轮机转轮进行了有限元模态分析计算,分别计算了转轮在有无预应力情况下对于模态计算结果的影响,并分别考虑了转轮在空气中和在水介质中的固有频率和振型。结果表明,转轮在有预应力情况下各阶固有频率会有所提高,提高幅度在0.5%以内,可以忽略预应力的影响;转轮在水中的各阶固有频率比在空气中均有明显的降低,且各阶频率降低程度不同,下降系数的总体趋势是随着阶次的提高而逐渐减小的。更多还原

【Abstract】 The resonance of turbine will cause resonance crack on the turbine blade,so it is necessary to calculate the natural frequency of turbine to avoid external excitation frequency. The fluid structure interaction(FSI) method which combines CFD software CFX and finite element software ANSYS Workbench is introduced in the present paper. The finite element modal analysis is made on a domestic Francis turbine to calculate the modal of the turbine with and without considering the pre-stress respectively. Natural frequencies and mode shapes of the turbine are calculated in the air and water respectively. The results show that the natural frequencies of the turbine will increase by considering the pre-stress. However,the increasing ratio is less than 0.5%, so the effects of pre-stress can be ignored. Natural frequencies in water are reduced significantly than that in air, and the declined degrees vary in different frequency order. The general trend of drop coefficient is reduced with the increase of frequency order.更多还原