多级叶盘结构动力特性分析的一种方法

因各级转子叶片数的不同,基于传统循环对称法的通用有限元程序无法直接用于多级叶盘结构动力特性分析.发展了一种方法,分别对每一级扇区模型施加相应的循环对称边界条件,级间则通过施加自由度耦合来保证位移场的连续.若对每一级叶盘结构选取合理的扇区数目进行建模,最大程度地考虑级间耦合效应,则精度可进一步提高.由于循环对称边界条件和级间耦合通过对位移自由度施加约束方程来实现,因此该方法易于在通用有限元程序系统中实现.对两级叶盘结构分别采用该方法和全环模型进行动力特性分析,两种方法的频率差控制在3%内.探讨了多级叶盘结构中级间耦合对模态的影响,在低节径模态两级叶盘结构耦合效应较为明显,随着节径数的增加,耦合效应降低. 

A method of structural dynamic characteristics analysis for multistage bladed disks

Concerning different blade numbers in each stage, the commercial finite element solvers developed on the traditional cyclic symmetry method can not be applied directly to the structural dynamic analysis of multistage bladed disks. A method was developed to deal with this issue by applying corresponding cyclic symmetry boundary constraints on each stage's sector model, and coupling constraints were also applied on the inter-stage's nodes to ensure continuous displacement field.To achieve a better accuracy, appropriate number of sectors for each stage was selected to consider the coupling effects to the greatest degree. The method could be easily implemented in the commercial finite element solvers since the cyclic symmetry boundary conditions for each stage and the inter-stage coupling constraints could be handled by the displacement degrees of freedom respectively. The modal analysis got by this method shows a good agreement with the full circle method and the frequency difference is below 3%. The influence of coupling effect on the multistage bladed disks structure was presented and with the increase of nodal number the coupling effects decrease.