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.