Reduction of Multistage Disk Models: Application to an Industrial Rotor

Abstract

The present study deals with the reduction of models of multistage bladed disk assemblies. The proposed method relies on the substructuring of the rotor into sectors. The bladed disks are coupled by intermediate rings, which remove the problem of incompatible meshes. The sectors are represented by superelements whose kinematic subspaces are spanned by a set of cyclic modeshapes and a set of normal modes when their left and right interfaces are fixed. The first step is to compute the cyclic modeshapes that are defined on the full rotor by enforcing the uncoupling of the spatial Fourier harmonics. This leads to a family of subproblems parametrized by the harmonic coefficient, similar to the classical approach used to deal with tuned bladed disks. The subsequent reduction process leads to compact reduced models whose accuracy has been extensively tested on simple but realistic academic models. The proposed methodology was then applied to an industrial rotor to conduct an analysis at a wider scale. This case was also the occasion to point out the fact that the assembly of individual disk models into a rotor model is really straightforward and provides an efficient tool to observe and predict coupled phenomena.