Reduced Order Modeling of Mistuned Bladed Disks under Rotation

Abstract

In this paper, a substructure-based reduced order model for mistuned bladed disks is extended to account for the effect of rotational-dependent dynamic properties. To reduce the overall size of the structural model, successive transformations to reduced modal subspaces of smaller dimension are performed by means of a fixed-interface Component Mode Synthesis, a Wave-Based Substructuring, and a Secondary Modal Truncation. Since the threedimensionally shaped rotor blades tend to untwist under the influence of centrifugal forces, the modal reduction bases may undergo significant changes for different speeds of rotation. To prevent the necessity of identifying individual modal subspaces for each operating point and a repetitious passing through the full reduction process, a multi-model formulation is used to obtain a parameterized reduced order model in terms of rotational speed. The accuracy of this approach is assessed by comparison with full finite element models for various steady operating conditions. In terms of computational solution time, the proposed approach outperforms the finite element calculation by 90%. Finally, numerical results are presented addressing the mitigating influence of constant and variable rotational speeds on the amplitude amplification of mistuned bladed disks.