The effects of aerodynamic asymmetric perturbations on forced response of bladed disks

Conference Paper

Most of the existing mistuning research assumes that the aerodynamic forces on each of the blades are identical except for an interblade phase angle shift. In reality, blades also undergo asymmetric steady and unsteady aerodynamic forces due to manufacturing variations, blending, mis-staggered blades or in-service wear or damage, which cause aerodynamically asymmetric systems. This paper presents the results of sensitivity studies on forced response due to aerodynamic asymmetry perturbations. The focus is only on the asymmetries due to blade motions. Hence, no asymmetric forcing functions are considered. Aerodynamic coupling due to blade motions in the equation of motion is represented using the single family of modes approach. The unsteady aerodynamic forces are computed using CFD methods assuming aerodynamic symmetry. Then, the aerodynamic asymmetry is applied by perturbing the influence coefficient matrix in the physical coordinates such that the matrix is no longer circulant. Therefore, the resulting aerodynamic modal forces in the traveling wave coordinates become a full matrix. These aerodynamic perturbations influence both stiffness and damping while traditional frequency mistuning analysis only perturbs the stiffness. It was found that maximum blade amplitudes are significantly influenced by the perturbation of the imaginary part (damping) of unsteady aerodynamic modal forces. This is contrary to blade frequency mistuning where the stiffness perturbation dominates. Copyright © 2008 by ASME.

Full Text

Duke Authors

Cited Authors

  • Miyakozawa, T; Kielb, RE; Hall, KC

Published Date

  • December 1, 2008

Published In

  • Proceedings of the Asme Turbo Expo

Volume / Issue

  • 5 / PART B

Start / End Page

  • 779 - 790

International Standard Book Number 13 (ISBN-13)

  • 9780791843154

Digital Object Identifier (DOI)

  • 10.1115/GT2008-50719

Citation Source

  • Scopus