Further Reduction of the Fundamental Mistuning Model Using Mistuned Aeroelastic Modes

Abstract

Despite decades of research and attention to the problem of mistuning in bladed disks, both industry and academic efforts have yet to yield a comprehensive design solution for the phenomenon. Regardless, reduced order models based on finite element models have equipped designers and researchers with valuable tools to understand and combat the behaviors of mistuned bladed disks. These models, when employed in probabilistic modeling, can yield accurate predictive distributions for the forced response and flutter characteristics of mistuned bladed disks. This effort focuses on the improvement of one such model by novel application of classical modal decomposition methods. In order to elucidate the status of mistuning research, a brief literature survey is conducted to preface the implementation of an additional reduction to the already simple fundamental mistuning model. Mistuned aeroelastic modes are computed after summing the effects of mistuning, structural coupling, and aerodynamic coupling. This new modal basis is then employed to diagonalize fully the forced response problem, allowing for greater computational efficiency and additional insights to be gained. The exactness of this approach is confirmed with a number of academic bladed disk examples and timing of the new methods yields operational cost reductions of more than 75% for most usage conditions. The new method is then employed in a probabilistic forced response analysis of a mistuned rotor. These results are compared to experimental data to further validate the effectiveness of the fundamental mistuning model.