Reduced Order Modeling of Cyclically Symmetric Bladed Disks with Geometric and Contact Nonlinearities

In the current economic and environmental context, aircraft engines manufacturers try to design more efficient engines in order to reduce their fuel consumption. First, aerodynamic losses are decreased by reducing the clearance between the blades and the surrounding casing. This can lead to contact events between the blades and the casing even in nominal operating conditions. Then, the engine weight is reduced by designing lighter, and therefore more flexible, blades. As a consequence, the blades can undergo large displacements and deformations.

A methodology has been recently derived to study the contact interactions of single blades undergoing large displacements. In this article, this methodology is extended to full bladed disks with cyclic symmetry. In order to be computationally efficient and compatible with the use of large industrial models, the methodology is based on a reduction procedure. Each sector of the high fidelity model is projected onto a basis composed of Craig-Bampton modes and a selection of their modal derivatives. The internal nonlinear forces due to large displacements are evaluated in the reduced basis with the stiffness evaluation procedure. Contact is numerically handled with Lagrange multipliers.

The numerical strategy is applied on an open industrial compressor model, the NASA rotor 37, in order to promote reproducibility of results. This work demonstrates that reduced order models provide a computationally efficient alternative to full order finite element models for the accurate prediction of the time response of structures with both distributed and localized nonlinearities.