In an increasingly competitive global market, aircraft engines manufacturers try to design more efficient engines in order to reduce their fuel consumption both for economic and environmental reasons. Over the past decade, different avenues have been considered to achieve this goal. First, aerodynamic losses can be 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. In order to lower contact severity, an abradable coating acting as a sacrificial material is often deposited along the stator circumference. Then, the engine weight can be reduced by designing lighter, and therefore more flexible, blades. As a consequence, the blades can undergo large displacements and deformations. Contact nonlinearities and geometrical nonlinearities are therefore two important aspects to consider when studying blades dynamics.In this article, a recently derived methodology is used to study the rubbing contact interactions of industrial blades accounting for geometric nonlinearities. In order to be computationally efficient and compatible with the use of large industrial models, the methodology is based on a reduction procedure. The high fidelity model is projected onto a basis composed of Craig-Bampton modes and a selection of their modal derivatives. The nonlinear forces due to large displacements are evaluated with the stiffness evaluation procedure. Contact is numerically handled with Lagrange multipliers and abradable wear is managed with a macroscopic model of the material removal through a piecewise linear plastic law.The numerical strategy is applied on an open industrial compressor blade model, the NASA rotor 37 blade, in order to promote reproducibility of results. Two contact scenarios are investigated: one with direct contact between the blade and the casing and one with abradable material deposited on the casing. The influence of geometric nonlinearities is assessed in both cases with in-depth analyses over a wide angular speed range. In particular, contact interaction maps and abradable coating wear pattern maps are used to characterize the main interactions that can be detrimental for the engine integrity.

Assessment of geometric nonlinearities influence on NASA rotor 37 response to blade tip/casing rubbing events

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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