Highly Loaded LPC Blade and Non Axisymmetric Hub Profiling Optimization for Enhanced Efficiency and Stability

The present contribution fits into the frame of the ongoing 7th Framework European Project DREAM (valiDation of Radical Engine Architecture systeMs). One of its main themes targets the development of contra-rotating open rotors with variable pitch blades which are known to provide 10 to 15% fuel burn reduction but are noisier than high by-pass turbofans. More specifically, the present research was conducted in the frame of work package 3.4 lead by Techspace Aero, dedicated for one part to the design of a high speed booster adapted to open rotor configurations, and for the second part, from which this paper is issued, to the investigation of 3D geometries to improve LPC efficiency. A reference rotor blade has first been designed, with high loading, especially at hub. To improve its efficiency, a backward sweep has then been applied as it tends to unload midspan sections. However, this performance gain came at the price of severe stall margin degradation, the criticality of the hub region being increased. Based on 1.5 stage 3D RANS simulations, automated surrogate-assisted optimization has then been exploited to respectively evaluate the potential benefit of tailored 2D contouring and 3D hub profiling a posteriori applied to the swept rotor blade and of joint 3D hub profiling and sweep optimization of the unswept baseline rotor blade. The potential benefit of 3D profiling will be demonstrated while the joint 3D profiling and blade stacking optimization shed light on the achievable interesting 3D effects combinations.Copyright © 2011 by ASME