Aero-mechanical optimization method with direct CAD access - Application to counter rotating fan design

The detailed design of three-dimensional turbomachinery blades is a very challenging problem requiring multi-disciplinary analysis (MDA), efficient numerical optimization techniques and efficient shape parameterization techniques. Moreover, CAD systems have become an integral and critical part of the complete design process in various fields, and in particular in the field of turbomachine design. The connection of an automated design system to drive CAD geometry directly in the native CAD software is therefore mandatory in order to obtain an integrated design system that can be used in an industrial design chain. This paper presents and discusses an effort to incorporate these technologies into a single and integrated design system for the automatic optimization of turbomachinery blades. First, a brief summary of the algorithms and software used in this design system is presented. Then, the performance of this design system is first demonstrated on the automatic optimization of a counter-rotating fan stage. The fan is redesigned for several aerodynamic operating conditions as well as for multi-disciplinary objectives with constraints involving a CFD solver and structural mechanics FEM solver. The fan geometry is parameterized using 70 design variables and an optimum solution is found in 300 optimization cycles. The peak efficiency is increased by 1.5%, while the static stresses and dynamic vibration modes satisfy the constraints imposed during the optimization. Finally, a second application demonstrates the design optimization of a CAD model of the counter-rotating fan performed with direct integration to the CAD system using the CAPRI middleware. In this case the tip section of the first rotor is parameterized using 7 design variables. The efficiency is increased by 0.5% and the CAD integration in the optimization cycle is demonstrated.© 2006 ASME