Multi-Objective and Multi-Point Aerodynamic Optimization of Transonic Fan Blades

Abstract

A multi-objective and multi-point optimization methodology is developed for aerodynamic design of transonic fan blades. The optimization method aims to increase design efficiency, near stall efficiency and stall margin while maintaining the required design pressure ratio and high speed choke margin. Numerical analyses are performed by solving three-dimensional Reynolds-Averaged Navier-Stokes equations combined with shear stress turbulence model. A multi-level blade parameterization is employed to modify the blade geometry. The proposed method is applied to redesign NASA rotor 67. First, an optimization case with considering two operating conditions at peak efficiency and near stall is performed to demonstrate the relation between near stall efficiency and stall margin. An investigation on Pareto optimal solutions of this optimization shows that the stall margin is increased with improving near stall efficiency. Then, in order to maintain the required choke margin, an operating point at high speed choked flow is added to the optimization process. A final optimized design is selected by considering the interaction of design requirements at all three operating points. The new design presents higher efficiency and stall margin without any reduction in the chocking mass flow rate.