Aerodynamic Shape Optimization of Fan-Flow Deflectors for Noise Reduction Using Adjoint Method

This article presents application of an adjoint method to the aerodynamic shape optimization of deflector vanes installed in the fan nozzle of a turbofan engine. The purpose of the vanes is to reduce jet noise radiated towards the community, and the specific application of this study is for a supersonic turbofan engines with bypass ratio 2.7. The cost function used in the optimization includes entropy generation and a penalty for deviating from a target deflection angle. The initial vane airfoil is the NACA0012. The vane airfoil arising from the optimization produces flat distributions of pressure coefficient over the surface of the vane thus preventing the formation of sonic bubble and strong shocks. For a fixed flow deflection angle, the optimal airfoil is up to 22.5% more efficient in terms of specific thrust loss compared to the NACA0012. Importantly, the optimization leads to a thicker airfoil with 15% thickness which may be advantageous for structural reasons.