Low-Noise Blade Design Optimization for a Transonic Fan Using Adjoint-Based MDO Approach

The target of reducing the environmental footprint of the aviation industry has continually driven the need to design more efficient and quieter aircraft engines. In this paper, the aeroacoustic adjoint formulization for low-shock tone noise fan blade design is first proposed and combined with the aerodynamic adjoint analysis to develop an adjoint-based, multi-disciplinary design optimization process for transonic fan blade design. High-fidelity numerical simulations are employed in the optimization loop to predict aeroacoustic and aerodynamic objectives and gradients. Aeroacoustic and aerodynamic design optimizations of an industrial transonic research fan are conducted using the proposed adjoint-based approach, demonstrating that the noise performance and the efficiency of the fan can be improved simultaneously. Results indicate that the significant reduction in the sound power level of the fan shock-associated tone noise is achieved by a compound leading-edge sweep pattern generated by the optimizations. Flow fields and acoustic results of the optimized blades are then analyzed to understand the noise reduction mechanism.