Aero-Mechanical Optimization Design of a Transonic Fan Blade

Abstract

This paper presents the optimization design of a high bypass ratio civil fan blade with the consideration of aerodynamics, static and dynamic mechanics. The baseline fan blade was designed with a conventional approach without using automatic optimization techniques on both the aero side and the mechanical side. Therefore, the objective of this paper is to achieve a higher aero-mechanical performance under the multiple aerodynamic and mechanical constraints. Before the optimization, the static stress and modal analysis are performed on the baseline fan blade with/without the introduction of the arc dovetail root and shank. The results are compared to investigate the necessity of including the arc root and shank in the aero-mechanical optimization. With respect to the optimization process, the numerical design of experiment (DOE) by means of high fidelity CFD/FEA computations is firstly performed to construct the database for the initialization of Kriging surrogate mode. After that, the surrogate model is integrated with the optimization design process, and the non-dominated sorting genetic algorithm (NSGAII) is implemented to obtain the Pareto front, based on which the optimal design is selected. Utilizing this optimization process, both the aero-only and aero-mechanical optimizations are carried out. The results show that the attenuation of the 3D shock wave strength between the middle and shroud span improves the overall aero performance of the fan blade in both the aero-only optimal design and the aero-mechanical optimal design. Compared with the aero-only optimal design, the aero-mechanical optimal design shows the efficiency penalty within all the operation range simulated, however, the mechanical performance is significantly enhanced by the mitigation of the static stress level on the entire arc dovetail root and shank as well as the increase of the resonance margin.