Ducted Fan Design for VTOL Aircraft Flight Mission Based on Bayesian Optimization

Vertical takeoff and landing (VTOL) aircraft have great potential in both military and civil applications. Due to the high power and energy requirements of VTOL and its potential widespread use in the future, it is important to improve the overall efficiency of VTOL aircraft, where one promising way is using the ducted fan concept because of the potentially higher aerodynamic performance and noise shielding effects. The goal of this paper is to adopt an approach that can efficiently include both continuous and discrete ducted fan design variables and further to design and to optimize the ducted fan for conceptual VTOL aircraft design study. Firstly, the open-source Ducted Fan Design Code (DFDC) tool is employed for fast and efficient ducted fan analysis. Then, we formulate the ducted fan design and optimization problem as mixed integer nonlinear programming to include both class-shape-transformation-based parameters and intuitive ducted fan parameters. The performance of the ducted fan was optimized for hovering, cruising, and the overall flight mission based on the Bayesian optimization approach. The results showed that optimization considering only hovering or cruising can enhance the performance of the ducted fan at the corresponding phase, but the overall aircraft performance might not be improved. As such, the whole aircraft flight mission performance was set as the design objective while carrying out the ducted fan optimization, which in the end led to the reduction of fuel consumption from the original 828.41 kg to 713.46 kg, i.e., about 15.9% fuel saving for the selected flight mission.