Research on the aerodynamic characteristics of eVTOL aircraft ducted rotor tip embedded inside the ducted body.

The lift system constitutes a pivotal technology in the makeup of vertical takeoff and landing aircraft systems. The application of ducted rotors in urban air mobility(UAM) has advantages and is one of the future development trends. Due to their compact structure, low noise, safety and reliability, the ducted rotors have been widely used as a thrust or lift device in aircraft design of the electric vertical takeoff and landing (eVTOL) aircraft. In order to further improve the power load of ducted rotors, this paper proposes a method of increasing the lift by embedding the rotor tip into the inner wall of the ducted body to improve the slip boundary and lip disturbance inside the ducted body. Then, CFD method is used to calculate and analyze the flow field, flow state, and aerodynamic characteristics under hovering, axial flow, and oblique flow states, and to compare and analyze the aerodynamic forces with isolated rotors of the same diameter and ducted rotors under the same working conditions. The results indicate that in hover mode, the lift generated by the embedded ducted rotors is greater than that of the ducted rotors and the isolated rotors, while consuming the same amount of power. In the axial flow state, when the vertical ascent speed is greater than 8 m/s, the power load of the embedded ducted rotors is smaller than that of the ducted rotors and the isolated rotors, and the overall aerodynamic efficiency advantage is obvious. When in an oblique flow state, under the same forward inclination angle, the thrust generated by the embedded ducted rotors is greater than that of the ducted rotors, and the drag generated by the ducted rotors is smaller than that of the ducted rotors. In addition, the principle of aerodynamic advantage of embedded ducted rotors is analyzed comprehensively. The advantages of the embedded ducted rotors over the ducted rotors are obtained, which provides a theoretical basis for the design and optimization of the ducted rotors lift system of eVTOL aircraft.