Design of Propeller Duct for Small Multi-Rotor Aircraft

Abstract

The design of the isolated propeller duct for multi-rotor aircraft has been investigated by using numerical simulation. The paper is intended to discuss the influences of three factors, i.e., the profile of the duct, the angle of incidence in the duct’s profile, and the spacing between the propeller tip and the duct’s inner wall, on the static performance of the ducted propeller system. Simulation results show that the pull of one propeller in a duct system is smaller than that of an isolated propeller, but the overall pull of the system is greater than that of the isolated propeller. When the airfoil with a large lift-to-drag (L/D) ratio is adopted as the profile of the duct, and the duct’s inner wall is set in the expansion type, the overall pull is substantially increased with the other conditions unchanged. If the airfoil with a large L/D ratio is adopted as the profile of the duct, and its designed angle of incidence is set at 0 degree, the ducted propeller system have the largest pull coefficient, and so on. By exploring the optimal design and pattern of the propeller duct, some propositions have been made in an attempt to improve the design method.