Implementation of ducted fan design on open rotor quadcopter, with a focus on optimization of duct lip geometry
Lim, Ian Tze An
Date of Issue2015
School of Mechanical and Aerospace Engineering
The use of Unmanned Aerial Vehicles (UAVs) have become increasingly popular for use in military intelligence, surveillance and reconnaissance (ISR) missions. Their deployment helps to safeguard the lives of soldiers who would otherwise have to risk their physical safety to conduct the ISR mission. In light of the move toward urban warfare, this project aims to develop an autonomous UAV that is capable of undertaking indoor ISR missions. A standard quadcopter with 10-inch rotor was used as the starting point for this project. This report entails the structural segment of the project, which attempts to design a ducted 8-inch rotor that is able to match the performance characteristics of the original 10-inch open rotor. The duct was designed from scratch and an emphasis was placed on varying the duct lip geometry to obtain the desired results. The duct lip geometry exerts considerable influence on the aerodynamics of the duct; flow separation occurring on the lip greatly reduces the lift and hence, the thrust produced by the duct. However, having flow separation helps to lessen the impact of an adverse pitching moment that the duct inherently experiences in crosswinds or forward flight. Simulations were performed on 12 different lip variations and the lip with leading edge radius 4mm, height 2mm ultimately satisfied the selection criterion best. The criterion was to select the lip that allowed 4 ducts to produce the minimum amount of thrust needed to lift the quadcopter. This was done so that the quadcopter would suffer minimal effects from the adverse pitching moment experienced during forward flight. Open rotor thrust experiments were also conducted to determine the characteristics of different propellers. The 8 x 4.5 inch propeller showed promising results and was selected for use in the new ducted rotor design. An initial prototype of the duct with diffusion ratio 1.05 was 3D-printed was affixed onto the same thrust meter used for the open rotor test. A closed rotor thrust test was performed in similar fashion to the open rotor test and the data collected was compared with that from the open rotor experiment. The ducted 8 x 4.5 inch rotor exhibited excellent power efficiency characteristics compared to the 10-inch open rotors, suggesting that it could supply a longer flight time. However, its thrust characteristics could not match up to the 10 x 3.8 inch open rotor, although they were comparable to the 10 x 4.5 inch open rotor. More work would have to done to augment the thrust characteristics of the 8 x 4.5 inch ducted rotor before it can match that of the 10 x 3.8 inch open rotor.
Final Year Project (FYP)
Nanyang Technological University