Effect of Motor-Rotor Geometry on the Performance of Electric VTOL UAVs

This paper aims to quantify the impact of the orientation and position of a vertical lifting motor-rotor system on the aerodynamic performance of a wing. The analysis was conducted on the scaled wing of an electric uncrewed aerial vehicle using wind tunnel measurements to quantify the difference in performance between configurations. The wind tunnel model was produced by applying a set of non-dimensional parameters to scale an existing quad-plane design, conserving important features to make the result both feasible and generalised. The design was analysed at a Reynolds number of 430,000 to be comparable to the operating conditions of the existing vehicle. The analysis is conducted using two-bladed rotors that are prevented from rotating in the oncoming flow (braked). The influence of the braked angle of the front and rear rotors on the aerodynamic performance of the wing was tested at 30◦ brake angle increments between 0-150◦ over wing angles of attack between -4◦ and 10◦. Results show that the braked angles of the front and rear rotor have a significant impact on the aerodynamic drag. In particular, aligning both rotors so that the blades are perpendicular to the wing chord can result in a 25-30% increase in drag when compared to the case of both rotors aligned parallel to the chord direction. Additionally, the aerodynamic penalty incurred by the vertical lifting subsystem (motors and supporting structure) was also measured.