Experimental Analysis of Thrust Efficiency of Toroidal Propellers for Quadcopters and Hybrid UAVs

Toroidal propellers have emerged as a promising alternative to conventional blade designs due to their potential for reduced noise and improved aerodynamic performance. This study investigates the feasibility of toroidal propellers for quadcopters and hybrid UAVs through experimental testing of three propeller variants: a conventional 4-bladed design, a toroidal configuration, a modified toroidal configuration, and segments of toroidal propellers featuring a tip angle designed to maintain effective angle of attack at the blade tips. Each design was manufactured to mimic the DJI 9450 and was evaluated in static and dynamic wind tunnel conditions with incoming flow conditions ranging from 2.5 to 10 m/s. The angle of incoming flow was varied from +90° (head-on) to -90° (descent condition) to simulate all possible flight configurations. Particle Image Velocimetry (PIV) was conducted at selected inflow angles (90°, 15°, and 0°) to assess wake structure and flow behavior. The results indicate that the modified toroidal propeller performs better in direct-inflow conditions, while the conventional toroidal propeller excels in oblique and descent angles. The modified toroidal also maintains higher efficiency in a broader range of inflow conditions than standard designs, suggesting its viability for hybrid UAV propulsion systems operating in variable aerodynamic environments.