Experimental and Numerical Analysis of a Toroidal Propeller

This study presents an experimental and numerical analysis of a 254 mm toroidal propeller, focusing on its aerodynamic performance and acoustic characteristics. Experiments were conducted in an anechoic chamber, where a load cell and microphones captured propeller performance and aeroacoustic data. The propeller achieves a figure of merit of approximately 0.45, indicating moderate efficiency. Pressure differentials near the blade tips are identified as the primary contributors to thrust and torque, with the leading blade in a single loop reducing lift on the trailing blade by up to 50%. Vortex structures in the propeller’s slipstream, including root, tip, and central vortices, are analyzed, and curve-fitting techniques are used to model tip vortex trajectories at various rotational speeds. The Spalart–Allmaras model, coupled with the Ffowcs-Williams and Hawkings model in Reynolds-averaged Navier–Stokes equations, accurately predicts tonal noise but underestimates broadband noise and the overall sound pressure level (OASPL) due to its tendency to smooth out pressure fluctuations. A comparison with conventional advanced precision composite and wood propellers shows that the primary tonal noise, broadband noise, and OASPL increase with disk loading, underscoring the importance of consistent test conditions when comparing toroidal propellers with conventional designs. Overall, the study provides valuable insights into the performance characteristics of toroidal propellers and offers recommendations for future research.