Toroidal Propellers
- Project Type
- Additive Manufacturing, Electronics, Python
- Year
- 2023
A published preprint paper measuring how toroidal and asymmetric propeller shapes reduce tonal noise compared to conventional blades.
01
Quieter propellers for a world with more drones
Drones are becoming a common sight over populated areas, and the noise from their propellers is a real concern. Together with seven co-authors, I studied whether the shape of the propeller itself could make that noise less annoying, and we published the results as a preprint on arXiv.
02
Three shapes, one airfoil
We designed every propeller in Fusion 360 from the same custom airfoil, all 6 inches across and 3D printed the same way, so the shape was the only thing that changed. A conventional six-blade propeller was the baseline. The toroidal propeller sweeps the tips of its three blades into one another to form closed loops, which cuts down the tip vortices behind broadband noise. The third design keeps six blades but spaces them unevenly, which spreads the tonal noise of evenly spaced blades across more frequencies.
03
Lower peaks, less annoyance
We measured thrust on a load cell and recorded each propeller in a foam-lined chamber, then weighted the sound to match how people hear it. The toroidal propeller made the most thrust of the group, 2.90 N at 12,000 RPM against 2.71 N for the conventional baseline, so the quieter shape costs nothing in lift.
In the results plot, the red trace is the conventional propeller. Each tall spike is a pure tone at a multiple of the blade passing frequency, and those tones are what people find most annoying. The black trace, the unevenly spaced propeller, keeps those spikes much lower. The toroidal propeller did better still, with the lowest peaks and the least annoying sound of everything we tested.