The silent revolution: New rotor design makes drones much quieter

[11:43 Fri,3.February 2023 by Thomas Richter]

Drones are extremely popular as flying cameras and have become an indispensable part of movies and TV documentaries - but their unpleasant buzzing noise when hovering is often very disturbing and makes some recordings impossible. But a quasi-random discovery by MIT researchers now raises hopes that drones could become much quieter in the future.

Drone with toroidal propellers

The actual goal of the research was to develop a silent aircraft - made possible by a completely new propulsion technology, a

ion engine with no moving parts. When comparing the noise level of this new concept with a classic propeller drive, the team came up with the idea of changing the classic shape of the propeller to make it quieter. The impetus for this was an old concept from the early days of aviation, namely annular blades. The result was a toroidal propeller (also known as a loop propeller), whose blades are effectively a closed circle. After some testing with different 3D-printed toroidal designs, a model was quickly found that was not only quieter overall than a comparable classic rotor, but also specifically in the high-frequency part of the spectrum from 1-5 kHz, which humans find particularly unpleasant. The noise generated by the new rotors was about as disturbing as that of a normal drone at twice the distance.

The team explains the protective effect by the closed structure of the rotor (the two blades of the toroidal propeller converge in a loop) which reduces the air resistance caused by the air tunnels (i.e. vortices) created at the blade tips. This results in a lower noise level, which fortunately is not at the expense of performance.

Comparison of the new propellers with DJI&s rotors

The toroidal propeller was installed on a DJI commercial drone for testing purposes and

showed that the thrust is comparable to that of conventional propellers (DJI&s standard rotor as well as the special noise-reduced model were tested - but with the old DJI Phantom 3), while at the same time the noise level was reduced by half.

Drone with toroidal propellers.

Another advantage over classic rotors relates to the safety aspect: the new loop shape of the rotors not only gives them additional stability, but also reduces the risk of injury if the drone accidentally collides with a person or the risk of damaging itself or other objects in a collision.

The new toroidal propeller could represent a small revolution for drone technology, greatly increasing the acceptance of drone missions for various tasks that were previously precluded by the annoying noise. This could include drone photography at close range as well as package deliveries by drone, for example.

Toroidal propeller.

Interestingly, the toroidal propeller also promises to be of great benefit in another class of vehicle, namely shipping. Here, however, less in terms of noise reduction than a respectable

performance increase when using toroidal propellers compared to traditional models.

more infos at bei newatlas.com

deutsche Version dieser Seite: Weniger Sirren: Neues Rotorendesign macht Drohnen endlich leiser