Drones have become increasingly popular in recent years and provide us with spectacular images of cities and nature. But especially in the second case, there is a catch. Because if you let a drone fly in the silence of nature, you will immediately disturb it. The reason for this is, of course, the high-frequency noise of the propellers, which is capable of disrupting any idyll in the long term.
Silent flying is approaching
But now a team from the Lincoln Laboratory at the Massachusetts Institute of Technology (MIT) has developed a propeller that works almost silently (via NewAtlas). In a video, Thomas Sebastian, a researcher at MIT’s Structural and Thermal-Fluids Engineering Group, explains that he was actually working on a different project, an ion-powered aircraft. This has practically no moving parts and is therefore almost silent.
To do this, Sebastian needed a way to compare this new technology to a propeller. But the problem was that they are very loud. So Sebastian and his team looked for ways to improve the propeller in this regard. To do this, they looked into the distant past of aviation when they experimented with ring-shaped wings.
3D printed rings as a solution
In fact, this was a promising approach and toroidal or ring-shaped propellers were built with it. This made it possible to significantly minimize the turbulence. “We came up with the idea of using an annular blade shape to hopefully get a quieter propeller,” says Sebastian. “An intern of mine who was just phenomenal took this idea further. He took the concept and created a series of iterations with 3D printers.”
These propellers have not yet been optimized – but they already work better and more quietly
The key here was to distribute the vortices generated by the propeller over the entire shape of the propeller and not just at the tip. Sebastian: “As a result, it dissolves faster in the atmosphere. The vortex no longer spreads so far, so you hear it less often.” The amazing thing about it: The new type of propeller shape also had no disadvantage in terms of the thrust generated. On the contrary: The best design to date, numbered B160, was not only much quieter than a conventional propeller, but also more powerful – and this despite the fact that the development and optimization of the toroidal propeller has not yet been completed.
However, the new propellers do not come without disadvantages either, because their more complex shape is more difficult to manufacture. According to the researchers, 3D printing can and will help here. Incidentally, this not only applies in the air, but also in the water (where people have been working with it for a long time), where noise development can also be significantly reduced.
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