Recently, a team from the Lincoln Laboratory of Massachusetts Institute of Technology (MIT) in the United States has developed a propeller that works almost silently. The new propeller is designed in a circular shape. It is also one of the award-winning works of the R&D 100 Innovation Award of the laboratory. The propeller has a unique closed propeller design, making it a quieter alternative to the common multi-rotor propeller on commercial unmanned aerial vehicles.

Thomas Sebastian, a member of the team and a researcher of the Massachusetts Institute of Technology's Structural and Thermal Fluid Engineering Group, said that the appearance of the annular propeller could be regarded as an "accident". Its initial research focus was actually the ion-powered aircraft, which was basically silent because it had almost no moving parts. Sebastian needs a way to compare this new technology with the propeller. But the problem is that ordinary propellers are loud. Therefore, Sebastian and his team are looking for ways to improve the propeller in this regard.

So the team built annular or annular propellers. This makes it possible to significantly reduce turbulence. Sebastian said: "Our idea is to use the annular wing shape, hoping to get a quieter propeller. One of my interns put forward this extraordinary idea. He then created a series of iterations using 3D printers based on this concept.".

                Annular propeller prototype

Surprisingly, the new propeller shape does not reduce the thrust generated. On the contrary, the best design model so far numbered B160 is not only much quieter than the traditional propeller, but also more powerful. The new propellers are not without disadvantages, because their more complex shapes make it more difficult to manufacture. But researchers said that 3D printing technology can effectively solve this problem. Besides being used in the air, this annular propeller can also significantly reduce noise underwater.