Quiet cyclorotor with low friction material on the blade surface

Abstract

Cyclorotors are quieter than conventional propeller types, but further noise reduction is desirable. A quiet blade design using a jagged structure based on the principle of an owl's wing is conceivable, but the complex shape makes it prone to dirt and difficult to maintain. Therefore, we provide a cyclorotor configuration that reduces noise by distinctively arranging low-friction materials rather than a jagged structure. [Solution] By disposing a low-friction material in a longitudinal stripe pattern on the front and / or rear surface of the blade from the leading edge to the trailing edge and / or from the trailing edge to the leading edge, the air flowing in the boundary layer on the front and / or rear surface of the blade is straightened, forming a dispersed pattern in which air with different flow speeds alternates vertically, suppressing the generation of large turbulence on the front and / or rear surface of the blade, thereby reducing the noise generated by the turbulence.

Description

[Background technology]

[0001] Owls can fly quietly by using the comb-like three-dimensional jagged structure on their wings to finely disperse the air flowing within the boundary layer of the wings and suppress the generation of large turbulence, thereby reducing the sound generated by turbulence. Quiet designs that apply this technique already exist, and there are examples of the introduction of three-dimensional jagged structures in wind turbine blades and aircraft engine fan blades.

[0002] Cyclortors have superior maneuverability compared to conventional propeller systems, and are expected to be installed in aircraft such as drones, wind power generation systems, blowers, etc. Cyclortors effectively control air flow, reducing noise, but it would be desirable to reduce noise even further. Regarding noise reduction designs for cyclorotors, there are currently no designs that use a three-dimensional jagged structure on the blade surface, as described in 0001, but this could be considered as one method of reducing noise. However, a three-dimensional jagged structure tends to have a complex shape, and it is thought that dirt easily adheres to and accumulates in the grooves of the jagged structure. If dirt adheres to and accumulates in the grooves of the jagged structure, it will no longer have the effect of finely dispersing the air flowing in the boundary layer of the blade surface, and as a result, it is thought that the noise reduction effect will not be achieved. Furthermore, the three-dimensional jagged structure is difficult to clean due to its complex shape, and is also expected to have poor maintenance, such as cracks easily occurring from the jagged grooves. Therefore, we came up with a method to reduce noise by finely dispersing the air flowing in the boundary layer of the blade surface and suppressing the generation of large turbulence by distinctively arranging a low-friction material on the blade surface of the cyclorotor, rather than using a three-dimensional jagged structure. An embodiment of the invention will now be described. As an example of a possible embodiment, a cyclorotor having a low-friction material such as carbon nanotubes or graphene vertically arranged in stripes on the front and / or back surface of the blade from the leading edge to the trailing edge and / or from the trailing edge to the leading edge by application or arranging the material may be considered. Because friction is low within the boundary layer of the blade surface portion where the low-friction material is arranged, the air flowing within the boundary layer tends to slip. Therefore, the air flow speed differs between "air flowing within the boundary layer of the blade surface portion where the low-friction material is not arranged" and "air flowing within the boundary layer of the blade surface portion where the low-friction material is arranged." According to this embodiment, the low friction material is arranged in stripes in the longitudinal direction on the front and / or rear surface of the blade from the leading edge to the trailing edge and / or from the trailing edge to the leading edge, so that the air flowing in the boundary layer on the front and / or rear surface of the blade is straightened and forms a dispersed pattern in which air with different flow speeds alternates vertically, suppressing the generation of large turbulence on the front and / or rear surface of the blade, thereby reducing noise caused by turbulence. Furthermore, since it does not have a complex three-dimensional shape such as a three-dimensional jagged structure, it is easy to clean and maintain, is less susceptible to dirt, and is less likely to crack.

Claims

[Claim 1] A cyclorotor, characterized in that a low-friction material is arranged in vertical stripes on the front and / or back surfaces of the blades from the leading edge to the trailing edge and / or from the trailing edge to the leading edge.