Silent cyclorotor with low-friction material placed on the blade surface.

Abstract

While cyclorotors are quieter than conventional propeller-type rotors, 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 its complex shape makes it prone to dirt and difficult to maintain. Therefore, instead of a jagged structure, this design provides a cyclorotor form that reduces noise by strategically arranging low-friction materials. [Solution] By arranging low-friction material in a vertical stripe pattern on the surface and / or back of the blade, from the leading edge to the trailing edge and / or from the trailing edge to the leading edge, the air flowing within the boundary layer on the surface and / or back of the blade is straightened, forming a dispersed pattern in which air of different velocities is arranged alternately in a vertical direction, thereby suppressing the generation of large turbulence on the surface and / or back of the blade. As a result, noise generated from turbulence is reduced.

Description

Background Art

[0001] By means of the comb-like three-dimensional serrated structure on the wings, owls can finely disperse the air flowing within the boundary layer of the wings, suppress the generation of large-scale turbulence, reduce the noise generated from the turbulence, and fly quietly. There are already noise reduction designs applying this principle, such as the introduction of three-dimensional serrated structures in the blades of wind turbines and the fan blades of aircraft engines. Detailed Description of the Invention

[0002] Cyclo-rotors have better mobility compared to conventional propeller systems and are expected to be installed in aircraft such as drones, wind power generation systems, and blowers. Although cyclo-rotors reduce noise by effectively controlling the air flow, it is desirable to further reduce the noise. Regarding the noise reduction design for cyclo-rotors, there is currently no such noise reduction design using a three-dimensional serrated structure on the blade surface as described in 0001, but it is considered as one of the methods to reduce noise. However, three-dimensional serrated structures tend to have complex shapes, and it is considered that dirt easily adheres to and accumulates in the grooves of the serrated structures. If dirt adheres to and accumulates in the grooves of the serrated structure, the effect of finely dispersing the air flowing within the boundary layer of the blade surface will be lost, and thus the noise reduction effect cannot be exerted. And due to their complex shapes, three-dimensional serrated structures are difficult to clean, resulting in poor maintainability, and it is also expected that they have poor durability, such as being prone to cracking starting from the grooves of the serrated structure. Therefore, instead of a three-dimensional serrated structure, a method was considered where a low-friction material is characteristically arranged on the blade surface of the cyclo-rotor to finely disperse the air flowing within the boundary layer of the blade surface and suppress the generation of large-scale turbulence to reduce noise. Embodiments of the invention will be described. As an example of a conceivable embodiment, a cyclo-rotor is considered in which a low-friction material such as carbon nanotubes or graphene is arranged in a stripe shape in the longitudinal direction on the front and / or back surfaces of the blade by means of coating or arrangement of materials from the leading edge to the trailing edge and / or from the trailing edge to the leading edge of the blade. Within the boundary layer of the blade surface where low-friction material is placed, the friction is low, so the air flowing within the boundary layer is slippery. Therefore, the airflow velocity differs between "air flowing within the boundary layer of the blade surface where low-friction material is not placed" and "air flowing within the boundary layer of the blade surface where low-friction material is placed". According to this embodiment, by arranging low-friction material in a vertical stripe pattern on the surface and / or back of the blade from the leading edge to the trailing edge and / or from the trailing edge to the leading edge, the air flowing within the boundary layer on the surface and / or back of the blade is rectified, forming a dispersed pattern in which air of different velocities is arranged alternately in a vertical direction, thereby suppressing the generation of large turbulence on the surface and / or back of the blade. As a result, noise generated from turbulence is reduced. Furthermore, because it does not have a complex three-dimensional shape such as a jagged structure, it is easy to clean and maintain, less prone to dirt accumulation, and less likely to crack.

Claims

[Claim 1] A cyclorotor characterized by having low-friction material arranged in a vertical stripe pattern on the surface and / or back of the blade, from the leading edge to the trailing edge and / or from the trailing edge to the leading edge.