Rotary wing and rotary wing aircraft

Abstract

The present disclosure discloses a rotor blade including a plurality of protruding structures protruding convexly, wherein the plurality of protruding structures are sequentially spaced along the span direction of the blade, and there is a height difference between adjacent protruding structures.

Description

Technical Field

[0001] (Reference to Related Applications) This disclosure claims the priority of a Chinese patent application filed on December 26, 2022, with the application number 202211679092.1 and the invention title "Rotary Wing and Rotary Wing Aircraft", and all of its content is incorporated herein by reference.

[0002] (Technical Field) This disclosure relates to the field of aircraft technology, and particularly to rotary wings and rotary wing aircraft.

Background Art

[0003] Rotary wing aircraft can take off and land vertically and fly at low altitudes. Due to their unique flight advantages, they are widely used in military and civilian fields and will become the main means of transportation for future urban air traffic.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the invention is to provide a rotary wing and a rotary wing aircraft that can improve the noise reduction effect of the rotary wing in order to solve the technical problems in the related art.

Means for Solving the Problems

[0005] In a first aspect, this disclosure provides a rotary wing including a blade with a plurality of protruding structures convexly provided on its surface, wherein the plurality of protruding structures are sequentially spaced along the span direction of the blade, and there is a height difference between adjacent protruding structures.

[0006] In the rotary wing described above, the heights of the plurality of protruding structures decrease sequentially along the span direction of the blade, forming a stepped distribution.

[0007] In the rotary wing described above, the height difference between the protruding structure closest to the rotation center of the blade and the protruding structure farthest from the rotation center is 0.1 mm.

[0008] In the rotor blade described above, the protruding structure is a polygonal boss.

[0009] In the rotor blade described above, the polygonal boss includes a front portion having a triangular cross section.

[0010] In the rotor blade described above, the inner angle closest to the leading edge of the blade in the triangle is 30° or more and 90° or less.

[0011] In the rotor blade described above, the height of the protruding structure satisfies the following,

Number

[0012] In the rotor blade described above, the local Reynolds number satisfies the following requirements,

Number

[0013] In the rotor blade described above, the local Reynolds number is 10,000 or more and 500,000 or less.

[0014] In the rotor blade described above, the chordwise length of the protruding structure is 0.05c or more and 0.2c or less, where c is the local chord length.

[0015] In the rotor blade described above, the ratio of the spanwise width of the protrusion structure to the chordwise length of the protrusion structure is greater than 0.01 and less than 0.2.

[0016] In the rotor blade described above, the ratio of the spacing distance between adjacent protrusion structures to the spanwise width of the protrusion structure is greater than 0.1 and less than 2.

[0017] In the rotor blade described above, the spacing distance between the protrusion structure and the leading edge of the blade is 0.05c or more and 0.5c or less, where c is the local chord length.

[0018] In a second aspect, the present disclosure further provides a rotary wing aircraft including the rotary wing.

Advantages of the Invention

[0019] Compared with the related art, in the present disclosure, a plurality of protrusion structures are sequentially provided at intervals along the spanwise direction of the blade, and a plurality of protrusion structures with height differences are used to increase the contact area with air, realize a forced transition for the laminar separation bubbles on the blade, make the airflow fit better with the surface of the blade, reduce the thickness of the boundary layer at the trailing edge, thereby reducing the noise generation area and achieving the purpose of reducing noise.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0021] The embodiments described below with reference to the drawings are illustrative and are used only to explain the present disclosure and cannot be construed as a limitation on the present disclosure.

[0022] In the related art, rotary-wing aircraft can take off and land vertically and fly at low altitudes. Due to their unique flight advantages, they are widely applied in military and civilian fields and will become the main means of transportation for future urban air traffic. However, aircraft noise greatly limits its application scenarios, and the importance of reducing propeller aerodynamic noise has gradually emerged.

[0023] In order to solve the technical problems in the related art, the present disclosure provides a rotary wing and a rotary-wing aircraft that can improve the noise reduction effect of the rotary wing. The following is an explanation.

[0024] It should be noted here that all the parameters related to the present disclosure are defined in the normal manner in the art. Taking the blade in FIG. 2 as an example. The airfoil is defined as the two-dimensional cross-section at any position in the span direction of blade 1. A coordinate system is established with the rotation center as the origin. The rotation center means the rotation center point of blade 1. Blade 1 rotates around the rotation center. The end close to the rotation center of the airfoil is the blade body 3, and the end far from the rotation center of the airfoil is the blade tip 4. The extending direction from the blade body 3 to the blade tip 4 is defined as the span direction (from left to right in FIG. 2). Correspondingly, the direction perpendicular to the span direction is the chord direction. The chord direction of blade 1 includes a leading edge 5 and a trailing edge 6. The extending direction from the trailing edge 6 to the leading edge 5 is the rotation direction of the blade.

[0025] As shown in FIGS. 1 to 4, the rotor blade according to the present disclosure includes a blade 1 with a plurality of protrusion structures 2 protruding from its surface. The plurality of protrusion structures 2 are sequentially spaced along the span direction of the blade 1, and there is a height difference between adjacent protrusion structures 2. By using the plurality of protrusion structures 2 with height differences, the contact area with air is increased, the forced transition of the laminar separation bubble on the blade 1 is realized, the airflow fits better on the surface of the blade 1, the thickness of the boundary layer at the trailing edge is reduced, thereby reducing the noise generation area and achieving the purpose of reducing noise. Based on actual noise tests, the rotor blade provided with the protrusion structure 2 can achieve a maximum noise reduction of 5 dBA at the same tensile force.

[0026] In an embodiment according to the present disclosure, the heights of the plurality of protrusion structures 2 decrease sequentially along the span direction of the blade 1, forming a stepped distribution, which is advantageous for the forced transition of the laminar separation bubble, effectively reducing the total sound pressure level, and further reducing the noise of the entire blade 1. Preferably, the plurality of protrusion structures 2 exhibit an equidistant distribution, and there is a gap of the same size between adjacent protrusion structures 2. The height difference between the height of the protrusion structure 2 closest to the rotation center of the blade 1 and the height of the protrusion structure 2 farthest from the rotation center of the blade 1 is 0.1 mm. In one possible embodiment, the height of the protrusion structure closest to the rotation center of the blade 1 is 0.2 mm, the height of the protrusion structure 2 farthest from the rotation center of the blade 1 is 0.1 mm, and 40 to 50 protrusion structures 2 are provided therebetween. The heights of the plurality of protrusion structures 2 exhibit a linearly decreasing distribution. The protrusion structure 2 farthest from the rotation center of the blade 1 is located at the end of the blade tip 4, and the local span direction position r of the protrusion structure 2 closest to the rotation center of the blade 1 is 1 / 4 - 1 / 3 of the length R from the blade tip 4 to the rotation center of the blade 1.

[0027] As will be understood by those skilled in the art, the plurality of protrusion structures 2 may form other shaped distributions. For example, they may be arranged along the span direction of the blade 1 to form a sawtooth distribution, or may exhibit periodic height changes along the span direction of the blade 1.

[0028] To further reduce noise, referring to FIGS. 3 and 4, the protrusion structure 2 is a polygonal boss, and the end of the blade 1 of the polygonal boss facing the leading edge 5 forms a triangular front portion 7. The front portion 7 includes two inclined outer wall surfaces. One end of the two outer wall surfaces intersects, and the other end of the two outer wall surfaces is connected to the two side surfaces of the protrusion structure 2 respectively. The opening of the front portion 7 is provided toward the trailing edge 6 of the blade 1, and the extending direction of the center line of the front portion 7 is parallel to the rotation direction of the blade 1. The front portions 7 of the plurality of protrusion structures 2 are provided parallel to each other. Preferably, the inner angle of the triangle closest to the leading edge 5 of the blade is 30° or more and 90° or less. Such an optimal design for the front end of the protrusion structure 2 can weaken the vortex at the front end of the protrusion structure 2, reduce the interference of the vortex, and achieve the purpose of reducing noise.

[0029] In the embodiment according to the present disclosure, a recess 8 is provided at the end of the blade 1 of the protrusion structure 2 facing the trailing edge 6. The recess 8 is an arrow-shaped concave groove formed by recessing at the rear part of the protrusion structure 2. The concave groove has an arrow shape and includes two inclined inner wall surfaces. One end of the two inner wall surfaces intersects, and the other end of the two inner wall surfaces is connected to the two side surfaces of the protrusion structure 2 respectively. The opening of the recess 8 is provided toward the trailing edge 6 of the blade 1, and the extending direction of the center line of the recess 8 is parallel to the rotation direction of the blade 1. The recesses 8 of the plurality of protrusion structures 2 are provided parallel to each other. Preferably, the included angle of the recess 8 is 30° - 90°. Such an optimal design for the rear end of the protrusion structure 2 can weaken the vortex at the rear end of the protrusion structure 2, reduce the interference of the vortex, and achieve the purpose of reducing noise.

[0030] In the embodiment according to the present disclosure, the protrusion structure 2 has a set height t, and the height satisfies the following:

Equation

[0031] By controlling the size and arrangement of the protrusion structure 2, the total sound pressure level can be effectively reduced. As can be seen from the first formula, the height t of the protrusion structure 2 changes, mainly based on the value of the local Reynolds number Re. Specifically, along the span direction of the blade 1, the farther away from the rotation center, the larger the local Reynolds number Re, and the height t of the protrusion structure 2 decreases in a gradient along the span direction. As a result, the airflow fits better on the surface of the blade 1, which is beneficial for the forced transition of the laminar separation bubble, and the optimal noise reduction of the entire blade 1 can be realized.

[0032] In the embodiments according to the present disclosure, the range of the value of k is 0.01 - 0.2, including the end point values. The value of the proportionality coefficient k can maintain a reasonable correspondence relationship among the local chord length c, the local Reynolds number Re, and the height t of the protrusion structure 2. When the local chord length c and the local Reynolds number Re change, the protrusion structure 2 undergoes an appropriate height change. The change in the height t of the protrusion structure 2 can achieve both the aerodynamic performance and noise suppression of the aircraft, and can reduce the rotor blade noise to a certain extent as long as it does not affect the aerodynamic efficiency of the blade 1.

[0033] Furthermore, the value of Re satisfies the following:

Equation

[0034] The local Reynolds number Re is the air density TIFF2025523951000012.tif9119, the rotational angular velocity of the blade 1 TIFF2025523951000013.tif9119, local spanwise position r, local chord length c, and kinematic viscosity of air It changes with the numerical change of TIFF2025523951000014.tif9119. When the rotational speed of blade 1 is constant, the local Reynolds number Re is mainly correlated with the local spanwise position r and the local chord length c. The higher the local Reynolds number Re, the smaller the height t of the protrusion structure 2; the lower the local Reynolds number Re, the larger the height t of the protrusion structure 2. The protrusion structure 2 with a higher height is closer to the rotation center, which is beneficial to improving the aerodynamic efficiency of the rotary-wing aircraft. To improve the aerodynamic efficiency of the rotary-wing aircraft, in the case of the same lift surface distribution, the required rotational speed becomes lower, and it becomes possible to reduce the noise generated during the flight of the rotary-wing aircraft. Preferably, the local Reynolds number is 10,000 or more and 500,000 or less in order to obtain a higher noise reduction effect.

[0035] In an embodiment according to the present disclosure, the protrusion structure 2 has a chordwise length L set to be 0.05c or more and 0.2c or less. L is the chordwise length of the protrusion structure 2, and c is the local chord length. The chordwise length L of the protrusion structure 2 maintains a direct proportional relationship with the local chord length c. The longer the local chord length c, the longer the chordwise length L of the protrusion structure 2, and the larger the action area of the protrusion structure 2, thereby reducing the noise generation area.

[0036] In an embodiment according to the present disclosure, the protrusion structure 2 has a set spanwise width h1. The ratio of the spanwise width h1 to the chordwise length L of the protrusion structure is greater than 0.01 and less than 0.2. H1 is the spanwise width of the protrusion structure 2, and L is the chordwise length of the protrusion structure 2. By presenting an elongated structure, the protrusion structure 2 allows the airflow to flow gently to the trailing edge, and better aerodynamic performance and noise reduction effect can be obtained.

[0037] In an embodiment according to the present disclosure, the ratio of the spacing distance h2 between a plurality of protrusion structures 2 to the spanwise width h1 of the protrusion structure 2 is greater than 0.1 and less than 2. h1 is the spanwise width of the protrusion structure 2, and h2 is the spacing distance between two adjacent protrusion structures 2. In order to further reduce the noise caused by the rotation of the blade 1, as shown in FIGS. 1 and 2, the plurality of protrusion structures 2 are provided close to the leading edge 5 of the blade 1. Specifically, the spacing distance between the protrusion structure 2 and the leading edge 5 of the blade 1 is not less than 0.05c and not more than 0.5c.

[0038] d is the spacing distance between the protrusion structure 2 and the leading edge 5 of the blade 1, and c is the local chord length. Based on the flow characteristics of a low Reynolds number laminar airfoil, the laminar separation bubble is located near the leading edge 5 of the blade 1. By providing the protrusion structure 2 close to the leading edge 5 of the blade 1, the laminar separation bubble at the leading edge 5 can be forced to transition, the spanwise flow of air at the leading edge 5 of the blade 1 can be cut off when the blade 1 rotates, the vortices formed at the leading edge 5 of the blade 1 can be reduced, and the noise caused by the rotation of the blade 1 can be further reduced.

[0039] As shown in FIGS. 1 to 4, the cross-section of the protrusion structure 2 is an arrow-shaped structure. As will be understood by those skilled in the art, the cross-section of the protrusion structure 2 may further include regular or irregular shapes such as circular, triangular, rectangular, or polygonal shapes, which are not limited herein.

[0040] Based on the above embodiments, the present disclosure provides a rotary-wing aircraft including the above rotary wing and having all the beneficial effects thereof, which will not be further described herein.

[0041] The structure, features, and effects of the present disclosure have been described in detail based on the embodiments shown in the drawings above. The above are only one or more embodiments of the present disclosure, but the present disclosure is not limited to the implementation scope as shown in the drawings. When implemented according to the concept of the present disclosure or when the equivalent embodiments modified by equivalent changes do not exceed the scope included in the specification and the drawings, they should be within the protection scope of the present disclosure.

Description of Reference Numerals

[0042] 1-blade 2-protrusion structure 3-blade body 4-blade tip 5-leading edge 6-trailing edge 7-front part 8-recess.

Claims

1. A rotating wing including blades provided with a plurality of protrusion structures on the surface, wherein the plurality of protrusion structures are provided at intervals along the span direction of the blade, and there is a height difference between adjacent protrusion structures. Rotating wing.

2. The heights of the plurality of protrusion structures gradually decrease along the span direction of the blade, forming a stepped distribution. The rotating wing according to claim 1.

3. The height difference between the protrusion structure closest to the rotation center of the blade and the protrusion structure farthest from the rotation center is 0.1 mm. The rotating wing according to claim 2.

4. The protrusion structure is a polygonal boss. The rotating wing according to claim 1.

5. The polygonal boss includes a front part with a triangular cross-section. The rotating wing according to claim 4.

6. The inner angle closest to the leading edge of the blade in the triangle is 30° or more and 90° or less. The rotating wing according to claim 5.

7. The height of the protrusion structure satisfies the following: 【Number 0001】 t is the height of the protrusion structure, k is a proportionality coefficient, and the value range of k is 0.01 - 0.2, c is the local chord length, Re is the local Reynolds number. The rotating wing according to claim 1.

8. The local Reynolds number satisfies the following requirements: 【Number 0002】 【Number】 is the air density, 【Number】 is the rotational angular velocity of the blade, r is the local spanwise position, 【Number】 is the kinematic viscosity of air. The rotating wing according to claim 7.

9. The local Reynolds number is 10,000 or more and 500,000 or less. The rotating wing according to claim 8.

10. The chordwise length of the protrusion structure is 0.05c or more and 0.2c or less, where c is the local chord length. The rotating wing according to claim 1.

11. The ratio of the spanwise width of the protrusion structure to the chordwise length of the protrusion structure is greater than 0.01 and less than 0.

2. The rotating wing according to claim 1.

12. The ratio of the spacing distance between adjacent protrusion structures to the spanwise width of the protrusion structure is greater than 0.1 and less than 2. The rotating wing according to claim 1.

13. The spacing distance between the protrusion structure and the leading edge of the blade is 0.05c or more and 0.5c or less, where c is the local chord length. The rotating wing according to claim 1.

14. A rotary-wing aircraft including the rotating wing according to any one of claims 1 - 13.

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