Rotorcraft and rotor blade

Abstract

To provide a rotorcraft which enables reduction of noise.SOLUTION: A rotorcraft includes a rotor blade and a prime mover. The rotor blade extends in a radial direction. The prime mover is configured to rotate the rotor blade. The rotor blade includes a blade body and a blade end portion. The blade end portion is disposed on an outer side of the blade body in a radial direction. The blade end portion includes a leading edge that inclines in a rotational direction to the outer side in the radial direction. The leading edge of the blade end portion is an edge facing in the rotation direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to rotorcraft and rotors. [Background technology]

[0002] In recent years, rotary-wing aircraft such as industrial drones have become popular. For example, a drone described in Patent Document 1 has a rotor and a motor that rotates the rotor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-184048 Summary of the Invention [Problem to be solved by the invention]

[0004] The rotary wing aircraft described above has a problem in that noise is generated by the rotation of the rotors. Therefore, an object of the present invention is to provide a rotary wing aircraft that can reduce noise. [Means for solving the problem]

[0005] A rotary wing aircraft according to a first aspect includes a rotor and a prime mover. The rotor extends in a radial direction. The prime mover is configured to rotate the rotor. The rotor has a wing main body and a wing tip. The wing tip is disposed radially outward relative to the wing main body. A leading edge of the wing tip is inclined radially outward in the direction of rotation. The leading edge of the wing tip is the edge facing the direction of rotation.

[0006] With this configuration, the leading edge of the blade tip is inclined radially outward in the direction of rotation, which increases the pressure on the upper surface of the blade tip. This reduces the difference between the pressure on the lower surface and the pressure on the upper surface of the blade tip, suppressing the generation of a turnaround vortex that flows from the lower surface to the upper surface of the blade tip. As a result, the generation of a tip vortex is suppressed, thereby reducing the noise generated by the rotation of the blade.

[0007] A rotorcraft according to a second aspect is the rotorcraft according to the first aspect, but configured as follows: The wing main body has at least one protrusion that protrudes in the direction of rotation. With this configuration, the protrusion can suppress the growth of vortices that occur behind the wing main body.

[0008] A rotary wing aircraft according to a third aspect is the rotary wing aircraft according to the first or second aspect, and is configured as follows: The wing tips are inclined upward and radially outward.

[0009] A rotor according to a fourth aspect is configured to rotate in a rotational direction. The rotor includes a blade body and a blade tip. The blade tip is disposed radially outward relative to the blade body. The leading edge of the blade tip is inclined radially outward in the rotational direction. [Effects of the Invention]

[0010] According to the present invention, noise can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] Plan view of a rotorcraft. [Figure 2] Plan view of the rotor blade. [Figure 3] Front view of the rotor blade. [Figure 4] 10 is a diagram showing the pressure distribution of a rotor blade with a first inclination angle α of 30° and a second inclination angle β of 0°. [Figure 5] 10 is a diagram showing the pressure distribution of a rotor blade in which the first inclination angle α is 0° and the second inclination angle β is 0°. [Figure 6]10 is a diagram showing the pressure distribution of a rotor blade with a first inclination angle α of 30° and a second inclination angle β of 15°. [Figure 7] 10 is a diagram showing the pressure distribution of a rotor blade with a first inclination angle α of 0° and a second inclination angle β of 15°. [Figure 8] 10 is a diagram showing the pressure distribution of a rotor blade with a first inclination angle α of −30° and a second inclination angle β of 15°. [Figure 9] FIG. 7 shows the pressure distribution of a rotor whose tip is longer than that of FIG. 6. [Figure 10] FIG. 7 shows the pressure distribution of a rotor with a blade tip that is shorter than that shown in FIG. 6. [Figure 11] FIG. 8 is a diagram showing the pressure distribution of the rotor blade in which only the leading edge of the blade tip of FIG. 7 is inclined. DETAILED DESCRIPTION OF THE INVENTION

[0012] The rotorcraft 100 and rotor 3 according to this embodiment will be described below with reference to the drawings. In the following description, the axial direction refers to the direction in which the rotation axis O of the rotor 3 extends. The circumferential direction refers to the circumferential direction of a circle centered on the rotation axis O, and the radial direction refers to the radial direction of a circle centered on the rotation axis O.

[0013] As shown in FIG. 1 , the rotary-wing aircraft 100 has a plurality of electric motors 2 (an example of a prime mover) and a plurality of rotors 3. In detail, the rotary-wing aircraft 100 has a main body 101, a plurality of arms 102, and a plurality of rotors 103. Each rotor 103 has an electric motor 2 and a plurality of rotors 3. In this embodiment, the rotary-wing aircraft 100 has four rotors 103. That is, in this embodiment, the rotary-wing aircraft 100 is a multicopter-type drone. Each rotor 103 has two rotors 3.

[0014] The main body 101 has a battery (not shown), a control unit (not shown), etc. The arms 102 extend radially from the main body 101. The rotors 103 are attached to the tips of the arms 102.

[0015] The electric motors 2 are configured to rotate the rotors 3. The rotation direction differs depending on the electric motor 2. For example, the electric motors 2 in the rotors 103 at the top right and bottom left of FIG. 1 rotate clockwise, while the electric motors 2 in the rotors 103 at the top left and bottom right of FIG. 1 rotate counterclockwise.

[0016] FIG. 2 is a plan view of the rotor 3, and FIG. 3 is a front view of the rotor 3. FIG. 3 is a front view of the rotor 3 as seen from the rotation direction side. As shown in FIGS. 2 and 3, the rotor 3 extends in the radial direction. Specifically, the rotor 3 extends radially outward from the center. The center is the part of the rotor 3 that is the center of rotation. In FIG. 2, the rotor 3 rotates counterclockwise around the rotation axis O. That is, in FIG. 2, the rotation direction of the rotor 3 is counterclockwise.

[0017] The rotor 3 has a blade main body 31 and a blade tip 32. The blade main body 31 extends in the radial direction. Specifically, the blade main body 31 extends from the center outward in the radial direction. The material of the rotor 3 is not particularly limited, but may be, for example, a composite material (such as CFRP) or an aluminum alloy.

[0018] As shown in Figure 2, the blade main body 31 has multiple protrusions 311 that protrude in the rotation direction. Since the rotation direction of the rotor 3 shown in Figure 2 is downward, the protrusions 311 protrude downward. In this embodiment, the blade main body 31 has two protrusions 311, but the number of protrusions 311 is not limited to this. In other words, the number of protrusions 311 may be one, or three or more.

[0019] The protrusions 311 are spaced apart from one another in the radial direction. The tip of each protrusion 311, i.e., the lower end in FIG. 2, is curved. The tip of each protrusion 311 may be sharp without being curved. Although each protrusion 311 protrudes in a triangular shape, the shape of each protrusion 311 is not limited to this. For example, each protrusion 311 may be rectangular or semicircular.

[0020] The blade tip 32 is disposed radially outward relative to the blade body 31. The leading edge 321 of the blade tip 32 is inclined radially outward in the direction of rotation. That is, the leading edge 321 of the blade tip 32 is inclined so that it faces the direction of rotation and also faces radially inward. Specifically, in Figure 2, the leading edge of the blade tip 32 extends at an incline downward and left towards the tip. The leading edge 321 of the blade tip 32 is the edge of the blade tip 32 that faces the direction of rotation.

[0021] The first inclination angle α of the leading edge 321 is not particularly limited, but can be, for example, about 10 to 50°. The first inclination angle α of the leading edge 321 of the wing tip 32 is the angle with respect to the leading edge of the wing main body 31. In other words, the leading edge 321 of the wing tip 32 is inclined with respect to the leading edge of the wing main body 31.

[0022] The trailing edge 322 of the blade tip 32 is inclined radially outward in the rotational direction. That is, the trailing edge 322 of the blade tip 32 is inclined in the same direction as the leading edge 321. Note that the trailing edge 322 of the blade tip 32 may not be inclined, or may be inclined in the opposite direction.

[0023] As shown in Figure 3, the blade tip 32 is inclined upward toward the radially outer side. The second inclination angle β of the blade tip 32 is not particularly limited, but may be, for example, about 5 to 25°. The second inclination angle β of the blade tip 32 is measured at the leading edge. The blade tip 32 does not have to be inclined in the vertical direction, and may be inclined downward.

[0024] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention. Note that the following modifications can basically be applied simultaneously.

[0025] (a) In the above embodiment, a multicopter drone is used as an example of the rotary-wing aircraft 100, but the rotary-wing aircraft 100 is not limited to this. For example, the rotary-wing aircraft 100 may be a helicopter.

[0026] (b) The number of rotors 3 and the number of rotors 103 are not limited to those in the above embodiment.

[0027] (c) In the above embodiment, the electric motor 2 is given as an example of the prime mover, but the prime mover may be an internal combustion engine or the like. [Example]

[0028] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0029] Fluid analysis was performed on a rotor 3 with a first inclination angle α of the blade tip 32 of 30° and a rotor 3 with a first inclination angle α of the blade tip 32 of 0°. The pressure distribution was calculated for each, and the results are shown in Figures 4 and 5. Note that Figure 4 shows the pressure distribution when the first inclination angle α is 30°, and Figure 5 shows the pressure distribution when the first inclination angle α is 0°. In Figures 4 and 5, the conditions other than the first inclination angle α are essentially the same, and the second inclination angle β is 0°. Figures 4 and 5 are plan views of the blade tip 32 viewed from above. Furthermore, the darker the color in Figures 4 and 5, the lower the pressure. For the fluid analysis, general-purpose thermal fluid analysis software was used, a K-ε turbulence model was adopted, and the rotational speed was 3000 r / min.

[0030] Comparing Figures 4 and 5, it can be seen that the pressure at the radially outer edge of the blade tip 32 is higher in Figure 4 than in Figure 5. In other words, the difference between the pressure on the lower surface side and the pressure on the upper surface side of the blade tip 32 is smaller in Figure 4 than in Figure 5, and it can be seen that the generation of a blade tip vortex is suppressed.

[0031] From the above results, it can be seen that by inclining the leading edge 321 of the blade tip 32 radially outward in the direction of rotation, the generation of the blade tip vortex is suppressed, and noise can be reduced.

[0032] Next, fluid analysis was performed in the same manner as above for the rotor 3 with the first inclination angle α of the blade tip 32 set to 30°, the rotor 3 with the first inclination angle α of the blade tip 32 set to 0°, and the rotor 3 with the first inclination angle α of the blade tip 32 set to -30°. The pressure distribution was calculated for each of these rotors, and the results are shown in Figures 6, 7, and 8. Note that Figure 6 shows the pressure distribution when the first inclination angle α is 30°, Figure 7 shows the pressure distribution when the first inclination angle α is 0°, and Figure 8 shows the pressure distribution when the first inclination angle α is -30°. In Figures 6 to 8, the conditions other than the first inclination angle α are essentially the same, and the second inclination angle β is 15°. Figures 6 to 8 are plan views of the blade tip 32 viewed from above. Furthermore, the darker the color in Figures 6 to 8, the lower the pressure.

[0033] Comparing Figures 6 and 7, it can be seen that the pressure at the radially outer edge of the blade tip 32 is higher in Figure 6 than in Figure 7. In other words, the difference between the pressure on the lower surface side and the pressure on the upper surface side of the blade tip 32 is smaller in Figure 6 than in Figure 7, and it can be seen that the generation of a blade tip vortex is suppressed.

[0034] Furthermore, a comparison of Figures 7 and 8 reveals that the pressure at the radially outer edge of the blade tip 32 is lower in Figure 8 than in Figure 7. In other words, the difference between the pressure on the lower surface side and the pressure on the upper surface side of the blade tip 32 is greater in Figure 8 than in Figure 7, and it was found that more blade tip vortices are generated.

[0035] From the above results, it can be seen that even if the second inclination angle β of the blade tip 32 is set to 15°, the generation of the blade tip vortex can be suppressed and noise can be reduced by inclining the leading edge 321 of the blade tip 32 radially outward in the direction of rotation.

[0036] Furthermore, a comparison of Figures 4 and 6 reveals that the pressure at the radially outer edge of the blade tip 32 is higher in Figure 6 than in Figure 4. That is, the difference between the pressure on the lower surface side and the pressure on the upper surface side of the blade tip 32 is smaller in Figure 6 than in Figure 4, and it can be seen that the generation of a blade tip vortex is more suppressed. In other words, it can be seen that the generation of a blade tip vortex is further suppressed when the blade tip 32 is inclined upward. Note that the conditions other than the second inclination angle β are the same between Figure 4 and Figure 6.

[0037] Figure 9 shows the pressure distribution of a rotor 3 in which the length of the blade tip 32 is 1.07 times that of the rotor 3 in Figure 6, and Figure 10 shows the pressure distribution of a rotor 3 in which the length of the blade tip 32 is 0.93 times that of the rotor 3 in Figure 6. Note that the conditions in Figures 6, 9, and 10 are essentially the same except for the length of the blade tip 32. These pressure distributions were calculated by performing the same fluid analysis as above.

[0038] A comparison of Figure 7 with Figures 9 and 10 shows that even if the length of the blade tip 32 is changed, by inclining the leading edge 321 of the blade tip 32 radially outward in the direction of rotation, the difference in pressure between the lower surface side and the upper surface side of the blade tip 32 is reduced, and the generation of a blade tip vortex is suppressed.

[0039] Figure 11 shows the pressure distribution of a rotor 3 in which only the leading edge 321 of the blade tip 32 is inclined at a first inclination angle α of 30°, and the trailing edge 322 is not inclined. The second inclination angle β of the blade tip 32 is 15°. Note that the conditions in Figures 7 and 11 are essentially the same except for the shape of the leading edge 321 of the blade tip 32. This pressure distribution was calculated by performing the same fluid analysis as above.

[0040] Comparing Figure 7 and Figure 11, it can be seen that the pressure at the radially outer edge of the blade tip 32 is higher in Figure 11 than in Figure 7. In other words, the difference between the pressure on the lower surface side and the pressure on the upper surface side of the blade tip 32 is smaller in Figure 11 than in Figure 7, and it can be seen that the generation of a blade tip vortex is suppressed more effectively. In other words, it can be seen that the generation of a blade tip vortex is further suppressed if only the leading edge 321 of the blade tip 32 is inclined in the direction of rotation. [Explanation of symbols]

[0041] 2: Electric motor 3: Rotor 31: Wing body 311: Convex part 32: Wing tip 321: Leading edge 100:Rotorcraft

Claims

1. a rotor blade extending in a radial direction; a prime mover configured to rotate the rotor; and Equipped with The rotor has a blade main body and a blade tip disposed radially outward from the blade main body, a leading edge of the blade tip facing the rotation direction is inclined radially outward in the rotation direction; Rotorcraft.

2. The blade main body has at least one protrusion protruding in the rotation direction. The rotorcraft of claim 1 .

3. The blade tip is inclined upward toward the radially outward direction. The rotorcraft of claim 1 .

4. A rotor configured to rotate in a rotational direction, a wing main body; a blade tip portion disposed radially outward relative to the blade main body portion; Equipped with a leading edge of the blade tip facing the rotation direction is inclined radially outward in the rotation direction; Rotor blade.

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