flying object

Abstract

To reduce pressure resistance of a rotor head in a flight vehicle.SOLUTION: A flight vehicle is equipped with a rotor shaft protruding upward from a fuselage, a rotor head connected to the rotor shaft, above the fuselage, and a pair of plate units arranged above the fuselage and extended in a longitudinal direction at a right side and a left side of the rotor shaft. The pair of plate units include front ends, rear ends, inside surfaces pointing inward in a lateral direction, and outside surface pointing outward in the lateral direction, respectively. The front ends of the pair of plate units separate from each other in the lateral direction. The rear ends of the pair of plate units separate from each other in the lateral direction. The pair of plate units have shapes in which pressure at the outside surfaces becomes lower than pressure at the inside surfaces during a forward flight.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an air vehicle with rotors. [Background technology]

[0002] When a rotorcraft such as a helicopter flies forward, air resistance occurs. Air resistance limits the maximum speed and reduces fuel consumption. Patent Document 1 discloses a fairing for reducing the resistance generated by a rotor shaft that protrudes upward from the fuselage of a helicopter. The fairing covers the rotor shaft in the space between the fuselage and the rotor head, and has a streamlined shape that tapers toward the rear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,232,929 Summary of the Invention [Problem to be solved by the invention]

[0004] The resistance that a rotary wing aircraft experiences during forward flight can be caused by a variety of factors. The inventors have noted that a wake region is created when airflow attaches to the rotor head and flows around to the rear of the rotor head, and the pressure resistance of the rotor head caused by this wake region becomes resistance to the aircraft.

[0005] Therefore, an object of the present disclosure is to reduce the pressure resistance of a rotor head in an aircraft. [Means for solving the problem]

[0006] An aircraft according to one aspect of the present disclosure includes a fuselage, a rotor shaft protruding upward from the fuselage, a rotor head connected to the rotor shaft above the fuselage, and a pair of plate units disposed above the fuselage and extending in the front-to-rear direction to the right and left of the rotor shaft. Each of the pair of plate units includes a front end, a rear end, an inner surface facing inward in the left-to-right direction, and an outer surface facing outward in the left-to-right direction. The front ends of the pair of plate units are spaced apart from each other in the left-to-right direction. The pair of plate units have a shape such that the pressure on the outer surface side is lower than the pressure on the inner surface side during forward flight. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, air that enters between a pair of plate units from the front during forward flight of an aircraft flows rearward, but also flows from the inner surface of the plate units over the upper ends of the plate units to the outer surface of the plate units due to the pressure difference. As a result, the air flow that passes through the plate units generates a longitudinal vortex that, when viewed from the front-to-rear direction, moves from the outside of the plate units, around below the plate units, and returns to the inside of the plate units. Therefore, the air in this vortex flows upward from the inner region of the plate units in the left-to-right direction, suppressing the pressure drop in the wake region of the rotor head and reducing the pressure resistance of the rotor head. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of an aircraft according to an embodiment. [Figure 2] FIG. 2 is a side view of the main part of the aircraft of FIG. [Figure 3] FIG. 3 is a plan view of the main part of the aircraft of FIG. [Figure 4] FIG. 4 is a plan view illustrating the air flow around the plate unit of FIG. [Figure 5] FIG. 5 is a rear view illustrating the air flow around the plate unit of FIG. [Figure 6A] FIG. 6A is a side view showing the analysis results of the streamline distribution of the comparative example. [Figure 6B] FIG. 6B is a side view showing the analysis results of pressure distribution in the comparative example. [Figure 6C] FIG. 6C is a plan view showing the analysis results of pressure distribution in a comparative example. [Figure 7A] FIG. 7A is a side view showing the analysis results of the streamline distribution in the example. [Figure 7B] FIG. 7B is a side view showing the analysis results of pressure distribution in the example. [Figure 7C] FIG. 7C is a plan view showing the analysis results of the pressure distribution in the example. [Figure 8A] FIG. 8A is a plan view of a first modified example of the rotor head of FIG. 1 and its vicinity. [Figure 8B] FIG. 8B is a side view of the rotor head and its vicinity in FIG. 8A. [Figure 9A] FIG. 9A is a plan view of a second modified example of the rotor head of FIG. 1 and its vicinity. [Figure 9B] FIG. 9B is a side view of the rotor head and its vicinity in FIG. 9A. [Figure 10A] FIG. 10A is a plan view of a third modified example of the rotor head of FIG. 1 and its vicinity. [Figure 10B] FIG. 10B is a side view of the rotor head and its vicinity in FIG. 10A. [Figure 11A] 11A is a plan view of a first modified example of the plate unit of FIG. 3. FIG. [Figure 11B] 11B is a plan view of a second modified example of the plate unit of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings.

[0010] Figure 1 is a perspective view of an aircraft 1 according to an embodiment. As shown in Figure 1, aircraft 1 is a rotary-wing aircraft equipped with a main rotor 3, and as an example, aircraft 1 is a compound helicopter equipped with a fuselage 2, main rotor 3, a pair of main wings 4, a pair of propellers 5, a pair of horizontal stabilizers 6, and a vertical stabilizer 7. Note that aircraft 1 may also be a normal helicopter other than a compound helicopter, and the number of main rotors may be two or more.

[0011] In the description of this embodiment, when the aircraft 1 has landed, the extension direction of the rotor shaft 8 (described below) connecting the fuselage 2 and the rotor head 16 of the main rotor 3 is defined as the vertical direction of the aircraft 1, and the direction in which the rotor head 16 is located relative to the fuselage 2 is defined as the upward direction. A plane perpendicular to the vertical direction is defined as a horizontal plane, and each direction within the horizontal plane is defined as the horizontal direction. Additionally, within the horizontal plane, the extension direction of the pair of main wings 4 is defined as the left-right direction of the aircraft 1, and the direction perpendicular to the left-right direction is defined as the fore-aft direction. In this case, the direction in which the pair of horizontal stabilizers 6 and vertical stabilizers 7 are located relative to the center of the fuselage 2 is the rearward direction, and the opposite direction is the forward direction.

[0012] The fuselage 2 has a front section 11, a middle section 12, a top section 13, and a rear section 14. The front section 11 of the fuselage 2 has a shape that tapers forward. A pair of main wings 4 are connected to the middle section 12 of the fuselage 2, protruding from the middle section 12 on both the left and right sides. Propellers 5 are provided on the main wings 4. The top section 13 of the fuselage 2 protrudes upward from the middle section 12 in a columnar shape. The rear section 14 of the fuselage 2 has a shape that tapers backward. Connected to the rear section 14 of the fuselage 2 are a vertical tail 7 that protrudes upward from the rear section 14, and a pair of horizontal tails 6 that protrude from the rear section 14 on both the left and right sides.

[0013] The main rotor 3 is disposed above the top 13 of the fuselage 2. As shown in FIG. 2, the main rotor 3 is rotationally driven by a rotor shaft 8 that is driven by a prime mover disposed inside the fuselage 2, thereby generating lift. The main rotor 3 has a rotor head 16 and a plurality of rotor blades 17. The rotor head 16 is connected to the rotor shaft 8 that protrudes upward from the top 13. The plurality of rotor blades 17 protrude radially from the rotor head 16 in a substantially horizontal direction.

[0014] The rotor head 16 is the portion of the main rotor 3 excluding the rotor blades 17 that does not undergo translational or rotational displacement in the fixed coordinate system of the rotor shaft 8. In other words, the rotor head 16 is the portion of the main rotor 3 excluding the rotor blades 17 that only rotates around the axis of the rotor shaft 8 during flight.

[0015] The rotor head 16 in this embodiment has a circular disk shape in a plan view. The rotor head 16 has, for example, a hub connected to the rotor shaft 8 and a hub cap that entirely covers the hub and has a disk-shaped outer shape. The outer shape of the rotor head 16 is the outer shape of the hub cap. If the actual rotor head is non-circular in a plan view, it is sufficient to assume that the rotation trajectory of the radially outer end of the rotor head is the outer shape of the rotor head 16 in terms of fluid dynamics. Note that if the actual rotor head is circular in a plan view, the rotation trajectory of the radially outer end of the rotor head matches the outer shape of the actual rotor head 16.

[0016] Figure 2 is a side view of the main parts of the aircraft 1 of Figure 1. Figure 3 is a plan view of the main parts of the aircraft 1 of Figure 1. As shown in Figures 2 and 3, the top 13 of the fuselage 2 has a flat top surface 13a that extends horizontally. An upper opening 13b through which the rotor shaft 8 passes is defined in the top surface 13a. A disc-shaped rotor head 16 is disposed above the top surface 13a. In this embodiment, the top 13 is longer in the front-to-rear direction than in the left-to-right direction. The top 13 has a bilaterally symmetrical shape in a plan view. The top 13 has a streamlined shape that extends in the front-to-rear direction in a plan view.

[0017] The shape of the top 13 is not limited to this, but as will be described later, a shape tapering toward the rear of the top 13 is less likely to obstruct the flow created by the pair of plate units 30 of the present disclosure than other shapes, and is a shape that can be suitably applied to the pair of plate units 30. The rotor shaft 8 protrudes upward from inside the fuselage 2 through the upper opening 13b. The rotor head 16 is connected to the rotor shaft 8 above the fuselage 2. The top surface 13a faces the lower surface 16b of the rotor head 16 in the vertical direction.

[0018] The top portion 13 is provided with a pair of plate units 30 protruding upward from the top surface 13a. The pair of plate units 30 are arranged separately on the right and left sides of the rotor shaft 8. One of the pair of plate units 30 extends in the front-rear direction to the right of the rotor shaft 8, and the other of the pair of plate units 30 extends in the front-rear direction to the left of the rotor shaft 8. The vertical height of the plate units 30 is smaller than the vertical distance between the top surface 13a and the rotor head 16. In other words, the upper end of the plate unit 30 is located below the lower surface 16b of the rotor head 16. The lower surface 16b of the rotor head 16 refers to the surface that forms the lower contour of the rotor head 16 and faces downward. The right plate unit 30 and the left plate unit 30 are arranged symmetrically with respect to a virtual vertical plane that passes through the axis of the rotor shaft 8 and extends in the front-rear direction.

[0019] Each of the pair of plate units 30 is a plate extending in the front-rear direction and having a main surface facing in the left-right direction. The plate unit 30 includes a front end 30a, a rear end 30b, an inner surface 30c facing inward in the left-right direction, and an outer surface 30d facing outward in the left-right direction. In this embodiment, the pair of plate units 30 extend along the outer left-right edge of the top surface 13a of the top portion 13.

[0020] The plate unit 30 of this embodiment has a substantially rectangular shape in a side view. Specifically, the front end of the plate unit 30 has a tapered shape with an oblique ridgeline from top to bottom in a side view, and the rear end 30b of the plate unit 30 extends in a direction perpendicular to the top surface 13a. The thickness of the plate unit 30 in this embodiment is, for example, constant. However, the plate unit 30 is not limited to this and various shapes can be adopted. For example, the plate thickness of the plate unit 30 may vary along the front-to-rear direction. In other words, the arrangement of the inner surface 30c and the outer surface 30d of the plate unit 30 in a plan view can be determined independently.

[0021] The front ends 30a of the pair of plate units 30 are spaced apart from each other in the left-right direction. The rear ends 30b of the pair of plate units 30 are spaced apart from each other in the left-right direction. The left-right distance L1 between the front ends 30a of the pair of plate units 30 is longer than the left-right distance L2 between the rear ends 30b of the pair of plate units 30.

[0022] The front end 30a of the plate unit 30 is located rearward of the front end of the top surface 13a. The front end 30a of the plate unit 30 is located forward of the rotor shaft 8. The rear end 30b of the plate unit 30 is located forward of the rear end of the top surface 13a. The rear end 30b of the plate unit 30 is located rearward of the rotor shaft 8. The top 13 has a rear portion 13c that is rearward of the rear end 30b of the plate unit 30. The rear portion 13c of the top 13 has a shape that tapers rearward.

[0023] The rear end 30b of the plate unit 30 is disposed forward of the rear end 16a of the rotation trajectory of the radially outer end of the rotor head 16. In this embodiment, the front end 30a of the plate unit 30 is disposed rearward of the front end of the rotor head 16, but may be disposed forward of the front end of the rotor head 16. At least a portion of the plate unit 30 may overlap with the rotor head 16 in a plan view.

[0024] Figure 4 is a plan view illustrating the airflow around the plate unit 30 of Figure 3 during forward flight of the aircraft 1. Figure 5 is a rear view illustrating the airflow around the plate unit 30 of Figure 4 during forward flight of the aircraft 1. As shown in Figures 4 and 5, the inner surface 30c of the plate unit 30 extends obliquely inward and rearward in the left-right direction. The outer surface 30d of the plate unit 30 extends obliquely inward and rearward in the left-right direction.

[0025] In this embodiment, the thickness of the plate unit 30 is constant, so the entire plate unit 30 extends diagonally inward and rearward in the left-right direction. When the aircraft 1 flies forward, the plate unit 30 has a non-zero angle of attack with respect to the surrounding flow field. Note that although the plate unit 30 in this embodiment has an arch shape that protrudes outward in the left-right direction, it is made linear as shown in the explanatory diagram in FIG. 4. In other words, the effects described below can be obtained even if the plate unit 30 has a linear shape as shown in FIG. 4.

[0026] In the flow field around the plate unit 30 during forward flight of the aircraft 1, a stagnation point P occurs on the inner surface 30c of the plate unit 30, and the pressure on the inner surface 30c side of the plate unit 30 becomes higher than the pressure on the outer surface 30d side of the plate unit 30. Furthermore, in the flow field around the plate unit 30 during forward flight of the aircraft 1, the air flow along the outer surface 30d of the plate unit 30 is bent obliquely relative to the front-to-rear direction, increasing the flow velocity and lowering the pressure on the outer surface 30d side of the plate unit 30. In this way, the plate unit 30 has a shape in which the pressure on the outer surface 30d side is lower than the pressure on the inner surface 30c side during forward flight.

[0027] During forward flight of the aircraft 1, air that enters between the pair of plate units 30 from the front flows from the inner surface 30c of the plate unit 30 over the upper end of the plate unit 30 to the outer surface 30d of the plate unit 30 due to the pressure difference between the inner surface 30c and the outer surface 30d of the plate unit 30. As a result, the air flow that has passed through the plate unit 30 generates a longitudinal vortex V that flows from the outside of the plate unit 30, around below the plate unit 30, and returns to the inside of the plate unit 30, as viewed from the front-to-rear direction. The air in this longitudinal vortex V induces an upward flow from an inner region of the plate unit 30 in the left-to-right direction, and this flow passes through the wake region W of the rotor head 16. This prevents the air flow from attaching to the rotor head 16 and going around to the rear side of the rotor head 16, thereby suppressing a drop in pressure in the wake region W of the rotor head 16.

[0028] The distance L2 in the left-right direction between the rear ends 30b of a pair of plate units 30 is a value between two and six times the maximum height H of the plate units 30 in the up-down direction. If the radius of a longitudinal vortex V that can be generated by the plate unit 30 and pass through the wake region W is R and the length of the plate unit 30 in the front-to-rear direction is L, then when the aspect ratio (= H / L) of the plate unit 30 is less than 1, it can be assumed that R = H. When the aspect ratio (= H / L) of the plate unit 30 is 1 or more, it can be empirically assumed that R = L, and the range of L2 can be defined as between two and six times L using R = L.

[0029] The radius R of the longitudinal vortices V can be defined as the radius of curvature of the outer edge of the region where vorticity exists. For example, in the Rankine vortex model, it can be defined as the radius of curvature of the line where the rotational velocity is maximum. If the distance L2 is at least twice the radius R, it is possible to suppress interference between the respective longitudinal vortices V generated behind the left and right plate units 30, i.e., loss due to collision in the vortex swirling direction. Furthermore, if the distance L2 is no more than six times the radius R, it is possible to effectively induce upward flows of the left and right longitudinal vortices V, and the flows of the longitudinal vortices V can effectively reach the wake region W of the rotor head 16.

[0030] 3, the rear part 13c of the apex 13 has a shape that tapers toward the rear, making it difficult for the longitudinal vortex V behind the plate unit 30 to hit the apex 13, thereby promoting the upward flow of the longitudinal vortex V. The longitudinal position of the rear end 30b of the plate unit 30 may be the same as or further forward than the longitudinal position of the rear end of the apex 13.

[0031] Below, we will explain the results of a simulation analyzing the flow field around an aircraft equipped with the plate unit 30 as an example, and the results of a simulation analyzing the flow field around a conventional aircraft not equipped with the plate unit 30 as a comparative example.

[0032] In this analysis, a model is used in which the rotor blades 17 are omitted and only the disk-shaped rotor head 16 is used as the main rotor. In an actual main rotor, the flow field is disturbed locally and instantaneously by the rotor blades, but the global flow field, including the area around the rotor head 16, is not affected by the rotor blades. The flow field near the rotor head 16 converges to the same flow field as when there are no rotor blades immediately after the rotor blades pass. Therefore, even when there are rotor blades, the flow field around the rotor head 16 is the same as when there are no rotor blades when viewed on a time average.

[0033] FIG. 6A is a side view showing the analysis results of the streamline distribution of the comparative example. FIG. 6B is a side view showing the analysis results of the pressure distribution of the comparative example. FIG. 6C is a plan view showing the analysis results of the pressure distribution of the comparative example. As shown in FIG. 6A, in the comparative example related to a conventional flying object, a typical wake is observed behind the rotor head 16. As shown in FIGS. 6B and 6C, in the comparative example, a large pressure drop occurs in the wake region of the rotor head 16. This increases the pressure resistance to the forward movement of the rotor head 16.

[0034] FIG. 7A is a side view showing the analysis results of the streamline distribution of the embodiment. FIG. 7B is a side view showing the analysis results of the pressure distribution of the embodiment. FIG. 7C is a plan view showing the analysis results of the pressure distribution of the embodiment. As shown in FIG. 7A, in the embodiment relating to the aircraft equipped with the plate unit 30, the airflow that passes rearward through the plate unit 30 heads obliquely upward and passes through the wake region of the rotor head 16. As shown in FIGS. 7B and 7C, in the embodiment, no significant pressure drop occurs in the wake region of the rotor head 16. Therefore, pressure resistance to the forward movement of the rotor head 16 is small.

[0035] According to the configuration described above, the plate unit 30 has a shape in which the pressure on the outer surface 30d side is lower than the pressure on the inner surface 30c side during forward flight of the aircraft 1. Therefore, air that enters between the pair of plate units 30 from the front during forward flight of the aircraft 1 flows rearward, but due to the pressure difference, flows from the inner surface 30c side of the plate unit 30 over the upper end of the plate unit 30 to the outer surface 30d side of the plate unit 30.

[0036] As a result, the air flow that has passed through the plate unit 30 generates a vertical vortex V that, when viewed from the front-to-rear direction, moves from the outside of the plate unit 30, around below the plate unit 30, and returns to the inside of the plate unit 30. Therefore, the air in this vertical vortex V flows upward from the region inside the left-to-right direction of the plate unit 30, thereby suppressing the pressure drop in the wake region W of the rotor head 16 and reducing the pressure resistance of the rotor head 16.

[0037] The inner surface 30c of the plate unit 30 extends obliquely inward and rearward in the left-right direction. Therefore, in the flow field around the plate unit 30 during forward flight of the aircraft 1, a stagnation point P occurs on the inner surface 30c of the plate unit 30, and the pressure on the inner surface 30c side of the plate unit 30 becomes higher than the pressure on the outer surface 30d side of the plate unit 30. This promotes the generation of the aforementioned longitudinal vortex V, thereby reducing the pressure resistance of the rotor head 16.

[0038] The outer surface 30d of the plate unit 30 extends obliquely inward and rearward in the left-right direction. Therefore, in the flow field around the plate unit 30 during forward flight of the aircraft 1, the air flow along the outer surface 30d of the plate unit 30 is bent obliquely, increasing the flow velocity and lowering the pressure on the outer surface 30d side of the plate unit 30. This promotes the generation of the aforementioned longitudinal vortex V, thereby reducing the pressure resistance of the rotor head 16.

[0039] The rear ends 30b of the pair of plate units 30 are disposed forward of the rear end 16a of (the rotation locus T of the radially outer end of) the rotor head 16. Therefore, the aforementioned longitudinal vortex V is likely to ride on the rearward flow and appropriately head toward the wake region W of the rotor head 16.

[0040] By making the lateral distance L2 between the rear ends of the pair of plate units 30 at least twice the maximum height H of the plate units 30, interference between the longitudinal vortex V caused by the right plate unit 30 and the longitudinal vortex V caused by the left plate unit 30 is reduced, and the upward flow of the longitudinal vortex V can be promoted. By making the lateral distance L2 between the rear ends 30b of the plate units 30 at most four times the maximum height H of the plate units 30, the flow of the longitudinal vortex V toward the wake region of the rotor head 16 can be strengthened.

[0041] The rear part 13c of the top part 13 has a shape that tapers rearward, which makes it difficult for the longitudinal vortex V behind the plate unit 30 to hit the top part 13 of the fuselage 2, thereby promoting the upward flow of the longitudinal vortex V.

[0042] Fig. 8A is a plan view of a first modified example of the rotor head 16 in Fig. 1 and its vicinity. Fig. 8B is a side view of the rotor head 16A in Fig. 8A and its vicinity. As shown in Figs. 8A and 8B, the rotor head 16A of the first modified example has a main rotor 3 of a variable pitch type that does not have a hub cap. The main rotor 3A of the first modified example includes a hub 21, a connector 22, a flapping hinge 23, and rotor blades 17. The hub 21 is fitted onto the upper part of the rotor shaft 8 so as to rotate together with the rotor shaft 8.

[0043] A connector 22 connects the rotor blades 17 to a hub 21. One end of the connector 22 is connected to the hub 21 so as to be capable of pitching. The rotor blades 17 are connected to the other end of the connector 22 via flapping hinges 23. A swash plate 24 is disposed below the hub 21. The connector 22 is connected to the swash plate 24 via a pitch link 25.

[0044] The rotor head 16A of the first modified example is a hub 21 that rotates only about the axis of the rotor shaft 8 during flight. The connecting body 22, flapping hinge 23, swash plate 24, and pitch link 25 are not included in the rotor head 16A because they perform operations other than rotation about the axis of the rotor shaft 8 during flight. The two-dot chain line shown in Figures 8A and 8B indicates the rotation trajectory T of the rotor head 16A. Furthermore, the lower surface 16Ab of the rotor head 16A of the first modified example is the main surface facing downward on the rotation trajectory T of the hub 21.

[0045] 9A is a plan view of the rotor head 16 of FIG. 1 and its vicinity in a second modified example. FIG. 9B is a side view of the rotor head 16B of FIG. 9A and its vicinity. As shown in FIGS. 9A and 9B, the rotor head 16B of the second modified example has a main rotor 3 of a variable pitch type equipped with a hub cap. The main rotor 3B of the second modified example includes a hub 21, a connector 22, a flapping hinge 23, rotor blades 17, and a hub cap 26. The hub 21, connector 22, flapping hinge 23, and rotor blades 17 are the same as those of the first modified example.

[0046] The hub cap 26 is fixed to the hub 21 so as to cover the hub 21. The rotor head 16B of the second modified example is an assembly of the hub 21 and the hub cap 26 that rotates only about the axis of the rotor shaft 8 during flight. The two-dot chain lines shown in Figures 9A and 9B indicate the rotation trajectory T of the rotor head 16B. The lower surface 16Bb of the rotor head 16B of the second modified example is the main surface facing downward on the rotation trajectory T of the hub 21.

[0047] Fig. 10A is a plan view of a third modified example of the rotor head 16 of Fig. 1 and its vicinity. Fig. 10B is a side view of a rotor head 16C of Fig. 10A and its vicinity. As shown in Figs. 10A and 10B, the rotor head 16C of the third modified example has a fixed-pitch main rotor 3. The main rotor 3C of the third modified example includes a hub 21 and rotor blades 17. The hub 21 is fitted onto the upper part of the rotor shaft 8 so as to rotate together with the rotor shaft 8.

[0048] The rotor blades 17 are fixed to a hub 21. The rotor head 16C of the third modified example has a hub 21 that rotates only about the axis of the rotor shaft 8 during flight. The two-dot chain lines shown in Figures 10A and 10B indicate the rotation trajectory T of the rotor head 16C. The lower surface 16Cb of the rotor head 16C of the third modified example is the main surface facing downward on the rotation trajectory T of the hub 21.

[0049] FIG. 11A is a plan view of a first modified example of the plate unit 30 of FIG. 3. As shown in FIG. 11A, the plate unit 130 of the first modified example has an arch shape that protrudes outward in the left-right direction. The rear half of the pair of plate units 130 extends obliquely inward and rearward in the left-right direction. The left-right distance L3 between the front ends 130a of the pair of plate units 130 is the same as the left-right distance L4 between the rear ends 130b of the pair of plate units 130. In other words, the angle of attack of the plate unit 130 is zero.

[0050] Because the plate unit 130 has a camber in a plan view, a fluid dynamic circulation occurs in the flow field around the plate unit 130 during forward flight, and a stagnation point P occurs on the inner surface 130c of the plate unit 130. As a result, the pressure on the inner surface 130c side of the plate unit 130 becomes higher than the pressure on the outer surface 130d side of the plate unit 130.

[0051] During forward flight, air that enters between the pair of plate units 130 from the front flows from the inner surface 130c of the plate unit 130 over the upper end of the plate unit 130 toward the outer surface 130d of the plate unit 130 due to the pressure difference around the plate unit 130. This generates the aforementioned longitudinal vortex V, reducing the pressure resistance of the rotor head 16.

[0052] The angle of attack of the plate unit 130 of the first modified example described above does not have to be zero. For example, the left-right distance L3 between the front ends 130a of the pair of plate units 130 may be greater than the left-right distance L4 between the rear ends 130b of the pair of plate units 130.

[0053] 11B is a plan view of a second modified example of the plate unit 30 of FIG. 3. As shown in FIG. 11B, the plate unit 230 of the second modified example is an assembly of multiple plate elements 231-233 arranged adjacent to one another, and has a generally plate shape as a whole. In this modified example, the individual plate elements 231-233 extend obliquely inward in the left-right direction and rearward, and are arranged offset from one another in the front-rear direction. The plate unit 230 as a whole extends obliquely inward in the left-right direction and rearward. In this modified example, the plate unit 230 is divided into three plate elements 231-233, but may be divided into two or four or more plate elements.

[0054] In the above-described embodiment, the plate unit has a rectangular shape extending in the longitudinal direction as viewed from the side. However, this is not limited to this, and may have a trapezoidal, triangular, semicircular, or other shape. In the rear view shown in FIG. 5 , the plate unit is attached perpendicular to the top surface 13a and protrudes vertically from the fuselage 2. However, the protruding direction of the plate unit from the fuselage 2 may be inclined relative to the vertical direction in the rear view, depending on the angle of the top surface 13a, etc. The plate unit may also have holes or recesses to reduce weight. The plate unit may have an airfoil shape in plan view so that the pressure on the outer surface is lower than the pressure on the inner surface during forward flight. The plate unit 30 may be fixed to the outer surface of the top portion 13 while positioned above the top portion 13. The plate unit may be supported on the top portion 13 via a bracket while positioned above the top surface 13a with a gap therebetween.

[0055] As described above, the above-described embodiments have been described as examples of the technology disclosed in this application. However, the technology of the present disclosure is not limited to these embodiments and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above-described embodiments can be combined to create new embodiments. For example, some configurations or methods in one embodiment may be applied to other embodiments, and some configurations in one embodiment may be separated from other configurations in that embodiment and extracted as desired. Furthermore, the components described in the accompanying drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem, and are used to illustrate the technology. [Explanation of symbols]

[0056] 1. Aircraft 2. Torso 3 Main rotor 8 Rotor shaft 13 Top 13b Upper opening 13c rear 16 rotor head 16a rear end 17 rotor blades 30,130,230 Itaden 30a front end 30b backend 30c,130c inner side 30d,130d outer side T rotation trajectory

Claims

1. The torso and a rotor shaft protruding upward from the fuselage; a rotor head connected to the rotor shaft above the fuselage; a pair of plate units disposed above the fuselage and extending in the front-to-rear direction on the right and left sides of the rotor shaft, Each of the pair of plate units includes a front end, a rear end, an inner surface facing inward in the left-right direction, and an outer surface facing outward in the left-right direction, The front ends of the pair of plate units are spaced apart from each other in the left-right direction, The rear ends of the pair of plate units are spaced apart from each other in the left-right direction, The pair of plate units have a shape such that the pressure on the outer surface side is lower than the pressure on the inner surface side during forward flight.

2. The aircraft according to claim 1 , wherein the inner surfaces of the pair of plate units extend obliquely inward and rearward in the left-right direction.

3. 3. The aircraft according to claim 1, wherein the outer surfaces of the pair of plate units extend obliquely inward and rearward in the left-right direction.

4. 2. The aircraft according to claim 1, wherein the pair of plate units have an arch shape that protrudes outward in the left-right direction.

5. The aircraft according to claim 1 , wherein the rear ends of the pair of plate units are disposed forward of a rear end of a rotation locus of a radially outer end of the rotor head.

6. 6. The aircraft according to claim 1, wherein the distance between the rear ends of the pair of plate units in the left-right direction is at least twice the maximum height of the plate units.

7. 7. The aircraft according to claim 1, wherein the distance between the rear ends of the pair of plate units in the left-right direction is equal to or less than six times the maximum height of the plate units.

8. the fuselage includes a top defining an upper opening through which the rotor shaft passes; The flying vehicle according to claim 1 , wherein the top portion has a rear portion that is located rearward of the rear end of the plate unit.

Images