Kite with spoilers

Abstract

To provide a kite connected with a tether to fly in the air including a spoiler which can exert effective stripping action even at a small angle of elevation.SOLUTION: A kite 1 with right and left wings includes tabular 3a spoilers 3L, 3R installed on respective top faces of the right and left wings in which a forward edge 3af of the spoiler is pivoted on a top face 1a of the wing and a rear edge 3ar is pivotable in a direction apart from the top face of the wing. A tabular part 3b is arranged at the rear edge 3ar of the spoiler in which the tabular part crosses a surface direction of the flat plate of the spoiler and extends in a direction apart from the top face of the wing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a kite that is flown in the air and moored, and more particularly to the shape of a spoiler, which is an aerodynamic device provided on the surface of the kite. [Background technology]

[0002] The use of kite systems, which send kites or other flying objects into the sky to generate wind power, has been studied (see, for example, Patent Document 1). The flying objects in kite systems primarily use airflow energy, such as the westerly winds or trade winds that flow at high altitudes, as the energy for their flight and flight time, making them extremely advantageous from the perspective of energy conservation. Regarding kites, which are flying objects in such kite systems, Patent Document 2, for example, discloses a technology for improving the flight stability of a flying object (kite) connected to a linear member (tether). The technology includes a deforming section that elastically deforms in response to the force applied to the wing section at a connection point connecting a wing section that generates lift from wind pressure to a base section on the linear member. The deformation of the deforming section allows the ratio between the distance from the base section to one end of the wing section and the distance from the base section to the other end of the wing section to be changed. Furthermore, Patent Document 3 proposes a structure for improving flight stability while maintaining the strength of a kite-type flying vehicle (kite) with swept-back wings. This structure involves attaching plate-like members to the trailing edges of the left and right wings, closer to the ends of the left and right wings than the intersection of a line extending laterally through the center of gravity of the kite-type flying vehicle and a curve connecting the lift application points of the left and right wing sections, and tilting the rear ends of the plate-like members so that they are positioned above the swept-back wing surfaces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-94521 [Patent Document 2] Patent Publication No. 2021-154976 [Patent Document 3] Patent Publication No. 2022-37630 Summary of the Invention [Problem to be solved by the invention]

[0004] One effective configuration for controlling the kite's roll attitude in the kite system described above is to provide an aerodynamic device, such as a spoiler, on the upper surface of the kite's left and right wings to appropriately separate the airflow flowing over the upper surface of the left and right wings and reduce the magnitude of lift acting on the left and right wings. Furthermore, in the case of an air vehicle with an elastic structure like a kite, installing an aerodynamic device near the rear end of the wing can cause the rear of the wing to twist, reducing the aerodynamic effect or even causing an effect in the opposite direction to the desired effect (e.g., aileron reversal). Therefore, spoilers are often provided near the front end of the wing. When a kite is nearly stationary in the air, the wind force acting on the kite and the tension from the tether are approximately balanced, and the kite's speed is approximately zero. This means that the impact of wind fluctuations on the kite's attitude is relatively large. Therefore, it is preferable that the aerodynamic effect (lift reduction) provided by the spoiler be effective over as wide a range of attitude conditions as possible.

[0005] Regarding spoilers attached to the upper surface of the kite as described above, according to research by the inventor of the present invention, in the case where spoilers for adjusting the lift on the upper surfaces of the left and right wing sections are located near the front end of the wing section, if the spoiler is simply flat in shape, when the angle of attack of the wing section (the angle in the fore-and-aft direction of the wing section relative to the wind direction - see α in Figure 2(B)) becomes small, the aerodynamic effect of the spoiler decreases, and it has been found that this effect can also be reversed. More specifically, the aerodynamic effect of a spoiler is that the flat spoiler protrudes outward from the upper surface of the wing in a direction intersecting the plane, separating the airflow flowing from the leading edge of the wing from the upper surface of the wing and reducing the lift acting on the upper surface of the wing. However, it was discovered that if a flat spoiler is simply provided near the leading edge of the wing, the airflow that has separated at the spoiler reattaches or turns around in the spoiler wake at small angles of attack, preventing the separation effect from being fully realized (see Figure 3(B)). Therefore, the inventors of the present invention studied spoiler shapes and found that an effective separation effect can be achieved even at small angles of attack by adopting a spoiler shape in which a plate-like portion extends or stands upright at the trailing edge of the flat spoiler in a direction away from the upper surface of the wing. This finding is utilized in the present invention.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a spoiler for a kite that can effectively separate the airflow on the upper surface of the wing even when the angle of attack is small. [Means for solving the problem]

[0007] According to the present invention, the above problem is solved by a kite that is connected to a tether and is launched into the air, The left and right wings a flat spoiler provided on each of the upper surfaces of the left and right wing sections, the leading edge of which is pivotally attached to the upper surface and the trailing edge of which is pivotable in a direction away from the wing section upper surface; A kite in which a plate-like portion is provided at the trailing edge of the spoiler, intersecting the surface direction of the flat plate of the spoiler and extending in a direction away from the upper surface of the wing portion. This is achieved by:

[0008] In the above configuration, the term "kite" may refer to any type of kite connected to a tether and launched into the air in a kite system. A kite has wings extending laterally from a longitudinal central axis, and is launched into the air by airflow (wind) flowing from the leading edge to the trailing edge of the wings, generating lift. The tether may be a tether (rope) connecting the kite to a ground facility or another flying object. As described above, a "flat spoiler" is an aerodynamic device whose leading edge is pivotally attached to the upper surface of each of the left and right wings, and whose trailing edge is pivotally attached in a direction away from the upper surface of the wing. When the angle (spoiler angle) of the extension direction of the spoiler's flat plate relative to the upper surface of the wing becomes significant, the spoiler separates the airflow flowing from the leading edge of the wing along the upper surface of the wing, thereby reducing the lift of the wing accordingly. The spoiler angles of the spoilers on the left and right wing sections may be controlled by any method, and as described in detail in the embodiment section, the larger the spoiler angle, the greater the effect of reducing the lift of the wing section.Therefore, by adjusting the left and right spoiler angles respectively, the lift of the left and right wing sections is adjusted, and the roll attitude of the kite is controlled.

[0009] As mentioned above, if the shape of the spoilers provided on the upper surfaces of the left and right wings of the kite is simply flat, the effect of reducing the lift of the wing will decrease as the angle of attack of the kite decreases. For example, when the angle of attack is 0°, the effect of reducing the lift of the wing will be almost nonexistent, and in fact, the effect of increasing the lift of the wing will occur. Therefore, in the kite spoiler of the present invention, as described above, a plate-like portion is provided at the trailing edge of the spoiler so as to intersect with the surface direction of the flat spoiler and extend in a direction away from the upper surface of the wing. With this configuration, even when the angle of attack of the kite is small, the spoiler's effect of separating the airflow along the upper surface of the wing will be more effective, and the lift of the wing will be significantly reduced, even when the angle of attack is 0°.

[0010] In the above-described configuration of the present invention, the plate-like portion at the trailing edge of the spoiler may extend in a direction approximately perpendicular to the surface direction of the spoiler plate. This allows the spoiler to more effectively achieve forced separation of the airflow. Furthermore, evaluation of the balance between the effect of reducing lift by the spoiler and the resistance experienced by the wing in wind tunnel tests and the like has revealed that the appropriate length from the connection point of the plate-like portion with the trailing edge of the spoiler to the trailing edge is 5 to 20% of the length from the leading edge to the trailing edge of the spoiler.

[0011] The spoiler may be positioned closer to the leading edge of the wing than to the trailing edge. As mentioned above, in the case of an aircraft with an elastic structure such as a kite, positioning the aerodynamic device closer to the trailing edge is likely to result in a reduction in aerodynamic effect due to twisting deformation at the rear of the wing. In addition, in the case of a kite, the wing is formed thicker at the leading edge, making it easier to reinforce the structure, and the load distribution for generating lift is biased toward the leading edge. For these reasons, more effective lift control can be achieved by positioning the spoiler closer to the leading edge than to the center of the wing, as described above. [Effects of the Invention]

[0012] Thus, according to the above-mentioned structure of the present invention, by providing the spoilers on the upper surface of each of the left and right wings of the kite for lift control with a plate-like section that rises from the trailing edge of the wing, an effective separation of the airflow can be obtained on the upper surface of the wing even when the kite's angle of attack is small, thereby enabling efficient control of the kite's roll attitude. The effect of the present invention is also advantageous in that it can be obtained with a relatively simple structure that only requires the provision of the above-mentioned plate-like section on the trailing edge of the spoiler.

[0013] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0014] [Figure 1]Fig. 1(A) is a schematic perspective view of a kite to which this embodiment is applied, Fig. 1(B) is a schematic perspective view of a spoiler attached to the upper surface of the wing of the kite, and Fig. 1(C) is a schematic side view of the spoiler attached to the upper surface of the wing of the kite. [Figure 2] Figure 2(A) is a schematic diagram of the kite seen from behind, illustrating the rolling moment generated by the spoiler, and Figure 2(B) is a schematic side view of the kite, illustrating the angle of attack α relative to the wind direction W. [Figure 3] Figure 3(A) is a graph showing the change in roll moment coefficient with respect to spoiler angle for a kite with a flat spoiler on the wing. The values in the figure represent the angle of attack of the kite. Figure 3(B) is a diagram showing a schematic representation of the airflow af on a wing with a flat spoiler attached. Figure 3(C) is a graph showing the change in roll moment coefficient with respect to spoiler angle for a kite with a spoiler according to this embodiment attached to the wing. The values in the figure represent the angle of attack of the kite. Figure 3(D) is a diagram showing a schematic representation of the airflow af on a wing with a spoiler according to this embodiment attached. [Explanation of symbols]

[0015] 1. Kite 1L, 1R...Left wing, right wing 1a...Top surface of wing section 2, 2a...Tether 3L, 3R...Left spoiler, Right spoiler 3a...Flat part of spoiler 3b...Upright plate part of spoiler 4...Bridle W…wind BEST MODE FOR CARRYING OUT THE INVENTION

[0016] Kite configuration 1(A), the kite 1 to which this embodiment is applied may be a flying object connected to a tether 2 in a kite system and launched into the air. As shown in the figure, the kite 1 has wings 1L and 1R extending in the left and right directions. In the air, the kite 1 is lifted by the force of wind W and is anchored in the air by the balance between the wind force and the tension T from the tether 2 connected between the kite 1 and the ground or another flying object. The attitude of the kite 1 can be controlled by detecting the attitude angles (roll angle, yaw angle, pitch angle), angular velocity, and acceleration using a motion sensor (not shown) attached to the kite 1, and based on these detected values, appropriately operating aerodynamic devices such as spoilers 3L and 3R attached to the upper surfaces 1a of the left and right wing sections 1L and 1R of the kite 1 to change the airflow around them, or by adjusting the length of the tether 2a connected from the bridle 4 to the left and right parts of the kite 1 using a bridle 4 attached to the tether 2.

[0017] Spoiler structure and function 1(B) and 1(C), in this embodiment, spoilers 3L and 3R attached to the upper surface 1a of the wing are formed to have a flat portion 3a and a plate-like portion 3b extending from a trailing edge 3ar in a direction away from the wing surface 1a, as shown. The spoilers 3L and 3R are each configured such that a leading edge 3af of the flat portion 3a is pivotally attached to the wing surface 1a, and the flat portion 3a pivots about the leading edge 3af relative to the wing surface 1a. That is, the spoilers 3L and 3R are installed so as to extend from the front f of the wing surface 1a to the rear r, rotatably about the leading edge 3af. The angle δ at which the flat portion 3a and the plate-like portion 3b intersect may typically be approximately right angles, but may be changed as appropriate as long as the airflow separation effect, which will be described later, can be achieved. The angle (spoiler angle) β of the flat plate-shaped portion 3a of the spoilers 3L, 3R relative to the wing surface 1a may be adjusted appropriately within a range of 0° or more by a driving device (such as a step motor) not shown.

[0018] In the kite 1, when the spoilers 3L and 3R are activated, they protrude upward from the upper surface 1a of each of the left and right wing sections 3L and 3R, separating the airflow flowing along the upper surface 1a from the leading edge of the wing section 1A, thereby reducing the upward lift. Referring to FIG. 2(A), for example, in the kite 1, when the right spoiler 3R is activated and protrudes upward from the upper surface 1a of the right wing section 1R, the airflow on the upper surface 1a is separated, thereby reducing the lift that pulls the right wing section 1R upward. As a result, a downward force Fl_d acts on the right wing section 1R due to the difference in lift between the upper and lower sections. This generates a rolling moment Mr that lifts the left wing section 1L and pushes down the right wing section 1R, thereby controlling the roll attitude of the kite 1.

[0019] Since the kite 1 typically has an elastically deformable structure, if an aerodynamic device such as a spoiler is provided near the trailing edge of the wing, twisting deformation will occur at the rear of the wing, and the expected aerodynamic effect may not be achieved (e.g., aileron reversal). On the other hand, as shown in the figure, the leading edge of a kite wing is generally thicker, making it easier to reinforce the structure, and the load distribution for generating lift is biased toward the leading edge. Therefore, the aerodynamic effect of the aerodynamic device is more effective when the aerodynamic device is installed near the leading edge of the wing. Therefore, as shown in Figure 2(B), the spoilers 3L and 3R are preferably provided near the leading edge f of the wing of the kite 1, rather than the center C.

[0020] Effects of the spoiler with a plate-shaped section Unlike aircraft that fly by propulsion, such as airplanes, the kite 1 may be moored in a state where the wind force acting on the kite and the tension from the tether are nearly balanced, and the kite is nearly stationary in the sky. In such a state, the speed becomes nearly zero, and the influence of wind fluctuations on the kite's attitude becomes relatively large, so it is preferable that the aerodynamic effect of the spoiler (reduction of lift) be effective over as wide a range of attitude conditions as possible.

[0021] In this regard, as mentioned in the Summary of the Invention, when the spoiler is a simple flat plate and is located near the leading edge of the wing (see Figure 2(B)), it has been found that when the angle of attack α of the kite 1 (the angle of the kite's front-to-rear direction relative to the wind direction) is relatively small, the spoiler's aerodynamic effect, i.e., lift reduction effect, is almost zero, and when the angle of attack α is 0°, the spoiler may actually increase lift slightly. In fact, as shown in Figure 3(A), when the angle of attack α of the kite is in the range of 0° to 20° and the right spoiler is activated, the roll moment coefficient CI is measured. When the angle of attack α is below 5°, even if the spoiler angle is increased, the roll moment coefficient CI does not increase significantly, and when the angle of attack α is 0°, the roll moment coefficient CI becomes negative, resulting in an effect opposite to the expected effect. This is thought to be because, as shown schematically in Figure 3(B), the airflow af from the front of the wing, which flows from the leading edge 1f of the wing along the upper surface 1a, is separated by spoilers 3L and 3R near the leading edge of the wing, and then reattaches (Rt) or turns around behind the wing, preventing the airflow separation effect from being fully achieved. (The roll moment coefficient CI is a dimensionless quantity of the aerodynamically generated rolling moment Mr, and is given by the following formula: CI=Mr / (1 / 2·ρV 2 S) where ρ, V, and S are the air density (kg / m 3 ), wind speed, and wing area. The larger the positive value of the roll moment coefficient CI, the larger the rolling moment generated by the spoiler.

[0022] On the other hand, according to research conducted by the inventor of the present invention, it has been found that when a spoiler shape is adopted in which a plate-like portion 3b extending in a direction intersecting the flat portion 3a is provided as a spoiler shape as shown in Figures 1(B) and (C) above, a significant airflow separation effect can be obtained even when the angle of attack α of the kite 1 is small. In fact, as shown in Figure 3(C), when the angle of attack α of the kite is in the range of 0° to 20° and the right spoiler is activated, the roll moment coefficient CI was measured, and it was found that in the case of a spoiler with a plate-like portion 3b, the roll moment coefficient CI becomes a significant value on the positive side even when the angle of attack α of the kite is 0°. This is thought to be because, as shown schematically in Figure 3(D), the flat plate-like portion 3a of the spoilers 3L, 3R has a plate-like portion 3b extending in a direction intersecting the flat plate-like portion 3a, and the airflow af flowing from the leading end 1f of the wing along the upper surface 1a is disturbed by the characteristic shape of the spoilers 3L, 3R, and is forcibly separated even at the rear of the wing without reattaching to the upper surface 1a.

[0023] Thus, by using a spoiler having a flat portion 3a and a plate-like portion 3b extending in a direction intersecting it, as in the above embodiment, an effective separation of the airflow on the upper surface of the wing can be obtained even when the kite's angle of attack is small.

[0024] Furthermore, based on knowledge gained from evaluation of the balance between the lift reduction effect of the spoiler and the resistance experienced by the wing in wind tunnel tests of the wing, the length from the connection point of the plate-shaped portion 3b with the trailing edge 3ar of the spoiler to the trailing edge may be 5 to 20% of the length from the leading edge 3af to the trailing edge 3ar of the spoiler.

[0025] Although the above description has been made in relation to the embodiments of the present invention, it will be apparent that many modifications and changes can be easily made by those skilled in the art, and the present invention is not limited to the above-described exemplary embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A kite that is connected to a tether and launched into the air, The left and right wings a flat spoiler provided on each of the upper surfaces of the left and right wing sections, the leading edge of which is pivotally attached to the upper surface and the trailing edge of which is pivotable in a direction away from the wing section upper surface; The spoiler is disposed at a position closer to the leading edge of the wing than to the trailing edge, A plate-like portion is provided at the trailing edge of the spoiler, the plate-like portion intersecting the plane direction of the flat plate of the spoiler and extending in a direction away from the upper surface of the wing portion, A kite in which the plate-like portion extends in a direction approximately perpendicular to the surface direction of the flat plate of the spoiler.

2. 2. A kite according to claim 1, wherein the length of the plate-shaped portion from the connection point with the trailing edge of the spoiler to the distal edge is 5 to 20% of the length from the leading edge to the trailing edge of the spoiler.

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