Windmill rotor

Abstract

To provide a rotor that can improve rotational characteristic of a vertical axis windmill in a wide range from start up to high-speed rotation.SOLUTION: A windmill rotor is formed by fitting a flat plate along a rotation circumference or a flat plate-like rear fin 10 curved along a circumference in the vicinity of rear edge 7 of a rotor 5 of a vertical axis windmill, where an interval 9 between the rear edge 7 of the rotor 5 and the rear fin 10 is substantially equal to the blade chord of the rear fin 10, thereby reducing fluid resistance.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a device for utilizing wind energy, and more particularly to a wind turbine rotor having a structure in which the span is substantially parallel to the rotation axis. [Background technology]

[0002] Wind turbines currently in practical use can be broadly divided into two types: horizontal axis and vertical axis. The former is a so-called propeller type consisting of a rotating shaft extending horizontally and a propeller attached to it, while the latter is composed of a rotating shaft in a nearly vertical direction and rotor blades whose span extends nearly parallel to the rotating shaft. This invention relates to the latter type, and aims to improve the performance of such wind turbines.

[0003] Vertical axis wind turbines are generally used as a means of providing inexpensive products due to their simple structure, and there has not been sufficient research aimed at improving their performance. As a result, there has been insufficient pursuit of important functions such as starting characteristics and high-speed rotation performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] We will now discuss known documents related to Patent No. 6398095. For the reasons mentioned above, there are few effective prior art documents, but the applicant's patent achieves the effect of significantly improving starting characteristics by attaching a slat with a curved cross section to the leading edge of the rotor. However, this leading edge slat technology has a somewhat large air resistance, and there is room for improvement in performance at high speed rotation of the wind turbine. The rotor blade for a vertical axis wind turbine of the present invention improves on these points and can improve the rotation characteristics of the wind turbine widely, from startup to high speed rotation. Summary of the Invention

[0005] As mentioned above, the present invention is a means for improving the performance of vertical axis wind turbines, and not only can it improve the starting characteristics but also can be expected to significantly improve rotational performance without increasing air resistance even at high speed rotation. Furthermore, it provides a rotor that functions extremely effectively in combination with an angle-of-attack control system that changes the angle of attack to an optimum angle depending on the wind direction and strength in the rotor's installation state to accurately control torque fluctuations, thereby making it possible to greatly expand the range of applications of vertical axis wind turbines. [Problem to be solved by the invention]

[0006] The problem to be solved by this invention is to provide a rotor that can improve the rotation characteristics of a vertical axis wind turbine over a wide range, from startup to high speed rotation. This rotor is a highly independent technology that can demonstrate its effects simply by replacing the blades of a conventional wind turbine with the rotor of this invention, and has extremely high applicability. [Means for solving the problem]

[0007] The means for solving the above problems of the present invention is specifically a rear fin in the form of a flat plate along the rotation circumference or a plate curved along the circumference attached near the trailing edge of the rotor of a vertical axis wind turbine, and by allowing airflow to flow through the gap between the trailing edge of the rotor and the rear fin, it is possible to supply wind vector energy to the wake when the angle of attack is slightly excessive, preventing separation and making the flow smooth and reducing fluid resistance. The structure and operation will be explained below. When a vertical axis wind turbine is placed in natural wind, its rotor blades will encounter wind from directions ranging up to ±180° depending on their angular position and wind direction. For a wind turbine with three rotor blades attached to the tip of the support arms at 120° intervals, the most favorable angle of attack for starting the turbine is 30°. The wind striking the blade splits into upwind and downwind sides from the leading edge to the trailing edge, attempting to flow along the blade surface. However, the flow along the downwind side loses energy along the way, separating from the blade surface and heading downwind. If airflow passes through the gap between the trailing edge of the blade and the rear fin, the vector energy of this flow toward the trailing edge is replenished, preventing the flow on the underside from separating and traveling along the downwind side of the rear fin. It merges with the airflow flowing over the surface, maintaining a smooth downward flow. The reaction force of this flow generates a rotational force on the rotor blade, starting the turbine. Once the rotor is started, its angle of attack becomes smaller than when it is stopped, and less air flows through the gap. However, this does not increase the air resistance of the rotor as a whole; rather, it reduces it, so it does not interfere with the rotation of the wind turbine. As a result, the increase in air resistance due to the gap and rear fin is small. Furthermore, if the rotor is attached to the support arm so that it can rotate at a fixed angle around the rotation axis in the blade span direction, the rear fin shifts the aerodynamic center (moment) of the rotor as a whole toward the trailing edge, so the trailing edge of the blade automatically bends downwind, effectively reducing the angle of attack and further improving starting characteristics. Details of the rotation mechanism between the rotor and the support arm will be described later. [Effects of the Invention]

[0008] As is clear from the above explanation, the wind turbine rotor of the present invention has the function of improving the starting performance and high-speed rotation performance of the wind turbine by itself, and furthermore, depending on the method of installation, it can contribute to improving the performance of the entire wind turbine, and its substantial effect on natural energy utilization technology is extremely remarkable. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a top view showing one embodiment of the present invention. [Figure 2] FIG. 2 is a partial top view showing one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment for simplifying and realizing the wind turbine rotor blade of the present invention without impairing its function will be described. [Example]

[0011] Fig. 1 is a top view showing one embodiment of the present invention, and Fig. 2 is a partial top view showing one embodiment of the present invention. The dotted line indicates the air flow, and the operating state is indicated by a two-dot chain line. In Figures 1 and 2, A hub 3 equipped with multiple support arms 2 is fixed to the rotating shaft 1 of the wind turbine, and rotors 5 are attached to the tips of the support arms 2 via shafts 4. The leading edges 6 of the rotors 5 are rounded and the trailing edges 7 are pointed, giving the rotors 5 an overall shape similar to the cross section of an aircraft wing. If necessary, the rotors 5 may be curved to fit the circumference 8 to which the rotors 5 are attached. A rear fin 10 is provided at a position along the circumference 8, a gap 9 away from the trailing edge 7. The cross section of the rear fin is a plate-like shape curved along the circumference 8, but it is preferable to make the front end round and the rear end pointed to reduce air resistance. Furthermore, a stay 11 extends forward from the leading edges 6 of the rotors 5, and an interlocking hole 12 is formed at the tip of the stay 11. [Effect]

[0012] The operation of the wind turbine rotor blade having the above structure will now be described. When a vertical axis wind turbine is placed in natural wind, its rotor blades 5 are subject to wind from directions ranging up to ±180° depending on their angular position and wind direction. For a wind turbine with three rotor blades 5 attached to the tips of the support arms 2 at 120-degree intervals, even the rotor blades 5 with the most favorable angle of attack for startup are 30°. The wind striking these rotor blades 5 splits into upwind and downwind sides from the leading edge 6 to the trailing edge 7 of the rotor blades 5 and attempts to flow along the blade surface. However, the flow along the downwind side loses energy along the way, separates from the blade surface, and flows downwind. If there is airflow passing through the gap 9 between the blade trailing edge 7 and the rear fin 10, the vector energy of this airflow toward the trailing edge is replenished, preventing the flow on the underside from separating. It merges with the airflow flowing over the surface at the trailing edge of the rear fin 10, allowing it to flow smoothly downward. The reaction force of this flow generates a rotational force on the rotor blades 5, starting the wind turbine.

[0013] Once started, the angle of attack of the rotor 5 becomes smaller than when it is stopped, and the amount of air passing through the gap 9 decreases, but this does not increase the air resistance of the entire rotor 5, but rather reduces it, so it does not interfere with the rotation of the wind turbine. Furthermore, if the rotor 5 is attached to the support arm 2 so that it can rotate at a fixed angle around the axis 4 in the blade span direction, the aerodynamic center of the rotor 5 as a whole moves toward the trailing edge, so that the trailing edge 7 of the rotor 5 automatically bends downwind, effectively reducing the angle of attack and further improving the starting characteristics. The rotation mechanism between the rotor 5 and the support arm 2 will be described in detail below. Ordinarily, pointing the leading edge 6 into the wind reduces the angle of attack of the rotor 5, reducing air resistance. However, when the angle of attack reaches 0°, lift is zero and no rotational force is generated. When wind strikes the rotor 5 at a certain angle of attack, if the aerodynamic center 13 of the rotor 5 is closer to the trailing edge 7 than the shaft 4, the rotor will bend toward the trailing edge 7 without the stay 11, resulting in an angle of attack approaching 0°. If the stay 11, supported by the support arm via the interlocking hole 12, has appropriate elastic properties (spring deflection characteristics), the stay 11 will deflect due to wind force, allowing the angle of attack to be appropriately smaller than when the rotor 5 is fixed to the support arm 2. Furthermore, the aforementioned elastic properties prevent the angle of attack from immediately reaching 0, preventing lift from reaching 0, thereby preventing rotational force from reaching 0. This characteristic allows for smoother rotation of the wind turbine and greater rotational force. Furthermore, since the angle of attack of the rotor 5 does not become excessive, it is also effective in preventing a so-called stall condition. [Industrial Applicability]

[0014] As is clear from the above explanation, the wind turbine rotor of the present invention has the characteristic of keeping the angle of attack of the rotor within an appropriate range during practical use with an extremely rational action that does not require control by external forces, thereby making it possible to maintain a high level of rotational performance of the wind turbine from start-up to high-speed rotation. This opens up the future for vertical axis wind turbines, which have not been considered very practical until now, and its technological and industrial effects related to the use of natural energy are extremely significant. [Explanation of symbols]

[0015] 1 Rotation axis 2 support arms 3. Hub 4th axis 5 rotor blades 6 leading edge 7 Trailing edge 8 Circumference 9. Gap 10 rear fin 11 Stay 12 Connection holes

Claims

1. A hub having a plurality of support arms is fixed to the rotating shaft of the windmill, and a rotor blade substantially parallel to the rotating shaft is attached to the tip of the support arm. The leading edge of the rotor blade in the rotation direction has a rounded shape, the trailing edge has a pointed shape, and the overall shape resembles the cross-section of an aircraft wing. The entire rotor blade has a streamlined shape parallel to the circumferential direction or is curved along the circumference. A rear fin is provided at a position where a gap distance is provided rearward along the circumference from the trailing edge. The cross-sectional shape of the rear fin is a plate shape curved along the circumference or a plate shape curved along the circumference. It is preferable to make the front end rounded and the rear end pointed to reduce air resistance. The distance in the chord direction of the gap is substantially equal to the chord of the rear fin. A rotor blade for a windmill having such a configuration.

2. A shaft parallel to the rotating shaft is provided at the tip of the support arm, and the rotor blade is rotatably attached to the shaft. A stay extending forward from the leading edge of the rotor blade is provided, and it is attached to the support arm through an interlocking hole at its tip. The stay has springy bending elasticity. The rotor blade for a windmill according to claim 1, characterized in that.

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