JP2003227453A - Vertical shaft windmill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical shaft windmill stably generating power with high efficiency. <P>SOLUTION: In the vertical shaft windmill having a plurality of symmetrical aerofoil blades disposed around a rotating shaft and rotating about the shaft, the blades have turbulent flow forming accelerating parts at the front edges. The turbulent flow forming accelerating parts form unevenness with a length of 0.1% to 10% of a chord length. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical axis wind turbine suitable for uses such as wind power generation and pumping power.

[0002]

2. Description of the Related Art Global environmental problems have become a major theme to be solved by today's human society, for example, December 1997.
Specific improvement targets have been set on a global scale, as proposed in the Protocol of the Kyoto International Conference on Prevention of Global Warming held in March. Under such circumstances, utilizing natural energy such as wind power is an extremely effective means for improving the global environment. Needless to say, wind energy is the mechanical energy of the wind that exists in the natural world. Specifically, it is used by converting it to electrical energy through a generator, or directly as mechanical energy such as pumping power. Used.

By the way, wind turbines for utilizing wind energy are roughly classified into a horizontal axis wind turbine and a vertical axis wind turbine. As is well known, the horizontal axis wind turbine is a system in which the rotation axis of the wind turbine is kept substantially horizontal to the ground, and the vertical axis wind turbine is such that the rotation axis of the wind turbine is kept substantially vertical to the ground as shown in FIG. This is the method used. Among them, the horizontal axis wind turbine has advanced based on the propeller theory of aircraft accumulated since ancient times,
For example, it can be said that the technology has already reached the practical range as disclosed in "Wind Power Generation Technology" (Revised in February 1992, Power Co.).

On the other hand, the vertical axis wind turbine is a wind turbine of which the rotation axis is installed almost vertically to the ground, and the technology is not yet well established. But,
Since this vertical axis wind turbine has the following features compared to the horizontal axis wind turbine, it is a method that is expected to be further developed in the future for power generation and the like. (1) The structure can be simplified because direction control (pivoting mechanism) for changes in the wind direction is unnecessary. Also, since there is no twist of the wing, the structure is simple and the production cost can be reduced. (2) Vibration due to the gyro effect does not occur even if the wind direction changes. Further, there is no strength burden due to the gyro moment. (3) There is no delay with respect to changes in wind direction. (4) Since the performance is stable with respect to the peripheral speed ratio, that is, the ratio between the turning speed and the inflowing wind speed, high performance can be maintained even if there is a wind speed distribution in the height direction or temporal variation. (5) Since the generator can be fixed to the ground, there are few restrictions on size and weight, and direct power generation at low rotation speed is also possible. The mechanism for rotating the vertical axis wind turbine will be described later in detail, but once the wind turbine starts rotating in either direction, the lift force acting on the blades generates a torque for rotation, and this torque causes the wind turbine to rotate. The rotation of is continuous.

[0005]

The inventor has decided to promote experimental research in order to put a vertical axis wind turbine having such advantages into practical use. However, in the process, the inventor faced the problems that the conventional vertical axis wind turbine does not always provide a stable output and the efficiency is still insufficient. Therefore, an object of the present invention is to propose a vertical axis wind turbine that can perform more stable operation and highly efficient power generation in view of the problems that the above-described conventional vertical axis wind turbine has.

[0006]

Means for Solving the Problems The inventor has made a detailed observation and examination of the air flow in the vicinity of the blade from a wind tunnel experiment using a symmetric blade type blade. As a result, the blade can be efficiently rotated. It is effective to increase the angle of attack of, but when the angle of attack is increased, the occurrence of boundary layer separation on the blade surface is large, which adversely affects it.
In addition, in order to suppress this boundary layer separation, by providing irregularities on the surface near the leading edge of the blade, separation is delayed because the airflow boundary layer on the back surface of the blade rapidly transitions to turbulence, and blade performance is significantly improved. I found out that.

The present invention has been made on the basis of the above findings, and in a vertical axis wind turbine in which a plurality of symmetrical blade blades are arranged around a rotation axis and rotate about the rotation axis, the blades are provided. Is a vertical axis wind turbine characterized by having a turbulent flow formation promoting portion at its front edge. Further, in the above invention, the turbulent flow formation promoting portion has a blade chord length of 0.
It is preferable that the unevenness has a length of 1% or more and 10% or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a vertical shaft type wind turbine has a rotating shaft 2 installed vertically and a supporting column 3 on the rotating shaft 2.
The wing-shaped blade 1 (the number of blades in FIG. 1 is three) is fixed via the blades. Further, the generator 4 is directly fixed to the rotary shaft 2 or rotatable via a transmission mechanism. Here, each blade is a symmetric airfoil blade, as shown in FIG. That is, these blades have a columnar shape, and the cross section perpendicular to the axis of the columnar body is substantially symmetrical with respect to the major axis a, and the cross-sectional shape of the blade is streamlined. It should be noted that although the actual machine also requires a brake and a clutch, the description of the apparatus not directly related to the present invention will be omitted.

The rotating mechanism of the vertical axis wind turbine will be described in detail with reference to FIG. In FIG. 3, it is assumed that the blade is rotating clockwise in the air flow in the wind direction from left to right. A relative speed W is formed as a total speed of the wind speed U and the blade peripheral speed V, and a lift force L is generated perpendicularly to W based on the total speed W. Thus, the blade becomes the rotation direction (t direction) component L _t of the lift L is generated, the L _t becomes a driving force, the rotation of the blades persists around the rotation axis. Since the blade has a symmetrical blade shape or a shape close thereto, there is a rotational direction component of the lift L regardless of the rotational axis position of the blade, and the rotation of the wind turbine can be continued. The wind turbine shown in FIG. 1 and FIG. 3 was provided with three symmetrical blade blades around the rotation axis, but the above-described rotation mechanism is similarly applicable if the number of blades is two or more. . It is widely known that surface irregularities are useful for boundary layer control, such as golf ball dimples. The present invention is characterized in that the turbulence promoting device is placed on the leading edge, so that the turbulent promoting effect is effectively exerted only on the necessary surface of the blade.

According to the research conducted by the inventor, the efficiency of the vertical axis wind turbine equipped with such conventional symmetrical blade type blades is not yet sufficiently exerted because the rotating blade is located at the position shown in FIG. 4 (a), for example. Back side of the blade (Fig.
This is because boundary layer (laminar flow boundary layer) separation occurs on the upper surface side. The inventor has confirmed that such boundary layer separation reduces the efficiency of a vertical axis wind turbine. Therefore, the inventor diligently studied the shape of the symmetrical blade blade for preventing such boundary layer separation. as a result,
As illustrated in 1a of FIG. 4 (b), when a turbulent flow formation promoting portion of an uneven portion (correctly, a concave portion and / or a convex portion) is formed on the leading edge of the symmetrical blade blade, the vicinity of the leading edge is formed. It was found that the laminar flow of the above became turbulent, and the timing of boundary layer separation was delayed and shifted behind the blade.

When the symmetrical blade blade rotates about the rotation axis and the angle of attack of the symmetrical blade blade reaches a position (-α) opposite to that in FIG. 4 (α), the boundary is reached. Delamination occurs on the underside of the blade. Even when the symmetrical blade is present at this position, the function of promoting turbulent flow formation by the uneven portion formed at the leading edge is similarly exerted, and the desired effect is obtained. In this way, in the present invention, since the turbulent flow formation promoting portion is provided at the leading edge of the symmetrical blade blade, the boundary layer separation that is likely to be formed on the back surface side is always delayed regardless of the angle of attack with respect to the wind. The effect of allowing it to be obtained.
Furthermore, when the wind direction is from the front (at an angle of attack of 0), the turbulent flow formation promoting part exists in the part with less flow near the stagnation point, so there is almost no obstacle caused by the turbulent flow formation promoting part, and it can be ignored. It is possible.

The inventor then conducted further detailed investigations and examinations, and found that the turbulent flow formation promoting portion formed at the leading edge had a column of convex projections as shown in FIG. 5 (a). In addition to those that are continuous in the axial direction of the body, those in which convex protrusions are distributed in dots as shown in FIG. 5 (b), and those that consist of concave depressions as shown in FIG. It was found that the same effect can be obtained if the ridges and the protrusions are mixed and the shape is such that the turbulent flow is promoted regardless of the arrangement. Further, the size of the turbulent flow formation promoting portion has a height (the height of the peak in the case of a convex portion, the depth of the valley in the case of a concave portion, the sum of the height of the valley and the depth of the valley in the case of mixed irregularities) of which the chord length is 0 It was also found that the length is preferably 0.1% or more and 10% or less. At less than 0.1% of the chord length, no separation delay was observed and no effect was seen. On the other hand, if it exceeds 10%, the resistance against flow increases and the efficiency decreases. Here, the chord length is the length in the advancing direction of the blade (the direction of a in FIG. 2), and the leading edge means the leading edge of the blade. If the symmetrical blade type blade of the vertical axis wind turbine is provided with the uneven portion for promoting the turbulent flow formation as described above, the boundary layer separation that is likely to be formed on the back side of the blade is suppressed by the turbulent flow generation function, resulting in In addition, the efficiency of the wind turbine is improved. Furthermore, by providing the unevenness of the present invention, since the flow around the blade causes wraparound, the rotation is easily started, which is also advantageous for the self-starting characteristic which was conventionally difficult.
This is because even if the flow hits directly from the side, the propulsive force is generated because the flow has less separation on the back surface of the blade due to the unevenness.

[0013]

[Example] Thickness 45 mm, chord length 250 mm, length 24
Symmetrical airfoil blades with a dimension of 00 mm were made using a material of hard vinyl chloride. The radius was 1800 mm, and the configuration was three blades. 2.5 mm high on the front edge of the blade
The wind turbine shown in FIG. 1 was manufactured by using three blades each having the point-like unevenness (Example of Invention) and three blades not having such unevenness (Comparative Example). The wind turbine manufactured in this manner was placed in an air stream with wind speeds of 5 m / s and 8 m / s, and the output performance was measured. The results obtained are shown in Table 1.
A typical measurement example is shown, though it varies depending on the peripheral speed ratio and load conditions. Table 2 shows the comparison result of the output coefficients at that time. By applying the unevenness according to the present invention, 1
It was found that the performance was improved by about 5%.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

As described above, according to the present invention,
Since the turbulent flow formation promoting portion is provided on the leading edge of the symmetrical blade, the following effects can be expected. 1) It becomes possible to provide a vertical axis wind turbine capable of stable operation and highly efficient power generation. 2) Since the peripheral speed ratio can be set low, high performance can be achieved at low speed rotation, noise problems can be avoided, and centrifugal force is reduced, which increases the degree of freedom in strength design. 3) Since strength can be exhibited even with a thick blade, strength design becomes easy. 4) A wraparound occurs in the flow around the blade, which is advantageous for the self-starting characteristic, which was conventionally difficult. 5) It will greatly contribute to the improvement of the global environment by using wind energy.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a vertical axis wind turbine.

FIG. 2 is a perspective view and a plan view showing a symmetrical blade type blade used in a vertical axis wind turbine.

FIG. 3 is a schematic diagram for explaining a rotating mechanism of a vertical axis wind turbine.

FIG. 4 is a schematic diagram showing a state of an air flow in the vicinity of a symmetric shaft blade type blade.

FIG. 5 is a schematic diagram showing an example of a turbulent flow formation promoting portion formed at the leading edge of a symmetrical blade blade.

[Explanation of symbols]

1: Symmetrical airfoil blade 2: Rotation axis 3: Support 4: Generator 1a: Turbulent flow formation promoting section

Claims (2)

[Claims] 1. In a vertical axis wind turbine in which a plurality of symmetrical blades are arranged around a rotation axis and rotate about the rotation axis, the blade has a turbulent flow formation promoting portion at its leading edge. The vertical axis wind turbine is characterized by having. 2. The vertical axis wind turbine according to claim 1, wherein the turbulent flow formation promoting portion has an uneven shape having a length of 0.1% or more and 10% or less of the chord length.