JP2011179417A - Darius type vertical shaft wind turbine having startability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Darius type vertical shaft wind turbine as improvement of a conventional one, involving the problem that it has a poor starting performance and that centrifugal force in association with rotation may act on blades to result in a poor rigidity, i.e. durability, of the blades and arms. <P>SOLUTION: Each band-shaped blade in curved form of this Darius type vertical shaft wind turbine is given a twist of any arbitrary angle in the rotating direction from the blade center toward both ends, and in the section form of the blade, the camber is made convex to the rotary shaft side, so as to generate a lift, which is used as a centripetal force and set off with the centrifugal force, resulting in enhancement of the durability and also enhancement of the rotational torque. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

    It relates to the structure of the blade and arm of a Darius type vertical axis wind turbine.

There are many types of vertical axis windmills. Among them, a windmill using lift generated in the blade is suitable for wind power generation. There are two types, the Darrieus type, in which the blade is curved, and the type in which the blade is fixed to an arm that is linear and extends from the rotating shaft. These windmills have many improvements for wind power generation.

Especially in Japan, it is often difficult to obtain a constant wind due to poor wind environment. For example, wind fluctuations are severe in urban buildings, mountainous terrain, and typhoon seasons, and wind turbines are often damaged by gusts. Patent document 1 is an example of this countermeasure.

As described in Non-Patent Document 1 (Chapter 5.8, Centrifugal Force Acting on the Vertical Axis), in the vertical axis wind turbine, a large stress is generated in the blade and the arm due to the centrifugal force. It has become. Patent document 2 is an example of this countermeasure.

Japanese Patent No. 3330141

JP 2005-226616 A

Kazuichi Seki and Izumi Ushiyama “Vertical Axis Windmill” published by Power Company January 2008

Mitsuo Makino "Basics of Aerodynamics (2nd edition)" Sangyo Tosho Publishing 1989

Many technologies have been developed to improve startability in Darius type vertical axis wind turbines. In general, a combination with a Savonius windmill or a method of changing the mounting angle of the blade according to the direction of the wind.
US Patent No. 3,918,839 However, in these methods, the apparatus becomes complicated, and there are difficulties in durability and manufacturing method. Therefore, it must be said that the practicality is poor.

The second problem with vertical axis wind turbines is how to deal with centrifugal force. As the rotational speed increases, a greater centrifugal force is applied to the blade, sometimes leading to blade damage or sudden breakage. A fundamental solution is needed.

The problem with the vertical axis windmill is not enough to cope with the improvement of the rotational torque and the fluctuation of the wind in the vertical direction such as the direction and the wind force and the wind up and down. Although the vertical axis wind turbine can cope with winds from around 360 °, it is a third problem to solve these problems in order to cope with a wind environment that is fluctuating rapidly such as an urban area.

In order to improve the startability of the problem, the blade according to claim 1 of the present invention is a belt-like blade having a curved shape, and the upper and lower ends thereof at an arbitrary angle in the rotation direction from the center of the blade toward both ends. Has a twist. By doing so, the drag force of the wind blowing from the front becomes smaller than the drag force of the wind blowing from the rear, so that the blade obtains a force to rotate forward. In other words, it has startability due to the difference in wind resistance.

The blade according to claim 2 of the present invention has a configuration in which a convex camber is provided on the rotating shaft side of the blade according to claim 1. Therefore, when the blade rotates, lift force directed toward the rotating shaft is generated. This lift becomes the centripetal force, and when it antagonizes the centrifugal force due to the rotation, a constant speed of rotation is obtained. At this time, the centrifugal force is apparently offset, so that no stress is generated on the blade, and the damage to the blade is significantly reduced.

The blade according to claim 3 of the present invention has a convex camber on the rotating shaft side in the same manner as the blade according to claim 2. However, since the blade is curved, the rotation speed is high and the lift is large in the central portion of the blade. In addition, the rotation speed is small and the lift is small in the vicinity of the rotation axis. In order to reduce the difference in lift, the maximum camber height of the blade is increased in the vicinity of the rotating shaft.

The blade according to claim 4 of the present invention produces lift and centripetal force. The rotational torque increases as the point of action of lift increases from the center of rotation. Therefore, by moving the blade so that the rotating shaft comes near the rear end of the blade, the distance from the rotating shaft is increased, and the rotational torque is improved.

As described in claim 5 of the present invention, by fixing the upper end or lower end of the blade by being advanced by a fixed angle in the rotational direction, a function of averaging small fluctuations in wind power is dynamically generated, and claim 1 is provided. The vertical axis wind turbine rotates smoothly and smoothly.

In addition, since the blade is curved, it has sufficient response to not only horizontal wind but also vertical wind fluctuations such as blowing up and down. With this configuration, the output of the wind turbine is averaged and becomes a smooth and stable output.

As described above, the starting performance is improved by twisting the blade in the present invention. Also, since the camber has a convex camber on the rotating shaft side, lift is generated and this is used as a centripetal force to cancel out the centrifugal force, so that the effect of reducing a large stress applied to the blade is exhibited. Furthermore, since the upper end or the lower end of the blade is fixed at a predetermined angle in the rotation direction, there is an effect of averaging small fluctuations in wind force and obtaining a smooth rotation.

Overview of vertical axis wind turbine with twisted blades Overview of vertical axis wind turbine with blades advanced and fixed in the direction of the axis of rotation Overview of vertical axis wind turbine with twisted blades fixed to the arm Overview of a vertical axis wind turbine with a blade fixed to an arm that has advanced in the direction of rotation Cross section of blade without camber Diagram showing twist of blade Sectional view of FIG. Lift and centrifugal force of blade with camber Cross section of FIG. Sectional view of FIG. Sectional view of FIG.

As a first example of implementing the results obtained above, FIG. 1 shows a Savonius type vertical axis wind turbine having two curved blades.
In FIG. 1, the two blades 6 have the same shape and are disposed at positions 180 ° symmetrical with respect to the rotation axis Os, and are fixed to the rotary column 1.

In general, the number of blades is not limited to two, and a configuration in which the number is increased depending on the wind conditions and the required performance and capacity of the wind turbine is adopted.

In addition, as shown in FIG. 5, the cross-sectional shape of the blade is an airfoil cross-section in order to reduce wind resistance, and is vertically symmetrical and has zero camber that does not generate lift. ω is the rotation direction, and the center line Ls connects the front end 3 and the rear end 4 of the blade and is called a chord line.
Mitsuo Makino "Basics of Aerodynamics (Second Edition)" Published in 1989 by Sangyo Tosho

Next, twisting of the blade 6 will be described with reference to FIG. FIG. 6 is a view of the blade 6 viewed from three directions. [A] is a front view, [B] is a side view, and [C] is a top view. The angle ψ shown in the top view of [C] takes a value larger than zero. ω indicates the direction of rotation.

The twist angle θ is close to zero degrees at the center of the blade 6, and the angle θ is twisted forward near the upper end 11 and the lower end 12. That is, the twist angle θ gradually increases in the forward direction from the vicinity of the center toward the upper and lower ends.

[A], [B], and [C] in FIG. 7 respectively show a P1-P1 cross-sectional view, a P2-P2 cross-sectional view, and a P3-P3 cross-sectional view in FIG. The rotating column 1 is not shown.
The two blades drawn in the cross-sectional view are arranged at a position of 180 degrees across the rotation axis Os. At each cross-sectional point, the blades have a relationship of θ1, θ2, θ3 degrees from the angles perpendicular to the rotation axis center Os, and θ1>θ2>θ3> 0.

The maximum twist angle θ at the upper and lower ends is usually 90 ° or less. In FIG. 6, it is drawn at 40 °.

In FIG. 6, by configuring as described above, the drag force of the wind W1 blowing in the rotation direction of the blade becomes larger than the drag force of the wind W2 blowing from the opposite direction of the blade. Accordingly, the blade is pushed by the wind W1 blowing in the rotation direction and generates a rotational torque. Rotation due to drag difference. Therefore, a high rotational torque can be generated even in a region where the wind speed is low, and the wind turbine has high starting performance.

  Since the blade 6 does not have a camber, lift does not occur. Hold the camber to generate lift and use this lift. First, a blade having a camber will be described with reference to FIG.

A line connecting the leading edge 3 and the trailing edge 4 of the blade 10 having a camber is a chord line, and a line connecting the middle between the upper surface 9 and the lower surface 8 is a camber line Cb, also called a center line. The blade 10 has a configuration in which the camber protrudes inward, that is, toward the rotation axis Os. The lift generated is a lift Lf starting from Po by the angle of attack β between the chord line and the wind direction W. In general, the lift Lf and the starting point Po are determined by the shape of the blade and the angle β.
Please refer to.

The lift Lf generated by taking the above-described configuration and having the convex camber line Cb on the rotating shaft side generates rotational torque and becomes the centripetal force of the rotating blade and faces the centrifugal force Cf generated in the blade 10 in the opposite direction. The two forces will cancel out.

That is, it greatly contributes to the reduction of blade damage or sudden breakage, which is the second problem, along with the improvement of the rotational force.

  From FIG. 8, if the distance δr between the rotation axis Os and the starting point Po of the lift Lf is increased, the value of the rotational torque Lf · δr increases. Therefore, the blade 10 is moved in the rotation direction so that the vicinity of the rear end of the blade 10 intersects the rotation axis. Therefore, in FIG. 6, the configuration is such that Os is moved to Op.

  Further, the upper end 11 or the lower end 12 of the blade 10 is advanced in the rotation direction and coupled to the rotation shaft. The amount of advance is displayed as an angle and is represented by φ. The value of φ will generally be greater than zero and take a range of 360 ° divided by the number of blades. FIG. 2 shows an example in which the value of φ is 90 °. FIG. 9 shows a cross-sectional view of each point shown in FIG.

  In FIG. 9, [A], [B], [C], [B] and [E] are respectively a P1-P1 cross-sectional view, a P2-P2 cross-sectional view, a P3-P3 cross-sectional view, and a P4-P5 cross-sectional view in FIG. , P5-P5 sectional view, the value of φ takes the value of the figure. The rotating column 1 is not shown. The twist angle θ and the maximum height of the blade 6 change with φ.

  By taking the above configuration, even if the wind fluctuates between 0 ° and 90 °, the blade 6 acts as an average value between 0 ° and 90 °. In other words, wind fluctuations are smoothly received, and the windmill having the blade 6 having the configuration rotates smoothly.

As a second embodiment, FIG. 3 shows a Savonius type vertical axis wind turbine having two blades slightly curved on an arm extending from a rotating shaft. This type is called a straight Darius type or H type if the blade is straight. These can be discussed roughly as follows.

The two blades 7 are arranged at a position symmetric with respect to the rotation axis Os by 180 °. As in FIG. 1, the twist angle θ is the same as in FIG. 1, where the central twist angle is θ 3, the twist angle at a slightly separated position is θ 2, and the twist angle near the arm is θ 1. The relationship> θ2> θ3> 0 is established. However, since there is no great difference in the distance between the rotating shaft and the mounting position, the values of θ1 and θ2 are smaller than in the case of FIG. FIG. 10 shows an example of a cross-sectional view at each position.

[A], [B], and [C] in FIG. 10 are a P1-P1 cross-sectional view, a P2-P2 cross-sectional view, and a P3-P3 cross-sectional view, respectively, in FIG. The rotating column 1 is not shown.

  In FIG. 10, each blade 7 is fixed in the vicinity of the rear end of the blade 7 in order to increase the value of δr in the direction of the rotation axis in the same manner as described above, and contributes to an increase in rotational torque and offsetting of centrifugal force.

  In FIG. 4, similarly to the above, the upper end or the lower end of the blade 7 is advanced in the rotation direction and coupled to the rotation shaft. The amount of advance φ is greater than zero and generally takes a range of 360 ° divided by the number of blades. FIG. 11 shows a cross-sectional view. An example in which the maximum value of φ is 90 ° is shown.

11, [b], [c], [c], [c], [c], [c], [c], [c], [c], [c], [c], [c], [c], [c] , P5-P5 cross-sectional view, each showing the value of φ. The rotating column 1 is not shown.

If the vertical axis wind turbine is used for a wind power generator, the startability is high and the durability is improved, and wind power can be efficiently converted into electric power. Therefore, the use of clean energy is accelerated. In particular, since it is suitable for use in small power generators and areas where the wind direction changes frequently, the spread of wind power generation is promoted particularly in urban areas where the wind environment is poor.

DESCRIPTION OF SYMBOLS 1 Rotating strut 2 Arm 3 Blade front end 4 Blade trailing edge 5 Maximum height 6 Blade fixed in the vicinity of the prop 7 Blade fixed to the arm 8 Upper surface, wing non-rotating shaft side 9 Lower surface, wing rotating shaft side 10 Blade with camber 11 Upper end of blade 12 Lower end of blade Os Rotation axis Op Rotation axis near rear end of blade φ Advance angle ω Rotation direction θ Twist angle Lf Lift Cf Centrifugal force

Claims (5)

A vertical axis windmill in which the upper and lower ends of a belt-shaped blade having a curved shape are fixed to the vicinity of the rotation axis or to an arm extending from the rotation axis,
A vertical axis wind turbine characterized by a structure in which a twist of an arbitrary angle is provided in a rotational direction from the center of the blade toward both upper and lower ends.   The vertical axis wind turbine according to claim 1, wherein the blade according to claim 1 has a camber convex on the rotating shaft side. The blade according to claim 2, wherein the maximum height of the camber of the blade gradually increases as the blade according to claim 2 approaches the upper and lower ends from the center. The vertical axis wind turbine according to claim 1, wherein the blade according to claims 2 and 3 is fixed to the rotary shaft near the rear end of the blade. The vertical axis wind turbine according to claim 1, wherein the upper end or the lower end of the blade according to claim 2 or 3 is advanced at an arbitrary angle in the rotation direction and fixed to the rotation axis or an arm extending from the rotation axis.