JP2001289151A - Structure of blade of large windmill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems that it is impossible to thin the blade made of a lightweight material of low rigidity, such as a fiber-glass reinforced plastic or the like used as a material of the blade of a large windmill, which causes the noise by the vortex produced near a tip part of an outer periphery of a blade, particularly at a high speed, and the flattering phenomenon, the vibrational fault and the impairing of the performance by the deflection and torsion of the blade. SOLUTION: The tip part of the outer periphery of the blade is made of a metallic material having high elastic modulus and high specific gravity such as stainless steel, and connected to a blade mounting member at a hub side by means of a tension rod of lightweight and high strength such as carbon fiber. By applying this constitution, a thickness of the tip part of the outer periphery of the blade can be remarkably reduced, whereby not only the noise caused by the vortex can be reduced, but also the deflection and the torsion of the blade can be recovered as the blade is radially pulled by the weight effect (centrifugal force) of the metallic material, and the flattering phenomenon, the vibrational fault or the like caused by the turbulence of the wind can be prevented effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wing structure that facilitates upsizing of a wind turbine.

[0002]

2. Description of the Related Art Generally, the construction cost per unit output of a power generation facility and the unit cost of power generation become lower as the size of the generator increases, but one of the factors preventing the increase in size is noise, deflection and torsion of the blades. That is,
Since the diameter of a large wind turbine is enormous due to the fate of using wind power with a low energy density, the conventional wing has been made of a lightweight material such as glass fiber reinforced plastic (hereinafter referred to as GFRP). However, the rigidity (elastic modulus) of these lightweight materials is significantly lower than that of steel or the like. For example, the elastic modulus of GFRP is less than one-tenth that of steel, and the blade thickness cannot be made very thin. In the vicinity of the tip, noise generated from vortices generated at the abdomen and trailing edge of the wing increases. If the entrance and exit ends of the wing are tapered to reduce these vortex sounds, the wing itself may vibrate and generate noise.

Further, not only an excessive bending moment due to wind pressure is applied to the vicinity of the root of the wing, but also the deflection at the tip of the outer periphery of the wing becomes large and the torsion is large. If the angle of attack changes from the design value due to the twisting of the wing, the performance naturally declines.

[0004]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to suppress the generation of vortices on the abdomen and trailing edge of a wing and to prevent the vibration noise of the wing itself in a large wind turbine, and to warp or twist the wing tip. It is an object of the present invention to prevent vibration disturbance such as a flutter phenomenon due to wind turbulence by suppressing as much as possible, and to suppress a change in an angle of attack based on deflection or torsion of a wing, thereby preventing performance degradation.

[0005]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the fact that the above-mentioned problems associated with an increase in the size of a windmill are caused by the rigidity of the wing material. Is
In windmill blades made of lightweight materials such as GFRP,
A blade structure for a large wind turbine, characterized in that a blade outer peripheral tip is constructed of a metal material having a high elastic modulus and a high specific gravity such as stainless steel.

According to a second aspect of the present invention, in the first aspect of the invention, the tip of the outer periphery of the wing is connected to the wing mounting member on the hub side by a lightweight and high-strength tension rod such as carbon fiber. This is the structure of the wing of a large wind turbine.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing the structure and principle of the present invention, FIG. 2 is a perspective explanatory view showing a main part of the present invention, that is, the vicinity of a tip of a blade outer periphery, and FIG. FIG. 4 is an explanatory view of a QQ section of FIG. 2, and FIG. 5 is an explanatory view of a Karman vortex at the outlet of the thick wing.

As shown in FIGS. 1, 2, 3, and 4, the blade of the wind turbine according to the present invention has a blade body 1 made of the same material as the conventional one, that is, a lightweight material such as GFRP, and a high elastic modulus such as stainless steel. The wing outer peripheral tip 2 made of a metal material having a high specific gravity is bonded to the wing outer peripheral tip 2. The wing outer peripheral tip 2 is formed by a tension rod 4 made of a lightweight and high-strength material such as carbon fiber.
And the tension rod 4
Is formed integrally with the wing body 1 to receive the centrifugal force of the wing outer peripheral tip 2 generated during rotation by the combined tension between the wing body 1 and the tension rod 4. In addition,
In the figure, details of the wing on the hub 3 side are omitted.

With the above configuration, the distance from the center of gravity G of the blade outer peripheral tip 2 to the center of the hub is R, the increased weight is m, the acceleration of gravity is g, and the increased centrifugal force of the blade outer peripheral tip 2 at the rotation speed Nrpm. When the ratio of F to the increasing gravity is obtained, F / mg = R
(ΠN / 30) ² / g, the following values can be obtained by introducing the specifications of two large wind turbines of the known example and estimating this ratio. In the case of 1,000 kW: R = about 27 meters, N = 21
rpm, ΔF / mg = 13.3 For 1,500 kW: R = about 31 meters, N = 1
7.3 rpm, ΔF / mg = 10.4 That is, since the increased centrifugal force is one digit larger than the increased gravity,
It can be seen that the effect of the increased mass of the blade outer peripheral tip 2 can be ignored by substantially considering only the centrifugal force ignoring gravity.

On the other hand, in conventional large wind turbines, the stiffness of the blades is small, so that not only does the angle of attack Θ of the blades change due to the torsional torque T of the blades generated by wind power, but also the performance is affected, and the torsion generated by the turbulence of the wind is also increased. Fluctuations in the torque T tend to cause vibration disturbances such as blade flutter. The deflection d of the wing due to the wind force during operation is extremely large, and according to publicly known data, the deflection of the outer peripheral end of the wing having a diameter of 56 m reaches about 1.5 m at the rated wind speed. It also affects Θ.

However, as described above, according to the configuration of the present invention, the specific gravity of the metal (stainless steel) at the outer peripheral tip portion 2 of the blade is about five times that of GFRP. Since the centrifugal force F is generated, the centrifugal force pulls the blade body 1 in the radial direction, so that M = Fd
The bending moment acts in reverse to the bending moment of the wind force to alleviate the bending stress in the vicinity of the root of the blade main body 1 and at the same time restore the torsion due to the bending d of the blade outer peripheral tip 2 and the torsional torque T. As a result, it is possible to obtain an effect of preventing a vibration obstacle such as a flutter phenomenon caused by the deflection or torsion of the wing, a performance decrease due to a change in the angle of attack, and the like.

Next, since the conventional wind turbine blade has low rigidity, it is necessary to use a thick-walled blade 1 'as shown by a dashed line in FIG. A vortex 7 in the abdomen and a vortex 8 on the trailing edge caused by the turbulence, and a Karman vortex 9 at the exit end of the thick wing 1 'as shown in FIG.
Were easily generated, each of which was a source of noise, which is a weak point of large wind turbines. If the wing inlet end 5 and the wing outlet end 6 are tapered to prevent these vortices, the flexible wing itself may vibrate and generate whistle noise.

According to the present invention, when the blade outer peripheral tip portion 2 is made of, for example, stainless steel, the rigidity (elastic modulus) is equal to that of the conventional GF.
One or more digits larger than RP. Therefore, the blade thickness of the blade outer peripheral tip 2 where noise is most likely to be generated can be greatly reduced as illustrated in FIG. 3, and it is easy to taper the inlet end 5 and the outlet end 6 of the blade. Therefore, noise can be effectively prevented. The shape of the blade outer peripheral tip 2 may be formed in a U-shape as shown in FIGS. 2 and 4, and the range of the tapered portion of the inlet end 5 and the outlet end 6 may be increased as necessary.

[0014]

As is apparent from the above description, according to the present invention, it is possible to reduce the noise caused by the vortex generated near the tip of the outer periphery of the high-speed blade in a large wind turbine and the vibration of the blade itself.
There are various effects such as reducing the deflection and torsion of the wing to prevent vibration disturbance such as flutter phenomenon due to wind turbulence, and to suppress the change in the angle of attack of the wing to prevent performance degradation, making it easy to increase the size of the windmill Therefore, it is possible to contribute to the reduction of the construction cost per unit output and the unit cost of power generation due to the increase in size.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the configuration and principle of the present invention.

FIG. 2 is a perspective explanatory view showing a main part of the present invention, that is, a vicinity of a blade outer peripheral tip portion;

FIG. 3 is an explanatory diagram viewed from a viewing arrow P in FIGS. 1 and 2;

FIG. 4 is an explanatory diagram of a QQ cross section of FIG. 2;

FIG. 5 is an explanatory diagram of a Karman vortex at the outlet of a thick wing.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 blade main body 1 ′ thick wing 2 blade outer peripheral tip 3 hub 4 tension rod 5 blade inlet end 6 blade outlet end 7 abdominal vortex 8 trailing edge vortex 9 Karman vortex

Claims (2)

[Claims] 1. A wind turbine blade made of a lightweight material such as glass fiber reinforced plastic, wherein the tip of the outer periphery of the blade is constructed of a metal material having a high elastic modulus and a high specific gravity such as stainless steel. Wing structure. 2. The wing structure of a large wind turbine according to claim 1, wherein the wing outer peripheral tip is connected to a hub-side wing mounting member by a lightweight high-strength tension rod made of carbon fiber or the like.