A wind turbine structure with variable pitch blades

Abstract

The present invention discloses a variable pitch blade for a wind turbine generator structure, in which only a first spar cap and a second spar cap in a blade tip section are cut, while a blade root section remains unchanged; a wing of the first spar cap close to the leading edge of the blade starts from its end face facing the blade tip and cuts toward the blade root direction while cutting off a portion obliquely toward the leading edge of the blade; a wing of the second spar cap close to the trailing edge of the blade starts from its end face facing the blade tip and cuts toward the blade root direction while cutting off a portion obliquely toward the trailing edge of the blade; the first spar cap and the second spar cap after cutting are staggered when viewed from their end faces facing the blade tip, so that under strong wind conditions, the main axis of the blade structure in the cross section is twisted, forming a structural bending-torsion coupling, which is equivalent to performing local variable pitch on the blade tip section, and can reduce the load without losing power generation or with less loss, and solve the air-elasticity problem at a minimum cost.

Description

Technical Field

[0001] The invention relates to the technical field of passive pitch control of a wind generator set, and in particular to a pitch control blade of a wind generator set structure. Background Art

[0002] With existing wind turbine blades, as wind speed increases, blade pitch control is activated, the blade root pitch bearing is electrically controlled to produce a pitch action, the entire blade is pitched, and all sections rotate at the same angle. At this time, the aerodynamic efficiency of the blade root section and the blade tip section are reduced.

[0003] As blade structures develop towards larger and more flexible directions, the flutter problem becomes more prominent. Flexible blades generally have stall flutter problems caused by swing-torsion coupling. There are usually two ways to solve this stall flutter problem: a. Increasing torsional stiffness, adjusting the shear center and other measures will lead to increased weight; b. Reducing the load through variable pitch control means will be accompanied by a loss of power generation. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to propose a wind turbine structure with variable pitch blades that reduces the load without losing power generation or with less loss, and solves the air elasticity problem at a minimum cost.

[0005] To achieve the above-mentioned purpose, the first technical solution provided by the present invention is: a wind turbine structure variable pitch blade, the main beam of the blade is composed of a first beam cap, a second beam cap and a web, the first beam cap is in contact with the blade pressure surface and extends in the blade length direction, the second beam cap is in contact with the blade suction surface and extends in the blade length direction, two webs extending side by side in the blade length direction are connected between the first beam cap and the second beam cap, two webs extend outward on both sides of the first beam cap and the second beam cap respectively to form two side wings, the blade is divided into a tip section and a root section, only the first beam cap and the second beam cap in the tip section are cut, and the root section remains unchanged, wherein the first beam cap A winglet on one side close to the leading edge of the blade starts cutting from its end face facing the blade tip toward the blade root, and at the same time, a part is cut off obliquely toward the leading edge of the blade, so that the width of its cross section gradually decreases from the blade root toward the blade tip. A winglet on one side close to the trailing edge of the blade starts cutting from its end face facing the blade tip toward the blade root, and at the same time, a part is cut off obliquely toward the trailing edge of the blade, so that the width of its cross section gradually decreases from the blade root toward the blade tip. When viewed from the end face facing the blade tip, the end faces of the first and second spar caps after cutting are staggered, so that under strong wind conditions, the main axis of the blade structure in the cross section is twisted, forming a structural bending-torsion coupling, which is equivalent to performing local pitch change on the blade tip section.

[0006] Furthermore, the cut-off parts of the first beam cap and the second beam cap are triangular-like structures.

[0007] The second technical solution provided by the present invention is: a wind turbine structure variable pitch blade, the main beam of the blade is composed of a first beam cap, a second beam cap and a web, the first beam cap fits the blade pressure surface and extends in the blade length direction, the second beam cap fits the blade suction surface and extends in the blade length direction, two webs extending side by side in the blade length direction are connected between the first beam cap and the second beam cap, two webs extend outward on both sides of the first beam cap and the second beam cap respectively to form two side wings, the blade is divided into a tip section and a root section, only the first beam cap and the second beam cap in the tip section are cut, and the root section remains unchanged, wherein the first beam cap is close to the blade A wing on the trailing edge starts cutting from its end face facing the blade tip toward the blade root, and at the same time, a part is cut off obliquely toward the trailing edge of the blade, so that the width of its cross section gradually decreases from the blade root toward the blade tip. A wing on the second beam cap close to the leading edge of the blade starts cutting from its end face facing the blade tip toward the blade root, and at the same time, a part is cut off obliquely toward the leading edge of the blade, so that the width of its cross section gradually decreases from the blade root toward the blade tip. When viewed from the end face facing the blade tip, the end faces of the first beam cap and the second beam cap after cutting are staggered, so that under strong wind conditions, the main axis of the blade structure in the cross section is twisted, forming a structural bending-torsion coupling, which is equivalent to local pitch change of the blade tip section.

[0008] Furthermore, the cut-off parts of the first beam cap and the second beam cap are triangular-like structures.

[0009] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0010] 1. Structural torsion increases the damping in the swing direction and reduces the damping in the flapping direction. However, since flapping vibration is a low-frequency vibration with a large damping, and swing vibration is a high-frequency vibration with a small damping, it is sufficient to consider the swing vibration when studying flutter. The increase in the swing vibration damping will reduce the speed and displacement amplitude of the swing vibration, and the structural load and fatigue load will also decrease accordingly, while reducing the structural load changes caused by gust response.

[0011] 2. The structural pitch range is only in the blade tip area, and the area from the blade root to the middle of the blade does not change. Due to the existence of bending-torsion coupling, the load is reduced without significantly reducing the power generation, and the aeroelastic problem is solved at the lowest cost.

[0012] 3. Due to the reduction of blade load, the amount of material used can be reduced, thereby reducing the blade cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view of the variable pitch blade of the wind turbine generator structure in Example 1.

[0014] Figure 2 Schematic diagram of the pressure surface direction of the variable pitch blade of the wind turbine generator structure in Example 1 (the dotted line area in the figure is the cut part).

[0015] Figure 3 Schematic diagram of the suction surface direction of the variable pitch blade of the wind turbine generator structure in Example 1 (the dotted line area in the figure is the cut part).

[0016] Figure 4 Schematic diagram of the twisting of the tip section of the variable pitch blade of the wind turbine structure in Example 1.

[0017] Figure 5 It is a cross-sectional view of the variable pitch blades of the wind turbine generator structure in Example 2. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with specific embodiments.

[0019] Example 1

[0020] See also Figures 1 to 3 As shown, this embodiment discloses a wind turbine structure variable pitch blade, the main beam of the blade is composed of a first beam cap 3, a second beam cap 4 and a web 5, the first beam cap 3 is in contact with the blade pressure surface 1 (PS surface) and extends in the blade length direction, the second beam cap 4 is in contact with the blade suction surface 2 (SS surface) and extends in the blade length direction, two webs 5 extending side by side in the blade length direction are connected between the first beam cap 3 and the second beam cap 4, two webs 5 extend outwardly on both sides of the first beam cap 3 and the second beam cap 4 to form two side wings, the blade is divided into a blade tip section and a blade root section, and the improvement is that only the first beam cap 3 and the second beam cap 4 in the blade tip section are The blade root section remains unchanged, wherein a wing of the first spar cap 3 close to the leading edge 7 of the blade is cut from its end surface facing the blade tip toward the blade root, and a portion is cut off obliquely toward the leading edge 7 of the blade (the portion cut off is similar to a triangular structure), so that the cross-sectional width gradually decreases from the blade root toward the blade tip, and a wing of the second spar cap 4 close to the trailing edge 6 of the blade is cut from its end surface facing the blade tip toward the blade root, and a portion is cut off obliquely toward the trailing edge 6 of the blade (the portion cut off is similar to a triangular structure), so that the cross-sectional width gradually decreases from the blade root toward the blade tip, and the first and second spar caps after cutting are viewed from their end surfaces facing the blade tip (similar to Figure 1 In the case of the first spar cap 3 and the second spar cap 4, the end faces are staggered. This design causes the main axis of the blade structure in the cross section to twist under strong wind conditions, and the tip area moves in the swing direction, making the angle of attack smaller. Figure 4As shown, torsion is generated to form structural bending-torsion coupling, which is similar to the concept of increasing the pitch angle through blade pitch control and then reducing the airfoil angle of attack, thereby reducing the blade load, which is equivalent to local pitch control of the blade tip section. The difference between it and the traditional technology is that pitch control requires a servo system, which is active control through electrical control, and the pitch action will affect the entire blade, while the structural pitch blade is to offset the main beam in the tip area, causing the structural performance of the tip area to change, which is passive control. The pitch angle can also be changed in the power generation state when the servo motor is not working, and only the tip area is affected. Without reducing the pitch angle in the root area, the risk of stall flutter is reduced and the blade safety is improved. At the same time, the structural torsion increases the damping in the swing direction and reduces the damping in the flapping direction. However, since the flapping vibration is a low-frequency vibration with large damping, and the swing vibration is a high-frequency vibration with small damping, therefore, when studying flutter, it is sufficient to consider the swing vibration. The increase in the swing vibration damping will reduce the speed and displacement amplitude of the swing vibration, and the structural load and fatigue load will also be reduced accordingly. In short, when the impeller of a wind turbine rotates, the tip of the blade twists in the swing direction when subjected to wind load, causing the aeroelastic properties of the blade to change, the power generation efficiency to slightly decrease, the aerodynamic damping to increase, and the risk of stall flutter to decrease.

[0021] Example 2

[0022] See also Figure 5 As shown, what is different from Example 1 is that in this embodiment, a side wing of the first spar cap 3 close to the blade trailing edge 6 is cut from its end surface facing the blade tip toward the blade root, and a part is cut off obliquely toward the blade trailing edge 6, so that the cross-sectional width gradually decreases from the blade root to the blade tip, and a side wing of the second spar cap 4 close to the blade leading edge 7 is cut from its end surface facing the blade tip toward the blade root, and a part is cut off obliquely toward the blade leading edge 7, so that the cross-sectional width gradually decreases from the blade root to the blade tip.

[0023] The above-described embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, all changes made according to the shape and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A wind turbine structure pitch blade, wherein the main beam of the blade is composed of a first beam cap, a second beam cap and a web, wherein the first beam cap is in contact with the blade pressure surface and extends in the blade length direction, and the second beam cap is in contact with the blade suction surface and extends in the blade length direction, two webs extending side by side in the blade length direction are connected between the first beam cap and the second beam cap, two webs extend outward from both sides of the first beam cap and the second beam cap to form two side wings, and the blade is divided into a blade tip section and a blade root section, characterized in that: Only the first spar cap and the second spar cap in the blade tip section are cut, while the blade root section remains unchanged, wherein a wing of the first spar cap close to the leading edge of the blade is cut from its end face facing the blade tip toward the blade root, and a part is cut off obliquely toward the leading edge of the blade, so that the width of its cross section gradually decreases from the blade root to the blade tip, and a wing of the second spar cap close to the trailing edge of the blade is cut from its end face facing the blade tip toward the blade root, and a part is cut off obliquely toward the trailing edge of the blade, so that the width of its cross section gradually decreases from the blade root to the blade tip. When the first spar cap and the second spar cap are cut, the end faces of the first spar cap and the second spar cap are staggered when viewed from their end faces facing the blade tip, so that under strong wind conditions, the main axis of the blade structure in the cross section is twisted, forming a structural bending-torsion coupling, which is equivalent to performing local pitch change on the blade tip section.

2. The wind turbine generator structure variable pitch blade according to claim 1, characterized in that: The cut-off parts of the first beam cap and the second beam cap are triangular structures.

3. A wind turbine structure pitch blade, wherein the main beam of the blade is composed of a first beam cap, a second beam cap and a web, the first beam cap is in contact with the blade pressure surface and extends in the blade length direction, the second beam cap is in contact with the blade suction surface and extends in the blade length direction, two webs extending side by side in the blade length direction are connected between the first beam cap and the second beam cap, two webs extend outward from both sides of the first beam cap and the second beam cap to form two side wings, the blade is divided into a blade tip section and a blade root section, and is characterized in that: Only the first spar cap and the second spar cap in the blade tip section are cut, while the blade root section remains unchanged, wherein a wing of the first spar cap close to the trailing edge of the blade is cut from its end face facing the blade tip toward the blade root, and a part is cut off obliquely toward the trailing edge of the blade, so that the width of its cross section gradually decreases from the blade root to the blade tip, and a wing of the second spar cap close to the leading edge of the blade is cut from its end face facing the blade tip toward the blade root, and a part is cut off obliquely toward the leading edge of the blade, so that the width of its cross section gradually decreases from the blade root to the blade tip. When viewed from the end face facing the blade tip, the end faces of the first spar cap and the second spar cap after cutting are staggered, so that under strong wind conditions, the main axis of the blade structure in the cross section is twisted, forming a structural bending-torsion coupling, which is equivalent to local pitch change of the blade tip section.

4. The variable pitch blade structure of a wind turbine generator set according to claim 3, characterized in that: The cut-off parts of the first beam cap and the second beam cap are triangular structures.

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