Wind turbine blade root connecting structure and method for improving load bearing capacity of wind turbine blade root

Abstract

The application discloses a wind turbine blade root connecting structure and a method for improving the bearing capacity of a wind turbine blade root, and belongs to the technical field of wind turbine blade roots.The wind turbine blade root connecting structure comprises a flange, an inner bearing, an outer bearing, a roller, a hub, a blade root and a blade root bolt assembly.The flange is connected with the inner bearing, the inner bearing is connected with the outer bearing through the roller, and the outer bearing is connected with the hub.Double rows of through holes are arranged on the blade root, each row of through holes is uniformly distributed along the circumference of the blade root, the centers of the two rows of through holes are kept at a preset axial distance, and the blade root is connected with the flange through the blade root bolt assembly arranged in the double rows of through holes.The blade root is provided with multiple layers of laminates along the thickness direction of the blade root.The application can improve the bearing capacity of the blade root glass steel, replace the transition flange to enhance the bearing capacity of the blade root bolt, reduce the overall weight increase of the structure, and retain the transition flange structure to further improve the bearing capacity of the blade root bolt.

Description

Technical Field

[0001] This invention relates to the technical field of wind turbine blades, and in particular to a wind turbine blade root connection structure and a method for improving the load-bearing capacity of wind turbine blade roots. Background Technology

[0002] Currently, blade root connections are divided into pre-embedded and drilled types, using bolts to connect the blades and bearings. The resultant bending moment on the blade gradually increases from the tip to the root, reaching its maximum at 0m at the root. At the blade root, it is crucial to ensure both the blade itself and the safety of the root bolts. Mass failure of the root bolts would put the blades at risk of falling off.

[0003] As the power demand for wind turbines increases, wind turbine blades are becoming larger, leading to greater loads on the blade roots. The bolts in the original structure are struggling to withstand these increasing loads, posing a risk of breakage. To address this issue, a transition flange structure is introduced to enhance the relative stiffness of the connected components, thereby reducing the load borne by the bolts and increasing the relative load-bearing capacity. While the introduction of transition flanges effectively reduces the load on the bolts, it also has drawbacks. Firstly, the transition flange significantly increases the overall structural weight. Secondly, there is a threshold to the impact of increasing the thickness of the transition flange on the load-bearing capacity of the blade root bolts; therefore, the flange cannot be increased indefinitely. Furthermore, the load-bearing capacity of the fiberglass reinforced plastic (FRP) in the blade roots is gradually reaching its limit, necessitating improvements in its load-bearing capacity. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and propose a wind turbine blade root connection structure and a method to improve the bearing capacity of wind turbine blade roots. By designing a double-row hole blade root connection structure and simultaneously optimizing the blade root fiberglass layup scheme, the advantages and disadvantages of different schemes are compared and calculated using the finite element method, so as to achieve the effect of improving the bearing capacity of the blade roots.

[0005] The objective of this invention is achieved through the following technical solution: a wind turbine blade root connection structure, comprising a flange, an inner bearing, an outer bearing, rollers, a hub, a blade root, and a blade root bolt assembly. The flange is connected to the inner bearing, the inner bearing is connected to the outer bearing via rollers, and the outer bearing is connected to the hub. The blade root has double rows of through holes, each row of through holes being evenly distributed along the circumference of the blade root, and the centers of the double rows of through holes maintaining a preset axial distance. The blade root is connected to the flange via blade root bolt assemblies disposed within the double rows of through holes. The blade root has multiple layers along its thickness direction, the layers including an outer reinforcing layer and an inner reinforcing layer. Both the outer and inner reinforcing layers are combinations of uniaxial and biaxial fiberglass cloth, wherein the number of layers of uniaxial and biaxial fiberglass cloth maintains a preset ratio.

[0006] Furthermore, the layup also includes an outer skin layer, a thickening layer, and an inner skin layer, which are arranged sequentially from the outside to the inside along the thickness direction of the leaf root.

[0007] Furthermore, the outer skin layer is a biaxial fiberglass cloth with a layup angle of ±45°.

[0008] Furthermore, the thickening layer is a triaxial fiberglass cloth with a layup angle of 0° and ±45°.

[0009] Furthermore, the inner skin layer is a biaxial fiberglass cloth with a layup angle of ±45°.

[0010] Furthermore, the two rows of through holes are not located on the same busbar, and the row of through holes near the bottom of the leaf root maintains a preset distance from the bottom of the leaf root.

[0011] Furthermore, the leaf root bolt assembly includes a long bolt assembly and a short bolt assembly. The long bolt assembly includes a round nut, a long bolt, and a nut connected in sequence, and the short bolt assembly includes a round nut, a short bolt, and a nut connected in sequence. Multiple sets of the long bolt assembly are installed in one row of through holes, and multiple sets of the short bolt assembly are installed in another row of through holes.

[0012] Furthermore, the cross-sectional shape of the through hole is circular or figure-eight shaped.

[0013] A method for improving the load-bearing capacity of wind turbine blade roots, using the aforementioned wind turbine blade root connection structure, includes the following steps:

[0014] S1. In the blade root layup, by adjusting the ratio of uniaxial fiberglass cloth and biaxial fiberglass cloth in the outer and inner reinforcing layers, various blade root fiberglass layup ratio schemes are set.

[0015] S2. Set the specifications of the blade root bolt assembly, the radial diameter of the through hole, and the spacing between the row of through holes near the bottom of the blade root and the bottom of the blade root, as well as the axial distance between the two rows of through holes.

[0016] S3. Select one of the blade root fiberglass ply mix ratio schemes, change the axial distance between the double rows of through holes, use the finite element simulation method to calculate the load-bearing capacity and safety margin of the blade root bolt assembly and fiberglass ply, and select the scheme in which both the blade root bolt assembly and fiberglass ply meet the preset safety margin requirements under the preset load.

[0017] S4. Change the fiberglass layup ratio of the leaf roots and repeat step S3.

[0018] S5. Compare the safety margins calculated from the various blade root fiberglass layup ratio schemes, and select the scheme with the largest safety margin to improve the load-bearing capacity of the wind turbine blade roots.

[0019] A wind turbine generator set includes the aforementioned wind turbine generator blade root connection structure.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] This invention can improve the load-bearing capacity of the blade root fiberglass, replace the transition flange to enhance the load-bearing capacity of the blade root bolts, reduce the increase in the overall weight of the structure, and at the same time retain the transition flange structure, which can be used to further improve the load-bearing capacity of the blade root bolts. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of the leaf root connection structure.

[0023] Figure 2 This is a schematic diagram of the blade root bolt assembly.

[0024] Figure 3 A schematic diagram of the leaf root layup structure.

[0025] Figure 4 This is a schematic diagram of the ply angle direction.

[0026] Figure 5 This is a schematic diagram of a circular double-row through-hole positioning structure.

[0027] Figure 6 This is a schematic diagram of a circular through-hole.

[0028] Figure 7 This is a schematic diagram of a figure-eight shaped through hole.

[0029] Figure 8 A flowchart for methods to improve the load-bearing capacity of wind turbine blade roots. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Example 1

[0032] See Figures 1 to 2 As shown, the wind turbine blade root connection structure provided in this embodiment includes a blade root 1, a flange 2, an inner bearing 3, an outer bearing 4, a radial roller 5, an axial roller 6, a hub 7, and a blade root bolt assembly.

[0033] The flange 2 is connected to the inner bearing 3, and the inner bearing 3 is connected to the outer bearing 4 via radial rollers 5 and axial rollers 6. The outer bearing 4 is connected to the hub 7, which can be considered as a fixed end. The blade root is provided with double rows of through holes, each row of through holes being evenly distributed along the circumference of the blade root, and the centers of the double rows of through holes maintaining a preset axial distance. The blade root is connected to the flange via blade root bolt assemblies provided in the double rows of through holes. The blade root bolt assembly includes a long bolt assembly and a short bolt assembly. The long bolt assembly includes a round nut 8, a long bolt 9, and a nut 11 connected in sequence. The short bolt assembly includes a round nut 8, a short bolt 10, and a nut 11 connected in sequence. Each of the long bolt assembly and the short bolt assembly corresponds to a row of through holes. Multiple sets of the long bolt assembly are installed in one row of through holes, and multiple sets of the short bolt assembly are installed in another row of through holes. The blade root has multiple layers along its thickness direction.

[0034] See Figure 3 As shown, the structure of the leaf root layup is provided on the mold surface 12. The layup includes an outer skin layer 13, an outer reinforcing layer 14, an inner reinforcing layer 15, a thickening layer 16, and an inner skin layer 17. The outer skin layer 13, outer reinforcing layer 14, inner reinforcing layer 15, thickening layer 16, and inner skin layer 17 are arranged sequentially from the outside to the inside along the leaf root thickness direction.

[0035]

[0036] Table 1. Structural Layers and Corresponding Fiberglass Cloth Types

[0037] Table 1 shows the structural layers and corresponding fiberglass cloth types. Monoaxial cloth is 0 degrees, biaxial cloth is a combination of ±45 degrees, and triaxial cloth is a combination of 0 degrees and ±45 degrees. (See also...) Figure 4 As shown, 18 is the 45-degree direction, 19 is the 0-degree direction, and 20 is the -45-degree direction. The triaxial fabric consists of 63% by weight of 0-degree fiberglass cloth, 18.5% by weight of 45-degree fiberglass cloth, and 18.5% by weight of -45-degree fiberglass cloth.

[0038] Potential failure modes of fiberglass reinforced plastic (FRP) in bolted connections include tensile failure of the net cross-section, compressive failure, shear failure, and transverse splitting. Compressive failure is primarily affected by the bolt preload, which can be addressed by adjusting the preload. Tensile failure is resisted by the fiberglass cloth in the 0-degree direction, while shear failure and transverse splitting are resisted by the fiberglass cloth in the ±45-degree directions. With a constant total thickness, increasing the proportion of monoaxial cloth increases the safety factor for tensile failure of the net cross-section, but decreases the safety factors for shear and transverse splitting.

[0039] Therefore, the method to optimize FRP layup design is to adjust the ratio of monoaxial and biaxial fiberglass fabrics:

[0040] Keeping the inner skin layer, outer skin layer, and thickening layer unchanged, the ratio of uniaxial and biaxial fiberglass cloth in the outer reinforcement layer and inner reinforcement layer is changed, resulting in three schemes with uniaxial cloth layer to biaxial cloth layer ratios of 1:1, 2:1, and 3:1, respectively.

[0041] If the solution obtained by adjusting the outer and inner reinforcing layers still does not meet the requirements, the thickening layer is further adjusted. If the net cross-sectional tensile strength is insufficient, the proportion of 0-degree fiber weight in the triaxial fabric is increased, and vice versa.

[0042] See Figure 5 As shown, this is a circular double-row through-hole positioning structure. The distance between the blade root position 0m21 (the bottom of the blade root) and the center of the first row of through holes is denoted as A. The axial distance between the centers of the double rows of through holes is denoted as B. The diameter of the through holes is denoted as Φ. These three dimensions, A, B, and Φ, will affect the ultimate load-bearing capacity of the blade root fiberglass. Improper matching may lead to a decrease in the load-bearing capacity of the blade root fiberglass. The value of Φ varies with the specifications of the blade root bolt assembly. Therefore, when improving the load-bearing capacity of the blade root, it is necessary to obtain appropriate values ​​of A and B through multiple iterations. The values ​​of A and B are shown in Table 2.

[0043]

[0044]

[0045] Table 2. Corresponding Values ​​of A and B

[0046] See Figures 6 to 7 As shown, the cross-sectional shape of the through hole can be circular or figure-eight. When the modulus of the transition flange is not less than 200 GPa, the double-row through hole structure increases the circumferential distance between the holes, that is, the net cross-sectional area increases, and the performance of fiberglass will be improved.

[0047] Example 2

[0048] See Figure 8 As shown, the method for improving the bearing capacity of wind turbine blade roots provided in this embodiment uses the wind turbine blade root connection structure described in Embodiment 1, and includes the following steps:

[0049] 1. In the leaf root layup, various leaf root fiberglass layup ratio schemes are designed by adjusting the ratio of uniaxial fiberglass cloth and biaxial fiberglass cloth in the outer and inner reinforcing layers;

[0050] 2. Design the specifications of the blade root bolt assembly and determine the radial diameter of the through hole;

[0051] 3. Design the distance between the center of the first row of holes and the blade root, that is, the distance between the row of through holes near the bottom of the blade root and the bottom of the blade root, and the axial distance between the centers of the two rows of through holes;

[0052] 4. Select one of the blade root fiberglass layup ratio schemes, change the axial distance between the double rows of through holes, and use the finite element simulation method to calculate the load-bearing capacity and safety margin of the blade root bolt assembly and fiberglass layup. Select the scheme in which both the blade root bolt assembly and fiberglass layup meet the preset safety margin requirements under the preset load.

[0053] 5. Change the fiberglass layup ratio of the leaf roots and repeat step 4;

[0054] 6. Result evaluation: Select the scheme that simultaneously satisfies the safety of blade root bolts and FRP, compare the safety margins calculated from various blade root FRP layup ratio schemes, and select the scheme with the largest safety margin to improve the load-bearing capacity of wind turbine blade roots.

[0055] Example 3

[0056] The wind turbine provided in this embodiment includes the wind turbine blade root connection structure described in Embodiment 1.

[0057] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, any changes made in accordance with the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for improving the bearing capacity of wind turbine blade roots, characterized in that, A wind turbine blade root connection structure is used, comprising a flange, an inner bearing, an outer bearing, rollers, and a hub. The flange is connected to the inner bearing, the inner bearing is connected to the outer bearing via rollers, and the outer bearing is connected to the hub. The structure is characterized by: a blade root and blade root bolt assemblies; the blade root has double rows of through holes, each row evenly distributed along the circumference of the blade root, with the centers of the double rows of through holes maintaining a preset axial distance; the blade root is connected to the flange via blade root bolt assemblies disposed within the double rows of through holes; the blade root has multiple layers along its thickness direction, including an outer reinforcing layer and an inner reinforcing layer, both of which are combinations of uniaxial and biaxial fiberglass cloth, wherein the number of uniaxial and biaxial fiberglass cloth layers maintains a preset ratio; the layers also include an outer skin layer, a thickening layer, and an inner skin layer, which are sequentially arranged from the outside to the inside along the thickness direction of the blade root. The method includes the following steps: S1. In the blade root layup, by adjusting the ratio of uniaxial fiberglass cloth and biaxial fiberglass cloth in the outer and inner reinforcing layers, various blade root fiberglass layup ratio schemes are set. S2. Set the specifications of the blade root bolt assembly, the radial diameter of the through hole, and the spacing between the row of through holes near the bottom of the blade root and the bottom of the blade root, as well as the axial distance between the two rows of through holes. S3. Select one of the blade root fiberglass ply mix ratio schemes, change the axial distance between the double rows of through holes, use the finite element simulation method to calculate the load-bearing capacity and safety margin of the blade root bolt assembly and fiberglass ply, and select the scheme in which both the blade root bolt assembly and fiberglass ply meet the preset safety margin requirements under the preset load. S4. Change the fiberglass layup ratio of the leaf roots and repeat step S3. S5. Compare the safety margins calculated from the various blade root fiberglass layup ratio schemes, and select the scheme with the largest safety margin to improve the load-bearing capacity of the wind turbine blade roots.

2. The method for improving the bearing capacity of wind turbine blade roots according to claim 1, characterized in that: The outer skin layer is a biaxial fiberglass cloth with a layup angle of ±45°.

3. The method for improving the bearing capacity of wind turbine blade roots according to claim 1, characterized in that: The thickening layer is a triaxial fiberglass cloth with a layup angle of 0° and ±45°.

4. The method for improving the bearing capacity of wind turbine blade roots according to claim 1, characterized in that: The inner skin layer is a biaxial fiberglass cloth with a layup angle of ±45°.

5. A method for improving the bearing capacity of wind turbine blade roots according to claim 1, characterized in that: The two rows of through holes are not located on the same busbar, and the row of through holes near the bottom of the leaf root maintains a preset distance from the bottom of the leaf root.

6. The method for improving the bearing capacity of wind turbine blade roots according to claim 1, characterized in that: The leaf root bolt assembly includes a long bolt assembly and a short bolt assembly. The long bolt assembly includes a round nut, a long bolt, and a nut connected in sequence. The short bolt assembly includes a round nut, a short bolt, and a nut connected in sequence. Multiple sets of the long bolt assembly are installed in one row of through holes, and multiple sets of the short bolt assembly are installed in another row of through holes.

7. The method for improving the bearing capacity of wind turbine blade roots according to claim 1, characterized in that: The cross-sectional shape of the through hole is circular or figure-eight shaped.

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