Nested UD rod and embedded thread sleeve structure and wind power blade root forming method

Abstract

The invention belongs to the technical field of wind power blade root connecting structures, and relates to a nested UD rod and embedded thread sleeve structure and a wind power blade root forming method, and the section appearance of a UD rod is reduced in equal proportion from the blade root end to the blade tip end; the diameter of the section of the embedded screw sleeve is increased in equal proportion from the blade root end to the blade tip end; the reduction rate of the cross section of the UD rod is synchronous with the increase rate of the cross section of the pre-embedded thread sleeve so as to ensure that the UD rod is tightly attached to the thread sleeve after yarn winding. The maximum section part of the UD rod is placed close to the blade root end, and the minimum diameter end of the pre-embedded threaded sleeve is close to the blade root end, so that continuous stress transmission from the blade root to the blade tip is realized, high-strength alternating load can be dispersed, the local stress concentration phenomenon is reduced, and the service life of the blade is prolonged. The problems that in the prior art, an interface between an embedded threaded sleeve and a pultrusion UD rod is prone to layering and failure, and the embedded threaded sleeve is prone to being pulled out are solved, and therefore the reliability and durability of a whole blade root connecting system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine blade root connection structures, and particularly relates to a nested UD rod and embedded bushing structure and a method for forming the root of a wind turbine blade. Background Art

[0002] During the operation of the wind turbine blade connected to the hub, its root bears high-strength alternating loads, testing the structural design of the entire blade root connection system and the performance of the root material. During the operation of the blade, problems such as bolt loosening or fracture, and bushing pulling out bring potential safety hazards to the blade operation and increase the later operation and maintenance costs. From the perspectives of design and material selection, there are many methods to improve the stability of the blade root connection, in order to solve or enhance the strength of the blade root connection system, improve the reliability of blade operation, reduce the failure rate, and increase the service life of the blade.

[0003] Common blade root connection methods generally use pultruded UD rods with a fixed cross-sectional shape (smooth arc / rectangle, etc.) and embedded bushings placed side by side (the outer shapes of the two are nested and fitted). For example, the publication number: CN106739022A discloses an embedded bushing assembly, its mold and its production method, including an embedded bushing, a pultruded UD rod, a PET wedge and resin. The root embedded assembly is prefabricated by a separate molding method, and then reassembled into a root integrated perfusion during the blade shell laying, which can confirm the perfusion quality in advance, identify defects, and shorten the production cycle. Another example is the publication number: CN118008678A, which proposes an embedded bushing assembly, a molding method and a root embedded connection structure. The solid UD rod in the traditional root structure is divided into two hollow UD sleeves with a fixed cross-section in the upper and lower parts, which are used for secondary pultrusion molding to complete the root unit containing the embedded bushing assembly. Then, during the production of the blade root, the above root units are assembled side by side and can be integrally perfused with the blade shell. This root unit can be continuously produced, improving production efficiency. The UD rods and embedded bushings used in the above patents, or the outer shapes of the prefabricated root units are all parallel to each other. The adjacent interfaces rely on the chemical bonding after the reaction of the perfusion resin matrix and the composite material reinforcement. If the interface between adjacent materials is weak, it is easy to cause interface failure of the root structure, and the overall load-bearing capacity of the root is not fundamentally improved.

[0004] Therefore, there is an urgent need to design a new type of UD rod and a root forming method to solve the problem of easy delamination failure at the interface between the embedded bushing and the pultruded UD rod existing in the prior art. Summary of the Invention

[0005] In view of this, the present invention aims to propose a nested UD rod and embedded bushing structure and a method for forming the root of a wind turbine blade to solve the problem of easy delamination failure at the interface between the embedded bushing and the pultruded UD rod existing in the prior art.

[0006] To solve this problem, the present invention changes the fixed cross-sectional shape of the traditional pultruded UD rod and the embedded nut, and adopts a structure in which the cross-section of the UD rod is reduced proportionally from the root to the tip of the blade, and the cross-section of the embedded nut is enlarged proportionally from the root to the tip of the blade. During the root forming process, in addition to the original chemical bonding effect between the UD rod and the embedded nut, a physical nesting structure is added, thereby improving the load-bearing capacity of the entire root connection system.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows:

[0008] One object of the present invention is to disclose a nested UD rod and embedded nut structure, wherein the cross-sectional shape of the UD rod is reduced proportionally from the root end to the tip end of the blade;

[0009] The cross-sectional diameter of the embedded nut increases proportionally from the root end to the tip end of the blade;

[0010] The reduction rate of the cross-section of the UD rod is synchronized with the increase rate of the cross-section of the embedded nut to achieve continuous stress transfer from the root to the tip of the blade.

[0011] Furthermore, the height of the UD rod remains unchanged, and the UD rod and the embedded nut are matched.

[0012] Furthermore, the formula for the reduction rate of the cross-section of the UD rod:

[0013]

[0014] 0 ≤ x ≤ L;

[0015] Where: x: the distance from the root of the blade;

[0016] L: the length of the UD rod;

[0017] A max: the maximum cross-sectional area of the UD rod at the root end of the blade;

[0018] Amin: the minimum cross-sectional area of the UD rod at the tip end of the blade.

[0019] Furthermore, the formula for the increase rate of the cross-section of the embedded nut:

[0020]

[0021] 0 ≤ x ≤ L;

[0022] Where: x: the position from the root of the blade;

[0023] L: the length of the UD rod;

[0024] Dmin: the minimum diameter of the nut at the root end of the blade;

[0025] Dmax: the maximum diameter of the nut at the tip end of the blade.

[0026] The embedded screw sleeve needs to be flush with the upper and lower surfaces of the UD rod in height to facilitate the laying of the fiber fabric skin in the later stage.

[0027] Furthermore, the cross-section of the UD rod is one of an arc, a regular polygon, or a special shape.

[0028] Another object of the present invention is to disclose a method for forming the root of a wind turbine blade. Based on the nested UD rod and embedded screw sleeve structure described in any one of the preceding claims, the method includes the following specific steps:

[0029] S1: First, clean the blade root mold and complete the work of laying the lower skin cloth.

[0030] S2: Lay the lower skin cloth and the transition layer cloth of the blade root.

[0031] S3: Lay the first UD rod with a variable diameter profile.

[0032] S4: Then closely fit the variable diameter embedded screw sleeve with the UD rod.

[0033] S5: Lay the wedge-shaped core material strip near the tip of the embedded screw sleeve.

[0034] S6: Alternately lay the variable diameter UD rod, the embedded screw sleeve, and the core material wedge-shaped strip along the circumferential circle of the blade root mold in sequence.

[0035] S7: Lay the upper transition layer cloth and the skin cloth of the blade root.

[0036] Furthermore, the largest cross-section of the UD rod is placed near the root end of the blade.

[0037] Furthermore, the smallest diameter end of the embedded screw sleeve is placed near the root end of the blade.

[0038] Furthermore, the variable diameter embedded screw sleeve needs to be treated by sandblasting and yarn winding.

[0039] Furthermore, if the last embedded screw sleeve cannot be placed in parallel, it needs to be inserted from the tip direction towards the root direction of the blade, and then the wedge-shaped core material strip is inserted.

[0040] Compared with the prior art, the nested UD rod and embedded screw sleeve structure and the method for forming the root of a wind turbine blade of the present invention have the following advantages:

[0041] 1. By placing the largest cross-section part of the UD rod near the root end of the blade and making the smallest diameter end of the embedded screw sleeve close to the root end of the blade, the present invention realizes the continuous stress transfer from the root to the tip of the blade, helps to disperse the high-strength alternating load, reduces the occurrence of local stress concentration, solves the problem of easy delamination failure at the interface between the embedded screw sleeve and the pultruded UD rod in the prior art, and thus improves the reliability and durability of the entire blade root connection system.

[0042] 2. In the present invention, through the design of alternately laying the UD bar and the embedded sleeve in a nested structure, in addition to relying on the traditional chemical bonding method, a physical nested structure is added, greatly enhancing the bonding force between the two. In addition, this design increases the contact area between the UD bar and the upper and lower skins as well as the embedded sleeve, further strengthening the interfacial bonding between adjacent materials and reducing the risk of delamination failure.

[0043] 3. The present invention provides a systematic method for dealing with the assembly problem of the blade root, which facilitates the design and use of the mold, is beneficial to improving production efficiency. At the same time, by optimizing the material utilization, unnecessary material waste is reduced, the overall manufacturing cost is lowered, the structure is made more stable, and the need for later maintenance and repair is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0045] Figure 1 is a schematic diagram of the overall structure of the nested UD bar and the embedded sleeve structure of the present invention;

[0046] Figure 2 is a top view of the layout of the parts at the root of the wind turbine blade of the present invention;

[0047] Figure 3 is a schematic diagram of the structure of the root of the wind turbine blade of the present invention.

[0048] DESCRIPTION OF THE REFERENCE NUMERALS:

[0049] 1, UD bar; 2, embedded sleeve; 3, wedge-shaped core material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] In order to make the technical means, the achieved purpose and the effects of the present invention easy to understand, the embodiments of the present invention will be described in detail below with reference to the specific drawings.

[0051] It should be noted that all the terms indicating direction and position in the present invention, such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "top", "bottom", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection situation between components in a specific state, and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features.

[0052] In the description of the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", and "coupled" shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0054] In a wind turbine blade, the root end refers to the end close to the blade root, and the tip end refers to the end close to the blade tip.

[0055] The present invention discloses a nested UD rod and embedded bushing 2 structure.

[0056] The cross-sectional shape of the UD rod 1 is reduced proportionally from the root end to the tip end of the blade.

[0057] The cross-sectional diameter of the embedded bushing 2 is increased proportionally from the root end to the tip end of the blade.

[0058] The reduction rate of the cross-section of the UD rod 1 is synchronized with the increase rate of the cross-section of the embedded bushing 2 to achieve the adjacent fitting of the UD rod and the embedded bushing 2, so as to ensure the continuous transfer of the stress of the entire blade weight at the root part.

[0059] The cross-sectional shape of the UD rod 1 is proportionally reduced from the root end to the tip end of the blade, making the transition of the UD rod 1 from the root to the tip of the blade smoother, increasing the contact area with the embedded bushing 2, helping to enhance the interfacial bonding between adjacent materials, improving the overall utilization efficiency of the materials. The cross-sectional diameter of the embedded bushing 2 is proportionally increased from the root end to the tip end of the blade. As the cross-section of the UD rod 1 gradually shrinks, the cross-section of the embedded bushing 2 increases proportionally accordingly, ensuring that they can maintain a tight fit throughout the entire length direction, forming a physical nesting structure, enhancing the physical nesting effect, further optimizing the stress distribution, enabling the stress to be continuously transmitted between the root components of the blade, improving the load-bearing capacity of the entire connection system. The design of their synchronous change ensures that the stress distribution from the root to the tip of the blade is more uniform, avoiding the occurrence of local stress concentration. In addition, after the wind turbine blade is connected to the mainframe flange through bolts and the embedded bushing 2, the physical nesting structure increases the difficulty of pulling out the embedded bushing 2, that is, it is very difficult for the embedded bushing 2 to withdraw from the tip end to the root end of the blade, improving the load-bearing capacity and structural stability of the overall root part.

[0060] This setting improves the overall structural strength and reliability of the blade, reduces the risk of fatigue damage caused by stress concentration, realizes a more efficient stress transmission mechanism, helps to extend the service life of the blade, and improves the operation safety, solves the common problems in the traditional blade root connection such as bolt loosening or fracture, bushing pulling out, etc., and significantly improves the overall performance of the blade root connection system.

[0061] Specifically, the heights of the UD rod 1 and the embedded bushing 2 remain unchanged.

[0062] Although the height of the UD rod 1 remains unchanged, the gradual shrinkage of its cross-section cooperates with the gradual increase of the cross-section of the embedded bushing 2 to form a tight physical nesting structure, enhancing the bonding force between the UD rod 1 and the embedded bushing 2, making the entire connection system more stable, which can simplify the production process to a certain extent, facilitate the design and use of the mold, and is beneficial to improving production efficiency and reducing manufacturing costs.

[0063] Specifically, the cross-section shrinkage rate formula of the UD rod 1:

[0064]

[0065] 0 ≤ x ≤ L;

[0066] Where: x: the distance from the root of the blade;

[0067] L: the length of the UD rod 1;

[0068] A

[0065] , , max , ,

[0069] , min , ,

[0068] , ,

[0067] ,

[0066] : the maximum cross-sectional area of the UD rod 1 at the root end of the blade;

[0069] A min: Minimum cross-sectional area of the UD bar 1 at the leaf tip.

[0070] During the operation of the blade, especially near the root part of the blade, it will bear large alternating loads. By gradually reducing the cross-section of the UD bar 1 from the root to the tip of the blade, it can better match the stress requirements of different parts inside the blade, making the stress distribution more uniform and reasonable, and avoiding material fatigue or damage caused by local stress concentration. Therefore, adopting the design of gradually reducing the cross-section of the UD bar 1 can reduce unnecessary weight while ensuring strength, which helps to improve the aerodynamic efficiency of the entire blade and reduce the manufacturing cost.

[0071] The cross-section of the blade at the root end is wide and thick, bearing the maximum bending moment and shear force. The cross-section of the UD bar 1 is the largest, providing high strength and high stiffness. From the root to the tip of the blade, the cross-section of the UD bar 1 increases moderately, which can balance the connection strength and material distribution. The cross-section of the UD bar 1 is the smallest, reducing weight and maintaining the necessary stiffness.

[0072] This setting optimizes the stress distribution and improves the structural performance, achieving effective control of weight without sacrificing strength, thereby enhancing the safety, reliability, and economy of the entire wind turbine blade.

[0073] Preferably, the height of the UD bar 1 changes gradually, consistent with the height change after the cross-sectional circle of the embedded bushing 2 increases.

[0074] Although the height of the UD bar 1 changes gradually, the gradual shrinkage of its cross-section cooperates with the gradual increase of the cross-section of the embedded bushing 2 to form a tight physical nested structure, enhancing the bonding force between the UD bar 1 and the embedded bushing 2, making the entire connection system more stable. In this way, the embedded bushing 2 can also save the machining steps of cutting height, which can simplify the production process to a certain extent, facilitate the design and use of the mold, and is beneficial to improving production efficiency and reducing manufacturing costs.

[0075] Specifically, the cross-section reduction rate formula of the UD bar 1:

[0076]

[0077] 0 ≤ x ≤ L;

[0078] Where: x: distance from the root of the blade;

[0079] L: length of the UD bar 1;

[0080] A max : Maximum cross-sectional area of the UD bar 1 at the root end of the blade;

[0081] A min : Minimum cross-sectional area of the UD bar 1 at the leaf tip.

[0082] Specifically, the height change rate formula of the UD bar 1:

[0083]

[0084] 0 ≤ x ≤ L;

[0085] where: x: distance from the blade root;

[0086] L: length of the UD bar 1;

[0087] H min : minimum height of the UD bar 1 at the blade root end;

[0088] H max : maximum height of the UD bar 1 at the blade tip end.

[0089] During the operation of the blade, especially in the part near the blade root, it will bear large alternating loads. By making the cross-section of the UD bar 1 gradually decrease from the blade root to the blade tip, it can better match the stress requirements of different parts inside the blade, making the stress distribution more uniform and reasonable, and avoiding material fatigue or damage caused by local stress concentration. As the cross-section of the UD bar 1 decreases and the height increases, it can better match the increase in the cross-section of the embedded bushing 2, avoiding the occurrence of bonding mutations and resulting in stress concentration problems. Therefore, using a gradually decreasing cross-section design for the UD bar 1 and increasing the height can reduce unnecessary weight while ensuring strength, which helps to improve the structural stability of the entire blade and reduce the manufacturing cost.

[0090] Specifically, the formula for the increase rate of the cross-section of the embedded bushing 2:

[0091]

[0092] 0 ≤ x ≤ L;

[0093] where: x: position from the blade root;

[0094] L: length of the UD bar 1;

[0095] D min : minimum diameter of the embedded bushing 2 at the blade root end;

[0096] D max : maximum diameter of the embedded bushing 2 at the blade tip end.

[0097] As the cross-section of the UD rod 1 gradually decreases, the cross-section of the embedded screw sleeve 2 increases accordingly, which can achieve continuous transmission of stress along the entire length of the blade and avoid the problem of local stress concentration. Since the blade will be subjected to a large alternating load during operation, especially near the root of the blade, the stress distribution can be effectively optimized by adjusting the cross-sectional size of the embedded screw sleeve 2 to match the stress requirements of different parts. The gradually increased cross-sectional area of the embedded screw sleeve 2 can form a tight physical nested structure with the UD rod 1, which not only enhances the bonding force between the two, but also ensures the stability and reliability of the overall structure. Blades are usually thicker at the root and gradually become thinner towards the tip. The increased cross-sectional area design of the embedded screw sleeve 2 just adapts to this changing trend, making the connection structure more in line with the actual geometric shape of the blade and improving the consistency and coordination of the overall structure.

[0098] The embedded screw sleeve 2 at the blade root has the smallest diameter, allowing for a wide and thick blade cross-section and high load capacity, thereby avoiding excessive metal material accumulation and reducing weight. The sleeve diameter increases moderately from the blade root to the tip, balancing connection strength and material distribution. The sleeve diameter is largest at the blade tip, enhancing local connection stiffness, compensating for the reduced stiffness of the composite UD rod 1, and preventing loosening.

[0099] This setting optimizes the mechanical properties of the blade root connection structure by matching the cross-sectional gradient of the embedded screw sleeve 2 with the size of the UD rod 1 inversely.

[0100] Preferably, the embedded screw sleeve 2

[0101] The embedded screw sleeve 2 and the UD rod 1 are kept flush with each other in terms of height, so as to facilitate the later laying of the fiber fabric skin.

[0102] Specifically, the cross section of the UD rod 1 is one of an arc shape, a regular polygon shape, or an irregular shape.

[0103] The arc-shaped cross-section UD rod 1 can be semicircular, elliptical, parabolic, etc., which can reduce stress concentration at sharp corners and make it easier for the fibers to maintain a straight line arrangement when laid. If the inner wall of the screw sleeve is arc-shaped, it can form surface-to-surface contact, reduce interfacial stress, and enhance the fit with the embedded screw sleeve 2. This setting helps to avoid stress concentration at the edge or end of the material, improve fatigue life, reduce redundant materials, and achieve weight reduction.

[0104] The regular polygonal cross-section UD rod 1 can be a quadrilateral, hexagon, octagon, etc. The more sides a polygon has, the closer it is to a circle, and the stronger its torsion resistance is. When it is matched with a polygonal screw sleeve, it can prevent relative rotation and facilitate nested assembly. The polygonal shape is easy to mold and reduce manufacturing costs.

[0105] The UD rod 1 with a special cross section can be T-shaped, I-shaped, grooved, etc. It has good pertinence, is easy to solve specific problems, and is convenient for integrating new functions. It is applicable to a wide range of occasions.

[0106] Another object of the present invention is to disclose a method for forming the root of a wind turbine blade. Based on the structure of the nested UD rod 1 and the embedded sleeve 2, the method specifically includes the following steps:

[0107] S1: First, clean the blade root mold and prepare for laying the lower skin cloth.

[0108] Ensure the interface is clean to avoid impurities affecting the interlayer bonding strength.

[0109] S2: Lay the lower skin cloth and the transition layer cloth of the blade root.

[0110] Provide a basic load-bearing layer. The transition layer optimizes stress transfer and may use new types of fiber cloth such as hybrid woven glass fiber / carbon fiber.

[0111] S3: Lay the first UD rod 1 with a variable diameter profile.

[0112] The variable diameter design matches the blade load gradient, with the root of the blade being thick and the tip being thin, matching the decreasing bending moment load of the blade and avoiding material waste. Traditional UD rods 1 are mostly of equal diameter or have simple stepped changes.

[0113] S4: Then closely fit the variable diameter embedded sleeve 2 with the UD rod 1.

[0114] The diameter of the sleeve changes in the opposite direction, with the root of the blade being thin and the tip being thick, forming a complementary nested structure to compensate for the decrease in the stiffness of the UD rod 1, achieving a continuous stiffness transition and close fitting, reducing the risk of interlayer delamination. Three wedge-shaped cores 3 such as balsa wood or PET foam are used to fill the gap to prevent resin accumulation and pore formation during curing. Traditional sleeves are usually of equal diameter, which is likely to cause local stress concentration.

[0115] S5: Lay three wedge-shaped cores 3 near the tip of the embedded sleeve 2.

[0116] Fill the gap between the sleeve and the UD rod 1 to prevent defects caused by resin enrichment, reducing the defect rate.

[0117] S6: Alternately lay the variable diameter UD rod 1, the embedded sleeve 2, and the wedge-shaped core strips along the circumcircle of the blade root mold in sequence.

[0118] Form a gradient material distribution and optimize the load transfer path.

[0119] S7: Lay the upper transition layer cloth and the skin cloth of the blade root.

[0120] [[ID=4,4]]Close the structure, protect the internal components, and improve the surface flatness.

[0121] This method for forming the root of the blade has significant advantages in mechanical properties, lightweight, and process efficiency through variable diameter nested design + wedge filling process, and is especially suitable for the high reliability requirements of large MW wind turbine blades.

[0122] Specifically, in step S3, the largest cross-section of the UD rod 1 is placed near the root end of the blade.

[0123] Since the blade root bears a large alternating load, placing the largest cross-section part of the UD rod 1 near the blade root can more effectively disperse these loads, helping to ensure the continuous stress transfer from the blade root to the tip, reducing the occurrence of local stress concentration, and lowering the risk of material fatigue. By placing the largest cross-section part of the UD rod 1 at the root end of the blade, while the embedded bushing 2 adopts the opposite design, that is, the smallest diameter end is near the root end of the blade, a tight physical nesting structure can be formed between the two. This structure enhances the bonding force between the UD rod 1 and the embedded bushing 2, improving the stability and reliability of the entire connection system. As the cross-section of the UD rod 1 gradually shrinks, the contact area between it and the upper and lower skins as well as the embedded bushing 2 increases, thus enhancing the interfacial bonding strength between adjacent materials. This helps to prevent the occurrence of delamination failure and improves the stability of the overall structure.

[0124] This setting optimizes the stress distribution, enhances the physical nesting effect, increases the interfacial bonding strength, and improves the reliability and performance of the entire wind turbine blade root structure.

[0125] Specifically, in step S4, the smallest diameter end of the embedded bushing 2 is placed near the root end of the blade.

[0126] By placing the smallest diameter end of the embedded bushing 2 near the root end of the blade and closely fitting it with the UD rod 1 with a gradually shrinking cross-section, a physical nesting structure can be formed, enhancing the bonding force between the UD rod 1 and the embedded bushing 2, and improving the stability and reliability of the entire connection system. Since the blade root bears a large alternating load, placing the smallest diameter end of the embedded bushing 2 near the root end of the blade helps to achieve continuous stress transfer from the blade root to the tip, enabling the stress to be more evenly distributed at the blade root, reducing the occurrence of local stress concentration, and lowering the risk of material fatigue.

[0127] This setting enhances the physical nesting effect, optimizes the stress distribution, increases the interfacial bonding strength, and improves the reliability and performance of the entire wind turbine blade root structure.

[0128] Specifically, in step S4, the stepped embedded bushing 2 needs to be treated by sandblasting and winding with yarn.

[0129] Sandblasting can form a uniform rough texture on the surface of the embedded bushing 2, increasing the surface area, significantly enhancing the shear strength between the composite material and the bushing, contributing to improving the mechanical interlocking effect between the subsequent winding yarn or resin layer and the bushing surface, enhancing the interfacial bonding force, and effectively removing possible oxide scales, rust or other contaminants on the surface of the embedded bushing 2, ensuring surface cleanliness, providing a good foundation for subsequent processing. Through the surface characteristics after sandblasting, when performing the winding treatment, it can better ensure the close contact between the yarn and the bushing surface, thereby improving the bonding performance between the fiber and the matrix such as resin.

[0130] The yarn wound around the embedded bushing 2, usually high-strength fiber, can significantly enhance the rigidity and load-bearing capacity around the bushing. Especially in the high-stress concentration area, the winding layer can disperse the load to a certain extent, reduce the local stress concentration phenomenon, further improve the stability and durability of the overall structure, and prevent the bushing from being worn or damaged in other forms during installation or use.

[0131] This setting enhances the mechanical properties of the embedded bushing 2 itself, greatly improves the interfacial bonding force between it and the UD rod 1 and other composite materials, thus comprehensively improving the reliability and service life of the entire blade root connection structure, being able to effectively cope with complex working conditions, and reducing maintenance costs and downtime.

[0132] Specifically, in step S6, if the last embedded bushing 2 cannot be placed in parallel, it needs to be inserted from the tip direction towards the root direction of the blade, and then 3 wedge-shaped core materials are inserted.

[0133] Due to the complex structure of the blade root, especially when all other UD rods 1 and embedded bushings 2 have been laid according to the design requirements, there may be a situation where there is not enough space to accommodate the last embedded bushing 2. By inserting from the tip direction towards the root direction of the blade, the limited space can be utilized more flexibly to ensure that all components can be properly placed. Using this insertion method can ensure that even in a limited space, a good combination between the embedded bushing 2 and other components can be achieved, contributing to maintaining the consistency and stability of the entire blade root structure and avoiding potential problems caused by improper assembly.

[0134] This setting provides an effective solution to the space limitation problem encountered in the actual installation process, increases the flexibility and adaptability during the installation process, helps to ensure the close combination between each component, reduces problems caused by improper assembly, such as delamination failure, weak interface, etc., thereby enhancing the reliability of the entire blade root structure.

[0135] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A nested UD rod and embedded bushing structure, characterized in that, The cross-sectional shape of the UD rod (1) is reduced proportionally from the root end to the tip end of the blade; The cross-sectional diameter of the embedded bushing (2) increases proportionally from the root end to the tip end of the blade; The reduction rate of the cross-section of the UD rod (1) is synchronized with the increase rate of the cross-section of the embedded bushing (2) to achieve continuous stress transfer from the root to the tip of the blade.

2. The nested UD rod and embedded bushing structure according to claim 1, characterized in that, The height of the UD rod (1) remains unchanged, and the UD rod (1) matches the embedded bushing (2).

3. The nested UD bar and embedded bushing structure according to claim 2, characterized in that, The formula for the reduction rate of the cross-section of the UD rod (1): 0 ≤ x ≤ L; Where: x: the distance from the root of the blade; L: the length of the UD rod; A max: the maximum cross-sectional area of the UD rod at the root end of the blade; Amin: the minimum cross-sectional area of the UD rod at the tip end of the blade.

4. The nested UD bar and embedded bushing structure according to claim 2, characterized in that, The formula for the increase rate of the cross-section of the embedded bushing (2): 0 ≤ x ≤ L; Where: x: the position from the root of the blade; L: the length of the UD rod; Dmin: the minimum diameter of the bushing at the root end of the blade; Dmax: the maximum diameter of the bushing at the tip end of the blade.

5. The nested UD rod and embedded bushing structure according to claim 3, characterized in that, The cross-section of the UD rod (1) is one of an arc, a regular polygon, or a special shape.

6. A method for forming the root of a wind turbine blade, characterized in that, Based on the nested UD rod and embedded bushing structure according to any one of claims 1-5, the following specific steps are included: S1: First, clean the mold at the root of the blade and do the work of laying the lower skin cloth; S2: Lay the lower layer skin cloth and transition layer cloth at the root of the blade; S3: Lay the first UD rod with a variable diameter shape; S4: Then closely fit the variable diameter embedded bushing with the UD rod; S5: Lay the wedge-shaped core material strip near the tip end of the embedded bushing; S6: Alternately lay the variable diameter UD rod, the embedded bushing, and the core material wedge-shaped strip along the circumcircle of the root mold of the blade in sequence; S7: Lay the upper layer transition layer cloth and skin cloth at the root of the blade.

7. The method for forming the root of a wind turbine blade according to claim 6, wherein In step S3, the maximum cross-section of the UD rod is placed near the root end of the blade.

8. The method for forming the root of a wind turbine blade according to claim 6, characterized in that, In step S4, the minimum diameter end of the embedded bushing is placed near the root end of the blade.

9. The method for forming the root of a wind turbine blade according to claim 6, wherein, In step S4, the variable diameter embedded bushing needs to be treated by sandblasting and yarn winding.

10. The method for forming the root of a wind turbine blade according to claim 6, characterized in that, In step S6, if the last embedded bushing cannot be placed in parallel, it needs to be inserted from the tip end direction to the root end direction, and then the wedge-shaped core material strip is inserted.

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