A core material for filling gaps in wind turbine blades and its application method

Abstract

This invention relates to a core material for filling gaps in wind turbine blades. By incorporating shallow grooves and S-shaped grooves on the top, bottom, and two sides of the core material—with shallow grooves and S-shaped grooves on all four sides—the resin flow rate is accelerated and the localized filling effect is improved regardless of the angle from which the core material fills the gap. The S-shaped grooves of this invention gradually decrease in density along the length direction, meaning the number of S-shaped grooves per unit length decreases. A centerline formula for the S-shaped grooves is also established. This flow channel design allows the resin to gradually stabilize and distribute evenly during flow, contributing to improved filling efficiency. A fabric is attached to the surface of the core material to protect its edges and corners, preventing missing or broken pieces. The core material has a relatively small thickness and can be cut on-site according to actual needs, allowing for more effective gap filling.

Description

Technical Field

[0001] This invention relates to core materials for wind turbine blades, and more particularly to a core material for filling the gaps in wind turbine blade layers. Background Technology

[0002] Wind power is a clean and renewable energy source with broad application prospects. Currently, the main materials used in wind turbine blade design include fiberglass, pultruded sheets, and core materials. The core material is primarily used in the blade's shell and web. In different layup structures of the shell and web, there will be gaps at the interfaces between the core material and other materials, such as between the pultruded sheet main beam and the core material, between the fiberglass cloth main beam and the core material, and between core materials of different thicknesses. These gaps should be filled with appropriate materials.

[0003] The current conventional method for handling blade ply gaps involves first gently tapping or continuously applying pressure using a tool (such as a rubber mallet or other controllable pressure tapping device) to evenly distribute and fill the gaps with core material or other materials. This process helps improve the uniformity and stability of the internal structure. To further ensure the robustness and stability of the blade's internal structure, additional filling work is required after tapping. This involves filling the gaps with core material blocks of appropriate thickness or directly filling them with beveled core material strips. Filling with core material blocks or beveled core material strips fills the remaining voids, increases the density of the blade's internal structure, improves the overall strength and durability of the blade, and ensures the efficient operation of the entire blade during wind energy conversion.

[0004] Existing technologies include solutions for core material structures. In CN214821035U, a V-shaped groove is added to the existing deep and shallow grooves on the upper and lower surfaces of the core material. The overall shape of the groove is V-shaped, which reduces the generation of defects such as gaps, wrinkles, and protrusions during actual use and accelerates the flow rate.

[0005] Existing technologies also include methods for manufacturing beveled core materials. CN102562477A discloses a method for manufacturing beveled core materials for wind turbine blades, which is achieved through the following steps: selecting a double-sided felt core material of a fixed width; installing the core material on a cutting machine in a fixed position; cutting the core material according to the cutting line; and forming two beveled pieces of the same size and angle. This manufacturing method can form two core materials at once, which improves work efficiency and reduces material waste.

[0006] Existing technologies also include design methods for the flow channels of core materials. CN113738603A discloses grooves on the upper and lower surfaces of the core material in different directions, which can promote the flow of resin in different directions of the core material, improve the resin impregnation ability of the core material, and thus improve the fixation and bonding performance between the core material and the reinforcing fiber. By adjusting the depth of the grooves, the resin content in the core material can be increased while avoiding waste of resin raw materials. Moreover, the core material in this solution has a good flow guiding effect, eliminating the need for a flow guiding net during use and avoiding resin residue due to the flow guiding net. At the same time, the deep grooves allow the core material to bend freely, making it highly adaptable.

[0007] Through understanding the existing technology, it was found that when using core material bevels or core material blocks to fill gaps, the size, shape, and dimensions of the core material bevels or core material blocks obtained by the existing manufacturing methods are relatively fixed. When filling gaps, multiple core material bevels or core material blocks may need to be stacked, resulting in the core materials being too tightly packed and unable to adapt to different gap requirements. Furthermore, the deep and shallow grooves of the existing core materials may affect the injection effect or result in resin overload during the injection process.

[0008] In addition to affecting the grouting effect, since the filling core material or core material bevel in the existing technology is mostly pure foam flat plate, the performance after grouting is low. There may be local performance problems due to low filling performance, resulting in small performance weaknesses in the blade structure.

[0009] In addition, the core material used for filling is mostly in small pieces, and there may be missing corners or broken pieces. In actual operation, it is necessary to find suitable core material blocks or core material at the bevel on site for splicing and filling, which is inconvenient. Summary of the Invention

[0010] (I) Purpose of the Invention

[0011] In view of the above-mentioned defects and deficiencies of the prior art, the present invention proposes a core material for filling gaps in wind turbine blade layup, which can fill the gaps generated during the blade layup process and can also be used to smooth the transition of thickness differences.

[0012] (II) Technical Solution

[0013] To achieve the objective of this invention, the present invention adopts the following technical solution:

[0014] A core material for filling gaps in wind turbine blades, the core material being a cuboid, comprising a top surface, a bottom surface, two side surfaces, and two end surfaces along its length; characterized in that: shallow grooves are formed in all four surfaces of the core material—the top surface, the bottom surface, and the two side surfaces—each shallow groove being located at the midpoint of the width direction of each surface, extending along the length direction of the core material, and all shallow grooves being straight grooves; furthermore, S-shaped grooves extending along the length direction are also provided in all four surfaces—the top surface, the bottom surface, and the two side surfaces.

[0015] To improve the infusion effect and make the resin flow in the core material more uniform, this invention further optimizes the S-grooves of the S-shaped path in the length direction. The resin flows along the length of the core material, and the S-grooves of the S-shaped path change from dense to sparse, that is, the number of S-grooves per unit length of the S-shaped path decreases. The resin first enters the more densely designed flow channel section, where it encounters some resistance, but the flow is relatively stable due to the dense flow channel. Subsequently, the resin gradually transitions to the more sparsely designed flow channel section. In this stage, the resin undergoes adjustments in speed and flow direction to adapt to the changes in the flow channel structure. As the resin flows upstream, its flow velocity decreases, while the flow resistance decreases in the sparse flow channel section. Through this flow channel design, the resin can gradually stabilize and distribute evenly during the flow process, which helps to improve the infusion effect.

[0016] Preferably, along the length of the core material, the number of S-grooves per unit length decreases.

[0017] Preferably, the width of the S-groove is b, and the virtual line connecting the midpoints of the S-groove along its width direction is the centerline of the S-groove.

[0018] The formula for the centerline f(x) of the S-shaped groove is:

[0019]

[0020] Where 'a' is the width of the top surface, bottom surface, or both sides; 'h' is the depth of the S-groove; 'L' is the length of the top surface, bottom surface, or both sides; 'η' is a coefficient related to the viscosity of the resin; 'x' is the length extending from left to right along the length direction of the top surface, bottom surface, or both sides, with a value of 0-L; and 'α' is a coefficient related to the core material. The higher the flow viscosity of the resin, the larger the value of 'η'. 'α' is related to the material of the core material; the greater the roughness of the core material, the smaller the value of 'α'. Preferably, the core material used for the blade layup in this invention should be a conventional core material used in blades, such as PET, PVC, or HPE. The actual filling material used should be the same as the type of core material used for the actual large-area layup of the blade.

[0021] Preferably, the core material thickness can be set according to the actual required gap height, generally 5mm. The thickness direction should be consistent with the thickness direction of the conventional core material of the blade. Shallow grooves are opened on the four sides of the core material, on the top, bottom and sides, located in the middle of each side, with a groove width of 1mm. In addition, S-shaped grooves with S-shaped paths are added on the four sides at the same time, with a groove width of 1mm.

[0022] Preferably, fiberglass fabric is attached to the four surfaces of the core material—the top, bottom, and sides—using an adhesive system identical to the resin system used for blade infusion. The total basis weight of the fiberglass fabric should not exceed 600 g / m².2 The weaving direction can be 0° / 90° or ±45°.

[0023] The present invention also includes a method for filling the gaps in the ply of the wind turbine blade with a core material. Specifically, a cutting line is set on the end face of the core material. The cutting line is a straight line or an arc on the end face of the core material. The core material is cut along the length direction of the core material according to the cutting line to form a core material corner. The core material corner formed after cutting has at least two surfaces with shallow grooves and S-shaped grooves, and the fiberglass fabric at one corner of the core material corner is kept intact.

[0024] The specific steps are as follows:

[0025] S1: Prepare several core materials, set cutting lines on the end faces of the core materials, cut the core material strips along the length direction according to the cutting lines to form core material corners, ensure that at least two faces have shallow grooves and S-shaped grooves after cutting, and ensure that the fiberglass fabric at one corner of the core material corner is intact.

[0026] S2: Lay the core material corner in the gap, set up a grouting device, vacuum the glue, and heat and cure after the glue is injected.

[0027] (III) Technical Effects

[0028] Compared with the prior art, the core material for filling the gaps in wind turbine blades of the present invention has the following beneficial and significant technical effects:

[0029] This invention solves the blade layup gap problem while improving the performance of the local filling material, ensuring good injection effect in the corresponding locations, and protecting the edges and corners of the filler core material to a certain extent, thus reducing the product rejection rate. Specific beneficial effects are as follows:

[0030] 1) The core material is covered with fiberglass fabric on all four sides, which can improve the performance of the core material at the filling location and improve the bonding effect between different materials.

[0031] 2) The core material has a processing method with shallow grooves on all four sides and S-shaped grooves with S-shaped paths. No matter which angle the core material fills the gap from, it can accelerate the flow rate of the injection resin and improve the local injection effect.

[0032] 3) This invention further optimizes the S-grooves of the S-shaped path in the length direction. The resin flows along the length of the core material, and the S-grooves in the S-shaped path become less dense, meaning the number of S-grooves per unit length decreases. The resin first enters the more densely designed flow channel section, where it encounters some resistance. However, due to the dense flow channel, the resin flow is relatively stable. Subsequently, the resin gradually transitions to the more sparsely designed flow channel section. In this stage, the resin undergoes adjustments in speed and flow direction to adapt to the changes in the flow channel structure. Because the resin has flowed upstream, its flow velocity decreases, while in the sparse flow channel section, the flow resistance decreases. Through this flow channel design, the resin can gradually stabilize and distribute evenly during flow, which helps improve the potting effect.

[0033] 4) The centerline formula in this invention is related to the viscosity coefficient η of the resin, the material α of the core material, the width a of the top surface, bottom surface, or both sides, the depth h of the S-groove, and the length L of the top surface, bottom surface, or both sides. Resin flow data in the S-groove is obtained through simulation experiments, and the centerline formula is derived by data fitting. Using this formula, the curve shape of the S-groove along the length of the core material from left to right can be designed. The S-groove can then be fabricated according to this curve, allowing the resin to gradually stabilize and distribute evenly during flow, thus improving the potting effect. Different parameter values ​​can be used on different core materials to obtain corresponding curves.

[0034] 5) The surface is covered with fabric, which can protect the edges and corners of the core material to prevent it from being missing or falling off.

[0035] 6) The core material is relatively thin and can be cut on-site according to actual needs, so that the core material can fill the gaps more effectively. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall appearance of the core material for filling the gaps in the wind turbine blades according to the present invention;

[0037] Figure 2 (a) is a schematic diagram of core material strip cutting; (a)-(f) are schematic diagrams of cutting lines set on the end face of the core material strip.

[0038] Explanation of reference numerals in the attached figures:

[0039] Core material strip 1, shallow groove 2, V-groove 3, cutting line 4. Detailed Implementation

[0040] To better understand the present invention, the following embodiments further illustrate its content. Throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The structure and technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings, providing one embodiment of the present invention.

[0041] Example 1

[0042] like Figure 1 As shown, the core material 1 of the present invention is a cuboid. Along the length direction of the core material, the cuboid includes a top surface, a bottom surface, two side surfaces, and two end surfaces. The top surface, bottom surface, and two side surfaces are four circumferentially arranged surfaces of the core material along its length. The two end surfaces are two surfaces at the left and right ends of the core material. Shallow grooves 2 are formed in the four surfaces of the core material strip 1 along its length, namely, shallow grooves 2 are provided on all four circumferentially arranged surfaces along its length. The shallow grooves 2 are located at the middle position of the width direction of each surface. The shallow grooves are straight grooves and extend along the length direction. In this embodiment, the core material thickness is 5mm and the groove width is 1mm. S-shaped grooves 3 with S-shaped paths are also provided in the four surfaces of the top surface, bottom surface, and two side surfaces. The groove width of the S-shaped grooves 3 is 1mm, and the vertices of the S-shaped grooves coincide with the edges of each surface.

[0043] Along the length of core material strip 1, the S-grooves of the S-shaped path change from dense to sparse, that is, the number of S-grooves per unit length of the S-shaped path changes from more to less.

[0044] Example 2

[0045] Based on the core material set in Example 1, since the S-grooves have a certain width, in order to achieve a change from dense to sparse S-grooves along the length direction, and a decrease in the number of S-grooves per unit length along the length of the core material, the width of the S-grooves is b. The virtual line connecting the midpoints of each S-groove along its width direction is the centerline of the S-groove. Resin flow data in the S-grooves is obtained through simulation experiments, and the centerline formula is obtained using data fitting.

[0046] The formula for the centerline f(x) of the S-shaped groove is:

[0047]

[0048] Where a is the width of the top surface, bottom surface, or both sides, h is the depth of the S-groove, L is the length of the top surface, bottom surface, or both sides, η is a coefficient related to the viscosity of the resin, x is the length extending from left to right along the length direction of the top surface, bottom surface, or both sides, x takes a value of 0-L, and α is a coefficient related to the core material. The greater the flow viscosity of the resin, the greater the value of η. α is related to the material of the core material; the greater the roughness of the core material, the smaller the value of α.

[0049] Using this centerline formula, the S-groove can be designed as a curve from left to right along the length of the core material, and the S-groove can be machined according to this curve.

[0050] Example 3

[0051] Based on the core material provided in Example 1 or 2, fiberglass fabric is attached to all four surfaces of the core material: the top surface, the bottom surface, and the two side surfaces. Specifically, adhesive can be used for bonding, and the adhesive system is the same as the resin system used for blade infusion. The total basis weight of the fiberglass fabric should not exceed 600 g / m². 2 The weaving direction can be 0° / 90° or ±45°.

[0052] Example 4

[0053] like Figure 2 As shown, when filling the gaps using the core material in Example 3, the core material can be cut on-site according to actual needs. Cutting lines can be set according to requirements. The cutting line on the end face of the core material strip can be represented as a straight line or an arc. The cutting line can be set along the diagonal of the end face of the core material, or it can be connected by any point on the upper and lower sides of the end face of the core material. The core material is cut according to the cutting line to ensure that at least two surfaces have shallow grooves and S-shaped grooves after cutting, and that the shallow grooves and S-shaped grooves on at least one of the at least two surfaces are complete, and that the fiberglass fabric at one corner of the core material is intact.

[0054] The specific steps for using this invention are as follows:

[0055] S1: Prepare several core materials as described in Example 3, set a cutting line on the end face of the core material, cut the core material along the length direction according to the cutting line to form a core material corner, ensure that two surfaces have shallow grooves and S-shaped grooves after cutting, and ensure that the fiberglass fabric at one corner of the core material is intact.

[0056] S2: Lay the core material corner in the gap, set up the injection device, vacuum the glue injection, and heat and cure after the glue injection is completed.

[0057] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A core material for filling gaps in wind turbine blade layers, wherein the core material is a cuboid, and along the length of the core material, the cuboid includes a top surface, a bottom surface, two side surfaces, and two end surfaces; characterized in that: Shallow grooves are formed on the top surface, bottom surface, and two side surfaces of the core material. The shallow grooves are all located at the middle of the width direction of each surface and extend along the length direction of the core material. The shallow grooves are all straight grooves. S-shaped grooves extending along the length direction are also provided on the top surface, bottom surface, and two side surfaces. Along the length of the core material, the number of S-grooves per unit length decreases, the width of each S-groove is b, and the virtual line connecting the midpoints of each S-groove along its width is the centerline of the S-groove. The formula for the centerline of the S-groove for: Where a is the width of the top surface, bottom surface, or both sides, h is the depth of the S-groove, L is the length of the top surface, bottom surface, or both sides, η is a coefficient related to the viscosity of the resin, x is the length extending from left to right along the length direction of the top surface, bottom surface, or both sides, x takes a value of 0-L, and α is a coefficient related to the core material.

2. The core material for filling the gaps in wind turbine blade plywood according to claim 1, characterized in that, The core material has fiberglass fabric attached to its top, bottom, and two side surfaces.

3. The core material for filling the gaps in wind turbine blade plywood according to claim 2, characterized in that, The fiberglass fabric is bonded to the four surfaces using adhesive.

4. The core material for filling the gaps in wind turbine blade plywood according to claim 2, characterized in that, The total weight of the fiberglass fabric shall not exceed 600 g / m². 2 .

5. A method for filling gaps in wind turbine blade plywood according to any one of claims 2-4, characterized in that: A cutting line is set on the end face of the core material. The cutting line is a straight line or an arc on the end face of the core material. The core material is cut along the length direction of the core material according to the cutting line to form a core material corner. The core material corner formed after cutting has at least two surfaces with shallow grooves and S-shaped grooves, and the fiberglass fabric at one corner of the core material corner is kept intact.

6. The method for filling gaps in wind turbine blade ply gaps according to claim 5, characterized in that, The specific steps are as follows: S1: Prepare several core materials, set cutting lines on the end faces of the core materials, cut the core material strips along the length direction according to the cutting lines to form core material corners, ensure that at least two faces have shallow grooves and S-shaped grooves after cutting, and ensure that the fiberglass fabric at one corner of the core material corner is intact. S2: Lay the core material corner in the gap, set up a grouting device, vacuum the glue, and heat and cure after the glue is injected.

7. The method for filling gaps in wind turbine blade ply gaps according to claim 6, characterized in that, The core material has a thickness of 5mm, the shallow groove has a width of 1mm, and the S-shaped groove has a width of 1mm.

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