A core material structure for wind turbine blades

Abstract

The present invention relates to a core material structure for wind turbine blades, comprising a core material body, wherein a plurality of slots are provided in parallel on the first surface of the core material body, each slot extending obliquely or vertically toward the second surface in the interior of the core material body, and the bottom of each slot does not reach the second surface; a plurality of circular holes are also provided on the first surface of the core material body along the length direction of the slots, each circular hole extending vertically toward the second surface in the interior of the core material body until it reaches the second surface, and finally forming a through hole on the core material body that penetrates the thickness direction of the core material body and is perpendicular to the first and second surfaces of the core material body, and when the slots extend obliquely toward the second surface in the interior of the core material body, the through hole just passes through the middle part of the corresponding slot. The present invention only requires unidirectional slotting, simple processing equipment, improved processing efficiency, reduced processing costs, and while ensuring the same shear performance of the core material, has a lower glue absorption amount, thus meeting the design requirements of the blade core material.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine blade manufacturing, and more particularly to a core material structure for a wind turbine blade sandwich structure. Background Art

[0002] Currently, wind turbine blades are manufactured using a sandwich structure, consisting of an upper and lower skin, and a core material laid between them. The core material is often slotted and perforated to guide the resin and enhance its performance. The core material in a blade is required to be orthotropic, but its shear properties are directional. Radial slotting only enhances performance in the radial direction, not in the chordal direction. Therefore, slotting in both the radial and chordal directions is necessary to ensure orthotropic shear properties of the core material.

[0003] The current slotting and punching method uses cross-grooving in two radial and chordal directions, which results in a high amount of glue absorption by the core material. In addition, the resin infusion speed needs to be strictly controlled during the infusion process. Too fast an infusion speed will cause the resin to flow quickly along the cross groove of the core material, resulting in the surface fabric layer not being fully infiltrated, thus forming defects such as white spots and dry yarn.

[0004] Patent application number 202210280344.7 discloses a slotting method that adjusts the chordal groove density to create different chordal and radial groove densities, thereby adjusting the strength and modulus of the core material structure to accommodate different design strength regions of the blade and reduce resin usage. Although the patent lists changes in compression performance, this method results in decreased shear performance in the direction with lower groove density, while increasing shear performance in the direction with more grooves. The core material after slotting is orthotropic, resulting in wasted performance in the direction with more grooves, and the excess resin absorbed also results in wasted performance. Summary of the Invention

[0005] To address the existing problem of radial chord-wise cross-grooving and perforation of blade core materials, which results in complex processing, high resin absorption, and the need to strictly control the resin infusion rate during the infusion process, the present invention provides a core material structure for wind turbine blades. The purpose is to simplify the slotting structure and processing flow, thereby achieving a core material with lower resin absorption, reducing blade weight, and achieving orthotropic properties.

[0006] The present invention is specifically achieved through the following technical solutions. According to the present invention, a core material structure for a wind turbine blade includes at least a core material body, wherein the upper surface of the core material body in the thickness direction is defined as a first surface, and the bottom surface in the thickness direction is defined as a second surface. The first surface of the core material body is provided with a plurality of parallel grooves, each of which extends obliquely or perpendicularly toward the second surface inwardly of the core material body, and the bottom of each groove does not reach the second surface.

[0007] The first surface of the core material body is provided with a plurality of circular holes along the length direction of the groove, and the plurality of circular holes are arranged evenly or unevenly, and each circular hole extends vertically toward the second surface in the direction of the interior of the core material body until it reaches the second surface, and finally forms a through hole on the core material body that penetrates the thickness direction of the core material body and is perpendicular to the first surface and the second surface of the core material body; a row of the circular holes is provided between every two adjacent grooves on the first surface of the core material body, and finally forms a row of the through holes between every two adjacent grooves on the core material body, and when the grooves extend obliquely toward the interior of the core material body toward the second surface, the through hole just passes through the middle part of the corresponding groove.

[0008] In the aforementioned core material structure for wind turbine blades, the plurality of slots extending obliquely toward the inside of the core material body and toward the second surface of the core material body have the same inclination angle, which is 30-90°.

[0009] Furthermore, the inclination angles of the multiple slots extending obliquely toward the inside of the core material body and toward the second surface of the core material body are all 45-65 degrees.

[0010] Furthermore, the inclination angles of the multiple slots extending toward the interior of the core material body toward the second surface of the core material body are all one of 45°, 46°, 47°, 48°, 49°, 50°, 51°, 52°, 53°, 54°, 55°, 56°, 57°, 58°, 59°, 60°, 61°, 62°, 63°, 64°, and 65°.

[0011] In the aforementioned core material structure for wind turbine blades, the vertical distance between the bottom of the groove and the second surface is 1-3 mm.

[0012] Furthermore, a vertical distance between the bottom of the groove and the second surface is 1.5±1 mm.

[0013] Preferably, the vertical distance between the bottom of the groove and the second surface is 1.5 mm.

[0014] In the aforementioned core material structure for wind turbine blades, the length direction of the slots is the radial or chordal direction of the core material body, and a row of the through holes is evenly arranged between every two adjacent slots. Finally, the through holes are evenly distributed in the radial and chordal directions of the core material body, and the through holes are perpendicular to the first and second surfaces of the core material body and intersect with the middle part of the corresponding slots.

[0015] The core material structure for the wind turbine blades has a plurality of slots arranged in parallel at equal intervals, and a plurality of through holes arranged evenly at equal intervals.

[0016] Preferably, the spacing between the through holes is equal to the spacing between the slots.

[0017] In the aforementioned core material structure for wind turbine blades, the pouring direction of the core material is located above the first surface, parallel to the first surface, and perpendicular to the length direction of the slot.

[0018] The core material structure of the aforementioned wind turbine blades can be made of any one of organic polymer foam materials such as PET, PVC or HPE; the infusion resin material can be any one of thermosetting resins such as epoxy resin, polyurethane resin, unsaturated resin, phenolic resin and thermoplastic resin such as PMMA.

[0019] Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solution, the present invention can achieve considerable technological advancement and practicality, and has a wide range of utilization value. It has at least the following advantages:

[0020] In response to the current situation in which the core material slotting and punching currently used in wind turbine blades are all radial chord-wise cross slotting and punching, the processing technology is complex, the resin absorption amount is large, and the resin infusion speed needs to be strictly controlled during the infusion process. The present invention innovatively designs a new type of low-glue-absorption orthogonal isotropic core material structure. By redesigning the core material slotting angle and punching position, not only can the core material after infusion have shear orthogonal isotropy, but also the specific modulus (shear modulus / density) of the core material after infusion can be improved, effectively reducing the amount of glue absorbed by the core material, solving many problems such as increasingly longer blade designs, greater pressure to reduce weight, and higher cost pressure.

[0021] The present invention has found through research that the shear performance of the core material after slotting and punching is related to the direction of the resin in the slot. By designing the slotting structure and punching position of the core material and testing the core material after pouring, it is determined that unidirectional inclined slotting or vertical slotting can be used. Unidirectional slotting refers to the parallel arrangement of multiple slots on the core material body (abandoning the original cross slotting), the length directions of all slots are parallel, and the length directions of all slots are longitudinal or chordal (the original slot length directions are longitudinal and chordal at the same time). Inclined slotting refers to the slot depth extending at an angle to the bottom of the core material, and the inclination angle is preferably 45-65°. Vertical slotting refers to the slot depth extension direction being perpendicular to the bottom of the core material (in some cases, some special core materials require unidirectional vertical slotting to ensure orthogonal isotropy). A row of through holes is provided between two adjacent slots. When the slots are inclined, the through holes pass through the middle part of the corresponding slots, thereby connecting the slots and the through holes. During the pouring process, the slots and the through holes have a synergistic diversion effect.

[0022] Compared with existing core materials, the blade core material structure of the present invention ensures the same shear performance while having lower glue absorption and orthogonal isotropy. It meets the design requirements of the blade core material while greatly reducing the resin usage and reducing the blade weight.

[0023] Compared with the existing core material, the blade core material structure of the present invention has a better infusion effect. The infusion direction is perpendicular to the length direction of the slot. No fast channel is formed during infusion. The resin in the slot flows obliquely. The through hole is connected to the slot, which can effectively form a coordinated infusion effect and ensure the infusion quality.

[0024] The present invention simplifies the process flow of the core material slotting and punching structure through the above design improvements. Only single-direction slotting is required, and cross slotting is not required. The processing equipment is simple, the processing efficiency is improved, and the processing cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the core material structure of the blade in the prior art.

[0026] Figure 2 This is a schematic diagram of a blade core material in the prior art that adopts cross-grooving and opening in two directions of radial chord.

[0027] Figure 3 It is a schematic diagram of the positions of unidirectional slotting and punching in the blade core material of the present invention.

[0028] Figure 4 yes Figure 3 sectional view of .

[0029] Figure 5 yes Figure 4 Example of another perfusion direction in .

[0030] 1-core material body, 2-first surface, 3-second surface, 4-slot, 5-circular hole, 6-through hole, 7-through hole A, 8-through hole B, 9-through hole C, 10-through hole D, 11-through hole E, 4.1-first slot, 4.2-second slot, 4.3-third slot. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be noted that the various components in the drawings may be enlarged for illustration and do not have to be drawn to scale. In the drawings, components that are the same or have the same functions have the same reference numerals.

[0032] In order to overcome the defects of the prior art, the present invention provides a core material structure for wind turbine blades. The core material structure is used to form the core material of the wind turbine blade. The core material is grooved and punched and resin material is poured. After the resin material is poured, it is guided along the grooves and through-holes of the core material and infiltrates the upper and lower skins laid on both sides of the core material to form a sandwich structure wind turbine blade.

[0033] The core material structure at least includes a core material body 1, and the upper surface of the core material body in the thickness direction is defined as the first surface 2, and the bottom surface in the thickness direction is defined as the second surface 3. The first surface of the core material body is provided with a plurality of slots 4 in a single direction. The single direction means that the length directions of all slots are parallel, and no slots intersect. Each slot extends obliquely or vertically toward the second surface inside the core material body. The oblique extension means that the angle α between the slot depth extension direction and the second surface is an acute angle, and the vertical extension means that the angle α between the slot depth extension direction and the second surface is a right angle. The bottom of each slot does not reach the second surface. Figures 3 to 5 shown.

[0034] In a preferred embodiment, the plurality of slots extend obliquely toward the second surface in the core material at the same angle. The oblique angle refers to the angle α between the oblique extension direction of the slot and the second surface (or first surface), such as Figure 4 shown.

[0035] Preferably, the plurality of slots extend obliquely toward the second surface in the core material at an angle α of 30-90°, preferably 45-65°. For example, the inclination angle α may be selected from, but not limited to, any one of 45°, 46°, 47°, 48°, 49°, 50°, 51°, 52°, 53°, 54°, 55°, 56°, 57°, 58°, 59°, 60°, 61°, 62°, 63°, 64°, and 65°.

[0036] The bottom of the groove is at a certain distance from the second surface. Specifically, the vertical distance between the bottom of the groove and the second surface may be 1-3 mm.

[0037] Furthermore, a vertical distance between the bottom of the groove and the second surface is 1.5 mm or 1.5±1 mm.

[0038] The first surface of the core material body is also provided with a plurality of circular holes 5 along the length direction of the groove, and each circular hole extends vertically toward the second surface inside the core material until it reaches the second surface, and finally forms a through hole 6 on the core material body that penetrates the thickness direction of the core material body and is perpendicular to the first surface and the second surface of the core material body.

[0039] Furthermore, the circular holes are evenly or unevenly arranged along the length direction of the slot.

[0040] In one embodiment, a row of the circular holes is arranged between every two adjacent slots on the core material body, and finally a row of the through holes is formed between every two adjacent slots on the core material body. Figure 3 Shown and Figure 4 shown.

[0041] Preferably, the through hole passes through the middle portion of the corresponding slot when extending vertically toward the second surface.

[0042] It can be seen from the above scheme that the core material body of the present invention is grooved in one direction, and the depth of the groove extends obliquely or vertically toward the second surface inside the core material body. Since the groove is grooved in one direction, it can be radial groove or chordal groove. The radial groove means that the length direction of the groove is the radial direction of the core material body, and the chordal groove means that the length direction of the groove is the chord direction of the core material body. A row of the through holes is arranged between every two adjacent grooves. Therefore, the through holes are finally evenly distributed in the radial and chord directions of the core material body, and the through holes are perpendicular to the first and second surfaces of the core material body. The through holes pass through the thickness direction of the core material and intersect with the middle part of the corresponding groove.

[0043] In order to ensure that the radial and chordal shear moduli of the core material are equal and orthogonal and isotropic after resin infusion, it should be ensured that: multiple slots are arranged in parallel with equal spacing, and multiple through holes are evenly arranged with equal spacing in the radial and chord directions.

[0044] In one embodiment, the through-hole pitch is equal to the slot pitch.

[0045] Furthermore, the plurality of through holes are evenly spaced in the radial and chord directions, which means that the spacing between the through holes arranged in the radial direction is equal to the spacing between the through holes arranged in the chord direction, and the spacing between adjacent through holes in the plurality of through holes arranged in the radial direction is equal; and the spacing between adjacent through holes in the plurality of through holes arranged in the chord direction is equal. For example: Figure 3 , the spacing between through hole A7 and through hole B8 is equal to the spacing between through hole A7 and through hole D10, and the spacing between through hole A and through hole B is equal to the spacing between through hole B and through hole C9, and the spacing between through hole A and through hole D10 is equal to the spacing between through hole D and through hole E11. The spacing between the first slot 4.1 and the second slot 4.2 is equal to the spacing between the second slot 4.2 and the third slot 4.3, and the spacing between through hole A and through hole B is equal to the spacing between the first slot and the second slot. Figure 3 As shown, the slots on the core material are unidirectional slots (the length of the slots extends only in the radial direction or only in the chordal direction), and the through holes are evenly distributed in both the radial and chordal directions.

[0046] It should be noted that the inclination angle α is related to the material of the core material. In one embodiment, when the core material is PET100 or PVC60, the optimal inclination angle α of the slot is 53°, which can ensure that the core material has orthogonal isotropy after slotting, punching and pouring according to the above scheme.

[0047] As a more preferred solution, when the core material is poured with resin using the above solution, the pouring direction is located above the first surface of the core material body, parallel to the first surface of the core material body and perpendicular to the extending direction of the slot length, such as Figures 3 to 5 This pouring direction does not allow the resin to flow quickly, and the resin in the slot flows obliquely. At the same time, because the through-holes are connected to the slots, the core material can be effectively coordinated with the pouring effect to ensure the pouring quality.

[0048] Furthermore, the material of the core body can be any one of organic polymer foam materials such as PET, PVC or HPE; the infusion resin material can be any one of thermosetting resins such as epoxy resin, polyurethane resin, unsaturated resin, phenolic resin and thermoplastic resin such as PMMA.

[0049] The following describes in detail with specific embodiments:

[0050] Example 1

[0051] The blade core structure includes a core body made of PET100 material. The upper surface of the core body in the thickness direction is defined as the first surface, and the bottom surface in the thickness direction is defined as the second surface. The first surface of the core body is provided with multiple parallel slots, with the spacing between two adjacent slots being 30 mm. Each slot extends at the same angle toward the second surface inward from the core material, and the angle α between the inclined extension direction of each slot and the second surface is 53°. The bottom of each slot does not reach the second surface, and the vertical distance between the bottom of each slot and the second surface is 1.5 mm. The width of each slot is 0.9 mm.

[0052] A row of evenly spaced through holes is provided between adjacent slots, ensuring a uniform distribution of the through holes in the radial and chordal directions of the core material. The spacing between adjacent radial through holes and the spacing between adjacent chordal through holes is 30 mm, and the diameter of each through hole is 2 mm. The through holes are perpendicular to both the first and second surfaces of the core material, extending through the thickness of the core material and intersecting the center of the corresponding slot.

[0053] Using the above solution, after pouring epoxy resin, the shear modulus of the core material in the radial and chord directions are both 85 MPa, which is orthotropic.

[0054] Comparative Example 1

[0055] The core material is PET100. Figure 1The cross-grooving and punching scheme shown is as follows: the core material is slotted in radial and chord directions perpendicular to the bottom surface (second surface) of the core material, the slotting spacing in radial and chord directions is 30 mm, the bottom of the slot does not reach the bottom of the core material and is 1.5 mm away from the bottom of the core material, the through holes are punched perpendicular to the bottom surface (second surface) of the core material, the through holes are evenly distributed in radial and chord directions, the through hole spacing is also 30 mm, and the rest is the same as Example 1.

[0056] Table 1 is a performance comparison of the core material structures of Example 1 and Comparative Example 1 after resin infusion. It can be seen from Table 1 that compared with Comparative Example 1, the solution of Example 1 reduces the number of slots and only requires slotting in one direction (that is, only radial slots or chordal slots are required), and can also ensure radial and chordal orthogonal isotropy. Compared with the solution of Comparative Example 1, the density of the solution of Example 1 after infusion is reduced by 14.3%, the amount of glue absorption is reduced by 25%, and the specific modulus is increased by 20.6%. The infusion effect is good, and no defects such as white spots and dry yarns are generated.

[0057] Table 1. Comparison of performance of core material structure after infusion between Example 1 and Comparative Example 1

[0058]

[0059] Example 2

[0060] The core material is made of PVC60, and the rest is the same as in Example 1.

[0061] Comparative Example 2

[0062] The core material is PVC60, and the rest is the same as that of Comparative Example 1.

[0063] Table 2 is a performance comparison of the core material structures of Example 2 and Comparative Example 2 after resin infusion. It can be seen from Table 2 that the density of the solution of Example 2 is reduced by 17.5% after infusion, the amount of glue absorption is reduced by 25.7%, and the specific modulus is increased by 25.0%. The infusion effect is good, and no defects such as white spots and dry yarn are produced.

[0064] Table 2 is a comparison of the performance of the core material structure of Example 2 and Comparative Example 2 after resin infusion. Table 2. Comparison of the performance of the core material structure of Example 2 and Comparative Example 2 after resin infusion

[0065]

[0066] Example 3

[0067] The core material body is made of PET200. A plurality of radially parallel grooves are formed on the first surface of the core material body. The spacing between two adjacent grooves is 25 mm. Each groove extends at the same angle toward the second surface inwardly of the core material. The angle α between the inclined extension direction of each groove and the second surface is 64°. The width of each groove is 0.9 mm. Other aspects are the same as those of Example 1.

[0068] Using the above solution, after pouring epoxy resin, the shear modulus of the core material in the radial and chord directions are both 113 MPa, which is orthotropic.

[0069] Comparative Example 3

[0070] The core material is PET200. Figure 1 The cross-grooving and punching scheme shown is as follows: the core material is slotted in radial and chord directions perpendicular to the bottom surface (second surface) of the core material, the slotting spacing in radial and chord directions is 30 mm, the bottom of the slot does not reach the bottom of the core material and is 1.5 mm away from the bottom of the core material, the through holes are punched perpendicular to the bottom surface (second surface) of the core material, the through holes are evenly distributed in radial and chord directions, the through hole spacing is 30 mm, and the rest are the same as Example 3.

[0071] The test results show that the radial shear modulus of comparative example 3 is lower than the chordal shear modulus. Only the radial shear modulus performance can be used in the use of the blade, and the chordal shear modulus causes performance waste (the PET200 body is not orthogonal and isotropic. To achieve orthotropic grooves after grooving and drilling, the groove density needs to be different).

[0072] Table 3 is a performance comparison of the core material structures of Example 3 and Comparative Example 3 after resin infusion. It can be seen from Table 3 that: compared with Comparative Example 3, the solution of Example 3 reduces the number of grooves, only requires grooves in a single direction, and can also ensure orthogonal isotropy in the radial and chord directions. Compared with the solution of Comparative Example 1, the density of the solution of Example 3 after infusion is reduced by 10.3%, the amount of glue absorption is reduced by 27.3%, and the specific modulus is increased by 11.8%. The infusion effect is good, and no defects such as white spots and dry yarns are generated.

[0073] Table 3. Comparison of performance of core material structure after infusion between Example 3 and Comparative Example 3

[0074]

[0075] The solution of the present invention is to make unidirectional inclined grooves on the core material body, and through holes are evenly arranged between every two adjacent grooves. The axial direction of the through hole is perpendicular to the upper and lower surfaces of the core material in the thickness direction and penetrates the core material in the thickness direction, and the through hole passes through the middle part of the corresponding groove. After resin infusion, the core material can be made shear-orthogonal isotropy, and the specific modulus of the core material after infusion can be improved, and the glue absorption and density of the core material can be reduced, which effectively solves many problems such as the blade design becoming longer and longer, the pressure to reduce weight, and the high cost pressure.

[0076] The above description is merely an embodiment of the present invention and does not constitute any form of limitation to the present invention. The present invention may also have other forms of embodiments based on the above structures and functions, which are not listed one by one. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments by any person skilled in the art based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A core material structure for a wind turbine blade, comprising at least a core material body (1), wherein the upper surface of the core material body in the thickness direction is defined as a first surface (2), and the bottom surface in the thickness direction is defined as a second surface (3), characterized in that The first surface of the core material body is provided with a plurality of grooves (4) in parallel, the length direction of the grooves being the radial direction or the chord direction of the core material body, each groove extending obliquely toward the second surface inwardly of the core material body, the plurality of grooves extending obliquely at the same angle, the bottom of each groove not reaching the second surface, and the vertical distance between the bottom of the groove and the second surface is 1-3 mm; the first surface of the core material body is provided with a plurality of circular holes (5) along the length direction of the grooves, the plurality of circular holes being arranged evenly or unevenly, each circular hole extending vertically toward the second surface inwardly of the core material body until reaching the second surface, and finally forming a through hole (6) on the core material body that penetrates the thickness direction of the core material body and is perpendicular to the first surface and the second surface of the core material body; a row of the circular holes is provided between every two adjacent grooves on the first surface of the core material body, and finally a row of the through holes is formed between every two adjacent grooves on the core material body, and the through holes pass through the middle portion of the corresponding grooves; the pouring direction is located above the first surface, parallel to the first surface and perpendicular to the length direction of the grooves.

2. The core material structure for wind turbine blades according to claim 1, characterized in that The multiple slots extend obliquely toward the inside of the core material body and toward the second surface of the core material body at an angle of 30-90 degrees.

3. The core material structure for wind turbine blades according to claim 1 or 2, characterized in that The inclination angles of the multiple slots extending obliquely toward the inside of the core material body and toward the second surface of the core material body are all 45-65 degrees.

4. The core material structure for wind turbine blades according to claim 1, characterized in that The vertical distance between the bottom of the groove and the second surface is 1.5±1 mm.

5. The core material structure for wind turbine blades according to claim 1, characterized in that The plurality of slots are arranged in parallel at equal intervals, and the plurality of through holes are evenly arranged at equal intervals.

6. The core material structure for wind turbine blades according to claim 1 or 5, characterized in that The through hole spacing is equal to the slot spacing.

7. The core material structure for wind turbine blades according to claim 1, characterized in that The material of the core body is any one of PET, PVC, and HPE; the infusion resin material is any one of epoxy resin, polyurethane resin, unsaturated resin, phenolic resin, and PMMA.

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