Uniaxial glass fiber fabric, wind power blade root structure and layering design method

Abstract

The invention discloses a uniaxial glass fiber fabric, a wind power blade root structure and a layering design method.The uniaxial glass fiber fabric is formed by interweaving 0-degree warp yarn and 90-degree weft yarn, the 0-degree warp yarn and the 90-degree weft yarn are sewn through sewing lines, and the uniaxial glass fiber fabric is divided into a reference area and at least one transition area in the axial direction; and the surface densities of all the areas are different. The method can solve the problem of cut-off point area damage caused by interlaminar shear stress concentration due to large thickness of a single layer of the glass fiber fabric at the blade root section; the transverse fatigue safety coefficient of the blade and the deformation under the shimmy fatigue load are synchronously calculated through finite element simulation, the layering structure of the blade root section is determined, and the structural failures such as cracks, layering and bonding cracking of the blade caused by insufficient transverse modulus and large deformation under the shimmy fatigue load of the blade are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine blades, and in particular to a uniaxial glass fiber fabric, a wind turbine blade root structure, and a layup design method. Background Art

[0002] Wind turbines are devices that convert wind energy into electrical energy. Blades, as the core component of this conversion, have a direct impact on the overall efficiency of the turbine. During this energy conversion process, shear forces, bending moments, and torques exerted on the blades are transmitted from the blade tip through the blade root to the hub. As such, the blade root becomes a critical load-bearing component, central to ensuring effective load transfer. The selection of blade root materials and the design of the layup structure play a decisive role in the structural safety of the entire blade.

[0003] Currently, tri-axial glass fiber fabrics are primarily used for blade root section layups, with TLX1350 (0° / ±45°) and TLX880 (0° / ±30°) being typical examples. Due to the excessive thickness of the single layer, TLX1350 (0° / ±45°) exhibits significant interlaminar shear stress concentration at the layup cutoff point. This problem can easily trigger the initiation and propagation of microcracks, causing damage to the blade during full-scale fatigue testing. Furthermore, the excessively high proportion of ±45° fibers results in redundant transverse tensile modulus in the blade, while the axial modulus only maintains a baseline value. TLX880 (0° / ±30°) improves layup continuity by thinning the single layer. The ±30° fiber arrangement increases the axial modulus, but reduces the transverse modulus, which in turn leads to transverse cracks in full-scale fatigue testing of the blade. Although tri-axial glass fiber fabrics can increase the blade layup speed, this imbalance in stiffness matching significantly restricts the lightweight design of the blade and poses a potential threat to the structural safety of the blade.

[0004] The current design specification system (such as DNVGL-ST-0376, IEC61400-5, etc.) clearly requires that blade structure verification must include core content such as strength analysis (such as fiber failure analysis, inter-fiber failure and strain analysis), stability analysis, fatigue analysis and bonding analysis. However, in the design practice of large-scale and lightweight blades, it is found that:

[0005] (1) Although a calculation method for the axial fatigue SN curve of glass fiber composite materials has been established based on the Palmgren-Miner criterion for blade fatigue analysis, there is still a lack of quantitative evaluation criteria for the lateral fatigue damage tolerance;

[0006] (2) In the full-scale vibration fatigue test of the blade, it was found that the root section of the blade showed obvious periodic deformation phenomenon - "breathing effect". When the deformation exceeds a certain threshold, the blade is prone to trigger structural failure modes such as delamination failure and cracking in the bonding area. Summary of the Invention

[0007] The first purpose of the present invention is to overcome the shortcomings of the existing technology and provide a uniaxial glass fiber fabric with variable surface density, which can solve the problem of damage to the cutoff point area caused by the concentration of interlayer shear stress in the glass fiber fabric at the root section due to the large thickness of the single layer; through finite element simulation, the lateral fatigue safety factor of the blade and the deformation under the shimmy fatigue load are simultaneously calculated to determine the ply structure of the root section of the blade, thereby solving the structural failure of the blade such as cracks, delamination and bonding cracking caused by insufficient lateral modulus and large deformation under the shimmy fatigue load.

[0008] A second object of the present invention is to provide a wind turbine blade root structure.

[0009] A third object of the present invention is to provide a ply design method for a wind turbine blade root structure.

[0010] The first object of the present invention is achieved through the following technical solutions:

[0011] A uniaxial glass fiber fabric with variable surface density is provided. The uniaxial glass fiber fabric is interwoven with 0° warp yarns and 90° weft yarns and sewn with a seam line. The uniaxial glass fiber fabric is divided into a reference area and at least one transition area along the axial direction, and the surface density of each area is different.

[0012] Furthermore, the surface density is 625 to 1380 g / m 2 .

[0013] Furthermore, the modulus of the 0° warp yarn is ≥87 GPa, the modulus of the 90° weft yarn is ≥76 GPa, and the seam line is polyester fiber.

[0014] The second object of the present invention is achieved through the following technical solutions:

[0015] A wind turbine blade root structure comprises a biaxial glass fiber fabric and the aforementioned uniaxial glass fiber fabric with variable surface density, wherein the transverse fatigue safety factor is ≥1 and the deformation under shimmying fatigue load is ≤20mm. The axial modulus is provided by the uniaxial glass fiber fabric, and the transverse modulus is provided by the biaxial glass fiber fabric.

[0016] Furthermore, the surface density of the reference area of ​​the uniaxial glass fiber fabric is 1250 g / m 2 or 1380g / m 2 The surface density of the transition area is 625g / m 2 or 1000g / m 2 The fiber direction of the biaxial glass fiber fabric is ±45° and its surface density is 600g / m 2 or 808g / m 2 .

[0017] The third object of the present invention is achieved through the following technical solutions:

[0018] A ply design method for a wind turbine blade root structure includes the following steps:

[0019] One layer of biaxial glass fiber fabric and two layers of uniaxial glass fiber fabric are laid in a cycle in the leading edge area of ​​the blade root;

[0020] In the main beam area of ​​the blade root, one layer of biaxial glass fiber fabric + two layers of uniaxial glass fiber fabric are laid as a cycle;

[0021] In the trailing edge area of ​​the blade root, one layer of biaxial glass fiber fabric + two layers of uniaxial glass fiber fabric are laid as a cycle;

[0022] The blade's lateral fatigue safety factor and deformation under shimmy fatigue load are calculated through finite element simulation, and the optimal blade root layup structure is obtained.

[0023] Furthermore, the blade lateral fatigue safety factor is calculated through finite element simulation, including the following steps: S1.1, establishing a three-dimensional model of the blade, defining the material type and ply boundary of each component;

[0024] S1.2. Select the appropriate element type and mesh size and generate the blade finite element model;

[0025] S1.3, obtain the Markov matrix, and convert the Markov matrix into the angle-dependent equivalent fatigue load using formula (1);

[0026]

[0027] Among them, n i is the number of cycles, S i is the full amplitude of stress, m is the slope of fatigue SN curve, S is the full amplitude of equivalent stress;

[0028] S1.4. Apply angle-dependent equivalent fatigue loads to the blade finite element model and calculate the transverse stress σ through post-processing.

[0029] S1.5. Calculate the transverse fatigue safety factor based on the calculated transverse stress σ and in combination with formulas (2), (3) and (4);

[0030] S k,A =σ / 2 Formula (2)

[0031]

[0032] Among them, N is the number of times allowed, R k,t is the ultimate tensile strength, Rk,c is the ultimate compressive strength, γ Ma is the limit analysis material reduction factor, S k,M is the mean, S k,A is the stress half amplitude, γ Mb is the material reduction factor for fatigue analysis, C 1b is the design correction factor, C 1b =N 1 / m .

[0033] Furthermore, the deformation of the blade under the shimmy fatigue load is calculated by finite element simulation, which includes the following steps:

[0034] S2.1. Build a three-dimensional blade model and define the material type and ply boundaries of each component.

[0035] S2.2. Select the appropriate element type and mesh size and generate the blade finite element model;

[0036] S2.3. Establish rod elements in the blade finite element model that connect the leading edge parting seam and the leading edge web, and the trailing edge parting seam and the trailing edge small web;

[0037] S2.4. Apply equivalent fatigue load to the rod element and calculate the deformation through post-processing.

[0038] U=Uymax-Uymin (5)

[0039] Among them, U is the deformation, Uymax and Uymin are the maximum and minimum deformation of the Y axis respectively.

[0040] Furthermore, the leading edge area is the area between the leading edge mold seam and the leading edge of the main beam of the blade, and the trailing edge area is the area between the trailing edge mold seam and the trailing edge of the spar cap of the blade.

[0041] Furthermore, the biaxial glass fiber fabric laid in the leading edge area has an area density of 600 g / mm 2 The biaxial glass fiber fabric laid in the main beam area and the trailing edge area has an area density of 808g / mm 2 .

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] 1. The uniaxial glass fiber fabric with variable surface density of the present invention can effectively reduce the shear stress concentration between the layers at the cutoff point of the fabric layer and prevent the occurrence of fatigue damage.

[0044] 2. The blade root structure of the present invention is laid with uniaxial and biaxial glass fiber fabrics. The uniaxial glass fiber fabric provides axial modulus, and the biaxial glass fiber fabric provides transverse modulus. Compared with triaxial glass fiber fabric, the structural efficiency is improved, the material consumption is reduced, and it is conducive to achieving lightweight blades.

[0045] 3. The blade root structure of the present invention combines the lateral fatigue safety factor and the deformation under the swing fatigue load to calculate and determine the ply structure, thereby achieving a lightweight design of the blade while ensuring the lateral fatigue safety of the blade, providing reliable technical support for blade safety design and performance evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the structure of the uniaxial glass fiber fabric of the present invention.

[0047] Figure 2 This is a schematic diagram of establishing a three-dimensional blade model in the ply design method of the blade root structure of the present invention.

[0048] Figure 3 This is a schematic diagram of establishing a rod unit in the ply design method of the blade root structure of the present invention.

[0049] Figure 4 This is a stress distribution diagram of the uniaxial glass fiber fabric in the blade root structure of the present invention.

[0050] Figure 5 This is a stress distribution diagram of the biaxial glass fiber fabric in the blade root structure of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the 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.

[0052] Example 1:

[0053] like Figure 1 As shown, this embodiment provides a uniaxial glass fiber fabric with variable surface density. The uniaxial glass fiber fabric is interwoven with 0° warp yarns 3 and 90° weft yarns 4 and sewn with a seam line 5. The uniaxial glass fiber fabric is divided into a reference area 1 and at least one transition area 2 along the axial direction. The surface density of each area is different, and the surface density range is 625 to 1380 g / m 2 .

[0054] This embodiment takes the uniaxial glass fiber fabric as an example, which is divided into a reference area and two transition areas along the axial direction. The surface density of the two transition areas is 1000 g / m 2 and 625g / m 2 The surface density of the reference area is 1380g / m 2 .

[0055] The modulus of the 0° warp yarn is ≥87 GPa, the modulus of the 90° weft yarn is ≥76 GPa, and the seam edge is polyester fiber. In this embodiment, the modulus of the 0° warp yarn is preferably 95 GPa, and the modulus of the 90° warp yarn is preferably 76 GPa.

[0056] Example 2:

[0057] This embodiment provides a wind turbine blade root structure, including a biaxial glass fiber fabric and a uniaxial glass fiber fabric with a variable surface density as described in Example 1, wherein the transverse fatigue safety factor thereof is ≥1, the deformation under the shimmying fatigue load is ≤20mm, the axial modulus is provided by the uniaxial glass fiber fabric, and the transverse modulus is provided by the biaxial glass fiber fabric.

[0058] Furthermore, the surface density of the reference area of ​​the uniaxial glass fiber fabric is 1250 g / m 2 or 1380g / m 2 The surface density of the transition area is 625g / m 2 or 1000g / m 2 The fiber direction of the biaxial glass fiber fabric is ±45° and its surface density is 600g / m 2 or 808g / m 2 .

[0059] Example 3:

[0060] This embodiment provides a ply design method for a wind turbine blade root structure, comprising the steps of:

[0061] A layer density of 600g / m2 is used in the leading edge area of ​​the blade root 2 The biaxial glass fiber fabric and two layers of uniaxial glass fiber fabric are laid as a cycle, and the leading edge area is the area between the leading edge mold seam and the leading edge of the main beam of the blade;

[0062] The main beam area of ​​the blade root adopts a surface density of 808g / m 2 Biaxial glass fiber fabric + 2 layers of uniaxial glass fiber fabric are laid as a cycle;

[0063] The trailing edge of the blade root is made of a 1-layer surface with a density of 808g / m 2The biaxial glass fiber fabric + 2 layers of uniaxial glass fiber fabric are laid as a cycle, and the trailing edge area is the area between the trailing edge mold seam and the trailing edge of the blade spar cap;

[0064] The blade's lateral fatigue safety factor and deformation under shimmy fatigue load are calculated through finite element simulation, and the optimal blade root layup structure is obtained.

[0065] The calculation of the blade lateral fatigue safety factor by finite element simulation includes the following steps:

[0066] S1.1. Build a three-dimensional blade model, including airfoil 10, chord length, twist angle, and pre-bend data, and define the material type and ply boundary 20 of each component, such as Figure 2 As shown;

[0067] S1.2. Select an appropriate element type (set to shell181 in this example) and mesh size (set to 100 mm in this example) and generate a blade finite element model.

[0068] S1.3, obtain the Markov matrix, and convert the Markov matrix into the angle-dependent equivalent fatigue load using formula (1);

[0069]

[0070] Among them, n i is the number of cycles, S i is the full amplitude of stress, m is the slope of fatigue SN curve, which is specifically 10 in this embodiment, and S is the full amplitude of equivalent stress;

[0071] S1.4. Apply angle-dependent equivalent fatigue loads to the blade finite element model using the RBE3 loading method, and calculate the transverse stress σ through post-processing.

[0072] S1.5. Calculate the transverse fatigue safety factor based on the calculated transverse stress σ and in combination with formulas (2), (3) and (4);

[0073] S k,A =σ / 2 Formula (2)

[0074]

[0075] Among them, N is the number of times allowed, R k,t is the ultimate tensile strength, R k,c is the ultimate compressive strength, γ Ma is the limit analysis material reduction factor, S k,M is the mean, S k,A is the stress half amplitude, γ Mb is the material reduction factor for fatigue analysis, C1b is the design correction factor, C 1b =N 1 / m .

[0076] The deformation of the blade under the shimmy fatigue load is calculated by finite element simulation, including the following steps:

[0077] S2.1. Build a 3D blade model, including airfoil, chord length, twist angle, and pre-bend data, and define the material type and ply boundaries of each component.

[0078] S2.2. Select an appropriate element type (set to shell181 in this example) and mesh size (set to 100 mm in this example) and generate a blade finite element model.

[0079] S2.3. In the blade finite element model, establish a rod element 300 connecting the leading edge mold seam and the leading edge web 100, and the trailing edge mold seam and the trailing edge small web 200. Set the element type to link180, such as Figure 3 As shown;

[0080] S2.4. Apply equivalent fatigue load to the rod element and calculate the deformation through post-processing.

[0081] U=Uymax-Uymin=-2.38-(-12.06)=9.68mm (5)

[0082] Among them, U is the deformation, Uymax and Uymin are the maximum and minimum deformation of the Y axis respectively.

[0083] The present invention effectively reduces the shear stress concentration between the layers at the cutoff point by adjusting the surface density of the fabric layer in the cutoff area. The blade root structure mainly provides the axial modulus through the uniaxial glass fiber fabric and the transverse modulus through the biaxial glass fiber fabric. The layer structure is determined by combining the transverse fatigue safety factor and the deformation under the shimmy fatigue load, effectively improving the blade structure efficiency and realizing the lightweight design of the blade. Figure 4 、 Figure 5 As shown, the minimum safety factor for transverse fatigue of uniaxial glass fiber fabrics is 1.06, and the minimum safety factor for transverse fatigue of biaxial glass fiber fabrics is 1.15.

[0084] The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and invention concept of the present invention within the scope disclosed by the present invention, which falls within the scope of protection of the present invention.

Claims

1. A uniaxial glass fiber fabric with variable surface density, characterized in that: The uniaxial glass fiber fabric is interwoven with 0° warp yarns and 90° weft yarns and sewn with a seam line. The uniaxial glass fiber fabric is divided into a reference area and at least one transition area along the axial direction, and the surface density of each area is different.

2. The uniaxial glass fiber fabric with variable surface density according to claim 1, characterized in that: The surface density is 625 to 1380 g / m 2 .

3. The uniaxial glass fiber fabric with variable surface density according to claim 1, characterized in that: The modulus of the 0° warp yarn is ≥87 GPa, the modulus of the 90° weft yarn is ≥76 GPa, and the seam line is polyester fiber.

4. A wind turbine blade root structure, characterized in that: The invention comprises a biaxial glass fiber fabric and a uniaxial glass fiber fabric with a variable surface density as claimed in any one of claims 1 to 3, wherein the transverse fatigue safety factor is ≥1, the deformation under the shimmying fatigue load is ≤20mm, the axial modulus is provided by the uniaxial glass fiber fabric, and the transverse modulus is provided by the biaxial glass fiber fabric.

5. The wind turbine blade root structure according to claim 4, characterized in that: The surface density of the reference area of ​​the uniaxial glass fiber fabric is 1250 g / m 2 or 1380g / m 2 The surface density of the transition area is 625g / m 2 or 1000g / m 2 The fiber direction of the biaxial glass fiber fabric is ±45° and its surface density is 600g / m 2 or 808g / m 2 .

6. A ply design method for a wind turbine blade root structure according to claim 4, characterized in that: Including steps, One layer of biaxial glass fiber fabric and two layers of uniaxial glass fiber fabric are laid in a cycle in the leading edge area of ​​the blade root; In the main beam area of ​​the blade root, one layer of biaxial glass fiber fabric + two layers of uniaxial glass fiber fabric are laid as a cycle; In the trailing edge area of ​​the blade root, one layer of biaxial glass fiber fabric + two layers of uniaxial glass fiber fabric are laid as a cycle; The blade's lateral fatigue safety factor and deformation under shimmy fatigue load are calculated through finite element simulation, and the optimal blade root layup structure is obtained.

7. The ply design method for a wind turbine blade root structure according to claim 6, characterized in that: The blade lateral fatigue safety factor is calculated through finite element simulation, including the following steps: S1.

1. Build a three-dimensional blade model and define the material type and ply boundaries of each component. S1.

2. Select the appropriate element type and mesh size and generate the blade finite element model; S1.3, obtain the Markov matrix, and convert the Markov matrix into the angle-dependent equivalent fatigue load using formula (1); Among them, n i is the number of cycles, S i is the full amplitude of stress, m is the slope of fatigue SN curve, S is the full amplitude of equivalent stress; S1.

4. Apply angle-dependent equivalent fatigue loads to the blade finite element model and calculate the transverse stress σ through post-processing. S1.

5. Calculate the transverse fatigue safety factor based on the calculated transverse stress σ and in combination with formulas (2), (3) and (4); S k,A =σ / 2 Formula (2) Among them, N is the number of times allowed, R k,t is the ultimate tensile strength, R k,c is the ultimate compressive strength, γ Ma is the material reduction factor for limit analysis, S k,M is the mean, S k,A is the stress half amplitude, γ Mb is the material reduction factor for fatigue analysis, C 1b is the design correction factor, C 1b =N 1 / m .

8. The ply design method for a wind turbine blade root structure according to claim 6, characterized in that: The deformation of the blade under the shimmy fatigue load is calculated by finite element simulation, which includes the following steps: S2.

1. Build a three-dimensional blade model and define the material type and ply boundaries of each component. S2.

2. Select the appropriate element type and mesh size and generate the blade finite element model; S2.

3. Establish rod elements in the blade finite element model that connect the leading edge parting seam and the leading edge web, and the trailing edge parting seam and the trailing edge small web; S2.

4. Apply equivalent fatigue load to the rod element and calculate the deformation through post-processing. U=Uymax-Uymin (5) Among them, U is the deformation, Uymax and Uymin are the maximum and minimum deformation of the Y axis respectively.

9. The ply design method for a wind turbine blade root structure according to claim 6, characterized in that: The leading edge area is the area between the leading edge mold seam and the leading edge of the main beam of the blade, and the trailing edge area is the area between the trailing edge mold seam and the trailing edge of the spar cap of the blade.

10. The ply design method for a wind turbine blade root structure according to claim 6, characterized in that: The biaxial glass fiber fabric laid in the leading edge area has an area density of 600g / mm 2 The biaxial glass fiber fabric laid in the main beam area and the trailing edge area has an area density of 808g / mm 2 .

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