Wind turbine blade

Abstract

In order to provide a wind turbine blade in which peeling fracture of spar caps can be minimized even when a carbon-fiber-reinforced resin having a high modulus of elasticity is used in the spar caps, provided is a wind turbine blade has spar caps disposed in contact with the inner side of a pressing-side skin and with the inner side of a contraction-side skin, wherein: at least one of the spar caps is essentially configured from a composite material obtained by impregnating reinforcing fibers with a resin; the value calculated using expression (1) below from the blade length L of the wind turbine blade, the elastic modulus E of the composite material, and the maximum thickness tmax of the spar caps is equal to or greater than 3.0 and less than 6.0; and the maximum value of a plate thickness change rate according to the definition below is equal to or less than 5.0.　Expression (1): L4 / (tmax 3×E). Plate thickness change rate: a value expressed by the absolute value of (t2−t1) / 0.5, where t1 is the spar cap thickness at a position where the distance r from a blade root is r1, and t2 is the spar cap thickness at a position separated from r1 by a distance of 0.5L.

Description

Wind turbine blades

[0001] The present invention relates to a wind turbine blade used in wind turbines for wind power generation and the like.

[0002] In recent years, wind turbine blades for wind power generation have become longer and larger in order to generate greater amounts of power. While longer blades increase the area that receives the wind, they also need to be rigid enough to withstand the centrifugal force and wind force that accompanies rotation.

[0003] Until now, glass fiber reinforced plastics, which are relatively inexpensive, have often been used as the material for wind turbine blades. However, for super-large blades exceeding 100 meters, the mechanical properties of glass fiber reinforced plastics are insufficient, resulting in significant bending deformation of the wind turbine blades. As a result, the blades come into contact with the tower that supports them, resulting in blade damage.

[0004] In response to these issues, Non-Patent Document 1 studies how to increase the rigidity of a 117m blade by using carbon fiber reinforced resin, which has better mechanical properties than glass fiber reinforced resin. Patent Document 1 also studies how to devise a thickness for the spar cap, which uses carbon fiber reinforced resin.

[0005] Definition of the IEA Wind 15MW Offshore Reference Wind Turbine (2020)

[0006] European Patent No. 2715118

[0007] However, Non-Patent Document 1 does not consider increasing the rigidity for longer blade lengths. Furthermore, Patent Document 1 only discloses a technology that is more effective for blades in the 50 to 100 m range compared to blades with lengths of 35 to 55 m, and does not verify the effectiveness for extra-large blades exceeding 100 m.

[0008] Spar caps for wind turbine blades are constructed by connecting multiple long, flat composite sheets, each made of reinforcing fibers impregnated with resin, in the length, width, and height directions. Generally, to accommodate extra-large blades, it is considered to ensure rigidity by using a composite material made of a higher-elasticity carbon fiber reinforced resin for the spar cap. However, according to the inventors' research, the mutual adhesion of high-elasticity carbon fiber reinforced resins decreases when a load is applied. Therefore, simply replacing a glass fiber reinforced resin composite with a high-elasticity carbon fiber reinforced resin composite would result in a new problem: delamination failure between the composite materials.

[0009] Therefore, an object of the present invention is to suppress peeling and fracture of a spar cap even when a composite material made of a carbon fiber reinforced resin with a high elastic modulus is used for the spar cap of a wind turbine blade.

[0010] The present invention for solving the above problems is as follows: [1] A wind turbine blade having spar caps arranged in contact with the inside of a pressure-side skin and the inside of a contraction-side skin, at least one of the spar caps being essentially made of a composite material in which reinforcing fibers are impregnated with a resin, and a blade length L of the wind turbine blade, an elastic modulus E of the composite material, and a maximum thickness t of the spar cap. ｍａｘ Therefore, the wind turbine blade has a value calculated by the following formula (1) of 3.0 or more and less than 6.0, and the maximum value of the thickness change rate as defined below is 5.0 or less. ４ / (t ｍａｘ ３× E) ... (1) Plate thickness change rate: A value expressed as the absolute value of (t2 - t1) / 0.5, where t1 is the spar cap thickness at a distance r from the blade root, r, of r1, and t2 is the spar cap thickness at a position 0.5L away from r1. [2] The wind turbine blade according to 1, wherein the value calculated by the formula (1) is 3.5 or more and less than 5.0. [3] The wind turbine blade according to 1 or 2, wherein the maximum value of the plate thickness change rate is 4.0 or less. [4] The wind turbine blade according to any one of 1 to 3, wherein the blade length L is 130 m or more. [5] The maximum thickness t of the spar cap ｍａｘ [6] The wind turbine blade according to any one of 1 to 4, wherein the spar cap is configured so that its thickness is greatest at a position where r / L is 0.3 to 0.5. [7] The wind turbine blade according to any one of 1 to 6, wherein the composite material is a composite material formed by impregnating reinforcing fibers aligned in one direction with a resin. [8] The wind turbine blade according to any one of 1 to 7, wherein the reinforcing fibers contained in the composite material are carbon fibers. [9] The wind turbine blade according to 8, wherein the elastic modulus E of the carbon fibers is 350 GPa or more.

[10] A wind turbine for wind power generation, comprising the wind turbine blade according to any one of 1 to 9.

[0011] According to the present invention, even when a composite material made of a carbon fiber reinforced resin with a high elastic modulus is used as the spar cap of a wind turbine blade, peeling of the composite material within the spar cap can be suppressed.

[0012] Fig. 1 is an overall view of a wind turbine for wind power generation. Fig. 2 is a perspective view showing a wind turbine blade 1, including a cross section when cut along a plane perpendicular to the length direction of the wind turbine blade. Fig. 3 is a side view of a wind turbine blade (A), and a schematic graph (B) showing the relationship between the distance r from the wind turbine root and the spar cap thickness t. Fig. 4 is a schematic diagram of when a pressure simulating wind is applied to the wind turbine blade to evaluate the amount of displacement of the wind turbine blade tip.

[0013] In this specification, the length direction of a wind turbine blade (hereinafter sometimes simply referred to as a blade) refers to the direction of a line connecting the center of gravity in a cross section near the part fixed to the hub and the part farthest from the part fixed to the hub (the blade tip) (z direction in each drawing). The width direction of the wind turbine blade refers to the direction connecting the leading edge and trailing edge in a cross section perpendicular to the length direction of the blade (y direction in each drawing), and the height direction of the wind turbine blade refers to the direction perpendicular to the y and z directions (x direction in each drawing).

[0014] Furthermore, the pressure-side refers to the positive pressure side, i.e., the side of the wind turbine blade that is in contact with the wind, and the suction-side refers to the depressurization side, i.e., the side of the wind turbine blade that is away from the wind.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the description of the specific embodiments shown in the drawings can also be understood as a description of the present invention as a general concept.

[0016] The wind turbine blade of the present invention is used in a typical wind turbine for wind power generation, for example, as shown in Figures 1(A) and 1(B). The wind turbine in Figure 1 is mainly composed of a blade 1, a tower 2, a nacelle 3, and a hub 4. The blade 1 is attached to the hub 4, and is rotated by wind force. This rotation is transmitted via the hub 4 to a power transmission shaft in the nacelle 3, driving a generator in the nacelle 3.

[0017] The blade 1 may be configured (pre-bent) so that the tip side is bent in advance in a direction away from the tower 2 so as to be less likely to collide with the tower 2. In the case of a pre-bend, the length direction of the wind turbine blade refers to the direction of a straight line connecting the center of gravity of the cross section of the blade base and the center of gravity of the cross section of the part farthest from the part fixed to the hub within the range up to the start position of the pre-bend.

[0018] 2 is a perspective view showing a wind turbine blade 1 according to one embodiment of the present invention, including a cross section taken along a plane perpendicular to the blade length direction. The wind turbine blade 1 has a skin 15 made up of a pressure-side skin and a contraction-side skin, a pressure-side spar cap arranged in contact with the inside of the pressure-side skin, a contraction-side spar cap arranged in contact with the inside of the contraction-side skin (in FIG. 2, the pressure-side spar cap and the contraction-side spar cap are collectively shown as spar cap 12), and shear webs 11 joined at both ends to the pressure-side spar cap and the contraction-side spar cap.

[0019] The shear web 11 is joined to the blade 1 via a spar cap 12 that extends along the inner wall of the blade 1 in the blade length direction.

[0020] Although the configuration of the share web 11 is not particularly limited, a sandwich structure consisting of a core material and a skin material is preferably used. The core material of the sandwich structure is preferably wood such as balsa or a foamed resin material, and the skin material is preferably a fiber-reinforced resin containing a reinforced fiber fabric.

[0021] In the present invention, the spar cap 12 is essentially composed of a composite material in which reinforcing fibers (typically unidirectionally arranged reinforcing fibers) are impregnated with resin. More specifically, the spar cap 12 is composed of a plurality of long, flat composite material sheets connected in the length, width, and height directions, and reinforces the portion of the wind turbine blade skin 15 that is joined to the share web 11 on the inside of the skin 15. Here, "essentially" means that the spar cap may contain other materials (e.g., an adhesive between the composite materials) as long as it contains a composite material in which reinforcing fibers are impregnated with resin. In addition, in the present invention, it is sufficient that at least one of the pressure-side spar cap and the contraction-side spar cap is composed of the aforementioned composite material, but it is preferable that both the pressure-side spar cap and the contraction-side spar cap are composed of the aforementioned composite material.

[0022] The preferred method for forming the spar cap is the resin infusion method, in which a large number of composite materials that will be the material for the spar cap 12 are arranged in the lengthwise, widthwise, and heightwise directions on the skin 15 that will form the outer shape of the blade, and covered with a film that will serve as the upper mold.The space formed between the film and the skin 15, which functions as the lower mold, is kept airtight, and resin is filled between the composite materials using vacuum pressure to connect the composite materials with resin.

[0023] In the present invention, the composite material constituting the spar cap preferably contains carbon fiber as a reinforcing fiber. From the viewpoint of reducing costs, other reinforcing fibers such as glass fiber may be used in addition to carbon fiber. In the case of a composite material containing only carbon fiber as a reinforcing fiber, the effects of the present invention are particularly pronounced in the case of a composite material using carbon fiber with an elastic modulus of 350 GPa or more. On the other hand, from the viewpoint of the strength of the carbon fiber, the elastic modulus of the carbon fiber is preferably 420 GPa or less. Note that the elastic modulus of the reinforcing fiber in the present invention is a value measured in accordance with JIS R7606 (2000).

[0024] The elastic modulus of the composite material in the present invention is preferably 140 GPa or more, more preferably 175 GPa or more. On the other hand, from the viewpoint of strength, etc., it is preferably 235 GPa or less. The elastic modulus of the composite in the present invention is a value measured in accordance with JIS K7161 (2014).

[0025] The resin contained in the composite material is not particularly limited, and examples thereof include thermosetting resins such as epoxy resins, unsaturated polyester resins, and vinyl ester resins, as well as thermoplastic resins such as polyamide resins, polyolefin resins, polyester resins, polyphenylene sulfide resins, ABS resins, polycarbonate resins, polyacetal resins, and polybutylene terephthalate resins. In particular, vinyl ester resins are preferred because they have an excellent balance between moldability and mechanical properties, and epoxy resins are preferred because they have excellent mechanical properties and adhesion to carbon fibers.

[0026] The volume content of the reinforcing fibers in the composite material is not limited as long as the required elastic modulus and strength are obtained, but a range of 45 to 75 vol% is preferable because it increases the elastic modulus of the composite material while maintaining moldability, and a range of 55 to 72 vol% is more preferable.

[0027] Maximum thickness t of the spar cap 12 ｍａｘ It is preferable to set the length to 90 mm or less, since this allows for a good balance between the bending rigidity of the blade and the resin impregnation property during the blade manufacturing process. ｍａｘ By setting the length to 90 mm or less, problems such as non-impregnated portions occurring during resin impregnation are less likely to occur, which is preferable. ｍａｘ If t is 80 mm or less, the possibility of defects such as non-impregnation of the resin during production is further reduced, which is preferable. ｍａｘ From the viewpoint of the rigidity required for the blade, the thickness t of the spar cap 12 is preferably 50 mm or more. The thickness t of the spar cap 12 is measured within a range of ±20% from the center in the width direction of the spar cap.

[0028] As for the position where the spar cap is thickest, t ｍａｘ It is preferable to design the blade so that the required rigidity is easily obtained. ｍａｘ Design it to be.

[0029] In the present invention, at least one of the spar caps has a blade length L, a modulus of elasticity E of the composite material, and a maximum thickness t of the spar cap. ｍａｘ Therefore, the value calculated by the following formula (1) is 3.0 or more and less than 6.0, and the maximum value of the thickness change rate defined below is 5.0 or less.

[0030] L ４ / (t ｍａｘ ３ × E) ... (1) The blade length L and the spar cap length are the same.

[0031] Equation (1) is derived from the deflection calculation formula (2) for a simple plate-shaped cantilever beam in material mechanics, and the deflection amount = qL４ / (8 x E x I) ... (2) Here, q is the load applied per unit area, L and E are the length of the beam and the modulus of elasticity of the constituent material. I is the second moment of area, which is derived from the width b and thickness t of the beam. An actual blade is made up of many parts, such as skins and ribs, in addition to the spar cap, and E and I differ for each, requiring a complex design that combines these. However, after careful consideration, the authors have selected the length L of the blade and the maximum thickness t of the spar cap from among these. ｍａｘ , and the elastic modulus E of the spar cap are particularly dominant, and equation (1) was derived.

[0032] If the value of formula (1) is less than 3.0, the spar cap is too thick or the elastic modulus of the composite material is too large, which causes large shear stress when the blade deforms, resulting in the problem of peeling of the composite material. On the other hand, if the value of formula (1) is 6.0 or more, the spar cap is too thin or the elastic modulus of the composite material is too small, which causes the blade to have insufficient rigidity, which also causes large shear stress when the blade deforms, resulting in the problem of peeling of the composite material. In other words, the unit of formula (1) is m / (N / m ２ ) and means the amount of deflection per unit area / load. In the present invention, by manufacturing the spar cap / wind turbine blade so that the value calculated by this formula is within the above-mentioned specific range, it is possible to suppress peeling and fracture of the spar cap, which is a problem particularly when a fiber reinforced resin with a high elastic modulus is used for the spar cap. The value of formula (1) is more preferably 3.5 or more and less than 5.0. In formula (1), the blade length L is m, the elastic modulus E is GPa, and the maximum thickness of the spar cap t ｍａｘ uses mm as the unit of calculation.

[0033] In the present invention, the maximum thickness change rate of the spar cap is 5.0 or less. The thickness change rate of the spar cap is a value expressed as the absolute value of (t2 - t1) / 0.5, where t1 is the spar cap thickness when the distance r from the root of the spar cap is r1 (here, r1 is an arbitrary distance), and t2 is the spar cap thickness at a position 0.5L away from the tip or opposite side of the distance r1. This value is an index indicating the gradual change in the thickness of the spar cap. To explain the profile of the spar cap thickness t (the thickness distribution of the spar cap in the blade length direction), FIG. 3(A) shows a side view of a wind turbine blade, and FIG. 3(B) shows a schematic graph of the spar cap thickness t at the distance r from the root of the wind turbine corresponding to the side view. In the present invention, the maximum thickness change rate of the spar cap is 5.0 or less. A small thickness change rate of the spar cap, i.e., a gradual transition in the thickness of the spar cap, suppresses delamination between the composite materials. If the thickness change rate exceeds 5.0, high shear stress occurs in this portion when the blade undergoes bending deformation, and in the case of a composite material using carbon fiber with a high elastic modulus, peeling occurs between the composite materials, making the blade more susceptible to damage. The maximum value of the thickness change rate is preferably 4.0 or less. There is no particular restriction on the lower limit of the thickness change rate, but a maximum thickness change rate of less than 2.0 indicates that the thickness of the spar cap is almost uniform, and this means that excessive composite material is placed in areas that are not actually necessary to ensure the minimum required rigidity, and is therefore generally not preferable. The position at which the thickness change rate is maximum is when the spar cap reaches its maximum thickness t ｍａｘ It is preferable that the pore size is located closer to the base than the position where the pore size is larger.

[0034] In the present invention, it is sufficient that at least one of the pressurized side spar cap and the contraction side spar cap has the above-described configuration, but it is preferable that both the pressurized side spar cap and the contraction side spar cap have the above-described configuration.

[0035] The above-described configuration of the present invention is particularly preferably applied to blades with a blade length of 130 m or more, since the above-described separation problem becomes particularly pronounced in wind turbines with a blade length of 130 m or more. The effects of the present invention are particularly pronounced when the above-described configuration is adopted in blades with a blade length of 130 m or more. Furthermore, the above-described configuration of the present invention is effective not only against bending deformation of the blade but also against torsional deformation. On the other hand, from the perspective of optimal design of the entire wind turbine, it is preferable that the blade length be 150 m or less.

[0036] As an example, an example in which the effect of the present invention was verified by computer simulation will be shown below.

[0037] (Evaluation method) The maximum shear stress generated in the spar cap was evaluated as shown in Figure 4. That is, as shown in the schematic diagram of Figure 4(A), a distributed load of 5778 Pa, simulating wind (indicated by the arrow in the figure), was applied to the surface of the wind turbine blade. Then, when the wind turbine blade root end 13 was completely constrained around one circumference, the amount of displacement in the x direction of the wind turbine blade tip 14 was evaluated. Here, the surface of the wind turbine blade refers to the surface that is assumed to receive the wind load when the wind turbine is viewed in the xy plane, as shown in Figure 4(B), and refers to the surface projected onto the yz plane as shown in Figure 4(C).

[0038] The simulation used structural analysis software "NX Nastran" manufactured by SIEMENS. The wind turbine was based on the wind turbine model "Definition of the IEA Wind 15MW Offshore Reference Wind Turbine" published by the National Renewable Energy Laboratory (NREL). The wind turbine blades were composed of a skin, spar cap, and shear web as shown in Figure 2, and the spar cap was composed of a composite material in which unidirectionally arranged carbon fibers were impregnated with resin. In all examples and comparative examples, the blade length was set to 140 m.

[0039] The elastic modulus E of the composite material used in the analysis in the wind turbine blade length direction and the maximum thickness t of the spar cap ｍａｘThe thickness profile of the spar cap was based on the model profile shown in Figure 3(B), and t ｍａｘ Position (t ｍａｘ The distance from the blade root at the time of ｍａｘ The position of r / L is at 0.37), and in the examples and comparative examples, t ｍａｘ The value of t was changed. ｍａｘ From the position toward the root, the thickness is defined according to the plate thickness change rate described in the examples and comparative examples, and from the position where the root thickness defined by the model is reached to the root portion, the root thickness defined by the model is constant. ｍａｘ From this position toward the blade tip, the thickness was defined at a uniform rate of change relative to the tip thickness defined in the model.

[0040] The longitudinal elastic modulus E of the composite material was determined as the value obtained by multiplying the assumed elastic modulus of the carbon fiber by a volume content of 60% in Examples 1 to 3 and Comparative Examples 1 to 6, and by multiplying the assumed elastic modulus E by a volume content of 70% in Examples 4 to 6.

[0041] The physical properties in Table 1 were entered into carbonUD1 and carbonUD2, which correspond to the spar caps in the above analysis model, and the difference between the X-direction stress generated in carbonUD1 and carbonUD from the calculation results was taken as the shear stress generated in the spar cap. The maximum value of the generated shear stress was compared with 20 MPa, which is generally considered to be the peel strength of composite materials, and 17 MPa, which is the safety strength that takes fatigue into consideration.

[0042]

[0043] (Example 1) A composite material containing carbon fiber with an elastic modulus of 258 GPa was used, and the fiber direction was set to the blade length direction, and the spar cap maximum thickness t ｍａｘ Assuming a configuration in which composite materials are stacked so that the values ​​shown in Table 1 are obtained, the physical property values ​​were input according to Table 1 and a simulation was performed.

[0044] The analysis showed that the X-direction displacement (deflection) of the blade tip was 30.2 m, indicating sufficient clearance with the tower. The maximum shear stress generated was 13.3 MPa, well below the assumed peel strength of 20 MPa.

[0045] (Comparative Example 1) t ｍａｘ A simulation was performed by inputting the physical property values ​​according to Table 1 in the same manner as in Example 1, except that the distance between the blade tip and the tower was changed to 100 mm. As a result of the analysis, the X-direction displacement (deflection) of the blade tip was 29.8 m, and although the clearance with the tower was sufficient, the maximum thickness of the spar cap was too thick, making actual molding difficult.

[0046] (Comparative Example 2) A simulation was performed by inputting physical property values ​​according to Table 1 in the same manner as in Example 1, except that the maximum value of the spar cap plate thickness change rate was changed to 7.0. As a result of the analysis, the X-direction displacement (deflection) of the blade tip was 30.2 m, and although the clearance with the tower was sufficient, the maximum shear stress that occurred was 20.4 MPa, a value that would cause peeling and fracture in the spar cap.

[0047] (Example 2) Assuming a configuration in which the composite material of Example 1 is changed to a carbon fiber with a high elastic modulus as the reinforcing fiber, t ｍａｘ The simulation was performed by inputting the physical properties of the blade tip and the maximum thickness change rate according to Table 1. The analysis results showed that the X-direction displacement (deflection) of the blade tip was 30.3 m, and there was ample clearance with the tower. The maximum shear stress generated was 19.9 MPa, which was below the assumed peel strength of 20 MPa.

[0048] (Example 3) A simulation was performed by inputting the physical property values ​​according to Table 1 in the same manner as in Example 2, except that the maximum value of the plate thickness change rate was changed to 3.0. As a result of the analysis, the X-direction displacement (deflection) of the blade tip was 30.2 m, and the clearance with the tower was sufficient. In addition, the maximum shear stress generated was 16.8 MPa, which was below the assumed peel strength of 20 MPa.

[0049] (Comparative Example 3) A simulation was performed by inputting physical property values ​​according to Table 1 in the same manner as in Example 2, except that the maximum value of the plate thickness change rate was changed to 7.0. As a result of the analysis, the X-direction displacement (deflection) of the blade tip was 30.4 m, which was sufficient clearance with the tower, but the maximum shear stress that occurred was 21.9 MPa, a value that would cause peeling and fracture in the spar cap.

[0050] (Comparative Example 4) t ｍａｘ The simulation was performed by inputting the physical property values ​​according to Table 1 in the same manner as in Example 2, except that the volume fraction was changed to 60 mm. As a result of the analysis, the X-direction displacement (deflection) of the blade tip was 35.2 m, which was a deflection that would cause a tower hit. (Example 4) ｍａｘ The simulation was performed by entering the physical properties according to Table 1 in the same way as in Example 1, except that the distance between the blade tip and the tower was changed to 86 mm. The analysis results showed that the X-direction displacement (deflection) of the blade tip was 30.0 m, and the clearance with the tower was sufficient. The maximum shear stress generated was 13.7 MPa, which was significantly lower than the expected peel strength of 20 MPa.

[0051] (Example 5) t ｍａｘ The simulation was performed by inputting the physical properties according to Table 1 in the same way as in Example 4, except that the thickness change rate was changed to 83 mm and the thickness change rate to 3.8. The analysis results showed that the X-direction displacement (deflection) of the blade tip was 30.2 m, and the clearance with the tower was sufficient. In addition, the maximum shear stress generated was 11.8 MPa, which was significantly lower than the assumed peel strength of 20 MPa.

[0052] (Example 6) t ｍａｘ The simulation was performed by entering the physical properties according to Table 1 in the same way as in Example 4, except that the distance between the blade tip and the tower was changed to 74 mm. The analysis results showed that the X-direction displacement (deflection) of the blade tip was 32.2 m, ensuring sufficient clearance with the tower. The maximum shear stress generated was 17.3 MPa, which was lower than the expected peel strength of 20 MPa.

[0053] (Comparative Example 5) t ｍａｘA simulation was performed by inputting the physical property values ​​according to Table 1 in the same manner as in Example 1, except that the distance was changed to 74 mm. As a result of the analysis, the displacement (deflection) of the blade tip in the X direction was 35.3 m, which was a deflection that would cause a tower hit.

[0054] (Comparative Example 6) t ｍａｘ The simulation was performed by inputting the physical property values ​​according to Table 1 in the same manner as in Example 2, except that the thickness change rate was changed to 84 mm and the thickness change rate was changed to 4.9. As a result of the analysis, the displacement (deflection) of the blade tip in the X direction was 30.1 m, and the clearance with the tower was sufficient, but the maximum shear stress generated was 20.2 MPa, a value that caused peeling of the spar cap.

[0055] REFERENCE SIGNS LIST 1 Wind turbine blade 2 Tower 3 Nacelle 4 Hub 11 Shear web 12 Spar cap 13 Wind turbine blade root 14 Wind turbine blade tip 15 Skin L Blade length of wind turbine blade r Distance from wind turbine blade root t Spar cap thickness at distance r t ｍａｘ Maximum thickness of spar cap

Claims

1. A wind turbine blade having spar caps arranged in contact with the inside of a pressure-side skin and the inside of a contraction-side skin, at least one of the spar caps being essentially made of a composite material in which reinforcing fibers are impregnated with a resin, the blade length L of the wind turbine blade, the elastic modulus E of the composite material, and the maximum thickness t of the spar cap ｍａｘ A wind turbine blade, in which a value calculated by the following formula (1) is 3.0 or more and less than 6.0, and a maximum value of a plate thickness change rate defined as below is 5.0 or less. ４ / (t ｍａｘ ３ × E) ... (1) Plate thickness change rate: A value expressed by the absolute value of (t2-t1) / 0.5, where t1 is the spar cap thickness at a distance r from the blade root of r1, and t2 is the spar cap thickness at a position 0.5L away from r1.

2. The wind turbine blade according to claim 1, wherein the value calculated by the formula (1) is equal to or greater than 3.5 and less than 5.

0.

3. The wind turbine blade according to claim 1 or 2, wherein the maximum value of the plate thickness change rate is 4.0 or less.

4. The wind turbine blade according to claim 1 or 2, wherein the blade length L is 130 m or more.

5. The maximum thickness t of the spar cap ｍａｘ The wind turbine blade according to claim 1 or 2, wherein the width of the wind turbine blade is equal to or smaller than 90 mm.

6. The wind turbine blade according to claim 1 or 2, wherein the spar cap is configured to be thickest at a position where r / L is 0.3 to 0.

5.

7. The wind turbine blade according to claim 1 or 2, wherein the composite material is a composite material in which reinforcing fibers arranged in one direction are impregnated with a resin.

8. The wind turbine blade according to claim 1 or 2, wherein the reinforcing fibers contained in the composite material are carbon fibers.

9. The wind turbine blade according to claim 8, wherein the carbon fiber has an elastic modulus E of 350 GPa or more.

10. A wind turbine for wind power generation, comprising the wind turbine blade according to claim 1 or 2.