Blade root of wind turbine blade and manufacturing method therefor

Abstract

Disclosed in the present application are a blade root of a wind turbine blade and a manufacturing method therefor. The blade root comprises: a body, which comprises an inner skin and an outer skin, the inner skin and the outer skin being both cylindrical, and the inner skin being arranged on the radial inner side of the outer skin; and a blade root preform, which is integrally mounted between the inner skin and the outer skin, and comprises an embedded bolt sleeve, a strip-shaped member and a composite material layer, the strip-shaped member being connected to the tail end of the embedded bolt sleeve facing the blade tip in the axial direction, and the composite material layer being formed on the radial periphery of the embedded bolt sleeve and the strip-shaped member by means of a pultrusion process. The production of the blade root comprises: first connecting an embedded bolt sleeve and a strip-shaped member; by means of the pultrusion process, performing integral pultrusion to form a blade root preform; then integrally mounting the blade root preform on the radial inner side of an outer skin; and finally laying an inner skin. Integral prefabrication using the embedded bolt sleeve, the strip-shaped member and the composite material layer reduces the number of parts needing to be mounted during a mounting process, thus facilitating assembly of blade roots and improving the efficiency of blade root production.

Description

Blade root of wind turbine blade and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. 202410077967.3, filed on January 18, 2024, entitled “Blade root of wind turbine blade and preparation method thereof,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present application belongs to the technical field of wind power generation, and in particular relates to a blade root of a wind turbine blade and a preparation method thereof. Background Art

[0004] Wind power generation, as an important clean energy source, is experiencing increasing development. Wind turbine blades, a crucial component of wind turbines, are primarily connected to the turbine's pitch bearings via the blade root. Currently, pre-embedded bolt sleeves are a common connection method for large blades.

[0005] However, due to the continuous expansion of the blade root diameter, the assembly of the blade root prefabricated parts is time-consuming and labor-intensive, which brings great difficulties to the personnel operation and results in low blade root preparation efficiency.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a blade root of a wind turbine blade and a preparation method thereof, so as to facilitate the assembly of the blade root and improve the production efficiency of the blade root.

[0008] According to the first aspect of the present application, the present application provides a blade root of a wind turbine blade, which includes: a main body, including an inner skin and an outer skin, the inner skin and the outer skin are both cylindrical, and the inner skin is arranged on the radial inner side of the outer skin; and a blade root preform, which is installed as a whole between the inner skin and the outer skin, and the blade root preform includes an embedded bolt sleeve, a strip and a composite material layer, the strip is connected to the end of the embedded bolt sleeve axially facing the blade tip, and the composite material layer is formed radially around the embedded bolt sleeve and the strip by a pultrusion process.

[0009] Optionally, the inner skin and the outer skin are both made of infused fiberglass; and / or the inner skin, the outer skin and the composite material layer satisfy: |E1-E0| / E0≤0.1; wherein E0 is the equivalent modulus of the inner skin and the outer skin; and E1 is the modulus of the composite material layer.

[0010] Optionally, the strip is made of fiberglass; and / or the strip, inner skin, and outer skin satisfy: |E2-E0| / E0≤0.1; wherein E0 is the equivalent modulus of the inner skin and the outer skin; and E2 is the modulus of the strip.

[0011] Optionally, the inner skin and the outer skin both include at least one layer of unidirectional fiber cloth and at least one layer of bidirectional fiber cloth, and the at least one layer of unidirectional fiber cloth and the at least one layer of bidirectional fiber cloth are alternately stacked along the radial direction of the blade root. The layer of the inner skin and the outer skin adjacent to the blade root preform are both bidirectional fiber cloth, and the modulus of the bidirectional fiber cloth is lower than the modulus of the unidirectional fiber cloth.

[0012] Optionally, a plurality of annular protrusions are provided on the radial outer surface of the embedded bolt sleeve, the plurality of annular protrusions are distributed at intervals along the axial direction of the embedded bolt sleeve, and each annular protrusion has an arc-shaped tip.

[0013] Optionally, an annular groove is formed between two adjacent annular protrusions, and a depth of the annular groove is less than or equal to 3 mm.

[0014] Optionally, the inner diameter of the terminal end portion of the embedded bolt sleeve facing the blade tip in the axial direction gradually increases from the blade root toward the blade tip.

[0015] Optionally, the first end of the strip piece in the axial direction is embedded in the terminal end portion of the embedded bolt sleeve, and the first end of the strip piece in the axial direction is in a cone shape that matches the shape of the terminal end portion of the embedded bolt sleeve.

[0016] Optionally, the first end of the strip in the axial direction is connected to the embedded bolt sleeve, the second end of the strip opposite to the first end in the axial direction is wedge-shaped, the ratio between the height of the strip and the axial length of the second end is less than or equal to 1:10, and the height direction of the strip, the axial direction of the strip and the chord direction of the strip are perpendicular to each other.

[0017] Optionally, the first axial end of the strip is connected to the embedded bolt sleeve, and the second axial end of the strip opposite to the first end is wedge-shaped; the thickness of the section of the inner skin corresponding to the second end gradually increases along the axial direction from the first end to the second end.

[0018] Optionally, the minimum thickness of the end portion of the embedded bolt sleeve facing the blade tip in the axial direction is less than or equal to 2 mm; and the thickness direction, axial direction and chord direction of the embedded bolt sleeve are perpendicular to each other.

[0019] Optionally, the minimum thickness of the terminal end portion of the blade root preform axially facing the blade tip is less than or equal to 0.5 mm; and the thickness direction, axial direction and chord direction of the blade root preform are perpendicular to each other.

[0020] Optionally, there are multiple blade root preforms; the blade root also includes a guide material layer, which is bent or curved along the circumference of the outer skin to form a plurality of first grooves and a plurality of second grooves. The plurality of first grooves and the plurality of second grooves are alternately arranged along the circumference of the outer skin, with the notches of the first grooves facing the outer skin and the notches of the second grooves away from the outer skin. A blade root preform is accommodated in each first groove and each second groove.

[0021] Optionally, a release cloth is provided on the radial outer surface of the blade root preform; or, the radial outer surface of the blade root preform is polished to form a rough layer.

[0022] According to the second aspect of the present application, an embodiment of the present application also provides a method for preparing a blade root according to any of the above embodiments, comprising the following steps: preparing a blade root preform; laying an outer skin on a preset blade mold; installing multiple blade root preforms along the circumference of the outer skin to the radial inner side of the outer skin; laying an inner skin on the radial inner side of multiple blade root preforms; and pouring resin into the blade mold and curing it into shape.

[0023] Optionally, multiple blade root preforms are installed to the radial inner side of the outer skin along the circumference of the outer skin, including: installing the multiple blade root preforms one by one to the inner side of the outer skin along the circumference of the outer skin, and laying a guide material layer between the multiple blade root preforms, so that the guide material layer is bent or curved along the circumference of the outer skin, thereby forming a plurality of first grooves and a plurality of second grooves, the plurality of first grooves and the plurality of second grooves are alternately arranged along the circumference of the outer skin, the notches of the first grooves face the outer skin, and the notches of the second grooves face away from the outer skin, and a blade root preform is accommodated in each first groove and each second groove.

[0024] Optionally, preparing a blade root preform includes: connecting a strip-shaped member to one end of the embedded bolt sleeve axially facing the blade tip to form a preassembled member; laying a composite material layer on the outside of the preassembled member; and pultruding the preassembled member and the composite material layer to form the blade root preform through a pultrusion process.

[0025] Optionally, before connecting the strip to the end of the embedded bolt sleeve axially facing the blade tip, the method further includes: applying an interface enhancer or adhesive to the radial outer surface of the embedded bolt sleeve.

[0026] The blade root of the wind turbine blade provided in the embodiment of the present application includes a body and a blade root prefabricated part. The body includes a cylindrical inner skin and an outer skin, wherein the inner skin is located radially inward of the outer skin. The blade root prefabricated part includes an embedded bolt sleeve, a strip and a composite material layer, the strip is connected to the end of the embedded bolt sleeve axially facing the blade tip, and the composite material layer is formed radially around the embedded bolt sleeve and the strip by a pultrusion process. During the production of the blade root, the embedded bolt sleeve and the strip can be connected together first, and then prefabricated into a blade root prefabricated part as a whole through a pultrusion process, and then the blade root prefabricated part is installed as a whole to the radial inner side of the outer skin, and finally the inner skin is laid. The embedded bolt sleeve, the strip and the composite material layer are prefabricated as a whole, which reduces the number of parts that need to be installed during the installation process, facilitates the assembly of the blade root, and improves the production efficiency of the blade root. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] FIG1 is a schematic structural diagram of a blade root of a wind turbine blade provided in one embodiment of the present application.

[0029] FIG2 is a schematic diagram of the cross-sectional structure of the blade root shown in FIG1 taken along a direction parallel to the axis thereof.

[0030] FIG3 is a schematic diagram of the cross-sectional structure of the blade root shown in FIG1 taken along a direction perpendicular to the axis thereof.

[0031] FIG4 is a schematic cross-sectional view of the embedded blade root component of the blade root shown in FIG1 , taken along a direction perpendicular to the axis thereof.

[0032] FIG5 is a schematic cross-sectional view of the embedded bolt sleeve of the blade root shown in FIG1 taken along a direction parallel to the axis thereof.

[0033] FIG6 is a schematic cross-sectional view of the strip-shaped member of the blade root shown in FIG1 taken along a direction parallel to the axis thereof.

[0034] FIG7 is a schematic flow chart of a method for preparing a blade root provided in one embodiment of the present application.

[0035] FIG8 is a schematic structural diagram of a pre-assembled component formed by connecting the embedded bolt sleeve and the strip-shaped component of the blade root shown in FIG1 . DETAILED DESCRIPTION

[0036] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present application and are not configured to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present application by illustrating the examples of the present application.

[0037] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, the elements defined by the phrase "comprising..." do not exclude the presence of other identical elements in the process, method, article, or device comprising the elements.

[0038] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The embodiments will be described in detail below with reference to the accompanying drawings.

[0039] Figure 1 is a schematic structural diagram of a blade root of a wind turbine blade provided in one embodiment of the present application, Figure 2 is a schematic structural diagram of a cross-section of the blade root shown in Figure 1 taken along a direction parallel to its axis, and Figure 3 is a schematic structural diagram of a cross-section of the blade root shown in Figure 1 taken along a direction perpendicular to its axis. Referring to Figures 1 to 3, the blade root 100 of a wind turbine blade provided in an embodiment of the present application includes a body 10 and a blade root preform 20. The body 10 includes an inner skin 11 and an outer skin 12, both of which are cylindrical, and the inner skin 11 is arranged radially inward of the outer skin 12. The blade root preform 20 is integrally installed between the inner skin 11 and the outer skin 12. Figure 4 is a schematic structural diagram of a blade root embedded part of the blade root shown in Figure 1 taken along a direction perpendicular to its axis. The blade root preform 20 includes an embedded bolt sleeve 21, a strip 22, and a composite material layer 23. The strip 22 is connected to the end of the embedded bolt sleeve 21 facing the blade tip in the axial direction, and the composite material layer 23 is formed radially around the embedded bolt sleeve 21 and the strip 22 by a pultrusion process.

[0040] The main body 10 forms the outer shape of the blade root structure. The main body 10 comprises two layers: an inner skin 11 and an outer skin 12, each layer forming a cylindrical structure. Multiple blade root preforms 20 can be positioned within the space enclosed between the inner and outer skins 11, 12. Each blade root preform 20 is arranged axially along the main body 10, with the preforms 20 arranged circumferentially.

[0041] The strip 22 and the embedded bolt sleeve 21 are connected along the axial direction of the body 10, and the strip 22 is connected to the end of the embedded bolt sleeve 21 axially facing the blade tip. It can be understood that a wind turbine blade has a blade root and a blade tip, wherein the direction facing the blade tip is opposite to the direction facing the blade root. The direction facing the blade root refers to the direction toward the generator hub to which the blade is fixed, and the direction facing the blade tip refers to the direction away from the generator hub to which the blade is fixed.

[0042] The embedded bolt sleeve 21 and the strip 22 can both be rods, and after the embedded bolt sleeve 21 and the strip 22 are connected, the axes of the two coincide. Optionally, the strip 22 can be a cylindrical rod.

[0043] The composite material layer 23 may be coated on the radially outer portion of the embedded bolt sleeve 21 and the strip-shaped member 22 , and may be seamlessly bonded to the radially outer surfaces of the embedded bolt sleeve 21 and the strip-shaped member 22 .

[0044] To improve the bonding strength of the outer surface of the embedded bolt sleeve 21, the outer surface of the embedded bolt sleeve 21 can be cleaned before the pultrusion process, and then a layer of interface enhancer or adhesive can be applied to the outer surface to improve the pullout resistance of the embedded bolt sleeve 21. Alternatively, the outer surface of the embedded bolt sleeve 21 can be cleaned by sandblasting. Optionally, the interface enhancer applied to the outer surface of the embedded bolt sleeve 21 can be a silane coupling agent.

[0045] The blade root 100 of the wind turbine blade provided in the embodiment of the present application includes a body 10 and a blade root preform 20. The body 10 includes a cylindrical inner skin 11 and an outer skin 12, wherein the inner skin 11 is located radially inward of the outer skin 12. The blade root preform 20 includes an embedded bolt sleeve 21, a strip 22 and a composite material layer 23. The strip 22 is connected to the end of the embedded bolt sleeve 21 facing the blade tip in the axial direction. The composite material layer 23 is formed radially around the embedded bolt sleeve 21 and the strip 22 through a pultrusion process. During the production process of the blade root, the embedded bolt sleeve 21 and the strip 22 can be connected together first, and then prefabricated into the blade root preform 20 as a whole through a pultrusion process. The blade root preform 20 is then installed as a whole to the radial inner side of the outer skin 12, and finally the inner skin 11 is laid. The embedded bolt sleeve 21, the strip 22 and the composite material layer 23 are integrally prefabricated, which reduces the number of components required to be installed during the installation process, facilitates the assembly of the blade root 100, improves the production efficiency of the blade root 100, and reduces the mold occupying time.

[0046] In some embodiments, the inner skin 11, the outer skin 12 and the composite material layer 23 meet the following requirements:

[0047] |E1-E0| / E0≤0.1;

[0048] Wherein, E0 is the equivalent modulus of the inner skin 11 and the outer skin 12 ; E1 is the modulus of the composite material layer 23 .

[0049] |E1-E0| is the absolute value of the difference between the modulus E1 of the composite material layer 23 and the equivalent modulus E0 of the inner skin 11 and the outer skin 12. It can be understood that the ratio of this absolute value to E0 is greater than or equal to zero.

[0050] That is, the modulus of the composite material layer 23 formed around the embedded bolt sleeve 21 and the strip 22 is close to the equivalent modulus of the inner skin 11 and the outer skin 12. After the blade root 100 is assembled, the composite material layer 23 formed around the embedded bolt sleeve 21 and the strip 22 abuts the inner skin 11 and the outer skin 12. In this embodiment of the present application, the modulus of the composite material layer 23 is set to be close to the equivalent modulus of the inner skin 11 and the outer skin 12. This can avoid stress concentration caused by inconsistent stiffness at adjacent interfaces, thereby improving the interface bearing capacity between the composite material layer 23 and the inner skin 11 and the outer skin 12.

[0051] In some embodiments, the strip 22, the inner skin 11, and the outer skin 12 satisfy: |E2-E0| / E0≤0.1;

[0052] Wherein, E0 is the equivalent modulus of the inner skin 11 and the outer skin 12 ; E2 is the modulus of the strip 22 .

[0053] |E2-E0| is the absolute value of the difference between the modulus E2 of the strip 22 and the equivalent modulus E0 of the inner skin 11 and the outer skin 12. It will be appreciated that the ratio of this absolute value to E0 is greater than or equal to zero.

[0054] That is, the modulus of the strip 22 is close to the equivalent modulus of the inner skin 11 and the outer skin 12. Thus, stress concentration caused by inconsistent stiffness of adjacent interfaces can be avoided, thereby improving the interface bearing capacity.

[0055] In related art, the strips connected to the embedded bolt sleeves 21 are often made of lightweight foam. While this reduces weight, it can easily lead to delamination failure at the foam locations. Therefore, in some embodiments, the strips 22 are constructed of a composite material. Alternatively, the strips 22 can be made of fiberglass reinforced plastic.

[0056] In the embodiment of the present application, the strip-shaped member 22 is configured as a composite material to replace the existing foam material, which can improve the anti-delamination capability of the blade root preform 20 and improve the structural bearing capacity of the blade root preform 20 .

[0057] In some embodiments, the inner skin 11 and the outer skin 12 can both be composite materials. Optionally, the inner skin 11 and the outer skin 12 can both be infused fiberglass reinforced plastics.

[0058] The composite material layer 23 may be pultruded glass fiber reinforced plastics or other fiber reinforced composite materials.

[0059] In some embodiments, the inner skin 11 and the outer skin 12 each include at least one layer of unidirectional fiber cloth and at least one layer of bidirectional fiber cloth, and the at least one layer of unidirectional fiber cloth and the at least one layer of bidirectional fiber cloth are alternately stacked along the radial direction of the blade root. A layer of the inner skin 11 adjacent to the blade root preform 20 and a layer of the outer skin 12 adjacent to the blade root preform 20 are both bidirectional fiber cloths, and the modulus of the bidirectional fiber cloth is lower than the modulus of the unidirectional fiber cloth.

[0060] The inner skin 11 may be formed by alternating at least one layer of inner unidirectional fiber cloth and at least one layer of inner bidirectional fiber cloth, wherein the modulus of the inner bidirectional fiber cloth is lower than that of the inner unidirectional fiber cloth. The outer skin 12 may be formed by alternating at least one layer of outer unidirectional fiber cloth and at least one layer of outer bidirectional fiber cloth, wherein the modulus of the outer bidirectional fiber cloth is lower than that of the outer unidirectional fiber cloth.

[0061] Both the inner skin 11 and the outer skin 12 are made of a low-modulus bidirectional fiber cloth and are arranged adjacent to the blade root preform 20 to improve the interface bearing capacity between the inner skin 11 and the blade root preform 20, as well as the interface bearing capacity between the outer skin 12 and the blade root preform 20.

[0062] The bidirectional fiber cloths of the inner skin 11 and the outer skin 12 both have two fiber arrangement directions, and the two fiber arrangement directions respectively form an angle of ±45° with the axial direction of the blade root preform 20 .

[0063] Optionally, the unidirectional fiber cloth and the bidirectional fiber cloth of the inner skin 11 and the outer skin 12 may both be glass fibers.

[0064] Figure 5 is a schematic cross-sectional view of the embedded bolt sleeve of the blade root shown in Figure 1, taken along a direction parallel to its axis. Referring to Figure 4, in some embodiments, the radially outer surface of the embedded bolt sleeve 21 is provided with a plurality of annular protrusions 211, which are spaced apart axially along the embedded bolt sleeve 21 and each annular protrusion 211 has an arc-shaped tip.

[0065] Optionally, the tip of the arc-shaped protrusion may be in an arc shape, which provides a better transition effect.

[0066] The multiple annular protrusions 211 form a wave-shaped structure on the outer surface of the embedded bolt sleeve 21, which can increase the bonding area between the embedded bolt sleeve 21 and the composite material layer 23, thereby improving the structural bearing capacity.

[0067] Each annular protrusion has an arc-shaped tip, which is equivalent to the arc-shaped end of the annular protrusion 211. Compared with stepped or sawtooth annular protrusions, annular protrusions with arc-shaped tips have better buffering and transition effects, can reduce stress concentration caused by geometric mutations, and improve structural bearing capacity.

[0068] In some embodiments, an annular groove 212 is formed between two adjacent annular protrusions 211 , and a depth of the annular groove 212 is less than or equal to 3 mm.

[0069] The depth of the annular groove 212 refers to the radial vertical distance between the bottom of the annular groove 212 and the highest point of the tip of the annular protrusion 211 .

[0070] It is understood that the groove depth of the annular groove 212 is greater than 0. Optionally, the groove depth of the annular groove 212 can be 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm or 3.0 mm.

[0071] Adjacent annular grooves 212 and annular protrusions 211 are connected by smooth transitions of planes or curved surfaces.

[0072] In the embodiment of the present application, the groove depth of the annular groove 212 between two adjacent annular protrusions 211 is set to be less than or equal to 3 mm, which can ensure that no pores appear at the bonding interface between the outer surface of the embedded bolt sleeve 21 and the composite material layer 23 during the pultrusion process, thereby improving the molding effect of the pultrusion process and the structural strength of the blade root preform 20.

[0073] In some embodiments, the inner diameter of the terminal end portion 213 of the embedded bolt sleeve 21 facing the blade tip in the axial direction gradually increases from the blade root toward the blade tip.

[0074] It is understandable that the terminal end portion 213 is one of the end sections of the embedded bolt sleeve 21 in the axial direction, which has a certain length along the axial direction of the embedded bolt sleeve 21 and does not only include the axial end surface of the embedded bolt sleeve 21 .

[0075] The embedded bolt sleeve 21 has a starting end 214 facing the blade root and a terminal end 213 facing the blade tip. The starting end 214 and the terminal end 213 are opposite each other along the axial direction of the embedded bolt sleeve 21. The inner diameter of the terminal end 213 of the embedded bolt sleeve 21 gradually increases from the blade root toward the blade tip, so that the interior of the terminal end 213 of the embedded bolt sleeve 21 defines a tapered space.

[0076] In the embodiment of the present application, the inner diameter of the terminal end portion 213 of the embedded bolt sleeve 21 is set to gradually increase from the blade root toward the blade tip, which can reduce the stress concentration at the terminal end and thus improve the structural bearing capacity of the blade root.

[0077] Figure 6 is a schematic cross-sectional view of the strip member of the blade root shown in Figure 1, taken along a direction parallel to its axis. Referring to Figures 2, 4, 5, and 6, in some embodiments, the first axial end 221 of the strip member 22 is embedded in the terminal end 213 of the embedded bolt sleeve 21. The first axial end 221 of the strip member 22 is tapered to match the shape of the terminal end 213 of the embedded bolt sleeve 21.

[0078] It can be understood that the first end 221 is one of the end sections of the strip 22 in the axial direction. The first end 221 has a certain length along the axial direction of the strip 22 and does not only include the axial end surface of the strip 22 .

[0079] The outer diameter of the first end 221 of the strip member 22 gradually increases from the blade root toward the blade tip, and the increase in the outer diameter of the first end 221 of the strip member 22 from the blade root toward the blade tip is the same as the increase in the inner diameter of the terminal end 213 of the embedded bolt sleeve 21 from the blade root toward the blade tip, so that the conical space formed inside the terminal end 213 of the embedded bolt sleeve 21 matches the conical structure formed by the first end 221 of the strip member 22.

[0080] The first end 221 of the strip 22 is inserted into the terminal end 213 of the embedded bolt sleeve 21 , and the outer surface of the first end 221 is in close contact with the inner surface of the terminal end 213 .

[0081] In this embodiment, the embedded bolt sleeve 21 and strip 22 are connected using a tapered structure, which reduces stress concentration at the connection point between the embedded bolt sleeve 21 and the strip 22, thereby improving the structural bearing capacity of this connection point. The strip 22 is embedded in the end 213 of the embedded bolt sleeve 21, which prevents the formation of a step between the strip 22 and the embedded bolt sleeve 21, which could cause wrinkles in the surrounding fiber cloth.

[0082] In some embodiments, the embedded bolt sleeve 21 and the strip 22 are bonded together by composite material adhesive.

[0083] During the blade root preparation process, composite material glue can be first applied to the outer surface of the first end 221 of the strip 22, and then the first end 221 of the strip 22 is embedded in the terminal end 213 of the embedded bolt sleeve 21. After the composite material glue contacts the inner wall of the terminal end 213, the first end 221 and the terminal end 213 are bonded together. Of course, it is also possible to first embed the first end 221 of the strip 22 in the terminal end 213 of the embedded bolt sleeve 21, and then inject composite material glue between the first end 221 and the terminal end 213. After the composite material glue is cured, the first end 221 and the terminal end 213 are bonded together.

[0084] Optionally, the composite material glue may be a resin glue or a colloid of other composite materials.

[0085] The embodiment of the present application uses composite material glue to bond the embedded bolt sleeve 21 and the strip piece 22, which can improve the connection strength between the embedded bolt sleeve 21 and the strip piece 22, thereby avoiding cracks or faults at the connection position of the embedded bolt sleeve 21 and the strip piece 22, and improving the structural stability and structural bearing capacity of the blade root.

[0086] In some embodiments, a first axial end 221 of the strip 22 is connected to the embedded bolt sleeve 21, and a second axial end 222 of the strip 22, opposite the first axial end 221, is wedge-shaped. The ratio of the height H of the strip 22 to the axial length L of the second end 222 is less than or equal to 1:10, and the height direction, axial direction, and chordal direction of the strip 22 are perpendicular to each other.

[0087] It can be understood that the first end 221 and the second end 222 are respectively two end sections of the strip 22 in the axial direction. The first end 221 and the second end 222 have a certain length along the axial direction of the strip 22, rather than just including the axial end surface.

[0088] It is also understood that the ratio between the height H of the strip 22 and the axial length L of the second end 222 is greater than zero, preferably greater than 1:30. In other words, the ratio between the height H of the strip 22 and the axial length L of the second end 222 is greater than 1:30 and less than or equal to 1:10.

[0089] The wedge-shaped surface of the second end 222 can be formed by cutting a cylindrical rod along a predetermined cutting plane, where the predetermined cutting plane intersects with the axis of the cylindrical rod but is not perpendicular to it.

[0090] The height of the strip 22, the axial length of the second end 222, and the inclination direction of the wedge-shaped surface of the second end 222 can collectively form a right triangle. The degree of inclination of the wedge-shaped surface depends on the ratio between the height of the strip 22 and the axial length of the second end 222. The greater the ratio, the greater the inclination of the wedge-shaped surface, and the smaller the ratio, the smaller the inclination of the wedge-shaped surface.

[0091] In the embodiment of the present application, the ratio between the height of the strip 22 and the axial length of the second end 222 is set to be less than or equal to 1:10, so that the inclination of the wedge surface is smaller and the transition of the wedge surface is smoother, which is conducive to laying the inner skin 11.

[0092] Because the blade root preform 20 includes an axially connected embedded bolt sleeve 21 and a strip 22, as well as a composite material layer 23 formed radially around the embedded bolt sleeve 21 and strip 22 via a pultrusion process, the height of the blade root preform 20 is greater than the outer diameter of the embedded bolt sleeve 21. The thickness of the blade root 100 includes not only the height of the blade root preform 20 but also the thickness of the inner and outer skins 11 and 12. Therefore, the thickness of the blade root 100 is greater than the height of the blade root preform 20.

[0093] In some embodiments, a first axial end 221 of the strip 22 is connected to the embedded bolt sleeve 21, and a second axial end 222 of the strip 22, opposite the first end 221, is wedge-shaped. The thickness of the section 111 of the inner skin 11 corresponding to the second end 222 gradually increases axially from the first end 221 to the second end 222.

[0094] Because the second end 222 of the strip 22 is wedge-shaped, the height of the second end 222 gradually decreases from the blade root to the blade tip, forming a thickness transition region of the blade root preform 20. The thickness and height directions of the blade root preform 20 coincide. The section 111 of the inner skin 11 corresponding to the second end 222 includes at least the section where the inner skin 11 covers the second end 222. In this thickness transition region of the blade root preform 20, the thickness of the inner skin 11 gradually increases axially from the first end 221 to the second end 222. In other words, the lower the height of the second end 222, the thicker the inner skin 11. This improves the safety factor of the thickness transition region of the blade root preform 20.

[0095] In some embodiments, the minimum thickness h of the terminal end portion 213 of the embedded bolt sleeve 21 facing the blade tip in the axial direction is less than or equal to 2 mm; the thickness direction, axial direction, and chord direction of the embedded bolt sleeve 21 are perpendicular to each other.

[0096] It is understood that the minimum thickness of the end portion 213 of the embedded bolt sleeve 21 is greater than zero. Optionally, the minimum thickness h of the end portion 213 of the embedded bolt sleeve 21 can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2.0 mm, etc.

[0097] The minimum thickness h of the terminal end portion 213 may be a thickness at an axial end surface adjacent to the terminal end portion 213. The thickness may be half the difference between the outer diameter and the inner diameter of the terminal end portion 213 at this position.

[0098] In the embodiment of the present application, the minimum thickness of the terminal end 213 of the embedded bolt sleeve 21 is set to be less than or equal to 2 mm, which can reduce stress concentration caused by sudden changes in geometry and stiffness, thereby improving the bearing capacity of the embedded bolt sleeve 21.

[0099] In some embodiments, the minimum thickness of the terminal end portion 24 of the blade root preform 20 axially facing the blade tip is less than or equal to 0.5 mm; the thickness direction, the axial direction, and the chord direction of the blade root preform 20 are perpendicular to each other.

[0100] The end portion 24 of the blade root preform 20, axially facing the blade tip, is formed by pultruding the first end 221 of the strip 22 and the composite material layer 23. Because the first end 221 of the strip 22 is wedge-shaped, the end portion 24 has a minimum thickness at its axial end surface.

[0101] It is understood that the minimum thickness of the terminal end portion 24 is greater than or equal to 0. Optionally, the minimum thickness of the terminal end portion 24 can be 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm.

[0102] In the embodiment of the present application, the minimum thickness of the terminal end portion 24 of the blade root preform 20 is set to be less than or equal to 0.5 mm, which can reduce stress concentration at the terminal end portion of the blade root preform 20 and avoid wrinkling of fibers around the blade root preform 20, thereby improving the structural bearing capacity.

[0103] To improve the surface roughness and enhance the interfacial strength of the blade root preform 20, in some embodiments, a release sheet may be provided on the radially outer surface of the blade root preform 20. After the blade root preform 20 is formed by the pultrusion process, the release sheet may be covered on the radially outer surface of the blade root preform 20. The outer covering film of the release sheet is then removed when the blade root preform 20 is mounted on the outer skin 12.

[0104] In other embodiments, the radially outer surface of the blade root preform 20 may be polished to form a rough layer. After the blade root preform 20 is formed by the pultrusion process, the rough layer may be polished to form the radially outer surface of the blade root preform 20. This can also improve the surface roughness of the blade root preform 20 and enhance the bonding strength of the blade root preform 20.

[0105] In some embodiments, there are multiple blade root preforms 20. Referring to FIG3 , the blade root 100 further includes a flow guide material layer 30 that bends or curves along the circumference of the outer skin 12 to form a plurality of first grooves 31 and a plurality of second grooves 32. The plurality of first grooves 31 and the plurality of second grooves 32 are alternately arranged along the circumference of the outer skin 12. The notches of the first grooves 31 face the outer skin 12, while the notches of the second grooves 32 face away from the outer skin 12. Each first groove 31 and each second groove 32 accommodates a blade root preform 20.

[0106] Multiple blade root preforms 20 are arranged along the circumference of the outer skin 12. A flow-guiding material layer 30 is laid between the multiple blade root preforms 20. The flow-guiding material layer 30 is alternately located radially inward of the multiple blade root preforms 20, in the gaps between two adjacent blade root preforms 20, and radially outward of the blade root preforms 20. A first portion of the flow-guiding material layer 30 is located radially inward of the blade root preform 20, a second portion is located between two adjacent blade root preforms 20, and a third portion is located radially outward of the blade root preform 20. The first, second, and third portions are sequentially connected and alternately arranged.

[0107] The cross-sections of the first groove 31 and the second groove 32 may be arc-shaped, U-shaped, or inverted U-shaped.

[0108] The guide material layer 30 can be biaxial cloth, composite material felt, etc.

[0109] In the embodiment of the present application, a guide material layer 30 is laid between multiple blade root preforms. During the blade root preparation process, the guide material layer 30 can be used to guide the resin poured into the blade mold, so that the resin is fully filled, thereby improving the infusion effect and the molding effect of the blade root 100.

[0110] According to a second aspect of the present application, an embodiment of the present application further provides a method for preparing a blade root according to any of the above embodiments. FIG7 is a flow chart of a method for preparing a blade root provided by an embodiment of the present application. Referring to FIG7 , the method for preparing a blade root of the present application includes:

[0111] Step S10, preparing a blade root preform 20;

[0112] Step S20, laying the outer skin 12 on the preset blade mold;

[0113] Step S30, installing a plurality of blade root preforms 20 to the radial inner side of the outer skin 12 along the circumference of the outer skin 12;

[0114] Step S40, laying the inner skin 11 on the radial inner side of the plurality of blade root preforms 20; and

[0115] Step S50: pouring resin into the blade mold and curing it to form a shape.

[0116] The blade root preform 20 prepared in step S10 is shown in Figure 4 and includes at least an embedded bolt sleeve 21, a strip 22, and a composite material layer 23. It should be understood that there is no particular order in which steps S10 and S20 can be performed. The blade root preform 20 can be prepared first, followed by the outer skin 12, or the outer skin 12 can be laid first, followed by the preparation of the blade root preform 20.

[0117] The blade root preparation method provided in the embodiment of the present application first prepares a blade root preform 20, and then installs the blade root preform 20 as a prefabricated whole to the radial inner side of the outer skin 12, thereby reducing the number of parts that need to be installed during the installation process, improving the preparation efficiency of the blade root 100, and reducing the mold occupying time.

[0118] In some embodiments, step S30 of installing the plurality of blade root preforms 20 to the radial inner side of the outer skin 12 along the circumference of the outer skin 12 may specifically include:

[0119] A plurality of blade root preforms 20 are installed one by one on the inner side of the outer skin 12 along the circumference of the outer skin 12, and a flow guide material layer 30 is laid between the plurality of blade root preforms 20 so that the flow guide material layer 30 is bent or curved and extended along the circumference of the outer skin 12, thereby forming a plurality of first grooves 31 and a plurality of second grooves 32. The plurality of first grooves 31 and the plurality of second grooves 32 are alternately arranged along the circumference of the outer skin 12, with the notches of the first grooves 31 facing the outer skin 12 and the notches of the second grooves 32 facing away from the outer skin 12. Each first groove 31 and each second groove 32 accommodates a blade root preform 20.

[0120] The installation of multiple blade root preforms 20 and the placement of the flow guide material layer 30 can be performed simultaneously. Optionally, the flow guide material layer 30 is bent or folded twice each time a blade root preform 20 is installed, so that the flow guide material layer 30 is alternately located radially inward of the blade root preform 20, between two adjacent blade root preforms 20, and radially outward of the blade root preform 20.

[0121] In step S50 , the guide material layer 30 can guide the resin poured into the blade mold so that the resin is fully filled, thereby improving the pouring effect and the molding effect of the blade root 100 .

[0122] FIG8 is a schematic structural diagram of a pre-assembled part formed by connecting the embedded bolt sleeve and the strip of the blade root shown in FIG1. ​​In some embodiments, step S10 of preparing the blade root preform 20 may specifically include:

[0123] Connect the strip 22 to the end of the embedded bolt sleeve 21 facing the blade tip in the axial direction to form a pre-assembled component, see the structure shown in FIG8 ;

[0124] Laying a composite material layer 23 on the outside of the pre-assembly; and

[0125] The pre-assembled component and the composite material layer 23 are pultruded into the blade root preform 20 by a pultrusion process.

[0126] The first end 221 of the strip 22 in the axial direction is embedded in the terminal end 213 of the embedded bolt sleeve 21. During the preparation process, the first end 221 of the strip 22 can be plugged into the terminal end 213 of the embedded bolt sleeve 21.

[0127] During the preparation of the blade root preform 20, the two strips 22 can be integrally formed into a cylindrical rod, with tapered first ends 221 formed at each axial end of the cylindrical rod. An embedded bolt sleeve 21 can be connected to each end of the cylindrical rod. After the two embedded bolt sleeves 21 and the cylindrical rod are pultruded, the cylindrical rod is cut to form two blade root preforms 20, improving the production efficiency of the blade root preform 20.

[0128] Optionally, before the first end 221 of the strip-shaped member 22 is inserted into the terminal end portion 213 of the embedded bolt sleeve 21 , composite material glue may be applied to the outer surface of the first end 221 .

[0129] Optionally, after the first end 221 of the strip 22 is inserted into the terminal end 213 of the embedded bolt sleeve 21 , composite material glue may be injected between the first end 221 and the terminal end 213 .

[0130] Optionally, after the preassembly and the composite material layer 23 are pultruded to form the blade root preform 20, and before the blade root preform 20 is installed on the outer skin 12, the preparation method of the embodiment of the present application further includes: covering the outer surface of the blade root preform 20 with a release cloth or polishing the outer surface of the blade root preform 20 to form a rough layer, so as to improve the bonding strength between the blade root preform 20 and the outer skin 12.

[0131] In some embodiments, before connecting the strip 22 to the end of the embedded bolt sleeve 21 axially facing the blade tip, the preparation method of the embodiment of the present application further includes:

[0132] An interface enhancer or adhesive is applied to the radial outer surface of the embedded bolt sleeve 21 to improve the bonding strength of the outer surface of the embedded bolt sleeve 21 .

[0133] Optionally, before applying the interface reinforcing agent or adhesive to the radial outer surface of the embedded bolt sleeve 21 , the outer surface of the embedded bolt sleeve 21 may be cleaned by sandblasting the outer surface of the embedded bolt sleeve 21 .

[0134] Optionally, the interface enhancer applied to the outer surface of the embedded bolt sleeve 21 may be a silane coupling agent.

[0135] In some embodiments, the outer skin 12 includes at least one layer of outer unidirectional fiber cloth and at least one layer of outer bidirectional fiber cloth, wherein the modulus of the outer unidirectional fiber cloth is higher than the modulus of the outer bidirectional fiber cloth. In these embodiments, the step of laying out the outer skin 12 on a predetermined blade mold may specifically include: alternately laying out the outer unidirectional fiber cloth and the outer bidirectional fiber cloth on the blade mold, wherein the outer bidirectional fiber cloth is located radially innermost.

[0136] In some embodiments, the inner skin 11 includes at least one layer of inner unidirectional fiber cloth and at least one layer of inner bidirectional fiber cloth, wherein the modulus of the inner unidirectional fiber cloth is higher than the modulus of the inner bidirectional fiber cloth. In these embodiments, the step of laying the inner skin radially inwardly of the plurality of blade root preforms 20 may specifically include: sequentially and alternately laying the inner bidirectional fiber cloth and the inner unidirectional fiber cloth radially inwardly of the plurality of blade root preforms 20.

[0137] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0138] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0139] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, m and / or n can represent: m exists alone, m and n exist simultaneously, and n exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0140] In the description of the embodiments of the present application, the term "plurality" refers to more than two (including two).

[0141] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "vertical", "horizontal", "top", "bottom", "inside", "outside", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0142] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0143] In the embodiments of this application, "parallel" includes not only absolute parallelism but also approximately parallelism as commonly understood in engineering practice. Similarly, "perpendicular" also includes not only absolute perpendicularity but also approximately perpendicularity as commonly understood in engineering practice. For example, if the angle between two directions is 85°-90°, they are considered perpendicular; if the angle between two directions is 0°-5°, they are considered parallel.

[0144] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and such modifications or substitutions should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A root of a wind turbine blade, comprising: A body, including an inner skin and an outer skin, both the inner skin and the outer skin are cylindrical, and the inner skin is arranged radially inside the outer skin; And A root preform, integrally installed between the inner skin and the outer skin, the root preform includes an embedded bolt sleeve, a strip-shaped member, and a composite material layer, the strip-shaped member is connected to the end of the embedded bolt sleeve facing the blade tip axially, and the composite material layer is formed around the radial periphery of the embedded bolt sleeve and the strip-shaped member by a pultrusion process.

2. The root according to claim 1, wherein, Both the inner skin and the outer skin are pultruded fiberglass; and / or The inner skin, the outer skin, and the composite material layer satisfy: |E1 - E0| / E0 ≤ 0.1; Wherein, E0 is the equivalent modulus of the inner skin and the outer skin; E1 is the modulus of the composite material layer.

3. The root according to claim 1, wherein, The strip-shaped member is made of fiberglass; and / or The strip-shaped member, the inner skin, and the outer skin satisfy: |E2 - E0| / E0 ≤ 0.1; Wherein, E0 is the equivalent modulus of the inner skin and the outer skin; E2 is the modulus of the strip-shaped member.

4. The root according to claim 1, wherein, Both the inner skin and the outer skin include at least one layer of unidirectional fiber cloth and at least one layer of bidirectional fiber cloth, the at least one layer of unidirectional fiber cloth and the at least one layer of bidirectional fiber cloth are alternately stacked along the radial direction of the root, and the layer of the inner skin and the outer skin adjacent to the root preform is the bidirectional fiber cloth, and the modulus of the bidirectional fiber cloth is lower than that of the unidirectional fiber cloth.

5. The root according to claim 1, wherein, The outer surface of the embedded bolt sleeve along the radial direction is provided with a plurality of annular protrusions, the plurality of annular protrusions are spaced apart axially along the embedded bolt sleeve, and each of the annular protrusions has an arc-shaped tip.

6. The root according to claim 5, wherein, An annular groove is formed between two adjacent annular protrusions, and the depth of the annular groove is less than or equal to 3 mm.

7. The root according to claim 1, wherein, The inner diameter of the end of the embedded bolt sleeve facing the blade tip axially gradually increases from the root towards the blade tip.

8. The root according to claim 7, wherein, The first end of the strip-shaped member axially is embedded in the end of the embedded bolt sleeve, and the first end of the strip-shaped member axially is conical and matches the shape of the end of the embedded bolt sleeve.

9. The root according to claim 1, wherein, The first end of the strip-shaped member axially is connected to the embedded bolt sleeve, the second end of the strip-shaped member axially opposite to the first end is wedge-shaped, and the ratio of the height of the strip-shaped member to the length of the second end along the axial direction is less than or equal to 1:10, and the height direction, the axial direction, and the chord direction of the strip-shaped member are perpendicular to each other in pairs.

10. The root according to claim 1, wherein, The first end of the bar-shaped member in the axial direction is connected to the embedded bolt sleeve, and the second end of the bar-shaped member opposite to the first end in the axial direction is wedge-shaped; The thickness of the section of the inner skin corresponding to the second end gradually increases along the axial direction from the first end to the second end.

11. The blade root according to claim 1, wherein, The minimum thickness of the end portion of the embedded bolt sleeve facing the blade tip in the axial direction is less than or equal to 2 mm; the thickness direction, axial direction and chord direction of the embedded bolt sleeve are perpendicular to each other in pairs.

12. The blade root according to claim 1, wherein, The minimum thickness of the end portion of the blade root preform facing the blade tip in the axial direction is less than or equal to 0.5 mm; the thickness direction, axial direction and chord direction of the blade root preform are perpendicular to each other in pairs.

13. The blade root according to claim 1, wherein, The number of the blade root preforms is multiple; The blade root further includes a flow guiding material layer, and the flow guiding material layer is bent or curved along the circumferential direction of the outer skin to form a plurality of first grooves and a plurality of second grooves, and the plurality of first grooves and the plurality of second grooves are alternately arranged along the circumferential direction of the outer skin, the notch of the first groove faces the outer skin, the notch of the second groove faces away from the outer skin, and each of the first grooves and each of the second grooves contains one of the blade root preforms.

14. The blade root according to claim 1, wherein, A demoulding cloth is provided on the outer surface of the blade root preform in the radial direction; or, the outer surface of the blade root preform in the radial direction is polished to form a rough layer.

15. A method for preparing the blade root according to any one of claims 1-14, comprising the following steps: Preparing the blade root preform; Laying the outer skin on a preset blade mold; Installing a plurality of the blade root preforms along the circumferential direction of the outer skin to the inner side in the radial direction of the outer skin; Laying the inner skin on the inner side in the radial direction of the plurality of blade root preforms; And Pouring resin into the blade mold and curing and molding.

16. The preparation method according to claim 15, wherein, The step of installing a plurality of the blade root preforms along the circumferential direction of the outer skin to the inner side in the radial direction of the outer skin includes: Installing a plurality of the blade root preforms one by one along the circumferential direction of the outer skin to the inner side of the outer skin, and laying a flow guiding material layer between the plurality of blade root preforms, so that the flow guiding material layer is bent or curved along the circumferential direction of the outer skin, thereby forming a plurality of first grooves and a plurality of second grooves, and the plurality of first grooves and the plurality of second grooves are alternately arranged along the circumferential direction of the outer skin, the notch of the first groove faces the outer skin, the notch of the second groove faces away from the outer skin, and each of the first grooves and each of the second grooves contains one of the blade root preforms.

17. The preparation method according to claim 15, wherein, The step of preparing the blade root preform includes: Connecting the bar-shaped member to one end of the embedded bolt sleeve facing the blade tip in the axial direction to form a pre-assembled component; Laying a composite material layer on the outside of the pre-assembled component; The root preform is formed by pultruding the pre-assembled component and the composite material layer through a pultrusion process.

18. The preparation method according to claim 17, wherein, before connecting the bar-shaped member to the axially tip-facing end of the embedded bolt sleeve, further comprising: coating an interface enhancer or an adhesive on the radially outer surface of the embedded bolt sleeve.

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