Manufacture of a wind turbine blade

Abstract

A shear web flange (36) for a shear web (32) of a wind turbine blade (18) is described. The flange (36) extends longitudinally and comprises a bonding surface (50) for bonding to an inner surface of a wind turbine blade (18). One or more protruding features (52a, 52b) protrude from the bonding surface (50). A method of making such a shear web flange (36) is also described as are a shear web (32) for a wind turbine blade (18), a wind turbine blade (18) and a method of making a wind turbine blade (18).

Claims

1. A wind turbine blade shear web comprising: a web panel having first and second edges; and first and second flange structures, each flange structure including: a flange extending longitudinally and including a bonding surface for bonding to an inner surface of a wind turbine blade, the bonding surface having one or more protruding features configured to extend toward the inner surface of the wind turbine blade; wherein the protruding features protrude from the bonding surface by approximately 0.5 to 5 mm; and an upstand extending from a surface of the flange opposite the bonding surface of the flange, wherein at least a portion of the upstand of the first and second flange structures is positioned inside the web panel at respective first and second edges.

2. The shear web of claim 1, wherein the one or more protruding features are formed integrally with the flange.

3. The shear web of claim 1, wherein the flange is a pultruded component.

4. The shear web of claim 1, wherein the one or more protruding features comprise one or more longitudinally extending ridges.

5. The shear web of claim 4, wherein the one or more ridges extend along the length of the flange.

6. The shear web of claim 4, wherein the one or more ridges are continuous along the length of the flange.

7. The shear web of claim 4, wherein the flange comprises a plurality of ridges that are mutually spaced apart in a lateral direction across the width of the flange.

8. The shear web of claim 4, wherein the flange comprises first and second peripheral ridges that are respectively laterally spaced inwardly of first and second longitudinal edge regions of the flange.

9. The shear web of claim 4, wherein the flange comprises a central ridge located substantially centrally between first and second longitudinal edges of the flange.

10. The shear web of claim 9, wherein the central ridge and the upstand are aligned in a lateral direction.

11. The shear web of claim 1, wherein the flange comprises a main portion defining the bonding surface and first and second longitudinal edge regions defining first and second longitudinal edges of the flange, wherein the first and second longitudinal edge regions have a reduced thickness relative to the thickness of the main portion.

12. The shear web of claim 1, wherein the flange comprises reinforcing fibres in a cured resin matrix.

13. The shear web of claim 12, wherein the protruding features comprise unidirectional reinforcing fibres and a portion of the flange comprises reinforcing fibres oriented in more than one direction.

14. The shear web of claim 1, wherein the shear web comprises a longitudinally extending web panel and the flange is arranged transversely to the web panel.

15. A wind turbine blade comprising a shear web as claimed in claim 1, wherein the flange is bonded to an inner surface of the blade by means of adhesive and the bonding surface of the flange is spaced apart from the inner surface of the blade with a layer of adhesive between the bonding surface of the flange and the inner surface of the blade.

16. The wind turbine blade of claim 15, wherein the one or more protruding features are in contact with the inner surface of the blade.

17. A method of making the shear web as claimed in claim 1, the method comprising forming the shear web flange by: providing a pultrusion die defining an aperture having a shape corresponding to a cross-sectional shape of the flange; drawing resin-coated fibrous material through the aperture; and curing the resin.

18. The method of claim 17, wherein the fibrous material comprises fibrous tape.

19. The method of claim 17 wherein the fibrous material comprises a combination of unidirectional fibres and fibres arranged in more than one direction.

20. A method of making a wind turbine blade comprising: providing a shell portion of the wind turbine blade having an inner surface; providing a shear web as claimed in claim 1; applying adhesive to the inner surface of the shell portion and/or to the bonding surface of the flange of one of the first or second flange structures; arranging the bonding surface of the flange opposite the inner surface of the shell; and providing relative movement between the shear web and the shell portion such that the adhesive is squeezed between the inner surface of the shell portion and the bonding surface of the flange.

21. The method of claim 20, further comprising continuing to provide said relative movement until the one or more protruding features make contact with the inner surface of the blade shell.

22. A wind turbine blade shear web comprising: a flange extending longitudinally and including a bonding surface for bonding to an inner surface of a wind turbine blade, the bonding surface having one or more longitudinally extending peripheral ridges configured to extend toward the inner surface of the wind turbine blade, wherein the peripheral ridges protrude from the bonding surface by approximately 0.5 to 5 mm; wherein an upstand extends from a surface of the flange opposite the bonding surface of the flange, wherein a central ridge is located substantially centrally between first and second longitudinal edges of the flange, and wherein the central ridge and the upstand are aligned in a lateral direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order that the invention may be more readily understood, embodiments of the invention will now be described by way of non-limiting example only with reference to the accompanying figures, in which:

(2) FIG. 1 is a schematic front view of a wind turbine comprising a plurality of blades;

(3) FIG. 2a is a schematic cross-sectional view of an airfoil portion of a wind turbine blade taken along the line 2a-2a in FIG. 1;

(4) FIG. 2b is a schematic cross-sectional view of a circular root end of the wind turbine blade taken along the line 2b-2b in FIG. 1;

(5) FIG. 3 is a cross-sectional view of a shear web comprising a web panel and two flange structures;

(6) FIG. 4 is an enlarged cross-sectional view of a flange structure of the shear web;

(7) FIG. 5 is a schematic representation of a pultrusion die used in the manufacture of the flange structure;

(8) FIGS. 6a and 6b show a process of bonding the shear web to the inner surface of a blade shell; and

(9) FIG. 7 is a cross-sectional view of a flange structure in accordance with another example of the present invention.

DETAILED DESCRIPTION

(10) Referring initially to FIG. 1, a wind turbine 10 according to an embodiment of the present invention is shown schematically. The wind turbine 10 comprises a tower 12 supporting a nacelle 14 to which a rotor 16 is mounted. The rotor 16 comprises a plurality of wind turbine blades 18 that extend radially from a root end 20, attached to a central hub 22, to a tip end 24. In this example, the rotor comprises three blades 18.

(11) FIG. 2a shows a schematic cross-sectional view of an airfoil portion of a wind turbine blade 18 taken along the line 2a-2a in FIG. 1. The blade 18 may comprise a hollow shell 26 made up of two half-shells bonded together along the leading and trailing edges 28, 30 of the blade 18. Two shear webs 32 are located within the internal cavity of the blade 18. The shear webs 32 extend longitudinally along the length of the blade 18, transverse to the plane of the page.

(12) In this example, each shear web 32 comprises a central web element 34 with two mounting flanges 36 respectively provided along first and second longitudinal edges 38 of the web element 34. As viewed in cross-section in the orientation shown in FIG. 2a, the mounting flanges 36 are respectively located at top and bottom edges 38 of a substantially vertical web element 34. As such, the shear webs 32 may be substantially I-shaped in cross-section. The mounting flanges 36 of each shear web 32 are bonded to the inner surface 40 of the shell 26.

(13) As will be readily apparent to persons skilled in the art, the profile of the wind turbine blade 18 may vary along its length. To accommodate the changing geometry of the shell 26 along the length of the blade 18, the shape of the shear webs 32 may vary along the length of the blade 18 depending upon the local profile of the blade 18. For example, FIG. 2b shows a schematic cross-sectional view of a circular root end 20 of the wind turbine blade 18 taken along the line 2b-2b in FIG. 1. In this example, the web elements 34 of the shear webs 32 are kinked to accommodate the high degree of curvature at the root end 20 of the blade 18.

(14) FIG. 3 shows a cross-sectional view of a shear web 32 suitable for the wind turbine blades 18 of FIG. 1. As shown in FIG. 3, the shear web 32 may be formed of three component sections: an elongate web panel 42 and first and second flange structures 44. In this example, the web panel 42 forms the web element 34 of the shear web 32 and the flange structures 44 form the respective mounting flanges 36. As will be described in more detail later, the flange structures 44 may be manufactured separately before being assembled into a layup that is cured to form the finished shear web 32.

(15) The shear web 32 may be manufactured as a single unitary component extending along the length of the blade 18. Alternatively, the shear web 32 may comprise a plurality of longitudinal sections. For example, the shear web 32 may comprise a plurality of flange structures 44 arranged end-to-end along the length of the shear web 32 to define each mounting flange 36. In this case, each flange structures 44 may be substantially identical or may be dissimilar along the longitudinal extent of the shear web 32 to adapt to the changing geometry of the blade shell 26 along the length of the blade 18.

(16) The flange structures 44 will now be described in more detail with reference to FIG. 4, which shows an enlarged cross-sectional view of one of the flange structures 44 in isolation. It should be noted that the cross-section of the flange structure 44 is uniform along its length in this example (where the length direction extends perpendicular to the plane of the page).

(17) As shown in FIG. 4, the flange structure 44 generally comprises a flange 36 and an upstand 46. In this example, the upstand 46 projects from the centre of a first or ‘inner’ surface 48 of the flange 36 in a substantially perpendicular direction. As such, the flange structure 44 is substantially T-shaped in cross-section. A second, or ‘outer’, surface 50 of the flange 36 (opposite to the surface 48 from which the upstand 46 projects) defines the bonding surface 50 of the flange 36. In the orientation of the flange structure 44 as shown in FIG. 4, the first surface 48 of the flange 36 is the upper surface of the flange 36 and the second surface 50 of the flange 36 is the lower surface of the flange 36. After the flange structure 44 has been assembled into a shear web, the bonding surface 50 may be bonded to the inner surface 40 (see FIG. 2a or 2b) of the blade shell 26, as will be described in more detail later.

(18) The bonding surface 50 has a generally flat profile in this example. However, the flange 36 includes a plurality of features 52a, 52b that protrude from the bonding surface 50. In this example, the flange 36 includes three protruding features 52a, 52b in the form of ridges extending longitudinally and continuously along the length of the bonding surface 50. In this example, the protruding features 52a, 52b have constant cross-section along the length of the flange structure 44. In particular, the protruding features 52a, 52b in this example are approximately semi-circular in cross-section and protrude from the bonding surface 50 by approximately 2 to 3 mm. In other examples, the flange 36 may have other arrangements, numbers and/or sizes of protruding features.

(19) As shown in this example, the protruding features 52a, 52b may be mutually spaced apart in a lateral direction across the width W of the flange 36. The three protruding features 52a, 52b comprise a central ridge 52a and two peripheral ridges 52b. The central ridge 52a is located centrally with respect to the flange 36, equidistant from first and second longitudinal edges 54 of the flange 36. As such, in this example, the central ridge 52a is directly opposite the upstand 46 extending from the upper surface 48 of the flange 36. In the orientation of the flange structure 44 shown in FIG. 4, the central ridge 52a is directly beneath the upstand 46. The peripheral ridges 52b are located either side of the central ridge 52a, laterally spaced apart from the central ridge 52a towards the respective longitudinal edges 54. The peripheral ridges 52b are laterally spaced inwardly of first and second longitudinal edge regions 56 of the flange 36.

(20) The flange structure 44 may be a unitary component. Forming the flange structure 44 as a unitary component advantageously simplifies the manufacturing process of the flange structure 44. One method of manufacture will now be described with reference to FIG. 5.

(21) In this example, the flange structure 44 is of composite construction and comprises a plurality of reinforcing fibres (such as glass fibres) embedded in a cured resin matrix. The flange structure 44 may be formed by pultrusion. As the skilled person will appreciate, this process may involve using an appropriately-shaped pultrusion die, such as the one shown in cross-section in FIG. 5.

(22) As shown in FIG. 5, the pultrusion die 58 defines an aperture 60 having a shape corresponding to the cross-sectional shape of the flange structure 44. The pultrusion process may involve drawing resin-coated fibrous material through the aperture 60 of the pultrusion die 58 whilst curing the resin. This process advantageously allows a flange structure 44 of uniform cross-section, including continuous protruding features 52a, 52b of constant cross-section, to be produced easily and relatively inexpensively. However, it should be noted that a flange structure 44 of varying cross-section may be manufactured by varying the size of the aperture 60 or the angle of the pultrusion die 58 whilst fibrous material is drawn through the aperture 60.

(23) The fibrous material drawn through the pultrusion die 58 may comprise fibre tape. In this case, the fibre tape may include fibres in any orientation. In preferred embodiments, triax tape is used in which the fibres are arranged predominantly in three directions which are respectively +45 degrees, −45 degrees and 0 degrees relative to the direction of pultrusion. In some embodiments, unidirectional tape may be drawn through the pultrusion die 58 in combination with the triax tape to form the flange structure 44. The flange 36 and the upstand 46 may comprise triax tape. The orientation of the fibres allows for efficient transfer of loads between the web panel 42 and the shell to which the flange structure is adhesively bonded. The protruding features 52a, 52b may comprise unidirectional fibres oriented at 0 degrees relative to the direction of pultrusion. The protruding features 52a, 52b are relatively small and it is simpler to draw unidirectional fibres though these small holes in the die rather than triax tape.

(24) To manufacture the shear web 32, the flange structures 44 may be arranged in a mould along with the other shear web components, including the web panel components, to form a layup that is cured to form the shear web 32. The flange structures 44 are arranged such that in the finished shear web 32, the upstand 46 of each flange structure 44 forms the interface of the flange structure 44 with the web panel 42, as shown in FIG. 3. One example of an appropriate moulding process to manufacture the shear web 32 is described in the applicant's co-pending application number PCT/DK2016/050111.

(25) A process for bonding the shear web 32 to the inner surface 40 of a blade shell 26 will now be described with reference to FIGS. 6a and 6b.

(26) Referring to FIG. 6a, an end region of the shear web 32 is shown in cross-section, in close proximity to a portion 62 of a blade shell 26. The blade shell portion 62 may be a blade half-shell. As shown in FIG. 6a, the shell portion 62 includes a reinforcing structure or ‘spar cap’ 64 integrated within the structure of the shell portion 62.

(27) To bond the shear web 32 to the inner surface 40 of the shell portion 62, adhesive 66 may be applied to the inner surface 40 of the shell portion 62 along a longitudinally-extending shear web mounting region. As shown in this example, the shear web mounting region may coincide with the position of the reinforcing spar cap 64. The shear web 32 may then be maneuvered into position such that the bonding surface 50 of the mounting flange 36 is arranged against the adhesive 66, as shown in FIG. 6a.

(28) The shear web 32 and shell portion 62 may be moved relative to one another to bring the bonding surface 50 of the mounting flange 36 closer to the inner surface 40 of the shell portion 62 such that the adhesive 66 is squeezed between the two surfaces 40, 50. The skilled person will appreciate that this relative movement may be provided by pressing the shear web 32 against a stationary shell portion 62. Alternatively, the shear web 32 may be maintained in a stationary position whilst the shell portion 62 is moved towards the shear web 32. In other embodiments, the shear web 32 and shell portion 62 may both be moved, either sequentially or simultaneously.

(29) As shown in FIG. 6b, the shear web 32 and shell portion 62 are brought together to compress the adhesive 66 between the mounting flange 36 of the shear web 32 and the inner surface 40 of the shell portion 62. As the mounting flange 36 and shell portion 62 are brought together, the protruding features 52a, 52b may make contact with the inner surface 40 of the shell portion 62. At this point, the shear web 32 and shell portion 62 cannot be brought closer together. Thus, the protruding features 52a, 52b prevent the bonding surface 50 from making contact with the inner surface 40 of the shell portion 62. Therefore, the protruding features 52a, 52b ensure that the bonding surface 50 of the mounting flange 36 is spaced apart from the inner surface 40 of the shell portion 62 by a predetermined minimum distance corresponding to the depth of the protruding features 52a, 52b (2-3 mm in this example). In this regard, the protruding features 52a, 52b function as depth stops and ensure that there is a minimum thickness of adhesive 66 (equal to the depth of the protruding features 52a, 52b) between the bonding surface 50 of the flange 36 and the inner surface 40 of the shell portion 62.

(30) As such, the protruding features 52a, 52b prevent over-compression of the adhesive 66; i.e. they prevent too much adhesive 66 from being squeezed out of the region between the bonding surface 50 of the mounting flange 36 and the inner surface 40 of the shell portion 62. Therefore, the protruding features 52a, 52b ensure sufficient adhesive 66 is present in the bondline between the shell portion 62 and the mounting flange 36 of the shear web 32 and hence ensure a high-quality bond.

(31) During compression, the central region of the mounting flange 36 may experience the most force as the compression force is transferred to the flange 36 from the centrally located upstand 46. The central ridge 52a, being laterally aligned with the upstand 46 relative to the width of the flange 36, is directly opposite the base of the upstand 46. As such, in the orientation of the shear web 32 shown in FIG. 3, the central ridges 52a of the flange structures 44 are respectively located directly above and below the bases of their respective upstands 46. Being aligned with the base of the upstand 46, the central ridge 52a supports the region of the mounting flange 36 that experiences most force during compression. This prevents the mounting flange 36 from flexing during compression which may result in a kissing bond.

(32) Since the cross-section of the protruding features 52a, 52b is constant along the length of the flange structure 44, the minimum thickness of the bondline is ensured along the entire length of the flange structure 44. Furthermore, since the protruding features 52a, 52b comprise a plurality of ridges spaced apart laterally across the width W of the flange 36, the minimum thickness of the bondline is ensured across the width of the flange 36. Therefore, the protruding features 52a, 52b advantageously ensure a consistent high-quality bond between the shear web 32 and the shell portion 62 across the entire bonding surface 50 of the flange 36.

(33) The skilled person will appreciate that the other mounting flange 36 may be bonded to the inner surface 40 of the blade shell 26 by a similar process to the one described above. In some cases, the adhesive 66 may be applied directly to the bonding surface 50 of the mounting flange 36 rather than to the inner surface 40 of the blade shell 26.

(34) The present invention is not limited to the exemplary embodiments described above and many other variations or modifications will be apparent to the skilled person without departing from the scope of the present invention as defined in the following claims.

(35) For example, the flange structure 44 may take many other forms. FIG. 7 shows one alternative example of a flange structure 44 in cross-section. Similarly to the flange structure 44 described above, the flange structure 44 shown in FIG. 7 generally comprises a flange 36 and an upstand 46 and is substantially T-shaped in cross-section. The flange 36 may comprise a main portion 68 defining the bonding surface 50 of the flange 36 from which protruding features 52a, 52b in the form of three ridges project. As shown in FIG. 7, the flange 36 may also comprise ‘glue-catcher’ portions 56 in the form of first and second longitudinal edge regions 56 respectively defining first and second longitudinal edges 54 of the flange 36. In this example, the main portion is located between the glue-catcher portions 56. As shown in FIG. 7, the glue-catcher portions 56 may have reduced thickness relative to the main portion of the flange 36.

(36) The glue-catcher portions 56 are provided to catch any excess adhesive 66 that is squeezed out when the shear web 32 is bonded to the blade shell 26. The reduced thickness of the longitudinal edge regions 56 provides a volume between the inner surface 40 of the blade shell 26 and the glue-catcher portions 56 of the flange structure 44 within which any excess adhesive 66 can collect during compression. The glue-catcher portions 56 advantageously collect any excess adhesive 66 that detaches from the blade shell 26.

(37) In some examples, the upstand 46 may not project perpendicularly from the first surface 48 of the flange 36. As shown in FIG. 7, the upstand 46 may be inclined relative to the first surface 48 of the flange 36. This allows the flange structure 44 to be integrated into the shear web 36 such that the mounting flange 36 defined by the flange structure 44 is arranged at an angle to the web element 34 of the shear web 36. As discussed previously, this may be desirable to accommodate the curvature of the blade shell 26.

(38) Other modifications to the form of the flange structure 44 will be evident to persons skilled in the art depending on the requirements of the shear web 36.

(39) The skilled person will be aware of alternative shear web configurations to which the present invention is applicable. For example, the mounting flanges may be formed integrally with the shear web panel.