DK201870407A1

DK201870407A1 - Pultruded shear web flange and associated method of manufacture

Info

Publication number: DK201870407A1
Application number: DKPA201870407A
Authority: DK
Inventors: Smith Jonathan
Original assignee: Vestas Wind Systems A/S
Priority date: 2018-06-15
Filing date: 2018-06-15
Publication date: 2019-06-17

Abstract

A wind turbine blade shear web flange is described. The flange extends longitudinally along a longitudinal axis and has a cross-sectional profile perpendicular to the longitudinal axis. The flange is formed as a continuous pultrusion and twists along its length about the longitudinal axis. An associated pultrusion process is also described in which a rotating device is provided in line with a pultrusion die and is configured to twist the pultrusion during the pultrusion process.

Description

Pultruded shear web flange and associated method of manufacture

Technical field

The present invention relates generally to wind turbine blades, and more specifically to an improved flange for a wind turbine blade shear web, and to a method of making a flange.

Background

Modern wind turbine blades comprise a shell defining the aerodynamic contour of the blade and one or more longitudinally-extending spars that act as the main load-bearing structures of the blade. A spar typically comprises a shear web connected between opposed spar caps. The spar caps are provided respectively on windward and leeward sides of the blade and are generally bonded to or are integral with the blade shell. The shear web is typically a longitudinally-extending structure comprising a web panel arranged between windward and leeward flanges. These flanges are bonded respectively to the opposed spar caps during manufacture of the blade.

An example of a known shear web flange is described in applicant’s PCT application WO2016/177375A1. The flange is T-shaped in cross-section and comprises an upstand extending transversely to the base. The upstand is integrated with the shear web panel, whilst the base defines a bonding surface for bonding to a spar cap. It is known to form the flange using a pultrusion process, in which resin-coated fibres are drawn through a pultrusion die having a Tshaped cross-sectional profile. The resulting flange has a planar base and a constant crosssection along its length. It is known to form the shear web flanges as a plurality of pultruded sections, which are arranged end-to-end in the blade.

Optimally designed modern blades are generally twisted along the length of the blade, between the root and the tip. Accordingly, when the flange sections are mounted inside the blade, adjacent flange sections are inclined relative to one another to accommodate the blade twist. In some cases, adjacent flange sections may have different profiles, for example the angle of the upstand with respect to the base of the flange may vary between flange sections to better accommodate blade twist.

Whilst the above solution works well, the flanges can be relatively expensive to produce, in particular where different profiles are required for the various flange sections, because a number of different pultrusion dies must be used to form the various flange profiles. In addition, the planar base of the flange sections means that it is not possible to form bondlines between the flange and spar caps of consistent thickness along the length of the flange. Instead, additional adhesive must be used in certain regions to accommodate the blade twist into the bondline. It can also be difficult to bond adjacent flange sections together when the profiles are different or not aligned. In some

DK 2018 70407 A1 cases it may be necessary to use additional adhesive to fill gaps between the flange sections, which further increases the cost and weight of the blade.

Against this background, the present invention has been made.

Summary

According to a first aspect of the present invention, there is provided a wind turbine blade shear web flange, the flange extending longitudinally along a longitudinal axis and having a crosssectional profile perpendicular to the longitudinal axis, wherein the flange is formed as a continuous pultrusion and twists along its length about the longitudinal axis.

The flange may be formed as a single piece to extend along substantially the entire length of a shear web panel. Alternatively, the flange may be formed as a plurality of individual flange sections, which may be arranged end-to-end along the length of a shear web panel. For the avoidance of doubt, each flange section constitutes a flange according to Claim 1, and is formed as a continuous pultrusion that twists along its length.

The flange may comprise a base defining a mounting surface and an upstand extends transversely from the base. The flange may take any one of a number of forms suitable for use as a shear web flange. Preferably the flange is substantially T-shaped in cross-section. The flange may alternatively comprise a cross-section that is substantially U-shaped, substantially C-shaped or substantially L-shaped. The flange may comprise a different cross-sectional shape that is suitable to the function of the shear web flange. The base of the twisted flange is non-planar. In some embodiments, the twisted flange may be formed as a helix.

The flange may have a first end having a first cross-sectional profile and a second end having a second cross-sectional profile. The second cross-sectional profile may be the same shape as the first cross-sectional profile but rotated relative to the first cross-sectional profile about the longitudinal axis.

At least part of the flange may twist at a constant rate between the first and second ends. At least part of the flange may twist at a variable rate between the first and second ends. The flange may include at least one longitudinally-extending section in which the flange is not twisted.

The present invention also encompasses a shear web comprising a twisted flange as defined in any preceding claim. The present invention further encompasses a wind turbine blade comprising the shear web. The wind turbine blade may comprise a longitudinally-extending shell that twists along its length. The twist in the flange may substantially follow the twist in the shell.

DK 2018 70407 A1

According to a second aspect of the present invention, there is provided a method of making a wind turbine blade shear web flange, the method comprising: providing a first pultrusion die having a cross-sectional shape defining a cross-sectional profile of the flange to be produced; drawing resin-coated fibres through the first pultrusion die in a pultrusion direction to form a partially-cured flange; twisting the partially-cured flange in a plane substantially perpendicular to the pultrusion direction to form a twisted flange; and curing the twisted flange.

In preferred embodiments, the first pultrusion die is substantially T-shaped in cross-section. The method may comprise heating the resin-coated fibres in the first pultrusion die to form the partially-cured flange.

The method may comprise providing a rotating device in-line with the first pultrusion die and downstream from the first pultrusion die. The rotating device may be configured to twist the partially-cured flange. The rotating device may be a second die or a clamp. The method may comprise rotating the rotating device at a constant rate or at a variable rate. The method may further comprise controlling a pultrusion rate and/or controlling a rate of rotation of the rotating device to produce a twisted flange having a degree and rate of twist corresponding to the degree and rate of twist of at least part of a wind turbine blade shell to which the flange will be mounted.

The method may comprise heating the partially-cured flange in the second die or in the region of the clamp to fully cure or further cure the flange such that a fully-cured or further cured twisted flange emerges from the second die or clamp. Alternatively or additionally, the flange may be heated further downstream of the second die or clamp to fully cure the resin.

Brief description of the drawings

The present invention will now be described in further detail by way of non-limiting example only with reference to the following figures in which:

Figure 1 is a schematic cross-sectional view of a wind turbine blade comprising a shear web;

Figure 2 schematically shows first and second flange sections of a known shear web arranged end-to-end;

Figure 3 is a perspective view of a twisted shear web flange according to an embodiment of the present invention;

Figure 4 is an end view of the twisted shear web of Figure 3;

DK 2018 70407 A1

Figure 5 shows a pultrusion process for making a twisted shear web flange according to one embodiment of the present invention; and

Figure 6 shows a pultrusion process for making a twisted shear web flange according to another embodiment of the present invention.

Detailed description

Figure 1 is a cross-sectional view of a wind turbine blade 10. The blade 10 comprises an outer shell 12 defining a substantially hollow interior 14. The blade 10 extends longitudinally in a spanwise direction generally perpendicular to the plane of the page. The blade 10 extends transversely in a chordwise direction (C) between a leading edge 16 and a trailing edge 18.

The blade 10 includes a spar 20, which is the primary load-bearing structure of the blade 10. The spar 20 extends longitudinally in the spanwise direction, and includes a pair of mutually opposed spar caps 22, 24 arranged respectively on windward and leeward sides 26, 28 of the blade 10. In this example, the spar caps 22, 24 are integrated within the structure of the shell 12.

The spar 20 further includes a shear web 30 arranged inside the blade 10 and bonded between the respective spar caps 22, 24. The shear web 30 extends longitudinally in the spanwise direction and comprises a shear web panel 32 disposed between upper and lower mounting flanges 34.

The shear web flanges 34 are generally T-shaped in cross-section and comprise a base 36 and an upstand 38 extending transversely to the base 36. The upstand 38 is integrated with the panel 32, whilst the base 36 is bonded to a respective spar cap 24, 26 via adhesive 40. The flanges 34 are composite components, which are formed by pultrusion. A plurality of pultruded flange sections 34 (shown in Figure 2) may be arranged end to end along the shear web panel 32.

Referring to Figure 2, this schematically shows first and second flange sections 34a of a known shear web 30a arranged end-to-end. As discussed by way of background, the adjacent flange sections 34a are inclined relative to one another in order to accommodate the twist of a wind turbine blade shell 12a. The two flange sections 34a shown in Figure 2 are substantially identical, and each has a planar base 36a. The lengths of the flange sections 34a are selected depending on the degree and rate of twist of the blade 10. For example, in straight, i.e. untwisted, portions of the blade 10, it is possible to use a relatively long flange section 34a. However, in regions of extreme twist, it may be necessary to use several relatively short flange sections 34a arranged end-to-end.

DK 2018 70407 A1

In general, the lengths of the sections 34a are selected such that the amount of blade twist between the two ends 42a, 44a of a flange section 34a does not exceed two degrees. The flange sections 34a therefore approximate the blade twist to the nearest two degrees. As the blade 10 twists between the two ends 42a, 44a of a given flange section 34a, additional adhesive must be used to accommodate this blade twist in the bondlines between the flange 34a and the spar caps 22, 24. Further, when the flange sections 34a are bonded together, further adhesive may be required to fill any gaps between the abutting ends 42a, 44a of adjacent flange sections 34a, which result from the necessary non-alignment between the flange sections 34a. Therefore, the known flanges 34a shown in Figure 2 rely on additional adhesive to accommodate blade twist, which adds to the overall cost and weight of the blade 10.

Figures 3 and 4 are schematic perspective and end views respectively of a shear web flange 34 or flange section according to an embodiment of the present invention.

The flange 34 extends longitudinally along a longitudinal axis (A). The flange 34 has a T-shaped cross-sectional profile perpendicular to the longitudinal axis (A). The flange 34 comprises a base 36 defining a mounting surface 46 and an upstand 38 extends transversely from the base 36. The flange 34 in this example is a composite component, comprising reinforcing fibres such as glass or carbon fibres embedded in a cured resin matrix.

In contrast to the flanges 34a previously described, the flange 34 according to this embodiment twists along its length about the longitudinal axis (A). Accordingly, flange 34 has a first end 42 having a first cross-sectional profile 48 and a second end 44 having a second cross-sectional profile 50. The second cross-sectional profile 50 is the same shape as the first cross-sectional profile 48, i.e. both ends are T-shaped, however the second cross-sectional profile 50 is rotated relative to the first cross-sectional profile 48 about the longitudinal axis (A). The base 36 of the flange 34 is therefore non-planar and defines a twisted mounting surface 46.

The twisted flange 34 presents a number of advantages in comparison to the known non-twisted flanges 34a described above and by way of background. In particular, the twisted flange 34 may be formed such that its twist follows, i.e. substantially matches, the twist of the blade shell 12. This allows the blade twist to be accommodated entirely by the flanges 34 without the need for excess adhesive 40 to be used in the bondlines to accommodate twist. Therefore, bondlines of uniform thickness can be achieved along the length of the flange 34 in a twisted blade 10. As blade twist is accommodated by the twisted flange 34, it is possible to use longer flange sections 34 in comparison to the prior art arrangement previously described. It is also possible to form the entire flange 34 as a single piece having a twist that matches the blade twist along the entire length of the blade 10. When the flange 34 is formed as a plurality of flange sections 34, the abutting ends 42, 44 of adjacent sections 34 can be precisely aligned allowing them to be connected together without gaps.

DK 2018 70407 A1

The twisted flange 34 shown in Figures 3 and 4 is formed as a continuous pultrusion. The twist is imparted to the flange 34 during the pultrusion process. A novel pultrusion process has been developed for forming the twisted flange 34, as will be described in further detail below. Pultrusion processes in general are well known to persons skilled in the art and are used to produce the known flanges 34a described with reference to Figure 2. The skilled person is therefore familiar with standard pultrusion processes. In contrast to standard pultrusion processes, the examples described below provide a process in which a pultruded part 52 can be twisted after in emerges from a pultrusion die 54 (shown in Figure 5).

Figure 5 schematically shows a pultrusion process for forming a twisted flange 34 in accordance with an example of the present invention. The pultrusion apparatus shown in Figure 5 comprises a first pultrusion die 54 having a T-shaped cross-section corresponding to the cross-sectional shape of the flange 34 to be produced. In use, resin-coated fibres 55 are drawn (i.e. pulled) through the first pultrusion die 54 along a pultrusion direction, indicated by the horizontal arrow P in Figure 5. The first pultrusion die 54 shapes the fibres into a continuous pultruded part 52 having a constant T-shaped cross-section. In this example, the first pultrusion die 54 is also configured to heat the part 52 as it is pulled through the die 54, such that the resin is partially cured when the part 52 emerges from the first die 54.

A rotating device 56 is arranged in-line with, and downstream from, the first pultrusion die 54 along the pultrusion direction P. In this embodiment, the rotating device 56 is a second die. The second die 56 also is T-shaped in cross-section. The second die 56 is arranged to rotate about a rotation axis 57, which coincides with the pultrusion direction P. The second die 56 is connected to a controller 58, which is configured to control the rate of rotation of the second die 56. In this example, the controller 58 also controls the overall pultrusion process, including the rate of pultrusion, i.e. the speed at which the fibres 55 are pulled through the dies 54, 56 along the pultrusion direction P.

After the partially cured pultrusion 52 emerges from the first pultrusion die 54, it is pulled through the rotating second die 56. The rotating second die 56 twists the partially cured pultrusion 52 as the pultrusion 52 passes through it. In this example, the rotating second die 56 is located inside an oven 60, which heats the partially-cured pultrusion 52 as it passes through the second die 56. This second heating stage fully cures the resin, such that the pultruded part 52 emerges from the second die 56 in a fully cured state.

The rate of rotation of the second die 56 may be controlled according to the required twist of the flange 34. In preferred embodiments, the rate of rotation is controlled to match the rate of change in twist angle of the blade 10. Accordingly, the pultruded flange 34 can be produced with a twist that matches the blade twist. Alternatively or additionally, the pultrusion rate, i.e. the speed at

DK 2018 70407 A1 which the fibres are pulled in the pultrusion direction P, may be controlled to impart the desired twist to the pultrusion 52.

In some embodiments, the second die 56 may rotate at a constant rate and the pultrusion rate may be varied. In other embodiments, the pultrusion rate and the rate of rotation may be varied. In other embodiments, the pultrusion rate may be constant and the rate of rotation may vary. Varying the rate of pultrusion and/or the rate of rotation during a single pultrusion operation can be used to produce a pultruded flange 34 having varying rates of twist along its length. By means of this process, it is possible to produce a flange 34 in one piece that may extend along the entire shear web 30 and accommodate blade twist along the entire length of the blade 10. In some embodiments, the rotating device 56 may be held in a fixed position for part of the pultrusion process to form a non-twisted section of the flange 34.

In other embodiments, both the pultrusion rate and the rate of rotation may be constant. This process would produce a helical pultruded flange 34 having a constant rate/pitch of twist. The rate of pultrusion and/or the rate of rotation may be varied between production runs to produce helical flanges 34 having a constant rate of pitch different to the previously-produced flange 34. These pultruded flanges 34 may be cut into sections and arranged end-to-end in the blade 10 to accommodate blade twist.

Figure 6 shows an alternative embodiment of a pultrusion system for producing twisted flanges 34. In this embodiment the rotating device is a clamp 62. Specifically, the clamp 62 is a toroidal clamp. A roller 64 or gear 64 is provided adjacent the clamp 62 to rotate the clamp 62 about a longitudinal axis 66 coincident with the pultrusion direction P. The partially-cured pultrusion 52 is pulled through the rotating clamp 62, which grips and twists the pultrusion 52. Heat is applied to the partially-cured pultrusion 52 during the twisting process to fully cure the resin. The rate of rotation of the clamp 62 and/or the pultrusion rate may be variable or constant in the same way as previously described.

Many modifications may be made to the above examples without departing from the scope of the invention as defined in the accompanying claims.

Claims

Claims

1. A wind turbine blade shear web flange, the flange extending longitudinally along a longitudinal axis and having a cross-sectional profile perpendicular to the longitudinal axis, wherein the flange is formed as a continuous pultrusion and twists along its length about the longitudinal axis.
2. The flange of Claim 1, wherein the flange is substantially T-shaped in cross-section.
3. The flange of any preceding claim, wherein the flange comprises a base defining a mounting surface and an upstand extends transversely from the base.
4. The flange of any preceding claim, wherein the flange has a first end having a first crosssectional profile and a second end having a second cross-sectional profile, wherein the second cross-sectional profile is the same shape as the first cross-sectional profile but is rotated relative to the first cross-sectional profile about the longitudinal axis.
5. The shear web flange of Claim 4, wherein at least part of the flange twists at a constant rate between the first and second ends.
6. The shear web flange of Claim 4, wherein at least part of the flange twists at a variable rate between the first and second ends.
7. The shear web flange of any preceding claim, wherein the flange includes at least one longitudinally-extending section in which the flange is not twisted.
8. A shear web comprising a twisted flange as defined in any preceding claim.
9. A wind turbine blade comprising the shear web of Claim 8.
10. The wind turbine blade of Claim 9, wherein the wind turbine blade comprises a longitudinallyextending shell that twists along its length, and wherein the twist in the flange substantially follows the twist in the shell.
11. A method of making a wind turbine blade shear web flange, the method comprising:

providing a first pultrusion die having a cross-sectional shape defining a cross-sectional profile of the flange to be produced;

drawing resin-coated fibres through the first pultrusion die in a pultrusion direction to form a partially-cured flange;

twisting the partially-cured flange in a plane substantially perpendicular to the pultrusion direction to form a twisted flange; and

DK 2018 70407 A1 curing the twisted flange.
12. The method of Claim 11, comprising providing a rotating device in-line with the first pultrusion die and downstream from the first pultrusion die, the rotating device being configured to twist the

5 partially-cured flange.
13. The method of Claim 12, wherein the rotating device is a second die or a clamp.
14. The method of Claim 12 or Claim 13, comprising rotating the rotating device at a constant rate 10 or at a variable rate.
15. The method of any of Claims 12 to 14, further comprising controlling a pultrusion rate and/or controlling a rate of rotation of the rotating device to produce a twisted flange having a degree and rate of twist corresponding to the degree and rate of twist of at least part of a wind turbine blade

15 shell to which the flange will be mounted.