WO2015003717A1

WO2015003717A1 - Wind turbine blades

Info

Publication number: WO2015003717A1
Application number: PCT/DK2014/050208
Authority: WO
Inventors: Steve WARDROPPER
Original assignee: Vestas Wind Systems A/S
Priority date: 2013-07-11
Filing date: 2014-07-08
Publication date: 2015-01-15

Abstract

A method of making a wind turbine blade is described. The method comprises forming at least part of a shell of the blade; mounting a plurality of spar support elements to an inner surface of the shell, the spar support elements being spaced apart in a longitudinal direction; supporting an elongate spar structure in position against the shell with the spar support elements; and securing the spar structure to the inner surface of the shell.

Description

Wind Turbine Blades

Technical field The present invention relates to wind turbine blades and to methods of manufacturing wind turbine blades.

Background Figure 1 is a schematic illustration of a wind turbine blade 10. The wind turbine blade 10 has a leading edge 12 and a trailing edge 14, which each extend generally in a longitudinal or 'spanwise' direction of the blade from a root end 16 of the blade to a tip end 18 of the blade. The blade 10 extends in a transverse or 'chordwise' direction, perpendicular to the spanwise direction, between the leading edge 12 and the trailing edge 14. The width or 'chord' of the blade 10 is defined as the straight line distance between the leading and trailing edges 12, 14.

The root end 16 of the blade 10 is substantially circular in cross-section and includes connection means (not shown) for connecting the blade 10 to a hub of a wind turbine. The profile of the blade 10 rapidly transitions from the circular profile at the root end 16 into an airfoil profile moving in the spanwise direction towards the tip end 18 of the blade 10. The aerodynamic profile of the blade 10 varies along the length of the blade in order to optimise the performance of the blade. Consequently, wind turbine blades typically exhibit a certain twist moving along the length of the blade. The blade 10 also tapers in thickness moving from the root end 16 of the blade 10 towards the tip end 18.

The dashed line 20 in Figure 1 show an airfoil profile of the blade at the position of maximum chord of the blade 10; this position is also referred to as the 'shoulder' of the blade 10.

Figure 2 is a transverse cross-section of the blade 10 taken at the position of maximum chord and illustrates the construction of the blade 10. Referring to Figure 2, the blade 10 comprises an outer shell 22 formed from first and second half shells 24a, 24b bonded together along their respective leading and trailing edges 12, 14. The outer shell 22 is typically formed from glass-fibre reinforced plastic (GRP). The blade 10 further includes reinforcing members located inside the shell 22. The reinforcing members are commonly referred to as 'spars' and extend longitudinally inside the blade 10.

In this example, the blade 10 includes a box-shaped main spar 26 and a trailing edge spar 27. The main spar 26 is located substantially centrally inside the blade 10 and comprises a pair of opposed spar caps 28a, 28b integrated respectively with the first and second half shells 24a, 24b, and a pair of shear webs 30a, 30b extending longitudinally and connecting the spar caps 28a, 28b. The trailing edge spar 27 is located towards the trailing edge 14 of the blade 10. Trailing edge spars are typically, although not exclusively, used in very large wind turbine blades, where additional reinforcement is required towards the trailing edge.

The half shells 24a, 24b of the blade 10 are moulded separately in respective mould halves, which are initially arranged side-by-side in an open configuration of the mould. Each half shell 24a, 24b is manufactured by laying up the various components of the half shell in the respective mould halves. For example, dry glass fibre cloth may be arranged in the mould, covered with a vacuum bag and infused with resin in a vacuum-assisted resin infusion process. The respective half shells 24a, 24b are then cured to harden the resin. Other suitable materials and moulding techniques may also be used, for example prepreg.

Once the half shells 24a, 24b have been formed, the shear webs 30a, 30b are positioned on the lower half shell 24a and bonded to an inner surface 32 of the lower half shell 24a to form the main spar structure 26. The trailing edge spar 27 is also positioned on the lower half shell 24a and bonded to an inner surface 32 of the lower half shell 24a. Adhesive is then applied along the leading and trailing edges 12, 14 of the lower half shell 24a and along the upper surfaces of the shear webs 30a, 30b and the trailing edge spar structure 27. The mould is then closed by lifting the upper half shell 24b and placing it on top of the lower half shell 24a. Once the adhesive has cured, the blade 10 is fully formed, and thereafter may be painted and/or subject to a number of other finishing processes.

It is important that the spar structures 26, 27 are precisely positioned in the wind turbine blade 10. However, it can be difficult to position spar structures 26, 27 on certain parts of the blade 10, for example on steeply inclined sections of the shell 22. In the case of the trailing edge spar 27 described above, this is particularly difficult to position close to the root end 16 of the blade 10 where the blade has a generally barrel-shaped profile. When attaching the spar 27 to the shell 22 in such locations it is therefore necessary to support the spar 27 firmly in place in order to prevent it from falling or otherwise sliding out of position under gravity. However, once the blade 10 is complete, health and safety considerations mean that it is not always possible to enter the confined space inside the blade 10 to retrieve any tooling that may have been required to support the spar 27 during the manufacturing process.

The present invention aims to provide an improved manufacturing process that addresses one or more of the aforementioned problems.

Summary of the invention

According to a first aspect of the present invention there is provided a method of making a wind turbine blade, the method comprising: (a) forming at least part of a shell of the blade; (b) mounting a plurality of spar support elements to an inner surface of the shell, the spar support elements being spaced apart in a longitudinal direction; (c) supporting an elongate spar structure in position relative to the shell with the spar support elements; and (d) securing the spar structure to the inner surface of the shell.

The spar support elements assist in positioning the spar structure and support the spar structure whilst the spar structure is fixed to the inner surface of the shell. The spar structure is thereby prevented from sliding or slipping out of place, particularly in regions where the surface of the shell is inclined, such as near the trailing edge at the root of the blade. Where the surface of the shell is "inclined" this means that the local surface is at an angle to the horizontal when the shell is being formed. In particular, the spar structure is thereby prevented from sliding or slipping out of place in steeply inclined regions, where the local surface is at an angle of 30 degrees or greater relative to the horizontal, for example

The spar structure may comprise a shear web. In preferred embodiments of the invention, the spar structure is a trailing edge spar and the spar support elements are hence mounted in a trailing edge region of the shell. However the invention is not limited in this respect and the spar support elements could equally be mounted in other regions of the shell and used to support other spar structures. Preferably the method involves permanently mounting the spar support elements to the shell. Hence, the spar support elements remain in place once the blade is complete. This is particularly advantageous because there is then no requirement for personnel to enter inside the confined space within the blade to retrieve any tooling once the blade is formed.

In preferred embodiments of the invention, the spar support elements are made from relatively lightweight material such as foam or balsa. This is advantageous if the support elements are to remain in place for the lifetime of the blade because the support elements then do not appreciably add to the weight of the blade nor do they affect the performance or stability of the blade in use.

The spar support elements are preferably bonded to the shell using an adhesive or such like. This means of attachment is convenient and does not require any holes to be made in the blade shell which could weaken the blade. The method may comprise clamping the spar support elements against the shell during the bonding process, for example by means of one or more jigs attached to a mould in which the shell is formed.

The spar structure may be placed on or against the support elements but is preferably placed over the spar support elements. The spar support elements are preferably shaped to correspond to the shape of an inner profile of the spar structure. In a particular embodiment of the invention, the spar structure has a generally V-shaped cross section whilst the spar support elements are generally triangular. When the spar structure is placed over the spar support elements the support elements effectively form bulkheads inside the spar structure.

In steeply inclined regions of the shell, the method may involve hanging the spar structure on one or more of the spar support elements. The spar structure therefore preferably has suitable engagement features such as hook formations that engage with the spar support elements to facilitate this. In a particular embodiment of the invention, the spar structure comprises a panel that is partially cut away to leave a series of legs. The cut-away portions of the spar structure serve to reduce the weight and cost of the spar structure, whilst the legs serve as hooks that enable the spar structure to hang from the support elements. Whilst the shell could be formed in a single piece, typically the shell comprises first and second half shells that are formed independently and subsequently joined together. In order to join the half shells together, the method may involve arranging the first and second half shells one on top of the other. Typically the second half shell is lifted and placed on top of the first half shell. The spar support elements conveniently support the spar structure during this process and prevent the spar structure from being dislodged. Typically the half shells are formed in respective mould halves in an open configuration and the mould is then closed in order to position the mould halves one on top of the other. Adhesive is applied between the shells to join the shells together.

The method preferably further comprises securing the spar structure to the second half shell. To this end, adhesive is preferably applied along an upper edge of the spar structure to effect a bond between the spar structure and the second half shell when the shells are brought together such as when the mould is closed.

According to a second aspect of the present invention there is provided a wind turbine blade comprising: a blade shell; an elongate spar structure mounted to an inner surface of the blade shell; and a plurality of spar support elements mounted to an inner surface of the blade shell, the spar support elements being spaced apart in a longitudinal direction and abutting the spar structure.

Optional and advantageous features described above in relation to the first aspect of the invention are equally applicable to the second aspect of the invention but are not repeated herein for brevity.

Brief description of the drawings

Figures 1 and 2 have already been described above by way of background to the present invention. In order that the present invention may be more readily understood, embodiments of the invention will now be described, by way of example only, and with reference to the following figures, in which:

Figure 3 is a perspective view of an inboard part of a first half shell of a wind turbine blade, in which a plurality of spar support elements are mounted to an inner surface of the shell and a trailing edge spar is shown above the support elements prior to being positioned over the support elements; Figure 4 shows a spar support element being bonded to the inner surface of the first half shell and supported by a jig coupled to a trailing edge flange of the first half shell;

Figure 5 is a close-up view of the jig and support element of Figure 4 as viewed from the trailing edge flange of the first half shell;

Figure 6 shows a plurality of spar support elements bonded to the inner surface of the first half shell with the respective jigs removed;

Figure 7 shows the trailing edge spar positioned over the spar support elements; and Figure 8 shows a variant of the trailing edge spar having a rear panel that is cut away.

Detailed description Referring to Figure 3, this shows an inboard part of a first half shell 40 of a wind turbine blade 42 according to an embodiment of the present invention, as viewed from a root end 44 of the blade 42. The half shell 40 has a generally concave inner surface 46, which extends in a chordwise direction between the leading edge 12 and the trailing edge 14 of the shell 40. The half shell 40 is fabricated in a half mould 41 which comprises a mould leading edge flange 48 and a mould trailing edge flange 50.

A plurality of spar support elements 52 are mounted to the inner surface 46 of the half shell 40. The spar support elements 52 are spaced at regular intervals (typically of 3-4 metres) along a longitudinal path in a trailing edge region 54 of the shell 40, close to the mould trailing edge flange 50. In view of its concave curvature, the inner surface 46 of the shell 40 is steeply inclined near the trailing edge 14, and particularly so close to the root end 44 of the blade 42 where the surface 46 of the shell 40 is near vertical.

In this example, the spar support elements 52 are foam blocks made from expanded polyurethane. The blocks 52 are substantially triangular planar elements, which have a truncated apex defining a flat upper surface 56. The bases 58 of the respective blocks 52 are generally rectangular and are bonded to the inner surface 46 of the first half shell 40.

A trailing edge spar structure 60 is shown in Figure 3. The spar structure 60 in this example is a shear web, which is designed to resist buckling at the trailing edge of the blade 42. The spar 60 extends longitudinally and comprises front and rear generally rectangular panels 62a, 62b, which are inclined relative to one another and joined along their respective longitudinally-extending upper edges 64 such that the spar 60 is generally V-shaped in cross-section. The apex of the V is truncated to define a generally flat upper surface 66.

The base of the spar 60 includes first and second longitudinally-extending flanges 68a, 68b, which splay out from respective lower edges of the front and rear panels 62a, 62b in a direction substantially parallel to the inner surface 46 of the shell 40. These flanges 68a, 68b are used to mount the spar 60 to the first half shell 40, whilst the flat truncated upper surface 66 of the spar 60 is used to mount the spar to an inner surface of a second half shell of the blade 40 (not shown).

The trailing edge spar 60 is placed over the spar support elements 52 as represented by the arrows in Figure 3. The truncated triangular profiles of the spar support elements 52 are complementary to the truncated-triangular inner profile of the trailing edge spar 60. Hence the trailing edge spar 60 fits snugly over the support elements 52 and is firmly supported by the support elements 52 during bonding of the spar 60 to the inner surface 46 of the shell 40.

Further details of the blade manufacturing process employing the spar support elements 52 will now be provided with reference to Figures 4 to 7.

Referring to Figure 4, the spar support elements 52 are initially arranged in position near the mould trailing edge flange 50 and bonded to the inner surface 46 of the first half shell 40. To this end, fast-setting glue such as fast polyurethane is applied to the bases 58 (Figure 3) of the blocks 52 and the blocks are supported in place using jigs 70.

Referring to Figure 5, the jig 70 comprises an elongate rectangular metal strip, which is bent to define a flat end 72 and a hook end 74. The flat end 72 attaches to the mould trailing edge flange 50, whilst the hook end 74 hooks around the truncated upper end 76 of the block 52 and clamps the block 52 against the inner surface 46 of the shell 40. In this example the jig 70 is attached to the mould trailing edge flange 50 via a 'poke yoke' system, in which a pair of dowels 78 attached to the lower surface of the flat end 72 of the jig 70 are received in a corresponding pair of holes defined in the mould trailing edge flange 50. Other means of mounting the jig 70 to the mould flange 50 may be employed for example the flat end 72 of the jig 70 may instead be hooked around the mould flange 50 or clamped to the mould flange 50.

Referring to Figure 6, once all of the foam blocks 52 have been positioned in place along the longitudinal path and the glue has cured, the jigs 70 (Figure 5) are removed.

Referring to Figure 7, an adhesive such as epoxy structural adhesive is applied to the longitudinally-extending flanges 68a, 68b (see also Figure 3) at the lower edges of the trailing edge spar 60 and the spar 60 is then positioned in place over the foam blocks 52. The adhesive serves to bond the spar 60 to the inner surface 46 of the first half shell 40. The foam support blocks 52 support the spar 60 during the bonding process and prevent the spar 60 from slipping, particularly in the steeply inclined regions of the shell 40 such as near the root end 44. Whilst not shown in Figure 7, one or more further shear webs (referred to hereafter as 'spars' for convenience) may also be bonded to the first half shell 40, e.g. the shear webs 30a, 30b shown in Figure 2. Once the spar(s) 60 have been fixed to the first half shell 40, adhesive is applied along the leading and trailing edges 12, 14 of the first shell 40, and further adhesive is applied to the upper surfaces of the spars, e.g. along the flat upper surface 66 of the trailing edge spar 60. A second half shell (not shown) is then lifted and placed on top of the first half shell 40 and once the adhesive between the two shells has cured, the blade is complete subject to finishing processes such as painting etc.

The foam blocks 52 also serve to support the trailing edge spar 60 during closing of the mould, i.e. during lifting and placement of the second half shell on top of the first half shell 40, and prevent the spar 60 from being dislodged during this process. The foam blocks 52 remain in place once the blade is complete and are not removed. There is therefore no requirement for personnel to enter inside the blade to retrieve tooling once the blade is complete. Figure 8 shows a variant of the trailing edge spar 80. In this variant, the rear panel of the trailing edge spar 80 is cut away to leave a series of legs 82 at spaced-apart intervals (typically 3-4 metres) along the spar 80. The front panel 84 of the spar 80 is identical to the front panel 62a of the spar 60 described above with reference to Figure 3 and includes a longitudinal mounting flange (not shown) on its lower surface. A lower edge of the legs 82 also includes a mounting flange 86. Glue is applied to the mounting flanges and the spar 80 is placed over the foam blocks 52. The legs 82 of the spar 80 hook over the foam blocks 52 that are mounted to the inner surface 46 of the first half shell 40 to prevent the spar 80 from slipping during the bonding process and during mould closing. In steeply inclined sections of the shell 40 the spar 80 effectively hangs from the foam blocks 52 via the legs 82.

Many modifications may be made to the examples described above without departing from the scope of the present invention as defined in the accompanying claims. For example, whilst a trailing edge spar has been described above by way of example, the support elements are suitable for supporting any type of spar structure in a wind turbine blade.

Claims

1 . A method of making a wind turbine blade, the method comprising:

(a) forming at least part of a shell of the blade;

(b) mounting a plurality of spar support elements to an inner surface of the shell, the spar support elements being spaced apart in a longitudinal direction;

(c) supporting an elongate spar structure in position relative to the shell with the spar support elements; and

(d) securing the spar structure to the inner surface of the shell.

2. The method of Claim 1 , wherein step (b) comprises permanently mounting the support elements to the shell.

3. The method of any preceding claim, wherein step (b) comprises mounting the spar support elements in a trailing edge region of the shell.

4. The method of any preceding claim, wherein step (b) comprises mounting one or more of the spar support elements to an inclined region of the shell.

5. The method of Claim 4, further comprising hanging the spar structure on one or more of the spar support elements in the inclined region of the shell.

6. The method of any preceding claim, wherein step (c) comprises placing the spar structure over the spar support elements.

7. The method of any preceding claim, wherein step (b) comprises bonding the spar support elements to the shell.

8. The method of Claim 7, further comprising clamping the spar support elements against the shell during the bonding process.

9. The method of Claim 8, wherein the method further comprises clamping the spar support elements against the shell by means of one or more jigs attached to a mould in which the shell is formed.

10. The method of any preceding claim, wherein step (d) comprises bonding the spar structure to the shell.

1 1 . The method of any preceding claim, wherein step (a) comprises forming a first half shell of the blade and the method further comprises forming a second half shell of the blade and joining the first and second half shells together.

12. The method of Claim 1 1 , wherein step (e) comprises arranging the first and second half shells one on top of the other.

13. The method of Claim 1 1 or Claim 12, further comprising forming the first and second half shells in respective first and second mould halves of a wind turbine blade mould in an open configuration.

14. The method of Claim 13, further comprising closing the mould to join the first and second half shells together.

15. The method of any of Claims 1 1 to 14, further comprising securing the spar structure to the second half shell.

16. The method of Claim 15, comprising applying adhesive along an upper edge of the spar structure and bonding the spar structure to the second half shell.

17. A wind turbine blade comprising:

a blade shell;

an elongate spar structure mounted to an inner surface of the blade shell; and a plurality of spar support elements mounted to an inner surface of the blade shell, the spar support elements being spaced apart in a longitudinal direction and abutting the spar structure.

18. The wind turbine blade of Claim 17, wherein the spar support elements are permanently mounted to the blade shell.

19. The wind blade of Claim 17 or Claim 18, wherein the spar support elements are made from lightweight material such as foam or balsa.

20. The wind turbine blade of any of Claims 17 to 19, wherein one or more of the spar support elements are mounted to an inclined section of the blade shell.

21 . The wind turbine blade of any of Claims 17 to 20, wherein the spar support elements and the spar structure are located in a trailing edge region of the blade.

22. The wind turbine blade of any of Claims 17 to 21 , wherein the spar structure substantially encloses the spar support elements.

23. The wind turbine blade of any of Claims 17 to 22, wherein the spar support elements have a shape substantially corresponding to a transverse cross-sectional shape of the spar structure.

24. The wind turbine blade of any of Claims 17 to 23, wherein the spar structure is substantially V-shaped in cross section.

25. The wind turbine blade of any of Claims 17 to 24, wherein the spar support elements are substantially triangular in cross section.

26. The wind turbine blade of any of Claims 17 to 25, wherein the spar support elements are bonded to the blade shell with adhesive.

27. The wind turbine blade of any of Claims 17 to 26, wherein the spar structure comprises a plurality of engagement features spaced at intervals along its length, and wherein the engagement features engage with the respective spar support elements.

28. The wind turbine blade of Claim 27, wherein the engagement features comprise legs that hook over the spar support elements.

29. The wind turbine blade of Claim 28, wherein the legs are defined between cut away portions of the spar structure.

30. The wind turbine blade of any of Claims 17 to 29, wherein the blade shell comprises first and second half shells and the spar support elements are mounted to a first half shell.

31 . The wind turbine blade of any of Claims 17 to 30, wherein the spar structure comprises a shear web.