IMPROVEMENTS RELATING TO WIND TURBINE BLADE MANUFACTURE

Abstract

Method of bonding a shear web (50) to a wind turbine blade shell (75) and the obtained blade, wherein the shear web (50) comprises a web and a mounting flange (56) oriented transverse to the web (50). The method involves: providing a seal (66, 68) on the mounting flange (56) of the shear web (50) such that when the mounting flange (56) is positioned against the blade shell (75), a cavity (76) is defined by the seal between the mounting flange (56) and the blade shell (75). The air of the cavity (76) is then evacuated and adhesive is injected into the cavity (76). The use of pieces (80) to keep the distance between the mounting flange (56) and the blade shell (75) is preferred.

Claims

1. A method of bonding a shear web to a wind turbine blade shell, the shear web comprising a web and a mounting flange oriented transverse to the web, and the method comprising: positioning the shear web relative to the blade shell such that the mounting flange is in mutually opposed relation with an inner surface of the blade shell; providing a primary seal between the mounting flange and the inner surface of the blade shell, the seal defining a substantially enclosed primary cavity between the mounting flange and the inner surface of the blade shell; removing air from the primary cavity to create a vacuum in the primary cavity; admitting adhesive into the primary cavity; and curing the adhesive.

2. The method of claim 1, further comprising: providing one or more spacer elements in the primary cavity between the mounting flange and the inner surface of the blade shell, the spacer elements being configured to maintain the mounting flange and the inner surface of the blade in spaced apart relation when a vacuum is created in the primary cavity.

3. The method of claim 1, further comprising monitoring a pressure in the primary cavity and determining when the primary cavity is full of adhesive by a sudden change in the monitored pressure.

4. The method of claim 1, further comprising admitting adhesive into the primary cavity via one or more adhesive ports arranged in fluid communication with the primary cavity.

5. The method of claim 4, wherein the adhesive inlet ports are provided in the mounting flange of the shear web.

6. The method of claim 1, further comprising removing air from the primary cavity through one or more vacuum ports provided in fluid communication with the primary cavity.

7. The method of claim 6, wherein the vacuum ports are provided in the mounting flange of the shear web.

8. The method of claim 1, further comprising: providing a secondary seal between the mounting flange and the inner surface of the blade shell, the secondary seal at least partially surrounding the primary seal and being spaced apart from the primary seal to define a peripheral cavity between the primary and secondary seals, the peripheral cavity at least partially surrounding the primary cavity; and removing air from the peripheral cavity to create a vacuum in the peripheral cavity.

9. The method of claim 8, further comprising removing air from the peripheral cavity through one or more vacuum ports provided in fluid communication with the peripheral cavity.

10. The method of claim 9, wherein the vacuum ports are provided in the mounting flange of the shear web.

11. The method of claim 8, comprising reducing the pressure in the peripheral cavity to a lower level than in the primary cavity so as to create a stronger vacuum in the peripheral cavity than in the primary cavity.

12. The method of claim 8, further comprising monitoring a pressure in the peripheral cavity and detecting the presence of a leak in the primary seal from a sudden change in the monitored pressure.

13. The method of claim 8, comprising admitting adhesive into the primary cavity once a vacuum has been created in both the primary and peripheral cavities.

14. The method of claim 1, further comprising causing the adhesive to flow in a longitudinal direction within the primary cavity.

15. A method of making a wind turbine blade comprising bonding a shear web to an inner surface of a wind turbine blade shell according to the method of claim 1.

16. The method of claim 15, wherein the blade shell is a first half shell of the wind turbine blade and the method further comprises bonding a second half shell to the first half shell.

17. A wind turbine blade made according to the method of claim 15.

18. A wind turbine blade comprising a blade shell and a shear web located inside the blade shell, wherein the shear web comprises a web and a mounting flange oriented transverse to the web, the mounting flange being bonded to an inner surface of the blade shell by cured adhesive within an adhesive-filled cavity bounded by a primary seal between the mounting flange and the inner surface of the blade shell.

19. The wind turbine blade of claim 18, further comprising one or more spacer elements within the adhesive-filled cavity between the mounting flange and the inner surface of the blade shell.

20. The wind turbine blade of claim 19, wherein the spacer elements are made of substantially incompressible material.

21. The wind turbine blade of claim 18, wherein the mounting flange of the shear web includes one or more adhesive inlet ports and/or one or more vacuum ports.

22. The wind turbine blade of claim 18, further comprising a secondary seal between the mounting flange and the inner surface of the blade shell, the secondary seal at least partially surrounding the primary seal and being spaced apart from the primary seal to define a peripheral cavity between the first and secondary seals.

23. The wind turbine blade of claim 22, wherein the peripheral cavity is substantially free from adhesive.

24. The wind turbine blade of claim 18, wherein the shear web comprises a pair of mounting flanges that extend respectively along opposite longitudinal edges of the shear web, and wherein one of the mounting flanges is bonded to the inner surface of the blade shell on a windward side of the shell, and the other mounting flange is bonded to the inner surface of the blade shell on a leeward side of the shell.

25. A wind turbine having a wind turbine blade according to claim 18.

26. A shear web for the wind turbine blade comprising a web and a mounting flange oriented transverse to the web, wherein one or more seals are integrated with the mounting flange.

27. The shear web of claim 26, wherein the mounting flange further comprises one or more adhesive ports and/or one or more vacuum ports.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIGS. 1 and 2a-2c have already been described above by way of background to the present invention. In order that the present invention may be more readily understood, examples of the invention will now be described with reference to FIGS. 3-9, in which:

[0043] FIG. 3 is a perspective view of part of a shear web comprising a web disposed between upper and lower mounting flanges according to an embodiment of the present invention;

[0044] FIG. 4 is a transparent perspective view of part of the lower mounting flange of the shear web;

[0045] FIG. 5 is a plan view of an outer surface of the lower mounting flange of the shear web;

[0046] FIG. 6 is a plan view of an inner surface of the lower mounting flange of the shear web;

[0047] FIG. 7 is a schematic cross-sectional view of the lower mounting flange of the shear web taken along the line A-A in FIG. 4, with the shear web positioned against an inner surface of a blade shell;

[0048] FIG. 8 is a cross-sectional view of the lower mounting flange of the shear web when sealed against the inner surface of the blade shell; and

[0049] FIG. 9 shows a vacuum system and an adhesive system connected to vacuum ports and adhesive inlet ports located on the lower mounting flange of the shear web.

DETAILED DESCRIPTION

[0050] Referring to FIG. 3, this shows a first end of a longitudinally-extending shear web 50 according to an embodiment of the present invention. The shear web 50 is approximately 80 metres in length (L) and varies in height (H) along its length, with a maximum height at one end of about 4.5 metres. The shear web 50 is substantially I-shaped in cross section and comprises a substantially vertical web 52 disposed between upper and lower mounting flanges 54, 56. The mounting flanges 54, 56 are arranged substantially perpendicular to the web 52 in this example, i.e. substantially horizontal.

[0051] The lower mounting flange 56 comprises an inner surface 58 and an outer surface 60. The terms ‘inner’ and ‘outer’ are relative to a central longitudinal axis of a wind turbine blade in which the shear web 50 is affixed in use (e.g. the central longitudinal axis (C) of the blade 10 in FIG. 1, which extends perpendicular to the page in FIG. 1). The outer surface 60 of the lower mounting flange 56 is shown in plan view in FIG. 5, whilst the inner surface 58 of the lower mounting flange 56 is shown in plan view in FIG. 6. The dashed lines in FIG. 6 indicate the position of the web 52.

[0052] Referring now also to FIG. 4, which is a transparent perspective view of the lower mounting flange 56 in which the web 52 has been omitted for clarity, and also to the plan views of FIGS. 5 and 6, a plurality of vacuum ports 62a, 62b and a plurality of adhesive inlet ports 64 are located on the inner surface 58 of the lower mounting flange 56. A primary seal 66 and a secondary seal 68 are provided on the outer surface 60 of the lower mounting flange 56.

[0053] The primary and secondary seals 66, 68 are vacuum-tight seals and are made from butyl-rubber. The primary seal 66 is arranged in a rectangle such that a rectangular primary region 70 is defined within the primary seal 66. The secondary seal 68 is also arranged in a rectangle and surrounds the primary seal 66. The secondary seal 68 is spaced slightly apart from the primary seal 66, by approximately 2 cm in this example, such that a peripheral region 72 is defined between the two seals 66, 68.

[0054] When the lower mounting flange 56 of the shear web 50 is positioned against a surface (see FIG. 7), such as the inner surface 74 of a blade shell 75, the primary seal 66 defines a substantially rectangular primary cavity 76 between the lower mounting flange 56 and the surface 74, and the secondary seal 68 defines a peripheral cavity 78 surrounding the primary cavity 76. In other words, the primary region 70 and the peripheral region 72 described above become substantially enclosed cavities 76, 78. The primary cavity 76 is located directly below the web portion 52 of the shear web 50.

[0055] Referring still to FIGS. 4-6 in addition to FIG. 7, the plurality of vacuum ports 62a, 62b referred to above includes a first set of vacuum ports 62a and a second set of vacuum ports 62b. The first set of vacuum ports 62a are in fluid communication with the primary cavity 76 in use, i.e. they extend into the primary region 70 bound by the primary seal 66. The second set of vacuum ports 62b are in fluid communication with the peripheral cavity 78, i.e. they extend into the peripheral region 72 defined between the seals 66, 68. The adhesive inlet ports 64 referred to above are in fluid communication with the primary cavity 76. Notably, the first set of vacuum ports 62a are spaced apart from the adhesive inlet ports 64 in a longitudinal direction L (see FIG. 1) of the shear web 50. The effect of this arrangement will be described in further detail later.

[0056] As shown most clearly in FIG. 3, the vacuum ports 62a, 62b and the adhesive inlet ports 64 project upwardly from the inner surface 58 of the lower mounting flange 56 for easy access. Referring to the plan view of FIG. 6, the various ports 62a, 62b, 64 are distributed around the web 52, which also projects upwardly from the lower mounting flange 56.

[0057] Referring now specifically to FIG. 7, which is a partial cross-section through the shear web 50 taken along the line A-A in FIG. 4, a plurality of spacers 80 are also mounted to the outer surface 60 of the lower mounting flange 56. The spacers 80 are located inside the primary region 70 bounded by the primary seal 66, i.e. inside the primary cavity 76 when the shear web 50 is against the surface 74. The spacers 80 are made from substantially non-compressible material such as wood.

[0058] During the manufacture of a wind turbine blade, the shear web 50 is bonded to an inner surface 74 of a blade shell as will now be described.

[0059] Referring to FIG. 9, a first set of vacuum lines 82 (one of which is shown in FIG. 9) are connected respectively to the first set of vacuum ports 62a and a second set of vacuum lines 84 (one of which is shown in FIG. 9) are connected to the second set of vacuum ports 62b. The first set of vacuum lines 82 are connected to a first vacuum pump 86, and the second set of vacuum lines 84 are connected to a second vacuum pump 88. The first vacuum pump 86 includes a first pressure gauge 90 and the second vacuum pump 88 includes a second pressure gauge 92. A plurality of adhesive inlet hoses 94 are each connected at one end to a respective adhesive inlet port 64 and at the other end to a source of adhesive 96. One or more adhesive inlet valves 98 are provided in the adhesive lines 94 for controlling the flow of adhesive. One or more adhesive pumps may also be provided in the adhesive inlet lines 94 if required. The vacuum pumps 86, 88 and the adhesive source 96 are conveniently located remotely from the shear web 50, for example in a process room.

[0060] Referring again to FIG. 7, the shear web 50 is initially positioned against the inner surface 74 of the blade shell 75 and arranged such that the web 52 is located over a predefined bonding region 100 defined on the blade shell 75, i.e. the region where a bondline between the shear web 50 and the blade shell 75 is to be created. When positioned against the inner surface 74 of the blade shell 75, the shear web 50 is supported against the surface 74 by the primary and secondary seals 66, 68. In this position the seals 66, 68 are compressed slightly under the weight of the shear web 50. Notably, the thickness of the spacer blocks 80 is selected such that there is clearance 102 between the spacers 80 and the surface 74 of the shell 75 when the seals 66, 68 are compressed under the weight of the shear web 50.

[0061] Referring now additionally to FIG. 8, with the shear web 50 in position against the surface 74 of the blade shell 75, the vacuum pumps 86, 88 are turned on. The first vacuum pump 86 draws air out of the primary cavity 76 through the first set of vacuum lines 82 and the second vacuum pump 88 draws air out of the peripheral cavity 78 through the second set of vacuum lines 84. The removal of air from the primary and peripheral cavities 76, 78 creates an effective vacuum within each of the cavities 76, 78. The creation of a vacuum within the respective cavities 76, 78 causes the lower mounting flange 56 to be pulled closer to the inner surface 74 of the blade shell 75, which compresses the primary and secondary seals 66, 68 further and causes them to seal tightly against the surface 74.

[0062] The lower mounting flange 56 is pulled towards the surface 74 until the spacer blocks 80 make contact with the surface 74 of the shell 75. As the spacers 80 are incompressible, the lower mounting flange 56 is prevented from being pulled any closer towards the inner surface 74 of the blade shell 75. The spacers 80 thereby ensure that the primary cavity 76 remains open, i.e. that a clearance is maintained between the lower mounting flange 56 and the inner surface 74 of the blade shell 75 when a vacuum is established in the respective cavities 76, 78.

[0063] As the primary cavity 76 and the peripheral cavity 78 are sealed independently of one another, and are connected to independent vacuum systems, two distinct vacuum zones are created in the primary and peripheral cavities 76, 78 respectively. The vacuum pumps 86, 88 are configured to maintain a slightly stronger vacuum in the peripheral cavity 78 than in the primary cavity 76, or in other words a slightly lower pressure in the peripheral cavity 78 than in the primary cavity 76. In this example, a vacuum pressure of approximately −1 bar is maintained in the peripheral cavity 78 and a slightly higher pressure is maintained in the primary cavity 76. Accordingly, the vacuum in the peripheral cavity 78 pulls the lower mounting flange 56 of the shear web 50 at a higher level than the primary cavity 76 and functions as a clamp around the primary cavity 76.

[0064] Once vacuums have been established in the respective cavities 76, 78, adhesive is admitted into the primary cavity 76 via the adhesive inlet ports 64. As mentioned previously, the adhesive inlet ports 64 are spaced apart from the first set of vacuum ports 62a in the longitudinal direction L of the shear web 50. Accordingly, the adhesive flows or ‘infuses’ in a longitudinal direction L inside the primary cavity 76 from the adhesive inlet ports 64 towards the first set of vacuum outlet ports 62a. As the adhesive is drawn into the primary cavity 76 under vacuum, the injection back pressure is minimised and the primary cavity 76 fills with adhesive.

[0065] The vacuum pressures in the primary and peripheral cavities 76, 78 are monitored throughout the adhesive infusion process using the vacuum gauges 90, 92 associated with the vacuum pumps 86, 88. Once the primary cavity 76 is full of adhesive, the pressure inside the primary cavity 76 will suddenly change (i.e. the vacuum gauge 90 will suddenly register a very high negative pressure of, for example, around −200 bar). This sudden change in pressure indicates that the primary cavity 76 is full of adhesive, i.e. the adhesive injection process is complete. At this stage, the adhesive supply is turned off by closing the adhesive inlet valve(s) 98 to prevent further adhesive entering the primary cavity 76.

[0066] The adhesive is then left to cure, i.e. harden, which results in the lower mounting flange 56 forming a strong bond to the inner surface 74 of the blade shell 75.

[0067] As the peripheral cavity 78 pulls at a higher level than the primary cavity 76, the peripheral cavity 78 advantageously reacts the pressure from the injected adhesive at the adhesive inlet ports 64 and over the bond area and thus prevents the injected adhesive from forcing the two surfaces 60, 74 apart and breaking the primary seal 66. In other words, the evacuated peripheral cavity 78 serves to prevent leaks developing at the primary seal 66. In the unlikely event that the primary seal 66 does develop a leak, adhesive will flow into the peripheral cavity 78. This will cause a sudden change in pressure in the peripheral cavity 78, which can be detected by the pressure gauge 92 of the vacuum pump 88 associated with the peripheral cavity 78. If a leak is detected then it may be necessary to suspend the infusion process until the leak has been repaired.

[0068] A further advantage of the stronger vacuum in the peripheral cavity 78 is that any air ingress in the process will be removed from the system away from the bondline because the bondline is created within the primary cavity 76.

[0069] As the adhesive is contained within the primary cavity 76, wastage of adhesive caused by squeeze out is eliminated. This reduces the overall amount of adhesive required in the bondline and hence reduces the overall weight of the completed blade and the materials cost of the adhesive. The dimensions of the resulting bondline between the shear web 50 and the blade shell 75 are advantageously well defined, i.e. they are defined by the dimensions of the primary cavity 76. The dimensions of the primary cavity 76 are predefined by the shape of the region 70 bound by the primary seal 66 and the height of the spacers 80. Accordingly, the invention provides a repeatable process for creating consistently well-defined bondlines.

[0070] As the process can be controlled and monitored by the remotely-located vacuum gauges 90, 92, the entire bonding process can be controlled and monitored remotely from the blade. This is particularly advantageous and facilitates a single-stage bonding process, i.e. in which the shear web 50 is bonded to both the windward half shell and the leeward half shell simultaneously using simultaneous infusion at each bondline. Such a process is made possible with the bonding method of the present invention because there is no requirement to have direct access to the bondline during the bonding process.

[0071] Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

[0072] For example, whilst the above examples relate to the creation of a bond between the lower mounting flange 56 of the shear web 50 and the blade shell, the bond could alternatively or additionally be created between the upper mounting flange 54 and the blade shell. As mentioned above, the process could be used simultaneously along the upper and lower mounting flanges 54, 56 to bond the shear web 50 to both the windward shell and the leeward shell simultaneously. The method would therefore involve closing the mould prior to bonding the shear web 50 to the respective blade shells. Accordingly, the method lends itself to a single-stage bonding process.

[0073] Whilst a shear web 50 having an I-shaped cross section is described in the above examples, the shear web 50 may have a different shape in other examples. For example, the shear web 50 may be substantially C-shaped in cross-section or the web 52 may have L-shaped flanges at each end. The mounting flanges 54, 56 need not be perpendicular to the web 52, and in other examples the mounting flanges 54, 56 may be arranged at other transverse angles to the web 52, for example more or less than ninety degrees. The angle of the mounting flanges 54, 56 relative to the web 52 will depend on the local contour of the blade shell at which the shear web 50 is to be fixed, i.e. in a chordwise direction of the blade shell.

[0074] Whilst in the above examples the adhesive inlet ports 64 and the vacuum ports 62a are arranged so as to create a longitudinal, i.e. spanwise flow of adhesive in the primary cavity 76, the ports 62a, 64 may alternatively be arranged to create a chordwise flow for example. In this case, the resin inlet ports 64 may be spaced apart from the vacuum ports 62a in a widthwise direction of the primary cavity 76.

[0075] Whilst the various ports 62a, 62b, 64 in the above examples are provided in the mounting flange 56 of the shear web 50, the ports 62a, 62b, 64 may alternatively be provided in other suitable positions. For example, the ports 62a, 62b, 64 may be provided in the seals 66, 68 or in the blade shell or other such surface to which the shear web 50 is bonded.

[0076] Whilst the above examples relate to the creation of a bond between a shear web 50 and a wind turbine blade shell 75, various features of the invention (for example the double seal arrangement) may be utilised for other bonds, such as the bonds between respective half shells of a wind turbine blade.

[0077] For the avoidance of doubt, relative terms such as ‘upper’ and ‘lower’ as used in the preceding description are used for convenience and refer to the orientation of features as shown in the figures. These terms are not intended to limit the scope of the invention.