Technical field

The present invention relates generally to wind turbine blades and more specifically to an assembly comprising a wind turbine blade supported in a blade mould.

Background

Modern wind turbine blades typically comprise a shell defining the aerodynamic contour of the blade and one or more longitudinally-extending spars which act as the main loadbearing structures of the blade. A spar typically comprises a shear web which is configured to take up the shear loads experienced by the wind turbine blade in use. In some wind turbine blades, the shear web is adhesively bonded between inner surfaces of opposing windward and leeward sides of the shell. The shear web may comprise upper and lower flanges via which the web is bonded to the shell. Excess adhesive is typically provided between the shear web and shell to account for slight variations in shell geometry and web positioning, thereby ensuring that the shear web is bonded to the shell along its length.

The wind turbine blade may be inspected from the outside of the shell using nondestructive testing methods. Non-destructive testing (NDT) may for example involve emitting ultrasonic signals through the blade shell and receiving reflected signals to build up an image of the arrangement of materials in the shell and within the blade. The ultrasonic signals are reflected at the boundary between a material and a less dense material, such as air. This method of testing may be used to determine the position of the web flanges and assess the quality of the joint between the flanges and shell, for example.

However, surplus adhesive squeezed from between the shear web and shell can introduce challenges to the inspection of the blade. For example, surplus adhesive from between the upper flange and the shell and may land on or near to the lower flange, resulting in an irregular surface at the boundary with air inside the blade. This may cause NDT signals to be reflected outside the range of the receiver, resulting in incomplete or unreliable testing data. Further, surplus adhesive landing on or too near to the edge of the flange can make determining the actual position of the flange more challenging.

Unreliable or inaccurate results from non-destructive testing can cause “false negative” results that incorrectly suggest repairs or adjustments are required. Such unnecessary additional work may be expensive and increase manufacturing time for the wind turbine blade. It is against this background that the present invention has been developed. Summary of Invention

In a first aspect of the invention there is provided an assembly comprising a wind turbine blade and a blade mould, the wind turbine blade being supported in the blade mould. The wind turbine blade comprises an aerodynamic outer shell having an upper side and a lower side. The blade further comprises a shear web comprising a web panel, an upper web flange and a lower web flange. The web panel extends between the upper web flange and the lower web flange. The upper web flange is connected to the upper side of the outer shell and the lower web flange is connected to the lower side of the outer shell. The upper and lower web flanges are asymmetrically arranged such that, when the wind turbine blade is supported in the blade mould, the upper web flange overhangs the lower web flange.

The upper web flange may be connected to the web panel at a proximal edge and the upper web flange extends to a distal edge which is an edge of the upper web flange furthest from the web panel.

The lower web flange may be connected to the web panel at a proximal edge and the lower web flange extends to a distal edge which is an edge of the lower web flange furthest from the web panel.

Preferably the distal edge of the upper web flange extends beyond the distal edge of the lower web flange in a chordwise direction (C) when the blade in the mould, i.e. the distal edges of the upper and lower flanges are not vertically aligned.

The web panel may have a first side facing a leading edge of the blade and a second side facing a trailing edge of the blade. Preferably, the upper web panel and the lower web panel are located on the same side of the web panel. The distal edges of both the upper web flange and the lower web flanges may be located between the web panel and the leading edge, or the distal edges of both the upper web flange and the lower web flange may be located between the web panel and the trailing edge.

The shear web may be rotated such that, when the wind turbine blade is supported in the blade mould, the shear web panel is non-vertical.

The shear web may be rotated such that, when the wind turbine blade is supported in the blade mould, the shear web panel is inclined at an angle in the range of 1 degree to 20 degrees relative to a vertical axis. Preferably, the shear web may be rotated such that the shear web panel is inclined at an angle in the range of 1 degree to 10 degrees relative to a vertical axis. More preferably still, the shear web may be rotated such that the shear web panel is inclined at an angle in the range of 1 degree to 5 degrees relative to a vertical axis.

The upper web flange and the lower web flange may be of substantially equal width.

The upper web flange may be wider than the lower web flange.

A first angle defined between the web panel and the upper web flange may be greater than a second angle defined between the web panel and the lower web flange. The first angle may be at least 5 degrees greater than the second angle.

The upper web flange may be adhesively bonded to the upper side of the outer shell. Preferably, the lower web flange may be adhesively bonded to the lower side of the outer shell.

The upper side of the outer shell of the wind turbine blade may comprise a first longitudinal reinforcing structure. The lower side of the outer shell may comprise a second reinforcing structure. The upper web flange may be connected to the first longitudinal reinforcing structure. The lower web flange may be connected to the second longitudinal reinforcing structure.

The first and second reinforcing structures may be spar caps, stringers, or thickened sections of the shell laminate for example. The reinforcing structures are preferably integrated, e.g. embedded, in the laminate structure of the shell. The reinforcing structures may instead be joined to an inner surface of the shell laminate. The reinforcing structures may be formed of fibre-reinforced polymer. Preferably, the reinforcing structures may be formed of carbon fibre reinforced polymer.

The first and second reinforcing structures may be symmetrically arranged. When the wind turbine blade is supported in the blade mould, the first reinforcing structure may not substantially overhang the second reinforcing structure.

The first and second longitudinal reinforcing structure may be of substantially equal width.

The shear web may be a trailing edge web. The wind turbine blade may further comprise a main shear web arranged in a first plane. The trailing edge web may be arranged in a second plane that is inclined relative to the first plane.

In a second aspect of the invention there is provided a method of manufacturing a wind turbine blade. The method comprises providing an outer shell structure having an upper side and a lower side, and providing a shear web comprising a web panel, an upper web flange and a lower web flange, the web panel extending between the upper web flange and the lower web flange. The method further comprises arranging the shear web between the upper and lower sides of the outer shell structure, and adhesively bonding at least the upper web flange to the upper side of the outer shell structure. The shear web is arranged such that the upper web flange overhangs the lower web flange during bonding of the upper web flange to the upper side of the outer shell, such that excess adhesive that is squeezed out from between the upper web flange and the outer shell substantially does not collect on the lower web flange.

In a further aspect of the invention there is provided a wind turbine blade comprising an aerodynamic outer shell having an upper side and a lower side. The wind turbine blade further comprises a shear web comprising a web panel, an upper web flange and a lower web flange. The web panel extends between the upper web flange and the lower web flange. The upper web flange is adhesively bonded to the upper side of the outer shell and the lower web flange is connected to the lower side of the outer shell. The upper and lower web flanges are asymmetrically arranged such that the upper web flange overhangs the lower web flange during manufacture of the wind turbine blade according to the method described above.

The upper side of the outer shell may be one of a windward or a leeward side. The lower side of the outer shell may be the other of the windward or leeward side.

Brief description of Figures

Embodiments of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

Figure 1 is a schematic exploded view of a wind turbine blade comprising a plurality of shear webs arranged inside an outer shell comprising an upper side and a lower side;

Figure 2 is a schematic perspective view of a mould used to form one of the sides of the outer shell;

Figure 3 is a schematic cross-sectional view of an assembly comprising a wind turbine blade supported in a mould, wherein the blade comprises shear webs with substantially vertical web panels and substantially symmetrical upper and lower web flanges; Figure 4 is a schematic cross-sectional view of the assembly wherein the wind turbine blade supported in the mould comprises a shear web having an upper flange that is wider than the lower web flange such that it overhangs the lower flange; and

Figure 5 is an enlarged view of Figure 4 showing a trailing edge portion of the wind turbine blade in more detail;

Figure 6 is a schematic cross-sectional view of the assembly wherein the wind turbine blade supported in the mould comprises a shear web that is rotated such that the web panel is non-vertical and the upper and lower flanges are asymmetrically arranged; and

Figure 7 is an enlarged view of Figure 6 showing a trailing edge portion of the wind turbine blade in more detail.

Detailed description

Figure 1 is a schematic exploded view of a wind turbine blade 10. The blade 10 extends longitudinally in a spanwise direction (S) between a root end 12 and a tip end 14, and transversely in a chordwise direction (C) between a leading edge 16 and a trailing edge 18. The blade 10 comprises an aerodynamic outer shell 20 that has an upper side 22a and a lower side 22b. The shell 20 may be formed of a first (e.g. windward) half shell 24a and a second (e.g. leeward) half shell 24b. For example, the upper side of the shell 22a may comprise the windward half shell 24a, and the lower side of the shell 22b may comprise the leeward half shell 24b. In some examples, the half shells 24a, 24b are of composite construction, formed of materials such as glass-fibre reinforced plastic (GFRP). When the half shells 24a, 24b are connected together, the shell 20 defines a substantially hollow interior.

The wind turbine blade 10 comprises a shear web 26 that extends longitudinally in the spanwise direction (S) inside the shell 20, i.e. inside the hollow interior of the blade 10. In some examples, as shown in Figure 1 , the wind turbine blade 10 may comprise a plurality of shear webs 26, such as a trailing edge shear web 26a and a main shear web 26b. Each shear web 26 forms part of a spar structure which is configured to absorb bending and torsional loading of the blade 10 in use.

The shear webs 26 comprise a web panel 28 that extends between upper and lower web flanges 30a, 30b. The upper web flange 30a is connected to the upper side of the shell 22a, and the lower web flange 30b is connected to the lower side of the shell 22b. As described in more detail below with reference to Figures 3 to 7, the shear web 26 is preferably bonded to the shell 20 by adhesive between the flanges 30a, 30b and a respective inner surface 32a, 32b of the shell 20.

Where the shell 20 is formed of two half shells 24a, 24b connected together, each half shell may be formed separately in a respective mould. Figure 2 shows a mould 34 which may, for example, be used to form the leeward half shell 24b. The mould 34 comprises a mould surface 36 shaped to form a half shell 24 with an aerodynamic contour. The various materials forming the half shell 24 are arranged on the mould surface 36 in a layup 38. In some examples, parts of the shell 20 may have a composite sandwich structure, comprising core material 40 arranged between skins comprising fibrous material 42. The fibrous material 42 may comprise fibres such as glass fibres provided in non-crimp fabrics or chopped strand mats or woven fabrics for example. Additional materials such as reinforcing fibres may be arranged in the mould 34 in some examples to form longitudinally-extending reinforcing structures that are embedded in the laminate structure of the shell 20.

In some examples the fibrous material 42 is so-called pre-preg material, which is fibrous material that is pre-impregnated with resin prior to being arranged in the mould 34. In other examples, the materials arranged in the mould 34 may comprise dry fibrous material 42. In such an example, the layup 38 may be infused with resin, for example in a vacuum- assisted resin transfer moulding (VARTM) process. Once the fibrous material 42 in the mould 34 is provided with resin, the resin may be cured to form one side 22 of the outer shell 20.

Whilst Figure 2 shows a mould 34 configured to form the leeward side of the shell 22b, it will be understood that the same process may be followed to form the windward side of the shell 22a, and this is not repeated herein for conciseness. Once formed, the half shells 24a, 24b may be joined together in a join-up process to form the complete aerodynamic outer shell 20. The join-up process typically involves arranging the half shells 24a, 24b one on top of the other, as shown in Figures 3, 4 and 6 for example. The windward half shell 24a may be arranged on top of the leeward half shell 24b and the two shells may be bonded together with adhesive applied along the leading and trailing edges 16, 18. During the join-up process, one or more shear webs 26 are arranged between the half shells 24a, 24b and connected between respective inner surfaces 32a, 32b as will now be described in more detail with reference to the remaining figures. Referring initially to the cross-sectional view of Figure 3, the web panel 28 of each shear web 26 in this example is oriented substantially vertically when the blade 10 is supported in the mould 34. The vertically-oriented web panels 28 of each shear web 26 extend between respective pairs of upper and lower flanges 30a, 30b which are substantially the same width. As such, the flanges 30a and 30b are substantially vertically aligned, i.e. edges 44a of the upper web flanges 30a are directly above the corresponding edges 44b of the lower web flanges 30b. The shear webs 26 are typically arranged with one of the half shells 24 first before the half shells 24 are arranged together to form the complete outer shell 20. Adhesive 46 is arranged such that the upper and lower flanges 30a, 30b of the shear webs 26 are respectively connected to the upper and lower sides 22a, 22b of the shell 20 by adhesive 46 when the half shells 24a, 24b are arranged on top of one another to complete the outer shell 20.

During bonding of the shear web 26 to the shell 20, excess adhesive 46 may be squeezed out from the regions between the flanges 30a, 30b and the shell 20. In particular, excess adhesive 46 squeezed from between the upper web flange 30a and the upper side of the shell 22a may fall under gravity and collect on or near to the lower web flange 30b. As described by way of background above, such surplus adhesive collecting on or too near to the lower flange 32b can interfere with non-destructive testing signals, such as ultrasonic signals, resulting in poor or unreliable testing data.

Excess adhesive 46 can make inspection of joints between the shell 20 and both the trailing edge and main shear webs 26a, 26b challenging. However, non-destructive testing from outside of the blade 10 is relied on more heavily for inspection of the trailing edge web joints due to access constraints, whereas it may be possible to visually inspect the main shear web joints from within the shell 20. Further, again due to access constraints, it may be easier to clear excess adhesive 46 squeezed from the main shear web joints than surplus adhesive from the trailing edge web joints. As such, issues caused by the excess squeezed adhesive 46 may be particularly challenging in relation to the trailing edge shear web 26a.

The shear webs 26 of the blades 10 shown by way of example in the remaining figures are configured to mitigate the issues related to excess adhesive 46 squeezing out from the regions between the flanges 30a, 30b of the shear webs 26 and the outer shell 20 of the blade 10. Referring now to the cross-sectional view of Figure 4 which shows the blade 10 supported in a blade mould 34, the trailing edge shear web 26a is arranged such that the upper web flange 30a overhangs the lower web flange 30b. The flanges 30a, 30b are connected at their respective proximal edges 48a, 48b to the web panel 28 and extend in a generally chordwise direction (C) to a distal edge 44a, 44b which is the edge of the flange 30 furthest from the web panel 28. The distal edge 44a of the upper flange 30a extends beyond the distal edge 44b of the lower flange 30b in the chordwise direction (C) when the blade 10 is supported in the mould 34.

In some examples, the overhang of the upper web flange 30a results from the configuration of the web flanges 30a, 30b whilst the shear web panel 28 may be oriented substantially vertically. With reference for example to the trailing edge web 26a shown in Figure 4, the upper flange 30a of the web 26a may be wider than the lower web flange 30b. With the blade 10 supported in the mould, the upper flange 30a may therefore extend further from the shear web panel 28 in a generally chordwise direction (C) than the lower flange 30b. Accordingly, the distal edge 44a of the upper flange 30a may extend beyond the distal edge 44b of the lower flange 30b in the chordwise direction (C) when the blade 10 is supported in the mould 34, i.e. the distal edges 44a, 44b of the upper and lower flanges 30a, 30b are not vertically aligned.

Excess adhesive 46 squeezed out during bonding of the upper web flange 30a to the upper side 22a of the outer shell 20 does not fall and collect on the lower web flange 30b because of the overhanging upper flange 30a. Such adhesive 46 instead falls and collects on the inner surface 32b of the lower half shell 24b. The widths of the upper and lower web flanges 30a, 30b are configured such that any surplus adhesive 46 falling onto the shell 24b lands sufficiently far away from the distal edge 44b of the lower web flange 30b. For example, the web flanges 30a, 30b are preferably configured such that the upper flange 30a extends at least 12.5 mm, preferably at least 25 mm, beyond the distal edge 44b of the lower flange 30b in the chordwise direction (C). Such an overhang helps to ensure that any surplus adhesive 46 lands far enough away from the distal edge 44b of the flange 30b that the non-destructive testing apparatus can accurately determine the edge 44b of the flange 30b and produce a clear image of the joint between the shear web 26 and shell 20.

In some examples, the outer shell 20 of the blade 10 may be reinforced to take up loads experienced by the blade 10 in use and improve the structural rigidity of the blade 10. For example, the upper and lower sides 22a, 22b of the shell 20 may optionally comprise longitudinally-extending reinforcing structures 50a, 50b, as shown in Figure 5. The shell 20 may be configured with longitudinally extending thickened portions to provide additional structural support to the blade 10. In other examples, the reinforcing structures 50 may comprise additional reinforcing components such as spar caps or stringers. The reinforcing structures 50 are preferably embedded within the shell laminate 20 as shown in Figure 5, although in other examples the reinforcing structures 50 may be joined to the inner surfaces 32a, 32b of the shell 20. The reinforcing structures 50 may be formed of fibre- reinforced polymer, such as carbon fibre in preferred examples. For example, the reinforcing structures 50 may be formed of a stack of carbon fibre reinforced polymer pultrusions in some examples.

The reinforcing structures 50a, 50b of the upper and lower sides of the shell 22a, 22b may be substantially the same width. Further, the reinforcing structures 50a, 50b may be symmetrically arranged, i.e. the reinforcing structures may be substantially vertically aligned. As such, in preferred examples, the reinforcing structure 50a of the upper side of the shell 22a does not substantially overhang the reinforcing structure 50b of the lower side of the shell 22b when the blade 10 is supported in the mould 34.

Preferably, the upper web flange 30a is connected to the reinforcing structure 50a of the upper side 22a of the shell 20 if the blade 10 comprises such a reinforcing structure 50a. Similarly, if the lower side 22b of the shell 20 comprises a reinforcing structure 50b, the lower web flange 30b is preferably connected to this reinforcing structure 50b. The shear web 26 and reinforcing structures 50a, 50b may together form a longitudinally-extending reinforcing spar. Whilst the blade 10 shown in the example of Figure 5 optionally comprises reinforcing structures 50, such reinforcing structures may not be included in other examples. For example, the upper and lower web flanges 30a, 30b may simply be connected to upper and lower sides 22a, 22b of the shell laminate 20.

Figures 6 and 7 show a further example of the blade 10 supported in a mould 34 and comprising a shear web 26 arranged such that the upper web flange 30a overhangs the lower web flange 30b. In some examples, the shear web 26 may be rotated in order to offset the upper and lower flanges 30a, 30b and create the required overhang X. As such, the web panel 28 may be non-vertical when the wind turbine blade 10 is supported in the blade mould 34. With reference to the trailing edge web 26a in Figure 6 for example, the shear web panel 28 may be inclined relative to a vertical axis V at an angle a> which is preferably in the range of 1 degree to 20 degrees. More preferably still, the shear web panel 28 may be inclined relative to the vertical axis V at an angle a> in the range of 1 degree to 5 degrees. In particular, the main shear web 26b may be arranged in a first plane Pi , and the trailing edge web 26a may be arranged in a second plane P2 that is inclined relative to the first plane Pi, as shown in Figure 6 for example.

In examples where the shear web 26 is rotated, the upper and lower flanges 30a, 30b may be offset, i.e. not vertically aligned, despite being substantially the same width. As such, excess adhesive 46 squeezed out during bonding of the upper web flange 30a to the upper side 22a of the outer shell 20 does not fall and collect on the lower web flange 30b. The flanges 30a, 30b may therefore be configured to provide the same surface area via which to bond the shear web 26 to the shell 20 as a symmetrical shear web such as that shown in Figure 3, whilst also negating the issues relating to excess squeezed adhesive 46 collecting on the lower flange 30b.

Figure 7 shows a trailing edge portion of the blade 10 comprising a rotated trailing edge shear web 26a in more detail. In some examples, the upper and lower flanges 30a, 30b may extend from the web panel 28 at different angles. For example, a first angle a defined between the web panel 28 and the upper web flange 30a may be greater than a second angle /3 defined between the web panel 28 and the lower web flange 30b. As such, the upper and lower flanges 30a, 30b may be substantially parallel to the corresponding inner surface 32a, 32b of the upper or lower side 22a, 22b of the shell 20, despite the shear web 26a being rotated.

Preferably, the first angle a is at least 5 degrees greater than the second angle /3. This helps to ensure that when the upper and lower flanges 30a, 30b are bonded to the upper and lower sides 22a, 22b of the shell 20, the flanges 30 are sufficiently offset in the chordwise direction (C) that adhesive squeezed from the joint with the upper side 22a does not land on the lower flange 30b. Preferably, the shear web 26 is rotated such that the upper flange 30a extends at least 12.5 mm, preferably at least 25 mm, beyond the distal edge 44b of the lower flange 30b in the chordwise direction (C) as described above with reference to the example of Figure 4.

The upper flange 30a is connected to the upper side 22a of the outer shell 20, and the lower flange 30b is connected to the lower side 22b. For example, the flanges 30a, 30b may be bonded to the respective upper and lower sides 22a, 22b of the shell 20 by adhesive 46. In examples where the shell 20 comprises reinforcing structures 50a and/or 50b, such as spar caps or stringers, the upper and lower flanges 30a, 30b are preferably connected to such reinforcing structures 50a, 50b as previously described. In the examples described with reference to Figures 4 to 7, the wind turbine blades 10 comprise shear webs 26 having asymmetrically arranged upper and lower web flanges 30a, 30b. The upper web flange 30a overhangs the lower web flange 30b when the blade 10 is supported in the mould 34. The flanges 30a, 30b are therefore not vertically aligned, and adhesive 46 squeezed out from between the upper flange 30a and the upper side 22a of the shell 20 does not land and collect on or too near to the lower flange 30b. The asymmetrically arranged flanges 30a, 30b therefore facilitate improvements in the accuracy and reliability of non-destructive testing of the blade 10 due to the absence of surplus adhesive 46 collecting on or too near to the lower flange 30b.

In some further examples not shown in the accompanying figures, the blade 10 supported in the mould 34 may comprise a shear web 26 having both a web panel 28 that is inclined relative to a vertical axis V, and an upper web flange 30a that is wider than the lower web flange 30b.

In some examples, one or more of the webs 26 may be l-shaped in cross section, comprising upper and lower flanges 30a, 30b extending on both a first and second side of the web panel 28. Any references herein to an upper or lower flange 30a, 30b will be understood to relate to upper and lower flanges 30a, 30b on the same side of the shear web 26 in such an example.

The description provided herein with reference to the trailing edge web 26a as an example is equally applicable to features of the main shear web 26b. As such, in some examples the main shear web 26b and/or trailing edge shear web 26a may comprise an inclined web panel 28, wider upper web flange 30a or any other combination of features described herein.

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. It will be appreciated that features described in relation to each of the examples above may be readily combined with features described with reference to other examples without departing from the scope of the invention as defined by the following claims.