DK179500B1

DK179500B1 - A method of making a wind turbine blade

Info

Publication number: DK179500B1
Application number: DKPA201670994A
Authority: DK
Inventors: Morbech Halling Kaj; Smith Jonathan; Rimmer John
Original assignee: Vestas Wind Systems A/S
Priority date: 2016-12-15
Filing date: 2016-12-15
Publication date: 2019-01-16
Also published as: DK201670994A1

Abstract

A method of making a wind turbine blade is described. The method comprises the following steps in any suitable order: (a) providing a blade shell extending in a chordwise direction between a leading edge and a trailing edge, the blade shell defining a substantially hollow interior; (b) providing a shear web within the interior of the blade shell; (c) providing adhesive on a bonding surface of the shear web and/or on a bonding surface of the blade shell; and (d) providing motive force on the shear web in asubstantially chordwise direction such that the bonding surface of the shear web is moved towards the bonding surface of the blade shell and the adhesive is compressed therebetween.

Description

A METHOD OF MAKING A WIND TURBINE BLADE

Technical field

The present invention relates to a method of making a wind turbine blade. More specifically, the present invention relates to a method of installing a shear web within an internal cavity of a wind turbine blade shell.

Background

Modern wind turbine blades typically comprise a hollow shell made up of two half shells bonded together along leading and trailing edges of the blade. Two reinforcing structures in the form of longitudinally-extending shear webs are typically provided inside the internal cavity of the blade. Conventionally, each shear web comprises two longitudinallyextending mounting flanges that are bonded to opposed inner surfaces of the respective half shells by means of adhesive.

The height of the shear web is slightly less than the separation between the opposed half shells to provide room for the adhesive between the mounting flanges and the blade shell. The distance between a shear web mounting flange and the inner surface of the blade shell defines the ‘bondline thickness' at that bond interface.

It is important that a sufficient amount of adhesive is deposited at each bond interface, not only to fill the gap between the shear web and the blade shell but also to ensure proper squeezing of the adhesive. However, it is difficult to control the bondline thickness between the shear web and the blade shell. The curved cross-section of the blade shell means that the bondline thickness is sensitive to the position and orientation of the shear web relative to the blade shell. Furthermore, any manufacturing tolerances in the half shells or the shear webs will also impact the bondline thicknesses at the interfaces.

Since the bondline thickness cannot be accurately predicted, a sufficient amount of adhesive must be deposited at each bond interface to accommodate the full range of potential bondline thicknesses, i.e. to accommodate the maximum possible spacing between the shear web and the blade shell. This leads to significant wastage of adhesive. When the adhesive is squeezed at the interfaces, the excess adhesive is squeezed out of the bondline and is effectively wasted, yet it still contributes significantly to the overall weight of the completed wind turbine blade, and represents a substantial material cost.

Furthermore, manufacturing processes for shear webs typically mean that it is prohibitive in terms of cost to vary the design of a shear web from one blade to another. For example, it is not generally possible to vary the height of shear webs to accommodate varying shell thicknesses employed in high and low wind class blade designs. Therefore, shear webs must be designed and manufactured to accommodate the thickest shells with additional adhesive being employed in the bond lines of thinner shell designs. This additional adhesive disadvantageously contributes significantly to the overall weight and material cost of the blade.

Against this background, it is an object of the present invention to provide an improved method of making a wind turbine blade which addresses one or more of the problems outlined above.

GB2527587 describes a method for the manufacture of wind turbine blades, and more specifically to a method and apparatus for ensuring the correct position of shear webs during blade manufacture. EP2843227 describes a method for installing a shear web insert within a segmented rotor blade assembly.

Summary of the Invention

According to a first aspect of the invention, there is provided a method of making a wind turbine blade. The method comprises the following steps in any suitable order: (a) providing a blade shell extending in a chordwise direction between a leading edge and a trailing edge, the blade shell defining a substantially hollow interior; (b) providing a shear web within the interior of the blade shell; (c) providing adhesive on a bonding surface of the shear web and/or on a bonding surface of the blade shell; and (d) providing motive force on the shear web in a substantially chordwise direction such that the bonding surface of the shear web is moved towards the bonding surface of the blade shell and the adhesive is compressed therebetween; characterised in that an actuator is provided within the interior of the blade and is activated to provide the motive force on the shear web.

The actuator may comprise a piston and/or a spring and/or an inflatable bladder. Any other actuator capable of varying its dimensions in the chordwise direction may be used. Activating the actuator may comprise extending the piston and/or extending the spring and/or inflating the inflatable bladder.

The actuator may be configured to push at least part of the shear web towards the leading edge or towards the trailing edge of the blade shell. In other configurations, the actuator may be configured to pull the shear web in the requisite direction.

The motive force provided in step (d) may cause the shear web to move towards the leading edge or towards the trailing edge of the blade shell. The motive force provided in step (d) may cause the shear web to rotate within the interior of the blade.

Step (b) may comprise providing first and second shear webs within the interior of the blade shell. In this case, step (c) may comprise providing adhesive on a first bonding surface of the first shear web and/or on a first bonding surface of the blade shell, and providing adhesive on a second bonding surface of the second shear web and/or on a second bonding surface of the blade shell. Step (d) may comprise moving at least part of the first shear web towards the leading edge and/or moving at least part of the second shear web towards the trailing edge of the blade shell.

Step (b) may comprise providing the shear web inside the blade in an inclined orientation. In a particular embodiment, a pair of shear webs are arranged initially such that the chordwise spacing between their respective upper edges is less than the chordwise spacing between their respective lower edges. Step (d) may further comprise moving the shear web towards a substantially vertical orientation. For example the actuator may be configured to push the shear webs from an inclined position to a substantially vertical position.

The method may comprise providing the motive force between the first and second shear webs. For example, the actuator may be arranged between the first and second shear webs.

The bonding surface of the blade shell may be defined by an inner surface of the blade shell. Alternatively, one or more flanges may be integrated with the blade shell. The one or more flanges may define the bonding surface of the blade shell. For example, the one or more flanges may comprise a portion projecting into the interior of the blade shell and defining the bonding surface of the blade shell. The one or more flanges may be Tshaped in cross-section, and an upstand of the T may define the bonding surface. The motive force applied in step (d) may cause the shear web to move towards the bonding surface of a flange.

The inventive concept includes a wind turbine blade made according to the method described above.

Brief Description of the Drawings

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

Figure 1 shows a transverse cross-section of a wind turbine blade comprising two shear webs;

Figure 2 shows the wind turbine blade during installation of the shear webs wherein gaps exist at bond interfaces between the shear webs and the blade shell;

Figure 3 illustrates a first example of the invention in which an actuator is provided between the shear webs and the actuator pushes the shear webs outwardly in opposite directions in a chordwise direction;

Figure 4 illustrates a second example of the invention in which the actuator pushes one shear web in the chordwise direction whilst the other shear web remains stationary;

Figures 5, 6 and 7 illustrate third, fourth and fifth examples of the invention in which both shear webs are moved from an inclined position to a substantially vertical position;

Figure 8 illustrates a sixth example of the invention in which one shear web is moved from an inclined position to a substantially vertical position and the other shear web remains stationary;

Figure 9 illustrates a seventh example of the invention in which one shear web is translated outwardly in a chordwise direction and the other shear web is moved from an inclined position to a substantially vertical position;

Figure 10a illustrates an eighth example of the invention in which T-shaped flanges are integrated with the blade shell and the shear webs are bonded between the flanges; and

Figure 10b illustrates the process of bonding the shear webs between the T-shaped flanges in which an actuator is used to move the shear webs from an inclined position towards a vertical position in which the shear webs are pressed against the flanges.

Detailed Description

Referring to Figure 1, a wind turbine blade 10 is shown in transverse cross-section. The blade 10 comprises a hollow shell 12 defining an internal cavity 14. In this example, the shell 12 is formed from a windward half shell 16 and a leeward half shell 18 which are moulded separately in respective moulds before being bonded together along the leading and trailing edges 20, 22 of the blade.

Each half shell 16, 18 has a concave inner surface 24, 26 extending in a chordwise direction C between leading and trailing edges 20, 22 of the blade 10. The vertical separation S between the opposed inner surfaces 24, 26 of the half shells 16, 18 defines the height of the internal cavity 14. As shown in Figure 1, the height of the internal cavity 14 decreases progressively towards the leading and trailing edges 20, 22 of the blade.

Two shear webs 28, 30 are provided within the internal cavity 14 of the blade 10. The shear webs 28, 30 are bonded between the opposed inner surfaces 24, 26 of the half shells 16, 18 by means of adhesive 31a, 31b. The shear webs 28, 30 extend in a longitudinal direction along the length of the blade 10 and are mutually spaced apart in the chordwise direction C.

The shear webs 28, 30 are substantially I-shaped in cross-section. More specifically, each shear web 28, 30 comprises a generally vertical web element 32, 34 disposed between upper mounting flanges 36, 38 and lower mounting flanges 40, 42 respectively provided at first and second ends of the web element 32, 34 as viewed in cross-section.

The outer surfaces 44, 46, 48, 50 of the upper and lower mounting flanges 36, 38, 40, 42 respectively define the upper and lower bonding surfaces 44, 46, 48, 50 of the shear webs 28, 30. The inner surfaces 24, 26 of the half shells 16, 18 define the bonding surfaces of the blade shell 12. Each shear web 28, 30 is arranged within the internal cavity 14 of the blade 10 with the upper and lower bonding surfaces 44, 46, 48, 50 facing the inner surfaces 24, 26 of the leeward and windward half shells 16, 18 respectively. The web elements 32, 34 extend between the mounting flanges 36, 38, 40, 42, bridging the internal cavity 14 of the blade 10.

In order to install the shear webs 28, 30 within the blade shell 12, adhesive 31a is applied along longitudinally-extending shear web mounting regions 52, 54 defined on the inner surface 24 of the windward half shell 16. The mounting regions 52, 54 typically coincide with the positions of reinforcing spar caps (not shown) embedded within the blade shell 12. The shear webs 28, 30 are then lifted into the windward mould and arranged against the inner surface 24 of the windward half shell 16. More specifically, the lower bonding surfaces 48, 50 of the shear webs 28, 30 are positioned against the adhesive 31a at the mounting regions 52, 54 defined on the windward half shell 16. It should be appreciated that additionally or alternatively, adhesive may be applied to the bonding surfaces 48, 50 of the lower mounting flanges 40, 42.

Adhesive (not shown) is then applied along the leading and trailing edges 20, 22 of the windward half shell 16. Further adhesive 31b is applied to the upper mounting flanges 36, 38 of the shear webs 28, 30. Alternatively or additionally, adhesive may be applied along mounting regions 56, 58 defined on the inner surface 26 of the leeward half shell

18. The leeward shell 18 is then lifted, turned and placed on top of the windward shell 16. With the leeward shell 18 positioned on top of the windward shell 16, the adhesive 31b applied to the upper mounting flanges 36, 38 of the shear webs 28, 30 is squeezed against the inner surface 26 of the leeward shell 18. The shear webs 28, 30 are thus installed at a nominal position within the internal cavity 14 of the blade 10.

At this stage, it is difficult or impossible to predict the spacing between the bonding surfaces 44, 46, 48, 50 of the shear webs 28, 30 and the inner surfaces 24, 26 of the blade shell 12. As mentioned above by way of background, the bondline thickness is sensitive to the position and orientation of the shear webs 28, 30 and also sensitive to any manufacturing tolerances in the shear webs 28, 30 and in the blade half shells 16,

18. Accordingly, in some cases there may be voids between the adhesive 31a, 31b and the blade shell 12 with the shear webs 28, 30 in their nominal position, and/or there may not be sufficient compression of the adhesive 31a, 31b in the bondlines if the spacing between the shear webs 28, 30 and the half shells 16, 18 is too large.

Figure 2 shows an example of a case in which there are voids 60, 62 between the adhesive 31b applied to the upper mounting flanges 36, 38 of the shear webs 28, 30 and the inner surface 26 of the leeward blade shell 18. These voids 60, 62 may arise when the spacing between the shear webs 28, 30 and the blade half shells 16, 18 is too large, for example if insufficient adhesive 31b is applied to the upper mounting flanges 36, 38 of the shear webs 28, 30 or if the adhesive 31a between the lower mounting flanges 40, 42 and windward half shell 16 is compressed too much. This problem is addressed by means of the present invention, as will now be discussed in relation to the remaining figures.

Referring to Figure 3, an actuator 64 is provided between the shear webs 28, 30 within the internal cavity 14 of the blade shell 12. The actuator 64 is configured to provide a motive force on the shear webs 28, 30 in the chordwise direction C during the process of bonding the shear webs 28, 30 to the blade shell 12. The actuator 64 allows the shear webs 28, 30 to be moved from their nominal position to an adjusted or modified position in order to adjust the bondline thickness at the bond interfaces between the shear webs 28, 30 and the blade shell 12. In this example, the actuator 64 extends between the two shear webs 28, 30 and is capable of providing motive forces in opposite directions to the respective shear webs 28, 30.

The actuator 64 may be any suitable means capable of providing a motive force to the shear webs 28, 30. For example, the actuator 64 may comprise a piston, a spring and/or an inflatable bladder. The actuator 64 may be provided in place before or after the two half shells 16, 18 are brought together. However, the actuator 64 is preferably positioned between the shear webs 28, 30 prior to positioning the two half shells 16, 18 together, which allows for easy access to the shear webs 28, 30. Multiple actuators may be provided, for example a plurality of actuators spaced at intervals along the lengths of the shear webs 28, 30.

After the shear webs 28, 30 have been installed at their nominal positions within the internal cavity 14 of the blade 10, the actuator is activated. Activation of the actuator 64 causes the actuator 64 to extend its dimensions in the chordwise direction. When activated, the actuator 64 exerts an outward chordwise force on each shear web 28, 30.

Under the action of this motive force, each shear web 28, 30 moves outwardly towards a respective edge 20, 22 of the blade. That is to say, each shear web 28, 30 is translated in a substantially chordwise direction. The first shear web 28 is moved slightly in the chordwise direction towards the leading edge 20 of the blade 10 and the second shear web 30 is moved slightly in the chordwise direction towards the trailing edge 22 of the blade 10.

Since the height of the internal cavity 14 progressively decreases towards the leading and trailing edges 20, 22 of the blade 10, the size of the gaps between the bonding surfaces 44, 46, 48, 50 of the shear webs 28, 30 and the inner surfaces 24, 26 of the half shells 16, 18 decreases as the shear webs 28, 30 are translated in their respective outward chordwise directions. In other words, the bonding surfaces 44, 46, 48, 50 of the shear webs 28, 30 are effectively moved towards the bonding surfaces 24, 26 of the blade shell 12. The adhesive between the bonding surfaces 24, 26, 44, 46, 48, 50 is therefore progressively compressed as the shear webs 28, 30 are moved. (For ease of illustration and enhanced clarity, the adhesive is not shown in Figure 3.)

As the adhesive is compressed, the shear webs 28, 30 experience progressively increasing resistance to their outward movement. This is because the hydrostatic pressure in the adhesive increases as the adhesive is compressed. In addition, the polymeric adhesives typically used in wind turbine blades have a viscosity that tends to increase as they are compressed. Other forces, for example due to friction between the adhesive and the bonding surfaces 24, 26, 44, 46, 48, 50, may also contribute to the resistive forces acting against the outward movement of the shear webs 28, 30. In an example, the adhesive is an epoxy adhesive.

As the resistance increases, the net force on the shear webs 28, 30 decreases until eventually the resistive forces balance the motive force provided by the actuator 64. At this point, the net force is zero and the shear webs 28, 30 naturally come to rest at adjusted positions 66, 68 (indicated by dashed lines in Figure 3). In some embodiments, the actuator 64 may be configured to have a maximum extension so that the shear webs 28, 30 can only be moved by a predetermined maximum amount.

Once the shear webs 28, 30 are at their adjusted positions 66, 68, the adhesive is then cured. Heat may be applied to the adhesive to accelerate the curing process. Optionally, the actuator 64 may then be removed from the blade cavity 14. In some examples, the actuator 64 may be removed from the blade cavity 14 before the adhesive is cured.

In summary, the shear webs 28, 30 may be initially installed at a nominal position in which there may be a gap between the adhesive and the blade shell 12 and/or at which the adhesive may not be compressed or may not be sufficiently compressed. Under the action of a substantially chordwise motive force, the shear webs 28, 30 may be moved to an adjusted chordwise position 66, 68 that provides sufficient compression of the adhesive. The ability to move the shear webs 28, 30 in the chordwise direction allows an optimal bondline thickness to be obtained and allows less adhesive to be used whilst still ensuring that the adhesive is suitably compressed.

It should be noted that, for ease of illustration, the accompanying figures are highly schematic. In particular, the relative proportions of the shear webs, the gaps at the bond interfaces and the chordwise movement of the shear webs are not intended to be accurately dimensioned.

Further examples of the invention will now be described with reference to Figures 4 to 10b, each of which shows a wind turbine blade 10 comprising two shear webs 28, 30 in transverse cross-section. For convenience, features corresponding to those shown and described with reference to Figure 1 are given the same reference numerals in Figures 4 to 10b.

Referring to Figure 4, in this example only one shear web 30 is moved under the action of the motive force provided by the actuator 64. The nominal position of the first shear web 28 is such that the bondline thickness at the bond interfaces is sufficiently small that the adhesive is sufficiently compressed. In other words, the nominal position of the first shear web 28 is an optimal position. The resistive forces are sufficient to balance the motive force on the first shear web 28 provided by the actuator 64. Therefore, the first shear web 28 is not moved from its nominal position by the actuator 64.

In contrast, the nominal position of the second shear web 30 is such that the bondline thickness at the bond interfaces is sufficiently large that the adhesive is not sufficiently compressed. In other words, the nominal position of the second shear web 30 is suboptimal. The motive force provided by the actuator 64 on the second shear web 30 is sufficient to overcome the resistive forces opposing the chordwise movement of the second shear web 30. The second shear web 30 therefore moves in an outward chordwise direction slightly towards the trailing edge 22 of the blade 10. As described above, the second shear web 30 experiences increasing resistance to its chordwise motion and naturally comes to rest at an adjusted position 68 at which the adhesive is suitably compressed.

In the examples described above with reference to Figures 3 and 4, the shear webs 28, 30 are translated in a chordwise direction from their nominal positions to their adjusted positions 66, 68. However, in other examples, the motive force provided by the actuator 64 may cause the shear webs 28, 30 to rotate slightly, as will now be described with reference to Figures 5, 6 and 7.

Each of Figures 5, 6 and 7 shows two actuators 64 provided between the shear webs. The actuators each extend between the shear webs 28, 30 and are spaced apart in a vertical direction (in the orientation of the figures), i.e. they are spaced at different heights relative to the shear webs 28, 30. In these examples, each actuator 64 is capable of providing substantially chordwise motive forces to the shear webs 28, 30.

The actuators 64 may be activated individually or jointly. However, in these examples, each actuator 64 is able to extend its dimensions in the chordwise direction independently of the other actuator 64. That is to say, the actuators 64 are capable of extending their chordwise dimensions by different amounts during the shear web bonding process. This allows the upper and lower mounting flanges 36, 38, 40, 42 of each shear web 28, 30 to be moved different distances from their nominal position to their adjusted position 66, 68. Thus, the shear webs 28, 30 can be rotated as well as translated from their nominal positions to their adjusted positions 66, 68. However, it should be appreciated that rotation can also be achieved under the action of a single actuator.

Referring to Figure 5, each shear web 28, 30 in this example is installed at an inclined nominal position, e.g. the shear webs are each slightly inclined to the vertical in the orientation of the blade 10 shown in the figures. In particular, the lower mounting flange 40 of the first shear web 28 is located closer to the leading edge 20 of the blade 10 than the upper mounting flange 36 is. Similarly, the lower mounting flange 42 of the second shear web 30 is located closer to the trailing edge 22 of the blade 10 than the upper mounting flange 38 is. In other words, the chordwise spacing between the respective lower edges of the shear webs 28, 30 is greater than the chordwise spacing between their respective upper edges. Therefore, the two actuators 64 have differing chordwise dimensions when they are installed between the shear webs 28, 30.

As will now be described, under the action of the motive force provided by the actuators 64, the shear webs 28, 30 are moved to substantially vertical adjusted positions 66, 68.

In this example, the bondline thickness at each bond interface between the lower mounting flanges 40, 42 of the shear webs 28, 30 and the inner surface 24 of the windward half shell 16 is such that the adhesive is sufficiently compressed. In other words, the lower mounting flange 40, 42 of each shear web 28, 30 is already in an optimal position. Therefore, the motive force provided by the actuators 64 is not sufficient to overcome the resistive forces opposing the outward chordwise movement of the lower mounting flanges 40, 42. The lower mounting flanges 40, 42 therefore do not move appreciably in a chordwise direction relative to the blade shell 12 when the actuators 64 are activated.

In contrast, the adhesive at the bond interfaces between the upper mounting flanges 36, 38 and the inner surface 26 of the leeward shell 18 is not sufficiently compressed or there may be voids between these mounting flanges 36, 38 and the blade shell 12. In other words, the upper mounting flanges 36, 38 of the shear webs 28, 30 are initially in a sub-optimal position. The motive force provided by the actuators 64 is sufficient to overcome the resistive forces acting on the upper mounting flanges 36, 38. Therefore, under the action of the chordwise motive force provided by the actuators 64, the upper mounting flanges 36, 38 move in respective outward chordwise directions relative to the blade shell 12. This chordwise movement moves the upper bonding surfaces 44, 46 of the shear webs 28, 30 closer to the bonding surface of the blade shell 12 (i.e. closer to the inner surface 26 of the leeward half shell 18). The adhesive between the upper mounting flanges 36, 38 and the inner surface 26 of the leeward half shell 18 is therefore progressively compressed. At a position where the adhesive is sufficiently compressed, the shear webs 28, 30 naturally come to rest at respective adjusted positions 66, 68. In this example, the adjusted shear web positions 66, 68 are substantially vertical.

In this example, each shear web 28, 30 is effectively rotated (or turned) about a respective axis of rotation extending along the length of the wind turbine blade 10 (i.e.

into the plane of the page of Figure 5). In this example, the shear webs 28, 30 are rotated in opposite directions. The first shear web 28 is rotated slightly in an anticlockwise direction and the second shear web 30 is rotated slightly in a clockwise direction. In this example, each shear web 28, 30 is moved from an inclined nominal position to a substantially vertical adjusted position 66, 68.

Whilst the adjusted position in this and other examples is substantially vertical, in other examples the shear web(s) may still be inclined slightly (i.e. non vertical) in their adjusted position(s).

Figure 6 shows another example of the invention in which both shear webs 28, 30 are rotated in opposite directions from respective inclined nominal positions to respective substantially vertical adjusted positions 66, 68. In this example, the upper mounting flanges 36, 38 of the first and second shear webs 28, 30 are located closer to the leading and trailing edges 20, 22 respectively than the lower mounting flanges 40, 42 are. As will now be described, in this example the lower mounting flanges 40, 42 are moved in outward chordwise directions and the chordwise positions of the upper mounting flanges 36, 38 remain substantially stationary.

In this example, the bondline thickness at each bond interface between the upper mounting flanges 36, 38 of the shear webs and the inner surface 26 of the leeward half shell 18 is such that the adhesive is sufficiently compressed. In other words, the nominal positions of the upper mounting flanges 36, 38 of the first and second shears webs 28, 30 are optimal. Therefore, the motive force provided by the actuators 64 is not sufficient to overcome the resistive forces acting on the upper mounting flanges 36, 38. Therefore, the upper mounting flanges 36, 38 do not move appreciably in a chordwise direction relative to the blade shell 12.

In contrast, the adhesive at the bond interfaces between the lower mounting flanges 40, 42 and the inner surface 24 of the windward shell 16 is not sufficiently compressed. In other words, the lower mounting flanges 40, 42 of the shear webs 28, 30 are in suboptimal positions. Therefore, under the action of the motive force provided by the actuators 64, the lower mounting flanges 40, 42 move in respective outward chordwise directions relative to the blade shell 12.

In view of the concave curvature of the inner surface 24, 26 of the blade 10, this chordwise movement effectively moves the lower bonding surfaces 48, 50 of the shear webs 28, 30 closer to the bonding surface of the blade shell 12 (i.e. the lower mounting flanges 40, 42 are moved closer towards the inner surface 24 of the windward half shell 16). The adhesive between the lower mounting flanges 40, 42 and the inner surface 24 of the windward shell 16 is therefore progressively compressed. At a position where the adhesive is sufficiently compressed, the shear webs 28, 30 naturally come to rest at an adjusted chordwise position 66, 68. In this example, the adjusted shear web positions 66, 68 are substantially vertical.

Figure 7 illustrates an example of the invention in which the shear webs 28, 30 are rotated in the same direction from respective inclined nominal positions to respective substantially vertical adjusted positions 66, 68.

In this example, the adhesive between the lower mounting flange 40 of the first shear web 28 and the inner surface 24 of the windward shell 16 is sufficiently compressed. In other words, the lower mounting flange 40 of the first shear web 28 is already in an optimal position. The chordwise motive force provided by the actuators 64 is therefore insufficient to overcome the resistive forces acting on the lower mounting flange 40 and the lower mounting flange 40 does not move appreciably in a chordwise direction relative to the blade shell 12.

However, the adhesive between the upper mounting flange 36 of the first shear web 28 and the inner surface 26 of the leeward half shell 18 is not sufficiently compressed or there may be a gap between this mounting flange 36 and the blade shell 12. In other words, the upper mounting flange 36 of the first shear web 28 is in a sub-optimal nominal position. The motive force provided by the actuators 64 is therefore sufficient to overcome the resistive forces opposing the outward chordwise motion of the upper mounting flange 36. Therefore, under the action of the motive force provided by the actuators 64, the upper mounting flange 36 moves in a chordwise direction towards the leading edge 20 of the blade 10. Thus, the first shear web 28 is rotated in an anticlockwise direction, and its upper mounting flange 36 is moved closer to towards the inner surface 26 of the leeward half shell 18 compressing the adhesive in-between

Referring now to the second shear web 30, the adhesive between the upper mounting flange 38 and the inner surface 26 of the leeward shell 18 is sufficiently compressed. In other words, the upper mounting flange 38 of the second shear web 30 is already in an optimal position. The motive force provided by the actuators therefore does not overcome the resistive forces and the upper mounting flange 38 does not move in a chordwise direction relative to the blade shell 12.

However, the adhesive between the lower mounting flange 42 of the second shear web 30 is not sufficiently compressed. In other words, the lower mounting flange 42 of the second shear web 30 is in a sub-optimal nominal position. Therefore, under the action of the motive force provided by the actuators 64, the lower mounting flange 42 moves in a chordwise direction towards the trailing edge 22 of the blade. Thus, the second shear web 30 is also rotated in an anti-clockwise direction. The lower mounting flange 42 of the shear web 30 is thus moved closer towards the inner surface 24 of the windward half shell 16 and the adhesive is further compressed in-between.

Figure 8 illustrates an example of the invention in which the second shear web 30 is rotated from an inclined nominal position to a substantially vertical adjusted position 68 whilst the first shear web 28 remains stationary.

Referring to Figure 8, the adhesive between the upper and lower bonding surfaces 44, 48 of the first shear web 28 and the bonding surfaces of the blade shell 12 (i.e. the inner surfaces 24, 26 of the windward and leeward half shells 16, 18) is sufficiently compressed that the motive force provided by the actuators 64 is not sufficient to overcome the resistive forces. In other words, the first shear web 28 is already in an optimal position. Therefore, the first shear web 28 does not move appreciably under the action of the motive force provided by the actuators 64.

However, the second shear web 30 is initially in a sub-optimal inclined position without sufficient compression of adhesive between the upper mounting flange 38 and the leeward half shell 18. In this example, the lower mounting flange 42 of the second shear web 30 is already in an optimal position. That is to say, the adhesive between the lower mounting flange 42 of the second shear web 30 and the inner surface 24 of the windward shell 16 is sufficiently compressed.

The motive force provided by the actuators 64 is sufficient to overcome the resistive forces acting on the upper mounting flange 38 but insufficient to overcome the resistive forces acting on the lower mounting flange 42. Therefore, the upper mounting flange 38 moves in an outward chordwise direction under the action of the motive force. However, the lower mounting flange 42 does not move appreciably in a chordwise direction relative to the blade shell 12 when the actuators 64 are activated. Accordingly, the second shear web 30 is caused to rotate slightly in a clockwise direction under the action of the motive force provided by the actuators 64. This clockwise rotation causes the upper mounting flange 38 to move closer towards the inner surface 26 of the leeward half shell 18 and compress the adhesive in-between.

As will now be described with reference to Figure 9, in some examples one shear web 28 may be translated and the other shear web 30 may be rotated under the action of the motive force.

In this example, both shear webs 28, 30 are installed at a sub-optimal nominal position. In particular, the bondline thickness at the bond interfaces between the upper and lower mounting flanges 36, 40 of the first shear web 28 are such that the adhesive at those interfaces is insufficiently compressed. The motive force provided by the actuators 64 is therefore sufficient to overcome the resistive forces acting on both mounting flanges 36, 40. In this example, the nominal position of the first shear web 28 is such that the first shear web 28 is translated in a chordwise direction towards the leading edge 20 of the blade shell 12 under the action of the motive force. In view of the concave curvature of the inner surfaces 24, 26 of the half shells 16, 18, this chordwise translation results in the upper and lower mounting flanges 36, 40 of the first shear web 28 being moved closer to the inner surfaces 24, 26 of the leeward and windward half shells 16, 18, respectively, and the adhesive at these interfaces being optimally compressed.

Referring to the second shear web 30, the bondline thickness at the interface between the upper mounting flange 38 and the inner surface 26 of the leeward shell 18 is such that the adhesive is already sufficiently compressed. In other words, the upper mounting flange 38 is already at an optimal chordwise position. The motive force is therefore insufficient to overcome the resistive forces acting on the upper mounting flange 38 and the upper mounting flange 38 does not move appreciably under the action of the actuators 64.

In contrast, the bondline thickness at the interface between the lower mounting flange 42 and the inner surface 24 of the windward half shell 16 is such that the adhesive is insufficiently compressed. In other words, the lower mounting flange 42 is at a suboptimal position. Therefore, the motive force is sufficient to overcome the resistive forces acting on the lower mounting flange 42 and the lower mounting flange 42 moves in an outward chordwise direction. Thus, the second shear web 30 is rotated slightly in an anticlockwise direction under the action of the motive force provided by the actuators 64. This anti-clockwise rotation causes the lower mounting flange 42 of the second shear web 30 to move closer towards the inner surface 24 of the windward half shell 16 and further compress the adhesive in-between.

It should be appreciated that in other examples, the shear webs may undergo different patterns of movement from their nominal positions to their adjusted positions. For example, under the action of the motive force, both the upper and lower mounting flanges of a shear web may move in a chordwise direction relative to the blade shell but not necessarily by the same distance. In this case, the angle of inclination of the shear web is adjusted as well as its chordwise position. This course of movement is equivalent to a superposition of a rotation and a translation.

In the above-described examples, the problems associated with the uncertainty in the bondline thickness between the shear webs and the blade shell are addressed by adjusting the chordwise position of the shear webs relative to the blade shell. However, in some circumstances, it may be important for the shear webs to be installed at specific predetermined chordwise locations. Another example of the present invention will now be described that addresses the problems identified with the prior art whilst also allowing the shear webs to be bonded at predetermined chordwise locations.

Referring to Figure 10a, a wind turbine blade 10 comprising two shear webs 28', 30' is shown in transverse cross section. Similarly to the examples described above, the blade 10 comprises a hollow shell 12 formed from a windward half shell 16 and a leeward half shell 18. However, in this example, each half shell 16, 18 comprises two mounting flanges: a first mounting flange 36', 40' and a second mounting flange 38', 42'. The mounting flanges 36', 38', 40', 42' may be moulded integrally with the blade shell 12 or, as shown in Figure 10a, the mounting flanges 36', 38', 40', 42' may be integrated with the blade shell 12 by bonding, i.e. the mounting flanges may be bonded to the inner surfaces 24, 26 of the half shells 16, 18.

In this example, the mounting flanges 36', 38', 40', 42' are substantially T-shaped in cross-section. (In other example, the mounting flanges may be L shaped). More specifically, each mounting flange 36', 38', 40', 42' comprises a base 70 and an upstand

72. A first surface 74 of the base 70 is bonded to the inner surface 24, 26 of the half shell

16, 18 to integrate the mounting flange 36', 38', 40', 42' with the blade shell 12. The upstand 72 projects from a second surface 76 of the base 70 in a substantially perpendicular direction. Therefore, the upstand 72 projects into the internal cavity 14 of the blade 10. As will be described, the upstand 72 of each mounting flange 36', 38', 40', 42' defines a bonding surface of the blade shell 12.

The first and second mounting flanges 36', 38', 40', 42' are spaced apart in the chordwise direction. In this example, the mounting flanges 36', 38', 40', 42' are integrated with the half shells 16, 18 such that when the half shells 16, 18 are assembled to form the full blade 10, the respective first mounting flanges 36', 40' are arranged opposite one another and the respective second mounting flanges 38', 42' are arranged opposite one another. The first mounting flanges 36', 40' are located towards the leading edge 20 of the blade shell 12 and the second mounting flanges 38', 42' are located towards the trailing edge 22 of the blade shell. As will now be explained, the chordwise positions of the mounting flanges 36', 38', 40', 42' define the chordwise positions (relative to the blade shell 12) of the shear webs 28', 30'.

As mentioned above, the blade 10 comprises two shear webs 28', 30'. In this example, the shear webs 28', 30' are in the form of flat longitudinally-extending panels having a substantially rectangular cross-section. The shear webs 28', 30' are arranged substantially vertically and bridge the internal cavity 14 of the blade 10. Each shear web 28', 30' is bonded to the blade shell 12 by means of adhesive 31a, 31b. The first shear web 28' is bonded between the first mounting flange 40' of the windward half shell 16 and the first mounting flange 36' of the leeward half shell 18. Similarly, the second shear web 30' is bonded between the second mounting flanges 38', 42' of the windward and leeward half shells 16, 18.

More specifically, bonding surfaces of the shear webs 28', 30' are bonded to the bonding surfaces of the blade shell 12. In this example, the outer surfaces 78 of the shear webs 28', 30' are bonded to inner surfaces 80 of the upstands 72 of the respective mounting flanges 36', 38', 40', 42'. In other words, the outer surfaces 78 of the shear webs 16, 18 define the bonding surfaces of the shear webs 16, 18 and, as mentioned above, the bonding surfaces of the blade shell 12 are defined by the inner surfaces 80 of the upstands 72 of the integrated mounting flanges 36', 38', 40', 42'.

A method of installing the shear webs 16, 18 within the internal cavity 14 of the blade 10 will now be described with reference to Figure 10b. After the half shells 16, 18 have been produced and the mounting flanges 36', 38', 40', 42' have been appropriately integrated therewith, the blade 10, including the shear webs 28', 30' is assembled.

Referring to Figure 10b, adhesive 31a is applied to shear web bonding regions 82 defined at lower edges 84 of the outer surfaces 78 of the respective shear webs 28', 30'. Alternatively or additionally, adhesive may be applied to the bonding surfaces of the first and second mounting flanges 40', 42' integrated with the windward half shell 16 (i.e. to the inner surfaces 80 of the upstands 72).

The shear webs 28', 30' are then lifted into the windward half shell 16 and arranged at a nominal position. In this example, the shear webs 28', 30' are arranged with the outer surfaces 78 of the shear webs 28', 30' facing the inner surfaces 80 of the upstands 72 of the windward mounting flanges 40', 42'.

In this example, the shear webs 28', 30' are arranged in an inclined nominal position. More specifically, the lower edges 84 of the first and second shear webs 28', 30' are positioned closer to the leading and trailing edges 20, 22 respectively of the blade shell 12 than their upper edges 86 are. In other words, the shear webs 28', 30' are inclined towards one another such that the chordwise spacing between the lower edges 84 of the shear webs 28', 30' is greater than the chordwise spacing between the upper edges 86 of the shear webs 28', 30'. The lower edges 84 of the shear webs 28', 30' are positioned closer to their respective windward mounting flanges 40', 42' than the upper edges 86 are to their respective leeward mounting flanges 36', 38'. In this particular example, the lower edges 84 of the shear webs 28', 30' are in contact with the windward mounting flanges 40', 42'.

Adhesive (not shown) is then applied along the leading and trailing edges 20, 22 of the windward half shell 16. Further adhesive 31b is applied along shear web bonding surfaces defined at upper edge regions 88 of the outer surfaces 78 of respective shear webs 28', 30'. Alternatively or additionally, adhesive may be applied directly to the mounting flanges 36', 38', 40', 42' integrated with the leeward half shell 18, i.e. to the inner surfaces 80 of the upstands 72. The leeward shell 18 is then lifted, turned and placed on top of the windward shell 16. The shear webs 28', 30' are thus installed at an inclined nominal position within the internal cavity 14 of the blade 10.

At this stage, the adhesive 31a, 31b provided to the bonding surfaces 78 has not experienced any compressive force. Furthermore, there are gaps between the adhesive 31b at the upper edge regions 88 of the shear webs 28', 30' and the leeward mounting flanges 36', 38'. In order to close these gaps and appropriately compress the adhesive 31a, 31b provided at the bond interfaces, an actuator 64 is provided within the internal cavity 14 of the blade shell 10 between the two shear webs 28', 30'.

In common with the previous examples, the actuator 64 is configured to provide a motive force on the shear webs 28', 30' in the chordwise direction during the process of bonding the shear webs 28', 30' to the blade 10. The actuator 64 allows the shear webs 28', 30' to be moved from their nominal position to an adjusted or modified position in order to appropriately compress the adhesive 31a, 31b at the bond interfaces between the shear webs 28', 30' and the mounting flanges 36', 38', 40', 42' integrated with the blade shell

12. In this example, the actuator 64 extends between the two shear webs 28', 30' and is capable of providing motive forces in opposite directions to the respective shear webs 28', 30'. The actuator 64 may be the same actuator as described in relation to the previous embodiments.

After the shear webs 28', 30' have been installed at their nominal positions within the internal cavity 14 of the blade 10, the actuator 64 is activated. As with the previous embodiments, activation of the actuator 64 causes the actuator 64 to extend its dimensions in the chordwise direction. When activated, the actuator 64 exerts an outward chordwise force on each shear web 28', 30'. Under the action of this motive force, each shear web 28', 30' moves outwardly towards respective mounting flanges 36', 38', 40', 42'. More specifically, the outer surfaces 78 of the shear webs 28', 30' are moved towards the inner surfaces 80 of the upstands 72 of the mounting flanges 36', 38', 40', 42'.

In this example, the shear webs 28', 30' are installed at an inclined nominal position and are rotated in opposite directions (as indicated by the arrows 90) under the action of the motive force to a substantially vertical adjusted position. The shear webs are shown in their adjusted positions in Figure 10a. In other examples, the shear webs may be installed in a vertical or near vertical nominal position. The adjusted position in other examples may be a non-vertical position.

As the shear webs 28', 30' are moved towards the mounting flanges 36', 38', 40', 42' under the action of the motive force, the adhesive 31a, 31b provided at the bond interfaces is progressively compressed between the outer surfaces 78 of the shear webs 28', 30' and the inner surfaces 80 of the upstands 72. The actuator 64 provides the necessary force to squeeze the adhesive 31a, 31b. The upstands 72 of the mounting flanges 36', 38', 40', 42' act as stops to limit the outward chordwise motion of the shear webs 28', 30'.

Once the shear webs 28', 30' are at their adjusted positions, the adhesive 31a, 31b is then cured. Heat may be applied to the adhesive 31a, 31b to accelerate the curing process. Optionally, the actuator 64 may then be removed from the blade cavity 14 as shown in Figure 10a. In some examples, the actuator 64 may be removed from the blade cavity 14 before the adhesive 31a, 31b is cured.

In summary, the shear webs 28', 30' are initially installed at a nominal position in which there may be a gap between the bonding surfaces 78, 80 at the bond interfaces and/or at which the adhesive 31a, 31b may not be compressed or may not be sufficiently compressed. Under the action of a substantially chordwise motive force, the shear webs 28', 30' may be moved to an adjusted chordwise position that provides sufficient compression of the adhesive 31a, 31b. The ability to move the shear webs 28', 30' in the chordwise direction allows an optimal bondline thickness to be obtained between the shear webs 28', 30' and the mounting flanges 36', 38', 40', 42' of the blade shell 10.

In this example, the shear webs 28', 30' are installed at inclined nominal positions with the lower edges 84 of the shear webs 28', 30' positioned closer to the mounting flanges 40', 42' of the windward half shell 16 compared to the separation between the upper edges 86 of the shear webs 28', 30' and the mounting flanges 36', 38' of the leeward half shell 18. However, it should be appreciated that in other examples, the shear webs may be installed at a different nominal position.

For example, the shear webs may be installed at inclined nominal positions with the upper edges of the shear webs positioned closer to the leeward mounting flanges compared to the separation between the lower edges of the shear webs and the windward mounting flanges.

Alternatively, a first shear web may be installed at an inclined nominal position with the lower edge closer to the windward mounting flange than the upper edge is to the leeward mounting flange. A second shear web may be installed at an inclined nominal position with the upper edge closer to the leeward mounting flange than the lower edges is to the windward mounting flange. The shear webs would then be rotated in the same direction to a substantially vertical adjusted position.

In other examples, the shear webs may be installed at substantially vertical nominal positions and translated in respective outward chordwise directions to their adjusted positions.

In the above-described example, the shear webs are bonded to the inner surfaces of the upstands of the mounting flanges. However, in other examples, the shear webs may be bonded to the outer surfaces of the upstands of the mounting flanges. In this case, the shear webs may be installed at nominal positions situated outwards of the mounting flanges. One or more actuators may be provided configured to provide an inward chordwise force to each shear web

As will be evident from the various examples discussed above, the present invention provides a method of making a wind turbine blade that ensures a good quality bond between the shear webs and the blade shell without significant wastage of adhesive. This is achieved by providing a chordwise motive force on the shear webs to reduce the bondline thickness between the shear webs and the blade shell. This force ensures that bondline thicknesses between the shear webs and the blade shell are sufficiently small that the provided adhesive is sufficiently compressed between the bonding surfaces. In addition, methods of the present invention allow varying blade shell thicknesses to be accommodated without the need to provide additional adhesive in the bondlines of thinner shell designs. Instead, optimal bondline thicknesses can be achieved in blade shells of varying thickness by adjusting the position of the shear webs relative to the blade shell, as described above. Thus, compared to the prior art, the present invention provides better quality bondlines and allows less adhesive to be used. The ability to use less adhesive in the bondlines advantageously reduces the cost and weight of the blades.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims. For example, more or fewer shear webs may be installed within the internal cavity of the blade and in this case, an appropriate number of actuators may be provided to apply chordwise motive forces to each shear web.

Whilst the actuators described in each of the above embodiments are configured to push the shear webs outwardly in the chordwise direction, in other embodiments the actuators may be configured to move the shear webs inwardly in the chordwise direction. For example, an actuator may be installed between the shear webs and configured to contract in length or otherwise reduce its chordwise dimensions when activated. In such 10 cases, the actuator would effectively pull the shear webs towards one another in the chordwise direction. This arrangement may be suited when using mounting flanges with the shear webs bonded to outer surfaces of the flanges. Alternatively or additionally, an actuator could be arranged between a shear web and the leading edge or between a shear web and the trailing edge of the blade. The actuator may be arranged to push or 15 pull the shear web when activated, by extending or contracting in length, in order to move the shear web away from or towards the respective edge.

Claims

A method of manufacturing a wind turbine blade (10), the method comprising the steps of in any suitable order:

(a) providing a wing shell (12) extending in a chord direction between a leading edge (20) and a trailing edge (22), the wing shell defining a substantially hollow interior (14);

(b) providing a bracing member (28, 30) within the interior of the wing shell;

(c) providing adhesive (31a, 31b) on an attachment surface (44, 46, 48, 50) of the bracing member (28, 30) and / or on an attachment surface of the wing shell (12); and (d) providing a moving force on the bracing member (28, 30) substantially in the chord direction so that the attachment surface (44, 46, 48, 50) of the bracing member is moved against the attachment surface of the wing shell and the adhesive (31a, 31b) is compressed therebetween ; characterized in that an actuator (64) is provided inside the interior (14) of the wing and is actuated to provide the moving force on the bracing member.

The method of claim 1, wherein the moving force provided in step (d) causes the bracing member (28, 30) to move toward the leading edge (20) or toward the trailing edge (22) of the wing shell (12).

A method according to claim 1 or claim 2, wherein the moving force provided in step (d) causes the stiffening member (28, 30) to rotate within the interior of the wing (14).

A method according to any one of the preceding claims, wherein step (b) comprises providing the bracing member (28, 30) within the wing (10) in an inclined orientation and step (d) comprises moving the bracing member against a substantially vertical orientation.

The method of claim 1, wherein the actuator (64) comprises a piston and / or a spring and / or an inflatable bladder.

The method of claim 5, wherein activating the actuator (64) comprises extending the piston and / or extending the spring and / or inflating the inflatable bladder.

The method of claim 1, wherein the actuator (64) is adapted to push at least a portion of the bracing member (28, 30) against the leading edge (20) or against the trailing edge (22) of the wing shell.

A method according to any one of the preceding claims, wherein:

step (b) comprises providing first and second bracing elements (28, 30) within the interior of the wing shell;

step (c) comprises providing adhesive (31a, 31b) on a first attachment surface of the first bracing member (28) and / or on a first attachment surface of the wing shell, and providing adhesive (31a, 31b) on a second attachment surface of the second bracing member (30) and / or on another attachment surface of the wing shell; and step (d) comprises moving at least a portion of the first bracing member (28) toward the leading edge (20) and / or moving at least a portion of the second bracing member (30) toward the trailing edge (22) of the wing shell.

The method of claim 8, further comprising providing the moving force between the first and second bracing members (28, 30).

A method according to claim 8 or claim 9, wherein the actuator (64) is arranged between the first and the second stiffening element (28, 30).

A method according to any one of the preceding claims, wherein the attachment surface of the wing shell (12) is defined by an inner surface

5 (24, 26) of the wing shell.

A method according to any one of the preceding claims, wherein one or more flanges (36 ', 38', 40 ', 42') are integrated in the wing shell (12), the one or more flanges comprising a part which protrudes into the interior of the wing shell and defines the attachment surface of the wing shell.

10

The method of claim 12, wherein the one or more flanges (36 ', 38', 40 ',

42 ') are T-shaped in cross section and a riser (72) of the T defines the attachment surface.

A method according to claim 12 or claim 13, wherein the moving force applied in step (d) causes the bracing member (28, 30) to move against

15 the attachment surface of a flange (36 ', 38', 40 ', 42').