Reinforcement assembly for the bolted connection of the root of a wind turbine blade to a wind turbine hub and wind turbine comprising the same

Abstract

The present invention discloses a reinforcement assembly for the bolted connection of the root of a wind turbine blade to a wind turbine hub, said assembly comprising a first reinforcement or tongue (12), a second reinforcement or separator (16), and a third reinforcement or reinforcement bolt (20). The reinforcement assembly of the present invention may also comprise a fourth reinforcement or perimeter clamp (21) configured to be arranged along the outer wall of the blade (5) at the beginning of the root (6). The invention further discloses a wind turbine comprising a hub (1) with a pitch change bearing (2); a blade (5) attached by its root (6) to the pitch change bearing (2) by means of a bolted connection comprising a front stiffening plate (7) and a rear stiffening plate (8); and a reinforcement assembly according to the present invention.

Description

[0001] DESCRIPTION

[0002] REINFORCEMENT ASSEMBLY FOR THE BOLTED JOINT OF THE ROOT OF A WIND BLADE TO A WIND TURBINE HUB AND WIND TURBINE COMPRISING THE SAME

[0003] Field of technology

[0004] The invention falls within the energy sector, within wind energy, and more specifically referring to a wind turbine and the union of wind blades.

[0005] Specifically, it refers to the sector of wind turbines, which include a tower, a generator, a nacelle, and a rotor. The rotor includes a rotating hub with one or more wind blades. The rotor blades are attached to the hub by a blade root.

[0006] The connection at the root of a wind turbine blade is the subject of the present invention, a reinforcement assembly, to increase the service life of the connection at the root of a wind turbine blade. The present invention also relates to a wind turbine comprising the aforementioned reinforcement assembly.

[0007] State of the art

[0008] Wind turbine blades are connected to the rest of the turbine by a prestressed bolted connection between the blade root and the pitch bearing or bushing (the latter in the case of machines with passive stall control). This bolted connection consists of a large number of bolts (between 50 and 90 for blades between 1 MW and 2 MW, for example). Therefore, the failure of a single bolt does not lead to catastrophic failure of the blade, but it does cause it to stop working properly and overload the rest of the adjacent inserts and bolts.

[0009] Depending on the size of the blade, the stresses in the connection between the blade root and the hub change, being greater the larger the size of the blades, which means that the extreme events and fatigue cycle requirements to which said blades will be subjected must be taken into account, and in particular the maintenance of the connection between the blade root and the hub, all of which is a challenge in the design of said blade root and which has led to the fact that there are in fact a multitude of inventions that refer to and are aimed precisely at the manufacture and structure of said roots of the wind blades of wind turbines, in very different ways and thus we can refer to the publications of the inventions ES2940570T3, ES2934863T3, ES2905221T3 and ES2897951T3, among many others.

[0010] Similarly, there are different methods or devices for joining the wind turbine blade by the root to the pitch change bearing or hub, a union that is extremely important since it is also a point where loads are transferred from the blade to the hub, a union that is usually achieved with the combination of nuts screwed onto the bolts and that these in turn are found on one side joined to the blade compound also by different methods.

[0011] Due to the load transfer that these joints must withstand, and particularly the joining elements fixed to the blade root, which are subject to wear, which is verified at the blade root itself. This wear can ultimately lead to breakage or catastrophic failure, resulting in high costs for the wind turbine owner.

[0012] In this sense, there are already patents that aim to repair the root of a rotor blade of a wind turbine, as is the case of ES2870132T3 which consists of a whole procedure that involves the extraction of part of the material of the blade, affecting the structure of the blade itself, which in the present case that concerns us, the assembly object of the present invention, is totally external, without any drilling being carried out in the blade, nor is any new element being inserted into it, nor is its surface being extracted.

[0013] Since the assembly object of the present invention is preferably intended for a type of wind turbine that has a pitch change bearing, as well as hollow, corrugated metal inserts embedded inside the root laminate (with an internal thread where the bolt is screwed) that are joined to the blade by means of a mainly mechanical (corrugation) and partially chemical (resin) connection, in this case the length of the bolt is usually in the range of 400 mm.

[0014] In this type of joint, the problem of fatigue or wear manifests itself in the fact that some of the inserts, and very particularly the metal that is attached to the fiber, separate from the main body of the blade, causing that bolted joint to stop working properly, with the aforementioned overload on the rest of the inserts and adjacent bolts.

[0015] This process of wear or degradation can spread to such an extent that the blade ends up completely detaching from the wind turbine, which represents a catastrophic failure, which is what is intended to be avoided with the reinforcement assembly of the connection at the root of the wind turbine blade of a wind turbine object of the present invention.

[0016] The maintenance plans for wind blades include the inspection of said union between the wind blades and the pitch change bearing, knowing the large transmission loads to which they are subjected, so that within said maintenance task, and in the event of any failure alert of any of the inserts that may have separated, before these can even cause other types of cracks or damage, the assembly object of the present invention would be used in order to mitigate the risk of damage progression, as well as extending the life and effectiveness of the wind turbine itself and its parts, otherwise, it could be exposed to serious damage that could render the blade unusable (forcing its replacement by another and the interruption of electrical production, entailing a high economic cost), or even cause the complete destruction of the wind turbine.

[0017] Wind turbine blades are generally hollow, and at the root in particular, it is feasible to access both for the installation of the assembly object of the present invention, and for its permanent fixation, without creating problems in the production or operation of the wind turbine. They are also areas of very easy inspection and maintenance for competent personnel.

[0018] The present invention relates to a reinforcement assembly for the joint at the root of the wind turbine blade, which reinforces the joint without requiring the wind turbine blade to be dismantled, nor affecting the proper functioning of the wind turbine to which the assembly is installed, but rather guaranteeing its maintenance and extending its life.

[0019] The present invention also relates to a wind turbine comprising a reinforcement assembly according to the invention.

[0020] Brief description of the invention

[0021] For wind turbines in which the blades are attached to the rest of the turbine by means of a prestressed bolted connection between the blade root and the pitch bearing (or the hub in the case of machines with passive stall control), the connection basically consists, on the pitch bearing side, of a bolt, a washer, and a nut. On the blade side, there are different methods for joining the blade-composite screw. In our case, we will refer to those blades in which the hollow, corrugated metal inserts, with internal threads into which the threaded bolt is screwed, are preferably joined to the blade by means of either a mechanical bond (corrugation) or a chemical bond (resin).

[0022] In this type of wind turbines with these joints, over time and due to the wear and tear to which this joint, which supports large loads, is subjected, it has been possible to determine how this wear leads in certain cases to some inserts that are made of metal and that are attached to the composite, becoming separated from the main body of the blade, which causes this bolted joint to stop working properly, overloading the adjacent inserts and bolts.

[0023] The present invention provides a solution to mitigate the risk of progression of the damage described, reducing the stress that exists in the original screwed joint, in the threaded bolt, but above all in the joint between the metal insert and the composite material that contains the blade at the root.

[0024] The present invention discloses a reinforcement assembly for the connection at the root of the wind turbine blade according to claim 1.

[0025] Preferred embodiments are the subject of dependent claims.

[0026] The present invention also provides a wind turbine according to claim 6. Preferred embodiments are the subject of dependent claims.

[0027] The assembly object of the present invention consists of making a deviation in the transmission of the load that is produced at that point between the blade and the pitch change bearing using for this purpose a path parallel to the original or initial bolted joint, not diverting the entire load that is transmitted at that point, but rather reducing the load that was being produced by the original path in order to thus increase the useful life of the blade, by not transmitting said loads to the adjacent inserts and bolts.

[0028] The reinforcement assembly of the connection at the root of the wind turbine blade of a wind turbine object of the present invention is installed between the hub, the pitch change bearing, with its corresponding cooling plates, and the hollow blade of the wind turbine and for this purpose there is a combination of three reinforcement elements which are mainly:

[0029] First reinforcement or language.

[0030] Second reinforcement or separator.

[0031] Third, a reinforcement bolt.

[0032] These elements have the structure and are arranged in a very specific way and position in the joint to be able to provide this load deflection. As a first reinforcement, there is a tongue that at its upper part joins with the wall of the root of the inner part of the blade, for example, approximately one meter in length, aligned with the root of the blade and parallel to the junction of the threaded bolt of the insert, which at one end has a front plate along its entire edge perpendicular, i.e. at 90° and said angle is maintained by means of brackets. In turn, this front plate has a hole through which the reinforcement bolt passes, joining it to the protruding lower part of the front stiffening plate that is arranged at the junction between the root of the blade and the inner race of the pitch change bearing.

[0033] The pitch change bearing has two stiffening plates joined to the sides of its inner race, a front stiffening plate located at the top at the junction between the root of the blade and the lower race of the pitch change bearing and another rear stiffening plate which is located on the opposite side also joined at the top to the lower race of the pitch bearing, both plates in parallel have holes to allow the reinforcement bolt of the union to pass through.

[0034] In the space separating the two stiffening plates, front and rear, which corresponds to the width of the lower race of the pitch change bearing, there is a second reinforcement consisting of a separator with two parallel walls, a first of said parallel walls being in contact with the front stiffening plate and a second of said parallel walls being in contact with the rear stiffening plate. Each of the parallel walls comprises a hole facing a corresponding hole already provided in these stiffening plates. Said parallel walls can be joined by a "II" structure on three of their sides, leaving one of them free, which is the lower side used to inspect the reinforcement bolt, and aligned both in direction and position with the parallel bolted connection that is fixed to the tongue.The purpose of this separator is to prevent the plates from collapsing under the pretension of the joint and to prevent the blade pitch bearing from being overloaded due to said pretension.

[0035] As a third reinforcement, a reinforcement bolt is proposed that passes through the front plate of the tongue, passes through the front stiffening plate, through the parallel walls of the separator and exits through the rear stiffening plate, and is fixed with a washer and a nut on this rear stiffening plate on the side of the hub, to join the entire assembly, establishing a prestressed bolted joint parallel to the one originally designed for the blade.

[0036] Finally, a fourth reinforcement can be provided, as a complementary but unnecessary addition: a perimeter clamp along the outer wall of the blade at the root tip. This clamp exerts compression on both the outer wall and the root core, as well as on the outer laminate. This also reduces the peeling stress that occurs in the laminate and thus prevents the spread of possible delaminations along the blade. This clamp is divided into at least two sections to facilitate installation, and the pretension is achieved through the connecting elements of the different sections.

[0037] By means of this assembly, object of the present invention of reinforcement of union in the root of the wind blades of a wind turbine, as has been indicated, a deviation is made in the transmission of the load that occurs at that point between the blade and the pitch change bearing using the assembly that confers a transmission path in parallel to the original or initial bolted union, in addition to the fact that with the pressure that is produced between the walls of the root of the blade from the outside with the clamp, the peeling stress that appears in said root of the blade is reduced, which guarantees the correct operation, as well as the safety and an increase in the life of the wind turbine.

[0038] As many sets of the tongue joint assembly, spacers and reinforcement bolts as are considered appropriate and necessary in each case may be arranged.

[0039] Brief description of the drawings

[0040] The various parts and arrangements of the wind turbine blade root reinforcement assembly, which is the subject of the present invention, as well as of a generator according to the present invention, are explained below by means of the drawings. This complements the specification and illustrates the preferred example, but in no way limits the invention.

[0041] Figure 1 shows an arrangement of the set of wind turbines for which the reinforcement assembly of the connection at the root of the wind turbine blade is intended, of which the hub (1) has a pitch change bearing (2) in which its outer race (3) is directly connected to the hub (1) and its inner race (4) is connected to the wind blade (5) by its root (6), arranging a front hygidizing plate (7) at the junction between the blade (5) by its root (6) and the inner race (4) of the pitch change bearing (2) and another rear hygidizing plate (8) also connected to the opposite side of the inner race (4) of the pitch change bearing (2).

[0042] Figure 2 shows the assembly of the metal insert (9) to which the threaded bolt (10) is screwed, which is attached to the blade (5) by the mechanical connection with the metal insert (9) and by the resin (11), in which the bolt at the other end is attached to the rear stiffening plate (8) of the pitch change bearing (2).

[0043] Figure 3 shows a top view of the first tongue reinforcement (12) with the front plate (13) and the bracket (14).

[0044] Figure 4 shows a bottom view of the first reinforcement of the tongue (12), showing the brackets (14) of the front plate (13) with the passage hole (15).

[0045] Figure 5 shows a top view of the second separator reinforcement (16) in which its parallel side walls (17) and its through holes (18) and its structure (19) can be seen.

[0046] Figure 6 shows a bottom view of the second separator reinforcement (16) in which it can be seen how the parallel side walls (17) are joined by a “U” structure (19) on three of its sides, leaving the bottom side open.

[0047] Figure 7 shows a bottom view of the assembly of Figure 1 in which the elements of the first reinforcement of the tongue (12) have been incorporated into the interior (22) of the blade (5) and the second reinforcement of the separator (16) in the space between the front stiffening plate (7) and the rear stiffening plate (8) under the inner race (4) of the pitch change bearing.

[0048] (2).

[0049] Figure 8 is a view of a vertical section at the height of the passage of the bolts, which very specifically shows the reinforcement bolt (20) as a third reinforcement to join the entire reinforcement assembly in parallel to that originally designed for the blade (5), from the rear stiffening plate (8) passing through the separator (16) as a second reinforcement, the front stiffening plate (7), the front plate (13) of the tongue (12) at the height of the root (6) of the blade (5).

[0050] Figure 9 is a top view of the assembly with the same elements as the previous figure 7, which very specifically shows the fourth reinforcement of the perimeter clamp (21) along the outer wall of the blade (5) at the beginning of the root (6).

[0051] Below is a list of the different elements represented in the figures that make up the invention:

[0052] (1) Bushing.

[0053] (2) Pitch change bearing.

[0054] (3) Outer race of pitch change bearing (2).

[0055] (4) Inner race of the pitch change bearing (2). (5) Wind blade.

[0056] (6) Root of the blade (5) wind.

[0057] (7) Front stiffening plate.

[0058] (8) Rear stiffening plate.

[0059] (9) Metal insert.

[0060] (10) Threaded stud in the metal insert (9).

[0061] (11) Resin.

[0062] (12) Language as first reinforcement.

[0063] (13) Perpendicular front plate at one end of the tongue (12).

[0064] (14) Tongue square (12) to join the plate (13) at 90°.

[0065] (15) Hole for the reinforcement bolt (20) in the plate (13).

[0066] (16) Separator as a second reinforcement.

[0067] (17) Parallel side walls of the separator (16) carrying the through holes (18).

[0068] (18) Through holes in the parallel side walls (17) of the separator (16).

[0069] (19) “II” structure that joins the parallel side walls (17) of the separator (16).

[0070] (20) Reinforcement bolt as third reinforcement.

[0071] (21) Perimeter clamp as a fourth reinforcement.

[0072] (22) Inner part of the blade (5)

[0073] (23) Parallel and opposite holes of the front plate (7) and rear plate (8)

[0074] Detailed description of the invention and some embodiments

[0075] The following details, with specific examples and drawings, show how the invention is best embodied in order to define and illustrate its concept, for the purpose of facilitating understanding. Changes and modifications may be made to improve the present invention, but always within the context of the invention.

[0076] The reinforcement assembly of the union at the root (6) of the wind turbine blade (5) object of the present invention, is installed in parallel to the original or initial bolted union, between the hub (1), the pitch change bearing (2) and the hollow blade (5) of the wind turbine and for this purpose the combination of the following reinforcement elements is available, such as: First reinforcement or tongue (12); Second reinforcement or separator (16); Third a reinforcement bolt (20); Fourth reinforcement clamp (21).

[0077] These elements are arranged, have the following structure and configuration:

[0078] All the reinforcements described are metallic or made of other material with similar characteristics. The first reinforcement of the tongue (12), of a length of approximately one meter, which at its upper part is joined with the wall of the root (6) of the inner part (22) of the blade (5) and in parallel to the union of the threaded bolt (10) of the insert (9) as an original screwed union. Tongue (12) that at the end closest to the pitch change bearing (2) has a front plate (13) joined along its entire edge perpendicularly, that is to say at 90°, and that said angle is maintained by means of brackets (14) arranged in the lower part of the tongue (12), in turn the front plate (13) has a hole (15) through which the reinforcement bolt (20) passes that joins it to the lower protruding part of the front stiffening plate (7) that is located at the junction between the root (6) of the blade (5) and the inner race (4) of the pitch change bearing (2).

[0079] The pitch change bearing (2) on the sides of its inner race (4) has a front stiffening plate (7) joined at its top to the pitch change bearing (2) and to the root (6) of the blade (5) and in parallel another rear stiffening plate (8) which is joined on the opposite side also at its top to the lower race (4) of the pitch bearing (2), both front (7) and rear (8) stiffening plates have parallel holes (23) to allow the reinforcement bolt (20) of the union to pass through.

[0080] In the space separating both front (7) and rear (8) stiffening plates below the lower race (4) of the pitch change bearing (2), there is a second reinforcement consisting of a separator (16) with two parallel side walls (17). One of said parallel side walls (17) is in contact with the front stiffening plate (7) and the other parallel side wall (17) is in contact with the rear stiffening plate (8). Said front (7) and rear (8) stiffening plates are joined to said parallel side walls (17) by means of a structure (19) in the form of an inverted “U” such that the lower part is free, the separator (16) being aligned both in direction and in parallel position with the original screwed joint of the threaded bolt (10) of the insert (9) to which the tongue (12) is fixed.

[0081] As a third reinforcement, a reinforcing bolt (20) is provided which, passing through the front plate (13) of the tongue (12) and its hole (15), passes through the front stiffening plate (7), through the parallel walls of the separator (16) and the through holes (18) of its walls (17) and exits through the rear stiffening plate (8) and the parallel holes (23) that said plates have, joining and prestressing the assembly.

[0082] A fourth perimeter clamp reinforcement (21) along the outer wall of the blade (5) at the beginning of the root (6), which is made up of at least two parts. Preferably, as many sets of the joining assembly of the set of tongues (12), separators (16) and reinforcement bolts (20) as necessary would be arranged.

[0083] By means of this reinforcement assembly at the junction of the root of the wind turbine blade of a wind turbine object of the present invention, the life of the wind turbine is extended, maintaining proper operation and providing greater safety for its components.

Claims

CLAIMS 1. Reinforcement assembly for the bolted connection of the root of a wind blade to a hub of a wind turbine, characterized in that said assembly comprises: a first reinforcement or tongue (12), a second reinforcement or separator (16) and a third reinforcement or reinforcement bolt (20), wherein: - The tongue (12), which at one of its ends has a front plate (13) joined perpendicularly to said tongue (12), the front plate (13) having a hole (15), said tongue (12) being configured for its connection on its outer part with a wall of the root (6) of the inner part (22) of the blade (5), the front plate (13) being configured for its connection to a front stiffening plate (7) of the bolted connection; - The separator (16) has two parallel side walls (17), each parallel side wall (17) having a through hole (18), said parallel side walls (17) being joined together by a structure (19), one of the two parallel side walls (17) being configured to be in contact with the front stiffening plate (7) and the other of the two parallel side walls (17) being configured to be in contact with a rear stiffening plate (8) of the bolted joint; - The reinforcement bolt (20) is configured to pass through the hole (15) of the front plate (13) of the tongue (12), to pass through the front stiffening plate (7) through a parallel hole (23), to pass through the separator (16) through the through holes (18) of its parallel side walls (17) and to pass through the rear stiffening plate (8) through a parallel hole (23); and to join and prestress the set of elements through which it passes.

2. Reinforcement assembly, according to claim 1, characterized in that it additionally comprises a fourth reinforcement or perimeter clamp (21) configured to be arranged on the outer wall of the blade (5) at the beginning of the root (6).

3. Reinforcement assembly, according to claim 2, characterized in that said perimeter clamp (21) is made up of at least two parts.

4. Reinforcement assembly, according to any of the preceding claims, characterized in that the tongue (12) has at least one bracket (14) attached to the front plate (13) and to the inner surface of the tongue (12).

5. Reinforcement assembly according to any of the preceding claims, characterized in that the two parallel side walls (17) of the separator (16) are joined together by a structure (19) in the form of an inverted “II”.

6. Wind turbine comprising: - a hub (1) with a pitch change bearing (2); - a blade (5) connected by its root (6) to the pitch change bearing (2) by means of a bolted connection comprising a front stiffening plate (7) and a rear stiffening plate (8); and - a reinforcement assembly according to any one of claims 1 to 5; wherein the tongue (12) is connected at its upper part to the root wall of the inner part of the blade (5) and the front plate (13) of the tongue (12) is connected to the front stiffening plate (7); wherein one of the two parallel side walls (17) of the separator (16) is in contact with the front stiffening plate (7) and the other of the two parallel side walls (17) is in contact with the rear stiffening plate (8); and in which the reinforcement bolt (20) passes through the hole (15) of the front plate (13) of the tongue (12), passing through the front stiffening plate (7) through a parallel hole (23), passing through the separator (16) through the through holes (18) of its parallel side walls (17) and passing through the rear stiffening plate (8) through a parallel hole (23); joining and prestressing the set of elements through which it passes.

7. Wind turbine, according to claim 6, characterized in that the blade is connected by its root to the pitch bearing by means of at least one threaded bolt (10) and at least one metal insert (9).

8. Wind turbine according to claim 7, characterized in that the spacer (16) is aligned with a threaded bolt (10).

9. Wind turbine according to claim 7 or 8, characterized in that the at least one threaded bolt (10) and the at least one metal insert (9) are joined to the root of the blade mechanically by corrugation and chemically by resin.

10. Wind turbine according to any one of claims 6 to 9, characterized in that the pitch change bearing (2) comprises an outer race (3) and an inner race (4); the front stiffening plate (7) and the rear stiffening plate (8) being connected to said inner race (4).

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