Method of rotating wind turbine blade

Abstract

The invention relates to a method and an assembly for rotating a wind turbine blade (10). The method includes providing a wind turbine blade (10) and determining a center of gravity (66) of the wind turbine blade (10). The first fixture (70) and the second fixture (80) are attached to different portions of the wind turbine blade (10) such that respective centers of the first fixture (70) and the second fixture (80) are aligned with a center of gravity (66) of the wind turbine blade (10) to define a common axis of rotation (90).

Description

Technical Field

[0001] The present invention relates to a method of rotating a wind turbine blade and an assembly for rotating a wind turbine blade, for example in the context of performing post-moulding operations. Background Art

[0002] Climate change has created an urgent need for sustainable energy, making wind energy a cost-effective and clean energy source. A wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades that capture the kinetic energy of the wind using the known airfoil principle. With the increasing demand for energy, modern wind turbines can have a rated power of more than 10 MW and can have rotor blades that are more than 100 meters in length.

[0003] Wind turbine rotor blades are typically made of fiber reinforced polymer materials and include a pressure side shell half and a suction side shell half, also called a blade half. The cross-sectional profile of a typical blade includes an airfoil for generating air flow to cause a pressure difference between the two sides. The resulting lift generates torque for generating electricity.

[0004] The shell halves of rotor blades are typically manufactured using a blade mold. First, a blade gel coat or primer is applied to the mold. Subsequently, fiber reinforcements and / or fabrics are placed into the mold, followed by infusion of resin. A vacuum is typically used to draw the epoxy resin material into the mold. Alternatively, prepreg technology may be used, in which fibers or fabrics pre-impregnated with resin form a uniform material that can be introduced into the mold. Several other molding techniques, including compression molding and resin transfer molding, are known for manufacturing wind turbine blades. The shell halves are assembled by gluing or bolting together substantially along the chord plane of the blade.

[0005] After the blade body is molded and removed from the blade mold, a number of post-molding operations are typically performed, which may require rotating the blade. These may include external blade surface grinding or coating operations. To this end, some known approaches rely on a blade cart that includes a rotatable frame to receive a portion of the molded wind turbine blade. The blade can thus be supported during the rotational movement, which can be performed using a set of rollers or drive wheels or by using a chain and pulley system.

[0006] Typically, such known devices include a root station and a corresponding tip station with rollers to assist in the rotation of the blade.Other known systems use a crane to lift and rotate the blade from two or more suspension points.

[0007] However, as wind turbine blades become longer and heavier, existing systems face significant challenges in terms of the force required to rotate the blades and keep the blades in the desired position. As modern blades can weigh over 50 tons, work safety may be compromised when using existing solutions.

[0008] It is therefore a first object of the present invention to provide a safer and more cost-effective way of rotating a wind turbine blade for post-molding operations.

[0009] Another object of the present invention is to provide a method and system for wind turbine blade rotation that is more flexible and more energy-saving. Summary of the invention

[0010] The present invention solves one or more of the above objects by providing a method of rotating a wind turbine component, preferably a wind turbine blade, comprising the following steps: providing a wind turbine component, preferably a wind turbine blade, determining a center of gravity of a wind turbine component, providing a first rotatable fixture and a second rotatable fixture, each fixture comprising a circular or partially circular periphery and a center, attaching a first fixing device to a first portion of the wind turbine component, Attaching the second fixture to the second portion of the wind turbine component such that the center of gravity of the wind turbine component is located between the first fixture and the second fixture, wherein respective centers of the first fixture and the second fixture are aligned with the center of gravity of the wind turbine component to define a common rotation axis, and rotating the wind turbine component about the common rotation axis by rotating the first fixture and the second fixture simultaneously.

[0011] Since modern wind turbine blades usually have a pre-bent, twisted and / or curved blade shape, the center of gravity of the entire blade is usually eccentric. This means that certain rotational positions of the blade about its longitudinal axis require a lot of force to stabilize the blade in said position or to rotate the blade into said position. It has been found that with the solution of the invention, there are almost no rotational forces, regardless of the rotational position of the blade. Thus, according to the arrangement of the invention, the blade can be easily and safely rotated by rotating the attached fixing device.

[0012] Moreover, the solution of the invention facilitates holding and fixing the blade in any given rotational position without applying the forces required by the known techniques, which results in a more energy-efficient and safer method. Thus, the blade is fully accessible in a post-molding operation, wherein, contrary to the known methods, no hydraulic equipment is required for the blade rotation.

[0013] It is particularly preferred that the wind turbine component is a wind turbine blade. The blade length is advantageously at least 40 meters, or at least 45 meters, or at least 50 meters, or at least 55 meters, preferably at least 60 meters. In other embodiments, the wind turbine component may be a tower or a part thereof, or a part of a wind turbine blade, such as a shell half or a shear web of a blade.

[0014] A wind turbine blade will typically be molded in a blade mold, where two blade halves are bonded to each other. Subsequently, the blade may be removed from the blade mold to perform one or more post-molding operations. In this context, the method of the invention is advantageously used to allow access to the blade from all sides.

[0015] The step of determining the center of gravity of a wind turbine component, preferably a wind turbine blade, is advantageously performed by calculation, for example using a CAD model. Alternatively or in addition, an experimental method may be used to determine the center of gravity of a wind turbine blade. For example, this experimental method may rely on a load cell system or a combination of a pivotable table and a force sensor, wherein the center of gravity position may be derived by moment measurements. Exemplary methods for determining the center of gravity position of a blade are disclosed in RU2224228C1, KR101496995B1 or in Noever-Castelos et al. Validation of a modeling methodology for wind turbine rotor blades based on a full-scale blade test (Wind Energ. Sci., 7, 105–127, 2022).

[0016] A first fixture and a second fixture are provided, each fixture comprising a circular or part-circular periphery and a geometric center. Preferably, the first fixture and the second fixture are substantially circular fixtures, i.e. having a substantially circular circumference or periphery. Thus, the first fixture and the second fixture preferably have a substantially circular cross-section.

[0017] The first fixture and the second fixture are advantageously rotatable about at least one axis passing through their respective centers. The center of a fixture having a circular perimeter is a point equidistant from each point on the circular perimeter. In some embodiments, the first fixture and the second fixture are formed as circular plates or circular frames. It is particularly preferred that the first fixture is a root end fixture mountable to the root end of the blade, preferably a circular root end fixture.

[0018] Preferably, the first and second fixtures are arranged to rotate, for example relative to the base, about a substantially horizontal axis, so as to change the orientation of the blade held in the fixture. Preferably, the blade is arranged in a substantially horizontal orientation when supported by the first and second fixtures. Thus, in this embodiment, the longitudinal axis of the blade will be substantially horizontal, or parallel to the floor surface. Preferably, when the blade is arranged in the first and second fixtures, the tip end of the blade is located 1 to 3 meters above the ground, regardless of the rotational position of the blade.

[0019] Preferably, the first fixing device is fixed to the root end of the wind turbine blade, in particular to a bolt circle at the root end of the blade. Typically, the root end of the blade is substantially circular and comprises a circular arrangement of axially extending fastening bolts, which can be used to attach the blade to the hub of the wind turbine. Therefore, in a preferred embodiment, the first fixing device comprises a circular arrangement of openings and / or bushings for receiving axially extending fastening bolts of the root end of the wind turbine blade to attach the first fixing device to the root end of the wind turbine blade. To this end, the bolts can be attached to the fixing device using corresponding nuts after passing the bolts through corresponding openings of the fixing device. Preferably, the circular arrangement of the openings and / or bushings of the first fixing device is eccentric with respect to the first fixing device, i.e. the center of the circular arrangement of the openings and / or bushings is offset from the center of the first fixing device. It has been found that this arrangement allows a particularly good alignment with the center of gravity of the pre-bent blade and thus an efficient blade rotation process.

[0020] Preferably, the second fixture is attached to a portion of the wind turbine blade closer to the tip end than to the root end of the blade. In a preferred embodiment, the second fixture comprises a first support having a support surface for receiving a pressure side of the wind turbine blade and a second support having a support surface for receiving a suction side of the wind turbine blade. At least one of the first support and the second support is selectively actuatable to engage with a surface of the wind turbine blade, preferably linearly actuatable, from a first retracted position in which the support is positioned away from the wind turbine blade received in the frame to a second advanced position in which the support abuts against the surface of the wind turbine blade received in the frame.

[0021] The center of gravity of the blade is located between the first fixture and the second fixture, wherein the respective centers of the first fixture and the second fixture are aligned with the center of gravity of the wind turbine blade to define a common axis of rotation. This can be achieved by designing the size and shape of the first fixture and the second fixture and the respective attachment structures or retaining means of the fixtures to determine the mounting position of the blade on the respective fixtures accordingly, i.e. such that all three points, i.e. the center of gravity of the wind turbine blade, the center of the first fixture and the center of the second fixture, fall on a single straight line, which is preferably substantially horizontal, corresponding to said axis of rotation.

[0022] Typically, due to the pre-bent, twisted and / or curved shape of modern wind turbine blades, the first fixture and the second fixture are designed such that they hold the respective blade portion in an eccentric position relative to each respective fixture. Consequently, the respective geometrical centres of the cross section of the blade at the first portion and the second portion will typically not coincide with the respective geometrical centres of the first fixture and the second fixture. It is therefore particularly preferred that the centre of the blade cross section at the first portion is offset from the centre of the first fixture. Likewise, it is particularly preferred that the centre of the blade cross section at the second portion is offset from the centre of the second fixture. Thus, in a particularly preferred embodiment, the blade rotation is eccentric relative to the centre of the circular blade root.

[0023] Then, by rotating the first fixture and the second fixture simultaneously, the wind turbine blade can be rotated about the common rotation axis, wherein the force required for rotation is minimal. Thus, the blade can be rotated clockwise or counterclockwise about the rotation axis, for example, between end positions approximately 180 degrees apart. This advantageously enables many post-molding operations to be performed, such as performing surface finishing, coating, painting, or performing inspection or repair processes. In a particularly preferred embodiment, the common rotation axis is a substantially horizontal axis. Once the desired rotating blade position is reached, the blade can be advantageously prevented from further rotation by preventing the first fixture and the second fixture from rotating, for example, by applying a brake or a triangular stop to secure the fixture to prevent accidental rotation. In other embodiments, a pin may be passed through a corresponding opening in the respective fixture and its base to prevent accidental rotation of the fixture.

[0024] Therefore, it is particularly preferred that the respective centres of the first and second fixing means and the centre of gravity of the wind turbine blade each lie on a common rotational axis, which is preferably oriented substantially horizontally.

[0025] In a preferred embodiment, the first portion of the wind turbine blade is spaced apart from the second portion of the wind turbine blade in the spanwise direction of the blade. The spanwise distance between the first portion and the second portion is preferably at least 10 meters, more preferably at least 20 meters, most preferably at least 30 meters. The first portion of the blade is preferably the root end of the blade. The second portion is preferably located within a length interval of 10% to 90%, more preferably within a length interval of 40% to 90%, of the length of the blade as calculated from the root end to the tip end, i.e. 0% is the root end and 100% is the tip end. Preferably, the second portion is closer to the tip end of the blade than to the root end of the blade.

[0026] In a preferred embodiment, each of the first fixture and the second fixture comprises a retaining device or attachment structure for releasably securing at least a portion of the wind turbine blade to the respective fixture. Preferably, the retaining device is adjustable to accommodate different blade sizes or can be attached to various locations along the wind turbine blade. In some embodiments, the retaining device of the second fixture comprises a substantially cushioned surface for engaging a surface of the wind turbine blade. In a preferred embodiment, the retaining device of the second fixture comprises a bracket or a set of claws.

[0027] In a preferred embodiment, the retaining means of the first fixture comprises a plurality of fastening members arranged along a circular or part-circular path. Particularly preferably, the first fixture comprises a plurality of bushings arranged along a circular or part-circular path. In a preferred embodiment, the circular or part-circular path is eccentric relative to the first fixture.

[0028] In a preferred embodiment, the first fixture comprises a circular plate. Preferably, the first fixture is shaped as a circular plate or disk, wherein the plate or disk is provided with a circular opening therein. The circular opening can advantageously be aligned with the circular opening of the blade at its root end, thereby allowing access to the internal parts within the blade. It is particularly preferred that the circular opening is eccentric with respect to the circular plate or disk of the first fixture, so that the center of the circular opening does not coincide with the center of the circular plate or disk. This design will allow access to the interior of the blade while allowing the center of gravity of the blade to be aligned with the corresponding centers of the first fixture and the second fixture. It is also preferred that the diameter of the substantially circular opening of the first fixture corresponds to the diameter of the substantially circular opening at the root end of the blade, so that the two openings can be aligned when the first fixture is attached to the blade.

[0029] In a preferred embodiment, the first fixture comprises a circular opening, wherein a plurality of apertures and / or fastening components (such as bushings) are arranged along a circular or part-circular path around the opening. Preferably, the center of the circular path coincides with the center of the circular opening offset from the center of the first fixture.

[0030] In a preferred embodiment, the second fixture comprises a frame having a circular perimeter. Thus, the second fixture may take the form of a circular frame with a plurality of frame rods extending between the circular perimeters. The second fixture preferably comprises a bracket or a set of claws engageable with the blade, preferably with a portion of the blade located at 50% to 100% of the length of the blade as viewed from the root end. Typically, the center of the cross-section of the portion of the blade engaged with the second fixture will be offset from the center of the second fixture. Thus, the rotation of the blade is typically an eccentric rotation relative to the second fixture. It is also preferred that the rotation of the blade is an eccentric rotation relative to the geometric center of the substantially circular cross-section of the blade at the root end of the blade.

[0031] In a preferred embodiment, the first fixture and / or the second fixture are rotatably arranged on a respective base part, wherein the base part preferably rests on a floor surface, such as a factory floor surface. Preferably, each of the first fixture and the second fixture is releasably mountable in or on its respective base part, wherein the base part is preferably fixed to the floor surface. Thus, one or both of the fixtures can be mounted to the blade in the blade mould, or after the blade has been lifted from the blade mould (e.g. using a crane), and then the blade with the fixture attached can be lowered into the respective base so that the first fixture and the second fixture are received in / on its respective base. Typically, when the blade is mounted in the first fixture and the second fixture, the blade cannot rotate relative to the fixture.

[0032] In a preferred embodiment, the corresponding base of the corresponding fixture comprises a plurality of rollers or drive wheels mounted on the base, wherein the first fixture or the second fixture is mounted on the rollers or drive wheels and is operable to rotate on the rollers or drive wheels. Therefore, preferably, the base is used to support the corresponding fixture so that the fixture can rotate relative to the base. In a preferred embodiment, each base may be provided with a drive wheel, which engages with a part of a circle or a circular periphery of the frame, such as by frictional engagement. In some embodiments, the base comprises a gear arrangement. The rollers or drive wheels of the base can be rotated by using a motor (such as an electric motor).

[0033] In some embodiments, the base comprises a plurality of trolley wheels operable to roll the base in any direction on the floor surface. Thus, the base and the supporting fixture may be used as a mobile unit movable between different locations.

[0034] In some embodiments, a third fixture may be attached to another portion of the blade, the third fixture having a circular or partially circular perimeter and a center. In this embodiment, the respective centers of the first fixture, the second fixture, and the third fixture are aligned with the center of gravity of the wind turbine blade to define a common axis of rotation. Rotation of the blade may then be achieved by rotating the first fixture, the second fixture, and the third fixture simultaneously.

[0035] In a preferred embodiment, the method further comprises the steps of attaching a clamping collar around a third portion of the wind turbine blade, the clamping collar comprising a circular or part-circular periphery and a center, wherein the center of the clamping collar and the respective centers of the first fixture and the second fixture are aligned with the center of gravity of the wind turbine blade to define a common rotation axis; removing the first fixture from the wind turbine blade; and rotating the wind turbine blade around the common rotation axis by rotating the second fixture and the clamping collar simultaneously. The third portion of the wind turbine blade is preferably located between the first portion and the second portion.

[0036] In a preferred embodiment, the clamping collar comprises an opening, preferably a substantially circular opening, for receiving a portion of the wind turbine blade therein, wherein the opening is eccentric with respect to the clamping collar. Thus, preferably, the center of the opening is offset from the center of the clamping collar.

[0037] In a preferred embodiment, the clamping collar comprises a first part and a second part, each part having a substantially semicircular periphery to define an opening therebetween. The first part and the second part are advantageously connectable to each other for closing the clamping collar around a third portion of the wind turbine blade. Thus, the clamping collar may be applied around the blade at the third blade portion, which is preferably located near the root end of the blade, preferably within the first 5% of the blade length as seen from the root end. Using the clamping collar provides an efficient way of replacing the function of the first fixing means with the clamping collar, for example in situations where a free root end of the blade is required during post-moulding operations. Thus, after the clamping collar has been applied to the blade, the first fixing means may be removed from the blade and blade rotation may be achieved by rotating the second fixing means and the clamping collar simultaneously.

[0038] In another aspect, the present invention relates to an assembly for a rotating wind turbine component, preferably a wind turbine blade, comprising A wind turbine component, preferably a wind turbine blade, a first fixing device and a second fixing device, each fixing device comprising a circular or part-circular periphery and a center, the first fixing device being attached to a first portion of the wind turbine component and the second fixing device being attached to a second portion of the wind turbine component, wherein the center of gravity of the component is located between the first fixture and the second fixture, and wherein respective centers of the first fixture and the second fixture are aligned with the center of gravity of the wind turbine component to define a common rotation axis for rotating the wind turbine component. The assembly is advantageously used to support the wind turbine component above a ground surface, for example for performing post-molding operations.

[0039] In a preferred embodiment of the assembly, the first fixture and / or the second fixture are rotatably arranged on a respective base member, wherein the base member preferably rests on a floor surface, such as a factory floor surface. The first fixture and the second fixture preferably have a circular perimeter and a diameter of 5-12 meters, more preferably 6-10 meters. In a preferred embodiment, each base member comprises a set of rollers or drive wheels for engaging and rotating a respective fixture arranged in the base member.

[0040] In the assembly of the invention, the common axis of rotation is preferably a substantially horizontal axis, which is preferably substantially parallel to a floor surface, such as a factory floor surface. Preferably, each of the first fixture and the second fixture of the assembly comprises a retaining device for releasably fastening at least a portion of the wind turbine blade to the respective fixture. In a preferred embodiment, the retaining device of the second fixture comprises a bracket or a set of claws. In another preferred embodiment, the retaining device of the first fixture comprises a plurality of openings and / or fastening components arranged along a circular or part-circular path. Preferably, the circular or part-circular path is eccentric with respect to the first fixture.

[0041] The first fixing means of the assembly may comprise a circular plate or a circular disc. The second fixing means of the assembly may comprise a circular frame. In a preferred embodiment, the assembly further comprises a clamping collar as described above, comprising a circular or part-circular periphery and a center, wherein the center of the clamping collar is aligned with the center of gravity of the wind turbine blade to define a common rotation axis.

[0042] In another aspect, the invention relates to an apparatus for turning or rotating a wind turbine blade having a substantially circular root end, the apparatus comprising a rotatable first fixture and a rotatable second fixture, each fixture comprising a circular or part-circular periphery, and each fixture comprising an attachment structure for attaching a portion of the wind turbine blade to the respective fixture, wherein the attachment structure of the first fixture is adapted to receive the circular root end of the blade such that the circular root end is eccentric relative to the first fixture. In other words, the geometric center of the circular cross-section at the root end of the blade is offset from the geometric center of the first fixture. It has been found that this enables particularly efficient turning / rotation of the wind turbine blade, wherein only a minimum of energy input is required to provide the turning / rotation movement.

[0043] The apparatus is advantageously used to support a wind turbine component, preferably in a substantially horizontal orientation, above a ground surface, for example for performing post-molding operations.

[0044] It should be understood that any embodiments and features described above with respect to the method of rotating a wind turbine component are equally applicable to the assembly and apparatus of the present invention, and vice versa.

[0045] As used herein, the term "longitudinal" refers to an axis or direction that is substantially parallel to the largest linear dimension of the element in question (eg, a wind turbine blade). BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention is explained in more detail below with reference to the embodiments shown in the accompanying drawings, in which: Figure 1 A wind turbine is shown, Figure 2 shows a schematic diagram of a wind turbine blade, Figure 3 Shown by Figure 4 Schematic diagram of the airfoil profile of Section II, Figure 4 A schematic diagram showing a wind turbine blade seen from above and from the side, Figure 5 is a schematic diagram of an assembly and method of rotating a wind turbine blade according to the present invention, Figure 6 shows a perspective view of an assembly according to the invention, Figure 7 is a more detailed perspective view of a second fixing device according to the present invention, Figure 8 is a more detailed perspective view of a first fixing device according to the present invention, Fig. 9 is a schematic end view of an assembly according to the invention in two different rotational positions, Fig.10 The clamping collar of the invention is shown in an open state and in a closed state, and Figures 11 to 13 Different stages of a method of using a clamping collar with the assembly of the invention are shown. DETAILED DESCRIPTION

[0047] Figure 1 A conventional modern upwind wind turbine according to the so-called "Danish concept" is shown, having a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor axis. The rotor comprises a hub 8 and three blades 10 extending radially from the hub 8, the blades each having a blade root 16 closest to the hub and a blade tip 14 farthest from the hub 8.

[0048] Figure 2 A schematic diagram of an embodiment of a wind turbine blade 10 according to the invention is shown. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profile or airfoil region 34 furthest from the hub, and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10 when the blade is mounted on the hub, and a trailing edge 20 facing in the opposite direction of the leading edge 18.

[0049] The airfoil region 34 (also referred to as the profile region) has an ideal or almost ideal blade shape with respect to generating lift, while the root region 30 has a substantially circular or elliptical cross section for structural considerations, for example, which makes it easier and safer to mount the blade 10 to the hub. The diameter (or chord) of the root region 30 can be constant along the entire root region 30. The transition region 32 has a transition profile that gradually changes from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 generally increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0050] The shoulder 40 of the blade 10 is defined as the location where the blade 10 has its maximum chord length. The shoulder 40 is generally provided at the boundary between the transition region 32 and the airfoil region 34.

[0051] It should be noted that the chords of different sections of the blade generally do not lie in a common plane because the blade can be twisted and / or bent (i.e. pre-bent), thereby providing the chord plane with a corresponding twisted and / or bent path, this is to compensate for the most common case of the local speed of the blade depending on the radius from the hub.

[0052] Figure 3 and 4 Parameters are plotted which serve to illustrate the geometry of a wind turbine blade according to the invention. Figure 3A schematic diagram of an airfoil profile 50 of a typical blade of a wind turbine is shown, wherein various parameters commonly used to define the geometry of an airfoil are depicted. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during use (i.e., during rotation of the rotor) generally face the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60, wherein the chord length c extends between the leading edge 56 and the trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from the symmetrical profile is given by the camber line 62, which is the center line passing through the airfoil profile 50. The center line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. The center line is along the center of these inscribed circles, and the deviation or distance from the chord 60 is called the camber f. Asymmetry may also be defined using parameters referred to as upper camber (or suction side camber) and lower camber (or pressure side camber), which are defined as the distance from the chord 60 to the suction side 54 and the pressure side 52, respectively.

[0053] The airfoil profile is usually characterized by the following parameters: chord length c, maximum camber f, location d of maximum camber f f , the maximum airfoil thickness t (which is the maximum diameter of the inscribed circle along the mid-camber line 62 ), the location d of the maximum thickness t t , and the nose radius (not shown). These parameters are usually defined as ratios to the chord length c. Thus, the local relative blade thickness t / c is given as the ratio between the local maximum thickness t and the local chord length c. In addition, the location of the maximum pressure side camber d p can be used as a design parameter, and of course, so is the location of maximum suction camber.

[0054] Figure 4 Other geometric parameters of the blade are shown. The blade has a total blade length L. Figure 3 As shown in FIG. 1 , the root end is located at position r=0, and the tip end is located at r=L. The shoulder 40 of the blade is located at position r=L W , and has a shoulder width W that is equal to the chord length at the shoulder 40. The diameter of the root is defined as D. The curvature of the trailing edge of the blade in the transition region can be defined by two parameters, namely, the minimum outer radius of curvature r o and the minimum inner radius of curvature r i , which are defined as the minimum radius of curvature of the trailing edge seen from the outside (or behind the trailing edge), and the minimum radius of curvature seen from the inside (or in front of the leading edge), respectively. Furthermore, the blade is provided with a prebend defined as Δy, which corresponds to an out-of-plane deflection from the pitch axis 22 of the blade.

[0055] Figure 5 It is a schematic diagram of the principle used in the present invention. It has been found that Figure 5As shown by the dashed lines in FIG, when the blade 10 is supported in a substantially horizontal position, the blade 10 can be easily rotated so that its center of gravity 66 is located on the center / rotational axis 90 of the imaginary / virtual tube or cylinder. The tube shown will generally not be part of the assembly of the present invention, but is shown only to illustrate the basic concept. This arrangement minimizes the force required to rotate the blade from any given rotational position to another. Figure 5 In the drawings, the fixing devices 70, 80 are shown in simplified form as annular components or annular disks.

[0056] Figure 6 1 is a perspective view of an assembly 100 for rotating a wind turbine blade 10 of the present invention using the above-described approach. The method of rotating a wind turbine blade 10 comprises the steps of providing a wind turbine blade 10 and determining its center of gravity 66. Advantageously, the center of gravity of the blade can be calculated, for example using a CAD model. A first fixture 70 and a second fixture 80 are then provided, each fixture comprising a circular or partially circular periphery 72, 82 and a center 71, 81, which are Figure 7 and Figure 8 Best seen in.

[0057] In the illustrated embodiment, the first fixture 70 comprises a circular plate 76 having a circular opening 78 that is eccentric relative to the circular plate 76; see Figure 8 and Fig. 9 The first fixing device 70 is mounted to the root end of the blade, which root end is generally of substantially circular cross-section; see e.g. Figure 2 , root end 17. To this end, the first fixing device 70 shown comprises a retaining device comprising a plurality of fastening members 75, which may be in the form of openings and / or bushings, or alternatively bolts, arranged along a circular or part-circular path 74 around an opening 78. Thus, as Figure 8 As can be seen in FIG. 7 , the circular path 74 is also off-center relative to the first fixture 70. Fig. 9 As shown in , the opening 78 in the first fixture may be aligned with the circular opening at the root end of the blade, wherein the center of the opening 78 is offset from the center of the first fixture, and thus from the axis of rotation.

[0058] The root end of the blade typically also comprises a bolt circle, or a circular arrangement of bushings, which is used to secure the root end of the blade to the hub. Advantageously, this arrangement can be used to detachably connect the first fixing device to the root end of the blade, for example by using a plurality of bolts.

[0059] Similarly, the second fixture 80 comprises a retaining device 84 in the form of a bracket 84 for releasably securing a portion of the wind turbine blade 10 proximate the tip end thereof to the fixture; see Figure 7Furthermore, the second fixture 80 comprises a circular frame 85. Furthermore, it is preferred that the first fixture 70 and / or the second fixture 80 are rotatably arranged on the respective base components 73, 83, each base component comprising a set of drive wheels or rollers 77a, 77b, 87a, 87b, which can be used to rotate the respective fixture on the base. Furthermore, as Figure 7 and Figure 8 As shown in , both of the fixtures 70 , 80 have a center 71 , 81 .

[0060] The first fixture 70 and the second fixture 80 are attached to the wind turbine blade 10 such that the center of gravity 66 of the blade 10 is located between the first fixture 70 and the second fixture 80, wherein the respective centers 71, 81 of the first fixture 70 and the second fixture 80 are aligned with the center of gravity 66 of the wind turbine blade 10 to define a common rotation axis 90. This enables the wind turbine blade 10 to be rotated about the common rotation axis by rotating the first fixture 80 and the second fixture 80 simultaneously with the minimum force required. Preferably, as Figure 6 As shown in , the common axis of rotation 90 is a substantially horizontal axis, which shows the assembly standing on a floor surface 110 (eg, a factory floor).

[0061] Fig. 9 The alignment of the invention is further illustrated in the end view of FIG, which shows a view from the root end of the blade or from the first fixture 70 in two different rotational positions; see a) and b). For illustration purposes, the portion of the blade between the first fixture and the second fixture has been removed. Also, for simplicity, the corresponding base of the fixture has been omitted in this figure. The root end of the blade is attached to the first fixture 70 using a circular arrangement 74 of fastening members 75. As shown in FIG. Fig. 9 As can be seen in FIG. 1 , the center of gravity 66 of the blade 10 is perfectly aligned with the corresponding centers of the first fixture 72 and the second fixture, a portion of which is shown in dotted lines. Thus, all three points lie on a line forming the axis of rotation of the arrangement. Fig. 9 b shows that the blade has been Fig. 9 The rotational position of a is a rotational position of about 180 degrees clockwise or counterclockwise about the axis of rotation. Thus, it is seen that the blade rotation is eccentric relative to the center of the circular blade root.

[0062] Fig.10 A clamping collar 92 is shown which may be used in one embodiment of the rotation method of the present invention. The clamping collar includes a first member 93 and a second member 94, each member including a substantially semicircular perimeter 98, the first member 93 and the second member 94 defining an opening 97 therebetween. Fig.10The first component 93 and the second component 94 can be connected to each other for closing the clamping collar around the third portion of the wind turbine blade. The opening 97 is designed for receiving a portion of the wind turbine blade 10, i.e., clamping and closing a portion of the wind turbine blade between the first component 93 and the second component 94. Fig.10 As best shown in b, the opening 97 is off-center relative to the clamping collar 92, wherein the center of the opening is offset from the center 96 of the clamping collar.

[0063] like Figure 11-13 As shown in , a clamping collar 92 is attached around a third portion of the wind turbine blade 10, preferably close to or adjacent to the first fixture, but slightly moved away from the root end of the blade. Preferably, the third portion of the blade to which the clamping collar is attached is located between the first portion and the second portion to which the first fixture and the second fixture are attached. The clamping collar includes a circular periphery 95 and a center 96, wherein the center 96 of the clamping collar and the corresponding centers of the first fixture 70 and the second fixture 80 are aligned with the center of gravity 66 of the wind turbine blade 10 to define a common rotational axis.

[0064] like Fig.12 and 13 , the first fixture 70 is then removed from the wind turbine blade 10 to allow the wind turbine blade 10 to be rotated about the common rotation axis by simultaneously rotating the second fixture 80 and the clamping collar 92. This therefore provides an efficient way of replacing the functionality of the first fixture by the clamping collar 92, for example in situations where the free root end of the blade is required during post-molding operations.

[0065] The invention is not limited to the embodiments described herein and may be modified or varied without departing from the scope of the invention.

[0066] Reference Mark List 2 Wind Turbines 4 Tower 6 Cabin 8 hub 10 blades 14 Leaf Tips 16 Blade root 18 Front Edge 20 Back Edge 22 Pitch axis 30 Root Zone 32 Transition Area 34 Airfoil area 40 Shoulder / Maximum Chord Location 50 Airfoil Profile 52 Pressure side 54 Suction side 56 Front Edge 58 trailing edge 60 chord 62 crown line / center line 66 Blade center of gravity 70 First Fixing Device 71 Center of the first fixture 72 Circular perimeter of the first fixture 73 Base member of the first fixing device 74Circular path for fastening components 75 Fastening parts 76 round plate 77 roller 78 opening of the first fixing device 80 Second Fixing Device 81 Center of the second fixture 82 Circular perimeter of the second fixture 83 Base member of the second fixing device 84 bracket 85 round frame 87 roller 90 degree rotation axis 92 clamping ring 93 First part of the clamping collar 94 Second part of the clamping collar 95Circular circumference of the clamping collar 96 Center of clamping collar 97 Clamping collar opening 98 semicircular perimeter 99 semicircular perimeter 100 components 110 Floor Surface c Chord length d t Location of maximum thickness d f Position of maximum camber d p Maximum pressure side camber position f Camber L Blade length r local radius, radial distance from the blade root Thickness △y pre-bend

Claims

1. A method of rotating a wind turbine blade (10), comprising the following steps providing a wind turbine blade (10), determining a center of gravity (66) of the wind turbine blade (10), A first fixing device (70) and a second fixing device (80) are provided, each fixing device comprising a circular or part-circular periphery (72, 82) and a center (71, 81), attaching the first fixing device (70) to a first portion of the wind turbine blade (10), attaching the second fixture (80) to a second portion of the wind turbine blade (10) such that the center of gravity (66) of the blade (10) is located between the first fixture (70) and the second fixture (80), wherein respective centers of the first fixture (70) and the second fixture (80) are substantially aligned with the center of gravity (66) of the wind turbine blade (10) to define a common rotation axis (90), and By rotating the first and second fixing devices (80) simultaneously, the wind turbine blade (10) is rotated about the common rotation axis.

2. The method according to claim 1, wherein the first fixing device (70) and / or the second fixing device (80) are rotatably arranged on the respective base part (73, 83).

3. A method according to claim 1 or claim 2, wherein the common axis of rotation (90) is a substantially horizontal axis.

4. The method according to any of the preceding claims, wherein each of the first fixing device (70) and the second fixing device (80) comprises holding means (74, 84) for releasably fastening at least a portion of the wind turbine blade (10) to the respective fixing device.

5. The method according to claim 4, wherein the retaining means of the second fixing device (80) comprises a bracket (84) or a set of claws.

6. Method according to claim 4 and claim 5, wherein the retaining means of the first fixing means (70) comprises a plurality of openings and / or fastening members (75) arranged along a circular or part-circular path (74).

7. The method of claim 6, wherein the circular or part-circular path (74) is eccentric relative to the first fixture (70).

8. Method according to any one of the preceding claims, wherein the first fixing device (70) comprises a circular plate (76).

9. Method according to any one of the preceding claims, wherein the second fixing device (80) comprises a circular frame (85).

10. The method according to any one of the preceding claims, further comprising the following steps attaching a clamping collar (92) around a third portion of the wind turbine blade (10), the clamping collar comprising a circular or part-circular perimeter and a center, wherein the center of the clamping collar and the respective centers of the first fixture (70) and the second fixture (80) are aligned with the center of gravity (66) of the wind turbine blade (10) to define a common axis of rotation, removing the first fixing device (70) from the wind turbine blade (10), and By rotating the second fixing device (80) and the clamping collar simultaneously, the wind turbine blade (10) is rotated about the common rotation axis.

11. The method of claim 10, wherein the clamping collar comprises an opening (97) for receiving a portion of the wind turbine blade (10) therein, wherein the opening (97) is eccentric with respect to the clamping collar.

12. A method according to claim 10 or claim 11, wherein the clamping collar comprises a first part (93) and a second part (94), the first part (93) and the second part (94) defining an opening (97) therebetween, wherein each of the first part (93) and the second part (94) comprises a substantially semicircular perimeter.

13. An assembly (100) for rotating a wind turbine blade (10), the assembly comprising A wind turbine blade (10), A first fixture (70) and a second fixture (80), each fixture comprising a circular or part-circular periphery (72, 82) and a center (71, 81), the first fixture (70) being attached to a first portion of the wind turbine blade (10) and the second fixture (80) being attached to a second portion of the wind turbine blade (10), wherein a center of gravity (66) of the blade (10) is located between the first fixture (70) and the second fixture (80), and wherein respective centers of the first fixture (70) and the second fixture (80) are substantially aligned with the center of gravity (66) of the wind turbine blade (10) to define a common rotation axis for rotating the wind turbine blade (10).

14. Assembly (100) according to claim 13, wherein the first fixing device (70) and / or the second fixing device (80) are rotatably arranged on the respective base part.

15. The assembly (100) of claim 14, wherein each base component includes a set of rollers or drive wheels for engaging and rotating a corresponding fixture disposed in the base component.

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