Rotor blade extension

Abstract

A wind turbine rotor blade extension fitting element, which extension fitting element is designed as a rotor blade rib with a recess and which can be pushed onto the rotor blade tip of a rotor blade to be extended, in such a way that the rotor blade tip protrudes through the recess and contacts the circumferential surface of the recess in an positive-locking manner. The extension fitting element has, on its outer circumference, an outer circumferential surface onto which a shell-like rotor blade extension can be pushed in an positive-locking manner. A core of the extension fitting element has slits and/or boreholes which, for stabilization, are filled with a material that has a higher strength and/or stiffness than the material of the core. In this way, the extension fitting element is strengthened for the transfer of high loads.

Claims

1. An extension fitting element for a rotor blade of a wind turbine, which extension fitting element is configured as a rotor blade rib with a recess and which can be pushed onto a rotor blade tip of a rotor blade to be extended, in such a way that the rotor blade tip protrudes through the recess and contacts a circumferential surface of the recess in a positive-locking manner, wherein the extension fitting element has, on its outer circumference, an outer circumferential surface onto which a rotor blade extension can be pushed in a positive-locking manner, wherein the extension fitting element has a core made of a lightweight construction material, and has, on the outer circumferential surface and/or on an inner circumferential surface, a coating made of a fiber-reinforced layered composite material comprising a composite of matrix material and reinforcement fibers, and wherein the core of the extension fitting element has recesses, which are filled with a material that has a higher strength and/or rigidity than the material of the core.

2. The extension fitting of claim 1, wherein the core is made of a foam or balsa wood.

3. The extension fitting of claim 1, wherein the recesses are slits and/or boreholes.

4. The extension fitting element according to claim 3, wherein the recesses, in the form of slits and/or boreholes, in a region which lies between flanges of the rotor blade in the event of use on a rotor blade to be extended, extend with their slit planes and/or longitudinal borehole axes transversely.

5. The extension fitting element according to claim 3, wherein the slits and boreholes, in the extension fitting element are positioned in such a way that, once the extension fitting element and the rotor blade extension have been installed, at least some of the slits and/or boreholes, are arranged in a region of load-bearing regions of a profile of the rotor blade to be extended between flanges of the rotor blade to be extended.

6. The extension fitting element according to claim 1, wherein an expansion of the extension fitting element in a direction of a longitudinal axis of the rotor blade is at least 20% of a greatest expansion of the extension fitting element in a pivot direction (t-direction) of the rotor blade.

7. The extension fitting element according to claim 1, wherein the recesses of the core are in the form of boreholes, a borehole longitudinal axes of which extend perpendicularly or at an angle between 90 and 45 degrees to the outer circumferential surface of the extension fitting element in a plane perpendicular to a chord of the extension fitting element and which are filled with a material that has a higher strength and/or stiffness than the material of the core.

8. The extension fitting element according to claim 1, wherein the recesses of the core comprise a plurality of boreholes of which a borehole longitudinal axes extend in a plane perpendicular to a chord of the extension fitting element and which in pairs enclose an angle of between 30 and 150 degrees, to one another and are filled with a material that has a greater strength and/or stiffness than the material of the core.

9. The extension fitting element according to claim 1, wherein at least some of the slits and/or boreholes, are arranged in load-bearing regions of the extension fitting element and in each instance extend as far as the coating on the outer or inner circumferential surface of the extension fitting element.

10. An extended rotor blade for a wind turbine with an original rotor blade and the extension fitting element according to claim 1 pushed onto said rotor blade, further comprising a rotor blade extension pushed onto the extension fitting element.

11. An extended rotor blade for a wind turbine with an original rotor blade and the extension fitting element according to claim 1 pushed onto said rotor blade, wherein the extension fitting element is connected to a rotor blade extension in such a way that the extension fitting element forms an integral part of the rotor blade extension.

12. An extended rotor blade for a wind turbine with a rotor blade to be extended and the extension fitting element according to claim 1 pushed onto said rotor blade, wherein the extension fitting element is connected to a rotor blade extension in such a way that the coating formed from the fiber-reinforced layered composite material on the outer circumferential surface of the extension fitting element forms a layer of the rotor blade extension.

13. A method for producing an extension fitting element for a rotor blade of a wind turbine, which extension fitting element is formed as a rotor blade rib with a recess and which can be pushed onto a rotor blade tip of a rotor blade to be extended, in such a way that the rotor blade tip protrudes through the recess and contacts a circumferential surface of the recess in a positive-locking manner, wherein the extension fitting element has, on its outer circumference, an outer circumferential surface onto which a rotor blade extension can be pushed in a positive-locking manner, wherein a core of the extension fitting element is firstly formed from a lightweight construction material, and in that then, starting from an inner and/or outer circumferential surface of the core, slits or boreholes are formed in the core, wherein slit planes extend transversely to a chord of the extension fitting element or borehole longitudinal axes extend in the direction of the slit planes thus defined, and in that the core is coated with a fiber-reinforced layered composite material comprising a composite of matrix material and reinforcement fibers, wherein the slits or boreholes are filled with an infusion.

14. The method according to claim 13, wherein the slits/boreholes as well as the recess and outer contour are removed using a saw, milling machine, ultrasonic cutter, or hot wire.

15. The method according to claim 13, wherein slits/boreholes, in an individual step or jointly with the reinforcement fibers of the coating, are infused using a vacuum assisted resin transfer molding (VARTM) method with an infusion material, including the matrix material.

16. The method according to claim 13, wherein the core of the extension fitting element is formed either from a block of a lightweight construction material by material removal or by foaming into a mold or by an additive production method.

17. The method according to claim 16, wherein the core of the extension fitting element is formed by an additive production method, wherein the slits and/or boreholes are left void during the additive production method or are produced directly by replacing an application head with another material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be shown and described hereafter based on figures of a drawing. In the drawing:

(2) FIG. 1 shows a perspective view of an extended rotor blade with the used coordinate system,

(3) FIG. 2 shows a perspective view of an extension fitting element,

(4) FIG. 3 shows a cross-sectional illustration of an extension fitting element perpendicularly to the z-direction,

(5) FIG. 4 shows a further cross-sectional illustration of an extension fitting element with a different arrangement of the reinforcement elements,

(6) FIG. 5 shows a further illustration of an extension element with a further arrangement of reinforcement elements,

(7) FIG. 6 shows a cross-sectional illustration of an extension fitting element perpendicularly to the t-plane, wherein boreholes which are filled with an infusion material are provided for reinforcement,

(8) FIG. 7 shows an illustration of a rotor blade extension with an integrated extension fitting element,

(9) FIG. 8 shows a view of the element from FIG. 7 from the direction denoted in FIG. 7 by VIII,

(10) FIGS. 9, 10, and 11 show a detailed view of a surface portion of an extension fitting element in cross-section with a slit in various stages of the production process, and

(11) FIG. 12 shows a perspective view of an extension fitting element which is packed in a vacuum film for infusion.

DETAILED DESCRIPTION

(12) FIG. 1 shows, in a perspective illustration, an extended rotor blade which has an original rotor blade 1 to be extended and also a rotor blade extension 2 and an extension fitting element 4. The extension fitting element is pushed onto the original rotor blade 1 to be extended and has the form of a rib, which surrounds the original rotor blade 1. The rib 4 extends around the front and the rear profile edge of the original rotor blade 1 and receives the original rotor blade in a recess.

(13) The rotor blade extension 2, which for example is joined together from two half-shells and constructionally may have a form similar to that of a conventional blade, is pushed onto the tip of the original rotor blade 1 and the extension fitting element 4. The rotor blade extension 2 may be adhesively bonded to the extension fitting element 4 on the outer circumferential surface of said element. The rotor blade extension 2 protrudes beyond the extension fitting element 4 in the direction of the rotation axis of the wind turbine and is rigidly connected in the region 3 (adhesive bonding region) to the original rotor blade 1, for example by a glued joint. The extension fitting element 4 may be connected to the original rotor blade 1 to be extended at the inner circumferential surface of the extension fitting element 4 likewise by adhesive bonding.

(14) For further orientation, a coordinate system with reference to the rotor blade in FIG. 1 is also shown for the other figures. The z-axis in this case points in the direction of the longitudinal axis of the rotor blade; the t-axis in the pivot direction, i.e. within the rotation plane of the rotor blades, and the s-axis in the impact direction, i.e. perpendicularly to z and t.

(15) An extension fitting element 4 is shown in FIG. 2 in a perspective view. It may have the form of an aerodynamic profile with an outer circumferential surface 5. The extension fitting element 4 may consist primarily of a lightweight construction material, such as balsa wood or a foam. The extension fitting element 4 has a recess 4a in the form of a through-opening, which is formed such that it positive-lockingly receives a region of the original rotor blade 1 to be extended. The recess 4a is surrounded by the inner circumferential surface 6 of the extension fitting element 4. In FIG. 2, a slit 7 is additionally shown by way of example, which penetrates the lightweight construction material of the extension fitting element and which is infused with a solidified infusion material for stabilization. The slit 7 is shown merely by way of example for the provided recesses in the lightweight construction material, and it is explained further below how a plurality of slits or other forms of recesses may be distributed on the extension fitting element in order to achieve an increased mechanical stability.

(16) The extension fitting element has two side faces 4b, 4c, which for example may be planar and which for example may also extend parallel to one another. The side faces may, however, also enclose an acute angle with one another.

(17) The expansion D of the extension fitting element, i.e. in the case of parallel side faces 4b, 4c the distance between them, in the case of non-parallel side faces the distance of the side faces from one another in the z-direction at the narrowest point, is at least 20%, in particular at least 30% or 40% or 50% of the expansion E of the extension fitting element in the t-direction (likewise measured at the narrowest point).

(18) FIG. 3 shows a cross-section through an extension fitting element 4, wherein the viewing direction lies in the z-direction of the coordinate system. In the figure, a coating 8 of the extension fitting element with a solid material, for example a resin material, is shown on the outer circumferential surface 5 and may also be fiber-reinforced. The fiber reinforcement may be uniaxial or multiaxial. The inner circumferential surface 6 of the extension fitting element 4 may also be provided, for example, with a coating 9, for example formed from a resin material, which likewise may be fiber-reinforced uniaxially or multiaxially.

(19) In FIG. 3, slits 7 are additionally shown, wherein in particular in the load-bearing region of the extended rotor blade, which is illustrated by a dashed rectangle 18, a plurality of slits distributed equidistantly in parallel with one another is shown, and wherein a first group of slits extends into the core and the lightweight construction material of the extension fitting element, perpendicularly to the core, starting from the inner circumferential surface 6, and wherein a second group of slits, likewise arranged equidistantly from one another, extends into the core of the extension fitting element, perpendicularly thereto, starting from the outer circumferential surface 5. The slits 7 are infused with a resin material, which may also be reinforced by fibers. Due to such an arrangement of the reinforcement elements created by the infusion, a particularly good strength and stiffness of the extension fitting element is achieved in the load-bearing regions. Corresponding infused slits may also be provided in the regions which are not primarily load-bearing regions. Since the slits open out as recesses in the core at the surface of the core/extension fitting element, they may be filled, for example during the course of the coating and application of a coating 8, 9, which may contain an infusion material, in particular they may be filled also with the same infusion material that is used for the coating. A good cohesion of the fillings in the recesses, which form reinforcement regions, with the coating is thus provided.

(20) The slits which extend into the core of the extension fitting element 4 from the outer circumferential surface 5 and the slits which extend into the core from the inner circumferential surface 6 of the extension fitting element may be offset from one another along the circumferential surfaces, in particular in each instance by half the distance provided between adjacent slits.

(21) In the region of the front and rear profile edge, there may also be provided recesses/slits which extend substantially perpendicularly on the inner or outer circumferential surface of the extension fitting element in this region. For the sake of clarity, the main flanges 10a, 10b of the rotor blade extension and also the main flanges 11a, 11b of the original rotor blade to be extended are shown in FIGS. 4 and 5 on the extension fitting element 4 in the position that they assume relative to the extension fitting element following installation of the rotor blade extension. In addition, a front edge flange 12 of the rotor blade extension and also a front edge flange 13 of the rotor blade to be extended and a rear edge flange 14 of the rotor blade extension and also a rear edge flange 15 of the rotor blade to be extended are shown.

(22) By way of example, slits are shown in FIG. 5 in the lightweight construction material 17 of the extension fitting element 4, at least some of which may also penetrate through the entire extension fitting element in some sections and may be filled with resin for stabilization. However, it is also possible, instead of the slits, to provide a multiplicity of boreholes, which extend parallel to one another in groups and together form a group of recesses which have the contour of a slit, wherein the slit thus formed is broken open.

(23) This structure is shown in more detail in FIG. 6 in a different cross section, which is considered from the axial direction t. In the figure, the extension fitting element 4 is shown with main flanges 10a, 10b of the rotor blade extension and also main flanges 11a, 11b of the original rotor blade. Boreholes 19 are formed in the core region of the extension fitting element, which is produced from the lightweight construction material 17, and extend at an angle of 45 degrees from the outer and inner circumferential surfaces 5, 6 of the extension fitting element and in a plane that lies parallel to the z-direction of the rotor blade. In this case, a first group of boreholes is inclined in a first direction by 45 degrees relative to a circumferential surface of the extension fitting element, and another group of boreholes is inclined by 45 degrees in the opposite direction, so that the boreholes of the various groups cross one another and penetrate through one another. In the shown example, the core region of the extension fitting element form a through-opening within the drawing plane, whose enveloping contour has the form of a continuous slot. Since the boreholes penetrate one another, they may advantageously be infused jointly, so that a cohesive reinforcement lattice is produced.

(24) FIGS. 7 and 8 show a structural integration of an extension fitting element 4 in a rotor blade extension 2. The number and arrangement of the slits within the extension fitting element may be provided in this variant in a manner similar to that shown with reference to FIGS. 3 to 6.

(25) The component shown in FIG. 7 may be prefabricated at the factory, so that this part including the extension fitting element 4 inside the rotor blade extension 2 may be pushed onto the rotor blade tip of the rotor blade 1 to be extended and may be adhesively bonded there.

(26) The connection between the core region of the extension fitting element 4 and the rotor blade extension 2, in particular the outer skin of the rotor blade extension 2, may be realized for example in that the lightweight construction material 17 from which the core of the extension fitting element 4 consists is introduced directly into the outer skin of the rotor blade extension 2, i.e. for example is foamed in or glued in. The assembly effort on site when attaching an extension to the rotor blades to be extended is hereby reduced.

(27) FIG. 8 shows a cross section of the rotor blade extension 2 with the extension fitting element 4 in the direction VII as shown in FIG. 7.

(28) A detail of the core material of an extension fitting element 4 is shown in each of FIGS. 9, 10 and 11, wherein in FIG. 9 the starting state once one or more slits 7 have been made in the core material is shown.

(29) In FIG. 10 it is shown that a coating 8 made of an infusion material has been applied to the surface of the extension fitting element 4 and at the same time has been introduced into the slits 7. In FIG. 11 it is additionally shown that one or more fiber layer(s)/laid scrim layer(s) may also be applied in or on the infusion material as reinforcement. The coating 8 and the filling of the slits/recesses may cure jointly.

(30) In FIG. 12 the possible structure and also the approach for vacuum infusion are shown. The outer and inner circumferential surface of the rib/the extension fitting element are covered in each instance with vacuum film and, at the ends thereof, as indicated by the dashed lines 20, 21, is connected with two layers of a vacuum-tight adhesive tape, in particular what is known as Tacky Tape, both at the outer and inner circumferential surface to form a tube in each case. At the end faces for both sides of the extension fitting element, vacuum film is trimmed in accordance with the inner and outer contour and is connected in a vacuum-tight manner along the dashed lines 22, 23 to the film tubes of the outer and inner circumferential surface via a vacuum-tight adhesive tape, in particular Tacky Tape. The extension fitting element is thus completely surrounded in a vacuum-tight manner by a vacuum film. A line 24 for extracting air may penetrate through the vacuum film at a profile edge, in particular the front profile edge. A vacuum line may be arranged on the extension fitting element along the profile edge.

(31) At the opposite profile edge, that is to say in the present example the rear profile edge, a sprue line 25 may be provided for introducing the resin, which line is guided out from the film in a vacuum-tight manner. Once the vacuum has been applied, the film adapts to the contour of the rib and closely reproduces the shapte of the infusion of the resin flowing in.