Aerodynamic structure

Abstract

Provided is an aerodynamic structure for mounting to a surface of a wind turbine rotor blade, which aerodynamic structure includes a number of comb elements, a comb element including comb teeth arranged in a comb plane, wherein the comb plane of a mounted comb element is essentially perpendicular to the trailing edge of the rotor blade and to the airfoil surface of the rotor blade. A wind turbine rotor blade including at least one such aerodynamic structure, and a method of equipping a wind turbine rotor blade with such an aerodynamic structure, is also provided.

Claims

1. An aerodynamic structure for mounting to a surface of a rotor blade of a wind turbine, comprising: a plurality of comb elements, each comb element of the plurality of comb elements comprising a set of comb teeth extending from an inner mounting line to an outer terminating line, wherein inner ends of the comb teeth are disposed along the inner mounting line and outer ends of the comb teeth are disposed along the outer terminating line; wherein the set of comb teeth are stacked in a comb plane defined by the inner mounting line and the outer terminating line, each layer of comb teeth aligned with a neighboring layer of comb teeth; wherein the inner mounting line extends in a direction that is perpendicular to a trailing edge of the rotor blade and the outer terminating line extends in a direction that is perpendicular to an airfoil surface of the rotor blade.

2. The aerodynamic structure according to claim 1, wherein the plurality of comb elements are mounted to the airfoil surface of the rotor blade.

3. The aerodynamic structure according to claim 2, wherein the plurality of comb elements are arranged at intervals of 0.5 cm to 5 cm between the inner mounting line and the outer terminating line.

4. The aerodynamic structure according to claim 1, wherein additional comb elements are mounted onto a serration of a serrated trailing edge assembly of the rotor blade.

5. The aerodynamic structure according to claim 1, wherein the comb teeth are inclined at an angle in a range of 0° to 45° relative to the mounting surface.

6. The aerodynamic structure according to claim 1, wherein additional comb elements are mounted between serrations of a serrated trailing edge assembly of the rotor blade.

7. A wind turbine rotor blade comprising: at least one aerodynamic structure comprising: a plurality of comb elements, each comb element of the plurality of comb elements comprising a set of comb teeth extending from an inner mounting line to an outer terminating line, wherein inner ends of the comb teeth are disposed along the inner mounting line and outer ends of the comb teeth are disposed along the outer terminating line; wherein the set of comb teeth are stacked in a comb plane defined by the inner mounting line and the outer terminating line, each layer of comb teeth aligned with a neighboring layer of comb teeth; wherein the inner mounting line extends in a direction that is perpendicular to a trailing edge of the rotor blade and the outer terminating line extends in a direction that is perpendicular to an airfoil surface of the rotor blade.

8. The wind turbine rotor blade according to claim 7, wherein the airfoil surface is a suction side of the wind turbine rotor blade.

9. The wind turbine rotor blade according to claim 7, wherein the airfoil surface is a pressure side of the wind turbine rotor blade.

10. The wind turbine rotor blade according to claim 7, further comprising a series of serrations along the trailing edge, wherein the inner mounting line extends along a centre line of a serration.

11. The wind turbine rotor blade according to claim 7, further comprising a series of serrations along the trailing edge, and further comprising a serration comb element arranged between two adjacent serrations, wherein comb teeth of the serration comb element originate at an apex formed by the adjacent serrations, and wherein the comb teeth of a serration comb element terminate along a terminating line that is essentially perpendicular to a plane containing the serrations.

12. A method of equipping a rotor blade of a wind turbine with an aerodynamic structure, the method comprising: forming a comb element comprising a set of comb teeth extending from an inner mounting line to an outer terminating line, wherein inner ends of the comb teeth are disposed along the inner mounting line and outer ends of the comb teeth are disposed along the outer terminating line; wherein the set of comb teeth are stacked in a comb plane defined by the inner mounting line and the outer terminating line, each layer of comb teeth aligned with a neighboring layer of comb teeth; arranging the comb element on an airfoil surface of the rotor blade such that the comb plane is perpendicular to a trailing edge of the rotor blade and to the airfoil surface of the rotor blade.

13. The aerodynamic structure according to claim 1, wherein the set of comb teeth are stacked in the direction that is perpendicular to an airfoil surface of the rotor blade.

14. The wind turbine rotor blade according to claim 7, wherein the set of comb teeth are stacked in the direction that is perpendicular to an airfoil surface of the rotor blade.

15. The method according to claim 12, wherein the set of comb teeth are stacked in the direction that is perpendicular to an airfoil surface of the rotor blade.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

(2) FIG. 1 shows an embodiment of an aerodynamic structure;

(3) FIG. 2 shows an alternative embodiment of the aerodynamic structure of FIG. 1;

(4) FIG. 3 shows a further embodiment of the aerodynamic structure;

(5) FIG. 4 shows an alternative embodiment of the aerodynamic structure of FIG. 3;

(6) FIG. 5 shows an alternative realisation of a comb element;

(7) FIG. 6 shows a rotor blade of a wind turbine;

(8) FIG. 7 illustrates the development of turbulence over a rotor blade;

(9) FIG. 8 show a rotor blade of a conventional wind turbine with a serrated component attached to the rotor blade; and

(10) FIG. 9 illustrates the development of turbulence as a rotor blade moves in a direction of rotation.

DETAILED DESCRIPTION

(11) In the diagrams, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.

(12) FIG. 1 shows an embodiment of the inventive aerodynamic structure 1, attached to the suction side 20S of a wind turbine rotor blade 2. In this exemplary embodiment, the aerodynamic structure 1 comprises a number of triangle comb elements 10T arranged on a mounting means 11T in such a way that the comb elements 10 act as span-wise separators. These can be separated by a distance of 0.5-5 cm. The mounting means 11T has a depth or width 11W to accommodate the comb elements 10T, and is mounted at a distance 11D from the trailing edge TE of the rotor blade 2.

(13) Each triangle comb element 10T has a shape defined by an inner mounting line M and an outer terminating line T. Here, the mounting line M of each comb element 10T extends in a direction that is essentially perpendicular to the trailing edge TE of the rotor blade 2, and the terminating line T of each comb element 10T extends in a direction that is essentially perpendicular to the airfoil surface 20S of the rotor blade 2. In this exemplary embodiment, the mounting line M can extend over a length of 3-10 cm, for example, and the terminating line T can extend to a height of up to 4 cm.

(14) The rotor blade 2 also has a serrated trailing edge assembly, i.e. a series of serrations 30 is arranged along the trailing edge TE to reduce the aerodynamic noise arising from the flow of vortices past the rotor blade's trailing edge as it passes through the air. The drawing also shows additional in-plane comb elements 31 between neighbouring serrations 30, with the aim of further reducing the trailing edge noise.

(15) The triangle comb elements 10T are arranged evenly along the mounting means 11T, and are separated by a distance 10D. In this embodiment, there are about two span-wise separators per serration 30, arranged so that the mounting line M of every second comb element 10T extends along the centre lines 30C of a serration 30. Alternatively, up to ten such triangle comb elements 10T could be arranged along the mounting means for every serration 30 at the trailing edge TE.

(16) Instead of a single row of span-wise separators as shown here, the mounting means may carry two or more rows of span-wise separators. For example, one row of span-wise separators can be arranged upstream of a second row of span-wise separators. Alternatively, a staggered arrangement can be provided, in which the span-wise separators of a second row start in between the span-wise separators of a first row.

(17) Another version of this embodiment is shown in FIG. 2, which (for the sake of clarity) shows just one such comb element 10T per serration 30. The diagram also indicates the parallel arrangement of comb teeth 100 as these extend from the mounting line M to the perpendicular terminating line T. The comb teeth 100 or comb fibres 100 are essentially aligned with the main flow direction over the surface of the rotor blade 2. The diagram also shows a supporting rib 101 that acts to maintain the upright shape of a comb element 10T.

(18) In this embodiment, the mounting means 11T is attached to the airfoil surface 20S of the rotor blade in such a way that the terminating lines T of the comb elements 10T effectively intersect with the trailing edge TE of the rotor blade 2. On the left-hand side of the diagram, three intersecting planes PX, PY, PZ are shown. The comb plane 10P of a triangle comb element or span-wise separator 10T coincides with plane PZ, which is effectively perpendicular or orthogonal to plane PX of the airfoil surface 10S, and also to plane PY which contains the trailing edge TE and which is perpendicular to plane PX.

(19) FIG. 3 shows another embodiment, in this case with two rows of comb elements 10T mounted upstream of the trailing edge TE. For clarity, the diagram only indicates an outboard portion f a rotor blade 2. The comb elements 10T of one row are offset from the comb elements 10T of the other row. In this exemplary embodiment, the spacing between comb elements 10T decreases with increasing radial distance outward along the rotor blade 2. The size of the comb elements 10T can decrease towards the tip of the rotor blade. Of course, more than two rows of comb elements 10T may be used, and the rows need not comprise the same number of comb elements, and can comprise comb elements of different sizes.

(20) FIG. 4 shows another possible embodiment of the inventive aerodynamic structure. Again, two rows of comb elements 10T are shown. In this case, the comb elements 10T of the rows are mounted in line with each other. In this exemplary embodiment, the size of the comb elements 10T decrease with increasing radial distance outward along the rotor blade 2. In this embodiment, the mounting lines M of the comb elements 10T subtend a right angle to the trailing edge at the more inboard position, while the more outboard comb elements 10T have mounting lines M that subtend larger angles θ to the trailing edge TE.

(21) Of course, any combination of these embodiments can be used. For example, an arrangement of offset rows with relatively large comb elements and relatively large spacing intervals may be used in the more inboard part of the outermost blade half. Smaller comb elements at smaller spacing intervals may be used in the remainder of the outboard part of the rotor blade.

(22) FIG. 5 shows another embodiment, in which a row of span-wise separators are arranged along the trailing edge TE of a rotor blade 2. In this embodiment, a planar “canopy” 21 is also mounted to the suction side 20S of the blade 2 in order to assist in pushing the boundary layer away from the suction side of the blade 2. The canopy 21 is preferably inclined at a low angle β of less than 45° relative to the airfoil surface 20S. The canopy 21 and the arrangement of span-wise separators can be mounted on a common mounting means that is then attached to the airfoil surface 20S, or these can be mounted separately.

(23) Another version of this embodiment is shown in FIG. 6. Here, the span-wise separators are mounted on serrations 30 of a trailing edge assembly. The mounting means 11T in this case can be a triangular adhesive sheet that fits onto the outer surface of a serration 30. This diagram also shows an additional planar canopy 21 that can be mounted to the airfoil surface 20S, with the purpose of pushing turbulence away from the surface.

(24) FIG. 7 shows an alternative embodiment. Here, a fan-shaped comb element 10F is arranged between adjacent serrations 30 along the trailing edge TE of the rotor blade 2. The terminating line 12T of the fan comb element 10F is perpendicular to the plane of the serrations 30. The effect of such a fan comb element 10F is to further diffuse the turbulent flow between serrations 30, and such a fan comb element 10F can be used in any of the embodiments described above, for example in place of any in-plane comb elements between serrations 30 along the trailing edge TE. A fan comb element 10F can be formed so that all comb teeth originate at an apex between serrations or just upstream of such a point. A mounting means 11F can be any suitable means that can attach the comb element 10F between the serrations 30.

(25) FIG. 8 shows a rotor blade 2 of a wind turbine. The diagram shows the leading edge LE, trailing edge TE and suction side 20S. In the prior art, it is known to attach a serrated component 3 along a mounting length L of the trailing edge TE in the outboard part of the rotor blade. In the embodiments of the inventive aerodynamic structure 1 described above, the mounting means may be assumed to be attached in a direction parallel to the trailing edge TE over a similar mounting length L.

(26) FIG. 9 illustrates the development of turbulence as a rotor blade 2 moves in a direction of rotation. The diagram shows an initially laminar airflow F.sub.20s in the boundary layer over the suction side 20S of the rotor blade 2, and an initially laminar airflow F.sub.20P in the boundary layer over the pressure side 20P of the rotor blade 2. The boundary layer generally cannot remain stable, so that, as the airflow passes over the airfoil, trailing edge turbulence V.sub.TE develops. Acoustic noise is generated from the breakup of vortices in the turbulence region V.sub.TE.

(27) Although the diagrams mainly show an aerodynamic structure in place on the suction side of the rotor blade, it will be understood that an aerodynamic structure can—alternatively or in addition—be arranged on the pressure side. As explained above, the inventive aerodynamic structure acts to reduce the aerodynamic noise generated as a result of turbulence upstream of the trailing edge. Therefore, although some diagrams indicate a serrated trailing edge, it shall be understood that such a serrated trailing edge is not required by the inventive aerodynamic structure but can be implemented on account of its contribution in reducing trailing edge noise.

(28) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

(29) For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.