Vortex generator for a wind turbine

Abstract

A blade for a wind turbine having an airfoil with a thickness of at least 20% and in particular at least 25% including a vortex generator pair between chord wise position 20% c and 70% c, the vortex generator pair including 2 not directly connected fins and a base which interconnects the fins and where the fins are placed under opposite angles of attack. The fins are cambered by at least 1% in particular by at least 2% and more particularly by a least 3% of the fin chord. According to an embodiment the base of the vortex generator pair is W-shaped, the fins of a pair are designed to generate contra rotating vortices and the distance between the suction sides of the fins is approximately 150% of that between the pressure sides and the trailing part of the fins is rounded so that non-concentrated vortices are generated.

Claims

1. A wind turbine comprising: a blade having a leading edge, a trailing edge, and opposing first and second surfaces extending between the edges; and a vortex generator pair including: a planar base attached to the first surface, wherein the base is W-shaped, V-shaped, or U-shaped, and first and second spaced apart fins extending outwardly from opposing portions of the base such that the first and second fins are not touching each other to define an air gap defined between the first and second fins and extending completely over the base, the first and second fins each having a leading edge, a trailing edge, a suction side and a pressure side, each of the suction sides having a trailing half and a leading half, wherein a surface area of the trailing half is less than 200 percent of a surface area of the leading half.

2. The wind turbine of claim 1, wherein the surface area of the trailing half is less than 150 percent of the surface area of the leading half.

3. The wind turbine of claim 1, wherein the first and second fins are angled relative to each other such that a distance between the leading edges of the first and second fins is greater than a distance measured between the trailing edges.

4. The wind turbine of claim 1, wherein the first and second fins define an area in between and the base covers less than 90% of this area.

5. The wind turbine of claim 1, wherein each of the first and second fins are cambered inwardly.

6. The wind turbine of claim 1, wherein the vortex generator pair is located on the blade at a radial position and is located at a blade chord-wise position that is between 20 to 70 percent of a chord of the blade at the radial position.

7. A wind turbine comprising: a blade having a leading edge, a trailing edge, and opposing first and second surfaces extending between the edges; and a vortex generator pair including: a planar base attached to the first surface and having opposing first and second edge portions, wherein the base is W-shaped, V-shaped, or U-shaped, and first and second spaced apart fins extending outwardly from the first and second edge portions, respectively, the first and second fins being completely spaced apart to define an air gap extending over the base.

8. The wind turbine of claim 7 further comprising a second vortex generator pair, having a same structure as the vortex generator pair, disposed on the first surface at a radially spaced position relative to the vortex generator pair.

9. The wind turbine of claim 8, wherein a distance between the vortex generator pair and the second vortex generator pair is greater than a width of the vortex generator pair.

10. The wind turbine of claim 7, each of the fins having a leading edge, a trailing edge, a suction side and a pressure side, wherein a surface area of the trailing half is less than 200 percent of a surface area of the leading half.

11. The wind turbine of claim 10, wherein the surface area of the trailing half is less than 150 percent of the surface area of the leading half.

12. The wind turbine of claim 10, wherein each of the fins are cambered inwardly by at least 1 percent of the chord of the fin.

13. The wind turbine of claim 7, wherein the first and second fins are angled relative to each other such that a distance between the leading edges of the first and second fins is greater than a distance measured between the trailing edges.

14. A wind turbine comprising: a blade having a leading edge, a trailing edge, and opposing first and second surfaces extending between the edges; and a vortex generator pair including: a base attached to the first surface, the base defining a trailing edge, and a leading edge together forming a total edge length, wherein the base is W-shaped, V-shaped, or U-shaped, and first and second spaced apart fins extending outwardly from opposing portions of the base such that the first and second fins are not touching each other to define an air gap defined between the first and second fins and extending over the base, wherein the vortex generator pair includes an inflow direction, and at least 70% of the total edge length is angled relative to the inflow direction by 50 degrees or less.

15. The wind turbine of claim 14, wherein at least 80% of total edge length is angled relative to the inflow direction by 50 degrees or less.

16. The wind turbine of claim 14, wherein each of the suction surfaces has a trailing half and a leading half wherein a surface area of the trailing half is less than 200 percent of a surface area of the leading half.

17. The wind turbine of claim 14, wherein the base is planar.

18. The wind turbine of claim 14, wherein the first and second fins are angled relative to each other such that a distance between the leading edges of the first and second fins is greater than a distance measured between the trailing edges.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: Lift coefficient improvement by vortex generator.

(2) FIG. 2: Lift/drag ratio improvement by vortex generator.

(3) FIG. 3: Airfoil with 3 vortex generator pairs.

(4) FIG. 4: Side view of a vortex generator pair.

(5) FIG. 5A: Front view of a vortex generator pair.

(6) FIG. 5B: Top view of a vortex generator pair without cambered fins.

(7) FIG. 5C: Top view of a vortex generator pair with cambered fins.

(8) FIG. 6: Top view of a W-shaped vortex generator pair.

(9) FIG. 7: Top view of a U-shaped vortex generator pair.

(10) FIG. 8: Top view of a V-shaped vortex generator pair.

(11) FIG. 9: Car roof top container.

DETAILED DESCRIPTION

(12) FIG. 1 shows the lift coefficient c.sub.1 as a function of the angle of attack of a 40% thick airfoil. It can be seen that the lift coefficient for the case with vortex generators installed at 30% c (label VG30 cl) is (much) higher in the range from 0 to 26 degrees compared to the result without vortex generators (label NVG cl). FIG. 2 shows the ratio of lift over drag for the same configuration. It can be seen that L/D is (much) better for the angle of attack range between 2 and 22 degrees. The results are obtained by CFD-simulation.

(13) FIG. 3 shows an airfoil 1 with chord 2 and three vortex generator pairs 3 which are installed on the airfoil surface 6. The vortex generator pairs are shown on a larger scale than the airfoil for illustrative reasons. The airfoil 1 includes a leading edge 30, a trailing edge 32, and oppposing first and second surfaces 34, 36 extending between the edges 30, 32.

(14) The vortex generator pairs 3 may be attached to the first surface 34. Each vortex generator pair has two fins 5 and a base 4 which are only labelled for one vortex generator pair, also labelled for one vortex generator pair in FIG. 3. The distance 8 between the pressure sides 42 of the fins of a vortex generator pair 3 is less than the distance 9 between the suction sides 44 of the adjacent fins of different vortex generator pairs.

(15) FIG. 4 shows a side view of a vortex generator pair which is fixed by double-sided adhesive tape which has an adhesive layer 10 fixed to the base of the vortex generator pair and an adhesive layer 11 fixed to the airfoil surface 6 and a foam layer 12 in between. The thickness of layers 10, 11 and 12 are shown thicker than realistic for illustrative reasons. The fin chord 39 is taken at 10% of the fin height.

(16) Each of the suction surfaces 44 has a leading half 46 and a trailing half 48 relative to the design inflow direction 14. The surface area of the trailing half 48 may be less than 200% of the surface area of the leading half 46 to provide a more symmetrical fin. In other embodiments, the surface area of the trailing half 48 may be less than 150% of the surface area of the lead half 46.

(17) FIG. 5A shows a front view of a vortex generator looking at the pressure sides 42 of the fins 5. The height of the fins 45 is the maximum height above the blade surface 6 and includes the adhesive tape 43. In FIG. 5B a vortex generator pair with base 47 has fins 44 which are not cambered, however, the fins may be cambered in other embodiments as shown in FIG. 5C. Referring to FIG. 5C, the fins 45 have a camber 51 of at least 1% of the fin chord, or in other embodiments, at least 2% or 3% of the fin chord. The camber of the fins resulted in better aero dynamic performance and gave stiffness to the fins 45 at the same time. The fins 45 could be made very thin without becoming too flexible due to the camber. And thinner fins require less material. Furthermore, thanks to the camber of the fins, the baseplate 4 becomes flexible and can follow a range of curvatures of the airfoil surface where the vortex generator pair is attached. The base has leading edge 54 and trailing edge 56 which together form the edge length. The angle 47 is the angle between the design inflow direction 14 and the edge along the edge length.

(18) FIG. 6 shows a top view of a W-shaped vortex generator pair and the design inflow direction 14. The lateral direction is defined as perpendicular to the design inflow direction and in the base plane of the vortex generator pair. The base 4 may include a leading edge 54 and a trailing edge 56. The leading edge 54 includes multiple edges, that are interconnected to form a continuous edge extending between the leading edges 38 of the fins 5, also the trailing edge 56 includes multiple edges to form a continuous edge extending between the trailing edges 40 of the fins 5. In the W-shaped embodiment, the base has four surfaces, or segments such as surfaces 57, 58, 59, and surface 60. The surfaces 58 and 60 are interconnected at a vortex 61 and extend outwardly away from each other towards the trailing edge 56. This causes the surface 58 and 60 to extend towards the fins 5 and to be angled in a direction opposite to their corresponding fin. The surfaces 58 and 60 may be referred to as subfins.

(19) FIG. 7 shows a top view of a U-shaped vortex generator pair. FIG. 8 shows a top view of a V-shaped vortex generator pair. FIG. 9 shows a car roof top container 20, with a length L between the front end 21 and a rear end 22, whereon a vortex generator fin 23 is installed. The upper surface of the trailing part of the container 24 has an angle 25 with the horizontal.

(20) Although the illustrative embodiments of the present invention have been described in greater detail with reference to the accompanying drawings, it will be understood that the invention is not limited to those embodiments. Various changes or modifications may be effected by one skilled in the art without departing from the scope or the spirit of the invention as defined in the claims. Furthermore the validity of the claims is not dependent on the correctness of physical explanations.

(21) It is to be understood that in the present application, the term comprising does not exclude other elements or steps. Also, each of the terms a and an does not exclude a plurality. Any reference sign(s) in the claims shall not be construed as limiting the scope of the claims.

(22) As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

(23) While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.