Wind turbine rotor blade with two rows of vortex generators

Abstract

A wind turbine rotor blade includes a first row of vortex generators having two adjacent vortex generators each having a longitudinal axis and two first fins having trailing ends arranged in a distance d from each other. The two longitudinal axes define a center line. A second row of vortex generators includes a second fin having a trailing end arranged closer to the center line than a leading end of the second fin. The second fin is arranged on the same side of the center line as the first fin such that the trailing end of the second fin is arranged in a chordwise distance c from the trailing end of that first fin. A distance x of the trailing end of the second fin from the center line is within a certain defined range.

Claims

1. A wind turbine rotor blade comprising: a rotor blade body having a blade root, a blade tip, a leading edge, and a trailing edge; a first row of vortex generators; a second row of vortex generators; said first row of vortex generators and said second row of vortex generators extending in a spanwise direction; said first row of vortex generators being arranged closer to said leading edge than said second row of vortex generators; said first row of vortex generators including a first vortex generator defining a first longitudinal axis extending in a chordwise direction and a second vortex generator defining a second longitudinal axis extending in a chordwise direction; said first vortex generator and said second vortex generator being mutually adjacent; said first vortex generator including a first fin and a second fin arranged symmetrically to the first longitudinal axis; said second vortex generator including a third fin and a fourth fin arranged symmetrically to the second longitudinal axis; each of said first fin, said second fin, said third fin, and said fourth fin having a respective leading end and a respective trailing end; said trailing ends of said first fin and said second fin being arranged at a distance d to each other; said distance d being greater than a distance between said leading end of said first fin and said leading end of said second fin; the first longitudinal axis and said second longitudinal axis being arranged at a distance D from each other and mutually defining a center line extending in a chordwise direction; said second row of vortex generators including a fifth fin having a fifth fin leading end and a fifth fin trailing end, wherein said fifth fin trailing end is arranged closer to the center line than said fifth fin leading end; said fifth fin being positioned in relation to said first fin, which is arranged on a same side of the center line as said fifth fin, with said fifth fin trailing end closer to the center line than said fifth fin leading end such that said fifth fin trailing end is arranged at a chordwise distance c from said trailing end of said first fin; wherein a distance x of said fifth fin trailing end from the center line is within a range between (i) an upper limit x.sub.U defined by: TABLE-US-00007 x.sub.U ≤ 0.30 D for c > 1.43 D − 3.57 d x.sub.U ≤ D/2 − d/2 − 0.14 c for c ≤ 1.43 D − 3.57 d; and, (ii) a lower limit x.sub.L defined by TABLE-US-00008 x.sub.L ≥ 0.07 D for c > 0.75 D − 0.87 d x.sub.L ≥ D/2 − d/2 − 0.58 c for c ≤ 0.75 D − 0.87 d.

2. The wind turbine rotor blade of claim 1, wherein said upper limit x.sub.U is defined by TABLE-US-00009 x.sub.U ≤ 0.18 D for c > 1.19 D − 1.87 d x.sub.U ≤ D/2 − d/2 − 0.27 c for c ≤ 1.19 D − 1.87 d.

3. The wind turbine rotor blade of claim 1, wherein said lower limit x.sub.L is defined by TABLE-US-00010 x.sub.L ≥ 0.10 D for c > 0.85 D − 1.06 d x.sub.L ≥ D/2 − d/2 − 0.47 c for c ≤ 0.85 D − 1.06 d.

4. The wind turbine rotor blade of claim 2, wherein said lower limit x.sub.L is defined by TABLE-US-00011 x.sub.L ≥ 0.10 D for c > 0.85 D − 1.06 d x.sub.L ≥ D/2 − d/2 − 0.47 c for c ≤ 0.85 D − 1.06 d.

5. The wind turbine rotor blade of claim 1, wherein said chordwise distance c is greater than said distance d.

6. The wind turbine rotor blade of claim 1, wherein said chordwise distance c is greater than twice said distance d.

7. The wind turbine rotor blade of claim 1, wherein said second row of vortex generators includes a third vortex generator including said fifth fin and a sixth fin; and, said sixth fin being arranged and positioned relative to said second fin as said fifth fin is arranged and positioned relative to said first fin.

8. The wind turbine rotor blade of claim 1, wherein said second row of vortex generators includes a fourth vortex generator including a seventh fin and an eighth fin; said seventh fin being arranged and positioned relative to said third fin as said fifth fin is arranged and positioned relative to said first fin; and, said eighth fin being arranged and positioned relative to said fourth fin as said fifth fin is arranged and positioned relative to said first fin.

9. The wind turbine rotor blade of claim 1, wherein said first vortex generator and said second vortex generator are arranged in a longitudinal section of the wind turbine rotor blade in which the wind turbine rotor blade has an aerodynamic profile with a relative thickness of 0.35 or more.

10. The wind turbine rotor blade of claim 9, wherein said aerodynamic profile has a flat trailing edge.

11. The wind turbine rotor blade of claim 10, wherein said flat trailing edge has a thickness of at least 2% of a chord length of said aerodynamic profile.

12. The wind turbine rotor blade of claim 1, wherein said first vortex generator has a base plate; said base plate is mounted on a wind turbine rotor blade surface; and, said first fin and said second fin of said first vortex generator are connected to said base plate.

13. The wind turbine rotor blade of claim 1, wherein said fifth fin has a base plate; said base plate is mounted in a wind turbine rotor blade surface; and, said fifth fin is the only fin connected to said base plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with reference to the drawings wherein:

(2) FIG. 1 is a wind turbine rotor blade in a schematic, perspective view;

(3) FIG. 2 shows the wind turbine rotor blade of FIG. 1 in cross section; and,

(4) FIG. 3 shows the wind turbine rotor blade of FIG. 1 in a schematic view on a section of the suction side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The wind turbine rotor blade 10 of FIG. 1 has a blade root 12, a blade tip 14 and a pitch axis 68. The pitch axis 68 may also be referred to as longitudinal axis of the wind turbine rotor blade 10. At the blade root 12, the wind turbine rotor blade 10 has a cylindrical cross section and is adapted for attachment to a wind turbine rotor hub (not shown). The cross section with increasing distance from the blade root 12 transforms into an aerodynamic profile, as illustrated by the dotted lines. The surface of the wind turbine rotor blade 10 facing the viewer forms a suction side 16, the opposite surface of the wind turbine rotor blade 10 forms a pressure side 18. The pressure side 16 and the suction side 18 both extend from a leading edge 20 to a trailing edge 22.

(6) A first row 24 of vortex generators and a second row 26 of vortex generators are arranged in a generally spanwise direction in a longitudinal section 28 of the wind turbine rotor blade 10, on the suction side 16. The first row 24 of vortex generators is positioned closer to the leading edge 20 than the second row 26 of vortex generators. In the embodiment of FIG. 1, each vortex generator of the first row 24 and of the second row 26 includes two fins. However, this is not mandatory in particular for the second row 26, in which one or more of the vortex generators may consist each of a single second fin only.

(7) The cross section of FIG. 2 lies within the longitudinal section 28 of the wind turbine rotor blade 10, close to the blade root 12. At this longitudinal position, the aerodynamic profile has a relative thickness of about 40%, calculated as the profile thickness 70 divided by the chord length 72, and a flat trailing edge 22 with a height 74 of about 20% of the chord length 72.

(8) On the suction side 16, one can see a first fin 30 of a vortex generator of the first row 24. The first fin 30 has a trapezoidal shape with a leading end 34 formed by a short edge arranged approximately perpendicular to the surface of the suction side 16, and a trailing end 36 arranged approximately perpendicular to the surface of the suction side 16. One can also see a second fin 32 of a vortex generator of the second row 26. The second fin 32 has a trapezoidal shape with a leading end 38 formed by a short edge arranged approximately perpendicular to the surface of the suction side 16, and a trailing end 40 arranged approximately perpendicular to the surface of the suction side 16. The chordwise distance c is measured between the trailing ends 36 and 40 along the wind turbine rotor blade's surface.

(9) FIG. 3 shows the positions of the vortex generators in greater detail, looking onto a section of the suction side 16 of the wind turbine rotor blade 10. The leading edge 20 is shown to the left, the trailing edge 22 is shown to the right of FIG. 3. The first row 24 of vortex generators includes a vortex generator having a first fin 30 and a further first fin 42 arranged symmetrically to a longitudinal axis 44 of this vortex generator. The distance d is indicated between the trailing end 36 of first fin 30 and the trailing end of first fin 42. It corresponds to a width of the vortex generator.

(10) Another, adjacent vortex generator of the first row 24 of vortex generators is arranged in a spanwise distance D. It includes two fins 46, 48 and a longitudinal axis 50. The longitudinal axes 44, 50 of both vortex generators of the first row 24 of vortex generators are arranged in a generally chordwise direction. They define a center line 52 arranged halfway between the longitudinal axes 44, 50. The spanwise distance D is measured between the longitudinal axes 44, 50.

(11) The second row 26 of vortex generators includes a second fin 32 having a leading end 38 and a trailing end 40. The trailing end 40 is arranged in a spanwise distance x from the center line 52, and in a chordwise distance c from the trailing end 36 of the first fin 30. The trailing end 40 is arranged in a specific surface area 54 shown with a shading. The range of spanwise positions x within the surface area 54 is defined by an upper limit x.sub.U given by a first line 56 and a second line 58 and by a lower limit x.sub.L given by a third line 60 and a fourth line 62.

(12) The first line 56 is described by the term x.sub.U=D/2−d/2−0.14 c and applies as an upper limit x.sub.U for the spanwise distance x where c≤1.43 D−3.57 d. The slope of −0.14 c corresponds to an angle α=8°. The second line 58 is described by the term x.sub.U=0.30 D.

(13) The third line 60 is described by the term x.sub.L=D/2−d/2−0.58 c and applies as a lower limit x.sub.L for the spanwise distance x where c≤0.75 D−0.87 d. The slope of −0.58 c corresponds to an angle β=30°. The fourth line 62 is described by the term x.sub.L=0.07 D.

(14) When looking from the leading edge 20 at the air flow close to the suction side 16, the first fin 30 will generate a vortex rotating counter-clockwise and roughly covering the surface area 54 when flowing towards the trailing edge 22. The second fin 32 with its trailing end 40 arranged within this surface area 54 will not generate a new vortex, but will strengthen the vortex generated by the first fin 30.

(15) One can see from FIG. 3 that each of the second fins included in the second row 26 of vortex generators is arranged with reference to one of the first fins 30, 42, 46, 48 of the first row 24 of vortex generators, as has been explained in detail for the second fin 32, that is in a specific surface area shown with a shading.

(16) FIG. 3 also shows that the vortex generators of the first row 24 of vortex generators each include two first fins (30/42, and 46/48, respectively) connected to a common base plate 64, while each of the second fins of the vortex generators of the second row 26 of vortex generators is connected to a separate base plate 66.

(17) It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE NUMERALS

(18) 10 wind turbine rotor blade 12 blade root 14 blade tip 16 suction side 18 pressure side 20 leading edge 22 trailing edge 24 first row of vortex generators 26 second row of vortex generators 28 longitudinal section 30 first fin 32 second fin 34 leading end of first fin 30 36 trailing end of first fin 30 38 leading end of second fin 32 40 trailing end of second fin 32 42 first fin 44 longitudinal axis 46 first fin 48 first fin 50 longitudinal axis 52 center line 54 surface area 56 first line 58 second line 60 third line 62 fourth line 64 common base plate 66 separate base plate 68 pitch axis 70 profile thickness 72 chord length 72 height α, β angles x distance of the trailing end of the second fin from the center line x.sub.U upper limit of the value x x.sub.L lower limit of the value x