A Wind Turbine Blade Comprising A Noise Reducing Device

Abstract

This invention relates to a noise reducing device and a wind turbine blade comprises such a noise reducing device. The noise reducing device comprises noise reducing elements projecting from a base part towards a second end. Airflow modifying elements projects further from the base part towards a first end. The noise reducing elements and airflow modifying elements are arranged on opposite sides of the base part and preferably have different dimensions and/or shapes.

Claims

1. A noise reducing device (19) for a wind turbine blade (5), having a first end (22), a second end (25), a first local side surface (27) and a second local side surface (29) arranged between the first end (22) and the second end, wherein the noise reducing device (19) is configured for attachment to a side surface of the wind turbine blade (5), the noise reducing device (19) comprising a plurality of a plurality of airflow modifying elements (20) and a plurality of noise reducing elements (23), the airflow modifying elements (20) extending from a first proximal end (21) to the first end (22), the noise reducing elements (23) extending from an opposite facing second proximal end (24) to the second end (25), characterised in that the airflow modifying elements (20) and the noise reducing elements (23) extend in opposite longitudinal directions from the first end (22) to the second end (25), said the airflow modifying elements (20) are configured to contact or to be directly attached to said side surface of the wind turbine blade (5).

2. A noise reducing device according to claim 1, characterised in that the noise reducing device (19) further comprising at least one base part (26), wherein said at least one base part (26) extends from the first proximal end (21) to the second proximal end (24).

3. A noise reducing device according to claim 2, characterised in that at least the airflow modifying elements (20) or the noise reducing elements (23) are integrally formed with the at least one base part (26).

4. A noise reducing device according to claim 1, characterised in that the first proximal end (21) is substantially equal to the second proximal end (24).

5. A noise reducing device according to claim 4, characterised in that the airflow modifying elements (20) are integrally formed with the noise reducing elements (23).

6. A noise reducing device according to claim 1, characterised in that each airflow modifying element (20) has a first length measured from the first proximal end (21) to the first end (22) and each noise reducing element (23) has a second length measured from the second proximal end (24) to the second end (25), wherein the first length is equal to or less than the second length.

7. A noise reducing device according to claim 1, characterised in that each airflow modifying element (20) has a first width measured along the first proximal end (21) and each noise reducing element (23) has a second width measured along the second proximal end (24), wherein the first width is equal to or less than the second width.

8. A noise reducing device according to claim 1, characterised in that each airflow modifying element (20) has a first profile and each noise reducing element (23) has a second profile, wherein the first profile differs from the second profile.

9. A noise reducing device according to claim 1, characterised in that said first local side surface (27) of at least the airflow modifying elements (20) has a tapered profile in a width direction and/or in a length direction.

10. A noise reducing device according to claim 1, characterised in that at least the airflow modifying elements (20) are serrations.

11. A noise reducing device according to claim 10, characterised in that the noise reducing elements (23) are serrations.

12. A wind turbine blade (5) for a wind turbine, extending in a longitudinal direction from a blade root (7) to a tip end (8) and further in a chordwise direction from a leading edge (9) to a trailing edge (10), the wind turbine blade comprising a first side surface defining a pressure side (12) and a second side surface defining a suction side (13), wherein at least one noise reducing device (19) is attached to one of said first and second side surfaces, the at least one noise reducing device (19) is arranged relative to the trailing edge (10), characterised in that said at least one noise reducing device (19) is configured according to claim 1.

13. A wind turbine blade according to claim 12, characterised in that at least the airflow modifying elements (20) or at least one base part (26) of the at least one noise reducing device (19) is arranged on said one of the first and second side surfaces and extends towards the leading edge (9).

14. A wind turbine blade according to claim 12, characterised in that the trailing edge (10) is a truncated trailing edge (10) having a trailing edge surface (32), wherein the noise reducing device (19) has a local edge surface (28) extend along at least part of said trailing edge surface (32) in a flapwise direction.

Description

DESCRIPTION OF DRAWINGS

[0076] The invention is explained in detail below with reference to embodiments shown in the drawings, in which

[0077] FIG. 1 shows a wind turbine,

[0078] FIG. 2 shows an exemplary embodiment of the wind turbine blade,

[0079] FIG. 3 shows a first exemplary embodiment of the noise reducing device,

[0080] FIG. 4 shows a second exemplary embodiment of the noise reducing device,

[0081] FIG. 5 shows a third exemplary embodiment of the noise reducing device,

[0082] FIG. 6 shows a fourth exemplary embodiment of the noise reducing device,

[0083] FIG. 7 shows a fifth exemplary embodiment of the noise reducing device,

[0084] FIG. 8 shows a first embodiment of the airflow modifying elements,

[0085] FIG. 9 shows a second embodiment of the airflow modifying elements,

[0086] FIG. 10 shows a cross-sectional view of the noise reducing device attached to the wind turbine blade with a sharp trailing edge, and

[0087] FIG. 11 shows a cross-sectional view of the noise reducing device attached to the wind turbine blade with a sharp trailing edge.

LIST OF REFERENCES

[0088] 1. Wind turbine [0089] 2. Wind turbine tower [0090] 3. Nacelle [0091] 4. Hub [0092] 5. Wind turbine blades [0093] 6. Pitch bearing [0094] 7. Blade root [0095] 8. Tip end [0096] 9. Leading edge [0097] 10. Trailing edge [0098] 11. Blade shell [0099] 12. Pressure side [0100] 13. Suction side [0101] 14. Blade root portion [0102] 15. Aerodynamic blade portion [0103] 16. Transition portion [0104] 17. Length of wind turbine blade [0105] 18. Chord length of wind turbine blade [0106] 19. Noise reducing device [0107] 20. Airflow modifying elements [0108] 21. First proximal end [0109] 22. First end [0110] 23. Noise reducing elements [0111] 24. Second proximal end [0112] 25. Second end [0113] 26. Base part [0114] 27. First local side surface [0115] 28. Local edge surface [0116] 29. Second local side surface [0117] 30. Central line [0118] 31. Peripheral edges [0119] 32. Trailing edge surface

[0120] The listed reference numbers are shown in abovementioned drawings where no all reference numbers are shown on the same figure for illustrative purposes. The same part or position seen in the drawings will be numbered with the same reference number in different figures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0121] FIG. 1 shows a modern wind turbine 1 comprising a wind turbine tower 2, a nacelle 3 arranged on top of the wind turbine tower 2, and a rotor defining a rotor plane. The nacelle 3 is connected to the wind turbine tower 2, e.g. via a yaw bearing unit. The rotor comprises a hub 4 and a number of wind turbine blades 5. Here three wind turbine blades are shown, but the rotor may comprise more or fewer wind turbine blades 5. The hub 4 is connected to a drive train, e.g. a generator, located in the wind turbine 1 via a rotation shaft.

[0122] The hub 4 comprises a mounting interface for each wind turbine blade 5. A pitch bearing unit 6 is optionally connected to this mounting interface and further to a blade root of the wind turbine blade 5.

[0123] FIG. 2 shows a schematic view of the wind turbine blade 5 which extends in a longitudinal direction from a blade root 7 to a tip end 8. The wind turbine blade 5 further extends in a chordwise direction from a leading edge 9 to a trailing edge 10. The wind turbine blade 5 comprises a blade shell 11 having two opposite facing side surfaces defining a pressure side 12 and a suction side 13 respectively. The blade shell 11 further defines a blade root portion 14, an aerodynamic blade portion 15, and a transition portion 16 between the blade root portion 14 and the aerodynamic blade portion 15.

[0124] The blade root portion 14 has a substantially circular or elliptical cross-section (indicated by dashed lines). The blade root portion 14 together with a load carrying structure, e.g. a main laminate combined with a shear web or a box beam, are configured to add structural strength to the wind turbine blade 5 and transfer the dynamic loads to the hub 4. The load carrying structure extends between the pressure side 12 and the suction side 13 and further in the longitudinal direction.

[0125] The blade aerodynamic blade portion 15 has an aerodynamically shaped cross-section (indicated by dashed lines) designed to generate lift. The cross-sectional profile of the blade shell 11 gradually transforms from the circular or elliptical profile into the aerodynamic profile in the transition portion 16.

[0126] The wind turbine blade 5 has a longitudinal length 17 of at least 35 metres, preferably at least 50 metres. The wind turbine blade 5 further has a chord length 18 as function of the length 17, wherein the maximum chord length is found between the blade aerodynamic blade portion 15 and the transition portion 16.

[0127] FIG. 3 shows a first exemplary embodiment of a noise reducing device 19 configured for attachment to the wind turbine blade 5. An array of noise reducing devices 19 is optionally arranged on the wind turbine blade 5 along the trailing edge 10, as indicated in FIG. 2.

[0128] The noise reducing device 19 comprises a plurality of airflow modifying elements 20 having a first profile which extends from a first proximal end 21 to a first end 22. The noise reducing device 19 further comprises a plurality of noise reducing elements 23 having a second profile which extends from a second proximal end 24 to a second end 25. The airflow modifying elements 20 and the noise reducing elements 23 face in opposite longitudinal directions.

[0129] The airflow modifying elements 20, the base part 26 and the noise reducing elements 23 has first local side surface 27 and an opposite second side surface (see FIGS. 8 and 9). Here both the first and second local side surfaces form a continuous side surface.

[0130] A base part 26 is arranged between the first and second proximal ends 21, 24 and extends in a transverse direction. The base part 26 is formed by a single continuous element, as indicated in FIGS. 4 and 5. Alternatively, the base part 26 is formed by a first sub-part 26a and at least a second sub-part 26b, as indicated in FIG. 3.

[0131] Here, the airflow modifying elements 20 and the noise reducing elements 23 are shaped as serrations having the same overall triangular profile. The airflow modifying elements 20 have a first local length and the noise reducing elements 23 have a second local length. As illustrated in FIG. 3, the first local length is less than the second local length, e.g. less than 50% of the second local length. The airflow modifying elements 20 further have a first local width and the noise reducing elements 23 further have a second local width. As illustrated in FIG. 3, the first local width is less than the second local width, e.g. less than 33% of the second local width.

[0132] FIG. 4 shows a second exemplary embodiment of the noise reducing device 19 where the noise reducing elements 23 have a different profile than the noise reducing elements 23.

[0133] The noise reducing elements 23 comprises a thickened portion arranged on the second local side surface, wherein this thickened portion tapers from the second proximal end 24 to the second end 25. The thickened portion has a local edge surface 28 facing the first end 22.

[0134] Here, the noise reducing elements 23 has a substantially three-dimensional pyramid-shaped profile. The noise reducing elements 23 in FIG. 3 has a substantially two-dimensional pyramid-shaped profile.

[0135] FIG. 5 shows a third exemplary embodiment of the noise reducing device 19 where the airflow modifying elements 20 have a different profile than the noise reducing elements 23. Here, the noise reducing elements 23 have a triangular profile while the airflow modifying elements 20 have a semi-elliptical profile.

[0136] FIG. 6 shows a fourth exemplary embodiment of the noise reducing device 19 where the airflow modifying elements 20 have different geometrical properties than the airflow modifying elements 20 of FIG. 3.

[0137] Here, the first local length is less than the second local length, e.g. between 50% to 100% of the second local length. The first local width is less than the second local width, e.g. between 33% to 100% of the second local width. The first local width may further be between 50% to 100% of the second local width, as indicated in FIG. 7.

[0138] FIG. 7 shows a fifth exemplary embodiment of the noise reducing device 19 where the base part 26 is omitted. Here, the first and second proximal ends 21, 24 form a common proximal end.

[0139] FIG. 8 shows a first embodiment of the airflow modifying elements 20 seen in the transverse direction. The second local side surface 29 of at least the airflow modifying elements 20 and the base part 26 form a flat side surface facing the respective side surface of the wind turbine blade 5 when attached, as illustrated in FIGS. 10 and 11. The first local side surfaces 27 of the airflow modifying elements 20 and the base part 26 face in an opposite flapwise direction when attached.

[0140] The first local side surface 27 of at least the airflow modifying elements 20 has a tapered profile in the longitudinal direction, which tapers from the first proximal end 21 to the first end 22.

[0141] FIG. 9 shows a second embodiment of the airflow modifying elements 20 wherein the first local side surface 27 of at least the airflow modifying elements 20 has a tapered profile in the transverse direction. The first local side surface 27 tapers from a central line 30 to the opposite peripheral edges 31 of the airflow modifying elements 20.

[0142] Optionally, the first local side surface 27 of the airflow modifying elements 20 has a 30 combined tapered profile which tapers in both the longitudinal direction and the transverse direction.

[0143] FIG. 10 shows a cross-sectional view of the noise reducing device 19 attached to the wind turbine blade 5. Here, the wind turbine blade 5 has a sharp trailing edge 10. The 35 airflow modifying elements 20 and the base part 26 are arranged on the pressure side 12, alternatively on the suction side 13, of the wind turbine blade 5. The airflow modifying elements 20 and/or the base part 26 are/is attached to the respective side surface of the wind turbine blade 5.

[0144] The second proximal end 24 is placed in a retracted position relative to, alternatively aligned with, the sharp trailing edge 10. The noise reducing elements 23 thus project freely from the trailing edge 10 so that the second end 25 is located behind the trailing edge 10.

[0145] FIG. 11 shows a cross-sectional view of the noise reducing device 19 attached to the wind turbine blade 5 with a truncated trailing edge 10. The truncated trailing edge 10 has a trailing edge surface 32 facing the second end 25 of the noise reducing device 19.

[0146] Here, the thickened portion of the noise reducing elements 23 is arranged relative to this truncated trailing edge 10 so that the local edge surface 28 is contacting the trailing edge surface 32. Alternatively, the thickened portion is further attached to the truncated trailing edge 10, e.g. using an adhesive between the local edge surface 28 and the trailing edge surface 32.

[0147] The abovementioned embodiments may be combined in any combinations without deviating from the present invention.