TRAILING EDGE AIR DUCT OF A WIND TURBINE ROTOR BLADE

Abstract

A rotor blade of a wind turbine, wherein the rotor blade) includes a suction side, a pressure side, a trailing edge section with a trailing edge, and a leading edge section with a leading edge is provided. The rotor blade furthermore includes an air duct at the trailing edge section which provides a flow path from the pressure side to the suction side. The air duct includes an inlet portion) and an outlet portion, and the air duct is configured such that at least a portion of the airflow from the leading edge section to the trailing edge section is permanently guided through the air duct.

Claims

1. A rotor blade of a wind turbine, comprising: a suction side; a pressure side; a trailing edge section with a trailing edge; a leading edge section with a leading edge; and an air duct at the trailing edge section which provides a flow path from the pressure side to the suction side; wherein the air duct comprises an inlet portion and an outlet portion, the air duct being configured such that at least a portion of an airflow from the leading edge section to the trailing edge section is permanently guided through the air duct.

2. The rotor blade according to claim 1, wherein a configuration of the air duct is independent of an operational mode of the wind turbine.

3. The rotor blade according to claim 1, wherein the air duct is a part of a flap which is composed as a separate piece with regard to the remaining trailing edge section of the rotor blade.

4. The rotor blade according to claim 3, wherein the flap comprises an attachment portion for attaching the flap to the remaining trailing edge section of the rotor blade.

5. The rotor blade according to claim 4, wherein the flap comprises a pressure side portion, the pressure side portion at least partially substitutes and extends the pressure side of the remaining trailing edge section of the rotor blade, and an angle between the attachment portion and the pressure side portion is between one degrees and twenty-five degrees.

6. The rotor blade according to claim 3, wherein the flap is attached to the remaining trailing edge section of the rotor blade by an adhesive bond.

7. The rotor blade according to claim 1, wherein a spanwise extension of the air duct is between 1% and 200% of a chord length.

8. The rotor blade according to claim 1, wherein a chordwise extension of the air duct between an upstream end of the inlet portion and a downstream end of the outlet portion is between 2% and 50% of the chord length.

9. The rotor blade according to claim 1, wherein a minimum height of the air duct in a direction perpendicular to a span and perpendicular to a chord is between 0.1% and 10% of the chord length.

10. The rotor blade according to claim 1, wherein an upstream end of the outlet portion is arranged between 75% and 100% of a chord length.

11. The rotor blade according to claim 1, wherein a spanwise extension of the inlet portion of the air duct increases from an upstream end of the inlet portion towards the trailing edge of the rotor blade.

12. The rotor blade according to claim 1, wherein a spanwise extension of the entire outlet portion of the air duct is substantially constant.

13. The rotor blade according to claim 1, wherein the air duct is arranged at a spanwise position of the rotor blade between 20% and 80% of a total length of the rotor blade.

14. The rotor blade according to claim 5, wherein the angle between the attachment portion and the pressure side portion is between five degrees and fifteen degrees.

15. The rotor blade according to claim 7, wherein the spanwise extension of the air duct is between 2% and 50% of the chord length.

16. The rotor blade according to claim 8, wherein the chordwise extension of the air duct between an upstream end of the inlet portion and a downstream end of the outlet portion is between 5% and 20% of the chord length.

17. The rotor blade according to claim 9, wherein the minimum height of the air duct in the direction perpendicular to the span and perpendicular to the chord is between 0.5% and 5% of the chord length.

18. The rotor blade according to claim 10, wherein the upstream end of the outlet portion is arranged between 85% and 100% of the chord length.

19. The rotor blade according to claim 13, wherein the air duct is arranged at the spanwise position of the rotor blade between 30% and 70% of the total length of the rotor blade.

Description

BRIEF DESCRIPTION

[0039] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0040] FIG. 1 shows a rotor blade of a wind turbine in a top view;

[0041] FIG. 2 shows a cross sectional view of a first embodiment of the rotor blade;

[0042] FIG. 3 shows a cross-sectional view of a second embodiment of the the rotor blade;

[0043] FIG. 4 shows a first perspective view of a embodiment of a flap with an air duct;

[0044] FIG. 5 shows a second perspective view of an embodiment of the flap as illustrated in FIG. 4;

[0045] FIG. 6 shows a first perspective view of an embodiment of aflap with an air duct;

[0046] FIG. 7 shows a second perspective view of an embodiment of the flap with the air duct; and

[0047] FIG. 8 shows a top view of an embodiment of a a pressure side portion of the flap as illustrated in FIGS. 6 and 7.

DETAILED DESCRIPTION

[0048] The illustration in the drawings is in schematic form. It is noted that in different figures, similar or identical elements may be provided with the same reference signs.

[0049] FIG. 1 shows a rotor blade 20 of a wind turbine. The rotor blade 20 comprises a root section 21 with a root 211 and a tip section 22 with a tip 221. The root section 21 is connected with the tip section 22 via the span 25. The span 25 is defined as a straight line connecting both sections, the root section 21 and the tip section 22. It is basically a virtual line which, however, can e.g. coincide with a spar of the rotor blade. The span 25 also generally coincides with the pitch axis of the rotor blade.

[0050] Furthermore, the rotor blade 20 comprises a trailing edge section 23 with a trailing edge 231 and a leading edge section 24 with a leading edge 241.

[0051] Furthermore, chords 26 can be attributed to the rotor blade at each spanwise position. The chord with the maximum chord length is referred to as the chord which is located at the shoulder 27 of the rotor blade 20. The chord 26 and the span 25 define the chordwise direction 261 and the spanwise direction 251 of the rotor blade.

[0052] FIG. 2 shows a first embodiment of an inventive rotor blade. FIG. 2 shows a cross sectional view of a part of the rotor blade. In particular, it illustrates the trailing edge section 23 of the rotor blade. In this example, there exists the remaining rotor blade with the remaining trailing edge section 232 and a flap 30 which is attached to the remaining rotor blade at the remaining trailing edge section 232. Also note that a suction side 281 and a pressure side 282 can be attributed to the rotor blade in FIG. 2.

[0053] Coming back to the flap 30, the flap 30 comprises a first portion which is attached to the remaining trailing edge section 232 and a second part which comprises the trailing edge 231 of the entire rotor blade. Both parts are divided or separated by a gap which is referred to as the air duct 31. This air duct 31 can also be referred to as an air channel. The air duct 31 has the technical effect that a part of the airflow 40 which is flowing from the leading edge section to the trailing edge section of the rotor blade at the pressure side 282 is deflected and diverted through the air duct 31.

[0054] In FIG. 2, this portion of the airflow 40 which is deflected and guided through the air duct 31 is referenced by the reference numeral 42. In contrast, this portion of the airflow 40 which is un-deflected by the air duct 31 is referred to as the un-deflected portion 41 of the airflow. Note that the airflow, i.e. the un-deflected portion 41 of the airflow 40, is also slightly deflected by the mere presence of the flap 30, but it is not specifically deflected by the air duct 31. The presence and the provision of the air duct 31 leads to a reduction of the lift coefficient of the airfoil and to the reduction of noise that is generated at the trailing edge section of the rotor blade.

[0055] FIG. 3 shows a similar view of a very similar flap 30 and focuses on the dimensions of the air duct 31. It can be seen that the chordwise extension of the air duct 31 needs to be measured from the upstream end 321 of the inlet portion 32 of the air duct 31 to the downstream end 322 of the outlet portion 33 of the air duct 31. This chordwise extension of the air duct 31 is referred to by the reference numeral 312.

[0056] The height of the air duct 31 is substantially uniform and constant in the example of FIG. 3. The minimum height 313 is measured and determined by the length of the distance referred to by the reference numeral 313.

[0057] Another embodiment of the invention is illustrated in FIGS. 4 and 5. Here, perspective views of a flap 30 comprising an air duct 31 are shown. The inlet portion 32 and the outlet portion 33 can be seen in FIG. 4 and FIG. 5, respectively. Also the attachment portion 34 and the pressure side portion 36 of the flap can be well discerned. In the embodiment as shown in FIGS. 4 and 5, the flap also comprises an alignment rim 35. This alignment rim is to be arranged at the trailing edge of the remaining trailing edge section of the rotor blade. The rim has the beneficial effect of facilitating alignment of the flap 30 during connection of the flap 30 with the remaining rotor blade. This alignment is even more facilitated by this alignment rim 35 if the flap has to be mounted and attached to an already existing rotor blade which is e.g. already mounted on a hub of a wind turbine.

[0058] FIGS. 6 to 8 show another embodiment of a flap 30 with an air duct 31. FIGS. 6 and 7 show perspective views focusing on the attachment portion 34 and the pressure side portion 36 of the flap 30. FIG. 6 also shows the angle 37 between the attachment portion 34 and the pressure side portion 36. It can be seen, that the width of the air duct 31, i.e. the spanwise extension of the air duct 31, is increasing in the direction of the airflow. In other words, the side walls of the air duct 31 are diverting towards the trailing edge. By this measure, a particularly favorable flow guidance can be achieved.

[0059] FIG. 8 illustrates some dimensions of the air duct 31 and the flap 30: It can be seen that the spanwise extension exemplarily amounts to a few centimeters, while the minimum height 313 of the air duct is one centimeter and the ramp angle 37 amounts to one degree. The chordwise extension of the flap 30 as illustrated in the example of FIGS. 6 to 8 amounts to 20 centimeters.

[0060] 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.

[0061] 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.