ROTOR BLADE AND WIND TURBINE

Abstract

A rotor blade of a wind turbine, to an associated wind turbine and to an associated method. A rotor blade for a wind turbine which extends in the longitudinal direction with a profile course from a blade connector to a blade tip, wherein the profile course comprises a course of a lift coefficient, comprising a hub portion adjacent to the blade connector and a tip portion adjacent to the blade tip, a middle portion adjacent to the hub portion and to the tip portion, wherein the middle portion substantially comprises those profile sections which have a relative profile thickness, which is defined as the ratio of maximum profile thickness to profile depth, of between 20% and 30%, and wherein the middle portion comprises a local minimum of the course of the lift coefficient.

Claims

1. A rotor blade for a wind turbine, which comprising: a rotor blade body having a profile comprising a plurality of profile sections extending in a longitudinal direction from a blade connector to a blade tip, wherein the profile has a plurality of profile sections, wherein the profile comprises a plurality of coefficients corresponding to the plurality of profile section, respectively, the rotor blade body comprising: a hub portion adjacent to the blade connector and a tip portion adjacent to the blade tip, and a middle portion between the hub portion and the tip portion, wherein the middle portion comprises a set of profile sections of the plurality of profile sections having a relative profile thickness, wherein the relative profile thickness is a ratio of a maximum profile thickness to a profile depth and is between 20% and 30% of the rotor blade length, and wherein the middle portion comprises a local minimum lift coefficient.

2. The rotor blade as claimed in claim 1, wherein each of the plurality of profile sections has a thickness setback, wherein each thickness setback is defined as a ratio of the distance between the maximum profile thickness and a leading edge of the rotor blade in a direction of a profile chord to the profile depth, wherein the middle portion comprises a local maximum thickness setback.

3. The rotor blade as claimed in claim 2, wherein the plurality of thickness setbacks in the longitudinal direction between blade connector and blade tip forms an S-shape including a local minimum thickness setback and the local maximum thickness setback.

4. The rotor blade as claimed in claim 3, wherein the plurality of thickness setbacks in the longitudinal direction has first, second, and third turning points, wherein the first turning point lies in the range between 10% and 25% of the rotor blade length, and/or the second turning point lies in the range between 40% and 50% of the rotor blade length, and/or the third turning point lies in the range between 65% and 90% of the rotor blade length.

5. The rotor blade as claimed in claim 3, wherein the local minimum thickness setback is greater than 0.35.

6. The rotor blade as claimed in claim 2, wherein between 30% and 80% of the rotor blade length, a thickness setback of the plurality of thickness setbacks is between 0.35 and 0.4.

7. The rotor blade as claimed in claim 2, wherein between 0% and 30% of the rotor blade length, a thickness setback of the plurality of thickness setbacks is between 0.25 and 0.5.

8. The rotor blade as claimed in claim 2, wherein between 80% and 100% of the rotor blade length, a thickness setback of the plurality of thickness setbacks is between 0.25 and 0.35, and wherein, between 80% to 100% of the rotor blade length, a thickness setback of the plurality of thickness setbacks comprises a local minimum.

9. The rotor blade as claimed in claim 2, wherein, between 0% and 40% of the rotor blade length, the rotor blade comprises a minimum thickness setback.

10. The rotor blade as claimed in claim 1, wherein: the hub portion extends between 0% and 30% of the rotor blade length, and/or the middle portion extends between 30% and 80% of the rotor blade length, and/or the tip portion extends between 80% and 100% of the rotor blade length.

11. The rotor blade as claimed in claim 1, wherein the relative profile thickness of the rotor blade is between 15% and 100% of the rotor blade length.

12. The rotor blade as claimed in claim 1, wherein at least a portion of the rotor blade has a flatback profile.

13. A wind turbine comprising a tower, a rotor, and at least one rotor blade as claimed in claim 1 coupled to the rotor.

14. A windfarm having at least two wind turbines as claimed in the claim 13.

15. A method comprising: forming a rotor blade having a profile comprising a plurality of profile sections that extend in a longitudinal direction from a blade connector to a blade tip, wherein the profile comprises a plurality of lift coefficients corresponding to the plurality of profile section, respectively, the rotor blade comprising a hub portion adjacent to the blade connector and a tip portion adjacent to the blade tip, and a middle portion between the hub portion and the tip portion, wherein, the middle portion comprises a set of profile sections from the plurality of profile sections and are selected to have a relative profile thickness, wherein the relative profile thickness is a ratio of maximum profile thickness to profile depth, of between 20% and 30% of the rotor blade length, and wherein the plurality of lift coefficients in the middle portion is selected in such a manner that the middle portion comprises a local minimum lift coefficient.

16. The rotor blade as claimed in claim 5, wherein the local minimum thickness setback is greater than 0.4.

17. The rotor blade as claimed in claim 7, wherein the thickness setback decreases between 0% to 30% of the rotor blade length.

18. The rotor blade as claimed in claim 9, wherein the minimum thickness setback is less than 0.35.

19. The rotor blade as claimed in claim 18, wherein the minimum thickness setback is less than 0.3.

20. The rotor blade as claimed in claim 12, wherein the flatback profile is arranged in the hub portion.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0037] Preferred exemplary embodiments will be explained by way of example with reference to the attached figures, in which:

[0038] FIG. 1 shows a schematic three-dimensional view of an exemplary embodiment of a wind turbine;

[0039] FIG. 2 shows schematic courses of thickness setbacks of a conventional rotor blade and of a rotor blade with a local minimum of the course of the lift coefficient in the middle portion;

[0040] FIG. 3 shows schematic courses of blade depths of a conventional rotor blade and of a rotor blade with a local minimum of the course of the lift coefficient in the middle portion;

[0041] FIG. 4 shows schematic profiles of blade thicknesses of a conventional rotor blade and of a rotor blade with a local minimum of the profile of the lift coefficient in the middle portion; and

[0042] FIG. 5 shows schematic courses of lift-to-drag performances of a conventional rotor blade and of a rotor blade with a local minimum of the course of the lift coefficient in the middle portion.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a schematic three-dimensional view of an exemplary embodiment of a wind turbine 100. The wind turbine 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 having three rotor blades 108, which each have a rotor blade length R, and a spinner 110 are provided on the nacelle 104. During operation of the wind turbine 100, the aerodynamic rotor 106 is set into a rotational movement by the wind and therefore also rotates an electrodynamic rotor or runner of a generator which is coupled directly or indirectly to the aerodynamic rotor 106. The electric generator is arranged in the nacelle 104 and generates electrical energy. The pitch angles of the rotor blades 108 can be changed by pitch motors at the rotor blade roots of the respective rotor blades 108.

[0044] The rotor blades 108 each have a hub portion 108a, a middle portion 108b and a tip portion 108c. The hub portion 108a faces a hub arranged on the nacelle 104. The tip portion 108c is the distal portion of the rotor blade 108 and faces away from the hub and the nacelle 104. The tip portion 108c extends from a blade tip 109 in the direction of the hub. The middle portion 108b is arranged between the hub portion 108a and the tip portion 108c.

[0045] The rotor blades 108 have a profile in the longitudinal direction. The profile sections therefore change over the longitudinal direction of a rotor blade. The profile is distinguished by a plurality of a lift coefficients. The relative thickness of the rotor blades 108 is between 20% and 30% in the respective middle portion 108b. The lift coefficients are smaller in the middle portion 108b than in the hub portion 108a and smaller than in the tip portion 108c. A lift coefficient is understood here as meaning a design lift coefficient.

[0046] FIG. 2 shows schematic courses of thickness setbacks of a conventional rotor blade and of a rotor blade with a local minimum of the plurality of the lift coefficients in the middle portion. On the abscissa, the relative rotor blade length is plotted between 0 and 1, or between 0% and 100%. The thickness setback is plotted on the ordinate.

[0047] The first course of a thickness setback 200 represents the course of a thickness setback of a conventional rotor blade. The thickness setback 200 of the conventional rotor blade decreases from 0.5 in the region close to the hub to a value of approx. 0.4 and is then virtually constant between 30% and 100% of the relative rotor blade length.

[0048] In contrast thereto, a course of a thickness setback 202 of a rotor blade changes to a more pronounced extent along the relative rotor blade length. In the region in the vicinity of the hub, i.e., in the hub portion 108a, the thickness setback is greatly reduced between 0% and 30% of the relative rotor blade length. At approx. 30% of the relative rotor blade length, the course of the thickness setback 202 comprises a minimum 206. From the minimum 206 at 30% of the relative rotor blade length, the course of the thickness setback 202 of the rotor blade 108 increases to a local maximum 208 at approx. 60% of the relative rotor blade length. From the maximum 208, which is at approx. 0.4, the course of the thickness setback 202 decreases between 60% and 90% of the relative rotor blade length. Between 90% and 100% of the relative rotor blade length, the course of the thickness setback 202 is substantially constant. At 90% of the relative rotor blade length, there is a local minimum of the course of the thickness setback 202.

[0049] In short, it can be seen that the course of the thickness setback 202 over the rotor blade length is S-shaped, that is to say initially comprises a local minimum 206 and then a local maximum 208 between blade connector and blade tip.

[0050] FIG. 3 shows schematic courses of blade depth of a conventional rotor blade and of a rotor blade 108 with a local minimum of the lift coefficient in the middle portion. On the abscissa, the relative rotor blade length of between 0 and 1, or between 0% and 100%, is also plotted here. The profile depth of rotor blades is plotted qualitatively on the abscissa. The course of the profile depth 210 represents the profile depth of a conventional rotor blade. The course of the profile depth 212 represents the course of a profile depth of a rotor blade.

[0051] It is apparent that the profile depth in a range 214 of between 30% and 80% of the relative rotor blade length is greater than in the case of conventional rotor blades. By means of the increased profile depth 212 in the range 214, this rotor blade 108 can be provided with a greater profile thickness, with nevertheless a constant relative profile thickness being achieved. Owing thereto, the lift-to-drag performance of the rotor blade 108 in the middle portion 108b, in particular in the range 214, with the course of the profile depth 212 can be improved.

[0052] FIG. 4 shows schematic courses of blade thicknesses of a conventional rotor blade and of a rotor blade 108 with a local minimum of the lift coefficient in the middle portion. On the abscissa, the relative rotor blade length of between 0 and 1, or between 0% and 100%, is also plotted here. The course of the blade thickness 220 represents the course of the blade thickness of a conventional rotor blade. The course of the blade thickness 222 represents the course of a rotor blade 108. It is apparent that the blade thickness 222 in a range of between 30% and 80% of the relative rotor blade length is greater than in the case of the conventional rotor blade. Consequently, with the greater profile depth, shown in FIG. 3, in said rotor blade portion, a substantially consistent relative thickness can be achieved and nevertheless an increased lift-to-drag performance can be obtained.

[0053] FIG. 5 shows schematic courses of lift-to-drag performances of a conventional rotor blade and of a rotor blade 108 with a local minimum of the lift coefficient in the middle portion. On the abscissa, the relative rotor blade length of between 0 and 1, or between 0% and 100%, is again plotted. The lift-to-drag performance is plotted qualitatively on the ordinate. The profile of the lift-to-drag performance 230 represents the course of a lift-to-drag performance of a conventional rotor blade. The course of the lift-to-drag performance 232 represents the course of a lift-to-drag performance of a rotor blade 108.

[0054] It is apparent that the lift-to-drag performance 232 in two portions is significantly higher than the lift-to-drag performance of the conventional rotor blade. In particular in the range between 20% and 45% and between 50% and 80% of the relative rotor blade length, increases in the lift-to-drag performance can be achieved by a greater profile depth, a greater profile thickness and a reduced lift coefficient being realized.

REFERENCE SIGNS

[0055] 100 Wind turbine [0056] 102 Tower [0057] 104 Nacelle [0058] 106 Rotor [0059] 108 Rotor blades [0060] 109 Blade tip [0061] 110 Spinner [0062] 108a Hub portion [0063] 108b Middle portion [0064] 108c Tip portion [0065] 200 Course of a thickness setback [0066] 202 Course of a thickness setback [0067] 206 Minimum [0068] 208 Maximum [0069] 210 Course of a profile depth [0070] 212 Course of a profile depth [0071] 214 Range of greater profile depth [0072] 220 Course of a blade thickness [0073] 222 Course of a blade thickness [0074] 230 Profile of a lift-to-drag performance (L/D) [0075] 232 Course of a lift-to-drag performance (L/D) [0076] R Rotor blade length