Low noise wind turbine blade

Abstract

A wind turbine blade and a wind turbine having such a wind turbine blade are disclosed. The wind turbine blade has a contoured profile including a pressure side and a suction side, and a leading edge and a trailing edge with a chord extending between the leading edge and the trailing edge, the chord defining a chordwise direction. The wind turbine blade extends in a longitudinal direction between a root end and a tip end and has a blade length in the longitudinal direction. The wind turbine blade has a first airfoil blade section in the longitudinal direction, the first airfoil blade section being located between 40% and 100% of the blade length measured from the root end. Within the first airfoil blade section, the pressure side is substantially straight proximate the trailing edge.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a wind turbine blade having a trailing edge. More specifically, to an airfoil of a wind turbine blade optimized to reduce noise emissions. BACKGROUND

[0002] Wind power generation provides a clean and environmentally friendly source of energy. A wind turbine typically comprises a tower, a generator, a gearbox, a nacelle and one or more rotor blades. The wind turbine blades use known airfoil principles to capture the kinetic energy of the wind. Modern wind turbines can have rotor blades with a length exceeding 90 meters.

[0003] It is well known that large wind turbine blades used for modern wind turbines are affected by trailing edge noise generated by the airflow over the aerodynamic profile of the wind turbine blade. The airflow is transformed from a substantially laminar flow over the blade surface into a turbulent flow and is scattered at the trailing edge, generating so-called trailing edge noise. The airflow can further separate from the boundary layer at a separation point and emit airflow separation noise. This noise generated by the wind turbine can cause annoyance and disturbance to the surrounding environment.

[0004] Some suggestions have previously been made involving the installation of trailing edge serrations and brush hairs in an attempt to reduce the noise generation in the vicinity of the trailing edge of a wind turbine blade. SUMMARY

[0005] It is an object of the present disclosure to provide a solution for a wind turbine blade to eliminate, reduce or at least provide an alternative to the above-mentioned problems. In particular, it is an object of the present disclosure to provide a solution for reducing the noise generation of a wind turbine. It is a further object of the present disclosure to provide a solution that balances several mutually conflicting requirements of a wind turbine, such as optimizing power generation and reducing noise generation.

[0006] Thereby, the present disclosure relates to an airfoil, such as for a wind turbine blade. Accordingly, the present disclosure also relates to a wind turbine blade employing such an airfoil and to a wind turbine comprising the disclosed wind turbine blade, preferably comprising two or more, such as three, such wind turbine blades.

[0007] The inventors have found that the airfoils and wind turbine blades disclosed herein provide an advantageous noise reduction compared to prior art airfoils and wind turbine blades, while at least maintaining, and possibly even enhancing, the advantageous aerodynamic efficiency.

[0008] SUMMARY The disclosed wind turbine blade has a profiled contour comprising a pressure side and a suction side. The wind turbine blade further comprises a leading edge and a trailing edge, with a chord extending between the leading edge and the trailing edge, the chord defining a chord-wise direction and a chord length between the leading edge and the trailing edge. The wind turbine blade extends in a longitudinal direction between a root end and a tip end. The wind turbine blade has a blade length along the longitudinal direction from the root end to the tip end. The blade length can exceed 40 meters, such as more than 60 meters, such as more than 70 meters. In some examples, the blade length can exceed 100 meters.

[0009] The wind turbine blade has a first airfoil blade section having a first blade section length along the longitudinal direction and being located between 40% and 100% of the blade length measured from the root end. In some embodiments, the first airfoil blade section can be located between 40% and 95% or between 40% and 90% of the blade length measured from the root end.

[0010] The first airfoil blade section can employ the disclosed airfoil, i.e. the disclosed airfoil can have a shape as described below in relation to the first airfoil blade section of the disclosed wind turbine blade.

[0011] Within the first airfoil blade section, the pressure side and the suction side meet at the trailing edge in a cross-section perpendicular to the longitudinal direction, forming a first trailing edge angle between the pressure side and the suction side at the trailing edge. The first trailing edge angle can be at least 15 degrees, such as between 15-30 degrees, preferably between 17-25 degrees.

[0012] Within the first airfoil blade section, the pressure side can be substantially straight near the trailing edge, e.g. for all positions between 85% and 100% of the chord measured from the leading edge, and / or for all positions between 85% and 98% of the chord measured from the leading edge, and / or for all positions between 90% and 98% of the chord measured from the leading edge.

[0013] Within the first airfoil blade section, the pressure side in the cross-section can be convex between the leading edge and a first chord position. The first chord position can be at a first chord distance from the leading edge, e.g. between 40-60% of the chord measured from the leading edge, e.g. between 45-55% of the chord, such as approximately 50% of the chord.

[0014] Within the first airfoil blade section, the pressure side in the cross-section can be concave between the first chord position and a second chord position. The second chord position can be at a second chord distance from the leading edge, e.g. between 80-100% of the chord measured from the leading edge, such as 90%, 95%, 98% or 100% of the chord. The second chord distance can be greater than the first chord distance. In some examples, the second chord position can be at the trailing edge.

[0015] The maximum curvature of the pressure side in the range between the first chord position and the trailing edge can be located between the first chord position and a third chord position. In other words, the maximum curvature of the concave portion of the pressure side can be located further forward than the third chord position, i.e. more towards the leading edge. The third chord position can be between the first chord position and the second chord position. The third chord position can be less than 80% of the chord measured from the leading edge. For example, the third chord position can be 75% of the chord measured from the leading edge, or 70% of the chord measured from the leading edge.

[0016] Within the first airfoil blade section, the pressure side in the cross section can be substantially linear between the second chord position and the trailing edge. For example, the curvature of the pressure side in the cross section between the second chord position and the trailing edge can be less than 0.2, such as less than 0.1, such as less than 0.05.

[0017] In the entire (or almost the entire) airfoil cross section within, for example, the first airfoil blade section, the chord can be located between the pressure side and the suction side, i.e. the pressure side and the suction side can be on different sides of the chord. For example, at least 95% of the chord can be located between the pressure side and the suction side within the first airfoil blade section. For other airfoils, it is typically the case that, for example, near the trailing edge, the chord extends outside the airfoil, i.e. such that the suction side and the pressure side are on the same side of the chord. For the airfoils of the present disclosure, i.e. within the first airfoil blade section of a wind turbine blade, for example, at least for all positions between 70% and 95% of the chord measured from the leading edge, the chord can be located between the pressure side and the suction side.

[0018] The pressure side can be close to the chord near the trailing edge. For example, within the first airfoil blade section, for all positions between 80% and 100% of the chord measured from the leading edge, the pressure side to chord distance between the pressure side and the chord measured perpendicular to the chord can be less than 0.5% of the chord length.

[0019] In some examples, the pressure side can be substantially parallel to the chord near the trailing edge. For example, within the first airfoil blade section, the pressure side can be substantially parallel to the chord near the trailing edge, and / or for all positions between 85% and 100% of the chord measured from the leading edge, and / or for all positions between 85% and 98% of the chord measured from the leading edge, and / or for all positions between 90% and 98% of the chord measured from the leading edge, the pressure side can be substantially parallel to the chord. A deviation of less than a few degrees, such as less than 1 degree, such as less than 0.5 degrees, between the pressure side and the chord can be considered substantially parallel.

[0020] The blade thickness can be defined as the distance between the pressure side and the suction side measured perpendicular to the chord. Alternatively, this can be expressed as the airfoil thickness. Within the first airfoil blade section, the maximum blade thickness, i.e. the maximum value of the blade thickness, can be at a position between 20-30% of the chord measured from the leading edge. More preferably, the maximum blade thickness can be at a position between 25-30% of the chord measured from the leading edge, such as between 25-29% of the chord measured from the leading edge.

[0021] Within the first airfoil blade section, the maximum blade thickness, i.e. the maximum value of the blade thickness, can be between 18-27% of the chord length, such as between 19-24% of the chord length, such as between 19-23% of the chord length, such as between 20-21% of the chord length.

[0022] The wind turbine blade can comprise a plurality of airfoil blade sections along a longitudinal direction of the wind turbine blade, i.e. between the tip end and the root end of the wind turbine blade. The plurality of airfoil blade sections comprises a first airfoil blade section and a second airfoil blade section, and optionally a third airfoil blade section. The second airfoil blade section and / or the third airfoil blade section can have a different geometry, i.e. a different airfoil, than the first airfoil blade section. The third airfoil blade section can have a different geometry, i.e. a different airfoil, than the second airfoil blade section and / or the first airfoil blade section. In some examples, the second airfoil blade section is a state-of-the-art airfoil. Additionally or alternatively, in some examples, the third airfoil blade section is a state-of-the-art airfoil.

[0023] The first airfoil blade section can adjoin the second airfoil blade section and / or the first airfoil blade section can adjoin the third airfoil blade section. The first airfoil blade section can be between the second airfoil blade section and the third airfoil blade section. In some examples, the second airfoil blade section can be located between the first airfoil blade section and the tip end, i.e. 100% of the blade length measured from the root end. In other examples, the second airfoil blade section can be located between the root end and the first airfoil blade section, or the second airfoil blade section can be located between 40% of the blade length measured from the root end and the first airfoil blade section. In other words, the first airfoil blade section can be located between the second airfoil blade section and the tip end, i.e. 100% of the blade length measured from the root end.

[0024] Each of the plurality of airfoil blade sections can have a respective blade section length along the longitudinal direction. For example, the second airfoil blade section can have a second blade section length along the longitudinal direction and / or the third airfoil blade section can have a third blade section length along the longitudinal direction.

[0025] The plurality of airfoil blade sections, e.g. the first airfoil blade section, the second airfoil blade section and / or the third airfoil blade section, can be located between 40% and 100% of the blade length measured from the root end. In some embodiments, the plurality of airfoil blade sections, e.g. the first airfoil blade section, the second airfoil blade section and / or the third airfoil blade section, can be located between 40% and 95% or between 40% and 90% of the blade length measured from the root end.

[0026] Some or each of the plurality of airfoil blade sections can be longer than 10% of the blade length. For example, the first blade section length, the second blade section length and / or the third blade section length can be at least 10% of the blade length. In some examples, the first blade section length can be at least 50% of the blade length.

[0027] The second airfoil blade section can be located between the first airfoil blade section and 100% of the blade length measured from the root end, i.e. the second airfoil blade section can be located between the first airfoil blade section and the tip end.

[0028] While the present disclosure exemplifies the airfoil of the present disclosure as being applied to a wind turbine blade, this application is particularly advantageous, it is emphasized that the airfoil of the present disclosure can alternatively or additionally be applied for other purposes, such as hydroelectric turbine blades, aircraft wings, helicopter rotor blades, etc. BRIEF DESCRIPTION OF DRAWINGS

[0029] Embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. These drawings show one way in which the present disclosure can be implemented and should not be construed as limiting the other possible embodiments that fall within the scope of the claims attached.

[0030] Figure 1 illustrates an exemplary wind turbine, Figure 2 shows a schematic view of an exemplary wind turbine blade, Figure 3 is a schematic view illustrating a cross-sectional view of an exemplary wind turbine blade, Figure 4a and 4b is a schematic view illustrating a cross-sectional view of an exemplary airfoil, Figure 5a and 5b schematically illustrates an exemplary airfoil in comparison to a prior art wind turbine airfoil, Figure 6a and 6b shows the noise level of the airfoil at various angles of attack, and Figure 7a and 7b shows the aerodynamic efficiency of the airfoil at various lift coefficients. DETAILED DESCRIPTION

[0031] Various exemplary embodiments and details will be described below with reference to the relevant drawings. It should be noted that the drawings may or may not be drawn to scale, and elements having similar structures or functions are represented by similar reference numerals throughout the drawings. It should also be noted that the drawings are intended only to facilitate the description of the embodiments. They are not intended to be an exhaustive description of the invention, nor are they intended to limit the scope of the invention. Furthermore, the illustrated embodiments may not have all the aspects or advantages shown. Aspects or advantages described in conjunction with a particular embodiment are not necessarily limited to that embodiment and may be implemented in any other embodiment, even if not illustrated or explicitly described as such.

[0032] Figure 1 An exemplary wind turbine 2 is shown, such as a conventional, modern upwind wind turbine according to the so-called "Danish concept." The wind turbine 2 has a tower 4, a nacelle 6, and a rotor having a substantially horizontal rotor axis. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each blade having a blade root 16 closest to the hub and a blade tip 14 furthest from the hub 8.

[0033] Figure 2 A schematic diagram of an exemplary wind turbine blade 10 is shown, such as Figure 1 . The wind turbine blade 10 of the wind turbine 2 is shown in FIG. The wind turbine blade 10 extends in a longitudinal direction Ld between a root end 17 and a tip end 15, and has a blade length L along the longitudinal direction Ld from the root end 17 to the tip end 15. The blade length L may exceed 60 meters, such as more than 70 meters. In some examples, the blade length L may exceed 100 meters.

[0034] The wind turbine blade 10 has the shape of a conventional wind turbine blade and includes a root region 30 closest to the hub, a profiled or airfoil region 34 farthest from the hub, and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 includes a leading edge 18 and a trailing edge 20, with the leading edge 18 facing in the direction of rotation of the blade 10 when the blade is mounted on the hub, and the trailing edge 20 facing in the opposite direction of the leading edge 18.

[0035] The airfoil region 34 (also referred to as the profiled region) has an ideal or nearly ideal blade shape with respect to lift generation, while the root region 30 has a generally circular or elliptical cross-section for structural reasons, for example, to make it easier and safer to mount the blade 10 on the hub. The diameter (or chord) of the root region 30 can be constant throughout the entire root region 30. The transition region 32 has a profile that gradually transitions from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile in which the chord extends between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0036] The airfoil region 34 may include a plurality of airfoil blade segments, each of which may have different profiles. For example, the wind turbine blade 10 may include a first airfoil blade segment 34a having a first blade segment length La, a second airfoil blade segment 34b having a second blade segment length Lb, and a third airfoil blade segment 34c having a third blade segment length Lc. In some examples, the airfoil region 34 may include fewer or more airfoil blade segments. The first blade segment length La may be at least 10% of the blade length L, such as at least 50% of the blade length L.

[0037] The plurality of airfoil blade sections 34a, 34b, 34c may be located between 40% and 100% of the blade length L measured from the root end. In some embodiments, the plurality of airfoil blade sections 34a, 34b, 34c may be located between 40% and 95% or between 40% and 90% of the blade length measured from the root end.

[0038] The shoulder 40 of the blade 10 is defined as the location where the blade 10 has its maximum chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0039] It should be noted that the chords of the different sections of the blade do not typically lie in a common plane, as the blade may be twisted and / or curved (i.e., pre-bent) to provide a chord plane with a correspondingly twisted and / or curved trajectory, most often in order to compensate for variations in the local velocity of the blade with radius from the hub.

[0040] The wind turbine blade 10 comprises a blade shell, which typically comprises two blade shell parts or halves, i.e. a first blade shell part 24 and a second blade shell part 26, typically made of fibre-reinforced polymer. The wind turbine blade 10 can comprise additional shell parts, such as a third shell part and / or a fourth shell part. The first blade shell part 24 is typically the pressure side or windward blade shell part. The second blade shell part 26 is typically the suction side or leeward blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together along a joint line or glue joint 28, e.g. extending along the trailing edge 20 and the leading edge 18 of the blade 10, with an adhesive, such as glue. Typically, the root end of the blade shell parts 24, 26 has a semi-circular or semi-elliptical outer cross-sectional shape.

[0041] Figure 3 is a schematic cross-sectional view illustrating an exemplary wind turbine blade 10, e.g. such as the one described with respect to Figure 2 is a cross-sectional view of a wing profile region of a wind turbine blade 10 of a wind turbine blade 10 as described. The wind turbine blade 10 comprises a leading edge 18, a trailing edge 20, a pressure side 24 and a suction side 26. The wind turbine blade 10 further comprises two spar caps (sometimes also referred to as main laminate structures) 46, one spar cap being arranged towards the pressure side 24 and the other spar cap being arranged towards the suction side 26. The wind turbine blade 10 comprises a chord 38 between the leading edge 18 and the trailing edge 20. The leading edge 18 is the point of the wing profile furthest away from the trailing edge 20, i.e. maximising the length of the chord 38. Furthermore, a blade midline (sometimes also referred to as camber line) is illustrated, which can be defined between the pressure side 24 and the suction side 26. The blade midline 39 is a midline between the pressure side 24 and the suction side 26 measured perpendicular to the chord 38. The blade midline can be obtained by drawing an inscribed circle from the leading edge 18 to the trailing edge 20. The blade midline extends along the centre of these inscribed circles.

[0042] The wind turbine blade 10 comprises shear webs, such as a leading edge shear web 42 and a trailing edge shear web 44. The shear webs 42, 44 extend between the pressure side 24 and the suction side 26 of the wind turbine blade 10, e.g. between the spar caps 46.

[0043] Figure 4a and 4b is a schematic cross-sectional view illustrating an exemplary wing profile 100 of an exemplary wind turbine blade 10. Figure 4b is a close-up view of a trailing edge portion 100a of the wing profile 100. The wing profile 100 can be Figure 2The airfoil of any or all of the airfoil blade sections 34, 34a, 34b, 34c is illustrated and described in the middle. For example, the airfoil 100 can belong to an airfoil blade section, such as the first airfoil blade section 34a. The airfoil 100 can belong to an airfoil blade section located between 40% and 100% of the blade length L measured from the root end. In some examples, the airfoil blade section having the airfoil 100, such as the first airfoil blade section 34a, can be located between 40% and 95% or between 40% and 90% of the blade length measured from the root end.

[0044] The airfoil blade section having the airfoil 100, such as the first airfoil blade section, can have a first blade section length along the longitudinal direction of the wind turbine blade, which can be at least 10% of the blade length L, such as at least 50% of the blade length L. In other words, the airfoil 100 can be employed over a range of blade lengths that is more than 10% of the blade length L, such as more than 50% of the blade length L.

[0045] The airfoil 100, as Figure 3 The airfoil illustrated in the middle comprises a leading edge 18, a trailing edge 20, a pressure side 24 and a suction side 26, wherein a chord 38 extends between the leading edge 18 and the trailing edge 20. The chord 38 defines a chord-wise direction Cd. A thickness direction Td is defined as perpendicular to the chord 38. A chord length c is measured between the leading edge 18 and the trailing edge 20 along the chord-wise direction Cd. The position of the airfoil is typically designated as the position along the chord measured from the leading edge (which can be denoted as chord position), typically relative to the chord (i.e. the chord length c), such as for example X% of the chord measured from the leading edge 18. Thus, for example, the leading edge 18 will be at a chord position of 0% of the chord measured from the leading edge 18, and the trailing edge 20 will be at a chord position of 100% of the chord measured from the leading edge 18.

[0046] As illustrated, in a cross-section perpendicular to the longitudinal direction of the wind turbine blade, the pressure side 24 and the suction side 26 meet at the trailing edge 20, forming a first trailing edge angle 102. The first trailing edge angle 102 is between the pressure side 24 and the suction side 26 at the trailing edge 20. The first trailing edge angle 102 can be at least 15 degrees, such as between 15-30 degrees. In some examples, the first trailing edge angle 102 can be between 17-25 degrees. Such a trailing edge angle is typically higher than the airfoils of conventional prior art wind turbine blades, which have much lower trailing edge angles.

[0047] For all positions between, for example, 90% and 98% of the chord measured from the leading edge 18 and / or for all positions between, for example, 85% and 100% of the chord measured from the leading edge 18, the pressure side of the airfoil of the present disclosure can be substantially straight near the trailing edge.

[0048] As illustrated in cross-section, the pressure side 24 is convex between the leading edge 18 and a first chord position 104. This portion of the pressure side 24 can be denoted as a convex pressure side portion 106. The first chord position can be at a first chord distance, e.g., at approximately 50% of the chord measured from the leading edge 18 in the illustrated example.

[0049] As illustrated in cross-section, the pressure side is concave between the first chord position 104 and a second chord position 108. This portion of the pressure side 24 can be denoted as a concave pressure side portion 110. The second chord position 108 can be at a second chord distance, e.g., at approximately 85% or 90% of the chord measured from the leading edge 18. As can be seen, the second chord distance, i.e., the distance between the leading edge 18 and the second chord position 108, can be greater than the first chord distance, i.e., the distance between the leading edge 18 and the first chord position 104. Thus, the second chord position 108 is positioned more toward the trailing edge 20 than the first chord position 104.

[0050] In some examples, the concave pressure side portion 110 can extend all the way or almost all the way to the trailing edge 20, i.e., the second chord position 108 can be at or near the trailing edge 20, i.e., at a distance of 100% or close to 100% of the chord measured from the leading edge 18. However, in other examples, the pressure side 24 is substantially straight near the trailing edge 20. In other words, the pressure side 24 can be substantially linear between the second chord position 108 and the trailing edge 20. This portion of the pressure side 24 can be denoted as a straight pressure side portion 112.

[0051] The maximum curvature of the pressure side 24 in the range between the first chord position 104 and the trailing edge 20 can be located between the first chord position 104 and 75% of the chord measured from the leading edge. In other words, the maximum concavity of the pressure side 24 can be obtained on the leading edge side of the 75% chord position. Thus, the pressure side 24 can be more straight between the 75% chord position and the trailing edge 20.

[0052] As illustrated, the disclosed airfoil 100 can have a chord 38 located between the pressure side 24 and the suction side 26. This is in contrast to known prior art airfoils in which the chord extends out of the blade near the trailing edge due to an increase in curvature of the pressure side 24 near the trailing edge 20. In some examples, the disclosed airfoil can have a chord 38 located between the pressure side 24 and the suction side 26 for all positions of the chord, or at least for all positions between 70% and 100% of the chord measured from the leading edge 18 or for all positions between 70% and 95%.

[0053] The pressure side 24 can be substantially parallel to the chord 38 near the trailing edge, e.g. within 1 degree of the chord 38. This can be the case, for example, for all positions between 85% and 100% of the chord measured from the leading edge and / or for all positions between 90% and 98% of the chord measured from the leading edge.

[0054] The airfoil 100 has a pressure side to chord distance 114 between the pressure side 24 and the chord 38, measured perpendicular to the chord 38. As can be seen, the pressure side to chord distance 114 has a maximum value within the convex pressure side portion 106 and is smaller near the trailing edge 20. In some examples not specifically illustrated, the pressure side to chord distance 114 can be negative at positions where the chord 38 extends outside the blade, e.g. when the curvature of the concave pressure side portion 110 is such that the pressure side 24 near the trailing edge 20 bends over the chord 38. As can be seen in the illustrated example, the pressure side to chord distance 114 can be very small, e.g. less than 0.5% of the chord length c, for positions near the trailing edge 20, e.g. for all positions between 80% and 100% of the chord measured from the leading edge.

[0055] The airfoil 100 has a blade thickness 116, defined as the distance between the pressure side 24 and the suction side 26, measured perpendicular to the chord 38. The maximum blade thickness, i.e. the position where the blade thickness 116 is largest, can be at a position between 20-30% of the chord measured from the leading edge 18, such as at a position between 25-30%, such as at a position between 25-29%. The maximum blade thickness of the airfoil 100 of the present disclosure can be closer to the leading edge 18 than prior art airfoils for wind turbine blades. In some examples, the maximum blade thickness can be between 19-23% of the chord length c.

[0056] Figure 5a and 5b An exemplary airfoil 100 of the present disclosure is shown in dashed lines compared to two prior art wind turbine airfoils 200a, 200b shown in solid and dash-dot lines, respectively. As can be seen, the airfoil 100 of the present disclosure has a substantially flat pressure side 24 near the trailing edge 20 and a more open, i.e. larger, trailing edge angle between the pressure side 24 and the suction side 26 at the trailing edge 20. The illustrated airfoils 100, 200a, 200b have the same maximum relative thickness, i.e. the maximum thickness relative to the chord length.

[0057] Figure 5a and 5b Simulation data for the airfoils 100, 200a, 200b illustrated in Figures 6a-7b are illustrated in Figure 5aThe data for the profile 200a shown in the middle is represented by the solid line, and is used as Figure 5b The data for the profile 200b shown in the middle is represented by the solid dotted line.

[0058] Figure 6a and 6b The noise level for each profile at various angles of attack is shown. Thereby, the horizontal axis shows the angle of attack (AoA), and the vertical axis shows the noise level in A-weighted sound pressure level (SPL). Figure 6a The data for the profiles in clean conditions is shown, while Figure 6b The data in disturbed conditions is shown, which is used to affect the boundary layer, to simulate a more realistic environment, for example.

[0059] As can be seen from Figure 6a and 6b The profile 100 of the present disclosure has lower noise over a wide range of angles of attack compared to the prior art profiles 200a, 200b. The lower noise emission is Figure 6b particularly significant in disturbed conditions, as shown. A proposed explanation for this surprising effect is that the limited concave curvature of the pressure side is the main reason for this noise reduction, as the concave curvature of the pressure side creates a strong pressure gradient when the airflow reaches the trailing edge, which gradient will affect the growth of the turbulent boundary layer and induce more noise. The profile of the present disclosure at least reduces this effect by having a flatter pressure side and a more open trailing edge angle near the trailing edge.

[0060] Figure 7a and 7b The aerodynamic efficiency, more specifically the lift-drag ratio, for each profile at various lift coefficients is shown, which is influenced by factors such as angle of attack, Reynolds number, and leading edge roughness. Thereby, the horizontal axis shows the lift coefficient, and the vertical axis shows the lift / drag ratio. Figure 7a The data for the profiles in clean conditions is shown, while Figure 7b The data in disturbed conditions is shown.

[0061] As can be seen from Figure 7a The profile 100 of the present disclosure has aerodynamic performance in clean conditions between the other two tested prior art profiles 200a, 200b, while in disturbed conditions, as can be seen in Figure 7b The profile 100 of the present disclosure outperforms the other two tested prior art profiles 200a, 200b. Thereby, it can be seen that the low noise emission obtained by the profile 100 of the present disclosure is achieved without negatively affecting the aerodynamic performance, as can be seen from Figure 6a and 6b As is evident, the low noise emission obtained by the profile 100 of the present disclosure is achieved without negatively affecting the aerodynamic performance.

[0062] The present disclosure has been described with reference to the preferred embodiments. However, the scope of protection of the present application is not limited to the embodiments shown, but various changes and modifications can be made without departing from the scope of protection of the present application.

[0063] Throughout the description, the use of the terms "first", "second", "third", "fourth", "primary", "secondary", "tertiary", and the like does not imply any particular order or importance, but is used to identify individual elements. Also, the use of the term "first" element does not imply the existence of a second element, and vice versa.

[0064] List of reference signs 2 wind turbine 4 tower 6 outer cover 8 hub 10 blade 14 blade tip 15 tip 16 blade root 17 root end 18 leading edge 20 trailing edge 24 first blade shell part (pressure side) 26 second blade shell part (suction side) 28 joint line / glue joint 30 root region 32 transition region 34 airfoil region 34a, 34b, 34c airfoil blade segment 38 chord line 39 blade midline 40 shoulder 42 leading edge shear web 44 trailing edge shear web 46 spar cap 48 joint 100 airfoil 102 first trailing edge angle 104 first chord position 106 convex pressure side part 108 second chord position 110 concave pressure side part 112 straight pressure side part 114 pressure side to chord distance 116 blade thickness Ld longitudinal direction La, Lb, Lc blade segment length Cd chordwise direction c chord length Td thickness direction

Claims

1. A wind turbine blade, the wind turbine blade having a profiled profile, the profiled profile comprising a pressure side and a suction side, and a leading edge and a trailing edge, wherein a chord extends between the leading edge and the trailing edge, the chord defining a chordwise direction and a chord length between the leading edge and the trailing edge, the wind turbine blade extending in a longitudinal direction between a root end and a tip end, the wind turbine blade having a blade length from the root end to the tip end along the longitudinal direction, in, The wind turbine blade has a first airfoil blade section having a first blade section length in the longitudinal direction and being located between 40% and 100% of the blade length measured from the root end, wherein, in the first airfoil blade section, the pressure side and the suction side meet at the trailing edge in a cross section perpendicular to the longitudinal direction, forming a first trailing edge angle between the pressure side and the suction side at the trailing edge, wherein the first trailing edge angle is at least 15 degrees, such as between 15-30 degrees, preferably between 17-25 degrees, and Therein, within the first airfoil blade section, the pressure side is substantially straight near the trailing edge.

2. The wind turbine blade according to claim 1, wherein: In the first airfoil blade section: - the pressure side in the cross section is convex between the leading edge and a first chord position, the first chord position being at a first chord distance measured from the leading edge, and - the pressure side in the cross-section is concave between the first chord position and a second chord position, the second chord position being at a second chord distance measured from the leading edge, wherein the second chord distance is greater than the first chord distance, and wherein a maximum curvature of the pressure side in a range between the first chord position and the trailing edge is located between the first chord position and 75% of the chord measured from the leading edge.

3. The wind turbine blade according to claim 2, wherein: In the first airfoil blade section, the pressure side in the cross-section is substantially linear between the second chord position and the trailing edge.

4. A wind turbine blade according to any one of the preceding claims, wherein Within the first airfoil blade section, for all positions between 70% and 95% of the chord measured from the leading edge, the chord is between the pressure side and the suction side.

5. A wind turbine blade according to any one of the preceding claims, wherein In the first airfoil blade section, for all positions between 80% and 100% of the chord measured from the leading edge, a pressure side to chord distance between the pressure side and the chord measured perpendicular to the chord is less than 0.5% of the chord length.

6. A wind turbine blade according to any one of the preceding claims, wherein Within the first airfoil blade section, the pressure side is substantially straight for all positions between 90% and 98% of the chord measured from the leading edge.

7. A wind turbine blade according to any one of the preceding claims, wherein: Within the first airfoil blade section, near the trailing edge and / or for all positions between 90% and 98% of the chord measured from the leading edge, the pressure side is substantially parallel to the chord.

8. A wind turbine blade according to any one of the preceding claims, wherein Blade thickness is defined as the distance between the pressure side and the suction side measured perpendicular to the chord, and wherein, within the first airfoil blade section, a maximum blade thickness is at a position between 20-30% of the chord measured from the leading edge, such as at a position between 25-30% of the chord measured from the leading edge, such as at a position between 25-29% of the chord measured from the leading edge.

9. A wind turbine blade according to any one of the preceding claims, wherein In the first airfoil blade section, the maximum blade thickness is between 19-23% of the chord length.

10. A wind turbine blade according to any one of the preceding claims, wherein The first blade section length is at least 10% of the blade length, such as at least 50% of the blade length.

11. A wind turbine blade according to any one of the preceding claims, wherein The blade length is more than 60 meters, such as more than 70 meters.

12. A wind turbine comprising two or more wind turbine blades, wherein: Each of the two or more wind turbine blades is a wind turbine blade according to any one of the preceding claims.

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