Serrated panel for wind turbine rotor blade

Abstract

A serrated panel for a trailing edge of a wind turbine rotor blade, comprising: at least two teeth, each tooth having a tip, a base, a length measured in a chordwise direction between the base and the tip, a width measured at the base, where the length is greater than the width, each tooth further having two edges extending from the tip to the base, each edge has a tip section extending from the tip to an intermediate point of the edge, and a main section extending from the intermediate point to the base; the convex strips are arranged side by side in the chordwise direction, and each convex strip starts from one of the edges and extends backwards; all the ridges starting from one of the main sections have the same first length that is between 20% and 60% of the length of the respective tooth, and all the ridges starting from one of the tip sections are shorter than the first length.

Description

Technical Field

[0001] The present invention relates to a serrated panel for the trailing edge of a wind turbine rotor blade. Background Technology

[0002] These types of panels have been proposed for reducing noise in wind turbines. The panels are designed with a series of teeth arranged along the trailing edge of the wind turbine rotor blades, which helps reduce the aerodynamic noise generated by the rotor blades. Specifically, the serrations on the trailing edge of the wind turbine rotor blades help reduce the formation of vortices, thereby lowering the overall noise level generated by the wind turbine.

[0003] Studies have shown that using serrated panels can significantly reduce the noise levels of wind turbines. By reducing the impact of noise pollution, this can help increase the acceptance of wind turbines in local communities.

[0004] A wind turbine rotor blade with a serrated panel at the trailing edge is known from document DE 10 2011 056 491 A1. The panel has multiple triangular teeth and multiple bristles extending from the trailing edge of the teeth.

[0005] A wind turbine rotor blade with a trailing edge noise reduction device is known from document WO 2018 / 130651 A1. The noise reduction device includes a panel with multiple teeth and multiple bristles arranged between adjacent teeth.

[0006] A wind turbine rotor blade with a serrated panel having the features of the preamble of claim 1 is known from document EP 3 268 605 B1. Summary of the Invention

[0007] Based on this, the purpose of the present invention is to provide a serrated panel that is easy to manufacture and provides improved noise reduction performance.

[0008] This problem is solved by a serrated panel having the features of claim 1. Preferred aspects are given in the dependent claims. The serrated panel for the trailing edge of a wind turbine rotor blade comprises:

[0009] - At least two teeth, each tooth having a tip, a base, a length chordally measured between the base and the tip, and a width measured at the base, wherein the length is greater than the width; each tooth also has two edges extending from the tip to the base, each edge having a tip section extending from the tip to a midpoint of the edge, and a main section extending from the midpoint towards the base; and

[0010] - A plurality of raised ribs arranged side by side along a chordal direction, each rib starting from one of the edges and extending rearward, characterized in that:

[0011] - All ribs beginning in one of the main sections have the same first length, which is between 20% and 60% of the length of the corresponding tooth, and all ribs beginning in one of the tip sections are shorter than the first length.

[0012] This panel, used for the trailing edge of a wind turbine rotor blade, has a longitudinal orientation. The teeth are arranged in rows along this longitudinal direction. The panel is positioned with reference to the rotor blade, such that the longitudinal direction of the panel is aligned with the trailing edge of the rotor blade. The longitudinal direction of the panel extends approximately along the span of the rotor blade, which is perpendicular to the chord direction of the rotor blade.

[0013] Each tooth may be a triangle with straight edges. However, the tip may also be rounded, and / or the edges may be curved. Typically, the longitudinal extension length of each tooth (measured chordally along the rotor blade) is greater than the width of the tooth (measured along the length of the rotor blade). Teeth may be arranged with or without spacing between adjacent teeth.

[0014] The outer contour of each tooth is formed by two edges, each extending from the tip to the base. Each edge includes a tip segment extending from the tip to the midpoint of the edge. The two tip segments of the two edges of a tooth meet at the tip, thus corresponding to the tip segment at the very end of the tooth. The main segment of each edge begins at the midpoint and extends from the midpoint towards the base. The main segment may extend all the way to the base. The main segment may also be shorter, terminating at a distance from the base. In this case, each edge also has an additional basal end segment extending from the end of the main segment to the base. It is noted that the main segment may be longer than the tip segment. However, the main segment may also be the same length as the tip segment or shorter than the tip segment.

[0015] A rib is a slender element that originates at an edge and extends chordally from the edge, roughly corresponding to the direction of aerodynamic flow. The ribs may not be arranged exactly chordally, for example, when different angles are used in different panels, or due to variations in the angle of the trailing edge relative to the pitch axis. For example, a deviation of ±10° or ±5° is possible. The ribs possess a certain stiffness so that during operation, they may only deform to a limited extent due to aerodynamic flow. Specifically, the stiffness of the ribs can be greater than that of fine fibers or bristles also used in the prior art to influence aerodynamic flow.

[0016] All ribs originating from the main section have the same length, referred to herein as the first length. This first length is between 20% and 60% of the length of the corresponding tooth (i.e., the tooth from which the rib extends). When the main section is straight, the free ends of the ribs extending from it are arranged on a straight line at a fixed distance from the main section. When the main section is curved, the ends of the ribs extending from it are arranged on a curve that may differ from the curve of the main section. However, the area between the edge of the main section and the straight line or curve formed by the free ends of the ribs will always have the same amount of extension in the flow direction, which corresponds to the length direction of the ribs.

[0017] All ribs originating from one of the tip sections are shorter than the first length. In other words, the ribs arranged in the region near the tip are shorter than the ribs arranged in the main section.

[0018] Noise reduction for sawtooth panels is a complex process. The size of the teeth used in known sawtooth panels is related to the typical length scale of the flow, such as the boundary layer thickness. However, the geometric boundary conditions, especially in combination with the ridges added to the teeth, are quite complex, as many different length scales may emerge in the boundary layer, each of which generates noise within a certain frequency range. Therefore, the overall noise is not tonal (single-frequency) noise but broadband noise, and the most promising noise reduction strategies must target different length scales and frequencies.

[0019] The inventors realized that the claimed combination of "equal-length ridges (the specific length of which matches the length of the teeth) in the main section and shorter ridges in the tip section" provided optimal noise reduction in the most relevant frequency range. Its noise reduction effect was even superior to similar panels using longer ridges in the main section. This was surprising, as one would typically expect longer ridges to have a stronger effect.

[0020] However, the inventors noted that there appears to be an upper limit depending on the serration length, beyond which the noise reduction effect cannot be significantly improved. Simultaneously, the inventors observed that shorter serrations are sufficient in the tip section, possibly due in part to the fact that the turbulence lengthscale flowing through this area is more easily reduced by shorter serrations. In summary, a specific choice of serration length provides a superior level of noise reduction.

[0021] Furthermore, since the length of the ridge does not exceed the necessary length, it is particularly easy to manufacture the serrated panel of the present invention, and maintainability and long-term stability are improved.

[0022] On one hand, the length of the ridge starting from one of the tip segments is chosen such that the ridge extends at least to the straight line connecting the tips of adjacent teeth. This ensures that even a shorter ridge has a length that fits the geometry of the teeth, and is long enough to provide good noise reduction.

[0023] On one hand, the length of the ridge starting from one of the tip sections is chosen such that the ridge terminates at a straight line connecting the tips of adjacent teeth. It has been found that these shorter ridges of specific lengths provide both good noise reduction and a reduced risk of damage to the ridges during transport or operation.

[0024] In one aspect, the serrated panel includes a fastening section adapted to be integrated into or attached to a wind turbine rotor blade, wherein at least two teeth extend from the rear end of the fastening section. Integrating the serrated panel into the rotor blade can be achieved by placing the serrated panel in a layup of a rotor blade shell component or between two half-shells of the rotor blade. Attaching the serrated panel to the wind turbine rotor blade can include an adhesive disposed between the outer surface of the rotor blade and the adhesive surface of the fastening section. In both cases, the serrated panel can be secured such that the teeth extend beyond the trailing edge of the rotor blade, wherein the base of the teeth can be substantially aligned with the trailing edge. In another aspect, the teeth and the ribs extending from the teeth are integrally formed, particularly by injection molding. This makes the manufacture of the serrated panel particularly easy and cost-effective. Both the teeth and the ribs can be made of the same material.

[0025] In one respect, the serrated panel is made in one piece, particularly by injection molding. In this respect, the entire serrated panel is particularly easy to manufacture and can be composed of the same material.

[0026] On the one hand, the rib has a constant cross-section. It has been found that this gives the rib sufficient flexibility and rigidity, and it is easy to manufacture.

[0027] On one hand, the ribs have both width and thickness, with the thickness ranging from 1 to 3 times the width. This helps to give the ribs higher stiffness. The stiffness of the ribs is roughly the same as that of the teeth, which allows the ribs to remain aligned during wind turbine operation.

[0028] On the one hand, the distance between adjacent ridges corresponds to 50% to 200% of the ridge width. It has been found that this ratio of the width covered by the ridges to the spacing maintained between the ridges provides good noise reduction.

[0029] On one hand, the thickness of the raised strip is in the range of 1 to 3 times the thickness of the edge of the tooth. The thickness of the edge is measured along the longitudinal direction perpendicular to the serrated panel and the tangential direction perpendicular to the serrated panel. When the thickness of the raised strip is at least the same as or preferably greater than the thickness of the edge, good noise reduction effect and high rigidity can be obtained.

[0030] On one hand, the at least two teeth have the same size. This makes the serrated panel particularly versatile in use. However, serrated panels with teeth of different sizes can also be used, especially serrated panels where the length of the teeth gradually increases from one end of the serrated panel to the other end.

[0031] The aforementioned problem is also solved by a wind turbine rotor blade comprising a blade root, a blade tip, a leading edge, a trailing edge, an aerodynamic airfoil, and at least one serrated panel according to any one of claims 1 to 11, wherein the at least one serrated panel is arranged at the trailing edge. This wind turbine rotor blade can be designed for use in wind turbines with horizontal-axis rotors. The wind turbine rotor can be operated by changing the rotor speed and / or controlled by variable pitch.

[0032] In one aspect, the at least one serrated panel is arranged such that the bases of the at least two teeth are located at or behind the trailing edge.

[0033] In one aspect, the at least one serrated panel includes a first serrated panel with teeth of a first size and a second serrated panel with teeth of a second size different from the first size. This allows for easy fitting of the rotor blades with teeth adapted to the rotor blade size, particularly teeth adapted to the local chord length and / or local flow parameters. Attached Figure Description

[0034] The present invention will now be described in more detail with reference to the accompanying drawings:

[0035] Figure 1 A perspective view shows a wind turbine rotor blade with a serrated panel.

[0036] Figure 2 The serrated panel is shown in top view, where the raised strips are not shown.

[0037] Figure 3 Showing with raised stripes Figure 2 The serrated panel,

[0038] Figure 4a , Figure 4b Another serrated panel is shown in a top view.

[0039] Figure 5 The following view shows Figures 2 to 4aAnd a portion of the serrated panel of any of 4b,

[0040] Figure 6 The diagram illustrates the noise reduction effect of three different sawtooth panels. Detailed Implementation

[0041] Figure 1 A wind turbine rotor blade 10 is shown, having a root 12, a tip 14, a leading edge 16, and a trailing edge 18. In cross-section, the wind turbine rotor blade 10 has an aerodynamic airfoil. The spanwise direction extends from the root 12 toward the tip 14. The chordwise direction extends perpendicularly to the spanwise direction from the leading edge 16 toward the trailing edge 18.

[0042] An outer length section of a wind turbine rotor blade is provided with a serrated panel 20, which is attached to the outer surface of the wind turbine rotor blade 10 and has a plurality of teeth 22. The serrated panel 20 is positioned such that the base 26 of the teeth 22 (see...) Figure 2 Align with trailing edge 18.

[0043] Figure 2 Show Figure 1 A section of the serrated panel 20, wherein the raised strips are not shown for clarity. The serrated panel 20 has teeth 22, each tooth 22 having a tip 24 and a base 26. The length 28 of the tooth is measured tangentially between the tip 24 and the base 26. The width 30 of the tooth 22 is measured longitudinally. A small gap 50 is formed between the bases 26 of each pair of adjacent teeth 22.

[0044] The tooth 22 is an isosceles triangle, wherein the two edges 32 that meet at the tip 24 have the same length. Each edge 32 has a tip segment 34 that begins at the tip 24 and extends to the midpoint 36. The main segment 38 of each edge 32 begins at the midpoint 36 and extends from the midpoint toward the base.

[0045] In addition to the teeth 22, the serrated panel 20 also includes a fastening section 40. The teeth 22 extend from the rear end of the fastening section 40. The fastening section 40 has an adhesive surface 42 disposed on the back side of the fastening section 40, away from the observer's line of sight.

[0046] Figure 3 Showing a design with multiple raised strips 44 Figure 2The serrated panel is shown. It can be seen that the protrusions 44 extending from the edge of the main section 38 all have the same first length 46, which is approximately 50% of the length 28 of the tooth 22. A straight line 47 connecting the free ends of the protrusions in the main section 38 extends parallel to the edge of the corresponding tooth 22. The protrusions 44 extending from the tip section 34 are shorter, their length chosen such that their free ends are located at the straight line 48 connecting the tips 24 of adjacent teeth 22. In the illustrated embodiment, the tip section includes five protrusions. None of the protrusions contact the straight line 47. Within each gap 50, an additional protrusion 44 is provided, its length being shorter than the first length 46. The free ends of the additional protrusions 44 are located on the straight line 47.

[0047] Figure 4a Another serrated panel 20 is shown. In the main section 38, it includes protrusions 44, each having a first length 46, which is approximately 30% of the length 28 of the teeth 22. Figure 3 Compared to the serrated panel 20, the midpoint 36 is closer to the tip 24, making the main section 38 longer than the tip section 34. The straight line 47 connecting the free ends of the protrusions in the main section 38 extends parallel to the edge of the corresponding tooth 22. In this embodiment, the free end of the outermost tip-side protrusion also contacts the straight line 48. Furthermore, Figure 3 and Figure 4a The serrated panel shown is the same.

[0048] Figure 4b Other embodiments of the sawtooth panel 20 are shown. The raised strip 44 located in the main section 38 has a... Figure 4a The same shape as shown. The positions of the tip segment 34 and the midpoint 36 are also the same. Figure 4a The difference lies in the fact that the ribs in the tip sections 34 of the first and second teeth, viewed from the left, extend beyond the straight line 48 connecting the tooth tips. In the illustrated embodiment, an additional rib is provided at the outermost tips of these two teeth. At the first tooth, the free end of the rib in the tip section 34 terminates at a straight line 49 located a certain distance behind the straight line 48. At the second tooth, the free end of the rib in the tip section 34 terminates at two straight lines 49 extending at an angle to each other, such that the end shape provided by the rib has a gentler angle than the teeth of the serrated panel. In both embodiments, the ribs in the main section 38 have the same length, and the length of the rib in the tip section is shorter than the length of the rib 44 in the main section 38.

[0049] Figure 5 In the middle, the following view is shown Figure 3 The smaller portion of the serrated panel 20 shown (including one tooth) is positioned such that the tip 24 faces the observer. The centerline 58 of the tooth 22 is also shown in the figure. The adhesive surface 42 of the fastening section... Figure 5The middle side is facing down.

[0050] In this figure, edge 32 can be seen to have a thickness of 52. The cross-section of rib 44 is also elliptical. The rib has a thickness (height) of 54 and a width of 56, with the width 56 being less than the thickness 54. The thickness 52 of edge 32 is less than the thickness 54 of rib 44. There is a distance 60 between adjacent ribs 44, which is approximately the same size as the width 56 of rib 44.

[0051] Figure 6 The results of acoustic measurements taken in a wind tunnel using three different serrated panels 20 attached to a section of a wind turbine rotor blade 10 are shown. The acoustic measurements recorded sound pressure levels over a wide frequency range.

[0052] Curve 62 corresponds to the sound pressure level measured using a standard serrated panel 20 without any ridges 44. Curve 64 corresponds to the sound pressure level measured using a serrated panel 20 with ridges 44, wherein these ridges terminate at a straight line 49 extending a distance from the tip 24 of the tooth 22, as is known in the prior art. Curve 66 corresponds to the sound pressure level measured using a serrated panel 20 with ridges designed according to the claimed invention. It can be seen that the present invention can significantly reduce the sound pressure level in the low-frequency range of approximately 200 Hz to 400 Hz.

[0053] List of reference numerals

[0054] 10 Wind turbine rotor blades

[0055] 12 leaf roots

[0056] 14 Leaf tips

[0057] 16. Prelude

[0058] 18. Trailing edge

[0059] 20. Serrated panel

[0060] 22 teeth

[0061] 24 Tips

[0062] 26 Base

[0063] Length of 28 teeth

[0064] 30 teeth width

[0065] 32 Edge

[0066] 34 Tip Section

[0067] 36 Midpoint

[0068] 38 Main Segments

[0069] 40 Fastening Section

[0070] 42 Adhesion Surface

[0071] 44 ridges

[0072] 46 First Length

[0073] 47. Straight Line

[0074] 48. Straight Line

[0075] 49. Straight Line

[0076] 50 gap

[0077] 52 (32 at the edge) thickness

[0078] Thickness 54 (for the 44-inch convex strip)

[0079] 56 (width of 44 convex strip)

[0080] 58 Middle Line

[0081] 60 distance

Claims

1. A serrated panel (20) for a trailing edge (18) of a wind turbine rotor blade (10), the serrated panel (20) comprising: - at least two teeth (22), each tooth (22) having a tip (24), a base (26), a length (28) measured in chordwise direction between the base (26) and the tip (24), a width (30) measured at the base (26), wherein the length (28) is greater than the width (30), each tooth further having two edges (32) extending from the tip (24) to the base (26), each edge (32) having a tip section (34) extending from the tip (24) to a mid-point (36) of the edge (32), and a main section (38) extending from the mid-point (36) to the base (26); and - a plurality of ridges (44) arranged side by side in chordwise direction, each ridge (44) starting at one of the edges (32) and extending rearward, characterized in that: - all ridges (44) starting at one of the main sections (38) have a same first length (46), the first length being between 20% and 60% of the length (28) of the respective tooth (22), and all ridges (44) starting at one of the tip sections (34) are shorter than the first length (46).

2. The sawtooth panel (20) according to claim 1, characterized in that The length of the ridges (44) starting at one of the tip sections (34) is chosen such that the ridges (44) extend at least to a straight line (48) connecting the tips (24) of adjacent teeth (22).

3. The sawtooth panel (20) of claim 1, wherein, The length of the ridges (44) starting at one of the tip sections (34) is chosen such that the ridges (44) terminate at a straight line (48) connecting the tips (24) of adjacent teeth (22).

4. The sawtooth panel (20) according to any one of claims 1 to 3, characterized in that The serrated panel (20) comprises a fastening section (40) adapted to be integrated into or attached to a wind turbine rotor blade (10), wherein the at least two teeth (22) extend from a rear end of the fastening section (40).

5. The sawtooth panel (20) according to any one of claims 1 to 4, characterized in that, The teeth (22) and the ridges (44) extending from the teeth (22) are integrally manufactured, in particular by injection molding.

6. The sawtooth panel (20) according to any one of claims 1 to 5, characterized in that The serrated panel (20) is integrally manufactured, in particular by injection molding.

7. The sawtooth panel (20) according to any one of claims 1 to 6, characterized in that The ridges (44) have a constant cross-section.

8. The sawtooth panel (20) according to any one of claims 1 to 7, characterized in that The ridges (44) have a width (56) and a thickness (54), wherein the thickness (54) of the ridges is in the range of 1 to 3 times the width (56) of the ridges.

9. The sawtooth panel (20) according to any one of claims 1 to 8, characterized in that The distance (60) between adjacent ridges (44) corresponds to 50% to 200% of the width (56) of the ridges (44).

10. The sawtooth panel (20) according to any one of claims 1 to 9, characterized in that, The thickness (54) of the ridges (44) is in the range of 1 to 3 times the thickness (52) of the edges (32).

11. The sawtooth panel (20) according to any one of claims 1 to 10, characterized in that The at least two teeth (22) have the same dimensions.

12. A wind turbine rotor blade (10) comprising a blade root (12), a blade tip (14), a leading edge (16), a trailing edge (18), an aerodynamic airfoil, and at least one serrated panel (20) according to any one of claims 1 to 11, the at least one serrated panel (20) being arranged at the trailing edge (18).

13. A wind turbine rotor blade (10) according to claim 12, characterised in that, The at least one serrated panel (20) is arranged such that the base (26) of the at least two teeth (22) is disposed at or rearward of the trailing edge (18).

14. A wind turbine rotor blade (10) according to claim 12 or 13, characterised in that, The at least one serrated panel (20) comprises a first serrated panel (20) having teeth (22) of a first size and a second serrated panel (20) having teeth (22) of a second size different from the first size.

Images