Wind turbine rotor blade leading edge protectors

Abstract

The present invention relates to a leading edge protector for a wind turbine rotor blade. The present invention describes a leading edge protector (1) for a wind turbine rotor blade (2), comprising: a curved body (10) shaped to be attached to the rotor blade (20) along at least a portion of the leading edge (LE) of the rotor blade (20); a plurality of fins (11), each fin (11) extending radially outward from the curved body (10) and terminating at a blunt outer face (11B); and a plurality of reinforcing bands (11R), wherein the reinforcing bands (11R) are attached to the blunt outer face (11B) of the fins (11). The present invention also describes a method for manufacturing such a leading edge protector (1).

Description

Technical Field

[0001] A leading edge protector for a wind turbine rotor blade is described. Background Art

[0002] The impact force of airborne particles of ice, sand, etc. traveling at high relative speeds may cause damage, particularly along the leading edge of the rotor blades. Damage from such particles may appear as scratches, gouges, pits, or dents in the surface of the rotor blades. Any such damage at the outer surface or skin of the rotor blades may subsequently be exacerbated, for example, water may collect in pits or scratches at the surface, and cracks may form when the water expands as it freezes. If a lightning strike to the rotor blades occurs, such failures may in turn cause catastrophic damage. The structural damage may be so severe that the rotor blades require repair. Such maintenance work results in downtime of the wind turbine and further reduces the annual power generation.

[0003] Furthermore, pits or scratches in an otherwise smooth rotor blade will degrade the aerodynamic performance of the rotor blade and can have a significant negative impact on the annual energy production of the wind turbine.

[0004] In order to protect the leading edge of a wind turbine rotor blade from impact and erosion damage, it is known to attach a protective cap along the leading edge. The protective cap may be shaped to be located above the leading edge and to extend a distance into the suction and pressure sides of the rotor blade. Such a protective cap may be made of a polymer and may be formed directly on the rotor blade (e.g., by pouring a liquid polymer into place and allowing it to solidify). Alternatively, the protective cap may be formed as a separate body mounted to the rotor blade.

[0005] However, such protective covers are substantially subject to the damage that would otherwise be inflicted on the rotor blade. This means that while the protective cover can help avoid maintenance downtime by preventing structural damage to the rotor blade, it cannot prevent a reduction or deterioration in aerodynamic performance. This is because any pits or cracks in the protective cover will have the same negative impact on the aerodynamic performance of the rotor blade. Summary of the invention

[0006] It is therefore an object of the present invention to provide an improved leading edge protection for a rotor blade of a wind turbine.

[0007] This object is achieved by a leading edge protector according to the invention and by a method for producing a leading edge protector according to the invention.

[0008] According to the present invention, a leading edge protector for a wind turbine rotor blade comprises: a curved body shaped for attachment to a rotor blade along at least a portion of the leading edge of the rotor blade; a plurality of substantially parallel arcuate fins or protrusions, each fin extending substantially radially outward from the curved body and terminating in a blunt outer face; and a plurality of reinforcing bands, wherein the reinforcing bands are attached to the blunt outer faces of the fins.

[0009] One advantage of the leading edge protector (LEP) of the present invention is that the outwardly protruding fins can significantly reduce the extent of corrosion or impact damage. Because the fins extend radially outward from the curved body, they should be understood to have steep sidewalls. Due to their steep sidewalls, the presence of these fins increases the likelihood of particles impacting at an obtuse angle. When a particle such as sand or hail impacts the leading edge reinforcement at an obtuse angle, it will most likely be deflected, thereby losing momentum. If the deflected particle does contact the leading edge, any such impact will be without any significant force. In this way, the fins of the leading edge protector of the present invention can significantly reduce corrosion or impact damage to the leading edge.

[0010] Another advantage of the leading edge protector of the present invention is that any exposed or vulnerable areas are given additional protection by the reinforcement strip. In this context, an exposed or vulnerable area is an area where particles can impact the leading edge reinforcement at an angle close to the normal, i.e. perpendicular to the surface or at a very acute angle. With such a trajectory, the impact force is greatest. In the leading edge protector of the present invention, any such area is protected from damage by the reinforcement strip.

[0011] Therefore, the leading edge protector of the present invention can significantly reduce downtime associated with maintenance. In addition, the leading edge protector of the present invention can effectively reduce the extent to which the aerodynamic performance of the rotor blade is affected by corrosion damage and impact damage.

[0012] According to the present invention, a method of manufacturing such a leading edge protector comprises the following steps: forming a curved body for attachment to a wind turbine rotor blade along at least a portion of the leading edge of the rotor blade; forming a plurality of fins extending radially outward from the curved body, each fin terminating in a blunt outer face; and attaching a plurality of reinforcing bands to the blunt outer faces of the fins.

[0013] Particularly advantageous embodiments and features of the invention are given by the dependent claims, as disclosed in the following description. Features of different claim categories can be combined as appropriate to give further embodiments not described herein.

[0014] The aerodynamic rotor of a wind turbine typically comprises a plurality of rotor blades (usually three) mounted to a hub. The purpose of the aerodynamic rotor is to rotate the generator component. The rotor blades typically comprise a root end for mounting to the hub and an airfoil portion shaped to generate lift. The airfoil portion is typically shaped to have a pressure side and a suction side and tapers to a flat tip at the outermost end of the rotor blade. The pressure and suction sides meet at a rounded leading edge (LE) and a (usually) tapering trailing edge (TE). Since the leading edge is at the front most when the rotor blade moves through the air, it is most susceptible to erosion and impact damage as mentioned in the introduction.

[0015] In the following, it may be assumed that the curved body of the LEP of the invention is shaped to extend onto the suction side of the rotor blade and onto the pressure side of the rotor blade. For example, the curved body may extend to a short distance into the suction side or the pressure side, terminating slightly beyond the maximum thickness of the airfoil. The shape of the fin may be understood to follow the curved shape of the LEP, i.e. the fin is substantially arc-shaped when viewed from the side.

[0016] The fin of the LEP of the present invention comprises two sides, each side extending from the curved body toward the blunt outer face. The side of the fin is preferably substantially planar and can gradually transition to meet the curved body. As described above, the sidewalls of the fin are steep, i.e., highly inclined. The angle between the side and the normal preferably includes at most 30°, more preferably at most 20°, and most preferably at most 10°. In an extreme embodiment, the sidewalls of the fin may be more steeply inclined, thereby approaching vertical. Similarly, it may be acceptable to have an inclination angle greater than 30°, i.e., the sidewalls of the fin do not rise so steeply. It is also not required that the opposite sidewalls of the fin have the same inclination angle.

[0017] In a preferred embodiment of the invention, the fins protrude significantly outward from the curved body, i.e., the ratio of fin height to fin width is at least 3:1, more preferably at least 4:1, and most preferably at least 5:1. In other words, the height of the fin is at least 3 times, more preferably at least 4 times, and most preferably at least 5 times its width. With this "tall and thin" form, the fins can effectively deflect most of the incoming impact particles. The fins can also have the effect of reducing the noise of the aerodynamic rotor.

[0018] In a particularly preferred embodiment of the invention, the reinforcing strip is shaped as a continuation of the side surface of the fin. For example, the inclined surface of the side wall of the fin may continue into the inclined outer side surface of the reinforcing strip, so that the cross-section of the fin with its reinforcing strip has an overall parabolic shape. Basically, the reinforcing strip is preferably shaped to present only a steeply inclined face to the incoming airflow. In this way, the impact force of any airborne particles is greatly reduced.

[0019] In the following, the reinforcement bands mounted to the outer blunt faces of the fins are referred to as “external reinforcement bands.” The function of the fins and the external reinforcement bands is to increase the life of the LEP and the rotor blades.

[0020] Preferably, the fin comprises a tapered outer end or tip such that the two tapered outer ends of the fin transition or continue into the curved body on the suction and pressure sides of the LEP. The fins of the LEP of the present invention can be shaped in such a way that when the LEP is attached to the rotor blade, the tip-to-tip span of the fin does not exceed the maximum thickness of the airfoil.

[0021] The fins can be spaced at any suitable distance. For example, an embodiment of the LEP of the present invention may be implemented with 10-15 fins per meter, each fin having an average width of about 2-5 cm. The fin spacing and fin size need not be regular, i.e., the average fin width, fin height, and fin spacing may vary depending on the location of the LEP along the rotor blade. For a particular rotor blade type, the appropriate size of an embodiment of the LEP 1 of the present invention may be identified with the aid of simulations, wind tunnel testing techniques, etc.

[0022] The negative space between adjacent fins has the shape of a narrow and deep valley. Therefore, the shape of these fins can lead to an increased airflow with higher speed and pressure along the bottom of such a "valley". This concentrated airflow can act as a cushion to safely carry the deflected airborne particles over the leading edge of the rotor blade. However, some particles may still follow a trajectory directly towards the "valley bottom". Therefore, in another preferred embodiment of the present invention, the LEP also includes a plurality of internal reinforcement bands, wherein the internal reinforcement bands are arranged at the base of the "valley" between two adjacent fins and are shaped to extend along the curved body of the LEP.

[0023] The LEP of the present invention may be made of any suitable material. In a preferred embodiment of the present invention, the curved body and the fins may be molded as a single component and may be made of a suitable material. Since the curved body should fit tightly around the leading edge of the rotor blade, it is preferably made of a material such as an elastomer. An example of a suitable material may be a polyurethane based elastomer.

[0024] Alternatively, the fins may be prepared separately and may be made of a rigid material such as a hard polymer, and the fins may be partially embedded in a curved body made of a different material, such as a polyurethane-based elastomer as described above.

[0025] The reinforcing strip is preferably made of a rigid material that can withstand repeated direct impacts of airborne particles such as sand, hail, freezing rain, etc. In a preferred embodiment of the present invention, the reinforcing strip is made of a thermoplastic material such as polycarbonate plastic.

[0026] The materials from which the LEPs of the invention are made may be selected according to the environmental conditions prevailing at the installation site of the wind turbine where they will be used.

[0027] The LEP may extend along the entire leading edge of the rotor blade (i.e. along the entire length of the rotor blade) or along at least a large part of the airfoil portion. For example, a wind turbine may include three rotor blades, each having a root end and an airfoil portion. The rotational speed of a point along a wind turbine rotor blade increases with increasing distance from the root. This means that the impact force of airborne particles will also increase with increasing distance from the root. Therefore, the LEP of the present invention may have great benefits in the outer region of the rotor blade. Therefore, in a particularly preferred embodiment of the present invention, each rotor blade may be equipped with an embodiment of the LEP of the present invention, which extends along the outermost 20%, more preferably the outermost 30%, more preferably the outermost 40% of the length of the rotor blade. For example, a rotor blade having a length of 80m is preferably equipped with an embodiment of the LEP of the present invention, which is at least on the last 16m of the length of the rotor blade, thereby terminating at the terminal end of the blade. Conventional LEPs may be used in more inward regions of the rotor blade. The range of the LEP may be selected according to the prevailing environmental conditions at the installation site.

[0028] As explained above, the reinforcing band is attached to the blunt face of the fin and / or the channel between the fins. The reinforcing band can be installed in a variety of ways. In a preferred embodiment of the present invention, the LEP is manufactured to include a plurality of recesses along the blunt face of the fin and / or in the channel formed between adjacent fins along the curved body. The recess can be a simple hole, such as a circular orifice, and is preferably shaped to receive a corresponding column extending from the underside of the reinforcing band to complete the snap fastener. In order to attach such a reinforcing band, it is sufficient to apply pressure to the reinforcing band to press the column into the recess or opening. The advantage of snap fasteners is that the reinforcing band can be attached quickly and can be removed just as quickly (just by pulling the reinforcing band away from the curved body or fin). Alternatively or additionally, the reinforcing band can be attached by fasteners such as screws, pins or bolts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed for illustration purposes only and not as a definition of the limits of the present invention.

[0030] Figure 1 and Figure 2 An embodiment of a leading edge protector of the present invention is shown;

[0031] Figure 3 A wind turbine is shown;

[0032] Figure 4 The diagram illustrates the effect of the leading edge protector of the present invention;

[0033] Figure 5 and Figure 6 The reinforcing strip in the embodiment of the leading edge protector of the present invention is shown;

[0034] Figure 7 A prior art leading edge protector is shown.

[0035] In the drawings, like reference numerals refer to like objects throughout. Objects in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0036] Figure 1 An embodiment of a LEP 1 of the invention is shown relative to a wind turbine rotor blade 20 to which it is to be mounted. The LEP 1 is mounted along the LE of the rotor blade 2, i.e. as a shroud around the area where the pressure side meets the suction side. The LEP 1 of the invention comprises a curved body 10 which is shaped to be located on either side of a leading edge LE on the rotor blade 2. In this embodiment, a row of substantially identical fins 11 are shown. Each fin 11 protrudes from the curved body 10. Each fin 11 is substantially arcuate and has a blunt outer face to which an external reinforcement band 11R is mounted. The walls 11W or sides of the fin 11 are steeply inclined, i.e. the height h11 of the fin 11 is significantly greater than its average width w11, as shown in FIG. Figure 2 As shown in Figure 2 A cross-section of the LEP 1 is shown through a plane defined by the leading edge LE and its normal. The figure also shows that the sidewall 11W of the fin 11 is at a steep angle θ relative to a normal extending outwardly from the rotor blade surface. Figure 2 The LEP 1 is shown in a partially assembled state before external reinforcing straps are attached to the blunt or flat outer faces 11B of the fins 11, and before internal reinforcing straps are attached to the valleys 10C between the fins 11. The complete assembly is shown in FIG. Figure 4 and Figure 5 , where each fin 11 is provided with an external reinforcement band 11R on top, and each "valley" 10C is lined with an internal reinforcement band 10R.

[0037] Figure 3A wind turbine 2 is shown having a plurality of rotor blades 20 mounted to a hub 21 which rotates components of a generator housed in a nacelle 22. The nacelle 22 is mounted on a tower 23 which may be located at an onshore or offshore location. The LEP of the present invention may be used along the entire leading edge LE of each rotor blade 20, or along a suitable portion such as shown here. As explained above, suitable parameters such as fin spacing, fin width, fin height, etc. may be identified for this particular type of rotor blade 20 by means of simulation, wind tunnel testing techniques, etc.

[0038] Figure 4 Exemplary shapes of LEP reinforcements are shown, showing a preferred convex shape of the outer reinforcement band 11R and a preferred concave shape of the inner reinforcement band 10R. The figure also illustrates the beneficial effects of the LEP 1 of the present invention, showing an exemplary impact of a particle P such as hail or sand relative to the normal of the surface at the impact point. Any particle P that impacts on the steep side 11W of the fin 11 will be safely deflected, thereby losing speed. In the two exemplary conditions on the left, the obtuse impact angles β, β' relative to the normal mean that the impact force is negligible, or at least so low that it does not cause any significant damage. In the two exemplary conditions on the right, the particle P impacts the LEP 1 at an acute impact angle α, α' relative to the normal. However, the vulnerable blunt surface 11B of the fin 11 and the vulnerable channel 10C between the fins 11 are protected by reinforcement bands 11R, 10R, which are configured to absorb the impact force to a large extent.

[0039] Figure 5 10R and the fins 11. The figure also shows the snap-stud connections S between the reinforcing band 11R and the fins 11 and between the reinforcing band 10R and the channels 10C between the fins 11. The press-studs allow the reinforcing bands 11R, 10R to be installed relatively easily and removed with some difficulty, such as Figure 6 (for clarity, the opening for the snaps is not shown).

[0040] Figure 7 A prior art LEP 70 is shown for installation over the leading edge LE of a rotor blade 20. While the prior art LEP 70 may prevent damage to the rotor blade 20 in the leading edge region, the protector 70 will be damaged by corrosion or pitting, as shown in the enlarged image portions. These illustrations show pitting 71 and gouging 72 caused by high-speed impacts from particles such as hail or sand.

[0041] 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.

[0042] For the sake of clarity, it is to be understood that the use of "a", "an" or "an" throughout this application does not exclude a plurality, and "comprising" does not exclude other steps or elements.

Claims

1. A leading edge protector (1) for a wind turbine rotor blade (2), comprising: - a curved body (10) shaped for attachment to said rotor blade (20) along at least a portion of a leading edge (LE) of said rotor blade (20); - a plurality of fins (11), each fin (11) extending radially outwardly from the curved body (10) and terminating at a blunt outer face (11B), and wherein each fin (11) comprises two side faces (11W), each side face (11W) extending from the curved body (10) towards the blunt outer face (11B); and - a plurality of reinforcing strips (11R), wherein the reinforcing strips (11R) are attached to the blunt outer face (11B) of the fin (11), and wherein the reinforcing strips (11R) are shaped as a continuation of the side face (11W) of the fin (11), The cross section of the fin (11) with its reinforcement band (11R) has an overall parabolic shape.

2. The leading edge protector according to claim 1, wherein: The angle (θ) formed between the side surface (11W) and the normal line is at most 30°.

3. The leading edge protector according to claim 2, wherein: The angle (θ) formed between the side surface (11W) and the normal line is at most 20°.

4. The leading edge protector according to claim 3, wherein: The angle (θ) formed between the side surface (11W) and the normal line is at most 10°.

5. The leading edge protector according to claim 1 or claim 2, wherein: The ratio of the fin height (h11) to the average fin width (w11) is at least 3:

1.

6. The leading edge protector according to claim 5, wherein: The ratio of the fin height (h11) to the average fin width (w11) is at least 4:

1.

7. The leading edge protector according to claim 6, wherein: The ratio of the fin height (h11) to the average fin width (w11) is at least 5:

1.

8. The leading edge protector according to claim 1, wherein: The fin (11) has the form of an arc, and wherein the tip-to-tip span of the fin (11) does not exceed the maximum thickness of the rotor blade airfoil at the location of the fin (11).

9. The leading edge protector according to claim 1, wherein: The fin (11) comprises a tapered outer end.

10. The leading edge protector according to claim 1, comprising a plurality of internal reinforcement strips (10R), wherein: An internal reinforcement band (10R) is arranged between two adjacent fins (11) and extends around the curved body (10).

11. The leading edge protector according to claim 1, wherein: The fin (11) and / or the curved body (10) are made of a polyurethane-based elastomer.

12. The leading edge protector according to claim 1, wherein: The reinforcement strips (11R, 10R) are made of polycarbonate plastic.

13. A wind turbine (2) comprising a plurality of rotor blades (20), wherein: A rotor blade (20) is provided with a leading edge protector (1) according to any one of claims 1 to 12.

14. A method for manufacturing a leading edge protector (1) according to any one of claims 1 to 12, the method comprising the following steps: - forming a curved body (10) for attachment to a wind turbine rotor blade (20) along at least a portion of a leading edge (LE) of the wind turbine rotor blade (20); - forming a plurality of fins (11) extending radially outward from the curved body (10), each fin (11) terminating at a blunt outer face (11B) and comprising two side faces (11W), each side face (11W) extending from the curved body (10) towards the blunt outer face (11B); as well as - attaching a plurality of external reinforcing strips (11R) to the blunt external face (11B) of the fin (11), wherein the reinforcing strips (11R) are shaped as a continuation of the side faces (11W) of the fin (11).

15. The method according to claim 14, comprising the steps of: A plurality of internal reinforcement straps (10R) are attached to the curved body (10) between the fins (11).

16. A method according to claim 14 or claim 15, comprising the steps of: A plurality of recesses are formed along the blunt surface (11B) of the fin (11) and / or along the curved body (10) between adjacent fins (11), wherein the recesses are formed to receive fasteners extending from the underside of the reinforcement band (10R, 11R), and wherein the step of attaching the reinforcement band (10R, 11R) is accomplished by applying pressure to push the fasteners into the corresponding recesses to form a snap connection (S).

17. The method according to claim 16, wherein: The reinforcing band (10R, 11R) is configured to allow detachment of the reinforcing band (10R, 11R) by pulling to release the fastener from the recess.

18. The method according to claim 14 or claim 15, wherein: The curved body (10) and the fins (11) are molded as a single piece.

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