Rotor blade for a wind turbine and rotor blade tip

Abstract

The invention relates to a rotor blade (110) for a wind turbine (100), having a main rotor blade body (111) and a rotor blade tip (119) adjacent to the main rotor blade body (111), a suction-side surface (124), a pressure-side surface (122), and a profiled trailing edge (140), wherein the downstream edges (152) of the suction-side surface (124) and the pressure-side surface (122) are joined together at the profiled trailing edge (140), and the rotor blade tip (119) has a flexible trailing-edge element (150) which, in terms of its shape,is flush with the outer contour of the suction-side surface (124) and the pressure-side surface (122) of the rotor blade (110) and forms a portion (156) of the profiled trailing edge (140) of the rotor blade (110) such that the profiled trailing edge (140) of the rotor blade (110) extends monotonically in the direction of the lateral end (154) of the rotor blade (110) at the tip of the rotor blade (119). The invention also relates to the tip of the rotor blade (119).

Description

[0001] The invention relates to a rotor blade for a wind turbine, comprising a rotor blade body, a rotor blade tip adjoining the rotor blade body, a suction-side surface, and a pressure-side surface. Furthermore, the invention relates to a rotor blade tip for a rotor blade.

[0002] Wind turbines are used to convert wind energy into electrical energy. They conventionally have one or more rotor blades (also called wind turbine rotor blades) for this purpose.

[0003] Rotor blades can be equipped with aerodynamically effective attachments to selectively influence the airflow around the wind turbine rotor blade during operation. For example, attachments arranged along the leading edge of the profile are known to improve the blade's aerodynamic properties by means of serrations. In this regard, reference is made, for example, to publications DE 10 2011 052 930 A1 or WO 2017 / 148669 A1.

[0004] During the patent granting procedure, the following documents, among others, were considered: US 2007 / 025858 A1 and US 2012 / 141274 A1.

[0005] Following current trends, modern wind turbines are using increasingly longer rotor blades, which can weigh up to 35 tons and reach lengths of up to 90 meters. With such long rotor blades, a particularly high angle-of-attack oscillation typically occurs, resulting from the blade rotation and the associated change in the angle of attack at the blade tip. This is primarily because such long rotor blades are generally much more flexible compared to smaller, especially shorter, blades (e.g., 60 meters long). This phenomenon leads to airflow separation during operation, which is the primary cause of unwanted noise.

[0006] One of the objectives of the invention is to provide a rotor blade and a rotor blade tip which contribute to a particularly effective reduction of noise or even its complete avoidance.

[0007] The problem is solved by the subordinate claims.

[0008] According to one aspect, a rotor blade for a wind turbine is disclosed. The rotor blade has a main body, a tip adjoining the main body, a suction surface, a pressure surface, and a trailing edge. Downstream edges of the suction and pressure surfaces are connected at the trailing edge. The tip has a flexible trailing element whose shape is flush with the outer contour of the suction and pressure surfaces of the rotor blade and which forms a section of the trailing edge, such that the trailing edge at the tip, or at least that section, is monotonous in the direction of a tip-side end of the rotor blade.

[0009] The invention provides for a trailing edge element at the rotor blade tip, flush with the outer contour of the rotor blade. This element is designed to be flexible enough to deform under the influence of the airflow during normal operation of the rotor blade. For example, it can yield or bend in the direction of the airflow towards the suction side or the pressure side. In other words, the trailing edge element allows for a change in the profile cross-section in the area of ​​the trailing edge or a section thereof, whereby this cross-section changes its orientation (in the direction of the profile thickness) at least partially depending on the airflow. Using such a flexible trailing edge enables particularly effective pressure equalization between the pressure side and the suction side. Furthermore, it helps to prevent or reduce the likelihood of flow separation on the pressure and / or suction side.Furthermore, the improved pressure equalization helps to reduce the size of so-called rotor blade tip vortices, which represent another source of noise for a wind turbine. The invention thus makes it possible to reduce or avoid aeroacoustic noise at the rotor blade tip, especially with particularly long rotor blades.

[0010] The rotor blade tip can be understood as a section of the rotor blade. For example, the rotor blade tip and the rotor blade body define two (longitudinal) sections of the rotor blade. The rotor blade tip can be constructed identically to the rotor blade body. In a comparative example, the rotor blade tip is formed integrally with the rotor blade body.

[0011] The rotor blade tip is a separate component from the main rotor blade body. In this case, the rotor blade tip has a different structure than the main body and / or it may be made of a different material. For example, the rotor blade tip is made of a metallic material. For example, the rotor blade tip is designed as a lightning receptor, in which case the rotor blade tip is made of aluminum.

[0012] Alternatively, the rotor blade tip is designed as a rotor blade segment of a rotor blade divided (perpendicular to the longitudinal axis). In this case, the rotor blade tip and the main rotor blade body are, for example, identical or similar in construction. They can also have different constructions.

[0013] The rotor blade tip, regardless of which of the above-mentioned configurations, has, for example, a length of up to 10%, particularly preferably 0 to 3%, of the total length of the rotor blade along a longitudinal axis of the rotor blade (i.e., from the rotor blade root to the tip end of the rotor blade). In this context, the rotor blade tip always has an axial extension along the longitudinal axis of the rotor blade and does not, for example, define a point or an endpoint of the rotor blade.

[0014] The rotor blade tip is an integral part of the rotor blade and incorporates the end-edge element according to the invention. The end-edge element is a separate element from the rotor blade tip. For example, the rotor blade tip has a recessed area (extending from the profile trailing edge) or a cutout for the end-edge element, so that the end-edge element is flush with the outer contour of the rotor blade. In other words, the end-edge element is flush with the rest of the rotor blade or the remaining rotor blade tip, at least on the suction and pressure sides. Preferably, the end-edge element is flush with the rotor blade on all outer surfaces, so that a seamless transition is provided along the entire outer contour.

[0015] The flexible design means that the end edge element has greater elastic deformability compared to the rest of the rotor blade or the rotor blade tip.

[0016] The monotonous profile of the airfoil trailing edge defined by the trailing edge element at the rotor blade tip means that the profile remains the same or changes in the same direction, for example, relative to the longitudinal axis of the rotor blade. For instance, the profile is curved, but the direction of the curvature does not change. In other words, the trailing edge element does not form an airfoil trailing edge section with a wavy, jagged, or otherwise alternating profile.

[0017] The trailing edge of the airfoil is the edge of the rotor blade furthest downstream in the direction of airflow. The edges of the suction-side and pressure-side surfaces are therefore those edges that are furthest downstream with respect to the airflow during normal operation of the rotor blade.

[0018] According to one embodiment, a substantially seamless, and in particular stepless, transition is formed between the trailing edge element and the rest of the rotor blade along the airfoil trailing edge. This allows the trailing edge element to seamlessly continue the profile trailing edge of the rest of the rotor blade in the area of ​​the blade tip. In other words, the trailing edge element seamlessly continues the profile trailing edge. This contributes particularly favorably to the aeroacoustic properties of the rotor blade at the blade tip.

[0019] The trailing edge element is free of any chord extension at the trailing edge. This means that a so-called chord extension of the rotor blade at the blade tip is not included. This contributes to the aforementioned aeroacoustic properties of the rotor blade at the blade tip.

[0020] According to one embodiment, the section of the rotor blade's trailing edge formed by the end-edge element has a curvature that changes monotonically. This enables the aforementioned advantages and functions.

[0021] According to one embodiment, the end edge element is made of an elastomeric material. This provides a flexible, elastic plastic material. For example, it could be a rubber, PU (polyurethane), or a PU compound / hybrid that remains flexible under temperature fluctuations.

[0022] The rotor blade tip is designed separately from the main rotor blade body and connected to it. This allows for separate manufacturing of the rotor blade tip. For example, the trailing edge element can be attached or mounted separately. It also facilitates the replacement of the trailing edge element, for instance, in case of wear.

[0023] According to one embodiment, the rotor blade tip is formed from an electrically conductive material, in particular a metallic material. This is particularly advantageous for the assembly of the trailing edge element, as especially precise geometries, surfaces, and the like can be provided for its mounting. Furthermore, this facilitates the replacement of the trailing edge element.

[0024] According to one embodiment, the end-edge element is fixed to the rotor blade tip by means of a positive fit. This contributes to the advantages and effects mentioned above.

[0025] According to one embodiment, the end-edge element is fixed to the rotor blade tip via a rail system, a tongue-and-groove connection, or a dovetail joint. This contributes to the aforementioned advantages and effects, such as easy replacement in case of wear.

[0026] According to one embodiment, the leading edge of the rotor blade profile runs monotonically along a longitudinal axis of the rotor blade, starting from a position of maximum profile depth and ending at the tip. This results in particularly good aeroacoustic properties of the rotor blade.

[0027] According to another aspect, a rotor blade tip for a wind turbine rotor blade is described, wherein the rotor blade tip is designed separately from the main rotor blade body and connectable to the main rotor blade body. The rotor blade tip has a flexibly designed end-edge element, which, with regard to its shape, is flush with an outer contour of a suction-side surface and a pressure-side surface of the rotor blade tip and is designed to form a section of the profile end edge of the rotor blade, wherein the profile end edge section is monotonic.

[0028] The rotor blade tip essentially enables the aforementioned advantages and functions.

[0029] Further advantages, features, and enhancements will become apparent from the following description of exemplary embodiments, which will be explained in conjunction with the figures. Identical, similar, or equivalent elements may be designated with the same reference numerals in the figures.

[0030] The figures show: Figure 1 a schematic representation of a wind turbine according to an exemplary embodiment, Figure 2 a schematic representation of a rotor blade of a wind turbine, Figure 3 a schematic representation of a cross-sectional profile of a conventional rotor blade tip, Figure 4 a schematic top view of a rotor blade at the rotor blade tip according to an embodiment of the invention, Figure 5 a schematic representation of a cross-sectional profile of the rotor blade tip according to Figure 4, and Figures 6 and 7 Schematic representations of a connection of an end-edge element to the rotor blade tip according to two embodiments of the invention.

[0031] Figure 1 Figure 1 shows a schematic representation of a wind turbine 100. The wind turbine 100 has a tower 102. The tower 102 is attached to a ground by means of a foundation 104. A nacelle 106 is rotatably mounted at one end of the tower 102 opposite the ground. The nacelle 106 includes, for example, a generator which is coupled to a rotor 108 via a rotor shaft (not shown). The rotor 108 has one or more rotor blades 110, which are arranged on a rotor hub 112.

[0032] During operation, the rotor 108 is set in motion by an airflow, for example, wind. This rotational motion is transmitted via the rotor shaft and, if necessary, a gearbox to the generator. The generator converts the kinetic energy of the rotor 108 into electrical energy.

[0033] Figure 2Figure 1 schematically shows a rotor blade 110. The rotor blade 110 has the shape of a conventional rotor blade and is formed by a rotor blade body 111 and a rotor blade tip 119. The rotor blade tip 119 is designed as a separate element. The rotor blade tip 119 is firmly connected to the rotor blade body 111 by an adhesive bond. Of course, the rotor blade tip 119 can be connected to the rotor blade body 111 in a different manner. The rotor blade body 111 is formed by two interconnected half-shells made of fiber-reinforced composite material and is essentially hollow inside, defining a rotor blade cavity 113. The rotor blade 110 has a rotor blade root region 114, which faces the rotor hub 112. The rotor blade root region 114 typically has an essentially circular cross-section.The rotor blade root region 114 is adjoined by a transition region 116 and a profile region 118 of the rotor blade 110. With respect to a longitudinal direction 120, the rotor blade 110 has a pressure side 122 (also referred to here as the pressure-side surface) and an opposite suction side 124 (suction-side surface). A rotor blade connection end 126 with a flange connection 128 is provided in the rotor blade root region 114, by means of which the rotor blade 110 is mechanically connected to a pitch bearing or an extender.

[0034] The trailing edge 140 and the leading edge 142 of the rotor blade 110 are formed by the trailing edges and leading edges of both the rotor blade body 111 and the rotor blade tip 119. A chord length 144 is defined as the distance from the trailing edge 140 to the leading edge 142 with respect to a profile cross-section 132. A thickness 146 is defined as the distance from the pressure side 122 to the suction side 124, where, in this context, the maximum thickness of the corresponding profile cross-section 132 is meant. The thickness 146 is measured perpendicular to the longitudinal axis 120 and the chord length 144. A (profile) cross-section lies in a plane normal to the longitudinal axis 120.

[0035] Figure 3Figure 1 shows an example of a profile cross-section 132 at the rotor blade tip 119 of a conventional rotor blade. Especially with long rotor blades, undesirable noise can occur in the area of ​​the profile trailing edge 140 due to flow separation and air turbulence (indicated by the arrows).

[0036] Figures 4 and 5 relate to a rotor blade tip 119 according to an embodiment of the invention. Figure 5 shows the AA section according to the in Figure 4 The section plane is shown. The rotor blade tip 119 is formed separately from the rotor blade main body 111. The rotor blade tip 119 is formed by a tip main body 148 and a trailing edge element 150, which are mechanically securely connected to each other. The trailing edge element 150 is elastically designed and thus flexibly deformable. Figure 5Figure 150, which represents a profile cross-section 132 at the rotor blade tip 119, shows that the downstream edges 152 of the suction-side surface 124 and the pressure-side surface 122 are connected via the profile trailing edge 140. The trailing edge element 150 is shaped to be flush with the outer contour of the suction-side surface 124 and the pressure-side surface 122 of the rotor blade 110 and forms a section 156 of the profile trailing edge 140 of the rotor blade 110. A substantially seamless, in particular stepless, transition 153 is formed between the trailing edge element 150 and the rest of the rotor blade 110 along the profile trailing edge 140. In particular, the flush transition 153 is provided between the rotor blade body 111 and the trailing edge element 150.

[0037] The fully flush fitting of the end-edge element 150 into the rotor blade 110 or its outer skin ensures that the profile end edge 140 of the rotor blade 110 at the rotor blade tip 119 follows a monotonous curve towards a tip-side end 154 of the rotor blade 110. In other words, the curvature 155 (relative to the direction of the rotor blade longitudinal axis 120) of the profile end edge 140 at the rotor blade tip 119 is monotonous. Due to the flexible design of the end-edge element 150, it can adapt to airflow patterns, such as... Figure 5 as indicated. This means that the profile trailing edge 140 or the section 156 at the rotor blade tip 119 is flexible, i.e. . Movable. This enables the aforementioned advantages and functions. An extension of the profile depth 144 (so-called "chord extension") is not achieved with the end edge element 150.

[0038] With regard to the in Figure 2In the illustrated rotor blade 110, it is particularly preferred that the profile end edge 140 of the rotor blade 110 has a monotonous profile over a particularly large longitudinal section, for example starting from 50% of the total length (coming from the direction of the rotor blade root area 114) up to the tip end 154.

[0039] The tip section 148 is made of a metallic material, such as aluminum or an aluminum alloy. The trailing edge element 150 is made, for example, of a plastic material such as polyurethane and has a modulus of elasticity in the range of 0.01 to 1.5. In particular, the trailing edge element 150 is more flexible than the rest of the rotor blade 110 and especially than the tip section 148.

[0040] The end-edge element 150 can be attached to the rotor blade tip 119 in various ways, i.e. .are connected to the tip body 148. Preferably, the end edge element 150 is positively connected to the tip body 148. Manufacturing the tip body 148 from metal is advantageous because this allows for particularly precise geometries and thus secure and stable connections. For example, see Figures 6 and 7 Reference is made to a rail-like connection 158 (otherwise: rail mechanism) or a dovetail connection 160. Other types of connection are also conceivable, such as an adhesive connection or a screw, bolt, and / or rivet connection. Reference symbol list

[0041] 100 Wind turbine 102 Tower 104 Foundation 106 Nacelle 108 Rotor 110 Rotor blade 111 Rotor blade body 112 Rotor hub 113 Rotor blade cavity 114 Rotor blade root area 116 Transition area 118 Profile area 119 Rotor blade tip 120 Longitudinal direction 122 Pressure side 124 Suction side 126 Rotor blade connection end 128 Flange connection 132 Profile cross-section 140 Profile end edge 142 Profile leading edge 144 Profile depth 146 Profile thickness 148 Tip body 150 End edge element 152 Downstream edge 153 Transition 154 Tip end 155 Curvature 156 Section of profile end edge 158 Rail-like connection 160 Dovetail joint A-A section

Claims

1. A rotor blade (110) for a wind turbine (100), comprising a rotor blade main body (111) and a rotor blade tip (119) adjoining the rotor blade main body (111), a suction-side surface (124), a pressure-side surface (122), and a profile trailing edge (140), wherein - downstream edges (152) of the suction-side surface (124) and the pressure-side surface (122) are connected to each other at the profile trailing edge (140), and - the rotor blade tip (119) has a flexibly designed trailing edge element (150) which, in terms of its shape, is adapted to fit flush with the outer contour of the suction-side surface (124) and the pressure-side surface (122) of the rotor blade (110) and forms a section (156) of the profile trailing edge (140) of the rotor blade (110), so that the profile trailing edge (140) of the rotor blade (110) at the rotor blade tip (119) extends monotonically toward a tip-side end (154) of the rotor blade (110), wherein the trailing edge element (150) is free of a profile depth extension at the profile trailing edge (140), and wherein the rotor blade tip (119) is formed separately from the rotor blade main body (111) and is connected to the rotor blade main body (111).

2. The rotor blade (110) according to claim 1, wherein a substantially seamless, in particular stepless, transition (153) is formed between the trailing edge element (150) and the remainder of the rotor blade (110) along the profile trailing edge (140).

3. The rotor blade (110) according to any of the preceding claims, wherein the section (156) of the profile trailing edge (140) of the rotor blade (110) formed by the trailing edge element (150) has a curvature that changes monotonically.

4. The rotor blade (110) according to any of the preceding claims, wherein the trailing edge element (150) is formed from an elastomeric material.

5. The rotor blade according to any of the preceding claims, wherein the rotor blade tip (119) is formed from an electrically conductive material.

6. The rotor blade according to any of the preceding claims, wherein the trailing edge element (150) is fixed to the rotor blade tip (119) by means of a form fit.

7. The rotor blade according to claim 6, wherein the trailing edge element (150) is fixed to the rotor blade tip (119) by means of a rail system (158), a tongue-and-groove connection or a dovetail connection (160).

8. The rotor blade according to any of the preceding claims, wherein the profile trailing edge (140) of the rotor blade (110) extends monotonically along a longitudinal axis (120) of the rotor blade (110) from a position of maximum profile depth (144) to the tip-side end (154).

9. A rotor blade tip (119) for a rotor blade of a wind turbine (100), wherein the rotor blade tip (119) - is formed separately from a rotor blade main body (111) of the rotor blade (110) and can be connected to the rotor blade main body (111), and - has a flexibly designed trailing edge element (150) which, in terms of its shape, is adapted to fit flush with an outer contour of a suction-side surface (124) and a pressure-side surface (122) of the rotor blade tip (119) and is designed to form a section (156) of the profile trailing edge (140) of the rotor blade (110), wherein the course of the section (156) of the profile trailing edge (140) is monotonic, wherein the trailing edge element (150) is free of a profile depth extension at the profile trailing edge (140).

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