Flow modifying element for wind turbine blade

Abstract

A flow modifying element for a wind turbine blade is provided. A wind turbine blade (10) comprises a blade body (20) having a leading edge (16), a suction surface (18) and a pressure surface (19). The flow modifying element (30) is configured to provide a trailing edge (17) for at least a longitudinal section (15) of the wind turbine blade (10). The flow modifying element (30) and the blade body (20) form an aerodynamic profile. The flow modifying element (30) comprises: a suction side (32); a pressure side (33); a trailing end (37) providing a trailing edge (17) of the aerodynamic profile; and a pressure surface extension section (39) on the pressure side (33), the pressure surface extension section (39) configured to extend the pressure surface (19) of the blade body (20) towards the aft end (37). A pressure side contour section (40) of the flow modifying element has the shape of a concave curve and forms a recessed portion (44).

Description

Technical Field

[0001] The present invention relates to a flow modifying element for a wind turbine blade, in particular for providing a trailing edge for such a blade, and also to a wind turbine blade comprising such a flow modifying element. Background Art

[0002] The use of wind energy is surging. To extract more energy from the wind, larger wind turbines are being manufactured and installed, requiring larger blades. Wind turbine blades are mounted at their root ends to the hub of the wind turbine rotor and extend to their tip ends. However, the properties of the blade's root region are often governed by structural considerations, so the mid-span and outboard regions of the blade are typically designed to achieve improved aerodynamic performance. Consequently, the aerodynamic profile in the blade's root region (also known as the "airfoil") typically has a large relative thickness.

[0003] To help the rotor start and generate electricity at moderate wind speeds, the profile in the root area of ​​the blade can have a large chord length and large twist. However, this makes the blade more expensive and difficult to manufacture, and also creates problems with logistics (such as transporting the blade) due to the size and weight of the blade.

[0004] To address this issue, US Pat. No. 7,204,674 B2 describes a rotor blade with a section at its trailing edge that allows the blade's chord length to be reduced, for example by providing an inflatable section that is deflated during transport and inflated during normal operation. Other solutions disclosed in this document include elements that can be extended to extend the blade's surface, or deformable materials that can be rolled up using extended folding arms. During high winds, the loads applied to such large blades further present a problem. In these documents, the inflatable elements can be deflated again to reduce the blade's area, or the surface elements can be retracted. A similar solution is disclosed in EP 2 322 793 A1, in which the blade's trailing edge section includes a collapsible chamber that collapses when a predetermined rotor speed is reached. This reduces the blade's aerodynamic performance, thereby achieving overspeed control. The reduced aerodynamic performance reduces the rotor speed, thereby preventing damage to the blade.

[0005] Rotor blade manufacturing also often results in a blunt trailing edge with an aerodynamic profile, which can be due, for example, to gluing together two shell parts of a certain thickness, which is increased by the thickness of the glue layer, as described in document WO 2011 / 157849 A2. This document proposes providing a prefabricated trailing edge portion with a well-defined shape and edges, which substantially extends the profile shape given by the blade. Another possibility for treating a blunt trailing edge in the inner region of the blade is described in document US 2021 / 0079886 A1, in which a splitter plate is attached to the blunt trailing edge, below the transition from the suction side to the trailing edge, and has a surface portion that is located in the shear layer generated by the suction side of the blade.

[0006] The above solutions still have drawbacks with respect to their aerodynamic performance. In particular, it would be desirable to allow the aerodynamic performance to be adjusted according to the design objectives of the blade designer. Providing lift increase and / or drag reduction may be particularly beneficial.

[0007] Document EP 2 806 156 A1 describes a ridge mounted or defined along the trailing edge of an airfoil for noise reduction. The sides of the ridge converge concavely from the respective suction and pressure sides of the trailing edge to a peak.

[0008] Document EP 2 811 156 A1 describes a rotor blade comprising a blade body having a trailing edge. The trailing edge comprises a trailing edge base and a separate trailing edge extension.

[0009] Document EP 3 204 634 A1 describes a wind turbine blade comprising a trailing edge vane having a vane portion protruding from the trailing edge on the pressure side of the blade. Summary of the Invention

[0010] There is therefore a need to alleviate at least some of the above mentioned disadvantages and to improve the aerodynamic properties of wind turbine blades, in particular in the root region thereof.

[0011] This need is met by the features of the independent claim.The dependent claims describe embodiments of the invention.

[0012] According to one aspect of the present invention, a flow modifying element for a wind turbine blade is provided, wherein the wind turbine blade includes a blade body having a leading edge, a suction surface, and a pressure surface. The flow modifying element is configured to provide a trailing edge for at least a longitudinal section of the wind turbine blade. The flow modifying element and the blade body form an aerodynamic profile. The flow modifying element includes a suction side, a pressure side, a rear end providing a trailing edge of the aerodynamic profile, and a pressure surface extension section on the pressure side. The pressure surface extension section is configured to extend the pressure surface of the blade body toward the rear end. The pressure surface extension section is shaped to provide a pressure side profile section in the aerodynamic profile, the pressure side profile section having a concave curve and forming a recessed portion that is recessed from the pressure side toward the suction side of the flow modifying element.

[0013] When mounted on or integrated into the blade body, a flow modifying element can reduce drag and increase lift on a wind turbine blade. The concavely curved shape can, in particular, result in a corresponding increase in lift and reduction in drag, which can lead to a higher lift-to-drag ratio. With this shape, the pressure surface extension section can be convex inward to form a longitudinal recess extending in the longitudinal direction of the flow modifying element.

[0014] To extend the pressure surface of the blade body, the pressure surface extension section can be configured to form a continuous surface with the pressure surface of the blade body. For example, a continuous surface may imply the absence of a step. For example, the pressure surface does not first transition into the trailing edge of the blade body, where the flow modifying element is mounted, but rather the pressure surface transitions directly into the pressure surface extension section. Consequently, there may be no step or jump in the aerodynamic profile (with the chord line of the blade body as a reference axis). The pressure surface extension section can be formed to smoothly transition from the pressure surface or to form an edge with the pressure surface of the blade body.

[0015] A reference frame can be defined according to which the leading edge is located in front of the trailing edge and the suction side is arranged above the pressure side. References to "above" and "below" and "forward" and "aft" or "rear" are all with reference to this reference frame.

[0016] Optionally, the pressure side profile segment may have a first portion extending rearwardly and upwardly (i.e., towards the rear end and suction side) and possibly reaching an apex, and a second portion extending rearwardly and downwardly (i.e., towards the rear end and pressure side). Thus, the profile segment may have a (symmetrical or asymmetrical) arcuate shape, with its open side facing the chord line of the blade body.

[0017] The recessed portion may be located above the extrapolation line of the pressure surface of the blade body, towards the rear end. For simplicity, in this document, the extrapolation line of the pressure surface refers to the extrapolation line of the curve segment of the contour of the blade body corresponding to the pressure surface of the blade body. It should be noted that the extrapolation line refers to the estimated extension of the corresponding surface or curve segment, that is, it refers to an imaginary surface or curve, which is used in this document to describe the relative arrangement of components in a geometric way. Such an extrapolation line can use a straight line or a curved line, the straight line being tangent to the point where the curve segment corresponding to the pressure surface ends (that is, it can be a linear extrapolation line), the curvature of the curved line corresponding to the curvature of the contour segment / surface to be extrapolated. However, it should be noted that the shape of the pressure surface towards the rear end is usually quite straight in contour. Therefore, it is preferred to use linear extrapolation lines of the suction side and the pressure side.

[0018] In an optional example, the pressure side profile section can be shaped to have an apex perpendicular to the chord line of the blade body in the direction of the suction side, wherein the apex is located above the extrapolated line of the pressure surface of the blade body in the direction of the suction side in the profile. Preferably, the apex is located above the center line between the extrapolated line of the suction side and the extrapolated line of the pressure side of the blade body in the profile. Such a center line can also be called a "center line" and is usually the geometric midpoint between the two reference lines. It can have the same distance from the two lines and can, for example, halve the intersection angle between the two reference lines. By providing a recess of such a depth, the lift coefficient can be further increased.

[0019] In the profile, the largest area of ​​the recessed portion may in particular be located below the center line.

[0020] A first portion of the pressure side profile segment can be configured to form an obtuse angle in profile with the pressure surface of the blade body or its extrapolated line. This first portion can extend toward the suction side and toward the rear end. This angle can be measured, for example, between a tangent line on the pressure side profile segment and a tangent line on the pressure surface at the point where the pressure surface terminates (towards the trailing edge). This obtuse angle can be in the range of 95° to 160°.

[0021] In a specific example, the pressure surface extension section can be configured to intersect the pressure surface of the blade body at this obtuse angle. The element can have a corresponding edge at the intersection of the two corresponding surfaces. From the intersection point, the pressure surface extension section can extend upward and toward the rear end. Alternatively, the point where the two surfaces intersect can be rounded, and the angle can be measured between two tangents to the surfaces in the profile just before such rounding. Providing such an obtuse angle at the intersection point can reduce drag, particularly compared to a conventional flat rear edge.

[0022] The shape of the pressure side profile segment, in particular the concave curve, may have a first tangent at a first point arranged toward the blade body and a second tangent at a second point arranged toward the rear end. The first tangent and the second tangent may form an angle of less than 140°, preferably less than 120°, more preferably less than 100°. The profile segment may in particular have a corresponding length and / or curvature to achieve such an angle. The concave curve may be achieved, for example, by means of a quarter circle and straight sides at each end of the quarter circle, which would correspond to an angle of 90° between the first tangent and the second tangent. However, this is only an example, and the concave curve may be formed by any suitable combination of straight segments and / or curved segments. In particular, the pressure side of the flow modification element may have a corresponding arc shape or claw shape.

[0023] The radius of curvature of the concave curve section can be less than the thickness of the trailing edge of the blade body, preferably less than half the thickness of the trailing edge of the blade body. The thickness of the trailing edge of the blade body can be measured, for example, perpendicular to the chord line of the blade body from the point where the pressure surface of the blade body ends (i.e., transitions to the pressure surface extension section) to the suction surface or an extrapolation of the suction surface of the blade body. This angle between the tangent lines or curvatures of the concave portion can achieve a compact component and further reduce drag.

[0024] The pressure surface extension section can be shaped so that the pressure surface extension section and the trailing end intersect at a point located toward the suction side (above the chord line) or toward the pressure side (below the chord line) relative to the chord line of the blade body. This point can be the lowest point of the trailing edge and can be adjusted according to the desired aerodynamic properties of the element. Preferably, this point is located below the aforementioned centerline. In an exemplary embodiment, this point can be located on an extrapolated line of the pressure surface of the blade body.

[0025] Preferably, the trailing end of the flow modifying element can be configured to be arranged above the extrapolated line of the pressure surface of the blade body or below the extrapolated line of the pressure surface of the blade body. It can be arranged completely above or below such extrapolated line, or at least the center of the trailing edge can be arranged above, below or on such extrapolated line.

[0026] In some examples, the shape of the concave curve of the pressure side profile section may extend from the pressure surface of the blade body to the rear end of the flow modifying element, preferably without an inflection point. Thus, a simple and aerodynamically efficient shape may be obtained.

[0027] In an example, the flow modifying element may include a suction surface extension section configured to extend the suction surface of the blade body toward the rear end. Preferably, the suction surface extension section is configured to form a continuous surface with the suction surface of the blade body. This can further reduce drag and enhance lift.

[0028] The suction surface extension section may be a surface on the suction side of the element, and the pressure surface extension section may be a surface on the pressure side of the element. The rear end may be arranged between the suction surface extension section and the pressure surface extension section and may connect the suction surface extension section and the pressure surface extension section. The element may have only a single rear end in its profile.

[0029] The suction surface extension section may be shaped to provide a curved end section in an aerodynamic profile that extends towards the rear end and bends away from the suction side towards the pressure side, ie bends downwards. This shape of the suction side of the element may further reduce drag.

[0030] In an example, the suction surface extension section can be shaped to provide an intermediate suction profile section in the aerodynamic profile, the intermediate suction profile section having the shape of a concave curve and forming a further recessed portion recessed from the suction side toward the pressure side of the flow modifying element. Thus, the suction surface extension section of the element can have a surface shape that bulges inwardly toward the suction side and can thus form a recess extending in the longitudinal direction. This further recessed portion and the recessed portion formed in the pressure surface extension section of the element can be spaced apart in the direction of the chord of the blade body. Considering a line parallel to the chord line of the blade body, the apex of the recessed portion can be located above this line and the apex of the further recessed portion can be located below this line (in other words, the projections of the recessed portion and the further recessed portion in the chord direction overlap). The recessed portion can be arranged closer to the rear end than the further recessed portion.

[0031] By means of such two recessed portions, the rear portion of the flow modifying element may have a claw shape including a rear end.

[0032] In some embodiments, the pressure surface extension section and the suction surface extension section may have a (substantially) constant distance from each other over at least 40% of their extension towards the rear end (thus, the claw shape may have a constant thickness). This distance may be measured perpendicular to the respective surface sections. This constant thickness may be provided over more than 50%, 60%, or even 70% of the chordwise extension of the rear portion of the element. The shape of the suction surface extension section may in particular follow the shape of the pressure surface extension section, while maintaining a constant distance, for example, over at least 40%, 50%, or 60% of the chordwise extension of the element.

[0033] The flow modifying element may have a thickness of at least 5% of the thickness of the rear end of the blade body, preferably between 5% and 100% of the thickness of the trailing edge of the blade body, over at least 25%, 40% or 50% of its extension in the chord-wise direction adjacent to the trailing edge. Thus, the claw shape formed by this element may be of medium thickness or may even have a thickness corresponding to the thickness of the trailing edge of the blade body.

[0034] The intermediate suction profile section may comprise a first portion extending substantially perpendicularly to the chord line of the blade body towards the pressure side and continuing into a curved portion which bends towards the rear end and has a tangent parallel to the chord line (e.g. a tangent at the vertex of the further recessed portion). Thus, a corresponding edge extending in the longitudinal direction may be formed in the element by the substantially perpendicularly extending first portion.

[0035] The suction surface extension section may also form a transition suction profile section in the profile, which is configured to extend from the suction surface of the blade body in a direction towards the rear end. Such a transition section may include a substantially straight portion or a curved portion, the substantially straight portion providing an edge towards the middle section, the curved portion providing a smooth transition to the middle section and including an inflection point.

[0036] In another exemplary configuration, the suction surface extension section can be shaped to provide a suction side profile curve in the aerodynamic profile, the suction side profile curve including a straight or substantially straight section that can be configured to be tangential to the suction surface of the blade body or to form a positive or negative angle with an extrapolation line of the suction surface of the blade body. By having such an extension with a straight section, the aerodynamic properties can be adjusted to provide more lift increase (negative angle) or more drag reduction (positive angle) or a combination of both (tangential). If, in the profile, the leading edge is on the left-hand side, the negative angle can correspond to a counterclockwise rotation, and the positive angle corresponds to a clockwise rotation. The straight section can extend over a majority of the length of the suction side profile curve corresponding to the suction surface extension section (e.g., over more than 30% or 50% of its length).

[0037] The straight or substantially straight section may be followed in the rearward direction by an end section or may terminate at the rear end of the element and may thereby form an edge or a rounded transition to the rear end.

[0038] The flow modifying element may be formed as a single integral part or may consist of two or more parts. The element may, for example, comprise a first part forming a recessed portion and a further recessed portion, and this part may be mounted to the blade body or may be integral with the blade body. It may also comprise a second part, which covers the further recessed portion and may provide a (substantially) straight section of the suction surface extension section. This second part may be mounted to the first part, or the two parts may be integrally formed. Such a configuration may allow a first (e.g., standardized) part to be provided and the aerodynamic properties to be adjusted by providing a second part of different shapes.

[0039] The aft end of the flow modifying element may be a flat end or may be a rounded end. In some examples, the aft end may extend perpendicular to the chord line of the blade body or may extend perpendicular to a tangent to an extended section of the pressure surface at the aft end.

[0040] The element may also include one or more reinforcing elements, which may extend across the recessed portion at one or more longitudinal positions of the element. Thus, the mechanical stability of the element can be improved, particularly when a relatively thin claw shape is provided. For example, one or more reinforcing elements may be provided depending on the material from which the element is made, for example to provide the desired mechanical stability. One or more corresponding reinforcing elements may also be provided across another recessed area. Therefore, one or more reinforcing elements may be provided on the pressure side, on the suction side, or on both sides. The reinforcing element may extend in a front-to-rear direction (for example, parallel to the contour plane), or it may extend parallel to the main flow direction of the air at the corresponding longitudinal position. The reinforcing element may be plate-shaped. In some embodiments, it may not extend beyond the recess. In other embodiments, the reinforcing element may extend (slightly) beyond the rear end of the element, and / or may extend (slightly) beyond the point where the pressure surface extension section intersects with the pressure surface of the blade body. This configuration may depend on structural and / or design requirements.

[0041] The flow modifying element may be an active element, or may be a passive element.

[0042] For example, the element may also include one or more actuators configured to change the extension, orientation, and / or curvature of the flow-modifying element. By controlling the length and / or curvature, for example, the aerodynamic profile can be adapted to the prevailing wind speed and operating conditions (e.g., taking into account flow velocity and angle of attack, etc.). The actuators for changing the shape of the element may be arranged in the blade body. In particular, the height (perpendicular to the chord line) or width (parallel to the chord line) of the rear portion of the flow-modifying element can be adjusted by such actuators.

[0043] The element may comprise at least one hinge point, for example in the pressure side profile section. The rear portion of the flow modifying element, including the trailing edge, may be pivoted about the hinge point, for example by operating an actuator. Thus, the position of the rear end may be adjusted.

[0044] In another example, the pressure side profile section may include at least two hinge points arranged to allow adjustment of the width of the flow modifying element in the chordwise direction of the blade body and / or adjustment of the height of at least a portion of the flow modifying element in a direction perpendicular to the chordwise direction. For example, two actuators may be provided, each controlling pivoting about a respective hinge point.

[0045] The actuator may be, for example, electric (motor), magnetic (solenoid), chain and gear system, hydraulic or pneumatic actuator, or other actuators known in the art may be used.

[0046] The flow-modifying element can be configured to have a shape that matches the thickness of the rear portion of the blade body, wherein the flow-modifying element can be arranged so that the thickness of the aerodynamic profile is continuous at the transition from the blade body to the flow-modifying element. This smooth transition can provide further drag reduction. Continuous can specifically mean the absence of steps.

[0047] The element may be solid or may include a void or cavity. Such a void or cavity can reduce weight and the material required for manufacturing. Such a void or cavity may, for example, extend through the body of the element in a longitudinal direction and may be closed in a transverse direction perpendicular to the longitudinal extension of the element.

[0048] The element may be made of a plastic material, a fiber-reinforced material (eg glass fiber or carbon fiber reinforced), a composite material or any other suitable material.

[0049] The flow modifying element can be an add-on element that also includes a mounting section configured to be mounted to the trailing edge of the blade body, or the flow modifying element and the blade body can be integrally formed to form the wind turbine blade. In the former case (add-on), the blade body can have its own trailing edge, to which the add-on element is mounted, and the element then provides the trailing edge for the wind turbine blade by means of its rear end. Thus, the trailing edge of the blade body can be covered and essentially replaced by the trailing edge provided by the element. In the latter case (integrated element), the flow modifying element can be formed during the manufacture of the wind turbine blade so that the rear end of the element is identical to the trailing edge of the wind turbine blade. In this case, the blade body may not have a trailing edge in the corresponding longitudinal section, but the trailing edge of the blade body can be estimated to be at the position where the airfoil from which the blade body is formed would have its trailing edge.

[0050] In an example, the mounting section of the flow modifying element may have a rounded shape configured to be mounted to the rounded trailing edge of the blade body. The mounting section may in particular be configured to adapt to the surface shape of the trailing edge of the blade body. Thus, a larger attachment area may be achieved, which may result in a more secure mounting of the element to the blade body. The trailing edge of the blade body may, for example, be formed by a suction surface of the blade body that is curved towards the pressure surface of the blade body so as to intersect the pressure surface at an angle greater than 45°, preferably greater than 70° or 80°, for example approximately 90°. The radius of curvature of the trailing edge of the blade body may, for example, be equal to or less than the thickness of the blade body at its trailing edge.

[0051] The additional element may be configured to attach to the substrate by means of adhesives, touch fasteners (e.g. ), mechanical fasteners or any other mounting elements mounted to the blade body.

[0052] In the aerodynamic profile, the trailing edge of the blade body may be covered by the flow modifying element in thickness direction by at least 50%, preferably at least 70%, eg completely. Thereby, a strong mechanical connection may be achieved between the flow modifying element and the trailing edge of the blade body.

[0053] The width of the flow modifying element may be defined in the direction of the chord of the blade body from a position where the pressure surface extension section adjoins the pressure surface of the blade body to a rear end of the element.

[0054] The element may be an additional element configured to be mounted to the blade body and may have a width selected from the range of 3%c to 50%c, preferably 5%c to 50%c, more preferably 10%c to 40%c, where c is the chord length of the blade body at the longitudinal position of the flow modifying element, or the average chord length, which is considered to be the average of the chord lengths of the blade body over the longitudinal extent of the blade over which the flow modifying element (e.g. the corresponding segment) extends. In this case, the chord length may not include the element.

[0055] When the flow modifying element is integral with the blade body, the width of the element may be selected from the range of 3%c to 35%c, preferably 5%c to 35%c, more preferably 9%c to 30%c, where c is the chord length of the wind turbine blade at the longitudinal position of the element or the average chord length, the average chord length being considered as the average of the chord lengths of the blade over the longitudinal extent of the blade body above which the element (e.g. the corresponding segment) extends. Since in this case the element forms an integral part of the blade, the chord length may include the element.

[0056] The flow modifying element may be a continuous element extending continuously over a predetermined longitudinal section of the blade, or the element may be provided as a longitudinal segment having a predetermined length in the longitudinal direction of the blade. A plurality of such segments may be arranged adjacent to each other along the longitudinal direction of the blade to cover the predetermined longitudinal section of the blade.

[0057] The flow modifying element may have the same width over its longitudinal extension or may have a variable width over its longitudinal extension.Longitudinal extension may refer to the extension in the longitudinal direction of the blade.

[0058] In an example, a wind turbine blade can extend in the longitudinal direction from a position at 0% L, at which the wind turbine blade can be mounted to the hub of a wind turbine rotor, to a blade tip at a position at 100% L, where L corresponds to the blade length. The flow modifying element can be configured to be provided on the blade body within a longitudinal region between 0% L and 60% L, preferably between 5% L and 50% L, and more preferably between 10% L and 40% L, or within any subcombination of these region boundaries, such as between 10% L and 50% L. Thus, the element can be provided in the root region of the blade, where the profile typically has a large relative thickness and can have a blunt trailing edge. Consequently, the root region of a blade including one or more corresponding elements can have improved aerodynamic performance and, in particular, can contribute more to the annual energy production (AEP). The flow modifying element can, in particular, increase lift and / or reduce drag in the root region of the blade, thereby increasing the AEP.

[0059] For example, the element may be configured to be provided on the blade body in a longitudinal region where the relative thickness (t / c) of the blade is in the range of 30% to 100%, preferably 35% to 95%. The thickness t may be defined as the maximum dimension of the profile perpendicular to the chord line, and the relative thickness is defined as t / c. Such relatively thick profiles may particularly benefit from flow-modifying elements.

[0060] The flow modifying element may not span the entire respective area but may be provided over only a portion of the area, eg a plurality of longitudinal segments of the flow modifying element may be provided within the respective area.

[0061] The flow modifying element may, for example, be configured to be provided on the blade body over a longitudinal section having a longitudinal extension of at least 10% L, preferably at least 15% L, more preferably at least 20% L, wherein L corresponds to the blade length. The flow modifying element may extend continuously over this longitudinal section, or segments of the element may be arranged adjacent to each other so as to cover this section.

[0062] According to a further aspect of the present invention, a wind turbine blade is provided, comprising a blade body having a leading edge, a suction surface, and a pressure surface. The wind turbine blade further comprises a flow modifying element having any of the configurations described herein. The flow modifying element is mounted to the blade body, or the flow modifying element and the blade body are integrally formed, to form the wind turbine blade. The flow modifying element is configured to provide a trailing edge for at least a longitudinal section of the wind turbine blade. With such a wind turbine blade, advantages similar to those outlined further above can be achieved.

[0063] According to a further aspect, a wind turbine comprising a respective wind turbine blade is provided.

[0064] According to a further aspect, a method of operating a wind turbine is provided, wherein the wind turbine comprises wind turbine blades having any of the configurations described herein.By this method, the annual energy production of the wind turbine may be increased.

[0065] It will be appreciated that the features mentioned above and those not yet explained below may be used not only in the respective combinations indicated, but also in other combinations or alone, without departing from the scope of the present invention. In particular, unless otherwise indicated, the features of the different aspects and embodiments of the present invention may be combined with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The foregoing and other features and advantages of the present invention will become more apparent from the following detailed description read in conjunction with the accompanying drawings, in which like reference numerals refer to like elements.

[0067] Figure 1 is a schematic diagram illustrating a wind turbine according to an embodiment, the wind turbine including a wind turbine rotor having wind turbine blades.

[0068] Figure 2 is a schematic diagram illustrating a wind turbine blade according to an embodiment, wherein a longitudinal section over which a flow modifying element extends is shown.

[0069] Figure 3 is a schematic diagram showing the outline of a blade body of a wind turbine blade without flow modifying elements.

[0070] Figure 4 is a schematic diagram illustrating an outline of a wind turbine blade including a flow modifying element according to an embodiment.

[0071] Figure 5 It shows the Figure 4 Schematic diagram of the modification of the flow modifying element.

[0072] Figure 6 and Figure 7 It shows Figure 4 and Figure 5 Schematic illustration of different geometries of flow modifying elements.

[0073] Figure 8 is a schematic diagram illustrating a perspective view of a flow modifying element according to an embodiment.

[0074] Figures 9-11 are schematic diagrams each showing a flow modifying element according to further embodiments.

[0075] Figure 12 is a schematic diagram showing a perspective view of a flow modifying element according to a further embodiment.

[0076] Figure 13 It shows the corresponding Figure 12 Schematic diagram of the outline of the flow modifying element.

[0077] Figure 14 is a schematic diagram illustrating the outline of an active flow modifying element according to an embodiment.

[0078] Figure 15 is a schematic diagram illustrating the outline of an active flow modifying element according to a further embodiment. DETAILED DESCRIPTION

[0079] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description of the embodiments is provided for illustrative purposes only and should not be considered as having a limiting meaning. It should be noted that the accompanying drawings should only be considered as schematic representations, and the elements in the accompanying drawings may not be drawn to scale with each other. On the contrary, the representations of the various elements are selected so that their functions and general uses become apparent to those skilled in the art. As used herein, the singular forms "a", "an" and "the" are also intended to include plural forms, unless the context clearly indicates otherwise. The terms "include", "have", "include" and "comprising" will be interpreted as open terms (i.e., meaning "including, but not limited to"), unless otherwise noted.

[0080] Figure 1 A wind turbine 100 according to an example is schematically illustrated. The wind turbine 100 comprises a wind turbine rotor 101 and a wind turbine tower 103. The rotor 101 has a hub 102 to which are mounted three rotor blades 10, which may be configured according to any of the examples and embodiments described herein.

[0081] Figure 2A wind turbine blade 10 according to an embodiment is schematically illustrated. The blade has a length L, which may, for example, exceed 30 m, 50 m, or even 60 m. Blade 10 has a root end 11, at which blade 10 can be mounted to a hub 102, and a tip end 12, at which the tip of the rotor blade is located. The root end is located at 0% L, and the tip end is located at 100% L. A root region 30 may span from 0% L to approximately 50% L, although this root region may be defined differently.

[0082] The blade 10 may include a blade body 20 and a flow modifying element 30. The blade body 20 and the flow modifying element 30 may be integrally formed to form the wind turbine blade 10, or the flow modifying element 30 may be an additional element mounted to the blade body 20. The flow modifying element may be provided within a longitudinal region between 0% L and 60% L, preferably between 5% L and 50% L (e.g., between 10% L and 50% L or between 10% L and 40% L). Within each longitudinal region, several longitudinal segments of the element 30, each having a predetermined length, may be provided, and these segments may be provided continuously or spaced apart. Within the longitudinal region, the element 30 may also be provided continuously over a longitudinal segment 15. The longitudinal segment 15 over which the element 30 is provided may, for example, be at least 10% L, at least 15% L, or at least 20% L. The element may, for example, extend over a longitudinal segment 15 between 10% L and 40% L. The element may cover this section continuously, or longitudinal sections of the element may be arranged adjacent to each other to cover this section.

[0083] The blade 10 has a leading edge 16 and a trailing edge 17, wherein in the longitudinal region of the blade where the element 30 is not provided, the trailing edge 21 of the blade body 20 may form the trailing edge 17 of the blade; whereas in the longitudinal region covered by the element 30, the rear end 37 of the element 30 may form the trailing edge 17 of the blade 10.

[0084] Typically, a profile is a cross section of the blade perpendicular to the longitudinal axis of the blade. Such a profile (also referred to herein as an "aerodynamic profile") typically has a thinner airfoil shape in the outer regions of the blade, a thicker airfoil shape in the root region of the blade, and may even approach a circular shape at the root end 11. Figure 3 The figure shows an exemplary profile that can be used for the blade body 20 in the root region 13. The chord line 26 can be defined as the line that intersects the two profile points that have the greatest mutual distance. In the case of a profile with a flat trailing edge 21 (e.g. Figure 3(As shown in the example of ), the chord line 26 may cut the trailing edge in the middle of the trailing edge. The chord length c is the distance between these two profile points. The profile thickness t can be defined as the maximum thickness perpendicular to the chord direction. The relative thickness of the profile is the ratio of thickness to chord length, t / c. Chord length and thickness can be measured without attachments or extensions.

[0085] The profile of the blade body 20 comprises a leading edge 16 and a trailing edge 21 which correspond to the leading edge 16 and the trailing edge 17 of the blade without the attachment. The blade body 20 also comprises a suction surface 18 and a pressure surface 19 which correspond to Figure 3 The corresponding suction side profile section 28 and pressure side profile section 29 in the profile shown in FIG. These profile curves extend from the leading edge 16 of the blade body 20 to the trailing edge 21. Since the profile of the body 20 has a flat trailing edge 21, it can be called a flat-back airfoil. The blunt trailing edge of such an airfoil in the root region can also be rounded. In particular, as Figure 4 As shown in , the suction side trailing edge may be rounded; for example, the profile curve of the trailing edge may bend away from the suction side toward the pressure side profile section 29 and may intersect it at a substantially right angle. Such a shape of the trailing edge 21 may have advantages from a manufacturing perspective, but may be associated with reduced aerodynamic performance.

[0086] Figure 4 Schematically illustrated is a flow modifying element 30 mounted to the trailing edge 21 of the blade body 20. The element 30 includes a mounting surface 31 that may be adhered or otherwise attached to the trailing edge 21. The element 30 includes a suction surface extension section 38 that extends the suction surface 18 (shown as the suction side profile section 28) of the blade body 20. The element 30 also includes a pressure surface extension section 39 that extends the pressure surface 19 (at Figure 4 As can be seen in the figure, the extension sections 38, 39 are continuous with the suction surface 18 and the pressure surface 19 respectively, that is, there is no intermediate step or part of the trailing edge 21. Figure 4In the example shown, the profile of element 30 includes a pressure side profile section 40 shaped as a concave curve that forms a recessed portion 44. In this profile, the primary area of ​​recess 44 lies above the extrapolated line of chord line 26 and also above extrapolated line 29e of pressure surface section 29. Recess 44 extends from pressure side 33 of element 30 toward suction side 32. Suction side 32 can be considered to be above pressure side 33, and leading edge 16 can be considered to be in front of trailing edge 21. In this reference frame, profile section 40 includes a first section 41 that extends rearward and upward from a transition point 45 where pressure surface 19 terminates. An obtuse angle 49 is formed between pressure surface 29 and first section 41. This angle 49 can be, for example, greater than 95° and less than 170°, preferably less than 140°. At transition point 45, an edge is formed. In other embodiments, the first section 41 may not be straight, but may be curved; it may, for example, be S-shaped and include an inflection point to provide a smooth transition.

[0087] The curved section 42 includes an apex 47 (the maximum distance from the chord line 26) and further bends downward again toward the pressure side 33. In the present example, the curved section 42 is circular (e.g., a quarter circle), but it may have any other concavely curved shape and may be composed of several different curved sections and / or straight sections. The pressure profile section 40 also includes a second section 43, which is straight in the present example, but may also be curved. The second section 43 intersects the trailing end 37 at an intersection 46. In order to adjust the lift and drag depending on the airfoil shape and longitudinal mounting position of the blade body 20, the intersection 46 and / or the trailing end 37 may be arranged above, above, or below the extrapolated line 29e of the pressure surface 19. The intersection 46 and / or the trailing end 37 may be arranged above, above, or below the chord line 26. The concave shape of the pressure side profile segment 40 may extend from the transition point 45 to the intersection point 46 , or may span only a portion thereof (eg, where an inflection point exists in the segment 41 or 43 ).

[0088] The apex 47 of the concave portion 44 is preferably located above the chord line 26, or above the extrapolated line 29e of the pressure surface 19. Reference numeral 60 denotes a center line (or midline) which is equidistantly disposed between the extrapolated line 28e of the suction surface 18 and the extrapolated line 29e of the pressure surface 19. Figure 4 As shown in . Apex 47 may be located above centerline 60 .

[0089] In the present example, the aft end 37 is a flat end that is substantially perpendicular to the chord line c. In other embodiments, the aft end 37 may be perpendicular to the end section 43 of the pressure surface extension section 39, in particular to its tangent at the intersection 46. The edges of the aft end 37 may be rounded, or the entire aft end 37 may be rounded, which in profile may correspond, for example, to a semicircle or to a curve.

[0090] The width w of element 30 is measured parallel to the chord line c, from the transition point 45 where the pressure surface extension section 39 intersects the pressure surface 19, to the rear end 37. The width w can be adjusted according to the desired aerodynamic properties of element 30. The length w can be between 5% c and 60% c, where c represents the chord length of the blade body 20. Preferably, the width w can be between 10% c and 50% c, or between 15% c and 40% c. The shape of pressure surface extension section 39 can provide an increase in lift on the underside of the profile, while having a relatively low impact on the increase in drag. The properties and configurations discussed above can be applied to any embodiment and example of element 30 discussed herein.

[0091] Figure 4 3. A specific configuration of the shape of the suction surface extension section 38 is shown. It comprises a suction side profile section 50 which is shaped to provide a further concave portion 54 extending towards the pressure side 33. The further concave portion 54 has an apex 57 relative to the chord line c, which may be located below the extrapolated line 28e of the suction surface 18 and may in particular be located below the centre line 60. The profile section 40 comprises a transition suction profile section 51 which forms a continuous surface with the suction surface 18 and which in this example curves (convexly) up to an inflection point 53. It also comprises an intermediate profile section 52 which is curved and may also comprise a straight section up to an additional inflection point 53. It may also comprise a curved end section 55 which curves downwards towards the aft end 37 and forms an intersection 56 with the aft end 37. In this example, the curved end section 55 forms an apex 58 (in the suction side direction relative to the chord line c) which is located opposite the apex 47 .

[0092] In the rear portion, over a large portion of the width w (>50%), the shape of the suction side profile segment 50 follows the shape of the pressure side profile segment 40, thereby forming a claw shape of the rear portion of the element 30. The vertex 58 can be arranged above or below the extrapolation line 28e of the suction surface 18. The suction side profile segment 50 can in particular be S-shaped, with an inflection point 53 between the curved segment 52 and the curved segment 55, as shown in FIG. Figure 4This shape can result in higher lift and lower drag. By means of this shape, flow separation on the suction side can be reduced or prevented, and the lift increase can be higher at high angles of attack compared to conventional chord extensions, in particular due to the curvature on the pressure side.

[0093] The curved section 55 may also be tangent to the extrapolated line 28 e of the suction surface 18 .

[0094] The element 30 may cover the entire trailing edge 21 of the blade body 20. In particular with a rounded trailing edge 21 a larger attachment area may be achieved, thus ensuring a strong and secure attachment.

[0095] Figure 5 A further exemplary embodiment of the element 30 is shown. The element 30 can be formed integrally with the blade body 20, for example in a common manufacturing process. Therefore, the position of the trailing edge 21, which would be positioned for a conventional blade body, is only schematically illustrated with a dashed line. For each embodiment and example disclosed herein, both possibilities (additional element or integration into the blade body) can be provided. Figure 5 In the example of FIG. 5 , the transition suction profile section 51 is also straight and extends tangentially to the suction surface 18. It intersects the curved section 52 at an intersection point 59, which forms the longitudinally extending edge of the element 30 (see also FIG. 5 ). Figure 8 ). Thus, the intermediate profile section 52 may also comprise a straight section extending downwardly from the point 59 towards the chord line c.

[0096] It should be clear that the curved section may consist of a mixture of straight and / or curved sections having different curvatures. Figure 4 and Figure 5 In the example, the curvature radius of the curved section 42 is greater than the curvature radius of the curved section 52. The curvature radius of the section 42 is less than the thickness tt of the rear end of the blade body 20 (which may be as shown in FIG. Figure 7 It should be clear that these are only exemplary configurations and that the geometry can be adapted according to the desired aerodynamic properties.

[0097] Figure 6 Different examples of the height of the claw portion of the element 30 are provided. In the upper example, both the apex 47 and the apex 58 are arranged below the extrapolated line 28e of the suction surface profile segment 28. In the example shown in the middle, the apex 47 of the recessed portion 44 and the apex 58 of the suction surface extension segment are arranged above the extrapolated line 28e of the suction surface profile segment 28. In the lower example, the suction side profile segment 50 is approximately tangent to the extrapolated line 28e of the suction surface extension segment 28. Figure 6In the example of FIG, the intersection point 46 of the rear end 37 is located on the extrapolated line 29e of the pressure side profile segment 29. The extrapolated line 29e may be tangential to the profile segment 29, for example, at the transition point 45. It should be clear that the point 46 may also be located above or below this extrapolated line.

[0098] Figure 7 The thickness te of the rear portion of the element 30 is shown, which may be defined perpendicularly to the pressure side profile section 40 and the suction side profile section 50. The thickness tt of the trailing edge 21 of the blade body 20 may be defined perpendicularly to the chord line 26 from the transition point 45 to the intersection with the suction surface profile section 28 or its extrapolated line 28e. The thickness TE may be, for example, between 5% and 100% of the trailing edge thickness tt. Figure 7 In the upper example, the thickness of the claw is approximately te=11%tt; in the lower example, it is approximately te=90%tt. Of course, any other values ​​in between are conceivable. The thickness can be substantially constant over the rear 50% of the extension of the element 30 in width w.

[0099] Figure 8 A perspective view of the element 30 mounted to the trailing edge 21 of the blade body 20 is shown. The rear end 37 is rounded, and the suction surface extension section 38 includes an edge 59 and an additional recessed portion 54. As shown, a reinforcing element 65 can be provided across the recessed portion 44. The element 65 is configured to provide mechanical stability. It can extend in a plane parallel to the profile plane, or can extend at a desired aerodynamically beneficial angle (e.g., parallel to the expected air flow direction). Similar mechanical reinforcing elements (not shown) can be provided across the recessed portion 54 on the suction side. A plurality of such elements can be distributed longitudinally along the length l of the element 30. Figure 8 Only a small section is shown. The actual length l may be significantly longer, for example, it may span between 50 cm and 5 m.

[0100] The reinforcement element can be arranged on the suction side and / or the pressure side. It can be formed integrally with the element 30 or can be mounted on the element 30.

[0101] like Figure 9 As shown in FIG, the element 30 may include a first portion and a second portion 70, the first portion may have any of the above-described configurations. The second portion 70 may be placed in the further recessed portion 54. It may provide at least a portion of the suction surface extension section 38. In this example, it includes a straight section 71 that is generally tangential to the suction surface profile section 28 of the blade body 20, but it may also be angled at a positive or negative angle to the suction surface profile section 28 of the blade body 20, as shown in FIG. Figure 10 As shown in the figure. Figure 9In the example shown, the suction surface extension section 38 is formed by a tangentially intersecting straight section 71 and a curved end section 55. This configuration further reduces suction side flow separation and provides additional structural support. The curved section 55 is generally tangential to the extrapolated line of the suction side contour section 28, and the straight section 71 substantially bridges the gap between the two.

[0102] exist Figure 10 , the straight section 71 forms a negative angle 76 with the extrapolated line 28e of the section 28, wherein the angle is acute in the counterclockwise direction in the profile with the leading edge on the left-hand side and the suction surface on the upper side. The additional portion 70 also includes a second straight section 72 connecting the first straight section 71 to the curved end section 55. Of course, other configurations are conceivable, such as sections 71, 72 forming a smooth curved transition toward the curved section 55. The portion 70 and / or other parts of the element 30 may also include a cavity 75, which allows for a reduction in weight and a saving in material used to manufacture the element 30. The cavity 75 may have any desired shape that ensures the structural stability of the element 30.

[0103] Figure 11 A further exemplary embodiment of the element 30 is shown in which the further additional portion 70 is integrally formed with the remainder of the element 30. The element 30 is Figure 11 It is shown as an additional element, but can also be integrated with the blade body 20 as explained above. The shape of the suction surface extension section 38 is similar to Figure 9 The shapes shown in FIG are similar, but it should be understood that any shape described herein, as well as any variation thereof, may be used.

[0104] Figure 12 A further exemplary embodiment is shown in which no curved end section 55 is provided, but in which the straight section 71 intersects the rear end 37 directly at the intersection point 56. Figure 12 In the example of FIG. 3 , the element 30 is formed as a single integral element that can be mounted to the blade body 20 , but it can also be formed from multiple parts, as shown in FIG. Figure 9 and Figure 10 Likewise, the straight section 71 may not be tangential to the suction surface 18 but may form a positive or negative angle therewith. Thus, a corresponding second straight or curved section 72 may be provided and may intersect the rear end 37 at the intersection point 56.

[0105] exist Figure 12 In the example of FIG, the pressure side contour section 40 has a generally parabolic shape, with point 46 drawn down to the extrapolation of the pressure surface 19. Any of the other configurations of the pressure surface extension section 39 described herein may also be employed.

[0106] Figure 13An example is shown in which a pressure-side profile segment 40 is composed of a plurality of curved segments and straight segments. Two straight segments 41 and 43 are provided at the start and end of segment 40. Curved segment 42 is composed of a first curved segment, a straight segment, and a second curved segment, which together approximate a concave curve. This shape can be used in the embodiments and examples described herein, and other shapes are also contemplated.

[0107] The element 30 is preferably a rigid element. Figures 4 to 13 In the example shown, element 30 has a predefined shape and is a passive element. In some examples, element 30 may be an active element. A corresponding actuator may be provided that changes the shape of element 30 by, for example, changing one or a combination of element width (parallel to the chord direction), element height (perpendicular to the chord direction), element curvature, and the like. The geometry of element 30 may be actively adapted based on prevailing wind speed and operating conditions. The corresponding actuator may be mounted on element 30 and / or in blade body 20.

[0108] exist Figure 14 In the example of FIG, a hinge point 81 may be provided at the curved end section 55, for example, at a location adjacent to the apex 47. The end section, including the rear end 37, may be pivotable about the hinge point 81. At one or more locations along the longitudinal extension of the element 30, a hydraulically or pneumatically actuated piston, chain and gear system, an electric or hydraulic motor, or the like may be provided to controllably pivot the end portion of the element 30 about the hinge point 81. Thus, the shape of the element 30 may be adjusted to achieve additional lift increase, drag reduction, and / or an increase in lift-to-drag ratio.

[0109] exist Figure 15 A further example is illustrated in FIG, in which a second hinge point 82 is provided, about which the central part of the element 30 can be pivoted. A corresponding actuator may again provide controllability of the pivot angle about the point 82. Thus, the width w of the element 30 can be shortened or lengthened by pivoting about the points 81, 82. For example, the minimum achievable length may be between 5%c and 20%c and the maximum achievable length may be between 30%c and 60%c. When the element 30 is extended, the height of the rear part of the element 30 changes accordingly. For example, an electric motor and corresponding chains or belts may be provided inside the blade body 20 to pivot parts of the element 30 about one or more hinge points. By adjusting Figure 15 The position of the two movable segments illustrated in , and therefore the element width, can improve the aerodynamic properties according to the operating point and can optimize power generation. Depending on the circumstances, a larger width or a larger curvature of the element 30 may result in an optimal lift-to-drag ratio.

[0110] Thus, the flow modifying element 30 may provide significant advantages in both its active and passive configurations compared to conventional geometries of blade trailing edges.

[0111] Although specific embodiments are disclosed herein, various changes and modifications may be made without departing from the scope of the invention. The present embodiments are to be considered in all respects as illustrative and non-restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Claims

1. A flow modifying element for a wind turbine blade, wherein: The wind turbine blade (10) comprises a blade body (20) having a leading edge (16), a suction surface (18) and a pressure surface (19), wherein the flow modification element (30) is configured to provide a trailing edge (17) for at least a longitudinal section (15) of the wind turbine blade (10), wherein the flow modification element (30) and the blade body (20) form an aerodynamic profile, wherein the flow modification element (30) comprises: - Suction side (32); - pressure side (33); - a rear end (37) providing the trailing edge (17) of the aerodynamic profile; and a pressure surface extension section (39) on the pressure side (33) and configured to extend the pressure surface (19) of the blade body (20) towards the rear end (37), wherein the pressure surface extension section (39) is shaped to provide a pressure side profile section (40) in the aerodynamic profile, the pressure side profile section (40) having a concave curve shape and forming a concave portion (44) concave from the pressure side (33) toward the suction side (32) of the flow modifying element (30), wherein the pressure side profile section (40) is shaped to have an apex (47) on the suction side (32) in a direction perpendicular to the chord line (c) of the blade body (20), wherein the apex (47) is located in the profile in the direction of the suction side above a center line (60) between an extrapolated line (28e) of the suction surface and an extrapolated line (29e) of the pressure surface of the blade body (20), and The pressure side profile section (40) has a first portion and a second portion, wherein the first portion extends rearward and upward toward the rear end (37) and the suction side (32) to the apex (47), and the second portion extends rearward and downward toward the rear end (37) and the pressure side (33).

2. The flow modifying element according to claim 1, wherein The pressure surface extension section (39) is configured to intersect the pressure surface (19) of the blade body (20) at an obtuse angle (49), and the pressure surface extension section (39) is configured to extend from the pressure surface (19) toward the suction side (32).

3. A flow modifying element according to any one of the preceding claims, wherein The pressure side profile section (40) having the shape of a concave curve has a first tangent line at a first point located toward the blade body (20) and a second tangent line at a second point located toward the rear end (37), wherein the first tangent line and the second tangent line form an angle of less than 140 degrees, preferably less than 120 degrees, more preferably less than 100 degrees.

4. A flow modifying element according to any one of the preceding claims, wherein The concave curve shape of the pressure side profile section (40) is configured to extend from the pressure surface (19) of the blade body to the rear end (37), preferably without an inflection point.

5. A flow modifying element according to any one of the preceding claims, wherein The flow modification element (30) further comprises a suction surface extension section (38) configured to extend the suction surface (18) of the blade body (20) toward the rear end (37), wherein the suction surface extension section (38) is preferably configured to form a continuous surface with the suction surface (18) of the blade body (20).

6. A flow modifying element according to claim 5, wherein The suction surface extension section (38) is shaped to provide a curved end section (55) in the aerodynamic profile, the curved end section (55) extending towards the rear end (37) and bending away from the suction side (32) towards the pressure side (33).

7. A flow modifying element according to claim 5 or 6, wherein The suction surface extension section (38) is shaped to provide an intermediate suction profile section (52) in the aerodynamic profile, the intermediate suction profile section (52) having the shape of a concave curve and forming a further concave portion (54) concave from the suction side (32) towards the pressure side (33) of the flow modifying element (30).

8. A flow modifying element according to claim 5 or 6, wherein The suction surface extension section (38) is shaped to provide a suction side profile curve in the aerodynamic profile, the suction side profile curve including a straight or substantially straight section (71) configured to be tangential to the suction surface (18) of the blade body (20) or to form a positive or negative angle (76) with an extrapolated line (28e) of the suction surface (18) of the blade body (20).

9. A flow modifying element according to any of the preceding claims, further comprising one or more actuators configured to change the extension, orientation and / or curvature of the flow modifying element (30).

10. A flow modifying element according to any one of the preceding claims, wherein The flow modifying element (30) is configured to have a shape that matches the thickness of the rear portion of the blade body (20), wherein the flow modifying element (30) is arranged so that the thickness of the aerodynamic profile is continuous at a transition from the blade body (20) to the flow modifying element (30).

11. A flow modifying element according to any one of the preceding claims, wherein The flow modifying element (30) is an additional element further comprising a mounting section (31) configured to be mounted to the trailing edge (21) of the blade body (20), or wherein the flow modifying element (30) and the blade body (20) are integrally formed to form the wind turbine blade (10).

12. A flow modifying element according to claim 11, wherein The mounting section (31) has a rounded shape configured to be mounted to the rounded trailing edge (21) of the blade body.

13. A flow modifying element according to any one of the preceding claims, wherein The wind turbine blade (10) extends in a longitudinal direction from a position at 0% L to a blade tip (12) at a position at 100% L, at which position the wind turbine blade is mountable to a hub (102) of a wind turbine rotor (101), wherein L corresponds to the length of the blade, wherein the flow modifying element (30) is configured to be arranged on the blade body (20) in a longitudinal region between 0% L and 60% L, preferably between 5% L and 50% L, more preferably between 10% L and 40% L.

14. A wind turbine blade comprising a blade body (20) having a leading edge (16), a suction surface (18) and a pressure surface (19), wherein: The wind turbine blade (10) further comprises: A flow modifying element (30) according to any one of the preceding claims, wherein the flow modifying element (30) is mounted to the blade body (20), or wherein the flow modifying element (30) and the blade body (20) are integrally formed to form the wind turbine blade (10), wherein the flow modifying element (30) provides a trailing edge (17) for at least a longitudinal section (15) of the wind turbine blade (10).

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