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), a pressure surface (19) and a trailing edge (17). The blade body (20) has a chord length c with the leading edge (16) corresponding to a position of 0% c in the chord direction and the trailing edge (17) corresponding to a position of 100% c in the chord direction. The flow modifying element (30) is configured to be arranged on the pressure surface (19) of the blade body (20) in a range between 40% c and 100% c in the chord direction. The flow modifying element (30) is further configured to form a projection (33) projecting outwardly from the pressure surface (19) of the blade body (20).

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 for 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 the 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. Further problems arise due to the loads applied to such large blades during high wind conditions. 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 2322793 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] Furthermore, it is known from documents US2014 / 0112780 A1 and US2009 / 074574 A1 to provide a deformable airfoil that allows the airfoil shape to be changed between different airfoil types. It is also known from US2012 / 0141271 A1 to modify the flow on the suction side in the outer part of the blade by means of devices, in particular spoilers, that separate the air flow from the outer surface of the blade in order to reduce the lift generated by the blade and thus reduce the loads acting on the blade.

[0006] The above solutions still suffer from 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 2716906 A2 describes a tab element for mounting on the pressure side of a blade.

[0008] WO 2014064195 A1 describes a wedge-shaped element for mounting on the pressure side of a rotor blade. The wedge-shaped element has a projection that projects outward from the pressure side.

[0009] Document WO 2022 / 136547 A1 describes a blade element suitable for mounting on the pressure side of a blade, wherein the blade element has a convex shape which bulges outwards from the pressure side. Summary of the Invention

[0010] Therefore, there is 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. The wind turbine blade includes a blade body having a leading edge, a suction surface, a pressure surface, and a trailing edge. The blade body has a chord length c, wherein the leading edge corresponds to a position of 0% c in the chord direction, and the trailing edge corresponds to a position of 100% c in the chord direction. The flow modifying element is configured to be arranged on the pressure surface of the blade body within a range between 40% c and 100% c in the chord direction. The flow modifying element is further configured to form a raised portion that protrudes outward from the pressure surface of the blade body.

[0013] Such a flow modifying element (herein simply referred to as an "element") can increase the lift of the blade, in particular with respect to the longitudinal extent over which the element is provided. ) can reduce flow disturbances compared to conventional blades. Furthermore, such an element can be compatible with additional suction-side attachments (such as vortex generators) and trailing-edge attachments or other trailing-edge solutions. Thus, the aerodynamic properties of the respective section of the blade can be adjusted according to the longitudinal position and the desired characteristics. The raised portion can provide a shape with optimized aerodynamic performance and, in particular, can lead to an increase in the lift coefficient (CL). The raised portion can also have a smooth transition to the pressure surface of the blade, thus reducing the increase in the drag coefficient (CD); thus, it can maximize the CL / CD.

[0014] Preferably, the suction surface and the pressure surface correspond to respective profile curves of the blade body, wherein each of the respective profile curves of the suction surface and the pressure surface extends from a leading edge to a trailing edge of the blade body.

[0015] In particular, in a stationary state of the wind turbine blade (ie in a state in which the rotor blade is not rotating), the flow modifying element has or comprises a projection. Thus, the projection may be present both in a rotating blade and a non-rotating blade situation.

[0016] The raised portion may extend in the longitudinal direction of the blade, in particular in the direction of the trailing edge. It may extend substantially parallel to the trailing edge of the blade body. It may be continuous in longitudinal extent or may provide one or more longitudinal segments having a predefined length in the longitudinal direction.

[0017] The position of the element in the chordwise direction can be determined by the center (or middle) between the leading and trailing ends of the element in the chordwise direction, in particular by the position of the middle of a line connecting these two points in the element's profile. This center can be arranged between 40%c and 100%c, or the entire chordwise extension of the element can be within this range. The range can, in particular, extend from a position where the center of the element is arranged at 50%c to a position where the trailing end of the element is arranged at 100%c.

[0018] In an optional embodiment, the flow modifying element can be shaped and configured to increase the lift coefficient of the aerodynamic profile of the blade body by increasing the pressure on the leading portion of the projection. The projection can be shaped in particular so that, during operation, the pressure of air flowing through the projection is increased on the leading portion of the projection. The projection can reduce the local flow velocity on the pressure side of the blade, thereby generating an increased pressure coefficient, which can lead to an increase in the lift coefficient. Lift can be increased particularly in the root region of the blade.

[0019] The flow modifying element may in particular be configured to increase energy extraction from the wind. Thus, its mode of operation may differ from known spoilers or vortex generators that introduce energy into the flow.

[0020] The flow modifying element and the blade body may form an aerodynamic profile, wherein the projection may be shaped to provide a convex profile segment in the aerodynamic profile that approximates a convex curve or is a convex curve. The profile segment may include straight segments and (convex) curved segments; however, a continuously curved shape is preferred. The convex profile segment may approximate a Gaussian curve shape, a polynomial curve shape, a circular curve shape, an elliptical curve shape, a hyperbolic shape, or a portion of another type of curved shape.

[0021] The flow modifying element may comprise a first transition section providing a continuous (in particular smooth) transition between the pressure surface of the blade body and the front part of the projection and / or may comprise a second transition section providing a continuous (in particular smooth) transition between the pressure surface of the blade body and the rear part of the projection. Such a transition section may form part of the projection. Thus, the element may provide a smooth shape and a smooth transition to the blade surface at its front and rear sides, which may have a positive effect on the drag coefficient. The element may in particular be configured to provide a pressure side surface which is continuous with the pressure surface of the blade body at the front end and / or rear end of the element.

[0022] As an example, the element can be configured so that the angle formed between the first and / or second transition section and the pressure surface of the blade body can be between 140° and 180°, which can be in particular an obtuse angle or a tangent angle. Thus, tangency with the pressure surface can be maintained at the leading end and / or trailing end of the element. The first transition section can be shaped to provide a first concave curve section, and / or the second transition section can be shaped to provide a second concave curve section. The convex profile section can be arranged between the first concave curve section and the second curve section. For example, in this aerodynamic profile, the flow modification element can include a first inflection point at which the first concave curve section transitions to the convex profile section and / or a second inflection point at which the second concave curve section transitions to the convex profile section. Thus, a smooth aerodynamic shape of the element can be provided.

[0023] The curvatures of the first concave curve segment and the second concave curve segment may be the same, similar, or different.

[0024] The flow modifying element may have a width from the leading end to the trailing end of the flow modifying element in the aerodynamic profile. This width may be between 7%c and 45%c, preferably between 10%c and 40%c, and more preferably between 10%c and 30%c. Providing the element with these dimensions in the chord-wise direction may allow the element to be tuned to achieve the desired aerodynamic properties. The width may be defined as the distance between the leading end and the trailing end of the element in the profile (i.e., in a cross-section perpendicular to the longitudinal extension of the blade).

[0025] The flow modifying element, in particular the projection, may have a thickness of 5%c to 30%c, preferably 10%c to 20%c. One or both of the width of the element, in particular the projection, and the thickness of the element, in particular the projection, may be adjusted, for example, depending on the position in the longitudinal direction of the blade and the twist or operating pitch at the corresponding position. Similarly, the curvature of the element in the profile may be adjusted depending on the desired aerodynamic properties at the corresponding position and operating pitch. The thickness of the element, in particular the projection, may correspond in the aerodynamic profile to the maximum distance of the projection perpendicular to a straight line connecting the leading and trailing ends of the element in the profile.

[0026] The flow-modifying element can be configured to be compatible with trailing edge attachment devices (which may, for example, not extend beyond the trailing edge of the blade body) and / or suction surface attachment devices. By being compatible with the additional attachment devices for the blade, additional CL increases can be achieved. Furthermore, such a combination can achieve lower CD values, as the drag penalties associated with individual devices can be minimized by combining the aerodynamic devices, i.e., the corresponding adjustments to the devices can at least partially compensate for the drag increases associated with the individual devices.

[0027] In an optional example, the flow modifying element is an active element and is configured to be adaptable in at least one of the following: position in the chord-wise direction, thickness of the element (particularly the projection), and shape of the projection. This adaptability may, in particular, allow the element to be adjusted according to current operating conditions (such as the operating pitch angle and the longitudinal position of the element on the blade). Furthermore, the element may be dynamically adjusted according to current wind conditions, the rotational speed of the rotor, the angle of attack, and the like. The variability of the thickness, chord-wise position, and / or shape (i.e., the range within which the respective parameter may vary) may depend on the position in the longitudinal direction of the blade and the operating pitch of the respective blade section.

[0028] The thickness of the element, in particular the projection, may vary, for example, between a minimum value of 5%c to 10%c and a maximum value of 10%c to 30%c. The thickness may vary between 3%c and 25%c.

[0029] The flow modification element may comprise one, two, three or more chambers and may also comprise flow connections towards the respective chambers, allowing the pressure inside the chambers to be varied to adjust the shape and / or thickness of the protrusions. Thus, a technically simple embodiment of actively modifying the thickness and / or shape can be achieved.

[0030] Exemplary embodiments include a central chamber, or a front chamber and a rear chamber, or an additional central chamber between the latter two. The one or more chambers can, for example, be pressurized with the same pressure to adjust the height. Applying different pressures to different chambers can allow the curvature of the element to be adjusted. For example, each chamber can be provided with a flexible surface or surface portion on the pressure side. This can, for example, allow deformation of the shape of the corresponding surface by changing the amount of outward or inward projection or by changing from outward projection to inward projection, or vice versa. It is also conceivable to provide a portion of the pressure side surface of the element (for example the central portion) with a rigid material so that it does not change its shape, and to provide other flexible portions (for example towards the front and rear ends) which allow adjustment of the height and optionally deformation of the shape in these portions.

[0031] Each chamber may have a separate flow connection for the respective medium, such as a gas, eg air, or a liquid.In particular, pneumatic or hydraulic actuators may be provided (eg inside the blade body) for controlling the thickness and / or shape.

[0032] The element may be provided as longitudinal segments, and each chamber may extend through the element in the longitudinal direction; it may be closed at the ends of the segments.

[0033] The element may comprise one or more tensioning elements extending between the pressure side surface of the element and a mounting section of the element facing the blade body. Such tensioning elements may allow the basic shape of the one or more chambers to be maintained; they may also allow the thickness to be controlled by applying pressure.

[0034] The tensioning element can, for example, be a wall extending in the longitudinal direction of the element. The tensioning element can provide a separation between two adjacent chambers. For example, one tensioning element can be provided between two chambers, and two tensioning elements can be provided to separate three chambers of the flow modifying element. In other conceivable embodiments, a plurality of tensioning members can be provided in the form of tethers, and a plurality of such tethers can be provided within a chamber to maintain the shape of the chamber or to allow controlled adjustment of the shape of the chamber. Such a tensioning element can, in particular, provide tension between the pressure-side surface and the mounting section when pressure is applied to the respective chamber.

[0035] The flow modifying element may further comprise a guide element configured to guide the movement of the flow modifying element on the blade body in a direction that allows adjustment of the distance of the flow modifying element from the trailing edge of the blade body. Such a guide element may be configured to guide along the chordwise direction of the blade body or at an angle relative to the chordwise direction (e.g., perpendicular to the trailing edge). Preferably, at least two guide elements are provided for each longitudinal section of the element, spaced apart in the longitudinal direction. This allows for mechanically robust and secure guidance of the element.

[0036] The guide element may, for example, be or include a pin or stud, a carriage, a track, or the like. A complementary guide element may be provided on the pressure side of the blade body. For example, the guide element may be configured to allow adjustment of the chord-wise position of the flow-modifying element from a position where the trailing end of the element is at 100% c to a position where the trailing end is at 50% c, preferably between 100% c and 40% c. By allowing such active adjustment of the chord-wise position of the element, the CL / CD ratio can be optimized for the respective operating conditions.

[0037] In examples, the flow modifying element is a separate element comprising a mounting section configured to be mounted to a pressure surface of a blade body, or the flow modifying element and the blade body are integrally formed to form the wind turbine blade.

[0038] The mounting section may include a mounting surface configured to face the pressure surface of the blade body. The mounting surface may be adapted or capable of adapting to the shape of the pressure surface. To provide an adaptable surface, the surface may, for example, be made of a flexible material that can conform to the shape of the pressure surface. For example, when the element is provided as an active element movable in the chordwise direction, such a mounting surface may adapt to the shape of the pressure surface as the element moves in the chordwise direction. If the element is immovable, the mounting surface may also be flexible, which may simplify manufacturing, or the mounting surface may be rigid and pre-shaped to complement the pressure surface at the mounting location.

[0039] The mounting section may also comprise the above-mentioned guide elements and may be mounted by them, or the mounting surface itself may be fixedly mounted to the pressure surface of the blade body, for example in case the element is not movable.

[0040] For example, the element may be an additional element that is configured to be attached by means of an adhesive, a touch fastener such as ), mechanical fasteners or other suitable fastening elements are mounted to the blade body.

[0041] The element may be solid (without an internal cavity); or the element may include one or more internal cavities extending in the longitudinal direction of the element. When provided as a passive element, such cavities can reduce the amount of material required and can make the element lighter. When provided as an active element, such cavities can correspond to the above-mentioned chambers that can be pressurized. The element can be formed from a rigid (non-deformable) material. If the element has an adjustable thickness and / or shape, it is preferably formed at least in part from a flexible material. Similarly, the mounting surface can be formed from a flexible material, or the entire element can be formed from a flexible material.

[0042] The element may be formed, for example, of a plastic material, a fiber-reinforced material (e.g., glass fiber or carbon fiber reinforcement), a composite material, or any other suitable material. The flexible portion of the element (such as the actively deformable portion and / or the mounting surface) may be formed of a rubber material, a flexible plastic material, or any other suitable flexible material.

[0043] The element may be provided as a continuous element extending continuously over a predetermined longitudinal extent of the blade (preferably substantially parallel to its trailing edge). The element may also be provided as a longitudinal segment having a predetermined length in the longitudinal direction of the blade. A plurality of such segments may then span the predetermined longitudinal extent, i.e., they may be arranged adjacent to each other to cover this longitudinal extent.

[0044] The chord length of the blade body can vary in the longitudinal range. The flow modification element can have a width that varies accordingly on its extension in the longitudinal direction of the blade. In other embodiments, the width of the element can be constant on the longitudinal extension of the segment of the element or on the predetermined longitudinal range. The average chord length of the blade body on the longitudinal extension of the segment or on the longitudinal extension of the predetermined longitudinal range can be regarded as a reference chord length for determining the geometric parameters of the element (such as thickness and / or width). Alternatively, the median chord length (such as at the center of the corresponding longitudinal extension or the predetermined longitudinal range) can be regarded as a reference chord length. The longitudinal extension of the segment of the element can, for example, be in the range of 0.5 to 4 m, for example between 0.75 and 2 m.

[0045] As an example, a wind turbine blade may extend in the longitudinal direction from a position at 0% L, at which the wind turbine blade is mountable 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 may be configured to be provided on the blade body within a longitudinal region between 0% L and 60% L, preferably between 0% L and 50% L, and more preferably between 10% L and 50% L. For example, it may be provided within a region between 20% L and 50% L, or any subcombination of these disclosed regions. It should be understood that providing the element within such a region does not necessarily mean that the element covers the entire region.

[0046] For example, the flow modifying element may be configured to be provided on the blade body in a longitudinal range having a longitudinal extension of at least 10% L, preferably at least 15% L, more preferably at least 20% L. Thus, such a range of longitudinal extension may be covered by the flow modifying element, wherein this range is preferably within the aforementioned longitudinal area.

[0047] For example, flow modifying elements may be provided on the transition region of the blade from the cylindrical root region of the blade to the shoulder and from the shoulder to the mid-span region of the blade.

[0048] The blades may have a length L greater than 25m, 30m or 50m.

[0049] According to another aspect of the present invention, a wind turbine blade is provided, comprising a blade body having a leading edge, a suction surface, a pressure surface, and a trailing edge. 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 pressure surface of 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 form a projection that projects outwardly from the pressure surface of the blade body. With such a wind turbine blade, advantages similar to those outlined further above can be achieved. The blade may comprise any of the features described herein with respect to the blade or the blade body.

[0050] The flow modifying element may be configured to provide a portion of a pressure side profile section of an aerodynamic profile formed by the blade body and the flow modifying element.

[0051] The blade body may further comprise at least one guide arranged on the blade body, which guide may be complementary to a guide element on the flow modifying element.The flow modifying element is movable in a direction towards and away from the trailing edge by means of the guide, eg by sliding in the guide.

[0052] The guide member may be, for example, a guide rail, and the rail may be configured to provide the flow modifying element with a range of motion (e.g., in the chord-wise direction), the range of motion being dimensioned such that the flow modifying element covers the rail in any position. For example, the length of the rail may be equal to or less than half the extension of the element in the direction of motion (e.g., in the chord-wise direction if the rail extends in the chord-wise direction).

[0053] The blade body may comprise respective ports for providing a connection to one or more chambers formed in the flow modifying element, wherein the one or more chambers may be pressurized via these ports. The blade body may also comprise respective actuators for effecting movement of the element in the direction of the trailing edge and / or for pressurizing the one or more chambers of the element, for example hydraulically or pneumatically.

[0054] The flow modifying element may be a longitudinal segment extending in the longitudinal direction of the blade, and the blade may comprise a plurality of such segments arranged in the longitudinal direction of the blade.

[0055] According to another aspect of the invention, there is provided a wind turbine comprising a wind turbine blade having any of the configurations described herein.The wind turbine may, for example, comprise a rotor having three respective blades.

[0056] According to a further aspect of the invention there is provided a method of operating a wind turbine, wherein the wind turbine has any of the configurations described herein, and wherein the method may comprise operating the wind turbine to convert wind energy into electrical energy.

[0057] It will be appreciated that the features mentioned above and those to be 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

[0058] 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.

[0059] 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.

[0060] Figure 2 is a schematic diagram illustrating a wind turbine blade according to an embodiment, wherein the longitudinal extent over which the segments of the flow modifying elements extend is shown.

[0061] Figure 3 is a schematic diagram showing the outline of a blade body of a wind turbine blade without flow modifying elements.

[0062] Figure 4 is a schematic diagram illustrating an outline of a wind turbine blade including a flow modifying element according to an embodiment.

[0063] Figure 5 is a schematic diagram showing the outline of a flow modifying element according to an embodiment.

[0064] Figure 6 is a schematic diagram illustrating a perspective view of a flow modifying element according to an embodiment.

[0065] Figure 7 is a schematic diagram illustrating an outline of a wind turbine blade including a trailing edge addition and a flow modifying element according to an embodiment.

[0066] Figure 8 is a schematic diagram illustrating an outline of a flow modifying element according to a further embodiment.

[0067] Figure 9 and Figure 10 is a schematic diagram illustrating an outline of a wind turbine blade comprising a flow modifying element for two different adjusted thickness values ​​of the flow modifying element according to an embodiment.

[0068] Figure 11 is a schematic diagram illustrating a wind turbine blade comprising a section of guides and flow modifying elements according to an embodiment.

[0069] Figure 12 and Figure 13 is a schematic diagram illustrating a profile of a wind turbine blade comprising a flow modifying element for two different adjustment positions of the flow modifying element in the chord-wise direction according to an embodiment. DETAILED DESCRIPTION

[0070] 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 representation of the various elements is selected so that its function and general purpose become apparent to those skilled in the art. As used herein, the singular forms "one", "an" and "the" are also intended to include plural forms, unless the context clearly indicates otherwise. The terms "comprise", "have", "include" and "comprising" will be interpreted as open terms (i.e., meaning "including, but not limited to"), unless otherwise noted.

[0071] 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.

[0072] Figure 2 A wind turbine blade 10 according to an embodiment is schematically illustrated. The blade has a length L, which may be, for example, more than 30 m, 50 m, or even more than 60 m. The blade 10 has a root end 11, at which it may 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.

[0073] The blade 10 may include a blade body 20 and a flow modification element 30. The blade body 20 and the flow modification element 30 may be integrally formed to form the wind turbine blade 10; or the flow modification element 30 may be an additional element mounted to the blade body 20, and in particular mounted on an outer surface of the blade body 20. The flow modification element may be provided in a longitudinal region that may correspond to the root region 13 or in a longitudinal region extending between 0% L and 60% L, preferably between 5% L and 50% L, for example between 10% L and 50% L or between 10% L and 40% L.

[0074] The element 30 extends over the longitudinal extent 15, ie it covers this extent. The element 30 may be continuous over the extent 15 or may be provided in the form of segments placed next to each other. Figure 2 In the example of , the flow modifying elements 30 are provided in the form of respective segments 30-1, 30-2, ..., 30-5. The dashed lines 14 indicate the divisions between these longitudinal segments.

[0075] 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 17 (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.

[0076] The profile of the blade body 20 includes a leading edge 16 and a trailing edge 17. The blade body 20 also includes a suction surface 18 and a pressure surface 19, which correspond to Figure 3 . These contour curves extend from the leading edge 16 of the blade body 20 to the trailing edge 17. Since the profile of the body 20 has a flat trailing edge 17, it can be called a flat-back airfoil. The blunt trailing edge of such an airfoil in the root region can also be rounded.

[0077] Figure 4 The figure shows an outline of an exemplary embodiment of a blade 10 comprising a blade body 20 and a flow modifying element 30. The element 30 provides a raised portion 33 extending outwardly from the pressure surface 19. The element 30 extends between a leading end 31 (facing the leading edge 16) and a trailing end 32 (facing the trailing edge 17). The raised portion 33 extends along the blade ( Figure 2 ) extends in the longitudinal direction, for example substantially parallel to the trailing edge 17; thus, it may be substantially perpendicular to Figure 4 . The element 30 includes a mounting section 34 for mounting the element 30 to the pressure surface 19; this is optional, as the element 30 can be integrated with the blade body 20. The position of the element 30 in the chordwise direction can be defined as the center (or middle) of a line connecting the leading end 31 and the trailing end 32 of the element 30. Figure 4The relative position x / c of ​​element 30 in the chordwise direction is shown, measured relative to the chord length c. When measured from leading edge 16 (0% c), the position of element 30 is preferably within the range of 50% c to 100% c. While tail end 32 may extend beyond trailing edge 17, it is preferred that tail end 32 does not extend beyond trailing edge 17 to ensure compatibility with trailing edge attachment equipment.

[0078] Figure 5 The figure shows a detail of the outline of element 30, i.e., it shows a section through element 30 perpendicular to its longitudinal extension. The width we of element 30 can be defined as the distance between leading end 31 and trailing end 32. Width we is preferably between 10%c and 30%c. The thickness te of element 30 can be defined as the maximum distance of protrusion 33 from a line connecting leading end 31 and trailing end 32, in a direction perpendicular to this line. This thickness can preferably be between 5%c and 30%c, for example, between 8%c and 25%c.

[0079] The element 30 may include a first transition section 35 and a second transition section 36, which may be considered to form part of the boss 33. These transition sections may provide a smooth transition between a pressure side surface 39 of the element 30 and the pressure surface 19 of the blade body 20. In particular, these transition sections may be configured such that the pressure side surface 39 intersects the pressure surface 19 at an obtuse angle 37 that is less than 180° and greater than 90°, preferably greater than 130°. This smooth transition may reduce drag.

[0080] In this profile, the raised portion 33 may include a raised profile section 42 that is approximately a convex curve (meaning that the corresponding surface is a convex surface that bulges outward; see Figure 6 ). Although Figure 53. The convex profile section 42 is shown as a continuous convex curve, but the convex profile section 42 can also consist of a mixture of straight sections and sections with different (convex) curves. The first transition section 35 at the front portion of the convex portion corresponds to the concave curve section 41, and the second transition section 36 corresponds to the second concave curve section 43. Respective inflection points 45 are provided between the convex curve section 42 and the concave curve sections 41, 43. Thus, in this profile, the pressure side surface 39 of the element 30 can be approximated as a Gaussian curve, a section of a sine curve, or a high-order polynomial curve. As a result, the additional drag caused by the element 30 can be kept small. It should be understood that the transition sections 35, 36 are optional and can have different shapes (such as straight shapes) so as to intersect the pressure surface 19 at an obtuse angle 37. In addition, to adjust the aerodynamic properties of the element 30, the curvature of the first transition section 41 and the second transition section 43 can be different (or absent if straight sections are used). Furthermore, the curvature of section 42 may be asymmetric about the anterior and caudal sides.

[0081] The mounting section 34 may comprise a mounting surface 38. The mounting surface 38 may be rigid and its shape may be adapted to the shape of the pressure surface 19 at the mounting location. Alternatively, the mounting surface 38 may be flexible to allow the surface 38 to adapt to the shape of the pressure surface 19. This is particularly advantageous if the element 30 is to be mounted at different locations in the chordwise direction or if the element 30 is movable in the chordwise direction; thus, the surface 38 may always adapt to the required shape. The flexibility of the mounting surface 38 may also ensure that the angle 37 may be close to 180° (tangent). It may be made of a rubber material or other polymeric flexible material. The surface 38 may be formed by means of an adhesive, Mechanical fasteners (including screws, brackets, or the like) or other conceivable mounting methods are mounted to the pressure surface 19 .

[0082] The element 30 may include a cavity 50 extending through the element in a longitudinal direction. The cavity 50 may reduce the weight of the element 30 and the material required to manufacture the element 30. Figure 6 A perspective view of the element 30 is shown, from which the shapes of the cavities and the element can be inferred. One, two, three or more cavities may be provided, and their size may be adapted according to the required mechanical strength of the element 30. The element 30 may also be solid and not include any cavities. Figure 6 , the width we of the element 30 may remain constant over the longitudinal extension l of the element 30. Thus, the shape of the element 30 may not change in the longitudinal direction. Figure 6 A segment element 30 is shown having a defined length l, wherein l can be selected according to the longitudinal position along the blade where the segment is to be mounted and according to the longitudinal extension L of the blade. The length l can be, for example, between 0.5 and 4 m, wherein Figure 6The shorter segments are shown for illustration purposes. The different segments can be provided with bosses 33 of different sizes we, te and different shapes, which allow the aerodynamic properties of the element 30 to be adjusted according to the longitudinal position along the blade where the segment will be installed and according to the current twist angle and angle of attack at this position.

[0083] Figure 7 The figure shows an element 30 according to another example, which is a Figures 4 to 6 In this example, the element 30 is not provided with a mounting section 34 but is integrated with the blade body 20. The leading end 31 and the trailing end 32 are identified by the transition from the pressure side surface 39 to the pressure surface 19. Figure 7 In the example shown, the blade 10 includes a trailing edge attachment device 25. The device 25 can be configured to provide an extension of the suction surface 18 and / or the pressure surface 19 and can be configured to provide lift increase and / or drag reduction. As can be seen, the element 30 is compatible with the corresponding attachment device 25. Compatibility with suction-side attachment devices is also ensured.

[0084] Figures 4 to 7 The element 30 is a passive device, but may also be implemented as an active device. For example, one or a combination of the thickness te, the position in the chord-wise direction or the shape of the protrusion 33 may be adjusted during operation.

[0085] Figure 8 The illustration shows an example in which one, two, three or more chambers 61 are provided inside the element 30, which are sealed off at the longitudinal ends of the element 30. Ports 62 are provided through which the medium can enter and leave the chambers 61. Thus, the pressure inside the chambers 61 can be varied so that a force can be generated which pushes the corresponding section of the pressure surface 39 outwards or pulls it inwards. Thus, the shape of the pressure side surface 39 adjacent to the respective chamber 61 can be adjusted by controlling the pressure inside the respective chamber 61. For example, the curvature can be increased by applying a higher pressure to the central chamber, or the curvature can be reduced by reducing the pressure in the central chamber. In order to make all chambers controllable, each chamber can be provided with a corresponding flow connection 62, in particular a port. Two or more chambers can be supplied via the same flow connection 62 in order to control the pressure in these chambers together. By pressurizing all chambers with the same pressure, the thickness te of the element 30 can be increased; and by reducing the pressure in each chamber, the thickness te can be reduced. This is schematically illustrated in Figure 9 and Figure 10 middle.

[0086] As can be seen, in Figure 9 In the embodiment, the pressure inside the chamber or chambers 61 is reduced, resulting in a relatively low thickness te. Figure 10By applying a pressure between the minimum pressure and the maximum pressure, the thickness of the element 30 can be adjusted to Figure 9 and Figure 10 Any thickness within the minimum and maximum values ​​shown in FIG. Figure 9 The minimum value of may be, for example, a thickness te between 5%c and 10%c, and Figure 10 The maximum value in can be a thickness te between 10%c and 30%c. The thickness can vary by a value of at least 5%c and up to a value of 25%c.

[0087] The element 30 may comprise one or more tensioning elements 63 which provide tension between the mounting surface 38 and the pressure side surface 39 in order to maintain the shape of the element 30. If a plurality of chambers are provided, the tensioning element 63 may extend in the longitudinal direction of the element 30 and may provide a partition wall between two adjacent chambers. It may seal adjacent chambers from each other (if a flow connection 62 is provided to each chamber) or it may provide a flow connection between the chambers. If only a single chamber 61 is provided in the element 30, the tensioning element 63 may be, for example, a tether connecting the surfaces 38 and 39. The tensioning element 63 may be flexible in the thickness direction so that its extension in the thickness direction may be varied depending on the force applied to the element 63 due to the pressure in the chamber. Thus, the element 63 may maintain the shape of the protrusion 33 while allowing its thickness to be adjusted.

[0088] Through Figure 8 As shown in FIG, three chambers 61 are provided, which can adapt the curvature on the leading and trailing sides of the element 30. In addition, the thickness of the entire element 30 can be adapted. It is also conceivable to provide one, two or four chambers. In the blade body 20, corresponding ports and flow ducts can be provided and connected to the flow connection 62. The medium can be a hydraulic or pneumatic medium, and a pressure reservoir can be provided in the blade body and supplied from the nacelle of the wind turbine, or a hydraulic / pneumatic actuator can be provided in the blade body 20. Controllable valves can also be provided in the blade body 20 to control the flow from such a reservoir or pressure source to the chamber 61 and / or to control the flow from the chamber 61 to the discharge port.

[0089] To allow movement in a direction towards and away from the trailing edge 17 of the blade body (eg in the chordwise direction), the element 30 may comprise a guide element 71. The guide element 71 may be provided on the blade body ( Figure 11) interact with the complementary guide elements 75 in the blade body 20 to provide movement of the element 30 in the desired direction. In this configuration, the mounting surface 38 may not be fixedly mounted to the pressure surface 19, but rather may slide on the pressure surface 19 to allow movement. The mounting surface 38 may be flexible to allow its shape to adapt to the shape of the pressure surface 19 during movement. Thus, the element 30 may be movably attached to the blade body 20 by means of the guide elements 71 or other attachment means that allow corresponding movement.

[0090] Figure 11 The figure shows a complementary guide element 75 (which is provided in the form of a track) within which the guide element 71 (which can be a pin, a carriage, etc.) can move. The complementary guide element 75 (in particular the track) preferably extends substantially perpendicularly to the trailing edge 17 of the blade body 20 so that the distance to the trailing edge 17 of the element 30 is adjustable. Figure 11 As shown in FIG, one or more, preferably two, guide elements 75 may be provided for each segment 30-1, ..., 30-5 of the element 30. Thus, each segment can be moved independently. A corresponding number of guide elements 71 may be provided on each segment of the element 30. As can be seen, the segments can move in different directions.

[0091] As an example, Figure 12 The element 30 is shown in profile in the maximum chord position, with the arrows indicating adjustability. Figure 13 In the same profile the element 30 is shown in the position of minimum chord, the arrow indicating the adjustability of this position. It will be clear that the element 30 can be controlled to take Figure 12 、 Figure 13 . The maximum position may be, for example, at 100% c and the minimum position may be at 50% c, and the position may be adjustable to take any position therebetween. However, the extension of the guide element 75 (e.g., a track) is preferably limited to a certain size so that the track is covered by the element 30 in any position. The maximum length of the track may, for example, correspond to half the width we of the element 30, so that in both the maximum and minimum positions, the track is covered by the element 30. It should be clear that the length of the guide element 75 limits movement in the corresponding direction.

[0092] The movement of the element 30 guided by the guide elements 71, 75 can be achieved by means of electric actuators, hydraulic actuators, pneumatic / hydraulic actuators or other conceivable actuation devices. The electric motor or the hydraulic or pneumatic compressor can be installed in the blade body 20 or in the nacelle of the wind turbine. In the latter case, corresponding transmission elements (such as rotating shafts or hydraulic or pneumatic lines) can then extend through the blade to the location of the element 30. As an example, a pneumatic or hydraulic piston can be used to controllably move the guide 71 back and forth in the track 75, or a rack and pinion arrangement can be provided to convert the rotary motion of the electric motor into a linear motion that moves the guide element 71 in the track 75.

[0093] Although the present example uses pins on the element 30 and tracks on the blade body 20 as guide elements, it will be clear that other configurations are conceivable and that the arrangement could be reversed, for example by providing a track along the width of the element 30 and by providing one or more corresponding pins or studs on the blade body 20 that move in such a track.

[0094] Of course, the two actuation mechanisms can be combined. For example, the flow connection 62 can be connected by a flexible hose provided in a recess or slit on the surface of the blade body 20, so that a flow connection to the chamber 61 can be established while allowing movement of the element 30 in the chord direction. Although the flow connection 62 and the guide element 71 are Figure 8 1 and 2. They are shown in the same plane, but it will be clear that they may be distributed along the longitudinal extension of the element 30 so that they do not interfere with each other when the element 30 is moved.

[0095] The corresponding electric / pneumatic / hydraulic actuators and / or control valves can be controlled by a wind turbine controller of wind turbine 100. This controller can be located in the nacelle of the wind turbine and can include a corresponding processor and memory (not shown) for processing control commands and generating corresponding electrical control signals. Depending on the operating point of the wind turbine and / or environmental conditions (such as wind speed), the parameters of the active element 30 can be adjusted to achieve the desired aerodynamic properties of the blade. This adjustment can depend on the longitudinal position along the blade at which the corresponding segments 30-1, ..., 30-5 are installed. In particular, the chord position of the element and the thickness of the element can be adjusted to optimize the CL / CD ratio for the current operating conditions.

[0096] Thus, by means of the flow modifying element 30, improved aerodynamic properties of the blade can be achieved for both the passive and active versions of the element. The element 30 allows more energy to be extracted from the air flow, in particular by increasing the lift of the blade. The smooth shape of the flow modifying element also minimizes additional drag.

[0097] 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 not 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), a pressure surface (19) and a trailing edge (17), wherein the blade body (20) has a chord length c, wherein the leading edge (16) corresponds to a position of 0% c in the chord direction and the trailing edge (17) corresponds to a position of 100% c in the chord direction, wherein the flow modification element (30) is configured to be arranged on the pressure surface (19) of the blade body (20) in a range between 40%c and 100%c in the chord direction, and wherein the flow modifying element (30) has a projection (33) projecting outwardly from the pressure surface (19) of the blade body (20), wherein the flow modifying element (30) is shaped and configured to be arranged to increase the lift coefficient of the aerodynamic profile of the blade body (20) by increasing the pressure of air flowing through the boss (33) on a forward portion of the boss (33), and The flow modification element (30) is an active element and is configured to be adaptable in at least one of the following: the position in the chord direction, the thickness (te) of the protrusion (33), and the shape of the protrusion (33).

2. A flow modification element according to claim 1, wherein the flow modification element (30) and the blade body (20) form an aerodynamic profile, wherein the protrusion (33) is shaped to provide a convex profile section (42) that is approximately a convex curve or a convex curve in the aerodynamic profile.

3. A flow modification element according to claim 2, wherein the flow modification element (30) includes a first transition section (35) and / or includes a second transition section (36), the first transition section (35) being configured to provide a continuous transition between the pressure surface (19) of the blade body (20) and the front part of the protrusion (33), and the second transition section (36) being configured to provide a continuous transition between the pressure surface (19) of the blade body (20) and the tail part of the protrusion (33).

4. A flow modifying element according to claims 2 and 3, wherein in the profile, the first transition section (35) is shaped to provide a first concave curve section (41), and / or the second transition section (36) is shaped to provide a second concave curve section (43), the convex profile section (42) being preferably arranged between the first concave curve section (41) and the second concave curve section (43).

5. A flow modifying element according to any one of claims 2 to 4, wherein the flow modifying element (30) has in the profile a width from a leading end (31) to a trailing end (32) of the flow modifying element (30), wherein the width (we) is between 7%c and 45%c, preferably between 10%c and 40%c.

6. Flow modifying element according to any of the preceding claims, wherein the flow modifying element (30), in particular the projection (33), has a thickness (te) of 5%c to 30%c, preferably 10%c to 20%c.

7. A flow modifying element according to any of the preceding claims, wherein the flow modifying element (30) comprises one, two, three or more chambers (61) and further comprises a flow connection (62) towards the respective chambers (61) to allow the pressure inside the chambers (61) to be changed in order to adjust the shape and / or thickness of the protrusion (33).

8. A flow modification element according to any of the preceding claims, wherein the flow modification element (30) further comprises a guide element (71), the guide element (71) being configured to guide the movement of the flow modification element (30) on the blade body (20) in a direction allowing adjustment of the distance of the flow modification element (30) to the trailing edge (17) of the blade body (20).

9. A flow modifying element according to any of the preceding claims, wherein the flow modifying element (30) is a separate element comprising a mounting section (34) configured to be mounted to the pressure surface (19) 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).

10. A flow modifying element according to claim 9, wherein the mounting section (34) comprises a mounting surface (38) configured to face the pressure surface (19) of the blade body (20), wherein the mounting surface (38) is adapted or adaptable to the shape of the pressure surface (19).

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

12. A flow modifying element according to any of the preceding claims, wherein the flow modifying element (30) is configured to be provided on the blade body (20) within a longitudinal extent (15) 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 length of the blade (10).

13. A flow modifying element according to any of the preceding claims, wherein the flow modifying element (30) is configured to be mounted to the pressure surface of the blade body, and / or wherein the flow modifying element (30) does not include or form the trailing edge (17) of the blade body (20).

14. A wind turbine blade comprising a blade body (20) having a leading edge (16), a suction surface (18), a pressure surface (19) and a trailing edge (17), wherein the wind turbine blade (10) further comprises: A flow modifying element (30) according to any of the preceding claims, wherein the flow modifying element (30) is mounted to the pressure surface (19) 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).

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