Wind turbine rotor blade with passively modified trailing edge component

Abstract

Wind turbine rotor blade (16), comprising: a foot section (28); a rotor blade section (32) extending from the foot section (28) and defined by a leading edge (24) and a trailing edge (26); wherein the rotor blade section (32) has a main blade section (34) and a trailing edge section (36) which is pivotably connected to the main blade section (34) along a hinge line (38) extending in a span direction (48); a passive torsion element (44) that is attached between the main blade section (34) and the trailing edge section (36), wherein the torsion element (44) is prestressed in a neutral position in which the trailing edge section (36) is pivoted in the chord direction relative to the main blade section (34) into a position of low wind speed; wherein the trailing edge section (36) automatically moves from a position of low wind speed relative to the main blade section (34) to a position of higher wind speed depending on the preload force of the passive torsion element (44) and a wind speed present at the rotor blade section (32), wherein the torsion element (44) is designed such that the trailing edge section (36) is in an aligned position with the main blade section (34) with respect to a chord-directed axis (46) of the rotor blade (16) at a wind speed that is optimal for the design of the rotor blade (16), and where the position of higher wind speed is defined between the position of lower wind speed and the aligned position.

Description

[0001] The subject matter under discussion generally concerns wind turbines and, in particular, wind turbine rotor blades that have a passive trailing edge component which responds to changing wind conditions and changes its position depending on these conditions.

[0002] Wind power is currently considered one of the cleanest and most environmentally friendly energy sources available, and wind turbines are therefore receiving increasing attention. A modern wind turbine typically consists of a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. Using known aerodynamic principles, the rotor blades extract kinetic energy from the wind and convert it into rotational energy to drive a rotating shaft. This shaft connects the rotor blades to a gearbox, or, if no gearbox is used, directly to the generator. The generator then converts the mechanical energy into electrical energy, which can be fed into a power grid.

[0003] Wind turbine rotor blades are essentially designed for optimal wind speeds and are therefore less efficient at other wind speeds. State-of-the-art approaches to increasing the effective wind speed range for rotor blades involve active systems that modify or alter the aerodynamic profile of the rotor blade by moving or adjusting extensions, flaps, or other control surfaces attached to the rotor blade in an active control loop. Electromechanical systems are usually integrated into the rotor blade to move the control surfaces. For example, reference is made to US patent US 7,922,450 B2, which describes a rotor blade with a trailing edge section that is moved by an internal piezoelectric actuator depending on aerodynamic forces acting on the blade.US patent application US 5 181678 A discloses a flexible airfoil section for a wing or sheet, having a streamlined shape and an elastic structure whose stiffness distribution along its chord and span is tailored to provide a desired cambered shape with proportional increases in camber with increases in lift, and which is attached to a supporting structure such that the airfoil sections can pivot freely about axes near their leading and trailing edges.

[0004] These systems were also introduced for load control purposes, reducing blade stress under high-wind conditions by modifying the rotor blade's aerodynamic profile using active control surfaces. Efforts have been made to increase the energy yield of wind turbines by increasing the length and surface area of ​​the rotor blades. However, the magnitude of bending forces and the stress on a rotor blade, along with wind speed, turbine operating conditions, blade stiffness, and other variables, is essentially a function of the blade length.This increased stress not only leads to material fatigue on the rotor blades and other wind turbine components, but can also increase the risk of a sudden catastrophic failure of the rotor blades, for example if excessive stress leads to a bending of a rotor blade, resulting in an impact on the frame.

[0005] Load monitoring is therefore an important consideration with regard to the operation of modern wind turbines. Besides active angle-of-attack control systems, modifying the aerodynamic characteristics of individual rotor blades is also a known means of load control, for example, by means of controllable vortex elements, flaps, noses, and the like, which are provided on the blade surfaces. For example, US patent US 6,972,498 B2 describes various wind turbine rotor blade designs in which a retractable extension is provided on a base rotor blade segment to reduce the effective length of the rotor blade under high-load conditions.In a special embodiment, the rotor blade extension is pivotably attached to the base rotor blade segment and changes its position between a fully extended position and a fully retracted position, in which the rotor blade extension fits into the base rotor blade segment.

[0006] For industry, an improved wind turbine rotor blade design would therefore be advantageous, one that has a larger effective wind speed range, while avoiding the costs and use of relatively complicated components associated with active improvement systems.

[0007] Aspects and advantages of the invention are partly discussed in the following description, may be obvious from the description, or may be experienced through the practice of the invention.

[0008] According to aspects of the invention, a wind turbine rotor blade comprises a root section and a rotor blade section extending from the root section and defined by a leading edge and a trailing edge. The rotor blade section also includes a main blade section and a trailing edge section, which is pivotably connected to the main blade section along a hinge line extending in the span direction. A passive torsion element is arranged between the main blade section and the trailing edge section. The torsion element is pre-tensioned in a neutral position, with the trailing edge section pivoted relative to the main blade section in the chord direction to a position suitable for low wind speeds.In this low-wind position, the rotor blade exhibits an aerodynamic profile that is more effective at capturing energy at lower wind speeds. As the wind speed increases, the leading edge section moves relative to the main blade section automatically against the preload force of the torsion element from the low-wind position to a higher-wind position, depending on the wind speed above the rotor blade section. With increasing wind speed, the leading edge section moves further away from the neutral position towards a high-wind position.

[0009] In a specific embodiment, the rotor blade includes several pivotably connected trailing edge sections that are aligned in the spanwise direction along the trailing edge, with all of these trailing edge sections having a corresponding passive torsion element. In a modified embodiment, a single trailing edge section can extend along the rotor blade and have one or more torsion elements.

[0010] According to the invention, the torsion element is designed such that, at an optimal wind speed for the rotor blade, the trailing edge section is in an alignment with the main blade section with respect to a chord-oriented axis of the rotor blade. The trailing edge section can thus be variably positioned at any point between the low-wind-speed position and the alignment position. In this embodiment, it may be desirable to provide a stop defined between the trailing edge section and the main blade section, which prevents movement of the trailing edge section beyond the alignment position.

[0011] The torsion element can be constructed in different ways. For example, in one embodiment, the torsion element is a torsion spring in which one leaf is connected to the stationary main blade section and the other leaf is connected to the pivotable trailing edge section. In a modified embodiment, the torsion element can be a flexible element, for example, a homogeneous elastomer material, pre-formed into a neutral position. The flexible element can have the shape of a strip element extending between one or more trailing edge sections and the main blade section in the spanwise direction. The strip element can be continuous or interrupted.

[0012] It should be understood that the invention is not limited to a specific size or chord dimension of the leading edge section, and that such dimensions may differ from the root to the tip of the rotor blade or between different leading edge sections. In specific embodiments, the main blade section extends by at least 50% of the rotor blade chord (measured from the leading edge towards the trailing edge) along the span of the rotor blade. Thus, in this embodiment, the leading edge section of the rotor blade is less than 50% of the rotor blade chord.

[0013] The present invention also relates to any type of wind turbine construction having one or more rotor blades provided with a trailing edge extension as set out herein.

[0014] These and other features, aspects, and advantages of the present invention will become clearer with reference to the description and the accompanying claims. The accompanying drawings, which are incorporated into and form part of this description, illustrate exemplary embodiments of the invention and, together with the description, serve to explain the basic principles of the invention.

[0015] A complete and practically applicable description of the present invention, which includes the best mode of the invention and is addressed to the person skilled in the art, is provided in the description with reference to the accompanying figures: Fig. Figure 1 illustrates a conventional wind turbine in a perspective view, Fig. Figure 2 shows a sectional view of an embodiment of a wind turbine rotor blade according to aspects of the invention. Fig. Figure 3 shows an embodiment of a wind turbine rotor blade according to aspects of the invention in a perspective view. Fig. Figure 4 shows a sectional view of an embodiment of a wind turbine rotor blade that uses a passively actuated trailing edge section, Fig. Figure 5 shows a cross-sectional view of a modified embodiment of a wind turbine rotor blade that uses a passively actuated trailing edge section, and Fig. Figure 6 shows a cross-sectional view of an embodiment of a wind turbine rotor blade that uses a passively actuated trailing edge section.

[0016] Reference will now be made in detail to exemplary embodiments of the invention, some examples of which are illustrated in the drawings. All examples serve to explain the invention and are not intended to limit it. The person skilled in the art will readily recognize that numerous modifications and changes can be made to the present invention without deviating from the subject matter or scope of protection of the invention. For example, features illustrated or described as part of one exemplary embodiment can be used in conjunction with another exemplary embodiment to produce yet another exemplary embodiment. The present invention is therefore intended to cover such modifications and deviations insofar as they fall within the scope of protection of the appended claims and their equivalent forms.

[0017] By now discussing the drawings, it is illustrated Fig. Figure 1 shows a perspective view of a wind turbine 10 with a horizontal axis. It should be clear that the wind turbine 10 can also be a wind turbine with a vertical axis. In the illustrated embodiment, the wind turbine 10 comprises: a tower frame 12 supported on a foundation, a nacelle 14 attached to the tower frame 12, and a rotor hub 18 connected to a power generation unit housed in the nacelle 14. The rotor has rotor blades 16 connected to the hub 18 and extending radially outwards from it; for example, as shown in the figure, there are three rotor blades 16. However, in a modified embodiment, the rotor may have more or fewer than three rotor blades 16.

[0018] With reference to Fig. 2 Each of the rotor blades 16 of the wind turbine has an upper housing element 20 and a lower housing element 22, with an interior space 25 formed between the housing elements. The upper housing element 20 can be designed as the suction side surface of the rotor blade 16, while the lower housing element 20 can be designed as the pressure side surface of the rotor blade. The rotor blade 16 has a leading edge 24 and a trailing edge 26, as well as a root section 28 and a tip section 30. As is well known from the prior art, the upper housing element 20 and the lower housing element 22 are connected to each other at corresponding connection lines along the leading edge 24 and at the trailing edge 26. Furthermore, any type of internal structural element 27 can be provided, for example, a shear rib, spar covers, and the like.

[0019] The rotor blades 16 can generally be dimensioned with any suitable length that allows the wind turbine 10 to fulfill its function according to the design criteria. For example, the rotor blades 16 can have a length ranging from approximately 9 meters (m) to approximately 100 m. The rotor blades 16 are spaced apart from one another around the hub 18 to achieve the conversion of the kinetic energy from the wind into usable mechanical energy and subsequently into electrical energy. Specifically, the hub 18 can be connected to a generator (not shown) located in the nacelle 14 to generate electricity. Furthermore, the rotor blades 16 are attached to the hub 18 by connecting the base section 28 of the rotor blade to the hub 18 at several power transmission points. In this way, forces acting on the rotor blades 16 are transmitted to the hub 18 via the power transmission points.

[0020] With reference to Fig. 2 and Fig. Figure 3 shows an embodiment of a rotor blade 16 of a wind turbine, comprising a rotor blade section 32 extending from the root section 28 to the tip section 30 of the rotor blade. The rotor blade section 32 is defined by the upper 20 and the lower 22 housing element between the leading edge 24 and the trailing edge 26. The rotor blade section 32 is divided into a main blade section 34 and a trailing edge section 36. A hinge line 38 separates the main blade section 34 from the trailing edge section 36. Thus, the trailing edge section 36 can be defined as the rotor blade section 32 extending from the trailing edge 26 to the hinge line 38. The trailing edge section 36 is pivotably connected to the main blade section 34 along the hinge line 38, which extends in the span direction (where the span direction is indicated by the arrow 48). Fig. 3 is shown).

[0021] With reference to Fig. 4 and Fig. 5 A passive torsion element 44 is attached between the main blade section 34 and the trailing edge section 36. This torsion element 44 is in a Fig. 4 neutral position shown, pre-tensioned, wherein the trailing edge section 36 is pivoted relative to the main blade section 34 in the chord direction into a position of low wind speed (where the chord direction is indicated by arrow 49 in Fig. 3 is indicated). With reference to Fig. 4 The rotor blade 16 has a chordal axis 46. In the neutral position of the trailing edge section 36, the axis 47 of the trailing edge section 36 is angled or pivoted towards the lower housing element 22 (which can be considered the pressure side of the rotor blade 16). Thus, the trailing edge section 36 is pivoted essentially in the chordal direction relative to the main blade section 34.

[0022] The neutral position of the outflow edge section 36 in Fig. 4 corresponds to a low wind speed position of the trailing edge section 36, where the aerodynamic profile of the rotor blade 16 is different from the profile for which the rotor blade is designed with a view to an optimal wind speed ( Fig. 2) is modified to better capture wind energy at lower wind speeds. From this neutral position of low wind speed, the trailing edge section 36 moves relative to the main blade section 34 automatically against the preload force of the torsion element 44 into a position of increased wind speed, depending on the wind speed. As the wind speed (and the force on the blade) increases, the pivot position of the trailing edge section 36 relative to the main blade section 34 also increases.

[0023] Fig. Figure 5 illustrates an example of the wind turbine rotor blade 16 according to the invention, wherein the trailing edge section 36 is pivoted relative to the main blade section 34 into a position corresponding to higher wind speeds (shown in solid lines). In this position, the axis 47 of the trailing edge section 36 is aligned with the axis 46 of the main blade section 34. This position of the trailing edge section 36 can correspond to an overall aerodynamic profile of the rotor blade 16 of the wind turbine, which is designed with a view to an optimal wind speed. It should be understood that the higher wind speed position of the trailing edge section 36 depends on the wind speed of any position of the section between the in Fig. 4 neutral position shown and the one in Fig. The position shown in section 5 can correspond to the optimal wind speed.

[0024] With reference to Fig. 4 In specific embodiments, it may be desirable to provide a stop mechanism between the downdraft edge section 36 and the main blade section 34, which prevents the downdraft edge section 36 from exceeding the Fig. 5 shown position swings out beyond the optimal wind speed. This stop 50 can include any type of shoulder, block, or other structure engaging between the trailing edge section 36 and the main blade section 34. For example, the stop 50 can, as in Fig. As shown in section 4, it can simply be formed as a shoulder on the main blade section 34, preventing the downdraft edge section 36 from extending beyond the area shown in Fig. 5 illustrated position to swing out.

[0025] In modified embodiments, the function of the "stop" can be a specific feature of the passive torsion element. For example, the torsion element can have a range of movement that defines the stop position. In the case of a torsion spring 52 ( Fig. 4) The spring can, for example, be designed to have a maximum torque in the stop position.

[0026] With further reference to Fig. 4 and Fig. 5. The trailing edge section 36 can be pivotally attached to the main blade section 34 by any suitable pivoting mechanism. For example, the pivoting mechanism can include a sliding friction design between a rounded end face 42 formed on the trailing edge section 36 and a correspondingly shaped recess or seat 40 formed in the main blade section 34. The passive torsion element 44 can connect the two components along the interface of the seat 40 and the end face 42 along the span length of the rotor blade 16. Fig. 3) It is understood that in this respect any suitable pivoting joint mechanism may be used to enable the pivoting movement between the trailing edge section 36 and the main blade section 34, as set out herein.

[0027] With reference to Fig. 3. It should be clear that the invention comprises various designs of a rotor blade 16, wherein the trailing edge section 36 can be designed in the form of a single component or several components along the span length of the trailing edge 26. For example, in Fig. Figure 3 shows several individual downdraft edge sections 36. Each of these sections can be independently attached to and actuated by a single corresponding passive torsion element 44. In a modified embodiment, a single downdraft edge section 36 can span a length of the downdraft edge 26 and be connected to one or more passive torsion elements 44.

[0028] The torsion element 44 can be constructed differently within the scope of protection of the invention. For example, the torsion element 44 is, as in Fig. 4 and Fig. Figure 5 shows a torsion spring 52 having a leaf that engages with the main leaf section 34 and an opposing leaf that engages with the trailing edge section 36 to counteract the Fig. 4 to define the neutral position of the outflow edge section 36 shown. The outflow edge section 36 pivots against the preload of the torsion spring 52 into the position shown. Fig. 5 position shown. Depending on any number of factors, e.g. the weight of the downdraft section, the force expected at the downdraft section 36, the length of the downdraft section 36, and so on, several of the torsion springs 52 can be arranged spaced apart along the downdraft section.

[0029] The embodiment according to the invention according to Fig. Figure 6 illustrates a modified embodiment of the passive torsion element 44, wherein the passive torsional force is provided by a compliant element 58. This element 58 can, for example, be a strip 60 ( Fig. 3) be made of a flexible elastomeric material, for example a rubber material, which is pre-shaped into a neutral form to conform to the shape indicated by the dashed lines in Fig. The downstream edge section 36 shown in Figure 6 is designed to provide a low wind speed position. For example, the flexible element 58 can be a longitudinally extending strip element 60 having a pre-formed curved cross-sectional profile, the profile being as shown in Figure 6. Fig. 6 shows that it assumes a relatively flat shape, while the outflow edge26 pivots in the direction of the aligned position.

[0030] It should be readily understood that any number or combination of passive torsion elements can be used to provide the passive torsional force between the main blade section 34 and the pivotable trailing edge section 36 in accordance with the scope of protection of the invention.

[0031] It should also be considered an advantage that the present invention encompasses any type or design of a wind turbine which uses one or more rotor blades which, as discussed above, have a passively actuated trailing edge section.

[0032] The present description uses examples to describe the invention, including the best mode, and also to enable any person skilled in the art to put the invention into practice, for example, to manufacture and use any devices and systems and to carry out any related processes. The patentable scope of the invention is defined by the claims and may include other examples that may occur to a person skilled in the art. Such other examples shall fall within the scope of the claims if they contain structural elements that do not differ from the wording of the claims or if they contain equivalent structural elements with insignificant differences from the literal content of the claims.

[0033] A wind turbine rotor blade has a root section and a rotor blade section extending from the root section, defined by a leading edge and a trailing edge. The rotor blade section also has a main blade section and a trailing edge section, which is pivotally connected to the main blade section along a hinge line extending in the spanwise direction. A passive torsion element is located between the main blade section and the trailing edge section. The torsion element is pre-tensioned to a neutral position, whereby the trailing edge section pivots in the chord direction relative to the main blade section into a low-wind-speed position.Depending on the preload force of the torsion element and the wind speed above the rotor blade section, the trailing edge section moves automatically from a position of low wind speed relative to the main blade section towards a position of higher wind speed. Reference symbol list 10 wind turbines 12 Tower scaffolding 14 gondolas 16 rotor blades 18 Rotor hub / hub 20 Upper housing element 22 Lower housing element 24 Leading edge 25 Interior 26 Egress edge 27 Internal support structure 28-foot section 30 Peak section 32 Rotor blade section 34 Main Sheet Section 36 Outflow edge section 38 hinge line 40 seats 42 Front surface 44 Torsion element 46 Axis running in the direction of the chord 47 Outflow edge axis 48 Span direction 49 tendon 50 strikes 52 Torsion spring 58 Flexible element 60 strip elements

Claims

[1] Wind turbine rotor blade (16), comprising: a foot section (28); a rotor blade section (32) extending from the foot section (28) and defined by a leading edge (24) and a trailing edge (26); wherein the rotor blade section (32) has a main blade section (34) and a trailing edge section (36) which is pivotably connected to the main blade section (34) along a hinge line (38) extending in a span direction (48); a passive torsion element (44) that is attached between the main blade section (34) and the trailing edge section (36), wherein the torsion element (44) is prestressed in a neutral position in which the trailing edge section (36) is pivoted in the chord direction relative to the main blade section (34) into a position of low wind speed; wherein the trailing edge section (36) automatically moves from a position of low wind speed relative to the main blade section (34) to a position of higher wind speed depending on the preload force of the passive torsion element (44) and a wind speed present at the rotor blade section (32), wherein the torsion element (44) is designed such that the trailing edge section (36) is in an aligned position with the main blade section (34) with respect to a chord-directed axis (46) of the rotor blade (16) at a wind speed that is optimal for the design of the rotor blade (16), and where the position of higher wind speed is defined between the position of lower wind speed and the aligned position. [2] Wind turbine rotor blade (16) according to claim 1, comprising several of the pivotably connected trailing edge sections (36) which are aligned in the span direction (48) along the trailing edge (26), wherein each of the trailing edge sections (36) has a corresponding passive torsion element (44). [3] Wind turbine rotor blade (16) according to claim 1 or 2, further comprising a stop (50) formed between the trailing edge section (36) and the main blade section (34) which prevents movement of the trailing edge section (36) beyond the aligned position. [4] Wind turbine rotor blade (16) according to one of the preceding claims, wherein the torsion element (44) includes a torsion spring (52). [5] Wind turbine rotor blade (16) according to one of claims 1 to 3, wherein the torsion element (44) includes a flexible element (58) which is preformed into the neutral position. [6] Wind turbine rotor blade (16) according to claim 5, wherein the flexible element (58) is a strip element (60) extending in the span direction (48) between the trailing edge section (36) and the main blade section (34). [7] Wind turbine rotor blade (16) according to one of the preceding claims, wherein the main blade section (34) extends by at least 50% of the rotor blade chord measured from the leading edge (24) along the span of the wind turbine rotor blade (16). [8] Wind turbine (10) comprising a nacelle (14), a rotor hub (18) and at least one wind turbine rotor blade (16) according to one of the preceding claims, wherein the foot section (28) is connected to the rotor hub (18). [9] Wind turbine according to claim 8, comprising several wind turbine rotor blades (16) according to any one of the preceding claims 1 to 7.

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