ROTOR WITH ROTOR BLADE, WIND ENERGY PLANT AND METHOD FOR OPTIMIZING A WIND ENERGY PLANT

Description

[0001] The present invention relates to a rotor with a rotor blade for a wind turbine, an associated wind turbine, and an associated wind farm. The present invention also relates to a corresponding method for optimizing a wind turbine. In particular, the invention relates to a rotor with two-part rotor blades, i.e., those that have at least one separation point along a rotor blade longitudinal axis.

[0002] Rotor blades for wind turbines are well known. Mounted on a wind turbine rotor, the rotor blades have an aerodynamic profile that generates an aerodynamic force when exposed to the wind, which is ultimately converted to generate electrical power in the wind turbine. Maximizing the yield of wind turbine rotor blades has always been a goal.

[0003] The goal of maximizing rotor blade yield has led to ever larger rotor blades, so that rotors with diameters well over 100 meters are no longer uncommon. While a longer rotor blade offers yield advantages, it also presents ever greater challenges in terms of manufacturing and transport.

[0004] One possible solution to these transport problems is to divide the rotor blades longitudinally. A so-called split or two-piece rotor blade has an outer blade with a blade tip and an inner blade that are joined at a separation point. The inner blade thus runs from the rotor hub to the separation point, where the outer blade joins up to the blade tip. Of course, the outer blade can also be divided into several further blade sections. All types of rotor blades that have at least one separation point are referred to below as split rotor blades.

[0005] However, it is also known that the provision of the separation point represents an aerodynamic and, above all, structural challenge due to the associated weight.

[0006] At the same time, with increasing rotor blade length, the probability of flow separation in the area near the hub, i.e., near the center of the rotor surface, also increases. In these areas, profiles with a high relative thickness must be used, which tend to cause flow separation, especially when the rotor blade surface is dirty. For example, it is known to arrange swirl elements, such as vortex generators, on the rotor blade near the hub. These elements are designed to introduce energy into the flow boundary layer and thus delay flow separation. These swirl elements inevitably generate increased drag, so the benefits of the swirl elements must be weighed against the associated disadvantages.

[0007] The German Patent and Trademark Office searched the following prior art in the priority application for the present application: DE 10 2012 107 415 A1, US 2018 / 0038343 A1, EP 1 944 505 A1, EP 2 634 418 A2, EP 2 657 513 A2, EP 2 799 710 A1. Further prior art is disclosed in US 2016 / 047357 A1 and in: Gyatt GW: "Development and testing of vortex generators for small horizontal axis wind turbines," Final Report, DOE / NASA / 0367-1, XX, XX, July 1, 1986.

[0008] Against this background, it was an object of the present invention to provide a rotor with at least one at least two-part rotor blade for wind turbines, which enables an improved yield.

[0009] According to a first aspect, the object is achieved by a rotor with at least one rotor blade for a wind turbine as defined in claim 1.

[0010] The present invention is based on the finding that there is a significant relationship between the position of the separation point and the extension of the swirl elements into an outer region of the blade. In particular, it has been found that the outer length, i.e., the length that the swirl element extends beyond the separation point toward the blade tip, should not exceed a certain ratio to the total length of the swirl element in order to keep the drag generated within limits.

[0011] The particular relevance of the separation point arises from the fact that the rotor blade profile is specially designed because of the separation point. In particular, a thicker profile, i.e. one with a higher relative thickness, i.e. a ratio of profile thickness to profile length, must be provided than in an undivided blade, since the loads acting on the separation point are too great with a thinner profile. The position of the separation point therefore interacts with the relative thickness of the blade, which in turn interacts with the extent and effectiveness of the turbulence elements. An alternative separation point can also be provided on thinner profiles, particularly in a very outer region of the rotor blade. Analogously, the separation point requires a special adaptation of the design of the rotor blade profile.

[0012] The swirling element does not have to be continuous and can also, for example and preferably, have interruptions in the radial direction. According to the invention, the swirling element is formed from several sub-elements. The beginning and end of the swirling element always correspond to the absolute beginning and end of all parts of the swirling element, thus remaining unchanged even if the swirling element is designed in multiple parts or with interruptions.

[0013] The claimed value of the ratio of less than 0.25, preferably less than 0.2, and particularly preferably less than 0.15, of the outer length to the total length of the swirl element takes into account this finding of the interaction between the position of the separation point and the position and extent of the swirl element and has reliably proven to be an upper limit. It should be noted that the outer length can also assume a negative value, namely if the swirl element does not extend outward to the separation point in the longitudinal direction of the rotor blade, but ends earlier.

[0014] Previously used wind turbines with two-piece blades, such as the Enercon E-126 EP4 or E-141 EP4, also feature turbulence elements. In these known wind turbines, the turbulence elements are currently extended to a point further outward near the blade tip, resulting in a larger ratio of outer length to total length. However, it has been shown that the rotor blades can be improved by modifying the turbulence elements and maintaining the ratio specified in the invention.

[0015] In one embodiment, the swirling element comprises one or more vortex generators. The vortex generators are arranged, in particular, on a suction side of the rotor blade.

[0016] It is well known that rotor blade profiles run from a leading edge to a trailing edge, which are connected to a so-called pressure side and suction side. A separation-free flow around the suction side is particularly important for achieving the design profile lift and drag values.

[0017] In one embodiment, the vortex generators are designed as fins arranged in pairs, essentially perpendicular to the suction side. This paired arrangement allows counter-rotating vortices to be introduced into the boundary layer. The fin configuration, for example, in a triangular shape, is a particularly simple embodiment of vortex generators, although other suitable shapes are also known to those skilled in the art. Essentially perpendicular to the suction side is understood to mean an angle between the rotor blade surface and the fin that is greater than 45°, preferably greater than 60°, and particularly preferably at least 80°.

[0018] Particularly preferably, the swirling element comprises or consists of a plastic material, in particular short fiber reinforced plastic material.

[0019] In one embodiment, the vortex generators have a geometry as a function of the position in the longitudinal direction of the rotor blade. It is therefore preferable to provide different geometries of the vortex generators depending on their position in the longitudinal direction of the rotor blade. For example, a height, i.e., an extension perpendicular to the rotor blade surface, or a length, i.e., an extension in the plane of the rotor blade surface, can be greater the closer the vortex generator is to the root section. Alternatively or additionally, a distance between two adjacent vortex generators and / or an angle between the main flow direction, in particular perpendicular to the leading edge of the rotor blade, and a direction of the vortex generator can be varied with a position in the longitudinal direction.

[0020] The beginning of the swirl element borders the root section. Accordingly, the swirl element extends into an area near the rotor blade root. In this area, the velocity component due to rotor rotation is lowest. Particularly preferably, the beginning of the swirl element is located at a section of the rotor blade that has an aerodynamic profile. An aerodynamic profile is defined as a profile capable of generating lift.

[0021] In one embodiment, the outer length is given a negative sign if the end of the swirling element is located closer to the root section in the longitudinal direction than the separation point. The ratio of outer length to total length is preferably negative. In other words, the swirling element in this preferred embodiment extends only in the inner region of the blade. This can be achieved by extending the separation point far outward and / or by dimensioning and arranging the swirling element accordingly.

[0022] In one embodiment, the outer blade section has an additional separation point. The rotor blade is thus not limited to a two-part division; in any case, the relevant separation point for determining the length of the swirl element is the first separation point, viewed from the blade tip.

[0023] The rotor diameter is at least 170 m. The arrangement and design of the swirling element according to the invention is particularly advantageous for rotors with a correspondingly large design.

[0024] According to a second aspect, the object is achieved by a wind turbine with a rotor according to the invention.

[0025] According to a third aspect, the problem is further solved by a wind farm with several wind turbines according to the second aspect.

[0026] According to a fourth aspect, the object is further achieved by a method for optimizing a wind turbine according to claim 9. The wind turbine has an aerodynamic rotor with at least one rotor blade, wherein the rotor blade is divided at a separation point into an inner blade section and an outer blade section, wherein the inner blade section extends from a root section for mounting the rotor blade on a rotor hub of the wind turbine to the separation point and the outer blade section adjoins the separation point up to a rotor blade tip, wherein a longitudinal direction of the rotor blade is defined from the root section to the blade tip.The method comprises the following steps: providing and mounting at least one swirling element which has an extension in the longitudinal direction of the rotor blade, wherein a distance between a start facing the root section and an end of the swirling element facing the rotor blade tip in the longitudinal direction is referred to as the total length and wherein a distance between the separation point and the outer end of the swirling element is referred to as the outer length, wherein the provision and mounting of the swirling element takes place in such a way that a ratio of outer length to total length is less than 0.25, preferably less than 0.2 and particularly preferably less than 0.15.

[0027] The method according to the invention makes it possible to achieve the same advantages as the rotor with rotor blade according to the invention and can be combined in the same way with the embodiments described for the rotor with rotor blade.

[0028] Further advantages and features are described below with reference to the attached drawings. These show: Fig. 1 schematically and exemplarily shows a wind turbine and Fig. 2 schematically and exemplarily shows a rotor blade of a wind turbine.

[0029] The explanation of the invention by way of examples with reference to the figures is essentially schematic, and the elements explained in the respective figure may be exaggerated and other elements simplified for better illustration. For example, Fig. 1 a wind turbine as such is schematic, so that an intended arrangement of turbulence elements is not clearly recognizable.

[0030] Fig. 1 shows a wind turbine 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. During operation, the rotor 106 is set in rotation by the wind, thereby driving a generator in the nacelle 104. The rotor blades 108 are adjustable in their blade angle.

[0031] Fig. 2 shows a schematic view of a single rotor blade 108 with a rotor blade leading edge 120 and a rotor blade trailing edge 122. The figure shows a plan view of a suction side 124 of the rotor blade; the opposite pressure side is not visible in the view.

[0032] The rotor blade 108 has a rotor blade root 114 and a rotor blade tip 116. The length between the rotor blade root 114 and the rotor blade tip 116 is referred to as the rotor blade length R along a longitudinal direction L. The distance between the rotor blade leading edge 120 and the rotor blade trailing edge 122 is referred to as the profile depth T. At the rotor blade root 114, or generally in the area near the rotor blade root 114, the rotor blade 108 has a large profile depth T. At the rotor tip 116, however, the profile depth T is much smaller.

[0033] In the longitudinal direction L of the rotor blade 108, a separation point 130 is provided approximately in a central region. The separation point divides the rotor blade into two sections, an inner blade section 132 and an outer blade section 134. The inner blade section 132 extends from the area of ​​the rotor blade root 114 to the separation point 130, and the outer blade section 134 adjoins the separation point 130 and extends to the rotor blade tip 116. Of course, more than one separation point 130 is also conceivable, in which case the outer blade section 134 is divided into several parts. The rotor blade 108 is joined at the blade separation point 130 before or during assembly at the installation site.

[0034] In the Fig. 2In the schematic plan view of the suction side 124 shown, a swirl element 140 is also arranged. In other embodiments, the swirl element 140 can also be arranged, for example, on the pressure side. The swirl element 140 delays flow separation in the region in which the swirl element 140 is arranged by introducing additional energy into the boundary layer. Various types of swirl elements 140 are known, including active and passive swirl elements.

[0035] The core of the present invention is that the interaction of the separation point 130 and the extension of the swirl element 140 in the longitudinal direction L of the rotor blade 108 has been discovered. A total extension L total denotes the extension of the swirl element 140, starting from the rotor blade root 114 in the longitudinal direction L up to a radially outer end 142. An outer length L outside of the swirl element 140 is referred to as the length in the longitudinal direction L, starting from the blade separation point 130 up to the radially outer end 142 of the swirl element 140. The value of L outside is given a negative sign if the separation point 130 is located further out than the end 142 of the swirl element 140.

[0036] To assess whether the arrangement of the swirling element 140 is advantageous or not, a ratio of the outer length or outer length L outer to the total length L total is calculated. This ratio is considered advantageous if it reaches a value of 0.25 or less. In other words, the blade separation point 130 must be relatively far outward relative to the total length of the swirling element 140.

[0037] The separation point 130 can also be located further outside than the end 142 of the swirling element 140, but it is disadvantageous if the swirling element 140 extends outwards in such a way that the ratio of L outside to L total becomes greater than 0.25.

[0038] It is a finding of the present invention that swirl elements extending further outwards generate excessive resistance, while they no longer have the stall-delaying effect to the extent that an overall efficiency-enhancing result follows.

[0039] Of particular relevance to this ratio is the special geometry and aerodynamics of the separation point 130, which must be taken into account with two-part rotor blades 108. Thus, the special finding of the present invention is that the extension of the turbulence element 140 must be related to the position of the separation point 130. According to the invention, the wind turbine has a rotor diameter D of at least 170 m, since the advantages of the turbulence element 140 and the multiple division of the rotor blades 108 are fully realized, especially with large rotors.

Claims

1. Rotor (106) with at least one rotor blade (108) for a wind turbine (100), wherein, prior to being mounted on the wind turbine (100), the rotor blade (108) is split at a parting point (130) into an inner blade section (132) and an outer blade section (134), wherein the inner blade section (132) extends from a root section (114) for mounting the rotor blade (108) on a rotor hub of the wind turbine (100) to the parting point (130), and the outer blade section (134) follows from the parting point (130) as far as a rotor blade tip (116), wherein a longitudinal direction (L) of the rotor blade (108) is defined from the root section to the blade tip, wherein the rotor blade (108) has at least one swirl element (140), wherein the swirl element (140) has an extent in the longitudinal direction (L) of the rotor blade (108), and is formed from multiple sub-elements, wherein the start and the end of the swirl element are always based on the absolute start and the absolute end, respectively, of all the parts of the swirl element, wherein a distance between a start, facing toward the root section (114), and an end, facing toward the rotor blade tip (116), of the swirl element (140) in the longitudinal direction (L) is referred to as total length (Ltot), and wherein a distance between the parting point (130) and the outer end (142) of the swirl element (140) is referred to as outer length (Louter), wherein a ratio of outer length (Louter) to total length (Ltot) is less than 0.25, preferably less than 0.2, and particularly preferably less than 0.15, wherein the start of the swirl element (140) is adjacent to the root section (114), and a diameter of the rotor (106) is at least 170 m.

2. Rotor (106) as claimed in claim 1, wherein the swirl element (140) has one or more vortex generators, which are arranged in particular on a suction side (124) of the rotor blade (108).

3. Rotor (106) as claimed in claim 2, wherein the vortex generators are formed as fins which are arranged in pairs and which are arranged so as to be perpendicular to the suction side (124).

4. Rotor (106) as claimed in claim 3, wherein the vortex generators have a geometry as a function of position in the longitudinal direction (L) of the rotor blade (108).

5. Rotor (106) as claimed in one of the preceding claims, wherein the outer length (Louter) acquires a negative sign if the end of the swirl element (140), in the longitudinal direction (L), is situated closer to the root section (114) than the parting point (130), wherein the ratio of outer length (Louter) to total length (Ltot) is negative.

6. Rotor (106) as claimed in one of the preceding claims, wherein the outer blade section (134) has a further parting point (130).

7. A wind turbine (100) having a rotor (106) according to one of the preceding claims.

8. A wind farm having multiple wind turbines (100) as claimed in claim 7.

9. A method for optimizing a wind turbine (100), wherein the wind turbine (100) has an aerodynamic rotor (106) having at least one rotor blade (108), wherein the rotor blade (108) is split at a parting point (130) into an inner blade section (132) and an outer blade section (134), wherein the inner blade section (132) extends from a root section (114) for mounting the rotor blade (108) on a rotor hub of the wind turbine (100) to the parting point (130), and the outer blade section (134) follows from the parting point (130) as far as a rotor blade tip (116), wherein a longitudinal direction (L) of the rotor blade (108) is defined from the root section (114) to the rotor blade tip (116), wherein the method comprises the following steps: providing and mounting at least one swirl element (140) which has an extent (Ltot) in the longitudinal direction (L) of the rotor blade (108) and is formed from multiple sub-elements, wherein the start and the end of the swirl element are always based on the absolute start and the absolute end, respectively, of all the parts of the swirl element, wherein a distance between a start, facing toward the root section (114), and an end, facing toward the rotor blade tip (116), of the swirl element (140) in the longitudinal direction (L) is referred to as total length (Ltot), and wherein a distance between the parting point (130) and the outer end of the swirl element (140) is referred to as outer length (Louter), wherein the swirl element (140) is provided and mounted in such a way that a ratio of outer length (Louter) to total length (Ltot) is less than 0.25, preferably less than 0.2, and particularly preferably less than 0.15, wherein the start of the swirl element (140) is adjacent to the root section (114) and a diameter of the rotor (106) is at least 170 m.