Method of forming an edge seal for a rotor blade appendage

Abstract

Method for forming an edge seal for a rotor blade attachment. The invention describes a method for forming an initial edge seal (S1) along a longitudinal edge step (3E) of an attachment component (3) mounted on an outer surface (2) of a rotor blade (1), the method comprising the following steps: - providing an initial edge seal (S1) along a longitudinal edge step (3E) of an attachment component (3) mounted on an outer surface (2) of the rotor blade (1), - removing a top layer (L) of the initial edge seal (S1). The invention further describes a corresponding wind turbine rotor blade.

Description

Technical Field

[0001] The present invention describes a method of forming an edge seal for a rotor blade appendage. In particular, the present invention describes a method for aerodynamic edge finishing of a step on the surface of a wind turbine blade. Background Art

[0002] The aerodynamic performance of wind turbine rotor blades is highly sensitive to surface defects, particularly those located near the leading edge of the rotor blade. This presents a challenge when steps or obstructions are present on the rotor blade surface, such as after the application of leading edge protection (LEP) covers and / or vortex generator (VG) panels, trailing edge (TE) panels, etc. LEP covers are also known as erosion protection covers or LEP shells.

[0003] Sharp steps can exist at the edges of panels or covers attached to rotor blades. Such abrupt height differences can cause the airflow to transition from laminar to turbulent, which will adversely affect the annual energy production (AEP) of the wind turbine and may also cause wind turbine noise.

[0004] For more invasive solutions, products like SGRE Power Polytech Wind tape or other products, steps caused by LEP or other attachments are particularly a problem.

[0005] One method of reducing turbulence generated by steps along the edge of an appendage is to provide an edge seal along the longitudinal edge of an appendage component mounted on the outer surface of a rotor blade. The method comprises the following steps: determining a height at the longitudinal edge of the appendage component; selecting a width of the edge seal to be applied to the surface of the rotor blade, wherein the edge seal width is selected to be at least twenty times the height at the longitudinal edge of the appendage component (i.e., a ratio of rotor blade edge seal width to appendage height of at least 20:1); and forming the edge seal by applying a sealant material at least within a volume defined by the height at the longitudinal edge of the appendage component and the determined blade surface edge seal width.

[0006] Advantageously, such an edge seal reduces the negative impact of steps or other obstructions on the aerodynamic performance of the rotor blade. By significantly reducing or even eliminating the negative impact of the abrupt edge change of the appendage on the aerodynamic performance of the rotor blade, the edge seal of the present invention ensures that the appendage is "AEP-neutral." This seal also enables the implementation of appendages with larger edge thicknesses, such as LEP shells and LEP covers. Generally speaking, edge seals help improve the aerodynamic performance of LEP solutions.

[0007] However, the edge seal has not been optimized to date. Due to shrinkage of the sealing material or manufacturing defects during the formation of the sealing material, a step may still exist between the appendage and the edge seal. Furthermore, depending on the manufacturing method, the sealing material can cause adverse effects, for example by partially loosening the appendage. Summary of the Invention

[0008] It is therefore an object of the present invention to provide a method for optimizing the edge seal between the surface of a rotor blade and an appendage and for improving the aerodynamic performance of the rotor blade.

[0009] The object is achieved by a method for forming an edge seal along a longitudinal edge step of an add-on component mounted on an outer surface of a rotor blade and by a wind turbine rotor blade.

[0010] This invention describes a method for forming edge seals along the longitudinal edges of an attachment component mounted on the outer surface of a rotor blade. This method is used for aerodynamic edge finishing of steps on the surface of a wind turbine blade. The proposed solution can, for example, be based on a soft shell of limited thickness applied to the leading edge, but the general concept is applicable to any type of step on the surface of a wind turbine blade. The method comprises the following steps.

[0011] An initial edge seal is provided along the longitudinal edge step of the attachment component mounted on the outer surface of the rotor blade, the initial edge seal preferably overlapping the attachment component. The initial edge seal can be provided so that it is already present on the rotor blade, but preferably it can be provided by applying a sealant to the rotor blade, forming the edge seal, and hardening or curing the sealant. The term "initial" should be understood to mean that the edge seal has not yet been optimized by the present invention.

[0012] - Removal of the top layer of the initial edge seal. This can be accomplished by a machining step, in particular by grinding, lapping, milling, or cutting. The top layer should be removable in such a way that the resulting edge seal forms a wedge with straight or curved lines, thereby forming a transition from the edge of the appendage to the rotor blade without any steps.

[0013] The proposed invention preferably comprises (or consists of) a sealing step and a grinding step. For example, both sides or either side of a leading edge shell or strip, a protective cover can be subjected to the edge treatment proposed here. Similar other additions placed on the blade, i.e. placed on the leading and / or trailing edge and on the pressure and / or suction side (in which one / more edges are produced) can also be subjected to the edge treatment proposed here. Such additions can include a base plate, on which aerodynamic devices or noise reduction devices are placed. Such devices include vortex generators, slats, flaps and / or spoilers. In any case, the installation of such a device attached to a base plate on a wind turbine blade can also make it possible to subsequently perform an edge treatment on the base plate at least at the edge facing the leading or trailing edge of the blade.

[0014] In the sealing step, a sealant / adhesive is used to form an edge seal on the edge step, preferably with a small overlap. The sealant or equivalent (compared to the material of the edge step and / or the adhesive used to secure the addendum) can be of different nature, but can also have the same composition.

[0015] The sealing range δ is preferably adjusted based on wind tunnel measurements to reduce the aerodynamic impact of the step created by the joint surface. The edge seal range δ depends on the edge step t at the joint point J1 (i.e., the location of the edge step). The ratio of δ to t can vary anywhere between 4:1 (preferably 20:1) and 100:1. In absolute terms, the edge step height is preferably at least 0.25 mm, particularly at least 0.5 mm, and / or the edge seal width is preferably between 5 mm and 150 mm. The edge seal is adjusted to prevent / delay the occurrence of a flow transition from laminar to turbulent flow on the blade surface caused by the edge step. The recommended ratio is greater than that typically used in solutions described in the prior art. The proposed edge seal utilizes a sealant of suitable viscosity to allow the viscous fluid to flow into gaps and surface cracks formed by application and ensure a smooth finish. At the same time, the viscosity of the adhesive drives the step at the joint point J2 (i.e., the point where the edge seal transitions into the rotor blade surface). The step height at the joint point J2 is preferably less than 100 μm. This can be accomplished using an edge seal application process such as that described below.

[0016] Preferably, after the seal has cured, the top layer of the seal is ground away to expose the joint J1. The grinding can be done using any common grinding tool (such as any orbital sander) or even by hand, but is preferably done with the aid of a dedicated edge grinding tool.

[0017] In theory, it is not necessary to have an overlapping edge seal to implement the solution of the present invention. However, in practice, applying the edge seal without overlapping leaves an edge step that may vary in height, depending on the hardness (rigidity) of the add-on component and the pressure applied with the spreading spatula during application and finishing of the edge seal. This leads to uncertainty as to how high the resulting edge step is and how much effort is required to remove it (e.g. grind it away). Likewise, depending on the add-on component, it may be difficult or indeed undesirable to grind away a large part of the surface of the add-on component. Having an overlapping seal ensures that only the top layer of sealing material needs to be removed until the overlap (almost) disappears, resulting in an easy and high-quality way to ensure optimal finishing and avoid significant grinding into the add-on component itself. Therefore, the sealant preferably overlaps the edge step of the add-on.

[0018] The solution can be applied to the blade before mounting it on a wind turbine or applied as a retrofit solution to a blade already mounted to the hub of an installed wind turbine.

[0019] A particular feature of the present invention is the application of a grinding process, in particular a combination of sealing and grinding processes, to produce an almost smooth surface finish. The combination of sealing and grinding is a preferred innovation of the present invention. This combination helps to reduce the step height at J1 (the location of the edge step) to preferably less than 100 μm. Although the grinding process is laborious, the inventors have found that it has important advantages in terms of the integrity of the edge seal and the quality of the transition between the appendage and the rotor blade surface. The present invention can make the LEP solution AEP neutral, which will provide a competitive advantage for the product in the market. By reducing the impact of the AEP of the LEP solution, this also helps to reduce the AEP risk of new and existing turbines. The solution can be applied both in the factory and in the field, providing similar results regardless of the application environment. In principle, the present invention can be used to avoid surface steps caused by any appendage / sensor on the blade surface, thereby maintaining the aerodynamic performance of the wind turbine.

[0020] A wind turbine rotor blade according to the invention comprises at least one add-on component mounted to the outer surface of the rotor blade and an edge seal formed using the method according to the invention.

[0021] Particularly advantageous embodiments and features of the invention are given by the preferred embodiments, as revealed in the following description. Features of different embodiment categories can be combined as appropriate to give further embodiments not described here.

[0022] According to the preferred method, the following steps are included:

[0023] A width of the edge seal overlap in an overlap region adjacent to a longitudinal edge step of the add-on component is determined, wherein the overlap width is determined based on a height at the longitudinal edge step of the add-on component.

[0024] According to a preferred method, providing an initial edge seal comprises the step of sealing a longitudinal edge step of an appendage component mounted on the outer surface of the rotor blade, wherein a liquid sealant is applied to the surface of the rotor blade at the edge, preferably overlapping the appendage component. Preferably, the liquid sealant is spread using a preliminary shaping tool and thereafter smoothed to its final shape by drawing a finishing tool over the spread sealant.

[0025] According to a preferred method, providing an initial edge seal comprises the following steps:

[0026] - using a thin and smooth masking tape, preferably with a thickness of less than 0.2 mm, to define the application area on the rotor blade surface and the attachment parts to be covered with the sealant compound,

[0027] - distributing the sealant over the application area, in particular by bead or spray application, wherein the seal is preferably applied in a meandering line overlapping the transition between the appendage and the blade surface,

[0028] - the distribution of the sealant is preferably carried out by using a flexible toothed spatula,

[0029] - (optionally) smoothing the adhesive using a preferably flexible tool that is moved in the longitudinal direction of the blade, wherein the tool is preferably designed to follow the contour of the blade,

[0030] - remove the masking tape,

[0031] - Smoothing the sealant transition step using a flexible tool, preferably with a Shore A hardness between 40 and 60.

[0032] The method preferably comprises, for example, using the following tools:

[0033] A toothed spatula, preferably of flexible material, is used to level the sealant or viscous sealant material after it has been dispensed onto the sealed application area on the add-on.

[0034] The second spatula, for example of a flexible material such as silicone, is characterized by a Shore A hardness of 40-60, having a cross-sectional profile suitable for application and a low-energy surface (surface free energy) that prevents adhesion of the sealing material. During use, the angle between the soft spatula and the blade surface at the point of contact with the blade surface is smaller than in the case of a hard spatula.

[0035] Regardless of whether the sealant material is formed to overlap the attachment edge or step, the sealant material can be applied using a tool set comprising multiple spatulas with different properties. In a preferred embodiment of the present invention, the step of forming the edge seal comprises depositing the sealant material onto the surface of the rotor blade at least along the longitudinal edge of the attachment component. A preliminary spatula is then used to spread the sealant material in the area defined by the longitudinal edge of the attachment component and the selected edge seal width. The preliminary tool preferably has a flexibility and shape that facilitates the initial spreading of the sealant.

[0036] In a subsequent step, a finishing spatula is used to finish the shape of the sealant spread by the preliminary tool.Preferably, the finishing tool has a lower hardness than the preliminary tool.

[0037] The method of the present invention can preferably include the step of defining the area of ​​the intended edge seal using a smooth, thin masking tape. A tape can extend along the outer edge of the intended edge seal at a distance outwards from the edge step. This distance is at least 20 times the height of the edge step. The thickness of the tape is as small as possible, preferably at most 0.2 mm. The other boundaries of the edge seal can be defined by the edge step. Alternatively, if an overlap is formed on the edge step, a second tape can be applied to the surface of the appendage, parallel to the longitudinal edge of the appendage. The sealant is then applied within these boundaries. The sealant can initially be roughly deposited on the rotor blade (and appendage), for example in the form of beads from a dispenser nozzle or by spraying. The roughly applied sealant is then spread using a preliminary shaping tool, for example a flexible toothed spatula.

[0038] Therefore, according to a preferred method, the distribution of the sealant is achieved by using a toothed spatula, preferably a toothed spatula of flexible material, which is used to level the sealant after it has been distributed to the application area, preferably wherein the teeth of the toothed spatula have a distance between 1 and 2 mm and / or a height between 0.2 and 5 mm.

[0039] Spreading can be accomplished by guiding a toothed spatula in the longitudinal direction of the rotor blade surface between the edge seal boundaries. After completing this preliminary step, the one or more strips are removed. By drawing a softer, flexible spatula over the spread sealant, the still liquid sealant is then smoothed into its final shape. This finishing or smoothing step using a second tool serves to further reduce the height of the "wedge" of the edge seal between the edge step and the outer boundary of the edge seal. The second flexible spatula is preferably made of a material such as silicone to ensure a relatively low Shore hardness, for example 50±10.

[0040] Therefore, according to a preferred method, the flexible tool is a second spatula having a Shore A hardness of between 30 and 70, in particular between 40 and 60, in particular between 48 and 52. A preferred Shore A hardness is greater than 30, in particular greater than 40, in particular greater than 45 and / or a preferred Shore A hardness is less than 70, in particular less than 60, in particular less than 55.

[0041] The application process is designed to minimize and ideally prevent AEP loss due to steps between the blade surface and the attached and bonded cover / plate.

[0042] According to a preferred method, the removal of the top layer of the initial edge seal is accomplished by machining, preferably by grinding and / or polishing and / or cutting and / or milling. Preferably, the resulting edge seal is flush with the edge step, i.e., there is no step between the appendage and the edge seal. This can be achieved by the removal step.

[0043] According to a preferred method, the angle between the surface of the resulting edge seal and the surface of the rotor blade is smaller at the point of the edge step than at the point where the edge seal transitions onto the rotor blade surface. This means that the surface of the edge seal is steeper at the portion of the edge seal opposite the edge step than at the surface of the rotor blade. It can be said that the slope of the edge seal in the direction pointing away from the edge step is constant or increases with increasing distance from the edge step. While the resulting edge seal can have a concave surface, it is preferred that the resulting edge seal has the shape of a wedge with a convex surface and / or a kink in its surface, wherein a surface with a flat area adjacent to the edge step is preferred. It is particularly preferred that the edge seal has the properties of a cubic curve and that the surface of the edge seal is convex near the edge step (higher surface) to the attachment component. Alternatively or additionally, it is preferred that the edge seal has a concave surface area near the end of the seal facing the rotor blade surface (lower surface). Due to the special shape of the resulting edge seal, this embodiment is easy to produce without the risk of damaging the surface of the rotor blade during removal of the top layer.

[0044] A sealant (sealant) or adhesive is used to form an edge seal along one or more edges (edge ​​steps) of the appendage, with or without overlap, as explained below. The edge seal geometry is adjusted and optimized to reduce the aerodynamic impact of the step created by the joining surface, i.e., the leading edge solution. Therefore, according to a preferred method, the seal width is preferably adjusted to reduce the aerodynamic impact of the step created by the joining surface based on wind tunnel measurements.

[0045] The terms "sealant," "edge sealant," and "sealant" may be used to refer to such an adhesive. Preferably, the adhesive used to secure the attachment comprises the same material as the edge sealant, or vice versa. The sealant can be an adhesive, however, this is not necessary in every case. In this application, the term "sealant" includes the term "adhesive."

[0046] Preferably, the seal is formed using a special liquid sealant (particularly an adhesive material) which solidifies after a certain time of application and which has special rheological properties when liquid, in particular adhesive viscosity, which provides a good balance between sag resistance and fluidity. The rheological properties of the sealant and the special adhesive viscosity are preferably tailored to the specific geometry and position of the seal. On the one hand, the viscosity must be low enough to allow the sealant / adhesive to spread easily and eliminate any streaks that may occur during spreading. On the other hand, however, the yield point (sag resistance) of the sealant must be high enough to avoid loss of sealant due to gravity, which would adversely affect the profile of the seal produced during the application process.

[0047] Preferably, the set sealant is (highly) flexible, abrasion resistant and preferably bonds well to the surface to which it is applied and also has good resistance to UV exposure.

[0048] In general, any liquid sealant / adhesive material that solidifies after application by a physical process, a chemical reaction, or a combination of both is suitable for the purposes of the present invention. Reactive two-part sealants are preferred due to their faster curing response and the resulting faster process. Preferably, physically hardening sealants, such as hot melt sealants that harden upon cooling and / or sealants that cure by a chemical reaction can be used. From the group of chemically curing sealants, two-part sealants are preferred due to their faster curing response and the resulting faster process.

[0049] It is preferred to use a sealant with a setting speed (open time) that, on the one hand, allows sufficient time for the application process, i.e., dispensing, leveling, and generating the profile according to the invention. On the other hand, to shorten the process time, further processing should be carried out as quickly as possible. Chemically crosslinking two-component adhesives offer advantages in this regard, particularly because their curing can be accelerated after the profile according to the invention has been formed, for example by moderate heating with the aid of IR emitters, thereby allowing further reductions in process time.

[0050] Exemplary materials include epoxies, polyurethanes, polyureas, silicones, silane-modified polymers (SMPs), methyl methacrylate (MMA), and mixed solutions, selected based on desired properties in both the liquid and cured states, particularly sag resistance and flowability, as described above. For example, the sealant material can be selected to have a specific adhesive viscosity that provides a good balance between sag resistance and flowability, as well as an advantageously high degree of flexibility in its cured state. Using such a material, the integrity of the edge seal formed along the longitudinal edge of the LEP will not be affected by repeated torsional bending of the rotor blade.

[0051] Preferably a two-component sealing material is used, which is mixed just before applying the sealing material to the mould surface of the blade, wherein preferably the viscosity of the two components is between 40.000-110.000 mPas for one component and between 100.000-380.000 mPas for the other component.

[0052] The sealant preferably has a surface tension less than the surface free energy of the surface to which it is applied, in order to allow sufficient wetting of such surfaces as a prerequisite for forming a bond. Increasing the surface free energy by appropriate methods, such as, but not limited to, cleaning, grinding, application of primers or adhesion promoters, and activation methods (such as, but not limited to, plasma activation, corona activation, flame activation, VUV (vacuum ultraviolet) activation) is explicitly part of the present invention. In addition to the aforementioned ability to wet the surface, good adhesion of the adhesive to the surface of the blade and the corresponding attachments is crucial to meeting the demanding service life requirements, especially under the harsh conditions of offshore installations.

[0053] In addition to good adhesion, the mechanical properties of the sealant are also important. High abrasion resistance to withstand aggressive rainwater conditions and sufficient fatigue strength to withstand the vibrations of the blade during operation are both required. Therefore, a sealant with sufficient resistance to peel forces (specifically greater than 2 N / mm) occurring on the corresponding surface throughout the blade's service life is preferred. Long-term resistance is tested using the procedure described in ISO 20340.

[0054] Due to the wide range of possible applications of the seal that is the subject of the present invention, the sealant is preferably tailored to the respective application with regard to the materials involved, the dimensions of the respective appendages and their position on the blade.

[0055] The sealant preferably has a tensile strength greater than 4 MPa and / or less than 8 MPa, particularly preferably 5 MPa±<0.5 MPa, in particular 5 MPa (according to DIN EN ISO 527). After 1000 h at 80° C., the tensile strength may be approximately 9 MPa or greater.

[0056] Alternatively or additionally, the elongation at break (according to DIN EN ISO 527) is greater than 80% and / or less than 130%, particularly preferably 90%±5%, in particular 90%. After 1000 h at 80°C, the elongation at break can reach values ​​of 100% or more.

[0057] Alternatively or additionally, the Young's modulus (according to DIN EN ISO 527) is greater than 8 MPa and / or less than 150 MPa, particularly preferably a value of 11 MPa±<2 MPa, in particular 11 MPa. After 1000 h at 80° C., the Young's modulus may have a value of 11 MPa or more.

[0058] Exposure to 80°C for 1000 hours is an accelerated aging test designed to simulate the high blade surface temperatures caused by sunlight during the turbine's lifetime. The maximum surface temperature under actual offshore conditions is estimated to be 60°C. Preferably, the sealant is selected so that the Young's modulus remains constant and / or the tensile strength and / or elongation at break increase, with the combination of all three requirements being highly beneficial for the sealant's long-term durability.

[0059] Thus, according to the preferred method, the sealant is fluid enough to flow into gaps and surface cracks formed during application of the add-on and ensure a smooth finish.

[0060] Preferably the sealant provides one or more of the following properties. The sealant has:

[0061] - a surface tension that is less than the surface free energy of the blade surface, and / or

[0062] - possess sufficient resistance to the peeling forces occurring on the corresponding surface throughout the service life of the blade (in particular greater than 2 N / mm), and / or

[0063] - a tensile strength greater than 4 MPa and / or less than 8 MPa, and / or

[0064] - an elongation at break greater than 80% and / or less than 130%, and / or

[0065] - A Young's modulus greater than 8 MPa and / or less than 150 MPa.

[0066] According to a preferred method, a filler is first applied along the longitudinal appendage edges before dispensing the sealant on the application area, wherein the filler is preferably a fast setting adhesive and / or a high tack adhesive and the sealant is applied over the cured or hardened filler.

[0067] According to a preferred method, the sealant comprises the same material as the adhesive used to bond the appendage to the surface of the rotor blade.

[0068] The sealing material preferably has good sandability so that a smooth, aerodynamically advantageous surface can be produced. Therefore, the maximum size of solid particles (e.g., filler particles, filler particle agglomerates, gel particles) in the sealing material in its liquid state and in the hardened or crosslinked state is preferably limited to a maximum of 200 μm, preferably to a maximum of 100 μm, particularly preferably to a maximum of 60 μm or even to a maximum of 50 μm, in particular as determined in accordance with DIN EN 21 524 or ISO 1524.

[0069] The present invention's method for aerodynamically optimizing the edge of an appendage is not limited to aerodynamic devices such as LEP covers. The appendage can be a plate containing a sensor, such as a flexible plate, which preferably conforms to the curved surface of the rotor blade. Fastening such a sensor plate to the rotor blade surface benefits from the present invention's sealing concept, thereby achieving improvements in AEP. Such a plate can be attached to the rotor blade surface at any location between the leading and trailing edges of the rotor blade and can be mounted on either the suction or pressure side of the rotor blade.

[0070] Preferably, edge seals are formed along the longitudinal edges of such a plate using aspects of the present invention. In this way, neither the upwind or windward edge (i.e., the edge closer to the leading edge of the rotor blade) nor the downwind edge (the edge closer to the trailing edge of the rotor blade) of such a plate will adversely affect the laminar airflow over the rotor blade surface. Thus, the present invention is not limited to shells or aerodynamic devices, but also encompasses any type of sensor mounted on a substrate (e.g., a flexible board) on, for example, a blade surface. Thus, improvements in AEP can also be applied to plates such as sensor plates and reduce the noise generated when such plates are mounted on a blade surface.

[0071] As an example, the edge step height (shell height) of the appendage can be any value between 0.25 mm and 2 mm, in particular between 0.5 mm and 1.5 mm or between 0.7 and 1 mm. The edge step height of the appendage is the sum of the thickness at the outer edge of the appendage plus the thickness of any adhesive or bonding layer used to attach the appendage to the rotor blade.

[0072] The preferred minimum width of the edge seal is 5 mm, preferably 20 mm, and particularly preferably 40 mm. The preferred maximum width of the edge seal is 150 mm, preferably 100 mm, and particularly preferably 60 mm. It is particularly preferred that the width is selected to correspond to the height of the corresponding edge step. For example, for an edge step height of 0.7 mm, the minimum width of the edge seal can be 14 mm (minimum value). For example, for an edge step height of 1.0 mm, the minimum width of the edge seal can be 20 mm (minimum value).

[0073] The ratio of the edge seal width to the step height can vary from 4:1 or 20:1 to 100:1. For an exemplary edge step height range of 0.5 mm to 1.5 mm, the edge seal will be at least 10 mm wide and up to 150 mm wide. It has been observed (in wind tunnel testing) that such relatively wide edge seals for rotor blade appendage components result in improved aerodynamic behavior. Therefore, according to a preferred approach, the ratio of the width and / or overlap width to the height at the longitudinal edge step is greater than 4:1 (or greater than 20:1) and / or less than 100:1.

[0074] A further preferred embodiment of the present invention is based on the recognition that the laminar nature of the airflow over the rotor blade surface can be maintained by forming an edge seal on the longitudinal edges of the appendage, i.e., by having an edge seal that "overlaps" with the outer surface of both the appendage and the rotor blade. Therefore, in a further preferred embodiment of the present invention, the method includes the step of determining the overlap width of the edge seal in the region of the appendage surface immediately adjacent to its longitudinal edge. The term "overlap width" should be understood to mean the width of the portion of the edge seal that extends onto the surface of the appendage. The overlap width is determined based on the appendage height.

[0075] The step of forming the edge seal then preferably includes applying the sealant material to the overlapping region of the appendage components. The overlapping of the edge seal can advantageously form a smooth layer on the edge of the appendage. Thus, according to a preferred method, the sealant is formed to overlap the edge of the appendage.

[0076] In the method of the invention, the edge seal width (and preferably also the overlap width) of the edge seal is preferably "tuned" for the particular appendage in order to prevent or at least significantly delay the flow transition from laminar to turbulent flow on the surface of the blade behind the edge of the appendage (i.e. on the downwind side of the appendage). Preferably, the extent (i.e. the width) of the edge seal and the extent of any overlap will be controlled by the height of the edge step at the longitudinal edge of the appendage.

[0077] The ratio of overlap width to step height can vary from 10:1 to 50:1. For an example edge step height of 0.5 mm, the overlap width would be 5 mm to 25 mm wide. For an edge step height of 1.5 mm, the edge seal width would be 15 mm to 75 mm wide. The recommended ratios described above are significantly greater than those typically used in solutions known in the prior art. The maximum possible width or range of the edge seal may also be determined or limited by the curvature of the rotor blade.

[0078] The edge sealing proposed herein can be achieved by using a sealant (sealant) or adhesive that has a sufficiently low viscosity so as to be sufficiently fluid to flow into any gaps and surface cracks formed during the application of the additive and to ensure a smooth finish. However, since the viscosity of the adhesive will determine the minimum height of the edge seal along its outer boundary, the sealant material is preferably also selected so as to ensure a smooth transition to the blade surface.

[0079] At the same time, the viscosity of the adhesive drives the step in the simple edge seal and the overlapping edge seal. The overlapping edge seal can eliminate the step by forming a smooth layer on the shell edge. The edge seal material is selected to ensure a smooth transition to the blade surface.

[0080] For large edge steps, filler material can be used to reinforce the edge seal. In this preferred embodiment of the invention, filler material is applied along the edge of the appendage to initially reduce the edge step, i.e. a compact wedge or bevel extending outwardly from the edge of the appendage. Sealant material is then applied over the filler. The filler material may have a greater viscosity than the sealant material to facilitate easy construction of the filler or substrate to a finite thickness. The extent (width) of the filler is preferably less than the width of the edge seal width to ensure that there is a uniform layer of edge seal on the surface, thereby enabling a smooth edge to be achieved at the end of the edge seal, i.e. a smooth transition to the rotor blade surface. The volume occupied by the filler material may be less than half the expected volume of the edge seal.

[0081] At a preferred wind turbine rotor blade, the add-on component comprises any one of a leading edge protection cover, a trailing edge panel, a vortex generator panel, a slat, a plate or a sensor panel.Other possibilities are listed above.

[0082] In the case of a preferred wind turbine rotor blade, the thickness of the add-on component at its longitudinal edges is in the range of 0.2 mm to 5.0 mm, preferably 0.25 or 0.5 mm to 1.5 mm.

[0083] Advantageously, the arrangement and method of the present invention reduces the aerodynamic impact of steps or other obstructions on the surface of the blade (e.g., due to LEP application) by reducing / avoiding edge steps. This solution also enables the use of LEP shells or LEP covers with greater edge thickness. This presents a significant opportunity for shell cost reduction, as the requirement for thin edges is a cost driver in the manufacture of these shells. Avoiding thinner shell edges also reduces the risk of wrinkling during application, which further contributes to reducing non-compliance costs and improving aerodynamic performance.

[0084] The edge sealing method described above helps improve the aerodynamic performance of the LEP solution. Edge sealing indirectly enables the use of shells with thicker edges, which helps reduce shell cost and compliance costs.

[0085] An overlapping finish is created using appropriate material to smooth the transition to the blade surface.

[0086] The advantage of the present invention is that the shrinkage of the sealant during curing is compensated by post-processing and a smooth transition between the appendage and the sealant can be achieved. It should be noted that overlapping itself is disadvantageous because it can cause disturbances in the laminar air flow if it separates or becomes loose from the appendage surface.

[0087] The present invention offers the following advantages: by reducing / avoiding edge steps, it reduces the aerodynamic impact of steps on the surface of the blade (e.g., caused by the application of LEP or any other aerodynamic device or noise reduction device attached to the surface of the blade). This solution also enables the use of LEP shells with greater edge thickness. This presents a significant opportunity for shell cost reduction, as the requirement for thin edges is a cost driver in the manufacture of these shells. Avoiding thinner shell edges also reduces the risk of wrinkling during application, which further contributes to reducing non-compliance costs and improving aerodynamic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It should be understood, however, that the drawings are designed for illustration purposes only and not as a definition of the limits of the present invention.

[0089] Figure 1 An embodiment of an edge seal applied to a longitudinal edge of a rotor blade appendage is shown;

[0090] Figure 2 Overlapping edge seals are shown;

[0091] Figure 3 An example of the shaping used for the edge seal of the present invention is shown;

[0092] Figure 4 A method for providing overlapping edge seals is shown;

[0093] Figure 5 A preferred method according to the present invention is shown;

[0094] In the drawings, like reference numerals refer to like objects throughout. Objects in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0095] Figure 1 An edge seal S is shown applied to an appendage 3, which can be any of a LEP cover, a shell, a TE cover, a VG panel, a TE panel, a sensor panel, etc. The edge seal can be the result of a method according to the invention. The appendage 3 is attached to the outer surface 2 of the rotor blade 1 by an adhesive bonding layer 4. For the purposes of discussion, the adhesive layer 4 can be considered as an element of the appendage 3. The height t of the appendage 3 at its edge step 3E is the sum of the thickness of the appendage 3 and the thickness of the adhesive layer 4. It can be assumed that the appendage edge step 3E extends in the longitudinal direction of the rotor blade 1. It can be assumed that the edge seal 3 is an idealized edge seal S, since there is no step between the edge step 3E of the appendage 3 and the edge seal S. The dotted line marks the edge step at the point (junction) J1. It can be seen that the transition between the appendage and the edge seal S should be smooth.

[0096] The edge seal S begins at a first point J1 at the attachment edge step 3E and extends to a second point J2, whereby the height of the edge seal S gradually decreases from a maximum value at point J1 to a minimum value at point J2. The ratio δ:t is preferably at least 20:1. In this case, the volume of the edge seal S is the cross-sectional area of ​​the edge seal S (i.e., (t·δ) / 2) multiplied by the length of the seal S (e.g., the length of the longitudinal edge step 3E of the attachment 3).

[0097] Figure 2 A further embodiment of the edge seal of the present invention is shown. Here, an initial edge seal S1 is applied to a longitudinal edge step 3E of an appendage 3, which in this case is an LEP cap mounted around the leading edge of a rotor blade 1. In this exemplary embodiment, the initial edge seal S1 overlaps the longitudinal edge step 3E of the appendage 3, i.e. the initial edge seal S1 starts at point J0 and extends to point J2. The total width δ1 of the initial edge seal S1 is therefore the overlap S1 extending from point J0 to point J1. ovThe width h of the overlap and the remaining edge seal width δ extending from point J1 to point J2. In this embodiment, the height t1 of the initial edge seal S1 gradually increases from a minimum value at point J0 to a maximum value at point J1 and gradually decreases from a maximum value at point J1 to a minimum value at point J2. Depending on the overlap width h and / or the edge seal width δ between points J1 and J2, the height t1 of the initial edge seal S1 at its maximum value can exceed the height of the appendage edge step 3E by up to 2.0 mm. This height t1 is based on the controlled layer thickness of the sealant or adhesive applied using a tool (such as a spatula). In principle, it does not matter how much the height t1 of the initial edge seal S1 exceeds the height of the edge step because the top layer of edge seal will be removed.

[0098] In this case, the edge seal S extends over a filler material F (also referred to herein as filler F) that is first applied along the longitudinal appendage edge 3E. The filler F can be a fast-setting adhesive and / or a high-viscosity adhesive. The filler F can be applied to form a wedge having a straight side that is shorter than the height of the appendage 3. In a subsequent step, a sealant material is applied to the cured or hardened filler F. Therefore, for large edge steps, the filler F can be used to initially reduce the edge step and the edge sealant can be applied subsequently. The filler material F can have a greater viscosity than the material of the edge seal S so that the bottom layer can be easily constructed into a limited thickness. The range of the filler F will be less than δ in order to ensure that there is a consistent layer of edge sealant on the surface to achieve a smooth edge at the junction J2.

[0099] Figure 3 A further embodiment of the edge seal S of the present invention is shown. First, an initial edge seal S1 has been applied, e.g. similar to Figure 2 In the sealing step, a sealant / adhesive is used to form an initial edge seal S1 with a small overlap on the edge step 3E of the appendage 3. The sealant or equivalent may be of different nature, but may also have the same composition.

[0100] The width δ (or δ1) of the initial edge seal S1 is preferably adjusted based on wind tunnel measurements to reduce the aerodynamic impact of the step created by the joint surface. Preferably, the width δ depends on the height t of the edge step 3E at the joint point J1. The ratio of δ to t can be varied anywhere between 20:1 and 100:1.

[0101] When creating the initial edge seal S1, sealant is applied to the blade 1 at the edge step 3E. It should have suitable viscosity to allow the sealant's viscous fluidity to flow into gaps and surface cracks. Simultaneously, the adhesive's viscosity drives the step at the junction J2. The step height at the junction J2 is preferably less than 100 μm. This can be achieved using an application process in which the edge seal is formed using a resilient spatula.

[0102] According to the present invention, the top layer L of the initial edge seal S1 (the component being inspected) has been removed (or must be removed) so that the remaining edge seal S is optimized. This can be achieved by grinding away the top layer L of the initial edge seal S1 after the sealant has cured to expose the joint J1. The grinding can be done using any common grinding tool such as a random orbital sander or even by hand, but is preferably done with the aid of a dedicated edge grinding tool. Alternatively, the top layer L can be ground, sanded or cut away.

[0103] There is (substantially) no step between the edge step 3E of the appendage 3 and the remaining edge seal S. Thus, the initial edge seal S1 is adjusted to an optimized edge seal S in order to prevent a flow transition from laminar to turbulent flow on the surface of the blade.

[0104] Figure 4 The appendage 3 is shown attached to the surface 2 of the rotor blade and preferably forms an initial edge seal S1. The appendage 3 can be attached using an adhesive 4, as explained above (adhesive not shown here). A liquid sealant LS is applied to the surface 2 of the blade 1 in the region of the edge step 3E of the appendage 3.

[0105] Before applying the sealant LS, the area of ​​the intended edge seal can be defined by using a smooth, thin masking tape (not shown). A tape can extend along the outer edge of the intended initial edge seal S1 at a distance outwards from the edge step 3E. This distance is at least 4 times, preferably at least 20 times, the height of the edge step. The thickness of the tape is as small as possible, preferably at most 0.2 mm. The other boundaries of the initial edge seal S1 can be defined by the edge step 3E. Alternatively, if an overlap 3E is formed on the edge step, a second tape can be applied to the surface of the appendage 3, parallel to the longitudinal edge of the appendage 3. The sealant LS is then applied within these boundaries. The sealant LS can initially be roughly deposited on the surface 2 of the rotor blade 1 and the appendage 3, for example in the form of beads from a dispenser nozzle or by spraying.

[0106] The roughly applied sealant LS is then spread using a preliminary shaping tool, for example a flexible toothed spatula 5. This can be done by guiding the toothed spatula 5 in the longitudinal direction of the rotor blade surface 2 between the edge seal boundaries.

[0107] After completing this preliminary step, the one or more strips are removed. The still liquid sealant LS is then smoothed into its final shape by drawing a relatively soft finishing tool (e.g., a flexible spatula 6) over the spread sealant LS. This finishing or smoothing step using a second tool serves to further reduce the height of the "wedge" of the initial edge seal S1 between the edge step 3E and the outer edge of the edge seal. The second flexible spatula 6 is preferably made of a material such as silicone to ensure a relatively low Shore hardness, e.g., 50±10.

[0108] Figure 5 Shown after curing Figure 4 The initial edge seal S1 is manufactured in the process of grinding the hardened sealing material by removing the top layer L (see Figure 3 ) to process the initial edge seal S1. The result is Figure 1 The optimized edge seal S shown in .

[0109] Although the present invention has been described in the form of preferred embodiments and variations thereof, it will be appreciated that numerous additional modifications and variations can be made thereto without departing from the scope of the invention. For the sake of clarity, it will be appreciated that "a" or "an" as used throughout this application does not exclude a plurality, and "comprising" does not exclude other steps or elements.

Claims

1. A method for forming an edge seal (S) along a longitudinal edge step (3E) of an appendage component (3) mounted on an outer surface (2) of a rotor blade (1), the method comprising the following steps: - providing an initial edge seal (S1) along a longitudinal edge step (3E) of an appendage part (3) mounted on an outer surface (2) of a rotor blade (1) by applying a liquid sealant (LS) and hardening or curing said liquid sealant (LS), wherein said initial edge seal (S1) overlaps said appendage part (3), - removing the top layer (L) of the initial edge seal (S1) by machining so that the resulting edge seal (S) is flush with the longitudinal edge step (3E) and the resulting edge seal (S) forms a wedge with a curve forming the transition from the edge of the appendage part (3) to the transition to the rotor blade (1) without any step, in, Providing the initial edge seal (S1) comprises the following steps: - depositing said liquid sealant on the application area, - Use a first flexible toothed spatula (5) to spread the liquid sealant, - smoothing the liquid sealant into the final shape of the initial edge seal (S1) using a second flexible spatula (6) having a lower hardness than the first flexible toothed spatula (5), the second flexible spatula (6) having a low energy surface that prevents adhesion of the sealing material.

2. Method according to claim 1, wherein providing the initial edge seal (S1) comprises the step of sealing a longitudinal edge step (3E) of an appendage component (3) mounted on the outer surface (2) of the rotor blade (1), wherein the liquid sealant (LS) is applied overlapping the appendage component (3). 3 . The method of claim 2 , wherein the width (δ) of the seal is adjusted to reduce the aerodynamic impact of the step due to the joining surfaces based on wind tunnel measurements.

4. The method according to claim 1, comprising the steps of: Determine an edge seal overlap (S) in an overlap region adjacent to the longitudinal edge step (3E) of the appendage component (3) ov ), wherein the edge seal overlap (S) is determined based on the height (t) at the longitudinal edge step (3E) of the appendage part (3). ov )’s width (h).

5. The method according to claim 4, wherein the width of the seal (δ) and / or the edge seal overlap (S ov ) to the height (t) at the longitudinal edge step (3E) is greater than 4:

1. The method according to claim 5 , wherein the ratio is greater than 20:1 and / or less than 100:

1.

7. The method according to any one of claims 1 to 6, wherein providing the initial edge seal (S1) further comprises the following steps: - prior to depositing the liquid sealant, defining the application areas on the outer surface of the rotor blade and the appendage components to be covered by the liquid sealant using a thin and smooth masking tape, - After spreading the liquid sealant and before smoothing the liquid sealant, removing the masking tape.

8. The method according to claim 7, wherein: The masking tape has a thickness of less than 0.2 mm.

9. The method of claim 7, wherein the liquid sealant is deposited by bead or spray application.

10. The method of claim 9, wherein the liquid sealant is applied in a serpentine line that overlaps a transition between the appendage component and the outer surface of the rotor blade.

11. The method according to claim 7, wherein the second flexible spatula (6) is designed to follow the contour of the rotor blade.

12. The method according to claim 7, wherein the second flexible spatula (6) has a Shore A hardness between 40 and 60.

13. The method according to any one of claims 1 to 6, wherein the machining is grinding and / or sanding and / or cutting and / or milling.

14. Method according to any one of claims 1 to 6, wherein the angle between the surface of the resulting edge seal (S) and the outer surface (2) of the rotor blade (1) is smaller at the point (J1) of the longitudinal edge step (3E) than at the point (J2) where the edge seal transitions into the outer surface of the rotor blade.

15. The method according to claim 14, wherein the resulting edge seal (S) has the shape of a wedge with a convex surface or a kink in its surface. 16 . The method according to claim 1 , wherein the liquid sealant (LS) has a maximum size of solid particles in the sealing material in its liquid and hardened or crosslinked state limited to a maximum of 200 μm.

17. The method according to claim 16, wherein the solid particles are filler particles, filler particle agglomerates or gel particles.

18. The method according to claim 16, wherein the maximum size of the solid particles is limited to a maximum of 60 μm.

19. Method according to any one of claims 1 to 6, wherein before distributing the liquid sealant (LS) on the application area, a filler (F) is first applied along the longitudinal edge step (3E), wherein the liquid sealant (LS) is applied on the cured or hardened filler (F).

20. The method according to claim 19, wherein the filler (F) is a quick-setting adhesive and / or a high-viscosity adhesive.

21. Method according to any one of claims 1 to 6, wherein the liquid sealant (LS) comprises the same material as the adhesive (4) used for fixing the add-on component (3) to the outer surface (2) of the rotor blade.

22. A wind turbine rotor blade (1) comprising at least one add-on component (3) mounted to an outer surface (2) of the rotor blade (1) and an edge seal (S) formed by the method according to any one of claims 1 to 21.

23. A wind turbine rotor blade according to claim 22, wherein the appendage component (3) comprises any one of a leading edge protection cover, a trailing edge panel, a base plate, a vortex generator panel, a slat, a spoiler, a flap and / or a sensor panel.

24. Wind turbine rotor blade according to claim 22 or 23, wherein the thickness of the appendage part (3) at its longitudinal edge step (3E) is in the range of 0.2 mm to 5 mm.

25. Wind turbine rotor blade according to claim 24, wherein the thickness of the appendage part (3) at its longitudinal edge step (3E) is in the range of 0.25-2 mm.

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