METHOD OF SHAPING AN EDGE SEAL FOR A ROTOR BLADE ADD-ON

Abstract

Provided is a method of shaping an initial edge seal along a longitudinal edge step of an add-on part mounted on the outer surface of a rotor blade, which method includes the steps of providing an initial edge seal along a longitudinal edge step of an add-on part mounted on an outer surface of a rotor blade, and removing a top layer of the initial edge seal. Further provided is wind turbine rotor blade.

Claims

1. A method of shaping an initial edge seal along a longitudinal edge step of an add-on part mounted on the outer surface of a rotor blade, which method comprises; providing an initial edge seal along a longitudinal edge step of an add-on part mounted on an outer surface of a rotor blade, removing a top layer of the initial edge seal.

2. A method according to claim 1, wherein the provision of the initial edge seal comprises the step of sealing a longitudinal edge step of an add-on part mounted on an outer surface of a rotor blade, wherein liquid sealant applied.

3. A method according to claim 2, wherein a width of the sealing is tuned in order to reduce the aerodynamic impact of the step due to the interfacing surfaces based on wind tunnel measurements.

4. A method according to claim 1, wherein the initial edge seal is overlapping with the add-on part.

5. A method according to claim 4, comprising a step of determining a width of an edge seal overlap in an overlap region adjacent to the longitudinal edge step of the add-on part, wherein the overlap width is determined on the basis of the height at the longitudinal edge step of the add-on part.

6. A method according to claim 5, wherein the ratio of width and/or overlap width to height at the longitudinal edge step is bigger than 4:1, bigger than 20:1 and/or smaller than 100:1.

7. A method according to claim 1, providing an initial edge seal, comprising: delimiting an application area on the rotor blade surface and the add-on part to be covered by sealant compound with a thin and smooth masking tape, dispensing of the sealant on the application area, especially by a bead or spray application, wherein the sealant is applied in a serpentine line overlapping the transition between the add-on and the blade surface, distribution of the sealant, by using a flexible toothed spatula, Or smoothening the adhesive with a, flexible, tool moved in the longitudinal direction of the blade, wherein the tool is so to meet the profile of the blade, removing the masking tape, smoothening of a sealant transition step with a flexible tool, with a Shore A hardness between 40 and 60.

8. A method according to claim 1, wherein removing a top layer of the initial edge seal is done by machining, by grinding and/or sanding and/or cutting and/or milling, so that the resulting edge seal is flush with the edge step.

9. A method according to claim 1, wherein 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 as it is at the point where the edge seal transitions into the rotor blade surface, wherein the resulting edge seal has the shape of a wedge with a convex surface or a kink in its surface.

10. The method according claim 1, wherein the sealant has a maximum size of solid particles, especially filler particles, agglomerates of filler particles or gel particles, in the sealing material both in its liquid as well as hardened or cross-linked state, that is limited to max. 200 μm, limited to max. 60 μm.

11. The method according to claim 1, wherein before dispensing of the sealant on the application area a filler is first applied along the longitudinal add-on edge, wherein the filler is a quick-setting adhesive and/or a high-viscosity adhesive, and the sealant is applied over the cured or hardened filler.

12. The method according to claim 1, wherein the sealant comprises the same material as an adhesive used for fixing the add-on the rotor blade surface.

13. A wind turbine rotor blade comprising at least one add-on part mounted to the outer surface of the rotor blade, and an edge seal shaped by a method according to claim 1.

14. The wind turbine rotor blade according to claim 13, wherein an add-on part comprises any of a leading-edge protective cover, a trailing edge panel, a base plate, a vortex generator panel, a slat, a plate, a spoiler, flaps and/or a sensor panel.

15. The wind turbine rotor blade according to claim 13, wherein the thickness of the add-on part its longitudinal edge step is in the range 0.2 mm to 5 mm, 0.25-2 mm.

Description

BRIEF DESCRIPTION

[0089] Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

[0090] FIG. 1 shows an embodiment of an edge seal applied to the longitudinal edge of a rotor blade add-on;

[0091] FIG. 2 shows an overlapping edge seal;

[0092] FIG. 3 shows an example for the shaping of an inventive edge seal;

[0093] FIG. 4 shows a method for providing an overlapping edge seal; and

[0094] FIG. 5 shows a method according to embodiments of the invention.

DETAILED DESCRIPTION

[0095] FIG. 1 shows an edge seal S applied to an add-on 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 could be the result of a method according to embodiments of the invention. The add-on 3 is attached to the outer surface 2 of the rotor blade 1 by an adhesive bonding layer 4. For the purpose of discussion, the adhesive layer 4 may be regarded as an element of the add-on 3. The height t of the add-on 3 at its edge step 3E is the sum of the thickness of the add-on 3 and the thickness of the adhesive layer 4. The add-on edge step 3E may be assumed to run in a longitudinal direction of the rotor blade 1. The edge seal 3 may be assumed an idealized edge seal S, since there is no step between the edge step 3E of the add-on 3 and the edge seal S. The dashed ellipsis marks the edge step at point (junction) J1. one could see that the transition between the add-on and the edge seal S should be smooth.

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

[0097] FIG. 2 shows a further embodiment of the inventive edge seal. Here, an initial edge seal S1 is applied to a longitudinal edge step 3E of an add-on 3, in this case an LEP cover mounted about 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 add-on 3, i.e., the initial edge seal S1 commences at point J0 and extends to point J2. The total width δ1 of the initial edge seal S1 is therefore the width δ of the overlap S.sub.OV extending from point J0 to point J1, 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 at point J0 to a maximum at point J1, and gradually decreases from the maximum at point J1 to a minimum at point J2. The height t1 of the initial edge seal S1 at its maximum may exceed the height of the add-on edge step 3E by up to 2.0 mm, depending on the overlap width h and/or on the edge seal width δ between point J1 and point J2. 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, since the top layer of the edge seal will be removed.

[0098] The edge seal S in this case extends over a filler material F (herein also referred to as filler F) that is first applied along the longitudinal add-on edge 3E. The filler F may be a quick-setting adhesive and/or a high-viscosity adhesive. The filler F can be applied to form a wedge with straight sides that are shorter than the height of the add-on 3. In a subsequent step, sealant material is applied over the cured or hardened filler F. Thus, for large edge steps, the filler F may be used to reduce the edge step initially and the edge sealer can be applied subsequently. The filler material F may have a higher viscosity than the material of the edge seal S in order to enable an easy build-up of the bottom layer to a finite thickness. The extent of the filler F will be less than δ in order to ensure that there is a uniform layer of edge sealer on the surface to enable a smooth edge at Junction J2.

[0099] FIG. 3 shows a further embodiment of the inventive edge seal S. First an initial edge seal S1 has been applied, e.g., similarly to the initial edge seal S1 of FIG. 2. In the sealing step, a sealing agent/adhesive is used to form an initial edge seal S1 on the edge step 3E of the add-on 3 with a small overlap. The sealing agent or the same may be of different properties but may also be of the same composition.

[0100] The width δ (or δ1) of the initial edge seal S1 is tuned in order to reduce the aerodynamic impact of the step due to the interfacing surfaces based on wind tunnel measurements. In an embodiment, the width δ is dependent on the height t of the edge step 3E at junction J1. The ratio of δ with respect to t can vary anywhere between 20:1 to 100:1.

[0101] When creating the initial edge seal S1, a sealing agent is applied on the blade 1 at the edge step 3E. It should have a suitable viscosity to allow the adhesive fluid of the sealing agent to flow into the gaps and surface crevices. At the same time the viscosity of the adhesive drives the step at junction J2. The step height at junction J2 is desirably of less than 100 μm. This can be achieved using an application process where the edge sealer is formed by an elastic spatula.

[0102] According to embodiments of the invention, the top layer L of the initial edge seal S1 (checked part) had been removed (or has to be removed) so that the remaining edge seal S is optimized. This can be achieved in that after the sealant has cured, the top layer L of the initial edge seal S1 is grinded away to expose the junction J.sub.1. The grinding may be done with any ordinary grinding tool, such as a random orbit sander, or even by hand, but with the help of a specialized edge grinding tool. Alternatively, the top layer L can be milled, sanded or cut away.

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

[0104] FIG. 4 shows an add-on 3 attached to a rotor blade surface 2 and the forming of an initial edge seal S1 in a desired manner. The add-on 3 may be attached using an adhesive 4 as explained above (the adhesive not shown here). Liquid sealant LS is applied on the surface 2 of a blade 1 in the region of the edge step 3E of an add-on 3.

[0105] Prior to applying the sealant LS the area of the intended edge seal may be delimited by using smooth, thin masking tape (not shown). One tape may extend along the outer edge of the intended initial edge seal S1, at a distance outward from the edge step 3E. This distance is at least 4 times, or at least 20 times, larger than the edge step height. The thickness of the tape is as small as possible, or at most 0.2 mm. The other boundary of the initial edge seal S1 may be defined by the edge step 3E. Alternatively, if an overlap is to be formed over the edge step 3E, a second tape may be applied to the surface of the add-on 3, parallel to the longitudinal edge of the add-on 3. The sealant LS is then applied within these bounds. The sealant LS can initially be roughly deposited on the surface 2 of the rotor blade 1 and add-on 3, for example in the form of a bead 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 bounds.

[0107] After this preliminary step is complete, the tape or tapes are removed. The still-liquid sealant LS is then smoothed to its final shape by drawing a softer finishing tool, e.g., a flexible spatula 6, over the spread sealant LS. This refining or smoothing step with the second tool serves to further decrease the height of the “wedge” of the initial edge seal S1 between the edge step 3E and the outer boundary of the edge seal. The second flexible spatula 6 is made of a material such as silicone to ensure a relatively low Shore hardness, for example 50±10.

[0108] FIG. 5 shows the initial edge seal S1 manufactured in FIG. 4 after curing. The initial edge seal S1 is treated by an abrasive tool 7 by removing the top layer L (see FIG. 3) from the hardened sealing material. The result is an optimized edge seal S as shown in FIG. 1.

[0109] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0110] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.