METHOD FOR CREATING A TRANSITION FROM AN EDGE OF AN ADD-ON PART MOUNTED ON THE OUTER SURFACE OF A ROTOR BLADE

Abstract

A method for creating a transition from an edge of an add-on part mounted on the outer surface of a rotor blade, including the steps: delimiting an application area on the rotor blade surface and the add-on part to be covered by a sealant compound with a thin and smooth masking tape; dispensing of the sealant on the application area; distribution of the sealant; removing the masking tape; and smoothening of a sealant transition step with a flexible tool, is provided.

A wind turbine rotor blade is also provided.

Claims

1. A method for creating a transition from an edge of an add-on part mounted on an outer surface of a rotor blade, the method comprising: delimiting an application area on the outer surface and the add-on part to be covered by a sealant compound with a thin and smooth masking tape; dispensing of the sealant compound on the application area; distributing of the sealant compound; removing the masking tape; and smoothening a sealant transition step with a flexible tool.

2. The method according to claim 1, wherein the sealant compound is formed to overlap the edge of the add on.

3. The method according to claim 1, wherein the distributing the sealant compound is achieved by using a toothed spatula of a flexible material, for levelling the sealant compound after the sealant compound has been dispensed to the application area, further wherein teeth of the toothed spatula have a distance between 1 to 2 mm and/or a height between 0.2 to 5 mm.

4. The method according to claim 1, wherein the flexible tool is a second spatula, with a Shore A hardness bigger than 30 and/or smaller than 70.

5. The method according to claim 1, wherein the flexible tool comprises a silicone material, with a cross-section profile adapted to the application and a low energy surface preventing adhesion of the sealing material.

6. The method according to claim 1, wherein the flexible tool comprises a tip where there is an intended contact area with the sealant compound, and a number of grooves running parallel to the tip and/or a number of fins at an opposite end of the tip.

7. The method according to claim 1, wherein the masking tape has a thickness less than 0.2 mm.

8. The method according to claim 1, wherein the dispensing of the sealant compound is achieved by bead or spray application, by roll application or using the a swirl process, by application of the sealant compound in a serpentine line overlapping transition, on both the add-on and the outer surface, or in a straight line on the add-on and/or the outer surface.

9. The method according to claim 1, wherein after distributing the sealant compound and before removing the masking tape, the sealant compound is smoothed with a tool, moved in a longitudinal direction of the blade, further wherein the tool is designed to meet a profile of the blade, with a curvature that matches that of a blade leading edge profile.

10. The method according to claim 1, wherein the sealant compound is fluid enough to flow into gaps and surface crevices formed during application of the add-on, and to ensure a smooth finish, further wherein: the sealant compound has a surface tension being lower than a surface free energy of the blade surface; and/or the sealant compound has a sufficient resistance to the peel forces occurring on respective surfaces over an entire service life of the blade, bigger than 2 N/mm, and/or the sealant compound has a tensile strength of bigger than 4 MPa and/or smaller than 8 MPa; and/or the sealant compound has an elongation at break bigger than 80% and/or smaller than 130%; and/or the sealant compound has a Young's Modulus bigger than 8 MPa and/or smaller than 150 MPa; and/or the sealant compound has a maximum size of solid particles, filler particles, agglomerates of filler particles, gel particles, in the sealing material both in a liquid as well as hardened or cross-linked state is limited to max. 200 μm.

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

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

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

14. The wind turbine rotor blade according to claim 13, wherein the at least one add-on part comprises any of a leading edge protective cover, a trailing edge panel, a vortex generator panel, a spoiler, a plate or a sensor panel.

15. The wind turbine rotor blade according to claim 13, wherein the thickness of the at least one add-on part at a longitudinal edge is in the range 0.5-1.5 mm.

Description

BRIEF DESCRIPTION

[0096] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0097] FIG. 1 depicts an embodiment of the inventive edge seal applied to the longitudinal edge of a rotor blade add-on, which is a panel;

[0098] FIG. 2 depicts a further embodiment of the inventive edge seal sealing a plate;

[0099] FIG. 3 depicts a further embodiment of the inventive edge seal sealing a cover;

[0100] FIG. 4 depicts a further embodiment of the present invention comprising overlapping edge sealing;

[0101] FIG. 5 depicts an embodiment of present invention comprising overlapping edge sealing with filler material;

[0102] FIG. 6 depicts a tooth spatula;

[0103] FIG. 7 depicts another view of a tooth spatula;

[0104] FIG. 8 depicts a smoothening tool;

[0105] FIG. 9 depicts a profile of the smoothening tool of FIG. 8;

[0106] FIG. 10 depicts a smoothening and distribution of sealant with a soft and a hard tool;

[0107] FIG. 11 depicts a smoothening and distribution of sealant sealing the edge of an add-on finished with a soft and a hard tool;

[0108] FIG. 12 depicts an example for the smoothening of an edge seal; and

[0109] FIG. 13 depicts a final smoothening of an edge seal.

DETAILED DESCRIPTION

[0110] In the diagrams, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.

[0111] FIG. 1 shows an embodiment of the inventive 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 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 3E may be assumed to run in a longitudinal direction of the rotor blade 1. The diagram clearly shows the “step” shape at the edge 3E of the add-on 3. Using the inventive method, an edge seal S is formed along the add-on edge 3E. The edge seal S commences at a first point J1 at the add-on edge 3E and extends to a second point J2, whereby the height t of the seal S gradually decreases from a maximum at point J1 to a minimum at point J2. The ratio of the height t and the width δ of the edge seal S 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 3E of the add-on 3.

[0112] FIG. 2 shows an embodiment of the inventive edge seal S, applied to an add-on 3 as shown in FIG. 1, wherein the add-on 3 here is a sensor panel covered with sensors 5.

[0113] FIG. 3 shows an embodiment of the inventive edge seal S, applied to an add-on 3 as shown in FIG. 1, wherein the add-on 3 here is a cover, e.g. a LEP cover.

[0114] FIG. 2 shows a further embodiment of the inventive edge seal S. Here, the edge seal S is applied to a longitudinal edge 3E of an add-on 3, in this case e.g. an LEP cover mounted about the leading edge of a rotor blade 1. In this exemplary embodiment, the edge seal S overlaps the longitudinal edge 3E of the add-on 3, i.e. the edge seal S commences at point J0 and extends to point J2. The total width δ1 of the edge seal S is therefore the width h of the overlap S.sub.O 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 of the edge seal S 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 of the seal S at its maximum may exceed the height of the add-on edge 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 is based on the controlled layer thickness of the sealant or adhesive applied using a tool such as a spatula.

[0115] Thus, the extent δ of the edge seal S and the extent of the overlap h are dependent on the height t of the edge step 3E at junction J1. The ratio of δ and h with respect tot can vary anywhere between 20:1 to 100:1 (δ) and 10:1 to 50:1 (h) respectively. The edge seal S and overlap extents are tuned in order to prevent/delay the onset of flow transition from laminar to turbulent on the surface of the rotor blade 1 due the edge step 3E. The recommended ratios are longer than typically used by solutions known in the art.

[0116] By example in respect of the figures (FIG. 4 in particular) the height t of the edge step 3E can be anywhere between 0.5 to 1.5 mm, 0.7 to 1 mm, which means that the minimum extent of the edge seal S would be at least 12 mm, e.g. between 12 to 70 mm, 14 to 50 mm, more 14 to 40 mm and most 14 to 20 mm.

[0117] The extent δ of the edge sealing is dependent on the curvature of the rotor blade 1 which puts a maximum on the extent of the edge seal S.

[0118] A edge seal S may use a sealant with a viscosity to make the adhesive/sealant fluid enough flow into the gaps and surface crevices formed due to the application and ensure a smooth finish. At the same time the viscosity of the adhesive/sealant 4 drives the step at junction J2 in the simple edge sealing S and at J0 and J2 in the overlapping edge seal S.sub.O. The overlapping edge seal S.sub.O may be able to eliminate the step at J1 forming a smooth layer over the shell edge 3E. The sealant is chosen such that a smooth transition to the blade surface 2 is assured.

[0119] FIG. 5 shows a further embodiment of the inventive edge seal S. Similarly to the edge seal S of FIG. 4, 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/sealant. 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 such that the resulting edge seal S overlaps the longitudinal edge 3E of the add-on 3, commencing at point J0 and extending to point J2. In this case also, the total width δ of the edge seal S is measured from point J0 to point J2. As described in FIG. 2 above, the height of the seal S gradually increases from a minimum at point J0 to a maximum at point J0, and gradually decreases from the maximum at point J1 to a minimum at point J2. The filler F shown here could also be used in the other embodiments.

[0120] 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.

[0121] Embodiments shown in FIGS. 3 to 5 may also comprise a panel, e.g. a VG panel or TE panel (trailing edge panel) instead of a cover. The cover may be e.g. an LEP or TE edge cover.

[0122] FIG. 6 shows a flexible tooth spatula 6 with a row of teeth 6a. This tooth spatula 6 is used as preliminary tool 6 to spread the sealant material in a region bounded by the longitudinal edge of the add-on part 3 and the chosen edge seal width δ. The preliminary tool 6 has a flexibility and shape that facilitates the initial spreading of the sealant. This is achieved with the teeth 6a. The tooth distance lies between 1 to 2 mm and the tooth height is about 0.2 to 5 mm.

[0123] FIG. 7 shows another view of a tooth spatula as shown in FIG. 6 made of a flexible material and used for adhesive levelling.

[0124] FIG. 8 shows a smoothening tool 7 in form of a refining spatula 7 that is used to refine the shape of the sealant spread by the preliminary tool 6. The refining tool has a lower hardness than the preliminary tool.

[0125] FIG. 9 shows a profile of the smoothening tool of FIG. 8 indicating the contact area 7e with sealant/adhesive during smoothening (arrow).

[0126] FIGS. 8 and 9 show a spatula with a number of grooves 7a running parallel to the tip 7d of the spatula (perpendicular to the direction of smoothening). These grooves 7a have the advantage that the refining spatula 7 is rigid in the direction of the grooves 7a but may easily bend when sweeping over a surface. For a better grip, a refining spatula 7 has two fins 7b, 7c at the opposite end of its tip 7d, wherein the fin 7c at the side of the contact area 7e is thinner than the fin at the other side.

[0127] FIG. 10 shows the smoothening and distribution of a sealant with a soft spatula/tool 7 versus a hard spatula/tool. When using a soft refining spatula 7, the resulting edge seal S will be flatter and wider (solid line) than an edge seal S.sub.H smoothened with a hard tool (dashed line).

[0128] FIG. 11 shows the smoothening effect of FIG. 10 at an edge seal S of an add-on 3. Again, the dashed line shows the edge seal S.sub.H made with a hard tool, the solid line the edge seal S made with a soft refining spatula 7 (for the spatula see e.g. FIG. 8). Shown are angles between the blade surface 2 and the sealing made with a hard spatula (angle θ.sub.H) and the soft refining spatula 7 (angle θ.sub.S). It can easily be seen that the angle θH between the blade surface 2 and the sealing made with a hard spatula is much bigger than the according angle θs made with the soft refining spatula 7.

[0129] From wind tunnel measurements, it has been observed that the angle θ between blade surface 2 and edge seal S (sealing edge angle) plays a vital role in the performance of the sealing concept. The lower the sealing edge angle θ, the better the performance of the sealing.

[0130] A soft spatula yields a lower sealing edge angle compared to a harder (stiffer) spatula as the spatula is able to bend more locally towards the point where the sealing ends and the blade surface starts. Hence, the impact sealing edge angle θ is a direct function of the spatula hardness (stiffness). Hence a spatula with a suitably low hardness is chosen.

[0131] FIGS. 12 and 13 show an add-on 3 attached to a rotor blade surface 2 and the forming of an edge seal S with a method according to the embodiment of the present invention. 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.

[0132] FIG. 12 shows the steps spreading the liquid sealant LS using a preliminary shaping tool 6 and smoothing the sealant with a flexible tool 7. FIG. 13 shows the final smoothening of the sealant LS.

[0133] Prior to applying the sealant LS the area of the intended edge seal is delimited by using a smooth, thin masking tape 8. One tape 8 may extend along the outer edge of the intended edge seal 51, at a distance outward from the edge step 3E. This distance is at least 20 times larger than the edge step height. The thickness of the tape 8 is as small as possible, at most 0.2 mm. The other boundary of the edge seal 51 may be defined by the edge step 3E. Alternatively, if an overlap is to be formed over the edge step 3E, a second tape 8 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.

[0134] The roughly applied sealant LS is then spread using a preliminary shaping tool 6, for example a flexible toothed spatula 6. This can be done by guiding the toothed spatula 6 in the longitudinal direction of the rotor blade surface 2, between the edge seal bounds. The flexibility of the preliminary shaping tool 6 is such that it can be bent in both axial directions to facilitate spreading of the sealant S.

[0135] After distribution of the sealant LS (before removing the masking tapes 8), the sealant LS is smoothed with a, flexible, tool 7 moved in the longitudinal direction of the blade 1.

[0136] After this preliminary step (FIG. 12) is complete, the tapes 8 are removed (see FIG. 13). The still-liquid sealant LS is then smoothed to its final shape by drawing a softer finishing tool 7, e.g. a flexible refining spatula 7, over the spread sealant LS. This refining or smoothing step with the smoothening tool 7 serves to further decrease the height of the “wedge” of the edge seal Si between the edge step 3E and the outer boundary of the edge seal S. The refining spatula 7 is made of a material such as silicone to ensure a relatively low Shore A hardness, for example 50±10 so that it can be curved as desired during spreading of the sealant in order to achieve the desired edge seal profile shape.

[0137] By using the refining tool 7, the still-soft liquid sealant LS is shaped as desired, e.g. as shown in FIG. 4 or 5, to form an overlap S.sub.O alongside the long edge 3E of the add-on 3.

[0138] Although the present invention has been disclosed in the form of exemplary 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 present invention.

[0139] 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.

[0140] 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.

[0141] 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.