Abstract
A method of providing an edge seal along a longitudinal edge of an add-on part mounted on the outer surface of a rotor blade is provided. The method includes determining a height at the longitudinal edge of the add-on part, choosing a width for the edge seal to be applied on the rotor blade surface, wherein the width of the edge seal is chosen to exceed the height at the longitudinal edge of the add-on part by a factor of at least twenty; and forming the edge seal by applying a sealant material to the rotor blade surface at least in a volume defined by the height at the longitudinal edge of the add-on part and the chosen edge seal width.
Claims
1. A method of providing an edge seal along a longitudinal edge of an add-on part mounted on an outer surface of a rotor blade, the method comprising: determining a height at the longitudinal edge of the add-on part; choosing a width for the edge seal to be applied on the rotor blade surface, wherein the width of the edge seal is chosen to exceed the height at the longitudinal edge of the add-on part by a factor of at least twenty; and forming the edge seal over the longitudinal edge of the add-on part by applying a sealant material to a portion of the add-on part and to the rotor blade surface adjacent to the longitudinal edge of the add-on part so that the edge seal overlaps the portion of the add-on part and the rotor blade surface.
2. The method according to claim 1, wherein the width is at least 12 mm.
3. The method according to claim 1, wherein a ratio of edge seal width to height at the longitudinal edge of the add-on part is at most 100:1.
4. The method according to claim 1, further comprising determining a width of an edge seal overlap in an overlap region adjacent to the longitudinal edge of the add-on part, wherein the overlap width is determined on a basis of the height at the longitudinal edge of the add-on part.
5. The method according to claim 4, wherein a ratio of overlap width to height at the longitudinal edge is in the range of 10:1 to 50:1.
6. The method according to claim 4, wherein the sealant material is applied over the overlap width and edge seal width such that the height of the edge seal exceeds the height at the longitudinal edge of the add-on part.
7. The method according to claim 1, wherein the forming the edge seal is preceded by applying a filler material along the longitudinal edge of the add-on part, whereby a volume occupied by the filler material is less than an intended volume of the edge seal.
8. The method according to claim 1, wherein the sealant material is applied using a template shaped to define a desired smooth transition from the longitudinal edge of the add-on part to the rotor blade surface.
9. The method according to claim 8, wherein the template is shaped to distribute the sealant material in the overlap region of the add-on part.
10. The method according to claim 1, wherein the forming the edge seal comprises: depositing sealant material at least onto the portion of the add-on part and the surface of the rotor blade alongside the longitudinal edge of the add-on part; using a preliminary tool to spread the sealant material in a region delimited by the longitudinal edge of the add-on part and the width; and using a refining tool to refine a shape of the sealant material spread by the preliminary tool, the refining tool having a lower hardness than the preliminary tool and a profile based on a desired edge seal shape.
Description
BRIEF DESCRIPTION
(1) Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:
(2) FIG. 1 depicts an embodiment of the edge seal applied to the longitudinal edge of a rotor blade add-on;
(3) FIG. 2 depicts a further embodiment of the edge seal;
(4) FIG. 3 depicts a further embodiment of the edge seal;
(5) FIG. 4 depicts an add-on attached to a rotor blade surface as known from the prior art;
(6) FIG. 5 depicts another add-on attached to a rotor blade surface as known from the prior art;
(7) FIG. 6 depicts templates used in the method;
(8) FIG. 7 depicts templates used in the method; and
(9) FIG. 8 depicts laminar airflow over an edge seal formed using the inventive method.
DETAILED DESCRIPTION
(10) In the diagrams, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.
(11) FIG. 1 shows an embodiment of the inventive edge seal S1 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 20 of the rotor blade 2 by an adhesive bonding layer 33. For the purpose of discussion, the adhesive layer 33 may be regarded as an element of the add-on 3. The height t1 of the add-on 3 at its edge 3E is the sum of the thickness of the add-on 3 and the thickness of the adhesive layer 33. The add-on edge 3E may be assumed to run in a longitudinal direction of the rotor blade 2. The diagram clearly shows the “step” shape at the edge 3E of the add-on 3. Using the inventive method, an edge seal S1 is formed along the add-on edge 3E. The edge seal S1 commences at a first point J1 at the add-on edge 3E and extends to a second point J2, whereby the height of the seal S1 gradually decreases from a maximum at point J1 to a minimum at point J2. The ratio δ1:tl is at least 20:1. The volume of the edge seal S1 in this case is the cross-sectional area of the edge seal S1, i.e. (t1×δ1)/2, multiplied by the length of the seal S1, e.g. the length of the longitudinal edge 3E of the add-on 3.
(12) FIG. 2 shows a further embodiment of the inventive edge seal. Here, the edge seal S01 is applied to a longitudinal edge 3E of an add-on 3, in this case an LEP cover mounted about the leading edge of a rotor blade 2. In this exemplary embodiment, the edge seal S01 overlaps the longitudinal edge 3E of the add-on 3, i.e. the edge seal S01 commences at point J0 and extends to point J2. The total width δ01 of the edge seal S01 is therefore the width δ0 of the overlap S.sub.OV extending from point J0 to point J1, and the remaining edge seal width M extending from point J1 to point J2. In this embodiment, the height of the seal S01 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 height of the seal S01 at its maximum may exceed the height of the add-on edge 3E by up to 2.0 mm, depending on the overlap width δ0 and/or on the edge seal width M 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.
(13) FIG. 3 shows a further embodiment of the inventive edge seal. Similarly to the edge seal S01 of FIG. 2, the edge seal S01F in this case extends over a 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 such that the resulting edge seal S01F 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 δ01 of the edge seal S01F is measured from point J0 to point J2. As described in FIG. 2 above, the height of the seal S01F 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 embodiment of FIG. 1.
(14) FIG. 4 shows an add-on 3 attached to a rotor blade surface 20 in a manner known from the prior art. The add-on 3 may be attached using an adhesive 33 as explained above. A longitudinal edge 3E of the add-on 3 forms an abrupt or distinct step, which can cause a laminar airflow A.sub.lam to break up, resulting in turbulence A.sub.turb downwind of the step 3E. Such turbulence A.sub.turb reduces the aerodynamic performance of the rotor blade 2, and accordingly lowers the AEP of the wind turbine.
(15) FIG. 5 shows another prior art approach to securing an add-on 3 to a rotor blade surface 20. Here, the step 3E formed by the longitudinal edge 3E of the add-on 3 is made less abrupt by a seal 50 applied along the edge 3E. The width of such a prior art edge seal 50 is generally only between 2-5 mm. The incoming laminar airflow A.sub.lam over the rotor blade 2 is not affected as severely as shown in FIG. 4 above, but even the less abrupt step presented by the seal 50 is insufficient to preserve the laminar nature of the airflow, resulting in turbulence A.sub.turb downwind of the seal 50, so that this approach also shows a negative effect on the aerodynamic performance of the rotor blade 2 and a corresponding reduction in the wind turbine AEP.
(16) FIGS. 6 and 7 show stages in forming an edge seal S01 using the inventive method. The sealant material S is roughly distributed along an edge 3E of the add-on 3, in this case a leading edge protector. With a preliminary tool T0, the roughly applied sealant S is spread to fill a volume between the long edge 3E of the add-on 3 and a mask tape 60. The mask tape is smooth with a thickness of at most 0.2 mm. Here, the preliminary tool T0 is a flexible toothed spatula. Its flexibility is such that it can be bent in both axial directions to facilitate spreading of the sealant S. Then, using a refining tool T1, the still-soft sealant S is shaped as desired, in this case to form an overlap Soy alongside the long edge 3E of the add-on 3. The mask tape 60 can be removed after this step. In a final step, the refining tool T1 is again used to further optimize the shape of the edge seal S01. This refining tool T1 is softer than the preliminary tool T0, for example with a Shore hardness of 40-60, so that it can be curved as desired during spreading of the sealant in order to achieve the desired edge seal profile shape.
(17) FIG. 8 shows airflow over an add-on that has been given an edge seal S1 using the inventive method. The diagram shows that the laminar nature of the airflow A.sub.lam is maintained due to the smooth extended edge seal S1.
(18) Although the embodiment of the present invention has been disclosed in the form of the 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.
(19) 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.
