The present Invention relates to a device for remedying erosion problems on wind turbine blades

When, for example, wind turbines blades/rotor are rotated by the wind, speeds excess above 300 km/h at the wing tips are achieved. At these speeds, even the air works, but to an even greater extent, precipitation (especially hail) and impurities in the air such as fly sand or salt particles, eroding on the blade's leading edge. This is especially a problem on the outer third of the blade where the highest speeds are achieved. Various solutions are currently being used to secure the front edge (leading edge) of a wind turbine blade against being eroded. Epoxy or other types of glue are often used to hold, for example, tape, plastic films, metal wire mesh, rubber shells or glass fiber reinforced shells on the blade edge. These are all devices which are attached after completed blade molding.

These solutions have typical disadvantages, they are difficult to replace and maintain, and they often have a limited life span.

An example of the prior art is shown in EP 2623773 A2, which describes a blade leading edge on which Is provided a detachable erosion profile attached to the blade using either an adhesive or a screw connection

It is the object of the present invention to improve the possibility of erosion protection of a wind turbine blade.

According to the invention, this object is achieved by means of a device of the type mentioned in the preamble, which is characterized in that It comprises a shock-absorbing and erosion-resistant and UV-resistant profile for positioning on the front edge of a wind turbine blade, which device further comprises a holding part in the blade ^' s leading edge, which holding part is formed in the blade during the blade molding process or retrofitted, and in which holding part Is formed a groove with two recesses racing each other, and in these two recesses two complementary flaps on the profile are engaged and the outer part of the profile is designed to match the front edge of the blade.

In this way a good protection of the blade against erosion is achieved and the protection is easily replaceable.

In an advantageous embodiment, the profile is provided with several wedge-shaped recesses which engage a complementary double wedge- shaped object, which also engages recesses in the holding part.

Where the wedge is fixed.

In this way, the wedge ensures that the erosion profile Is maintained during rotation by the centrifugal force (the two wedge parts pattern engaging one another). The number of wedges used depends on the centrifugal force (rpm) and the erosion profile of the material’s carrying capacity (deformation constant) in addition, the wedge acts as a lock for the profile during rotation. Upon rotation, the wedge will spread the profile tabs to both sides and thereby lock the tabs firmly in the two sides of the holding part.

By another embodiment, the groove of the holding member and the profile is shaped so that they have growing cross sections in the inward (forward to blade root section) direction of the groove and profile. Due to this design and the elasticity and elasticity of the material, the profile Is capable of retaining itself in the groove, with the help from the centrifugal force and the wind pressure helping to maintain the erosion profile to the leading edge of the blade.

According to the invention, it is advantageous that in the profile there are built-in channels which can be used for heating the front edge of the blade. Hereby it is possible to remove ice formation on the blade to improve the blade performance in cold weather. Channels can also be built into the holding pari.

It is also possible and convenient for channels to be incorporated in the profile which can be used to apply liquid material to the blade in order to clean the outer surface of the blade, the profile being provided with holes, slots or nozzles through which the material can be led out. In this way it is possible to remove smog, snow, ice and other deposits.

In an advantageous embodiment, a optic fiber Is embedded or mounted which can be used to indicate the state of wear of the erosion profile, and it is also possible that a optic fiber embedded or mounted can be used for transmission of aircraft warning lights placed on or near by the blade tip.

According to an alternative embodiment, erosion foil can be mounted outside the erosion profile, and the foil can be held by the clamping force between the holding part of the blade and the erosion profile. Hereby, a safe retention of the foil can be achieved, the erosion protection is improved and the lifetime of the erosion profile is extended.

There is also the possibility that the erosion profile can act as a vibration damper against edge and flap-wise blade oscillations.

The invention will be explained in more detail below with reference to the drawings, in which

FIG. 1 A shows an example or a wind turbine blade, to which the device according to the invention can be used, viewed from the front in relation to the conveying direction,

FIG. 1 B shows the wind turbine blade seen from the side with the front part (leading edge) at the top,

FIG. 2 shows a perspective view in section of an example of the device according to the invention;

FIG. 3 shows an exemplary embodiment in which additional protection Is mounted;

FIG. 4 shows an exploded view from above of a locking system for holding a profile in a track;

FIG. 5 is an exploded side view of the locking system of FIG. 4

FIG. 6 shows an area where an additional erosion protection cap can be mounted on the blade profile,

FIG. 7 shows a sketch of how the erosion cap can look with the integrated counter holder,

FIG. 8 shows an erosion protection cap with integrated lightning receptor, FIG. 9 shows an erosion protection cap with integrated wingiet, and FIG. 10 shows an erosion protection cap with Integrated flight warning light.

In FIG. 1 A and 1 B there is shown a wind turbine blade 1 of the type that is most often used for larger wind turbines. During the movement of the wind turbine rotor, in particular, the outermost third is subjected to excessive erosion, and it is preferably this third, which can suitably be provided with the device for remedying erosion problems according to the invention

FIG. 2 shows two main parts 4, 5 of the device according to the invention. The reference numeral 4 denotes the erosion-protective profile, and the reference numeral 5 denotes the holding part, which, as mentioned, may be a part which is Integrated in the molding process or subsequently processed into the front of the blade, or it may be retrofitted. The two parts are held together by the two branches or flaps 6 on the profiie 4 pressing outwards towards the areas 7 of the holding part 5. Flow channels 8 for flowing material are shown both in the holding part 5 and the erosion- protecting profile 4, in which holes or grooves can be formed so that It Is possible to discharge the flowing material, which can for example be a cleaning liquid or glycol for de-icing, to the blade surface.

The erosion protective profiie 4 can be manufactured as an extruded profile, and it can optionally be in a dynamic extrusion tool which allows the profile cross section to be changed during the extrusion process. The profile can also be moulded

The profile must be shock absorbing, and for this purpose a material having a Shore A hardness of from 30 to 90 may be suitable.

The material must also be weather-resistant and could withstand the Influence of, among other things, salt, sand, smog, acid rain, hail and snow, and it must be resistant to UV light and large temperature fluctuations (for example from -40 to +50 degrees C) and also be resistant to, among other things, hydraulic oil, lubricating oil and g!ycol.

As shown in FIG. 2 matches the erosion protective profile 4 the leading edge of the wing, and it can cover, for example, an arc surface of 250 mm on either side of the center (the wind angle of attack on the blade) of the leading edge of the wing.

The reference numeral 9 schematically denotes a optic fibre (light guide) which can be used with an alarm sensor to indicate the state of erosion of the erosion profile. The optic fiber and / or optic fibers will be embedded during the extrusion of the erosion protection profile. In addition to being used for the erosion profile wear, they can be used as light energy transmission elements that can be utilized for aircraft warning lights mounted on or near the blade tip.

It is central that the profile is adapted to the actual wind turbine blade and at least has the same flexibility as the blade and remains flexible over the blade ^' s design life.

FIG. 3 shows another embodiment of the device according to the invention. The profile 4 and the holding part 5 have a slightly different design, but the principle is the same. The profile 4 is coated with an easily replaceable protective film 1 1 , which can for instance be the so-called helicopter tape, which Is often used for wind turbine blades. The foil may be provided with a glue back side, but it will be further retained by the clamping force between the profile 4 and the holding pari 5.

FIG. 4 and 5 show exploded views of an embodiment of the invention using a wedging system for holding the erosion profile 4, seen from above and from the side, respectively. This construction may suitably be used when the profile has the same cross-sectional dimension over Its entire extent, and therefore may need to be retained in the holding part 5. The erosion profile 4 is maintained by being formed with several wedge-shaped recesses 12 which engage with matching wedge elements 1 1 , which are mounted on the holding part 5. The wedge further has the function of pushing the branches / tabs of the profile out to both sides and thereby locking the branches / tabs 6 to the sides 7. The wedges are turned so that they engage with each other when the profile 4 is affected by the centrifugal force (double locking of the profile).

An erosion profile of the type described also has the advantage that it can be used to change the vibration characteristic of the wing and act as a vibration damper in relation to edge and flap-wise oscillation.

In a further aspect of the invention, a shock absorbing and erosion and UV resistant cap is attached to the outer portion of the blade tip. It is advantageous that the protective cap encloses the entire wind turbine blade tip. The primary purpose of the cap is to protect the tip of the blade tip from erosion.

FIG. 6 shows a wind turbine blade 20 with a blade tip 21 , where an erosion protection cap 22 (Fig. 2) can be placed.

In FIG. 7 is zoomed in on the detail which makes it possible to hold the erosion protection cap 22 on to the tip 21 of the blade 20. The erosion protection cap 22 is held by a staircase of barbs 23 which are embedded or post-processed both In the blade tip 21 of the blade profile 20 and in the erosion protection cap 22. The stair steps 23 In this preferred embodiment extend 360 degrees around the chord of the wing, but the extension may vary. Likewise, the number of steps may vary, and the depth of the steps may vary. An adhesive / glue can be used to secure the cap.

FIG. 8 shows the erosion protection cap with integrated lightning receptor 24. The lightning receptor 24 also has the function of helping to fix / hold the erosion protection cap 22 to the tip 21 of the blade 20.

FIG. 9 shows the erosion protection cap 22 with integrated wingiet 25. The function of the wingiet is partly that It gives the blade 20 a better performance and partly that it, with proper design, reduces noise from the blade.

FIG. 10 shows the erosion protection cap 22 with another Integrated wingiet 26 containing an aircraft warning light

To ensure that the solution is power curve neutral measured against the original blade profile, the blade tip profile is manufactured in such a way that the cap material thickness has been taken into account and the blade profile stays the same when cap has been mounted. This can be done, for example, by placing an insert in the blade shape during the molding process corresponding to the material thickness, size and extent of the cap.

The erosion cap is retained as mentioned by a staircase of barbs which are embedded in both the blade profile and the erosion cap. In the preferred embodiment, the stair treads are 360 degrees around the blade of the blade, however, this may vary. The number of steps may vary and the depth of the steps may vary. An adhesive / glue can be used to secure the cap.

The erosion protection cap is formed with drain holes (not shown) to avoid water pockets between the blade surface and the mounted erosion cap.

The erosion protection cap can be designed with an integrated lightning receptor and or a winglef to ensure a better blade performance (effect curve) and thereby a better annual energy production, also known as AEP (Annual Energy Production). The winglei can also help to make the blade quieter - sonica!!y.

There may be built-in light guide (optic fibres) for conveying aircraft warning lights and for warning of wear and tear on the erosion protection cap.

This concept of protecting the blade tip against erosion, together with the aforementioned erosion profile, covers the entire outer part or the blade which Is especially exposed for erosion.

The erosion cap is thus intended to counteract erosion of the wind turbine blade's wing tip. The erosion cap acts as a protective layer between the leading edge of the blade and the degrading factors to which the blade tip is subjected to during normal operation.

Erosion protection is power curve neutral measured against the original blade profile. The blade tip profile is produced so that the material thickness of the cap is taken into account. This is done by placing an insert in the blade shape during the molding process corresponding to the material thickness, size and extent of the cap.

The erosion protection cap may be inserted as part of the molding process. The profile can also be retrofitted after finishing production of the blade in the mold.

The erosion cap is designed with a built-in elasticity with a resilient effect, which means that the profile is able to retain itself. Retention Is possible due to the design of a staircase of barbs embedded both in the profile of the blade and In the erosion cap. The staircase step advantageously goes 360 degrees around the blade (pressure and suction side) chord line. The number of steps may vary and the depth of the steps may vary. An adhesive / glue can be used to secure the cap.

The known techniques In the field all assume that glue or epoxy Is used to maintain an erosion reinforcement material In the form of tape, plastic films, metal wire mesh, glass fiber reinforced U-shaped shells, etc , which are intended to protect the blade edge. These are solutions that are attached after the blade Is molded and which are difficult to retrofit and maintain and all have a negative impact on the power curve.

According to the invention, a shock absorbing and erosion and UV resistant cap is attached to the outer part of the blade tip. In the preferred embodiment, the protective cap encloses the entire blade tip. The primary purpose of the cap Is to protect the tip tip edge "Tip Leading Edge" against erosion.

The erosion protection cap further has the feature that it has a design geometry that corresponds to the original blade tip. The erosion protection cap protects the entire tip in the area it covers and is power curve neutral. The erosion protection cap is retained as mentioned by a staircase of barbs embedded both in the wing profile and in the erosion cap. In the preferred embodiment, the step steps are 360 degrees around the blades chord line. The number of steps and the depth of the steps may vary.

There can be applied adhesive to ensure a retention of the erosion protection cap.

In summary, the erosion protection cap is designed with the following characteristics and / or features: a) The erosion protection cap is molded so that it fits exactly to the wind turbine blade tip profile geometrically

b) The erosion protection cap is mounted on the wind turbine blade tip c) The erosion protection cap is designed to be power curve neutral d) The erosion protection cap is used primarily to counteract the

erosion of the wing leading edge

e) The erosion cap is held by a staircase of barbs embedded in both the blade profile and the erosion cap. The stair steps can walk 360 degrees around the blade on pressure and suction side in the chord line of the blade. The number of steps may vary and the depth of the steps may vary. An adhesive / glue can be used in addition to retaining the cap

f) In the erosion protection cap design an elasticity is built In, which means that the profile is able to retain itself.

g) The design of the erosion protection cap barbs also retains the blade profile barbs when centrifugal force are in action caused when the blade rotates.

h) The erosion protection cap is flexible / elastic

i) The erosion protection cap is designed with drain holes to avoid water pockets between the blade surface and the mounted erosion cap.

j) Erosion protection cap Is easy to mount and service maintain k) The erosion protection cap may be designed with an integrated lightning receptor

L) The erosion protection cap can be designed with an integrated wingiet to ensure a better blade performance (power curve / AEP) m) The integrated wing!et in the erosion protection cap can also help to make the blade !ess noisy

n) The erosion protection cap is designed so that It can absorb and convert (neutralize) the erosion energy to which the blade is exposed during operation.

o) The erosion protection cap is able to resist aging due to UV radiation p) The erosion protection cap can be designed with an integrated

aviation warning light.

q) integrated fiber optic (light guide) embedded / mounted in the

erosion protection cap used with alarm sensor to indicate wear pattern in the profile

r) Erosion film can be mounted outside the erosion protection cap