FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
PREVENTION OF DEBRIS ACCUMULATION AT THE LEADING EDGE OF THE WIND TURBINE BLADES;
SUZLON ENERGY LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS ONE EARTH, OPPOSITE MAGARPATTA CITY, HADAPSAR, PUNE - 411 028, MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of invention
The present invention relates to wind turbine blades, and more particularly to a leading edge protection means of a wind turbine blade.
Background of the invention
The wind turbine blades typically have a shape of an airfoil when seen as a cross-section. The wind turbine blades have a leading edge and a trailing edge and two sides, namely an upper side and a lower side. The upper and lower sides extend between the leading edge and the trailing edge. The upper side is generally known as a suction side. The suction side is more curvaceous in geometry that leads to acceleration of flow and reduction in pressure. The lower side is generally known as a pressure side. The pressure side is much flatter and is configured to have a little change in pressure. The leading edge is also known as a nose of the wind turbine blade as it faces towards the wind. The trailing edge preferably remains at a downstream of the airfoil. A line that joins the leading edge to the trailing edge is known as a chord and the length of the said line is therefore known as a length of the chord or a chord length.
A major problem associated with wind turbines is debris accumulation on the leading edge of the wind turbine blades. The debris accumulation is generally in form of dust deposition and/or insect splatter contamination. The debris accumulation mainly occurs in the proximity to the leading edge. Many wind farms experience dusty surroundings along with the hot and humid weather which promotes growth of insects. Particularly, the insects can fly up-to turbine's nacelle height in the low wind season and subsequently hit hard against the leading edge due to high rotational speed of the blades thereby causing

insect splatter contamination. The dead insect protein gets combined with the surrounding dust which sticks hard to the leading edge. This accumulation of the debris at the leading edge of the blade leads to the disruption of the aerodynamic flow and causes overall turbine to underperform during operation. Cleaning of debris accumulation is a tedious process and generally requires substantial manual efforts iri the same. However, manual cleaning requires shutdown of the turbine, resulting in the loss of power production. Moreover, the operation of the blade access and uplifting of the cleaning equipment at a height under windy conditions requires highest degree of skill otherwise the equipment itself can cause damage to the sensitive leading edge area.
There are attempts seen in the art towards protection of the leading edge of the wind turbine blade. For example, US 20100952552 A to Benito et al. discloses a rotor blade assembly for a wind turbine that includes an erosion protection coating on the surface of the rotor blade. However, these prior art coatings are limited only to erosion protection. Moreover, these protective coatings have high surface energy. For example, the surface energy of typical polyurethane paint coatings is normally found to be 40mN/m. The high surface energy of these protective coatings largely encourages accumulation of debris. Also, some of the polyurethane based leading edge protection coatings add shine to the leading edge of the wind turbines. This would create a problem to eyesight of the nearby population residing in the vicinity of the wind mill farms under the sunlight. Further, the leading edge of the wind turbine blades has limitations during transportation and installation. For example, the leading edges of the prior art wind turbine blades abrade due to the friction between the holder and the leading edge. Also, damage may occur to the leading edge during the commissioning of the blades due to use of holding means such as ropes, ratchet belts and the like.
Accordingly, there exists a need of a protection means for a leading edge of a wind turbine blade that overcomes all the drawbacks of the prior art.

Objects of the invention
An object of the present invention is to prevent debris accumulation on a leading edge of a wind turbine blade.
Another object of the present invention is to remove insect splatter contamination on the leading edge of the wind turbine blade.
Still another object of the present invention is to provide protection to the leading edge of the wind turbine blade.
Summary of the invention
Accordingly, the present invention provides a wind turbine blade assembly adapted for preventing debris accumulation on a leading edge or a nose of a wind turbine blade. The wind turbine blade assembly comprises a protection member that positions on the leading edge of the wind turbine blade. The protection member includes a plurality of metal sheet segments. Each of the metal sheet segments has a C-shaped section formed therein. Each of the C-shaped sections positions on the leading edge. The C-shaped sections extend over a predefined length along a suction side and a pressure side of the wind turbine blade. The metal segments facilitate uniform stress distribution during a plurality of flap-wise bending movements of the wind turbine blade. The protection member facilitates surface energy reduction of the wind turbine blade.
Brief description of the drawings
FIG. 1 is a top perspective view of a wind turbine blade assembly constructed in accordance with the present invention;

FIG. 2 is a horizontally exploded perspective view of the wind turbine blade assembly of FIG. 1;
FIG. 3 is a front view of the wind turbine blade assembly of FIG. 1;
FIG. 4 is a front view of an alternative embodiment of the wind turbine assembly of FIG. 1;
FIG. 5 is a top perspective view of a segment section of the wind turbine blade assembly of FIG. 1;
FIG. 6 is a perspective view of a section of the wind turbine blade of FIG. 1 having a segment section of positioned thereon;
FIG. 7 is a cross- sectional view of the section of the wind turbine blade of FIG. 6 taken along lines 7-7; and
FIG. 8 illustrates a preferred method of forming a C-section of the segment section on a leading edge of the wind turbine blade of FIG. 1.
FIG. 9 illustrates the functionality of segmented protective member 12 when the blade is bended during flap-wise movements.
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

Referring to FIGS. 1-3, a wind turbine blade assembly 10 is shown. The wind turbine assembly 10 includes a protection member 12 that is positioned over a wind turbine blade 14 preferably in a direction indicated by an arrow-A. The protection member 12 is specifically adapted to protect a leading edge or a nose 16 of the wind turbine blade 12. The wind turbine blade 14 has a root 18, a tip 20, and a trailing edge 22. The root 18 is a cylindrical side of the wind turbine blade 14 that positions inside a hub of the wind turbine. The tip 20 is an end portion that defines a full span extent of the blade 14. A distance between the root 18 and tip 20 defines a total blade length or span 'L' of the turbine bladeH. In this one embodiment, the wind turbine blade 14 has a blade length of 47 meter and a wind turbine of 2.1 MW. However, it is understood that the length of the wind turbine 'L' and the type of turbine may vary in other alternative embodiments of the wind turbine blade assembly 10.
The protection member 12 is formed out of a plurality of metal sheet segments 24. In this one embodiment, a leading edge area- LI, mainly outer 25% of the total blade length 'L' is covered by the protective member 12. Specifically, the curved metal sheet segments 24 are placed on LI which is preferably outer 25% percent of the blade span to get the best cost to benefit ratio.
Referring to FIG. 4, an alternative embodiment of the wind turbine blade 14 is shown wherein the protective member 12 substantially totally extends over a full length 'L2' of the leading edge 16 wherein the segments 24 are configured to protect the blade 14 from the root 18 to the tip 20. In this one alternative embodiment, the protective member 12 protects entire leading edge 16 of the bladeH.
Referring to FIG. 5, each of the metal sheet segments 24 are formed in the form of C shaped sections 26 in this one preferred embodiment. The metal sheet segments 24 are specifically made of malleable material in general and of Aluminum in particular. The malleable material facilitates each of the sheet

metal segments 24 to achieve the shape of C shaped section 26 that is substantially identical to the shape of the leading edge 16 on which the C shaped section 26 is being positioned. Also, the malleable material of the sheet metal segments 24 lead to the easy manufacturing of pre-fabrication parts in form of C-sections 26 that are preferably riveted to the blade 14. The C-shaped sections 26 are preferably fabricated using a die-pressing process wherein a thin flat metal sheet segment 24 is placed on a die having the shape of the leading edge airfoil, preferably of a location of the leading edgel6 where the segment 26 is being attached.
Referring to FIG. 6, a portion 14A of wind turbine blade 14 that is positioned with respective C-shaped sheet metal segments 26A, 26B is illustrated. In this one particular embodiment, the sheet metal segment 26A has a length L3. The sheet metal segment 26B has a length LA The metal segments 26A and 26B are positioned preferably at a gap Gl. It is understood here that, the gap Gl normally ranges anywhere between 2 mm to 40 mm.
Each of the sheet metal segments 24 has a length that is defined as a percentage of a radius of the blade 14. In particular, the length of each segment is between 0.5% and 5% of the blade radius. The sheet metal segments 24 may range in number of 5 to 35 along the total length of the blade. However, it is understood that the number of segments 26 is substantially dependent on the radius of the blade 14 that is to be protected. It is also understood that, the length of each segment 26 may vary across the radius of the blade 14 per the bending and twisting characteristics of the wind turbine blade 14. This would also mean that the length of the segments 26 would be different for diverse length of blades 14.
Referring to FIGS. 6-7, a cross-sectional view of a C-shaped leading edge segment 26 for a small part of the wind turbine blade span is shown. Each of the segments 26 has a shape that conforms to the shape of the leading edge 16 at a section where the segment 26 is being applied. Each of the segments 26 has a

curvature that matches a curvature of the leading edge 16. The segments 26 preferably stretch by a length "a" on a suction side 28. The segments 26 preferably stretch by a length "b" on a pressure side 30. The lengths "a" and "b" are specifically defined in terms of a local chord length 32 starting from an apex point 34 on the leading edge 16 to the end point 35 on the trailing edge 22 for each respective section thereof. It is understood here that the lengths "a" and "b" vary in a range of 5% to 25% of the local chord length 32.
Referring to FIG. 8, C-shaped sections 26 preferably connect to the turbine blade 14 by a co-curing process in this one preferred embodiment. The co-curing process is such that each of the C-shaped sections 26 are formed into two halves, namely a first half 26-a and a second half 26-b. The halves 26-a, 26-b are placed in the area that is in proximity to the leading edge 16 of the mould during lay ups of respective glass layers. These halves 26-a A, 26-b are embedded in an outer side of the blade 14 and subsequently regular curing and mould closing processes are carried out thereby forming the metal segments 26 as integral part of the blade 14.
However, it is understood here that other types of joining processes may be used to connect the C-shaped sections 26 of the metal segments 24 to the turbine blade 14 such as a fast curing process, riveting, connecting via double sided tapes and the like. The fast curing process is adapted for connection of C-shaped sections 26 in post manufacturing process wherein the blades 14 are in a dry finish area. In the fast curing process, the C-shaped sections 26 are adhered to the leading edge 16 by sandering inner sides of C-shaped sections 26 and the leading edge area which is followed by a fast curing resin. The fast curing process ensures good bonding between the C-sections and the blade 14. The riveting process is such that the C-shaped sections 26 are riveted to the leading edge 16 using a riveting gun. A surface thickness of the blade 14 in the leading edge area is preferably kept as 6 mm to facilitate easy riveting of the C-shaped sections 26 on the leading edge 16. The double sided tape process is such that

high strength double sided tapes known in the art are used to adhesively connect the C-shaped sections 26 to the blade 14. The relevant thickness range for aluminum segmented sheet 24 in this one preferred embodiment would be between 4 gauge to 25 gauge. The corresponding thickness for said gauge range is 5.18922 mm to 0.45466 mm respectively. However, it is understood here that the thickness of sheet 26 may change in other alternative embodiments of the present invention.
As shown in FIG. 9, the C-shaped sections 26 on the wind turbine blade 14 uniformly distribute a plurality of flap-wise bending/ fluttering movements over the C-shaped metal sheet segments 26 during operation of the wind turbine blade 14. In this one embodiment, the wind blade 14 is shown fluttered in a direction indicated by an arrow-E. The metal sheet segments 26 advantageously prevent formation of cracks on the protection member 12, in case it was not segmented, arising due to concentration of stress and allows for the flap-wise movement and twisting of the blade 14.
Referring to FIGS. 1-9, the protective member 12 is coated with a Teflon coating which reduces its surface energy along length LI. The reduced surface energy leads to higher angle of contact that substantially minimizes dirt deposition on the surface of the protection member 12 thereby keeping the leading edge 16 of the wind turbine blade 14 substantially clean. The surface energy achieved at the leading edge 16 of the wind turbine blades 14 is at least one third times less than the surface energy produced by paint coatings known in the art. It is understood here that the surface energy achieved at the leading edge of the wind turbine blades is 14 mN/m in this one embodiment.
In operation, the reduced surface energy on the leading edge 16 embedded with Teflon coated protection member 12 prevents aerodynamic losses which subsequently allow designed power production. The reduced surface energy keeps the leading edge 16 aerodynamically efficient. Further, the lowered

surface energy prevents debris accumulation due to insect splatter such that insect protein fails to remain on the leading edge of blade that is subsequently removed from the surface of the protection member 12 by itself. This also prevents/reduces reduction in algae and moss deposition on the protection member 12 of the blades 14.
In operation, the Teflon coating prevents debris from staying or accumulating on the protection member 12 of the leading edge 16 of blade by getting automatically removed from the surface thereof. Teflon coating also eliminates the actual need of external/ manual cleaning which enables the leading edge to remain clean during entire operation thereof.
In operation, the protection member 12 advantageously protects the leading edge 16 during the transportation from the friction between the holders and the leading edge thereby protecting it from abrasion. The metal segments 26 facilitate damage protection of the leading edge 16 during handling and movement in the rotor blade manufacturing units. The metal segments 26 safeguard the leading edge 16 when the blade is in the dry and wet finishing area when being held by a holder. Further, the metal segments 26 provide damage protection of the leading edge 16 during commissioning of the blades 14 wherein ropes and ratchet belts are used'in conjunction with blades 14 which would otherwise harm the leading edge 16.
In operation, the metal segments 26 reduce static charge from the blade during the rotational operation of the blades 14 that reduces attraction of dust accumulation on the surface of the blades. The protection member 12 provides very high abrasion resistance by withstanding higher wind velocity impact thereby resulting in restoration of curvature of the leading edge 16 over design life of at least 20 years.

In operation, the metal sheet segments 26 add high strength and durability that enable the protection member 12 to remain on the blade 14 in the best operational form for number of years without any structural failure. Further, the protection member 12 adds erosion resistance to the leading edge in harsh weather conditions. In addition, the metal segments 26 avoid porosity and hence degradation of paint coating of the leading edge 16. The metal sheet segments 26 make the protection member 12 substantially lightweight without increasing overall weight of the blade 14. The protection member 12 is highly cost effective and is capable of being implemented on the serial production.
During manufacturing operation of the blade 14, the protection member 12 eliminates nose contour measurements at the manufacturing locations. These measurements are done to ensure the leading edge contour in manufacturing has been achieved as per the design. The metal segments 26 are made as prefabricated parts as per the leading edge 16 design of the blade 14 and are placed in proximity to the nose. This eliminates the requirement of measuring the nose contour and then subsequently carrying out the necessary repair work thereof.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient,

but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We Claim:
1. A wind turbine blade assembly for preventing debris accumulation on a
leading edge or a nose of a wind turbine blade, the wind turbine blade assembly
comprising:
a protection member including a plurality of metal sheet segments, each of the metal sheet segments having a C-shaped section formed therein, each of the C-shaped sections positioning over the leading edge of the wind turbine blade, the C-shaped sections extending over a predefined length along a suction side and a pressure side of the wind turbine blade, the metal segments facilitating uniform stress distribution during a plurality of flap-wise bending movements of the wind turbine blade, the protection member facilitating surface energy reduction of the leading edge of the wind turbine blade.
2. The wind turbine blade assembly as claimed in claim 1, wherein the predefined length of the C-shaped section is in a range of about 5% to 25% of a total chord length of an aerofoil of the wind turbine blade.
3. The wind turbine blade assembly as claimed in claim 1, wherein the predefined length of the C-shaped section is in a range of about 0.5% to 5% of a radius of the wind turbine blade.
4. The wind turbine blade assembly as claimed in claim 1, wherein the metal segments cover an outer 25 % of a total blade length of the wind turbine blade.
5. The wind turbine blade assembly as claimed in claim 1, wherein the metal sheet segments include a Teflon coating.
6. The wind turbine blade assembly as claimed in claim 5, wherein the metal segments coated with Teflon facilitate high angle of contact that minimizes dirt deposition to keep the leading edge substantially clean.

7. The wind turbine blade assembly as claimed in claim 1, wherein the surface energy achieved by the wind turbine blades is about 14 mN/m.
8. The wind turbine blade assembly as claimed in claim 1, wherein the surface energy reduction further reduces aerodynamic losses which subsequently reduce power production losses.
9. The wind turbine blade assembly as claimed in claim 1, wherein the surface energy reduction reduces debris accumulation on the surface of the wind turbine blade.
10. The wind turbine blade assembly as claimed in claim 1, wherein the protection member 14 facilitates protection to the leading edge of the wind turbine blade during transportation thereof.
11. The wind turbine blade assembly as claimed in claim 1, wherein the protection member facilitates abrasion resistance to the wind turbine blade.