DESC:FIELD OF THE INVENTION:

The invention relates to techniques for measuring and adjusting the angular position of a rotatable blade, and more particularly to an improved method and system for calibration of a wind turbine blade, and to a wind turbine.

BACKGROUND

In equipment such as wind turbines, a rotor axis (e.g. horizontal) defines an axis of rotation of a hub to which blades are attached, and a blade root at one end of the blade is coupled to the hub shell (rotor) via a blade bearing. Prior to operation of the wind turbine, a blade may be rotated – about an axis of elongation thereof substantially transverse to the axis of rotation of the hub – so as to angularly position the blade (root) in alignment with or at a predetermined angle to a reference orientation or reference line on the hub/rotor of a wind turbine.

Typically, the positioning of a blade (root) in alignment with a reference orientation or reference line, i.e. calibration at a 0 degree position, must be performed at the outset, so as to enable determination that the blade is in the 0 degree position, or confirmation of what angle to the 0 degree position the blade is currently at. In this way, the pitch (angle) of the blade (e.g. relative to a reference orientation or reference line) can be set or maintained, in order to ensure safe and optimal or substantially maximized operational efficiency, given the (expected) wind load in the environment.

Due to the limited amount of space in wind turbine housing or nacelle, difficulties arise for a maintenance engineer in accessing the hub/bearing area and carrying out such calibration and/or angular positioning of a blade (root) at a predetermined angle to a reference orientation or reference line (pitch setting).

It is known to use a rotary laser that forms a visible plane of laser light, for example for use in indicating a level on walls in a building environment.

However, to date suitable or optimised solutions do not exist for enabling precise calibration and/or angular positioning of a blade (root) on the hub/rotor of a wind turbine.

The present invention seeks to overcome the aforementioned problems and provide an improved method and system for calibration of a wind turbine blade, and a wind turbine.

OBJECT OF THE INVENTION

It is the object of the invention is to design and develop a method and system for calibration of a wind turbine blade and wind turbine which provides an effective techniques for measuring and adjusting the angular position of a rotatable blade.

Another object of the present invention is to design and develop a method and system for calibration of a wind turbine blade and wind turbine which provides for improved method and system for calibration of a wind turbine blade.

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided a calibration arrangement for calibrating the angular position of a blade of a wind turbine, the calibration arrangement comprising: a projection device, adapted to be mounted on a rotor hub of the wind turbine, the projection device being configured to project visible light in a plane in a first predetermined orientation in relation to the rotor hub; a scale fixedly attached to a blade root of the blade, the blade root being coupled to the rotor hub via a blade bearing, whereby the blade is rotatable about its axis of elongation, the axis lying substantially in the plane; wherein the projection device is fixedly positioned on the rotor hub such that in the first predetermined orientation the plane intersects at least a first rotor marking on the rotor hub; wherein the scale includes thereon a first calibration marking; and wherein, in use, the blade is rotatably positionable on and fixable to the rotor hub whereby the plane intersects the first calibration marking, thereby calibrating the blade at an angular position of 0 degrees in relation to the rotor hub.

Preferably, in the first predetermined orientation the plane intersects at least a first rotor marking, a second rotor marking and a third rotor marking on the rotor hub.

In one embodiment, a first set and a second set of rotor markings are disposed on the rotor hub, the rotor markings of the first set and a second set lying in planes orthogonal to each other.

In one embodiment, the first rotor marking, a second rotor marking and a third rotor marking comprise the first set of rotor markings. A fifth rotor marking, a sixth rotor marking and a seventh rotor marking may comprise the second set of rotor markings and correspond to a second predetermined orientation of the plane.

Preferably, the scale comprises a plurality of linearly arranged angle markings. Preferably, adjacent angle markings on the scale are separated by predetermined spacing. Preferably, the predetermined spacing corresponds to k degrees of rotation, where k lies in the range 0.1-2.0, more preferably 0.2-1.0, and more preferably 0.2-0.5.

Preferably, the first calibration marking and/or the angle markings each comprise a line or strip extending perpendicular to the axis of elongation of the scale.

Preferably, the first calibration marking and/or the angle markings extend along or parallel to the plane.

Preferably, the projection device comprises a rotary laser.

According to another aspect of the invention there is provided a calibration method for calibrating the angular position of a blade of a wind turbine, the calibration method characterized by comprising: providing a calibration arrangement according to any of claims 1 to 11 of the appended claims; mounting the projection device on a rotor hub of the wind turbine such that in the first predetermined orientation the plane intersects at least a first rotor marking (M1) on the rotor hub; fixedly attaching the scale to a blade root of the blade; rotating the blade about the axis to a position in which the plane intersects the first calibration marking (M4); and fixing the blade in the position on the rotor hub, thereby calibrating the blade at an angular position of 0 degrees in relation to the rotor hub.

According to another aspect of the invention there is provided a wind turbine comprising: a rotor hub; a blade bearing; a plurality of blades coupled to the rotor hub via the blade bearing; and, for at least one blade, a calibration arrangement according to any of claims 1 to 11 of the appended claims.
An advantage of the invention is that the calibration of the blade (angle/pitch) of a wind turbine is facilitated and/or expedited.

A further advantage is reduced measurement inaccuracy and/or high repeat accuracy.

A further advantage is that the measuring arrangement or the laser plane is not disturbed by the reinforcement member. With known mechanical solutions, there are angular errors.

A further advantage of the invention is that, in embodiments, it provides an inexpensive solution as an inexpensive rotating laser can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention will become apparent from the drawings according to the description. In the drawings:

Figure 1 (PRIOR ART) shows a known wind turbine with multiple blades; and
Figure 2 shows a perspective, partially cut-away view of a coupling of a blade root to the (rotor) hub of Figure 1, showing a calibration arrangement according to an embodiment of the invention.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures. Any ambiguity or confusion in relation to the functioning/working of the present invention can be understood by way of conjoint reading of detailed description in light of the drawings annexed herewith.
DETAILED DESCRIPTION OF THE INVENTION

Figure 1 (PRIOR ART) shows a known wind turbine (1) with multiple blades. The wind turbine (1) includes a tower (3) and a nacelle (2) rotatably mounted on the tower (3). The nacelle (2) comprises a nacelle cover (4) mounted on a main frame (not shown), which will be discussed in further detail below. On a rotor shaft (not shown) inside the nacelle (2) a rotor (7) is arranged, which in turn comprises a hub (5) and at least one rotor blade (6) (here, three).

Near the axis of the hub (5), an end portion or blade root (8) of blade (6) is retained in place, e.g. within jacket (9). In use, hub (5) is rotatable about the z-axis, and during installation, maintenance and/or calibration, blade (6) is rotatable about the x-axis, as described in further detail hereinafter. In this embodiment, the blade (6) is made of glass fibre. However, it will be appreciated that the blade (6) may be made of other materials, such as carbon or carbon composites.

Figure 2 shows a perspective, partially cut-away view of a coupling of a blade root (8) to the (rotor) hub (5) of Figure 1, showing a calibration arrangement (11) according to an embodiment of the invention. The disposition of one calibration arrangement (11) for one blade is shown; and it will be appreciated that a calibration arrangement (11) may be used for one, two or all of the blades (6).

As seen in Figure 2, blade root (8) is coupled to (rotor) hub (5) via blade bearing (10), whereby rotation of the blade root relative to the hub (5) is facilitated by blade bearing raceway (12) of bearing (10). Preferably, a blade reinforcement member (13) is provided (e.g. made of steel), for reinforcing the structure in the region of the blade bearing (10). The hub (5) includes on an inner portion thereof an annular shoulder (14) terminating in an annular ring (15) defining an axially extending first annular surface (16). In this embodiment, on the first annular surface (16) are provided fixed first and second rotor markings M1, M2, which are diametrically opposed on first annular surface (16). In addition, a fixed third rotor marking M3 is provided on another portion of the hub (5) axially spaced apart from rotor marking M1, e.g. on bracket (23) fixed to second annular surface (24). The marking may be made of a luminescent material so as to luminesce when exposed to light, e.g. laser light. The first rotor marking (M1), a second rotor marking (M2) and a third rotor marking (M3) comprise the first set of rotor markings.

Optionally, on the first annular surface (16) are provided fixed fifth and sixth rotor markings M5, M6, which are diametrically opposed on first annular surface (16). In addition, a fixed seventh rotor marking M7 is provided on another portion of the hub (5) axially spaced apart from rotor marking M1. In this way, the fifth rotor marking (M5), sixth rotor marking (M6) and seventh rotor marking (M7) comprise the second set of rotor markings and correspond to a second predetermined orientation of the plane (18). The first set and a second set of rotor markings are disposed on the hub (5) such that the rotor markings of the first set and a second set lie in planes orthogonal to each other.

Each of the markings M1, M2, M3, M5, M6 and M7 may be on the first annular surface (16) by adhesive or magnetic bonding or similar. Alternatively, the markings M1, M2, M3, M5, M6 and M7 can be mechanically incorporated into the hub, that is when the hub is processed at a milling centre, to planar mill the surfaces for the blade bearing.

In accordance with this embodiment of the invention, the calibration arrangement (11) comprises a projection device (17) fixedly mounted on upper surface (27) of annular ring (15), e.g. by bolting or via a magnetic base (not shown), and/or by adhesive bonding. In embodiments, the projection device (17) comprises a rotary laser, e.g. as described in DE10054627C2 or DE102013217479A1. However, it will be appreciated that other projection devices may be used. In operation, the projection device (17) produces a beam of visible light (e.g. a high speed rotating beam) that appear as a planar sheet of light or plane (18).

In accordance with this embodiment of the invention, the calibration arrangement (11) further comprises a scale (20) fixedly bonded to second annular surface (19), e.g. by strong adhesive, and so as to extend generally circumferentially over a small arc. The scale includes a plurality of linearly arranged angle markings (21) that are separated by predetermined spacing. The predetermined spacing may correspond to k degrees of rotation about the x-axis, where k lies in the range 0.1-2.0, more preferably 0.2-1.0, and more preferably 0.2-0.5. For example, rotation of blade 8 so that a point of intersection of plane (18) moves from one angle marking (21) to the next may correspond to rotation about the x-axis by 1 degree of arc.

Also provided on scale (20) is a calibration marking M4, as will be discussed in further detail below.

In accordance with this embodiment, the first calibration marking M4 and/or the angle markings (21) each comprise a line or strip extending perpendicular to the axis of elongation of the scale (20). Also, the first calibration marking M4 and/or the angle markings (21) may extend along or parallel to the plane (18).

For calibration, the calibration arrangement (11) is installed and set up as described above. The plane (18) is formed by the projection device (17). Then, drive is applied (e.g. via gears (25, 26)) so as to impart rotation about the x-axis to blade root (8). Once the calibration marking M4 is brought into alignment with the plane (18), rotation is ceased, and the blade root (8) is fixed to the hub (5) (e.g. by means of bolting). The blade (6) is thus accurately located in the 0 degree (calibration) position.

Subsequently, further rotation of the blade root may be performed (e.g. using an external drive and via gears (25, 26)) to alter the pitch angle of the blade (6), the amount of angle being visible on scale (20).

List of Reference Signs

1 wind turbine
2 nacelle
3 tower
4 nacelle cover
5 hub
6 rotor blade
7 rotor
8 blade root
9 jacket
10 blade bearing
11 calibration arrangement
12 blade bearing raceway
13 blade reinforcement member
14 annular shoulder
15 annular ring
16 first annular surface
17 projection device
18 plane
19 second annular surface
20 scale
21 angle marking
23 bracket
24 second annular surface
25 gear
26 gear
27 upper surface

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly not limited.
,CLAIMS:CLAIMS

We claim:

1. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1), the calibration arrangement (11) comprising:

- a projection device (17), adapted to be mounted on a rotor hub (5) of the wind turbine (1), the projection device (17) being configured to project visible light in a plane (18) in a first predetermined orientation in relation to the rotor hub (5);

- a scale (20) fixedly attached to a blade root (8) of the blade (6), the blade root (8) being coupled to the rotor hub (5) via a blade bearing (10), whereby the blade (6) is rotatable about its axis (x) of elongation, the axis (x) lying substantially in the plane (18);

wherein the projection device (17) is fixedly positioned on the rotor hub (5) such that in the first predetermined orientation the plane (18) intersects at least a first rotor marking (M1) on the rotor hub (5);

wherein the scale (20) includes thereon a first calibration marking (M4); and

wherein, in use, the blade (6) is rotatably positionable on and fixable to the rotor hub (5) whereby the plane (18) intersects the first calibration marking (M4), thereby calibrating the blade (6) at an angular position of 0 degrees in relation to the rotor hub (5).

2. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 1,wherein in the first predetermined orientation the plane (18) intersects at least a first rotor marking (M1), a second rotor marking (M2) and a third rotor marking (M3) on the rotor hub (5).

3. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 1, wherein a first set and a second set of rotor markings are disposed on the rotor hub (5), the rotor markings of the first set and a second set lying in planes (18) orthogonal to each other.

4. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 3, wherein the first rotor marking (M1), a second rotor marking (M2) and a third rotor marking (M3) comprise the first set of rotor markings.

5. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 3, wherein a fifth rotor marking (M5), a sixth rotor marking (M6) and a seventh rotor marking (M7) comprise the second set of rotor markings and correspond to a second predetermined orientation of the plane (18).

6. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 1, wherein the scale (20) comprises a plurality of linearly arranged angle markings (21).

7. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 6, wherein the adjacent angle markings (21) on the scale (20) are separated by predetermined spacing.

8. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 7, wherein the predetermined spacing corresponds to k degrees of rotation, where k lies in the range 0.1-2.0, more preferably 0.2-1.0, and more preferably 0.2-0.5.

9. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 1, wherein the first calibration marking and/or the angle markings (21) each comprise a line or strip extending perpendicular to the axis of elongation of the scale (20).

10. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 1, wherein the first calibration marking and/or the angle markings (21) extend along or parallel to the plane (18).

11. A calibration arrangement (11) for calibrating the angular position of a blade (6) of a wind turbine (1) as claimed in claim 1, wherein the projection device (17) comprises a rotary laser.

12. A calibration method for calibrating the angular position of a blade (6) of a wind turbine (1), the calibration method characterized by comprising:

- providing a calibration arrangement (11) according to any of the preceding claims;
- mounting the projection device (17) on a rotor hub (5) of the wind turbine (1) such that in the first predetermined orientation the plane (18) intersects at least a first rotor marking (M1) on the rotor hub (5);
- fixedly attaching the scale (20) to a blade root (8) of the blade (6);
- rotating the blade (6) about the axis to a position in which the plane (18) intersects the first calibration marking (M4);
- fixing the blade (6) in the position on the rotor hub (5), thereby calibrating the blade (6) at an angular position of 0 degrees in relation to the rotor hub (5).

13. A wind turbine (1) comprising:
- a rotor hub (5);
- a blade bearing (10);
- a plurality of blades (6) coupled to the rotor hub (5) via the blade bearing (10); and, for at least one blade (6),
- a calibration arrangement (11) according to any one of claims 1 to 11.