BACKGROUND OF THE INVENTION
The subject matter described herein relates generally to methods
and systems for the maintenance of wind turbines, and more particularly, to methods
and systems for avoiding sounds from loose particles moving around freely in the
interior of wind turbine rotor blades.
At least some known wind turbines include a tower and a nacelle
mounted on the tower. A rotor is rotatably mounted to the nacelle and is coupled to a
generator by a shaft. A plurality of blades extend from the rotor. The blades are oriented
such that wind passing over the blades turns the rotor and rotates the shaft, thereby
driving the generator to generate electricity.
The blades are generally hollow, their bodies include laminates
including glass fibre and resin. Typically, two halves are laminated together during the
manufacturing process of a rotor blade. After the rotor blade is produced by joining the
two halves, on the inside of the blade some fibers of the laminate may stick out of the
inner surface or the like. During subsequent operation of the wind turbine, as the blade is
subject to changing loads resulting in slight deformation of its body, fibers and particles
may become loose. As a result, after some time a number of loose particles may build up
in the interior of the blade. These particles have typical sizes from about 0.2 cm to 4 cm.
This is undesirable, as they move around during operation of the
turbine, or even during idle operation of the turbine, when the blades are in a feathered
position. This may lead to damage if, e.g., bigger pieces hit a sensor inside the rotor
blade. A further disadvantage is that once a certain number of particles are moving inside
the blade, the sound of the particles sliding along the interior of the blade is audible
outside the turbine as a kind of noise. Though this is only audible during idle or
standtstill of the turbine, as during operation there are many louder sound sources, it is
2
still not desirable. For instance, persons not informed about the cause of the sound may
tend to think that there is a malfunction in the turbine.
In view of the above, it is desirable to have a method and system
for avoiding the sounds caused by loose particles inside rotor blades.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, a particle trap for collecting loose particles in a
rotor blade is provided. The particle trap includes a container having an enclosure and at
least one opening, and a feed hopper, wherein the feed hopper is connected to the at least
one opening of the container, and wherein the particle trap is adapted for collecting
particles moving in a direction of an opening of the feed hopper.
In another aspect, a wind turbine is provided. The turbine
includes a tower, a nacelle, a rotor having at least one rotor blade, and at least one
particle trap located inside the at least one rotor blade, wherein the particle trap includes
at least one container having at least one opening.
In yet another aspect, a method of collecting particles inside a
wind turbine rotor blade is provided. The method includes providing a container inside
the wind turbine rotor blade, having at least one opening; and turning the wind turbine
rotor.
Further aspects, advantages and features of the present
invention are apparent from the dependent claims, the description and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A full and enabling disclosure including the best mode thereof,
to one of ordinary skill in the art, is set forth more particularly in the remainder of the
specification, including reference to the accompanying figures wherein:
Fig. 1 is a perspective view of an exemplary wind turbine.
3
Fig. 2 is an enlarged sectional view of a portion of the wind
turbine shown in Fig. 1.
Figs. 3 to 6 are different views of a particle trap according to
embodiments.
Fig. 7 is a view of a wind turbine with three particle traps,
according to embodiments.
Fig. 8 is a sectional view of the wind turbine rotor blade of the
wind turbine of Fig. 7.
Fig. 9 is another cross sectional view of the wind turbine rotor
bladeof Fig. 7.
Fig. 10 is a view of a wind turbine according to embodiments,
including two detailed sectional views.
Figs. 11 to 13 are schematic views of a wind turbine rotor
according to embodiments.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the various
embodiments, one or more examples of which are illustrated in each figure. Each
example is provided by way of explanation and is not meant as a limitation. For
example, features illustrated or described as part of one embodiment can be used on or
in conjunction with other embodiments to yield yet further embodiments. It is intended
that the present disclosure includes such modifications and variations.
The embodiments described herein include a particle trap, a
wind turbine system and a method that enable the collection of loose particles inside a
rotor blade.
As used herein, the term "particle" is intended to representative
of any element which does not have a structural connection to any part of the rotor
4
blade, and which moves freely inside the blade. Particles are not limited to any kind of
material, and not limited to a certain origin or source. As used herein, the term "blade"
is intended to be representative of any device that provides a reactive force when in
motion relative to a surroimding fluid. As used herein, the term "wind turbine" is
intended to be representative of any device that generates rotational energy from wind
energy, and more specifically, converts kinetic energy of wind into mechanical energy.
As used herein, the term "wind generator" is intended to be representative of any wind
turbine that generates electrical power from rotational energy generated from wind
energy, and more specifically, converts mechanical energy converted from kinetic
energy of wind to electrical power.
Figure 1 is a perspective view of an exemplary wind turbine 10.
In the exemplary embodiment, wind turbine 10 is a horizontal-axis wind turbine.
Alternatively, wind turbine 10 may be a vertical-axis wind turbine. In the exemplary
embodiment, wind turbine 10 includes a tower 12 that extends from a support system
14, a nacelle 16 mounted on tower 12, and a rotor 18 that is coupled to nacelle 16.
Rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and
extending outward from hub 20. In the exemplary embodiment, rotor 18 has three rotor
blades 22. In an alternative embodiment, rotor 18 includes more or less than three rotor
blades 22. In the exemplary embodiment, tower 12 is fabricated from tubular steel to
define a cavity (not shown in Figure 1) between support system 14 and nacelle 16. In
an alternative embodiment, tower 12 is any suitable type of tower having any suitable
height.
Rotor blades 22 are spaced about hub 20 to facilitate rotating
rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical
energy, and subsequently, electrical energy. Rotor blades 22 are mated to hub 20 by
coupling a blade root portion 24 to hub 20 at a plurality of load transfer regions 26.
Load transfer regions 26 have a hub load transfer region and a blade load transfer region
(both not shown in Figure 1). Loads induced to rotor blades 22 are transferred to hub 20
via load transfer regions 26.
5
In one embodiment, rotor blades 22 have a length ranging from
about 15 meters (m) to about 91 m. Alternatively, rotor blades 22 may have any
suitable length that enables wind turbine 10 to function as described herein. For
example, other non-limiting examples of blade lengths include 10 m or less, 20 m, 37
m, or a length that is greater than 91m. As wind strikes rotor blades 22 from a direction
28, rotor 18 is rotated about an axis of rotation 30. As rotor blades 22 are rotated and
subjected to centrifugal forces, rotor blades 22 are also subjected to various forces and
moments. As such, rotor blades 22 may deflect and/or rotate from a neutral, or nondeflected,
position to a deflected position.
Moreover, a pitch angle or blade pitch of rotor blades 22, i.e.,
an angle that determines a perspective of rotor blades 22 with respect to direction 28 of
the wind, may be changed by a pitch adjustment system 32 to control the load and
power generated by wind turbine 10 by adjusting an angular position of at least one
rotor blade 22 relative to wind vectors. Pitch axes 34 for rotor blades 22 are shown.
During operation of wind turbine 10, pitch adjustment system 32 may change a blade
pitch of rotor blades 22 such that rotor blades 22 are moved to a feathered position, such
that the perspective of at least one rotor blade 22 relative to wind vectors provides a
minimal surface area of rotor blade 22 to be oriented towards the wind vectors, which
facilitates reducing a rotational speed of rotor 18 and/or facilitates a stall of rotor 18.
In the exemplary embodiment, a blade pitch of each rotor blade
22 is controlled individually by a control system 36. Alternatively, the blade pitch for
all rotor blades 22 may be controlled simultaneously by control system 36. Further, in
the exemplary embodiment, as direction 28 changes, a yaw direction of nacelle 16 may
be controlled about a yaw axis 38 to position rotor blades 22 with respect to direction
28.
In the exemplary embodiment, control system 36 is shown as
being centralized within nacelle 16, however, control system 36 may be a distributed
system throughout wind turbine 10, on support system 14, within a wind farm, and/or at
a remote control center. Control system 36 includes a processor 40 configured to
perform the methods and/or steps described herein. Further, many of the other
6
components described herein include a processor. As used herein, the term "processor"
is not limited to integrated circuits referred to in the art as a computer, but broadly refers
to a controller, a microcontroller, a microcomputer, a programmable logic controller
(PLC), an application specific integrated circuit, and other programmable circuits, and
these terms are used interchangeably herein. It should be understood that a processor
and/or a control system can also include memory, input channels, and/or output
channels.
In the embodiments described herein, memory may include,
without limitation, a computer-readable medium, such as a random access memory
(RAM), and a computer-readable non-volatile medium, such as flash memory.
Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magnetooptical
disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in
the embodiments described herein, input channels include, without limitation, sensors
and/or computer peripherals associated with an operator interface, such as a mouse and
a keyboard. Further, in the exemplary embodiment, output channels may include,
without limitation, a control device, an operator interface monitor and/or a display.
Processors described herein process information transmitted
from a plurality of electrical and electronic devices that may include, without limitation,
sensors, actuators, compressors, control systems, and/or monitoring devices. Such
processors may be physically located in, for example, a control system, a sensor, a
monitoring device, a desktop computer, a laptop computer, a programmable logic
controller (PLC) cabinet, and/or a distributed control system (DCS) cabinet. RAM and
storage devices store and transfer information and instructions to be executed by the
processor(s). RAM and storage devices can also be used to store and provide temporary
variables, static (i.e., non-changing) information and instructions, or other intermediate
information to the processors dixring execution of instructions by the processor(s).
Instructions that are executed may include, without limitation, wind turbine control
system control commands. The execution of sequences of instructions is not limited to
any specific combination of hardware circuitry and software instructions.
7
Figure 2 is an enlarged sectional view of a portion of wind
turbine 10. In the exemplary embodiment, wind turbine 10 includes nacelle 16 and hub
20 that is rotatably coupled to nacelle 16. More specifically, hub 20 is rotatably coupled
to an electric generator 42 positioned within nacelle 16 by rotor shaft 44 (sometimes
referred to as either a main shaft or a low speed shaft), a gearbox 46, a high speed shaft
48, and a coupling 50. In the exemplary embodiment, rotor shaft 44 is disposed coaxial
to longitudinal axis 116. Rotation of rotor shaft 44 rotatably drives gearbox 46 that
subsequently drives high speed shaft 48. High speed shaft 48 rotatably drives generator
42 with coupling 50 and rotation of high speed shaft 48 facilitates production of
electrical power by generator 42. Gearbox 46 and generator 42 are supported by a
support 52 and a support 54. In the exemplary embodiment, gearbox 46 utilizes a dual
path geometry to drive high speed shaft 48. Alternatively, rotor shaft 44 is coupled
directly to generator 42 with coupling 50.
Nacelle 16 also includes a yaw drive mechanism 56 that may be
used to rotate nacelle 16 and hub 20 on yaw axis 38 (shown in Figure 1) to control the
perspective of rotor blades 22 with respect to direction 28 of the wind. Nacelle 16 also
includes at least one meteorological mast 58 that includes a wind vane and anemometer
(neither shown in Figure 2). Mast 58 provides information to control system 36 that
may include wind direction and/or wind speed. In the exemplary embodiment, nacelle
16 also includes a main forward support bearing 60 and a main aft support bearing 62.
Forward support bearing 60 and aft support bearing 62 facilitate
radial support and alignment of rotor shaft 44. Forward support bearing 60 is coupled to
rotor shaft 44 near hub 20. Aft support bearing 62 is positioned on rotor shaft 44 near
gearbox 46 and/or generator 42. Alternatively, nacelle 16 includes any number of
support bearings that enable wind turbine 10 to function as disclosed herein. Rotor
shaft 44, generator 42, gearbox 46, high speed shaft 48, coupling 50, and any associated
fastening, support, and/or securing device including, but not limited to, support 52
and/or support 54, and forward support bearing 60 and aft support bearing 62, are
sometimes referred to as a drive train 64.
8
Fig. 3 shows a side view of a particle trap 120 according to
embodiments. The trap includes a container 130 having an opening 135. Formed into
container 130 is a feed hopper 140, typically forming a part of the container. Typically,
the container has the basic shape of a cuboid, wherein one side face of the cuboid is
replaced by the larger opening 142 of feed hopper 140, whereas the smaller opening of
the feed hopper is typically identical with the opening 135 of the container.
Fig. 4 shows a cross-sectional side view of particle trap 120 of
Fig. 3. Fig. 5 shows a top view of the particle trap 120 of Fig. 3.
In embodiments, the particle trap 120 includes cardboard or a
polymer, for instance, polyethylene, PET, polyester, combinations thereof, or a similar
material. Also fibre/resin materials are suitable, like glass fibre or carbon fibre
compound. There are no particular restrictions on the material in terms of structural
features, as long as the trap may be formed from it to be stable enough to carry its own
weight in any direction while being mounted at one face, without being deformed.
Fig. 6 is a perspective view of the particle trap 120 of Fig. 3
according to embodiments, with an additional tube section 136 connected to the opening
135. The tube section may further improve the trapping capabilities. In Fig. 6, typical
dimensions of an embodiment of a particle trap are marked as a, b, c, and d. The
dimensions are strongly dependent on the size of the wind turbine in which the trap is
employed, and more specifically on the dimensions, shape and inner structure of the
rotor blades. Exemplary ranges for wind turbines with a power output from 1.5 to 3
MW are: Dimensions a and b fi:om 1 m to 3 m, more typically from 1.5 m to 2.5 m;
dimension c from 0.15 m to 0.8 m, more typically fi-om 0.2 m to 0.5 m. The area of
opening 135 of the feed hopper may have a size fi-om 0.005 m^ up to 0.2 m^, more
typically from 0.01 m to 0.1 m . The opening typically has a rectangular, square or
round shape; also other forms of the opening 135 are possible. Dimension d is the
distance between opening 135 and the larger opening 142 of the feed hopper.
Dimension d may be from 0.5 m to 2.8 m, more typically from 1.2 m to 2 m.
9
According to embodiments, the particle trap is typically located
inside a rotor blade 22 of a wind turbine 10, as shown in Fig. 7. In the embodiment,
three traps 120 are located in a-root portion 24 of a rotor blade 22 each. Typically, the
larger openings 142 of the feed hoppers 140 are directed in a direction of the tip
portions 160 of the rotor blades 22. For illustrational purposes, the rotor blades 22 in
Fig. 7 are shown in a position where the pitch angle has a maximum. For the collection
of particles according to embodiments, the rotor blades are typically, but not
necessarily, positioned differently, typically in a feathered position, which is laid out
further below.
Generally, particle traps 120 according to embodiments may be
positioned at any position inside the rotor blade 22, and the opening 142 may be
directed into a variety of directions, for instance, facing towards the tip region of the
blade, towards the root portion, or in an oblique angle with respect to the longitudinal
axis of the blade. If the trap is positioned close to a root portion, the accessibility for
maintenance is optimal. In case of maintenance, the trap may be cleaned of particles by
service persormel, e.g. using a type of vacuum cleaner. For this purpose, an extra
opening may be provided in the container section.
Fig. 8 is a cross sectional view through rotor blade 22. Fig. 9
shows another cross-sectional view of the rotor blade 22 and the trap 120. The larger
opening 142 of the feed hopper 140 is typically replacing one of the side faces of the
container 130. In other embodiments (not shown), the feed hopper may be formed as a
device separate from the container, and its smaller opening may be cormected to an
opening in a side face of container 130.
As can be seen in Fig. 9, which shows two cross sectional views
of the root portion 150 of embodiments of the wind turbine of Fig. 7, the particle trap is
mounted to one of the irmer faces of the rotor blade 22. In the upper part of Fig. 9, it is
mounted to an irmer face 137, and in the lower part of Fig. 9 it is mounted to an inner
face 138. Both options may be applied, they may even be combined in one rotor blade.
The container 130 of trap 120, which is basically a cuboid, can be mounted to an inner
face 137, 138 of the blade 22 by any suitable method such as gluing, laminating, using
10
screws, or other fixation methods known to the skilled person. The container 130,
respectively trap 120, may be produced to have a certain curvature in order to be able to
be seamlessly mounted to the inner face of blade 22. In other embodiments not shown,
the trap may also be located at other positions inside the rotor blade, for instance at the
inner faces close to or at the trailing edge or the leading edge. In these cases, the form of
the container has to be adapted due to the limitations of available space in those regions
of the blade.
If the particle trap is typically formed as a cuboid having
straight sides without any curvature, the material should provide enough flexibility, so
that the particle trap may be slightly deformed during mounting, so that the face of the
particle trap 130 contacting the irmer face of the blade may be seamlessly coimected
such as shown in the upper part of Fig. 9. If the particle trap is formed from cardboard,
for instance, a thickness of the material of 1 to 3 mm may provide for enough flexibility
of the trap.
To determine the best type and thickness of the material in
terms of both stability of the trap and flexibility for mounting, the properties of the
material, the dimensions of the trap and the curvature of the iimer face of the blade
should be taken into account, which is a standard task for a skilled person. The
appropriate outer dimensions of the particle traps according to embodiments are
strongly dependent on the dimensions of the wind turbine rotor blades in which they are
applied. Suitable dimensions will be easily derived by the skilled person from the
illustrations provided and this description. Further, depending on the individual use
case, the form of the particle trap may have to be modified from the examples
described, for instance when taking into account particular geometrical limitations by
structural elements inside a rotor blade.
Fig. 10 shows a wind turbine 10 according to embodiments,
having two particle traps 120 located in each rotor blade 22. One trap is positioned in
the root section 150 and one trap is located in the tip section 160 of each blade 22. The
two detailed sectional views on the right of Fig. 10 show the trap 120 in the root section
24 (above) and the trap 120 in the tip section 160 (below). As can be seen in the detailed
11
sectional views, the larger openings 142 of the feed hoppers 140 are each directed to the
respective other end section of the rotor blade 22.
Figs. 11 to 13 show partial views (only one rotor blade for
illustrational purposes) of a wind turbine rotor having a rotatable hub 20 and a rotor
blade 22 mounted thereto. The rotor blade is shown in different rotational angles about
the rotational axis of hub 20, illustrating the different positions of a rotor blade when the
rotor of a wind turbine 10 according to embodiments is turned. The rotor blade is
typically in a feathered position, which complies to the typical pitch angle during idle or
standstill of the wind turbine. When the particle trap 120 is located inside rotor blade 22
as shown before, the feathered position of the blades is typically the most appropriate
position for the trap to work as described. The wind turbine is, in this particular case, in
idle mode and typically does not produce electricity. The rotor is turned at a slow rate
by the wind, for instance at 0.1 to 1.5 rotations per minute, because the rotor blades in a
feathered (idle) position do not exert a significant torque. Hence, in the embodiments
described, the rotor moves significantly slower than during normal operation of the
turbine and the blades are in a feathered position.
In other embodiments, particularly if the trap is/are located at
different positions than shown in Figs. 11 to 13, other pitch angles of the blades may
allow collection of particles with the traps 120 as well. For instance, if a trap is located
close to a trailing edge in the rotor blade 22, particles may also be collected during
normal operation of the wind turbine, i.e., when the rotor blades have a pitch angle
significantly different from the pitch angle according to a feathered position.
In Fig. 11, the rotor blade is moving upwards. As can be seen in
the sectional view of the rotor blade 22 at root section 24, particles 200 moving around
freely inside rotor blade 22 are sliding/moving through gravitational forces in a
direction to the larger opening 142 of the feed hopper 140 of particle trap 120. As
shown, two particles are already inside feed hopper 140, where they are guided by the
faces of the feed hopper in a direction of the opening 135 of the container 130 of trap
120.
12
In Fig. 12, the rotor has proceeded further in its rotational
movement, and the rotor blade 22 is almost vertical. The sectional view on the right
shows how particles 200 are falling into container 130 of trap 120. Some particles have
already passed opening 135, some have fallen down to the lowest face (with respect to a
ground level) of the container 130.
Fig. 13 shows a further advanced position of rotor blade 22
during the turning of the rotor. All particles 200 shown in previous Figs. 11 and 12 are
collected in the container 130 of trap 120. As the rotor has advanced and the larger
opening 142 of the feed hopper 140 is now facing left/downwards, the particles 200
have slided along irmer faces of the container 130, whereby they did not pass the
opening 135. As is obvious, when the rotor proceeds in turning from the position shown
in Fig. 13, the particles 200 will sHde along the irmer faces of container 130 of trap 120,
but will not fall out through opening 135. Thus, they are trapped inside particle trap 120
and are no longer able to move around along the inside of rotor blade 22, where they
could cause noise or even damage.
If the particle trap is designed for the trapping of particles
during normal operation of the wind turbine, the above described process may be
influenced by centripetal forces acting on the particles due to faster movement of the
rotor. In this case, it may be appropriate to add a second particle trap 120 in each rotor
blade, located in the tip section 160, as shown in Fig 10.
The above-described systems and methods facilitate to
collect freely moving particles from the inside of wind turbine rotor blades. More
specifically, they prevent freely moving particles from causing noise and/or damage.
Exemplary embodiments of systems and methods for particle
traps for collecting loose particles in wind turbines are described above in detail. The
systems and methods are not limited to the specific embodiments described herein, but
rather, components of the systems and/or steps of the methods may be utilized
independently and separately from other components and/or steps described herein. For
example, they may be used in other cavities which need to be cleaned of loose particles,
13
and are not limited to practice with only the wind turbine systems as described herein.
Rather, the exemplary embodiment can be implemented and utilized in connection with
many other rotor blade applications.
Although specific features of various embodiments of the
invention may be shown in some drawings and not in others, this is for convenience
only. In accordance with the principles of the invention, any feature of a drawing may
be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the
invention, including the best mode, and also to enable any person skilled in the art to
practice the invention, including making and using any devices or systems and
performing any incorporated methods. While various specific embodiments have been
disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope
of the claims allows for equally effective modifications. Especially, mutually nonexclusive
features of the embodiments described above may be combined with each
other. The patentable scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other examples are intended
to be within the scope of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include equivalent structural elements
with insubstantial differences from the literal language of the claims.

WE CLAIM:
1. A particle trap for collecting loose particles in a rotor blade, comprising:
a) a container having an enclosure and at least one opening,
b) a feed hopper,
wherein the feed hopper is connected to the at least one opening of the container, and
wherein the particle trap is adapted for collecting particles moving in a direction of an
opening of the feed hopper.
2. The particle trap of claim 1, wherein the feed hopper is formed as a part of the
container.
3. The particle trap of claims 1 or 2, wherein the container is comprising cardboard or a
polymer.
4. The trap of any preceding claim, wherein the container is a cuboid.
5. The particle trap of claim 4, wherein the feed hopper is formed as a part of the
container such that a wider opening of the feed hopper replaces one of the side faces of
the cuboid, and that the smaller opening of the feed hopper lies inwardly from the wider
opening with respect to a center of the container.
6. A wind turbine, comprising a particle trap according to any of claims 1 to 5.
7. The wind turbine of claim 6, wherein the container is mounted to an inner face of the
rotor blade.
8. The wind turbine of any preceding claim, wherein the at least one container is located
in a root portion and/or a tip portion of the rotor blade.
9. The wind turbine of any preceding claim, wherein the at least one opening of the
container located in an end portion of the rotor blade faces towards the opposite end
portion of the rotor blade.
15
10. A method of collecting particles inside a wind turbine rotor blade, comprising:
- providing a container having at least one opening inside the wind turbine rotor
blade; and,
- turning the wind turbine rotor.