U.S. patent application number 13/973131 was filed with the patent office on 2015-02-26 for system and method for deicing wind turbine rotor blades.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is General Electric Company. Invention is credited to Philippe Giguere, Bart Jan Veldkamp.
Application Number | 20150056074 13/973131 |
Document ID | / |
Family ID | 52446912 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150056074 |
Kind Code |
A1 |
Veldkamp; Bart Jan ; et
al. |
February 26, 2015 |
SYSTEM AND METHOD FOR DEICING WIND TURBINE ROTOR BLADES
Abstract
A system and method for deicing a wind turbine rotor blade
includes simultaneously directing heated air through an internal
leading edge circulation loop and a separate internal trailing edge
circulation loop within the rotor blade.
Inventors: |
Veldkamp; Bart Jan;
(Enschede, NL) ; Giguere; Philippe; (Simpsonville,
SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
52446912 |
Appl. No.: |
13/973131 |
Filed: |
August 22, 2013 |
Current U.S.
Class: |
416/1 ;
416/39 |
Current CPC
Class: |
F01D 17/02 20130101;
Y02E 10/722 20130101; Y02E 10/72 20130101; F03D 80/40 20160501;
Y02E 10/721 20130101; F03D 1/0675 20130101 |
Class at
Publication: |
416/1 ;
416/39 |
International
Class: |
F01D 17/02 20060101
F01D017/02 |
Claims
1. A rotor blade for a wind turbine with integrated deicing
capability, the rotor blade comprising: a blade root; a blade tip;
a leading edge and a trailing edge extending between the blade tip
and blade root; structural members disposed within an internal
volume of the rotor blade; the structural members defining a
leading edge fluid circulation loop and a separate trailing edge
fluid circulation loop; and a fluid handling system disposed within
the internal volume of the rotor blade and configured with the
structural members so as to direct a heated fluid medium through
the leading edge and trailing edge fluid circulation loops.
2. The rotor blade as in claim 1, wherein, the structural members
define a span-wise extending middle circulation channel that is
common to the leading edge and the trailing edge fluid circulation
loops.
3. The rotor blade as in claim 2, wherein the structural members
comprise a first web disposed proximate to the leading edge and
defining a leading edge channel of the leading edge fluid
circulation loop, and a second web disposed proximate to the
trailing edge and defining a trailing edge channel of the trailing
edge fluid circulation loop, the middle circulation channel defined
between the first and second webs.
4. The rotor blade as in claim 2, wherein the fluid handling system
comprises at least one fan heater disposed within the blade root so
as to direct a heated outflow airstream through the leading edge
and trailing edge fluid circulation loops.
5. The rotor blade as in claim 4, wherein the fan heater is
disposed so as to direct the outflow airstream along the middle
circulation channel to adjacent the blade tip where the heated
outflow airstream separates into separate return airstreams that
flow through the leading edge and the trailing edge channels,
respectively, back to the blade root.
6. The rotor blade as in claim 4, wherein the fan heater is
disposed so as to direct the outflow airstream as separate streams
through the leading edge and trailing edge channels, wherein the
separate streams combine adjacent the blade tip into a single
return airstream through the middle circulation channel and back to
the blade root.
7. The rotor blade as in claim 4, wherein the heated outflow
airstream is a single airstream within the middle circulation
channel such that the leading edge and the trailing edge fluid
circulation loops share a combined outflow portion through the
middle fluid circulation channel.
8. The rotor blade as in claim 4, further comprising separating
structure within the middle circulation channel such that the
leading edge and the trailing edge fluid circulation loops have
separate flow portions along at least a portion of the middle
circulation channel.
9. The rotor blade as in claim 8, wherein the separating structure
extends from the blade tip into the middle circulation channel.
10. The rotor blade as in claim 8, wherein the separating structure
extends completely through the middle circulation channel and
divides the middle circulation channel into separate flow channels,
and further comprising a separate respective fan heater disposed
within the blade root for each of the separate flow channels,
wherein airflow through the leading edge and the trailing edge
fluid circulation loops is independently controllable.
11. The rotor blade as in claim 3, wherein the webs comprise
airflow passages defined therethrough along a span-wise portion of
the webs adjacent the blade tip.
12. A method for deicing a wind turbine rotor blade, the method
comprising directing heated air through an internal leading edge
circulation loop and a separate internal trailing edge circulation
loop within the rotor blade.
13. The method as in claim 12, further comprising directing the
heated air through a middle circulation channel that is common to
the leading edge and the trailing edge circulation loops.
14. The method as in claim 13, wherein the heated air is directed
as an outflow airstream from one or more fan heaters disposed in a
root area of the rotor blade through the middle circulation channel
towards a tip area of the rotor blade, wherein the outflow
airstream is directed at the tip area into separate return
airstreams through respective leading and trailing edge channels
within the rotor blade.
15. The method as in claim 14, wherein the outflow airstream is
maintained as a single combined airstream through the middle
circulation channel or is maintained as separate airstreams through
the middle circulation channel.
16. The method as in claim 14, wherein airflow through the
respective leading edge and trailing edge circulation loops is
independently controlled.
17. The method as in claim 13, wherein the heated air is directed
as separate outflow airstreams from one or more fan heaters
disposed in a root area of the rotor blade through respective
leading and trailing edge channels within the rotor blade towards a
tip area, wherein the outflow airstreams are directed at the tip
area through the middle circulation channel back to the root area
of the blade.
18. The method as in claim 17, wherein the separate outflow
airstreams are combined into a single return airstream in the
middle circulation channel.
19. The method as in claim 12, further comprising directing the
heated air through a middle circulation channel that is common to
the leading edge and the trailing edge circulation loops, and using
separating structure that extends from the blade tip at least
partially into the middle circulation channel to separate the
heated air into separate airstreams.
20. The method as in claim 12, wherein a span-wise extending middle
circulation channel is common to the leading edge and the trailing
edge fluid circulation loops, the middle circulation channel
defined by a first web disposed proximate to the leading edge and a
second web disposed proximate to the trailing edge, the method
further comprising directing the heated air through airflow
passages defined in the first and second webs along a span-wise
portion of the webs adjacent the blade tip.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of wind
turbines, and more particularly to a system and method for deicing
of the rotor blades, thereby increasing the overall operational
efficiency of the wind turbine.
BACKGROUND OF THE INVENTION
[0002] Wind turbines have gained increased acceptance as an
environmentally safe and relatively inexpensive alternative energy
source. With this growing interest, considerable efforts have been
made to develop wind turbines that are reliable and efficient.
[0003] Generally, a wind turbine includes a rotor having one or
more blades. The rotor is mounted on a housing or nacelle, which is
positioned on top of a truss or tubular tower. The turbine's blades
transform wind energy into a rotational torque or force that drives
one or more generators that are rotationally coupled to the rotor
through a gearbox. The gearbox steps up the inherently low
rotational speed of the turbine rotor for the generator to
efficiently convert mechanical energy to electrical energy, which
is fed into a utility grid. Gearless direct drive turbines also
exist.
[0004] Under certain combinations of atmospheric conditions, the
rotor blades can become covered with ice. For an operational wind
turbine, ice buildup typically occurs on the leading edge of the
blade, resulting in a modified airfoil shape and reduced lifting
capability. As the ice layer becomes increasingly thick, weight is
added to the airfoil, further reducing the lifting capability and
the aerodynamic performance of the rotor blade. Ice shedding (the
throwing off of ice as the blades rotate) can also be a safety
issue, particularly for wind turbines located near residential
areas. For wind turbines that are stopped or idling, ice will
generally form uniformly over the entire surface of the blades,
thereby necessitating deicing of the entire blade before the wind
turbine can be placed back in operation.
[0005] Methods and devices are known and practiced for deicing
rotor blades, which also encompasses preventing icing on the rotor
blades when atmospheric conditions are favorable for ice formation.
For example, installing resistive heating wires or other electrical
conductors onto the leading edge or other surfaces of the rotor
blade is known. This system, however, can provide a conduit for
lightning, and a lightning strike can render the rotor blade
useless. In another known technique for reducing icing, an
inflatable air bladder is bonded to the leading edge of the blades.
However, inflation of the air bladder alters the aerodynamics of
the rotor blade, and the air bladder itself may be or become
subject to fatigue and failure in certain environments.
[0006] The Canadian patent CA 2228145(counterpart to EP 0842360 B1)
describes a system for deicing wind turbine rotor blades wherein a
heated medium, which may be the air within the blade cavity, is
channeled to internal cavities within the blade. The heated medium
is directed from the blade root area into a cavity behind the
leading edge of the blade, and then diverted at the blade tip into
a cavity along the trailing edge of the blade and back to the root
area. A fan with integrated heating elements is provided in the
blade root to generate and maintain circulation of the heated
medium. The chambers or cavities may be defined by reinforcement
ribs that run parallel to the longitudinal axis of the blade.
[0007] A drawback to the system and method of the CA 2228145 patent
is that the warmest air is not directed to the tip of the blade
first, which may be the area of the blade most susceptible to
icing, but along the entire length of the leading edge before
reaching the blade tip. In addition, a thermal imbalance is created
within the rotor blade as a result of the unidirectional flow path
of the heated medium. The leading edge cavity is heated to a far
greater extent than the trailing edge cavity, and the trailing edge
cavity is heated to a greater extent than the reaming internal
space between the trailing and leading edge cavities. Thus, the
deicing capability of the system is focused primarily on the
leading edge, which may not be beneficial in certain situations,
such as when atmospheric conditions become harsh enough to cause
ice formation on the pressure and/or suction side surfaces, or
trailing edge.
[0008] The present invention provides an improved rotor blade
deicing system and method that addresses at least certain of the
drawbacks of conventional systems, including the type of system
described in the CA 2228145 patent.
BRIEF DESCRIPTION OF THE INVENTION
[0009] Aspects and advantages of the invention will be set forth in
part in the following description, or may be obvious from the
description, or may be learned through practice of the
invention.
[0010] In accordance with aspects of the invention, a rotor blade
for a wind turbine is provided with an integrated deicing
capability. It should be appreciated that the term "deicing" is
used herein to encompass removal or minimizing ice that has formed
on the rotor blade, as well as preventing formation of ice on the
rotor blade. The rotor blade includes a blade root, a blade tip,
and a leading edge and a trailing edge extending between the blade
tip and blade root. Any manner of structural members, such as webs,
walls, ducts, baffles, dampers, and so forth, are disposed within
an internal volume of the rotor blade, with these members defining
a leading edge fluid circulation loop and a separate trailing edge
fluid circulation loop. A fluid handling system is disposed within
the internal volume of the rotor blade and is configured with the
structural members so as to direct a heated fluid medium through
the leading edge and trailing edge fluid circulation loops. These
heated fluid medium streams may be directed simultaneously through
the leading edge and trailing edge fluid circulation loops, or may
be directed through one of the loops while the other loop is idle
or isolated. The loops may be independently controlled so that the
heated fluid medium streams have a different flow rate or
temperature.
[0011] In a particular embodiment, the heated fluid medium is the
air within the internal volume of the rotor blade, and the fluid
handling system includes any combination of air handling
components, such a one or more fans, heater elements, dampers,
ducts, and the like. The term "fan heater" is used herein to
encompass and combination of a fan and heating element within the
same or separate housings. In alternate embodiments, the heated
fluid medium may be, for example, an inert gas that is circulated
through the respective fluid circulation loops by any combination
of fluid handling components.
[0012] The structural members may define a span-wise extending
middle circulation channel that is common to the leading edge and
the trailing edge fluid circulation loops in that a portion of each
of the circulation loops simultaneously flows through the middle
circulation channel. This middle channel can be defined by any
combination of structural or non-structural webs, ducts, and so
forth.
[0013] In one embodiment, the structural members comprise a first
web disposed proximate to the leading edge and defining a leading
edge channel, and a second web disposed proximate to the trailing
edge and defining a trailing edge channel. The first and second
webs may be shear web components of the blades internal support
system. With this embodiment, the middle circulation channel is
defined between the first and second webs. In alternate
embodiments, any manner of ducting may be used to define the middle
circulation channel. For example, the blade may include only a
single shear web and an internal duct may serve the function as the
middle circulation channel. The fluid handling system may include
at least one fan heater disposed within the blade root so as to
direct a heated outflow airstream through the leading edge and
trailing edge fluid circulation loops, including the middle
circulation channel.
[0014] It should be appreciated that the system is not limited to a
single flow direction through the leading and trailing edge
circulation loops. For example, the fan heater may be disposed so
as to direct the heated outflow airstream along the middle
circulation channel to adjacent the blade tip where the outflow
airstream is directed into separate return airstreams that flow
through the leading edge and the trailing edge channels,
respectively, back to the blade root. In an alternate embodiment,
one or more fan heaters may be disposed so as to direct the outflow
airstream as separate streams through the leading edge and trailing
edge channels, wherein the separate streams combine adjacent the
blade tip into a single return airstream through the middle
circulation channel and back to the blade root.
[0015] In a particular embodiment, the heated outflow airstream may
be a single, combined airstream within the middle circulation
channel such that the leading edge and the trailing edge fluid
circulation loops share a combined outflow portion through the
middle fluid circulation channel. A single fan heater may be used
in this embodiment having sufficient airflow capacity to maintain a
desired minimum airflow through the leading and trailing edge fluid
circulation loops. With this embodiment separating structure may be
provided within the middle circulation channel such that the
leading edge and the trailing edge fluid circulation loops have
separate flow portions along at least a portion of the middle
circulation channel. For example, the separating structure may be a
wall or baffle that extends from the blade tip partially into the
middle circulation channel and that serves to separate the single
outflow airstream into the separate streams adjacent to the blade
tip.
[0016] In still a further embodiment, separating structure may
extend essentially completely within the middle circulation channel
and divide the middle circulation channel into separate flow
channels. Thus, with this embodiment, the leading and trailing edge
fluid circulation loops are not combined or mingled through the
middle circulation channel. Thus, airflow through the respective
loops may be individually controlled by, for example, separate
respective fan heaters disposed within the blade root for each of
the loops.
[0017] The present invention also encompasses various method
embodiments for deicing a wind turbine rotor blade in accordance
with the concepts discussed above. For example, an exemplary
embodiment includes directing heated air through an internal
leading edge circulation loop and a separate internal trailing edge
circulation loop within the rotor blade. The air may be directed
alternately or simultaneously through the leading edge and trailing
edge circulation loops, and may be independently controlled. This
method embodiment may include directing the heated air through a
middle circulation channel that is common to the leading edge and
the trailing edge circulation loops.
[0018] In a particular method, the heated air is directed as an
outflow airstream from one or more fan heaters disposed in a root
area of the rotor blade through the middle circulation channel
towards a tip area of the rotor blade, wherein the outflow
airstream is directed at the tip area into separate return
airstreams through respective leading and trailing edge channels
within the rotor blade. The method may include maintaining the
outflow airstream as a single combined (co-mingled) airstream
through the middle circulation channel, and dividing the combined
airstream into separate return airstreams at the tip area of the
rotor blade.
[0019] In an alternate method embodiment, the outflow airstream is
maintained as separate airstreams through the middle circulation
channel and are diverted into the respective leading and trailing
edge channels at the tip area of the rotor blade. In this
embodiment, airflow through the respective leading edge and
trailing edge circulation loops may be independently
controlled.
[0020] In still another method embodiment, the heated air is
directed as separate outflow airstreams from one or more fan
heaters disposed in a root area of the rotor blade through
respective leading and trailing edge channels within the rotor
blade towards a tip area of the blade. At the tip area, the outflow
airstreams are directed through a middle circulation channel back
to the root area of the blade. The separate outflow airstreams may
be combined into a single return airstream in the middle
circulation channel, or maintained as separate streams.
[0021] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth in the specification, which makes
reference to the appended figures, in which:
[0023] FIG. 1 is a perspective view of a conventional wind
turbine;
[0024] FIG. 2 is top view of a conventional wind turbine rotor
blade;
[0025] FIG. 3 is cross-sectional view of a conventional wind
turbine rotor blade;
[0026] FIG. 4 is a top cut-away view of an embodiment of a wind
turbine blade in accordance with aspects of the invention;
[0027] FIG. 5 is a top cut-away view of an alternate embodiment of
a wind turbine blade in accordance with aspects of the
invention;
[0028] FIG. 6 is a top cut-away view of still another embodiment of
a wind turbine blade in accordance with aspects of the
invention;
[0029] FIG. 7 is a top cut-away view of a different embodiment of a
wind turbine blade in accordance with aspects of the invention;
[0030] FIG. 8 is a top cut-away view of yet another embodiment of a
wind turbine blade in accordance with aspects of the invention;
[0031] FIG. 9 is a top cut-away view of an alternate embodiment of
a wind turbine blade in accordance with aspects of the invention;
and
[0032] FIG. 10 is a top cut-away view of still another embodiment
of a wind turbine blade in accordance with aspects of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0033] Reference now will be made in detail to embodiments of the
invention, one or more examples of which are illustrated in the
drawings. Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present invention without departing
from the scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used with
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0034] FIG. 1 illustrates a wind turbine 10 of conventional
construction. The wind turbine 10 includes a tower 12 with a
nacelle 14 mounted thereon. A plurality of turbine blades 16 are
mounted to a rotor hub 18, which is in turn connected to a main
flange that turns a main rotor shaft. The wind turbine power
generation and control components are housed within the nacelle 14.
The view of FIG. 1 is provided for illustrative purposes only to
place the present invention in an exemplary field of use. It should
be appreciated that the invention is not limited to any particular
type of wind turbine configuration.
[0035] FIGS. 2 and 3 are more detailed views of a conventional wind
turbine blade 16. The blade 16 includes an upper shell member 20
and a lower shell member 22. The upper shell member 20 may be
configured as the suction side surface of the blade 16, while the
lower shell member 22 may be configured as the pressure side
surface of the blade. The blade 16 includes a leading edge 24 and a
trailing edge 26, as well as a root portion 28, and a tip portion
30. The blade 16 extends in a longitudinal, span-wise direction 34.
As is well known in the art, the upper shell member 20, and lower
shell member 22 are joined together at the leading edge 24 and
trailing edge 26. The blade 16 includes an internal cavity 25 in
which various structural members, such as spar caps 32 and shear
webs 33, are configured. The construction and function of the
internal structural components of the blade 16, such as the spar
caps 32 and shear webs 33 are well known to those skilled in the
art and need not be described in detail herein for an understanding
and appreciation of the present invention.
[0036] FIG. 4 depicts an embodiment of a wind turbine rotor blade
16 incorporating an integrated deicing capability in accordance
with aspects of the invention. Any manner of structural members 50,
such as webs, walls, ducts, baffles, dampers, and so forth, are
disposed within the internal volume 25 of the rotor blade 16 and
define a leading edge fluid circulation loop 58 and a separate
trailing edge fluid circulation loop 60. These loops 58 and 60 may
include any configuration of structural members 50 that establish
separate flow paths along the leading edge 24 and trailing edge 26,
as compared to a single, continuous flow path wherein the leading
and trailing edge flows would be serial (one-after-the-other)
within the single loop. For example, as depicted in FIG. 4, the
separate fluid circulation loops 58 and 60 may be counter-rotating
flow paths. These flow paths may be simultaneous, as depicted in
FIG. 4, or may be independently established and controlled, as
discussed in greater detail below.
[0037] A fluid handling system, generally denoted as 65, is
disposed within the internal volume 25 of the rotor blade 16 and is
configured with the structural members 50 so as to direct a heated
fluid medium simultaneously through the leading edge and trailing
edge fluid circulation loops 58, 60, respectively, as indicated by
the arrows in FIG. 4 denoting the circulation loops 58, 60. In the
illustrated embodiment, the heated fluid medium is the air within
the internal volume 25 that is heated and recirculated by an air
handling system 65. This system may include any combination of air
handling components, such a one or more fans, heater elements,
dampers, ducts, and the like. In the embodiments depicted in the
various figures, the air handling system 65 includes a fan heater
66, which is intended to encompass any configuration of a fan and
heating elements. For example, the fan heater 66 may include a fan,
one or more diffusers/ducts, and heating element within the same
housing or separate housings. The heating elements may be resistive
elements, and any other suitable heating element or system. The fan
heater 66 (and any other components of the handling system 65) are
desirably selected to have sufficient capacity to generate a
desired flow rate through the circulation loops 58, 70, while
minimizing weight, power consumption, and the time needed to deice
the blades.
[0038] In particular embodiments illustrated in the figures, the
structural members 50 may define a span-wise extending middle
circulation channel 70 that is common to the leading edge and the
trailing edge fluid circulation loops 58, 60. For example,
referring to FIG. 4, the fluid circulation loops 58, 60 include
respective portions that that flow through the middle circulation
channel 70, which may be simultaneous in certain embodiments.
[0039] In various depicted embodiments (e.g., FIGS. 4 and 6), the
structural members 50 include a first web 52 that is disposed
proximate to the leading edge 24 such that a leading edge channel
62 is defined, and a second web 54 disposed proximate to the
trailing edge and defining a trailing edge channel 64. It should be
appreciated that these channels 62, 64 may be considered as any
manner of physically defined flow structure and may have a varying
cross-sectional profile. The channels 62, 64 are not limited to any
particular shape or dimension. The first and second webs 52, 54 may
correspond to the shear webs 33 described above with respect to the
conventional blade of FIGS. 2 and 3, or any other component of the
blades internal support system. With this embodiment, the middle
circulation channel 70 is defined between the first and second webs
52, 54 and corresponds to the space between the shear webs 33
(FIGS. 2 and 3).
[0040] In an alternate embodiment depicted in FIG. 5, the blade 16
has a single internal shear web 52. A duct 55 is attached to the
shear web 52 (or may be supported by any other structure) and
functions as the middle circulation channel 70.
[0041] As mentioned above, it should be appreciated that the
deicing system is not limited to a single flow direction through
the leading and trailing edge circulation loops 58, 60. For
example, in the embodiment of FIG. 4, the fan heater 66 is disposed
so as to direct a heated outflow airstream along the middle
circulation channel 70 to an area adjacent the blade tip 30. From
there, the outflow airstream is directed into separate return
airstreams or legs of the respective circulation loops 58, 60 that
flow through the leading edge and the trailing edge channels 62, 64
and back to the blade root, thereby establishing the
counter-rotating flow path loops depicted in the figure. However,
in alternate embodiments as depicted for example in FIG. 8, one or
more fan heaters 66 may be disposed so as to direct the outflow
airstream as separate streams that flow initially through the
leading edge and trailing edge channels 62, 64, wherein the
separate streams combine adjacent the blade tip 30 into a single
return airstream through the middle circulation channel 70 and back
to the blade root. Any manner of ducting 67 or other diverting
structure may be used to split the single output of the fan heater
66 into separate outflow streams.
[0042] FIGS. 4, 5, and 6 depict embodiments wherein a single
combined outflow stream from the fan heater 66 is directed through
the middle circulation channel 70 such that the leading edge and
the trailing edge fluid circulation loops 58, 60 share a combined
(co-mingled) outflow portion through the middle fluid circulation
channel 70. A single fan heater 66 may be used in this embodiment
having sufficient airflow capacity to maintain a desired minimum
airflow through the leading and trailing edge fluid circulation
loops 58, 60. Referring to FIG. 6, separating structure, such as a
middle web 56, may be provided at least partially within the middle
circulation channel 70 such that the leading edge and the trailing
edge fluid circulation loops 58, 60 have separate (not co-mingled)
flow portions along at least a portion of the middle circulation
channel 70. For example, the separating structure 56 may be a wall,
web, or baffle that extends from the blade tip 30 partially into
the middle circulation channel 70 and serves to separate the single
outflow airstream into separate streams in the area adjacent to the
blade tip 30.
[0043] The embodiments of FIGS. 4 through 6 may be particularly
advantageous in that the heated air is initially directed to the
blade tip area 30 through the middle channel 70, which is flow
channel most insulated from atmospheric conditions. The core
materials of the webs 52, 54 (e.g., shear webs 33) insulate the
channel 70 and minimizes heat loss along the channel. Thus, heating
is maximized at the critical blade tip 30 area that is most prone
to icing conditions.
[0044] In the embodiment depicted in FIG. 7, the middle web
separating structure 56 extends essentially completely through the
middle circulation channel 70 and divides the middle circulation
channel 70 into separate flow channels of the respective flow
circulation loops 58, 60. Thus, with this embodiment, the leading
and trailing edge fluid circulation loops 58, 60 are not combined
or co-mingled through the middle circulation channel 70. Separate
fan heaters 66 may be configured in the blade root area for the
respective fluid circulation loops 58, 60 such that airflow through
the loops may be individually controlled and adjusted for different
icing conditions along the leading and trailing edges 24, 26 of the
blade 16.
[0045] The embodiment of FIG. 9 is similar in structure to the
embodiment of FIG. 7, with the difference being that the separate
fan heaters 66 are configured to direct their respective outflow
streams into the leading edge and trailing edge channels 62, 64.
The outflow streams are maintained separate in their return flow
path within the middle circulation channel 70 by the middle web 56
that extends completely through the channel 70.
[0046] With the embodiments of FIGS. 7 and 9, separate fan heaters
66 are utilized to separately supply the leading edge and trailing
edge channels 62, 64. These fan heaters 66 may have different
capacities and outputs, and may be separately controlled. For
example, the system may be designed with an overall power rating of
20 KW, with this power divided differently between the channels 62,
64. The fan heater 66 assigned to the leading edge channel 62 may
have a 12 KW rating, while the fan heater 66 assigned to the
trailing edge channel 64 may have a 8 KW rating, and so forth. In
an alternate embodiment, the fan heaters 66 may have the same
rating, but are cycled and not operated at the same time. In
another embodiment, the system may have a total capacity rating of
20 KW between the fan heaters 66. The fan 66 assigned to the
leading edge channel 62 may have multiple settings, for example 10
KW and 20 KW settings, while the fan assigned to the trailing edge
channel 64 has a setting of 10 KW. With this configuration, all 20
KW may be used for heating the leading edge channel 62 when icing
conditions so dictate (with the fan assigned to the trailing edge
channel 62 turned off). With the fan assigned to the leading edge
channel 62 at the lower setting (e.g., the 10 KW setting), the fan
assigned to the trailing edge channel 64 can be energized.
[0047] The embodiment of FIG. 10 is similar in structure and
function to the embodiment of FIG. 4, with the difference being
that one or more airflow passages 68 are defined through the webs
52, 54 along a portion thereof adjacent to the blade tip 30. Thus,
air is directed out of the middle circulation channel 70 through
these airflow passages 68, as well as at the end of the channel 70
wherein the remaining stream is divided by the middle web 56. It
should be appreciated that the airflow passages may be defined at
any location along the webs 52, 54.
[0048] The present invention also encompasses various method
embodiments for deicing a wind turbine rotor blade 16 in accordance
with the concepts discussed above with respect to FIGS. 4 through
10. For example, an exemplary method embodiment includes
simultaneously directing heated air through an internal leading
edge circulation loop 58 and a separate internal trailing edge
circulation loop 60 within the rotor blade 16. This method
embodiment may include directing the heated air through a middle
circulation channel 70 that is common to the leading edge and the
trailing edge circulation loops 58, 60.
[0049] In a particular method, the heated air is directed as an
outflow airstream from one or more fan heaters 66 disposed in the
blade root area 28 through the middle circulation channel 70
towards a blade tip area 30, wherein the outflow airstream is
diverted at the tip area into separate return airstreams through
respective leading and trailing edge channels 62, 64 within the
rotor blade. The method may include maintaining the outflow
airstream as a single combined airstream through the middle
circulation channel 70, and dividing the combined airstream into
separate return airstreams at the blade tip area 30.
[0050] In an alternate method embodiment, the method may include
maintaining the outflow airstream from one or more fan heaters 66
as separate airstreams through the middle circulation channel 70,
and diverting these separate airstreams into the respective leading
and trailing edge channels 62, 64 at the tip area of the rotor
blade. In this embodiment, the method may include independently
controlling airflow through the respective leading edge and
trailing edge circulation loops 58, 60.
[0051] In still another method embodiment, the heated air is
directed as separate outflow airstreams from one or more fan
heaters 66 disposed in a root area 28 of the rotor blade through
respective leading and trailing edge channels 62, 64 towards the
blade tip area 30. At the tip area, the outflow airstreams are
directed through the middle circulation channel 70 back to the
blade root area 28. The separate outflow airstreams may be combined
into a single return airstream in the middle circulation channel
70, or maintained as separate streams.
[0052] 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. 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 include 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 languages of the claims.
* * * * *