U.S. patent application number 12/463606 was filed with the patent office on 2010-11-11 for turbine nozzle with sidewall cooling plenum.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to GARY MICHAEL ITZEL, DAVID RICHARD JOHNS, EVAN ANDREW SEWALL.
Application Number | 20100284800 12/463606 |
Document ID | / |
Family ID | 42979293 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100284800 |
Kind Code |
A1 |
SEWALL; EVAN ANDREW ; et
al. |
November 11, 2010 |
TURBINE NOZZLE WITH SIDEWALL COOLING PLENUM
Abstract
A turbine nozzle segment includes an outer band portion, an
inner band portion, and at least one nozzle vane extending between
the band portions. A cooling plenum is defined in a mating side
face of at least one of the band portions and extends transversely
at least partially through the respective band portion. First and
second cooling passages extend from the cooling plenum to
respective first and second cooling chambers.
Inventors: |
SEWALL; EVAN ANDREW;
(SIMPSONVILLE, SC) ; JOHNS; DAVID RICHARD;
(SIMPSONVILLE, SC) ; ITZEL; GARY MICHAEL;
(SIMPSONVILLE, SC) |
Correspondence
Address: |
DORITY & MANNING, P.A. and GENERAL ELECTRIC;COMPANY
POST OFFICE BOX 1449
GREENVILLE
SC
29602
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
SCHENECTADY
NY
|
Family ID: |
42979293 |
Appl. No.: |
12/463606 |
Filed: |
May 11, 2009 |
Current U.S.
Class: |
415/178 |
Current CPC
Class: |
F01D 9/041 20130101;
F05D 2240/81 20130101; F05D 2260/20 20130101; F05D 2260/201
20130101; F01D 25/12 20130101 |
Class at
Publication: |
415/178 |
International
Class: |
F01D 25/12 20060101
F01D025/12 |
Claims
1. A turbine nozzle segment, comprising: an outer band portion, an
inner band portion, and at least one nozzle vane extending between
said inner band portion and said outer band portion, said nozzle
vane having a leading edge and a trailing edge; each of said inner
band portion and said outer band portion further comprising axially
extending mating faces, and a combustion gas side and an opposite
back side; a first cooling chamber, and a second cooling chamber
defined at said back side of said inner band portion and said outer
band portion; a cooling plenum defined in at least one of said
mating faces of at least one of said inner band portion or said
outer band portion, said cooling plenum extending transversely at
least partially through said respective band portion; and at least
one first cooling air passage defined in said band portion from
said first cooling chamber into said cooling plenum, and at least
one second cooling air passage defined in said band portion from
said second cooling chamber into said cooling plenum.
2. The turbine nozzle segment as in claim 1, wherein said first and
second cooling chambers are separated at least partially by a
transversely extending rail member, said cooling plenum extending
transversely at least partially through said respective band
portion under said rail member.
3. The turbine nozzle segment as in claim 2, wherein said first
cooling chamber is a high pressure chamber, and said second cooling
chamber is a low pressure chamber, whereby cooling air moves from
said high pressure chamber into said cooling plenum via said first
cooling air passage, and into said low pressure chamber from said
cooling plenum via said second cooling air passage.
4. The turbine nozzle segment as in claim 3, wherein said first and
said second cooling air passages are axially offset along said
cooling plenum.
5. The turbine nozzle segment as in claim 2, wherein said cooling
plenum is defined in said respective band portion between said rail
member and said trailing edge of said nozzle vane.
6. The turbine nozzle segment as in claim 2, further comprising an
impingement plate carried by said rail member.
7. The turbine nozzle segment as in claim 1, wherein said mating
face further comprises a seal slot defined axially along said
mating face, said cooling plenum defined between said seal slot and
said combustion gas side of said respective band portion.
8. The turbine nozzle segment as in claim 1, wherein said first
cooling chamber is a high pressure impingement cooling chamber
supplied with compressor bleed-off air.
9. The turbine nozzle segment as in claim 1, wherein said cooling
plenum extends completely through said respective band portion
between opposite ones of said mating faces.
10. The turbine nozzle segment as in claim 1, wherein each of said
inner and said outer band portions comprises at least one said
cooling plenum.
11. A turbine nozzle segment, comprising: an outer band portion, an
inner band portion, and at least one nozzle vane extending between
said inner band portion and said outer band portion, said nozzle
vane having a leading edge and a trailing edge; each of said inner
band portion and said outer band portion further comprising axially
extending mating faces, and a combustion gas side and an opposite
back side; and a cooling plenum defined in at least one of said
mating faces of at least one of said inner band portion or said
outer band portion adjacent to said trailing edge of said nozzle
vane, said cooling plenum extending transversely at least partially
through said respective band portion across said trailing edge.
12. The turbine nozzle segment as in claim 11, further comprising a
first cooling chamber, and a second cooling chamber defined at said
back side of said respective band portion and separated at least
partially by a transversely extending rail member, said cooling
plenum extending at least partially under said rail member.
13. The turbine nozzle segment as in claim 11, further comprising
at least one first cooling air passage and at least one second
cooling air passage defined in said band portion in communication
with said cooling plenum, said first and second cooling air
passages directing cooling air from a first location to a second
location via said cooling plenum.
14. The turbine nozzle segment as in claim 13, wherein said first
and said second cooling air passages are axially offset along said
cooling plenum.
15. The turbine nozzle segment as in claim 11, wherein said mating
faces further comprise an axially extending seal slot defined
therein, said cooling plenum defined between said seal slot and
said combustion gas side of said respective band portion.
16. The turbine nozzle segment as in claim 11, wherein said cooling
plenum extends completely through said respective band portion
between opposite ones of said mating faces.
17. The turbine nozzle segment as in claim 1, wherein each of said
inner and said outer band portions comprises at least one said
cooling plenum.
18. A gas turbine comprising a plurality of nozzle stages, each
said nozzle stage further comprising a plurality of nozzle
segments, each said nozzle segment comprising: an outer band
portion, an inner band portion, and at least one nozzle vane
extending between said inner band portion and said outer band
portion, said nozzle vane having a leading edge and a trailing
edge; each of said inner band portion and said outer band portion
further comprising axially extending mating faces, and a combustion
gas side and an opposite back side; a first cooling chamber, and a
second cooling chamber defined at said back side of said inner band
portion and said outer band portion; a cooling plenum defined in at
least one of said mating faces of at least one of said inner band
portion or said outer band portion, said cooling plenum extending
transversely at least partially through said respective band
portion; and at least one first cooling air passage defined in said
band portion from said first cooling chamber into said cooling
plenum, and at least one second cooling air passage defined in said
band portion from said second cooling chamber into said cooling
plenum.
19. The gas turbine as in claim 18, wherein said first and second
cooling chambers are separated at least partially by a transversely
extending rail member, said cooling plenum extending transversely
at least partially through said respective band portion under said
rail member.
20. The gas turbine as in claim 18, said cooling plenum is defined
in said respective band portion so as to extend across said
trailing edge of said nozzle vane.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to turbines, and
more particularly to a means to cool particular regions of a nozzle
segment.
BACKGROUND
[0002] In a typical gas turbine, the turbine section is mounted at
the exit of the combustor and is therefore exposed to extremely
high temperature combustion gases. To protect turbine components
from the hot combustion gases, they are often cooled with a cooling
medium. One common approach to cooling turbine airfoil components
(e.g., rotor blades and nozzle vanes) is to bleed a portion of the
compressed air from the compressor and to direct this bleed air to
internal passages in the components. The air circulates through the
internal passages to remove heat from the component structure. The
air can exit through small film cooling holes formed in the airfoil
so as to produce a thin film layer of cooling air on the surface.
Film cooling can also be used for the inner and outer bands. In
this case, a band includes film cooling holes extending radially
therethrough and cooling air passes through the film cooling holes
to form a cooling air film on the hot side of the band.
[0003] With a known turbine nozzle construction, each of a
plurality of cast nozzle segments includes inner and outer band
portions and one or more nozzle vanes. The mating surfaces of the
band portions include seal slots, which accommodate seals that
extend between band portions of adjacent nozzle segments. The
nozzle vanes may be cooled by passing a cooling medium through a
plenum in the outer band portion of each nozzle segment, through
one or more cavities in the nozzle vanes to cool the nozzles, and
into a plenum in a corresponding inner band portion. In some nozzle
segments, the cooling medium then flows through the inner band
portion and again through the one or more nozzle vanes prior to
being discharged. In other nozzle segments, the cooling medium
flows only once through each nozzle segment.
[0004] It is generally recognized that cooling of certain regions
of a nozzle segment are not adequate, and that such regions are
prone to higher thermal stresses and fatigue. Efforts are being
made to improve cooling in these areas. For example, U.S. Pat. No.
7,029,228 describes a configuration wherein a cooling channel
extends axially through at least one of the outer and inner bands
generally parallel to the mating face of the nozzle segment to cool
the mating faces between the seal slots and the hot gas path.
[0005] A particularly problematic region for cooling in a nozzle
segment is the area in the band portions that extends from the
mating face and generally underlies a rail member, which may
include an impingement plate, on the back side of the band portion.
This area coincides with the trailing edge of the vane on the
opposite side of the band portion. Cooled band portions often
consist of more than one flow circuit, wherein compressor bleed air
is passed through an impingement plate in each circuit to cool the
back side of the band portion before exiting through film holes or
slots into the gas path. These circuits are divided by the rail
member, which is typically located on the back side of the band
portions opposite from the trailing edge of the vane. A series of
holes is typically drilled through this rail to allow cooling air
to pass from the high pressure circuit to the low pressure circuit.
However, the presence of the rail at the back side of the band
portion prevents impingement and film cooling of the inner face of
the band portions around the trailing edge of the vane. A need
exists in the art to address the inadequate cooling of this
region.
BRIEF DESCRIPTION OF THE INVENTION
[0006] The present invention provides a solution to improved
cooling of the band portions of a nozzle segment transverse to the
mating side face at the nozzle vane trailing edge. Additional
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.
[0007] In accordance with aspects of the invention, a turbine
nozzle segment is provided that includes an outer band portion, an
inner band portion, and at least one nozzle vane extending between
the inner and outer band portions. The nozzle vane has a leading
edge and a trailing edge. Each of the inner and outer band portions
include axially extending (relative to the axis of the turbine)
mating faces, a combustion gas side, and an opposite back side. A
first cooling chamber and a second cooling chamber are defined at
the back side of the band portions and, in one particular
embodiment, may be separated at least partially by a transversely
extending rail member. A cooling plenum is defined in the mating
face of at least one of the inner band portion and the outer band
portion and extends transversely at least partially through the
respective band portion. The cooling plenum may extend so as to run
essentially under the rail member in one embodiment, or under the
trailing edge of the nozzle vane in another embodiment. At least
one first cooling air passage is defined in the band portion from
the first cooling chamber into the cooling plenum, and at least one
second cooling air passage is defined from the second cooling
chamber into the cooling plenum. A plurality of these first and
second cooling air passages may be provided along the longitudinal
length of the cooling plenum. The passages serve to move air from
one cooling chamber to another via the cooling plenum. For example,
the first cooling chamber may be a high pressure impingement
cooling chamber supplied with compressor bleed-off air, and the
second cooling chamber may be a low pressure chamber, whereby the
cooling air moves from the high pressure chamber into the cooling
plenum via the first cooling air passage, and into the low pressure
chamber from the cooling plenum via the second cooling air passage.
Cooling air introduced into the cooling plenum thus cools the
region of the band portion under and alongside of the plenum and
adjacent to the cooling air passages, such as the area under the
rail member or the trailing edge of the nozzle vane.
[0008] It should be appreciated that the present invention also
encompasses a gas turbine having a plurality of nozzle stages, with
each of the nozzle stages further including a plurality of nozzle
segments as embodied herein.
[0009] 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
[0010] 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:
[0011] FIG. 1 is a perspective view of a nozzle segment
incorporating aspects of the present invention;
[0012] FIG. 2 is a partial perspective view of a nozzle segment
portion particularly illustrating a cooling plenum in the mating
face;
[0013] FIG. 3 is an enlarged partial perspective view of a portion
of a nozzle segment illustrating an alternate embodiment of a
cooling plenum in the mating face;
[0014] FIG. 4 is a diagram view of a nozzle segment band portion
illustrating potential high temperature areas at the trailing edge
of the nozzle vane and relevant location of a cooling plenum in
accordance with aspects of the invention; and
[0015] FIG. 5 is a partial perspective view of an alternative
embodiment of a nozzle segment 10 incorporating a cooling
plenum.
DETAILED DESCRIPTION
[0016] 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.
[0017] FIG. 1 is a perspective illustration of a nozzle segment 10
of an exemplary embodiment. The nozzle segment 10 includes an outer
band portion 12 having a combustion gas side 14 and a back side 16.
The nozzle segment 10 includes an inner band portion 20 having a
combustion gas side 22 and a back side 24. The outer band portion
has a mating side surface 18, which may include seals 52 disposed
in seal slots 50 (FIG. 2). Likewise, inner band portion 20 includes
a mating side face 26 having seals 52 disposed therealong.
[0018] The nozzle segment 10 includes at least one nozzle vane 30
extending between the combustion gas sides of the band portions 12,
20, with the nozzle vane having a leading edge 32 and a trailing
edge 34. The nozzle segment 10 may include a plurality of vanes 30
in a single segment. The nozzle vane 30 intersects with the
combustion gas side 22 of the lower band portion 20 at a root 56. A
fillet 58 having a concave radius of curvature is generally formed
along the root 56. The interface of the nozzle vane 30 with the
combustion gas side 14 of the outer band portion is formed in the
same way.
[0019] A plurality of the nozzle segments 10 are arranged
circumferentially about the axis of a turbine (not shown) and are
secured to the turbine shell to form a nozzle stage. Typically, the
turbine includes a plurality of these nozzle stages.
[0020] A flow path for hot combustion gases is defined through the
nozzle segment 10 by the nozzle vane 30 and the combustion gas
surfaces 14, 22, of the outer band portion 12 and inner band
portion 20, respectively. The hot gases flow tlirough the segments
and around the vanes 30 and engage downstream rotor buckets (not
shown) of the turbine to rotate the turbine rotor, as commonly
understood in the art.
[0021] The mating surfaces 18, 26 include the seals 52 in seal
slots 50 (FIG. 2) and are thus disposed in sealing engagement
between adjacent nozzle segments 10 in a nozzle stage. The seals 52
prevent cooling air from leaking into the combustion gas flow path
between the interfaces of the outer band portion 12 and inner band
portion 20.
[0022] Referring to FIG. 1, a nozzle segment 10 includes a first
cooling chamber 38 and a second cooling chamber 40. Typically, the
first cooling chamber 38 is configured to receive high pressure
cooling air, for example compressor bleed-off air. This high
pressure air may be conducted to the lower pressure second cooling
chamber 40 through an impingement plate 44, plenums, or any other
conducting means. The cooling chambers 40, 38 include a cover plate
(not shown) to seal the chambers. The nozzle vane 30 has a
generally hollow construction and includes cooling cavities 36 in
communication with the lower pressure cooling chamber 38. The
cooling cavities 36 may thus be considered a cooling chamber. A
rail member 42 is disposed between the mating side face surfaces 18
of the outer band portion 12 and the mating surfaces 26 of the
inner band portion 20. The rail members 42 on the outer and inner
band portions may have the same or a different configuration, and
may serve different purposes. Referring to the outer band portion
12, the structural rail member 42 may incorporate an impingement
plate 44, as illustrated in FIG. 1, and may separate the first or
high pressure cooling chamber 38 from the second or lower pressure
cooling chamber 40. It should be understood that cooling chambers
are also formed in the backside 24 of the inner band portion
20.
[0023] A cooling circuit is defined by the various cavities and
structural members of the nozzle segment 10. It should be
appreciated that the present invention is not limited by any
particular configuration of a cooling circuit. In the illustrated
embodiment, cooling air introduced into the first cooling chamber
38 provides impingement and/or convection cooling of structural
components of the nozzle segment 10 in this region. The cooling air
is introduced into the second or lower pressure cooling chamber 40
(or cavities 36 or other areas in communication with the cooling
chamber 40) through the impingement plate 44. A portion of the
cooling air may diffuse through film holes 54 through the band
portion 12 and into the combustion gas flow. This limited amount of
cooling air provides a film cooling to the combustion gas side
surfaces of the respective band portions 12, 20. Any array and
location of these film holes 54 may be utilized, as variously
illustrated in the figures.
[0024] The nozzle vane 30 is generally hollow and includes one or
more cavities 36. The cooling air moves through the cavities 36 to
cool the nozzle vane 30. The cavities 36 may also be in
communication with the suction side and pressure side of the nozzle
vane 30 through fluid holes 54 defined through the vane 30. In this
manner, the outside surface of the nozzle vane 30 is cooled by a
cooling air film induced on the surface. The cooling air moves
through the vane 30 into the cavities of the inner band portion 20,
and may diffuse through the film holes 54 in the band 20. Depending
on the configuration of the nozzle segments 10, the cooling air may
be re-circulated through other portions of the nozzle segment 10
before being exhausted from the cooling circuit.
[0025] Referring to the various figures, the rail member 42
extending between the mating side faces 18 of the outer band
portion 12, and the mating side faces 26 of the lower band portion
20, creates a problematic area with respect to cooling. The
presence of the structural rail inhibits impingement cooling,
particularly in the region of the trailing edge of the nozzle vane
30. FIG. 4 is a diagram view illustrating potential higher
temperature regions or "hot spots" (dashed line areas) concentrated
at the trailing edge of the nozzle vane 30 on the suction side of
the vane. The location of the structural rail member 42 is
indicated by the dashed lines in FIG. 4. Referring to FIGS. 2, 3,
and 5, it can be seen that the location of the rail member 42 in
these particular embodiments is along the mating side face 18
generally adjacent to the point of termination of the trailing edge
34 of the nozzle vane 30 relative to the mating side face. As can
be seen in FIGS. 1, 4, and 5, the rail member 42 bisects the
trailing portion of the nozzle vane 30 defined by the dashed lines
indicating the root 56 in FIG. 5. In other words, the rail member
42 runs or extends across the trailing portion of the nozzle vane
30, which adds to the thermal hot spots illustrated in FIG. 4.
[0026] Referring to the various figures and in accordance with
aspects of the invention, a cooling plenum 46 is defined in one of
the mating faces 18, 26 of at least one of the outer band portion
12 or inner band portion 20. It should be appreciated that this
cooling plenum 46 may be included in both of the outer and inner
band portions 12, 20, and in both mating faces of each respective
band portion. For purposes of discussion, the cooling plenum 46 is
described further herein by reference to mating side face 18 of the
upper band portion 12.
[0027] The cooling plenum 46 is defined in the mating face at any
desired location so as to extend transversely into the band portion
to cool a particular region of the band portion. In the illustrated
embodiments, the cooling plenum 46 is defined at a location
adjacent to the rail member 42. For example, referring to FIGS. 2
and 3, the cooling plenum 46 may be considered as aligned with or
running at least partially under the rail member 42 within the
upper band portion 12. The cooling plenum 46 extends transversely
at least partially through the respective band portion, and may
extend completely through the band portion so as to extend from one
mating side face surface 18 to the opposite mating side face
surface 18. Cooling air is introduced into the cooling plenum 46
and thus cools the region of the band portion 12 along the root or
base of the rail member 42. Thus, the region of the band portion 12
around the trailing edge 34 of the nozzle vane 30 is also cooled by
impingement and/or convection cooling as cooling air is moved
through the cooling plenum 46. This is particularly illustrated in
the diagram of FIG. 4 wherein the location of the cooling plenum 46
is illustrated by dashed lines. It can be seen from this figure
that the cooling plenum also crosses the trailing edge 34 region of
the nozzle vane 30, and will thus serve to cool the potential
problematic hot spots illustrated in FIG. 4 adjacent to the suction
side trailing edge of the nozzle vane 30.
[0028] The cooling plenum 46 may be provided with cooling air
through various means. In the illustrated embodiments, a plurality
of air passages are used to move or transport cooling air into,
along, and out of the cooling plenum 46. For example, referring to
FIGS. 1, 4, and 5, at least one first cooling air passage 48 may be
defined in the rail member 42 (or other structure of the band
portion 12) to place the cooling air plenum 46 in fluid air
communication with the first cooling chamber 38. Thus, the
compressor bleed off air, or other cooling air, introduced into the
cooling chamber 38 moves into the cooling plenum 46. At least one
second air passage 49 is defined in the rail member and places the
cooling plenum 46 in fluid air communication with the second
cooling chamber 40 (which includes and region or cavity in
communication with the chamber 40). Thus, the cooling air is able
to move through the cooling plenum 46 and exit into the cooling
chamber 40 via the second air passage 49. In the illustrated
embodiment, a plurality of the passages 48 and 49 are defined
longitudinally along the length of the cooling plenum 46. Any
number or locations of these passages are possible. Depending on
the particular regions of the band portions to be cooled, the
cooling plenum 46 may extend transversely completely across the
band portion 12, and the cooling passages 48, and 49 may be
positioned at various longitudinal locations along the entire
length of the cooling plenum 46. Although not a requirement, the
first cooling passages 48 and second cooling passages 49 may be
grouped in pairs such that each first cooling passage 48 includes a
corresponding second cooling air passage 49. The position of these
passages may be staggered along the longitudinal length of the
plenum 46.
[0029] It should be appreciated that the plenum 46 is not limited
to any particular cross-sectional profile or other configuration.
For example, in the embodiment illustrated in FIG. 2, the plenum 46
is a generally circular cross-sectional profile. In the embodiment
of FIG. 3, the cooling air plenum 46 has a generally oval
cross-sectional profile.
[0030] Still referring to FIGS. 2 and 3, in the illustrated
embodiment the cooling plenum 46 is defined in the respective band
portion mating side face 18 generally between the rail member 42 on
the backside of the band portion 12 and the trailing edge 34 of the
nozzle vane 30 on the combustion gas side of the band portion 12.
If the mating face surface 18 includes axially extending seal slots
50, the cooling plenum 46 is defined between the seal slot 50 and
the combustion gas side 14.
[0031] It should be appreciated that the present invention also
encompasses embodiments wherein a cooling air plenum 46 is defined
in the mating face surface 18 so as to extend transversely into the
band portion 12 adjacent to the trailing edge 34 of the nozzle vane
30 regardless of the length of any rail member on the back side 16
of the band portion 12. For example, the back side 16 of the band
portion 12 may include a structural member of any design that
inhibits impingement cooling of certain regions of the band
portion. In this situation, a cooling plenum 46 may be defined in
the mating side face surface 18 so as to extend into the band
portion 12 generally coincident with this structural member,
particularly in the trailing edge region of the nozzle vane 30.
Cooling air moving through the plenum 46 will cool the region of
the band portion 12 around the trailing edge of the nozzle vane 30.
Cooling passages 48, 49 may be defined in the band portion to place
the cooling plenum 46 in fluid air communication with a first
location and a second location, wherein the cooling air plenum also
serves to move air from one location to the other while providing a
beneficial impingement cooling to a problematic region of the band
portion 12. This concept is illustrated generally in FIG. 6 wherein
the cooling plenum 46 is defined in the mating face surface 26 of
the bottom band portion 20 so as to extend within the band portion
20 generally across the trailing end portion of the nozzle vane 30.
The plenum 46 may or may not extend under or along a rail member
that also extends transversely across the back side of the band
portion 20.
[0032] FIG. 5 illustrates an embodiment wherein at least one of the
cooling air passages 49 places the plenum 46 in fluid air
communication with the cavity 36 of vane 30. This configuration may
be used to introduce air from the plenum 46 directly into the
cavity 36, or remove air from the cavity 36 directly to the plenum
46.
[0033] While the present subject matter has been described in
detail with respect to specific exemplary embodiments and methods
thereof, it will be appreciated that those skilled in the art, upon
attaining an understanding of the foregoing may readily produce
alterations to, variations of, and equivalents to such embodiments.
Accordingly, the scope of the present disclosure is by way of
example rather than by way of limitation, and the subject
disclosure does not preclude inclusion of such modifications,
variations and/or additions to the present subject matter as would
be readily apparent to one of ordinary skill in the art.
* * * * *