U.S. patent application number 13/746457 was filed with the patent office on 2013-06-13 for gas turbine outer case active ambient cooling including air exhaust into a sub-ambient region of exhaust flow.
The applicant listed for this patent is John W. Finneran, Daryl J. Graber, Jonathan M. Leagon, Mrinal Munshi, Matthew R. Porter, Yevgeniy Shteyman. Invention is credited to John W. Finneran, Daryl J. Graber, Jonathan M. Leagon, Mrinal Munshi, Matthew R. Porter, Yevgeniy Shteyman.
Application Number | 20130149107 13/746457 |
Document ID | / |
Family ID | 48572117 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130149107 |
Kind Code |
A1 |
Munshi; Mrinal ; et
al. |
June 13, 2013 |
GAS TURBINE OUTER CASE ACTIVE AMBIENT COOLING INCLUDING AIR EXHAUST
INTO A SUB-AMBIENT REGION OF EXHAUST FLOW
Abstract
A gas turbine engine including an outer case extending
circumferentially around the central longitudinal axis. A cooling
channel is associated with the outer surface of the outer case, the
cooling channel having a channel inlet and a channel outlet. An air
duct is provided including an inlet end in fluid communication with
the channel outlet and an outlet end in fluid communication with an
exhaust gas flow from a turbine section of the gas turbine engine.
An exit structure is located at the air duct outlet end, and the
exit structure provides a sub-ambient pressure at the air duct
outlet end to induce a flow from the air duct inlet end to the air
duct outlet end.
Inventors: |
Munshi; Mrinal; (Orlando,
FL) ; Finneran; John W.; (Palm Beach Gardens, FL)
; Shteyman; Yevgeniy; (West Palm Beach, FL) ;
Graber; Daryl J.; (Palm Beach Gardens, FL) ; Porter;
Matthew R.; (West Palm Beach, FL) ; Leagon; Jonathan
M.; (Cassatt, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Munshi; Mrinal
Finneran; John W.
Shteyman; Yevgeniy
Graber; Daryl J.
Porter; Matthew R.
Leagon; Jonathan M. |
Orlando
Palm Beach Gardens
West Palm Beach
Palm Beach Gardens
West Palm Beach
Cassatt |
FL
FL
FL
FL
FL
SC |
US
US
US
US
US
US |
|
|
Family ID: |
48572117 |
Appl. No.: |
13/746457 |
Filed: |
January 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13314311 |
Dec 8, 2011 |
|
|
|
13746457 |
|
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Current U.S.
Class: |
415/116 |
Current CPC
Class: |
F05D 2260/202 20130101;
F01D 9/065 20130101; F01D 25/12 20130101; F01D 25/305 20130101 |
Class at
Publication: |
415/116 |
International
Class: |
F01D 25/12 20060101
F01D025/12 |
Claims
1. A gas turbine engine comprising: an outer case defining a
central longitudinal axis, and an outer surface of said outer case
extending circumferentially around the central longitudinal axis; a
cooling channel associated with said outer surface of said outer
case, said cooling channel having a channel inlet and a channel
outlet; an air duct including an inlet end in fluid communication
with the channel outlet and an outlet end in fluid communication
with an exhaust gas flow from a turbine section of said gas turbine
engine; and an exit structure at said air duct outlet end, said
exit structure providing a sub-ambient pressure at said air duct
outlet end to induce a flow from said air duct inlet end to said
air duct outlet end.
2. The gas turbine engine of claim 1, wherein said exit structure
interacts with a portion of said exhaust gas flow passing over said
exit structure for effecting a reduced pressure at said outlet end
to draw air from said cooling channel into said air duct.
3. The gas turbine engine of claim 2, wherein said exit structure
partially covers said air duct outlet end, shielding an upstream
side of said outlet end and defining a downstream facing opening
adjacent a downstream side of said outlet end.
4. The gas turbine engine of claim 1, wherein said exit structure
produces a jet pump effect at said air duct outlet end to produce a
sub-ambient pressure within said air duct and draw heated cooling
air from said cooling channel into said air duct.
5. The gas turbine engine of claim 1, wherein said outer case
surface comprises an exterior surface of said outer case, and said
cooling channel is defined by a panel structure located radially
outward from said exterior surface.
6. The gas turbine engine of claim 5, wherein said cooling channel
extends around the circumference of said outer case.
7. The gas turbine engine of claim 6, wherein said channel inlet is
at a first circumferential location, and said channel outlet is at
a second circumferential location circumferentially spaced from
said first circumferential location.
8. The gas turbine engine of claim 7, wherein said first
circumferential location of said channel inlet is diametrically
opposite from said second circumferential location of said channel
outlet.
9. The gas turbine engine of claim 1, wherein said cooling channel
is located at an axial location of an exhaust diffuser, and said
air duct outlet is located downstream from said exhaust diffuser at
an exhaust manifold.
10. The gas turbine engine of claim 1, wherein said air duct inlet
end is open to ambient air outside of said gas turbine engine to
provide ambient cooling air to said cooling channel.
11. A gas turbine engine comprising: an outer case defining a
central longitudinal axis, and an outer surface of said outer case
extending circumferentially around the central longitudinal axis;
an exhaust gas passage defined within said outer case for
conducting an exhaust gas flow from a turbine section of said gas
turbine engine; a cooling channel extending circumferentially
around said outer surface of outer case, said cooling channel
having a channel inlet and a channel outlet located in
circumferentially spaced relation to said channel inlet; an air
duct including an inlet end in fluid communication with the channel
outlet and an outlet end in fluid communication with the exhaust
gas flow; and an exit structure at said air duct outlet end
interacting with said exhaust gas flow for effecting a reduced
pressure at said outlet end of said air duct to draw air from said
cooling channel into said air duct.
12. The gas turbine engine of claim 11, wherein said cooling
channel is located at an axial location of an exhaust diffuser, and
said air duct outlet is located downstream from said exhaust
diffuser at an exhaust manifold.
13. The gas turbine engine of claim 12, wherein said air duct is
located outside of said outer surface of said outer case and
extends axially between said exhaust diffuser and said exhaust
manifold.
14. The gas turbine engine of claim 12, wherein said exhaust
manifold includes a manifold wall having a manifold outer surface
and a manifold inner surface, a manifold opening extending between
said manifold outer and inner surfaces, said air duct is attached
to said manifold outer surface and said exit structure is mounted
to said manifold inner surface.
15. The gas turbine engine of claim 14, wherein said exit structure
is defined by a plate-like exit shield plate having a first
circumferential edge attached to the said manifold inner surface
upstream of said manifold opening, and said exit shield having a
second circumferential edge downstream of said first
circumferential edge and spaced radially inwardly from said
manifold inner surface.
16. The gas turbine engine of claim 15, wherein said air duct
defines a central axis extending generally parallel to flow of air
through said air duct and said central axis intersects said exit
shield.
17. The gas turbine engine of claim 15, wherein said exit shield
diverts flow of exhaust gas in said exhaust manifold away from said
manifold opening and effects said reduced pressure at said outlet
end of said air duct.
18. The gas turbine engine of claim 11, including a thermal
barrier/cooling system for controlling a temperature of the outer
case, said thermal barrier/cooling system including: an internal
insulating layer supported on an inner surface of said outer case
opposite said outer surface of said outer case, the internal
insulating layer extending circumferentially along said inner
surface of said outer case and providing a thermal resistance to
radiated energy from said exhaust gas passage located radially
inwardly from said outer case; and said cooling channel defined by
a panel structure located in radially spaced relation to said outer
surface of said outer case and extending around the circumference
of said outer surface of said outer case, said cooling channel
being generally axially aligned with said internal insulating layer
and forming a flow path for an ambient air flow cooling said outer
surface of said outer case.
19. The gas turbine engine of claim 18, including an external
insulating layer supported on and covering said panel structure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of and claims
priority to U.S. patent application Ser. No. 13/314,311, filed Dec.
8, 2011, which application is herein incorporated by reference in
its entirety as if fully set forth herein.
FIELD OF THE INVENTION
[0002] The present invention relates to gas turbine engines and,
more particularly, to structures for providing thermal protection
to limit heating of the outer case of a gas turbine engine.
BACKGROUND OF THE INVENTION
[0003] A gas turbine engine generally includes a compressor
section, a combustor section, a turbine section and an exhaust
section. In operation, the compressor section may induct ambient
air and compress it. The compressed air from the compressor section
enters one or more combustors in the combustor section. The
compressed air is mixed with the fuel in the combustors, and the
air-fuel mixture can be burned in the combustors to form a hot
working gas. The hot working gas is routed to the turbine section
where it is expanded through alternating rows of stationary
airfoils and rotating airfoils and used to generate power that can
drive a rotor. The expanded gas exiting the turbine section may
then be exhausted from the engine via the exhaust section.
[0004] In a typical gas turbine engine, bleed air comprising a
portion of the compressed air obtained from one or more stages of
the compressor may be used as cooling air for cooling components of
the turbine section. Additional bleed air may also be supplied to
portions of the exhaust section, such as to cool portions of the
exhaust section and maintain a turbine exhaust case below a
predetermined temperature through a forced convection air flow
provided within an outer casing of the engine. Advancements in gas
turbine engine technology have resulted in increasing temperatures,
and associated outer case deformation due to thermal expansion.
Case deformation may increase stresses in the case and in
components supported on the case within the engine, such as bearing
support struts. The additional stress, which may operate in
combination with low cycle fatigue, may contribute to cracks,
fractures or failures of the bearing support struts that are
mounted to the casing for supporting an exhaust end bearing
housing.
SUMMARY OF THE INVENTION
[0005] In accordance with an aspect of the present invention, a gas
turbine engine is provided comprising an outer case defining a
central longitudinal axis, and an outer surface of the outer case
extending circumferentially around the central longitudinal axis. A
cooling channel is associated with the outer surface of the outer
case, the cooling channel having a channel inlet and a channel
outlet. An air duct is provided including an inlet end in fluid
communication with the channel outlet and an outlet end in fluid
communication with an exhaust gas flow from a turbine section of
said gas turbine engine. An exit structure is located at the air
duct outlet end, and the exit structure provides a sub-ambient
pressure at the air duct outlet end to induce a flow from the air
duct inlet end to the air duct outlet end.
[0006] The exit structure may interact with a portion of the
exhaust gas flow passing over the exit structure for effecting a
reduced pressure at the outlet end to draw air from the cooling
channel into the air duct.
[0007] The exit structure may partially cover the air duct outlet
end, shielding an upstream side of the outlet end and defining a
downstream facing opening adjacent a downstream side of the outlet
end.
[0008] The exit structure may produce a jet pump effect at the air
duct outlet end to produce a sub-ambient pressure within the air
duct and draw heated cooling air from the cooling channel into the
air duct.
[0009] The outer case surface may comprise an exterior surface of
the outer case, and the cooling channel may be defined by a panel
structure located radially outward from the exterior surface.
[0010] The cooling channel may extend around the circumference of
the outer case.
[0011] The channel inlet may be at a first circumferential
location, and the channel outlet may be at a second circumferential
location circumferentially spaced from the first circumferential
location.
[0012] The first circumferential location of the channel inlet may
be diametrically opposite from the second circumferential location
of the channel outlet.
[0013] The cooling channel may be located at an axial location of
an exhaust diffuser, and the air duct outlet may be located
downstream from the exhaust diffuser at an exhaust manifold.
[0014] The air duct inlet end may be open to ambient air outside of
the gas turbine engine to provide ambient cooling air to the
cooling channel.
[0015] In accordance with another aspect of the invention, a gas
turbine engine is provided comprising an outer case defining a
central longitudinal axis, and an outer surface of the outer case
extending circumferentially around the central longitudinal axis.
An exhaust gas passage is defined within the outer case for
conducting an exhaust gas flow from a turbine section of the gas
turbine engine. A cooling channel extends circumferentially around
the outer surface of outer case, the cooling channel having a
channel inlet and a channel outlet located in circumferentially
spaced relation to the channel inlet. An air duct is provided
including an inlet end in fluid communication with the channel
outlet and an outlet end in fluid communication with the exhaust
gas flow. An exit structure is located at the air duct outlet end
and interacts with the exhaust gas flow for effecting a reduced
pressure at the outlet end of the air duct to draw air from the
cooling channel into the air duct.
[0016] The cooling channel may be located at an axial location of
an exhaust diffuser, and the air duct outlet may be located
downstream from the exhaust diffuser at an exhaust manifold.
[0017] The air duct may be located outside of the outer surface of
the outer case and may extend axially between the exhaust diffuser
and the exhaust manifold.
[0018] The exhaust manifold may include a manifold wall having a
manifold outer surface and a manifold inner surface, a manifold
opening extending between the manifold outer and inner surfaces,
the air duct may be attached to the manifold outer surface and the
exit structure may be mounted to the manifold inner surface.
[0019] The exit structure may be defined by a plate-like exit
shield plate having a first circumferential edge attached to the
manifold inner surface upstream of the manifold opening, and the
exit shield having a second circumferential edge downstream of the
first circumferential edge and spaced radially inwardly from the
manifold inner surface.
[0020] The air duct may define a central axis extending generally
parallel to flow of air through the air duct and the central axis
intersects the exit shield.
[0021] The exit shield diverts flow of exhaust gas in the exhaust
manifold away from the manifold opening and effects the reduced
pressure at the outlet end of the air duct.
[0022] The gas engine further may include a thermal barrier/cooling
system for controlling a temperature of the outer case, the thermal
barrier/cooling system including: [0023] an internal insulating
layer supported on an inner surface of the outer case opposite the
outer surface of the outer case, the internal insulating layer
extending circumferentially along the inner surface of the outer
case and providing a thermal resistance to radiated energy from the
exhaust gas passage located radially inwardly from the outer case;
and [0024] the cooling channel defined by a panel structure located
in radially spaced relation to the outer surface of the outer case
and extending around the circumference of the outer surface of the
outer case, the cooling channel being generally axially aligned
with the internal insulating layer and forming a flow path for an
ambient air flow cooling the outer surface of the outer case.
[0025] The thermal barrier/cooling system may include an external
insulating layer supported on and covering the panel structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] While the specification concludes with claims particularly
pointing out and distinctly claiming the present invention, it is
believed that the present invention will be better understood from
the following description in conjunction with the accompanying
Drawing Figures, in which like reference numerals identify like
elements, and wherein:
[0027] FIG. 1 is a cross-sectional elevational view through a
portion of a gas turbine engine including an exhaust section
illustrating aspects of the present invention;
[0028] FIG. 2 is a partially cut-away perspective view of the
exhaust section illustrating aspects of the present invention;
[0029] FIG. 2A is a perspective view of a lower portion of the
structure illustrated in FIG. 2 illustrating a main air inlet;
[0030] FIG. 2B is a perspective view from a lower side of the
structure illustrated in FIG. 2 illustrating auxiliary air
inlets;
[0031] FIG. 3 is a cross-sectional axial view of the exhaust
section diagrammatically illustrating air flow provided around an
outer case of the gas turbine engine;
[0032] FIG. 4 is a cut-away perspective view of a portion of the
exhaust section adjacent to a top-dead-center location of the
exhaust section;
[0033] FIG. 5 is a perspective view illustrating an insulating
layer segment in accordance with an aspect of the invention;
[0034] FIG. 6 is a cross-sectional elevational view through a
portion of a gas turbine engine including an exhaust section having
an exhaust diffuser and an exhaust manifold illustrating an
additional aspect of the present invention including an air
duct;
[0035] FIG. 7 is a partially cut-away perspective view of the
exhaust section illustrating aspects of the present invention shown
in FIG. 6;
[0036] FIG. 8 is an enlarged perspective view of a manifold opening
and exit shield in accordance with aspects of the present
invention;
[0037] FIG. 8A is a view similar to FIG. 8 showing an alternative
configuration for the exit shield; and
[0038] FIG. 9 is a perspective view of the exhaust section and
exhaust manifold illustrating the air duct of FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0039] In the following detailed description of the preferred
embodiment, reference is made to the accompanying drawings that
form a part hereof, and in which is shown by way of illustration,
and not by way of limitation, a specific preferred embodiment in
which the invention may be practiced. It is to be understood that
other embodiments may be utilized and that changes may be made
without departing from the spirit and scope of the present
invention.
[0040] Referring to FIG. 1, a portion of an exhaust section 10 of a
gas turbine engine is shown located axially downstream from a
turbine section 12 to illustrate aspects of the present invention.
The exhaust section 10 generally comprises a cylindrical structure
comprising an outer case 11 extending circumferentially around a
generally horizontal central longitudinal axis A.sub.C and forms a
downstream extension of an outer case the gas turbine engine. The
outer case 11 of the exhaust section 10 includes an exhaust
cylinder or turbine exhaust case 14, and an exhaust spool structure
16 located downstream from the exhaust case 14.
[0041] The exhaust case 14 includes a downstream exhaust case
flange 18 that extends radially outwardly of a downstream end the
exhaust case 14, and the spool structure 16 includes an upstream
spool structure flange 20 that extends radially outwardly of the
spool structure 16. The downstream exhaust case flange 18 and
upstream spool structure flange 20 abut each other at a joint 22,
and may be held together in a conventional manner, such as by bolts
(not shown). In addition, an upstream exhaust case flange 21
extends radially outwardly from an upstream end of the exhaust case
14 and may be bolted to a radially extending flange 23 of the
turbine section 12 for supporting the exhaust case 14 to the
turbine section 12.
[0042] The exhaust case 14 comprises a relatively thick wall
forming a structural member or frame for supporting an exhaust end
bearing housing 24 and for supporting at least a portion of an
exhaust diffuser 26. The exhaust end bearing housing 24 is located
for supporting an end of a rotor 25 for the gas turbine engine.
[0043] The diffuser 26 comprises an inner wall 28 and an outer wall
30 defining an annular passage for conveying hot exhaust gases 31
from the turbine section 12. The bearing housing 24 is supported by
a plurality of strut structures 32. Each of the strut structures 32
include a strut 34 extending from a connection 36 on the exhaust
case 14, through the diffuser 26, to a connection 38 on the bearing
housing 24 for supporting and maintaining the bearing housing 24 at
a centered location within the exhaust case 14. The strut
structures 32 may additionally include a strut shield or fairing 40
surrounding the strut 34 for isolating the strut 34 from the hot
exhaust gases 31 passing through the diffuser 26, see also FIG.
3.
[0044] As a result of the hot exhaust gases 31 passing through the
diffuser 26, the outer wall 30 of the diffuser 26 radiates heat
radially outwardly toward an inner case surface 42 of the exhaust
case 14. As discussed above, conventional designs for cooling a
turbine exhaust section may provide bleed air supplied from a
compressor section of the engine to the exhaust section to provide
a flow of cooling air between the diffuser and the exhaust case in
order to control or reduce the temperature of the exhaust case
through forced convection. In accordance with an aspect of the
invention, a thermal barrier/cooling system 44 is provided to
reduce and/or eliminate the use of compressor bleed air to control
the temperature of the exhaust case 14 and spool structure 16.
[0045] Referring to FIGS. 2 and 3, the thermal barrier/cooling
system 44 generally comprises an internal insulating layer 46 and a
convective cooling channel 48. The internal insulating layer 46 is
supported on the inner case surface 42 and extends
circumferentially to cover substantially the entire inner case
surface 42. The internal insulating layer 46 forms a thermal
barrier between the diffuser 26 and the exhaust case 14 to provide
a thermal resistance to radiated energy from the outer wall 30 of
the diffuser 26.
[0046] The internal insulating layer 46 is preferably formed by a
plurality of insulating layer segments 46a (FIG. 5) generally
located in side-by-side relation to each other, and having a
longitudinal or axial extent that is about equal to the axial
length of the exhaust case 14 to provide a thermal barrier across
substantially the entire inner case surface 42 of the exhaust case
14. Hence, a substantial portion of the radiated heat from the
diffuser 26 is prevented from reaching the exhaust case 14, thereby
isolating the wall of the exhaust case 14 from the thermal load
contained within the exhaust case 14.
[0047] Referring further to FIG. 5, the insulating layer segments
46a may comprise rectangular segment members having a leading edge
50, a trailing edge 52, and opposing side edges 54, 56. The
insulating layer segments 46a have a lower thermal conductivity
than that of the wall of the exhaust case 14. The thermal
conductivity of the insulating layer segments 46a may have a
maximum value of about 0.15 W/mK, and preferably have a thermal
conductivity value of about 0.005 W/mK for resisting transfer of
heat from the diffuser to the engine case 14. The insulating layer
segments 46a may positioned on the inner case surface 42 of the
exhaust case 14 with the side edges 54, 56 of one insulating layer
segment 46a closely adjacent, or engaged with, the side edges 54,
56 of an adjacent insulating layer segment 46a.
[0048] The construction of the insulating layer segments 46a may
comprise a pair of opposing sheet metal layers 58, 60, and a
thermal blanket layer 62 located between the sheet metal layers 58,
60 and having a substantially lower thermal conductivity than the
sheet metal layers 58, 60. A plurality of metal bushings 64 may
extend through the sheet metal layers 58, 60 and the thermal
blanket layer 62 at mounting points for the insulating layer
segments 46a. In particular, each of the metal bushings 64 comprise
a rigid structure defining a predetermined spacing between the
sheet metal layers 58, 60, and are adapted to receive a fastener
structure, such as a standoff 66 (FIG. 4), for attaching each
insulating layer segment 46a to the exhaust case 14. The standoffs
66 may be configured to permit limited movement of the insulating
layer segments 46a relative to the inner case surface 42, such as
to provide for any thermal mismatch between the internal insulating
layer 46 and the exhaust case 14. For example the standoffs 66 may
each comprise a stud 67 having a radially outer end affixed at the
inner case surface 42 and having a threaded radially inner end for
receiving a nut 69 to retain the insulating layer segment 46a
between the nut and the inner case surface 42.
[0049] The insulating layer segments 46a may be provided with slots
65 extending from the trailing edge 52 to a rear row of the
bushings 64 to facilitate assembly of the insulating layer segments
46a to the exhaust case 14. In particular, the slots 65 facilitate
movement of the insulating layer segments 46a onto the studs 67
during assembly by permitting a degree of axial movement of the
rear row of bushings 64 onto a corresponding row of studs 67 at a
rear portion of the exhaust case 14 where there is a minimal space
between the exhaust case 14 and the diffuser 26.
[0050] It may be noted that a limited spacing may be provided
between adjacent insulating layer segments 46a at particular
locations around the inner case surface 42. For example, at the
locations of the connections 36 where the struts 34 extend inwardly
from the inner case surface 42 a spacing or gap may be provided
between adjacent insulating layer segments 46a located adjacent to
either side of each strut 34. Similarly, a limited gap may be
present between the insulating layer segments 46a that are directly
adjacent to structure forming the horizontal joints 92. It may be
noted that an alternative configuration of the insulating layer
segments 46a may be provided to reduce gaps at these locations. For
example, the insulating layer segments 46a may be configured to
include portions that extend closely around the struts 34 and
thereby reduce gap areas that may expose the inner case surface 42
to radiated heat.
[0051] Provision of multiple insulating layer segments 46a
facilitates assembly of the internal insulating layer 46 to the
engine case 14, and further enables repair of a select portion of
the internal insulating layer 46. For example, in the event of
damage to a portion of the internal insulating layer 46, the
configuration of the internal insulating layer 46 permits removal
and replacement of individual ones of the insulating layer segments
46a that may have damage, without requiring replacement of the
entire internal insulating layer 46.
[0052] It should be understood that although a particular
construction of the insulating layer segments 46a has been
described, other materials and constructions for the insulating
layer segments 46a may be provided. For example, the insulating
layer segments 46a may be formed of a known ceramic insulating
material configured to provide a thermal resistance for surfaces,
such as the inner case surface 42.
[0053] Referring to FIG. 1, the convective cooling channel 48
extends circumferentially around an outer case surface 68 of the
exhaust case 14, and is generally axially located extending from
the upstream exhaust case flange 21 to at least the downstream
exhaust case flange 18, and preferably extending to a downstream
spool structure flange 70 extending radially outwardly from a
downstream end of the spool structure 16. The convective cooling
channel 48 is defined by a panel structure 72 that extends from an
upstream location 74 where it is affixed to the exhaust section 10
at the upstream exhaust case flange 21 to a downstream location 76
where it is affixed to the exhaust section 10 at the downstream
spool structure flange 70. The panel structure 72 is located in
radially spaced relation to the outer case surface 68 to define a
first cooling channel portion 78 of the convective cooling channel
48, i.e., a recessed area between the upstream exhaust case flange
21 and the downstream exhaust case flange 18. The panel structure
72 is further located in radially spaced relation to an outer
surface 80 of the spool structure 16 to define a second cooling
channel portion 82 of the convective cooling channel 48, i.e., a
recessed area between the upstream spool structure flange 20 and
the downstream spool structure flange 70. The first and second
cooling channel portions 78, 82 define circumferentially parallel
flow paths around the exhaust section 10 and may be in fluid
communication with each other across the radially outer ends of the
flanges 18, 20.
[0054] Referring to FIGS. 2 and 3, the convective cooling channel
48 includes a main cooling air supply inlet 84 located at a first
circumferential location for providing a supply of ambient air to
the convective cooling channel 48. The convective cooling channel
48 further includes an exhaust air outlet 86 at a second
circumferential location that is diametrically opposite from the
first circumferential location. In accordance with a preferred
embodiment, the main air supply inlet 84 (FIG. 2A) is located at a
bottom-dead-center location of the outer case 11 of the exhaust
section 10, and the exhaust air outlet 86 is located at a
top-dead-center location of the outer case 11 of the exhaust
section 10.
[0055] As seen in FIG. 2, the exhaust section 10 may be formed in
two halves, i.e., an upper half 88 and a lower half 90, joined
together at a horizontal joint 92. In accordance with an aspect of
the invention, the panel structure 72 includes enlarged side
portions 94 formed as box sections extending across the horizontal
joints 92 from locations above and below the horizontal joints 92.
The side portions 94 are configured to provide additional clearance
for air flow around the horizontal joints 92, and may further be
configured to provide an additional air flow to the convective
cooling channel 48, as is discussed below.
[0056] The panel structure 72 comprises individual panel sections
72a that may be formed of sheet metal, i.e., relatively thin
compared to the outer case 11. The panel sections 72a are curved to
match the curvature of the outer case 11, and extend downwardly
from the side portions 94 toward the main air inlet 84, and extend
upwardly from the side portions 94 toward the air outlet 86. The
panel sections 72a are formed as generally rectangular sections
extending between the upstream and downstream locations 74, 76 on
the exhaust section 10, and preferably engage or abut each other,
as well as the side portions 94 at shiplap joints 98 along axially
extending edges of the panel sections 72a. The panel sections 72a
and side portions 94 may be attached to the exhaust section outer
case 11 by any conventional means, and are preferably attached as
removable components by fasteners, such as bolts or screws. It
should be understood that although the enlarged side portions 94
are depicted as box sections, this portion of the panel structure
72 need not be limited to a particular shape and may be any
configuration to facilitate passage of air flow past the horizontal
joints 92, which typically comprise enlarged and radially outwardly
extending flange portions of the exhaust section outer case 11.
Further, it should be noted that the main air inlet 84 and the air
outlet 86 may incorporated into respective panel sections 72a at
respective bottom-dead-center and top-dead-center locations around
the panel structure 72.
[0057] Referring to FIGS. 2 and 2B, the side portions 94 may be
formed with a lower portion 100 extending below the horizontal
joints 92 and terminating at a downward facing auxiliary air inlet
structure 102. The auxiliary air inlet structure 102 may include
first and second auxiliary air inlet openings 104, 106 located
side-by-side, each of which is illustrated as a downwardly facing
opening in the panel structure 72. The first and second auxiliary
air inlet openings 104, 106 may be axially aligned over the first
and second channel portions 78, 82, respectively. The auxiliary air
inlet openings 104, 106 are shown as being provided with respective
cover panels or plates 108, 110 that may be removably attached over
the openings with fasteners 112, such as bolts or screws. One or
both of the cover plates 108, 110 may be displaced or removed from
the auxiliary air inlet openings 104, 106 to permit additional or
auxiliary ambient air 116 into the convective cooling channel 48
through the auxiliary air inlet structure 102, as is further
illustrated in FIG. 3.
[0058] In accordance with an aspect of the invention, the
convective cooling channel 48 receives a non-forced ambient air
through the main air supply inlet 84. That is, air may be provided
to the convective cooling channel 48 without a driving or pressure
force at the air inlet 84 to convey air in a convective main air
supply flow 114 from a location outside the gas turbine engine
through the main air supply inlet 84. The main air supply inlet 84
may be sized with a diameter to extend across at least a portion of
each of the first and second channel portions 78, 82, such that a
portion of the main supply air flow 114 may pass directly into each
of the channel portions 78, 82.
[0059] The ambient air flow into the convective cooling channel 48
provides a decreased thermal gradient around the circumference of
the exhaust section 10 to reduce or minimize thermal stresses that
may occur with a non-uniform temperature distribution about the
exhaust section 10. In particular, stresses related to differential
thermal expansion of the exhaust case 14, and transmitted to the
struts 34, may be decreased by the increased uniformity of the
cooling flow provided by the convective cooling channel 48.
Further, the operating temperature of the exhaust case 14 may be
maintained below the material creep limit to avoid associated case
creep deformation that may cause an increase in strut stresses.
[0060] A multiport cooling configuration may be provided for the
convective cooling channel 48 by displacing or removing one or more
of the cover plates 108, 110 of the auxiliary air inlet structure
102 to increase the number of convective cooling air supply
locations. Hence, the amount of cooling provided to the channel
portions 78, 82 may be adjusted on turbine engines located in the
field to increase or decrease cooling by removal or replacement of
the cover plates 108, 110. For example, it may be desirable to
provide an increase in the cooling air flow by removing one or more
of the cover plates 108, 110, or it may be desirable to provide a
decrease in air flow by replacing one or more of the cover plates
108, 110 to prevent or decrease the auxiliary air flow 116,
depending on increases or decreases in the ambient air temperature.
Further, the cover plates 108, 110 may be used optimize the
temperature of the exhaust case 14 and spool structure 16 to
minimize any thermal mismatch between adjacent hardware and
components.
[0061] The exhaust air outlet 86 is located at the top of the
convective cooling channel 48, such that the heated exhaust air 118
may flow by convection out of the convective cooling channel 48.
The exhaust air outlet 86 may be sized with a diameter to extend
across at least a portion of each of the first and second channel
portions 78, 82, such that the heated air exhausting from the
convective cooling channel 48 may be conveyed directly to the
exhaust air outlet 86 from each of the channel portions 78, 82.
Subsequently, the heated air passing out of the exhaust air outlet
86 may be exhausted out of existing louver structure (not shown)
currently provided for existing gas turbine engine units.
[0062] It should be understood that the convective air flow through
the convective cooling channel 48 comprises a cooling air flow that
may be substantially driven by a convective force produced by air
heated along the outer case surface 68 and outer surface 80 of the
spool structure 16. The heated air within the convective cooling
channel 48 rises by natural convection and is guided toward the
exhaust air outlet 86. As the air rises within the convective
cooling channel 48, it draws ambient air into the channel 48
through the main cooling air supply inlet 84, effectively providing
a driving force for a continuous flow of cooling air upwardly
around the outer surface of the outer case 11. Similarly, when
either or both of the auxiliary air inlet openings 104, 106 on the
sides of the panel structure 72 are opened, natural convection will
draw the air upwardly around the channel 48 through the auxiliary
air inlet structure 102 to the exhaust air outlet 86.
[0063] It may be noted that as the cooling air flows upwardly as a
convection air flow 48, a lower pressure will be created within the
convective cooling channel 48 than the ambient air pressure outside
the convective cooling channel 48. Hence, any leakage at the panel
joints 98, or the joints 97, 99 (FIG. 2) where the edges of the
panel segments 72a are mounted to the exhaust section 10 at the
upstream and downstream locations 74, 76, will occur inwardly into
the convection cooling channel 48. In this regard, it may be
understood that it is not necessary to provide a leakage-proof
sealing at the peripheral edges of the panel segments 72a and side
portions 94, and that leakage into the convective cooling channel
48 may be viewed as an advantage facilitating the cooling function
of the thermal barrier/cooling system 44.
[0064] Optionally, as is illustrated diagrammatically in FIG. 3, a
fan unit 120 may be provided connected to the exhaust air outlet
86. The fan unit 120 may provide additional air flow from the
exhaust air outlet 86 to increase the cooling capacity of the
convective cooling channel 48, while maintaining an ambient airflow
into and through the convective cooling channel 48. Alternatively,
or in addition, an inlet fan unit (not shown) may be provided to
the main cooling air supply inlet 84 to provide an increase in the
ambient airflow into the channel 48. It should be understood that
even with the provision of a fan unit to facilitate flow through
the convective cooling channel 48, i.e., a fan unit 120 at the
outlet 86 and/or a fan unit at the inlet 84, the movement of the
air flow through the channel 48 may create a reduced pressure
within the channel 48 relative to the ambient area surrounding the
outside of the outer case 11.
[0065] The convective cooling channel 48 may further be provided
with an external insulating layer 122, as seen in FIGS. 1, 3, and 4
(not shown in FIG. 2). The external insulating layer may cover
substantially the entire exterior surface of the panel structure 72
defined by the panel segments 72a and side portions 94, and has a
low thermal conductivity to generally provide thermal protection to
personnel working or passing near the exhaust section 10.
[0066] Referring to FIG. 4, an optional further or second internal
insulating layer 124 may be provided to the spool structure 16,
extending circumferentially around an inner spool segment surface
126, radially outwardly from a Z-plate or spring plate structure
128 provided for supporting the diffuser 26. The second internal
insulating layer 124 may comprise separate insulating layer
segments having a construction and thermal conductivity similar to
that described for the internal insulating layer 46. Further, the
second internal insulating layer 124 may be mounted to the inner
spool segment surface 126 in a manner similar to that described for
the insulating layer segments 46a of the internal insulating layer
46. The second internal insulating layer 124 may be provided to
limit or minimize an amount of radiated heat transmitted from the
diffuser 26 to the spool structure 16. Hence, the convective air
flow requirement for air flowing through the second portion 82 of
the convective cooling channel 48 may be reduced by including the
second internal insulating layer 124.
[0067] As described above, the thermal barrier/cooling system 44
provides a system wherein the internal insulating layer 46
substantially reduces the amount of thermal energy transferred to
the outer case 11 of the exhaust section 10, and thereby reduces
the cooling requirement for maintaining the material of the outer
case 11 below its creep limit. Hence, the external cooling
configuration provided by the convective cooling channel 48
provides adequate cooling to the outer case 11 with a convective
air flow, with an accompanying reduction or elimination of the need
for forced air cooling provided to the interior of the outer case
11. Elimination of forced air cooling to the interior of the outer
case 11, i.e., by maintaining supply and exhaust of cooling air
external to the outer case 11, avoids problems associated with
thermal mismatch or thermal gradients between components within the
outer case 11.
[0068] Additionally, since the air supply for cooling the outer
case 11 does not draw on compressor bleed air or otherwise directly
depend on a supply of the air from the gas turbine engine, the
present thermal barrier/cooling system 44 does not reduce turbine
power, such as may occur with systems drawing compressor bleed air,
and the cooling effectiveness of the present system operates
substantially independently of the engine operating conditions.
Hence, the present invention may be implemented without drawing on
the secondary cooling air of the gas turbine engine, and may
provide a reduced requirement for usage of secondary cooling air
with an associated increase in overall efficiency in the operation
of the gas turbine engine.
[0069] In accordance with an alternative aspect of the invention,
the flow through the cooling channel 48 may be actively formed by
using a source of sub-ambient pressure within the engine 10. In
accordance with this aspect, and referring to FIGS. 6-9, a source
of sub-ambient pressure may be attached to the exhaust air outlet
86 illustrated in FIGS. 2, 3 and 4. In particular, as is shown in
FIGS. 6, 7 and 9, an air duct 130 is attached to the exhaust air
outlet 86 of the cooling channel 48 for providing a sub-ambient
pressure to the air outlet 86 in order to actively effect a flow of
ambient air though the cooling channel 48.
[0070] The air duct 130 includes a conduit, such as a conduit
defining a generally circular or similar cross-section, having an
inlet end 132 attached to the air outlet 86 and extending to an
outlet end 134 which is in fluid communication with exhaust gases
31 passing through an exhaust manifold 136. As illustrated herein,
the air duct 130 includes a first section 130a extending radially,
a second section 130b extending axially, and a third section 130c
extending radially and generally parallel to the first section
130a. The first section 130a may be formed with an enlarged portion
at the inlet end 132 to correspond to the size and shape of the air
outlet 86. Further, in order to accommodate thermal deflection that
may result in relative movement in the radial and axial directions
between the air duct 130 and the exhaust section outer case 11 and
exhaust manifold 136, the air duct 130 may be provided with bellows
structures 131, as is illustrated by the bellows structures 131 on
the second and third sections 130b and 130c.
[0071] The exhaust manifold 136 is attached to a downstream end of
the outer case 11 for receiving exhaust gas passing to the exit of
the diffuser 26. The exhaust manifold 136 includes a manifold outer
surface 138, a manifold inner surface 140 and a manifold opening
142 extending between the manifold outer and inner surfaces 138,
140.
[0072] The outlet end 134 of the air duct 130 is bolted or
otherwise attached to the manifold outer surface 138 at the
manifold opening 142, such that the air duct 130 provides a fluid
path placing the cooling channel 48 in fluid communication with the
exhaust flow 31 passing through the exhaust manifold 136.
[0073] Referring additionally to FIG. 8, an exit structure 144 is
attached to the manifold inner surface 140 at the location of the
manifold opening 142 and air duct outlet end 134. The exit
structure 144 is defined by a plate-like exit shield 146 having a
first circumferential edge 148 attached to the manifold inner
surface 140 upstream of the manifold opening 142, and a second
circumferential edge 150 located axially downstream of the first
circumferential edge 148 and spaced radially inwardly from the
manifold inner surface 140. Further, opposing side edges 152, 154
extend axially between the first and second circumferential edges
148, 150. The opposing side edges 152, 154 may extend generally
parallel to each other in the axial direction. Optionally, a pair
of radially extending legs 156, 158 may be located adjacent to the
side edges 152, 154 at the downstream second circumferential edge
150, and extend to an attachment point on the manifold inner
surface 140 for supporting the second circumferential edge 150 at a
predetermined radial spacing from the manifold opening 142. The
legs 156, 158 also increase the compliance of the exit shield 146
to enable the exit structure 144 to withstand thermally induced
stresses.
[0074] The air duct 130 defines a central axis 160 (FIG. 6)
extending generally parallel to flow of air through the air duct
130, and the central axis 160 intersects the exit shield 146.
Hence, the exit shield 146 is located at the circumferential and
axial location of the manifold opening 142. Further, the exit
shield 146 preferably has a circumferential dimension, parallel to
the edges 148, 150, that is greater than the diameter of the
manifold opening 142, such that the exit shield 146 provides a
cover that overlaps to either side of the manifold opening 142,
extending in the axial direction. The exit shield 146 has an axial
extent that begins upstream of the manifold opening 142 and that
substantially covers the manifold opening 142 to, or close to, an
axially downstream edge 142a of the manifold opening 142 (FIG. 6).
The exit shield 146 diverts flow of exhaust gases in the exhaust
manifold 136 radially inward from the manifold inner surface 140
and away from the manifold opening 142, and produces a "jet pump"
effect at the downstream edge 150 of the exit shield 146, effecting
a reduced (sub-ambient) pressure at the outlet end 134 of the air
duct 130.
[0075] The reduced or sub-ambient pressure created at the manifold
opening 142 induces a flow of air from the air duct 130 into the
exhaust manifold 136, and creates a sub-ambient pressure at the
exhaust air outlet 86 of the cooling channel 48. The sub-ambient
pressure at the exhaust air outlet 86 operates to actively produce
a flow of air around the circumference of the outer case 11 through
the cooling channel 48, facilitating the upward convective flow in
the channel 48 previously described, and drawing ambient cooling
air into the channel 48 through the cooling air supply inlet 84
(FIG. 7). Hence, it may be understood that the present aspect of
the invention provides a flow connection between a sub-ambient
pressure area in the engine, i.e., the exhaust manifold gas passage
at the manifold opening 142, and the ambient cooling air supply
inlet 84 to actively produce or facilitate a flow of ambient
cooling air without drawing on turbine power of the engine.
[0076] As noted above, the side edges 152, 154 are provided with
the legs 156, 158 to increase the thermal compliance of the exit
structure 144. This configuration of the exit structure 144 may
also be beneficial in embodiments of the invention where the
manifold opening 142 is located at or adjacent to a restricted flow
area that limits or restricts the size of the opening between the
downstream edge 150 and the manifold opening 144, and where an
additional opening area, i.e., along the sides, may be needed to
facilitate the "jet pump" effect. Alternatively, side panels 153,
155 (FIG. 8A) may be formed extending from the side edges 152, 154
to the manifold inner wall 140, and shaped to facilitate the "jet
pump" effect for increasing the flow of air through the duct 130
and cooling channel 148.
[0077] It should be understood that the aspects of the invention
utilizing sub-ambient pressure to draw the ambient air through the
cooling channel 48 and into the exhaust manifold 136 may be used in
combination with any of the aspects of the invention described
above, including the aspects of the external insulating layer 122
and internal insulating layers 46, 124 described above. However, it
should be noted that the present aspects of the invention,
providing the active ambient air flow through the duct 130, may be
implemented independently of the aspects described above for
providing insulating layers to the outer case 11. For example,
although the internal insulating layers 46, 124 are helpful to
controlling the temperature of the outer case 11, these layers are
not necessary to the operation of the sub-ambient flow through the
air duct 130 and the cooling flow provided through the cooling
channel 48.
[0078] Also, with regard to the panel structure 72 described above
for forming the cooling channel 48, the panels 72a forming the
panel structure 72 may be configured to permit ambient air to enter
the cooling channel 48 at select locations around the outer case
11. For example, certain locations on the outer case 11 may be
subject to localized heating or hot spots, and additional removable
panels 72a or panels 72a with removable windows or any other
opening configuration may be provided to permit an inflow of
ambient air through the panel structure 72 substantially directly,
or closer, to the hot spots to provide cooler air at these
locations than may be provided by the flow of air that has warmed
while passing through the cooling channel 48.
[0079] A further aspect described above that may be incorporated
with present embodiment utilizing the air duct 130 includes
providing a blower, such as is described above with reference to
the fan unit 120 in FIG. 3, wherein the blower may be provided to a
location along the air duct 130, or at the inlet 84 to the cooling
channel 48, to create an additional air flow through the duct 130
and facilitate the cooling effect in the cooling channel 48.
[0080] Additionally, it may be understood that the cooling channel
48 may be provided to other casings of the engine 10, such as to a
turbine casing, a compressor casing, a combustor casing of the
engine 10, or any other location that cooling may be required on
the engine.
[0081] Further, it may be noted that in accordance with aspects of
the invention, the duct providing a flow connection to a
sub-ambient location formed by exhaust gas flow may extend to any
location in the exhaust gas flow, including locations within the
turbine exhaust case 14 radially inwardly from the cooling channel
48. For example, structure defining a duct may extend through one
or more of the strut structures 32 and have structure defining an
axially downstream extending outlet in fluid communication with the
gas flow through the diffuser 26 at or adjacent to a trailing edge
of the strut structure 32, where the a portion of the strut shield
or fairing 40 may provide the sub-ambient effect of the exit
structure 144. A passage through the duct structure 32 forming a
radially extending air flow connection may be formed, for example,
by a radiation shield extending within the duct structure 32 and
have a radially outer end in fluid communication with the cooling
channel 48 in a manner such as is set out in the concurrently filed
Application U.S. Ser. No. ______ (Attorney Docket No. 2011P20816US)
entitled GAS TURBINE OUTER CASE ACTIVE AMBIENT COOLING INCLUDING
AIR EXHAUST INTO SUB-AMBIENT CAVITY, which is hereby incorporated
by reference herein. In this configuration, one or more ducts may
form passages from the interior region of the strut structure 32
that is in fluid communication with the cooling channel 48 to an
exterior surface of the fairing 40.
[0082] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *