U.S. patent application number 12/852129 was filed with the patent office on 2012-02-09 for contoured axial-radial exhaust diffuser.
This patent application is currently assigned to General Electric Company. Invention is credited to Asif Iqbal Ansari, Deepesh D. Nanda, Rohit Pruthi.
Application Number | 20120034064 12/852129 |
Document ID | / |
Family ID | 45495125 |
Filed Date | 2012-02-09 |
United States Patent
Application |
20120034064 |
Kind Code |
A1 |
Nanda; Deepesh D. ; et
al. |
February 9, 2012 |
CONTOURED AXIAL-RADIAL EXHAUST DIFFUSER
Abstract
In accordance with one embodiment, a system includes a gas
turbine diffuser. The gas turbine diffuser includes an axial
diffuser section including a first duct portion having an axial
flow path along a centerline of the gas turbine diffuser. The gas
turbine diffuser also includes an axial-radial diffuser section
coupled to the axial diffuser section, wherein the axial-radial
diffuser section includes a second duct portion having a curved
flow path along the centerline from the axial flow path to a radial
flow path and the axial-radial diffuser section excludes any
turning vane in the second duct portion.
Inventors: |
Nanda; Deepesh D.;
(Bangalore, IN) ; Pruthi; Rohit; (Bangalore,
IN) ; Ansari; Asif Iqbal; (Bangalore, IN) |
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
45495125 |
Appl. No.: |
12/852129 |
Filed: |
August 6, 2010 |
Current U.S.
Class: |
415/1 ;
415/206 |
Current CPC
Class: |
F01D 25/30 20130101 |
Class at
Publication: |
415/1 ;
415/206 |
International
Class: |
F04D 27/02 20060101
F04D027/02; F04D 29/44 20060101 F04D029/44 |
Claims
1. A system, comprising: a gas turbine diffuser, comprising: an
axial diffuser section comprising a first duct portion having an
axial flow path along a centerline of the gas turbine diffuser,
wherein the first duct portion has a first cross-sectional area
that expands along the axial flow path; and an axial-radial
diffuser section coupled to the axial diffuser section, wherein the
axial-radial diffuser section comprises a second duct portion
having a curved flow path along the centerline from the axial flow
path to a radial flow path, the second duct portion has a second
cross-sectional area that expands along the curved flow path, the
curved flow path has a radius of at least greater than or equal to
approximately 30 centimeters, and the axial-radial diffuser
excludes any turning vane in the second duct portion.
2. The system of claim 1, wherein the gas turbine diffuser
comprises a radial diffuser section coupled to the axial-radial
diffuser section, the radial diffuser section comprises a third
duct portion having the radial flow path along the centerline of
the gas turbine diffuser, and the third duct portion has a third
cross-sectional area that expands along the radial flow path.
3. The system of claim 1, wherein the radius is at least greater
than or equal to approximately 100 centimeters.
4. The system of claim 1, wherein the second duct portion comprises
a first curved wall offset from a second curved wall, the first
curved wall curves along the curved flow path with a first radius
of curvature, and the second curved wall curves along the curved
flow path with a second radius of curvature.
5. The system of claim 4, wherein the first curved wall is
proximate relative to a rotational axis of a gas turbine, and the
second curved wall is distal relative to the rotational axis of the
gas turbine.
6. The system of claim 4, wherein the first and second radii are
the same as one another.
7. The system of claim 4, wherein the first and second radii are
different from one another.
8. The system of claim 4, wherein the first and second curved walls
diverge from one another along the curved flow path.
9. The system of claim 1, wherein the first duct portion comprises
a first wall offset from a second wall, the first wall is proximate
relative to a rotational axis of a gas turbine, the second wall is
distal relative to the rotational axis of the gas turbine, and the
first and second walls diverge from one another along the axial
flow path.
10. The system of claim 9, wherein the first wall extends along the
axial flow path at a first angle relative to the rotational axis,
the second wall extends along the axial flow path at a second angle
relative to the rotational axis, and the first and second angles
are not 0 degrees.
11. The system of claim 10, wherein the first angle is less than or
equal to approximately 8 degrees, and the second angle is greater
than or equal to approximately 16 degrees.
12. The system of claim 10, wherein the second duct portion
comprises a first curved wall offset from a second curved wall, the
first curved wall curves along the curved flow path with a first
radius of curvature, the second curved wall curves along the curved
flow path with a second radius of curvature, and the first and
second angles of the first duct portion extend directly to the
first and second curved walls.
13. A system, comprising: a gas turbine diffuser, comprising: an
axial diffuser section comprising a first duct portion having an
axial flow path along a centerline of the gas turbine diffuser; and
an axial-radial diffuser section coupled to the axial diffuser
section, wherein the axial-radial diffuser section comprises a
second duct portion having a curved flow path along the centerline
from the axial flow path to a radial flow path, and the
axial-radial diffuser section excludes any turning vane in the
second duct portion.
14. The system of claim 13, wherein the first duct portion
comprises first and second walls disposed opposite from one another
about the axial flow path, the first wall is configured to mount
nearer to a rotational axis of a turbine than the second wall, the
first wall extends along the axial flow path at a first angle
relative to the rotational axis, the second wall extends along the
axial flow path at a second angle relative to the rotational axis,
and the first and second angles are not 0 degrees.
15. The system of claim 14, wherein the second duct portion
comprises first and second curved walls disposed opposite from one
another about the curved flow path, the first curved wall is
configured to mount nearer to the rotational axis than the second
curved wall, the first curved wall curves along the curved flow
path with a first radius of curvature, the second curved wall
curves along the curved flow path with a second radius of
curvature, and the first and second angles of the first duct
portion extend toward the first and second curved walls.
16. The system of claim 15, wherein the first and second angles of
the first duct portion extend directly to the first and second
curved walls.
17. The system of claim 15, wherein the first angle is less than or
equal to approximately 8 degrees, the second angle is greater than
or equal to approximately 16 degrees, the first radius of curvature
is at least greater than 100 centimeters, and the second radius of
curvature is at least greater than 100 centimeters.
18. A method, comprising: axially-radially diffusing an exhaust
flow from a turbine through a curved duct along a curved flow path
without any turning vanes, wherein the curved flow path has a
radius of at least greater than or equal to 2 times a
cross-sectional width of the curved duct.
19. The method of claim 18, wherein axially-radially diffusing the
exhaust flow comprises expanding the exhaust flow between first and
second curved walls that curve along the curved flow path, wherein
the first curved wall is oriented nearer to a rotational axis of
the turbine than the second curved wall.
20. The method of claim 19, comprising axially diffusing the
exhaust flow prior to axially-radially diffusing the exhaust flow,
wherein axially diffusing the exhaust flow comprises expanding the
exhaust flow between first and second angled walls that are angled
relative to an axial flow path, wherein the first angled wall is
oriented nearer to the rotational axis than the second angled wall.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to turbines, and
more specifically, to exhaust diffusers for use with gas turbines
and steam turbines.
[0002] Power generation plants often incorporate turbines, e.g., a
gas turbine engine. The gas turbine engine combusts a fuel to
generate hot combustion gases, which flow through a turbine to
drive a load and/or compressor. At high velocities and
temperatures, an exhaust gas exits the turbine and enters an
exhaust diffuser. The exhaust diffuser may be an axial-radial
exhaust diffuser that transitions the flow from an axial direction
to a radial direction. Axial-radial exhaust diffusers incorporate
internal structural features such as struts and turning vanes. The
internal struts hold walls of the diffuser in a fixed relationship
to one another and transfer loads from a rotor to a foundation. The
internal turning vanes help divert the flow from the axial to
radial direction. Unfortunately, the exhaust diffuser design
results in significant pressure losses, particularly at the
internal struts and turning vanes.
BRIEF DESCRIPTION OF THE INVENTION
[0003] Certain embodiments commensurate in scope with the
originally claimed invention are summarized below. These
embodiments are not intended to limit the scope of the claimed
invention, but rather these embodiments are intended only to
provide a brief summary of possible forms of the invention. Indeed,
the invention may encompass a variety of forms that may be similar
to or different from the embodiments set forth below.
[0004] In accordance with a first embodiment, a system includes a
gas turbine diffuser. The gas turbine diffuser includes an axial
diffuser section including a first duct portion having an axial
flow path along a centerline of the gas turbine diffuser, wherein
the first duct portion has a first cross-sectional area that
expands along the axial flow path. The gas turbine diffuser also
includes an axial-radial diffuser section coupled to the axial
diffuser section, wherein the axial-radial diffuser section
includes a second duct portion having a curved flow path along the
centerline from the axial flow path to a radial flow path, the
second duct portion has a second cross-sectional area that expands
along the curved flow path, the curved flow path has a radius of at
least greater than or equal to approximately 30 centimeters, and
the axial-radial diffuser excludes any turning vane in the second
duct portion.
[0005] In accordance with a second embodiment, a system includes a
gas turbine diffuser. The gas turbine diffuser includes an axial
diffuser section including a first duct portion having an axial
flow path along a centerline of the gas turbine diffuser. The gas
turbine diffuser also includes an axial-radial diffuser section
coupled to the axial diffuser section, wherein the axial-radial
diffuser section includes a second duct portion having a curved
flow path along the centerline from the axial flow path to a radial
flow path and the axial-radial diffuser section excludes any
turning vane in the second duct portion.
[0006] In accordance with a third embodiment, a method includes
axially-radially diffusing an exhaust flow from a turbine through a
curved duct along a curved flow path without any turning vanes,
wherein the curved flow path has a radius of at least greater than
or equal to 2 times a cross-sectional width of the curved duct.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a cross-sectional view of an embodiment of a gas
turbine engine sectioned through a longitudinal axis;
[0009] FIG. 2 is a cross-sectional view of an embodiment of a
contoured exhaust diffuser of the gas turbine engine of FIG. 1
according to an embodiment; and
[0010] FIG. 3 is a perspective view of an embodiment of a contoured
exhaust diffuser of the gas turbine engine of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0011] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, all features of an actual
implementation may not be described in the specification. It should
be appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0012] When introducing elements of various embodiments of the
present invention, the articles "a," "an," "the," and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements.
[0013] The disclosed embodiments are directed toward a turbine
diffuser contoured to provide a smooth flow path to transition the
flow from an axial to radial direction without a turning vane,
while maximizing the pressure recovery in the diffuser. As
discussed below, the disclosed turbine diffuser may include an
axial diffuser section, an axial-radial diffuser section, and a
radial diffuser section. The axial diffuser section includes
diverging walls about one or more struts to reduce pressure losses
around the struts and to gradually transition to the axial-radial
diffuser section. The axial-radial diffuser section includes a
vaneless duct with a large radius of curvature to reduce flow
separation and pressure losses. For example, the axial-radial
diffuser section gradually turns the exhaust flow without any
abrupt changes between the axial and radial directions, thereby
eliminating the need for internal turning vanes. Instead of a sharp
turn or small radius of curvature, the axial-radial diffuser
section has the large radius of curvature along radially inward and
outwards walls. The radius of curvature may be at least
approximately 1 to 100 times a cross-sectional width of the turbine
diffuser. For example, the radius of curvature may be greater than
or equal to approximately 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times
the cross-sectional width of the turbine diffuser. In addition, to
improved flow performance, the disclosed turbine diffuser
eliminates mechanical issues, such as cracks, associated with
turning vanes.
[0014] FIG. 1 is a cross-sectional side view of an embodiment of
the gas turbine engine 118 along a longitudinal axis 158. As
appreciated, contoured exhaust diffusers without turning vanes may
be used in any fluid flow system that includes rotary machines,
such as gas turbine engines and stem turbine engines, and is not
intended to be limited to any particular machine or system. As
described further below, the contoured exhaust diffuser may be used
within the gas turbine engine 118 to maximize diffuser performance
by providing a smooth flow path to transition the flow through the
diffuser from an axial to radial direction. For example, angles may
be disposed near the diffuser inlet to provide early flow diffusion
to reduce pressure losses around one or more internal struts and to
make the flow path from the axial direction to the radial direction
less abrupt and more contoured. Furthermore, the diffuser may
include portions that gradually expand along the flow path to
further enhance the transition of the flow from an axial to radial
flow direction, thus, improving the aerodynamics of the diffuser,
while eliminating a source of performance loss (e.g., internal
turning vanes).
[0015] The gas turbine engine 118 includes one or more fuel nozzles
160 located inside a combustor section 162. In certain embodiments,
the gas turbine engine 118 may include multiple combustors 120
disposed in an annular arrangement within the combustor section
162. Further, each combustor 120 may include multiple fuel nozzles
160 attached to or near the head end of each combustor 120 in an
annular or other arrangement.
[0016] Air enters through an air intake section 163 and is
compressed by a compressor 132. The compressed air from the
compressor 132 is then directed into the combustor section 162
where the compressed air is mixed with fuel. The mixture of
compressed air and fuel is generally burned within the combustor
section 162 to generate high-temperature, high-pressure combustion
gases, which are used to generate torque within turbine section
130. As noted above, multiple combustors 120 may be annularly
disposed within the combustor section 162. Each combustor 120
includes a transition piece 172 that directs the hot combustion
gases from the combustor 120 to the turbine section 130. In
particular, each transition piece 172 generally defines a hot gas
path from the combustor 120 to a nozzle assembly of the turbine
section 130, included within a first stage 174 of the turbine
130.
[0017] As depicted, the turbine section 130 includes three separate
stages 174, 176, and 178. Each stage 174, 176, and 178 includes a
plurality of blades 180 coupled to a rotor wheel 182 rotatably
attached to a shaft 184. Each stage 174, 176, and 178 also includes
a nozzle assembly 186 disposed directly upstream of each set of
blades 180. The nozzle assemblies 186 direct the hot combustion
gases toward the blades 180 where the hot combustion gases apply
motive forces to the blades 180 to rotate the blades 180, thereby
turning the shaft 184. The hot combustion gases flow through each
of the stages 174, 176, and 178 applying motive forces to the
blades 180 within each stage 174, 176, and 178. The hot combustion
gases may then exit the gas turbine section 130 through an exhaust
diffuser 188. The exhaust diffuser 188 functions by reducing the
velocity of fluid flow through the exhaust diffuser 188 while also
increasing the static pressure to reduce the work of the gas
turbine engine 118. The exhaust diffuser includes a strut 190
disposed between the walls of the exhaust diffuser 188. The strut
190 holds the walls in a fixed relationship to another. The number
of struts 190 is variable and may range between 1 to 10 or more.
The exhaust diffuser 188 includes a contoured shape to transition
the fluid flow from an axial to radial direction without any
internal turning vane, while also including angles near an inlet
192 of the exhaust diffuser 188 to allow early flow diffusion.
[0018] FIG. 2 is a cross-sectional side view of the exhaust
diffuser 188 of FIG. 1 further illustrating the angles near the
inlet 192 and the contoured shape of the exhaust diffuser 188. The
exhaust diffuser 188 includes an axial diffuser section 202, an
axial-radial diffuser section 204, and a radial diffuser section
206. A centerline 208 generally defining the flow path runs from
the inlet 192 of the exhaust diffuser 188 toward an outlet 210. In
general, the cross-sectional area of the exhaust diffuser 188
expands downstream along the flow path from the inlet 192 towards
the outlet 210.
[0019] The axial diffuser section 202 includes a first duct portion
212 having an axial flow path 214 along the centerline 208 of the
exhaust diffuser 188. The first duct portion 212 includes a first
wall 216 offset from a second wall 218. Further, the first wall 216
and the second wall 218 are disposed opposite one another about the
axial flow path 214. The first wall 216 is mounted nearer or
proximate relative to a rotational axis, indicated by dashed line
220, of the turbine 130, while the second wall 218 is more distal
relative to the rotational axis 220. The first wall 216 extends
along the axial flow path 214 at a first angle 222 relative to the
rotational axis 220 of the turbine 130. In certain embodiments, the
first angle 222 may be a negative angle that ranges between
approximately 0 to 8 degrees, 2 to 6 degrees, or 4 to 5 degrees.
For example, the first angle 222 may be at least equal to or
greater than approximately 2, 4, 6, or 8 degrees, or any angle
therebetween. In addition, the second wall 218 extends along the
axial flow path 214 at a second angle 226 relative to the
rotational axis 220. In certain embodiments, the second angle 226
may be a positive angle that ranges between approximately 16 to 20
degrees or 17 to 19 degrees. For example, the second angle 226 may
be at least equal to or greater than approximately 16, 17, 18, 19,
or 20 degrees, or any angle therebetween. In the illustrated
embodiment, the first angle 222 and the second angle 226 are not 0
degrees. In some embodiments, the first angle 222 is less than or
equal to approximately 8 degrees, and the second angle 226 is
greater than or equal to approximately 16 degrees.
[0020] Due to the first and second angles 222 and 226,
respectively, the first wall 216 and the second wall 218 diverge
from one another along the axial flow path 214. As a result of the
divergence of the first wall 216 and the second wall 218, the first
duct portion 212, as FIG. 2 illustrates, includes a first
cross-sectional area 228 (i.e., perpendicular to centerline 208)
that expands along the axial flow path 214 between the first wall
216 and the second wall 218. The expansion of the cross-sectional
area 228 across the flow path may provide early flow diffusion that
reduces the pressure losses in diffuser performance across strut
190. Further, this expansion smoothes the flow path transition from
the axial to radial direction, as described below.
[0021] The axial diffuser section 202 is coupled to the
axial-radial diffuser section 204. The axial-radial diffuser
section 204 transitions the flow from the axial diffuser section
202 to the radial diffuser section 206. The axial-radial diffuser
section 204 includes a second duct portion 230 having a curved flow
path 232 along the centerline 208 from the axial flow path 214 to a
radial flow path 234. The second duct portion 230 includes a first
curved wall 236 offset from a second curved wall 238. Further, the
first curved wall 236 and the second curved wall 238 are disposed
opposite one another about the curved flow path 232. The first
curved wall 236 is mounted nearer or proximate relative to the
rotational axis 220 of the turbine 130, while the second curved
wall 238 is more distal relative to the rotational axis 220. The
first and second angles 222 and 226 extend toward the first and
second curved walls 236 and 238, respectively. Indeed, in some
embodiments, the first and second angles 222 and 226 may extend
directly to the first and second curved walls 236 and 238,
respectively. The extension of the angles 222 and 226 to the curved
walls 236 and 238 makes the flow path transition from the axial
diffuser section 202 to the axial diffuser section 204 more
aerodynamic, thereby reducing pressure losses in diffuser
performance normally associated with sharp transitions in the flow
path direction.
[0022] The first curved wall 236 curves along the curved flow path
232 with a first radius of curvature 240, while the second curved
wall 238 curves along the curved flow path 232 with a second radius
of curvature 242. The average of these radii 240 and 242 may be
defined by an average radius of curvature 243 relative to the
centerline 208 along the curved flow path 232. In certain
embodiments, the radii of curvature 240, 242, and 243 may vary
along the lengths of the first curved wall 236 and the second
curved wall 238. Accordingly, centers 241 of the radii 240, 242,
and 243 may shift to increase or decrease the radii 240, 242, and
243. At certain points along the length of the second duct portion
230, the first radius of curvature 240 and the second radius of
curvature 242 may be different from each other, while at other
points the first radius of curvature 240 and the second radius of
curvature 242 may be the same. Alternatively, the first radius of
curvature 240 and the second radius of curvature 242 may be
different along the entire lengths of the first curved wall 236 and
the second curved wall 238. In certain embodiments, the difference
between the first radius of curvature 240 and the second radius of
curvature 242 may range between approximately 0 to 50 percent, 10
to 40 percent, or 20 to 30 percent. For example, the difference may
be approximately 15, 20, 25, 30, or 35 percent, or any percent
therebetween. In certain embodiments, the first radius of curvature
240 may be larger than the second radius of curvature 242. In
alternative embodiments, the second radius of curvature 242 may be
larger than the first radius of curvature 240. In other
embodiments, the first radius of curvature 240 and the second
radius of curvature 242 may be the same.
[0023] In certain embodiments, the first radius of curvature 240
may range approximately from 30 centimeters to 390 centimeters, 80
to 340 centimeters, 130 to 390 centimeters, 180 to 300 centimeters,
or 220 to 260 centimeters. For example, the first radius of
curvature 240 may be approximately 30, 40, 50, 60, 70, 80, 90, or
100 centimeters, or any distance therebetween. In some embodiments,
the first radius of curvature 240 may be at least greater than or
equal to approximately 100 centimeters. In certain embodiments, the
second radius of curvature 242 may range approximately from 30
centimeters to 510 centimeters, 80 to 460 centimeters, 130 to 410
centimeters, 180 to 360 centimeters, or 230 to 310 centimeters. For
example, the second radius of curvature 242 may be approximately
30, 40, 50, 60, 70, 80, 90, or 100 centimeters, or any distance
therebetween. In some embodiments, the first radius of curvature
240 may be at least greater than or equal to approximately 100
centimeters. In certain embodiments, the radius 243 of the curved
flow path 232 may range approximately from 30 centimeters to 450
centimeters, 80 to 400 centimeters, 130 to 350 centimeters, 180 to
300 centimeters, or 220 to 260 centimeters. For example, the radius
243 may be approximately 30, 40, 50, 60, 70, 80, 90, or 100
centimeters, or any distance therebetween. In some embodiments, the
radius 243 may be at least greater than or equal to approximately
30 centimeters. In other embodiments, the radius 243 may be at
least greater than or equal to approximately 100 centimeters.
[0024] The curvature of the walls 236 and 238 provides a smoother,
more aerodynamic, flow path transition that eliminates the need for
an internal turning vane in the second duct portion 230. Thus, the
axial-radial diffuser section 204 excludes any internal turning
vane. Indeed, the first and second curved walls 236 and 238,
respectively, diverge from one another along the curved flow path
232 to allow greater diffusion during the transition from the axial
to radial direction. The curved second duct portion 230 has a
second cross-sectional area 244 (i.e., perpendicular to the
centerline 208) that expands along the curved flow path 232 between
the first curved wall 236 and the second curved wall 238. In other
words, the cross-sectional area 244 has a cross-sectional width 246
that expands along the curved flow path 232. The expansion of the
cross-sectional width 246 within the axial-radial diffuser section
204 allows diffusion of the flow to increase, while also
transitioning the flow from an axial to radial direction.
[0025] In the certain embodiments, the radii 240, 242, and 243 may
be at least approximately 1 to 100, 1 to 50, 1 to 25, or 1 to 10
times the cross-sectional width 246 of the curved flow path 232.
For example, radii 240, 242, and 243 may be at least greater than
or equal to approximately 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times
the cross-sectional width 246.
[0026] From the axial-radial diffuser section 204, the flow is
transitioned to the radial diffuser section 206. The axial-radial
diffuser section 204 is coupled to the radial diffuser section 206.
The radial diffuser section 206 includes a third duct portion 248
having a radial flow path 234 along the centerline 208 of the
diffuser 188. The third duct portion 248 includes a first vertical
wall 250 offset from a second vertical wall 252. Further, the first
vertical wall 250 and the second vertical wall 252 are disposed
opposite one another about the radial flow path 234. The diverging
first and second curved walls 236 and 238 of the second duct
portion 230 extend into the first vertical wall 250 and second
vertical wall 252, respectively. The first vertical wall 250 also
diverges from the second vertical wall 252 along the radial flow
path 234. As a result, the third duct portion 248 includes a third
cross-sectional area 254 (i.e., perpendicular to the centerline
208) that expands along the radial flow path 234 between the first
vertical wall 250 and the second vertical wall 252 to increase
diffusion and diffuser performance. From the radial diffuser
section 206, the flow is directed to the outlet 210 of the diffuser
188.
[0027] FIG. 3 is a perspective view of the exhaust diffuser 188
illustrating the contours and expansion of the diffuser 188. The
exhaust diffuser 188 includes the axial diffuser section 202, the
axial-radial diffuser section 204, and the radial diffuser section
206, as described above. The axial diffuser section 202 includes
the first and second walls 216 and 218. The axial-radial diffuser
section 204 includes the first and second curved walls 236 and 238.
Both the first and second walls 216 and 218, as well as, at least
portions of the first and second curved walls 236 and 238 include a
semi-annular curvature in a circumferential direction, as indicated
by arrow 262, transverse to the longitudinal axis 158 of the gas
turbine engine 118. The annular curvature of the walls 216, 218,
236, and 238 allows for the annular distribution of the exhaust
diffuser 188 around the exit of the turbine 130. In some
embodiments, one or more exhaust diffusers 188 may be distributed
around the exit of the turbine 130. As shown in FIG. 3, the exhaust
diffuser 188 includes a third wall 264 and a fourth wall 266 that
follow the flow path generally defined by the centerline 208. The
third wall 264 and the fourth wall 266 are disposed opposite from
each other and located between the first wall 216 and the second
wall 218, the first curved wall 236 and the second curved wall 238,
and the first vertical wall 250 and the second vertical wall 252
along the length of the diffuser 188. The third wall 264 and the
fourth wall 266 diverge from each other from the inlet 192 in a
downstream direction 268 to the outlet 210. Also, the
cross-sectional area of the exhaust diffuser 188 (i.e.,
perpendicular to the downstream direction 268) expands downstream
from the inlet 192 to the outlet 210 of the diffuser 188 in both a
vertical dimension 270 and a horizontal dimension 272. The
dimension 270 may be defined as a radial dimension relative to axis
158, whereas the dimension 272 may be defined as a circumferential
dimension relative to the axis 158.
[0028] In accordance with certain embodiments, the exhaust diffuser
188 above may be operated in conjunction with the turbine 130. For
example, a method of operation may include axially-radially
diffusing an exhaust flow from the turbine through a curved duct
along the curved flow path 232 without any turning vanes, wherein
the curved flow path 232 has an enlarged radius 243 to reduce flow
separation and pressure losses. In some embodiments, the radius 243
may be at least greater than or equal to approximately 30
centimeters and/or 1 to 10 times the width 246. In other
embodiments, the radius 243 may be at least greater than or equal
to at least 2 times the width 246. Also, in the method,
axially-radially diffusing the exhaust flow may include expanding
the exhaust flow between the first curved wall 236 and the second
curved wall 238 that curve along the curved flow path 232. As
discussed above, the first curved wall 236 may be oriented nearer
to the rotational axis 220 of the turbine 130 than the second
curved wall 238. The method may further include axially diffusing
the exhaust flow prior to axially-radially diffusing the exhaust
flow. Axially diffusing the exhaust flow includes expanding the
exhaust flow between a first angled wall 216 and a second angle
wall 218 that are angled relative to the axial flow path 214. As
discussed above, the first angled wall 216 may be oriented nearer
to the rotational axis 220 of the turbine 230 than the second
angled wall 218.
[0029] Technical effects of the disclosed embodiments include
providing angled walls 216 and 218 to provide early flow diffusion
to reduce the pressure losses across the struts 190. In addition,
the angled walls 216 and 218 allow for a smoother transition from
the axial diffuser section 202 to the axial-radial diffuser section
204 to decrease pressure losses during the axial to radial shift in
flow direction. Providing an axial-radial diffuser section with
curved walls 236 and 238 also smoothes the axial-to radial
transition, while eliminating the need for turning vanes. Further,
diverging walls along the axial diffuser section 202, the
axial-radial diffuser section 204, and the radial diffuser section
206 allows the flow to expand along the flow path and to increase
diffuser performance. Overall, the aerodynamic design of the
diffuser 188 improves diffuser performance, while eliminating a
source of performance loss and mechanical problems (i.e., the
turning vanes).
[0030] 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 have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
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