U.S. patent application number 13/902619 was filed with the patent office on 2014-11-27 for exhaust diffuser for a gas turbine engine exhaust system.
This patent application is currently assigned to SOLAR TURBINES INCORPORATED. The applicant listed for this patent is SOLAR TURBINES INCORPORATED. Invention is credited to Hans D. Hamm, Ulrich Edmund Stang.
Application Number | 20140348647 13/902619 |
Document ID | / |
Family ID | 51934129 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140348647 |
Kind Code |
A1 |
Stang; Ulrich Edmund ; et
al. |
November 27, 2014 |
EXHAUST DIFFUSER FOR A GAS TURBINE ENGINE EXHAUST SYSTEM
Abstract
An exhaust diffuser for a gas turbine engine includes a diffuser
inlet, a diffuser exit, an inner diffuser wall, and an outer
diffuser wall. The inner diffuser wall may include a first tubular
member with a flared downstream portion. The outer diffuser wall
may include a second tubular member at least partially about the
inner diffuser wall and with a second flared downstream portion.
The outer diffuser wall and the inner diffuser wall extend between
the diffuser inlet and the diffuser exit, and form a diffusing
flowpath therebetween. The second flared downstream portion may
include a lower section and an upper section, with the upper
section extending further downstream in an axial direction than the
lower section, relative to the diffuser axis.
Inventors: |
Stang; Ulrich Edmund;
(Solana Beach, CA) ; Hamm; Hans D.; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SOLAR TURBINES INCORPORATED |
San Diego |
CA |
US |
|
|
Assignee: |
SOLAR TURBINES INCORPORATED
San Diego
CA
|
Family ID: |
51934129 |
Appl. No.: |
13/902619 |
Filed: |
May 24, 2013 |
Current U.S.
Class: |
415/207 |
Current CPC
Class: |
F01D 25/30 20130101;
F01D 11/00 20130101 |
Class at
Publication: |
415/207 |
International
Class: |
F01D 11/00 20060101
F01D011/00 |
Claims
1. An exhaust diffuser for a gas turbine engine, the exhaust
diffuser comprising: a diffuser inlet; a diffuser exit; an inner
diffuser wall including a first tubular member about a diffuser
axis extending between the diffuser inlet and the diffuser exit,
the first tubular member including a first flared downstream
portion proximate the diffuser exit, and an outer diffuser wall
including a second tubular member about the diffuser axis and at
least partially about the inner diffuser wall and extending between
the diffuser inlet and the diffuser exit, the outer diffuser wall
and the inner diffuser wall forming a diffusing flowpath between
the diffuser inlet and the diffuser exit, the second tubular member
including a second flared downstream portion, the second flared
downstream portion including a lower section, and an upper section,
the upper section extending further downstream in an axial
direction than the lower section, relative to the diffuser
axis.
2. The exhaust diffuser of claim 1, wherein the an outer diffuser
wall further includes a uniform section extending downstream from
the diffuser inlet, the uniform section including a surface of
revolution, the surface of revolution defined by a two-dimensional
curve rotated about the diffuser axis, the two-dimensional curve
including a linear segment and a curved segment, and an offset
extension extending downstream from the uniform section to the
diffuser exit, the offset extension including a truncated surface
of revolution terminating in an offset end, the offset end
substantially defining a truncation plane (549), the truncation
plane (549) forming a cutback angle (546) with a normal plane
(548), the normal plane (548) normal to the diffuser axis, the
cutback angle (546) between 1 degree and 5 degrees from the normal
plane (548); and wherein the uniform section and the offset
extension together encompass the lower section and the upper
section.
3. The exhaust diffuser of claim 1, wherein the first flared
downstream portion extends radially outward from the diffuser axis,
and includes a surface of revolution about the diffuser axis
including a flare with between 75 degrees and 105 degrees of arc,
the flare terminating in a substantially normal direction to the
diffuser axis at the diffuser exit.
4. The exhaust diffuser of claim 1, further comprising a plurality
of diffuser struts circumferentially distributed around the
diffuser axis and extending between the outer diffuser wall and the
inner diffuser wall.
5. An exhaust system for a gas turbine engine, the exhaust system
comprising the exhaust diffuser of claim 1, and further comprising
an exhaust collector configured to receive exhaust gas
circumferentially from the diffuser exit, the exhaust collector
including an exhaust collector exit located substantially opposite
from the lower section, relative to the diffuser axis, a forward
wall, an aft wall, and a circumferential wall extending between the
forward wall and the aft wall, the circumferential wall encircling
a majority of the diffuser exit.
6. The exhaust system of claim 5, wherein the exhaust collector
further includes an exhaust collector turning region opposite the
discharge direction; and wherein the forward wall is maintained a
minimum axial distance from the aft wall, the minimum axial
distance being at least double a distance between the inner
diffuser wall and the outer diffuser wall at the diffuser exit
measured in a plane including the diffuser axis and a point on a
maximum cutback of the lower section.
7. The exhaust diffuser of claim 5, further comprising a minimum
gap between the diffuser exit at a maximum cutback of the lower
section and the circumferential wall, the minimum gap being at
least one half a distance between the inner diffuser wall and the
outer diffuser wall at the diffuser exit, and as measured in a
plane including the diffuser axis and a point on the maximum
cutback.
8. The exhaust system of claim 5, wherein the gas turbine engine
includes a center axis; and wherein the exhaust collector exit is
configured to discharge the exhaust gas in a discharge direction
radially between positive 135 degrees and negative 135 degrees
around the center axis from top dead center, relative to the gas
turbine engine.
9. An exhaust system for a gas turbine engine, the exhaust system
comprising: an exhaust diffuser including a diffuser inlet, a
diffuser exit, an inner diffuser wall extending between the
diffuser inlet and the diffuser exit, the inner diffuser wall
defining a surface of revolution with a first flared downstream
portion about a diffuser axis, and an outer diffuser wall extending
between the diffuser inlet and the diffuser exit, the outer
diffuser wall defining a truncated surface of revolution with a
second flared downstream portion about the diffuser axis, the
second flared downstream portion obliquely truncated proximate the
diffuser exit and relative to a plane normal to the diffuser axis,
the second flared downstream portion including a maximum cutback,
the inner diffuser wall and the outer diffuser wall forming a
diffusing flowpath between the diffuser inlet and the diffuser
exit; and an exhaust collector including an exhaust collector exit
configured to discharge exhaust gas along a discharge direction,
the exhaust collector exit located substantially opposite from the
maximum cutback, relative to the diffuser axis and along the
discharge direction, a forward wall, an aft wall, and a
circumferential wall extending between the forward wall and the aft
wall, the circumferential wall encircling a majority of the
diffuser exit.
10. The exhaust system of claim 9, wherein the gas turbine engine
includes a center axis; and wherein the exhaust collector exit is
configured to discharge exhaust gas in a discharge direction
radially between positive 90 degrees and negative 90 degrees around
the center axis from top dead center, relative to the gas turbine
engine.
11. The exhaust system of claim 9, wherein the first flared
downstream portion extends radially outward from the diffuser axis,
and includes a flared surface of revolution about the diffuser axis
including a flare with between 75 degrees and 105 degrees of arc,
the flare terminating in a substantially vertical direction at the
diffuser exit.
12. The exhaust system of claim 9, wherein the exhaust collector
further includes an exhaust collector turning region opposite the
discharge direction; and wherein the forward wall is maintained a
minimum axial distance from the aft wall, the minimum axial
distance being at least double a distance between the inner
diffuser wall and the outer diffuser wall at the diffuser exit
measured in a plane including the diffuser axis and a point on the
maximum cutback.
13. The exhaust system of claim 9, further comprising a minimum gap
between the diffuser exit at the maximum cutback and the
circumferential wall, the minimum gap being at least one half a
distance between the inner diffuser wall and the outer diffuser
wall at the diffuser exit, and as measured in a plane including the
diffuser axis and a point on the maximum cutback.
14. The exhaust system of claim 9, wherein the exhaust collector
further includes an exhaust collector turning region opposite the
discharge direction; and wherein the forward wall is maintained a
minimum axial distance from the aft wall, the minimum axial
distance being approximately the same as an axial distance between
the forward wall and the aft wall opposite the exhaust collector
turning region and proximate the diffuser exit.
15. The exhaust system of claim 9, wherein the truncated surface of
revolution is at least partially defined by a two-dimensional curve
rotated about the diffuser axis, the two-dimensional curve
including linear segment at an upstream end and a curved segment at
a downstream end, the linear segment aligned with a tangent of the
curved segment at an interfacing point.
16. An exhaust system for a gas turbine engine, the gas turbine
engine having a center axis and a turbine, the exhaust system
comprising: an exhaust diffuser including a diffuser inlet, a
diffuser exit, an inner diffuser wall, and an outer diffuser wall,
the inner diffuser wall, and the outer diffuser wall extending
between the diffuser inlet and the diffuser exit and forming a
diffusing flowpath therebetween, the diffuser inlet configured to
axially receive exhaust gas from the turbine, the diffuser exit
configured to radially discharge the exhaust gas, the inner
diffuser wall including a first surface of revolution about the
center axis, the first surface of revolution including a first
conic region and a first flared downstream portion, the first
flared downstream portion including a first flare radius, the outer
diffuser wall including a second surface of revolution about the
center axis, the second surface of revolution including a second
conic region and a second flared downstream portion, the second
flared downstream portion including a second flare radius and an
cutback portion with a maximum cutback located substantially
radially opposite from the exhaust collector exit; and an exhaust
collector including an exhaust collector exit, a forward wall, a
circumferential wall, and an aft wall, the circumferential wall
extending between the forward wall and the aft wall, the exhaust
collector configured to receive the exhaust gas circumferentially
about the center axis from the diffuser exit, the exhaust collector
exit configured to discharge the exhaust gas in a discharge
direction radially between positive 135 degrees and negative 135
degrees around the center axis from top dead center, the discharge
direction substantially radially opposite from the maximum cutback,
relative to the center axis.
17. The exhaust system of claim 16, wherein the first flared
downstream portion extends radially outward from the center axis,
and includes a flared surface of revolution about the center axis
including a flare with between 75 degrees and 105 degrees of arc,
the flare terminating in a substantially vertical direction at the
diffuser exit.
18. The exhaust system of claim 16, wherein the forward wall is
substantially vertical.
19. The exhaust system of claim 16, wherein the first flare radius
and the second flare radius are concentric; and wherein the second
flare radius is constant.
20. The exhaust system of claim 16, wherein the discharge direction
is radially between positive 5 degrees and negative 5 degrees
around the center axis from top dead center.
Description
TECHNICAL FIELD
[0001] The present disclosure generally pertains to a gas turbine
engines, and is more particularly directed toward an exhaust system
for a gas turbine including exhaust diffuser.
BACKGROUND
[0002] A gas turbine engine generates high-temperature
high-velocity exhaust gas. The exhaust diffuser is defined by an
increase in flow area resulting in a reduction in the velocity of
the exhaust flow which, in turn, leads to an increase in static
pressure along its flow path. Because of this pressure recovery in
the diffuser, the inlet-to-exit pressure ratio of the turbine is
increased, resulting in an increase in both output power and
thermal efficiency. Additionally, the exhaust system serves to
redirect the exhaust gases away from downstream equipment or
towards site-specific interfaces.
[0003] U.S. Pat. No. 5,257,906 issued to Gray, et al. on Nov. 5,
1993 shows an exhaust system for a steam turbine. In particular,
the disclosure of Gray, et al. is directed toward an exhaust system
having a diffuser that directs the flow of working fluid from a
turbine exit to an exhaust housing having a bottom opening, thereby
turning the flow 90 degrees from the axial to radial direction. In
the exhaust housing, the flow exiting at the top of the diffuser
turns 180 degrees from the vertically upward direction to the
downward direction. The strength of the vortex formed in the
exhaust housing as a result of this turning is minimized by
orienting the outlet of an outer exhaust flow guide portion of the
diffuser so that it lies in a plane that makes an angle with a
plane perpendicular to the turbine axis. As a result, the minimum
axial length of the outer flow guide occurs at a location remote
from the exhaust housing outlet and the maximum axial length occurs
at a location proximate the opening, thereby crowding the vortex
against a radially extending baffle in the exhaust housing.
[0004] The present disclosure is directed toward overcoming known
problems and/or problems discovered by the inventors.
SUMMARY
[0005] An exhaust diffuser for a gas turbine engine includes a
diffuser inlet, a diffuser exit, an inner diffuser wall, and an
outer diffuser wall. The inner diffuser wall may include a first
tubular member with a flared downstream portion. The outer diffuser
wall may include a second tubular member at least partially about
the inner diffuser wall and with a second flared downstream
portion. The outer diffuser wall and the inner diffuser wall extend
between the diffuser inlet and the diffuser exit, and form a
diffusing flowpath therebetween. The second flared downstream
portion may include a lower section and an upper section, with the
upper section extending further downstream in an axial direction
than the lower section, relative to the diffuser axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic illustration of an exemplary gas
turbine engine.
[0007] FIG. 2 is an isometric view of an exhaust system of the gas
turbine engine of FIG. 1.
[0008] FIG. 3 is a cutaway side view of the exhaust system of FIG.
2.
DETAILED DESCRIPTION
[0009] Systems and methods disclosed herein include an exhaust
system for a gas turbine including an axial-to-radial exhaust
diffuser and a radial exhaust collector downstream of the diffuser.
Embodiments include an axial-to-radial exhaust diffuser wherein the
diffuser exit is cutback.
[0010] FIG. 1 is a schematic illustration of an exemplary
industrial gas turbine engine. Some of the surfaces have been left
out or exaggerated (here and in other figures) for clarity and ease
of explanation. Also, the disclosure will generally reference a
center axis 95 of rotation of the gas turbine engine, which may be
generally defined by the longitudinal axis of its shaft 120
(supported by a plurality of bearing assemblies 150). The center
axis 95 may be common to or shared with various other engine
concentric components. All references to radial, axial, and
circumferential directions and measures refer to center axis 95,
unless specified otherwise, and terms such as "inner" and "outer"
generally indicate a lesser or greater radial distance from,
wherein a radial 96 may be in any direction perpendicular and
radiating outward from center axis 95.
[0011] In addition, the disclosure may reference a "forward" and an
"aft" direction. Generally, all references to "forward" and "aft"
are associated with the flow direction of primary air (i.e., air
used in the combustion process), unless specified otherwise. For
example, forward is "upstream" relative to primary air flow (i.e.,
towards the point where air enters the system), and aft is
"downstream" relative to primary air flow (i.e., towards the point
where air leaves the system).
[0012] Generally, a gas turbine engine 100 includes an inlet 110, a
compressor 200, a combustor 300, a turbine 400, an exhaust system
500, and a power output coupling 600. The compressor 200 includes
one or more compressor rotor assemblies 220. The combustor 300
includes one or more injectors 350 and includes one or more
combustion chambers 390. The turbine 400 includes one or more
turbine rotor assemblies 420. The exhaust system 500 includes an
exhaust diffuser 520 and an exhaust collector 550.
[0013] In operation, air 10 enters the inlet 110 as a "working
fluid", and is compressed by the compressor 200. In the compressor
200, the working fluid is compressed in an annular flow path by a
series of compressor rotor assemblies 220. Once compressed, the
compressed air leaves the compressor 200 and enters the combustor
300, where it is diffused and fuel is added. The fuel and the
compressed air are injected into the combustion chamber 390 via the
injectors 350 and ignited. After the combustion reaction, energy is
extracted from the combusted fuel/air mixture via the turbine 400
by a series of the turbine rotor assemblies 420. Exhaust gas 90 is
then diffused in exhaust diffuser 520. The exhaust collector 550
collects, redirects, and releases the exhaust gas 90 from the
system. Exhaust gas 90 may also be further processed (e.g., to
reduce harmful emissions, and/or to recover heat from the exhaust
gas 90).
[0014] One or more of the above components (or their subcomponents)
may be made from stainless steel and/or durable, high temperature
materials known as "superalloys". A superalloy, or high-performance
alloy, is an alloy that exhibits excellent mechanical strength and
creep resistance at high temperatures, good surface stability, and
corrosion and oxidation resistance. Superalloys may include
materials such as HASTELLOY, INCONEL, WASPALOY, RENE alloys, HAYNES
alloys, INCOLOY, MP98T, TMS alloys, CMSX single crystal alloys,
Alloy X, Alloy 188/230, and the like.
[0015] FIG. 2 is an isometric view of an exhaust system of the gas
turbine engine of FIG. 1. In particular, this view is generally
looking forward and upstream but in isolation from the rest of gas
turbine engine 100. For clarity and illustration purposes, certain
features/components have been added, removed, and/or modified. For
example, in this view, an aft wall 554 of the exhaust collector 550
is only partially shown.
[0016] FIG. 3 is a cutaway side view of the exhaust system of FIG.
2. In particular, the side view coincides with a flow symmetry
plane. The symmetry plane is formed by the center axis 95 and a
discharge direction 559. For clarity and illustration purposes,
certain features/components have been added, removed, and/or
illustrated schematically. For example, in this view, components
internal to the inner diffuser wall 523 (e.g., shaft 120 and
bearings 150) are illustrated schematically with additional
components removed.
[0017] As illustrated in FIG. 2 and FIG. 3, the exhaust diffuser
520 is an axial radial diffuser configured to pneumatically couple
with and form a flowpath between the turbine 400 (FIG. 1) and the
exhaust collector 550. In general, the exhaust diffuser 520 may be
conceptualized as two concentric structures (e.g., tubes) having a
diffuser axis 535, joined to each other via a plurality of struts
525 circumferentially distributed around the diffuser axis 535. The
diffuser axis 535 may coincide with the center axis 95 when the
exhaust diffuser 520 is installed onto the gas turbine engine 100.
Accordingly, when installed, the flowpath may be an annular exhaust
flow path between the turbine 400 and the exhaust collector 550,
interrupted by only the struts 525 themselves. For convenience, the
center axis 95 will be referred hereinafter to include the diffuser
axis 535.
[0018] The exhaust diffuser 520 includes a diffuser inlet 521, a
diffuser exit 522, an inner diffuser wall 523, and an outer
diffuser wall 524. The exhaust diffuser 520 is configured to
receive exhaust gas 90 in a generally axial direction from the
turbine 400 via the diffuser inlet 521. The exhaust diffuser 520 is
further configured to discharge the exhaust gas 90 in a generally
radial direction into of the exhaust collector 550 via the diffuser
exit 522.
[0019] The inner diffuser wall 523 and the outer diffuser wall 524
are generally tubular members circumscribing the center axis 95.
The inner diffuser wall 523 includes a first flared downstream
portion 541 proximate the diffuser exit 522 that extends radially
outward. Similarly, the outer diffuser wall 524 includes a second
flared downstream portion 543 proximate the diffuser exit 522 that
extends radially outward.
[0020] At an upstream end, the inner diffuser wall 523 is
positioned radially within the outer diffuser wall 524. At a
downstream end, the inner diffuser wall 523 extends axially beyond
the outer diffuser wall 524. The inner diffuser wall 523 and the
outer diffuser wall 524 may be joined together by the plurality of
struts 525 extending therebetween. According to one embodiment, the
inner diffuser wall 523 and the outer diffuser wall 524 may be at
least partially concentric.
[0021] Together, the inner diffuser wall 523 and the outer diffuser
wall 524 form the diffuser inlet 521 and the diffuser exit 522. In
particular, the diffuser inlet 521 may be an annular opening formed
by concentric upstream ends of the inner diffuser wall 523 and the
outer diffuser wall 524. Similarly, the diffuser exit 522 may be a
circumferential band opening formed by an axial displacement of
first flared downstream portion 541 and second flared downstream
portion 543. According to one embodiment, the diffuser inlet 521
and the diffuser exit 522 may be interrupted or traversed by
members extending between the inner diffuser wall 523 and the outer
diffuser wall 524 (e.g., struts, vanes, etc.).
[0022] Together, the inner diffuser wall 523 and the outer diffuser
wall 524 also form the flowpath between the turbine 400 and the
exhaust collector 550. In particular, an outer surface of the inner
diffuser wall 523 and an inner surface of the outer diffuser wall
524 form an annular flowpath between the turbine 400 and the
exhaust collector 550. As the flowpath advances downstream it
transitions from a predominantly annular shape to a predominantly
circumferential band shape directed radially outward. According to
one embodiment, the flowpath may be interrupted or traversed by
members extending between the inner diffuser wall 523 and the outer
diffuser wall 524 (e.g., struts, vanes, etc.).
[0023] Additionally, an inner surface of the inner diffuser wall
523 and an outer surface of the outer diffuser wall 524 may differ
in shape from their opposing sides (discussed above). For example,
both the inner surface of the inner diffuser wall 523 and the outer
surface of the outer diffuser wall 524 may have a generally
cylindrical shape or a stepped cylindrical shape (each step having
a different diameter). Alternately, portions of both the inner
surface of the inner diffuser wall 523 and the outer surface of the
outer diffuser wall 524 may be cylindrical or stepped, and other
portions may be shaped similar to their respective opposing sides.
Note, hereinafter, discussion of the inner diffuser wall 523 and
the outer diffuser wall 524 refers to the flowpath surfaces (i.e.,
the outer surface of the inner diffuser wall 523 and the inner
surface of the outer diffuser wall 524) unless specifically
described otherwise.
[0024] As illustrated, the exhaust collector 550 is a radial
exhaust collector configured to pneumatically couple with the
exhaust diffuser 520, "collect" the exhaust gas 90 and redirect it
radially away in a single, convenient discharge direction 559 away
from the gas turbine engine 100 (FIG. 1). In one embodiment, the
exhaust collector 550 is an enclosure wrapping around the exhaust
diffuser 520 and having a single opening in a generally radial
direction for discharge of the exhaust gas 90. Here, the exhaust
collector 550 is configured to radially receive the exhaust gas 90
and redirect it radially upward, or along a discharge direction 559
of approximately 0 degrees or +/-5 degrees from top dead center
(TDC), without an axial component.
[0025] The exhaust collector 550 includes an exhaust collector exit
551, a forward wall 552, a circumferential wall 553, and the aft
wall 554. The exhaust collector 550 is configured to receive
exhaust gas 90 in a generally radial direction from the exhaust
diffuser 520 via the diffuser exit 522. The exhaust collector 550
is further configured to discharge the exhaust gas 90 in the
discharge direction 559 away from the gas turbine engine 100 via
the exhaust collector exit 551.
[0026] Together, the forward wall 552, the circumferential wall
553, and the aft wall 554 enclose the diffuser exit 522 such that
discharged exhaust gas 90 is directed to the exhaust collector exit
551. In particular, the circumferential wall 553 may encircle a
majority of the diffuser exit 522, about the center axis 95, and be
sufficiently offset to accept flow from the diffuser exit 522. In
addition, the circumferential wall 553 may be bound on a forward
side by the forward wall 552 and on an aft side by the aft wall
554.
[0027] Furthermore, the forward wall 552 and the aft wall 554 may
each extend radially inward from the circumferential wall 553 and
mate with the outer diffuser wall 524 and the inner diffuser wall
523, respectively, and/or any intervening member. According to one
embodiment, the forward wall 552 may be a vertical wall coupled to
the outer diffuser wall 524 forward of the diffuser exit 522, and
the aft wall 554 may be a vertical wall coupled to the inner
diffuser wall 523 aft of the diffuser exit 522.
[0028] Together, the forward wall 552, the circumferential wall
553, and the aft wall 554 form the exhaust collector exit 551. In
particular, the exhaust collector exit 551 may be an opening formed
by upstream ends of the forward wall 552, the circumferential wall
553, and the aft wall 554. For example, the upstream ends of the
forward wall 552, the circumferential wall 553, and the aft wall
554 may be joined, forming a single path to exit the enclosure. The
exhaust collector exit 551 may be of any convenient shape and
orientation to the discharge direction 559. For example and as
illustrated, the exhaust collector exit 551 may have a generally
rectangular shape that is normal to the discharge direction
559.
[0029] According to one embodiment, the exhaust collector exit 551
may include one or more transition members configured to interface
the exhaust collector 550 with additional exhaust ducting. In
particular, the one or more transition members may mate with both
the exhaust collector 550 (having a first shape and/or effective
flow area) and additional exhaust ducting (having a second,
dissimilar shape and/or effective flow area), transitioning between
the two. For example, the exhaust collector exit 551 may include a
hood configured to couple to the exhaust collector exit 551 in a
generally rectangular shape and first effective flow area, and
transition to a round exhaust duct having a second effective flow
area. Also for example, the one or more transition members may
interface with the exhaust collector exit 551 and/or additional
exhaust ducting at oblique angles, irregular or asymmetrical
shapes, or as otherwise convenient.
[0030] Although the exhaust collector 550 is configured here to
discharge the exhaust gas 90 upward, the exhaust collector 550 may
be configured to discharge the exhaust gas 90 along other discharge
directions 559. For example, the exhaust collector 550 may be
configured to discharge the exhaust gas 90 radially sideways, or
along a discharge direction 559 of approximately +/-90 degrees from
TDC without an axial component. Also for example, the exhaust
collector 550 may be configured to discharge the exhaust gas 90
along any discharge direction 559 between +90 degrees and -90
degrees from TDC, without an axial component. According to another
embodiment, the exhaust collector 550 may be configured to
discharge the exhaust gas 90 along any discharge direction 559
between +135 degrees and -135 degrees from TDC without an axial
component. Alternately, the exhaust collector 550 may be configured
to discharge the exhaust gas 90 along any of the abovementioned
discharge directions 559 or ranges of discharge directions 559, but
with an axial component up to 45 degrees aft.
[0031] The exhaust diffuser 520 may be mounted to the turbine 400
and configured to axially receive exhaust gas 90 leaving the
turbine 400 in a predominantly axial flow 531. As illustrated, the
predominantly axial flow 531 may have a velocity vector between
+/-15 degrees, relative to the center axis 95, but no greater than
+/-45 degrees, relative to the center axis 95. The exhaust diffuser
520 may be further configured to diffuse the exhaust gas 90, impart
a radial component to its flow, and radially discharge the exhaust
gas 90 as a predominantly radial flow 532 around the center axis 95
and into the exhaust collector 550. As illustrated, the
predominantly radial flow 532 may have a velocity vector between 75
degrees and 105 degrees, relative to the center axis 95, but no
less than 45 degrees and no greater than 135 degrees, relative to
the center axis 95.
[0032] The exhaust collector 550 may be mounted to the exhaust
diffuser 520 and/or any other supporting structure. The exhaust
collector 550 may be configured to receive exhaust gas 90 expelled
from the diffuser exit 522 and redirect it around and toward the
exhaust collector exit 551, and expel the exhaust gas 90 in the
discharge direction 559.
[0033] The exhaust diffuser 520 may include a linear diffusion
region 526 followed by a turning region 527. The linear diffusion
region 526 be shaped as an annular conical frustum, or the like,
configured to increase the effective flow area between the inner
diffuser wall 523 and the outer diffuser wall 524 from the diffuser
inlet 521 to turning region 527. In particular, the effective flow
area may increase relative to the operation conditions of the
exhaust gas 90 so as to increase recovery and inhibit separation.
For example, the effective flow area may be increased along the
flowpath by increasing the distance between the diffuser inlet 521
and the diffuser exit 522 with respect to the flowpath. Also for
example, the effective flow area may be increased along the
flowpath by increasing the average circumference of the
flowpath.
[0034] According to one embodiment, linear diffusion region 526 may
include a canted flowpath. In particular, the inner diffuser wall
523 may form a conical frustum about the center axis 95. For
example, the inner diffuser wall 523 may be angled between 0
degrees to 15 degrees away from the center axis 95 in the
downstream direction. Also for example, the inner diffuser wall 523
may be angled between 3 degrees to 10 degrees away from the center
axis 95 in the downstream direction. Also for example, the inner
diffuser wall 523 may be angled approximately 5 degrees away from
the center axis 95 in the downstream direction.
[0035] The turning region 527 is a curved region beginning at the
linear diffusion region 526 and terminating downstream at the
diffuser exit 522. The turning region 527 is configured to add a
radial component to the velocity vector of the exhaust gas 90 and
turn the exhaust gas 90 from the predominantly axial flow 531 to
the predominantly radial flow 532.
[0036] The linear diffusion region 526 and the turning region 527
may include separable axial sections of the inner diffuser wall 523
and the outer diffuser wall 524. In particular, portions of the
inner diffuser wall 523, or portions of the outer diffuser wall 524
may be joined to form the linear diffusion region 526. Likewise,
portions of the inner diffuser wall 523, or portions of the outer
diffuser wall 524 may be joined to form the turning region 527.
[0037] Moreover, each axial section forming the linear diffusion
region 526 and the turning region 527 may be smoothly joined
together, such that the linear diffusion region 526 coincides with
a tangent of the turning region 527 at their interface. For
example, the inner diffuser wall 523 may include a first surface of
revolution about the diffuser axis 535, with the first surface of
revolution including a first conic region and a first flared
downstream portion 541. Likewise, the outer diffuser wall 524 may
include a second surface of revolution about the diffuser axis 535,
with the second surface of revolution including a smoothly joined
second conic region and a second flared downstream portion 543 (the
second flared downstream portion 543 as described further
herein).
[0038] In addition, the inner diffuser wall 523 and the outer
diffuser wall 524 may each be made from one or more components, or
any combination thereof. In particular, the inner diffuser wall 523
and/or the outer diffuser wall 524 may be built up of a plurality
of assembled sections. Moreover, each component or assembly may be
manufactured differently and according to its shape or
replaceablity.
[0039] For example, the inner diffuser wall 523 and/or the outer
diffuser wall 524 may be made up of a plurality of assembled
sections. Also for example, the inner diffuser wall 523 and the
outer diffuser wall 524, including struts 525 may be made as an
inlet unit 528 (e.g., a single cast part), with the remainder of
the inner diffuser wall 523 and the outer diffuser wall 524 being a
stacked assembly of annular wall sections. Also for example and as
illustrated, the linear diffusion region 526 may built up as the
inlet unit 528 and a stacked assembly of annular wall sections, and
the turning region 527 may be made up of the first flared
downstream portion 541 and the second flared downstream portion
543.
[0040] According to one embodiment, the exhaust diffuser 520 may be
offset. In particular, the second flared downstream portion 543 may
include a lower section 536 and an upper section 537 where the
upper section 537 extends further downstream in an axial direction
than the lower section 537, relative to the diffuser axis 535.
Accordingly, and in contrast to a downstream tube end that is
normal to the diffuser axis 535, here, the lower section 536 and an
upper section 537 may terminate in an offset end 540. Note, the
terms "upper section" and "lower section" are used for convenience
to describe opposing sides of the second flared downstream portion
543 as illustrated in a vertical (0 degree) exhaust configuration,
however other opposing sections are contemplated, particularly in
exhaust systems having discharge directions other than 0 degrees.
For example, in an application having a 90 degree discharge
direction, the terms "upper section" and "lower section" could be
replaced with "right section" and "left section", respectively.
[0041] As illustrated, the offset end 540 may substantially define
a truncation plane 549. The truncation plane 549 may form a cutback
angle 546 with a normal plane 548, with the normal plane 548 being
a plane normal to the diffuser axis 535. The cutback angle 546 may
be approximately 2 degrees from the normal plane 548. Alternately,
the cutback angle 546 may be between 1 degree and 5 degrees from
the normal plane 548.
[0042] Similarly, the exhaust diffuser 520 may include an offset
outer diffuser wall 524. In particular, the outer diffuser wall 524
may include a uniform section 538 and an offset extension 539,
which together may encompass the lower section 536 and the upper
section 537 described above. For example, the uniform section 538
may extend downstream from the diffuser inlet 521, and include a
surface of revolution. The surface of revolution may be defined by
a two-dimensional curve rotated about the diffuser axis 535, with
the two-dimensional curve including a linear segment 526 and a
curved segment. In addition, the offset extension 539 may extend
downstream from the uniform section 538 to the diffuser exit 522,
and include a truncated surface of revolution, terminating in the
offset end 540 described above.
[0043] According to one embodiment, the exhaust diffuser 520 may
include a "cutback" outer diffuser wall 524, for example in the
second flared downstream portion 543, that is coordinated with the
exhaust collector exit 551. In particular, the outer diffuser wall
524 may include a complex shape that may be conveniently described
as a basic, "uncut", shape having a downstream portion absent or
"cutback", the absent portion being predominantly located on the
opposite side of, or substantially radially opposite from the
exhaust collector exit 551.
[0044] Moreover, the basic, "uncut", shape may be a surface of
revolution about the center axis 95 and the "cutback" may include
an oblique cut angle, relative to the center axis 95, such that it
includes a maximum cutback 545 opposite the discharge direction
559. In addition, the surface of revolution about the center axis
95 may include both the linear diffusion region 526 and the turning
region 527 described above.
[0045] For example the surface of revolution may be defined by a
two-dimensional curve rotated about the center axis 95, the
two-dimensional curve including linear segment and a curved
segment, wherein the linear segment is aligned with a tangent of
the curved segment. The linear segment and the curved segment may
be shaped, oriented, and positioned to form a surface of revolution
of both the linear diffusion region 526 and the turning region 527
described above for the outer diffuser wall 524.
[0046] The maximum cutback 545 is the point or portion of the outer
diffuser wall 524 corresponding to the greatest absent portion,
truncation, or "cutback" from the basic, "uncut", shape. In
particular, the outer diffuser wall 524 may have a single point (or
several points where the cut is not planar) on its downstream end
that is further from the downstream end of the basic, "uncut",
shape than all other downstream endpoints on the outer diffuser
wall 524.
[0047] The maximum cutback 545 may be measured along a curve. For
example, for each point on the outer diffuser wall 524 that forms
part of the diffuser exit 522 (i.e., each point on the downstream
end of the outer diffuser wall 524), a plane may be formed by the
center axis 95 and the point. Accordingly, a curve corresponding to
each point may be defined by the intersection of its respective
plane and the basic, "uncut", shape. The maximum cutback 545 may
then be defined as the point (or portion) of the outer diffuser
wall 524 that forms part of the diffuser exit 522 and has the
longest extrapolation from the respective point on the diffuser
exit 522 to the downstream end of the basic, "uncut", shape along
the in-plane curve.
[0048] The maximum cutback 545 may be measured along the center
axis 95. For example, the maximum cutback 545 may include the point
(or portion) of the outer diffuser wall 524 that forms part of the
diffuser exit 522 and has the greatest axial distance from a
reference plane that is normal to the center axis 95 and is located
aft of the diffuser exit 522.
[0049] Alternately, the maximum cutback 545 may be measured along a
radial 96. In particular, the maximum cutback 545 may include the
point (or portion) of the outer diffuser wall 524 that forms part
of the diffuser exit 522 and has the greatest radial distance from
a point on the circumferential wall 553 along the same radial.
Since the circumferential wall 553 may open up, or otherwise
increase its radius as it approaches the discharge direction 559,
this measurement of the maximum cutback 545 may be limited to a
range of radials 96 greater than 180 degrees from the discharge
direction 559.
[0050] According to one embodiment, the "cutback" of the outer
diffuser wall 524 may be located in the second flared downstream
portion 543. In particular, the second flared downstream portion
543 of the outer diffuser wall 524 may include an obliquely
truncated shape. For example, the second flared downstream portion
543 may include a surface of revolution about the center axis 95
that is obliquely truncated proximate the diffuser exit 522, and
further includes the maximum cutback 545 opposite the discharge
direction 559.
[0051] To illustrate, the second flared downstream portion 543 may
include an obliquely truncated trumpet bell shape having an
obliquely cutback portion aligned substantially radially opposite
from the exhaust collector exit 551. In particular, the obliquely
truncated second flared downstream portion 543 may include a shape
truncated from a basic, "uncut", flared shape. The obliquely
cutback portion generally refers to a surface of the second flared
downstream portion 543 corresponding to the truncation or cut from
an otherwise basic, "uncut" shape. The basic, "uncut", flared shape
is a flared surface of revolution, the surface being defined by a
two-dimensional curve rotated about the center axis 95. In
addition, the upstream end of the two-dimensional curve may be
tangentially aligned to a line corresponding to the linear
diffusion region 526 described above, thus forming the smooth
transition at their interface.
[0052] As illustrated, the two-dimensional curve may substantially
be quarter-circle (e.g., between 75 degrees and 105 degrees) having
a flare radius 544, and oriented such that a radial 96 of center
axis 95 runs tangential to the downstream end of the
two-dimensional curve. Also as illustrated, the flare radius 544
may be constant up to the diffuser exit 522 (i.e., a terminating
downstream end). Also, for reference, an extrapolation line 547 is
shown, indicating a continuing flare radius of an absent portion of
the two-dimensional curve at its maximum cutback 545.
[0053] Likewise, the two-dimensional curve may be made of other,
non-circular curvatures. In particular, the two-dimensional curve
may include a non-linear curve having an arc of approximately 90
degrees. For example the two-dimensional curve may have an arc
between 75 degrees and 105 degrees. According to one embodiment,
the flare radius 544 of the second flared downstream portion 543
may be concentric with a flare radius of the first flared
downstream portion 541.
[0054] The obliquely truncated second flared downstream portion 543
may be described as the difference between the basic, "uncut",
flare shape and the truncation, absent portion, or "cutback" of the
basic, "uncut", flare shape. Here, the truncation includes the
portion of the basic, "uncut", flare shape between a normal plane
548 and a truncation plane 549.
[0055] The normal plane 548 is normal to the center axis 95, and
defines the entire downstream end of the basic, "uncut", flare
shape. At least one point of the downstream end of the obliquely
truncated second flared downstream portion 543 lies on the normal
plane 548. The truncation plane 549 is normal to the flow symmetry
plane, but is oblique to the normal plane 548 by a cutback angle
546. According to one embodiment, the cutback angle 546 may be less
than 10 degrees from vertical. According to another embodiment, the
cutback angle 546 may be between 1 degree and 5 degrees from
vertical. According to another embodiment, the cutback angle 546
may be approximately 2 degrees from vertical. Alternately, the
truncation may include the portion of the basic, "uncut", flare
shape between a normal plane 548 and a non-planar cutback.
[0056] The obliquely truncated second flared downstream portion 543
is truncated in coordination with the exhaust collector exit 551.
In particular, the maximum cutback 545 of the obliquely truncated
second flared downstream portion 543 is aligned with an exhaust
collector turning region 555. The exhaust collector turning region
555 is generally defined as an area within the exhaust collector
550 that is opposite the discharge direction 559 where the exhaust
gas 90 expelled from the diffuser exit 522 separated into opposing
circumferential flows about the circumferential wall 553. For
example, here, the exhaust collector turning region is at the
bottom of the exhaust collector 550. Accordingly, here, the outer
diffuser wall 524 includes a maximum cutback 545 or maximum
truncation at its bottom end.
[0057] As above, the maximum cutback 545 is the point (or portion)
of the outer diffuser wall 524 corresponding to the greatest
truncation, absent portion, or "cutback" from the basic, "uncut",
flare shape, and may be measured along the center axis 95 and/or a
radial 96. In addition, the maximum cutback 545 may be measured
relative to its flare angle. In particular, the maximum cutback 545
may include the point (or portion) of the outer diffuser wall 524
that forms part of the diffuser exit 522 and has the shortest flare
angle or arc. As described above, the second flared downstream
portion 543 may be cut from a surface of revolution about the
center axis 95. As such, the degree of flare is constant on the
outer diffuser wall 524 at each axial location. Accordingly and for
example, where the discharge direction 559 of the exhaust collector
550 is upward or 0 degrees from TDC, the flare shape at the top of
the second flared downstream portion 543 may have a maximum arc
(e.g., approximately 90 degrees), and the flare shape at the bottom
of the second flared downstream portion 543 may have a minimum arc
(e.g., approximately 50 degrees).
[0058] According to one embodiment, the inner diffuser wall 523 may
be shaped similarly to the outer diffuser wall 524. In particular,
the first flared downstream portion 541 may include a surface of
revolution about the center axis 95 including a flare with between
75 degrees and 105 degrees of arc, and terminating in a
substantially vertical direction at the diffuser exit 522.
Moreover, the flare of the first flared downstream portion 541 may
travel through approximately the same arc as the maximum arc of the
second flared downstream portion 543. For example, the inner
diffuser wall 523 may include a flare that is concentric with the
flare radius 544 of the second flared downstream portion 543,
shares approximately 90 degrees of arc with the second flared
downstream portion 543 in a plane including the center axis 95 and
a radial 96 in the discharge direction 559. In addition the
downstream end of the inner diffuser wall 523 may be tangentially
aligned to the aft wall 554, thus forming the smooth joint at their
interface.
[0059] Furthermore, the inner diffuser wall 523 and the outer
diffuser wall 524 may be offset from each other. In particular, the
offset includes a substantially constant radial separation through
their shared arc, as measured in the plane including the center
axis 95. For example, the inner diffuser wall 523 and the outer
diffuser wall 524 may be offset from each other through their
shared arc by the length of the flare radius 544. Also for example,
the inner diffuser wall 523 and the outer diffuser wall 524 may be
offset from each other through their shared arc by the length of
the flare radius 544 +/-25 percent.
[0060] According to one embodiment, the obliquely truncated second
flared downstream portion 543 may be configured such that the
maximum cutback 545 provides for a minimum gap 557 between the
diffuser exit 522 at the maximum cutback 545 and the
circumferential wall 553. In particular, the obliquely truncated
second flared downstream portion 543 may be truncated so as to
provide the minimum gap 557 between the outer diffuser wall 524 and
the circumferential wall 553 of at least one half the distance
between the inner diffuser wall 523 and the outer diffuser wall 524
at the diffuser exit 522, and as measured in a plane including the
center axis 95 and a point on the maximum cutback 545. For example
and as illustrated, where the circumferential wall 553 runs
parallel with the center axis 95, the obliquely truncated second
flared downstream portion 543 may be truncated such that the
minimum gap 557 between the outer diffuser wall 524 and the
circumferential wall 553 is measured along a radial 96 passing
through the maximum cutback 545.
[0061] According to one embodiment, the exhaust collector 550 may
include an "extended" exhaust collector turning region 555. In
particular, the forward wall 552 may be configured such that a
minimum axial distance 558 is maintained from the aft wall 554
within the exhaust collector turning region 555 and proximate the
circumferential wall 553. For example, the minimum axial distance
558 may be at least four times the minimum gap 557. Also for
example, the minimum axial distance 558 may be at least double a
distance between the inner diffuser wall 523 and the outer diffuser
wall 524 at the diffuser exit 522 measured in a plane including the
center axis 95 and a point on the maximum cutback 545. Also for
example, the minimum axial distance 558 may be approximately the
same as an axial distance between the forward wall 552 and the aft
wall 554 opposite exhaust collector turning region 555 and
proximate the diffuser exit 522.
[0062] In the examples above, the forward wall 552 may be angled or
non-vertical. For example the forward wall 552 may be angled so as
to provide an expanding volume in the discharge direction 559.
Alternately, forward wall 552 and the aft wall 554 may be
substantially parallel to each other (e.g., both vertical) such
that the minimum axial distance 558 is substantially uniform
proximate the exhaust diffuser 520. Alternately, forward wall 552
may be substantially vertical.
INDUSTRIAL APPLICABILITY
[0063] The present disclosure generally applies to an exhaust
system for a gas turbine engine, and a gas turbine engine having an
exhaust diffuser. The described embodiments are not limited to use
in conjunction with a particular type of gas turbine engine, but
rather may be applied to stationary or motive gas turbine engines,
or any variant thereof. As applied, gas turbine engines, and thus
their components, may be suited for any number of industrial
applications, such as, but not limited to, various aspects of the
oil and natural gas industry (including include transmission,
gathering, storage, withdrawal, and lifting of oil and natural
gas), power generation industry, aerospace and transportation
industry, to name a few examples.
[0064] Generally, embodiments of the presently disclosed exhaust
system for a gas turbine engine are applicable to the use,
operation, maintenance, repair, and improvement of gas turbine
engines, and may be used in order to improve performance and
efficiency, decrease maintenance and repair, and/or lower costs. In
addition, embodiments of the presently disclosed exhaust system may
be applicable at any stage of the gas turbine engine's life, from
design to prototyping and first manufacture, and onward to
end-of-life. Accordingly, the exhaust system may be used as a
retrofit or enhancement to existing gas turbine engine, as a
preventative measure, or even in response to an event. Moreover,
the various combined features may be adapted to retrofit a previous
design. This is particularly true as the presently disclosed
exhaust system may be installed in a gas turbine engine having
identical interfaces to another exhaust system so as to be
interchangeable with an earlier type of exhaust system.
[0065] Gas turbine engines having exhaust collectors with a radial
discharge direction may have an area of low flow at the opposite
side of the exhaust collector exit (exhaust collector turning
region) forward of the diffuser exit. Embodiments of the presently
disclosed exhaust system may include and combine features, such as
an offset or "cutback" outer diffuser wall that is coordinated with
the exhaust collector exit, a flared inner diffuser wall, and an
"extended" exhaust collector turning region to reduce the pressure
at the turbine exit. Accordingly, the current disclosure provides
an exhaust diffuser wherein the outer diffuser wall is cut back or
radially extends less in the low flow area, relative to its
radially extension in the discharge direction, thereby reducing its
size and potential blockage within this turning region.
[0066] Use of the exhaust system as described above may result in
increased turbine pressure ratio, leading to more shaft power and
higher efficiency. In particular, through substantial analysis and
empirical testing, the inventors have seen significant efficiency
gains over previous designs. Accordingly, the combination of the
aforementioned features, may provide for overall improved engine
performance.
[0067] The preceding detailed description is merely exemplary in
nature and is not intended to limit the invention or the
application and uses of the invention. The described embodiments
are not limited to use in conjunction with a particular type of gas
turbine engine. Hence, although the present embodiments are, for
convenience of explanation, depicted and described as being
implemented in a stationary gas turbine engine, it will be
appreciated that it can be implemented in various other types of
gas turbine engines, and in various other systems and environments.
Furthermore, there is no intention to be bound by any theory
presented in any preceding section. It is also understood that the
illustrations may include exaggerated dimensions and graphical
representation to better illustrate the referenced items shown, and
are not consider limiting unless expressly stated as such.
* * * * *