U.S. patent application number 13/889871 was filed with the patent office on 2014-11-13 for system for distributing compressed air in a combustor.
This patent application is currently assigned to Solar Turbines Incorporated. The applicant listed for this patent is SOLAR TURBINES INCORPORATED. Invention is credited to Paul Stuart Cramer.
Application Number | 20140331678 13/889871 |
Document ID | / |
Family ID | 51513389 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140331678 |
Kind Code |
A1 |
Cramer; Paul Stuart |
November 13, 2014 |
SYSTEM FOR DISTRIBUTING COMPRESSED AIR IN A COMBUSTOR
Abstract
A system for distributing compressed air in a combustor of a gas
turbine engine. The system may include a flow splitter, a center
duct, an outer duct, and an inner duct configured to separate and
receive compressed air from a prediffuser exit, and to route
separate flows of the compressed air to separate downstream
locations for the combustion reaction and for cooling. The system
may include an axial mixer configured to axially receive a flow of
the compressed air and to direct the flow to mix with fuel provided
by an injector.
Inventors: |
Cramer; Paul Stuart;
(Escondido, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SOLAR TURBINES INCORPORATED |
San Diego |
CA |
US |
|
|
Assignee: |
Solar Turbines Incorporated
San Diego
CA
|
Family ID: |
51513389 |
Appl. No.: |
13/889871 |
Filed: |
May 8, 2013 |
Current U.S.
Class: |
60/746 ; 60/748;
60/751 |
Current CPC
Class: |
F23R 3/28 20130101; F23R
3/10 20130101; Y02T 50/60 20130101; Y02T 50/675 20130101 |
Class at
Publication: |
60/746 ; 60/748;
60/751 |
International
Class: |
F23R 3/10 20060101
F23R003/10 |
Claims
1. A gas turbine engine having a center axis and comprising: a
compressor; a prediffuser pneumatically coupled to the compressor,
the prediffuser including a prediffuser exit, an outer wall, and an
inner wall; and a system for mixing fuel and air, the system
including a flow splitter located proximate to the prediffuser exit
and configured to separate a center flow away from an outer flow
and an inner flow of compressed air from the prediffuser exit, the
center flow having a higher average velocity than the outer flow
and the inner flow, a center duct including a center duct inlet and
a center duct exit, the center duct configured to pneumatically
couple with a portion of the prediffuser exit offset from the outer
wall and the inner wall at the center duct inlet, the center duct
further configured to receive the center flow from the prediffuser
exit and to route the center flow to a combustion chamber of the
gas turbine engine, and an axial mixer within the center duct, the
axial mixer configured to direct the center flow to mix with fuel
provided by an injector.
2. The gas turbine engine of claim 1, wherein an effective flow
area of the center duct increases between the center duct inlet and
the center duct exit.
3. The gas turbine engine of claim 1, wherein the axial mixer
includes a lobe mixer, the lobe mixer having a plurality of
alternating lobes circumferentially distributed around an injector
axis.
4. The gas turbine engine of claim 3, wherein an effective flow
area of the center duct increases between the center duct inlet and
the plurality of alternating lobes; and wherein the effective flow
area of the center duct hold the effective flow area constant or
reduces the effective flow area between the plurality of
alternating lobes and the center duct exit.
5. The gas turbine engine of claim 1, wherein the center duct is
further configured to extend to and pneumatically couple with the
combustion chamber of the gas turbine engine.
6. The gas turbine engine of claim 1, wherein the axial mixer is
further configured to initially mix the center flow with the fuel
upon entering the combustion chamber of the gas turbine engine.
7. The gas turbine engine of claim 1, wherein the axial mixer is
further configured to direct the center flow to pre-mix with the
fuel upstream of the combustion chamber of the gas turbine
engine.
8. The gas turbine engine of claim 1, wherein the flow splitter
extends upstream of the prediffuser exit into the prediffuser, the
flow splitter further configured to separate the center flow away
from the outer flow and the inner flow while within the
prediffuser.
9. The gas turbine engine of claim 1, wherein the center duct is
configured such that the center flow only includes compressed air
leaving the prediffuser exit having a velocity, along a radial
velocity profile, that is greater than or equal to an average
velocity of all compressed air leaving the prediffuser exit, along
the radial velocity profile.
10. A gas turbine engine having a center axis and comprising: a
compressor; a prediffuser pneumatically coupled to the compressor,
the prediffuser including a prediffuser exit, an outer wall, and an
inner wall; and a combustor air duct network including a flow
splitter located proximate to the prediffuser exit and configured
to separate a center flow away from an outer flow and an inner flow
of compressed air from the prediffuser exit, the outer flow being
radially outward and the inner flow being radially inward from the
center flow, relative to the center axis; a center duct including a
center duct inlet and a center duct exit, the center duct
configured to pneumatically couple with a portion of the
prediffuser exit offset from the outer wall and the inner wall at
the center duct inlet, the center duct further configured to
receive the center flow from the prediffuser exit and to route the
center flow to a combustion chamber of the gas turbine engine; and
an outer duct including an outer duct inlet and an outer duct exit,
the outer duct configured to pneumatically couple with the
prediffuser exit at the outer duct inlet, adjacent to the center
duct inlet, the outer duct further configured to receive the outer
flow of compressed air from the prediffuser and to route the outer
flow to an outer side of the combustion chamber, relative to the
center axis; and an inner duct including an inner duct inlet and an
inner duct exit, the inner duct configured to pneumatically couple
with the prediffuser exit at the inner duct inlet, adjacent to the
center duct inlet and opposite the outer duct inlet, the inner duct
further configured to receive the inner flow of compressed air from
the prediffuser and to route the inner flow to an inner side of the
combustion chamber, relative to the center axis.
11. The gas turbine engine of claim 10, wherein the center duct is
further configured to extend to and pneumatically couple with an
injector port of the combustion chamber.
12. The gas turbine engine of claim 10, wherein a first portion of
the center duct includes the center duct inlet and is configured to
extend to an injector, and wherein a second portion of the center
duct is integrated into the injector, the first and second portions
of the center duct pneumatically coupled with each other.
13. The gas turbine engine of claim 10, wherein the gas turbine
engine has a plurality of injectors; and wherein the combustor air
duct network includes a plurality of the center duct, each
configured to interface one of the plurality of injectors.
14. The gas turbine engine of claim 10, wherein an effective flow
area of the center duct increases between the center duct inlet and
the center duct exit.
15. The gas turbine engine of claim 10, wherein the center duct is
configured such that the center flow only includes compressed air
leaving the prediffuser exit having a velocity, along a radial
velocity profile, that is greater than or equal to an average
velocity of all compressed air leaving the prediffuser exit, along
the radial velocity profile.
16. The gas turbine engine of claim 10, further comprising an
intermediate duct including an intermediate duct inlet and an
intermediate duct exit, the intermediate duct configured to bleed
off air from the center duct via the intermediate duct inlet, the
intermediate duct further configured to route the bled off air to a
portion of the combustion chamber for cooling.
17. The gas turbine engine of claim 10, further comprising an
intermediate duct including an intermediate duct inlet and an
intermediate duct exit, the intermediate duct configured to bleed
off air from at least one of the outer duct and the inner duct, via
the intermediate duct inlet, the intermediate duct further
configured to route the bled off air to a portion of the combustion
chamber for cooling.
18. A gas turbine engine having a center axis and comprising: a
compressor; a combustor coupled to the compressor, the combustor
including a prediffuser pneumatically coupled to the compressor,
the prediffuser including a prediffuser exit, an outer wall, and an
inner wall; and a system for distributing compressed air in the
combustor including a center duct including a center duct inlet,
the center duct configured to be pneumatically coupled to the
prediffuser exit at the center duct inlet and extend downstream of
the prediffuser exit, the center duct further configured to receive
a center flow of compressed air from the prediffuser exit, the
center flow being separated away from an outer flow and an inner
flow of compressed air from the prediffuser exit, the outer flow
also being radially outward and the inner flow being radially
inward from the center flow, relative to the center axis, the
center duct further configured to route the center flow to a
combustion chamber of the gas turbine engine; and an outer duct
including an outer duct inlet and an outer duct exit, the outer
duct configured to be pneumatically coupled to the prediffuser exit
at the outer duct inlet and to receive the outer flow of compressed
air from the prediffuser, the outer duct further configured to
route the outer flow to an outer side of the combustion chamber,
relative to the center axis; and an inner duct including an inner
duct inlet and an inner duct exit, the inner duct configured to be
pneumatically coupled to the prediffuser exit at the inner duct
inlet and to receive the inner flow of compressed air from the
prediffuser, the inner duct further configured to route the inner
flow to an inner side of the combustion chamber, relative to the
center axis. an axial mixer within the center duct, the axial mixer
configured to direct the center flow to mix with fuel provided by
an injector.
19. The gas turbine engine of claim 18, wherein the axial mixer
includes a lobe mixer, the lobe mixer having a plurality of
alternating lobes circumferentially distributed around an injector
axis.
20. The gas turbine engine of claim 18, further comprising an
intermediate duct including an intermediate duct inlet and an
intermediate duct exit, the intermediate duct configured to bleed
off air from the center duct via the intermediate duct inlet, the
intermediate duct further configured to route the bled off air to a
portion of the combustion chamber for cooling.
Description
TECHNICAL FIELD
[0001] The present disclosure generally pertains to a combustor in
a gas turbine engine, and is more particularly directed toward a
system for distributing compressed air in a gas turbine engine
combustor.
BACKGROUND
[0002] Gas turbine engines typically include a diffuser downstream
of the compressor. The diffuser's purpose is to reduce the high
velocity exit flow from the compressor to velocities suitable for
combustion while recovering as much of the velocity head as static
pressure as possible. After flowing through a prediffuser, the
compressed air is dumped into the rapidly expanding area
surrounding the combustion liner.
[0003] Presently, U.S. Pat. No. 4,527,386 issued to Markowski on
Jul. 9, 1985 shows a diffuser for gas turbine engine. In
particular, the disclosure of Markowski is directed toward a
diffuser system including a prediffuser and a piping system that
diverts the flow into two streams. One stream captures the
prediffuser discharge air at the center of the gas path where the
total pressure is at its highest level and provides an additional
stage of diffusing before dumping it around the burner to supply
liner cooling air, turbine cooling air and if necessary, small
amounts of dilution air to trim radial temperature profile. The
other stream is ducted directly into the burner avoiding the
typical dump diffuser losses.
[0004] The present disclosure is directed toward overcoming known
problems and/or problems discovered by the inventors.
SUMMARY
[0005] A system for mixing fuel and air in a gas turbine engine is
disclosed herein. The system includes a center duct including a
center duct inlet, the center duct configured to be coupled, for
example pneumatically coupled to the prediffuser exit at the center
duct inlet and extend downstream of the prediffuser exit, the
center duct is further configured to receive a center flow of
compressed air from the prediffuser exit, the center flow being
separated away from an outer flow and an inner flow of air from the
prediffuser exit, the outer flow also being radially outward and
the inner flow being radially inward from the center flow, relative
to the center axis, the center duct further configured to route the
center flow to a combustion chamber of the gas turbine engine. The
system also includes an axial mixer configured to axially receive
the center flow of compressed air and to direct the center flow to
mix with fuel provided by the injector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic illustration of an exemplary gas
turbine engine.
[0007] FIG. 2 is a cutaway side view of a combustor in the gas
turbine engine of FIG. 1.
[0008] FIG. 3 is a cutaway axial view along line 3-3 of FIG. 2.
[0009] FIG. 4 is an isometric view of an exemplary embodiment of a
ducting module attached to a portion of a prediffuser of the
combustor in FIG. 2.
[0010] FIG. 5 is an isometric view of a planar lobed mixer forming
vortex pairs.
DETAILED DESCRIPTION
[0011] The present disclosure relates to a system for distributing
compressed air in combustor that selectively extracts a high
velocity core of a prediffuser exit flow for combustion, and
provides additional diffusion and pressure recovery of lower
velocity outer regions of the prediffuser exit flow. A ducting
network is placed at the prediffuser exit such that the desired
portion of the high velocity core and the lower velocity outer
regions are separated and ducted as desired.
[0012] FIG. 1 is a schematic illustration of an exemplary gas
turbine engine. Some of the surfaces have been left out or
exaggerated (here and in other figures) for clarity and ease of
explanation. The disclosure may reference an axis of rotation of
the gas turbine engine ("center axis" 95), which may be generally
defined by the longitudinal axis of its shaft 120. 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.
[0013] 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).
[0014] Generally, the gas turbine engine 100 includes an inlet 110,
a shaft 120 (supported by bearings 150), a compressor 200, a
combustor 300, a turbine 400, an exhaust 500, and a power output
coupling 600. The compressor 200 includes one or more compressor
rotor assemblies 220. The turbine 400 includes one or more turbine
rotor assemblies 420.
[0015] The combustor 300 includes a combustor case 310, an inner
bearing housing 311, a plurality of struts 312, an outer shroud
314, an inner shroud 316, a plurality of injectors 350, and a
combustion chamber 390. The combustor case 310 and the inner
bearing housing 311 may be concentric clamshell casings forming a
generally annular cavity there between and extending from the
compressor 200 to the turbine 400. The combustor case 310 and the
inner bearing housing 311 may be joined together by the plurality
of struts 312. The combustion chamber 390 or "liner" is located
within the annular cavity and is configured to withstand the high
pressures and temperatures associated with combustion.
[0016] The outer shroud 314 and the inner shroud 316 define regions
outside the combustion chamber 390 where air may be directed for
cooling. In particular, the outer shroud 314 may be radially
outward from the combustion chamber 390 and the inner shroud 316
may be radially inward from the combustion chamber 390. For example
the outer shroud 314 and/or the inner shroud 316 may include
ducting configured to bring compressed air to the combustion
chamber 390 and may be tailored for heat exchange. According to one
embodiment, the outer shroud 314 may include portions of the
combustor case 310 and/or the inner shroud 316 may include portions
of the inner bearing housing 311, for example, where an inner wall
of either is configured to bring compressed air to the combustion
chamber 390 for cooling.
[0017] In operation, air 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, air leaves the
compressor 200, it enters the combustor 300, where it is diffused
and fuel is added. Fuel and some of the air are injected into the
combustion chamber 390 via injector 350 and ignited. Some of the
air is routed for cooling. After the combustion reaction, energy is
then extracted from the combusted fuel/air mixture via the turbine
400 by a series of turbine rotor assemblies 420. Exhaust gas leaves
the system via the exhaust 500.
[0018] The fuel delivered to combustor 300 may include any known
type of hydrocarbon based liquid or gaseous fuel. Liquid fuels may
include diesel, heating oil, JP5, jet propellant, or kerosene. In
some embodiments, liquid fuels may also include natural gas liquids
(such as, for example, ethane, propane, butane, etc.), paraffin oil
based fuels (such as, JET-A), and gasoline. Gaseous fuels may
include natural gas. In some embodiments, the gaseous fuel may also
include alternate gaseous fuels such as, for example, liquefied
petroleum gas (LPG), ethylene, landfill gas, sewage gas, ammonia,
biomass gas, coal gas, refinery waste gas, etc. This listing of
liquid and gaseous fuels is not intended to be an exhaustive list
but merely exemplary. In general, any liquid or gaseous fuel known
in the art may be delivered to combustor 300 through injector
350.
[0019] Similarly, 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", or a variety of
ceramic structures. 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, and CMSX single crystal alloys.
Ceramic structures may include monolithic components and/or
ceramic/ceramic and ceramic/metal matrix components.
[0020] FIG. 2 is a cutaway side view of the combustor in the gas
turbine engine of FIG. 1. For clarity and illustration purposes,
certain features/components have been added, removed, and/or
modified. As illustrated, the compressor 200 terminates at the
compressor discharge 290, located at its downstream end. The
compressor discharge 290 may form an annular passageway through
which high velocity compressed air may exit the compressor 200. The
compressor discharge 290 is coupled, for example fluidly coupled,
to a prediffuser 320.
[0021] The prediffuser 320 includes a prediffuser inlet 321 and a
prediffuser exit 322. The prediffuser inlet 321 is fluidly coupled
to the compressor discharge 290. The prediffuser 320 is configured
to diffuse compressed, high velocity compressed air exiting the
compressor 200 in a stable and controlled manner. The prediffuser
exit 322 is fluidly coupled to a combustor air duct network 330.
The combustor air duct network 330 is placed at the exit of the
prediffuser 320.
[0022] The combustor air duct network 330 includes a plurality of
ducts forming discrete air passageways or channels. In particular,
each duct segregates a flow in the duct from other, external flows.
The combustor air duct network 330 is configured to receive
compressed air from the prediffuser 320 and route it to
predetermined locations. The combustor air duct network 330 may
divide portions of the compressed air or may receive the compressed
air in separate flows split by a downstream flow separator. Each
air passageway may be smooth, of any convenient cross section, and
shaped to mitigate losses (e.g., from flow separation) during
routing. Together the ducts may form a separator configured to
separate and distribute compressed air exiting the prediffuser 320
while mitigating losses after leaving the prediffuser 320 (e.g.,
dump losses).
[0023] According to one embodiment, the combustor air duct network
330 may include one or more flow splitters or dividers. The flow
splitters or dividers may be radially and/or circumferentially
oriented. For example, a radially oriented flow divider may be
configured to divide the prediffuser exit 322 into annular sectors,
each having a radially distributed velocity profile of compressed
air. The radially distributed velocity profile of each annular
sector may be markedly slower proximate an outer wall 323 and an
inner wall 324 of the prediffuser 320 (e.g., slower due to boundary
layer build up, diffusion recovery, etc.) than between the outer
wall 323 and inner wall 324 (e.g., representing a minimally
diffused central flow).
[0024] Also for example, a circumferentially-oriented flow splitter
337 (FIG. 4) may be configured to separate a center flow away from
an outer flow and an inner flow prior to entering a duct. Here, the
outer flow is radially outward and the inner flow is radially
inward from the center flow, relative to the center axis 95. For
example the center flow may include a portion of compressed air
having an average velocity that is higher than the average velocity
the outer flow and the inner flow when leaving the prediffuser exit
322. Also for example, the center flow may include a portion of
compressed air leaving the prediffuser exit 322, where the ratio of
flow velocity/average velocity, along a radial velocity profile, is
greater than or equal to unity.
[0025] The ducts may be independent ducts or shrouds, forming the
air passageways. Alternately, one or more ducts may be combined
with other ducts so as to form a duct manifold, the duct manifold
having a plurality of air passageways. The ducts or duct manifolds
may be fixed to, or integrated into internal portions of the
combustor 300, and/or coupled to other internal components. In
addition, the ducts or duct manifolds may be uninterrupted or made
up of joined sections between inlet and exit. Moreover, one or more
sections of the ducts or duct manifolds may be integrated into one
or more other components (e.g., the injector 350, the outer shroud
314, the inner shroud 316, etc.).
[0026] FIG. 3 is a cutaway axial view along line 3-3 of FIG. 2.
According to one embodiment, the combustor air duct network 330 may
be made up of a plurality of ducting modules 331. In particular,
the combustor air duct network 330 may be made up of groups of
ducts joined together, each group forming a ducting module 331
including portion of the total air passageways in the combustor air
duct network 330. Likewise, the combustor air duct network 330 may
be made up of a plurality of duct manifolds, each duct manifold
forming a ducting module 331 including a portion of the total air
passageways in the combustor air duct network 330.
[0027] Each ducting module 331 may be supported within the
combustor 300 by any convenient means or combination of supports.
For example, the ducting module 331 may be supported at each end of
each of its respective air passageways. Also for example the
ducting module 331 may be supported by internal structures fixed to
the combustor case 310, the inner bearing housing 311, and/or the
struts 312. Also for example the ducting module 331 may be
supported by other internal components, such as the outer shroud
314, the inner shroud 316, the injector 350, the combustion chamber
390, and/or other ducting modules 331.
[0028] According to one embodiment, the ducting modules 331 may be
arranged or otherwise coordinated with each other to form an
annular array that is fluidly coupled to the prediffuser exit 322.
As illustrated, the combustor air duct network 330 may be made up
of a plurality of ducting modules 331 circumferentially distributed
about the center axis 95. Each ducting module 331 may occupy an
annular sector of the combustor 300. For example, each ducting
module 331 may be coupled, for example pneumatically coupled, with
the prediffuser exit 322, and segregate out an annular sector of
flow exiting the prediffuser 320. Also for example, each ducting
module 331 may pneumatically couple downstream with flow paths
radially inward from, radially outward from, and into the
combustion chamber 390, again occupying an annular sector of the
combustor 300.
[0029] For example, the combustor air duct network 330 may include
a separate ducting module 331 for each injector 350. Accordingly,
where the combustor has twelve injectors 350, as illustrated, the
combustor air duct network 330 may include twelve ducting modules
331, where the flow leaving prediffuser exit 322 is distributed to
the twelve ducting modules 331. Also, groupings (pairs, as
illustrated here) of the ducting modules 331 may be installed
between and/or attached to struts 312 within the combustor case
310.
[0030] FIG. 4 is an isometric view of an exemplary embodiment of a
ducting module attached to a portion of a prediffuser of the
combustor in FIG. 2. In particular, one ducting module 331
(simplified, without diffusion or an intermediate duct) is shown
pneumatically coupled with the prediffuser exit 322, without the
other ducting modules 331 installed. For clarity and to illustrate
the separation of flow into separate streams, only the trailing
edge of the prediffuser 320 (including prediffuser exit 322) is
shown. The view is generally looking downstream.
[0031] As illustrated, compressed air leaving the prediffuser exit
322 may be divided among the ducting modules 331. In particular,
the flow may be divided by members of the prediffuser exit 322
and/or members of the ducting modules 331. For example, the
prediffuser 320 may include internal struts that extend to the
prediffuser exit 322 and align with the inlets of each ducting
module 331, splitting the exiting flow in the circumferential
direction 339.
[0032] Also as illustrated, compressed air leaving the prediffuser
exit 322 may be split among the individual channels or ducts within
each ducting module 331. In particular, the system for distributing
compressed air may include a flow splitter 337. For example the
flow splitter 337 may be configured to separate a center flow away
from an outer flow and an inner flow of compressed air from the
prediffuser exit 322, the outer flow being radially outward and the
inner flow being radially inward from the center flow, relative to
the center axis 95.
[0033] The center flow may include a region of compressed air
having a higher average velocity than the outer and the inner
flows. The positions of the individual splitters within the flow
splitter 337 may be located such that the desired portion of the
high velocity minimally diffused central core of the radial profile
(center flow) is directed into a suitably constructed channel or
duct. Likewise, the positions of the splitters may also be located
such that the inner flow and the outer flow are similarly directed
into suitably constructed channels or ducts, these ducts may be
configured to both direct the flow and/or provide additional
diffusion of the flow. The positioning of the various splitters may
be determined by the flow requirements of the areas and devices
being fed by the various channels of ducts.
[0034] The flow splitter 337 is located proximate to the
prediffuser exit 322. In particular the flow splitter 337 may be
located at the interface of the prediffuser exit 322 and the
ducting module 331. In addition, the flow splitter 337 may be
integrated into the prediffuser exit 322, the ducting module 331,
and/or be an independent component. For example, the flow splitter
337 may be made up of the various duct inlets of the ducting module
331 at the interface with the prediffuser exit 322. Also for
example, each ducting module 331 may include a plurality of ducts
positioned radially adjacent to each other so as to split the
exiting flow in the radial direction 338 and among each duct of the
ducting module 331. In addition, the flow splitters 337 may extend
upstream of the prediffuser exit 322 into the prediffuser 320. In
this way, the flow splitter 337 may configured to separate the
center flow away from the outer flow and the inner flow while still
within the prediffuser 320.
[0035] According to one embodiment, each ducting module 331 may
include an outer duct 332, an inner duct 333, and a center duct
334. Together, the outer duct 332, the inner duct 333, and the
center duct 334 provides flow egress from an associated annular
sector of the prediffuser exit 322. Moreover, this arrangement may
direct a high velocity core of compressed air exiting the
prediffuser 320 with its substantially higher pressure head or
higher total pressure into a fuel/air mixing device that can take
advantage of the higher energy flow. This arrangement may also be
configured to aid in controlling the lower velocity flow for the
provisioning of cooling air to the inner and outer walls of the
combustion chamber 390 (also see FIG. 3, showing the downstream or
egress ends of the outer ducts 332, the inner ducts 333, and the
center ducts 334, distributed about center axis 95).
[0036] Returning to FIG. 2, the outer duct 332 may include an outer
duct inlet 341 and an outer duct exit 342. The outer duct 332 is
configured to be coupled, for example pneumatically coupled with
the prediffuser exit 322 at the outer duct inlet 341. The outer
duct 332 is further configured to receive an outer flow of
compressed air from the prediffuser 320 during operation, and to
route the outer flow to a radially outward portion of the combustor
300, relative to the center axis 95. For example, the outer duct
332 may be configured to route the outer flow to an outer side of
the combustion chamber 390, relative to the center axis 95. Also
for example, the outer duct 332 may be configured to be
pneumatically coupled to the outer shroud 314 at the outer duct
exit 342.
[0037] The pneumatic couple to the prediffuser exit 322 may be
formed by mounting the outer duct inlet 341 to the prediffuser 320,
or otherwise positioning the outer duct inlet 341 proximate the
prediffuser exit 322. In addition, the pneumatic couple may be
formed in combination with pneumatic couples of adjacent duct
inlets and/or adjacent ducting modules 331, where egress from the
prediffuser exit 322 is limited to the outer duct inlet 341 and the
adjacent duct inlets and/or adjacent ducting modules 331. The
pneumatic couple may also be formed in combination with flow
separators located at or upstream of the prediffuser exit 322.
[0038] The outer flow may be defined as a lower velocity flow
region exiting the prediffuser 320 proximate the outer wall 323 of
the prediffuser 320, and with respect to the portion or annular
sector of the prediffuser exit 322 associated with the ducting
module 331. In particular, the outer flow includes boundary layer
air associated with the outer wall 323 of the prediffuser 320. In
addition, the outer flow may include recovered air.
[0039] For example, the outer duct inlet 341 may be configured to
receive the outermost quarter of a radial span of the prediffuser
exit 322, with respect to the portion or annular sector of the
prediffuser exit 322 associated with the ducting module 331. Also
for example, the outer duct inlet 341 may be configured to receive
the radially outermost quarter of a flow velocity profile
associated with the ducting module 331. Also for example, the outer
duct inlet 341 may be configured to receive a radially outward
portion of the flow velocity profile associated with the ducting
module 331 that is below its average velocity.
[0040] According to one embodiment, the outer duct 332 may be
configured to further diffuse the outer flow. In particular, the
outer duct 332 may increase its effective flow area from the outer
duct inlet 341 to the outer duct exit 342. The increase in
effective flow area may be gradual, or otherwise limited such that
a boundary layer does not separate from the outer duct 332 during
operation.
[0041] The inner duct 333 may include an inner duct inlet 343 and
an inner duct exit 344. The inner duct 333 is configured to
pneumatically couple with the prediffuser exit 322 at the inner
duct inlet 343, as above. The inner duct 333 is further configured
to receive an inner flow of compressed air from the prediffuser
320, and route the inner flow to a radially inward portion of the
combustor 300, relative to the center axis 95. For example, the
inner duct 333 may be configured to route the inner flow to an
inner side of the combustion chamber 390, relative to the center
axis 95. Also for example, the inner duct 333 may be configured to
be pneumatically coupled to the inner shroud 316 at the inner duct
exit 344.
[0042] The inner flow may be defined as a lower velocity flow
region exiting the prediffuser 320 proximate the inner wall 324 of
the prediffuser 320, and with respect to the portion or annular
sector of the prediffuser exit 322 associated with the ducting
module 331. In particular, the inner flow includes boundary layer
air associated with the inner wall 324 of the prediffuser 320. In
addition, the inner flow may include recovered air.
[0043] For example, the inner duct inlet 343 may be configured to
receive the innermost quarter of a radial span of the prediffuser
exit 322, with respect to the portion or annular sector of the
prediffuser exit 322 associated with the ducting module 331. Also
for example, the inner duct inlet 343 may be configured to receive
the radially innermost quarter of a flow velocity profile
associated with the ducting module 331. Also for example, the inner
duct inlet 343 may be configured to receive a radially inward
portion of the flow velocity profile associated with the ducting
module 331 that is below its average velocity.
[0044] According to one embodiment, the inner duct 333 may be
configured to further diffuse the inner flow. In particular, the
inner duct 333 may increase its effective flow area from the inner
duct inlet 343 to the inner duct exit 344. The increase in
effective flow area may be gradual, or otherwise limited such that
a boundary layer does not separate from the inner duct 333 during
operation.
[0045] The center duct 334 may include a center duct inlet 345 and
a center duct exit 346. The center duct 334 is configured to
pneumatically couple with a portion of the prediffuser exit 322
offset from the outer wall 323 and the inner wall 324 via the
center duct inlet 345, and extend downstream. The center duct 334
is further configured to receive a center flow of compressed air
from the prediffuser exit 322, and route the center flow to a
radially central portion of the combustor 300, between the inner
and outer flows. For example, the center duct 334 may be configured
to route the center flow to the injector 350. Each injector 350 of
the combustor 300 may interface with and/or be integrated with an
independent center duct 334. Also for example, the center duct 334
may be configured to route the center flow to the combustion
chamber 390. Also for example, the center duct 334 may extend to,
and pneumatically couple with, an injector port 392 of the
combustion chamber 390.
[0046] According to one embodiment, the center duct 334 may be
segmented. In particular, the center duct 334 may be segmented such
that a first portion of the center duct 334 includes the center
duct inlet 345, and a second portion of the center duct 334
includes at the center duct exit 346, with the first and second
portions of the center duct 334 being pneumatically coupled
together. For example, the first portion of the center duct 334 may
be a plain duct member, whereas the second portion of the center
duct 334 may be formed from or otherwise integrated into the
injector 350. Moreover, the center duct 334 may include an
aggregation of members pneumatically coupled and forming a
continuous flow path. Also for example, the center duct 334 may be
segmented for ease of manufacturability, ease of installation,
etc.
[0047] The center flow may be defined as a higher velocity flow
region exiting the prediffuser 320 away from both the outer wall
323 and the inner wall 324 of the prediffuser 320, and with respect
to the portion or annular sector of the prediffuser exit 322
associated with the ducting module 331. In particular, the center
flow excludes boundary layer air associated with the outer wall 323
and the inner wall 324 of the prediffuser 320. In addition, the
center flow may include high velocity flow which may only be
partially recovered air.
[0048] For example, the center duct inlet 345 may be configured to
receive the center half quarter of a radial span of the prediffuser
exit 322, with respect to the portion or annular sector of the
prediffuser exit 322 associated with the ducting module 331. Also
for example, the center duct inlet 345 may be configured to receive
the fastest half of a flow velocity profile associated with the
ducting module 331. Also for example, the center duct inlet 345 may
be configured to receive the portion of the flow velocity profile
associated with the ducting module 331 that is at or above its
average velocity.
[0049] According to one embodiment, the center duct 334 may be
configured to further diffuse the center flow. In particular, the
center duct 334 may increase its effective flow area between the
center duct inlet 345 to the center duct exit 346. The increase in
effective flow area may be gradual or otherwise limited such that a
boundary layer does not separate from the inner duct 333 during
operation. According to one embodiment, center duct 334 may
increase its effective flow area from the center duct inlet 345 to
a predefined downstream location, and then hold the effective flow
area constant until the center duct exit 346.
[0050] According to one embodiment, the center duct 334 may change
in shape between the center duct inlet 345 and the center duct exit
346. In particular, the center duct 334 may have a complex shape,
smoothly transforming from a quadrilateral flow cross section at
the center duct inlet 345 to a round flow cross section at the
center duct exit 346 (see FIG. 4, isometric view of the ducting
module 331, showing the smooth transition between the center duct
inlet 345 and the center duct exit 346). According to one
embodiment, the center duct 334 may maintain a constant effective
flow area throughout the transition. According to another
embodiment, the center duct 334 may continuously increase its
effective flow area from the center duct inlet 345 to the round
flow cross section, being configured as a diffuser for the center
flow as described above.
[0051] According to one embodiment, the ducting module 331 may
further include an intermediate duct 335. The intermediate duct 335
may include an intermediate duct inlet 347 and an intermediate duct
exit 348. In addition, the intermediate duct 335 may share a wall
with at least one of the outer duct 332, the inner duct 333, and
the center duct 334. For example, an outer surface (relative to an
injector axis 359) of the center duct 334 may form an inner wall
(relative to the injector axis 359) of the intermediate duct
335.
[0052] The intermediate duct 335 is configured to bleed off air
from at least one of the outer duct 332, the inner duct 333, and
the center duct 334 via the intermediate duct inlet 347. For
example, the intermediate duct inlet 347 may include one or more
bleed holes (or other perforations) through an outer wall of the
center duct 334, the outer wall being with respect to the injector
axis 359. Also for example, the intermediate duct inlet 347 may
include one or more bleed holes (or other perforations) through an
inner wall of the outer duct 332 and/or the inner duct 333, the
inner wall also being with respect to the injector axis 359.
[0053] The intermediate duct 335 is further configured to route the
bled air to a portion of the combustion chamber 390 such as a dome
heat shield 393 for cooling. In particular, a portion of the
combustion chamber 390 perpendicular to the exit of the injector
350 (liner dome) may be cooled in a conventional manner, such as
with a strain isolated panel, which forms part of dome heat shield
393 and surrounds the injector port 392. For example, the
intermediate duct exit 348 may be configured so that the bled air
impinges on the dome heat shield 393 for cooling purposes.
[0054] According to one embodiment, the intermediate duct 335 may
have a complex shape. In particular, the intermediate duct 335 may
change between a generally round cross section (normal to the
injector axis 359) to a polygonal cross section. For example and as
illustrated, at an upstream end (relative to the injector axis
359), the intermediate duct 335 may have a round shape concentric
and integrated with the center duct 334, and at a downstream end
(relative to the injector axis 359), the intermediate duct 335 may
have a generally quadrilateral shape that is separated and offset
from the intermediate duct 335. The intermediate duct 335 may
smoothly transition between the two shapes. Also, the intermediate
duct 335 may change between a single chamber flow path and a dual
or multi chamber flow path, for example, where other structures
intervene in the flow path or otherwise create a discontinuity.
[0055] According to one embodiment, the ducting module 331 may
further include an axial mixer 336 ("axial voracity generator" or
"lobed mixer"). In particular, the axial mixer 336 is configured to
axially receive the center flow of compressed air (relative to the
injector axis 359, and as opposed to radially receiving). Moreover,
the axial mixer 336 may form an inner wall of the center duct 334
such that the center flow of compressed air would travel in an
annular flow path around the side of the mixer.
[0056] The axial mixer 336 may be further configured to direct the
received center flow of compressed air to mix with a stream of fuel
provided by the injector 350 on the opposite side of the annular
space around the mixer, and to produce counter rotating vortex
pairs (see FIG. 5) using fluid mechanic mechanisms at the exit.
Moreover, the center duct 334 may be configured for low loss such
that the center flow and the fuel stream 20 have a maximum velocity
gradient, further increasing shear between the two fluids and thus
mixing. In addition, the axial mixer 336 may be configured such
that air and fuel are initially mixed upon entering the combustion
chamber 390.
[0057] According to one embodiment, the axial mixer 336 may be
configured in a circumferential form. In this configuration the
axial mixer 336 may be adapted to the existing geometry and layout
of the injector 350 and the rest of the ducting module 331. For
example and as illustrated, the axial mixer 336 may include a lobed
mixer including a plurality of alternating lobes 349
circumferentially distributed about the injector axis 359. Also for
example, the lobed mixer may smoothly transition between a
generally cylindrical or otherwise smooth round shape and the
undulating lobed shape of its mixing features.
[0058] According to one embodiment, the circumferential lobed mixer
may be arranged such that it is surrounded coaxially with center
duct 334, which may be of constant or converging effective flow
area to encourage the center flow to attach and remain attached to
the surfaces of the lobes 349. According to one embodiment, the
center duct 334 may increase its effective flow area from the
center duct inlet 345 up to the lobes 349, and then hold the
effective flow area constant until the center duct exit 346.
Alternately, the center duct 334 may increase its effective flow
area from the center duct inlet 345 up to the lobes 349, and then
reduce the effective flow area across the lobes 349.
[0059] FIG. 5 is an isometric view of a planar lobed mixer forming
vortex pairs. To aid in describing the axial mixer 336 above, a
planar version of a lobed mixer is shown. Here, the planar lobed
mixer 836 is configured to generate mixing from the interplay of
both mechanical and viscous forces forming vortex pairs 813. As
illustrated, planar lobed mixer 836 directs streams of a first
fluid 811 and a second fluid 812 to cross downstream of the planar
lobed mixer 836, which creates high levels of shear between the two
fluid streams, and which generates the vortices responsible for
mixing. These directed high shear flows create the vortex pairs 813
that mix the two fluids. Each pair of alternating lobes 849
produces a pair of vortices which subsequently entwine as the
vortex pair 813, intimately mixing the first and the second fluid
811, 812.
[0060] With reference to FIG. 2 and FIG. 3, the axial mixer 336 is
conceptually similar to the planar lobed mixer 836 shown in FIG. 5.
Here however, as an axial lobed mixer, the axial mixer 336 directs
streams of fuel and air to cross in a radial direction downstream
of the axial mixer 336, which similarly creates high levels of
shear between the two fluid streams, and which generates the
vortices responsible for mixing. These directed high shear flows
also create the vortex pairs that mix the two fluids. Similar to
the lobes 849 of FIG. 5, here, each pair of alternating lobes 349
in the axial mixer 336 produces a pair of vortices which
subsequently entwine, intimately mixing the fuel and air for the
combustion reaction.
[0061] With reference to FIG. 2, according to another embodiment,
the axial mixer 336 may be configured such that mixing features
(e.g., lobes 349) of the axial mixer 336 are axially positioned
upstream from the combustion chamber 390, relative to the injector
axis 359. In particular, the mixing features may be recessed within
the injector 350, the center duct 334, and/or any other sheltered
area upstream of the combustion chamber 390. For example and as
illustrated, the mixing features of the axial mixer 336
(represented by the triangular section at its downstream end) may
extend up to the injector port 392 (the opening into the combustion
chamber 390). Also for example, the axial mixer 336 may be recessed
downstream (relative to the injector axis 359) of the injector port
392 and oriented such that a minimal aspect ratio is presented to
the hot gas (e.g., downstream end running parallel to the injector
axis 359). Additionally, the axial mixer 336 may be recessed such
that air and fuel are pre-mixed within the center duct 334 prior to
exiting the injector.
[0062] According to another embodiment, the ducting module 331 may
be configured such that air exiting the intermediate duct 335
provides additional protection to the axial mixer 336. In
particular, the intermediate duct exit 348 and/or the dome heat
shield 393 may be configured such that cooling air is discharged
after impinging on the dome heat shield 393 radially inward around
the periphery of the axial mixer 336. In addition, the discharged
cooling air may be aligned with mixing mechanism of the axial mixer
336 (e.g., air management lobes of a lobe mixer) to augment the
flow, and therefore the shear between the fuel and air streams.
[0063] According to one embodiment, a ducting module 331 may be
discontinuous for manufacturing or other design requirements. In
particular, one of more of the outer duct 332, the inner duct 333,
the center duct 334, the intermediate duct 335, and the axial mixer
336 may be integrated with other components. For example and as
illustrated, a support arm 352 may pass through of the outer duct
332, the intermediate duct 335, the center duct 334, and the axial
mixer 336 in order to position the injector on the injector axis
359. Also for example, the a first portion of ducting module 331
may be integrated with, or otherwise fixed to the prediffuser 320
while a second portion of the ducting module 331 may be integrated
with the injector 350.
[0064] According to an alternate embodiment, the ducting of each
ducting module 331 may be reversed from that described above. In
particular, a desired portion of the higher velocity core of
compressed air may be ducted to the inner and outer walls of the
combustion chamber 390 for cooling. This arrangement may also duct
the lower velocity flow (proximate the walls of the prediffuser
320) into the combustion chamber 390.
[0065] To illustrate, the inner and outer ducts may have inlets
configured to interface with the prediffuser 320 as described
above, but which merge into a single duct that is configured to
direct the joined inner and outer flows to the combustion chamber
390. Additionally, the center duct may have an inlet configured to
interface with the prediffuser 320 as described above, but which
then splits into two separate ducts. The two separate ducts may be
configured to route compressed air to the outer shroud 314 and the
inner shroud 316, respectively and similarly to the outer duct 332
and inner duct 333 as described above. In addition, the separate
ducts that direct this central core flow may have progressively
increasing cross-sectional area and begin with little or no
boundary layer on their walls, functioning as a post diffuser
stage, and reducing the velocity and dynamic pressure head of the
central core flow. Thus, the central core flow may be subsequently
discharged into the liner shrouds with a substantially reduced dump
loss, lower velocity (more fully recovered).
INDUSTRIAL APPLICABILITY
[0066] The present disclosure generally applies to gas turbine
combustors, and gas turbine engines having a prediffuser. 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.
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. In addition, the
present disclosure may apply to furnace applications.
[0067] Generally, embodiments of the presently disclosed system for
distributing compressed air in the combustor 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 system for
distributing compressed air in the combustor 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 system for distributing compressed air in the
combustor may be used as a retrofit or enhancement to existing gas
turbine engine, as a preventative measure, or even in response to
an event. This is particularly true as the presently disclosed
system for distributing compressed air in the combustor may be
installed in a combustor having identical interfaces to another
combustor so as to be interchangeable with an earlier type of
combustor.
[0068] In use, the system for distributing compressed air in a
combustor forms a reduced-loss ducting network within the
combustor. The leading edge of the ducts or splitters are located
such that a desired portion of high velocity, minimally diffused
central core of the radial profile of compressed air exiting the
prediffuser is directed into the combustor duct network. The ducts
that direct this central core flow may have progressively
increasing cross-sectional area and begin with little or no
boundary layer on their walls, functioning as a post diffuser
stage, and reducing the velocity and dynamic pressure head of the
central core flow. This central core flow may be subsequently
discharged into the injector with a substantially reduced dump
loss, lower velocity (more fully recovered). Alternately, this
central core flow may be subsequently discharged into about the
combustion chamber for cooling.
[0069] The preceding disclosure describes a combination of various
technologies into a unique configuration for a gas turbine
combustion system exhibiting low pressure losses and enhanced
mixing capabilities. In particular, system for distributing
compressed air in a combustor combines targeted-use flow splitting,
low-loss ducting, supplemental diffusion, and axial mixing, which
may result in improved diffuser recovery performance, lower
pressure losses, enhanced mixing, and/or lower emissions. In
addition, the system for distributing compressed air in a combustor
may provide for an integrated system to manage fuel and air mixture
preparation, reuse of spent cooling flows to augment mixing, and
potentially shorter overall system lengths. By eliminating the
traditional high pressure loss mixing devices currently employed in
combustion systems and substituting low loss more efficient mixing
devices lower overall systems pressure drops may be achieved with a
corresponding increase in overall system efficiency.
[0070] By combining the aforementioned technologies, improved
diffuser recovery performance and the low loss high mixing rate
lobed mixer may be combined to deliver an advance fuel air
management system. The coupling of these techniques in a combustion
system is adaptable to existing engines, especially of the
industrial nature since they often provide ample room for the
additional hardware and are not necessarily constrained by length
or weight limitations of aircraft engines.
[0071] 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.
* * * * *