U.S. patent application number 13/776638 was filed with the patent office on 2014-08-28 for fuel/air mixing system for fuel nozzle.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Yon Han Chong, Bryan Wesley Romig, Jong Ho Uhm.
Application Number | 20140238025 13/776638 |
Document ID | / |
Family ID | 51386738 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140238025 |
Kind Code |
A1 |
Uhm; Jong Ho ; et
al. |
August 28, 2014 |
FUEL/AIR MIXING SYSTEM FOR FUEL NOZZLE
Abstract
A system includes a fuel nozzle. The fuel nozzle includes a
central hub with a first annular passage extending along a
longitudinal axis of the fuel nozzle. A flow conditioner is
disposed along the first annular passage. The flow conditioner
includes at least one of a straightening vane, a mesh screen, or a
multi-passage body having multiple passages generally parallel with
the longitudinal axis. An outer shroud is disposed about the
central hub to define a second annular passage extending along the
longitudinal axis of the fuel nozzle.
Inventors: |
Uhm; Jong Ho; (Simpsonville,
SC) ; Romig; Bryan Wesley; (Simpsonville, SC)
; Chong; Yon Han; (Greer, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
51386738 |
Appl. No.: |
13/776638 |
Filed: |
February 25, 2013 |
Current U.S.
Class: |
60/737 ;
60/748 |
Current CPC
Class: |
F23R 3/14 20130101; F23R
3/286 20130101 |
Class at
Publication: |
60/737 ;
60/748 |
International
Class: |
F23R 3/28 20060101
F23R003/28; F23R 3/14 20060101 F23R003/14 |
Claims
1. A system, comprising: a fuel nozzle, comprising: a central hub
comprising a first annular passage extending along a longitudinal
axis of the fuel nozzle and a flow conditioner disposed along the
first annular passage, wherein the flow conditioner comprises at
least one of a straightening vane, a mesh screen, or a
multi-passage body having a plurality of passages generally
parallel with the longitudinal axis; and an outer shroud disposed
about the central hub to define a second annular passage extending
along the longitudinal axis of the fuel nozzle.
2. The system of claim 1, comprising a combustor or a gas turbine
engine having the fuel nozzle.
3. The system of claim 1, comprising a plurality of premixing tubes
downstream from the flow conditioner, wherein each tube of the
plurality of premixing tubes comprises an air inlet, a fuel inlet
disposed in a side wall, and an air-fuel mixture outlet.
4. The system of claim 1, comprising a plurality of swirl vanes
disposed in the second annular passage between the outer shroud and
the central hub, wherein an interior of each swirl vane of the
plurality of swirl vanes is configured to route a first air flow
into the first annular passage, an exterior of each swirl vane of
the plurality of swirl vanes is configured to swirl a second air
flow along the second annular passage, and the flow conditioner in
the first annular passage is disposed between the plurality of
swirl vanes and an outlet of the fuel nozzle.
5. The system of claim 1, wherein the flow conditioner comprises a
plurality of straightening vanes each gradually turning from a
radial direction toward an axial direction along the longitudinal
axis in a downstream direction toward an outlet of the fuel
nozzle.
6. The system of claim 1, wherein the central hub comprises a first
wall extending circumferentially about the longitudinal axis to
define a central passage, a second wall extending circumferentially
about the first wall to define the first annular passage, and a
third wall extending circumferentially about the second wall to
define a third annular passage, wherein the first annular passage
routes a first air flow along the flow conditioner, and the third
annular passage routes a first fuel flow.
7. The system of claim 6, wherein the second annular passage
comprises a swirler and the first annular passage comprises a
plurality of premixing tubes disposed downstream from the flow
conditioner, wherein each tube of the plurality of premixing tubes
comprises an air inlet, a fuel inlet in a side wall, and an
air-fuel mixture outlet.
8. The system of claim 7, wherein the straightening vane, the
perforated sheet or mesh screen, and the multi-passage body are
configured to reduce swirl in the first annular passage caused by
the swirler in the second annular passage.
9. A system, comprising: a fuel nozzle, comprising: a central hub
comprising a first annular passage extending along a longitudinal
axis of the fuel nozzle, a flow conditioner disposed along the
first annular passage, and a plurality of premixing tubes disposed
along the first annular passage downstream from the flow
conditioner, wherein each tube of the plurality of premixing tubes
comprises an air inlet, a fuel inlet, and an air-fuel mixture
outlet; an outer shroud disposed about the central hub to define a
second annular passage extending along the longitudinal axis of the
fuel nozzle; and a plurality of swirl vanes disposed in the second
annular passage between the outer shroud and the central hub,
wherein an air passage of each swirl vane of the plurality of swirl
vanes is configured to route a first air flow into the first
annular passage, an exterior of each swirl vane of the plurality of
swirl vanes is configured to swirl a second air flow along the
second annular passage, and the flow conditioner in the first
annular passage is disposed between the plurality of swirl vanes
and the plurality of premixing tubes.
10. The system of claim 9, comprising a gas turbine engine, wherein
the gas turbine engine comprises the fuel nozzle, a combustor
having the fuel nozzle, a compressor, and a turbine.
11. The system of claim 9, wherein the flow conditioner comprises a
straightening vane, a perforated sheet or mesh screen, or a
multi-passage body having a plurality of passages generally
parallel with the longitudinal axis.
12. The system of claim 9, wherein the flow conditioner comprises a
plurality of straightening vanes each having a turn gradually
directed along the longitudinal axis in a downstream direction
toward the plurality of premixing tubes.
13. The system of claim 9, wherein the flow conditioner comprises a
perforated sheet or mesh screen extending crosswise to the
longitudinal axis in the first annular passage.
14. The system of claim 9, wherein the flow conditioner comprises a
multi-passage body having a plurality of passages generally
parallel with the longitudinal axis.
15. The system of claim 9, wherein the flow conditioner comprises a
perforated sheet or mesh screen disposed with the first annular
passage upstream of a multi-passage body having a plurality of
passages generally parallel with the longitudinal axis.
16. The system of claim 9, wherein the central hub comprises a
first wall extending circumferentially about the longitudinal axis
to define a central passage, a second wall extending
circumferentially about the first wall to define the first annular
passage, and a third wall extending circumferentially about the
second wall to define a third annular passage, wherein the first
annular passage routes the first air flow to the air inlet of each
tube of the plurality of premixing tubes, and the third annular
passage routes a fuel flow to the fuel inlet of each tube of the
plurality of premixing tubes.
17. A system, comprising: a fuel nozzle, comprising: a central hub
comprising a first annular passage extending along a longitudinal
axis of the fuel nozzle and a flow conditioner disposed along the
first annular passage, wherein the flow conditioner comprises at
least one of a straightening vane, a perforated sheet or mesh
screen, or a multi-passage body having a plurality of passages
generally parallel with the longitudinal axis; an outer shroud
disposed about the central hub to define a second annular passage
extending along the longitudinal axis of the fuel nozzle; and a
plurality of swirl vanes disposed in the second annular passage
between the outer shroud and the central hub, wherein an interior
of each swirl vane of the plurality of swirl vanes is configured to
route a first air flow into the first annular passage, an exterior
of each swirl vane of the plurality of swirl vanes is configured to
swirl a second air flow along the second annular passage, and the
flow conditioner in the first annular passage is disposed between
the plurality of swirl vanes and an outlet of the fuel nozzle.
18. The system of claim 17, comprising a gas turbine engine,
wherein the gas turbine engine comprises the fuel nozzle, a
combustor having the fuel nozzle, a compressor, and a turbine.
19. The system of claim 17, wherein the flow conditioner comprises
a plurality of the straightening vanes each having a turn gradually
directed along the longitudinal axis in a downstream direction
toward the outlet of the fuel nozzle, wherein the flow conditioner
comprises the perforated sheet or mesh screen, or the multi-passage
body having the plurality of passages generally parallel with the
longitudinal axis.
20. The system of claim 17, comprising a plurality of premixing
tubes disposed downstream from the flow conditioner, wherein each
tube of the plurality of premixing tubes comprises an air inlet, a
fuel inlet, and an air-fuel mixture outlet.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to fuel nozzles,
and more specifically, to systems to increase fuel/air mixing
within the fuel nozzles.
[0002] A gas turbine engine combusts a mixture of fuel and air to
generate hot combustion gases, which rotate turbine blades to drive
a load, such as an electrical generator. The gas turbine engine may
include one or more fuel nozzles to direct the mixture of fuel and
air into a combustion region of the gas turbine. In addition, the
one or more fuel nozzles may be used to premix the fuel and the
air. Unfortunately, poor mixing of the fuel and the air may reduce
the flame stability within the combustion region. In addition,
non-uniform mixtures of fuel and air may increase the amount of
undesirable combustion byproducts, such as nitrogen oxides.
BRIEF DESCRIPTION OF THE INVENTION
[0003] Certain embodiments commensurate in scope with the
originally claimed invention are summarized below. These
embodiments are not intended to limit the scope of the claimed
invention, but rather these embodiments are intended only to
provide a brief summary of possible forms of the invention. Indeed,
the invention may encompass a variety of forms that may be similar
to or different from the embodiments set forth below.
[0004] In one embodiment, a system includes a fuel nozzle. The fuel
nozzle includes a central hub with a first annular passage
extending along a longitudinal axis of the fuel nozzle. A flow
conditioner is disposed along the first annular passage. The flow
conditioner includes at least one of a straightening vane, a mesh
screen, or a multi-passage body having multiple passages generally
parallel with the longitudinal axis. An outer shroud is disposed
about the central hub to define a second annular passage extending
along the longitudinal axis of the fuel nozzle.
[0005] In a second embodiment, a system includes a fuel nozzle. The
fuel nozzle includes a first annular passage extending along a
longitudinal axis of the fuel nozzle, a flow conditioner disposed
along the first annular passage, and a plurality of premixing tubes
disposed along the first annular passage downstream from the flow
conditioner. Each tube of the plurality of premixing tubes includes
an air inlet, a fuel inlet, and an air-fuel mixture outlet. The
fuel nozzle also includes an outer shroud disposed about the
central hub to define a second annular passage extending along the
longitudinal axis of the fuel nozzle. In addition, the fuel nozzle
includes a plurality of swirl vanes disposed in the second annular
passage between the outer shroud and the central hub, wherein an
interior of each swirl vane of the plurality of swirl vanes is
configured to route a first air flow into the first annular
passage, an exterior of each swirl vane of the plurality of swirl
vanes is configured to swirl a second air flow along the second
annular passage, and the flow conditioner in the first annular
passage is disposed between the plurality of swirl vanes and the
plurality of premixing tubes.
[0006] In a third embodiment, a system includes a fuel nozzle. The
fuel nozzle includes a central hub having a first annular passage
extending along a longitudinal axis of the fuel nozzle and a flow
conditioner disposed along the first annular passage. The flow
passage is at least one of a straightening vane, a mesh screen, or
a multi-passage body having a plurality of passages generally
parallel with the longitudinal axis. The fuel nozzle includes a
plurality of swirl vanes disposed in the second annular passage
between the outer shroud and the central hub, wherein an interior
of each swirl vane of the plurality of swirl vanes is configured to
route a first air flow into the first annular passage, an exterior
of each swirl vane of the plurality of swirl vanes is configured to
swirl a second air flow along the second annular passage, and the
flow conditioner in the first annular passage is disposed between
the plurality of swirl vanes and an outlet of the fuel nozzle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a schematic diagram of an embodiment of a gas
turbine system having a combustor and fuel nozzles with features to
improve fuel/air mixing;
[0009] FIG. 2 is a perspective view of an embodiment of the fuel
nozzles of FIG. 1, illustrating the arrangement of the fuel nozzles
within the combustor of the gas turbine system.
[0010] FIG. 3 is a perspective view of an embodiment of a fuel
nozzle of FIG. 2 having various flow conditioners to improve
fuel/air mixing;
[0011] FIG. 4 is a cross-sectional view of an embodiment of the
fuel nozzle of FIG. 3 taken along line 4-4, illustrating a
plurality of straightening vanes (e.g., coupled to an inner wall)
to improve fuel/air mixing;
[0012] FIG. 5 is a simplified perspective view of an embodiment of
a single straightening vane of FIG. 4 disposed between the inner
wall and a hub wall of the fuel nozzle directly beneath an outlet
of a vane curtain air passage, illustrating flow behavior in the
absence and presence of the straightening vane;
[0013] FIG. 6 is a perspective view of an embodiment of the
straightening vane 48 of FIGS. 4 and 5;
[0014] FIG. 7 is a cross-sectional view of an embodiment of the
fuel nozzle of FIG. 3 taken along line 7-7, illustrating an annular
segment with tubes or passages to improve fuel/air mixing;
[0015] FIG. 8 is a cross-sectional view of an embodiment of the
annular segment of FIG. 7 taken along line 8-8, illustrating
multiple passages through the annular segment; and
[0016] FIG. 9 is a cross-sectional view of an embodiment of the
fuel nozzle of FIG. 3 taken along line 4-4, illustrating a
plurality of straightening vanes (e.g., coupled to the hub wall) to
improve fuel/air mixing.
DETAILED DESCRIPTION OF THE INVENTION
[0017] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, all features of an actual
implementation may not be described in the specification. It should
be appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0018] When introducing elements of various embodiments of the
present invention, the articles "a," "an," "the," and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements.
[0019] The present disclosure is directed toward systems for
improving fuel and air mixing within fuel nozzles of combustors. In
particular, air is directed through a swirler and into one or more
premixing tubes (e.g., a group of 10 to 100 premixing tubes). A
flow conditioner is disposed between the swirler and the premixing
tubes, such that the flow conditioner generally straightens (e.g.,
axially) the flow of air into the premixing tubes. Straightening
the flow of air results a more uniform delivery of air into the
premixing tubes, thereby improving fuel/air mixing and increasing
the efficiency of the combustor.
[0020] In certain embodiments, the flow conditioner may be one or
more straightening vanes or an annular segment with a plurality of
passages or tubes disposed therethrough. As will be discussed
further below, the straightening vane is shaped like an airfoil and
is partially or entirely arcuate in an axial and circumferential
direction of the fuel nozzle. The arcuate shape reduces the
circumferential velocity (e.g., swirl) of the air, thereby
straightening (e.g., axially) the air upstream of the premixing
tubes. In another embodiment, the flow conditioner may be the
annular segment having the plurality of passages or tubes. The
passages or tubes are generally straight and serve to straighten
the air and to direct the air towards the premixing tubes with a
decreased swirl. Again, the decreased swirl axially straightens the
air, which improves fuel/air mixing within the fuel nozzle and
increases the efficiency of the combustor, and subsequently, the
gas turbine system.
[0021] As used herein, the term "annular" shall mean a ring-shaped.
The use of the term "annular" is not intended to limit the scope of
the present disclosure with respect to the shape, perimeter, or
other geometric feature of the hollow structure. That is, a hollow
cylinder, a hollow cone, a hollow polyhedron, a hollow prism, and
the like, are all encompassed by the term "annular".
[0022] Turning now to the figures, FIG. 1 illustrates a block
diagram of an embodiment of a gas turbine system 10 with a fuel
nozzle 12 (e.g., turbine fuel nozzle) designed to increase mixing
of fuel and air. Throughout the discussion, a set of axes will be
referenced. These axes are based on a cylindrical coordinate system
and point in an axial direction 14, a radial direction 16, and a
circumferential direction 18. For example, the axial direction 14
extends along a longitudinal axis 17 (shown in FIG. 3) of the fuel
nozzle 12, the radial direction 16 extends away from the
longitudinal axis 17, and the circumferential direction 18 extends
around the longitudinal axis 17.
[0023] As illustrated, the gas turbine system 10 includes a
compressor 20, a combustor 22 (e.g., turbine combustor), and a
turbine 24. The turbine system 10 may include one or more of the
fuel nozzles 12 described below in one or more combustors 22. The
compressor 20 receives air 26 from an intake 28 and compresses the
air 26 for delivery to the combustor 22. As shown, a portion of the
air 26 is routed to the fuel nozzle 12, where the air 26 may premix
with fuel 30 before entering the combustor 22. The air 26 and the
fuel 30 are fed to the combustor 22 in a specified ratio suitable
for combustion, emissions, fuel consumption, power output, and the
like. Unfortunately, if the air 26 and the fuel 30 are not well
mixed, the flame stability within the combustor 22 may be reduced.
Accordingly, the fuel nozzle 12 includes a flow conditioner within
an annular passage of the fuel nozzle 12. The flow conditioner
straightens the air 26 (e.g., in the axial direction 14) and
improves the mixing of the air 26 and the fuel 30 by providing a
uniform distribution of air downstream to the premixing tubes, as
will be discussed further below.
[0024] The mixture of the air 26 and the fuel 30 is subsequently
combusted in the combustor 22, forming hot combustion products. The
hot combustion products enter the turbine 24 and force blades 32 of
the turbine 24 to rotate, thereby driving a shaft 34 of the gas
turbine system 10 into rotation. The rotating shaft 34 provides the
energy for the compressor 20 to compress the air 26. For example,
in certain embodiments, compressor blades are included as
components of the compressor 20. Blades within the compressor 20
may be coupled to the shaft 34, and will rotate as the shaft 34 is
driven to rotate by the turbine. In addition, the rotating shaft 34
may rotate a load 36, such as an electrical generator or any device
capable of utilizing the mechanical energy of the shaft 34. After
the turbine 24 extracts useful work from the combustion products,
the combustion products are discharged to an exhaust 38.
[0025] As noted previously, the gas turbine system 10 includes one
or more fuel nozzles 12 with features to improve uniformity in the
air distribution and the mixing of the air 26 and the fuel 30. FIG.
2 illustrates an arrangement of the fuel nozzles 12 within the
combustor 22 of the gas turbine system 10. As shown, six fuel
nozzles 12 are mounted to a head end 40 of the combustor 22.
However, the number of fuel nozzles 12 may vary. For example, the
gas turbine system 10 may include 1, 2, 3, 4, 5, 10, 50, 100, or
any other number of fuel nozzles 12. The six fuel nozzles 12 are
disposed in a concentric arrangement. That is, five fuel nozzles 12
(e.g., outer fuel nozzles 42) are disposed about a central fuel
nozzle 44. As will be appreciated, the arrangement of the fuel
nozzles 12 on the head end 40 may vary. For example, the fuel
nozzles 12 may be disposed in a circular arrangement, in a linear
arrangement, or in any other suitable arrangement. The flow of the
air 26 and the fuel 30 within the fuel nozzles 12 is discussed
below with respect to FIG. 3.
[0026] FIG. 3 is a perspective view of an embodiment of the fuel
nozzle 12 equipped with flow conditioners 46 (e.g., straightening
vanes 48, mesh screen 50, and annular multi-passage segment 52) to
straighten and uniformly distribute a flow of the air 26 and
improve the mixing of the fuel 30 and the air 26. In other words,
the flow conditioners 46 may reduce large scale vortices, small
scale eddies, and other swirling motion, while also helping to
distribute the air more uniformly across the air flow passage
(e.g., more uniform velocity across the entire cross section).
Although the straightening vanes 48, mesh screen 50, and annular
segment 52 are illustrated in use within a singular fuel nozzle 12,
it should be noted that the various flow conditioners 46 may be
used independently or in other combinations. For example, an
embodiment of the fuel nozzle 12 may include the straightening
vanes 48 but not the mesh screen 50 or the annular segment 52.
Alternatively, the fuel nozzle 12 may include the mesh screen 50
and/or the annular segment 52 but not the straightening vanes 48.
Thus, it will be appreciated that the selection of the flow
conditioners 46 may be based on various factors, such as pressure
drop, flow rates, and the like.
[0027] The various flow conditioners 46, used independently or in
combination with each other, may provide varying degrees of air
straightening in the axial direction 14 (i.e., may reduce the swirl
of the air 26 by varying amounts or percentages). In certain
embodiments, it may be desirable to provide the fuel nozzles 12
with varying amounts of swirl, depending on their placement about
the head end 40 of the combustor 22. For example, it may be
desirable to straighten air flow within the central fuel nozzle 44
(e.g., upstream of the premixing tubes 70) in order to improve
flame stability. Accordingly, the outer fuel nozzles 42 and the
central fuel nozzle 44 may be equipped with different flow
conditioners 46. That is, in certain embodiments, the central fuel
nozzle 44 may include the straightening vanes 48, whereas the outer
fuel nozzles 42 include both the mesh screen 50 and the annular
segment 52. In yet other embodiments, the central fuel nozzle 44
may include one of the flow conditioners 46, while the outer fuel
nozzles lack the flow conditioners 46. Again, the fuel nozzles 12
may employ any combination of the straightening vanes 48, the mesh
screen 50, and the annular segment 52 to reduce the swirl of the
air 26. It should be noted that when more than one flow conditioner
46 is employed, their ordering may be implementation-specific. For
example, although the mesh screen 50 is illustrated as upstream of
the annular segment 52, in other embodiments, the mesh screen 50
may be downstream of the annular segment 52. As shown, the mesh
screen 50 (e.g., perforated sheet) is a permeable grid of material
(e.g., plastic, metal, ceramic, etc.) with small openings 51 that
allow fluid to pass through. The openings 51 may vary in size, and
may be, for example, between approximately 5 to 50 mm, or 0.1 to 20
mm, and all subranges therebetween. The mesh screen 50 extends
crosswise (e.g., circumferentially 18) to the longitudinal axis 17
of a first annular passage 60 defined below. The mesh screen 50 may
further axially straighten the air 26 and/or help distribute the
air 26 more uniformly across the flow passage.
[0028] The geometry of the fuel nozzle 12 is discussed below. As
illustrated, the fuel nozzle 12 includes a central hub 53 with an
inner wall 54 and a hub wall 56 (e.g., outer wall of the central
hub 53). The inner wall 54 defines a central passage 58 (e.g.,
inner cylindrical passage), and the hub wall 56 defines the first
annular passage 60 that surrounds the central passage 58. During
operation of the fuel nozzle 12, liquid fuel may be routed through
the central passage 58 in the axial direction 14, as shown by
arrows 62. The central hub 53 increases the flexibility of the fuel
nozzle 12 by enabling liquid fuels to be used in combination with
gas fuels for combustion within the combustor 22.
[0029] An outer wall 64 surrounds the hub wall 56, defining a
second annular passage 66. The second annular passage 66 surrounds
both the first annular passage 60 and the central passage 58.
During operation of the fuel nozzle 12, the fuel 30 is routed
through the second annular passage 66 in the axial direction 14, as
shown by arrows 68. The fuel 30 enters premixing tubes 70 in the
radial direction 16 through fuel holes or inlets 71 located in a
side wall 73 of the premixing tube 70, as indicated by arrows 72.
The premixing tubes 70 are circumferentially 18 distributed about
the annular passage 60. Air 26, via the first annular passage 60,
enters air inlets 75 of the premixing tubes 70 and flows in the
axial direction 14 towards outlets 76 (e.g., air-fuel mixture
outlets) of the premixing tubes 70. Within the premixing tubes 70,
the fuel 30 mixes with the air 26 to form a combustible mixture and
is directed into the combustor 22 via the outlets 76.
[0030] A shroud 78 (e.g., annular shroud wall) is disposed about
the outer wall 64, defining a third annular passage 80. The third
annular passage 80 surrounds the second annular passage 66, the
first annular passage 60, and the central passage 58. As depicted,
the third annular passage 80, the second annular passage 66, the
first annular passage 60, and the central passage 58 are
concentrically arranged with respect to the longitudinal axis 17 of
the fuel nozzle 12. A first portion of the air 26 enters the third
annular passage 80 upstream of a swirler 84 and travels in the
axial direction 14 toward the outlet 74 of the fuel nozzle 12, as
indicated by arrows 82. However, a second portion of the air 26
(e.g., vane curtain air) enters the first annular passage 60
radially 16 through the swirler 84, which includes one or more
swirl vanes 86 circumferentially 18 spaced about an axis 17 of the
fuel nozzle 12. More specifically, the second portion of the air 26
may enter the first annular passage 60 through the vane curtain air
passages 83 disposed within the swirl vanes 86. The fuel 30 may
enter the second annular passage 66 and flow through fuel passages
81 disposed within the swirl vanes 86 (upstream of the vane curtain
air passages 83) and subsequently injected through fuel holes 79
into the third annular passage 80, where the fuel 30 may mix with
the air 26 and enter the combustor.
[0031] Once the vane curtain air enters the first annular passage
60, the air 26 passes through one or more flow conditioners 46, as
shown by arrows 85. The flow conditioners 46 straighten the flow of
the air 26 (e.g., in the axial direction 14) upstream of the
premixing tubes 70, which provides a uniform distribution of the
air 26 to the premixing tubes 70 and improves fuel/air mixing
within the premixing tubes 70 and the overall efficiency of the gas
turbine system 10.
[0032] As shown, the flow path of the vane curtain air is defined
by a flow length or axial distance 87 from the vane curtain air
passages 83 of the swirler 84 to an upstream end 89 of the
premixing tubes 70. The flow conditioners 46 are disposed along the
flow length 87 (between the swirler 84 and the premixing tubes 70)
to straighten and uniformly distribute the vane curtain air before
it enters the premixing tubes 70. In certain embodiments, the flow
conditioners 46 may be disposed within the first air passage 60
directly at the outlet of the swirler 84 or at the inlet of the
premixing tubes 70 (see FIG. 5). As depicted, the straightening
vanes 48 are located downstream of where the air 26 exits from the
vane curtain air passages 83 of the swirler 84 (e.g., swirl vanes
86) into the first air passage 60 and upstream of the other flow
conditioners 46 (e.g., mesh screen 50 and annular segment 52) and
the premixing tubes 70. As will be appreciated, the amount of
straightening provided by the flow conditioners 46 may be affected
by the length of the flow conditioners 46, as is discussed in
greater detail with respect to FIGS. 6 and 8.
[0033] Returning to FIG. 3, as the air 26 enters the first annular
passage 60, the swirler 84 imparts a circumferential velocity to
the air 26. The air 26 flows axially 14 and circumferentially 18
towards the flow conditioners 46, which axially 14 straighten the
flow of the air 26 by reducing its circumferential velocity. Again,
an axially straightened flow of air provides a uniform distribution
of air 26 to the premixing tubes 70, thus improving the mixing of
the fuel 30 and the air 26 within the premixing tubes 70 and the
efficiency of the gas turbine system 10. In particular, the
straightened flow may result in a more uniform equivalence ratio
(i.e., ratio of the actual fuel/air ratio to the stoichiometric
fuel/air ratio) between each of the premixing tubes 70 and in each
premixing tube 70. For example, the equivalence ratios within each
premixing tube 70 may be between approximately 0.3 to 0.7, 0.4 to
0.6, or 0.53 to 0.56, and all subranges therebetween. The increased
uniformity of equivalence ratios (e.g., less than 1, 5, or 10
percent variance) among the premixing tubes 70 improves the flame
stability within the combustor 22. Features of the flow
conditioners 46 to straighten the air 26 to improve the uniformity
of the equivalence ratios are discussed in further detail below
with respect to FIGS. 4-8.
[0034] FIG. 4 is a cross-sectional view of the fuel nozzle 12 of
FIG. 3, taken along line 4-4. As shown, a plurality of
straightening vanes 48 is disposed within the first annular passage
60. For example, the fuel nozzle 12 may generally include
approximately 1, 2, 3, 4, 5, 6, or any other number of
straightening vanes 48. The straightening vanes 48 may be coupled
to the inner wall 54 and extend from the inner wall 54 towards the
hub wall 56 as depicted in FIG. 4. Alternatively, the straightening
vanes 48 may be coupled to the hub wall 56 and extend from the hub
wall 56 towards the inner wall 54 as depicted in FIG. 9. The
straightening vanes 48 are arcuate in the circumferential direction
18 and the axial direction 14 (see FIG. 5), which enables a greater
contact area between the flowing air 26 and the straightening vane
48. In addition, the straightening vanes 48 are circumferentially
18 spaced about the first annular passage 60, which improves the
uniformity of the air 26 as it flows along the straightening vanes
48.
[0035] As illustrated, vane curtain air (e.g., air 26) flows
radially 16 through the vane curtain air passages 83 of the swirl
vanes 86 of the swirler 84, as shown by arrows 88. The air 26 exits
the swirler 84 into the first annular passage 60 of the central hub
53. The radial entrance of the air 26 into the first annular
passage 60 results in a circumferential velocity about the axis 17
of the fuel nozzle 12, which may decrease the uniform profile of
the air across the first annular passage 60 and the premixing tubes
70. The air 26 continues to flow axially 14 and circumferentially
18 about the annular passage 60 until it encounters the
straightening vanes 48. When the air 26 encounters the
straightening vanes 48, they guide the air 26 along the axial
direction 14, thereby reducing the circumferential velocity of the
air 26. Accordingly, the shape of the straightening vanes 48 is
designed to reduce the circumferential velocity of the air 26, as
illustrated by FIG. 5.
[0036] FIG. 5 is a simplified perspective view of an embodiment of
a single straightening vane 48 of FIG. 4 disposed within the inner
wall 54 and the hub wall 56 of the fuel nozzle 12 directly beneath
an outlet 90 of the vane curtain air passage 83, illustrating flow
behavior in the absence and presence of the straightening vane 48.
Portions of the fuel nozzle 12 are not illustrated to facilitate
explanation of the flow behavior. As described above, the
straightening vane 48 is disposed within the first annular passage
60. The straightening vane 48 may be coupled to the inner wall 54
and extend from the inner wall 54 towards the hub wall 56 within
the first annular passage 60. Alternatively, the straightening vane
48 may be coupled to the hub wall 56 and extend from the hub wall
56 towards the inner wall 54 with the first annular passage 60. The
straightening vane 48 is arcuate in the circumferential direction
18 (see FIG. 4) and the axial direction 14, which enables a greater
contact area between the flowing air 26 and the straightening vane
48. The straightening vane 48 includes an upstream end portion 92
(e.g., leading edge) and a downstream end portion 94 (e.g.,
trailing edge) relative to the general direction of the flow of the
air 26 in the axial direction 14. The upstream end portion 92
includes a non-linear or arcuate portion 96 and the downstream end
portion 94 includes a linear or straight portion 98. The
straightening vane 48 gradually turns from the radial direction 16
toward the axial direction 14 along the longitudinal axis 17 of the
fuel nozzle 12 in the downstream direction (i.e., axial direction
14) toward the outlet 74 of the fuel nozzle 12.
[0037] As depicted in FIG. 5, the air 26 flows radially 16 thorough
the vane curtain air passage 83 into the first annular passage 60,
the air 26 enters off-center relative to the axis 17 (see FIG. 4).
In the absence of the straightening vane 48, the off-centered
entrance of the air 26 creates a swirling flow 100 (represented by
the double dotted-dashed line) that flows in both the
circumferential 18 and axial 14 directions. The circumferential
velocity of the swirling flow 100 about the axis 17 of the fuel
nozzle 12 may decrease the uniform profile of the air 26 across the
first annular passage 60 and the premixing tubes 70, while also
resulting in a pressure drop within the first annular passage
60.
[0038] The presence of the straightening vane 48 straightens the
flow of the air 26 within the first annular passage 60 (as
indicated by dashed line 102), while reducing the amount of
pressure drop (e.g., relative to the pressure drop in the absence
of the straightening vane 48) within the first annular passage 60.
As the air 26 exits the outlet 90 of the vane curtain air passage
83, it encounters the arcuate portion 96 of the upstream end
portion 92 of the straightening vane 48. The arcuate portion 96
gradually or smoothly transitions from the upstream end portion 92
to the downstream portion 94 of the straightening vane 48. This
gradual transition may reduce the amount of pressure drop
experienced by the air 26 as it enters and flows along the first
annular passage 60. Upon encountering the upstream end portion 92
of the straightening vane 48, the air 26 (i.e., dashed line 102)
flows downstream along the arcuate portion 96 to the straight
portion 98 of the downstream end 94 of the straightening vane 48.
The flow of the air 26 (i.e., dashed line 102) results in the
gradual straightening of the air flow 26 to flow generally in the
axial direction 14.
[0039] FIG. 6 is a perspective view of the straightening vane 48 of
FIGS. 4 and 5. In general, the straightening vane 48 is as
described above. As shown, the arcuate portion 96 gradually
decreases in curvature (e.g., angle with respect to the axial
direction 14 relative to the straight portion 98 of the
straightening vane) from the upstream end portion 92 to the
downstream end portion 94 until the straightening vane 48
transitions into the straight portion 98. The gradual decrease
enables a gradual reduction in the circumferential velocity of the
air 26. In certain embodiments, the arcuate portion 96 may be a
partial paraboloid, hyperboloid, or another quadric surface, or any
other suitable curved shape that gradually decreases in curvature.
For example, angle 104 near a proximal or upstream end of the
arcuate portion 96 may be between approximately 20 to 100, 40 to
60, or 45 to 50 degrees, and all subranges therebetween. In certain
embodiments, angle 106 near a distal or downstream end of the
arcuate portion 96 (and downstream of angle 104) may be between
approximately 0 to 30, 5 to 20, or 10 to 15 degrees, and all
subranges therebetween. The angle 106 is less than the angle 104,
which provides a smooth and gradual reduction in the
circumferential velocity of the air 26.
[0040] The straightening vane 48 has an axial length 108 from the
upstream end portion 92 to the downstream end portion 94. As noted
earlier, the axial length 108 may affect the straightening of the
air 26. In general, a longer axial length 108 increases the
straightening of the air 26. Thus, in certain embodiments, the
axial length 108 may be between approximately 5 to 95, 20 to 80, or
40 to 60 percent, and all subranges therebetween, of the total
axial distance 87 along the first annular passage 60 from the vane
curtain air passages 83 of the swirler 84 to the upstream end 89 of
the premixing tubes 70 (see FIG. 3), in order to reduce the swirl
of the air 26 and improve the efficiency of the gas turbine system
10. The arcuate portion 96 has an axial length 107 and the straight
portion 98 has an axial length portion 109. In some embodiments,
the axial length 107 of the arcuate portion 96 may be longer than
the axial length 109 of the straight portion 98. In other
embodiments, the axial length 109 of the straight portion 98 may be
longer than the axial length 107 of the arcuate portion 96. In
certain embodiments, the axial length 107 of the arcuate portion 96
may be approximately 5 to 95, 15 to 65, or 30 to 50 percent, and
all subranges therebetween, of the axial length 108 of the
straightening vane 48. In certain embodiments, the axial length 109
of the straight portion 98 may be approximately 5 to 95, 15 to 65,
or 30 to 50 percent, and all subranges therebetween, of the axial
length 108 of the straightening vane 48.
[0041] FIG. 7 is a cross-sectional view of the fuel nozzle 12 of
FIG. 3, taken along line 7-7. As shown, the multi-passage body or
annular segment 52 is disposed within the first annular passage 60
of the central hub 53. The annular segment 52 encloses a portion of
the volume between the inner wall 54 and the hub wall 56. The
annular segment 52 includes a solid body 110 that includes a
plurality of passages or tubes 112 (e.g., cylindrical tubes) that
extend throughout the solid body 110 in the axial direction 14
through which the air 26 can flow. The passages or tubes 112 are
generally parallel with the longitudinal axis 17. The annular
segment 52 may include any number of the passages or tubes 112,
such as 1, 2, 3, 4, 5, 10, 20, or any other number. The tubes or
passages 112 may include any cross-sectional shape (e.g.,
elliptical, rectilinear, etc.). The cross-sectional area of each
passage or tube 112 may be uniform or vary between passages or
tubes 112. The tubes or passages 112 may be arranged in a
symmetrical (or uniform) pattern. For example, as depicted, the
passages or tubes 112 are arranged concentrically in rows 114 about
the axis 17. In other embodiments, the tubes or passages 112 may be
arranged in non-symmetrical (or non-uniform) pattern. The
arrangement of passages or tubes 112 of the annular segment 52
functions to axially straighten the flow of the air 26 as it passes
through the annular segment 52 from an upstream axial end 116 to a
downstream axial end 118 (see FIG. 8). In particular, the annular
segment 52 straightens the air 26 that entered the first annular
passage 60 via the vane curtain air passages 83 prior to reaching
the premixing tubes 70 to provide a uniform profile of air 26 in
each premixing tube 70, which reduces the variation in the amount
of air 26 in each premixing tube 70.
[0042] FIG. 8 is a cross-sectional view of the annular segment 52
of FIG. 7, taken along line 8-8. As shown, the vane curtain air 26
flows from the upstream axial end 116 to the downstream axial end
118 of the annular segment 52, as shown by arrows 120. The air 26
follows the general shape of the passages or tubes 112, which are
generally parallel with the axis 17 in the axial direction 14.
Thus, the air 26 generally axially straightens as it flows from the
upstream axial end 116 to the downstream axial end 118.
[0043] As shown, the annular segment 52 extends an axial length
122. In general, a longer axial length 122 provides longer passages
or tubes 112, which increases the straightening of the air 26, but
also increases pressure drop through the annular segment 52.
Accordingly, in certain embodiments, the axial length 122 may be
optimized by having a length between approximately 5 to 95, 20 to
80, or 40 to 60 percent, and all subranges therebetween, of the
total axial distance 87 along the first annular passage 60 from the
vane curtain air passages 83 of the swirler 84 to the upstream end
89 of the premixing tubes 70 (see FIG. 3). As noted earlier, the
annular segment 52 may be employed with the mesh screen 50, which
may be either upstream or downstream of the annular segment 52.
Also, in certain embodiments, the mesh screen 50 may only be
used.
[0044] FIG. 9 is a cross-sectional view of an embodiment of the
fuel nozzle 12 of FIG. 3 taken along line 4-4, illustrating the
plurality of straightening vanes 48. The fuel nozzle 12 and
straightening vanes 48 are as generally described above. As
depicted, the straightening vanes 48 are coupled to the hub wall 56
and extend from the hub wall 56 towards the inner wall 54.
[0045] Technical effects of the disclosed embodiments include
providing the flow conditioners 46 to axially straighten the flow
of the air 26 within the first annular passage 60 of the fuel
nozzle 12. Straightening the air 26 uniformly distributes the air
26 into the premixing tubes 70, thus improving the mixing of fuel
and air within the premixing tubes 70 of the fuel nozzle 12,
thereby increasing the efficiency of the gas turbine system 10. The
flow conditioner 46 may be the straightening vanes 48, the mesh
screen 50, the annular segment 52, or any combination thereof.
[0046] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
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