U.S. patent application number 14/449339 was filed with the patent office on 2016-02-04 for seal in combustor nozzle of gas turbine engine.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is General Electric Company. Invention is credited to Thomas Edward Johnson, Christopher Paul Keener, Heath Michael Ostebee, Christian Xavier Stevenson.
Application Number | 20160033134 14/449339 |
Document ID | / |
Family ID | 55179639 |
Filed Date | 2016-02-04 |
United States Patent
Application |
20160033134 |
Kind Code |
A1 |
Johnson; Thomas Edward ; et
al. |
February 4, 2016 |
SEAL IN COMBUSTOR NOZZLE OF GAS TURBINE ENGINE
Abstract
A nozzle for use in a combustor of a combustion turbine engine,
the nozzle including: radial sections defined by sidewalls; a gap
formed between opposing sidewalls of adjacent ones of the radial
sections; a groove formed on each of the sidewalls that define the
gap, the grooves positioned correspondingly so to together form a
pocket; and a seal having a zigzagging profile disposed within the
pocket. The pocket may intercept the gap over a seal length, and
the seal may extend longitudinally within the pocket such that the
zigzagging profile intersects the gap over the seal length.
Inventors: |
Johnson; Thomas Edward;
(Greer, SC) ; Keener; Christopher Paul; (Denver,
NC) ; Stevenson; Christian Xavier; (Blanchester,
OH) ; Ostebee; Heath Michael; (Piedmont, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
|
Family ID: |
55179639 |
Appl. No.: |
14/449339 |
Filed: |
August 1, 2014 |
Current U.S.
Class: |
60/740 ;
239/589 |
Current CPC
Class: |
F23R 2900/00012
20130101; F23R 3/286 20130101 |
International
Class: |
F23R 3/28 20060101
F23R003/28; F23D 14/02 20060101 F23D014/02 |
Goverment Interests
FEDERAL RESEARCH STATEMENT
[0001] This invention was made with Government support under
Contract No. DE-FC26-05NT42643, awarded by the Department of
Energy. The Government has certain rights in the invention.
Claims
1. A nozzle for use in a combustor of a combustion turbine engine,
the nozzle comprising: radial sections defined by sidewalls; a gap
formed between opposing sidewalls of adjacent ones of the radial
sections; a groove formed on each of the sidewalls that define the
gap, the grooves positioned correspondingly so to together form a
pocket; and a seal having a zigzagging profile disposed within the
pocket; wherein the pocket intercepts the gap over a seal length;
and wherein the seal extends longitudinally within the pocket such
that the zigzagging profile intersects the gap over the seal
length.
2. The nozzle according to claim 1, further comprising: a fuel
plenum defined by a circumferentially extending shroud wall that
extends axially between a forward tubesheet and an aft tubesheet,
wherein the sidewalls radially section the fuel plenum so to form
the radial sections; and mixing tubes extending across each of the
radial sections of the fuel plenum so to define a passageway
connecting an inlet formed through the forward tubesheet to an
outlet formed through the aft tubesheet.
3. The nozzle according to claim 2, wherein the seal length extends
between a first end positioned near an inboard boundary of the fuel
plenum and a second end positioned near the shroud wall; wherein a
forward seam formed on the forward tubesheet and an aft seam formed
on the aft tubesheet define forward and aft ends of the gap;
wherein the forward and aft seams each extend linearly between the
inboard boundary of the fuel plenum and the shroud wall, and the
gap extends planarly between the forward and aft seams.
4. The nozzle according to claim 3, wherein the pocket comprises a
position between the forward and aft seams of the gap, and wherein
the pocket extends in a radially direction.
5. The nozzle according to claim 4, wherein the pocket comprises a
position approximately midway between the forward and aft seams;
and wherein each of the grooves and the pocket comprise rectangular
profiles.
6. The nozzle according to claim 2, wherein the grooves are formed
so that the gap bisects the pocket; and wherein the seal comprises
a compliant material selected for air loading flexion during
operation.
7. The nozzle according to claim 2, wherein the zigzagging profile
of the seal comprises at least two segments connected end-to-end at
a sharp turn.
8. The nozzle according to claim 7, wherein the sharp turn
comprises one of at least 120.degree.; and wherein the zigzagging
profile comprises at least one of a "V" or "U" shape.
9. The nozzle according to claim 2, wherein the zigzagging profile
comprises at least three segments connected end-to-end at
alternating sharp turns.
10. The nozzle according to claim 9, wherein the sharp turns each
comprises one of at least 90.degree..
11. The nozzle according to claim 10, wherein the segments are
curved so that the zigzagging profile comprises a sinusoidal
shape.
12. The nozzle according to claim 9, wherein the sharp turns each
comprises one of at least 120.degree.; and wherein the segments are
linear and the zigzagging profile comprises a "N" shape.
13. The nozzle according to claim 2, wherein the zigzagging profile
comprises at least four segments connected end-to-end at
alternating sharp turns.
14. The nozzle according to claim 13, wherein the sharp turns each
comprise one of at least 150.degree..
15. The nozzle according to claim 13, wherein the zigzagging
profile comprises an ".OMEGA." shape.
16. The nozzle according to claim 13, wherein the zigzagging
profile comprises a "M" shape.
17. The nozzle according to claim 16, wherein the "M" shape is
oriented within the pocket such that the middle sharp turn is
directed toward an expected leakage flow through the gap.
18. The nozzle according to claim 2, wherein dimensions of the
pocket and dimensions of the zigzagging profile of the seal are
correspondingly sized so that rotation of the seal about a
longitudinal axis beyond approximately 45.degree. is mechanically
prevented.
19. A combustor in a combustion turbine engine that includes a
nozzle for mixing a supply of compressed air with a supply of fuel,
wherein the nozzle further comprising: a fuel plenum comprising a
cylindrical shape that is axially stacked between a first chamber
and a second chamber, wherein the fuel plenum is defined between by
a circumferentially extending shroud wall that extends axially
between a planar forward tubesheet, which is adjacent to the first
chamber, and a planar aft tube sheet, which is adjacent to the
second chamber; a plurality of wedge-shaped nozzle sections formed
by sidewalls that radially section the fuel plenum; mixing tubes
positioned within each of the plurality of nozzle sections, each of
the mixing tubes including a tube extending between an inlet formed
through the forward tubesheet and an outlet formed through the aft
tubesheet and including a plurality of fuel ports connecting an
interior of the tube with the fuel plenum formed about it; wherein
a first nozzle section and an adjacent second nozzle section
comprise, respectively, a first sidewall and a second sidewall
opposed across a gap formed therebetween; wherein a groove is
positioned on each of the first and second sidewalls so to together
form a radially extending pocket that intercepts the gap over a
seal length; and wherein a seal having a zigzagging profile extends
longitudinally within the pocket such that the zigzagging profile
intersects the gap over the seal length.
20. The combustor according to claim 19, wherein the first chamber
is configured to receive a supply of compressed air and the second
chamber is configured as a combustion zone; wherein the seal length
extends between a first end positioned near an inboard boundary of
the fuel plenum and a second end positioned near the shroud wall;
and wherein the zigzagging profile comprises at least four segments
connected end-to-end at alternating turns of at least 120.degree..
Description
BACKGROUND OF THE INVENTION
[0002] The present invention relates to combustion systems in gas
turbine engines, and more particularly, to apparatus and systems
related to the configuration and design of combustor nozzles and
fuel injectors.
[0003] Combustion turbine engines or "gas turbines" are widely used
in industrial and power generating applications. As will be
appreciated, typical gas turbines includes an axial compressor
positioned at forward end, a turbine positioned at an aft end, and
one or more combustors about the middle portion of the engine. In
operation, ambient air enters the compressor, and rotating blades
and stationary vanes in the compressor progressively impart kinetic
energy so to produce a supply of compressed air. From the
compressor, the compressed air is directed into the combustor where
it is mixed with a supply of fuel. The air/fuel mixture is then
ignited and combusted within the combustor, and the resulting
highly energized flow or "working fluid" is then expanded through
the rotating blades of the turbine so work may be extracted
therefrom. For example, the rotation induced by the flow through
the turbine may rotate a shaft that connects to a generator so to
produce electricity.
[0004] Certain types of combustor nozzles--commonly referred to as
"micro-mixer nozzles"--include an array of mixing tubes about which
a fuel plenum is formed. The supply of compressed air from the
compressor is brought to a forward wall of the fuel plenum and the
created pressure boundary drives the air through the tubes toward a
combustion chamber or zone. The mixing tubes include fuel ports
that fluidly communicate with the interior of the fuel plenum, and
via these ports fuel is injected into the air moving through the
tubes. Brought together in this manner, the fuel and air are
suitably mixed before being expelled into the combustion zone for
combustion.
[0005] In combustors featuring micro-mixer nozzles, the nozzles
themselves typically cover and seal the forward end of the
combustion liner. A pressure drop is taken from one side of the
nozzle to the other, and the pressure drop is what drives the air
across the mixing tubes. Ideally all of the compressed air
delivered to the head end is sent through the nozzle and mixed with
the fuel that is injected in the nozzle from the fuel plenum. This
typically achieves an uniform and balanced fuel-air mixture for
combustion. Specifically, as will be appreciated, a given amount of
fuel is supplied to the combustor to produce a specific amount of
heat, and is controlled so to achieve a desirable fuel-air ratio.
It will be appreciated that air that bypasses the nozzle--through
gaps, leakage or otherwise--may result in a higher fuel to air
ratio within the nozzle. This fuel rich mixture typically results
in a locally higher flame temperatures, i.e., hotspots, and
therefore produces more oxides of nitrogen, which is a regulated
emission. Such leakage also negatively impacts engine efficiency.
As a result, there is a continuing need for nozzle configurations
that discourage such bypass air leakage. As will be appreciated,
micro-mixer nozzles often include a seam formed between abutting
nozzle sections that is highly susceptible to such leakage. A
cost-effective and robust seal that prevented leakage through this
seam would be commercially demanded.
BRIEF DESCRIPTION OF THE INVENTION
[0006] The present application thus describes a nozzle for use in a
combustor of a combustion turbine engine, the nozzle including:
radial sections defined by sidewalls; a gap formed between opposing
sidewalls of adjacent ones of the radial sections; a groove formed
on each of the sidewalls that define the gap, the grooves
positioned correspondingly so to together form a pocket; and a seal
having a zigzagging profile disposed within the pocket. The pocket
may intercept the gap over a seal length, and the seal may extend
longitudinally within the pocket such that the zigzagging profile
intersects the gap over the seal length.
[0007] The present application further describes a combustor in a
combustion turbine engine that includes a nozzle for mixing a
supply of compressed air with a supply of fuel. The nozzle further
includes: a fuel plenum having a cylindrical shape that is axially
stacked between a first chamber and a second chamber, wherein the
fuel plenum is defined between by a circumferentially extending
shroud wall that extends axially between a planar forward
tubesheet, which is adjacent to the first chamber, and a planar aft
tube sheet, which is adjacent to the second chamber; a plurality of
wedge-shaped nozzle sections formed by sidewalls that radially
section the fuel plenum; and mixing tubes positioned within each of
the plurality of nozzle sections, each of the mixing tubes
including a tube extending between an inlet formed through the
forward tubesheet and an outlet formed through the aft tubesheet
and including a plurality of fuel ports connecting an interior of
the tube with the fuel plenum formed about it. A first nozzle
section and an adjacent second nozzle section may include,
respectively, a first sidewall and a second sidewall opposed across
a gap formed therebetween. A groove may be positioned on each of
the first and second sidewalls so to together form a radially
extending pocket that intercepts the gap over a seal length. And a
seal having a zigzagging profile may extend longitudinally within
the pocket such that the zigzagging profile intersects the gap over
the seal length.
[0008] These and other features of the present application will
become apparent upon review of the following detailed description
of the preferred embodiments when taken in conjunction with the
drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other features of this invention will be more
completely understood and appreciated by careful study of the
following more detailed description of exemplary embodiments of the
invention taken in conjunction with the accompanying drawings, in
which:
[0010] FIG. 1 is a section view of a gas turbine engine in which
embodiments of the present invention may be used.
[0011] FIG. 2 is a simplified cross-section of a combustor in which
embodiments of the present invention may be used.
[0012] FIG. 3 is an enlarged sectional view of the head end of a
combustor in which embodiments of the present invention may be
used.
[0013] FIG. 4 is a sectional perspective view a head end and nozzle
configuration in accordance with aspects of the present
invention.
[0014] FIG. 5 is a side sectional view of a nozzle in accordance
with aspects of the present invention.
[0015] FIG. 6 is a perspective view of a nozzle sidewall having a
seal in accordance with exemplary embodiments of the present
invention.
[0016] FIG. 7 is an outboard sectional view of adjacent nozzle
sections in which the gap formed therebetween includes a seal in
accordance with embodiments of the present invention.
[0017] FIG. 8 is an outboard sectional view of adjacent nozzle
sections in which the gap formed therebetween includes a seal in
accordance with an alternative embodiment of the present
invention.
[0018] FIG. 9 is an outboard sectional view of adjacent nozzle
sections in which the gap formed therebetween includes a seal in
accordance with an alternative embodiment of the present
invention.
[0019] FIG. 10 is an outboard sectional view of adjacent nozzle
sections in which the gap formed therebetween includes a seal in
accordance with an alternative embodiment of the present
invention.
[0020] FIG. 11 is an outboard sectional view of adjacent nozzle
sections in which the gap formed therebetween includes a seal in
accordance with an alternative embodiment of the present
invention.
[0021] FIG. 12 is sectional view of adjacent nozzle sections
illustrating a typical axial shift between the nozzles during
operation.
[0022] FIG. 13 is an enlargement of the axially shifted nozzle
sections of FIG. 12 and how the shift may be accommodated according
to an exemplary seal of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] In the following text, certain terms have been selected to
describe the present invention. To the extent possible, these terms
have been chosen based on the terminology common to the field.
Still, it will be appreciate that such terms often are subject to
differing interpretations. For example, what may be referred to
herein as a single component, may be referenced elsewhere as
consisting of multiple components, or, what may be referenced
herein as including multiple components, may be referred to
elsewhere as being a single component. In understanding the scope
of the present invention, attention should not only be paid to the
particular terminology used, but also to the accompanying
description and context, as well as the structure, configuration,
function, and/or usage of the component being referenced and
described, including the manner in which the term relates to the
several figures, as well as, of course, the precise usage of the
terminology in the appended claims.
[0024] Because several descriptive terms are regularly used in
describing the components and systems within turbine engines, it
should prove beneficial to define these terms at the onset of this
section. Accordingly, these terms and their definitions, unless
specifically stated otherwise, are as follows. The terms "forward"
and "aft", without further specificity, refer to directions
relative to the orientation of the gas turbine. That is, "forward"
refers to the forward or compressor end of the engine, and "aft"
refers to the aft or turbine end of the engine. It will be
appreciated that each of these terms may be used to indicate
movement or relative position within the engine. The terms
"downstream" and "upstream" are used to indicate position within a
specified conduit relative to the general direction of flow moving
through it. (It will be appreciated that these terms reference a
direction relative to an expected flow during normal operation,
which should be plainly apparent to anyone of ordinary skill in the
art.) The term "downstream" refers to the direction in which the
fluid is flowing through the specified conduit, while "upstream"
refers to the direction opposite that.
[0025] Thus, for example, the primary flow of working fluid through
a turbine engine, which consists of air through the compressor and
then becoming combustion gases within the combustor and beyond, may
be described as beginning at an upstream location at an upstream
end of the compressor and terminating at an downstream location at
a downstream end of the turbine. In regard to describing the
direction of flow within a common type of combustor, as discussed
in more detail below, it will be appreciated that compressor
discharge air typically enters the combustor through impingement
ports that are concentrated toward the aft end of the combustor
(relative to the combustors longitudinal axis and the
aforementioned compressor/turbine positioning defining forward/aft
distinctions). Once in the combustor, the compressed air is guided
by a flow annulus formed about an interior chamber toward the
forward end of the combustor, where the air flow enters the
interior chamber and, reversing it direction of flow, travels
toward the aft end of the combustor. Coolant flows through cooling
passages may be treated in the same manner.
[0026] Given the configuration of compressor and turbine about a
central common axis as well as the cylindrical configuration common
to many combustor types, terms describing position relative to an
axis will be used. In this regard, it will be appreciated that the
term "radial" refers to movement or position perpendicular to an
axis. Related to this, it may be required to describe relative
distance from the central axis. In this case, if a first component
resides closer to the central axis than a second component, it will
be described as being either "radially inward" or "inboard" of the
second component. If, on the other hand, the first component
resides further from the central axis than the second component, it
will be described herein as being either "radially outward" or
"outboard" of the second component. Additionally, it will be
appreciated that the term "axial" refers to movement or position
parallel to an axis. Finally, the term "circumferential" refers to
movement or position around an axis. As mentioned, while these
terms may be applied in relation to the common central axis that
extends through the compressor and turbine sections of the engine,
these terms also may be used in relation to other components or
sub-systems of the engine. For example, in the case of a
cylindrically shaped combustor, which is common to many machines,
the axis which gives these terms relative meaning is the
longitudinal central axis that extends through the center of the
cross-sectional shape, which is initially cylindrical, but
transitions to a more annular profile as it nears the turbine.
[0027] The following description provides examples of both
conventional technology and the present invention, as well as, in
the case of the present invention, several exemplary
implementations and explanatory embodiments. However, it will be
appreciated that the following examples are not intended to be
exhaustive as to all possible applications the invention. Further,
while the following examples are presented in relation to a certain
type of turbine engine, the technology of the present invention
also may be applicable to other types of turbine engines as would
the understood by a person of ordinary skill in the relevant
technological arts.
[0028] FIG. 1 is a cross-sectional view of a known gas turbine
engine 10 in which embodiments of the present invention may be
used. As shown, the gas turbine engine 10 generally includes a
compressor 11, one or more combustors 12, and a turbine 13. It will
be appreciated that a flowpath is defined through the gas turbine
10. During normal operation, air may enter the gas turbine 10
through an intake section, and then fed to the compressor 11. The
multiple, axially-stacked stages of rotating blades within the
compressor 11 compress the air flow so that a supply of compressed
air is produced. The compressed air then enters the combustor 12
and directed through a nozzle, within which it is mixed with a
supply of fuel so to form an air-fuel mixture. The air-fuel mixture
is combusted within a combustion zone portion of the combustor so
that a high-energy flow of hot gases is created. This energetic
flow of hot gases then becomes the working fluid that is expanded
through the turbine 13, which extracts energy from it.
[0029] FIG. 2 is a simplified cross-section of a combustor 12 in
which embodiments of the present invention may be used, while FIG.
3 provides an enlarged sectional view of the forward portion of the
combustor 12. As one of ordinary skill in the art will appreciate,
the combustor 12 is axially defined by a forward end, which
typically is referred to as a head end 15, and an aft end, which,
as illustrated, may be defined by an aft frame 16 that connects the
combustor to the turbine. A nozzle 17 may be positioned toward the
forward end of the combustor 12. It will be appreciated that the
nozzle 17 is the primary component that brings together and mixes
the fuel and air that is combusted within the combustor 12. As
discussed in more detail below, the nozzle 17 may be configured as
a micro-mixer nozzle. As illustrated, the head end 15 generally
provides various manifolds, apparatus, and/or fuel lines 18 that
provide the fuel to the nozzle 17. The head end 15 also may include
an endcover 19 that forms the forward axial boundary of the large
interior cavity that is defined in most combustors 12.
[0030] The interior cavity of the combustor 12, as illustrated, is
divided into several chambers that are configured to direct the
working fluid of the engine along a desired flow path. These
include a first chamber that is typically defined by a component
referred to herein as cap assembly 21. The other chamber includes
the combustion zone and is typically defined by a liner and/or
transition piece, as discussed below. It will be appreciated that,
given this arrangement, these chambers may be described as being
axially stacked in their configuration.
[0031] The cap assembly 21, as shown, may extend afterward from a
connection it makes with the endcover 19, and be surrounded by a
combustor casing 29, which is formed outboard of and in spaced
relation to it. In this manner, the cap assembly 21 and the
combustor casing 29 thereby form an annulus shaped flowpath between
them. As discussed below, this annular flowpath--referred to herein
as flow annulus 28--continues in an aft direction. The cap assembly
29 may house and structurally support the nozzle 17, which may be
positioned at or near the aft end of the cap assembly 21. Given
this configuration, the cap assembly 21 may be described as
including a two smaller chambers or sections that are axially
stacked within it, with the first being the forward region that, as
indicated by arrows in FIG. 3, accepts a flow of compressed air
from the flow annulus 28. The second section within the cap
assembly 28 is the region in which the nozzle 17 is defined.
[0032] The combustion zone 23 defined just aft of the nozzle 17 is
circumferentially defined by a liner 24. The combustion zone 23 is
the region where the fuel-air mixture brought together in the
nozzle 17 is combusted. From the liner 24, this other chamber may
extend through a transition section toward the connection the
combustor 12 makes with the turbine 13. Though other configurations
are also possible, within this transition section, the
cross-sectional area of the second chamber transitions from the
circular shape of the liner 24 to a more annular shape that is
necessary for directing the flow of combustion products onto the
rotor blades of the turbine 13 in a desirable way.
[0033] Positioned about the liner 24 is a flow sleeve 25. The liner
24 and flow sleeve 25 may be cylindrical in shape and arranged
concentrically. In this manner, the flow annulus 28 formed between
the cap assembly 21 and the combustor casing 29 may connect to a
continuation of the flow annulus that extends toward the aft end of
the combustor 12. Similarly, as illustrated, an impingement sleeve
27 may surround the transition piece 26 so that the flow annulus 28
continues. According to the example provided, the flow annulus 28
loss may extend from approximately the endcover 19 of the head end
15 to the aft end of the combustor 12. More specifically, it will
be appreciated that the cap assembly 21/combustor casing 29, the
liner 24/flow sleeve 25, and the transition piece 26/impingement
sleeve 27 pairings extend the flow annulus 28 a significant portion
of the axial length of the combustor 12. The concentrically
arranged cylindrical walls that form the flow annulus 28 also may
be referred to herein as inner and outer radial walls.
[0034] The flow sleeve 25 and/or the impingement sleeve 27 may
include a plurality of impingement ports 32 that allow a flow of
compressed air external to the combustor 12 into the flow annulus
28. It will be appreciated that, as shown in FIG. 2, a compressor
discharge casing 34 may be define a compressor discharge cavity 35
about an aft section of the combustor 12. According to conventional
design, the compressor discharge cavity 35 may be configured to
receive a supply of compressed air from the compressor 11 and the
air may then enter the flow annulus 28 through the impingement
ports 32. The impingement ports 32 may be configured to impinge the
flow of air entering the combustor 12 against the liner 24 and/or
transition piece 26 so to convectively cool those components. Once
in the flow annulus 28, the compressed air is directed toward the
forward end of the combustor 12, where, via the inlets 31, the flow
enters the forward cavity of the cap assembly 21. Within the cap
assembly 21, the compressed air is directed to the nozzle 17 where,
as mentioned, it is mixed with fuel.
[0035] Referring now to FIGS. 4 and 5, a nozzle having a
micro-mixer configuration is shown that includes aspects of the
present invention. FIGS. 4 shows a sectional perspective view of a
combustor head end 15 having a cap assembly 21 and micro-mixer
nozzle 17 (as well as nozzle sections, as discussed below) that
includes elements of the present invention. FIG. 5 shows an
enlarged cross-sectional side view of a micro-mix nozzle 17 and the
typical components of this nozzle type. As illustrated, the fuel
nozzle 17 includes a shroud wall 45 that circumferentially
surrounds and defines a fuel plenum 43. The fuel plenum 43 may be
cylindrical in shape, though other shapes are also possible. The
planar ends of the cylindrically shaped plenum 43 are defined by a
forward tubesheet 51 and an aft tubesheet 52. It will be
appreciated that the fuel plenum 43 may be connected to a supply of
fuel by a fuel line 18 that extends through the endcover 19.
[0036] The nozzle 17 may include a number of mixing tubes 41 that
are arranged in a parallel configuration. The mixing tubes 41 may
extend across the axial thickness of the nozzle 17. As will be
appreciated, with the fuel plenum 43 defined about the mixing tubes
41, a fuel, such as natural gas, may be injected into the mixing
tubes 41 through fuel ports 44 defined therethrough. As shown in
FIG. 4, the nozzle 17 may be sectioned into radial sections, which
will be referred to as "nozzle sections 47". Given the circular
cross-sectional shape of the nozzle 17, the nozzle sections 47 may
be wedge shaped in a preferred embodiment. Other configurations are
also possible. The nozzle sections 47 are defined by sidewalls 48.
The sidewalls 48 of neighboring or adjacent nozzle sections 47, as
illustrated, may abut against each other so to form a seam or gap
49 therebetween. This gap 49 extends from an inner radial position
that defines the inboard boundary of the nozzle suction 47 to the
shroud wall 45, which, as described, defines the outboard boundary
of the nozzle suction 47.
[0037] The mixing tubes 41 may be configured to extend through the
fuel plenum 43 between the forward tubesheet 51 and aft tubesheet
52. More specifically, the mixing tubes 41, as illustrated, may be
configured to form a passageway that connects an inlet formed
through the forward tubesheet 51 to an outlet formed through the
aft tubesheet 52. It will be appreciated that, given this
configuration, the inlet provides the means by which the compressed
air within the cap assembly 21 enters the nozzle 17. As mentioned,
the mixing tube 41 may include one or more fuel ports 44. The fuel
ports 44 may be axially spaced along the length of the mixing tube
41, and connect the interior passageway of the mixing tube 41 to
the fuel plenum 43. Thus arranged, compressed air fed into the
mixing tubes 41 through the inlets on the forward tubesheet 51 is
brought together with fuel injected into to the mixing tubes 41
through the fuel ports 44. Within the mixing tubes 41, the fuel and
air is mixed and the mixture flows toward the outlet formed through
the aft tubesheet 52. In this manner, the outlets deliver an
air/fuel mixture to the combustion chamber 23 where it then is
combusted. Typically many separate mixing tubes 41 are positioned
within the fuel nozzle 17. Further, each of the nozzle sections 47
includes many mixing tubes 41. The mixing tubes 41 may be aligned
radially outward of an axial centerline 48 of the nozzle 12, and be
configured to extend in a parallel configuration across the axial
thickness of the fuel plenum 43.
[0038] It will be appreciated that the mixing tubes 41 may have a
cross-section that is circular, oval, square, triangular, or any
known geometric shape. In a preferred embodiment, as shown, the
mixing tubes 41 have a round cross-sectional shape. The inlet and
outlet of the mixing tube 41 may simply comprise openings formed
through the forward and aft tubesheets 51, 52. The opening may be
configured to correspond in a desired way with the size and shape
of the interior passageway defined within the mixing tube 41. The
upstream and downstream ends of the mixing tubes 41 may be formed
to permit air to freely flow through the mixing tubes 41 and mix
with fuel injected into the mixing tubes 41 via the fuel ports 44.
The fuel ports 44 may simply comprise small openings or apertures
in the wall of the mixing tube 41 that allow the fuel to flow from
the fuel plenum 43 into the mixing tube 41 in a desired manner. The
fuel ports 44 may be axially and circumferentially spaced so to
encourage a more uniform mixing of fuel with the air supply moving
through the mixing tubes 41. It will be appreciated that the fuel
ports 44 may be angled with respect to the axial centerline of the
mixing tube 41 to vary the angle at which the fuel enters the
mixing tube 41, thus varying the distance that the fuel penetrates
into the mixing tube 41 before mixing with the supply of air. In
this manner a more uniform mixture of fuel and air may be
achieved.
[0039] As mentioned, the nozzle 17 may be radially divided into
sections, which are referred to herein as nozzle sections 47. Each
nozzle section 47 may be supplied by a separate fuel line 18 and
include a plurality of the mixing tubes 41. The nozzle sections 47
include sidewalls 48 that separate each from the nozzle sections 47
positioned to each side of it. As illustrated, the sidewalls 48
extends between the forward tubesheet 51 and the aft tubesheet 52,
as well as between the outer radial boundary defined by the shroud
wall 45 and an inner radial boundary. The sidewalls 48 may be
planar and, in a preferred embodiment in which the nozzle 17 is
cylindrical in shape, the sidewalls 48 may have a rectangular
shape.
[0040] As now described in further detail and with reference to
FIGS. 6 through 13, the present invention teaches a manner in which
air leakage through the seam or gap 49 formed between adjacent
nozzle sections 47 may be limited or substantially prevented. As
mentioned, micro-mixer nozzles may include several wedge shaped
nozzle sections which necessarily form gaps at the sidewall
interfaces between them. (It will be appreciated that the present
invention also may be applicable to other types of nozzles that
include similar abutting sections that for seams or gaps such as
described herein.) The gaps 49 form leakage paths and, as will be
appreciated, air that leaks through these gaps bypasses the mixing
tubes, which typically negatively impacts combustor performance.
More specifically, leakage through these gaps may unbalance the
air-fuel mixture within the nozzle, which may cause uneven
combustion, the formation of localized hotspots, increased NOx
emissions, as well as negatively impact engine efficiency. It will
be appreciated that such leakage may quench the flame at low load
conditions and thereby cause increases in CO emissions, such as
during turn-down conditions. By preventing air from passing through
these gaps, which are common to many nozzle types, more air is
directed through the mixing tubes, proper mixing ratios maintained,
and combustor performance improved.
[0041] In addition, the seal of the present invention prevents
leakage while being compliant enough to accommodate the relative
movement that typically occurs between adjacent nozzles. That is,
the present invention provides a seal capable of maintaining its
sealing effectiveness even when adjacent nozzle sections shift
relative to each other. As will be appreciated, because this type
of relative movement is common given of the dynamic thermal and
mechanical loads within combustors, this is a significant feature.
To achieve this, the seal of the present invention is made
compliant and configured so that it is air loaded during operation.
Having a "zigzagging profile", as defined below, the seal may be
inserted radially into a pocket that is formed between two adjacent
nozzle sections. As illustrated, the shape and size of the seal and
the pocket may be configured so to prevent the seal from turning or
rotating once installed. The seal thus maintains its orientation,
and its zigzagging profile is made compliant enough so that air
loading through the gap maintains the contact points that block
flow through the gap. Given this configuration, it will be
appreciated that the seal of the present invention may accommodate
relative movement between the adjacent nozzle sections in both the
radial and axial directions while still maintaining its sealing
capabilities.
[0042] To operate most effectively, micro-mixer nozzles require a
large number of relatively small mixing tubes, and it is
challenging to position enough mixing tubes within the limited
space of the combustor head end while also maintaining the
necessary flow area through the nozzle. It is therefore desirable
to dedicate as much space as possible for the placement of mixing
tubes. Reducing flow area or the number of mixing tubes so to
provide gap sealing would be detrimental to overall performance.
The seal of the present invention, as described below, has an
efficient design that requires substantially no additional space
for implementation. This is not true of other types of possible
sealing solutions, such as Hula seals. As will be appreciated, the
seal configuration of the present invention features a low profile
so that it does not take away area that might otherwise be used for
mixing tube placement, thereby allowing a maximum number of mixing
tubes within each nozzle section. The present seal also is
relatively inexpensive compared to competing sealing schemes.
Another advantage is that the present seal may be configured so to
provide damping between nozzle sections. As will be appreciated,
this is a desirable feature in lean pre-mixed combustors.
[0043] The seal 61 of the present invention may be used, for
example, in the seams or gaps 49 formed between the radial sections
of a cylindrically fuel plenum 43 of a nozzle 17. The nozzle 17 may
be axially stacked between a first chamber that receives a supply
of compressed air (i.e., the cap assembly 21) and a second chamber
configured for combusting the fuel-air mix (i.e., combustion zone
23). The fuel plenum 43 may be defined between a circumferentially
extending shroud wall 45 that extends axially between a planar
forward tubesheet 51, which abuts the cap assembly 21, and a planar
aft tube sheet 52, which abuts the combustion zone 23. A plurality
of wedge-shaped nozzle sections 47 may be formed by sidewalls 48,
which radially section the fuel plenum 43. A plurality of mixing
tubes 41 may be positioned within each of the plurality of nozzle
sections 47. The sidewalls 48 of adjacent nozzle sections 47 form
the gap 49 in which the present seal may be used.
[0044] FIGS. 6 and 7 illustrate nozzle sidewalls 48 having a seal
61 in accordance with exemplary embodiments of the present
invention. As illustrated, as part of the seal configuration, a
groove 62 may be formed in the sidewall 48 of a nozzle section 47.
Between adjacent nozzle sections 47, the sidewalls 48 that are
opposed across the gap 49 may each include a groove 62 that are
correspondingly positioned so that, as FIG. 7 shows, together a
radially extending pocket 63 is formed. The pocket 63 may
intercepts the gap 49 over what will be referred to herein as a
seal length. The pocket 63 may extend longitudinally in the radial
direction and, according to a preferred embodiment, the seal length
may extend between an inner radial boundary 50 of the nozzle
section 47 and the shroud wall 49, which defines the outer radial
boundary of the nozzle section 47. The groove 62 formed in each
sidewall 48 may be rectangular, though other shapes are possible.
The pocket 63 may be rectangular in shape also. The depth of each
of the grooves 62 may be approximately the same. In this manner,
the gap 49 approximately bisects the pocket 63. The seal 61 may
include a zigzagging profile that extends longitudinally within the
pocket 63 formed between opposing sidewalls 48. The seal 61 may be
positioned such that the zigzagging profile intersects the gap 49
over the seal length. As will be appreciated, the gap 49 may extend
between a forward seam formed on the forward tubesheet and an aft
seam formed on the aft tubesheet. The pocket 63 may be axially
located between the forward and aft seams of the gap 49. In certain
embodiments, the pocked 63 is located approximately midway between
the forward and aft seams formed on the tubesheets.
[0045] As will be appreciated, the "profile" of the seal 61 is the
cross-sectional shape of the seal 61 shown in FIGS. 7 through 11
and 13. The seal 61 may have a constant or substantially constant
profile over the seal length. "Zigzagging", as used herein, is a
path characterized by short and sharp turns, as further delineated
below in relation to the several exemplary embodiments. As provided
in the several figures, the zigzagging profile of the seal 61 may
include a number of segments that are connected end-to-end at a
sharp turn. According to a simplified version of the seal 61, as
illustrated in FIG. 9, the zigzagging profile includes two segments
connected at a sharp turn. According to preferred embodiments, the
sharp turn is a turn of at least 90.degree.. Alternatively, the
sharp turn may be a turn of at least 120.degree., as well as, in
another preferred embodiment, 150.degree.. The segments may be
linear in shape, as the "V" shape of FIG. 9 illustrates. According
to other embodiments, the segments may be curved somewhat so that
an related embodiment has more of a "U" shape.
[0046] According to an alternative embodiment, the zigzagging
profile includes at least three segments connected end-to-end at
alternating sharp turns. An example of this embodiment is provided
in FIG. 10. In this case, the sharp turns may be ones that includes
at least a 90.degree., or 120.degree., or 150.degree. change in
direction. The segments may be linear or curved. Embodiments having
linear segments may have a "N" shaped profile, as shown in FIG. 10.
As will be appreciated, curved segments may produce more of a
sinusoidal shape.
[0047] According to certain other preferred embodiments, as
illustrated in FIGS. 6 through 8, 11 and 13, the zigzagging profile
includes at least four segments connected end-to-end at alternating
sharp turns. As before, the sharp turns may be ones that includes
at least a 90.degree., or 120.degree., or 150.degree. change in
direction, and the segments may be linear or curved. Embodiments
having linear segments may have a "M" shaped profile, as shown in
FIG. 7. As will be appreciated, curved segments may produce more of
a sinusoidal shape, such as the exemplary embodiment shown in FIG.
8. According to another embodiment, as shown in FIG. 11, the
zigzagging profile having four segments may have an approximate
".OMEGA." shape. As illustrated most clearly FIG. 8, the "M" shape
may be oriented within the pocket 63 in a preferred direction that
enhances its sealing characteristics. As shown, the middle sharp
turn of the "M" shaped embodiment may be directed toward an
expected leakage flow through the gap 49, which, given the
configuration of the nozzle, corresponds with the forward direction
of the gas turbine.
[0048] As will be appreciated the segments and the sharp turns that
connect them may provide a compliant profile which may
advantageously be air loaded by leakage moving through the gap 49.
Thus, for example, as indicated in FIG. 8, the "M" shaped profile
may have outer segments that the leakage forces against the
surrounding walls of the pocket 63, which would enhance the
effectiveness of it. Along with having a profile that encourages
such advantageous compliancy, the seal 61 may be made of a material
selected for its compliancy. This material may be selected to allow
a desired level of flexion during operation so that when the seal
61 is air loaded by leakage greater contact between the seal and
the walls defining the grooves 62 is maintained. Additionally, the
seal 61 and the pocket 63 may be correspondingly designed so to
prevent rotation and misalignment of the profile within the pocket
63. According to a preferred embodiment, the dimensions of the
pocket 63 and dimensions of the zigzagging profile of the seal 61
may be designed so to mechanically prevent rotation of the seal 61
about its longitudinal axis. In a preferred embodiment, rotation
greater than approximately 45.degree. is prevented.
[0049] Finally, as illustrated in FIGS. 12 and 13, the seal 61 of
the present invention is shown accommodating the relative shifting
that occurs between adjacent nozzles sections 47 during operation.
Specifically, as illustrated in FIG. 12, one nozzle selection 47
has shifted axially so to cause an axial offset 65 between it and a
neighboring section 47. In this case, as illustrated in FIG. 13,
the compliant profile of the seal 61 and the air loading of the
segments of the seal 61, allow the seal 61 to shift within the
pocket 63 and bend so to maintain contact with the walls of the
groove 62. In this manner, the effectiveness of the seal is
maintained.
[0050] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *