U.S. patent application number 14/256025 was filed with the patent office on 2014-10-30 for premixer assembly and mechanism for altering natural frequency of a gas turbine combustor.
This patent application is currently assigned to JEREMY METTERNICH. The applicant listed for this patent is JEREMY METTERNICH, KHALID OUMEJJOUD, BRIAN RICHARDSON. Invention is credited to JEREMY METTERNICH, KHALID OUMEJJOUD, BRIAN RICHARDSON.
Application Number | 20140318140 14/256025 |
Document ID | / |
Family ID | 51788070 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140318140 |
Kind Code |
A1 |
METTERNICH; JEREMY ; et
al. |
October 30, 2014 |
PREMIXER ASSEMBLY AND MECHANISM FOR ALTERING NATURAL FREQUENCY OF A
GAS TURBINE COMBUSTOR
Abstract
A system and method are provided for altering the natural
frequency of a dome plate portion of a premixer assembly of a gas
turbine combustor. The plate assembly has a dome plate with a
central pilot mixer and a plurality of extension tabs extending
radially outward from the pilot mixer. A plurality of radially
extending struts are secured to the extension tabs in order to
alter the natural frequency of the dome plate.
Inventors: |
METTERNICH; JEREMY;
(WELLINGTON, FL) ; OUMEJJOUD; KHALID; (PALM BEACH
GARDENS, FL) ; RICHARDSON; BRIAN; (JUPITER,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
METTERNICH; JEREMY
OUMEJJOUD; KHALID
RICHARDSON; BRIAN |
WELLINGTON
PALM BEACH GARDENS
JUPITER |
FL
FL
FL |
US
US
US |
|
|
Assignee: |
METTERNICH; JEREMY
WELLINGTON
FL
OUMEJJOUD; KHALID
PALM BEACH GARDENS
FL
RICHARDSON; BRIAN
JUPITER
FL
|
Family ID: |
51788070 |
Appl. No.: |
14/256025 |
Filed: |
April 18, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61815835 |
Apr 25, 2013 |
|
|
|
Current U.S.
Class: |
60/755 ;
29/890.01 |
Current CPC
Class: |
Y10T 29/49346 20150115;
F23R 3/60 20130101; F23R 2900/00017 20130101; F23R 3/002 20130101;
F23R 2900/00005 20130101; F23R 3/286 20130101 |
Class at
Publication: |
60/755 ;
29/890.01 |
International
Class: |
F23R 3/28 20060101
F23R003/28 |
Claims
1. A plate assembly for a gas turbine combustor comprising: a dome
plate having a central opening therein and a plurality of openings
arranged in an annular array about the central opening; a pilot
mixer assembly extending from the central opening, the pilot mixer
assembly having an outer wall, a center ring located within the
outer wall, a plurality of pilot vane swirler vanes extending
therebetween, and a pilot cone surrounding a portion of the outer
wall; a plurality of extension tabs extending from the outer wall
of the pilot mixer assembly and through the pilot cone; and, a
plurality of radially extending struts secured to the plurality of
extension tabs and the dome plate.
2. The plate assembly of claim 1, wherein the plurality of openings
in the dome plate are each sized to receive a swirler assembly.
3. The plate assembly of claim 2 further comprising a plurality of
swirler assemblies, each comprising a premix tube, a premix swirler
positioned within the premix tube, the swirler having a plurality
of turning vanes for imparting a swirl to a passing flow, and a
plurality of mounting of mounting blocks positioned on the outer
wall of the premix tube;
4. The plate assembly of claim 1, wherein the dome plate further
comprises a plurality of air holes extending through the dome
plate.
5. The plate assembly of claim 1, wherein the plurality of
extending tabs are secured to the outer wall of the pilot mixer
assembly.
6. The plate assembly of claim 1, wherein the pilot cone extends
through the dome plate and transitions into a divergent
portion.
7. The plate assembly of claim 4, wherein the radially extending
struts have an interrupted surface in contact with the dome plate
such that each of the struts are secured to the dome plate at
multiple locations.
8. The plate assembly of claim 1, wherein the radially extending
struts are positioned between adjacent plurality of openings.
9. A system for stiffening a premixer assembly comprising: a
generally circular dome plate having a central opening, an upstream
face, an opposing downstream face, and a plurality of cooling
holes; a pilot mixer assembly located within the central opening,
the pilot mixer assembly having an outer wall and a pilot cone
surrounding a portion of the outer wall; a plurality of extension
tabs extending from the outer wall of the pilot mixer assembly and
through the pilot cone; and, a plurality of struts extending
between the plurality of extension tabs and the dome plate and
radially outward from the outer wall of the pilot mixer assembly,
the plurality of struts being fewer than the plurality of extension
tabs; wherein the plurality of struts are positioned about the
pilot mixer assembly in order to provide a desired natural
frequency to the generally circular dome plate.
10. The system of claim 9, wherein the generally circular dome
plate further comprises a plurality of swirler assemblies oriented
in an annular array about the pilot mixer assembly.
11. The system of claim 9, wherein the plurality of extension tabs
are welded to both the outer wall and the plurality of struts.
12. The system of claim 11, wherein each of the plurality of struts
are secured to the dome plate at multiple locations.
13. The system of claim 12, wherein each of the plurality of
struts, further comprise a recessed portion between the multiple
locations where the plurality of support plates are secured to the
dome plate.
14. The system of claim 1, wherein the plurality of struts are
positioned in between the plurality of openings in the dome
plate.
15. The system of claim 1, wherein the pilot cone has a diffuser
section extending from proximate the downstream face of the dome
plate.
16. The system of claim 15 further comprising an outer cone
enveloping a portion of the pilot cone, the outer cone spaced a
distance from the pilot cone so as to maintain a gap
therebetween.
17. A method of altering natural frequency of a premixer assembly
comprising: providing a dome plate having a central opening therein
and a plurality of openings arranged in an annular array about the
central opening, a pilot mixer assembly located within the central
opening and having an outer wall, and a pilot cone surrounding a
portion of the outer wall, and a plurality of extension tabs
extending from the outer wall of the premixer and through the pilot
cone; securing the quantity of radially extending struts to the
plurality of extension tabs and the dome plate; and, securing
additional radially extending struts to the plurality of extension
tabs and the dome plate upon a determination to increase the
natural frequency of the dome plate.
18. The method of claim 17, wherein the quantity of radially
extending struts equals the plurality of openings arranged in an
annular array about the central opening.
19. The method of claim 17, wherein the natural frequency of the
premixer assembly is increased upon securing additional radially
extending struts to the plurality of extension tabs and the dome
plate.
20. The method of claim 17, wherein the natural frequency of the
premixer assembly is decreased by removing radially extending
struts from the premixer assembly such that the struts do not
contact the plurality of extension tabs and the dome plate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/815,835, filed on Apr. 25, 2013. This
application is related by subject matter to commonly-assigned U.S.
Non-Provisional Patent Applications entitled REMOVABLE SWIRLER
ASSEMBLY FOR A COMBUSTION LINER (Attorney Docket No.
PSM-316/PSSF.199280) and PREMIXER ASSEMBLY FOR A GAS TURBINE
COMBUSTOR (Attorney Docket No. PSM-317/PSSF.199281).
TECHNICAL FIELD
[0002] The present invention generally relates to a gas turbine
combustor. More specifically, embodiments of the present invention
relate to an apparatus and method for altering the natural
frequencies of the dome plate assembly for a gas turbine
combustor.
BACKGROUND OF THE INVENTION
[0003] In a typical gas turbine engine, a compressor having
alternating stages of rotating and stationary airfoils is coupled
to a turbine through an axial shaft, with the turbine also having
alternating stages of rotating and stationary airfoils. The
compressor stages decrease in size in order to compress the air
passing therethrough. The compressed air is then supplied to one or
more combustors, which mixes the air with fuel. An ignition source
proximate the one or more combustors ignite the mixture, forming
hot combustion gases. The expansion of the hot combustion gases
drives the stages of a turbine, which is coupled to the compressor
through an axial shaft. The exhaust gases can then be used as a
source of propulsion, to generate steam through a heat recovery
steam generator, or in powerplant operations to turn a shaft
coupled to a generator for producing electricity.
[0004] The combustion system of a gas turbine engine can take on a
variety of configurations. A combustion system for a gas turbine
engine can comprise a single combustion chamber, a plurality of
individual combustion chambers spaced about the axis of the engine,
a plenum-type combustion system, or a variety of other combustion
systems. Depending on the engine geometry, performance
requirements, and physical operating location, the exact combustor
arrangement will vary.
[0005] A typical combustion system generally comprises at least a
casing secured to the frame of the engine, a combustion liner
secured within at least a part of the casing, and one or more fuel
nozzles positioned within or adjacent to the combustion liner for
injecting a fuel (gas, liquid, or both) into the combustion
chamber. The combustion system is in fluid communication with the
engine. More specifically, the casing and liner arrangement
provides a way for air from the compressor to enter the combustion
system, where it mixes with fuel from the one or more fuel nozzles.
The fuel-air mixture is ignited by an ignition source, such as a
spark igniter. Hot combustion gases travel through the combustion
liner and often through one or more transition pieces and into the
turbine. The transition piece is essentially a duct having a
geometry that changes from the shape of the combustor to the inlet
of the turbine.
[0006] The combustion liner is at the center of combustor
operations. The combustion liner geometry is dictated by the
operating parameters of the engine, performance requirements, or
available geometry. While combustion liner geometries can vary, the
combustion liner typically includes at least a portion for
receiving fuel nozzles, for mixing fuel and air together and for
containing the reaction when the fuel and air mixture is
ignited.
[0007] Combustion liners of the prior art have met certain
performance requirements, but have also exhibited various
shortcomings. Combustion liners are subjected to various thermal
conditions and as such must be able to withstand the high thermal
and mechanical stresses of such operating conditions. By nature,
the combustion liner has a series of natural operating frequencies.
The gas turbine engine and combustion system also have a natural
frequency, and orders of the natural frequency (i.e. 1E, 2E, 3E,
etc.). When a component, such as the combustion liner, has a
natural frequency or mode that coincides with, or approaches, an
engine natural frequency or order thereof, the component can become
dynamically excited. If care is not taken to avoid the crossings of
these frequencies, operating at these frequencies, or minimizing
the time for the crossing, the component may experience excessive
wear or failure as a result of the vibratory stress that occurs
when operating at or near the natural frequency of the gas turbine
engine or combustion system.
SUMMARY
[0008] In accordance with the present invention, there is provided
a novel and improved component for a combustion liner of a gas
turbine engine. The combustion liner is generally cylindrical in
shape and has an inlet end and a discharge end, opposite the inlet
end. The combustion liner of the present invention comprises a
premixer assembly capable of receiving a plurality of fuel nozzles.
The premixer assembly is designed so as to provide a way of
altering its natural frequency.
[0009] In accordance with an embodiment of the present invention,
there is provided a plate assembly for a gas turbine combustor, the
plate assembly comprising a dome plate, a pilot mixer assembly, a
plurality of extension tabs extending from an outer wall of the
pilot mixer assembly, and a plurality of radially extending struts
secured to both the extension tabs and the dome plate.
[0010] In accordance with another embodiment of the present
invention, a system is provided for altering the natural frequency
of a premixer assembly. The system comprises a generally circular
dome plate, a pilot mixer having an outer wall portion, a plurality
of extension tabs fixed at one end to the outer wall and extending
through a pilot cone portion, and a plurality of struts extending
between the extension tabs and the dome plate.
[0011] In accordance with yet another embodiment of the present
invention, a method of altering the natural frequency of a premixer
assembly is provided. The method comprises the steps of providing a
dome plate, a pilot mixer assembly, a plurality of extension tabs,
and a quantity of radially extending struts. The quantity of
radially extending struts are secured to the plurality of extension
tabs and dome plate. Then, additional radially extending struts are
secured to the plurality of extension tabs and dome plate upon a
determination to increase stiffness of the dome plate. Altering the
stiffness of the dome plate in turn alters its natural frequency
such that its natural frequency is outside of the dynamic
frequencies generated by the combustion system.
[0012] Additional advantages and features of the present invention
will be set forth in part in a description which follows, and in
part will become apparent to those skilled in the art upon
examination of the following, or may be learned from practice of
the invention. The instant invention will now be described with
particular reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0013] The present invention is described in detail below with
reference to the attached drawing figures, wherein:
[0014] FIG. 1 is a partial cross section view of a gas turbine
engine of the prior art in which a combustion system in accordance
with an embodiment of the present invention is capable of being
used;
[0015] FIG. 2 is a cross section view of a gas turbine combustor of
the prior art capable of operating within the gas turbine engine of
FIG. 1;
[0016] FIG. 3 is a perspective view of a combustion liner
incorporating an embodiment of the present invention;
[0017] FIG. 4 is a cross section view of the combustion liner of
FIG. 3 taken through a pilot mixer assembly in accordance with an
embodiment of the present invention;
[0018] FIG. 5 is an alternate view of the cross section of FIG. 4,
in accordance with an embodiment of the present invention;
[0019] FIG. 6 is a cross section view of a combustion liner of FIG.
3 taken through the a swirler assembly and pilot mixer assembly in
accordance with an embodiment of the present invention;
[0020] FIG. 7 is an alternate view of the cross section of FIG. 6,
in accordance with an embodiment of the present invention;
[0021] FIG. 8 is a detailed cross section view taken through the
inlet portion of the combustion liner of FIG. 3 in accordance with
an embodiment of the present invention;
[0022] FIG. 9 is a partial cross section view of the main swirler
portion of the combustion liner in accordance with an embodiment of
the present invention;
[0023] FIG. 10 is a perspective view of a pilot mixer assembly in
accordance with an embodiment of the present invention;
[0024] FIG. 11 is cross section view of a portion of the pilot
mixer assembly of FIG. 10 in accordance with an embodiment of the
present invention;
[0025] FIG. 12 is a perspective view of a plate assembly of a gas
turbine combustor in accordance with an embodiment of the present
invention;
[0026] FIG. 13 is cross section view of the plate assembly of FIG.
12 in accordance with an embodiment of the present invention;
[0027] FIG. 14 is an alternate cross section view of the plate
assembly of FIG. 12 in accordance with an embodiment of the present
invention; and,
[0028] FIG. 15 is a flow diagram describing a method of altering
the natural frequency of a premixer assembly in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION
[0029] The subject matter of the present invention is described
with specificity herein to meet statutory requirements. However,
the description itself is not intended to limit the scope of this
patent. Rather, the inventors have contemplated that the claimed
subject matter might also be embodied in other ways, to include
different components, combinations of components, steps, or
combinations of steps similar to the ones described in this
document, in conjunction with other present or future
technologies.
[0030] Referring initially to FIG. 1, a gas turbine engine 100 of
the prior art in which the present invention can be used is
disclosed. The gas turbine engine 100 generally comprises an outer
casing 102, enveloping the main portions of the engine. A shaft 104
extends axially along engine axis A-A and couples a compressor 106
to a turbine 108. The compressor 106 receives air through inlet
region 110 and directs the air through alternating rows of rotating
and stationary airfoils of decreasing size in order to compress the
air passing therethrough, thereby increasing air temperature and
pressure. The compressed air is then directed through one or more
combustion systems 112 where fuel and air are mixed together and
ignited to form hot combustion gases. The hot combustion gases are
then directed into the turbine 108 to pass through alternating rows
of rotating and stationary airfoils of increasing size so as to
expand the fluid and harness the energy from the combustion gases
into mechanical work to drive the shaft 104. The shaft 104 may also
be coupled to a shaft of an electrical generator (not shown) for
purposes of generating electricity.
[0031] FIG. 2 discloses a cross section of a combustor 200 of a gas
turbine engine of the prior art. As such, this typical gas turbine
combustor 200 comprises a casing 202, a cover 204, one or more fuel
injectors 206, and a combustion liner 208. A transition piece 210
connects the combustion liner 208 to an inlet of the turbine
212.
[0032] The present invention is shown in detail in FIGS. 3-15 and
discloses a new and improved system and method for altering the
natural frequency of a dome plate in a gas turbine combustor.
Referring initially to FIGS. 3-7, a combustion liner 300, in which
the present invention operates, is disclosed and comprises a plate
assembly 430. The plate assembly 430 is part of a larger premixer
assembly 330 and is shown in more detail in FIGS. 12-14. The plate
assembly 430 generally comprises a dome plate 334 having a central
opening 432 contained therein, the central opening 432 passing
through the thickness of the dome plate 334. The dome plate 334
also comprises a plurality of openings 370 arranged in an annular
array about the central opening 432. The plurality of openings 370
are sized to contain swirler assemblies 332 for the premixer 330.
However, for clarity, the swirler assemblies 332 have been removed
from FIGS. 12-14. The plurality of swirler assemblies 332 are
oriented about the axis of the combustion liner and secured to a
dome plate 334. The main swirler assemblies 332, shown in more
detail in cross section in FIG. 8, comprise a swirler body 336
comprising a plurality of turning vanes 338 secured to a center
ring 340 and an outer sleeve 342. The turning vanes 338 impart a
swirl to a passing flow. Secured to the outer sleeve 342 is a
forward mounting block 344 and an aft mounting block 346. The
forward mounting block 344, aft mounting block 346, and fasteners
350 and 358 are used to secure the swirler assemblies 332 to the
combustion liner 300.
[0033] The dome plate 334 further comprises a plurality of
openings, or air holes, 374 extending through the thickness of the
dome plate 334. For the embodiment depicted in FIGS. 9 and 12-14,
the cooling holes 374 are oriented generally perpendicular to the
dome plate 334. Alternatively, the cooling holes 374 could be
oriented at a surface angle relative to the dome plate 334 as well
as a compound angle. The dome plate 334 includes numerous cooling
holes 374 for directing a flow of compressed air into the
combustion zone of the combustion liner 300. The exact quantity,
size, and shape of the cooling holes 374 can vary depending on the
amount of compressed air to be directed through the dome plate 334
as well as to maintain a desired pressure drop into the combustion
zone. For the dome plate depicted in FIGS. 12-14, the cooling holes
374 are approximately 0.165'' in diameter and the dome plate 334
includes over 200 cooling holes. The exact size, quantity, and
spacing of the cooling holes 374 in the dome plate 334 can vary
depending on factors such as the amount of air to pass through the
dome plate as well as the desired drop in pressure across the dome
plate.
[0034] The swirler assemblies 332 are positioned so as to be in
fluid communication with adjacent tubes 352, or hoovers, which pass
the flow of fuel and air from the swirler assembly 332 to the
mixing zone of the combustion liner 300. That is, the swirler
assemblies 332 are positioned so as to be adjacent to or slightly
engaged in the tubes 352.
[0035] The plate assembly 430 also comprises a pilot mixer assembly
440. The pilot mixer assembly 440, while shown in the plate
assembly 430 in FIGS. 12-14, is shown in detail in FIGS. 10 and 11.
The pilot mixer assembly 440 extends from the central opening 370
and has an outer wall 442, a center ring 444 located within the
outer wall 442. Extending between the center ring 444 and the outer
wall 442 are a plurality of swirler vanes 446. Located around a
portion of the outer wall 442 is a pilot cone 448. The pilot cone
448 is positioned radially outward of the outer wall 442, and
tapers radially inward towards the central opening 370. The pilot
cone 448 then extends through the dome plate 334 and transitions
into a divergent portion 448A.
[0036] The plate assembly 430 also comprises a plurality of
extension tabs 450 extending from the outer wall of the pilot mixer
assembly 440 and through the pilot cone 448. The plurality of
extending tabs 450 are secured to the outer wall 442 of the pilot
mixer assembly 440. The plurality of extending tabs can be secured
to the outer wall 442 via a weld, braze or other acceptable joining
process. Alternatively, the plurality of extending tabs 450 can be
integrally formed with the outer wall 442 of the pilot mixer
assembly 440, as would be produced via a casting process.
[0037] The plate assembly 430 also comprises a plurality of
radially extending struts 452 secured to the plurality of extension
tabs 450. The plurality of struts 452, or stiffeners, are used to
provide increased rigidity and support to the dome plate 334,
thereby increasing the stiffness of the plate assembly 430,
resulting in an increase in its natural frequency. The struts 452
are oriented generally perpendicular to the dome plate 334 and are
secured at one end to the plurality of extension tabs 450 and at an
opposing end to the dome plate 334, as shown in FIGS. 12 and 13.
More specifically, the radially extending struts 452 are secured to
the extension tabs 450 and the dome plate 334 by a weld, braze or
other acceptable securing means. As shown in FIGS. 12 and 13, the
radially extending struts 452 are positioned between adjacent
plurality of openings 370. For the embodiment depicted in FIGS. 13
and 15, four struts 394 are used. However, the number of struts
could be increased to equal the number of main swirler assemblies
332, which in an embodiment of the present invention is eight.
[0038] The radially extending struts 452 are secured to the dome
plate 334 at multiple locations, as shown in FIGS. 12 and 13. For
example, the radially extending struts 452 are secured at a
location radially inward, towards the central opening 370 and
radially outward towards an outer edge of the dome plate 334. That
is, the radially extending struts 452 have an interrupted surface
452A that is spaced a distance from the dome plate 334 in multiple
locations.
[0039] The radially extending strut and extension tab configuration
described herein is merely one such embodiment of a configuration
to adjust the natural frequency of the dome plate 334. The design
described herein, where the extension tab 450 is secured to the
radially extending strut 452, is one such embodiment that lends to
ease of manufacturing, lower manufacturing costs, while providing a
design that alters the natural frequency of the dome plate. It is
conceivable that other configurations for the radially extending
strut and extension tabs are possible.
[0040] The present invention also provides a system for altering
the natural frequency of a premixer assembly, where the system
comprises a generally circular dome plate 334 having a central
opening 432, an upstream face 334A, an opposing downstream face
334B, and a plurality of cooling holes 374. A pilot mixer assembly
440 is located within the central opening 432 where the pilot mixer
assembly 440 has an outer wall 442 and a pilot cone 448 that
surrounds a portion of the outer wall 442, as shown in FIGS. 10 and
11. The system for stiffening the premixer assembly also comprises
a plurality of extension tabs 450 extending from the outer wall 442
of the pilot mixer assembly 440 and through the pilot cone 448. A
plurality of struts 452 extend between the plurality of extension
tabs 450 and the dome plate 334, as shown in FIGS. 12 and 13. More
specifically, for the embodiment of the present invention shown in
FIGS. 12 and 13, the struts 452 extend radially outward from some
of the plurality of extension tabs 450 and are positioned in a way
to provide a desired natural frequency to the generally circular
plate assembly 430.
[0041] As discussed above, and shown clearly in FIGS. 12 and 13,
the plurality of struts 452 comprise an interrupted or recessed
portion 452A located between regions where the struts are in
contact and secured to the dome plate 334. This recessed portion
452A provides a way by which cooling air can pass between adjacent
swirler assemblies 332 in order to cool that portion of the dome
plate 334. In fact, to further aid in the cooling of the dome plate
334, the dome plate 334 includes multiple cooling holes 374
positioned under the recessed portion 452A of the struts 452.
[0042] Referring to FIGS. 13 and 14, the system for stiffening the
premixer assembly also comprises an outer cone 460 that envelopes a
portion of the pilot cone 448, and more specifically, the outer
cone 460 envelopes the divergent portion 448A of the pilot cone
448. The outer cone 460 is spaced a distance from the pilot cone
448 so as to maintain a flow of cooling air between the outer cone
460 and the pilot cone 448 for cooling the pilot cone 448,
including the divergent portion 448A. The gap between divergent
portion 448A and outer cone 460 can vary depending on operating
conditions, but for the embodiment depicted in FIGS. 13 and 14, is
approximately 0.055 inches. The gap is maintained by way of dimpled
portions in the outer cone 460 causing local contact with regions
of the pilot cone 448 when the combustor is operating. In a
non-operation, cold state, the dimpled portions in the outer cone
460 do not contact the pilot cone 448. In prior diffuser/pilot cone
configurations an outer cone similar to that disclosed herein was
welded to a pilot cone causing the welded assembly to be overly
constrained, resulting in high mechanical stresses and resulting in
component cracking and failure.
[0043] Referring now to FIG. 15, the present invention also
comprises a method 500 of altering natural frequency of a premixer
assembly. Specifically, in a step 502, a dome plate and pilot mixer
assembly are provided where the pilot mixer assembly has a
plurality of extension tabs. In a step 504, a quantity of radially
extending struts are secured to a plurality of extension tabs.
Depending on the desired natural frequency of the dome plate, in a
step 506, additional radially extending tabs are secured to the
dome plate and to additional extension tabs in order to increase
the natural frequency of the dome plate. Alternatively, in order to
decrease the natural frequency of the dome plate, one or more
radially extending struts can be removed from the premixer
assembly.
[0044] The present invention has been described in relation to
particular embodiments, which are intended in all respects to be
illustrative rather than restrictive. Alternative embodiments and
required operations, such as machining of shroud faces other than
the hardface surfaces and operation-induced wear of the hardfaces,
will become apparent to those of ordinary skill in the art to which
the present invention pertains without departing from its
scope.
[0045] From the foregoing, it will be seen that this invention is
one well adapted to attain all the ends and objects set forth
above, together with other advantages which are obvious and
inherent to the system and method. It will be understood that
certain features and sub-combinations are of utility and may be
employed without reference to other features and sub-combinations.
This is contemplated by and within the scope of the claims.
* * * * *