U.S. patent application number 11/074892 was filed with the patent office on 2005-07-07 for system and method to stage primary zone airflow.
This patent application is currently assigned to Ingersoll-Rand Energy Systems, Inc.. Invention is credited to Armstrong, Jeffrey, Dolak, Eric.
Application Number | 20050144960 11/074892 |
Document ID | / |
Family ID | 32326278 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050144960 |
Kind Code |
A1 |
Dolak, Eric ; et
al. |
July 7, 2005 |
System and method to stage primary zone airflow
Abstract
A method of operating a combustion turbine engine that includes
separating a flow of compressed air into a first flow stream and a
second flow stream. The method also includes preheating the first
flow stream to produce a preheated flow stream and premixing the
second flow stream with a flow of fuel to produce a premixture. The
method further includes mixing the premixture with a portion of the
preheated first flow stream to produce a combustible mixture and
combusting the combustible mixture to produce a flow of hot
products of combustion.
Inventors: |
Dolak, Eric; (Newmarket,
NH) ; Armstrong, Jeffrey; (Exeter, NH) |
Correspondence
Address: |
David B. Smith
Michael Best & Friedrich LLP
Suite 360
3773 Corporate Parkway
Center Valley
PA
18034
US
|
Assignee: |
Ingersoll-Rand Energy Systems,
Inc.
Portsmouth
NH
|
Family ID: |
32326278 |
Appl. No.: |
11/074892 |
Filed: |
March 8, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11074892 |
Mar 8, 2005 |
|
|
|
10417016 |
Apr 16, 2003 |
|
|
|
Current U.S.
Class: |
60/776 ;
60/39.511 |
Current CPC
Class: |
Y02E 20/348 20130101;
F02C 9/18 20130101; Y02E 20/34 20130101; F23R 3/26 20130101; F23L
15/04 20130101; F02C 7/08 20130101; F23R 3/286 20130101 |
Class at
Publication: |
060/776 ;
060/039.511 |
International
Class: |
F02C 007/10 |
Claims
What is claimed is:
1. A method of operating a combustion turbine engine comprising:
separating a flow of compressed air into a first flow stream and a
second flow stream; preheating the first flow stream to produce a
preheated flow stream; premixing the second flow stream with a flow
of fuel to produce a premixture; mixing the premixture with a
portion of the preheated first flow stream to produce a combustible
mixture; and combusting the combustible mixture to produce a flow
of hot products of combustion.
2. The method of claim 1, further comprising operating a compressor
to produce the flow of compressed air.
3. The method of claim 1, further comprising passing the first flow
of compressed air through a recuperator to preheat the flow of
compressed air, and bypassing the second flow of compressed air
around the recuperator.
4. The method of claim 1, further comprising dividing the first
flow stream into a primary air stream and a secondary air stream,
wherein the step of mixing the premixture with a portion of the
preheated first flow stream includes mixing the primary air stream
with the premixture.
5. The method of claim 4, further comprising mixing the hot
products of combustion with the secondary air stream.
6. The method of claim 5, further comprising directing the flow of
products of combustion into a turbine section of the engine and
rotating the turbine section in response to the flow of products of
combustion.
7. The method of claim 1, further comprising metering the flow rate
of at least one of the first and second flow streams.
8. The method of claim 7, wherein metering the flow rate of at
least one of the first and second flow streams includes moving a
valve member in the second flow stream between a first position and
a second position.
9. The method of claim 7, wherein metering the flow rate of at
least one of the first and second flow streams includes moving at
least one of a plurality of valve members in the second flow stream
between a first position and a second position.
Description
RELATED APPLICATION DATA
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/417,016 filed Apr. 16, 2003, the entire
contents of which are herein incorporated by reference.
BACKGROUND
[0002] The present invention relates to a system and apparatus for
optimizing airflow to a combustor and particularly to a system and
method for controlling airflow to the combustor. More particularly,
the present invention relates to a system and method for
controlling the quantity of airflow to the primary zone of the
combustor.
[0003] Present combustors are typically designed for a specific
fuel to be combusted. Each fuel requires a specific fuel-to-air
ratio (FAR) to be combusted efficiently without producing excessive
undesirable emissions (e.g., NO.sub.x, CO, and unburned
hydrocarbons). Thus, a combustor that operates well using natural
gas may not be efficient or may produce undesirable emissions when
operated using a different fuel such as butane. At present,
fuel-staging is used to allow one combustor design to operate with
multiple fuels. However, fuel-staging increases unwanted emissions
when operating at part power.
SUMMARY
[0004] The present invention provides a combustion turbine engine
adapted for use with a source of fuel. The engine includes a
compressor operable to produce a flow of compressed air, a
recuperator, and a bypass duct extending around said recuperator. A
flow divider selectively divides the flow of compressed air into a
first flow of compressed air flowing through said recuperator and a
second flow of compressed air flowing through said bypass duct
around said recuperator. The first flow of compressed air is
preheated within said recuperator. An adjustable valve operably
interacts with at least one of said first and second flows of
compressed air to selectively adjust the flow rate of the same. A
premix chamber is adapted to receive a flow of fuel from the source
of fuel. The premix chamber communicates with said bypass duct to
receive said second flow of compressed air and to mix said flow of
fuel and said second flow of compressed air into a premixture. The
invention also includes a combustor having a primary zone in
communication with both of said premix chamber and said recuperator
such that said preheated first flow of compressed air from said
recuperator and said premixture from said premix chamber are mixed
within said primary zone to create a combustible mixture. The
combustor combusts said combustible mixture to produce a flow of
products of combustion. The invention further includes a power
turbine driven by the flow of products of combustion from said
combustor and a power generator generating power in response to
operation of said power turbine, wherein the flow of products of
combustion flows through said recuperator to preheat said first
flow of compressed air.
[0005] In another embodiment, the invention provides a combustion
air delivery system comprising a compressor operable to provide a
stream of compressed air and a bypass duct positioned to divide the
stream of compressed air into a bypass flow stream and a primary
flow stream. A recuperator is operable to preheat the primary flow
to produce a flow of preheated compressed air. A premix chamber
receives the bypass flow stream and mixes the bypass flow stream
with a flow of fuel to produce a fuel-air flow. A can member at
least partially defines a primary zone that receives the fuel-air
flow and includes an aperture sized to admit a predetermined
portion of the flow of preheated compressed air. The fuel-air flow
and predetermined portion of the flow of preheated compressed air
mix in the primary zone to produce a combustible flow. An igniter
is operable to ignite the combustible flow.
[0006] In yet another embodiment, the invention provides a method
of operating a combustion turbine engine. The method includes
separating a flow of compressed air into a first flow stream and a
second flow stream and preheating the first flow stream to produce
a preheated flow stream. The method also includes premixing the
second flow stream with a flow of fuel to produce a premixture. The
invention further includes mixing the premixture with a portion of
the preheated first flow stream to produce a combustible mixture
and combusting the combustible mixture to produce a flow of hot
products of combustion.
[0007] Additional features and advantages will become apparent to
those skilled in the art upon consideration of the following
detailed description of preferred embodiments exemplifying the best
mode of carrying out the invention as presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The detailed description particularly refers to the
accompanying figures in which:
[0009] FIG. 1 is a perspective view of a combustion turbine
engine;
[0010] FIG. 2 is a schematic illustration of a combustion system
embodying the present invention and including a combustion
section;
[0011] FIG. 3 is a schematic illustration of another combustion
system embodying the present invention;
[0012] FIG. 4 is an enlarged view of an orifice plate;
[0013] FIG. 5 is a cross-sectional view of the combustion section
of FIG. 2 and including a swirler head;
[0014] FIG. 6 is a partially broken away perspective view of the
swirler head of FIG. 5;
[0015] FIG. 7 is another perspective view of the swirler head of
FIG. 6; and
[0016] FIG. 8 is a perspective view of the swirler head of FIG. 6
with a skirt attached.
DETAILED DESCRIPTION
[0017] With reference to FIG. 1, a combustion turbine engine 10 is
illustrated as including a compressor 15, a gasifier turbine 20, a
power turbine 25, a recuperator 30, a combustion section 35
including a combustor 37 (FIGS. 2, 3, and 5), and various air
passages. In addition, the engine 10 generally includes a driven
element such as a generator 40. In a two-turbine engine 10 such as
the one illustrated in FIG. 1, the gasifier turbine 20 is connected
to the compressor 15 such that operation of the gasifier turbine 20
drives the compressor 15. The power turbine 25 is connected to the
generator 40 or another component to be driven (e.g., a pump) such
that operation of the power turbine 25 drives the generator 40. In
a one-turbine engine 10, the single turbine would be sized to drive
both the compressor 15 and the generator 40.
[0018] During engine operation, atmospheric air is drawn into the
compressor 15 and compressed to produce a flow of compressed air 45
(shown in FIGS. 2 and 3). A portion of the flow of compressed air
45 flows through the recuperator 30 where it is preheated. The
preheated compressed air 50 enters the combustion section 35 and
combines with a flow of fuel 55 to produce a combustible fuel-air
mixture 60 (shown in FIGS. 2, 3, and 5). The fuel-air mixture 60 is
combusted to produce an expanding flow of combustion gas or
products of combustion 65. The flow of combustion gas 65 passes
through the gasifier turbine 20 to power the gasifier turbine 20
and drive the compressor 15. The flow of combustion gas 65 then
flows through the power turbine 25 to drive the generator 40. The
flow of combustion gas 65 proceeds through the recuperator 30 and
preheats the flow of compressed air 45a exiting the compressor 15
before being discharged to the atmosphere. In some constructions,
the flow of combustion gas 65 leaving the recuperator 30 is used in
another process before being discharged (e.g., heating water).
[0019] Turning to FIG. 2, the engine air passages are illustrated
in more detail. Before describing the passages, it should be noted
that various terms such as "passage," "duct," "pipe," and "flow
path," among others, are used herein to describe devices suited to
conducting fluids from one point to another. These terms should be
considered interchangeable and should not be read to limit the
invention in any way. For example, and without limiting the
foregoing, the term "pipe" should be interpreted broadly to include
"duct," "tube," "plenum," and "flow path" among other terms.
[0020] The flow of compressed air 45 exits the compressor 15 and is
divided into two distinct flow streams. The first flow stream 45a
enters the recuperator 30 and is preheated as described above. The
preheated compressed air 50 then flows to the combustion section
35. The second flow stream 45b, or bypass flow stream, enters a
bypass duct 70 that directs the bypass flow stream 45b around the
recuperator 30 and into the combustion section 35 without
preheating the air.
[0021] The second flow stream 45b is further divided into a
plurality of flow paths 75. Each of the plurality of flow paths 75
include a valve 80 that can control the flow through the individual
flow path 75 and an orifice 85 that limits the amount of flow to a
predetermined rate. In some constructions, the valve 80 itself acts
as the orifice 85 by limiting the amount of flow even when fully
opened. In other constructions, orifice plates 90 (shown in FIG. 4)
are positioned in each of the flow paths 75. The use of the orifice
plates 90 allows for precise control of the mass flow rate through
each of the flow paths 75 under given operating conditions. In
addition, the orifice plates 90 can be changed to increase or
decrease the flow capacity of a particular flow path 75 if desired.
It should be understood that even a pipe with no flow obstructions
could be considered "orificed," as the size or diameter of the pipe
limits flow under any given operating condition. As such, the
invention should not be limited to arrangements that require
orifice plates 90 or other components that act as orifices 85.
Rather, the orifices 85 are used to increase the accuracy and
predictability of engine performance.
[0022] The use of multiple flow paths 75 allows for more refined
control when compared to a single-path system, as one or more
valves 80 can be partially or totally opened to allow the desired
amount of air to bypass the recuperator 30. In most constructions,
each valve 80 is set to either an open position or a closed
position to reduce the likelihood of air leakage at the valve 80.
Thus, the use of multiple valves 80 and multiple flow streams 75
allows for adequate control over the quantity of air being bypassed
without the use of a complex control scheme or expensive valve.
[0023] Turning now to FIG. 3, a second construction of the engine
10a is illustrated in which the second flow stream 45b is not
divided into a plurality of flow paths 75. Rather, the engine 10a
includes a single flow path 45b having a controllable
multi-position valve 95. A controller 100 adjusts the valve 95 as
needed based on one or more control parameters (e.g., turbine
temperature, exhaust temperature, turbine inlet temperature,
turbine exhaust composition, combustor pressure, fuel type, power
level, operating temperature, ambient air temperature, etc.). In
some constructions, the valve position is preset and is not
adjusted during operation. For example, a particular engine that is
capable of operating on several different fuels (e.g., natural gas,
propane, butane, JP-8, etc.) operates most efficiently if the
combustor 37 is specifically configured for the particular fuel
being burned. A switch (not shown), operated by the user,
repositions the controllable valve 95 to a fuel-specific position
before operation of the engine 10a. Thus, the engine 10a operates
efficiently with any of the fuels. In another construction, the
valve 95 is controlled during engine operation by the controller
100. One or more engine parameters are used to periodically or
constantly adjust the position of the valve 95 to achieve the
desired performance. As one of ordinary skill in the art will
realize, many different control parameters and control systems
could be used to control the valve position.
[0024] A person of ordinary skill will also realize that the
controller 100 and system as just described with regard to FIG. 3
could be applied to the engine 10 of FIG. 2 to achieve similar
results. Thus, the use of controllable valves 95 should not be
limited to constructions similar to that of FIG. 3 alone.
Furthermore, the valve 95 of FIG. 3 could be manually controlled to
achieve the desired results. In these constructions, the valve 95
is positioned in predetermined positions based on various factors
(e.g., turbine temperature, exhaust temperature, turbine inlet
temperature, turbine exhaust composition, combustor pressure, fuel
type, power level, operating temperature, ambient air temperature,
etc.).
[0025] FIG. 5 shows a sectional view of a can-type combustor. As
seen in FIG. 5, the combustor 37 is positioned within an outer wall
105. In most constructions, the outer wall 105 is formed as part of
the recuperator 30 as shown in FIGS. 2 and 3. This arrangement
reduces the space occupied by the engine 10 and reduces the number
of components such as pipes, flanges, and valves needed to assemble
the engine 10. Other constructions may employ a combustion section
35 spaced some distance from the recuperator 30 and use pipes or
other ducts to direct the preheated compressed air 50 from the
recuperator to the combustion section 35 and from the combustion
section 35 to the turbine 20.
[0026] The combustor 37, illustrated in FIG. 5 includes a swirler
head 110 attached to a can 115 and positioned substantially within
the outer wall 105 defined by the recuperator 30. The combustor 37
is generally divided into zones including a primary zone 120 and a
secondary zone 125, with many constructions also including a
tertiary or dilution zone 130. In general, combustion is initiated
and maintained within the primary zone 120. Additional air may be
added in the secondary zone 125 to assure complete combustion and
reduce the quantity of undesirable emissions. The tertiary or
dilution zone 130, if employed, receives a large quantity of air to
cool the flow of combustion gas 65 to a desired combustor outlet
temperature before the flow of combustion gas 65 enters the turbine
20.
[0027] The primary zone 120 is defined by a portion of the swirler
head 110 and a portion of the combustor can 115. The swirler head
110, best illustrated in FIGS. 6 and 7, includes a body 135 that
defines a premix chamber 140 (shown broken away in FIG. 6 and in
cross-section in FIG. 5) and a plurality of flow guides 145. The
body 135 also includes a flange 150 that facilitates the attachment
of the combustor 37 to the recuperator 30. The flange 150 separates
the swirler head 110 into an outer portion 155, illustrated in FIG.
6, and an inner portion 160 illustrated in FIG. 7. The inner
portion 160 is substantially within the primary zone 120 of the
combustor 37, while the outer portion 155 is not. As illustrated
herein, the swirler head 110 is a separate component that attaches
to the can 115. However, other constructions employ a swirler head
110 that is formed as part of the can 115. In still other
constructions, the swirler head 110 is a separate component
positioned away from the remainder of the combustion section
35.
[0028] The premix chamber 140 is an annular chamber within the body
135 of the swirler head 110. As shown in FIG. 6, a bypass air inlet
170 and a fuel inlet 175 both attach to the outer surface of the
cover plate 165 and/or the body 135 of the swirler head 110 to
deliver bypass air and fuel to the combustor 37.
[0029] Also visible on the outer portion 155 of the swirler head
110 is a pilot fuel inlet 180 and an ignitor 185 that is received
in a hole 187 in the head 110. The pilot fuel inlet 180 provides a
separate flow of fuel that may be used to maintain the flame
stability within the combustor 37 at low power settings or to
initiate combustion within the combustor 37 during an engine start.
The igniter 185 is a spark-producing device that provides a spark
to initiate combustion during engine start-up or at any other time
when the flame is desired but not present. Alternatively, a
heat-producing device such as a glow plug is used. As one of skill
in the art will realize, many other devices are well suited to the
task of initiating a flame and as such are contemplated by the
present invention.
[0030] Both the fuel inlet 175 and the pilot fuel inlet 180 receive
a flow of fuel 55 from an external fuel source 190 (FIGS. 2 and 3)
such as a tank or gas line. In most constructions, a fuel
pump/compressor and/or assorted valves are in fluid communication
with the fuel source 190 and the swirler head 110 to control the
rate of fuel flow. Thus, the engine 10 is able to deliver fuel at a
desired rate to the combustor 37.
[0031] In one construction of a swirler head 110 shown in FIG. 7,
the inner portion 160 includes the plurality of flow guides 145
that are partially encircled by a skirt 195 (shown in FIGS. 5 and
8). The flow guides 145 are generally raised triangular blocks
having two planar surfaces 200 and an arcuate outer surface 205.
The outer surfaces 205 and the skirt 195 cooperate to define a
partial annular air chamber 210. The planar surfaces 200 of each
flow guide 145 are arranged such that they are substantially
parallel to the planar surfaces 200 of the adjacent flow guides
145. Using this arrangement, a plurality of flow paths 215, or
apertures, are defined between the annular air chamber 210 and a
primary zone neck 220 (FIG. 5). The skirt 195 guides compressed air
exiting the recuperator 30 into the flow paths 215. As one of
ordinary skill will realize, many different arrangements are
possible to direct compressed air into the primary zone 120. As
such, the present invention should not be limited to the
aforementioned example.
[0032] Within each flow path 215 are two fuel inlets. The first of
the inlets 225 is located adjacent the flow path inlets and
includes an injector 230 that directs the fuel flow in the flow
direction of the compressed air. The first fuel inlet 225 is in
fluid communication with, and receives a flow of fuel or fuel-air
from the premix chamber 140. The second fuel inlet 235 comprises a
small bore located adjacent the individual flow path outlets. This
inlet 235 is in fluid communication with the pilot fuel inlet
180.
[0033] The primary zone neck 220 is a substantially cylindrical
region of the can 115 that defines a portion of the primary zone
120 of the combustor 37. The flow paths 215 defined by the flow
guides 145 direct the compressed air from the annular air chamber
210 into the primary zone neck 220. The igniter 185 (shown in FIG.
5) is positioned within the primary zone 120 to enable it to ignite
the fuel-air mixture therewithin. Alternatively, the igniter 185
could be positioned elsewhere in the head 110 or neck 220.
[0034] The secondary zone 125 is positioned downstream of the
primary zone 120 and includes additional apertures 240 that admit
air. The apertures 240 direct compressed air along the inner wall
of the can 115 in the secondary zone 125. In other constructions,
additional apertures may be used to admit air to further sustain
combustion.
[0035] The tertiary zone or dilution zone 130 is located downstream
of the secondary zone 125 and includes large apertures 245 that
admit the remaining compressed air into the combustor as the air
exits the recuperator 30. In other constructions, the flow of
combustion gas 65 exits the can 115 and then mixes with the
remaining compressed air before finally flowing to the turbine 20.
In either construction, the remaining compressed air mixes with the
flow of combustion gas 65.
[0036] In operation, the compressed air exits the compressor 15 and
divides into the two flow streams 45a, 45b. The first flow stream
45a is directed to a plenum in the recuperator 30, then through the
recuperator 30 where the air is preheated until finally reaching
the air space between the recuperator 30 and the combustor 37.
Meanwhile, the second flow stream (bypass air stream) 45b proceeds
from the compressor 15 directly to the swirler head 110 without
passing through the recuperator 30.
[0037] The bypass air enters the premix chamber 140 through the
bypass air inlet 170. For engines configured as shown in FIG. 2, a
plurality of air inlets 170 may be used. However, in other
constructions the bypass air is recombined into a single flow
before being admitted into the premix chamber 140. The premix
chamber 140 for this construction would require only a single air
inlet 170, thereby simplifying the manufacture of the swirler head
110. One of ordinary skill in the art will realize that the premix
chamber 140 could be designed to have multiple air inlets 170 if
desired, no matter the arrangement of the engine 10.
[0038] Within the premix chamber 140, the bypass air and the fuel
mix to produce a fuel-air mixture. The fuel inlet(s) 175 and air
inlet(s) 170 are arranged such that the air and fuel mix thoroughly
within the premix chamber 140. The fuel/air ratio (FAR) of the
mixture within the premix chamber 140 is typically too high (i.e.,
rich mixture) to sustain combustion. Thus, additional air must be
added to the fuel-air mixture to initiate and sustain combustion.
After mixing, the fuel-air mixture within the premix chamber 140 is
injected into the primary zone 120 of the combustor 37 via the fuel
inlets 225.
[0039] The flow paths 215 are sized to admit sufficient air into
the primary zone 120 to sustain combustion at a desired or target
equivalence ratio (ER). The ER is defined as the ratio of the
actual FAR and the stoichiometric fuel-air ratio. The
stoichiometric fuel-air ratio is the ideal ratio of a particular
fuel and air for combustion. At the stoichiometric fuel-air ratio,
all of the fuel and all of the oxygen are consumed during
combustion.
[0040] In one construction, the target ER value is 0.5. Thus, the
fuel-air mixture in the primary zone 120 is lean (i.e., excess
oxygen is available for combustion). The lean mixture reduces the
undesirable engine emissions during operation.
[0041] As an example, many combustion turbine engines 10 use
natural gas as the primary fuel. Natural gas has a stoichiometric
fuel-air ratio of 0.058 (i.e., for every kilogram of fuel, 17.25
kilograms of air are required). For a target equivalence ratio of
0.5 using natural gas, the actual FAR must be 0.029 (i.e., for
every kilogram of fuel, 34.5 kilograms of air are supplied). A
portion of the necessary air is supplied in the fuel-air mixture
delivered from the premix chamber 140. As such, the flow paths 215
in the swirler head 110 are sized to admit the remaining air. For
example, at one operating condition, air may be supplied to the
premix chamber 140 at a fuel-air ratio of 0.10 (i.e., for every
kilogram of fuel, ten kilograms of air are supplied). Thus, the
flow paths 215 must be sized to admit the remaining 24.5 kilograms
of air needed to reach the targeted ER.
[0042] During turndown (part load) operation, the mixture in the
primary zone 120 tends to become more lean (excessive air). In some
cases, the FAR can fall below the lean extinction FAR of the
combustor 37, thereby causing blowout, flame extinction, or other
flame related problems. The present invention allows for the
maintenance of the target ER during turndown operation by reducing
the air flow into the premix chamber 140. This has the desirable
effect of reducing the total air in the primary zone 120 as the
quantity of fuel is reduced.
[0043] In addition to improved turndown operation, the present
invention facilitates the efficient and clean operation of a single
combustor 37 using multiple fuels. Continuing the example from
above, if the combustor 37 were switched from natural gas to
another fuel such as butane, its performance would suffer. Butane
has a stoichiometric fuel-air ratio of 0.067 (i.e., for every
kilogram of butane, 14.9 kilograms of air are required). Thus, to
operate at an ER of 0.5, 29.8 kilograms of air must be admitted to
the primary zone for each kilogram of fuel.
[0044] The above-described combustor 37 includes flow paths 215
sized to admit 24.5 kilograms of compressed air for every kilogram
of fuel. Thus, the ER would be 0.43 with the valves 80 and
combustor 37 configured as above for natural gas (i.e., 10
kilograms of air being mixed with one kilogram of fuel in the
premix chamber 140). This ER may be low enough to cause flame
instability and other operational problems. To counteract this and
return the combustor 37 to optimal performance, the flow rate of
bypass air to the premix chamber 140 is reduced. To return the
combustor 37 to an ER of 0.5, the actual FAR must be approximately
0.034. (i.e., for every kilogram of fuel, 29.8 kilograms of air are
present). To achieve this, the valve or valves 80 are adjusted to
allow the passage of 5.3 kilograms of air per kilogram of fuel,
rather than the 10 kilograms passed when operating with natural gas
as the fuel. The flow paths 215 remain fixed and admit the
remainder of the required air (i.e., 24.5 kilograms per kilogram of
fuel). As one skilled in the art will realize, the present system
can be designed to operate efficiently with several different fuels
rather than just the two described.
[0045] It should be noted that the above description is for
exemplary purposes only. The invention should in no way be limited
to mass flow rates similar to those described, as larger or smaller
fuel and air flow rates, as well as different ERs and FARs may be
desirable and would be achievable with the invention as described
herein.
[0046] Although the invention has been described in detail with
reference to certain preferred embodiments, variations and
modifications exist within the scope and spirit of the invention as
described and defined in the following claims.
* * * * *