U.S. patent application number 13/610083 was filed with the patent office on 2013-09-19 for method of controlling engine performance.
The applicant listed for this patent is Jacqueline R. Girouard, Raymond Girouard, Robert J. Moffat. Invention is credited to Jacqueline R. Girouard, Raymond Girouard, Robert J. Moffat.
Application Number | 20130239579 13/610083 |
Document ID | / |
Family ID | 43069205 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130239579 |
Kind Code |
A1 |
Girouard; Raymond ; et
al. |
September 19, 2013 |
METHOD OF CONTROLLING ENGINE PERFORMANCE
Abstract
The present invention provides a method of controlling engine
performance that includes obtaining at least one optical
wavelength-dependent measurement from at least one combustion event
in at least one combustion chamber. The method further includes
analyzing the optical wavelength-dependent measurement for
determining adjustments to the at least one combustion event.
Additionally, the method includes adjusting the at least one
combustion event or at least a next combustion event by changing at
least one physical parameter, at least one constituent parameter,
or at least one physical parameter and at least one constituent
parameter to control the engine performance, where the physical
parameter includes adjusting a turbine blade angle using a
vane-adjust actuator in response to a signal from a controller. The
engine can include steady-flow engines or periodic flow engines,
and the engine performance can be selected by an engine user.
Inventors: |
Girouard; Raymond;
(Atherton, CA) ; Moffat; Robert J.; (Los Altos,
CA) ; Girouard; Jacqueline R.; (Atherton,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Girouard; Raymond
Moffat; Robert J.
Girouard; Jacqueline R. |
Atherton
Los Altos
Atherton |
CA
CA
CA |
US
US
US |
|
|
Family ID: |
43069205 |
Appl. No.: |
13/610083 |
Filed: |
September 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12590373 |
Nov 6, 2009 |
8265851 |
|
|
13610083 |
|
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Current U.S.
Class: |
60/773 |
Current CPC
Class: |
F02C 9/00 20130101; F01D
17/06 20130101; F01D 17/08 20130101; F01D 17/085 20130101; F05D
2270/60 20130101; F01D 17/04 20130101; F02C 9/48 20130101; F01D
17/20 20130101; F02C 9/28 20130101; F02D 2200/604 20130101; F01D
21/12 20130101; F01D 17/02 20130101; F02D 2200/701 20130101; F01D
21/14 20130101; F01D 21/003 20130101; F05D 2260/80 20130101; F02D
35/022 20130101; F05D 2270/30 20130101 |
Class at
Publication: |
60/773 |
International
Class: |
F02C 9/00 20060101
F02C009/00 |
Claims
1. A method of controlling engine performance comprising: a.
obtaining at least one optical wavelength-dependent measurement
from at least one combustion event in at least one combustion
chamber of an engine; b. analyzing said at least one optical
wavelength-dependent measurement for determining adjustments to
said at least one combustion event; and c. adjusting said at least
one combustion event or at least a next combustion event by
changing at least one physical parameter, at least one constituent
parameter, or at least one physical parameter and at least one
constituent parameter to control said engine performance, wherein
said physical parameter comprises adjusting a turbine blade angle
using a vane-adjust actuator in response to a signal from a
controller.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/590373 filed Nov. 6, 2009, which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to managing engine and turbine
performance. In particular, the invention relates to using optical
wavelength-dependent measurements to monitor and adjust parameters
in engine and turbine combustion events.
BACKGROUND
[0003] Poor engine performance affects engine durability, power,
thermal efficiency and pollution. Recently, efforts have been
directed to optimizing power and propulsion systems for cleaner and
lower environmental impact power generation. One approach included
an integrated engine combustion monitoring system that uses a light
communication channel (LCC) and a sensor, which are embedded in a
cylinder head gasket, for monitoring air and fuel mixture, and/or
products of combustion, pressure, or temperature. Although this
approach offers real-time in-situ data acquisition of some engine
performance parameters, the approach requires manually refining
operational variables to the engine after sufficient data is
acquired. Another attempt included an optoelectronic measuring
device for monitoring combustion processes in the combustion
chamber of an internal combustion engine during operation using
optical sensors. The sensors were aligned so that the individual
viewing angles of the sensors uniformly cover at least one
predefined measuring sector of the combustion chamber.
Unfortunately, this device required a large optical system that
uses reflection/deflection to communicate a limited number of
performance parameters that are useful only for testing engine
performance in a controlled lab setting.
[0004] Recently introduced performance chips are used to boost
engine power. An engine control unit (ECU) uses a formula and a
large number of lookup tables to determine the fuel flow for a
given operating condition. A chip in the ECU holds all of the
lookup tables. The tables in the performance chip contain values
that result in higher fuel/air ratios during certain driving
conditions. For instance, they may supply more fuel at full
throttle at every engine speed, or change the spark timing, or
both. Performance chips as recently configured are not used for
monitoring vital aspects of engine performance such as engine
durability, output power versus efficiency, thermal efficiency,
acoustic output, or exhaust constituents, to name a few.
[0005] What is needed is a method of real-time, in-situ monitoring
pre-combustion state, during the combustion event and
post-combustion event in a cylinder and adjusting the combustion
event or at least a next combustion event by changing physical
parameters and/or constituent parameters to control the engine or
turbine performance.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method of controlling
engine performance that includes obtaining at least one optical
wavelength-dependent measurement from at least one combustion event
in at least one combustion chamber. The method further includes
analyzing the optical wavelength-dependent measurement for
determining adjustments to the at least one combustion event.
Additionally, the method includes adjusting the at least one
combustion event or at least a next combustion event by changing at
least one physical parameter, or at least one constituent
parameter, or at least one physical parameter and at least one
constituent parameter to control the engine performance, where the
physical parameter includes adjusting a turbine blade angle using a
vane-adjust actuator in response to a signal from a controller.
[0007] According to one aspect of the invention, the combustion
event can include a periodic event or a steady event.
[0008] In another aspect of the invention, the at least optical
wavelength-dependent measurements are obtained using at least one
optical sensor in the at least one combustion chamber and proximal
to a region of the combustion event.
[0009] In a further aspect of the invention, the engine includes
steady-flow engines or periodic-flow engines. Here, the steady-flow
engines can be gas turbine engines, jet engines, or shaft power
turbines. Further, the periodic-flow engines can be compression
ignition engines spark ignition engines, laser ignition engines,
pulse-jet engines, ram jet engines, or scram jet engines. According
to this aspect, controlling the periodic-flow engine performance
includes changing the combustion event physical parameters that
include combustion chamber volume, instantaneous temperature level
in a region proximal to a predetermined point, spatially averaged
temperature level, temporal temperature level, averaged values of
temperature level, temperature distribution within the combustion
space, pressure, intake flow rate, exhaust flow rate, ignition
timing, ignition energy per event, ignition energy delivery
location and combustion duration. Also, according to the current
aspect, controlling the steady-flow engine performance includes
changing at least one the combustion process physical parameters
that includes instantaneous temperature level, spatially
distributed temperature level, temperature distribution within the
combustion space, fuel flow rate, fuel composition, fuel
temperature, ignition characteristics and combustion duration,
wherein said ignition characteristics comprise timing, ignition
energy, ignition energy delivery location or combustion duration.
In this aspect, the periodic flow engine performance combustion
event constituent parameters are measured during an event phase
such as pre-combustion phase, combustion phase or end-stage
combustion phase. Further, the periodic flow engine control is
achieved using at least one actuator altering at least one
combustion parameter such as composition of the total intake
charge, pre-combustion fuel vapor or spray concentration and
distribution, pre-combustion water vapor concentration, combustion
chamber volume, ignition parameters (timing of initiation, duration
of energy delivery, temporal profile of energy delivery, timing of
the end of energy delivery), inlet charge temperature, intake valve
operating parameters (opening event, duration, valve lift or
equivalent, and closing event), exhaust valve operating parameters
(opening event, duration, valve lift or equivalent, and closing
event), fuel composition and fuel temperature. Here, portions of
the total intake charge can include air, exhaust products, water
droplets, water vapor or fuel additives. According to the current
aspect, controlling the steady-flow engine performance includes
least one actuator altering at least one combustion parameter such
as air flow rate, various cooling air flow rates, secondary air
flow rate, air temperature, air pressure, turbine tip clearance,
fuel concentration distribution in space and time, water vapor
concentration distribution in space and time, ignition timing,
ignition energy delivery rate, energy delivery duration, fuel
composition or fuel temperature.
[0010] According to another aspect, the engine performance can
include engine durability, output power, thermal efficiency,
acoustic output, or exhaust constituents, where the hierarchy of
engine performance can be selected by an engine user.
[0011] In another aspect of the invention, the controller adjusts
at least one the combustion parameter during the combustion events
upon receiving the at least optical wavelength-dependent
measurements.
[0012] According to another aspect of the invention, when the
engine is a steady flow engine, engine durability is enhanced by
adjusting a fraction of inlet air flow used for primary zone
combustion, secondary air combustion and liner cooling in the
response to commands from an engine control unit.
[0013] In another aspect of the invention, the engine performance
is enhanced by altering fuel composition in response to commands
from an engine control unit by injection of additives that can
include of a knock suppressor in a spark ignition engine, a NOx
suppressor, or a soot suppressor engine upon detection of an
incipient condition, wherein the soot suppressor is used in a
diesel or a gas turbine.
[0014] In another aspect of the invention, the engine is a steady
flow engine having a steady-flow event, where at least one actuator
alters at least one of the combustion parameters such as fuel
concentration, oxygen concentration, air flow, combustion chamber
pressure, combustion chamber temperature, fuel temperature or fuel
composition.
[0015] In a further aspect, the engine is a periodic engine having
at least one periodic event, where at least one actuator alters at
least one of the combustion parameters such as fuel concentration,
oxygen concentration, combustion chamber pressure, combustion
chamber temperature, ignition timing, ignition duration, intake
valve timing, exhaust valve timing, intake valve duration, exhaust
valve duration, fuel temperature or fuel composition.
[0016] In another aspect of the invention, a position indicating
device is coupled to an engine control unit to facilitate
compliance with all territorial or zonal requirements, where the
position indicating device comprises a global positioning
system.
BRIEF DESCRIPTION OF THE FIGURES
[0017] The objectives and advantages of the present invention will
be understood by reading the following detailed description in
conjunction with the drawing, in which:
[0018] FIG. 1 shows a schematic flow diagram of the method of
controlling engine performance according to the present
invention.
[0019] FIG. 2 shows a drawing of the expert system for monitoring
and optimizing engine performance of a periodic-flow engine
according to the current invention.
[0020] FIG. 3 shows a drawing of the expert system for monitoring
and optimizing engine performance of a steady-flow engine according
to the current invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Although the following detailed description contains many
specifics for the purposes of illustration, anyone of ordinary
skill in the art will readily appreciate that many variations and
alterations to the following exemplary details are within the scope
of the invention. Accordingly, the following preferred embodiment
of the invention is set forth without any loss of generality to,
and without imposing limitations upon, the claimed invention.
[0022] The current invention provides an expert system for
monitoring and optimizing engine performance. Specifically, the
invention provides a method of monitoring a combustion event in a
combustion chamber of an engine and, in real-time, altering the
physical parameters and/or altering the constituent parameters in
the combustion events using a high-speed controller to control the
actuators, which can include high-speed actuators. The term
combustion event includes a periodic event in periodic flow engines
or a steady event in steady-flow engines. Here, the periodic flow
engines can be compression ignition engines spark ignition engines,
laser ignition engines, pulse-jet engines, ram jet engines, or
scram-jet engines, and the steady-flow engines can be gas turbine
engines, jet engines, or shaft power turbines.
[0023] An actuator alters at least one of the combustion parameters
such as fuel concentration, oxygen concentration, combustion
chamber volume, combustion chamber pressure, combustion chamber
temperature, ignition timing, ignition duration, intake valve
timing, exhaust valve timing, intake valve duration, exhaust valve
duration, or fuel temperature. The controller adjusts at least one
combustion parameter during the combustion events, or at least one
before the next event in periodic-flow engines upon receiving the
commands from the ECTU, based on all of the inputs including
optical wavelength-dependent measurements.
[0024] Referring to the figures, FIG. 1 shows a flow diagram of the
method of controlling engine performance 100 according to the
present invention. The flow diagram 100 shows an engine 101 where
at least one optical wavelength-dependent measurement is obtained
102, where the measurement can include any sophisticated optical
measurement, for example line-of-sight absorption spectroscopy,
wavelength modulation spectroscopy applied, planar laser-induced
fluorescence (PLIF), wavelength-multiplexed, fiber-optic-based,
line-of-sight, diode-laser absorption, multi-spectral detection,
wavelength modulation spectroscopy using at least one tunable
diode-laser sensor, the ratio of measured absorbances of two water
vapor overtone transitions in the near infrared using a tunable
diode laser, a scanned wavelength technique with wavelength
modulation and 2 f detection using at least one diode laser,
density inferred from spectroscopic absorption by an oxygen
feature, velocity obtained from a Doppler frequency shift between
absorption features from two crossed paths, two tunable diode laser
temperature sensors comprising a first sensor using direct
absorption and a second sensor using wavelength-modulation
spectroscopy with second-harmonic detection, spectrally resolved
laser-induced fluorescence (LIF), a diode laser absorption sensor
inferring temperature from a ratio of optical absorption for two
overtone transitions and H.sub.2O concentration determined from
inferred temperature and absorption for one of the transitions,
time-resolved absorption-based measurements of temperature and fuel
vapor concentration using a two-wavelength mid-IR laser and a
difference-frequency-generation laser. Further shown in FIG. 1 the
method includes analyzing the optical wavelength-dependent
measurement 104 and, in combination with other inputs, determining
adjustments to the combustion event 106. Additionally, the method
includes adjusting the combustion event 108 or at least a next
combustion event by changing at least one physical parameter or, at
least one constituent parameter, or at least one physical parameter
and at least one constituent parameter to optimize the selected
engine performance parameters according to the relative importance
of engine durability, output power, thermal efficiency, acoustic
output, or exhaust constituents. Here, the engine performance can
be selected by an engine user, where the engine user is able to
select which performance parameter is to be optimized depending
upon the operator's needs at the time. For example, a pilot on take
off or climb out would optimize for power. A VLCC engineer with
3,000 nautical miles remaining to reach port may optimize for fuel
efficiency but opt to minimize emissions when nearing port. A
freight vehicle may select for maximum emissions control when
operating in a high-density urban environment, to name a few.
[0025] FIG. 2 shows a drawing of the expert system for monitoring
and optimizing engine performance of a periodic-flow engine 200
according to the current invention. Shown in FIG. 2 is an engine
block 202 with a combustion chamber and a piston 206. Further shown
is an intake valve 208 and an exhaust valve 210, a spark plug 212
for providing a spark to ignite a combustion event 214, where it is
understood that other engine types, such as diesel engines, do not
require a spark plug 212 to initiate a combustion event 214. The
current embodiment shown in FIG. 2 includes a combustion chamber
volume displacement device 216 and an optical sensor 218, where in
this example the optical sensor 218 is proximal to a region of the
combustion event 214 and may include a light source 220 such as a
laser for facilitating optical measurement of wavelength-dependent
information 222 from a combustion event 214. In FIG. 2 the sensor
218 measures combustion event constituent parameters in an event
phase such as pre-combustion phase, combustion phase or end-stage
combustion phase, and the measurement is received by a measurement
analyzer 226 that may function in real-time. The analyzer sends the
results to a controller 228 for determining what modifications, if
any, need to be made to the combustion event 214. If the controller
228 determines changes to the combustion event 214 are needed, a
signal is provided to an actuator to change at least one physical
parameter and/or at least one constituent parameter relating to the
present or subsequent combustion event 214. For example, the
controller 228 can operate an intake actuator 230 to provide
real-time adjustment of an intake parameter 232, where FIG. 2 shows
the intake parameter 232 as a generic circle to represent any one
of the intake parameters that can include, total intake charge per
intake event (or flow rate for steady flow), pre-combustion fuel
vapor or spray concentration and distribution, pre-combustion water
vapor concentration, intake temperature, fuel temperature, intake
valve operating parameters such as opening event, duration, valve
lift or equivalent, and closing event. Here, the total intake
charge can include air, exhaust products, water droplets or water
vapor.
[0026] FIG. 2 further shows the controller 228 can operate an
exhaust actuator 234 to provide real-time adjustment to an exhaust
parameter 236, where FIG. 2 again shows a generic circle to
represent any one of the exhaust parameters that can include
exhaust valve operating parameters such as opening event, duration,
valve lift or equivalent, and closing event, regeneration of the
exhaust heat to improve the combustion event 214, recirculation of
exhaust constituents to the combustion event 214,
[0027] According to the current embodiment, the controller 228 can
operate a sparkplug actuator 238 to operate on the spark plug 212
(the spark plug represents any other ignition generator) and
provide real-time adjustment to the ignition parameter that can
include timing of initiation, duration of energy delivery, temporal
profile of energy delivery, timing of the end of energy
delivery.
[0028] The controller 228 can further operate a combustion chamber
volume actuator 240 to operate on the combustion chamber volume
displacement 216 and provide real-time adjustment to the volume of
the combustion chamber 204 between compression events.
[0029] The controller 228 can operate any or all of the actuators
to alter combustion parameters such as fuel concentration, oxygen
concentration, combustion chamber volume, combustion chamber
pressure, combustion chamber temperature, ignition timing, ignition
duration, intake valve timing, exhaust valve timing, intake valve
duration, exhaust valve duration, or fuel temperature.
[0030] In another aspect of the invention, fuel additives are used
to modify the exhaust emissions, where a probe 242 is disposed in
the exhaust stream with the sensor input fed to the controller 228
enabling corrective action to be taken in real time. In one aspect,
an environmental control agency for a jurisdiction whose territory
the vessel/aircraft/truck is entering, a down-loadable file is
provided using a positioning indicating device 244, such as a
global positioning system (GPS), is captured and reviewed for
compliance showing the data stream from the exhaust. The
environmental control agency provides a time and location stamp and
identifies any out of compliance events. Here, the down-loadable
file has limited write/erase access to the file so that it couldn't
be modified.
[0031] FIG. 2 shows the controlling of a periodic flow engine
performance by changing the combustion event physical parameters
such as inlet charge temperature by blending air at a controlled
temperature with the intake charge using a fast-acting valved
injector. Alternatively, the fuel to air ratio could be changed
from combustion event to combustion event by changing the fuel
injector parameter.
[0032] In a further aspect of the invention, the engine performance
is enhanced by altering fuel composition in response to commands
from an engine control unit by injection of additives such as
injecting of a knock suppressor in a spark ignition engine or a
soot suppressor in a diesel of gas turbine engine upon detection of
an incipient condition.
[0033] According to the invention, the engine can include
steady-flow engines or periodic flow engines, where the steady-flow
engines can be gas turbine engines, jet engines, or shaft power
turbines, and the periodic flow engines can be compression ignition
engines spark ignition engines, laser ignition engines, pulse jet
engines, ram jet engines, or scram jet engines.
[0034] FIG. 3 shows a drawing of the expert system for monitoring
and optimizing engine performance of a steady-flow engine 300
according to the current invention. Shown in FIG. 3 is a
steady-flow engine housing 302 with a combustion chamber 304, where
the top chamber 304 is shown with some of the monitoring and
control elements and the bottom chamber 304 is shown with other
monitoring and control elements to simplify the drawing, and it is
understood that one or more combustion chambers 304 can include all
of the monitoring and control elements discussed here. Shown is an
air intake region 306, a compression region 308, a combustion
region 310 having the combustion chambers 304 and an exhaust region
312. The current embodiment shown in the top combustion chamber 304
includes an optical sensor 316, where in this example the optical
sensor 316 is proximal to a region of the combustion process 318
and includes a light source 320, such as a laser, for facilitating
the measurement of the wavelength-dependent information 322 from
the combustion process 318. In FIG. 3, the optical sensors 316
measure combustion process constituent parameters in the
pre-combustion region 315, the primary combustion region 317 and
the secondary combustion region 319 as shown in the lower
combustion chamber 304, where the measurements are received by a
measurement analyzer 331 which may function in real-time. The
analyzer sends the results to a controller 324 for determining what
modifications if any, need to be made to the combustion event 318.
If the controller 324 determines changes to the combustion process
318 are needed, a signal, which may be real-time or suitably
averaged is provided to an actuator to change at least one physical
parameter and/or at least one constituent parameter relating to the
combustion process 318. For example, the controller 324 can operate
a fuel intake actuator 326 to provide real-time adjustment of a
fuel intake parameter 328, where FIG. 3 shows the fuel intake
parameter 328 as a generic circle to represent any one of the fuel
intake parameters that can include for example, instantaneous fuel
flow rate, pre-combustion fuel vapor or spray concentration and
distribution, pre-combustion water vapor concentration, or fuel
temperature.
[0035] As shown, a sensor 330 is disposed in the exhaust stream 312
to provide exhaust data to the controller 324, where the controller
324 adjusts at least one actuator altering at least one combustion
parameter that can include primary air flow rate, secondary air
flow rate, air temperature, fuel concentration distribution in
space and time, water vapor concentration distribution in space and
time, ignition timing, ignition energy delivery rate, energy
delivery duration, fuel composition and fuel temperature. FIG. 3
further shows the lower combustion chamber 304 having the
combustion chamber lining 321 having operable valves 323 to open
and close ports 323b in the secondary combustion region 319 of
combustion chamber lining 321 to control the combustion event 318
cooling. The ports 323b may be smaller near the front of the flow
and become progressively larger down stream, and are operated by
the combustion chamber thermal actuator 325 as instructed by the
controller 324. The combustion chamber 304 further includes one or
more thermal monitoring elements 327 for monitoring the
temperatures of the combustion chamber lining 321, the combustion
event 318 and the air temperatures inside and outside of the
combustion chamber lining 321. Here a generic circle represents the
monitoring elements for determining the total flow parameters in
the combustion region 310. The thermal monitoring elements can be a
pyrometer, thermocouples or other such sensors.
[0036] FIG. 3 further shows the controller 324 disposed to operate
a vane-adjust actuator 332 to adjust the angle of the turbine
blades 334 in response to signals from the controller 324. Turbine
efficiency can be maintained at an optimum value if the angle of
the turbine blades 334 with respect to the combustion flow
parameter can be adjusted as the load point changes.
[0037] Another factor that affects efficiency in a steady-flow
engine 300 is the clearance between the tips of the turbine blades
334 and the shroud 338 surrounding the turbine 334. Leakage across
the tips of the blades 334 represents a loss that must be
minimized. According to the current invention, the clearance
between the tips of the turbine blades 334 and the shroud 338 can
be adjusted by a shroud actuator 340 that moves a moveable shroud
338 to change the clearance between the tips of the turbine blades
334 and the turbine shroud 338. The invention further includes an
inductive, capacitive or acoustic detector 342, to determine when
the blades 334 approach or touch the shroud 338. According to
another aspect of the invention the clearance between the tips of
the turbine blades 334 and the turbine shroud 338 are altered by
adjusting the temperature and/or the flow rate of the cooling
airflow between the shroud 338 and the tips of the turbine blades
334. Such temperature adjustment is done by the controller 324,
where the temperature of the shroud 338 is measured by a shroud
temperature sensor 344.
[0038] According to the current invention, controlling the
steady-flow engine performance includes changing at least one of
the combustion process physical parameters such as time-averaged
cooling air temperature level and/or temperature distribution
cooling air flow rate and ignitor performance (energy delivered or
location) controlling the steady-flow engine performance requires
at least one actuator altering at least one combustion parameter
such as an air flow rate (primary, secondary or cooling), the fuel
concentration distribution in space and time, water vapor
concentration distribution in space and time, ignition timing,
ignition energy delivery rate, energy delivery duration, fuel
composition and fuel temperature.
[0039] According to the current aspect, controlling the steady-flow
engine performance includes least one actuator altering at least
one combustion parameter such as primary or secondary or cooling
air flow rate, fuel concentration distribution in space and time,
water vapor concentration distribution in space and time, ignition
characteristics that include ignition energy delivery rate and
energy delivery duration, fuel composition and fuel
temperature.
[0040] According to another aspect of the invention, when the
engine is a steady flow engine, engine durability is enhanced by
adjusting a fraction of inlet air flow used for primary zone
combustion, secondary air combustion and liner cooling in the
response to commands from an engine control unit.
[0041] The present invention has now been described in accordance
with several exemplary embodiments, which are intended to be
illustrative in all aspects, rather than restrictive. Thus, the
present invention is capable of many variations in detailed
implementation, which may be derived from the description contained
herein by a person of ordinary skill in the art.
[0042] All such variations are considered to be within the scope
and spirit of the present invention as defined by the following
claims and their legal equivalents.
* * * * *