united states patent (lo) patent no.: us 7,966,801 b2 uuuu ui iiui iiui mu uui iuu lull uui imi umi...
TRANSCRIPT
mu uuuu ui iiui iiui mu uui iuu lull uui imi umi uu uii mi
(12) United States PatentUmeh et al.
(54) APPARATUS AND METHOD FOR GASTURBINE ACTIVE COMBUSTION CONTROLSYSTEM
(75) Inventors: Chukwueloka Umeh, Schenectady, NY(US); Leonardo C. Kammer,Niskayuna, NY (US); Minesh Shah,Clifton Park, NY (US); Jeffrey B.Fortin, Niskayuna, NY (US); AaronKnobloch, Mechanicville, NY (US);William J. Myers, West Chester, OH(US); Alfred Albert Mancini,Cincinnati, OH (US)
(73) Assignee: General Electric Company, Niskayuna,NY (US)
(*) Notice: Subject to any disclaimer, the term of thispatent is extended or adjusted under 35U.S.C. 154(b) by 1170 days.
(21) Appl. No.: 11/567,950
(22) Filed: Dec. 7, 2006
(65) Prior Publication Data
US 2008/0134684 Al Jun. 12, 2008
(51) Int. Cl.F02C 9100 (2006.01)
(52) U.S. Cl . ....................................... 60/39.281; 60/776(58) Field of Classification Search ............... 60/39.091,
60/39.281, 39.24, 772, 776; 701/100; 431/114See application file for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS2,766,583 A * 10/1956 Schirmer ................... 60/39.2814,508,127 A * 4/1985 Thurston ........................... 137/8
(lo) Patent No.: US 7,966,801 B2(45) Date of Patent: Jun. 28, 2011
5,349,811 A * 9/1994 Stickler et al ................... 60/776
5,428,951 A * 7/1995 Wilson et al . ................... 60/776
5,544,478 A * 8/1996 Shu et al . ........................ 60/7735,581,995 A * 12/1996 Lucenko et al . ................ 60/779
5,665,916 A * 9/1997 Puster et al . .................... 73/590
5,706,643 A * 1/1998 Snyder et al . ................... 60/776
5,755,090 A * 5/1998 Hu ............................. 60/39.091
5,791,889 A * 8/1998 Gemmen et al ................... 431/1
5,932,940 A * 8/1999 Epstein et al. .......... 310/40 MM
6,336,806 131* 1/2002 Paschereit et al ................. 431/1
6,530,228 132 * 3/2003 Wilson et al . ................... 60/776
6,601,393 132 * 8/2003 Wilson et al . ................... 60/776
2005/0056024 Al* 3/2005 Lieuwen et al . ................ 60/7792005/0058958 Al* 3/2005 Kobayashi et al . ............. 431/102005/0274116 Al* 12/2005 Thornton et al . ............... 60/7762005/0278108 Al* 12/2005 Norman et al . ............... 701/100
* cited by examiner
Primary Examiner Michael CuffAssistant Examiner Phutthiwat Wongwian(74) Attorney, Agent, or Firm Richard A. DeCristofare
(57) ABSTRACT
An Active Combustion Control System and method providesfor monitoring combustor pressure and modulating fuel to agas turbine combustor to prevent combustion dynamics and/or flame extinguishments. The system includes an actuator,wherein the actuator periodically injects pulsed fuel into thecombustor. The apparatus also includes a sensor connected tothe combustion chamber down stream from an inlet, wherethe sensor generates a signal detecting the pressure oscilla-tions in the combustor. The apparatus controls the actuator inresponse to the sensor. The apparatus prompts the actuator toperiodically inject pulsed fuel into the combustor at a prede-termined sympathetic frequency and magnitude, thereby con-trolling the amplitude of the pressure oscillations in the com-bustor by modulating the natural oscillations.
6 Claims, 12 Drawing Sheets
Controller P'comb 30
Puuel164 f
306 308 301162
Fuel Flow
FuelFuel actuator
Pilotinjector Flow
pump fuel line
• Pfuel — Fuel static pressure• Fcomb — dynamic pressure sensor
CombustorFuel
premixer
https://ntrs.nasa.gov/search.jsp?R=20110013145 2018-07-02T07:07:47+00:00Z
c0 4-jF-- VI C)V) 0= C 0 -E0-0 cn u
E Ln0—
-0ul)10
":^V
"4U 0
u- v0 N 0 U vi
LL L
O
0ca 14C14C
un 0d-+
V)
j< -0
s_- LO CV)CU 0
—CN L)
C_j
>
>
v
CO
cu>ca
Uj
:3 O
L7CLJ
cu
cuF= E
mCDC14 -0
4,O-FO0 co
CL uCN
O
O
O
mO
-0
OCN
0u- 0 0
u-
Cl-
0CN
4^
0 o--4 06=0
0
Ln
2
Ln C0L)
U.S. Patent Jun. 28,2011 Sheet I of 12
US 7,966,801 B2
0Ln4-
cnLL r-s CO
L- —
CL
C:)ca
ai "aJ 4 :3" aj VI4-LA :^i vca- X
u— ::D U-i
C)CN
coM
N
VLL-
U.S. Patent Jun. 28, 2011 Sheet 2 of 12 US 7,966,801 B2
U.S. Patent
Jun. 28, 2011 Sheet 3 of 12 US 7,966,801 B2
Mv
g
I..f^
M
v
^i EvL
U.S. Patent Jun. 28, 2011 Sheet 4 of 12 US 7,966,801 B2
i_l_
0 E-0 =QJ Ln
" G
-0
00
to
0
Hu—
4 -1(L)
Li
ca Eu- v cu
(U= 14--
V) 0CD -Fla
C:),—/—cc V)vi
=
.2=
.2)
cuc
EE 4-
ucu
CZLn
VlLIJ
< ECU U
CIDCl
a_ 0LO C
E :n>, 0- V V)Ln
41 CZ Ln EV)
V) E< 0
<
O C Ln.2 2vl
E V) V)cu
(u < E0IL u
LO
0
0Ln -0
0 E co41 Co 0vi2 V)
E
-0
4-ca
0
U.S. Patent
Jun. 28,2011 Sheet 5 of 12 US 7,966,801 B2
CU C)CZ
CC) -1-1 L-LA 0 = 0
CL
CID =3
E H<
E Evu- 2) E cv
.
0 0 -P n4^ H CL CrQJ C)V)
LL.
Ln0Ln
C;)LnV)
LO
> x0
V)
NC14
0CN
w CL0 >-co
Clio OaCN0 V
(N
0-
a_
4-j-2
V)(Li
Oc
CL
V)
CLCL:5u-J
LIJ
C-A
cuV)0M-0co ct
w E
L-L- V)c0V)O
E0VV)0-
9
U.S. Patent Jun. 28,2011 Sheet 6 of 12 US 7,966,801 B2
O
06 CNCN 7;pz Fl-u- cl- —
0
0 2-14^
o6 CUL. c0Z LZ
N cl-LL a_ 0
Li-4-
a- U Z cQ 2i -u u
CL0
LL
QJ
O
QJ
LO
LIJcl-
U.S. Patent
Jun.28,2011 Sheet 7 of 12 US 7,966,801 B2
C)LO
(N (NZu- 06
Cl 0 O
V4-
a-rz ZtL LL 0z 2Li-
41
CL cu=
0-1
u-
mV
O
QJ
4
Ln00
o EN41
Ln
c0
E0V
C'4
U-1a-
In0LO
—
cn
LnCN
uqGJ Qj LO4^1
XC)
C)CN
Q0ca
F-0 CL0 >-
cliO
00 CN0CN
(14
COcuc0
(.0
Cl- 67
Cl-
O
a.j>
-^6
>
C14
(.0V)V)
z 75;Lij
CL LLJ
U >
CD C:)^* CN
U.S. Patent
u00
6u-
Jun. 28,2011 Sheet 8 of 12 US 7,966,801 B2
M LO i-- mr-, Ln 1- 0 CO(0 u) m Ln 0
Ld CN 00 0000 CO r^ Ln LO
CD LO
N CO MC6 I'- LO
LO't
LOd- cLnLn LO a) a) LO
Cu-
OCO
E EE=5Ln
0LO
00LOLO
O
NC l
L..)
CN
0 [&C)C:*In Ln
Ln
OOC-0
LOOO ul^ V
E
"M
10 10 LO
CN — —
PHI A:)uDnb;)jj
0 LO 0 LOI
[!sd] DinssDAd
LOCSC NJ- CN 0 N
00 [!sd] Dinss;)Jd
00
dLL-
10
20
--30
-40
-50)0
COaL—j 600500400300200100
0
-10
5
0V)V)
-5
10 00
U.S. Patent Jun. 28,2011 Sheet 9 of 12 US 7,966,801 B2
FIG. 9 AKulite Dynamic Pressure
Time Is]
FIG. 9B
Time [s] - Pressure [psi]— ValveOut M
FIG. 9Czuu -100-
0-0 20 40 60 80 100
Time [s]
10-1
a^
^ 10-2c^.
U.S. Patent Jun. 28, 2011 Sheet 10 of 12 US 7,966,801 B2
F1619 D
0 100 200 300 400 500 600 700 800Frequency [Hz]
no forcing....•...I...130 Hz forcing
no forcing
FIG. 9E
• FFT at: 26-27s; 67-68s; 94-95s• Square wave forcing @a 1 Hz, 130 Hz, 140 Hz:• Frequency shifts from — 570Hz to —130Hz.Induced low freq persists after forcing stoppedand higher freq started growing.Conditions0 P3 = 190 psig; T3 = 704°F; FAR 0.029
10'
V)
R- 10-v
v
10'
U.S. Patent Jun. 28, 2011 Sheet 11 of 12 US 7,966,801 B2
FIG. 70A
15
10
5
0
-5
-10
-15
Pressure [psi]
0 20 40 60 80 100Time [s]
FIG. 10B1/n n A n r.. 9 4 -1
0 100 200 300 400 500 600 700
Frequency [Hz]
130 140 154 150 170 180 190
U.S. Patent Jun. 28, 2011 Sheet 12 of 12 US 7,966,801 B2
FIG. 10C
10-1
CL
tU
LnZn 1Q-2
CL
Frequency [Hz]
— _ KP 34-35s -11 01........ KP 61-62s -11 c2— Valve -11 c3
Square wave forcing ^7a 143 Hz
P3 = 190 prigT3 = 698 °F
US 7,966,801 B21
APPARATUS AND METHOD FOR GASTURBINE ACTIVE COMBUSTION CONTROL
SYSTEM
STATEMENT REGARDING FEDERALLYSPONSORED RESEARCH & DEVELOPMENT
This invention was developed with U.S. Government sup-port under U.S. Government Contract No. NAS 3-01135awarded by the National Aeronautics and Space Administra-tion (NASA) and is subject to the provisions of Section 305 ofthe National Aeronautics and Space Act of 1958 (42 U.S. C.2457). The U.S. Government may have certain rights in thisinvention.
BACKGROUND OF THE INVENTION
1. Field of the InventionThe present invention relates to controlling combustion in
a combustion chamber or combustor.2. Description of the Related ArtAir pollution concerns worldwide have led to stricter emis-
sions standards both domestically and internationally. Air-craft emissions are governed by both Environmental Protec-tion Agency (EPA) and International Civil AviationOrganization (ICAO) standards. These standards regulate theemission of oxides of nitrogen (NOx), unburned hydrocar-bons (UHC), and carbon monoxide (CO) from aircraft in thevicinity of airports, where they contribute to urban photo-chemical smog problems. Many aircraft engines are able tomeet current emission standards using combustor technolo-gies and theories proven over the past 50 years of enginedevelopment. However, stricter engine emissions standardswill not be within the capability of current combustor tech-nologies.
In general, engine emissions fall into two classes: thoseemissions formed because of high flame temperatures (NOx),and those emissions formed because of low flame tempera-tures which do not allow the fuel-air reaction to proceed tocompletion (UHC & CO).
A small window exists where both pollutants are mini-mized. For this window to be effective, however, the reactantsmust be well mixed, so that burning occurs evenly across themixture without hot spots, where NOx is produced, or coldspots, when CO and UHC are produced. Hot spots are pro-duced where the mixture of fuel and air is near a specific ratiowhen all fuel and air react (i.e. no unburned fuel or air ispresent in the products). This mixture is called stoichiomet-ric. Cold spots can occur if either excess air is present (calledlean combustion), or if excess fuel is present (called richcombustion).
Modern gas turbine combustors consist of between 1 and30 or more mixers, whichmix high velocity air with a fine fuelspray. These mixers usually consist of a single fuel injectorlocated at a center of a swirler for swirling the incoming air toenhance flame stabilization and mixing. Both the fuel injectorand mixer are located on a combustor dome plate or cap.
In general, the fuel to air ratio in the mixer is rich. Since theoverall combustor fuel-air ratio of gas turbine combustors islean, additional air is added through discrete dilution holesprior to exiting the combustor. Poor mixing and hot spots canoccur both at the dome, where the injected fuel must vaporizeand mix prior to burning, and in the vicinity of the dilutionholes, where air is added to the rich dome mixture. In addi-tion, many propulsion systems, such as those used in varioustactical missile systems, involve an enclosed combustor.
2Combustion instabilities are commonly encountered in
low emissions gas turbine engines. Combustion dynamics inthe form of fluctuations in pressure, heat-release rate, andother perturbations in flow may lead to problems such as
5 structural vibration, excessive heat transfer to a chamber, andconsequently lead to failure of the system. There are two basicmethods for controlling combustion dynamics in a combus-tion system: passive control and active control. As the namesuggests, passive control refers to a system that incorporates
l0 certain design features and characteristics to reduce dynamicpressure oscillations. Active control, on the other hand, incor-porates a sensor or sensors to detect dynamics (e.g., pressuresensor to detect pressure fluctuations) and to provide a feed-
15 back signal which, when suitably processed by a controller,provides an input signal to a control device. The controldevice in turn operates to reduce the combustion instabilities.
The combustion characteristics of an enclosed combustor,including flammability limits, instability, and efficiency are
20 closely related to the interaction between shear flow dynam-ics of the fuel and air flow at the inlet and acoustic modes ofthe combustor. Strong interaction, between the acousticmodes of the combustor and the airflow dynamics may lead tohighly unstable combustion. Specifically, unstable combus-
25 tion may occur when the acoustic modes of the combustormatch the instability modes of the airflow. For such condi-tions, the shedding of the airflow vortices upstream of thecombustor tends to excite acoustic resonances in the combus-tion chamber, which subsequently cause the shedding of
30 more coherent energetic vortices at the resonant frequency.The continued presence of such vortices provides a substan-tial contribution to the instability of the combustion process.
In a jet of fluid that exits from a conduit to a surroundingmedium of another fluid, sudden increase of the mass-flow
35 leads to formation of well-defined vortices that dominate theboundary between the jet fluid and the surrounding fluid.Because these vortices help transport chunks of fluid over alarge distance, the rate of turbulent mixing between the twofluids is closely linked to the dynamics of these vortices. One
40 way to manipulate the dynamics of vortices is to modulateperiodically the instantaneous mass-flux of the jet.
In combustion devices, actuators can be used to enhancecombustion performance such as efficiency improvement,pollutant reduction, flammability extension, and instability
45 suppression. Combustion apparatuses, which use actuatorshave been disclosed. One such disclosure includes severalactive control devices, including loudspeakers to modify thepressure field of the system or to obtain gaseous fuel flowmodulations, pulsed gas jets aligned across a rearward facing
50 step, adjustable inlets for time-variant change of the inlet areaof a combustor, and solenoid-type fuel injectors for controlledunsteady addition of secondary fuel into the main combustionzone.
The periodic shedding of vortices produced in highly55 sheared gas flows has been recognized as a source of substan-
tial acoustic energy for many years. For example, experimen-tal studies have demonstrated that vortex shedding from gasflow restrictors disposed in large, segmented, solid propellantrocket motors couples with the combustion chamber acous-
60 tics to generate substantial acoustic pressures. The maximumacoustic energies are produced when the vortex sheddingfrequency matches one of the acoustic resonances of thecombustor. It has been demonstrated that locating the restric-tors near a velocity antinode generated the maximum acoustic
65 pressures in a solid propellant rocket motor, with a highlysheared flow occurring at the grain transition boundary inboost/sustain type tactical solid propellant rocket motors.
US 7,966,801 B23
Lean running engines tend to have flame extinguishment(also known as Lean Blow Out or LBO) or large pressuredynamics (known as combustion dynamics) inside the com-bustor that can be detrimental to engine operation and longterm reliability. Lean premixed gas turbine combustors areprone to pressure fluctuations called combustion dynamics.Combustion dynamicsis a result of interaction between heatrelease from combusting fuel-air mixture and pressure oscil-lations in the combustion chamber. This phenomenon canresult in expensive damage to combustor and or the gas tur-bine system hardware.
Therefore, there exists a need for a control system forcombustors to operate near LBO boundaries without the riskof crossing the LBO boundary and also to near-simulta-neously reduce combustion dynamics.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with one embodiment of the present inven-tion, an apparatus for active modulation of a flame in a com-bustor having instabilities, is provided. The apparatusincludes an actuator, wherein the at least one actuator peri-odically pulses a fraction of the fuel flow delivered to thecombustor. The apparatus also includes at least one sensorconnected to the combustion chamber, wherein the sensorgenerates a signal in response to instabilities in the combus-tor. Lastly, the apparatus includes means for controlling theactuator in response to the sensor signals. The means forcontrolling prompts the actuator to periodically inject pulsedfuel into the combustor at a predetermined sympathetic fre-quency and magnitude, thereby controlling the amplitude ofthe oscillations in the combustor.
In accordance with another embodiment of the presentinvention, a method for active gas turbine combustion controlof a combustor is provided. The method includes sensing acombustion dynamic signal and determining a sound pressurelevel associated with the combustion dynamic signal. Themethod performs a spectral analysis of the combustiondynamic signal and determines if the sound pressure levelexceeds a predetermined threshold. The method then deter-mines from the spectral analysis a plurality of sympatheticfrequencies associated with the combustion dynamic signaland directs a MEMS actuator to inject pulsed fuel into thecombustor in accordance with the sympathetic frequencies.
The invention is also directed towards an active combus-tion control (ACC) system for near simultaneously balancinglean blow out avoidance, combustor dynamics mitigation,and combustor operability. The ACC includes a combustorpressure sensor and a fuel modulating system for providingfuel to a combustor. The fuel modulation system furtherincludes a MEMS microvalve for providing a predeterminedfraction of the total combustion fuel flow upstream of at leastone corresponding pilot fuel nozzle and at least one fuel flowsensor. The ACC also includes a combustion dynamics con-trol system for receiving input from the combustor pressuresensors and providing combustion dynamics control signalsto the fuel modulating system for modulating fuel to thecombustor at a frequency and amplitude derived from deter-mined sympathetic frequencies to reduce or cancel combus-tion dynamics. The ACC also includes a lean blow out (LBO)control system for receiving input from the combustor pres-sure sensors and providing a LBO control signal to the fuelmodulating system for modulating fuel to the combustor at afrequency and amplitude derived from determined sympa-thetic frequencies to prevent lean blow out.
4BRIEF DESCRIPTION OF THE DRAWINGS
FIG.1 is an illustration of the high level architecture of theActive Combustion Control System utilizing fuel modulation
5 system in accordance with an embodiment of the presentinvention;
FIG. 2 is an illustration of the high level architecture of theActive Combustion Control System in accordance with theinvention shown in FIG. 1;
10 FIG. 3 is an illustration of a combustor and control setup inaccordance with the invention shown in FIG. 1;
FIG. 4 is a cross-sectional view of a combustor used inaccordance with the present invention shown in FIG. 1;
15 FIG. 5 is a flow chart showing the behavior of the activecombustion control system in accordance with the inventionshown in FIG. 1;
FIG. 6 is an illustration of an embodiment of MEMS forindividual fuel nozzle flow trim/control. FIG. 6 includes a
20 pump 306, fuel nozzle control 504, and series of MEMs 202.The system includes forty CPFN valves and twenty MEMsvalves as shown in the FIG. 6. The other elements and sub-elements illustrated in FIG.6 are self explanatory for explain-ing the various embodiments of the invention.
25 FIG. 7 is an illustration of another embodiment of MEMSfor individual fuel nozzle trim/control. FIG. 7 includes apump 306, fuel nozzle control 504, and series of MEMs 202.The system further includes forty CPFN valves and twentyMEMs valves as shown in the FIG. 7. The other elements and
30 sub-elements illustrated in FIG. 7 are self explanatory forexplaining the various embodiments of the invention.
FIGS. 8A-8D presents graphs demonstrating the effects offuel forcing;
35 FIGS. 9A-9E shows a spectrogram of the frequencyresponse of the combustor 30 with no fuel forcing; and
FIGS. 10A-10C shows data without and with fuel forcing.
DETAILED DESCRIPTION OF THE INVENTION
40Referring to FIG. 1, the ACCS employing fuel flow modu-
lation system includes an upstream fuel metering & pressur-ization system 200, a split controller 201 for splitting fuelflow between cyclone valve 202b & pilot valve 202a, includ-
45 ing suitable external inputs 201A, a fuel modulation valve202, Valvevalve control electronics 203, and a fuel flow sen-sor 204. It will be appreciated that the fuel flow sensor 204may be any type of suitable sensor such as a volumetric ormass fuel flow sensor. It will also be appreciated the sensor
5o approaches may include piezoresistive cantilever, coriolis oranemometer approaches. Also shown in FIG. 1 is a combus-tion diagnostic sensor 210. Combustion diagnostic sensor210 may include any suitable sensor such as a combustordynamic pressure sensor, a combustor pressure sensor, a heat
55 release sensor, an emissions sensor, and a Fuel to Air Ratio(F/A) measurement sensor located downstream of nozzlebefore flame. The system shown in FIG. 1 includes an anti-aliasing/signal conditioning device 215, a real time controlplatform 216, and a signal conditioning device 217.
60 The ACCS in FIG. 1 controls fuel flow to a combustor 30.The anti-aliasing/signal conditioning device accounts forsensor linearity, bandwidth, output (V or mA, etc.), and delay.The real time control platform 216 uses algorithms to controlcombustion dynamics, LBO, and emissions and provides an
65 electrical signal to the signal conditioning device 217. Thesignal conditioning device 217 conditions the signal from thereal time control platform 216 accounting for bandwidth,
US 7,966,801 B25
6linearity, amplification, etc. and sends the appropriate volt- sub-frequencies. The control system then sends a commandage/current requirements (not pressure actuated) to the valve to the fuel modulator system enabling that system to inject acontrol electronics 203. fraction of the total combustion fuel flow upstream of the fuel
Referring also to FIG. 2, the Active Combustion Control
nozzle at a predetermined frequency and amplitude. This isSystem works by detecting lean blowout precursors and com- 5 known as fuel forcing.bustion dynamics within the combustion chamber 30 through
The modulated frequency coincides with either the peak or
pressure measurements from a combustion diagnostic sensor adjacent valley of one of the sympathetic frequencies. The210 such as a pressure sensor. In response to pressure oscil- fuel modulation at the lower frequency adds energy at thelations typical of the onset of LBO or unacceptable combus- lower frequency with the result of shifting the main combus-tion dynamics, amplitude and frequency modulations of fuel io for frequency towards the lower frequency. The net result isflow through nozzle (FIG. 3, item 162) is made in accordance the cancellation or at the minimum, a reduction in the soundwith the teachings herein to prevent LBO or combustion pressure level of the observed combustion dynamics. Fueldynamics. The modulation of the fuel flow is made by a fuel
forcing is maintained, with changes made to the frequency
modulation valve 202 on the pilot circuit of the nozzle. Fuel
and amplitude until the undesirable engine dynamics are can-modulation valve 202 may include Micro-Electro-Mechani- 15 celed, or until an acceptable pre-determined minimumcal Systems (MEMS)-based microvalves or macroscale
dynamics level is attained.
valves. Flow rate modulations are measured with a down- Referring to FIG. 2, there is shown an illustration of thestream fuel flow sensor 204 and high temperature flow sensor
high level architecture of the Active Combustion Control
readout electronics 203a in order to determine a signal within
System in accordance with the invention shown in FIG. 1; Inthe high temperature environment. The control system simul- 20 particular embodiments, the LBO controller 15 adjusts pilot/taneously balances lean blow out avoidance, combustor cyclone split via a MEMS valve 202 (refer to FIG. 3) or bulkdynamics mitigation and combustor operability. fuel flow. The dynamics mitigation controller 16 modulates
The fuel modulation valve 202 and the flow sensor 204 are
MEMS valve 202 to introduce Fuel/Air (F/A) ratio (hencelocated in the nozzle assembly while the diagnostic combus- heat release) perturbation to mitigate dynamics. The LBOtion sensor 210 is in the combustor 30. In a particular embodi- 25 precursor detection 13 employs signal processing and datament, the fuel modulation valve 202 is able to actuate at a 1
fusion algorithms.
kHz frequency at an elevated temperature and is able to
Referring to FIG. 3, there is shown a pictorial diagram ofmodulate a significant portion of the pilot flow. The flow one embodiment of the present invention. Fuel pump 306sensor 204 has a bandwidth capable of detecting the flow provides fuel through fuel flow device 308 to fuel actuatormodulations of the fuel modulation valve 202. The flow sen- so 301. Static pressure device 308A measures the static pressuresor readout electronics 203a associated with the flow sensor of the fuel prior to the fuel entering fuel actuator 301 and pilot204 are capable of measurements at elevated temperatures of
injector fuel line 162. A controller 304 controls fuel actuator
about 200 C. so that it can be co-located with the flow sensor
301 and also receives data from dynamic pressure sensor204. In a particular embodiment, the combustion diagnostic
308B. The fuel actuator 301 is able to control the frequencysensor 210 has a bandwidth greater than 1 kHz in order to 35 and amplitude of the fuel in the pilot injector fuel line 162.detect combustion instabilities in the combustor 30 while
Pilot injector fuel line 162 is connected to combustor 30.
having the capability to sustain reliable operation in a harsh
FIG. 4 is a cross-sectional view of a combustor 30 for useenvironment. Using the combustion diagnostic sensor 210
with a gas turbine engine. In one embodiment, the gas turbine
response along with control algorithms, the fuel modulation engine is a GE F414 engine available from General Electricvalve 202 will modulate the flow into the combustor 30. 40 Company, Cincinnati, Ohio. This example is illustrative, and
The ACCS with fuel modulation system enables lower the invention is not limited to specific engine models or com-emission engines with less instability. It uses valve 202 that
bustor designs. In the illustrated example, combustor 30
can operate at higher temperatures and at higher frequencies
includes an annular outer liner 40, an annular inner liner 42,than conventional valves. The ACCS with fuel modulation and a domed inlet end 44 extending between outer and innersystem puts the small size flow sensor 204 in the system so 45 liners 40 and 42, respectively. Domed inlet end 44 has a shapethat the flow pulsations and split levels can be monitored. of a low area ratio diffuser.
Referring to FIG. 2, there is shown a high level control
Outer liner 40 and inner liner 42 are spaced radially inwardarchitecture of the Active Combustion Control System
from a combustor casing 46 and define a combustion chamber
(ACCS) in accordance with an embodiment of the present
48. Combustor casing 46 is generally annular and extendsinvention. TheACCS includes an engine controller 10, engine 5o downstream from an exit 50 of a compressor, such-as com-control sensors 11, combustion pressure dynamic sensors 12, pressor 14 shown in FIG. 4. Combustion chamber 48 is gen-a LBO Precursor Detection 13, a LBO Threshold Comparator erally annular in shape and is disposed radially inward from14, a LBO Controller 15, a Dynamics Mitigation Controller
liners 40 and 42. Outer liner 40 and combustor casing 46
16 and a Fuel Control System 17. define an outer passageway 52 and inner liner 42 and com-In FIG. 2, the ACCS controls an Engine 18 and Combustor 55 bustor casing 46 define an inner passageway 54. Outer and
30 (See FIG. 1). The engine controller 10 modulates engine
inner liners 40 and 42, respectively, extend to a turbine inletactuators (guide vanes, variable stator vanes, etc.) to achieve nozzle 58 disposed downstream from diffuser 48.required performance while protecting engine against various
A trapped vortex cavity 70 is incorporated into a portion 72
constraints. The engine controller 10 also adjusts bulk fuel
of outer liner 40 immediately downstream of dome inlet endflow to meet engine performance requirements and pilot/ 60 44. Trapped vortex cavity 70 has a rectangular cross-sectionalcyclone fuel split for emissions. profile and because trapped vortex cavity 70 opens into com-
One embodiment of the control system performs a real
bustion chamber 48, cavity 70 only includes an aft wall 74, antime spectral analysis of the dynamic pressure signal 12 from upstream wall 76, and an outer wall 78 extending between aftthe combustor pressure sensor to determine the main pressure wall 74 and upstream wall 76. In an alternative embodiment,frequency in the combustor 30, along with two minor sub- 65 trapped vortex cavity 70 has a non-rectangular cross-sec-frequencies known as sympathetic frequencies (see FIGS. tional profile. In a further alternative embodiment, trapped8-10). In general, the main frequency is the sum of the two vortex cavity 70 includes rounded comers. Outer wall 78 is
US 7,966,801 B27
substantially parallel to outer liner 40 and is radially outwarda distance 80 from outer liner 40. A corner bracket 82 extendsbetween trapped vortex cavity aft wall 74 and combustorouter liner 40 and secures aft wall 74 to outer liner 40.Trapped vortex cavity upstream wall 76, aft wall 74, and outerwall 78 each include a plurality of passages (not shown) andopenings (not shown) to permit air to enter trapped vortexcavity 70.
Trapped vortex cavity upstream wall 76 also includes anopening 86 sized to receive a fuel injector assembly 90. Fuelinjector assembly 90 extends radially inward through com-bustor casing 46 upstream from a combustion chamberupstream wall 92 defining combustion chamber 48. Combus-tion chamber upstream wall 92 extends between combustorinner liner 42 and trapped vortex cavity upstream wall 76 andincludes an opening 94. Combustion chamber upstream wall92 is substantially co-planar with trapped vortex cavityupstream wall 76, and substantially perpendicular to combus-tor inner liner 42.
Combustor upstream wall opening 94 is sized to receive amixer assembly 96. Mixer assembly 96 is attached to com-bustion chamber up stream wall 92 such that a mixer assemblyaxis of symmetry 98 is substantially co-axial with an axis ofsymmetry 99 for combustion chamber 48. Mixer assembly 96is generally cylindrical-shaped with an annular cross-sec-tional profile (not shown) and includes an outer wall 100 thatincludes an upstream portion 102 and a downstream portion104.
Mixer assembly outer wall upstream portion 102 is sub-stantially cylindrical and has a diameter 106 sized to receivefuel injector assembly 90. Mixer assembly outer wall down-stream portion 104 extends from upstream portion 102 tocombustor upstream wall opening 94 and converges towardsmixer assembly axis of symmetry 98. Accordingly, a diameter110 of upstream wall opening 94 is less than upstream portiondiameter 106.
Mixer assembly 96 also includes a swirler 112 extendingcircumferentially within mixer assembly 96. Swirler 112includes an intake side 114 and an outlet side 116. Swirler 112is positioned adjacent an inner surface 118 of mixer assemblyouter wall upstream portion 102 such that swirler intake side114 is substantially co-planar with a leading edge '120 ofmixer assembly outer wall upstream portion 102. Swirler 112has an inner diameter 122 sized to receive fuel injector assem-bly 90. In one embodiment, swirlers 112 are single axialswirlers. In an alternative embodiment, swirlers 112 are radialswirlers.
Fuel injector assembly 90 extends radially inward intocombustor 16 through an opening 130 in combustor casing46. Fuel injector assembly 90 is positioned between domedinlet end 44 and mixer assembly 96 and includes a pilot fuelinjector 140 and a main fuel injector 142. Main fuel injector142 is radially inward from pilot fuel injector 140 and ispositioned within mixer assembly 96 such that a main fuelinjector axis of symmetry 144 is substantially co-axial withmixer assembly axis of symmetry 98. Specifically, main fuelinjector 142 is positioned such that an intake side 146 of mainfuel injector 142 is upstream from mixer assembly 96 and atrailing end 148 of main fuel injector 142 extends throughmixer assembly 96 radially inward from swirler 112 andtowards combustor upstream wall opening 94. Accordingly,main fuel injector 142 has a diameter 150 that is slightly lessthan swirler inner diameter 122.
Pilot fuel injector 140 is radially outward from main fuelinjector 142 and is positioned upstream from trapped vortexcavity upstream wall opening 86. Specifically, pilot fuel
8injector 140 is positioned such that a trailing end 154 of pilotfuel injector 140 is in close proximity to opening 86.
A fuel delivery system 160 supplies fuel to combustor 30and includes a pilot fuel circuit 162 and a main fuel circuit 164
5 to control nitrous oxide emissions generated within combus-tor 30. Pilot fuel circuit 162 supplies fuel to trapped vortexcavity 70 through fuel injector assembly 90 and main fuelcircuit 164 supplies fuel to mixer assembly 96 through fuelinjector assembly 90. During operation, as gas turbine engine
10 10 is started and operated at idle operating conditions, fueland air are supplied to combustor 30. During gas turbine idleoperating conditions, combustor 30 uses only the pilot fuelstage for operating. Pilot fuel circuit 162 injects fuel to com-
15 bustor trapped vortex cavity 70 through pilot fuel injector140. Simultaneously, airflow enters trapped vortex cavity 70through aft, upstream, and outer wall air passages and entersmixer assembly 96 through swirlers 112. The trapped vortexcavity air passages form a collective sheet of air that mixes
20 rapidly with the fuel injected and prevents the fuel fromforming a boundary layer along aft wall 74, upstream wall 76,or outer wall 78.
Combustion gases 180 generated within trapped vortexcavity 70 swirl in a counter-clockwise motion and provide a
25 continuous ignition and stabilization source for the fuel/airmixture entering combustion chamber 48. Airflow 182 enter-ing combustion chamber 48 through mixer assembly swirler112 increases a rate of fuel/air mixing to enable substantiallynear-stoichiometric flame-zones (not shown) to propagate
30 with short residence times within combustion chamber 48.Referring to FIG. 5, there is shown a flow chart showing the
behavior of the active combustion control system in accor-dance with the invention shown in FIG. 1. Sensors within orlocated substantially near combustor (FIG. 4, item 30) deter-
35 mine combustor sound pressure level magnitude associatedwith a combustion dynamic signal 1101.
A threshold comparator (FIG. 2. item 14A) determines1102 if the magnitude is below a predetermined threshold. Ifthe threshold comparator (FIG. 2. item 14A) determines the
40 magnitude is below the predetermined threshold, control ispassed back to the sensors for determining the combustordynamic signal 1101.
If the threshold comparator (FIG. 2. item 14A) determinesthe magnitude is above the predetermined threshold control is
45 passed to a spectral analysis module co-located within thelean-blow-out detector (FIG. 2, item 13A) for performing1103 a spectral analysis of the combustor dynamic signal.
In addition an acoustic analysis module co-located withinthe lean-blow-out precursor detector (FIG. 2, item 13B) also
50 performs 1104 an acoustic analysis of the combustor dynamicsignal.
The lean-blow-out (LBO) precursor detector (FIG. 2, item15) determines 1105 sympathetic frequencies associated witha dominant instability frequency of the combustor dynamic
55 signal. It will be appreciated that the sympathetic frequenciesare generally much lower frequency than the dominant insta-bility frequency.
LBO controller (FIG. 2, item 15) determines 1107 an opti-mum fuel forcing frequency and magnitude based upon the
60 sympathetic frequencies. LBO controller then sends 1108command signals to MEMS fuel actuator (FIG. 1, item 202)to force fuel input to the combustor (FIG. 4, item 30) pilotinput port (FIG. 4, item 162) at the determined optimum fuelforcing frequency and magnitude.
65 Experimental ResultsReferring also to FIG. 3 there is shown a depiction of a test
setup with a swirl stabilized combustor 30, a premixing fuel
US 7,966,801 B29
injector 308, a high-speed fuel actuator 301 and a controller304. This setup is representative of that used on the tunableacoustic test rig (TCA) tests.
FIGS. 8A-8E show data from the TCA single nozzle test rig(e.g., FIG. 3) operating with a twin annular premixing swirler(TAPS) premixing fuel injector. The tests were run with liquidJet-A fuel.
FIGS. 9A-9E shows a spectrogram of the frequencyresponse of the combustor 30 with no fuel forcing. Shifts inthe dominant frequencies that show up on the spectrogram aredue to the changing length of the combustor section. Analysisof unforced TCA rig data shows fundamental, its harmonics(in red) and various sums and differences (in green) of thesefrequencies
FIGS. 10A-10C shows data without and with fuel forcing.KP represents dynamic pressure signals, while valve showsthe fuel actuator frequency command. A reduction in pressurefluctuation amplitude is shown from about 45 s when the fuelis actuated with a square wave at 143 Hz. This suppression isshown in the time domain from 45-75 s, after which the signalstrength begins to build up again after the fuel forcingstopped.
This written description uses examples to disclose theinvention, including the best mode, and also to enable anyperson skilled in the art to make and use the invention. Thepatentable scope of the invention is defined by the claims, andmay include other examples that occur to those skilled in theart. Such other examples are intended to be within the scopeof the claims if they have structural elements that do not differfrom the literal language of the claims, or if they includeequivalent structural elements with insubstantial differencesfrom the literal languages of the claims.
What is claimed is:1. An active combustion control system (ACCS) compris-
ing:a combustor pressure sensor for measuring a dynamic pres-
sure within a combustor;a Micro-Electro-Mechanical System (MEMS) microvalve
adapted to modulate fuel flow into the combustor;a fuel flow sensor downstream of the microvalve and hav-
ing a bandwidth capable of detecting modulations of thefuel flow of the MEMS microvalve; and
a control system performing a real time spectral analysis ofthe dynamic pressure measured by the combustor pres-sure sensor and determining a main pressure frequencyand at least one sympathetic frequency in the combustor,
10wherein the control system sends a signal to the MEMS
microvalve to modulate fuel flow into the combustor at afrequency coinciding with the main pressure frequencyor the at least one sympathetic frequency in response to
5 pressure oscillations indicative of an onset of lean blowout (LBO) or unacceptable combustion dynamics withinthe combustor.
2. The ACCS as in claim 1 wherein the fuel flow sensorcomprises a Micro-Electro-Mechanical System (MEMS)
io fuel flow sensor.3. The ACCS as in claim 1 wherein the fuel flow sensor
comprises a mass flow rate fuel flow sensor.4. The ACCS as in claim 1 wherein the fuel flow sensor
comprises a volumetric flow rate sensor.15 5. The ACCS as in claim 1 further comprising an engine
controller for determining flow rate from fuel flow sensor andadjusting a bulk fuel flow to meet predetermined engine per-formance requirements.
6. An apparatus for active control modulation of a flame in20 a combustor having instabilities, wherein the instabilities
cause natural oscillation, the apparatus comprising:at least one actuator, wherein the at least one actuator
periodically injects pulsed fuel into the combustor;a sensor connected to the combustion chamber down
25 stream from an inlet, wherein the sensor generates asignal based on the pressure oscillations in the combus-tor;
a Micro-Electro-Mechanical System (MEMS) microvalveadapted to modulate fuel flow into the combustor;
30 a fuel flow sensor downstream of the microvalve and hav-ing a bandwidth capable of detecting modulations of thefuel flow of the MEMS microvalve; and
a control system coupled to the at least one loop actuatorand responsive to the sensor, the control system per-
35 forming a real time spectral analysis of the dynamicpressure measured by the combustor pressure sensor anddetermining a main pressure frequency and at least onesympathetic frequency in the combustor,
wherein the control system prompts the at least one actua-40 for to periodically inject pulsed fuel into the combustor
at the at least one sympathetic frequency and magnitude,and wherein the control system controls the amplitude ofthe pressure oscillations in the combustor by modulatingthe natural oscillations.
45