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Fundamental Mechanisms, Predictive Modeling,
and Novel Aerospace Applications of Plasma
Assisted Combustion
Yiguang Ju
AFOSR MURI Review Meeting
Ohio State University
Nov 9-10, 2011
Princeton Team members:
Wenting Sun, Joe Lefkowitz, Mruthunjaya Uddi, Sang Hee Won
Collaborators
AFRL: Campbell Carter, Timothy Ombrello
International: Fei Qi, Huijun Guo (USTC) 1
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4. TITLE AND SUBTITLE Fundamental Mechanisms, Predictive Modeling, and Novel AerospaceApplications of Plasma Assisted Combustion
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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18
Motivation
Hypersonic propulsion system
2
Hypersonic propulsion system
X-51A
Ignition time (~10ms)
Flow residence time (~1ms)Da= >>1
Challenges:• Ignition time, Ignition energy
• Flame stabilization
• Combustion completion
F135 engine: (F35, 2011)
Mach 6-8
Ignition instability
Plasma assisted combustion
Plasma
Ions/electrons
Excited species
Kinetic enhancement
Fuel fragmentsTemperature
increase
Transport enhancementThermal enhancement
RadicalsH2, CO
CH4
Understanding: Good poor
O, NO
O2(a∆g)
marginal
3
Change of ignition and extinction diagram: the S-curve transition
Residence time
Te
mp
era
ture
Scramjet
Plasma generated species:
O, H, O2(a∆g) …
4
Research goals
Understand the fundamental enhancement
mechanism of plasma-flame chemistry
Develop new experimental tools to validate
plasma flame kinetic mechanism
Develop numerical methods to achieve efficient
modeling of detailed plasma flame chemistry
5
Outline
1. Background
2. Experimental investigations
• Effects of plasma assisted fuel oxidation on
flame extinction
• Effects of in situ plasma discharge on
ignition enhancement
• Molecular beam mass spectrometry study of
low temperature chemistry
3. Conclusion and future work
6
Background and previous study: flame extinction
Air Air
1
2
5
15
16
3
14
N2
H2 &
N2
7
10
11 12
13
8 6
9
Fuel Fuel 4
N2 N2
1. Silicon Controlled Rectifier, 2. Silicon carbide heater, 3. R-typethermocouple, 4. Fuel injection spacer 5. MGA plasma power supply, 5.MGA device, 6. MGA power supply, 7. Cathode, 8. Anode, 9. Magnets,10. Gliding arc initiation wire, 11. MGA, 12. Insulator, 13. Nozzle withN2 co-flow, 14. K-type thermocouple & FT-IR probe, 15. Diffusionflame, 16. Water-cooled nozzle with N2 co-flow.
0
50
100
150
200
250
300
350
19 20 21 22 23 24 25 26
Str
ain
Rate
, 1
/s
Percent Methane Diluted in Nitrogen
Bundy et al.
Puri & Seshadri
No Plasma
33 Watts
44 Watts
60 Watts
78 Watts
0.00E+00
6.00E+15
1.20E+16
1.80E+16
-0.4 -0.2 0 0.2 0.4
Distance Between Nozzles, cm
Nu
mb
er
De
nis
ty o
f O
H0 Watts, a=83.3 1/s
48 Watts, a=183 1/s
78 Watts, a=127.7 1/s
Computation
Only thermal effect!Ombrello, et al, AIAA J, 2006
7
Previous work - Ignition study
NOx
catalytic effect
1. non in situ discharge
2. Short life times of radicals and excites species
CH4/air counterflow diffusion flame
2323 NOOCHNOOCH
NOOCHNOCH 323
H2/air counterflow diffusion flame
22 NOOHNOHO
NOOHNOH 2
Ombrello, et al, IEEE Plasma Sci, 20088
Previous researches – O3
u
bliftedL SS
0.2
0.3
0.4
0.5
0 0.005 0.01 0.015
Mixture fraction gradient dY F /dR
Sli
fted
[m
/s]
0
2
4
6
8
10
12
14
En
ha
nce
men
t [%
]
0 ppm O3 592 ppm O3
1110 ppm O3 1299 ppm O3
1299 ppm O3
1110 ppm O3
592 ppm O3
(~ 1/axial distance)
Flame speed extraction
Ombrello, et al, CNF, 20109
Previous researches – O2(a1∆g)
[O2(a1Δg)], ppm ΔHL, mm
3137 4.76
4470 6.82
4627 6.83
5098 7.31
0
1000
2000
3000
4000
5000
6000
4 5 6 7 8
Change of Flame Liftoff Height, ΔHL [cm]
Co
nce
ntr
ati
on
[p
pm
]
SDO (w/ NO)
SDO (w/o NO)
O3 (w/o NO)
Energy Coupling Into Flow
≈ 1 eV to produce O2(a1Δg)
≈ 5000 ppm O2(a1Δg) 2-3 % Lifted Flame Speed Enhancement
Nozzle Tip
O2 (a1Δg) + H = OH+O fast
O2 + H = OH +O slow
Ombrello, et al, CNF, 201010
Previous researches – Atomic oxygen effect
O quenched even at 60 Torr:
How to utilize radicals efficiently?
discharge
O2/Ar
CH4/Ar
0 5 10 15 20 25 30 35 40 45
0
2
4
6
8
10
12
14
O co
ncen
trat
ion
(10
15 cm
-3)
Pulse repetition frequency (KHz)
Crossover T: 900 K
Sun, et al, PCI, 2010
5000 ppm
1200 ppm
11
Research focus in the second year
Thrust 1. Kinetic effects of non-equilibrium plasma-assisted fuel
oxidation on diffusion flame extinction limits
Thrust 2. Direct ignition and the S-curve transition by in situ nano-
second pulsed discharge
Thrust 3. Plasma flame chemistry study in a flow reactor with
Molecular Beam sampling Mass Spectrum (MBMS)
Thrust 4. Development of a plasma assisted jet stirred reactor with
molecular beam sampling and a high pressure ignition
chamber
12
Thrust 1. Kinetic effects of non-equilibrium plasma-assisted fuel
oxidation on diffusion flame extinction limits
13
Experimental setup
14
FWHM= 12 ns
f = 0~50 kHz
20 & 28 mm ID
15 mm × 22 mm
10 mm
E/N~10-15 Vcm2
10 mm away from exit
Power~1.3 mJ/Pulse
FTIR/GC sampling
(heated)
-40 -20 0 20 40 60 80 100-3000
-1500
0
1500
3000
4500
6000
Vo
lta
ge (
V)
Time (ns)
O2/Ar/He/CH4
The thermocouple was coated with MgO and covered with grounded Nickel-Chrome sheath to remove EMI
OO
ffO
OU
U
L
Ua
1
2
P= 60 Torr
Laser diagnostics schematic
225nm mirrors
Filters
840nm
Collection lens
UV focusing lens
Photodiode
1064nm
225nm mirrors
225.7nm
Nd:Yag SHGTunable
Dye
Laser
BBO
DoublingBBO
Mixing
UV
Separator
Pulser
Boxcar
SRS272
PMT
Flow
direction
15
Numerical model
16
Kinetic model: OSU air
plasma model [1,2] with USC
mech II in addition of
Ar/He/CH4 related reactions.
Physical model: quasi-one
–dimensional flow equation +
steady two-term expansion
Boltzmann equation [1] Species concentrations
from simulation
ReactionsRate Const
(cm3s-1)
Ar(+) + CH4Ar +CH3 (+) + H 6.5×10-10
Ar(+) + CH4Ar +CH2 (+) + H2 1.4×10-10
Ar* + CH4Ar +CH3 + H 5.8×10-10
Ar* + CH4Ar +CH2 +H2 5.8×10-10
He(+) +O2 O(+) + O + He 0.6×10-11T0.5
Ar* + O2Ar+2O 2×10-10
He(+) +O2(a) O(+) + O + He 0.6×10-11T0.5
He+2O He* + O2 1×10-33
He* + CH4 CH + H2 + H+ He 5.6×10-13
Reference:
[1]. A. Bao, Ph.D thesis (2008) OSU [2]. M. Uddi et al, PCI 32(2009) 929 [3]. I.N. Kosarov et al, C&F 156(2009) 221 [4]. A. Hicks et al, JPD, 38(2005) 3812 [5]. D. S.
Stafford et al, JAP, 96(2004) 2451 [6]. M. Tsuji et al, JCP, 94(1991) 277 [7]. A.M. Starik et al, C&F, 157(2010) 313 [8]. I.N. Kosarev et al, C&F 154(2008) 569
Ar/He/O2/CH4
(0.32/0.4/0.26/0.02)
Counterflow nozzle exit
22 mm 10 mmelectrode
discharge
Reactions [1-8]Rate Const
(cm3s-1)
e+ O2 e+2O f(E/N)
e+ O2 e + O + O(D) f(E/N)
e + CH4 CH3 + H + e f(E/N)
e + ArAr* + e f(E/N)
e + ArAr(+) + 2e f(E/N)
e + He He* +e f(E/N)
e + He He(+) + 2e f(E/N)
Ar* + CH4Ar +CH2 +2H 3.3×10-10
Ar* + CH4Ar +CH +H2 + H 5.8×10-10
Exp
erim
enta
l observ
atio
ns o
f dis
cha
rges
f=30 k
Hz
O2 (0
.26
)/Ar(0
.32
)/He
(0.4
)/CH
4 (0.0
2)
Stro
ng
est e
mis
sio
n: A
r*, O*
Em
issio
ns: H
e*, O
H*, H
CO
*, an
d C
H*1
7~ ~ < ~ -~ = ~ .... =--= 9 '-"
w 0 0
~ 0 0
U"l
0
Intensity (a.u) ~ N w ~ U"l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
L- CH (43 1.4 nm) and 0 (431.2 nm)
0 I ?" He (501.6 nm) and 0 (502 nm) 0
0\ 0 0
';==-----He (587.5 nm)
~---.;.....--~ He (667.8 nm)
0\ -.....) 0 0 0 0 0 0 0 0
~ Ar (696.5 nm) 0 Ar (707 nm) and He (706.5 nm)
QO 0 0 0 0
QO 0 0
Ar (727 nm) and He (728.1 om)
§i~~i~~~~~~~~A~r~(7~3~8~.4~n~n~l):a:o:d::O (738.7 om) Ar (750 nm) Ar (772.4 nm) Ar (763.5 nm)
.r (7~5 ~ (777.4 nm) Ar (80r.~ nm) and 0 (801.7 nm)
:.\r (811 .4 nm) Ar (826 nm)
L 0 (844.7 om) 0 (853.4 nm)
Discharge repetition effect on species concentrations
4000 3500 3000 2500 2000 1500 10000.00
0.25
0.50
0.00
0.25
0.50
0.00
0.25
0.50
Wavenumber (cm-1
)
no plasma
2% CH4
Ab
sorb
an
ce f=4 kHz
f=10 kHz
4000 3500 3000 2500 2000 1500 1000
Wavenumber (cm
-1)
f=20 kHz
f=30 kHz
f=40 kHz
FTIR spectrum with different pulse frequency
H2O
CH4
CH4
H2O
CO2
COCH2O
18
Discharge repetition effect on species concentrations
0 5 10 15 20 25 30 35 40 450
4000
8000
12000
16000
20000
Concentration
Oxidization rate
Pulse repetition frequency (kHz)
CH
4 c
on
cen
tra
tio
n (
pp
m)
0
20
40
60
80
100
CH
4 ox
idiz
atio
n r
atio
(%)
0 5 10 15 20 25 30 35 40 45
0
4000
8000
12000
16000
20000
24000
28000
Pulse repetition frequency (kHz)
Co
ncen
tra
tio
n (
pp
m)
CO (exp)
CO2 (exp)
CH2O (exp)
H2O (exp)
H2 (exp)
CO (sim)
CO2 (sim)
H2O (sim)
H2 (sim)
CH2O (sim)
Carbon deficiency: 5%
Relative uncertainties:
<1% for CH4, CO, CO2
5% for H2O and H2
The uncertainty of CH2O measurement is 80 ppm
Under prediction: CO2
Over prediction: CO, H2, H2O
423 K
613 K
743 K
843 K
933 K
19
Reaction path analysis-CH4&H2
CH4
CH3
CH2OCH3O
HCO
CO
CO2
OH, O,
H, e,
Ar(+),
Ar*
98.5%
66%
0.2%
1.4%CH2 CH
1.3%
5.3%
27.3%
1.3%
23.4%
68.6%
5.3%
100%
100%
100%
100%
H2
H2O
98.8%
1.2%
21.6%
OH + H
H + M
Ar* + CH4
M=CH4, CH2O, HO2,
HCO, CH2, CH3
77.4%
e, Ar*
f = 40 kHz
P = 60 Torr
T = 300 to 933 K
20
Reaction path analysis-H&O
H CH4 +Ar*/e/Ar(+) 11.7%
CH3 + O
51%
OH + H2
11.5%
CH2* + H2
10.5%
CO + OH
4.1%
HCO + H2O/O5.6%
O + H2
3.2%
O
O2 + e33.5%
H + O2
33.6%
He(+) + O2
Ar* + O2
20.4%
O2(a1Δg)/O2(b
1Σ) + H 9.7%
2.8%
OH H O2
0.6%54.3% 47.6%
+ CH4, HO2,
CH2O, H2,
HCO
+ CH3, H2,
HCO, CH2,
the reaction rate at 300 K for O(1D) + H2 = H + OH (4.4×1010 /cm3s)is much larger than O + H2 = H + OH (2.6×103 /cm3s).
f = 40 kHz
P = 60 Torr
T = 300 to 933 K
Mechanism was not validated below 700 KLarge uncertainty at low temperature
21
Extinction limit measurement & calculation
0.34 0.35 0.36 0.37 0.38 0.39 0.400
100
200
300
400
500
600
700
simulation (To= 336 K)
simulation (To= 423 K)
simulation (To= 613 K)
Fuel mole fraction
Ex
tin
cti
on
str
ain
ra
te (
1/s
)
no plasma
with plasma (f=4 kHz)
with plasma (f=10 kHz)
0.0 0.2 0.4 0.6 0.8 1.0
150
200
250
300
350
400
450
500
550
40% CH4 was reformed
to CO and H2
E
xti
ncti
on
str
ain
ra
te (
1/s
)Oxidization or reforming ratio
Reference (2% CH4)
Fuel oxidization
Fuel reforming
40% CH4 was oxidized
to CO2 and H
2O
Simulations were performed with experimentally measured boundary conditions.
OH, H concentrations were estimated from simulation by matching O concentrations.
Case 1: fuel was oxidized to CO2 & H2OCase 2: fuel was reformed to CO & H2
Fuel reforming enhancement: fast H2
chemistryFuel oxidization enhancement: extracting chemical enthalpy rapidly
Faster fuel oxidization, larger extinction extension
22
Extinction limit measurement & calculation
10 15 20 25 30 35 40300
400
500
600
700
800
900
1000 Experiments
Simulation
Xf=0.2
Pulse repetition frequency (f)
Ex
tin
cti
on
str
ain
ra
te (
1/s
)
Simulations were performed with experimentally measured boundary conditions.
OH, H concentrations were estimated from simulation by matching O concentrations.
CH4 oxidization ratio (or f) increased, extinction limits increased significantly
The dominant enhancement mechanism is plasma introduced rapid fuel oxidization.
Deviation is due to additional reaction paths, but not significant (10%).
5.3% enhancement from H2
23
Thrust 2. Direct ignition and the S-curve transition by in situ nano-
second pulsed discharge
24
Experimental setup
25
25.4 mm
P = 72 Torrf = 24 kHz
Power ~ 17 W
Laser beam
ICCD images
26
OH* emission ~310 nm30 ms gate
Single shot Single shot
(a) ICCD image, He/O2 (0.6:0.4) and He/CH4 (0.75:0.25), 50 ns gate
(b) ICCD image, He/O2 (0.6:0.4) and He/CH4 (0.86:0.14), 50 ns gate
(c) direct photo of (a), 50 ms exposure time
(d) direct photo of (b), 50 ms exposure time
P = 72 Torr, f = 24 kHz, a = 175 1/s
Classical S-curve
27
Relationship between OH* emission intensity, local maximum temperature and fuel mole fraction, To=650 K, Tf=600 K He/O2 = 0.66:0.34 , P = 72 Torr, f = 24 kHz, a = 400 1/s
hysteresis between ignition and extinction: S curve
Rayleigh Scattering[1,2]
method for T measurement at 532 nm from Nd:YAG laser
[1] R.B. Miles, W.R. Lempert, J.N. Forkey, Meas. Sci. Technol. 2001 [2]J.A. Sutton, J.F. Driscoll, Exp Fluids 2006
S curve transition
28
Relationship between OH* emission intensity, local maximum temperature and fuel mole fraction, P = 72 Torr, f = 24 kHz, a = 400 1/s
He/O2 = 0.45:0.55 He/O2 = 0.38:0.62
ignition and extinction points were pushed to lower fuel concentrations
monotonic ignition and extinction curve (monotonicS curve)
Can the hysteresis be removed ?
Numerical modeling
29
e + O2 reactions Rate (cm3s-1)
e + O2 2O + e f(E/N)
e + O2 O + O(D) + e f(E/N)
e + O2 O2(+) + 2e f(E/N)
e + O2 O2(a) + e f(E/N)
He related reactions Rate (cm3s-1)
He + e He* +e f(E/N)
He + e He(+) + 2e f(E/N)
He* + O2 O2(+) + He + e 1.5×10-11T0.5
He(+) +O2 O(+) + O + He 0.6×10-11T0.5
He* + CH4 CH + H2 + H+ He 5.6×10-13
e + CH4 reactions Rate (cm3s-1)
e + CH4 CH3 + H + e f(E/N)
e + CH4 CH2 + H2 + e f(E/N)
e + CH4 CH4(+) + 2e f(E/N)
Recombination reactions Rate (cm3s-1)
e + O2(+) 2O 5.6×10-6T-0.5
He(+) + e + M He + M 1.4×10-8
e + O2 + M O2(-) + M 4.2×10-27T-1
e + CH4(+) CH3 + H 1.0×10-8
OPPDIF + electron impactKinetic mechanism: USC mech II + OSU air plasma model[1]
Rate constants: Boltzmann equation solver[1, 2]
[1]. A. Bao, Ph.D thesis (2008) OSU [2]. M. Uddi et al, PCI 32(2009) 929
E: electric field, N: particle density
Simulation results
30
XO2 = 0.34, XCH4 = 0.16, P = 72 Torr, f = 24 kHz, a = 400 1/s
no flame, but reaction zone was built up by radicals generated from plasma
e + CH4CH3 + H + e
fuel oxidizer
e + O2O+O(D) + eIn situ discharge, increased T, increased E/N, increased rate const
Path flux analysis
31
O
O2 + e47.7%
He(+) + O2
23.3%O2(a1Δg)/O2(b
1Σ) + He
21.7%
OH H O2
0.2%43.7% 56.1%
O2(+) + e 5.4%
1.9%
other paths
O
OH H27.5%
59.4%
O e
53.6% 37.9%
CH4
CH3
OH: 39.9%
e: 25.2%
O: 12.7%
H: 9.6%
(a)
CH4(+)11.5%
100%
CH3O6.3%
23.1%
CH2O
45.9%
HCO
CO
CO2
C2H6
24.5%
CH2*
14.8%
CH3OH
1.1%7.3%
17.9%
11.5%
82.1%
65.4%
(b)
O
O2 + e47.7%
He(+) + O2
23.3%O2(a1Δg)/O2(b
1Σ) + He
21.7%
OH H O2
0.2%43.7% 56.1%
O2(+) + e 5.4%
1.9%
other paths
Change of branching ratio
Change of the branching ratio at the reaction zone!
S curve transition
Increased productivities of radicals
76% of O production by e and ions from plasma
Radical generation initiated the reaction zone and controlled the transition!!
ReactionsNormalized
branching ratio
H + O2 = O + OH 1
e + O2 = O + O(D) + e 0.48
e + O2 = O + O(+) + e 0.42
e + CH4 = CH3 + H + e 0.22
He(+) + O2 = O + O(+) + He 0.52
e + O2 = 2O + e 0.06
H + O2 + M = HO2 + M 0.2
1.7
32
Thrust 3. Plasma flame chemistry study in a flow reactor with
Molecular Beam sampling Mass Spectrum (MBMS)
33
Characteristic of low T chemistry
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16
600
900
1200
1500
1800
2100
2400
1050 K
Te
mp
era
ture
(K
)
Time (sec)
650 K
j=1, n-heptane/air, 1 atm
ignition
Ignition delay,
H2O2 was stableH2O2 2OH
H2O2: low T chemistry indicator
Difficulties:
Absorption - overlap with H2O
GC – decomposition/low reactivity
Transition from low T
to high T ignitionLow T ignition
34
Molecular Beam Mass Spectrum
pump
Sampling system Time of fly
HeHeHeHe D
D
S
S
1111
S : signal intensity
D : mass discrimination factor
: cross sections
: mole fractions35
Schematic of experiments with MBMS
Molecular beam
Rea
cto
rex
itR
eact
ion
pro
du
cts
0.1-5 atm
Quartznozzle
Skimmer
1st Turbopump
2nd Turbopump
Chargedion separation
Mass analyzer
10-4
Torr10-6
Torr
Molecular beam
Rea
cto
rex
itR
eact
ion
pro
du
cts
0.1-5 atm
Quartznozzle
Skimmer
1st Turbopump
2nd Turbopump
Chargedion separation
Mass analyzer
10-4
Torr10-6
Torr
Laser beam
MBMS analysisFuel
Preheated air
High pressure, high temperature chamber
DBD discharge
MixingJet stirred reactor
Laser beam
MBMS analysisFuel
Preheated air
High pressure, high temperature chamber
DBD discharge
Mixing
Laser beam
MBMS analysisFuel
Preheated air
High pressure, high temperature chamber
DBD discharge
MixingJet stirred reactor
ovenJacket heater
MBMS
14 inch2 inch 36
480 520 560 600 640 680 720 760
0
500
1000
1500
2000
2500
3000
H2O
2 C
on
cen
tra
tio
n (
pp
m)
Temperature (K)
experiments
simulation
DME: 1%
O2: 5%
He: 94%
residence time: 0.2 S
Flow tube experiments
H2O2 measurement
DME: rich low temperature chemistry
Pressure: 1 atm
DME model: Zhao et al., Int. J. Chem. Kinet., (40) 200837
Flow tube experiments
DME: rich low temperature chemistry
Pressure: 1 atm
25 30 35 40 45 50 55 60 65
0
500
1000
1500
2000
2500
3000
3500
6000
6500
7000
7500
8000R
ela
tive
Sig
na
l
m/z
x2
0
60 (CH3OCHO)
46(DME)
45(CH3OCH
2)
(CO2)44
34(H2O
2,34
O2)
32(O2)
30(HCHO)
38
1. Plasma can significantly accelerate the fuel oxidization at low temperature to extend
the extinction limit dramatically.
2. Major kinetic pathways in plasma assisted combustion were identified .
3. A new counterflow burner with in situ discharge was developed. This burner
provides a new platform to study kinetic effect of plasma assisted combustion.
4. The In situ discharge can maximize E/N at high T flame region, therefore, maximize
the electron energy and effect on reaction zone, and enhance ignition and extinction.
5. The In situ discharge can dramatically enhance the ignition and modify the classical
S-curve to be a monotonic curve.
6. MBMS was developed and H2O2 was successfully measured directly for the first time
in reacting system, enabling diagnostics of intermediate species in plasma assisted
combustion at low T.
Conclusions
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Future work
MBMS part:
1. Develop a JSR to study the low temperature and high pressure chemistry
2. Integrate JSR with plasma discharge to investigate plasma chemistry
3. Develop advanced light source to ionize the molecular beam
Plasma part:
1. OH PLIF for counter flow diffusion flame with in situ discharge and compare
with simulations
2. Low temperature plasma assisted combustion for large alkanes
3. Flow reactor experiments on liquid fuel with QCL diagnostics on H2O, H2O2
and HO2
4. Develop validated plasma flame models
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Thanks the support from AFOSR!
Questions?
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Flow tube experiments
0 2 4 6 8 10 12 14
510
540
570
600
630
660
690
720
750
780
T/K
Distance/inch
upstream downstream
ovenJacket heater
MBMS
14 inch2 inch
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H2O2 calibration
Dissociation:
do it quickly
changing H2O2 concentrations
monitor O2 peak
Syringe pump Vaporizer
H2O2 solution
Dilution gas
MBMS
450 K
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0 2 4 6 8 10 12 14 16400
600
800
1000
1200
1400
1600
1800
2000
Tem
pera
ture (
K)
Position (mm)
w. discharge
w.o discharge
w. discharge
w.o discharge
O2 = 53.5%, CH4 = 20%, a = 400 1/s
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