New Flame Regimes and Kinetic Study of

Plasma Activated Low Temperature Combustion

Joseph Lefkowitz, Wenting Sun, Sanghee Won, and Yiguang Ju

Department of Mechanical and Aerospace Engineering, Princeton University Princeton, NJ 08544, USA

AFOSR Plasma MURI 4th Year Program Review 2013.10.22-24

MURI Facility Summary and collaborative team structure

(*All facilities designed and fabricated specifically for this program.)

3000K

1000K

300K

0.01atm 1atm 100atm

Flame chemistry (Ju, Sutton)

Flow Reactors ( Yetter,

Adamovich)

Shock Tube (Starikovskiy)

RCM (Starikovskiy)

MW+laser (Miles)

JSR/Flow reactor Species and kinetics

(Ju)

1. Plasma activated low temperature combustion: A comparative study of CH4 vs. dimethyl ether (Tasks 8 and 9: Kinetic model validation)

Today’s Presentation

3. Multispecies diagnostics in a flow reactor with Mid-IR and molecular beam mass spectroscopy (MBMS)

(Task 3: Multispecies measurements)

2. New combustion regime: Plasma activated Cool Flames (Task 6: Ignition and Flame)

4. Development of low temperature and high pressure kinetic mechanism for plasma combustion (HP-MECH)

(Task 8 and 9: Kinetic model validation)

Residence time

Tem

pera

ture

Scramjet, afterburner

Plasma generated species: O, H, O2(a∆g) …

Most combustors

New “S-curve” by Plasma assisted combustion for small molecule fuel such as H2, CH4

the classical S-curve

. Will PAC be able to activate low temperature combustion (LTC ) at conditions where normal LTC will not occur?

. If yes, will PAC activated LTC allow us to create a stable COOL FLAME?

Questions to answer:

1. New flame and ignition regimes with in situ nano-second pulsed discharge

Ignition

Extinction

Sun et al. Proc. Comb. Inst. 34, 2010

0.05 0.10 0.15 0.20 0.25 0.30 0.35

1x10152x10153x10154x10155x10156x10157x1015

SmoothTransition

Extinction

Ignition

χO2=34%χO2=62%

Fuel mole fraction

OH

num

ber d

ensit

y (c

m-3)

CH4

5

Residence time

Tem

pera

ture

Plasma activation

LTC

Ignition

Extinction HTC

LTC

t2

Experimental method (in-situ plasma discharge) Methane vs. Dimethyl ether (DME)

6

25.4 mm

P = 72 Torr f = 24 kHz

Power ~ 17 W (repetitive pulses)

Laser beam OH, CH2O PLIF

E = 7500 V/cm, E/N ~ 900 Td Peak Voltage = 7.8 KV

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

1x1015

2x1015

3x1015

4x1015

5x1015

6x1015

Ignition

ExtinctionOH

den

sity

(cm

-3)

Fuel mole fraction

χO2=55%

increase (CH4) decrease (CH4) increase (DME) decrease (DME)

Top burner

Bottom burner (fuel)

OH fluorescence

at Q1(6)

Direct image

OH PLIF measurements in CH4 and DME/O2 Ignition

OH density vs. fuel mole fraction XO = 0.55, P = 72 Torr, f = 24 kHz, for DME (a = 250 1/s) and CH4 (a = 400 1/s,) as the fuel, respectively (solid square symbols: increasing XF, open square symbols: decreasing XF)

S-shaped ignition and extinction curves

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

Simulation Experiments

Position (cm)

CH2O

mol

e fra

ctio

n

0

500

1000

1500

2000

2500

3000

3500

4000

CH2 O

PLIF (a.u.)

CH2O PLIF measurement and numerical modeling in DME flames

Fuel Oxidizer

Large amount of CH2O formation before ignition on the fuel side

DME consumption and CH2O/radicals formation pathways

LTC

H+O2=OH+O

XF = 0.01, XO = 0.4, P = 72 Torr, f = 24 kHz, a = 250 1/s

0.01 0.1 1 10 100 10000.0000

0.0005

0.0010

0.0015

0.0020T=650 K No O addition

1000 ppm O addition

CH2O

mol

e fra

ctio

n

Residence time (ms)

Residence time

Tem

pera

ture

Plasma generated

LTC

Ignition

Extinction

HTC

LTC

t2 t1

Effect of radical production by plasma on the enhancement of low temperature combustion

DME/O2/He (3%/9%/88%) at To = 650 K with atomic O addition at different levels, at P = 72 Torr

Ignition

PSR

HTC

LTC

Plasma activated LTC and Direct Ignition to Flame transition without extinction limit

11

0.00 0.02 0.04 0.06 0.08 0.10 0.12

1x105

2x105

3x105

4x105

5x105

6x105

Extinction

increase decrease

CH2O

PLI

F (a

.u.)

Fuel mole fraction

Hot Ignition

P = 72 Torr, a= 250 1/s, f = 24 kHz XO2=40%, varying Xf

LTC

HTC

S-Curve

0.00 0.02 0.04 0.06 0.08 0.10 0.12

1x105

2x105

3x105

4x105

5x105

6x105 increase decrease

CH2O

PLI

F (a

.u.)

Fuel mole fraction

P = 72 Torr, a= 250 1/s, f = 34 kHz, XO2=60%, varying Xf

New ignition/extinction curve without extinction limit

LTC HTC

Radical production by plasma can activate LTC at much shorter timescale, lower pressure and temperature; and enable new flame regimes

12

Plasma activated LTC at much shorter time, lower pressure….

2. Plasma activated Cool Flames :A new way to burn?

Plasma

Residence time

Tem

pera

ture

Plasma generated

LTC

Ignition

Extinction

HTC

LTC

t2 t1 t2

2. Plasma activated Cool Flames: A new way to burn

(a) Hot diffusion flame

(b) Cool diffusion flame

Heated N2 @ 550 K

N2 @ 300 K

Stagnation plane

Oxidizer @ 300 K with plasma discharge

Fuel/N2 @ 550 K

Fig. 1 Schematic of experimental setup

Fig. 2 Hot and cool n-heptane diffusion flames at the same condition

500

1000

1500

2000

0.1 1 10 100 1000 10000 100000

Max

imum

tem

pera

ture

Tm

ax[K

]

Strain rate a [1/s]

n-heptane/nitrogen vs oxygen/ozonein counterflow burner

Xf = 0.05 and XO3 = 0.03Tf = 550 K and To = 300 K

Extinction limit ofconventional hot diffusion flame

Extinction limit ofcool diffusion flame

Fig.3 Modeling of cool flame regime with plasma activation

Tf~1900 K

Tf~650 K

Patent application, 2013.10

3. Multispecies diagnostics in a flow reactor (Task 3: Multispecies time-history measurements)

In situ intermediate species diagnostics beyond radicals

• Will low temperature kinetics important for PAC of C2H4? •How well is the model prediction? •How do we develop and validate plasma-combustion kinetic model?

Experimental Setup of In Situ Mid-IR PAC Diagnostics

Detector

QCL Laser

Diluents

Diluents Oxidizer

Fuel

Vacuum Pump

Electrode

Heated Vacuum Chamber

Nanosecond - Pulsed

Power Supply

Pulsed Signal Generator

Digital Delay Generator

Function Generator

Oscilloscope Ge Etalon

Detector

Observation Window

Beam Splitter

Collimating Lenses

Mini-Herriott cell showing 24 pass

configuration

Reactor/Diagnostics Reactor size: 45 x 14 x 152 mm3

Fuel: C2H4 Pressure: 60 Torr Flow speed in the reactor: ~40 cm/s Mid-IR QCL laser: 1296 cm-1 – 1423 cm-1

Multi-pass Mini-Herriott cell (12.7 mm OD)

Plasma Properties • Electrode (40 x 45 mm2) • Repetitively -pulsed nanosecond DBD discharge • 0- 40 kHz pulse repetition rate • 12 nanosecond pulse duration • 5-20 kV peak voltage

Experimental Apparatus

Vacuum Chamber

Detector

Electrode Connection

Alignment Laser

QCL Laser

N2 Purge Box

Laser inlet purge tube

To Vacuum

Observation Window

Direct and ICCD Images of Plasma Discharge in a Reactor

Stoichiometric mixtures: C2H4/O2 with 75% AR, 60 Torr, Vmax= 6 kV

•Direct Image: 1 kHz, 3.6 mJ/pulse, 2 s exposure time. •ICCD images: Gate time = 100 ns, Gain = 250

1000 Hz

2000 Hz

3000 Hz

1000 Hz Direct

ICCD

Cathode

Anode

Absorption Spectroscopy and temperature measurement

Beer-Lambert Law

Iν = Transmitted Signal S = Line strength of absorption line α = Absorption coefficient gV = Voigt profile line broadening function ν i = Light wavelength of the ith line h = Planck’s constant P = Pressure c = Speed of light T = Temperature k = Boltzmann Constant N = Number density of absorbers E’’ = Energy of lower state of transition L= Path length of light

Two-line Temperature

( )( )

" "2 1

" "2 12 01

2 1 0 0

( )ln ln( )

A

A

hc E EkT

E ES TI hcI S T k T

−=

−+ +

[1] Simeckova et al., Journal of Quantitative Spectroscopy & Radiative Transfer 98 (2006)

( )

−−=−= ∑

iiVi NLgTSNLTPI

I )()(exp),,(exp0

ννναν

ν

Absorption spectrum and wavelength scan

0

0.1

0.2

0.3

0.4

0.5

0.6

-0.01 -0.005 0 0.005

Sign

al [

Arb.

Uni

ts]

Time [s]

AbsorptionBackgroundEtalonLaser Scan

0

100

200

300

400

0 0.001 0.002 0.003

Scan

Rat

e [c

m-1

/s]

Time [s]

Etalon Data

Polynomial Fit

CH4 C2H2

Calibrated wavelength vs. time Signal vs. laser scan time and etalon fringes

Experimental results: Species time history: C2H4 pyrolysis and oxidation

0

100

200

300

400

500

600

0 0.005 0.01 0.015

Mol

e Fr

actio

n (p

pm)

Time from first pulse (s)

AcetyleneMethane

Pyrolysis

Final Pulse

• Pyrolysis conditions – 0.9375 Ar/0.0625 C2H4 – V=40 cm/s – P=60 Torr – Ti=300 K – 150 Pulses, 30 kHz, 10 kV

0

100

200

300

400

500

0

100

200

300

400

500

600

0 0.005 0.01 0.015

Tem

pera

ture

(K)

Mol

e Fr

actio

n (p

pm)

Time from first pulse (s)

AcetyleneMethaneWaterTemperature

Oxidation

Final Pulse

• Oxidation Conditions – Stoichiometric C2H4/O2 – 25% Reactants, 75% Argon – V=40 cm/s – P=60 Torr – Ti=300 K – 150 Pulses, 30 kHz, 10 kV

Kinetic Modeling • Combustion chemistry: Princeton/Argonne High

Pressure Mech for low temperature oxidation • Plasma chemistry: air plasma model by Uddi et

al [2] + Argon/CH4/ reaction pathways Kosarev et al [3] – Ions: O2+, O+, O-, O2-, Ar+, CH4+, CH3+, CH2+ C2H4+,

C2H3+, C2H2+ – Excited Species: O2(a1Δg), O2(b1Σ), O(1D),

Ar(3p5(2P3/2)4s), Ar(3p5(2P1/2)4s), Ar(3p5(2P3/2)4p) (Ar* excitation energies of 11.5, 11.7, and 12.9 eV)

[2] M. Uddi, N. Jiang, E. Mintusov, I. Adamovich, W. Lempert, Proc. Combust. Inst., 2009(32), 929-936 [3] I. Kosarev, N. Aleksandrov, S. Kindysheva, S. Starikovskaia, A. Starikovskii, Combust. Flame, 2008(154), 569-586

• Pascal Diévart, Xue Liang Yang , Ting Tan, Emily A. Carter, Fredrick L. Dryer, Yiguang Ju • Raghu Sivaramakrishnan, Nicole J. Labbe, Stephen Klippenstein

High Pressure-Mech

H2/O2 Bulke et al., 2012

Reaction scheme

CO Li et al., 2004

CH3OH

HCOOCH3

Major Focus

PU-Argonne , 2013

DME/Biodiesel Hydrocarbons

•High pressure experiment (20 atm) •Lower tempreature (RO2 chemistry) •HO2/H2O2 kinetics • Pressure dependent reactions (Ab-initio

QC and measured rates) •H2O/CO2 effects

C1-C2

0.0E+00

2.0E-03

4.0E-03

6.0E-03

8.0E-03

1.0E-02

1.2E-02

0 500 1000 1500

CH3O

H M

ole

Frac

tion

Time [μs]

1266 K and 2.5 atm

1368 K and 2.4 atm

1458 K and 2.3 atm

1610 K and 2.2 atm

1% methanol in Argon

0

10

20

30

40

50

0 5 10 15 20

Flam

e Sp

eed

(cm

/s)

Pressure/ bar

USC Mech II

C2H2/O2/N2/HeN2/O2=3.76Phi=1.6Tf= 1900 K

0

0.05

0.1

0.15

0.2

0 5 10 15 20 25 30

Pressure, atm

Mas

s bu

rnin

g ra

te (g

cm

-2 s

-1)

0

0.02

0.04

0.06

0.08

0.1

0.12

USC-MECH IIUpdated H2 + USC-MECH II C1-C2

H2/add/O2/dilφ=0.7Tf ~1600K

H2/CO = 90/10

H2/C2H4 = 90/10H2/C2H6 = 90/10

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 5 10 15 20 25 30Pressure (atm)

Mas

s bu

rnin

g ra

te (g

/cm

^2s)

Present experimentsLi et al. (2007)Davis et al. (2005)Sun et al. (2007)Konnov (2008)O'Connaire et al. (2004)Saxena & Williams (2006)

H2/O2/Ar, φ=2.5Tf ~1600K

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0 5 10 15 20 25 30Pressure (atm)

Mas

s bu

rnin

g ra

te (g

cm

-2 s

-1)

0.000

0.020

0.040

0.060

0.080

0.100

0.120

Present experimentsTse et al. (2000)Li et al. (2004)Updated model

(a)

(b) Φ=0.85 (1600K) Φ=0.30 (1400K)

H2/O2/He mixture

High Pressure Mech: Validation for H2, C2H2, C2H4, C2H6, CH3OH

Electron Collision Reactions Rate (cm3 molecule-1 s-1) Reference C2H4 + e- = C2H3 + H + e- f(E/n) [2] C2H4 + e- = C2H2 + H2 + e- f(E/n) [2]

C2H4 + e- = C2H2 + H + H + e- f(E/n) [2] C2H4 + e- = C2H + H2 + H + e- f(E/n) [2]

Excited Species Reactions Ar* + C2H4 = Ar + C2H2 + H + H 4.39 x 10-10 [4]

Ar* + C2H4 = Ar + C2H3 + H 4.88 x 10-11 [4] Ar* + C2H4 = Ar + CH2 + CH2 4.88 x 10-11 [4] Ar* + C2H4 = Ar + C2H2 + H2 4.88 x 10-11 [4]

Ion-molecule Reactions Ar(+) + C2H4 = Ar + C2H4 (+) 4.40 x 10-11 [5]

Ar(+) + C2H4 = Ar + C2H3(+) + H 8.36 x 10-10 [5] Ar(+) + C2H4 = Ar + C2H2(+) + H + H 2.20 x 10-10 [5]

Electron-ion Dissociative Recombination e- + C2H2(+) = C2H + H 2.34 x 10-6 (300/T)0.5 [6] e- + C2H2(+) = C2 + H2 9.35 x 10-8 (300/T)0.5 [6]

e- + C2H2(+) = C2 + H + H 1.40 x 10-6 (300/T)0.5 [6] e- + C2H2(+) = CH2 + C 2.34 x 10-6 (300/T)0.5 [6] e- + C2H2(+) = CH + CH 6.08 x 10-7 (300/T)0.5 [6] e- + C2H3(+) = C2H2 + H 2.26 x 10-6 (300/T)0.5 [6] e- + C2H3(+) = C2H + H2 4.68 x 10-7 (300/T)0.5 [6]

e- + C2H3(+) = C2H + H + H 4.60 x 10-6 (300/T)0.5 [6] e- + C2H3(+) = C2 + H2 + H 2.34 x 10-7 (300/T)0.5 [6]

e- + C2H3(+) = CH3 + C 4.68 x 10-8 (300/T)0.5 [6] e- + C2H3(+) = CH2 + CH 2.34 x 10-7 (300/T)0.5 [6]

C2H4 plasma reactions (Added)

[4] J. E. Velazco, J. H. Kolts, D. W. Setser, J. Chem Phys 69, 4357 (1978) [5] Masaharu Tsuji, Hiroyuki Kouno, Kenichi Matsumura, Tsuyoshi Funatsu, Yukio Nishimura et al., J. Chem. Phys. 98, 2011 (1993) [6] J. B. A. Mitchell, Phys. Rep. 186 (5), 215 (1990)

Experiment/Model Comparison

• Conditions for Oxidiation case: – Stoichiometric C2H4/O2 – 25% Reactants, 75% Argon – V=40 cm/s – P=60 Torr – Ti=300 K – 150 Pulses, 30 kHz, 10 kV – E/n = 37 Td

• Acetylene measurements in the pyrolysis experiment were used to match the E/n ratio of model calculations

0

100

200

300

400

500

0 0.005 0.01 0.015

Mol

e Fr

actio

n (p

pm)

Time from first pulse (s)

Oxidation C2H2Oxidation CH4Oxidation H2OC2H2 ModelCH4 ModelH2O Model

0

100

200

300

400

500

600

0 0.005 0.01 0.015

Mol

e Fr

actio

n (p

pm)

Time from first pulse (s)

Pyrolysis C2H2Pyrolysis CH4C2H2 ModelCH4 Model

Oxidation Pyrolysis

• Conditions for pyrolysis case: – 0.9375 Ar/0.0625 C2H4 – V=40 cm/s – P=60 Torr – Ti=300 K – 150 Pulses, 30 kHz, 10 kV – E/n = 37 Td

• Methane is greatly over-predicted by the model

C2H4

C2H5

+ H +M 31%

+ Ar* 5%

C2H2

+ Ar(+) 13% C2H3+

+ e- 30% CH2CH2OH

+ OH 15%

CH3+ HCO

+ O 13%

H + CH2CHO

+ O 11%

+ e- 65%

C2H

CO + CH2O + OH

+ O2 46%

+ H 21%

CH20 + HCO

+ O 21%

CH3O2

+ O2 + M 85%

CH3O

+ X 95%

CH2O

+ X 96%

C2H5O2

+ O2 + M 97%

C2H5O2H

+ HO2 98%

HCO + CO

+ O2 100%

O2C2H4OH

+ O2 100%

2 CH2O + OH

100%

M = Third body collider X = Radical

Red = High temperature, Blue = Plasma Green= Low temperature

Ethylene Oxidation Pathways

LTC HTC

PAC activates C2H4 low temperature chemistry

Reaction Pathways of Measured Species

C2H2

e- + C2H4 Ar*+ C2H4

87% 13%

CH4

CH3 + HO2 O + C2H4

71% 18%

CH3 + CH3O

7%

H2O

C2H4 + OH

16% 41%

HO2 + OH

19%

CH2 + O2

4%

CH3O + H

8%

CH2CHO + OH

9%

CH2O + OH

Only sensitive to plasma-related reactions!

X = Radical M = Third body collider

Reaction Pathways of Radicals

O

58%

e- + O2

33%

Ar*+ O2

3%

O*+ O2

OH

28%

CH3O2 + H

27%

HO2 + X

35%

CH2CHO+ O2

6% CH2 + O2

H

3%

e- + C2H4

13%

Ar*+ C2H4

39%

Ar(+) + C2H4

27% O + C2H4

7% O2 + C2H3

X = Radical M = Third body collider

HO2

10%

H + O2 + M

85%

HCO + O2

3%

O2 + C2H5

C2H4

C2H5

+ H + M 50% + Ar* 14%

C2H2

+ Ar(+) 22%

C2H3+

+ e- 29%

+ e- 65%

C2H

C2H2+ + Ar(+) 6%

+ X 100%

+ e- 50%

+ e- 13%

+ e- 30%

C2

CH

+ H +M 100%

C2H3

+ H 5%

+ C2H5 95%

X = Radical M = Third body collider

Green= Low temperature Red = High temperature Blue = Plasma

Pathways for Ethylene Pyrolysis

Measured Species

C2H2

e- + C2H4 Ar*+ C2H4

87% 5%

CH4

CH3 + H + M CH3 + C2H5

95% 4%

X = Radical M = Third body collider

H + C2H4

6%

CH3

CH4 + C2H CH2 + C2H5

94% 6%

Ar*+ C2H4

100%

H + C2H4 +M

100%

H

3%

e- + C2H4

43%

Ar*+ C2H4

47%

Ar(+) + C2H4

32

µGC

Cross validation with MBMS

4. Species Measurements in RF Discharge using Molecular Beam Mass Spectrometry

Experimental setup

Thermocouple

20 mm

Copper electrodes

MBMS Probe nozzle

Quartz flow tube: Inner 9x4x0.4mm3

20 mm

Gas mixture

Fig. 1 Experimental setup of RF discharge and MBMS measurement, RF Power at 90 W, 13.56MHz, Flow rate at 1500 SCCM,

0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.250

1x104

2x104

3x104

4x104

Mol

e Fr

actio

n (p

pm)

Equivalence Ratio

Fuel: C2H4 Measured:C2H4

RF off RF on

0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.250.0

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

Mol

e Fr

actio

n (p

pm)

Equivalence Ratio

Fuel: C2H4 Measured: CO

RF off RF on

0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.250

1x104

2x104

3x104

4x104

5x104

Mol

e Fr

actio

n (p

pm)

Equivalence Ratio

Fuel: C2H4 Measured: CO2

RF on

0.5 1.0 1.5 2.00.0

4.0x103

8.0x103

1.2x104

1.6x104

Mol

e Fr

actio

n (p

pm)

Equivalence Ratio

Fuel: C2H4 Measured: H2O

RF off RF on

C2H4 (2.5%)-O2(He-Ar):

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2

0.0

5.0x103

1.0x104

1.5x104 Fuel: CH4 Measured: H2O

RF off RF on

Mol

e Fr

actio

n (p

pm)

Equivalence Ratio

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20.0

2.0x104

4.0x104

6.0x104

8.0x104

Mol

e Fr

actio

n (p

pm)

Equivalence Ratio

Fuel: CH4 Measured: O2

RF off RF on

Fig.2 H2O formation w/wo RF discharge Fig.3 O2 mole fraction w/wo RF discharge

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20.0

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

3.0x104

3.5x104M

ole

Frac

tion

(ppm

)

Equivalence Ratio

Fuel: CH4 Measured: CH4

RF off RF on

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20.0

5.0x103

1.0x104

1.5x104

Equivalence Ratio

Mol

e Fr

actio

n (p

pm)

Fuel: CH4 Measured: CO

RF on

CH4(3%)-O2-He-Ar(2%) mixture

Conclusions 1. In situ plasma discharge can activate low temperature chemistry and

enable LTC at shorter residence time, lower pressure, and leaner mixture.

2. Plasma activated Cool Flame and a new direct ignition to flame (DIF) regime was observed for large hydrocarbons with rich LTC chemistry.

3. A HP-MECH for PAC was developed. The results showed that low

temperature kinetics via RO2 is an important pathway for even PAC of C2H4.

4. In situ mid-infra red absorption spectroscopy and MBMS system are

developed. The results provide important validation targets and show that the existing plasma kinetics is not able to predict the intermediate species.

5. Future research should focus on kinetics and combustion phenomena of

plasma assisted low temperature combustion.

Acknowledgement

37

This work was supported by the plasma MURI and AFOSR research grants from the Air Force Office of Scientific Research (Drs. Chiping Li and Julian Tishkoff).

C2H4 Plasma Reactions Ar* + CH4 Quenching Ar* A (cm3/s) Branching ratio Kosarev et al. Calculated Ar(3P2) 4.98E-10 Ar + CH2 + H + H 0.650 3.30E-10 3.32E-10 Ar(3P0) 5.50E-10 Ar + CH + H2 + H 0.117 5.80E-11 5.96E-11 Average 5.11E-10 Ar + CH3 + H 0.117 5.80E-11 5.96E-11

[1] Ar + CH2 + H2 0.117 5.80E-11 5.96E-11 [2] [3]

Ar* + C2H6 Quenching Ar* A (cm3/s) Branching ratio Kosarev et al. Calculated Ar(3P2) 7.03E-10 Ar + C2H4 + H + H 0.860 7.00E-10 6.05E-10

[1] Ar + C2H5 + H 0.090 6.33E-11 Ar + CH3 + CH3 0.020 1.41E-11 Ar + C2H4 + H2 0.020 1.41E-11

[2] [3] Ar* + C2H4 Quenching Ar* A (cm3/s) Branching Ratio Calculated Ar(3P2) 5.85E-10 Ar + C2H2 + H + H 0.750 4.39E-10

[1] Ar + C2H3 + H 0.083 4.88E-11 Ar + CH2 + CH2 0.083 4.88E-11 Ar + C2H2 + H2 0.083 4.88E-11

Estimate

[1] J. E. Velazco, J. H. Kolts, D. W. Setser, J. Chem Phys 69, 4357 (1978) [2] J. Balamuta, M. F. Golde, Y. Ho, J. Chem Phys 79, 2822 (1983) [3] I. N. Kosarev, N.L Aleksandrov, S.V. Kindysheva, S. M. Starikoskaia, A. Yu. Starikovskii, Combust. Flame 154, 569 (2008)

C2H4 Plasma Reactions Ar(+) + C2H4 A (cm3/s) Branching Ratio Calculated

1.10E-09 Ar + C2H5 (+) 0.040 4.40E-11 [4] Ar + C2H3(+) + H 0.760 8.36E-10

Ar + C2H2(+) + H + H 0.200 2.20E-10 [4]

e- + C2H2+ A (cm3/s) (300/T)^n Branching Ratio Calculated

2.70E-07 0.5 C2H + H 0.500 2.34E-06 [5] C2 + H2 0.020 9.35E-08

C2 + H + H 0.300 1.40E-06 CH2 + C 0.050 2.34E-07 CH + CH 0.130 6.08E-07

[5] e- + C2H3+ A (cm3/s) (300/T)^n Branching Ratio Calculated

4.50E-07 0.5 C2H2 + H 0.290 2.26E-06 [5] C2H + H2 0.060 4.68E-07

C2H + H + H 0.590 4.60E-06 C2 + H2 + H 0.030 2.34E-07 CH3 + C 0.006 4.68E-08 CH2 + CH 0.030 2.34E-07

[5]

[4] Masaharu Tsuji, Hiroyuki Kouno, Kenichi Matsumura, Tsuyoshi Funatsu, Yukio Nishimura et al., J. Chem. Phys. 98, 2011 (1993) [5] J. B. A. Mitchell, Phys. Rep. 186 (5), 215 (1990)

New Flame Regimes and Kinetic Study of �Plasma Activated Low Temperature CombustionMURI Facility Summary and collaborative team structure�Slide Number 3Slide Number 4Slide Number 5Experimental method (in-situ plasma discharge)� Methane vs. Dimethyl ether (DME)Slide Number 7Slide Number 8Slide Number 9Slide Number 10Plasma activated LTC and Direct Ignition to Flame transition without extinction limitSlide Number 12Slide Number 13Slide Number 14Slide Number 15Experimental Setup of In Situ Mid-IR PAC DiagnosticsExperimental ApparatusDirect and ICCD Images of Plasma Discharge in a Reactor��Stoichiometric mixtures: C2H4/O2 with 75% AR, 60 Torr, Vmax= 6 kV�Absorption Spectroscopy and temperature measurementAbsorption spectrum and wavelength scanExperimental results: Species time history: �C2H4 pyrolysis and oxidationKinetic Modeling Slide Number 23Slide Number 24C2H4 plasma reactions (Added)Experiment/Model ComparisonEthylene Oxidation PathwaysReaction Pathways of Measured SpeciesReaction Pathways of RadicalsPathways for Ethylene PyrolysisMeasured SpeciesSlide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36AcknowledgementSlide Number 38Slide Number 39C2H4 Plasma ReactionsC2H4 Plasma Reactions