Plasma assisted high pressure combustion;

surface HP nanosecond DBD

Laboratoire de Physique des Plasmas

Svetlana Starikovskaia

Laboratory of Plasma Physics, Ecole Polytechnique, Paris, France

Our scientific team for PAI/PAC problem:

NeQ systems Laboratory, Moscow, 1998-2006

Laboratory for Plasma Physics, Ecole Polytechnique, Paris: Sergey Stepanyan, Andrei Klochko, Sergey Shcherbanev, NikitaLepikhin, Yifei Zhu, Brian Baron, James Williams, Mhedine Alicherif,Tat Loon Chng, Georgy Pokrovskiy, Chenyang Ding

2

Tat Loon Chng, Georgy Pokrovskiy, Chenyang Ding

Moscow State University, Skobeltsyn Institute of Nuclear Physics:Nikolay Popov

PC2A, Lille: Mohamed Boumehdi, Guillaume Vanhove, Pascale Desgroux

Plan of the presentation

Introduction: physics and chemistry of plasma-assistedcombustion

Shock tube experiments: 0D, low pressures, hightemperatures

3

temperatures

Rapid compression machine (RCM) experiments: 2D, highpressures, low temperatures

High pressure high temperature (HPHT) discharge cellexperiments: the discharge and the following combustion

High pressure discharge: streamer-to-filament transition

I. Physics and chemistry of plasma assisted combustion

4

plasma assisted combustion

Plasma assisted ignition/combustion: nonequilibrium plasma applications

• Lean mixtures H 2O 2 O 2H 2

5

• Fast flows (1998)

• High pressuresIgnitionpoint

Dieselengine

Petrolengine

HCCIengine

Multipleignitionpoints

Fuel and airmixture

Fuel and airmixture

Air

Combustion: chain reactions

6

Initiation H + O = 2 + 78 kJ2 2 OH

BreakH HO2 + O + M = + M 203 kJ -2

H + wall

H OH O + O = + kJ+ 70 2Branching

Development: 2x

O OH H + H = + 8 kJ+ 2

OH H + H = H O + 62 kJ2 - 2

Comparison of the reaction rates

7

Fast gas heating: time less than VT-relaxation

M* + A = M + A + Q A * + M = 1 A + M + Q1

8

e + M = e + M*

k=B exp(-E /k )na T T

Q Q e + M = e + A * + A1 2

First available experiments on plasma-assited combustion

100

150

0.5 A0.2 A

0 A

, To

rrSemenov N N (1958) Some problems of chemical kinetics and reactivity Pergamon Press

99

400 440 480 520 560 6000

50

5 A

2 A

1 A

Pre

ssu

re,

Temperature, oC

G.Gorchakov, F.Lavrov, Influence of electric discharge on the region of spontaneous

ignition in the mixture 2H2-O2. Acta Physicochim. URSS (1934), 1, 139-144

Energy branching vsreduced electric field E/N

N2 vib

1,0

O2 vibr

Ene

rgy

bran

chin

g

10

0,1 1 100,0

0,5

O2 electr

N2 electr

O2, N

2 ion

elastic

O2, N

2 rot

Ene

rgy

bran

chin

g

E/N, 10 -16 V cm 2

N.L. Aleksandrov, E.E. Son, 1980, in: Plasma Chemistry, B.M.Smirnov, ed., Atomizdat Publ., Moscow, V.7, pp. 35-75

Applied high voltage pulses

-10

-5

0

Vol

tage

, kV15

20

Vol

tage

, kV

Positive and negative polarity pulses

1111

0 5 10 15 20 25 30

-20

-15

-10

Vol

tage

, kV

Time, ns0 5 10 15 20 25 30

0

5

10

Vol

tage

, kV

Time, ns

Single pulse regime, 20 ns pulse duration, 2 ns front rise time

Kinetic approach to description of a gas discharge

12

Field of parameters where nanosecond PAI/PAC experiments are available

10

OSU LPP/PC2A MIPT 2002-2008 Princeton-ShT Princeton-AFRL Princeton - comb MIPT 2008-2014 Stanford Drexel

10.0

3.0

1.0

0.3

Pre

ssur

e, a

tm

Dashed lines: 0.03, 0.1, 0.3, 1, 3 and 10 n(atm)

13

500 1000 1500 20000.01

0.1

1

Drexel Delft USC LPP 2016

0.03Pre

ssur

e, a

tm

Temperature, K

0.1H2,CH4,C2H4,C3H8/O2/N2,ArCH4,C4H10,C7H16/O2/N2,ArH2,CnH(2n+2), n=(1-10)/O2,N2O/N2,Ar,HeC2H6/O2/N2,ArCH4,C2H4,C3H8/O2/N2,ArCH4,DME/O2/He,ArC2H2/O2/ArCH4/O2/N2CnH(2n+2), n=(1-5)/O2/N2C3H8/O2/N2C2H2,CH4/O2/N2

S M Starikovskaia, J. Phys. D: Appl. Phys., 47 (2014) 353001 (34pp)

All experiments were performed in a SINGLE-SHOT regime

1414

II. Shock tube experiments: [relatively] low P and high T

15

[relatively] low P and high T

Shock tube setup for plasma ignition

• Mixture composition

CH4/C2H6/C3H8/C4H10/C5H12

- O2 – Ar (90%)

• Temperature

1616

950-2000 K

• Pressure

0.2-1.0 atm

• T5, P5

• Tign

• E/N, I, W

Dielectric section of a shock tube

171717

CH :O : Ar; T =1 K, P =0.5 atm

4 2

5 5

N :300

2 U=-110 kV

Starikovskaia S M, Kukaev E N, Kuksin A Yu, Nudnova M M and StarikovskiiComb. and Flame, 2004, 139, 177-87

2 cm

The idea of the experiment

Auto-ignition

Ignition delay time (induction time)

181818

O, OH, H, CH3

Plasma assisted ignition

Shift of the ignition delay time: (CH4:O2):Ar = 90:10 mixture

-60

-40

-20

0

20

40

60

80

4

3

2

1

τ

Sig

nals

, a.u

.

T5=1770 K; P

5=0.5 bar

103

104

105

I'

II'

tim

e,

µs

191919

-400 -200 0 200-80

-60(a)

Time, µµµµs

-400 -200 0 200-60

-40

-20

0

20

40

3

2

1

(b)τ

Sig

nal

, a. u

.

Time, ms

T5=1400 K; P

5=0.5 bar

0.5 0.6 0.7 0.8

100

101

102

10

III

autoignition

Ign

itio

n d

ela

y t

1000/T5, KI N Kosarev, N L Aleksandrov, S V Kindysheva,

S M Starikovskaia, A Yu Starikovskii, Comb Flame, 154 (2008) 569-586

Dissociation in a nanosecond discharge (C2H6:O2):Ar, Hayashi (C2H6), Braginsky (O2), Tachibana (Ar)

15

20T

5=1300 K, P

5 = 0.65 bar, , w=23.1 mJ/cm3

H

OC

2H

6

cm-3

202020

10 100

0

5

10

C2H

3

C2H

4

C2H

5

H

Den

sity

, 10

15cm

E/n, TdI N Kosarev, N L Aleksandrov, S V Kindysheva, S M Starikovskaia, A Yu Starikovskii, Comb Flame, 156 (2009) 221-233

Decrease of ignition delay time:moderate gas densities; uniform ns discharge

103

104

105

CH4, auto, 0.4-0.7 atm

CH , auto, 2 atm

Ig

nitio

n de

lay

time,

µµ µµ s

Auto Exp, C2H6 Auto Calc, C2H6 PAI Exp, C2H6 PAI Calc, C2H6, , , C3H8, , , C4H10, , , C5H12

21

0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85

100

101

102

10

CH4-C

5H

12,

PAI, 0.2-0.7 atm

C2H

6-C

5H

12,

auto, 0.2-0.7 atm

CH4, auto, 2 atm

Igni

tion

dela

y tim

e,

1000/T, K-1

N L Aleksandrov, S V Kindysheva, I N Kosarev, S M Starikovskaia, A Yu Starikovskii, Proc. of Combustion Institute, 32 (2009) 205-212

Kinetics of the ignition: kinetic curves (T5=1530 K, n5=5x1018 cm-3)

1x10-4

10-3

10-2

10-1

OH,H,CO2,O

Tem

pera

ture

, K

CH3,H

2O,H

2,CO

CH4

O2

Mol

e fra

ctio

n

2000

2500

Autoignition

1x10-4

10-3

10-2

10-1

Plasma Assisted Ignition

CH2O

H2O

CO2

COH

2O

CH3

H

OH

O

CH4

O2

Mol

e fra

ctio

n

2000

2500

Tem

pera

ture

, K

222222

10-1 100 101 102 103 10410-6

1x10-5

1x10

Tem

pera

ture

, K

CH3,H

2O,H

2,COM

ole

fract

ion

Time, µµµµs

1500

10-1 100 101 102 103 10410-6

1x10-5

1x10-4

CO2

H2

OHMol

e fra

ctio

nTime, µµµµs

1500

Tem

pera

ture

, K

Plasma assisted ignition is characterized by:

– slow increase of gas temperature – developed kinetics of intermediates– partial fuel conversion during induction time

N L Aleksandrov, S V Kindysheva, I N Kosarev, S M Starikovskaia, A Yu Starikovskii, Proc. of Combustion Institute, 32 (2009) 205-212

II. Rapid compression machine (RCM) experiments:

23

machine (RCM) experiments: high P and [relatively] low T

Rapid compression machine (RCM)

24

Nanosecond surface dielectric barrier discharge (nSDBD, for flow control)

-

25Y Zhu, S Shcherbanev, B.Baron and S. StarikovskaiaPSST, 26 (2017) 125004

Cylindrical electrode system (for PAC)

Electrode configuration Cubic HP chamber

HV electrode,

2 cm in diameter

26

Rapid compression machine (RCM), Lille

27

Mixtures used in experiments:

1) CH4/O2/Ar, φ=1, 0.5, 0.3, 70-75 % of Ar

2) n-C H /O /Ar/N , φ=1, 38 % of N 38 % of Ar

2828

3) n-C4H10/O2/Ar, φ=1, 76 % of Ar

4) n-C4H10/O2/N2, φ=1, 76 % of N2

2) n-C4H10/O2/Ar/N2, φ=1, 38 % of N2, 38 % of Ar

P-T diagram for RCM experiments

CH4

n-C4H10

10

12

14

16 (CH4:O2, φφφφ=1) + 72% Ar

(n-C4H

10:O

2, φφφφ=1) + 77% Ar

φφφφ

(CH4:O2, φφφφ=0.3) + 77% Ar

(CH4:O2, φφφφ=0.5) + 75% Ar

TD

C /

bar

292929

n-C7H16(cool flame

modification)600 650 700 750 800 850 900 950 1000

2

4

6

8

10

(n-C7H

16:O

2, φφφφ=1) + 79% N

2

No autoignition

4 10 2

(n-C4H

10:O

2, φφφφ=1) + 77% N

2

No autoignition

Pre

ssur

e P

TD

C

Temperature Tc / K

Autoignition vs plasma ignition in RCM at PTDC=15 bar and TC=970 K, (CH4:O2)+76%Ar

30

40

Plasma assisted ignition, U=-24 kVPTDC=14.7 atm

TC=972 K

Pre

ssur

e, a

tm

30

40PTDC=14.7 atm

TC=972 K

Pre

ssur

e, a

tm

Autoignition

3030

0 50 100 150 2000

10

20

discharge initiation

(blue step)P

ress

ure,

atm

Time, ms

0 50 100 150 2000

10

20

Pre

ssur

e, a

tm

Time, ms

S.A. Stepanyan, M.A. Boumehdi, G. Vanhove, P. Desgroux, S.M. Starikovskaia, N.A. Popov,

Comb. Flame, 162 (2015) 1336-1349

Pressure trace and corresponding fast imaging of flame propagation

10

15

20

25

30

35

40

discharge

Pre

ssio

n / b

ar

S.A. Stepanyan, M.A. Boumehdi, G. Vanhove, P. Desgroux, S.M. Starikovskaia, N.A. Popov,

Comb. Flame, 162 (2015) 1336-1349

313131

200 205 210 215 2200

5discharge initiation

Time / ms

0.8 ms 1 ms 1.2 ms 1.4 ms

1.6 ms 1.8 ms 2 ms

31

Pressure detector

CH4:O2, ER=1 + 70% Ar,

TC=947 K, PTDC=15.4 bar

Ignition threshold and polarity of the high-voltage pulse

0 5 10 15 20 25 300

5

10

15

20

Vol

tage

, kV

Time, ns40

50

Thr

esho

ld v

olta

ge, k

V

limit of filamentation in air

n-C4H10/O2/N2, U>0

3232323232

0 5 10 15 20 25 30

-20

-15

-10

-5

0

Vol

tage

, kV

Time, ns

0.009 0.010 0.01120

30 n-C4H10/O2/N2, U<0

n-C4H10/O2/Ar, U<0

n-C4H10/O2/Ar, U>0

Thr

esho

ld v

olta

ge, k

V

P/T, bar/K

III. High pressure high temperature (HPHT) chamber

experiments:

33

experiments: high P and low T [T=300 K]

High-Pressure and High-Temperature (HPHT)discharge/combustion chamber

Electrode configuration General view of the HPHT setup

34

Discharge/combustion chamber

Experimental setup

The scheme of experimental setup. SR – Spectrograph, ICCD – camera, PC – computer,

BCS – back current shunt,

35

nSDBD and Flame Initiation, P=3 bar, U=-50 kV

Discharge (ns) and combustion (ms) emission pattern s

H2:Air, ER=0.6

36

time

ns discharge Intermediate chemistry Flame propagation, Combustion

N2(v), N2(A,B,C,…), H, O(1D), O2(a1∆g), etc.

O, OH, H, HO2, H2O2, H2O, etc.

Initiation of Combustion with nSDBD

-2

-1

0

1

Pre-flame

H2/Air mixture, P=3 bar, T

0=300 K, ER=0.6

PM

sig

nal,

V

U=-50 kV

8

10

12

14

Pressure, bar

Ignition delay?

50 µs

100 µs

ICCD gate: 50 µsDelay:

37

0 1 2 3 4 5 6 7 8 9-6

-5

-4

-3

Ignition

PM

sig

nal,

V

Time, ms

Discharge

0

2

4

6

8

Pressure, bar

- Yes, for combustion!

- No, for plasma chemistry

100 µs

200 µs

400 µs

Flame Initiation in H2/Air ER=0.5, P=6 bar

Polarity: U>0Energy deposition W= 3 mJ

First regime of ignition:Ignition kernels

38

Ignition with a few ignition kernels near HV electrode. Streamer discharge.

Pressure 6 bar, Temperature 300 K.

Flame Initiation in H2/Air ER=0.5, P=6 bar

Polarity: U>0Energy deposition W= 4.8 mJ

Second regime of ignition:Ignition along the perimeter of HV electrode

39

Quasiuniform ignition around HV electrode. Streamer discharge.

Pressure 6 bar, Temperature 300 K.

Flame Initiation in H2/Air ER=0.5, P=6 bar

Polarity: U>0Energy deposition W= 12 mJ

Third regime of ignition:Ignition along the discharge channels

40

Ignition along the channels. Filamentary discharge.

Pressure 6 bar, Temperature 300 K.

Discharges in different gas mixtures

φ=0 φ=0.3 φ=0.6 φ=1.2

Discharge in methane/O 2/Ar

Discharge in n-heptane/O 2/Ar

41

Discharges in CH4/O2/Ar (ER=0.6) and

n-C7H16/O2/Ar (ER=1) mixtures,

P0=3 bar, T0=300 K, voltage on the electrode U=+38 kV

IV. High pressure surface DBD discharge: streamer-to-filament

42

discharge: streamer-to-filament transition

Two modes of nSDBD (velocity is a few mm/ns)

Filamentary mode, V=-46 kV, 4 bar, Air

Electrode system

43

Camera gate is 0.5 ns

HV electrode

D=2 cm HV electrode

Cylindrical electrode configuration

Outer diameter 50 mm;HV electrode diameter 20 mm

Analysis of emission intensity (Streamer vs filamentary mode)

44

Radial distribution of the frontal discharge emission; P=4 bar, U=-47 kV.

Spatial distribution of emission

45

How to get the filament spectra

46

Single filament is aligned with the entrance slit of the spectrometer

Continuous spectra in filamentary discharge

4747

Broadening of Hα

line

Discharge starts

Filamentsstart

Filamentary discharge in N 2:H2 (7:1) mixture P=8 bar. Electron density measurements with H

αline (656 nm)

broadening. Camera gate 5 ns

4

30

35

19

630 635 640 645 650 655 660 665 670 675 680

-5 ns

0 ns

5 ns

7 ns

10 ns

4848

0 20 40 60

-1

0

1

2

3

Hig

h vo

ltage

, a.u

.

Discharge time, ns

0

5

10

15

20

25

30

FW

HM

, nm

1017

1018

1019

ne, c

m-3

630 635 640 645 650 655 660 665 670 675 680

10 ns

15 ns

20 ns

25 ns

30 ns

35 ns

Wavelength, nm

40 ns

Recombination emission in the filament

Electron density from recombination emission

SPS (337.1 nm) is a reference radiation

N2(C)=kC(E/N)·ne·N2/ νq

QC=N2(C)·FFK·A00

QC=3·1021quantum/cm3/s.

49

210 10)25.1()( ⋅−=

⋅⋅⋅= ω

ωω d

T

nnCQ

e

ioneCW η

At λ = 337 nm and ∆λ = 3 nm, dω = 5·1013 s-1

In the discharge Te~2-4 eV → ne~3·1018 cm-3

In the afterglow Te~0.5 eV → ne~1018 cm-3

quantum/cm3/s

QC=3·10 quantum/cm /s.

QC(t=0 ns)/QCW(t=5 ns)~(1.5-2)

1

1021

1022

543

Ne = 1*1018 cm -3

ne = 3*1018 cm -3

Q, q

uant

um /

cm3 /

sT

e, eV

2

Conclusions

Nanosecond dielectric barrier discharge (nSDBD) providesignition of different fuels in a wide range of stoichiometries

At high gas densities, nSDBD simultaneously provides

50

At high gas densities, nSDBD simultaneously provideshundreds of ignition sites distributed in space. The geometry ofthe ignition and following combustion can be adapted toprovide the highest possible efficiency of the system

Physics of filamentation in high pressure nSDBD is understudy now (ne=1019 cm-3 is achieves during a fewnanoseconds in a single-shot mode)