"Non-equilibrium chemically active plasma:
modeling with Chemical Workbench
Deminsky Maxim
KintechLab
23 July 2015
Outline
 Chemical Work Bench (CWB) – toll for conceptual design of
chemically oriented phenomena
 Problems arising during elaboration of plasma model
 Collection of plasma model in CWB environment
 Coupling of plasma models with other models
 Data needed for simulation: construction of plasma-chemical
mechanism in CWB
 Recovering of unknown characteristics of elementary plasmachemical processes in CWB
 Example of modeling of mercury-free light sources
 Example of modeling plasma-assisted combustion
CWB
computational environment
Quantum chemistry
Automated data import
Substance and
elementary process
properties
Khimera
Substance and
process properties,
kinetic mechanisms
KintechDB
Substance
properties
Chemical workbench
Kinetic mechanisms
CWB software tools
Kintech Lab develops methods and special software
tools for development of the predictive kinetic
mechanisms and conceptual design of complex
combustion and plasma systems:
 Chemical Workbench – an integrated environment for the
development and reduction of chemical mechanisms, and conceptual
design of the chemistry intensive technological processes
 Khimera – a unique tool for calculating microscopic parameters from
first-principles calculations
 KintechDB – a database of evaluated data for properties of
substances, elementary processes and chemical mechanisms
Chemical Workbench©
Integrated modeling environment for kinetic modeling,
kinetic mechanism development and conceptual reactors
design in the fields of






Combustion
Plasma Chemistry
Pollution Control
Waste Treatment and Recovering
Metallurgy
General Chemical Kinetics
and Thermodynamics
 High Temperature In-Organic Chemistry
 Thermal and Plasma Hydrocarbon Pyrolysis Processes
 Education
Problems arising during elaboration of plasma model
Design of model
Chose of
appropriate model
Adequacy of model to discharge type
Coupling with electric
network
Coupling with chemistry
Collection of data set
(“mechanism”)
Thermodynamic data
Kinetic data (rate
coefficient, cross sections)
Transport data
CWB model’s collection
Kinetic models and Surface kinetic models
Well Stirred Reactor (WSR), 2 models
Plug Flow Reactor (PFR), 3 models
Calorimetrics Bomb Reactor (CBR), 4 models
Calorimetric Reactor with Deviation (CRD)/Sensitivity (CRS), 4 models
Premixed Flame, 1 model
Thermodynamic models
Full Thermodynamic Equilibrium Reactor (TER), 8 models
Stoichometric Equilibrium Reactor (STR), 4 models
Plasma models and Plasma models with Surface kinetics
Detonation and aerodynamic models
Chapman-Jouguet Reactor (CJ), 1 models
Zel’dovich-von Neumann-Doering Reactor (ZND), 1 model
Exhaust Reactor (EXH), 1 model
CWB plasma model’s collection
CWB Plasma models
Is…
Is not…
0D or 0D(+) dimension
2D or 3D dimensions
uniform media (T,P,E/N, [Ci])
for non-uniform distributed
characteristics (T,P,E/N)
hydrodynamics time >> plasma
& chemical times
Navier-Stokes for CFD
coupling of EEDF solution with
chemical reactions
Thus, CWB models is for investigation of plasma-chemical
kinetic mechanisms and conceptual design of complex
chemically active plasma systems
EEDF solution with chemistry
iterative
The Boltzmann kinetic equation is solved with the use of two-spherical harmonics
expansion of electron velocity distributed function, which gives following equation
for EEDF:
Qel, Qrot, Qin, Qsup, Qatt, Qee elastic, rotational, inelastic, superelastic,
attachment and electron-electron collision integrals
- calculation of rate constant of non-elastic processes
d[Ci ]
a
  ki , j [Cl ] j ,l - solution of balance equations for chemical species
dt
j
l
CWB plasma model’s collection (Types)
Types:
Plasma Model – EEDF solution with
Chemical reactions
Calorimetric Bomb Reactor (CBR) –
0D, uniform, time dependent model
P type – pressure is constant
Q type – given heat exchange
V type – volume is constant
T type – temperature is constant
Plasma & Surface – EEDF solution with
Chemical reactions in gas and surface
Calorimetric Bomb Reactor with surface(CBRS) –
0D(+), uniform, time dependent model
CWB plasma model’s collection (Subtypes)
The reactor model is based on numerical solution of the Boltzmann kinetic equation for
electron energy distribution function (EEDF) and determination of rate coefficients of
electron induced chemical reactions, energy distribution and electron’s swarm
parameters in gas discharge. Gas composition in the reactor is changed as a result of
chemical and vibrational kinetics plasma.
Subtypes:
Nonequilibrium plasma reactor models available for different electric circuit
configuration:
• Current is given (J)– reactor with specified fixed value of the discharge current.
Corresponds to electric circuit with plasma-gap connected in series with current
generator (high voltage generator with high internal resistance).
• L-C-R Circuit – the dependence of reactor electric field intensity and current
density is determined by external LCR circuit. The plasma-gap is connected in series
with a resistor, capacitor and inductance. Initial voltage on the capacitor is used as
initial voltage on gap. It is assumed that the initial current at zero.
• E/N is given (U) – time dependence of the reduced electric field is specified.
• U-L-C-R Circuit – the plasma-gap is connected in series with resistor, capacitor,
inductance and voltage source. It is assumed that the initial current and initial
voltage on the capacitor is zero. Time dependence of the voltage at the voltage
source is specified.
• V-R – the plasma-gap is connected in series with a resistor and voltage source.
Extension of plasma models capabilities
by flow sheet simulations
Non-uniformity: treatment by many streamers
1st pulse
2nd pulse
Admixing of surrounding gas
FlowRate2
tmix
FlowRate1
Loop for number of pulses
1) Plasma
model with E/N(t)
3) Plug flow reactor
model
2) Well Stirred Reactor
model with
1) treatment 3) relaxation &
by plasma
chemistry
2) extension,
mixing with gas
Need to know:
a) FlowRate1/ FlowRate2 ~ Streamers Volume / Total Volume
b) Mixing time tmix
Time
Data needed for simulation:
construction of plasma-chemical mechanism in CWB
Tree of
plasma-chemical
processes
KintechDB - databank of physical-chemical data
and information system for multidisplinary R&D projects
Applications
-----------------------------------------------(CWB®, TRASS®, Chemkin®,
Fluent®, ANSYS CFX®, Star-CD®)
KintechDB
Quantum chemistry
-------------------------------------------(Gaussian®, GAMESS®,
Jaguar®)
Microkinetics
--------------------------------------(Khimera®)
Chemical kinetics
--------------------------------------(CWB®, Chemkin®)
Database content
Particle properties
Thermodynamic properties of
individual substances
Elementary processes
characteristics
Kinetic mechanism
Data analysis and visualization
tools
KintechDB data analysis and visualization tools
Thermodynamic and kinetic data. Analysis and visualization
• Substance thermodynamic
functions visualization and
comparison
• JANAF, TPIS table generation
• Thermochemical reaction
analysis
• Forward/reverse rate constants
calculation
• Rate constants
temperature/pressure dependence
visualization
•Rate constants for different
reactions/sources comparison
Operation with data:
How construct mechanism?
3 general ways:
1. Putting data by hands in the calculation
from external sources
2. Data export from database of processes
and substances
3. Mechanism export from database of
mechanism
Khimera© or “What to do if there is now data?”
•
Khimera: model library
– Chemistry of heavy particles
•
Direct Bimolecular Reactions
•
Bimolecular reactions via long lived Intermediate complex
•
Multi-channel unimolecular reactions
•
Dissociation of diatomic molecules
•
Ion - molecular reactions
•
Gas - Surface reactions
– Electron molecular reaction
•
Excitation
•
Ionization
•
attachment
– Vibrational Energy Transfer
•
VV and VT exchange
– Photochemical Reactions
•
photo dissociation
•
quenching
•
isomerization
– Classical trajectories methods
– Surface diffusion
– Multicomponent thermodynamic
properties model
– Multicomponent gas transport properties
model
Example: Te ionization cross section
The cross section of the reaction is evaluated in the framework of Born-Compton
similarity function method. Three subshells give the main contribution into the total
atomic ionization cross section, namely, 5p4 (IP=9 eV, N=4), 5s2 (IP=17.84 eV, N=2)
and 4d10 (IP=47 eV, N=10). The account of the contributions of these subshells to total
atomic cross section is sufficient for the incident electron energy up to 200–300 eV.
+
Te+e=Te +e+e
10
8
, A
2
6
Cross section of the process . Results of
calculations described are shown by red line,
experimental data is shown by black squares
(R.S.Freund et al. Phys.Rev.A, 41, 3575 (1990)).
4
experiment, R.S.Freund et al. 1990
Born-Compton results
2
0
0
50
100
E, eV
150
200
Transport properties calculation
Data Base of interaction potentials and collisional integrals
Transport properties calculation
Transport coefficients are calculated by the accurate formulas of the ChapmanEnskog method with account for higher approximations 14, here  is the
number of approximations, i.e. the number of retained terms in Sonine polynomials
expansions.
Example: calculation of transport properties of Air at P=1 atm
Example of modeling of mercury-free light sources
I2(-) +M*=>I2 + e +M
GaI3 + e =>GaI3(-)=>….
=>…GaI+e.=>Ga + I,I2(-)
j
j
Candidates:
Halides of Ga, Zn, In,
Cu, Al, Cd, Sb, Bi, Tl
Ga +e=>Ga*=> Ga + h
Рисунок лампы с травлением
etching
condensation
Ga, GaI2, GaI3 (wall)
Boltzmann
equation for
the EEDF
System of kinetic
equations for charged
and neutral species
Cross sections
data base
evaporation
GaI3(pellet)
Rate coefficients
data base
Electric circuit
equation
2.00 Torr Ar-Zn
T ~ 400oC,
Zn pressure ~ 10 mTorr
R~1.3 cm, J~300 mA
Hierarchy of the processes leading to Ga formation
+e
GaI2
+GaI2
GaI3
+e
GaI4-
+e
GaI
GaI3+2e
+e
Ga +3I
Ga+3I-
GaIy ,Ga, I +Wall  GaIn(wall)
Kinetic Modeling and Approach Validation
Calculation of emissivity properties of Ar-GaI plasma
Optimization of Emission
Sensitivity analysis
-0.6
-0.4
Emission Efficiency, %
Ga(4p1/2)+GaI3=>GaI+GaI2
Ga(4p1/2)=>Ga(Wall)
GaI=>GaI(Wall)
GaI2=>GaI2(Wall)
I=>I(Wall)
Ga(4p3/2)=>Ga(Wall)
Ga(4p1/2)+e=>Ga(5s)+e
Ga(4p3/2)+e=>Ga(5s)+e
Ga(4p1/2)+e=>Ga(4d)+e
Ga(4p3/2)+e=>Ga(4d)+e
GaI+e=>Ga(4p1/2)+I+e
GaI2+e=>GaI+I+e
GaI3+e=>GaI+I2+e
GaI+e=>Ga(4p3/2)+I+e
40
30
20
10
0
-0.2
0.0
Sensitivity
0.2
0.4
4
8
Ar
Pre 12
ssu 16
re ,
To 20
rr
60
70
80
Tem
tur
pe ra
90
e, C
100
Comparison with experiment:
emission spectra of GaI plasma
[1] J. Phys. D: Appl. Phys. 40 (2007) 3857–3881 Multiscale multiphysics nonempirical approach to calculation of light emission
properties of chemically active nonequilibrium plasma: application to Ar–GaI3 system, S Adamson, M Deminsky, et al.
[2] Journal of Physics D Applied Physics 05/2015; 48(20). Comparative nonempirical analysis of emission properties of the Ar–
MeIn glow discharge (Me = Ga, Zn, Sn, In, Bi, Tl) M Deminsky at al
Atomic emission
Molecular emission
6
1
Simulation
Experiment
1.0
Relative intensity
Emission Intesity, a.u.
4d => 4p3/2
2
4d => 4p1/2
3
6s => 4p3/2, 1/2
4
5s => 4p3/2
5
5s => 4p1/2
Simulation
Experiment
0.8
0.6
0.4
0.2
0
260 280 300 320 340 360 380 400 420
Wave length, nm
0.0
380
384
388
392
Wave length, nm
396
400
Modeling plasma-assisted combustion for turbine appl.
swirl
fuel
air
plasma
ns
after
glow
1 ms
Boltzmann
plug flow
Vibrkin
CBR
flame
0.5 ms
perfectly
WSR
stirred
down
stream
30 ms
plug flow
CBR
P=18.6 atm
Tgas inp=700 K
Process
plasma
electron-impact
t1 – discharge
cross-sections
on
duration
air + methane
Parameter
E/N=200 Td
afterglow
waiting for
ignition
burnout
Mechanism*
for natural
t2=L/v – afterglow
tresid = 0.5gas
msec,combustion, including NOx chemistry
time
T
=
1900
K for methane
t3=30 msec
+ low-temperature burn
extension
+ plasma species reactions (ions, excited)
t =3 msec
Discharge model. Calculated E/N and current
Pulse
generator
С
Air, 1 atm, T = 20 s, C = 33 pF
240
250
Electric chain
Discharge current, A
200
Air, 1 atm, T = 20 s, C = 33 pF
150
100
Discharge current, A
200
st
st pulse
1151
pulse
st
151
pulse
1st pulse
Experiment
160
120
80
40
0
50
-40
0
-50
-80
0.0
0.5
1.0
1.5
Time, ms
2.0
2.5
3.0
0
50
100
Time, ns
The waveform of the calculated form changes within about 20 pulses. In the established form
first and second half cycles are nearly equal. Experiment and theory reasonably agree.
150
equivalence ratio
Extension of combustion limits
320 J/g, 200 Td
pulsed plasma
rich
1
lean
0.4
0.1
no
plasma
[1]. Russian Journal of Physical Chemistry B,
2013, Vol. 7, No. 4, pp. 410–423.
LowTemperature Ignition of Methane–Air
Mixtures under the Action of Nonequilibrium
Plasma, M. A. Deminskii at al ,
10–5
0.31
10–4
10–3
residence time in recirculating flame zone (s)
equivalence
=
ratio
2 [CH4]
[O2]
Effect of additional NOx production by plasma
320 J/g, 200 Td pulse plasma 0.7
NOx (ppm)
1000
0.35
0.8
0.5
0.6
100
10
0.45
0.9
equivalence
ratios
25 ppm
9 ppm
3 ppm
plasma off
1
1600
2000
flame temperature (K)
2400
Optimization: flame stabilization vs NOx generation
ΔT turndown (K)
1000
240 J/l0
100 J/l0
100
100 J/l0
50 J/l0
10
10
100
ΔNOx (ppm)
1000
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