Non-equilibrium chemically active plasma modeling with Chemical Workbench

"Non-equilibrium chemically active plasma: modeling with Chemical Workbench Deminsky Maxim Kintech. Lab 23 July 2015

Outline ü Chemical Work Bench (CWB) – toll for conceptual design of chemically oriented phenomena ü Problems arising during elaboration of plasma model ü Collection of plasma model in CWB environment ü Coupling of plasma models with other models ü Data needed for simulation: construction of plasma-chemical mechanism in CWB ü Recovering of unknown characteristics of elementary plasmachemical processes in CWB ü Example of modeling of mercury-free light sources ü 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 Kintech. DB Substance properties Kinetic mechanisms Chemical workbench

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: ü Chemical Workbench – an integrated environment for the development and reduction of chemical mechanisms, and conceptual design of the chemistry intensive technological processes ü Khimera – a unique tool for calculating microscopic parameters from first-principles calculations ü Kintech. DB – 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 Ø Ø Ø Combustion Plasma Chemistry Pollution Control Waste Treatment and Recovering Metallurgy General Chemical Kinetics and Thermodynamics Ø High Temperature In-Organic Chemistry Ø Thermal and Plasma Hydrocarbon Pyrolysis Processes Ø 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… 0 D or 0 D(+) dimension 2 D or 3 D 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 - solution of balance equations for chemical species

CWB plasma model’s collection (Types) Types: Plasma Model – EEDF solution with Chemical reactions Calorimetric Bomb Reactor (CBR) – 0 D, 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) – 0 D(+), 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 1 st pulse 2 nd pulse Admixing of surrounding gas Flow. Rate 2 tmix Flow. Rate 1 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) Flow. Rate 1/ Flow. Rate 2 ~ 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

Kintech. DB - databank of physical-chemical data and information system for multidisplinary R&D projects Applications ------------------------(CWB®, TRASS®, Chemkin®, Fluent®, ANSYS CFX®, Star-CD®) Kintech. DB 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

Kintech. DB 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, 5 p 4 (IP=9 e. V, N=4), 5 s 2 (IP=17. 84 e. V, N=2) and 4 d 10 (IP=47 e. V, 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 e. V. 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)).

Transport properties calculation Data Base of interaction potentials and collisional integrals

Transport properties calculation Transport coefficients are calculated by the accurate formulas of the Chapman. Enskog 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 Candidates: Halides of Ga, Zn, In, Cu, Al, Cd, Sb, Bi, Tl 2. 00 Torr Ar-Zn T ~ 400 o. C, Zn pressure ~ 10 m. Torr R~1. 3 cm, J~300 m. A Boltzmann equation for the EEDF System of kinetic equations for charged and neutral species Cross sections data base Rate coefficients data base Electric circuit equation

Hierarchy of the processes leading to Ga formation

Kinetic Modeling and Approach Validation Calculation of emissivity properties of Ar-Ga. I plasma Sensitivity analysis Optimization of Emission

Comparison with experiment: emission spectra of Ga. I 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–Ga. I 3 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– Me. In glow discharge (Me = Ga, Zn, Sn, In, Bi, Tl) M Deminsky at al Atomic emission Molecular emission

Modeling plasma-assisted combustion for turbine appl. swirl fuel air plasma ns after glow 1 ms Boltzmann plug flow electron-impact cross-sections on air + methane flame 0. 5 ms perfectly stirred down stream 30 ms plug flow Mechanism* for natural gas combustion, including NOx chemistry + low-temperature extension for methane + plasma species reactions (ions, excited)

Discharge model. Calculated E/N and current

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. Low. Temperature 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 [CH 4] [O 2]

Effect of additional NOx production by plasma

Optimization: flame stabilization vs NOx generation

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