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Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník Faculty of Science, Masaryk University, Brno November 12, 2012
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Page 1: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Simulations of Ar/H2 and H2 MicrowavePlasma

Adam Obrusník

Faculty of Science, Masaryk University, Brno

November 12, 2012

Page 2: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Outline

1. Motivation

2. Geometry

3. Challenges

4. The model

5. Results and Outlook

Page 3: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Motivation

I Growing importance of plasma torches and jets

I Microwave plasma torch (MPT) in doc. Zajícková’s group - fast CNTand iron NP deposition

I Grant cooperation with the Institute of Physics, ASCR (dr.Bonaventura)

I Complex, challenging problem

I Software simulation available - COMSOL, Matlab

Page 4: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Geometry

The atmospheric-pressure microwave plasma torch - CNT, iron NPsynthesis (here at DPE)

Figure: The geometry - MPT

Page 5: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Geometry

Linear antenna microwave reactor - low pressure, NCD synthesis (FZUAV CR)

Figure: The geometry - Ak400

Page 6: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Challenges

I Very complex problemI Turbulent flow (Re ≈ 60 000 near main inlet)

I Highly inhomogeneous, non-isothermal gas mixture

I Relatively small plasma region⇒ very steep velocity/temperaturegradients

I Minimum 11 species and 16 plasma reactions

I All must be solved at least in 2D axial symmetry

I Necessary input data (cross sections, gas properties at very hightemperatures) scarcely available

I Out-of-the-box solutions (COMSOL Plasma Module, Fluent), usuallyinsufficient for such a complex problem (unstable, only for DC,Maxwellian EEDFs, etc...)

Page 7: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Model - schematic view

I Implemented in Matlab with COMSOL API

I Solved in 2D axial symmetry

A schematic overview of the iterative loop

Page 8: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Model - Equations

I Reynolds-averaged Navier-Stokes equations with the k − ε model

ρ∂U∂t+ρ (U · ∇) U−∇·〈ρ(uT ⊗ uT)〉 = −∇·P−∇·µ

[∇ ⊗ U + (∇ ⊗ U)T

]+F.

I Heat equation, diffusion equation for the neutral gas

I Continuity equation for electrons, energy equation for electrons

∂n j

∂t+ ∇ · Γ j + (~u · ∇)n j = R j, Γ j = −µiEni − Di∇ni

I 9 continuity equations for ionized and excited species

I EM field equation (time-harmonic approximation), plasma as a lossydielectric

ε = ε0 −ε0ω

2pe

ν2en + ω2

+ iε0ω

2peνen

ω(ν2

en + ω2)

Page 9: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Model - ReactionsThe following reactions were considered (+ rotational and vibrational H2excitations)

e− + Ar→ 2e− + Ar+

e− + Ar→ e− + Ar∗

e− + Ar+ → Are− + H2 → 2e− + H+2e− + H2 → e− + H + H(n = 2)e− + H2 → e− + H + H(n = 3)e− + H→ e− + H+

e− + H→ e− + H(n = 2)e− + H→ e− + H(n = 3)H2 + H(n = 2)→ H+3 + e−

H2 + H(n = 3)→ H+3 + e−

H2 + H+2 → H+3 + He− + H+ → H(n = 2)e− + H+ → H(n = 3)e− + H+3 → H2 + H(n = 3)2H + H2 → H2 + H23H→ H2 + H

Page 10: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Results - gas flow

Neutral gas properties - simplified fluid dynamics simulations without theplasma

Page 11: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Results - gas flow (MPT)

Experimental verification - fluid dynamics

Page 12: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Results - with plasma (MPT)

Basic plasma characteristics

Page 13: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Results - with plasma (linear antenna MW reactor)

Electron concentration (above), electron temperature (below)

Page 14: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Results - with plasma (linear antenna MW reactor)

Power deposition (above), neutral temperature (below)

Page 15: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Conclusion

1. A very promising algorithm for simulations of complex plasmasdeveloped and implemented using Matlab and COMSOLMultiphysics API

2. Takes into account both the plasma kinetics and neutral gasdynamics

3. Good results for the Linear Antenna MW Plasma source, not sogood for the MW plasma torch

4. Future experimental verification necessary

Page 16: Simulations of Ar/H2 and H2 Microwave Plasmaphysics.muni.cz/~dorian/Obrusnik.pdf · Simulations of Ar/H 2 and H 2 Microwave Plasma Adam Obrusník ... COMSOL, Matlab. Geometry The

Conclusion

Thank you for your attention.


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