Numerical Simulation of Atmospheric Pressure Discharges Controlled By Dielectric Barrier

Numerical Simulation of Atmospheric Pressure Discharges Controlled By Dielectric Barrier

Wang Dezhen, Wang Yanhui, Zhang Yuantao

State Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Department of Physics, Dalian University of Technology, Dalian 116024, P.R. China

Outline

• Model and equations

• Multipeak and mode of the homogeneous discharges in atmospheric pressure helium

• Radial evolution of the glow discharge in atmospheric pressure helium

• Inhomogeneity of the discharge in atmospheric pressure

helium

Model and equations

• ne / t+·je=Se

• ni / t+·ji =Si

• je = – Dene – e E ne

• ji = – Dini + i E ni

• (x) E / t+jc(x,t)=jT(t)

• G / t = - e [ ji( x1,t) – je ( x1,t) ]

• P / t = e [ ji( x2,t) – je ( x2,t)

A C Power

Dielectric

Multipeak and mode of the homogeneous discharges

Progress

• S.J.Okazaki, et al, “Stable glow plasma at atmospheric pressure”, J. Phys. D:Appl. Phys., 21, 836(1988)

• J.R. Roth, et al, “Surface Modification of Fabrics Using a One-Atmosphere Glow Discharge Plasma to Improve Fabric Wettability, Textile Res. J. 67(5), 359-369(1997)

• F. Massines, et al, “Experimental and Theoretical Study of A Glow Discharge at Atmospheric Pressure Controlled by Dielectric Barrier”, J. Appl. Phys. 83(6), 2950(1998)

• Yu B. Golubovskii, et al, “Modelling of the homogeneous barrier discharge in helium at atmospheric pressure”, J. Phys. D: Appl. Phys. 36, 39(2003)

Multipeak and mode of the homogeneous discharges

Electrical characteristics with one current peak

Fig.1 Electrical characteristics of the discharge with only one current pulse Fig.1 Electrical characteristics of the discharge with only one current pulse per half-cycle of the applied voltage. Simulation parameters: the discharge per half-cycle of the applied voltage. Simulation parameters: the discharge gap width is 0.7 cm, the amplitude and frequency of applied sinusoidal gap width is 0.7 cm, the amplitude and frequency of applied sinusoidal voltage are 3kV and 5kHz, respectively, the thickness and permittivity of voltage are 3kV and 5kHz, respectively, the thickness and permittivity of dielectric barriers are respectively 0.1 cm and 7.5.dielectric barriers are respectively 0.1 cm and 7.5.

Multipeak and mode of the homogeneous discharges

Multipeak characteristics

Fig. 2 Current characteristic for discharge gap width equalFig. 2 Current characteristic for discharge gap width equal to (a)0.5 cm, (b)0.4 cm, (c)0.3 cm, (d)0.2 cm.to (a)0.5 cm, (b)0.4 cm, (c)0.3 cm, (d)0.2 cm. (other conditions as fig.1.)(other conditions as fig.1.)

Multipeak and mode of the homogeneous discharges

Electric field and electron and ion densities for glow mode

Fig. 3 Fig. 3 Spatial variation of the electrical field and the ion and electron Spatial variation of the electrical field and the ion and electron densities over a half cycle for the gap width of 0.5cms. 1 corresponds densities over a half cycle for the gap width of 0.5cms. 1 corresponds to the first current peak, 2 corresponds to the second current peak. to the first current peak, 2 corresponds to the second current peak. Cathode is at x=0.5cm. (other conditions as Fig.1)Cathode is at x=0.5cm. (other conditions as Fig.1)

Multipeak and mode of the homogeneous discharges

Electron and ion densities for glow mode

Fig. 4 Spatio-temporal developments of (a) electron density Fig. 4 Spatio-temporal developments of (a) electron density and (b) ion density over a half cycle for the gap width and (b) ion density over a half cycle for the gap width of 0.5cm. The instantaneous cathode is at x=0.5cm.of 0.5cm. The instantaneous cathode is at x=0.5cm. (other conditions as Fig.1)(other conditions as Fig.1)

( a ) ( b )

Multipeak and mode of the homogeneous discharges

Electric field distributions for two modes

(a) Glow mode (b) Townsend mode

Fig. 5 Spatio-temporal distributions of the electric field Fig. 5 Spatio-temporal distributions of the electric field over a half cycle for the gap width of (a) 0.5cmsover a half cycle for the gap width of (a) 0.5cms and (b) 0.3cm.(other conditions as Fig.1)and (b) 0.3cm.(other conditions as Fig.1)

Multipeak and mode of the homogeneous discharges

Electric field and electron and ion densities for Townsend mode

Fig. 6 Spatial Fig. 6 Spatial structure of the structure of the discharge at 0.3cm discharge at 0.3cm gap width. gap width. (a) electric field. (a) electric field. (b) densities of (b) densities of electrons and ions. electrons and ions. The numbers 1,2,3,4 The numbers 1,2,3,4 corresponds four corresponds four current peaks.current peaks.The cathode is at The cathode is at 0.3cm. (other 0.3cm. (other conditions as Fig.1)conditions as Fig.1)

Multipeak and mode of the homogeneous discharges

Electron and ion densities for Townsend mode

Fig. 7 Spatio-temporal developments of (a) electron density Fig. 7 Spatio-temporal developments of (a) electron density and (b) ion density over a half cycle for the gap width and (b) ion density over a half cycle for the gap width of 0.3 cm. The instantaneous cathode is at x=0.3cm.of 0.3 cm. The instantaneous cathode is at x=0.3cm. (other conditions as Fig.1)(other conditions as Fig.1)

Multipeak and mode of the homogeneous discharges

Electric field and electron and ion densities for two modes

Fig. 8 Glow mode of homogenous barrier discharge with one current pulse per half cycle. Simulating conditions: f=5kHz, U0=2400V, d=0.1cm, dg=0.7cm, ε=7.5.

Fig. 9 Townsend mode of homogenous barrier discharge with one current pulse per half cycle. The barrier thickness d=0.2cm. Other conditions are the same as Fig 8.

Multipeak and mode of the homogeneous discharges

Multipeak discharge operating in two modes

Fig. 10 Multipeak discharge operating in two modes. Driving frequency f=10kHz, U0=3000V, d=0.1cm, dg=0.3cm, ε=7.5.

Multipeak and mode of the homogeneous discharges

Current characteristic for different driving frequency

Fig.11 Current characteristic under driving frequency Fig.11 Current characteristic under driving frequency equal to (a) 40kHz, (b) 10kHz. The gap width is equal to equal to (a) 40kHz, (b) 10kHz. The gap width is equal to 0.3cm and other conditions are as Fig.10.3cm and other conditions are as Fig.1

Multipeak and mode of the homogeneous discharges

Influence of the amplitude of applied voltage on the the discharge current characteristic

Fig. 12 Influence of the amplitude of applied voltage on the Fig. 12 Influence of the amplitude of applied voltage on the behavior of the discharge current. The applied voltage is behavior of the discharge current. The applied voltage is respectively equal to (a) 4000kV, (b) 3000kV, (c) 1800kV. respectively equal to (a) 4000kV, (b) 3000kV, (c) 1800kV. The gap width is equal to 0.3cm and other conditions are as Fig.1The gap width is equal to 0.3cm and other conditions are as Fig.1

Multipeak and mode of the homogeneous discharges

Conclusions1. A homogenous atmospheric pressure DBD in helium,

whether single peak discharge or multipeak discharge, even the same breakdown series of multipeak discharge, can operate in two different modes, i.e. Townsend and glow modes.

2. Discharge modes are governed by external parameters. The glow discharge usually requires thin dielectric layer, wide gas gap, big dielectric constant, high driving frequency or big peak voltage. Otherwise, Townsend discharge occurs. Moreover, in case of multipeak discharge, the Townsend discharge is more easily developed.

Radial evolution of the glow discharge in atmospheric pressure helium

Progress• L. Mangolini et al, “Radial structure of a low-frequency atmospheric-

pressure glow discharge in helium” , Appl. Phys. Lett.,80(10), 1723(2002)

Radial evolution of the glow discharge in atmospheric pressure helium

Radial evolution of the discharge current

ExperimentExperiment Simulation

The gap length is 6mm,driving frequency is 5khz,votage amplitude is 2.4KVL.Mangolini,et al, Appl. Phys.Lett. 80,1722(2002)

The gap length is 3mm,driving frequency is 10KHz,Votage amplitude is 2.0KV.The thickness and permittivity of The thickness and permittivity of dielectric barriers are respectively 0.1 dielectric barriers are respectively 0.1 cm and 7.5.cm and 7.5.

Radial evolution of the glow discharge in atmospheric pressure helium

Radial evolution of the discharge current

The gap length is 6mm,the driving frequency is 5KHz,and voltage is2.9KvL.Mangolini,et al, Appl. Phys.Lett. 80, 1722(2002)

The gap length is 3mm,the driving frequency is 10KHz,and voltage is 2.3Kv

ExperimentExperiment Simulation

Radial evolution of the glow discharge in atmospheric pressure helium

Radial evolution of ion and electron densities (One peak)

Ion densities at time (a) 358.8μs, (b)359.1μs Electron densities at time (c) 358.8μs, (d) 359.1μs

Radial evolution of the glow discharge in atmospheric pressure helium

Radial evolution of ion and electron densities (two peaks)

Ion densities at time (a) 364.5μs, (b)364.8μs Electron densities at time (c) 364.5μs, (d) 364.8μs

Radial evolution of the glow discharge in atmospheric pressure helium

Conclusions

1. In the case of single current peak, the breakdown firstly begins in the central region, and then expand to the edge.

2. In the case of two current pulses, the radial evolution of first peak is similar to the case of single current peak, but the breakdown for second peak firstly ignite at periphery and propagate toward to the center region.

3. Ion and electron densities are almost uniform along the radial direction in wide central region.