Download Numerical Simulation of Atmospheric Pressure Glow Discharges

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
•
AC
Power
 ne / t+·je=Se
Dielectric
•
 ni / t+·ji =Si
•
je = – Dene – e E ne
•
ji = – Dini + i E ni
•
e(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)
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 OneAtmosphere 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
per half-cycle of the applied voltage. Simulation parameters: the discharge
gap width is 0.7 cm, the amplitude and frequency of applied sinusoidal
voltage are 3kV and 5kHz, respectively, the thickness and permittivity of
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 equal
to (a)0.5 cm, (b)0.4 cm, (c)0.3 cm, (d)0.2 cm.
(other conditions as fig.1.)
Multipeak and mode of the homogeneous discharges
Electric field and electron and ion densities for glow mode
Fig. 3 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
to the first current peak, 2 corresponds to the second current peak.
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
(a)
Fig. 4
(b)
Spatio-temporal developments of (a) electron density
and (b) ion density over a half cycle for the gap width
of 0.5cm. The instantaneous cathode is at x=0.5cm.
(other conditions as Fig.1)
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
over a half cycle for the gap width of (a) 0.5cms
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
structure of the
discharge at 0.3cm
gap width.
(a) electric field.
(b) densities of
electrons and ions.
The numbers 1,2,3,4
corresponds four
current peaks.
The cathode is at
0.3cm. (other
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
and (b) ion density over a half cycle for the gap width
of 0.3 cm. The instantaneous cathode is at x=0.3cm.
(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
equal to (a) 40kHz, (b) 10kHz. The gap width is equal to
0.3cm 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
behavior of the discharge current. The applied voltage is
respectively equal to (a) 4000kV, (b) 3000kV, (c) 1800kV.
The gap width is equal to 0.3cm and other conditions are as Fig.1
Multipeak and mode of the homogeneous discharges
Conclusions
1.
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 atmosphericpressure 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
Experiment
The gap length is 6mm,driving frequency is
5khz,votage amplitude is 2.4KV
L.Mangolini,et al, Appl. Phys.Lett. 80,
1722(2002)
Simulation
The gap length is 3mm,driving frequency
is 10KHz,Votage amplitude is 2.0KV.
The thickness and permittivity of
dielectric barriers are respectively 0.1
cm and 7.5.
Radial evolution of the glow discharge in atmospheric pressure helium
Radial evolution of the discharge current
Experiment
The gap length is 6mm,the driving
frequency is 5KHz,and voltage is2.9Kv
L.Mangolini,et al, Appl. Phys.Lett.
80, 1722(2002)
Simulation
The gap length is 3mm,the driving
frequency is 10KHz,and voltage is 2.3Kv
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.