modeling of a dielectric barrier discharge lamp for uv production · 2009-01-29 · modeling of a...
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COMSOL CONFERENCE - Hannover – November 4th-6th 2008
Modeling of a Dielectric Barrier Discharge Lamp for
UV Production
Modeling of a Dielectric Barrier Discharge Lamp for
UV Production
S. Bhosle1,2, R. Diez1,2, H. Piquet1,2, D. Le Thanh1,2, B. Rahmani1,2, D. Buso1,2
1 LAPLACE, Université de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie); 118 route de Narbonne, F-31062 Toulouse cedex 9, France.2 CNRS; LAPLACE; F-31062 Toulouse, France.Université de Toulouse, 118 route de Narbonne, 31062 Toulouse cedex 9, France
Presented at the COMSOL Conference 2008 Hannover
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OutlineOutline
Introduction- What is an Excilamp?- Dielectric Barrier Discharges (DBD)- Applications of Excilamps
Model Description- Equations used- Boundary Conditions
Obtained results- Influence of the Power Supply Mode- Influence of External Elements- Tool for Efficient Power Converter Design
Conclusion
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E
R(1S0) + R(1S0)
R
hυ
R*2R(1S0) + R(3P2)
R(1S0) + R(3P1)
1Σg+ 3Σu
+
1Σu+
R+R
R+R*
Excimer: contraction of "Excited Dimer"
What is an Excilamp?What is an Excilamp?
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What is an Excilamp?What is an Excilamp?
Energy (x103cm-1)
68
65
2
0
3 4 5 R(Å)
01
13 SP +
01
23 SP +
u1
u1+Σu
1+Σu
3
+Σg1
01
01 SS +
2ndcontinuum173nm
1stcontinuum147nm
147nm
+g0
126Inte
nsi
ty (
a.u
.)
~10nm
Wavelength (a.u.)
Continua:1st 2nd
Excilamp:
-Excimer Lamp
Or
-Exciplex Lamp
(http://www.physics.mq.edu.au/~rmildren/DBDs.html)
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H.T.
Hig
hvo
ltage
gen
erat
or
DielectricDischargegap
Electrode
Electrode
H.T.
Discharge
H.T.
Hig
hvo
ltage
gen
erat
or
DielectricDischargegap
Electrode
Electrode
H.T.
Discharge
DBD: different geometriesDielectric Barrier Discharges (DBD) various geometries
What is an Excilamp?What is an Excilamp?
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What is an Excilamp?What is an Excilamp?
UV
UV
H.T.
Hig
hvo
ltage
gen
erat
or
Ground grid
Internal electrodeExternal tube
Internal tube
Cooling fluid
Discharge gap
DBD: the axisymetric geometry (coaxial)
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What is an Excilamp?What is an Excilamp?
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Applications of excilampsApplications of excilamps
300x103
200
100
0
Irrad
ianc
e (u
.a.)
700600500400300200Wavelength (nm)
Xenon/Chlorine excilamp
Xenon/Chlorine excilamp spectrum
Industrial:- Photochemistry
Environment:- Water Treatment- Sterilization
Health:- skin disease treatment
UVB radiation especially suited for treatment of psoriasis and vitiligo.
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Model DescriptionModel Description
Fluid model:
Plasma out of equilibrium Boltzmann equation
Drift-diffusion equations:
⎪⎩
⎪⎨⎧
±∇−=Γ
=Γ∇+∂∂
EnnD
Stn
rvr
rr
μ
.
⎪⎪⎪⎪⎪
⎩
⎪⎪⎪⎪⎪
⎨
⎧
=∇−∇−∇+∂∂
=∇+∇−∇+∂∂
−=∇−∇
........
.......
).(
).(
)().(
iiiiii
eeeeee
ei
SVnnDtn
SVnnDtn
nneV
rrr
rrr
rr
μ
μ
ε
PDE system to solve:
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*metXe
*resXe
*excXe
+Xe+2Xe
)0(*2
+uXe
)(1*2
+ΣuXe
)(3*2
+ΣuXe
Xe
−e
−e
−e
−e
Ene
rgy
(eV
)
0
8,45
12,13
8,32
Xe2
−e
Xe
XeXe
−e
Xe
Xe
Xe2
Xe2
CollisionsRadiative transitions
152n
m
172n
m
147n
m
Model DescriptionModel Description
Chosen kinetics scheme:
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Boundary conditions:1 - Coupling of volume densities and surface densities through the Weak Boundary Application mode
isesrecsesdesesadsese nnKnKnK
dtdn
−−=
siesrecsesdesesadsene nnKnKnKu +−=Γrr
.For electrons
1 – Boundary Conditions for the Electrostatic Potential
)10502sin(5000)2( ;0)1( 3 telectrodeVelectrodeV ×== π
dtAtIelectrodeVelectrodeV
t
∫=∇=0
)()2(;0)1(v
ε
Electric field discontinuity is taken into account at the charged dielecticboundaries
Voltage Source
Current Source
Model DescriptionModel Description
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Model DescriptionModel Description
0.0020.006
0.008
Metallic electrodes
Dielectriclayers
(dimensions in m)
Discharge gap
to the ground
to the voltage generator
Considered geometry:
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Results obtainedResults obtained
2.10-3
46
x1019
3Σu+ excimer
density (m-3)
position (m)6.10-3
ωt (rad)
0
2π4π
2
3Σu+ excimer
density (m-3)
1
2.10-3
34x1018
electrondensity (m-3)
position (m)6.10-3
ωt (rad)
0
2π
4π
electrondensity (m-3)
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10-5
-1.5
-1
-0.5
0
0.5
1
1.5x 10
4
Time (s)
Vol
tage
s an
d C
urre
nt (
units
in le
gend
)
Comparison between the electrical and the PDE model results in sine wave form at
50kHz Legend:
Applied voltage (V)Voltage drop in the whole gas gap according to the PDE model (V)Total current according to the PDE model(x106A)
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50 100 150 200 250 300 3500.45
0.5
0.55
0.6
Fréquence (kHz)
η172
Efficiency of the excilamp supplied with a sine waveform voltage source.
Results obtainedResults obtained
Frequency (kHz)
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10 30 40 50 800.55
0.6
0.65
0.7
0.75
0.8
Rapport cyclique α (%)
η172
Voltage (V)
-8kV
8kV
1μs 1μs
1μs 1μs
20μs
1τ
1τ
0τ
0τ
=τ
ττα 12
=
Time (μs)
Voltage (V)
-8kV
8kV
1μs 1μs
1μs 1μs
20μs
1τ
1τ
0τ
0τ
=τ
ττα 12
=
Time (μs)
Duty ratio (%)
Results obtainedResults obtained
Efficiency of the excilamp supplied with a pulsed waveform voltage source.
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0 0.5 1 1.5 2 2.5
x 10-5
-1
-0.5
0
0.5
1
1.5x 10
4
Tim e (s ec)
V
Ls=1e-5 H
Ls=5e-5 H
Ls=1e-4 HLs=5e-4 H
Vs
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x 10-3
10
20
30
40
50
60
70
80
90
100
Ls
Pe
rce
nta
ge E
ffic
ien
cyResults obtainedResults obtained
Electrical scheme
Effect of Ls on DBD Efficiency
DBD Voltage under different parasitic inductances
“Simulation of Dielectric Barrier Discharge Lamp Coupled to the External Electrical Circuit” - A. El-Deib, F.P. Dawson, S. Bhosle, D. Buso and G. Zissis – COMSOL Conference 2008 - Boston
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"Design of a Current Converter for the Study of the UV Emission in DBD Excilamps" - R. Díez, H.Piquet, S. Bhosle, J.M. Blaquière, N. Roux - ISIE 2008 IEEE International Symposium on IndustrialElectronics, 30 june-2 july 2008 - Cambridge (England)
Design of a dedicated powerconverter
Results obtainedResults obtained
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ConclusionConclusion
- A PDE model was used to compute the parameters of an operating excilamp- This model was implemented in COMSOL Multiphysics and could be successfully solved in 1D - time dependant- Thanks to COMSOL platform, the model can easily be shared with researchers from abroad of from different backgrounds- The obtained results help in the understanding of the mechanisms involved in the development of the discharge- They led to the design of new power converter topologies, specially dedicated to excilamps