Simple modelisa ion o ozone gene a ion by posi i e co ona
discha ge
K. Yanallah1, F. Pon iga2, A. Cas ellanos3, S. Hadj-Ziane1,
Y. Messlem1 and A. Belas i4
1Labo a oi e de Génie Physique, Uni e si é de Tia e , B.P.78, Tia e , Alge ia
2Dp . Física Aplicada II, Uni e sidad de Se illa, A . Reina Me cedes s/n, Spain
3Dp . Elec ónica y Elec omagne ismo, Uni e sidad de Se illa, A . Reina
Me cedes s/n, Spain
4Labo a oi e de Physique des Plasmas, des Ma é iaux Conduc eu e leu s
Applica ions, Uni e si é d’O an (USTO-MB)
Ozone molecule has unique oxidizing p ope ies ha a e in he base o i s many
indus ial applica ions, such as ai cleane s, wa e pu i ica ion, odo con ol, gas ea men ,
e c. [1-4]. The e o e, many s udies ha e been de o ed o un eil he mechanisms o gene a ion
o ozone in elec ical discha ges [5-7], and o inc ease he e iciency o ozone p oduc ion. In
his wo k, we p esen a nume ical s udy o ozone p oduc ion by posi i e DC co ona discha ge.
The elec ical discha ge occu s be ween a wi e and a coaxial cylinde , and pu e oxygen is
eed in o he discha ge cell (Fig. 1). As i is well known, he co ona discha ge is ini ia ed when
he elec ic ield nea he wi e is su icien ly high o ionize he gaseous species. The minimum
elec ic ield is a unc ion o he wi e adius, he su ace oughness o he wi e, ai empe a u e,
and p essu e [8].
Co ona discha ge has been simula ed by using a hyd odynamics model ha combines
he physical p ocesses in he co ona discha ge wi h he chemis y o ozone o ma ion and
des uc ion in he oxygen s eam. Basically, i consis s in a se o con inui y equa ions, coupled
wi h Poisson’s equa ion. The con inui y equa ions go e n he anspo and he gain/loss
balance o e e y species due o he chemical eac ions induced by he elec ical discha ge. The
cu en - ol age cha ac e is ic (CV) measu ed in expe imen s is used as inpu da a o he
nume ical simula ion.
Fig. 2 p esen s he adial dis ibu ion o cha ged species and he elec ic ield o a
posi i e DC co ona discha ge om he wi e (anode) o he cylinde (ca hode) a oom
empe a u e (T = 300 K) and a mosphe ic p essu e. The anode and ca hode adius a e
0.00625 cm and 1.35 cm, espec i ely, he applied ol age is 8 kV, and he gas low a e is 100
cm3/min.
Fig.1. Schema ic diag am o he posi i e co ona discha ge cell.
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0,01 0,1 1
101
103
105
107
109
1011
103
104
105
Densi y (cm-3)
Radial dis ance, (cm)
e
O2
+
O2
-
E(V/cm)
Fig. 2. Radial dis ibu ion o cha ged species (le axis) and elec ic ield ( igh axis) in a posi i e
co ona discha ge, o V = 8 kV and Q = 100 cm3/min.
The dis ibu ion o species is he esul o he compe i ion be ween ioniza ion and elec on
a achmen . Nea he wi e, he elec ic ield is e y high, so ioniza ion p e ails o e a achmen
and new elec ons a e p oduced. A ew millime e s away om he wi e, he ioniza ion a e
equals he a achmen a e. All newly p oduced elec ons a ach o oxygen molecules o o m
nega i e ions,
e + O2 + M → O2- + M (M = O3, O2, e c.).
Theses nega i e ions mo e hen owa ds he discha ge wi e. Ou side he ioniza ion
egion, he elec ic ield s eng h is insu icien o p oduce elec ons. The e o e, posi i e ions d i
in o his olume owa ds he g ounded cylinde . The plasma is in a non-equilib ium s a e and
has a low deg ee o ioniza ion.
0,2 0,4 0,6 0,8 1,0 1,2
0,0
7,0x1015
1,4x1016
2,1x1016
2,8x1016
3,5x1016
O3(cm-3)
Radial dis ance, (cm)
z=10 cm
z=3,6 cm
z=0,36 cm
z=0,036 cm
z=0,0 cm
Fig. 3. Radial dis ibu ion o ozone densi y a i e di e en loca ions along he cylinde , o V = 8
kV and Q = 100 cm3/min.
The adial a ia ion o he ozone densi y is ep esen ed in Fig. 3. As expec ed, ozone
concen a ion inc eases p og essi ely as he oxygen low ad ances along he cylinde . Jus
a e he en y o he oxygen gas in o he discha ge ube (z = 0.0 cm), he adial dis ibu ion o
ozone is highly inhomogeneous. In ha loca ion, he densi y o ozone has a maximum in he
icini y o he wi e, whe e he ac i e egion o he co ona discha ge is loca ed, and hen sha ply
declines. This decline e eals ha ozone di usion has no had enough ime o ac in he adial
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di ec ion. A c ude es ima e o he di usion ime o ozone gi es d ~ 5 s, which is much sho e
han elapsed ime o low. As oxygen gas ad ances along he cylinde , ozone di uses owa ds
he ca hode and i s concen a ion becomes mo e uni o m. Finally, Fig. 4 shows he axial
dis ibu ion o ozone a a cons an adial dis ance and o wo di e en alues o he applied
ol age. A e a ce ain en ance leng h, ozone densi y is obse ed o inc ease linea ly along he
axial di ec ion o low applied ol ages.
The p edic ions o he nume ical simula ion a e compa ed wi h he expe imen al
measu emen s in Fig. 5. In ha igu e, he a e aged ozone densi y has been plo ed as unc ion
o he applied ol age. The esul s o he simula ion a e in quali a i e ag eemen wi h he
expe imen al measu ed da a. The nume ical simula ion ends o o e es ima e he ozone
densi y, as he p edic ed ozone concen a ion is 50% highe han he ac ual measu ed
concen a ion.
0246810
0
1x1016
2x1016
3x1016
4x1016
O3(cm-3)
Axial dis ance, z(cm)
V= 6 K
V= 8 K
Fig. 4. Axial a ia ion o ozone densi y in he icini y o he wi e ( = 0.01668 cm) o wo
di e en applied ol ages and Q = 100 cm3/min.
68
1x1015
2x1015
3x1015
4x1015
10
O3(cm-3)
Applied ol age, V(K )
Expe imen al
Modelisa ion
Fig. 5. Expe imen al and nume ical esul s o ozone densi y as a unc ion he applied ol age o
Q = 100 cm3/min.
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