Effective dissociation temperature for estimation of electric arc plasma composition
Spectroscopy investigations of the thermal multicomponent plasma of the electric arc discharge between copper electrodes in carbon dioxide flow were carried out. The technique of calculation of plasma equilibrium composition is discussed. The influence of thermal dissociation of molecular gas on t...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2011 |
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| Формат: | Стаття |
| Мова: | Англійська |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2011
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| Цитувати: | Effective dissociation temperature for estimation of electric arc plasma composition / I.L. Babich, V.F. Boretskij, A.N. Veklich // Вопросы атомной науки и техники. — 2011. — № 1. — С. 98-100. — Бібліогр.: 9 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859667404920979456 |
|---|---|
| author | Babich, I.L. Boretskij, V.F. Veklich, A.N. |
| author_facet | Babich, I.L. Boretskij, V.F. Veklich, A.N. |
| citation_txt | Effective dissociation temperature for estimation of electric arc plasma composition / I.L. Babich, V.F. Boretskij, A.N. Veklich // Вопросы атомной науки и техники. — 2011. — № 1. — С. 98-100. — Бібліогр.: 9 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Spectroscopy investigations of the thermal multicomponent plasma of the electric arc discharge between copper
electrodes in carbon dioxide flow were carried out. The technique of calculation of plasma equilibrium composition is
discussed. The influence of thermal dissociation of molecular gas on the plasma state is estimated. It was assumed that
the thermal dissociation of molecules of working gas play the key role in deviation from local thermodynamic
equilibrium (LTE) in plasma.
Спектроскопічними методами досліджено термічну багатокомпонентну плазму електродугового розряду
між мідними електродами у потоці вуглекислого газу. Обговорюється методика розрахунку рівноважного
складу плазми. Оцінено вплив термічної дисоціації молекулярного газу на стан плазми. Припускається, що
термічна дисоціація молекул робочого газу є основним механізмом відхилення від локальної термодинамічної
рівноваги в плазмі.
Спектроскопическими методами исследована термическая многокомпонентная плазма электродугового
разряда между медными электродами в потоке углекислого газа. Обсуждается методика расчета равновесного
состава плазмы. Оценено влияние термической диссоциации молекулярного газа на состояние плазмы.
Предполагается, что термическая диссоциация молекул рабочего газа является основным механизмом
отклонения от локального термодинамического равновесия в плазме.
|
| first_indexed | 2025-11-30T12:07:07Z |
| format | Article |
| fulltext |
EFFECTIVE DISSOCIATION TEMPERATURE FOR ESTIMATION
OF ELECTRIC ARC PLASMA COMPOSITION
I.L. Babich, V.F. Boretskij, A.N. Veklich
Taras Schevchenko National University of Kiev, Radio Physics Faculty, Kiev, Ukraine
E-mail: boretskij@univ.kiev.ua
Spectroscopy investigations of the thermal multicomponent plasma of the electric arc discharge between copper
electrodes in carbon dioxide flow were carried out. The technique of calculation of plasma equilibrium composition is
discussed. The influence of thermal dissociation of molecular gas on the plasma state is estimated. It was assumed that
the thermal dissociation of molecules of working gas play the key role in deviation from local thermodynamic
equilibrium (LTE) in plasma.
PACS: 51.30.+i, 52.70.-m
1. INTRODUCTION
A large amount of arc plasma investigation has been
carried out. This is caused by wide application of electric
arc discharges in different shielding gases or their
mixtures in numerous industrial processes. Therefore it is
important to perform investigations to have full
understanding of physical processes in discharge plasma,
at the electrode surface and their interaction as well as
influence of environment.
In our previous investigations [1] we found that in
some experimental modes the plasma state is not in local
thermal equilibrium (LTE). It was shown that
hydrodynamic cooling does not effect on the deviation
from LTE in monoatomic. It was supposed that this effect
has no influence on state of molecule gas plasma too.
Therefore, it was assumed that only the thermal
dissociation plays the key role in deviation from LTE.
Naturally, partial LTE model must be used to describe
plasma properties in such case.
The main aim of this study is an estimation of plasma
composition under assumption of two temperature
behavior based on experimentally obtained plasma
temperature, electron density and metal content.
2. EXPERIMENTAL INVESTIGATIONS
The electric arc was ignited between copper non-
cooled electrodes in a working gas flow of 6.45 slpm. The
diameter of the rod electrodes was of 6 mm. All
experimental investigations were carried out in average
cross section of discharge gap of 8 mm at arc currents 3.5,
30, 50 and 100 A.
Monochromator coupled with CCD linear image
sensor (B/W) Sony ILX526A [2] were used in
investigations of spatial distribution of spectral line
emission. The control of the CCD linear image sensor was
realized by the IBM personal computer. The radial
temperature profiles T(r) were determined by Boltzmann
plot method using CuI spectral lines 427.5, 465.1, 510.5,
515.3, 521.8, 570.0, 578.2, 793.3 and 809.3 nm.
To determine the radial profile of electron density we
investigated the shape of copper spectral lines 515.3 and
448.0 nm broadened by the dominating quadratic Stark
effect. The measurements were carried out by techniques
based on a Fabri-Perot interferometer (FPI) [3].
Unfortunately the width of these spectral lines at arc
current 3.5 A is practically comparable with instrument
function of FPI. Therefore, to extend the measuring range
of the electron density we studied the radial distribution
of absolute intensity of a spectral line CuI 465.1 nm [2].
Copper atom concentration was obtained by linear
laser absorption spectroscopy technique [4].
3. RESULTS AND DISCUSSIONS
According to the previous results [1] the electric
discharge plasma in CO2 flow can be in LTE at arc
current 3.5 A but not at arc current 30 A. To check these
results we additionally carefully examined spectroscopic
data, which were used in temperature and electron density
determination.
Radial profiles of plasma temperature T(r) at different
arc currents are shown in Fig. 1. We used spectroscopic
data based on critical review in [5]. Distributions of
electron density Ne(r) obtained from the width of spectral
line CuI 448.0 nm for different experimental modes are
shown in Fig. 2. Shapes of spectral line CuI 515.3 nm
were omitted because of influence of self-absorption.
The values of T(r) and Ne(r) were used in calculation
of plasma compositions (Fig. 3) by approach discussed in
[1].
Copper atom concentrations in plasma obtained by
optical emission spectroscopy (OES) as well as by linear
laser absorption spectroscopy (LAS) techniques at arc
current 3.5 A are showed in Fig. 4. As one can see the
results are in good agreement which can be an additional
confirmation of the assumption of the plasma state in this
experimental mode.
0 1 2 3
6000
8000
10000
12000
r, mm
T, K
Fig. 1. Radial profiles of plasma temperature at arc
currents: – 3.5, – 30, – 50 and –100 A
98 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2011. № 1.
Series: Plasma Physics (17), p. 98-100.
mailto:boretskij@univ.kiev.ua
0 1 2 3 4
1E14
1E15
1E16
r, mm
Ne, cm-3
Fig. 2. Radial profiles of electron density at arc currents:
– 3.5, – 30, – 50 and –100 A
0 1
1E12
1E14
1E16
1E18
99
2
C+O+
CO2
O
O2
CO
Cu C
Cu+e
r, mm
Nj, cm-3
Fig. 3. Plasma composition at arc current 3.5 A
0 1
1E12
1E14
1E16
1E18
2r, mm
NCu, cm-3
Fig. 4. Radial profiles of NCu obtained by LAS ( ) and
OES ( ) techniques at arc current 3.5 A
0 1 2 3
1E12
1E14
1E16
1E18
r, mm
NCu, cm-3
Fig. 5. Radial profiles of NCu obtained by LAS technique
at arc current 30 A
Unfortunately, LTE in arc plasma at discharge current
30…100 A was not realized. Radial distribution of copper
atom concentrations in plasma at arc current 30 A was
obtained only by linear laser absorption spectroscopy
technique (Fig. 5).
In paper [1] was assumed that the thermal dissociation
play the key role in deviation from LTE in CO2 plasma at
arc current 30 A. Peculiarities of CO2 dissociation were
studied theoretically in [6]. Author showed that at
temperatures kT > 0.05 D (D - dissociation energy)
dissociation rate constant significantly lower than its
equilibrium value. Dissociation rate constant can be
estimated from the calculation of plasma composition
based on experimental values of plasma temperature,
electron density and copper atom concentration. In this
case we assumed dissociation rate constant to be an
unknown value.
In our previous papers [1, 7] two different schemes of
dissociation processes were discussed. One of them is
next:
CO2 ⇔ C + 2O. (1)
The result of our calculation showed that the value of
dissociation rate constant of the reaction (1) at axial point
of the average cross section of the discharge is lgK ≈ 23.
Equilibrium value of the dissociation rate constant for this
reaction can be found in [8] where the maximum value of
lgK is 6.7 for T = 10000 K. Extrapolation of lgK to
obtained in our calculation value 23 leads to temperatures
much higher than 10000 K. Therefore, one can conclude
that reaction (1) cannot be used to interpret dissociation
processes.
The second scheme of dissociation that we used
previously is:
CO2 ⇔ CO + ½O2, (2)
CO ⇔ C + O, (3)
O2 ⇔ 2O. (4)
Two of these reactions (2-3) can be responsible for
deviation from LTE in plasma. The third of them (4) can
be assumed equilibrium because of quite low relaxation
time of dissociation [9].
Further analysis was divided into three approaches:
1. calculation of dissociation rate constant for reaction (2),
reaction (3) was assumed equilibrium;
2. calculation of dissociation rate constant for reaction (3),
reaction (2) was assumed equilibrium;
3. calculation of effective dissociation temperature which
is the same for both non-equilibrium reactions (2-3).
The calculated dissociation rate constants were
compared with their equilibrium values to estimate
effective dissociation temperatures (Fig. 6).
0 1
2000
4000
6000
8000
2
1
2
3
T, K
r, mm
Fig. 6. Plasma temperature ( ) and effective dissociation
temperatures obtained by different approaches
REFERENCES
Concentration of CO2 and CO molecules calculated by
approaches 1-3 are shown in Fig. 7, 8. The results of the
approaches 1-2 lead to very extreme difference between
temperatures (see Fig. 6). Approach 3 gives more
plausible values of effective dissociation temperatures and
CO2 and CO concentration. Therefore, one can conclude
that dissociation of both reactions (2-3) is not equilibrium.
1. I.L. Babich, V.F. Boretskij, A.N. Veklich. Plasma of
electric arc discharge between copper electrodes in a
gas flow // Problems of Atomic Science and
Technology. Series “Plasma Physics” (14). 2008. N6,
p. 171-173.
2. I.L. Babich, V.F. Boretskij, and A.N. Veklich. Shapes
of spectral lines of nonuniform plasma of electric arc
discharge between copper electrodes// AIP Conference
Proc. 2007, v. 938, p. 252-257.
100
1E12
1E14
1E16
1E18
0 1 2
1
2
3
r, mm
NCO2
, cm-3
1E12
1E14
1E16
1E18
3. A.N. Veklich, V.Ye. Osidach. The determination of
electron density in electric arc discharge plasma //
Bulletin of the University of Kiev. Series “Physics &
Mathematics”. 2004, N2, p. 428-435 (in Ukrainian).
4. I.L. Babich, V.F. Boretskij, R.V. Minakova,
A.N. Veklich. Plasma of electric arc between electrodes
from composite materials // Problems of Atomic
Science and Technology. Series “Plasma Physics”
(14). 2008. N 6, p. 159-161.
5. I.L. Babich, V.F. Boretskij, A.N. Veklich, A.І. Ivanisik,
R.V. Semenyshyn, L.A. Kryachko, R.V. Minakova.
Spectroscopy of electric arc plasma between composite
electrodes Ag-CuO // Electrical contacts and
electrodes/ Kyiv: “Frantsevich Institute for Problems of
Materials Science”. 2010, p. 82-115 (in Ukrainian).
Fig. 7. CO2 concentration obtained by different
approaches
0 1 2
1
2
3
r, mm
N
CO
, cm-3
6. N.M. Kuznetsov. Problems in the theory of
monomolecular decay of one-component gas and the
rate constant for dissociation of CO2 at high tempe-
ratures // PMTF. 1972, N3, p. 46-52 (in Russian).
7. A.N. Veklich, I.L. Babich, A.I. Cheredarchuk. Thermal
dissociation in thermal plasma of electric arc discharges
in air and carbon dioxide// Proc. of 15th Int. Symp. on
Plasma Chem. V.III. Orleans 9-13 July, 2001/ GREMI,
CNRS, Orleans, 2001, p. 849-853.
Fig. 8. CO concentration obtained by different approaches
CONCLUSIONS 8. L.V. Gurvich, I.V. Veits, et al. Thermodynamic
properties of individual substances. M.: “Nauka”, 1979
(in Russian).
The assumptions of plasma state were confirmed using
approved set of spectroscopic data. It was shown that
reaction where carbon dioxide molecule dissociates into
atoms of oxygen and carbon cannot be used to interpret
dissociation processes. It was found that dissociation of
both reactions (2-3) is not equilibrium.
9. Y. B. Zeldovich and Y. P. Riser. Physics of Bow Shock
and High Temperature Phenomena. M.: “Nauka”, 1966
(in Russian).
Article received 15.09.10
ЭФФЕКТИВНАЯ ТЕМПЕРАТУРА ДИССОЦИАЦИИ В РАСЧЕТАХ СОСТАВА ПЛАЗМЫ
ЭЛЕКТРОДУГОВОГО РАЗРЯДА
И.Л. Бабич, В.Ф. Борецкий, А.Н. Веклич
Спектроскопическими методами исследована термическая многокомпонентная плазма электродугового
разряда между медными электродами в потоке углекислого газа. Обсуждается методика расчета равновесного
состава плазмы. Оценено влияние термической диссоциации молекулярного газа на состояние плазмы.
Предполагается, что термическая диссоциация молекул рабочего газа является основным механизмом
отклонения от локального термодинамического равновесия в плазме.
ЕФЕКТИВНА ТЕМПЕРАТУРА ДИСОЦІАЦІЇ В РОЗРАХУНКАХ СКЛАДУ ПЛАЗМИ
ЕЛЕКТРОДУГОВОГО РОЗРЯДУ
І.Л. Бабіч, В.В. Борецький А.М. Веклич
Спектроскопічними методами досліджено термічну багатокомпонентну плазму електродугового розряду
між мідними електродами у потоці вуглекислого газу. Обговорюється методика розрахунку рівноважного
складу плазми. Оцінено вплив термічної дисоціації молекулярного газу на стан плазми. Припускається, що
термічна дисоціація молекул робочого газу є основним механізмом відхилення від локальної термодинамічної
рівноваги в плазмі.
1. INTRODUCTION
3. RESULTS AND DISCUSSIONS
|
| id | nasplib_isofts_kiev_ua-123456789-90888 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-30T12:07:07Z |
| publishDate | 2011 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Babich, I.L. Boretskij, V.F. Veklich, A.N. 2016-01-05T18:19:04Z 2016-01-05T18:19:04Z 2011 Effective dissociation temperature for estimation of electric arc plasma composition / I.L. Babich, V.F. Boretskij, A.N. Veklich // Вопросы атомной науки и техники. — 2011. — № 1. — С. 98-100. — Бібліогр.: 9 назв. — англ. 1562-6016 PACS: 51.30.+i, 52.70.-m https://nasplib.isofts.kiev.ua/handle/123456789/90888 Spectroscopy investigations of the thermal multicomponent plasma of the electric arc discharge between copper electrodes in carbon dioxide flow were carried out. The technique of calculation of plasma equilibrium composition is discussed. The influence of thermal dissociation of molecular gas on the plasma state is estimated. It was assumed that the thermal dissociation of molecules of working gas play the key role in deviation from local thermodynamic equilibrium (LTE) in plasma. Спектроскопічними методами досліджено термічну багатокомпонентну плазму електродугового розряду між мідними електродами у потоці вуглекислого газу. Обговорюється методика розрахунку рівноважного складу плазми. Оцінено вплив термічної дисоціації молекулярного газу на стан плазми. Припускається, що термічна дисоціація молекул робочого газу є основним механізмом відхилення від локальної термодинамічної рівноваги в плазмі. Спектроскопическими методами исследована термическая многокомпонентная плазма электродугового разряда между медными электродами в потоке углекислого газа. Обсуждается методика расчета равновесного состава плазмы. Оценено влияние термической диссоциации молекулярного газа на состояние плазмы. Предполагается, что термическая диссоциация молекул рабочего газа является основным механизмом отклонения от локального термодинамического равновесия в плазме. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Низкотемпературная плазма и плазменные технологии Effective dissociation temperature for estimation of electric arc plasma composition Ефективна температура дисоціації в розрахунках складу плазми електродугового розряду Эффективная температура диссоциации в расчетах состава плазмы электродугового разряда Article published earlier |
| spellingShingle | Effective dissociation temperature for estimation of electric arc plasma composition Babich, I.L. Boretskij, V.F. Veklich, A.N. Низкотемпературная плазма и плазменные технологии |
| title | Effective dissociation temperature for estimation of electric arc plasma composition |
| title_alt | Ефективна температура дисоціації в розрахунках складу плазми електродугового розряду Эффективная температура диссоциации в расчетах состава плазмы электродугового разряда |
| title_full | Effective dissociation temperature for estimation of electric arc plasma composition |
| title_fullStr | Effective dissociation temperature for estimation of electric arc plasma composition |
| title_full_unstemmed | Effective dissociation temperature for estimation of electric arc plasma composition |
| title_short | Effective dissociation temperature for estimation of electric arc plasma composition |
| title_sort | effective dissociation temperature for estimation of electric arc plasma composition |
| topic | Низкотемпературная плазма и плазменные технологии |
| topic_facet | Низкотемпературная плазма и плазменные технологии |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/90888 |
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