Shock-wave dynamics under expansion of the spark channel in gas
The process of formation of shock waves arising at a spark discharge is considered. According to analysis of experimental statistics the results of the various authors about dynamics of development of the spark channel are exposed to a doubt. The definition of a concept of time of formation of a sho...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Cite this: | Shock-wave dynamics under expansion of the spark channel in gas / K.V. Korytchenko, Yu.Ya. Volkolupov, M.A. Krasnogolovets, M.A. Ostrizhnoy, V.I. Chumakov, T.A. Semenets // Вопросы атомной науки и техники. — 2001. — № 5. — С. 45-47. — Бібліогр.: 5 назв. — англ. |
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irk-123456789-784122015-03-17T03:02:11Z Shock-wave dynamics under expansion of the spark channel in gas Korytchenko, K.V. Volkolupov, Yu.Ya. Krasnogolovets, M.A. Ostrizhnoy, M.A. Chumakov, V.I. Semenets, T.A. The process of formation of shock waves arising at a spark discharge is considered. According to analysis of experimental statistics the results of the various authors about dynamics of development of the spark channel are exposed to a doubt. The definition of a concept of time of formation of a shock wave is offered and its quantitative evaluation is carried out. It has allowed to distinguish the process of formation from the process of development of a shock wave, and also to explain the fact of formation of several shock waves at a spark discharge. The offered work can be put in a basis of a technique for evaluation of the intensity of a shock wave formed at a spark discharge. 2001 Article Shock-wave dynamics under expansion of the spark channel in gas / K.V. Korytchenko, Yu.Ya. Volkolupov, M.A. Krasnogolovets, M.A. Ostrizhnoy, V.I. Chumakov, T.A. Semenets // Вопросы атомной науки и техники. — 2001. — № 5. — С. 45-47. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS numbers: 52.35.Tc, 52.90.+z http://dspace.nbuv.gov.ua/handle/123456789/78412 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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The process of formation of shock waves arising at a spark discharge is considered. According to analysis of experimental statistics the results of the various authors about dynamics of development of the spark channel are exposed to a doubt. The definition of a concept of time of formation of a shock wave is offered and its quantitative evaluation is carried out. It has allowed to distinguish the process of formation from the process of development of a shock wave, and also to explain the fact of formation of several shock waves at a spark discharge. The offered work can be put in a basis of a technique for evaluation of the intensity of a shock wave formed at a spark discharge. |
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Korytchenko, K.V. Volkolupov, Yu.Ya. Krasnogolovets, M.A. Ostrizhnoy, M.A. Chumakov, V.I. Semenets, T.A. |
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Korytchenko, K.V. Volkolupov, Yu.Ya. Krasnogolovets, M.A. Ostrizhnoy, M.A. Chumakov, V.I. Semenets, T.A. Shock-wave dynamics under expansion of the spark channel in gas Вопросы атомной науки и техники |
| author_facet |
Korytchenko, K.V. Volkolupov, Yu.Ya. Krasnogolovets, M.A. Ostrizhnoy, M.A. Chumakov, V.I. Semenets, T.A. |
| author_sort |
Korytchenko, K.V. |
| title |
Shock-wave dynamics under expansion of the spark channel in gas |
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Shock-wave dynamics under expansion of the spark channel in gas |
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Shock-wave dynamics under expansion of the spark channel in gas |
| title_fullStr |
Shock-wave dynamics under expansion of the spark channel in gas |
| title_full_unstemmed |
Shock-wave dynamics under expansion of the spark channel in gas |
| title_sort |
shock-wave dynamics under expansion of the spark channel in gas |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2001 |
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http://dspace.nbuv.gov.ua/handle/123456789/78412 |
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Shock-wave dynamics under expansion of the spark channel in gas / K.V. Korytchenko, Yu.Ya. Volkolupov, M.A. Krasnogolovets, M.A. Ostrizhnoy, V.I. Chumakov, T.A. Semenets // Вопросы атомной науки и техники. — 2001. — № 5. — С. 45-47. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-06T02:31:07Z |
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2025-07-06T02:31:07Z |
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| fulltext |
SHOCK-WAVE DYNAMICS UNDER EXPANSION
OF THE SPARK CHANNEL IN GAS
K.V. Korytchenko, Yu.Ya. Volkolupov1, M.A. Krasnogolovets1, M.A. Ostrizhnoy1, V.I. Chu-
makov1, T.A. Semenets1
Kharkov Military University, Kharkov, Ukraine
1 Kharkov National University of Radioelectronics, Kharkov, Ukraine
The process of formation of shock waves arising at a spark discharge is considered. According to analysis of experi-
mental statistics the results of the various authors about dynamics of development of the spark channel are exposed
to a doubt. The definition of a concept of time of formation of a shock wave is offered and its quantitative evalua-
tion is carried out. It has allowed to distinguish the process of formation from the process of development of a shock
wave, and also to explain the fact of formation of several shock waves at a spark discharge. The offered work can be
put in a basis of a technique for evaluation of the intensity of a shock wave formed at a spark discharge.
PACS numbers: 52.35.Tc, 52.90.+z
During study of a possibility of realization of a deto-
nation in the air by immediate initiation of a fuel mix-
ture, the shock wave, which is formed at an electrical
discharge detected qualitatively other character of dy-
namics of expansion of the spark channel.
It is known that the current of the high densities is
accompanied by the concentrated emission of Joule
heat. It leads to force heating of plasma, its thermaliza-
tion, probably, to the further growth of ionization al-
ready by a thermal way. The fast raise of the gas tem-
perature not compensated so fast warmly by a tap, re-
duces in a sharp raise of pressure in the current channel.
The cylindrical shock wave is appeared. The first ampli-
tude of a shock wave is supposed to be so great, that the
temperature behind front is sufficient for thermal ioniza-
tion of gas. Thus the boundary of the current channel is
almost inseparable from the front of a shock wave. But
soon, with deviation from the axes, the shock wave
weakens, ceases to ionize gas and comes off the slower
extending boundary highly of ionized area – spark chan-
nel. The channel extends now owing to a radial disper-
sion of gas enlarged by a shock wave, and operation of a
thermal conduction.
In Fig. 1, 2 the shock waves are reduced, the radiant
of which are the spark discharges [1]. As it is seen from
these photos, during a spark discharge some shock
waves are formed. Besides it is necessary, that the tem-
perature in the channel can reach 20000K [2]. If the last
value corresponds to translation temperature, then the
shock wave should be formed at a normal density of an
air and atmospheric pressure with an abrupt change of
pressure in front no less than 180 atm. In turn, it would
mean, that by a spark discharge it would be possible im-
mediately to initiate a detonation of fuel mixtures at
normal conditions. For example, for initiation of
propane–oxygen mixture one needs a shock wave in
these conditions with an abrupt change in front of the
order of 100 atm. Practically to realize the latter it was
not possible at atmospheric pressure, that basically dif-
fers from results obtained in early works [3, 4].
Fig.1. Shock waves caused by an electrical discharge in gas.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 45-47.
45
It is known that the initial energy of spark discharge
distribution has a nonequilibrium character as on the de-
gree of freedoms in gas in whole, and between gas
molecules on excitation levels of degree of freedoms. In
turn, each of processes has own characteristic time of
equilibrium steadying. A part of the discharge energy is
spent for ionization and dissociation of gas molecules
with appropriate, from time-to-time, recombinations.
Besides dynamics of an electric discharge immediately
influences a character of energy distribution in gas (how
it happens, is described below). As a radiant of shaping
a shock wave is the translation energy of gas molecules
it is important to carry out the analysis of all factors in-
fluencing the pumping velocity of this aspect of an ener-
gy.
To begin it is necessary to determine the time of
shaping a shock wave. There are experimental and theo-
retical works devoted to study of a stage of initial ex-
pansion of the spark channel [1]. Though the judge-
ments of the various authors concerning the process of
expansion of the channel will not be coordinated among
themselves, it is possible to consider as established, that
in the beginning of a current flow the fast expansion of
channels takes place with a velocity of the order of gas
molecules thermal velocity. At the later stage of its de-
velopment the spark channel extends considerably slow-
er. The shock wave velocity as a function of the dis-
tance to a center of the spark channel constructed by
Folye data is shown in Fig. 2.
Fig. 2. The velocity of shock wave rv versus the
distance r from the center of the spark channel.
Explanation of a concept of the shock wave forma-
tion time allows to remove incompatibilities in the
judgements of the various authors. The shock wave for-
mation time is a phase of time, during which the ther-
modynamic equilibrium on translation degree of free-
doms in a locally heated volume of gas (spark channel)
would be established, if it was in limited volume. In a
real discharge is actually formed such thermodynamic
distribution of parameters, which corresponds to a solu-
tion of a task about force explosion.
Distribution of densities and temperatures for a self-
similar solution in dimensionless magnitudes are re-
duced in Fig. 3, 4 [5]. The shock wave formation time
swτ is of the order of average time between gas-kinetic
collisions in gas gkτ :
vlgksw /=≈ ττ , (1)
where l is the average gas-kinetic track length; v is the
average velocity of molecules of gas.
Fig. 2. Distribution of density behind a shock wave
at γ = 1, 4.
Fig. 3. Distribution of temperature behind a shock
wave at γ = 1,4: 1 - spherical case; 2 – cylindrical
case, 3 – flat case.
It is explained that during a shock wave formation
all molecules which were in locally heated volume of
gas simultaneously participated.
The table with the calculated values of relaxation
time for various processes is shown below [1]. Dynam-
ics of shock wave development proceeds with the veloc-
ity that is not exceeding a sound velocity of heated
medium. Therefore the shock wave velocity distribution
as a minimum by an order is lower than a velocity of its
formation. It explains inconsistencies in data obtained
by the various authors.
The shock wave formation time shown in Table 1 is
no less then 10-4 s with the pressure =p 1 atm. With
46
growth of a volumetrical power density of discharge en-
ergy releasing the shock wave formation time is re-
duced, as the faster growth of temperature in the chan-
nel takes place.
Table 1. The calculated values of relaxation time for
various processes with р = 1atm.
Process τ∆ , s
Maxwell velocity of electrons distribu-
tion
Ionization
Transmission of an energy from elec-
trons to atoms
Maxwell velocity of atoms distribution
10-13
10-12
10-5 – 10-6
10-8– 10-10
The latter means magnification of an average veloci-
ty of molecules at preservation of average gas-kinetic
track length that calls a reduction of time of a translation
relaxation (following from expression 1).
Practically all electrical discharges have a duration
exceeding the shock wave formation time, therefore fur-
ther dynamics of development of a shock wave is deter-
mined by a relation between an energy release velocity
in the spark channel and velocity of a decrease of a vol-
umetric density of an energy in an outcome of distribu-
tion of a shock wave.
The offered work can be put in a basis of a technique
of an evaluation of shock wave intensity formed at a
spark discharge. It will allow to estimate safety of appli-
cation of electrical devices in easy detonated fuel mix-
tures.
REFERENCES
1. J.Mick, J.Krags. Electric breakdown in gases.
Мoscow: Izdatel’stvo inostrannoj literatury, 1960.
p. 76, 472-474 (in Rusian).
2. Yu.P.Raizer. Physics of the gas discharge.
Мoscow: Nauka, 1987. p. 476.
3. S.I.Drabkina // Zhournal Ehksperimental’noj i
Tekhnicheskoj Fiziki. 1951, v. 21, p. 473 (in Rus-
sian).
4. S.I.Braginsky // Zhournal Ehksperimental’noj i
Tekhnicheskoj Fiziki. 1958, v. 34, p. 1548 (in Rus-
sian).
5. L.I.Sedov. Methods of similarity and dimensionali-
ty in mechanics. Мoscow: Nauka, 1977.
p. 257-258.
47
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