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Submitted on 1 Jan 1979
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QUANTITATIVE ANALYSIS OF INTERACTION BETWEEN A HIGH-PRESSURE PLASMA COLUMN
AND SURROUNDING LIQUID
O. Havelka, Z. Vàvra
To cite this version:
O. Havelka, Z. Vàvra. QUANTITATIVE ANALYSIS OF INTERACTION BETWEEN A HIGH- PRESSURE PLASMA COLUMN AND SURROUNDING LIQUID. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-291-C7-292. �10.1051/jphyscol:19797143�. �jpa-00219117�
JOURNAL DE PHYSIQUE CoZZoque C7, suppzdment au n07, Tome 40, JuiZZet 1979, pagec7- 291
QUANTITATIVE ANALYSIS (W INTERACTION BETWEEN A HIGH-PRESSURE PLASMA COLUMN AND SURROUNDING LIUUID
0. Havelka and Z. VBvra.
Faculty of ElectricaZ Engineering of the TeohnicaZ University Bmo, C.S.S.R.
If there exists a plasma column in the calculation of pressure in a closed liquid a thermal decomposition of liquid space with a plasma column (electric arc) into charged particles, gases and vapour under the liquid level because it emanates starts in the plasma-liquid boundary, If from the calculation method selected as all this takes place in a closed space, well as from measurements under conditions the development of hot gases and vapour corresponding with a real state.
causes high pressure in this space. To de- Let us assume a closed chamber par- termine this pressure it is necessary to tially fiied with liquid only, that is, know the energy magnitude transformed by with a free space the liquid level of vo- the plasma column and the factors of li- lume W. The plasma under the liquid level quid transformation into gases and vapour, liberates energy Q, pressure p is formed
as well. in the chamber, which can be calculated
To simplify the complicated thermody- by applying Boyle 's law namical and thermochemical processes in
the contact area of plasma column and li- quid, we assume at least quasiisothermical conditions and we express the unit volume of gases and vapour reduced to standart atmospheric pressure pa (1 bar = 105pa) by coefficient f' [m 3 /q, from the view- point of usual calculation method. Then the total gas volume V developed from the energy Q can be estimated by the ex- g
pression
v,=p,COl =p9 (1)
Similarly, for the liquid volume V, trans- formed into gases and vapours by energy &, we can write
g =p,cQl=yQ ( 2 1 The dimensions of tranformation factors f
and/or 9 are m3/2 (m /We). They have not 3 been perfectly known yet. As direct trans- formation fact or measurements during the existence of plasma in liquids is practi- cally unrealizable, the authors have de- signed an indirrect method by combining measurements and calculation. Even though this method need not give us exact results from the viewpoint of physics (momentary
temperatures of gases and vapours are not known) it provides completely satisfactory results for the purpose required, i.e. for
In the chamber the pressure p is mea- sured with the aid of suitable equipment simultaneously the amount of liberated energy Q. If we realize the plasma column as an electric arc we determine energy Q from the values of current i and from arc voltage uo either by measuring or calcula- ting it from the relation
a=/&, Lo L cfi ( 4
observing the procedure [I.) . Thus, from relation ( 3 ) we know all magnitudes except
f and 7 . If we record all quantities in dependence upon time t during the test, we start from the intesities of pressures p. and energy Qi in different times tl and
1
t2 . Thus we get the following relations for coefficients gr and /Z ;
Nevertheless, the evaluation of the carried out measurments proved that there is no linear dependence between the volu- me of gases produced and decomposed liquid and energy Q, that means, transformation factdrs f and 7 are no constants as
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797143
assumed previously but power functions de- pendent on energy Q:
f = B x ~ ' ; 1 = p x ~ b (6) Then
~ = p ~ = 2 ~ ' 6 * ' & i x @ (7) If we substitute these modified relations into formulas (5 ) they become a new form:
The examinat ion of transformation factors according to this method was car- ried out for transformer oil used in oil circuit breakers. The tests were carried out in a steel chamber with the plasma co-.
lumn length of 3 0 to 45 mm with an elec- tric arc of 2000 A, 50 Hz AC. The arc bur- ning time changed from 20 t o 5 0 ms, the arc energy Q from 5 to 80 kJ. ddeasured pressures p in dependence on energy Q are represented ifl Fig.1 ,
With regard to the pressure disper- sion for the given magnitude of energy it is evident that the magnitude of produced gases and vapours changes, so that their medium tehperatures change correspondingly too. Then the magnitude factor f should change as well within the range given by limit c m e s of pressure field in Fig.1 .,
The decomposed liquid volume remains pro- portional to the liberated energy so that the transformation factor 7 has a unique magnitude. This consideration was confir- med by caluulation results obtained from
a digital computer. The calculation re- sults are the following:
/-='&& Q" e Z&. q-435
feh=b:b cr = t n 40"
(9).
Q" - (00. ioo9 Q-a*
? = ?
REF3 RENCES :
[I] 0.Havelka: The highest energy values of intensively cooled high-pressure arc of AC with constant and variable length.
11th ICPIG,Prague 1973, paper No 224
[2] Z.Vbvra: New method of measuring oil thermal decomposition with high-pressure arc in closed space.
Candidate s thesis, Brno 1978.
2kr I
-
Q ikJ1F i g . 4
Oil transformation factors dependence OIX enePgy Q is represented graphically in Fig.2 . The recalculated pressure field envelopes for O( = E + f = 0,65 have their courses drawn in Fig.1 in full lines and confirni the correctnese of values ( 9 ) .
