ISSN 0021-8944, Journal of Applied Mechanics and Technical Physics, 2018, Vol. 59, No. 1, pp. 86–92.
Pleiades Publishing, Ltd., 2018.
Original Russian Text
A.E. Zarvin, A.S. Yaskin, V.V. Kalyada.
EFFECT OF CONDENSATION ON THE LENGTH OF STRONGLY
UNDEREXPANDED JETS EXHAUSTING
INTO A RAREFIED SUBMERGED SPACE
Abstract: Exhaustion of supersonic argon and nitrogen jets through sonic and supersonic nozzles
into a rareﬁed submerged space at high stagnation pressures is studied experimentally. The shapes
and lengths of the jets are visualized by means of detecting radiation excited in the considered
ﬂow by an electron beam. Dependences of the geometric parameters of the jets on exhaustion
and clusterization conditions at low Reynolds numbers based on the reference length of the jet are
obtained. It is found that the coeﬃcient of proportionality between the length of the ﬁrst “barrel”
of the supersonic jet and the degree of jet expansion increases with an increase in the stagnation
pressure. Empirical dependences of the proportionality coeﬃcient on the size of clusters formed in
supersonic ﬂows are derived for the ﬁrst time.
Keywords: supersonic jet, clusterization, electron beam visualization .
Investigations of gas ﬂow formation behind sonic and supersonic nozzles has riveted attention of researchers
for the last decades because of a wide range of applications of such ﬂows [1–3]. Experiments in vacuum gas-dynamic
test rigs with limited capabilities of the evacuation system are usually performed with strongly underexpanded jets
escaping from sonic and supersonic nozzles. Gas ejection from the ambient space through the side shock waves
and the closing Mach disk (in the case of sonic nozzles) usually occurs in such jets; correspondingly, the Reynolds
) based on the reference length of the jet are not very high (in most cases, Re
< 100). If the
stagnation pressure P
in the settling chamber and also the product P
> 30 kPa · mm (d
is the diameter of
the nozzle throat cross section) have large values, clusterization occurs in nitrogen jets at early stages and intense
condensation is observed in readily condensed gases, such as argon or carbon dioxide . This range of ﬂow
regimes has not been considered in traditional aerodynamic research. Those scientists who studied the processes of
condensation in supersonic rareﬁed jets practically ignored the eﬀects of clusterizationonthejetlengthandshape,
including strongly underexpanded jet regimes.
For calculating the jet length and shape, empirical formulas are actively used [5–7], in particular, the formula
for determining the supersonic jet length
is the distance from the nozzle exit to the Mach disk or X-shaped conﬁguration, P
is the pressure in the
background gas (ambient space), k is the proportionality coeﬃcient depending on the gas type and on the Mach
number at the nozzle exit, and N = P
is the jet pressure ratio. It is assumed in the present work that the
jet exhausting into the submerged space contains clusters and that the proportionality coeﬃcient k depends on the
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 59, No. 1, pp. 99–106, January–February,
2018. Original article submitted August 29, 2016; revision submitted January 19, 2017.
2018 by Pleiades Publishing, Ltd.