Entrained droplets in underexpanded gas jet in water

Abstract

A visualization study was performed to investigate the flow of an underexpanded nitrogen gas jet injected into water. The stagnation pressure was varied in the range 0.5-8.0 MPa. The gas jet length and expansion angle were obtained from time-averaged images captured using a high-speed camera. The gas jet length and expansion angle increased approximately linearly with increasing stagnation pressure. The entrainment velocity and the velocity of entrained water droplets in the gas jet were obtained by particle image velocimetry.

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“…For void fraction measurements of the entrained water droplets into submerged gas jets, Loth and Faeth [Loth, 1989;Loth 1990] measured the local void fraction distribution and static pressure distribution of underexpanded jets submerged in water. Someya et al [Someya, 2011] investigated the spread angle and entrained droplet velocities of submerged gaseous jets and the velocity distribution of ambient water using their own visualization method. For diameter determination of entrained water droplets, several authors proposed empirical expressions which correlate droplets sizes with dimensionless numbers, even though all these correlations has been developed under aerodynamic break-up conditions ("free" droplets suddenly exposed to a high speed gas stream) or in annular flow (thin liquid film flowing on the pipe wall and a high velocity gas core flowing in its center, which carries the entrained liquid droplets).…”

“…Someya et al [Someya, 2011] investigated horizontal submerged gas jets. They found that a jet large expansion occurred rapidly and extended about 3 mm from the inlet point; then, expansion progresses at a slower rate (i.e., a narrower angle).…”

“…Recent experiments with submerged gaseous jets [Someya, 2011] suggest that the entrained droplets travel in the gaseous phase at smaller velocities (between 1/30-1/60 the gas velocity). Unfortunately, these data are too scarce, as are the only ones to give such a small value for droplet velocity, consequently further investigation are needed to give them full credit.…”

“…Unfortunately, these data are too scarce, as are the only ones to give such a small value for droplet velocity, consequently further investigation are needed to give them full credit. The correlation proposed by Someya et al [Someya, 2011] A very recent work proposes the following correlation for the determination of the entrained droplet velocity. This correlation uses the wave velocity of the gas-liquid interface (wave celerity, c), added to a percentage of the gas velocity to estimate the entrained droplet velocities .…”

“…Only a reduced number of previous investigations have been focused in the exploration of the physics of these processes. From them can be highlighted, among others, the works of Loth and Faeth [Loth, 1989;Loth 1990], Gamble et al [Gamble, 2001], Gulawani et al [Gulawani, 2007], Someya et al [Someya, 2011], Tang et al [Tang, 2011], Weiland et al [2013], Roger et al [Roger, 2014], etcetera.…”