Transverse jet breakup and atomization with rapid vaporization along the trajectory

Experiments for transverse injection of chilled Freon-12 into the Virginia Tech 23 x 23 cm blowdown wind tunnel were run at a freestream Mach number of 0.44 and freestream stagnation pressure and temperature of 2.5 atm and 298 K, respectively. The spray plume was documented with photographs and droplet measurements. The results showed a clear picture of the mechanisms of jet decomposition in the presence of rapid vaporization. Immediately after injection, a vapor cloud was formed in the jet plume, which then dissipated downsteam leaving droplets on the order of 8-10 microns in diameter. This represented a substantial reduction compared to baseline tests run at the same conditions with water, which had little vaporization. A simulation approach to studying hot-flow subsonic cross-stream fuel-injection problems in a less complex and costly cold-flow facility is proposed. The simulation parameters were developed and refined with the aid of a numerical solution for the simpler case of a rapidly evaporating laminar jet in a coaxial airstream. The experimental case was transformed (through two new similarity parameters involving injection and freestream properties) to a simulated case of a typical ramjet-combustion-chamber fuel-injection problem where ambient-temperature fuel (kerosene) is injected into a hot airstream.