An experimental simulation of liquid fuel injection into a heated subsonic gas crossflow

In this investigation, an approach to studying hot-flow subsonic cross-stream fuel injection problems with a less complex and less costly cold-flow facility was developed and implemented. An actual ramjet combustion chamber fuel injection problem was proposed where ambient temperature fuel was injected into a heated airstream. This case was transformed through similarity parameters involving injection and freestream properties to a simulated case where a chilled injectant was injected into an ambient subsonic airstream. This task was accomplished through injection of chilled Freon-12 into the Virginia Tech 23 x 23 cm. blow-down wind tunnel at a freestream Mach number of 0.44. The freestream stagnation pressure and temperature were held at 2.5 atm. and 300°K respectively. The resulting spray plume was carefully examined and documented with photographs and droplet measurements. The results showed a clear picture of the mechanisms of jet decomposition and vaporization. Immediately after injection a vapor cloud was formed in the jet plume, which dissipated downstream leaving droplets on the order of 8 to 10 microns in diameter for the conditions examined.