SINOPSIS

Recent experience gained at AFRL with the injection of cryogenic fluids into high back-pressures is summarized. In the experimental investigations described, a jet of a cryogenic fluid, typically liquid N₂, is injected into a chamber whose ambient pressure is varied to values exceeding the critical pressure of the injectant. The structure of the jet and the shear layer between the jet and the ambient has been examined. Results from visualization, jet growth rate, fractal analysis, and Raman scattering measurements indicate that the behavior of the injected fluid changes from spray-like behavior to gas jet-like behavior as pressure increased.