Experiences on Cryogenic Injection under Supercritical Condition
ENERGY RESEARCH CONSULTANTS INC LAGUNA HILLS CA
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Experience learned at the AFRL on injection of cryogenic jets into sub- and supercritical conditions using shadowgraphy and Raman scattering measurements are presented here. Metamorphic behavior of the jet boundary undergoing disruption has been shown to occur near the critical point of the injected fluid. At subcritical pressures, formations of droplets and ligaments are seen, resembling a second wind-induced liquid-jet breakup. The jet is incapable of reaching the classical full atomization regime due to existence of the critical point of the jet fluid within the operating range. At this point, the jet anatomy changes abruptly to imitate turbulent gas jet injection. The jet initial growth rate is plotted against the chamber-to-injectant density ratio, along with available data on other liquidgaseous jets and mixing layers, producing a unique and informative graph. For supercritical conditions, our measured growth rate agrees well with a theoretical equation proposed by Dimotakis 1 and closely follows the trend of Papamoschou and Roshko 2 for incompressible but variable-density gaseous turbulent mixing layers. Fractal analysis of the jet boundary also shows a similarity to gas jet behavior with comparable fractal dimension. This is the first time quantitative evidence has been provided to support qualitative visualizations suggesting that supercritical jets appear to behave like conventional gas jets.
- Fluid Mechanics
- Combustion and Ignition
- Liquid Propellant Rocket Engines