Qualitative investigation of cryogenic fluid injection into a supersonic flow field

The injection of sub- and supercritical-pressure, subcritical-temperature nitrogen into a two-dimensional, ambient, static-temperature and static-pressure Mach = 2.7 nitrogen flow field was observed. The flow interface is complex, since the pseudo-Leidenfrost interface formation resembles a bow shock and the injected fluid leaves the injector as essentially a two-phase choked flow. For normal and 20° injection and an injector diameter at 20 percent of the two-dimensional flow field thickness, the demonstration indicated minor penetration across the flow field width at low normalized injection pressure (Pi/Pc<0.5) and the fluid appeared to Leidenfrost along the wall with a major liquid stream exiting the flow field (nitrogen Pc, 495.5 psia). At elevated pressures (Pi/Pc>2) significant penetration of the flow field was observed, about half way for normal injection and one-quarter for 20° injection; minor amount of Leidenfrosting occurs along the wall with indications of droplet flow and nonuniform distribution of the exhaust stream. For injector diameters of the order of 10 percent of the two-dimensional flow field thickness penetration was about one-eighth of the flow field width. With injection parallel and 180° opposed to the flow field the static pressure adjacent to the injected stream decreased toward saturation, and a parabolic pseudo-Leidenfrost region was encased by a bow shock.