STRUCTURE AND PENETRATION OF A SUPERCRITICAL-FLUID JET IN SUPERSONIC-FLOW

The penetration characteristics and turbulent structure of transverse supercritical nitrogen (and reference subcooled liquid ethanol) jets were examined experimentally by the use of spark shadowgraph imaging. For given injection and freestream stagnation pressures, supercritical nitrogen jets penetrated significantly less into the supersonic stream than subcooled ethanol jets. The jet penetration further decreased with increases in the degree of superheat. The supercritical nitrogen jets were characterized by large-scale structure not generally observed for the case of subcooled ethanol injection. Practical difficulties inherent in the use of liquid fuel simulants in unheated supersonic flows for the simulation of supersonic combustion environments are discussed.