Radiative Emission in Incident Air Shocks From 3–7 km/S
Brett A. Cruden
Abstract
This paper reports experimental characterization of shock layer radiation in Air at low velocities (3-7 km/s) measured in the Electric Arc Shock Tube at NASA Ames Research Center. This included shock conditions from 3-5 km/s and 2-10 Torr to measure ultraviolet and mid-infrared radiation from NO and two nominal equilibrium conditions of 6 km/s, 2.0 Torr and 7 km/s, 1.4 Torr which were intended to produce 1 bar post-shock conditions and produced atomic N and O radiation along with the UV NO bands. The 10 Torr, 4 km/s has a 2.2 bar post-shock pressure and the mid-infrared measurement is in good agreement with equilibrium. The ultraviolet and visible ranges however show radiation in excess of equilibrium. Photorecombination and spin-splitting are shown to have significant impact on the spectrum, however there are also appears to be an overpopulation of the NO(A) state. The 4 km/s, 2.25 Torr condition is investigated as a reacting flow, and post-shock temperature and number density profiles are extracted. Finally, the 6 and 7 km/s conditions are shown to be in good agreement with similar measurements at the Oxford T6 facility but the radiation is again in excess of equilibrium.