ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
The boundaries for the onset of air liquefaction were experimentally determined. These boundaries indicate the regions where the liquefaction of air constituents has an effect on the flow properties in the test section. The boundaries were determined by making static and total head pressure measurements with varying temperature throughout the appropriate Mach and Reynolds number ranges of both the supersonic and hypersonic wind tunnels. The results show that air liquefaction occurs near the theoretical boundary Clausius-Clapeyron for Mach numbers 4.75 and 5.00 with little, if any, supersaturation. However, as the Mach number increases to 6.0, 7.5 and 9.2, there is an increase in the amount of supersaturation before liquefaction occurs, and at a given Mach number, the difference between the experimental and theoretical temperature at the onset of liquefaction is about the same at all pressure levels tested. These results may allow a relaxation of our stagnation temperature requirements by an amount which would be of considerable operational significance at M 9.2.