Nonequilibrium Nozzle Expansions of Partially Dissociated Air: A Comparison of Theory and Electron-Beam Measurements

摘要

A theoretical/experimental study was made of the rapid expansion of partially dissociated air in a high enthalpy wind tunnel. The theoretical model included the important nitrogen-oxygen reaction kinetics, as well as vibrational exchanges. Pressure measurements were supplemented by electron-beam measurements of static (translational) temperature, vibrational temperature, and static density. The primary result was general confirmation of finite-rate flow calculations. Secondarily, rotational temperature determination by electron beam was found to require a small empirical correction, vibrational-relaxation rates from shock experiments were inapplicable in rapid flow expansion, and the static temperature/density combination yielded the optimum comparison with theory. The nonequilibrium data were correlated with an entropy parameter for reservoir pressures from 5 to 20 atm and temperature from 2300 to 5000K. Verification of finite-rate theory at high density was inferred from data measured at large area ratios plus the simple nature of frozen flows downstream of the nozzle throat. (Author)