Measurement of Radiative Nonequilibrium for Air Shocks Between 7 and

Abstract

This paper describes a characterization of thermochemical nonequilibrium radiance for shock speeds between 7 and in the NASA Ames Electric Arc Shock Tube. Data are spectrally resolved from 190 to 1450 nm and spatially resolved behind the shock front on the order of 10 cm. The data are analyzed in terms of a spectral nonequilibrium metric, defined as the average radiance within of the peak radiance and presented in a format that may be used to test predictive nonequilibrium radiation tools. The data collected in two shock tubes of differing diameter (10 and 60 cm) at the same nominal shock condition agree within 30%. The spectra are compared with simulations using the DPLR/NEQAIR software tools using a combination of different modeling options (reaction rates, energy mode accounting, and electron impact excitation rates). The results show mixed agreement, with no one modeling option being a clear preference. This suggests that the data may be used to help to identify improvements to methodologies for modeling nonequilibrium air radiation.