Time-resolved infrared emission spectroscopy in high-enthalpy supersonic air flows

We describe a spectrally resolved infrared emission method for observing path-integrated number densities and temperatures in high-temperature supersonic flow on a time-continuous basis. We have conducted infrared emission measurements of the fundamental vibrational band of nitric oxide (NO) to determine NO number densities and vibrational temperatures in a high-temperature, Mach 3 air flow in the Physical Sciences, Inc. (PSI) shock-tunnel facility. A specially constructed infrared array spectrometer was used to observe spectral distributions of NO vibrational radiation between 5 and 7 μm. The instrument was calibrated on a conventional shock tube and was implemented on the PSI shock tunnel to diagnose the flow at the exit of a Mach 3 nozzle, as driven by a plenum of shock-heated air at 3000-4000 K and 10-40 atm