Velocity and Mach Number Measurements of CO Behind Incident Shock Waves

The University of Central Florida shock tube facility was used to generate incident shock waves up to Mach 7. The induced velocity region behind the incident shock was probed using two quantum cascade lasers targeting the fundamental vibrational band of carbon monoxide (CO) near 4.89 μm. One quantum cascade laser was used with the retroreflector velocimetry technique to target an absorption feature at 2047.38 cm-1. The second quantum cascade laser was used to target two absorption features at 2042.809 cm-1 and 2042.997 cm-1 for temperature and species concentration measurements. Results show that the retroreflector technique is fundamentally limited if the expected Doppler shift is less than the Doppler full width at half maximum of the targeted feature. Velocity increased steadily over test time, attributed to the boundary layer restricting the core flow region.