Pressure and thermochemistry measurements in high speed flows using rotational and vibrational Raman spectroscopy

Abstract

We present line imaging measurements of rotational / vibrational Raman in high speed, non-isobaric flows. The technique can be used to measure pressure, temperature, and density in in the wake of an underexpanded jet nozzle. Line images of rotational and vibrational Raman spectra are collected for a 8-mm linear laser probe, and are combined onto the same EMCCD detector. Temperature measurements along the laser test section are extracted from the rotational Raman spectra, whereas major species densities are measured by the levels of their respective vibrational Raman lines. Pressure can be calculated using an equation of state, in every location along the linear laser probe. We present detailed spatial measurements in the wake of an underexpanded jet issuing from a converging nozzle.