Multiscalar line measurements in nonisobaric high-pressure underexpanded supersonic jets using rotational-vibrational raman spectroscopy

Abstract

This work describes the development of a Raman spectroscopy system for measuring aerothermochemistry in high-speed jets and flames. A transmissive grating spectrometer was newly developed for capturing pure rotational Raman and rotationalvibrational Raman with a single CCD camera. Previous state-of-the-art experiments applied line imagining in known flowfields of constant pressure. The system described herein is designed to provide local measurement of pressure, with full thermochemistry, along a line. In every point, temperature will be measured by examining the Boltzmann decay of the rotational spectrum, while molar fraction will be measured from the vibrational Raman spectrum. The temperature and concentrations will then be combined to obtain partial pressure measurements via the equation of state. This work examines the phenomenology of rotational and vibrational Raman scattering and proposes algorithms that can be used for data extraction.