Multipass Raman spectroscopy applied to qualitative and quantitative combustion gas diagnostic

This paper introduces a novel laser-based system designed for real-time Raman spectroscopy applied to in-line combustion diagnostics. While Raman spectroscopy is a well-established technique for solid and liquid analysis, its application to gas samples is challenging due to their low density, which limits the intensity of Raman scattering. To address this issue, our system utilizes a multipass cell, strategically designed to enhance signal generation and its collection. The instrument performs calibrated analysis, providing qualitative and quantitative information about gas composition. Depending by the application, the system can work with spectra integration time ranging from 0.15 s up to 10 s. This study has demonstrated that Raman spectroscopy can be a useful tool for combustion diagnostics, as it can operate fast enough to follow the time scale of combustion phenomena.