Raman spectroscopy for inline analysis of combustion processes

A novel approach for cost-effective and time resolved combustion gas diagnostics based on spontaneous Stokes Raman spectroscopy is presented in this document. The proposed instrument uses a multi-pass configuration designed to increase the scattering generation, giving information about gas species concentrations, including H2 and N2 that are not commonly available from analysis with absorption spectroscopy techniques. The system performs calibrated analysis providing both qualitative and quantitative information about the gas composition. Depending on the application, the device can work with spectra integration time from 0.15 s up to 10 s, with a Raman spectrum ranging from the H2 rotational peak at Raman shift of 587 cm−1 up to the H2 vibrational peak at cm−1, covering all the Raman emissions of major combustion species. The device response was characterized with a working pressure from 0.7 bar to 7.5 bar; The instrument prototype has been made completely transportable and ready to be operated in relevant industrial environments (TRL6). The work presented in this thesis was carried out at the Institute of Photonics and Nanotechnologies of the Italian National Research Council (CNR-IFN), Padua branch, in collaboration with the PhD Course in Space Sciences, Technologies, and Measurements of the Center of Studies and Activities for Space - CISAS G.Colombo, University of Padua.