SPECTROSCOPIC INVESTIGATION ON A MILD COMBUSTOR WITH INTERNAL RECIRCULATION

摘要

The paper is focused on a spectroscopic analysis of UV and visible naturally emitted light from a MILD combustor operated in the facility COMET at the research center of Casaccia, ENEA. The aim of the work was the determination of the spatial abundance of the main intermediate products of combustion in flameless oxidation mode with natural gas and air. The study shows evidences of consistent contributions to natural emission from the usual radicals (OH, CH and C_2, as in the ordinary hydrocarbon flames) in the proximity of the gas injection. Their abundance has been found to be strongly dependent on temperature and equivalence ratio Φ. While temperature increase determines an understandable faster ignition of the chemical mechanisms which lead to the observed radicals, the change from a rich to a lean mixture gives a similar faster radical production. The spectral information has been compared with images taken for one radical species (CH) only. The images confirm the spectral analysis giving credit to a strong localization of CH radical near the gas entrance and with spatial abundance depending on Φ.