CH4/air/SO2 premixed flame spectroscopy with a 7.5-μm diode laser

As sulfur dioxide (SO2) is often involved in combustion processes, we present here SO2-concentration measurements in the post-flame region of a CH4/air/SO2 premixed flame. SO2 concentrations were deduced from high-resolution absorption spectra recorded with a mid-infrared tunable diode-laser (TDL) source operating at liquid nitrogen temperature. Single-mode, continuous frequency tuning around 1384.5 cm-1 (or 7.5 μm) is achieved by a fine TDL temperature ramp. These experiments lead us to develop in situ combustion-pollutant measurements with compact apparatus. We show that this non-intrusive method is efficient for detection and allows the retrieval of SO2 concentration and temperature.