High-speed supercontinuum laser absorption spectroscopy of light hydrocarbons in elevated pressures and temperatures

Abstract

10 kHz near-infrared supercontinuum laser absorption spectroscopy measurements of methane (CH4) and acetylene (C2H2) were demonstrated. Measured absorption spectra were processed using the HITRAN database to infer species concentrations and temperatures. High pressure and high temperature measurements up to 10 bar and 800 K, respectively, were made in dedicated optical cells. Reacting flow field was also probed over a 6 cm flat flame burner. Due to the very short pathlength over the burner surface, a toroidal multipass reflection cell was used to maximize measurement sensitivity. The multipass cell was designed specifically to withstand high temperature environment around the flat flame burner and supported multiple beam pathlength configurations. The beam paths within the cell exist on a thin plane and were used to measure temperatures at various heights above the burner surface. Despite relatively low signal-to-noise ratio at higher temperature environments, species concentration predictions agreed well with experiment conditions. Temperature results agreed well with simulated results to within 20.2 K in the preheat zone of a methane–air flame.