Mid-infrared laser absorption tomography for quantitative 2D thermochemistry measurements in premixed jet flames

Abstract

A tomographic laser absorption spectroscopy technique, utilizing mid-infrared light sources, is presented as a quantitative method to spatially resolve species and temperature profiles in small-diameter reacting flows relevant to combustion systems. Here, tunable quantum and interband cascade lasers are used to spectrally resolve select rovibrational transitions near 4.98 and 4.19 μ m to measure CO and CO <inf>2</inf>, respectively, as well as their vibrational temperatures, in piloted premixed jet flames. Signal processing methods are detailed for the reconstruction of axial and radial profiles of thermochemical structure in a canonical ethylene–air jet flame. The method is further demonstrated to quantitatively distinguish between different turbulent flow conditions.