One-dimensional direct absorption sensor for flat flame characterization

Laser absorption techniques are widely used in combustion research to provide a detailed characterization of reactive media. Recently, the improvements of high-speed infrared camera have enabled the development of laser absorption imaging (LAI) techniques with application to combustion environment. In this paper, we present the development and implementation of the first one-dimensional direct absorption (1D-DA) speciation sensor in the near-infrared, absorption transition near 1391.7 nm, for measuring water in a flat flame. Our 1D-DA sensor relies on a simple structure based on standard optical components, and a novel post-processing method was developed to correct diffraction-like signal deformation. With our 1D-DA sensor, we characterized two C2H4-O2-Ar flames with different equivalence ratios, and validated the results using both the traditional DA method based on a single pixel detector, and Cantera flame simulations using USC-Mech II. Our sensor achieves a spatial resolution better than 70 mu m along along the vertical direction, with an uncertainty estimated to be around 13%. Novelty and Significance Statement 1. First one-dimensional direct absorption (1D-DA) speciation sensor applied to a near-IR line-scan camera. 2. Novel approach to remove diffraction pattern related to laser light coherence. 3. High spatial resolution along along the vertical direction. 4. Strong potential for future tomographic applications