Mid-infrared CO2 sensor with blended absorption features for non-uniform laminar premixed flames

• Published in: Applied physics. B, Lasers and optics Vol. 128; no. 2
• Main Authors: Wang, Zhenhai, Wang, Weitian, Ma, Liuhao, Fu, Pengfei, Ren, Wei, Chao, Xing
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2022; Springer Nature B.V
• Subjects: Algorithms; Applied physics; Boundary layers; Carbon dioxide; Carbon dioxide concentration; Computational fluid dynamics; Engineering; Equivalence ratio; Infrared detectors; Lasers; Nonuniformity; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Premixed flames; Quantum Optics; Sensors; Signal to noise ratio; Simulation; Spectrum analysis
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-022-07758-2

We develop a novel mid-infrared CO 2 absorption sensor exploiting spectrally blended features to characterize thermochemical non-uniformity of laminar premixed flames. A new algorithm for interpreting spectra with significantly blended features is proposed for single line-of-sight multi-transition absorption thermometry. A CO 2 sensor covering eight absorption transitions near 2378.0 cm −1 is demonstrated in a laminar premixed CH 4 /Air flame at an equivalence ratio of φ = 1.0 . The average signal-to-noise ratio is 1293 with a measurement time of 1.0 s, and the estimated CO 2 detection limit is 42.8 ppm at 1543 K with 6 cm pathlength. Computational fluid dynamics (CFD) simulation with reduced GRI 1.2 mechanism is performed for comparison. Spatially resolved distributions are obtained with the laser absorption spectroscopy (LAS) measurements, combined with postulated distribution from CFD simulation. The LAS measurements agree with the CFD simulation, with a central-zone temperature difference of less than 1.1% and CO 2 concentration difference of less than 1.0%. Discrepancy is observed in the boundary layer region due to pronounced mixing with the ambient surroundings. The sensor developed provides a lead for general LAS sensor design (blended absorption features, ambient interference, or under optically thick conditions), and can serve for practical combustion sensing.