Measurement of ethylene in combustion exhaust using a 3.3-μm distributed feedback interband cascade laser with wavelength modulation spectroscopy

Abstract

A sensor for the detection of ethylene (C2H4) in combustion exhaust based on a mid-infrared wavelength modulation spectroscopic technique was constructed using a distributed feedback interband cascade laser (DFB-ICL) with a wavelength of 3.3 μm. The direct absorption spectrum of C2H4 in the range of 2978.8–2982.1 cm−1 was recorded, where the spectrum was in good agreement with the spectrum simulated using parameters from the HITRAN 2012 database. The absorption line at 2979.581 cm−1 [2.42 × 10−21 cm2 mol−1 cm−1, ν11, PP5(5)] was selected for C2H4 detection. This frequency was chosen to minimize spectral interference from other major combustion products in the emission frequency range of the DFB-ICL. A limit of detection for C2H4 of 96 parts per billion by volume was achieved at a signal-to-noise ratio of two under 3 kPa of pressure using 2f wavelength modulation spectroscopy. Using the developed sensor, the ethylene concentration in the exhaust from a portable power generator was also successfully determined.