A new line-shape asymmetry model for wavelength modulation spectroscopy in gaseous flows

Abstract

This communication reports technical notes on the development and application of an automated line-shape fitting procedure for wavelength modulation spectroscopy (WMS). Near-infrared transitions of carbon dioxide (CO2) around 1573 nm were measured in vertical cold (nonreacting) flow of CO2 at atmospheric pressure using WMS with demodulation at second harmonic frequency. Semi-empirical model based on the set of so-called Gabor functions was developed and parameters of Lorentzian line-shape profile and its asymmetry resulting from simultaneous frequency and amplitude response of the current-modulated semiconductor laser were determined. Nonlinear least-square fitting procedure employing differential evolution algorithm was successfully utilized for performing this task. Line-shape fitting procedure enabling efficient signal de-noising and background subtraction of wavelength modulation spectra was implemented into an open-source code.

Experimental Apparatus and Modeling Framework for Studying Counter-Flow Laminar Flames

“…Such design is presumed to provide steady laminar cool flames enabling to study their structure. Burner apparatus is installed in measurement section of the experimental facility suitable for optical diagnostics in laminar flames and gaseous flows [12,13]. Axis of the burner is aligned vertically to obtain symmetric shape of reaction zone at atmospheric pressure and normal gravity.…”