Measurement and validation of high-temperature CO spectral line parameters near 2.3 μm using TDLAS for combustion diagnostics.

Abstract

Accurate determination of spectral parameters for carbon monoxide (CO) transitions is crucial for the development of laser absorption spectroscopy-based CO sensors. This study reports the measurement of line strengths, self-broadening coefficients, and their temperature-dependent exponents for three transitions in the first overtone band near 2.3 μm. These transitions were selected for their strong absorbance and minimal interference from other major combustion species, such as H₂O and CO₂, making them particularly suitable for combustion diagnostics. High-resolution absorption spectra of the selected CO transitions were recorded over a temperature range of 300-1100 K using a distributed-feedback (DFB) tunable diode laser. The spectral data were fitted to derive the aforementioned key spectroscopic parameters with high precision. To verify the accuracy and applicability of these parameters, a CO sensor employing multi-pass absorption spectroscopy was developed. This sensor was used to infer CO concentration in a C₂H₄/air flame based on the direct absorption spectrum of the CO line at 4300.699 cm^-1, confirming the reliability of the measured parameters. The findings offer valuable spectroscopic data to support the development of advanced laser-based CO sensors, particularly for high-temperature applications.