Optimal Absorption Lines Selection for Gas Temperature Measurement by Using Two-Color Laser Absorption Spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) is widely used in gas temperature measurement. A two-color method is typically utilized to extract the gaseous temperature in TDLAS. The accuracy of two-color method is greatly determined by the selection of two absorption lines. A selection method of optimal absorption lines for two-color temperature measurement was proposed. All available spectral lines are classified and grouped to speed up the selection on the cloud supercomputer. A temperature error model was established to evaluate the performances of different line pairs. The candidate line pair was selected and randomly verified among the representative line pairs from all line groups until the optimal line pair is determined. Typical line pair selections in the literature are used to compare the temperature errors with the optimally selected line pairs in this work. Spectral lines of H2O, CO2, and CO were involved in the temperature ranging from room temperature to 2000 K. The error of optimal spectral line selected by using the proposed method is usually 10 K smaller than the spectral lines reported in the literature. Also, verification experiments were performed to measure a stable and uniform gas temperature. The experimental results verified that the optimal lines by using the proposed method in this work yield better performance than the typical lines, as the temperature errors in average were reduced to almost one half of the typical lines.