Improved Method for Quantitative Measurement of OH Radicals Based on Absorption Spectroscopy

OH-PLIF quantitative measurements suffer from high temperature sensitivity and poor applicability of calibration constants, this paper combines absorption spectroscopy with dual-line temperature inversion to establish an explicitly temperature-corrected OH radical concentration inversion model. By simultaneously acquiring PLIF images and absorption spectrum data under varying hydrogen-oxygen mixture flow rates, the equivalent absorption path length is calculated and the temperature-dependent absorption cross-section σ(<i>ν</i>,<i>T</i>) is incorporated. This enables the dynamic response of the integral absorption rate to high-temperature flame environments. Results demonstrate that the established temperature-corrected model significantly reduces systematic errors caused by temperature variations, with calibration constant <i>C</i> fluctuating less than ±5% across different operating conditions. Further optimization via least-squares method yielded the optimal constant <i>C_opt</i> = 0.01844. Its applicability was validated across various operating conditions, with average relative errors controlled within 4-6%. Compared to the uncorrected model, overall error decreased from 9.1% to 5.2%.