基于固定点波长调制光谱技术的气体浓度测量方法

Gas Concentration Measurement Method Based on Fixed Wavelength Modulation Spectroscopy

固定点波长调制光谱技术虽然具有时间分辨率高的优点,但随着激光器出光中心的波数漂移,气体浓度的测量会出现较大误差。为消除波数漂移对浓度测量的不利影响,本文提出了一种基于固定点波长调制光谱技术的气体浓度测量方法。引入一条带有封闭气池的参考光路,通过谐波高度来推算激光器出光中心的波数偏移量,使用循环迭代算法实现待测气体浓度的有效反演。搭建了一套基于固定点波长调制光谱技术的测量系统,通过改变激光器的工作温度来模拟波数漂移现象。选择CH_(4)分子在6046.955 cm^(-1)附近的吸收谱线进行浓度测量实验,结果显示:浓度测量的最大相对误差由90.510%降低至5.204%;对于低于70.000%的误差,修正后均可控制在2.000%以内。这说明所提方法能准确计算波数偏移量,提高气体浓度的测量精度,为使用固定点调制光谱技术实现快速场反演提供了技术保障。

Although fixed wavelength modulation spectroscopy has the advantage of high temporal resolution,a large measurement error of gas concentration appears with the wavenumber drift of the laser emission center.A gas concentration measurement method based on fixed wavelength modulation spectroscopy was proposed in this paper to eliminate the influence of wavenumber drift on concentration measurement.A reference optical path with a closed gas cell was introduced,and the wavenumber offset of the laser emission center was calculated according to the harmonic height.A cyclic iterative algorithm was adopted,and the gas concentration to be measured was calculated through inversion.A measurement system based on fixed wavelength modulation spectroscopy was built.The working temperature of the laser was adjusted to simulate wavenumber drift.The absorption line of CH_(4) molecules near 6046.955 cm^(-1) was selected to carry out concentration measurement experiments.The results show that the maximum relative error of concentration measurement is reduced from 90.510% to 5.204%.Errors smaller than 70.000% can be controlled within 2.000% after correction.This means that the proposed method can accurately calculate the wavenumber offset,improve the measurement accuracy of gas concentration,and thereby provide technical support for fast field inversion by fixed modulation spectroscopy.