温度和压强变化对二次谐波反演结果的影响

Effects of Temperature and Pressure Changes on the Second Harmonic Inversion Results

在气体质量流量测量系统中,波长调制光谱信号的谐波分量,特别是其二次谐波分量常被用作为检测对象,用于气体浓度、速度等信息的反演。基于波长调制原理,利用氧气(O2)分子在764.28nm附近的吸收谱线,分析了常见线型的半峰全宽,得出了不同温度、压强下洛伦兹线型的适用范围;研究了O2分子吸收谱线在不同温度、压强条件下的二次谐波峰值;对不同温度、压强下,采用二次谐波峰值反演气体浓度产生的误差进行了分析,并提出了误差修正方法;分析了实验过程中当最佳调制深度不能够随着温度、压强即时调整的情况下,最优调制系数在不同温度、压强变化下的适用范围,并给出了误差修正公式。

In mass flow measurement system, harmonic component of wavelength modulation spectroscopy signal, especially the second harmonic component is commonly used as test object, it is used for the inversion of gas concentration, velocity and other information. Based on the principle of wavelength modulation, using oxygen （02） molecules in the vicinity of 764.28 nm absorption lines, the full width at half maximum （FWHM） of common line profiles is analyzed, and the range of application of the Lorentzian line profiles at different temperature and pressure is obtained; absorption spectral lines of 02 molecules are studied under different conditions of temperature, pressure, and the second harmonic peak change relation between them is studied as well; the error of the second harmonic peak inversion is analyzed under different temperatures and pressures, and error correction methods are put forward; in the experiment, when the optimal modulation depth is impossible to immediately adjust with the temperature and pressure changes, the optimal modulation coefficient application range under different temperatures and pressures is analyzed, and the error correction method is given.