Voigt线型两翼拟合非均匀流场吸光度的方法研究

在吸收光谱领域特别是可调谐半导体激光直接吸收光谱(dTDLAS)技术中, 需要精确测量吸收光谱的积分吸光度值以精确反演出流场温度、组分浓度等参数。对于非均匀流场，单光路吸收光谱测量时，由于沿测量路径的谱线展宽随流场状态的变化而变化，见诸文献的研究主要采用Voigt或Lorentz线型对吸光度曲线拟合处理或直接对吸光度曲线数值积分获取积分吸光度值，针对方法可能引入的误差进行了模拟分析，并提出Voigt线型两翼拟合吸光度的方法来获取吸收光谱的积分吸光度值，以减小拟合误差。采用流场测量中常用的H₂O作为目标气体，选取了8条具有不同低态能级的吸收线，以实验室平焰炉为原型建立两种非均匀流场模型，并通过分段法对流场非均匀性进行等效处理。分别采用Voigt线型拟合法、数值积分法和Voigt线型两翼拟合法模拟计算两模型的积分吸光度值，通过与理论积分吸光度值对比得出各方法的误差大小，从而确定出在不同的非均匀流场情况下相适应的积分吸光度值获取方法。

Study on the Method of Voigt Profiles Two Wings Fitting Non-Uniform Flow Field Absorbance

In the field of the absorption spectrum,especially for direct tunable diode laser absorption spectroscopy (dTDLAS) technology,the integrated area of the absorption spectrum is needed to be measured accurately for calculating the temperature and the component concentration of the flow field .Doing single optical path absorption spectroscopic measurement in the non-uniform flow field,spectral lineshape broadening is varied with the flow changes,in previous research reports,researchers mainly use single Voigt or Lorentz profile to fit absorbance curve or use directly integral to obtain the integrated area of the absorption spectrum .There are some shortcomings in these method s,resulting in certain error between the fitting result and the actual area,which is not conducive to the accurate measurement of flow field parameters .Firstly,the error is analyzed theoretically,and then,we adopt the simulation method to obtain the error size of the method .Finally,we proposed the Voigt wings fitting absorbance method to reduce the fitting error .The operation of Voigt wings fitting method is to Select the wings of the spectral line,and then use Voigt profile fitting,The difference between the two wings was used the numerical integral method to calculate area,the integrated area is sum of Voigt profile fitting area and numerical integral area .We have used water vapor as the target g as,with eight absorption lines which have different low-level states energy from HITRAN 2012 database being selected-,building two kinds of non-uniform flow field model base on the flat flame furnace,and through the method of segmentation to equivalent processing the no uniformity of flow field .Using Voigt profile fitting method,numerical integral method and Voigt profile wings fitting method to obtain the integral area of models,the error size is obtained by comparing with the theoretical value .As the result of contrast,the fitting error of Voigt profile fitting method is large and related to the different absorption line,the error of numerical integral method is biggest but it is nothing to do wit h absorption line,the fitting error of Voigt profile wings fitting method is least and stable .By force of contrast,we determined the appropriate method to obtain integral area in the different non-uniform flow field,which is beneficial to obtain accurate integrated area and flow field parameters .