一种气体吸收的逐线计算模型及其实验验证

建立一种高分辨率的气体吸收光谱的逐线计算模型,分子谱线参数数据库采用了最新的低温库HITRAN2008和高温库HITEMP2010,能根据温度条件自动选择合适的谱带参数库,并可同时满足高温和常温气体辐射计算。计算波数采用等间隔取样,取样间隔大小以能分辨出典型分子谱线为条件确定。线翼截断采取等波数截断,总内配分函数由Gamache拟合三次多项式计算。谱线线型根据气体温度和压力来选择,最后,利用该模型计算了压力为1atm,不同温度、浓度和路径长度下CO2在4.3μm和2.7μm的透射率。考虑FTIR仪器增宽,将逐线计算结果降为窄带透射率,与中分辨率的试验结果对比均吻合,并能在较宽的温度范围内保证精度。

Experimental Verification for Line by Line Prediction Model of Gas Absorption

A high resolution line-by-line model to calculate the molecular gas spectra is developed. With the model, the absorption coefficients can be calculated using molecular data from the up-to-date spectroscopic databanks (HITRAN2008/HITEMP2010). The model can choose the proper databank according to the temperature condition. Thus, it can calculate the absorption coefficient on high temperature and room temperature. The sampling interval is set constant. The choice of interval depends on the factor that the resolution must be high enough to resolve the typical gas line fully. The model uses equal line wing cutoff to take account of contribution of the most important spectra lines. The total internal partition function for the spectra lines is calculated using the tertiary polynomial expression which is fitted by Gamache. The spectra line profile is determined according to the gas temperature and pressure. Finally, the model is employed to calculate the spectral transmissivity of CO2 at various temperatures, concentrations, and path lengths for the 4.3 μm and 2.7 μm bands. Then the line-by-line calculated data is used to calculate narrow band transmissivity at the measured resolution, accounting for instrument broadening by the FTIR. A comparison between the narrow band and measured transmissivity showed a good agreement among a wide temperature area.