利用可调谐激光吸收光谱技术对光路上气体温度分布的测量

利用可调谐激光吸收光谱技术(TDLAS)，扫描多条吸收谱线以实现气体温度分布的测量。文章给出了温度分布测量的原理和方程离散化的方法，在气体浓度和压力均匀时，利用带约束最小二乘法计算得到温度分布。根据HITRAN中6 330 cm-1附近的4条CO谱线的参数，建立了温度在300和600 K时，路径长度均为55 cm的两段温度分布模型，模拟了测量误差与温度区间长度约束条件的影响。结果表明随着测量误差的增大和约束条件的减弱，计算结果误差相应增大。在5％的测量误差下，计算结果的最大误差为11％，平均误差为2.2％。以管式炉中的高温段和室温下的低温段作为两段温度分布模型进行试验。利用6 330 cm-1处的垂直腔面发射激光二极管(VCSEL)扫描得到的4条CO谱线，通过背景信号的三次多项式拟合得到基线，求出温度分布计算所需的光谱吸收率积分值。在四种情况下， 计算温度分布结果与模型误差分别为7.3％，6.5％，4.7％和2.7％。

Measurement on Gas Temperature Distribution by Tunable Diode Laser Absorption Spectroscopy

The technique of tunable diode laser absorption spectroscopy(TDLAS) can be used for gas temperature distribution measurement by scanning multiple gas absorption lines with a tunable diode laser.The fundamental of gas temperature distribution measurement by TDLAS is introduced in the present paper,and the discretization strategy of equation for gas absorption is also given here.Using constrained linear least-square fitting method,the gas temperature distribution can be calculated with the help of physical constraints under the condition of uniform gas concentration and pressure.Based on the spectral parameters of four CO absorption lines near 6 330 cm-1 from HITRAN database,the model of two-temperature distribution at 300 and 600 K with each path length of 55 cm was set up.The effects of relative measurement error and different path length constraints of temperature bins on the gas temperature distribution measurement results were simulated by constrained linear least-square fitting.The results show that the temperature distribution calculation error increases as the relative measurement error rises.A measurement error of 5% could lead to a maximum relative error of 11%,and an average relative error of 2.2% for calculation result.And the weak physical constraints of path length for temperature bins could increase the calculation result error during the process of constrained linear least-square fitting.By setting up the model of two-temperature distribution with gas cells at room temperature as the cold section and in tube furnace as the hot section,the experiment of gas temperature distribution measurement in lab was carried out.Using four absorption lines of CO near 6 330 cm-1 scanned by VCSEL diode laser,and fitting the background laser intensity without absorption by the cubic polynomial to get the baseline signal,the integrals of spectral absorbance for gas temperature distribution measurement can be calculated.The relative calculation errors of path length for temperature bins are about 7.3%,6.5%,4.7% and 2.7% in the four cases.