Development of Temperature and Species Concentration Measurement Method of High Temperature Burnt Gas by Diode Laser Absorption Spectroscopy

半导体激光红外吸收光谱法是一种简单、先进的气体温度和组分浓度测量方法。该方法可同时连续测量气体的温度和浓度，并可利用多波长光源测量多种气体的浓度。在这项研究中，水蒸气作为吸收介质被选中。本研究的目的是检查的吸收光谱或吸收线的组合的特性，并开发在高温条件下通过选定的吸收线的气体温度测量。本研究获得的结果如下所述。(1)研究了用于高温测量的吸收光谱特性。选择作为吸收线的测量波长对作为注意以下项目的结果;（i）在吸收跃迁前它们之间的能量差大，（ii）在高温下它们具有大的吸收线强度，（iii）在参考温度下，中心线的吸收线强度大，并且吸收线强度的比率也大，以及（iv）它们与其它吸收带隔离。(2)采用两套半导体激光器，通过扫描水蒸气的红外吸收光谱，测量了1350 ~ 1800 K的火焰温度。(3)虽然所测量的吸收光谱与基于吸收系数数据库的计算结果基本一致，但是识别出在谱线强度和谱线宽度或吸收谱线强度的温度依赖性方面具有差异的部分。(4)从测量的吸收光谱获得的吸收线强度的比率对应于通过吸收系数数据库的计算结果。但在1600 K或更高的温度下，强度比的偏差较大。

The infrared absorption spectroscopy by use of diode laser is a simple and advanced gas temperature and species concentration measuring method. This method enables us to measure temperature and concentration of a gas simultaneously and continuously and to measure variety kinds of gas concentration by the light source of multi-wavelengths. In this study, water vapor as an absorbing medium was selected. The objectives of this study are to examine the characteristics of the absorption spectrum or the combination of the absorption lines and to develop gas temperature measurement by selected absorption lines under high temperature conditions. The results obtained by this study are described below.(1) The characteristics of the absorption spectrum used for high temperature measurement were examined. The pair of measurement wavelengths as absorption lines was selected as the result paying attention to the following items; (i) the energy difference between them before absorption transition is large, (ii) They have large absorption line intensity in high temperature, (iii) At the reference temperature, the absorption line intensity of the center line is large and the ratio of absorption line intensity is also large and (iv) they are isolated from other absorption bands. (2) Two sets of diode lasers were used to measure flame temperature from 1350K to 1800K by scanning the infrared absorption spectrum of water vapor. (3) Although the measured absorption spectrum is mostly in agreement with the calculation result based on an absorption coefficient database, the parts which has a difference in the line intensity and the line width or the temperature dependency of the absorption line intensity was recognized. (4) The ratio of the absorption line intensity obtained from the measured absorption spectrum corresponds to the calculation result by the absorption coefficient database. But, the deviation of the intensity ratio is large in 1600K or higher temperature.