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

利用半导体激光器的红外吸收光谱是一种简单、先进的气体温度和组分浓度测量方法。这种方法使我们能够同时、连续地测量气体的温度和浓度，并利用多波长的光源测量各种气体的浓度。本研究选择水蒸气作为吸收介质。这项研究的目的是研究吸收光谱的特征或吸收谱线的组合，并开发在高温条件下利用选定的吸收谱线测量气体温度。研究结果如下：(1)考察了高温测量用吸收光谱的特性。选择这对测量波长作为吸收线是考虑了以下几点：(I)吸收跃迁前它们之间的能量差较大，(Ii)它们在高温下具有较大的吸收线强度，(Iii)在参考温度下，中心线的吸收线强度较大，吸收线强度之比也较大，(Iv)它们与其他吸收带隔离。(2)利用两套半导体激光器扫描水蒸气的红外吸收光谱，对1350K~1800K的火焰温度进行了测量。(3)虽然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，但仍能识别出吸收谱线强度与谱线宽度或温度依赖性存在差异的部分。(4)由测量的吸收光谱得到的吸收谱线强度之比与吸收系数数据库的计算结果相吻合。但在1600K或更高温度下，强度比偏差较大。

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.