可调谐二极管激光吸收光谱技术测量低温流场水汽露点温度

露点温度是表征气体状态的一个重要参数,针对低温环境的低露点温度精确、快速、连续、原位测量的迫切需要,提出了可调谐二极管激光吸收光谱(TDLAS)技术对水汽露点温度测量的方案。首先与安徽省气象局的冷镜式露点仪一起对比测量标准温湿度箱内的露点温度,验证波长为1 381nm的TDLAS系统露点温度测量的可行性及精度,然后结合一套开放式的测量装置,进行低温度环境(最低温度100K)水汽露点温度原位测量。得到了实时的露点温度值,其中TDLAS露点测量结果与冷镜式露点仪测量结果一致性较好(相差小于1K),TDLAS测量的时间分辨率为0.83s,远远快于冷镜式露点仪的时间响应速度。对于更低气体温度的露点测量,获得了与气体温度变化趋势相同的露点温度,同时得到了随着环境温度降低,水汽逐渐趋向饱和的结论。

Measurement of low water vapor dew-point temperature based on tunable diode laser absorption spectroscopy

The dew-point temperature is an important parameter of gas. Moreover, there is an urgent need for developing techniques that can facilitate the accurate, rapid, continuous, and direct measurement of low dew point temperatures. In this regard, an approach based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) was developed. Firstly, our TDLAS hygrometer was compared with a chilled mirror hygrometer at Anhui Provincial Meteorological Bureau. Secondly, a free-path measurement apparatus was designed with an optical pathlength of approximately 3.8 m, and it was used to directly measure very low dew-point temperatures in a cryogenic chamber. Dew-point temperatures were obtained by standard formula. The results from TDLAS were compared with chilled mirror hygrometer.The maximum deviation is less than 1 K. In addition, the time resolution of the TDLAS system was determined to be approximately 0.83 s, which is shorter than the chilled mirror hygrometer.Through this experiment, we demonstrated that TDLAS technology was feasible to measure dew-point temperature at low temperatures.