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Due to the particularity of the high-speed flow, in order to accurately obtain its’ temperature, the measurement system
should has some characteristics of not interfereing with the flow, non-contact measurement and high time resolution. The
traditional measurement method cannot meet the above requirements, however the measurement method based on
tunable diode laser absorption spectroscopy (TDLAS) technology can meet the requirements for high-speed flow
temperature measurement. When the near-infared light of a specific frequency is through the media to be measured, it
will be absorbed by the water vapor molecules and then the transmission light intensity is detected by the detector. The
temperature of the water vapor which is also the high-speed flow temperature, can be accurately obtained by the
Beer-Lambert law. This paper focused on the research of absorption spectrum method for high speed flow temperature
measurement with the scope of 250K-500K. Firstly, spectral line selection method for low temperature measurement of
high-speed flow is discussed. Selected absorption lines should be isolated and have a high peak absorption within the
range of 250-500K, at the same time the interference of the other lines should be avoided, so that a high measurement
accuracy can be obtained. According to the near-infrared absorption spectra characteristics of water vapor, four
absorption lines at the near 1395 nm and 1409 nm are selected. Secondly, a system for the temperature measurement of
the water vapor in the high-speed flow is established. Room temperature are measured through two methods, direct
absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS) ,the results show that this system can
realize on-line measurement of the temperature and the measurement error is about 3%. Finally, the system will be used
for temperature measurement of the high-speed flow in the shock tunnel, its feasibility of measurement is analyzed.
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