Development of the Diode-Laser Absorption Spectroscopy System for the Diagnostics of High-Temperature Flows.

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In this academic year, we conducted spectroscopic measurements on high-enthalpy plumes generated in the wind tunnels at the university of Tokyo, Nagoya university, the Japan ultra-high temperature material research center (Nagoya), the national aerospace laboratory (Chofu), and the university of Stuttgart (Germany). The results are summarized as follows.1) Three-dimensional determination of arcjet argon-plume properties was achieved by computer tomographic reconstruction.2) In order to get the information of high-temperature air plume, we accessed to the atomic oxygen absorption line at the wavelength of 777.19 nm and successfully measured the translational temperature and the number density of excited atomic oxygen. From the measured three-dimension distribution, the diffusive mixing process of oxygen gas into nitrogen gas was clarified, and owing to this process, the degree of dissociation in the plume generated by constrictor-type arc-wind tunnels was found lower than the expected value.3) In the repetitively discharging inductive-heating wind tunnel, we succeeded in measuring the profiles of temperature and number density of atomic oxygen in high-temperature pure-oxygen flows.4) Diagnosis of the optically thick plumes, which is quite difficult for the Laser Induced Florescence or Emission Spectroscopy measurements, has been successfully done using Laser absorption spectroscopy. (The maximum absorption reached at 97%)5) The portability and wide-usage of our laser diagnostic system has been demonstrated by transporting and applying it to the wind tunnels located at Nagoya, Tokyo and Stuttgart, Germany.6) For the future improvement of system performance and for the measurement of ground level number density, the increase in its sensitivity by several orders of magnitude would be essential.