超音速自由分子流における非ボルツマン回転エネルギー分布の実験的解析(流体工学,流体機械)

概要

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In the present study, we measure the rotational population in supersonic nitrogen free jets using a REMPI (resonantly enhanced multi-photon ionization) method, which is not influenced by secondary electrons, unlike an electron beam method. Nitrogen ions are detected as a REMPI signal and its spectra depending on the wavelength of an irradiated laser beam are analyzed to measure rotational temperature through the Boltzmann plot. Nitrogen gas expands into a vacuum chamber from a sonic nozzle with a D=0.50mm diameter, setting P_0D (P_0: source pressure), depending inversely on the nozzle Knudsen number, at 15 Torr・mm or lower. For P_0D=15 Torr・mm, the rotational temperature distribution along the centerline of the jet, measured by Boltzmann plot, coincides with Marrone's data measured by electron beam fluorescence, and the rotational relaxation rate Z_R calculated by the relaxation equation results is 1.3. However, the non-Boltzmann rotational distribution appears evidently in the supersonic free molecular nitrogen flows for P_0D⩽15 Torr・mm and as a decrease in the P_0D, the deviation from the Boltzmann distribution and the partial freezing of the population arise more upstream.
社団法人日本機械学会の論文
2005-02-25