Preliminary Study on Atom O in High-Enthalpy Flow Field

With Two-photon absorption laser-induced fluorescence(TALIF) technology, leads pulse laser in pure high-enthply flow field from the direction of perpendicular to flow field, and obtains the two-dimension atom O fluorescent signal with ICCD setting outside of test section on the vertical direction of flat made with flow field and laser, this signal reflects the relative concentration of atom O. In paper, given the experimental environment and experimental equipment, to ensure that excitation laser wavelength in experiment is the best one, different angular quantum number on ground state of atom O are tested; finally, it is determined that J = 2, wavelength 225.584 nm shall be experimental excitation laser wavelength. To make sure that the obtaining atom O fluorescent signal is in unsaturated linear region, in same condition, changing the excitation laser energy from small to large to test fluorescent signal, ultimately acquiring laser energy linear region is below 3.4 mJ. To record ICCD fluorescent image clearly with optimum contrast, Nikon f=105 mm F/2.8 lens is chosen as experimental lens, and the results are got with an accumulation of 50 times exposure. By analyzing the experimental fluorescent signal, we can get two peak positions on left and right of central line about +/- 50 mm wide which are generated with compressional wave in supersonic flow field, and atom O concentration has 60 mm wide uniform area in central zone of subsonic flow field, the concentration decreases dramatically. This phenomenon is consistent with flow characteristics of wind tunnel, so the method can be applied to flow parameters measurement in the future.