The separation of binary gas mixtures of carbon dioxide and hydrogen in sonic-orifice-generated free jets is investigated over a source Reynolds number range of 100 to 3000 using the well-known electron beam fluorescence technique. The lighter species, hydrogen, is chosen as the minor species in order to examine the extent of the validity of Sherman’s first-order diffusive separation theory for large separation. The diffusive separation of mixtures containing approximately 2%, 5%, and 20% hydrogen in carbon dioxide is investigated by experimentally determining the relative number densities of the two species as a function of centerline axial distance within the free jets. Sherman’s diffusive separation theory is applied to the jets using axial Mach number profiles which were a combination of experimental and analytical results for γ=1.40 expansions. The γ=1.40 expansion is shown to approximate the CO2–H2 expansion quite well, and the calculated separation agrees remarkably well with the experimentally determined values.
Two-line fluorescence thermometry measurements based on excitation of the A-X (0, 0) band of nitric oxide were performed in the free-stream flow of a large-scale shock tunnel, the Arnold Engineering Development Center Impulse Facility. Because the flow is optically thick, effects of laser absorption must be taken into account. This can be accomplished by extending the two-line thermometry concept to three lines. We illustrate the three-line technique by combining two-line planar laser-induced fluorescence measurements from separate facility runs. The resulting free-stream temperature T(0) = 468 K ? 65 K is insensitive to assumptions regarding the laser propagation distance through the flow, the vibrational temperature of the flow, and the precise nature of the absorption line shape.
Approved for public release; distribution unlimited. 17. DISTRIBUTION STATEMENT ^ eleci naceemety end Identify by block number) leigh scattering lectron beam fluorescence measurement 20. ABSTRACT (Continue on rarer» elde It neceeeery and identity by block numl»rj Homogeneous condensation of nitrogen in hypersonic expansions from a sonic orifice source was investigated using both Rayleigb scattering and electron beam fluorescence diagnostics. Using a 3-mm orifice, the source pressure range of 100 to 4000 torr was investigated for a 300 K source temperature. Electron beam measurements of the rotational temperature, TR, of nitrogen (N2) were used to determine onset of condensation, and both radial and axial DD ,: FORM AH 73 1473 EDITION OF 1 MOV «S tS OBSOLETE UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE fWhan Dele Bnlortd) UNCLASSIFIED SECURITY CLASSIFICATION OF TmS PAQEpWran Dfa Eniirtd) 20. Continued. surveys of T R were performed. Similar electron beam measurements were performed for source temperatures of 116 K and 133 K for one pressure value. Rayleigh scattering measurements were used to observe both onset of condensation and growth of clusters along the centerline, and estimates of mole or mass fractions of condensate were obtained using both diagnostic techniques. Previously published supersaturation ratios of N 2 determined by other investigators were significantly larger than the present results which observed onset earlier in the flow field. UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGEfWian Data Enf.r«0
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Some recent experimental studies of the expansion of gases from a diverging nozzle into hard vacuum have shown that for some nozzle flow conditions there are large off-centerline spikes in the exit plane pitot pressure profiles. Based on the results of the present study it has been suggested that pressure spikes of this type result from the presence of condensation in the expanding flow.
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