Nitrogen condensation in a sonic orifice expansion flow

Homogeneous condensation of nitrogen in hypersonic expansions from a sonic orifice source was investigated using both Rayleigh 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 were used to determine onset of condensation, and both radial and axial surveys of TR were performed. 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 N2 are compared. (Modified author abstract)