Experimental study of condensation scaling laws for reservoir and nozzle parameters and gas species

A study of condensation of gases in expansion flow fields has been performed using laser Rayleigh scattering with the goal of determining the dependence of the spatial location of onset and subsequent condensate growth on gas reservoir conditions, gas source parameters, and gaseous species. Sonic-orifice and conical-nozzle expansions of N2 were studied for a range of reservoir-pressure values at a nominal reservoir temperature of 285 K. Sonic-orifice expansions produced by sources of two different diameters were investigated for flow fields of Ar, N2, O2 and CO. The Rayleigh-scattered intensity for the sonic-orifice expansion was found to vary as the cube of reservoir pressure and the square of orifice throat diameter in the spatial regions of the flow field for which massive condensation existed. The massive-condensation region of the nozzle expansions yielded scattered intensities which varied as the cube of reservoir pressure, the square of nozzle throat diameter, and the tangent of nozzle half-angle. Using reduced values of reservoir pressure, throat diameter, and reservoir temperature, nondimensionalized by appropriate intermolecular-potential parameters, similar gases were found to have a common onset-of-condensation locus in a reduced pressure-temperature domain.