Diffusive separation of binary mixtures of CO2–H2 in a sonic-orifice expansion

Abstract

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.