Diffusive separation in shock waves and freejets of nitrogen-helium mixtures.

Abstract

The effects of diffusive separation were measured in shock waves and underexpanded freejets for a binary mixture of nitrogen and helium by the electron-beam technique. The measurements consisted of mole-fraction ratios in the jets, and of partial density and nitrogen rotational temperature profiles through the shock. A number of initial compositions were tested and all indicate an enrichment of the heavier particles at the axis of the jet, and an enrichment of the lighter particles in the jet boundary. The measured shock profiles indicate a qualitative agreement with the theory in that an enrichment of the lighter particles was found in the upstream portion of the shock wave. The N2 rotational temperature profiles were used to compare the heavier particle temperatures with the shock-density profiles of both of the components of the gaseous mixture. Nomenclature A — Einstein's transition probability of spontaneous emission Bv = rotational constant Ci . . . C& = constants c = speed of light d = throat diameter e = electron charge F = constant f =