Numerical investigation on the mixing process within the two-strut supersonic ejector

Abstract

Free supersonic mixing layers have garnered considerable attention, while research on supersonic mixing layers in confined spaces remains limited. Therefore, in this paper, the supersonic mixing process within a two-strut supersonic ejector is investigated using numerical methods. The flow structure and mixing characteristics are analyzed in terms of mass, velocity, and total energy. Moreover, the influence of entrainment ratio and total temperature ratio on the mixing process is examined. Results indicate that the mixing process within the ejector is affected by the expansion of the primary flow and the contraction of wall, impacting flow parameters in non-mixing regions. Specifically, the acceleration of secondary flow in these regions leads to the formation of a Fabri choking area, altering the growth rate of the mixing layer thickness from rapid to slower progression. Analysis of mass thickness, velocity thickness, and total energy thickness reveals similar growth trends, with velocity thickness being the largest. However, velocity mixing uniformity does not accurately reflect the mixing degree, as momentum transfer alone does not account for velocity changes. Moreover, decreasing entrainment ratio and total temperature ratio result in higher convective Mach numbers and lower velocity ratios, thereby promoting mixing process between primary and secondary flows. Nevertheless, the significant increase in secondary flow temperature causes the Fabri choking region to vanish, which benefits the mixing process.