Secondary flow choking in axisymmetric supersonic air ejector with adjustable motive nozzle

Abstract

Supersonic ejectors have many applications across engineering, but their broader utilization is prevented by their generally low efficiency, which is related to a lack of understanding of the processes within them. This paper presents experimental and numerical analyses of the choking phenomenon within an axisymmetric supersonic air ejector with an adjustable motive nozzle. The effects of the operating and geometric conditions on the flow within the ejector were studied in detail. Five motive nozzle configurations were considered, and the results showed that the specific nozzle position (xp) could be changed to influence the choking of the secondary flow and hence achieve different working regimes while keeping the operating conditions constant. At xp = 1 or 2 mm, the secondary flow reached sonic conditions before even entering the mixing chamber and therefore before mixing with the primary flow. At xp = 3–5 mm, choking occurred within the mixing chamber, and two different choking mechanisms were identified. These results may serve as background for better understanding of flow choking in supersonic ejectors.