Supersonic pulsed jets for material sorting

Abstract

Air ejectors are used for sorting materials by displacing selected items through the action of aerodynamic drag. Subsonic units are common in the marketplace. This paper explores the potential for the use of an overexpanded supersonic jet because of it having reduced lateral spread and giving significantly higher particle drag. Experiments have been conducted to explore the flow field associated with a pulsed supersonic jet impacting particles in different positions relative to the jet exit, and of various shapes. The forces acting on a typical particle are measured and schlieren photography is used to visualize the flow.