This study aims to design a supersonic ejector, referred to as a liquid spray
gun, with a simple operating procedure for producing an aerosol spray with
adjustable droplet size distributions. A CFD model was developed to determine
the influence of nozzle exit position and the primary air pressure on the
supersonic patterns formed within the ejectors, providing a valuable insight
into their internal physics. Based on the single-phase numerical results, at an
air primary pressure of 2 bar, the flow may not reach a choking condition,
possibly resulting in unstable ejector operation. However, at pressures
exceeding 5 bar, the jet patterns emerging from the primary nozzle cause flow
separation or the formation of vortex rings. This phenomenon leads to a flow
configuration comparable to the diameter of the mixing tube, thereby reducing
the available area for entrainment of suction flow. The suitable ejector was
identified with a nozzle exit position of 13 mm and a primary pressure ranging
from 3 to 4 bar. Consequently, a high-speed imaging shadowgraph system was
successfully developed to experimentally analyze the water spray pattern within
the designed ejector. The experimental results indicate that the ejector
performs effectively under different operating conditions, producing a fine
water spray with predominantly small droplet sizes below 30 μm when the air
pressure is within the range of 3 to 4 bar. These results highlight the
capability of the supersonic ejector as a spray gun for generating aerosols
suitable for contaminated surface cleaning and other relevant applications.