Abstract
The flow characteristics of transonic and supersonic under-expanded jets issued from circular nozzle have been studied by many researchers and many things have been clarified already. For example, Donaldson & Snedeker classified the flow pattern of the transonic and supersonic under-expanded jets issued from a smoothly converged contour nozzle in three depending on the pressure ratio of the supplied pressure p0 to the ambient pressure pa. In the ranges of 1.89< p0/pa< 3.85 and 3.85<p0/pa jets are moderately under-expanded jet and highly under-expanded jet, respectively. We examined the flow characteristics of transonic and supersonic under-expanded jets issued from an orifice nozzle experimentally by visualised flow pattern by Schlieren method and measurements of velocity distribution by a supersonic Pitot-tube.
In this study, the effects of the nozzle shape on the flow characteristics such as decay of the jet centreline velocity and the increments of the jet-width and -flow rate to the downstream, and the velocity profile are examined. The orifice nozzle with small or large notches was used besides of circular and orifice nozzles. The notch was used to disturb the flow around outer edge of the jet and to enhance the entrainment flow rate there. This will help to improve the performance of a cylindrical ejector.
