A Study on Converging Thin Annular Jets

An interesting feature of jets from liquid-liquid coaxial swirl atomizers used in bipropellant rockets or elsewhere is that the outer jet results in a tulip shaped liquid bulb even at operating pressure levels. In this context, experiments have been performed to study the discharge and tulip characteristics of annular jets through qualitative simulation of outer jet flow conditions at which tulip bulb prevails. It is shown that the discharge coefficient increases steeply with Reynolds number, a trend which is distinct from that of circular orifices. The range of flow conditions at which tulip bulb prevails decreases with the annular gap. If a swirl component is introduced into the annular jet, it alters the discharge characteristics and the tulip range with a tendency to form multiple tulips. Variation of tulip length for different annular gaps shows a common trend when plotted against liquid flow rate. The experimental data of tulip length agree reasonably with the theoretical model reported in literature.