Influence of liquid properties on the internal flow characteristics of simplex swirl atomizers

The influence of liquid density and viscosity on the internal flow characteristics of simplex swirl atomizers is investigated. Expressions are derived to show how initial spray cone angle and velocity coefficient are affected by changes in these properties, and also by variations in atomizer dimensions and pressure drop. The results of this study indicate that the effects of viscosity on spray cone angle, velocity coefficient, liquid film thickness, and nozzle flow rate, are much more pronounced than those of density. Furthermore, it is shown that the well-established role of viscosity in opposing the disintegration of a liquid sheet into ligaments and then drops is not the only mechanism whereby viscosity forces adversely affect atomization quality. These forces also impair atomization by increasing the thickness of the conical liquid sheet formed at the nozzle exit, and by reducing the efficiency of the process whereby the pressure drop across the nozzle is converted into kinetic energy in the spray.