VISCOSITY AND SURFACE TENSION EFFECTS IN PRESSURE SWIRL ATOMIZATION

The development of phase-Doppler anemometry has provided a reliable measuring technique for studying local particle size and particle velocity distributions in sprays. Using this technique, the present article summarizes viscosity and surface tension effects on the properties of liquid sprays produced by pressure swirl atomizers. Mean droplet sizes and mean velocities were computed from the measured joint size/velocity distributions to discuss the spray properties in the terminology largely employed in the field of liquid sprays. The results indicate an increase of the mean diameter with increasing surface tension and increasing viscosity. Concerning the shape of the size distributions, the results suggest that narrow size distributions can be generated by low-viscosity and low-surface-tension fluids. Also, it is shown that surfactants do not lead to an effective surface tension reduction in atomization. Moreover, they introduce a non-Newtonian behavior, which results in a decrease of the number of droplets in the small size range.