Investigation of the pulsation phenomenon in close-coupled gas atomization

High speed photography coupled with sophisticated image analysis has been used to study the low frequency pulsation in the volume of melt being instantaneously delivered to the melt nozzle during close-coupled gas atomization. We find that at low gas pressures the distribution of material at the melt tip can be described by a log-normal distribution. At high gas pressure the distribution is better described by two superimposed log-normal distributions, one with a high standard deviation when there is little melt at the atomizer tip and a second with a lower standard deviation when there is more melt at the atomizer tip. We associate this behavior with the transition between open- and closed-wake conditions in the gas. We suggest that the methodology proposed represents a simple, non-invasive technique for characterising the performance of gas atomizers.