Formation mechanism of the pressure zone at the tip of the melt delivery tube during the spray forming process

The gas pressures at the tip of the melt delivery tube in two typical atomizers are measured in this work. Gas dynamics is used to study the gas flow and pressure zone at the tip of the delivery tube, and a mechanism for the formation of pressurization and aspiration is proposed. The results show that the atomization efficiency of an atomizer with a Laval nozzle is superior to that of an atomizer with a converging nozzle. The gas jet expands strongly at the nozzle exit of a converging atomizer, while the Prandtl–Meyer angle of the jet is very small for a Laval nozzle. When the jet expands strongly, pressurization is likely to form at the tip of delivery tube. Aspiration is formed when the jet pressure at the exit of nozzle is equal to or smaller than the back pressure.