Two phase flow model for the close-coupled atomization of metals

The use of the nozzle tip static (aspiration) pressure during the flow of atomizing gas in close-coupled atomization geometries is employed widely to characterize the operable atomization regime, and, in some cases, the expected metal flow rate. A single phase flow calculation of metal flow rate using this pressure shows that the actual metal flow during atomization is not determined simply by the aspiration pressure. An improved model has been developed by applying a force balance and momentum conservation at the metal/gas interface. Combined with numerical and experimental gas flow data, the model provides a rational interpretation of the relationship between aspiration pressure and metal flow during atomization. The model also provides a physical basis for some of the commonly observed limits on the operating envelope of close-coupled atomizers and establishes a rational basis for non-metal fluid modeling of the atomization process. A variety of metal and wafer flow test data and local static and dynamic pressure measurements are presented which demonstrate the validity and limitations of the model.