Analysis of atomizer performance using a discrete jet high pressure gas atomization system

The mass median powder diameter, d 50 , is measured as a function of atomization conditions for a discrete jet type high pressure gas atomization system. Five different gas pressures are used between 3.0 and 5.0 MPa and, for each pressure, four different melt flow rates are studied by independently varying the forcing pressure under which the melt is ejected and the bore of the melt delivery nozzle. A poor fit to the conventional Lubanska model is found. However, it is shown that d 50 correlates well with the ratio of melt flow rate to power embodied within the supersonic gas stream, as first suggested by Strauss & Miller [Adv. Powder Metall. Particulate Mater. 11, 2001, 2.17], provided their relationship is modified to include a minimum particle size at low melt flow rate. This we conjecture may be due to incomplete wetting of the melt nozzle at such low melt flow rates. We also note that the efficiency of atomizing systems in converting potential energy stored in the high pressure gas to kinetic energy embodied in the supersonic gas stream drops as the pressure increases, calling into question the current trend for increasing the atomizing pressure.