Experimental and numerical modeling of the gas atomization nozzle for gas flow behavior

Gas atomization is a widely used process for manufacturing of fine metal- and alloy-powder. To ensure a stable process with high yields of metal powder, the negative pressure at the melt delivery tube tip base and no flow separation conditions are necessary for a good atomization process. An important feature of these jets is that flow separation may occur over the outer surface of the liquid delivery tube for some conditions. Flow separation cause solidification and accumulation of metal, leading to a shape alteration of the liquid delivery tube in gas atomization process. Using computational fluid dynamics (CFD) software, a parametric study was conducted to determine the effects of atomizing gas pressure on the melt delivery tube tip base pressure and flow separation. Atomization gas pressures of 1.0, 1.3, 1.7, 2.2, and 2.7 MPa were used in the CFD model to initialize the pressure in gas inlet. CFD simulations were performed and the modeling results were compared with experimental data. These results showed that the CFD modeling can be used for the estimation of the melt tip base pressure of the nozzle. It is found that the flow separation formation is strongly dependent on the atomizing gas pressure.