Two-phase numerical modeling of gas atomization and calculation of particle size

Variables such as gas pressure and molten metal viscosity have a decisive effect on the size and size distribution of the powders produced by gas atomization. Although many models have been introduced about the disintegration mechanisms that determine the powder size, the atomization process has been modeled as a single phase flow in most of the numerical analysis with the Computational Fluid Dynamics (CFD) approach in the investigation of those effects. In some studies involving molten metal flow, atomization initiation was generally modeled and liquid metal-gas interactions, disintegration mechanisms and particle formations were not shown. In this study, it is aimed to model the gas atomization process as a two-fluid flow and to show that particle size can be obtained by numerical modeling. In this context, gas atomization process is modeled, CFD analysis is obtained and interactions between the two phases are shown, atomization mechanisms are explained and powder size is obtained with a new approach developed within the scope of the thesis. With the developed approach, numerical analysis is applied at the pressure values of 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa and 3.5 MPa and the effects of gas pressure on the particle size are investigated. The powder size was calculated to be 43.24 µm at 1.0 MPa pressure and 35.69 µm at 3.5 MPa pressure. It was found that the mean particle size decreased with increasing gas pressure. In order to examine the effect of liquid metal viscosity on powder size, numerical solution was repeated with a different viscosity value under 2.5 MPa pressure. The average powder size was found to be 41.47 µm when the viscosity of the liquid metal was 0.00133 kg/m-s, and the average powder size was 45.97 µm when the viscosity value of the liquid metal was 0.00623 kg/m-s under the same conditions. It has been observed that for the high viscosity melt the disintegration process is more difficult, therefore, it is hard to obtain fine-grained particles. In addition to these results, particle formation in two-phase gas atomization is shown by three-dimensional modeling with the developed approach.