Modeling and simulation of droplet formation in a centrifugal atomization process and a microfluidic process using T-junction

Abstract

The centrifugal atomization of melts using a rotating disk is an important process for producing powder with narrow size distribution and microstructurally refined and chemically homogeneous preforms. In the first part of this study, wave theory was applied to analyze the break-up of melted wax in the film disintegration regime during centrifugal atomization using a rotating disk. A matlab code was written to predict the spray characteristics. Powder size were calculated and compared with available experimental data in the literature and a good agreement was achieved. The influence of the break-up parameter was studied, and it is confirmed that the break-up parameter hardly affect the predicted powder particle size. Simulated results showed that fine powders can be produced by increasing disk size, disk speed and density of atomization environment and decreasing the melt flow rate. In the second part of this study, three dimensional numerical simulations were performed to understand the mechanisms of droplet formation in microfluidic T-junction with the help of COMSOL Multiphysics$\reg$ software. The influence of flow rate ratio, viscosity ratio and ratio of channel widths was systematically examined in the droplet generation process. Three different flow regimes were identified in the T-junction. Simulation results show that monodisperse droplets can be produced at moderate flow rates of both dispersed and continuous phase while maintaining low flow rate ratio between them. Also the plug size is found to increase with decrease in width of dispersed phase channel. It is expected that the results of this study will help in realizing the capabilities of both techniques and developing a better understanding of the break-up mechanisms for further control over the formation of fine droplets.