Computational and Heat Transfer Analysis of Convergent Nozzle Used for Gas Atomization of Liquid Metals

Gas atomization is a widely used process for manufacturing of fine metal- and alloy- powders. The idea is to transfer kinetic energy from a high velocity jetgas expanded through a nozzle, to a stream of liquid metal, resulting in fragmentation and break up into metal droplets. Gas atomization process is the powder production technique and nozzles play an important role in the gas atomization process. The gas to metal interaction is determined by geometry of the nozzles. The type of the nozzle and geometry of the flow is the most important parameter for atomization process. The design of an atomizing nozzle determines the degree of contact of the liquid metal with the atomizing gas. The atomizing nozzles have co-axially placed Metal Delivery Tube (MDT), which carry the molten metal to atomizing zone. The flow properties of gas are considerably affected by the presence of MDT. In the present analysis, an attempt has been made to analyze the flow pattern of gas in Convergent nozzle (C - nozzle) using Computational Fluid Dynamics (CFD) techniques. Flow characteristics of gas was determined inside the nozzle and the atomizing zone and different plots (ex: Mach number plot) were obtained using CFD software Fluent. Further, Radial and axial variations of Mach number were determined at the exit of the nozzle and the flow area. CFD results for gas velocity were compared with the analytical results. In addition, variation in pressure, temperature and shock waves were analyzed along axial direction at the nozzle exit and flow area with and without placing the co-axial MDT inside the sonic nozzle.