Numerical and experimental investigation of multiple gas jet flow behaviour in the gas atomization process

Sammanfattning: In several industrial applications, the interaction of supersonic gas jets is encountered such as gas atomization, jet engines and the basic oxygen furnace process. In the gas atomization process, high pressure gases are converted to high velocity gas jets through convergent-divergent nozzles. These high velocity gas jets break up the stream of the molten metal into fine droplets. Therefore, it is essential to develop a deep knowledge of interaction between the gas jets and the liquid metal and the dynamics of jets as a step towards optimizing the gas atomization process. This will enable higher process efficiency at lower cost and energy consumption. In this study, the gas interaction behaviour of the two gas jets from two convergent-divergent nozzles with the same geometry have been modelled using Ansys Fluent software. The result of the computational fluid dynamics simulation has been also compared with an experimental study that has been done under similar conditions to the simulation.  The results of this study have shown that, by decreasing the nozzle interaction angle the maximum velocity along the symmetry axis will be increased. However, according to the velocity contour plots the maximum velocity when the gas interaction angle is 20°, 5° and 0°, the maximum velocity reached to 676 m s-1, 698 m s-1 and 696 m s-1 respectively.   In addition, it was found that the maximum value of the jet velocity along the symmetry axis decreases with an increase in distance between the nozzles. However, according to the velocity contour plots for the 18mm, 10mm and 5mm distance between the nozzles the maximum velocity reached to 696 m s-1, 685 m s-1 and 683 m s-1 respectively. In general, when the gas jets have higher velocity, they have higher kinetic energy to disintegrate the stream of the molten metal. Therefore, higher gas jet velocity leads to powder with smaller particle size.   The results of this study can be used to design better nozzles configuration in gas atomization process in order to achieve better process efficiency. Moreover, the finding of this study will help to build more complex simulations with more nozzles in the model.