Computational fluid dynamics application for gas-powder flow investigation in a coaxial nozzle design for additive manufacturing

Abstract

Direct Energy Deposition (DED) is one of the seven Additive Manufacturing (AM) classes. It is increasingly used to repair and construct parts in the industry. The DED methodology uses heat to melt the substrate and the deposited material. There are different ways to perform this task, and over the years, additional patents and methods appeared. Other materials can be applied, such as metals, ceramics, polymers as well as mixtures, to produce composite materials. The nozzle plays an essential role in the overall process and studying its influence and mechanical design aspects is crucial. Computational Fluid Dynamics (CFD) is an important engineering tool, and it is being widely used for better and fast design. The use of a CFD tool to optimize the nozzle and improve the deposition system can be a quick and efficient way to increase the overall efficiency of this type of machine. The gas-solid model proposed in this current study improved the knowledge about particle transportation using a nozzle, and it was verified that for a low Reynolds Number, the higher the Stokes Number, the higher the particle Concentration on the desired area of deposition. It was also confirmed that decreasing the Reynolds Number implies an increase in particle Concentration. Considering higher Reynolds Numbers, Re = 1 000 and Re = 1 250, it was concluded that there is no pattern for the particle Concentration due to the agglomeration formation, changing the shape of the particles and generating a new solid body, modifying the drag force and, then, the particle deposition behavior. The research developed on this dissertation helped to understand the particle behavior considering different flow regimes applied for a range of multiple Reynolds and Stokes Numbers. It was possible, as well, to map the particle deposition pattern behavior and to understand the effects of the fluid flow over the particle concentration on the deposition point.