Simulation of powder transportation in directed energy deposition

To understand the mechanism of powder transportation in a coaxial feeding system, computational fluid dynamics and the discrete element method are coupled to simulate the gas flow and metal powder transportation characteristics in a directed energy deposition feeding system. Results indicate that powder diversion occurs in the bending region of powder transportation pipes. In a conveying pipe containing powders with a particle size of 53–85 μm, powder aggregation occurs at concentrations of 5.63 and 6.26 kg/m³ in bending curvatures of 11.13 and 13.33 m⁻¹, respectively. The ratio of the particles in the three conveying pipes transported into the mixture region is 92.8% for particles with diameters of 53–85 μm, 95.0% for particles with diameters of 85–117 μm, and 96.7% for particles with diameters of 117–150 μm. This is the reason for the smaller average size of particles in the mixture region.