The Influence of the Annular Nozzle's Structural Parameters on Powder Stream Convergence for Laser-Directed Energy...

Laser-directed energy deposition (L-DED) technology is increasingly used in the manufacturing industry, in which the powder convergence of the feeding nozzle affects the accuracy and quality of additive manufacturing parts. However, there is nothing in the literature that gives a comprehensive optimization scheme for the powder feeding structure of the ring nozzle. In order to investigate the effect of the internal structure for the annular nozzle on powder convergence, in this paper, finite element analysis models for the annular nozzle are established, and the Lagrangian-Eulerian method is used to analyze the influence of different outlet shapes, powder feeding inclination angles, outlet gaps, and inlet shapes of annular nozzles on the powder convergence. The results indicate that the parallel outlet shape is more suitable for the annular nozzle, and the waist diameter of the powder stream decreases gradually with the decrease in the power feeding inclination angle and the outlet gap. The inlet shape of the powder storage chamber plays a guiding role in the moving direction of the powder particles; when the powder feeding inclination angle is 17° and the outlet gap is 0.5 mm, the waist diameter of the powder stream is reduced by 49%. In addition, the effects of particle size, carrier gas rate, and laser shielding gas on the powder convergence are also studied, and the results indicate that, with the reduction of particle size and carrier gas rate, the powder convergence can be effectively improved, and the waist diameter of powder stream becomes 1.42 mm. With the increase in the laser shielding gas rate, the powder convergence position moves down. The research results provide a basis for the structural optimization to design a high-convergence annular nozzle for the laser additive manufacturing process.