Numerical simulation and experimental study for aerodynamic characteristics and powder transport behavior of novel nozzle

摘要

Aiming at saving manufacturing cost and optimizing nozzle structure, a novel coaxial nozzle was developed in this work. A three-dimensional (3D) numerical model was established to analyze the characteristics of aerodynamics and powder particle transport of the nozzle. Then the collision behavior, trajectory and velocity distribution of particles inside the nozzle, and the structure and convergence characteristics of the powder jet flow outside the nozzle were studied. And Later, the internal relations between the particle transport behavior inside the nozzle, the structure of powder jet flow outside the nozzle and the deposition characteristics were revealed. The results show that the gas dynamic characteristic of the nozzle is the key factor affecting the structure of powder flow field, moreover, the collision between the particles enhances the influence on it. When the powder-carrying gas flow falls in the range between 2.0 and 3.0 L/min, the powder jet flows converge as a "nail" shape with longer focal length, smaller divergence angle and higher concentration, which conduces to the stable focal length and concentration distribution, thus leading to the high utilization rate of powder flow and the excellent formability of sedimentary layer correspondingly.