| Popis: |
This paper presents a numerical and experimental characterization of the powder-gas jet during the coaxial directed energy deposition process in terms of flow velocity, particle velocity, jet symmetry, and powder stream shape. The latter parameters are linked to the blown powder settings, known as the carrier and shielding gas volumetric flow rate, the powder mass flow rate, and the particle diameter. First, 2D axisymmetric steady-state computational fluid dynamics simulations of the turbulent gas flow are presented to illustrate the flow behavior and the effect of the presence of a substrate under the gas jet. Next, the free powder flow is visualized experimentally using high-speed imaging techniques. The particle velocities are extracted from the high-speed images by means of particle image velocimetry and compared with in situ measurements of the powder flow. |
