Numerical study of the gas-particle flows with the two-way coupling formed by coaxial nozzles for laser cladding

Direct material deposition (DMD) is the technology of producing new parts and making coating depositions, where much powder should be transported with high accuracy. At high powder flow rates (50–100 g/min), the interaction between a gas and powder flow (two-way coupling), as well as collisions between particles, impose a significant influence on the powder jet focusing. In the light of these effects, the paper presents the numerical analysis of the structure of gas-dispersed flows formed by continuous coaxial nozzles. Considerable variations in the gas-dynamic flow are shown in the focus area when the powder volume fraction is above 0.5 %. The obtained results are in a good agreement with the experimental ones and show the importance of the two-way coupling of both phases. The efficiency of a triple coaxial nozzle with a non-parallel arrangement of channels for carrier and shaping gases is analyzed for different powder particle sizes. •Due to the two-way coupling, significant deceleration of the gas jet occurs in the focus area almost to particles velocities•In the area of high powder concentration (up to 13 %), a noticeable change in particle trajectories is observed•The necessity to consider the two-way coupling between phases is demonstrated if the powder concentration is more then 0.5 %•The efficiency of the modified external nozzle to improve the focusing of the powder jet is shown for various particles sizes