Numerical study on the collision effect of particles in the gas-powder flow by coaxial nozzles for laser cladding

In this work, the Computational Fluid Dynamics (CFD) modelling method based on the v2-f turbulence model is innovatively used to establish the numerical model of the gas-powder flow. In the model, the drag force is used to calculate the interaction between the gas and powders, and the Hertz elastic theory is used to calculate the collision force on the powder. Then, the calculation results of the impact rebound between the particles and the inner wall of the nozzle, the overall distribution of the powder flow, and the particle velocity at the nozzle outlet are verified. Finally, the effects of different carrier gas flow rates and powder feeding rates on the velocity and concentration distribution of powder particles with and without collision were compared and discussed. The movement state and concentration distribution of the particles from the inlet to the outlet and then to the convergence were compared with and without the collision effect. It was found that collisions between particles had enormous implications to the concentration distribution and movement state of the powder which cannot be ignored. The convergence can be improved to some extent by using higher carrier gas flow rate and lower powder feeding rate.