Numerical investigation of a particle-laden jet for cold spray coating

Cold spray metal coating requires accelerating metal particles to high speeds using a carrier gas to provide sufficient kinetic energy for the particles to embed in a substrate and thereby coat it. The dynamics of the carrier gas and of the dispersed phase have a significant effect on the effectiveness and efficiency of this metal processing technique. This paper investigates the flow and particle dynamics of a sonic jet lightly laden with copper particles, by computational fluid dynamic (CFD). The model uses an Eulerian-Lagrangian coupled formulation, in which copper particles are accelerated by the compressible flow up to sonic speeds. The predictions for the jet spreading rate, the velocity centerline distribution and decay rate, and the shear layer half-velocity are consistent with published experimental work. Three numerical experiments using different copper particle distributions of Rosin-Rammler type highlighted the significant role of the particle distribution on the particle deposition efficiency. It is found that particles behave differently depending on their size. Specifically, smaller particles are affected by turbulence and spread radially, thereby attaining a velocity lower than the critical velocity for deposition. By choosing a more appropriate size particle distribution, a high overall deposition efficiency can be obtained.