Macroscopic Modeling of an Agglomerated and Sintered Particle in Air Plasma Spraying

Existing modeling techniques can determine the heat transfer within idealized spherical particles with homogenous morphology. Agglomerated particles are not homogenous and consist of multiple smaller particles which are packed together. The reduced contact area between the individual smaller particles results in a drastic reduction in the effective thermal conductivity of the agglomerate. Conversely, it can enhance the heat transfer due to the increased particle surface area and gas penetration into the agglomerate. Moreover, the momentum transfer from the plasma to the agglomerate differs from that of a homogenous spherical particle, which can significantly affect the heating dynamics of the agglomerate. All of the mentioned phenomena have been taken into account in a novel particle modeling approach by resolving the 3-D geometry of the agglomerates and the flow around it. The presented model is coupled with the particle-laden free jet model. Differences in kinematics and heating dynamics of the agglomerates have been analyzed with regard to their packing densities. The presented model was compared to a simplified approach where the agglomerates were represented by spherical particles with their mass corresponding to the agglomerates with different packing distances. The comparison proved the necessity of 3-D resolution of the particle morphology.