Numerical Analysis of Fine Particle Behavior in Supersonic Hybrid Aerosol Deposition

In hybrid aerosol deposition (HAD), fine ceramic particles are sprayed using a plasma jet at low vacuum pressure to deposit ceramic coatings. Our previous work proved that using a supersonic nozzle in HAD was effective in decreasing porosity. However suitable nozzle geometry was not designed in that work. In cold spray, Mach number at the nozzle outlet has an optimum value to maximize the particle velocity at the nozzle outlet. Prior to the present study, we examined the optimum Mach number at the nozzle outlet for HAD by one-dimensional numerical simulation under isentropic flow assumption. The simulation results implied that the optimum Mach number for HAD was between 1.1 and 2.7, and depended on particle diameter, inlet stagnation temperature and pressure. However, the one-dimensional simulation ignored the effects of the boundary layer in the nozzle, flow expansion, and flow around the substrate surface on the particle velocity. Furthermore, the distribution of the plasma velocity and particle one in the radial direction were not considered. In this work, therefore, we studied the behavior of fine ceramic particles in HAD using a supersonic nozzle by two-dimensional numerical simulation. The effect of the nozzle geometry on the particle velocity is discussed.