The associated effect of powder carrier gas and powder characteristics on the optimal design of the cold spray nozzle

During cold spray, the temperature of the particle carrier gas is at room temperature, which is lower than the preheated propulsive gas and affects the mixed gas temperature and particle acceleration. This study is investigating the associated effect of the powder carrier gas and powder characteristics on the optimal design of the nozzle using numerical simulations. The results show that the heat exchange of mixed gas stabilizes, and temperatures of mixed gas and particles are higher in the nozzle when a larger inlet diameter and a longer convergent section are used. In addition, particle impact velocity is inversely related to its size and density. Therefore, heavier particles require longer divergent lengths and larger expansion ratios for a longer acceleration distance and increased kinetic energy. The nozzle geometry can be designed depending on the selected particles and the chosen propulsive gas, for a maximum particle impact velocity.