Computational analysis of the effect of nozzle cross-section shape on gas flow and particle acceleration in cold spraying

In cold spraying, the spraying of certain complicated surfaces may require nozzles with special cross-sections. In this study, numerical investigation is conducted to study the effect of nozzle cross-section shape on gas flow and particle acceleration in cold spraying. The comprehensive comparison between rectangular nozzles and elliptical nozzles indicates that rectangular nozzles result in slightly lower mean particle impact velocity than elliptical nozzles. However, for rectangular nozzles, more particles may achieve relatively high velocity due to the larger sectional area of their potential core. Furthermore, it can also be found from the numerical results that the mean particle impact velocity increases gradually with the decrease in Width/Length ratio (W/L) of the cross-section because of the diminishing bow shock size. However, when reducing the W/L to 0.2, the mean particle impact velocity begins to decrease steeply, which may be attributed to the rather small area of the potential core for the case of W/L = 0.2. Moreover, the systematic study on the powder release position shows that releasing particles from the nozzle inlet can ensure that particles achieve a high impact velocity and temperature.