Numerical study on the role of substrate size in supersonic jet flow and substrate preheating process in cold spraying

摘要

This study investigates the effect of substrate conditions on supersonic jet flow pattern, particle acceleration and substrate preheating process in cold spraying. Computational fluid dynamic (CFD) approach is employed in the present work to achieve this objective. The simulated results show that substrate diameter has some effects on gas flow regime and thus particle acceleration. When the substrate diameter is smaller than the nozzle exit diameter, the size of the bow shock formed in front of the substrate is rather small, which contributes to increase the particle impact velocity. With increasing the substrate diameter gradually, the flow regime becomes more and more insensitive to the substrate diameter and the pattern becomes uniform. Moreover, the current numerical work also reveals that substrate preheating process can be significantly influenced by substrate thickness. With the increment in substrate thickness, the preheating effect becomes increasingly undesirable and the substrate surface temperature presents a downward trend.