Numerical study on the effect of substrate size on the supersonic jet flow and temperature distribution within the substrate in cold spraying

This study investigates the effect of substrate size on the supersonic jet flow regime, particle acceleration and temperature distribution within the substrate in cold spraying. A computational fluid dynamics approach is employed in the present work to achieve this objective. The simulated results show that substrate diameter has some effect on the gas flow regime and the consequent particle motion. When the substrate diameter is smaller than the nozzle exit diameter, the thickness 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, the bow shock thickness increases gradually up to the point at which the substrate diameter is beyond the nozzle exit diameter. A further increase beyond this has almost no effect on the flow regime and the bow shock thickness. Besides, the current numerical work also reveals that the temperature distribution within the substrate can be significantly influenced by substrate thickness. With an increase in substrate thickness, the substrate temperature presents a downward trend, which means that higher inlet temperature may be required for thick substrate to achieve the same preheating effect.