Dimet Laval nozzle expansion section analysis and optimization

Abstract

The cold spray technology mainly accelerates the powder in the Laval nozzle by gas, ensuring that the powder has a greater velocity at the exit of the Laval nozzle, and achieving high-efficiency deposition on the substrate, thereby obtaining a better performance of the deposition coating. The article uses numerical simulation to study the influence of the length of the expansion section of the Dimet Laval nozzle on the acceleration effect of Al powder. The results show that the length of the expansion section of the nozzle is an essential factor affecting the velocity of the Al powder at the nozzle outlet. Through analysis, it can be known that the pressure inlet range of the Dimet Laval nozzle is 1.0 MPa, and the length of the expansion section is about 210 mm, which can ensure that the Al powder has a better acceleration effect in the nozzle and has a better velocity at the nozzle outlet. It is recommended that the joints between the small sections of the nozzle expansion section should be kept as smooth as possible so that the accelerating effect of the accelerating gas on the Al powder is more uniform and stable.