Study of a cold spray nozzle throat on acceleration characteristics via CFD

Abstract

Cold spray technology can obtain coatings in a solid state, suitable for deposition protection, repair, and additive manufacturing. In order to further expand the application areas of cold spraying nozzles, especially the inner surface of the components or areas where a Straight-line conical nozzle cannot be applied, because the study of the throat of the nozzle with the angle will directly reduce the total length of the nozzle (the horizontal direction), hence, the spray with the angle will show its advantage. This study discusses the influence of the throat structure of the conical cold spray nozzle on the acceleration characteristics, including the throat’s size, length, and angle. The results show the following. Firstly, under the premise of keeping the shrinkage ratio and divergence ratio unchanged at normal temperature, the throat diameter is between 2–6 mm in size, and the maximum growth rate exceeds 20 m/s. When the throat exceeds 6mm, the growth rate of the outlet slows down, and the growth rate is only 8 m/s. Secondly, the length of the throat has little effect on the acceleration characteristics, the total range fluctuated from 533 to 550 m/s, and 11 mm length of the throat is the closest to 0mm. Additionally, the 90° throat angle has the least effect on the acceleration characteristics. Finally, the particle trajectory is affected by inlet pressure, injection pressure, particle size, and other factors.