Investigation of a modified circular nozzle for cold spray applications

Abstract

The current work numerically evaluates the efficacy of a coflowing nozzle for cold spray applications with the aim to mitigate nozzle clogging by reducing the length of its divergent section. The high-pressure nitrogen flow through convergentdivergent axis-symmetric nozzles was simulated and the particle acceleration is modelled using a 2-way Lagrangian technique which is validated using experimental results. An annular co-flow nozzle with a circular central nozzle has been modelled for nitrogen gas. Reduction of nozzle divergent length from 189 mm to 99 mm showed an approximate 2.2% drop in particle velocity at high pressure operation while no variation at lower pressure operation was observed. Co-flow was introduced to the reduced nozzle length to compensate for particle velocity loss at higher operating conditions and it was found that co-flow facilitates momentum preservation for primary flow resulting in increased particle speed for a longer axial distance after the nozzle exit. The reduced divergent section nozzle, when combined with co-flow, is comparable to the original length nozzle.