The computational fluid dynamic approach is adopted in this work, using L16-Taguchi matrix, to study the effect of different secondary atomization gas outlet configurations on the gas velocity, jet divergence, and pressure distribution at cap outlet. The spraying process variables that are integrated in this study are primary and secondary atomization gas pressure, PG and SG respectively. In addition, the geometrical variables of the SG air-cap like the position, the number and the angle of the outlet holes for SG are a part of the L16-Taguchi matrix. The effect of the process variables and geometrical design variations are analyzed on the obtained gas flow characteristics. Increasing the number of the SG outlet holes leads to a higher gas velocity at the cap outlet. The amount and the angle of the SG outlet holes have a direct effect on the plume divergence. The SG outlet angle determines the distance between the flow intersection point (PG-flow and SG-flow) and the air-cap outlet. Increasing the SG outlet angle leads to a reduction of the gas velocity. The use of Design of Experiment (DoE) in the optimization of the air-cap design by implementing CFD-simulation was proved to be a very useful and efficient tool to design high performance air-caps of twin-wire arc-spraying.

In this work, CFD simulations are used to evaluate air cap configurations for twin wire arc spraying (TWAS). Investigators employed a design of experiments (DoE) approach to identify air cap parameters with the greatest impact on gas velocity, jet convergence, and pressure distribution. The ones selected for study are the convergence angle, the length and diameter of the throat, and the distance between the air cap outlet and the point where the wires intersect. In all configurations studied, the spray wires deflected the flow of the primary gas and narrowed the cross-section of the plume along one axis. The effects of each air cap parameter are discussed in the paper along with possible design improvements.