Abstract
The present study was devoted to the optimization of the nozzle exit geometry of a TAFA 9000 wire-arc spray gun. Computational Fluid Dynamic was first used in order to examine the effect of different nozzle configurations, considering small changes operated on the original design. Finally, one of the modified geometries tested numerically was retained in view of the CFD results and the corresponding new nozzle was machined. In a second step, experiments were performed in order to observe the effect of the new design on in-flight droplet characteristics. For this part, a comparison was made between the original design and the modified one for two different type wires (a steel wire and a stainless steel cored wire). These experiments were performed using the well known DPV 2000 device for different operating conditions. The results indicate that the modified design provides a significant increase in the droplet velocity (about 20% higher for the new design) with unchanged thermal spray parameters, indicating that the gun exit design may have a strong influence on inflight characteristics of the droplets. Moreover, droplets were collected in water and the size distribution was analyzed.
