Numerical study of the Coanda effect in a rotary spray paint atomiser

A rotating spray paint atomizer consists of a spinning cup from which paint droplets are ejected. Around the periphery of this disk, an axial air flow blows these liquid particles, which are projected against the surface to be painted. Under some particular circumstances which occur in industry, this axial air flow may be stopped and, owing to the Coanda effect, the radial flow of paint may be attracted backwards in the direction of the atomizer itself. This "reverse flow effect" is detrimental to industrial performance, and it is the purpose of this work to consider the possibility of predicting and even preventing this phenomenon. Using computational software, a simplified model of an atomizer is first considered and the illustration of the reverse flow effect is shown. In the second part, a full numerical modeling of a real geometry is treated and a solution is suggested to improve the performances of this type of equipment. Recommendations are given for an optimal design which prevents the reverse flow effect in a rotating atomizer. For a given air flow rate, it is shown that the highest output momentum of the jet flow should be obtained