Experimental Investigation of Uncertainty in Spray: A Case Study on Pressure-Swirl Atomizer

In this research, the uncertainty in the droplet size distribution has been studied as the most important characteristic of the pressureswirl atomizer spray. The size distribution of the spray droplets of a sample atomizer was measured using the shadowgraphy technique at different spray pressures and at different longitudinal, radial and peripheral positions of the spray cone. The minimum number of samples was obtained by optimizing the entropy of the non-parametric droplet size distribution. The log-normal, Rosin- Rammler and gamma parametric distribution functions were fitted to the experimental data and it was observed that the gamma distribution function is the most compatible with the experimental data. The effect of pressure on the gamma distribution function was investigated and it was observed that in the phase of changing the atomization regime, the two parameters of shape and scale change dramatically, but after that these parameters remain almost constant with the increase of pressure. Spray uniformity as another component of uncertainty was evaluated quantitatively with the two concepts of dispersion and heterogeneity. It was observed that in a certain axial distance, with the increase of spray pressure, the dispersion in different parts of the spray cone changes, but the total dispersion is almost constant.