Atomization and Sprays, Vol.12, No.1-3, 299-327, 2002
The influence of viscoelastic fluid properties on spray formation from flat-fan and pressure-swirl atomizers
The formation of sprays of viscoelastic polymer solutions from flat-fan and pressure-swirl atomizers was investigated experimentally. The fluids were characterized rheologically by means of a novel elongational device which allows the relaxation time and the steady terminal elongational viscosity of the fluids to be measured. These quantitites turned out to be significant for the breakup of ligaments and drop formation from prefilming atomizers. The elongational device furthermore quantifies differences between flexible and rigid polymers. With this rheological information and by means of dimensional analysis, the global nondimensional Sauter mean diameter of sprays from the flat-fan and the pressure-swirl atomizers is represented universally as a function of characteristic numbers. With the help of the same characteristic numbers, the volume fractions of small droplets in the sprays are quantified. These results are the basis of a design method for, e.g., agricultural sprays, where small fractions of small drops in the drop size spectra are required.