Effect of geometric parameters on the spray cone angle in the pressure swirl injector

Spray cone angle affects the droplet distribution after atomization and is one of the main targets of coaxial gas–liquid injector optimization. Experimental measurements and numerical modeling (volume of fluid method) were used to investigate the effects of geometric parameters on the spray cone angle in pressure swirl injectors. The non-dimensional impact factor, η, is defined to examine the influence of each parameter on the spray cone angle. Except for the atomizer constant, the most important parameters influencing the spray cone angle are the divergent angle at the injector exit, the diameter, and the length of the swirl chamber. Raising the divergent angle at the injector exit reduces spray cone angle, because it increases axial velocity and decreases tangential velocity. Meanwhile, the acceleration of the radial component declines due to the lower pressure differential force. The Malvern diffraction laser system was used to measure the droplet sizes. An empirical formula, which gives the relationship between the Sauter mean diameter and the geometric parameters, D_s/d₀, L₀/d₀, and divergent angle, θ, was deduced based on Lefebvre’s theory.