On the role of the liquid flow characteristics on low-Weber-number atomization processes

At low Weber numbers, the aerodynamic forces due to the interaction between gas and liquid do not influence liquid atomization processes. In these situations, atomization processes depend on issuing liquid flow characteristics only. According to the literature, the atomization efficiency is best when the issuing liquid flow shows a high turbulence level. Some injectors are based on this concept and promote the production of turbulence by imposing deflection of the flow inside the nozzle. However, many studies indicate that the level of turbulence does not solely control the atomization efficiency. By conducting a numerical and experimental study on the behavior of cavity nozzles, it is found that internal flow deflection to produce turbulence also produces a non-axial flow component at the nozzle exit whose effect on the atomization process is of paramount importance. Indeed, the results show that the surface energy produced during the atomization process is linearly dependent on the sum of the turbulent kinetic energy and the non-axial kinetic energy at the nozzle exit. This sum represents the energy available for the atomization process, and the influence of the injection pressure as well as of the nozzle geometry on this energy is investigated.