7. Cavitation

Long suspected of being an atomization mechanism at very high Reynolds numbers, the quasi-isothermal liquid-vapour phase change or cavitation inside the injection orifice has relatively recently been confirmed as a key agent in obtaining very small droplets in injection processes at very high pressures (figure 12 ). Soteriou et al, He and Ruiz, Arcoumanis and others have highlighted the appearance of vapor pockets inside injectors and their crucial influence on atomization characteristics. The implosion of cavitation bubbles creates disturbances that accelerate liquid break-up. The cavitation regime appears to be unsteady even under stable generating conditions, leading to periodic oscillations and even hydraulic tilting when the vapour pockets extend to the outside of the orifice...