Visualisation of cavitation in diesel engine injectors

Abstract The phenomenon of cavitation and its occurrence in diesel engine injector nozzles is discussed and examples are given of cavitation patterns formed in the sac volume and holes of multi-hole nozzles under realistic operating conditions. Experiments performed in real-size production nozzles incorporating glass windows have revealed the existence of string cavitation initiated within the sac volume and film cavitation formed at the inlet to the holes which interact along the hole length creating a highly turbulent two-phase flow at its exit. Although there is a consensus that the two-phase hole flow structure, which varies with cavitation and Reynolds number as well as the needle lift, has a noticeable effect on the subsequent global spray characteristics, details of the link between hole cavitation and fuel atomisation remain largely unclear.