Breakup characteristics of ultra-high-pressure GDI spray of a single-hole injector under various thermodynamic conditions

In this study, breakup characteristics of a single-hole GDI injector were investigated at various fuel temperatures and injection pressures. High-speed Mie-scattering imaging technique was employed. Injection pressure varied from 100 to 1000 bar, fuel temperature ranged from 21 to 120 degrees C, and ambient pressure was adjusted from 0.5 to 4.5 bar to simulate various actual engine conditions. Three semi-empirical models of spray penetration were evaluated. Results showed that the revised Hiroyasu and Arai model demonstrated the best match with an average R2 value of 0.986 at fuel temperature of 21 degrees C. For evaporating conditions, fuel temperature to ambient temperature ratio T/ T0 with an exponential index of -0.47 was incorporated into the model, and it provided excellent penetration prediction under all conditions with an average R2 value of 0.981. Results demonstrated that it is inapplicable to rise temperature to compensate penetration increment induced by increased injection pressure. Furthermore, the normalized variation in spray penetration resulted by increased injection pressure or fuel temperature was nearly independent of other injection parameters. Breakup time and length derived from the revised model closely matched the experimental data, although the accuracy decreased slightly at higher ambient pressures.