Effect of High Injection Pressures and Ambient Gas Properties Over the Macroscopic Characteristics of the Diesel Spray on Multi-Hole Nozzles

[EN] In this work, the effect of high injection pressures and ambient gas properties on diesel spray penetration and spreading angle are studied. To this end a multi-hole piezoelectric injector was used, MIE-scattering optical technique to visualize the spray. Injection pressures up to 270 MPa used throughout the experiments. Additionally, the spray behavior going from subsonic to supersonic state was analyzed by controlling the ambient gas speed of sound, promoting in this way jets. For this purpose, measurements were done using three different ambient gases (SF6,2, and N2) at isothermal conditions. The results showed that sprays near transonic or in supersonic state had a higher penetration rate than those in subsonic state. Furthermore, among the sprays transonic or in supersonic state, those with higher Mach number had faster penetration. Differently, within the sprays at subsonic state, no significant variations in spray penetration rate were, regardless of the difference in the Mach number. Shock waves appearances were pointed out a possible explanation for the spray penetration variations observed. Finally, a statistical analysis presented for the spray penetration under isothermal conditions and for each ambient gas.