In the modern GDI systems, the optimization of the fuel injection process is essential to prepare an air-fuel mixture capable to promote efficient combustion and reduce fuel consumption and pollutant emissions. A key feature for a better atomization is the fuel injection pressure. The increasing of the injection pressure is considered a good way for particle number (PN) reduction due to improved spray atomization, faster evaporation and better mixture formation.
In this paper, a multi-hole GDI injector was tested to investigate the effects of very high injection pressures (IVHP), in addition to different ambient densities and temperatures, on the fuel spray morphology, in a cycle-resolved images analysis. Commercial gasoline was injected at the pressures ranging between 40.0 to 70.0 MPa, at gas densities varying between 1.12 to 11.5 kg/m3, and gas temperature up to 200°C. Sequences of liquid and vapor images of the injected fuel were captured by Mie-scattering and shadowgraph optical techniques on a high-speed C-Mos camera and the characteristic parameters of the jets, tip penetrations, cone-angles, and fuel spread were extracted for both the phases by a customized image-processing procedure developed in C#. The effects of the single parameters affecting the spray evolutions, remaining constant the residual parameters, are reported and analyzed.