GASOLINE SPRAY MORPHOLOGY IN I.C. ENGINES AT VERY HIGH INJECTION PRESSURES FOR DIFFERENT AMBIEN T CONDITIONS

In internal combustion (i.c.) engines, the optimization of the fuel injection process is essential to prepare an air-fuel mixture capable to promote an efficient combustion and reduce both fuel consumption and pollutant emissions. The Gasoline Direct Injection (GDI) has demonstrated being an effective system to pursue these targets. This injection apparatus improves the spray characteristics in terms of a better atomization of the fuel, finer droplet size and better distribution in the combustion chamber to enhance the combustion efficiency. Nowadays, it is known that very high-pressure injections are adopted in GDI systems to improve the spray atomization and, subsequently, the evaporation processes in the engine combustion chamber. In this study, the investigation of the influence of the pressure on gasoline spatial spread and thermo-dynamic status was carried out for different ambient densities (from 0.2 to 11.50 kg/m3) and gas temperatures (from room to 200°C) by a hybrid optical setup, shadowgraph and Mie scattering, to acquire in a cycle-resolved mode both the vapor and the liquid phases of the spray. The study was performed in a constant volume chamber (CVC) using a ten-hole GDI injector, 0.10 mm in diameter, with the injection pressure ranging from 40.0 to 100.0 MPa. The influences of the ambient and injection conditions on the characteristic parameters of the jets, such as tip penetration, cone-angle, and fuel spread, were extracted by a customized image-processing procedure developed in C#.