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This paper presents the summary of the development of a two-phase spray model of a hollow-cone fuel injector commonly applied to spray-guided, gasoline direct injection, (SGDI) engines. The model was simulated using the Ricardo VECTIS CFD code and takes into account the physical and chemical effects of oxygenated fuel blends (flexfuels). The characteristics of the fuel sprays at typical gasoline part-load conditions, identified in a parallel study, were of particular interest. An injection duration of 0.3 ms was chosen which represented a stratified charge, unthrottled, part-load operating condition in a spray guided GDI engine with a piezoelectric fuel injector and a fuel injection pressure of 200 bar gauge. In the first instance, the spray model was validated against data recorded in a constant volume spray chamber. Secondly, the robustness of the model was tested against data measured in an optically-accessed engine.

Compared to conventional homogeneous direct injection or port-fuel injected engines, the second generation, spray guided, direct injection engine (SGDI) has the potential for significantly improved fuel economy during part load stratified charge operation. Multiple fuel injection strategies can be utilised to increase the unthrottled operating range, leading to further improvements in fuel economy. However, careful optimisation of these strategies is essential to ensure that benefits are maintained whilst further minimising emissions within combustion stability limits and consumer driveability demands. The effects of multiple injection strategies upon fuel consumption, emissions and combustion stability were investigated in a single cylinder Ricardo Hydra engine with a spray guided combustion system. An outwardly opening piezoelectric actuated injector was employed. The fuel injection strategy utilised up to five injections per engine cycle.