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Numerical Investigation on GDI Spray Under High Injection Pressure Up to 100MPa
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
In recent years the increase of injection pressure gasoline fuel is a way to improve thermal efficiency and lower engine-out emissions in GDI homogenous combustion concept. The challenge of controlling particulate formation as well in mass and number concentrations imposed by emissions regulations can be pursued improving the mixture preparation process and avoiding mixture inhomogeneities with ultra-high injection pressure values up to 100MPa. The increase of the fuel injection pressure meets the demand for increased injector static flow, while simultaneously improving the spray atomization and mixing characteristics that provide improvement of the combustion performance of GDI homogeneous systems. Few studies quantify the effects of high injection pressure on transient gasoline spray evolution. The aim of this work was to simulate with OpenFOAM the spray morphology of a commercial gasoline injected in a constant volume vessel by a prototypal 5-hole, L/d: 2.6, solenoid activated GDI injector. Different operating conditions were considered under very high injection pressure up to 100MPa. The transient spray evolution in a constant volume vessel was analysed from an experimental and numerical point of view in different ambient conditions. The resulting development of the jet plumes was assessed, along with the physical effects of injection pressure. A RANS Eulerian-Lagrangian approach was adopted to couple the gas phase with the liquid jet and a complete validation of atomization and secondary breakup models was performed. Furthermore, different values of ambient temperature and pressure were investigated to validate the robustness of the proposed numerical set-up in different ambient conditions. Experimentally, optical techniques characterized by a hybrid Mie-scattering/schlieren approach were adopted. The spatial distribution and the time-resolved evolution of the free sprays were derived under different operating conditions along with their characteristics.