CFD Modeling and Validation of the ECN Spray G Experiment Under a Wide Range of Operating Conditions
To be published on September 9, 2019 by SAE International in United States
The increasing diffusion of gasoline direct injection (GDI) engines requires a more detailed and reliable description of the phenomena occurring during the fuel injection process. Currently, one drawback of GDI engines is represented by the impingement on the piston wall, due to typically adopted hollow-cone fuel sprays, which can lead to high emissions of unburned hydrocarbons and soot formation. Within this context, the extensive validation of multi-dimensional models by means of experimental data represents a fundamental task to accurately predict the physical phenomena characterizing the injected spray. The aim of this work was to simulate with OpenFOAM different operating conditions of the 8-hole, ECN Spray G injector placed into a constant volume vessel. The resulting developments of the jet plumes were assessed, along with the physical effects of injection pressure and wall temperature on the wall impingement phenomenon. Furthermore, different values of ambient temperature and pressure were investigated to validate the robustness of the proposed numerical set-up. A RANS, Eulerian-Lagrangian approach was adopted to couple the gas phase with the liquid jet and a complete validation of atomization, secondary breakup and wall impingement models was performed. 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 post-impingement characteristics. A customized algorithm, capable to catch the contours of both liquid and vapour/atomized phases, was used to extract the most relevant parameters of the diffused and vaporized fuel.