Evolution of Gasoline Direct Injection System for Reduction of Real Mode Emission 2019-01-0265
Recent gasoline ICE is being developed based on direct injection system. Corresponding to the concerns of the global environment and energy security, engine performance and emission to be improved under all driving conditions, such as cold environmental temperature, various fuel quality and driving situation (short trip in downtown, long high speed drive among cities). In addition, the combination with electrification is also considered as total Powertrain. Especially, unburned fuel (HC) and particle matters (PM/PN) at low in cylinder temperature conditions are a key area of gasoline ICE emission improvement. Technologies are required for the emission reduction at low in cylinder temperature condition.
This research focuses on the mechanisms of both wall wetting of injected spray droplet and evaporation behavior of those wall-wetted fuels, especially at a lower temperature of the cylinder wall condition to provide solutions for emission at low temperature condition. As a result, it has been confirmed that the thin film makes wall wet evaporate rapidly, and the thin film can be realized spray homogeneity improvement, in addition to finer fuel atomization and shorter penetration, which are considered as important spray performance for wall wet reduction. As a new requirement for thin wall wet, the benefit of spray homogeneity improvement was confirmed by the nozzle specification (hold diameter, unique hole shape) and the fuel pressure up to 60MPa which can promote the air entrainment to the spray inside. Spray study with homogeneity improvement shows contribution to make thin wall wet. In addition, the actual engine test is conducted to confirm improvement of the emission in cold real mode operation by combining the multiple injections which is also effective for the temporal dispersion.