A new combustion concept for DISI gasoline engine was developed to achieve superior performances of high power and low environmental load. It realizes a high specific power and a good lean combustion performance simultaneously by utilizing a DI spray jet effectively to accelerate the in-cylinder tumble flow. Injection direction and configuration of the DI spray was optimized for intensification of the in-cylinder flow and high mixture homogeneity, a thin fan-shaped spray generated by a slit nozzle was adopted. As a result, combustion was accelerated by increase of in-cylinder turbulence intensity, and homogeneity of air-fuel mixture was improved.
In addition, in-cylinder fuel wall wetting, which causes emission of particulate matter (PM) and oil dilution, was drastically reduced by improvement of the fan-shaped spray. Atomization of the modified DI spray was improved by reduction of pressure loss inside the nozzle, utilization of fuel flow turbulence such as cavitation arising in the slit nozzle and raise of the fuel pressure. Furthermore penetration of the spray was reduced by its higher dispersion and the fine atomization.
The DI spray improvement also contributes to the high environmental performance which is realized by the fast catalyst heating. Ignition retard stratified combustion was stabilized and emission of unburned HC was reduced in the operation. As a result, the environmental performance is secured to be compatible with the super ultra low emission vehicle (SULEV) standard in North America.