Visualization Analysis of Fuel Flow inside the Slit Nozzle in a Direct Injection SI Gasoline Engine

摘要

In a direct injection spark ignition gasoline engine, to improve fuel economy further in actual traffic, the region of stratified charge combustion in the torque-engine speed map must be expanded by improving the fuel spray characteristics. The spray characteristics need to show increased levels of penetration and atomization. Since the fuel flow inside the nozzle has a large effect on the spray characteristics, visualization analysis of the fuel flow inside the nozzle using an acrylic slit nozzle enlarged to 10 times normal size was carried out to clarify this effect. Consequently, it was found that vortices are generated frequently within a nozzle sac even in the case of steady state conditions. The effect on the spray characteristics corresponds to the scale of the vortex. Reducing the scale of the vortex subsequently improves the spray characteristics, thereby expanding the region of stratified charge combustion.