Fuel-Spray Characteristics of High Pressure Gasoline Injection in Flowing Fields*

The direct injection into the cylinders has been regarded as a way of the reduction in fuel consumption and pollutant emissions. The spray produced from the direct injector is of paramount importance in GDI(Gasoline Direct Injection) engines in that the primary atomization process must meet the requirement of quick and complete evaporation and combustion especially to prohibit the excessive HC emissions. The spray geometry must be stable and compact showing controlled mixture formation by taking a benefit from in-cylinder charge flows. The interaction between air flow and fuel spray was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside the cylinder of the GDI engine. The spray developments in flowing fields with the mean velocity up to 17m/s were at first identified by spray visualization. The direct Mie scattered images and Shadowgraph images presented the macroscopic view of the liquid sprays and the spatial distribution of vapor fields. The microscopic characteristics of the spray were investigated by the velocity and particle size measurements using a Phase Doppler Anemometer(PDA). The processes of atomization and evaporation with a GDI injector were observed and consequently utilized to construct the data-base for the spray and fuel-air mixing mechanism as a function of the flow characteristics. This could give the way of optimization between the flow formulation and injection schemes in GDI engines