Effects of cross-flow and ambient pressure on fuel spray injected by hole-type nozzle for DISI Engine

The fuel economy and power output have been advanced significantly by the application of the direct injection spark ignition technique in gasoline engines. Air flow in the combustion chamber affects the spray significantly whatever in the stratified charge combustion mode or the homogeneous charge combustion mode. Crossflow, which is a special and typical air flow in the combustion chamber of the DISI gasoline engine, was obtained by an atmospheric wind tunnel and a high pressure wind tunnel in this study. These two wind tunnels were designed to provide the uniform cross-flows with various pressures. Such surroundings aim to simulate the cross-flows during the compression stroke in the stratified charge combustion mode and intake stroke in the homogeneous charge combustion mode in DISI gasoline engine. The injections were recorded by a high speed video camera with high frame rate. The droplet sizes of the spray were measure using the Fraunhofer diffraction method. The effects of the cross-flow and the ambient pressure on the spray break-up were discussed in this study. The cross-flow influences spray profiles distinctly, such as the bended structure, variations of the vertical and horizontal penetrations. Additionally, the atomization of the spray can be enhanced by the cross-flow according to the droplet size measurements. The cross-flow owns the ability of blowing the broken droplets with low number density in periphery into downstream, therefore the droplets with high number density in central core require the opportunity to be ex-posed in the ambient gas. The exposed droplets with high vertical momentum could break due to the increasing of the aerodynamic force.