Experimental study on fuel spray characteristics under atmospheric and pressurized cross-flow conditions

The air flow and ambient pressure in the cylinder affect the spray significantly when the fuel is injected into the cylinder in direct injection gasoline engine. To investigate the effects of air flow at ambient pressure on the fuel spray, a critical air flow called cross-flow was tested. The cross-flow is the air flow whose direction is perpendicular to the fuel injection direction. A special wind tunnel was designed to provide the controllable cross-flows with various pressures and velocities, and the spray was injected into the cross-flow field by a mini sac injector using dry solvent as the test fuel. The high speed photography and particle image velocimetry technology were employed to observe the fuel spray and measure the velocity distribution of the spray. When the ambient pressure is increased, the bended spray profile is compressed; namely, the penetrations decrease. The cross-flow provides horizontal momentum for the droplets of the spray. When the ambient pressure is increased the velocity distribution of fuel spray becomes more uniform; furthermore, the magnitude of the vertical velocities can exceed the cross-flow velocity. This study is an experiment investigation which is aimed at understanding the fundamental phenomena and accumulating the theoretical supports for the real engine conditions.