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Technical Paper

CFD Investigation of Wall Wetting in a GDI Engine under Low Temperature Cranking Operations

2009-04-20
2009-01-0704
The paper reports a numerical activity on the investigation of the spray evolution within the combustion chamber of an automotive DISI engine under low-temperature cranking operations. In view of the high injected fuel amount and the strongly reduced fuel vaporization at cold cranking, wall wetting becomes a critical issue. Under such conditions, fuel deposits around the spark plug region can affect the ignition process, and even prevent engine start-up. In fact, due to the low injection pressure at engine start-up, the fuel shows almost negligible atomization and breakup, and the spray structure at the swirl-type injector nozzle is characterized by a single column of liquid fuel, strongly limiting the subsequent vaporization and enhancing the fuel-wall interaction. In order to properly investigate and understand the many involved phenomena, experimental visualization of the full injection process by means of an optically accessible engine would be a very useful tool.
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