Ducted fuel injection for compression-ignition engines

The goal of the Ducted Combustion Chamber project is to reduce or eliminate soot emissions from diesel engines. This was done by enabling fuel to burn at a leaner mixture with a combustion strategy called Leaner Lifted-Flame Combustion (LLFC). A recent paper by Polonowski et al. [SAE Int. J. Fuels Lubr. 5(1):51-77, 2012], stated that “LLFC is defined as mixing-controlled combustion that does not produce soot because it occurs at equivalence ratios less than or equal to approximately 2.” The equivalence ratio is defined as the actual ratio of fuel over air divided by the stoichiometric ratio of fuel over air [McGraw-Hill, New York, 1988, p. 149]. Typically, diesel combustion occurs under conditions [Dec, SAE Technical Paper 970873, 1997], where the fuel inside of a diesel engine is not mixed evenly with the air. Fuel-rich regions of diffusion flames produce soot which is a pollutant. This project investigated whether injecting fuel into a duct in the combustion chamber will allow the fuel to mix more evenly with the surrounding air and produce LLFC. The process of injecting fuel into the duct should entrain (draw some of the surrounding) air into the duct. When the air and fuel are in the duct together they will mix together resulting in a more even fuel-air mixture and which will create the conditions for LLFC. Ducts of various lengths and diameters were SAND2014-17364R