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This paper reports the development of a model of diesel combustion and NO emissions, based on a modified eddy dissipation concept (EDC), and its implementation into the KIVA-3V multidimensional simulation. The EDC model allows for more realistic representation of the thin sub-grid scale reaction zone as well as the small-scale molecular mixing processes. Realistic chemical kinetic mechanisms for n-heptane combustion and NOx formation processes are fully incorporated. A model based on the normalized fuel mass fraction is implemented to transition between ignition and combustion. The modeling approach has been validated by comparison with experimental data for a range of operating conditions. Predicted cylinder pressure and heat release rates agree well with measurements. The predictions for NO concentration show a consistent trend with experiments. Overall, the results demonstrate the improved capability of the model for predictions of the combustion process.

We have developed a methodology for analysis of Premixed Charge Compression Ignition (PCCI) engines that applies to conditions in which there is some stratification in the air-fuel distribution inside the cylinder at the time of combustion. The analysis methodology consists of two stages: first, a fluid mechanics code is used to determine temperature and equivalence ratio distributions as a function of crank angle, assuming motored conditions. The distribution information is then used for grouping the mass in the cylinder into a two-dimensional (temperature-equivalence ratio) array of zones. The zone information is then handed on to a detailed chemical kinetics model that calculates combustion, emissions and engine efficiency information. The methodology applies to situations where chemistry and fluid mechanics are weakly linked.

Fuel-derived deposits on injectors and elsewhere in engines can severely impair engine performance. A laboratory test procedure was developed to produce thin deposit films from oxidized fuel on steel. The deposit films were analyzed using ESCA (XPS) and depth profiling with Ar i-ons. The deposits were carbonaceous in nature with lesser amounts of oxygen, and small amounts of sulfur and nitrogen. The total sulfur concentration in the deposits was approximately five-ten times higher than the concentration of sulfur in the original gasoline. Ion bombardment preferentially removed oxygen from the deposit layer, revealing that sulfur in the deposits was in the form of oxygenated compounds (RSO2 R, RSO2OR, RSO2OR, RSO2OSO2 R) and removal of oxygen converted them to lesser or non-oxygen-containing compounds (RSR, RSOR, RSSR, RSSO2 R). Fuel samples were spiked with two sulfur-containing chemicals, thioanisole and thianaphthene.