Application of a reduced kinetic model for soot formation and burnout in three-dimensional diesel combustion computations

Using a modified version of the Kiva-2 code, three-dimensional computations of combustion and soot formation were performed, burning tetradecane and n-heptane in a direct injection, naturally aspirated diesel engine. A coupled soot formation and combustion model is proposed. Assuming acetylene as the crucial pyrolitic species, the model takes into acount the fuel-to-acetylene pyrolysis, acetylene oxidation, soot nucleation, and surface growth and soot oxidation. The numerical predictions are compared with the expermental data of heat-release patterns and with the in-cylinder measurements of acetylene concentration and soot volume fraction. C2H2 data were collected using a fast-acting valve, while soot loading was measured with the two-color technique. The improved code is able to predict correctly the combustion and heat-release patterns of the two fuels without any retuning of the model constants. The computational results demonstrate that the reduced kinetic soot model is capable of predicting, with satisfactory accuracy, the local amount of soot and pyrolytic products in the combustion chamber, keeping the main features of the diesel combustion.