Simulation of Soot Formation Under Diesel Engine Conditions Using a Detailed Kinetic Soot Model

Numerical simulations of diesel engine combustion and emission formation have been performed using a detailed soot model. Operating conditions typical for modern truck-size engines have been investigated, and calculated results show encouraging agreement with experimental data for soot in engine exhaust gas. Predictions of details in the soot formation process compare well with detailed experimental data from the literature.

The modelling of the soot/flow-field interaction is based on a flamelet approach. Source terms of the soot volume fraction are taken from a flamelet library using a presumed probability density function and integrating over mixture fraction space. In order to save computer storage and CPU time, the flamelet library of sources was constructed using a multi-parameter fitting procedure resulting in simple algebraic equations and a proper set of parameters.

The CFD calculations included the simulation of fuel liquid atomization, droplet break up, detailed droplet-gas interaction and evaporation. Auto-ignition and combustion were modelled using a model of eddy-break up type incorporating a reduced chemical model. A simplified engine geometry was assumed in combination with realistic pressure and temperature variations.