Development and application of a comprehensive soot model for 3D CFD reacting flow studies in a diesel engine

A three-dimensional reacting flow modeling approach is presented for diesel engine studies that can be used for predictions of trends in soot emissions for a wide range of operating conditions. The modeling framework employs skeletal chemistry for n-heptane for ignition and combustion, and links acetylene chemistry to the soot nucleation process. The soot model is based on integration and modification of existing submodels for soot nucleation, agglomeration, oxidation, and surface growth. With the optimized modeling parameters, the simulations agree well with results of high-pressure shock tube studies of rich n-heptane mixtures, reproducing the trends for soot mass over a range of temperature and pressure conditions (T=1550-2050K, P=20, 40, and 80 MPa). Engine simulation results for soot mass are in excellent agreement with diesel engine smoke number measurements over a range of injection timings (−11° ATDC-2.4° ATDC) and two exhaust gas recirculation levels (16 and 26-27%). The model results demonstrate that correct description of the soot formation, as well as the soot transport processes, is critical for achieving reliable predictive capabilities in engine simulations.