LARGE EDDY SIMULATION OF DIESEL SPRAY COMBUSTION WITH A MULTI-COMPONENT DROP VAPORIZATION MODEL

摘要

Large-eddy simulation (LES) of diesel spray and combustion was performed to study its improvement in the simulation of engine in-cylinder dynamics compared to the Reynolds-averaged simulation. For the LES, the dynamic structure approach was used to model the sub-grid turbulence and its interaction with the moving droplets in the spray. A multicomponent vaporization model (MCV) based on the continuous thermodynamics approach and a gamma distribution to describe the distribution of the numerous fuel components, was used to simulate the vaporization of diesel fuel droplets. The MCV model was imbedded into the LES framework in the KIVA-4 program. Using this LES model, a non-evaporative spray in a constant-volume chamber was first simulated. More realistic spray structures and improved agreements in the spray penetration with the experimental data were obtained by the LES compared to a Reynolds-averaged simulation of the same spray. A further simulation of an evaporative diesel spray and the subsequent combustion process using both LES and MCV models was also performed. Improved agreements with the experimental data in the spray structures and soot distributions were also observed using both models.