Use of Modified Temperature-Composition PDF Formulation in Modeling of Flame Dynamics in Diesel Engine Combustion

In the present work, the modified temperature-composition (MT-C) PDF formulation was embedded in the KIVA to study the characteristics of flame development and emissions in a diesel engine. The model uses a time scale defined by an energy balance on the flame surface and a new normalization scheme exploiting the maximum attainable mass fractions of progress variables. Development of the latter in the T-ξ T-xi parameter space regulates the flame progress in the physical space and, thus, the approach presents some potential to capture the local flame extinction. The interactions of the swirl and spray penetration and their influence in the mixing process, combustion and emissions are also evaluated. Analyses of the temporal evolution of mixture fraction and temperature show that the swirl motion forms a homogeneous mixture on the lee sides of the spray jets where the ignition actually starts. Since the local time scales are considered in the model, the chemistry-controlled premixed combustion developing there is well predicted.