Numerical Modelling of Soot in Diesel Engines

Abstract

Numerical modelling of soot in diesel engines has evolved over four decades from simple empirical correlations to complex aerosol dynamics and detailed kinetics. These modelling approaches assist in cost-effective diesel engine combustion chamber design to meet the requisite emission legislations. This chapter presents a brief overview on modelling soot in diesel engines. The chapter starts with a description of the physical and chemical processes involved in soot formation, namely gas phase kinetics, nucleation, surface reactions, and coagulation. A brief literature review of the existing modelling techniques for soot formation in diesel engines till date has been presented. The models have been categorized as empirical, phenomenological, and statistical depending on the details of physics and chemistry represented by the models. The uncertainties and the model constants involved in most of these models and the possible effect on resulting soot have been discussed briefly. Considering the inclusion of control on soot particle number in the recent emission legislations, special emphasis has been given to soot models accounting for particle size and number predictions. Some models, both empirical and detailed, have been applied to closed cycle 3D CFD combustion simulations by the authors. The results are compared against published experimental data for crank angle history of soot at varying operating conditions. As part of the detailed soot models, soot particle dynamics has been modeled and coupled with gas phase kinetics. Simulated results have been compared against experimental data for soot particle size distribution at the exhaust of a diesel engine.