Modeling the Effect of Parametric Variations on Soot Particle Size Distribution in a Diesel Engine

Abstract

Stringent emission legislations, increasing environmental and health issues have driven extensive research in combustion engines to control pollutants. Modeling of emissions offers a cost saving alternative to experimental analysis for combustion chamber design and optimization. Soot modeling in diesel engines has evolved over four decades from simple empirical relations to detailed kinetics involving polycyclic aromatic hydrocarbons (PAH) and complex particle dynamics. Although numerical models have been established for predicting soot mass for parametric variations, there is a lack of modeling studies for predicting soot particle size distribution for parametric variations. This becomes important considering the inclusion of limits on soot particle count in recent emission norms. The current work aims at modeling the soot particle size distribution inside a heavy duty diesel engine and validating the results for a parametric variation of injection pressure and intake temperature. Closed cycle combustion simulations have been performed using CONVERGE, a 3D computational fluid dynamics (CFD) code. A sectional soot model coupled with gas phase kinetics has been used with source terms for inception, condensation, surface reactions and coagulation. Numerical predictions for soot mass and particle size distribution at the exhaust show good agreement with experimental data after increasing the transition regime collision frequency by a factor of 100.