CFD Analysis and Optimization of Combustion Chamber Geometry for Diesel Dedicated Hybrid Engines

This thesis presents a detailed three-dimensional Computational Fluid Dy- namics (CFD) analysis of a diesel engine optimized for hybrid powertrain applications. The main objective of the study is to investigate the influence of combustion chamber geometry on in-cylinder air motion, mixture formation, and combustion processes. Combustion efficiency and pollutant formation were evaluated to gain a deeper understanding of the effects of chamber design on engine performance. The case study focuses on a 2.2-liter, four-cylinder, direct-injection diesel engine intended for Light Duty Vehicle (LDV) applications, developed in collaboration with Stellantis. The simulations were carried out using the STAR-CCM+ software equipped with the In-Cylinder add-on. The simulations were orga- nized into two main phases. First, a cold-flow simulation was performed to characterize the air motion generated by the intake system and piston bowl geometry. Subsequently, a combustion simulation was conducted to analyze in-cylinder pressure evolution, heat release rate, and emission formation trends. The study began with a baseline configuration, which was validated against experimental data provided by the company. Once the baseline was validated, an alternative piston bowl geometry was analyzed to assess how modifications in chamber shape affect the combustion process. The comparison between the two configurations was carried out through two- dimensional plots and three-dimensional visualizations, providing a clear repre- sentation of the in-cylinder flow field, fuel–air interaction, and flame develop- ment.