Analysis and optimization of combustion in a dedicated engine for hybrid powertrains

The automotive industry is undergoing a substantial transformation driven by increasingly stringent regulations aimed at reducing greenhouse gas emissions to achieve sustainable mobility. In this context, Stellantis is continuously committed to reduce the environmental impact of its vehicles, in line with the newly updated legislation, by focusing on the development of highly efficient engines suitable for hybrid integration. The aim of this project is to study and analyze the combustion for an already existing Spark Ignition (SI) engine, developing a version optimized for hybrid powertrain, named Dedicated Hybrid Engine (DHE). The project follows, after a detailed analysis of all possible solutions, a well-defined path which enables significant results in terms of efficiency improvements through the adoption of mature existing technologies. These technologies require tuning for the studied engine, but do not demand major modifications to the engine architecture, thereby ensuring the possibility of a rapid industrialization. In particular, the engine will feature an increased compression ratio, a Low Pressure EGR, solutions to reduce the internal friction and a revised valve lift strategy. The development takes always in consideration that, thanks to the hybrid configuration, it is possible to focus on the optimization of efficiency mainly for a smaller portion of the engine working area. The study was carried out using 3D and 0D/1D Computational Fluid Dynamics (CFD) simulations to predict and optimize engine efficiency in the selected reduced area. Particular attention is given to the in-chamber turbulence generation through iterative analysis of the geometry of the components (intake ducts and piston design) with the aim of achieving a fast and robust combustion process. Key parameters such as velocity at the spark plug, together with both global and local Turbulent Kinetic Energy (TKE), are compared to identify most effective solutions. The outcome of this project is the identification of the most effective configuration capable of achieving the efficiency target set by Stellantis for the studied engine.