Experimental and Numerical Analyses Supporting the Development of a High-Efficiency Internal Combustion Engine: The PHOENICE Project

The regulations introduced by the European Commission are becoming increasingly stringent regarding both pollutant and greenhouse gas (GHG) emissions, shifting the focus in the transportation sector toward the development of innovative, environmentally friendly internal combustion engines (ICEs). A plausible short-term solution is represented by plug-in hybrid technology. In this context, the PHOENICE project aims to demonstrate the potential of a plug-in hybrid vehicle optimized to reduce both fuel consumption and pollutant emissions. The synergistic use of ultra-lean combustion, innovative in-cylinder charge motion, and an electrified turbocharger enables an increase in peak indicated efficiency of up to 47%. Moreover, to ensure compliance with EU7 emission standards, an advanced after-treatment system is implemented, consisting of an electrically heated three-way catalyst (TWC), a gasoline particulate filter (GPF), and a selective catalytic reduction (SCR) system. This thesis aligns with the experimental development of the PHOENICE project, supporting key stages of steady-state calibration at the Polytechnic University of Turin. The research begins with experimental data obtained from the IFP steady-state test campaign and focuses on evaluating the prototype engine’s performance and the optimal calibration to maximize the brake thermal efficiency. The study highlights the impact of extensive lean-burn operation and exhaust gas recirculation (EGR), which result in a significant reduction in CO and NOx emissions and an improvement in engine fuel conversion efficiency. To complement the experimental tests, a transient analysis of engine behaviour is conducted to estimate the effects of ultra-lean combustion and EGR implementation during a real driving cycle, represented by the Worldwide Harmonized Light Vehicle Test Procedure (WLTP). This analysis is carried out using a 0D numerical simulation, based on an interpolation algorithm applied to steady-state engine calibration maps obtained at PoliTo. Additionally, to further investigate the study’s findings, an optimized gearshift strategy is implemented using a simple rule-based algorithm, leading to a 5% improvement in fuel consumption and a 47% reduction in carbon monoxide emissions. To better characterize the key factors of the PHOENICE project that contribute to increased brake thermal efficiency, a GT-Suite engine model is developed. This model provides a more detailed analysis of the influence of lean-burn combustion, EGR usage, and innovative charge motion turbulence on engine performance. The successful correlation and calibration of the predictive combustion model validate its use as a digital twin of the real engine. Consequently, it serves as a valuable tool in conjunction with experimental research activities to further explore potential advancements and developments within the project.