Numerical Investigation of Sustainable Diesel Engine Performance and Emissions Using Directly Integrated Steam Methane Reforming Syngas

The transition toward sustainable energy systems necessitates innovative solutions that reduce greenhouse gas emissions while improving fuel efficiency in existing combustion technologies. Hydrogen has emerged as a promising clean energy carrier; however, its widespread deployment is limited by challenges associated with large-scale transportation and storage. This study investigates a practical alternative in which hydrogen-rich syngas produced via steam methane reforming (SMR) is directly integrated into the diesel engine intake, thereby eliminating the need for fuel transport, storage, and separation while supporting a more sustainable fuel pathway. A validated computational fluid dynamics (CFD) model was developed to examine the effects of varying SMR gas mixture ratios (0–20%) on engine combustion, performance, and emissions. The findings reveal that increasing the SMR fraction enhances in-cylinder pressure by up to 15.7%, heat release rate by 100%, and engine power output by 102.5% compared to conventional diesel operation. Additionally, under SMR20 conditions, CO 2 emissions are reduced by approximately 12%, demonstrating the potential contribution of this approach to decarbonization and climate mitigation efforts. However, the rise in in-cylinder temperatures was found to increase NO x formation, indicating the necessity for complementary emission control strategies. Overall, the results suggest that direct SMR syngas integration offers a promising pathway to improve the environmental and performance characteristics of conventional diesel engines while supporting cleaner energy transitions.