Integrated HFO Modeling and RSM-Based Synergistic Optimization of Combustion-Emission Performance for Marine Low-Speed Diesel Engines

Low-speed, two-stroke marine diesel engines are facing more severe challenges regarding nitrogen oxide (NOx) emission control and fuel economy with the increasingly stringent global emission regulations and the implementation of carbon tax policy. Based on the fixed-speed cruise operating condition data recorded in the engine log of a real ship, a marine heavy fuel oil (HFO) model was innovatively established in this study, as well as a simulation model of the engine operation on a real ship. By comprehensively evaluating the interaction between scavenge air and fuel injection parameters, a multiparameter synergistic optimization strategy was proposed to systematically reveal the mechanism of key operating parameters on the engine's combustion performance and emission characteristics. The results demonstrate that the lowest fuel consumption rate (SFOC_min) optimization scheme achieved a power increase of 2.34%, a fuel consumption rate reduction of 2.36%, and a CO₂ emission factor reduction of 2.28%. Meanwhile, the NO _<i>X</i>min optimization scheme significantly curtailed the NO <i>_X</i> emission factor of the original engine by 12.09%. This study offers a feasible implementation strategy for promoting the development of a green and energy-efficient shipping industry.