Design and Thermodynamics Analysis of Marine Dual Fuel Low Speed Engine with Methane Reforming Integrated High Pressure Exhaust Gas Recirculation System

The carbon-neutral target lead to the development of low-carbon\carbon free marine fuels. Natural gas is currently one of the most competitive low-carbon fuels, but the low compression ratio used to control knock combustion limits the improvement of thermal efficiency of natural gas engines. Meanwhile, there are some problems of methane slip or NOx emissions on low pressure injection natural gas engine. Therefore, a system including a fuel reformer and a natural gas engine with high-pressure EGR of 20% was proposed. EGR could reduce NOx emission and control methane slip but reduce thermal efficiency. Fuel reforming could improve engine thermal efficiency and increase flame propagation speed but increase NOx emission. The proposed system was designed to achieve the complementary advantages between EGR and fuel reforming. In addition, EGR could also provide higher temperature energy for fuel reforming. The results show that the thermal efficiency of proposed system is 49.3% at the reforming ratio of 5%, which is 2% higher than the original engine and 4.7% higher than the EGR engine. In addition, the methane slip was reduced by 20% and the NOx emission was 2.93 g/kWh, meeting IMO Tier III. Finally, the thermo-economic analysis of system and EEDI calculation were carried out. The results showed that ships were able to save $151,726 per year installing the system, reducing EEDI of 3.75%