Effect of Cylinder Initial Pressure on Marine Diesel Engine Combustion Characteristics

Diesel engines, known for their high efficiency and powerful output, remain the primary power source in marine applications.However, addressing marine environmental challenges requires both the advancement of future technologies and the continuous optimization of existing ship systems.This study investigated the impact of cylinder compression initial pressure on the combustion characteristics of two-stroke marine diesel engines using heavy fuel oil.The initial pressure was divided into five levels, ranging from 0.1 MPa to 0.2 MPa, and the analysis focused on combustion chamber pressure, fuel distribution, and the formation and decomposition of combustion intermediates such as OH radicals, carbon monoxide (CO), and nitrogen oxides (NOx).At 0.1 MPa, insufficient air led to slow combustion, increased harmful emissions, and 6.7% of the fuel remained unburned, negatively impacting efficiency.Conversely, at initial pressures of 0.15 MPa or higher, combustion was more rapid, nearly completing by ATDC 90 degrees, with significantly reduced residual fuel and CO emissions.However, nitrogen monoxide (NO) emissions, lowest at 0.1 MPa, increased as initial pressure rose due to higher combustion temperatures and reaction rates.These findings highlight the need for careful optimization of initial pressure to enhance performance while mitigating emissions and supporting cleaner and more efficient marine propulsion systems.