Numerical Simulation Investigation Into the Thermodynamic Impacts of Direct Injection Gasoline on Marine Natural Gas Engine

Abstract To address challenges of high ignition energy and slow combustion propensity in marine natural gas engines, this study proposes a dual-fuel combustion strategy using port fuel injection natural gas and centrally gasoline direct-injected (GDI). Through integrated computational fluid dynamics (CFD) simulations and experimental validation, the thermodynamic impacts of gasoline-induced active stratification near the spark plug are systematically evaluated. Results demonstrate that the GDI–natural gas (NG) configuration significantly enhances combustion performance compared to pure NG operation. Optimized ignition timing and fuel stratification elevate the peak heat release rate by 11.9%, increase indicated thermal efficiency (ITE) by 1%, raise peak cylinder pressure by 1.1 MPa, and reduce combustion duration by 6.2%. Kinetic analysis confirms that gasoline reactivity accelerates flame propagation, suppresses cycle variability, and extends the stable ignition window. This work provides a practical framework for implementing stratified combustion in marine engines to achieve higher efficiency.