Numerical investigation of diesel injection effects on unburnt hydrogen emissions in a marine hydrogen–diesel dual-fuel engine

Hydrogen/diesel dual-fuel engines represent a viable solution for low-carbon ship propulsion. However, low-temperature intake air hinders flame propagation, leading to increased unburnt hydrogen. This study investigates diesel injection strategies of a marine-scale hydrogen–diesel dual-fuel engine to minimize unburnt hydrogen. The CFD model is developed from a PFI marine medium-speed engine. A parametric study was conducted to investigate the effect of injection timing, tilt angle, and injection duration. The results indicate that optimized injection strategies reduce the unburnt hydrogen from 50% to 1%. Adjusting the injection timing from 9.5°CA BTDC to 49.5°CA BTDC decreases unburnt hydrogen from 50% to 3%. Furthermore, modifying the tilt angle from 75.5° to 55.5° decreases it to 2%, while shortening the injection duration from 35°CA to 34°CA achieves the lowest unburnt hydrogen at 1%. These findings highlight the potential of advanced injection strategies in hydrogen combustion, contributing to the development of efficient hydrogen marine engines.