Medium Speed Lean Hydrogen Engine Modelling and Validation

Hydrogen spark-ignition direct-injection engines result in no carbon emissions at use, but NOX remains a challenge. This study demonstrates that with lean combustion (ϕ < 0.38), in-cylinder NOX can be reduced to a quarter of the current maritime regulatory limit. An original contribution of this work is the use of speciesresolved emissions formation across multiple engine load conditions. A novel, chemically detailed combustion modelling framework was developed in CHEMKIN-Pro, incorporating the evolution of the CRECK C1–C3 NOX mechanism, for improved high-pressure accuracy. The framework was extensively validated using crank-angleresolved data across 9–18 bar loads. The model accurately reproduced pressure traces, heat release angles, and NOX. Mechanistic analysis revealed a shift from thermal Zeldovich NOX to intermediate-species (notably N2Odriven), as equivalence ratio and pressure varied. The findings highlighted the use of a high-fidelity chemical kinetic modelling framework, not only to match experimental results, but to gain physically grounded insight into actionable near-zero emission strategies.