DETERMINING THE OPERATING MODES OF THE ENGINE AND THE BOUNDARY CONDITIONS FOR THE HYDROGEN-GASOLINE MIXTURE

Abstract

The integration of hydrogen (H₂) as a secondary fuel in spark-ignition (SI) gasoline engines serves as a prominent path toward mitigating carbon emissions and improving thermal efficiency. However, the distinct physical-chemical properties of hydrogen-such as its rapid flame velocity, low ignition energy, and wide flammability limits-require exact control over operational strategies and computational configurations. This study establishes a systematic framework for determining engine operating modes and defining precise boundary conditions for numerical simulations of hydrogen-gasoline mixtures. Using a coupled 1D-3D thermodynamic and fluid dynamic approach, we evaluate performance criteria across varying engine speeds (1000–3000 RPM) and hydrogen energy substitution fractions. The boundary conditions required for multi-dimensional Computational Fluid Dynamics (CFD) modeling-including structural thermal boundaries, gas dynamics at valve closures, and species mass fractions-are formulated. Results indicate that adding hydrogen shortens the combustion duration and elevates peak in-cylinder pressures by up to 17.38%, shifting the optimal operating window toward ultra-lean mixtures (λ = 1.8–2.5) to prevent abnormal combustion phenomena such as pre-ignition and knocking.