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The use of green hydrogen as a fuel for internal combustion engines is a cleaner alternative to conventional fuels for the automotive industry. Hydrogen combustion produces only water vapor and nitrogen oxides, which can be avoided with ultra-lean operation, thus, eliminating carbon emissions, from a tank-to-wheel perspective. In this context, the aim of this study is to investigate the influence of hydrogen injection timing and duration on the homogeneity of the hydrogen-air mixtures. Computational fluid dynamic (CFD) simulations were performed to analyze the distribution of air-fuel ratios along the engine's combustion chamber. The simulation software was CONVERGE 3.0, which offers the advantage of automatic mesh generation, reducing the modeling efforts to adjusting the operating conditions of the studied case. Before comparing the injection parameters, a mesh independence test was conducted along with model validation using experimental data.

The use of green hydrogen as a fuel is a promising solution for reducing greenhouse gas emissions from our current fleet of petrol-fueled vehicles. However, achieving zero emissions remains a challenge due to the higher relative air-to-fuel ratio (lambda) required to avoid NOx formation during periods of increased load demand. On the other hand, the capability of hydrogen combustion to use a lean mixture with lower combustion variability presents a great advantage. In such cases, thermal efficiency can be improved by reducing pumping work through leaning the mixture and dethrottling to maintain the same load. This study investigates the efficiency and combustion parameters of hydrogen spark ignition operation while maintaining a constant load at several intake pressure conditions. Tests were conducted on a Ricardo Proteus spark ignition single-cylinder research engine to evaluate the impact of throttle aperture on pumping work and combustion parameters.