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The urgent need to combat global warming has spurred legislative efforts within the transport sector to transition away from fossil fuels. Hydrogen is increasingly being utilised as a green energy vector, which can aid the decarbonisation of transport, including internal combustion engines. Computational fluid dynamics (CFD) is widely used as a tool to study and optimise combustion systems especially in combination with new fuels like hydrogen. Since the behaviour of the injection event significantly impacts combustion and emissions formation especially in direct injection applications, the accurate modelling of H2 injection is imperative for effective design of hydrogen combustion systems. This work aims to evaluate unsteady Reynolds-Averaged Navier Stokes (URANS) modelling of the advective transport process and related numerical methods.

Ammonia as a fuel suffers from a high ignition energy requirement making it hard to ignite in stoichiometric mixtures, especially with normal spark plugs. On the other hand, pre-chambers are proven to provide high ignition energy by producing multiple ignition spots in the main chamber. A pre-chamber is usually categorized as “active” if it has a dedicated fueling system, and as “passive” if it depends solely on the air- fuel mixture being introduced from the main chamber and is therefore simpler than the active type. In this study, an SI light-duty engine was tested with a conventional spark plug with fuel mixtures of gasoline and gaseous ammonia (0%, 25%, 50%, 75%, 90%, and 100% NH3). The test was then repeated with a passive pre-chamber under the same operating conditions for comparison. Moreover, the engine exhaust was fitted with a fast response analyzer to measure NOX. The use of the conventional spark plug showed stable combustion throughout the fuel mixture sweep.