ABSTRACT
Hydrogen direct fuel injection in internal combustion engines is a potential strategy for improving in-cylinder combustion processes and performance while reducing risk of engine knocking and emissions outputs with respect to increasing hydrogen energy share (HES). This work presents numerical study of combustion performance and emissions of a diesel-hydrogen dual-fuel engine utilising a late compression/early power stroke direct gaseous hydrogen injection ignited by a diesel pilot at up to 99% HES. The combustion process of hydrogen in this type of engine was mapped out and compared to that of the same engine using methane direct injection. The results found four distinct phases of combustion which differ from that of pure diesel operation. Interaction of the injected gas jet with the chamber walls is found to have a considerable impact on performance and emission characteristics and is a factor which needs to be explored in greater detail in future studies. Excellent performance and carbon-based emission reductions are identified at up to 99% HES at high load, but low load performance greatly deteriorated when 95% HES was exceeded due to a much-reduced diesel pilot struggling to ignite the main hydrogen injection.
