Numerical Modelling of a Heavy-duty Diesel-hydrogen Dual-fuel Engine with Late High Pressure Hydrogen Direct Injection and Diesel Pilot

Direct gaseous fuel injection in internal combustion engines is a potential strategy for improving in-cylinder combustion processes and performance while reducing emissions and increasing hydrogen energy share (HES). Through use of numerical modelling, the current study explores combustion in a compression ignition 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 is mapped out and compared to that of the same engine using methane direct injection. Four distinct phases of combustion are found 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. Considerable performance increase 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.