Dilution Strategies for Load and NOx Management in a Hydrogen Fuelled Direct Injection Engine

A study has been undertaken on a boosted single cylinder research engine with direct injection of hydrogen. In order to reduce NOx emissions and tendency to knock, efforts have been made to reduce the temperatures and rate of heat release during combustion. Lean boosted operation, stoichiometric operation with exhaust gas recirculation, and water injection using a dual fluid direct injector were investigated and NOx emissions, thermal efficiency, and combustion stability were compared. Conclusions are developed for specific power optimisation and NOx management which may be applied for hydrogen fuelling of small general purpose through to heavy duty engines.