High-pressure direct injection as enabling technology for high-power density hydrogen SI engines: Experimental analysis of the influence of jet-guided combustion regimes on efficiency and abnormal combustion

The European Union (EU) aims to decarbonize the road transport sector by 2050. Hydrogen (H2), as a carbon-free option among alternative fuels, offers favourable properties for use in Internal Combustion Engines (ICEs), accompanied by the challenging control of engine-out emissions and abnormal combustion, especially towards stoichiometric conditions. The presented research project applies a non-premixed jet-guided combustion process to mitigate abnormal combustion while maintaining beneficial power density and NOX emissions compared to the stoichiometric homogeneous premixed engine operation. The experimental investigation involved a 500 cm3 Spark Ignition (SI) Single Cylinder Engine (SCE) designed for gasoline applications. This study analyses a variation of the ignition timing relative to the injection window for the jet-guided stoichiometric operation and compares it to the homogeneous stoichiometric and lean modes for an engine speed of 1500 RPM and different engine loads identified by the Indicated Mean Effective Pressure (IMEP) of 5, 7.5, 10, and 12.5 bar. The results show the potential of a non-premixed combustion process towards higher engine load to prevent pre-ignition or knocking in stoichiometric conditions while maintaining the power density. The experiments demonstrate the transition from a predominantly mixture-controlled combustion process driven by the fuel injection rate to a predominantly premixed process igniting around the End Of Injection (EOI) and the influence on combustion duration, efficiency, and engine-out emission.