DIH2jet (DI Hydrogen Combustion Process)

Hydrogen combustion engines are a viable solution for defossilizing mobility, mainly discussed in the heavy-duty sector. Conventional applications of hydrogen combustion in Internal Combustion Engines employ port or direct fuel injection with lean premixed, spark-ignited combustion strategies, which significantly lower engine-out NOX emissions and try to avoid abnormal combustion events at the price of low power density. This study aims to tackle the challenge of the demanding boost pressure requirements in lean conditions using a non-premixed jet-guided strategy at stoichiometric conditions, omitting the related risk for abnormal combustion. Results from a single-cylinder engine comparing stoichiometric and lean homogeneous operation to three jet-guided or stratified modes applying different delays between start of injection and ignition are presented, supported by findings from an optically accessible Rapid Compression Expansion Machine. The experiments reveal an advantage in engine-out NOX emissions for globally stoichiometric operation in jet-guided mode compared to homogeneous operation resulting in similar levels of indicated efficiency depending on the ignition timing. Early ignition of the jet shows potential for stable mixture-controlled combustion in combination with dedicated hydrogen injectors with higher mass flow rates.