Experimental investigation of lean burn H2ICE: A comparison of PFI and LPDI

Hydrogen internal combustion engine (H2ICE) is one of the promising technologies to fulfill the goal of carbon neutrality and sustainable transportation. This work experimentally compares port fuel injection (PFI) and low pressure direct Injection (LPDI) concepts on the same single cylinder heavy duty engine platform. Both PFI and LPDI strategies are investigated under varying excess air coefficient and spark timings. The study explores the effects of lean hydrogen combustion at stationary operating condition, and spark timing optimized to balance combustion efficiency and emission characteristics. The results demonstrate the high potential of H 2 ICEs for ultra-low engine-out NOx emissions. A maximum gross indicated efficiency (GIE) of 41.9% is achieved with the PFI configuration. Both PFI and LPDI meet the proposed Euro 7 NOx limits at λ = 2.5, while NOx approaches the analyzer detection limit at λ > 4. PFI generally shows lower NOx emissions than LPDI due to improved mixture homogeneity. GIE exhibits a parabolic dependence on λ and spark timing, independent of injection strategy. Differences in GIE between PFI and LPDI are within measurement uncertainty, indicating no clear efficiency advantage. Both configurations show comparable sensitivity of combustion phasing to ignition timing.