Experimental Combustion Analysis in a Gasoline Baseline Hydrogen-Fueled Internal Combustion Engine at Ultra-Lean Conditions

Hydrogen-fueled internal combustion engines (H₂ICEs) have emerged as a promising technology for reducing greenhouse gas emissions in the transportation sector. However, due to the unique properties of hydrogen, especially under ultra-lean conditions, the combustion characteristics of hydrogen flames differ significantly from those of conventional fuels. This research focuses on evaluating the combustion process and cycle-to-cycle variations (CCVs) in a single-cylinder port-fuel injection H₂ICE, as well as their impact on performance parameters. To assess in-cylinder combustion, three indicators of flame development are utilized and compared to the fundamental properties of hydrogen. The study investigates the effects of various factors including fuel-air equivalence ratio (ranging from 0.2 to 0.55), engine load (IMEP between 1 and 4 bar), and engine speed (900 to 1500 rpm). The analysis aims to understand the behavior of the flame initiation phase, which refers to the time from ignition to 10% of the mass fraction burned, as it is found to be the most sensitive period of combustion duration in H2ICEs with respect to the fuel-air equivalence ratio. The research reveals that within a wide range of equivalence ratios, there is minimal variability in combustion. The study also discusses the characteristics of the flame at ignition timing, considering the influence of factors such as turbulence and thermodiffusive instabilities. To aid in the analysis, 0D/1D engine simulations are employed, providing valuable insights into the underlying mechanisms shaping the flame behavior.