Computational study of excess air ratio impacts on performances of a spark-ignition H2/methanol dual-injection engine

Abstract

The impacts of excess air ratio (λ) on combustion, CO and NO regulated emissions, and formaldehyde (HCHO) and unburned methanol (CH3OH) unregulated emissions behaviors in a spark-ignition H2/methanol dual injection engine were studied numerically. The results show that the peak in-cylinder pressure (PIP), peak heat release rate (PHRR) and peak in-cylinder temperature (PIT) all decrease with the increase of λ, and their corresponding crank angles are also late; the ignition delay (ID) and combustion duration (CD) decrease with the increase of λ; the CO, HCHO and CH3OH emissions increase with the increase of λ, while the NO emission decreases with the increase of λ. At a constant λ, the PIP, PHRR and PIT for with 5 % H2 (RH2 = 5 %) are higher than those for without H2 (RH2 = 0 %), and their corresponding crank angles for RH2 = 5 % are earlier than those for RH2 = 0 %; the ID and CD for RH2 = 5 % are lower than those for RH2 = 0 %. The CO, HCHO and CH3OH emissions for RH2 = 5 % are also much lower than those for RH2 = 0 %, while the NO emission for RH2 = 5 % is also higher than that for RH2 = 0 %. The impact order of adding H2 to reduce emissions of H2/methanol dual-injection engine is: CO ≥ HCHO > unburned CH3OH.