Performance and emissions evaluation of a multi-cylinder research engine fueled with ethanol, methanol, gasoline Euro-6, E85, and iso-stoichiometric ternary GEM mixtures operated at lean conditions

Abstract

Limited biomass resources for ethanol production challenge its adoption as a fossil fuel substitute. To alleviate this constraint, methanol, with abundant production resources, is frequently proposed as a solution. Ternary blends of gasoline, ethanol, and methanol (GEM) are proposed as an alternative to binary gasoline and ethanol blends to ease the lack of feedstock for ethanol production. Furthermore, by incorporating a higher proportion of ethanol and methanol as low carbon fuels in ternary blends, the transport sector can effectively reduce its carbon footprint and contribute to mitigating the climate change issue. As a consequence, the impacts of these ternary blends, as well as Euro-6 gasoline, ethanol, methanol, E85, and M54 (the binary methanol-gasoline equivalent of E85), on the performance and emissions of a four-cylinder four-stroke 2.5-liter gasoline direct injection engine under ultra-lean conditions were evaluated. According to the study, Euro-6 gasoline fuel exhibited knocking and was unable to reach the minimum spark advance for best torque (MBT) operating point within the lambda range of 1–1.4 due to its lower RON and knock resistance. Conversely, methanol and the blends containing methanol demonstrated effectiveness in approaching the MBT point throughout the entire lambda sweep with less spark advance compared to ethanol, E85, and Euro-6 gasoline. Methanol and M54 maintained combustion stability up to lambda 1.9, while the GEM ternary blends and Euro-6 gasoline achieved stability up to lambda 1.85. Ethanol and E85, however, suffered degraded stability at lambda 1.8. Methanol had the lowest NOx and HC emissions during the lambda sweep, with ethanol second. At lambda 1.8, all tested fuels showed a substantial reduction in NOx emissions of 95 %–97 % compared to stoichiometric conditions. Under ultra-lean conditions, Methanol reduced HC emissions the most (51 %), while ethanol and E85 increased HC emissions at lambda 1.8 in comparison to Euro-6 gasoline. Methanol had the highest overall thermal efficiency because of its higher oxygen content and faster flame speed. E85 occupies the second position in the hierarchy of higher thermal efficiency, followed by the ternary blend G34E33M33 (containing equal volume percentages of gasoline, ethanol, and methanol at 33.3 % v/v each), which exhibits a similar trend to that of ethanol. Until lambda 1.7, all tested fuels were more efficient than Euro-6 gasoline; however, as lambda increased to 1.8, E85, ethanol, and G34E33M33 displayed lower efficiency levels.

Keywords

Emissions ternary and Binary blends Ultra-lean GDI engine Dual ignition coil Methanol