Impact of Oxygenated Fuel Components on Engine Performance and Particulate Emissions in Gasoline Blends

The challenges with electrification of the automotive industry have led to rethinking the decisions to ban internal combustion engines. Nonetheless, decarbonization of transportation remains a regulatory priority in many countries, irrespective of the source of energy for automotive powertrains. Oxygenated fuel components can help with the rapid decarbonization of gasoline fuels by lowering the carbon content and introducing renewable components in conventional fuels. Renewable ethanol is one of the primary renewable components typically used in types of gasoline with up to 20% v/v substitution which corresponds to 8% oxygen by mass. However, a range of oxygenates could be used instead of ethanol. The goal of this study was to determine if the engine could discriminate between different oxygenates in gasoline fuels blended at the same octane (RON) and oxygen levels. Oxygenates such as methyl-tert-butyl-ether and ethyl-tert-butyl-ether were considered in this study. Blends were made using a combination of n-heptane, iso-octane, toluene, and oxygenated components. Seven blends with a nominal RON of 98 +/-2 were evaluated in a single-cylinder engine. Four E10 equivalent and three E20 equivalent fuel blends were studied. The engine was operated at a range of test conditions that ranged from throttled, low-load points to boosted, high-load points that required knock retard. The results indicated that all blends had minimal differences in engine performance in terms of knocking behavior, spark timing, burn duration, fuel flow, and injection duration that could be compensated by the engine ECU. Particulate matter emissions (AVL soot meter, PN10, PN23) were also evaluated at the test conditions. While the fuels had lower PM-generating components compared to commercial fuels, we could demonstrate that the PM emissions largely correlated with the particulate matter index (PMI) (or the toluene content) of the fuels.