Effect of operation under lean conditions on NOx emissions and fuel consumption fueling an SI engine with hydrous ethanol–gasoline blends enhanced with synthesis gas

Abstract

For the purpose of creating a clean environment, achieving higher engine efficiency, and complying with increasingly strict emission regulations, many methods have been developed to enhance SI engines performance and decrease their pollutant emissions. In this study, the effects of using hydrous ethanol–gasoline blends and synthesis gas addition on NOx emissions and fuel consumption under lean and ultra-lean conditions (i.e. at air/fuel equivalence ratios (λ) = 1.13, 1.26 and 1.46) were investigated using a Spark-Ignition (SI) engine. The engine was fuelled with a Saudi Arabian gasoline grade (RON91), mixed with 5 % and 10 % of hydrous ethanol containing different water concentrations (5 %, 10 %, 30 %, and 40 %). An on-board plasma fuel reformer was employed for the production of hydrogen-rich syngas via the partial oxidation of gasoline. The results revealed the evident positive effect of operating under lean conditions using hydrous ethanol–gasoline blends on reducing the NOx emissions. In addition, NOx emissions decreased with increasing the air/fuel ratio to reach the minimum at the highest lean condition. However, fuel consumption increased with equivalence air/fuel ratio from low-lean at λ = 1.13 to high lean at λ = 1.46 conditions. Syngas addition to the fuel blend under lean conditions resulted in further reduction of NOx emissions but increased the overall fuel consumption. The results showed that up to 4 % of water enrichment of hydrous-gasoline blend can effectively enhance the engine thermal efficiency and reduce NOx emission.