Particulate matter (PM) emissions and performance of bio-butanol-methanol-gasoline blends coupled with air dilution in SI engines. (July 2020) - Zhao, Lifeng
Abstract: This study was conducted to investigate PM emissions and performance of SI engines fueled with butanol-methanol-gasoline during air dilution operation. Iso-butanol and methanol were blended with gasoline at volume concentrations of up to 40% (10, 20 vol% iso-butanol and methanol, respectively). The effects of lean mixture on engine performance and PM emissions with blends were investigated to find that the power performance of blended fuels is comparable to that of gasoline. High-proportion blends also showed higher brake thermal efficiency (BTE) than gasoline. The brake specific fuel consumption (BSFC) of blends was also about 10% higher than that of gasoline under stoichiometric conditions; with a lean mixture, a reduction of about 9% in the BSFC of blends was observed. The combustion stability of the blends was reduced relative to that of gasoline. CO emissions from the blends decreased rapidly as the mixture became leaner. The NOx emissions of blended fuels were about 30–50% lower than that of gasoline (lambda >1.15) and decreased rapidly as the mixture grew leaner – a reduction of up to 80% was observed. However, when the excess air ratio was less than 1.15, the NOx emissions were about 30% higher than that of gasoline. The increasing BTE trend of blended fuels was similar to that of gasoline as the load increased. A significant reduction in PM concentration was observed during lean mixture operation, which was further reduced with blended fuels. Reduction of accumulation mode particle was more pronounced for blended fuels relative to nucleation mode particles. The total surface area concentration markedly decreased due to a reduction in particle diameter and total concentration. These results altogether suggest that lean mixture reduces PM emissions of blends and improves BTE; n-butanol/methanol addition also contributed to higher BTE and lower gaseous and PM emissions. Highlights: B20M20 fuel and lean burn improved engine-out emissions and brake thermal efficiency. B20M20 reduced gaseous and particulate emissions with reducing particulate diameter. PM emissions from blended fuels were reduced during lean burn operation. The combustion stability of blended fuels was reduced with blended fuels. Higher brake thermal efficiency was observed in high-proportion blended fuel.