Effect of bioethanol as an alternative fuel on the emissions reduction characteristics and combustion stability in a spark ignition engine

Abstract

An experimental investigation was performed on the combustion performance, reduction characteristics of exhaust emissions, and engine performance of a spark ignition engine fuelled with bioethanol, ethanol—gasoline blend, and gasoline fuel. The test fuels were an ethanol—gasoline blend (E85), which consists of 85 vol% bioethanol and 15vol% gasoline, pure bioethanol (E100), and gasoline fuel without any additives (G100). In this work, the combustion and exhaust emission characteristics, including the combustion pressure, brake mean effective pressure (BMEP), and maximum brake torque (MBT) timing of the ethanol—gasoline blend and pure ethanol, were compared with those obtained with gasoline fuel. For the comparison of combustion and emissions characteristics for bioethanol, ethanol blends, and gasoline, the experiments were carried out under various engine operating conditions and the results were compared with those obtained using conventional gasoline fuel. The results of this study showed that an ethanol-blended fuel or pure ethanol led to a drastic decrease in exhaust emissions under all operating conditions. The exhaust emissions such as hydrocarbons, carbon monoxide, and nitrogen oxides were reduced when using the bioethanol-blended and undiluted ethanol fuel because of the highly oxygenated component of ethanol fuel. Because the ignition timing was advanced above MBT timing when the ethanol fuels were used, improved combustion stability and a better combustion phase were measured because of the high octane rating of the ethanol. Combustion performance such as the brake torque and BMEP remained nearly the same or increased over those found using conventional gasoline fuel under various spark ignition timings and throttle valve openings.