Combustion Characteristics and Cyclic Irregularity of an EFI Gasoline Engine Fueled with n-Butanol/gasoline Blends

Abstract

An experimental study was conducted to evaluate the combustion characteristics of blends of n-butanol to gasoline with volume ratios of 0%, 20%, 50%, and 85% in addition to neat n-butanol on an electronic fuel injection (EFI) gasoline engine. Without any modifications to the original engine, the tests were carried out using the above five test fuels, with the engine working at maximum torque speed (3000 rpm) and four loads (25%, 50%, 75% and 100% of the maximum torque). The combustion characteristics including cylinder pressure, instantaneous and cumulative heat release were analysed. The test results show that all the peak values of cylinder pressure (CP), pressure rise rate (PRR), instantaneous heat release rate (IHRR) as well as total heat release of n-butanol/gasoline blends are lower than those of gasoline, and the higher the percentage of n-butanol is, the larger the reduction becomes. The crank angles of the peak values of CP, PRR and IHRR are larger than those of gasoline, whereas the crank angle of the total heat release is smaller than that of gasoline. The cyclic irregularity of n-butanol/gasoline bends is higher than that of gasoline. Therefore, the combustion of n-butanol/gasoline blends becomes mild, which further gives the benefit of reducing NOX emissions. However, the spark timing of the prototype should be advanced more in order to avoid power decreasing of n-butanol /gasoline blends.