Investigating the effects of C3 and C4 alcohol blending on ignition quality of gasoline fuels

Abstract

The study of the ignition quality of alcohol blends with petroleum fuels is a subject of practical interest. It is well known that the ignition delay time (IDT), as well as octane number (ON), increases when gasoline fuels are blended with ethanol. This study focuses on the impact on inverse ignition delay time (IDT-1) when alcohols, such as n-propanol and n-butanol, are blended with gasoline fuels. A non-linear decrease in the IDT-1 of the blends was observed. Predicting the extent of non-linearity in blends is complicated because it involves unknown inter-molecular interactions between base fuel components and the blended components. The purpose of this study is to establish the dependence of base fuel composition (in terms of functional groups) on observed non-linearity. Gasoline fuel contains hundreds of compounds (predominantly hydrocarbons), making it a challenge to understand observed non-linearity when they blend with other components. In this study, the IDT of primary reference fuels (PRF, a binary mixture of iso-octane and n-heptane) and FACE gasolines (fuels for advanced combustion engines) blended with two alcohols (n-propanol and n-butanol) were obtained with an ignition quality tester (IQT) following ASTM D6890 standards. A mole-based Gaussian fit was used to model the blending effects of alcohol with gasoline. The synergistic effect of the different mixtures tested in this study was investigated by analyzing the Gaussian parameters. A multiple linear regression model was formulated to provide information about the impact of the structural composition (functional group) on the synergistic blending effects of gasoline-alcohol mixtures. Constant volume homogenous batch reactor simulations were also conducted, using Chemkin-Pro for alcohols blended with a FACE J surrogate mixture to provide kinetic information about the blending effects observed in the IQT measurements.