Blends of ethanol, n-butanol and isobutanol with 5% oxygen in ordinary engines: effects on exhaust emissions over the Artemis cycle

In the EU, alcohol fuels are used mostly in the form of ethanol, sold either as E85, or mixed in less than 10% concentrations into gasoline for the general fleet. This work examines the effects of extending the ethanol share to 15%. Additionally, considering the high hygroscopicity and corrosivity of ethanol, two isomers of butanol, n-butanol and isobutanol, were blended with gasoline at 25% by volume, all blends corresponding to approximately 5% oxygen by weight. These four fuels were examined in two typical spark ingition automobile engines, a Ford Focus car with a Euro 6 EcoBoost direct injection (DISI) engine, and a Skoda Fabia car with a Euro 5 multipoint injection (MPI) engine. Both cars were tested on chassis dynamometer using the Artemis driving cycle. There were no measurable effects on the emissions of hydrocarbon and carbon monoxide. The alcohol fuels increased the emissions of nitrogen oxides on the MPI engine. On the DISI engine over the Artemis cycle, the number of emitted solid particles and the emissions of elemental carbon and polyaromatic hydrocarbons were reduced relative to gasoline, by about one half for both butanol isomers, while ethanol did not yield observable effects. Particle emissions of the MPI engine were generally smaller. The results suggest that both n-butanol and isobutanol are viable fuels, which could be considered as an alternative to ethanol.