Effects of n-Butanol and Isobutanol on Particulate Matter Emissions from a Euro 6 Direct-injection Spark Ignition Engine During Laboratory and on-Road Tests 2015-24-2513

N-butanol and isobutanol are alcohols that can be produced from biomass by fermentation and are possibly more compatible with existing engines than ethanol. This work reports on the effects of these two isomers on exhaust emissions of an unmodified direct injection spark ignition (DISI) engine. A Ford Focus car with a 1.0-liter Euro 6 Ecoboost DISI engine has been tested on a chassis dynamometer using WLTP and Artemis driving cycles, and on the road on a one-hour test loop containing urban, rural and motorway driving. Two isomers of butanol, 1-butanol and 2-methyl-propanol, were each blended with gasoline at 25% volume. Non-oxygenated gasoline and 15% ethanol in gasoline (E15) were used as reference fuels.

The vehicle performed well in terms of cold start, drivability, general performance, and off-cycle particle emissions, staying within several mg of particle mass and about 2×10¹² particles (per PMP procedure) per km during laboratory tests. While E15 had little effect, both butanol blends have decreased PN emissions by about one half; effects on other pollutants were less consistent or not significant. Only roughly one half of particles was larger than 23 nm, and of these, only about half were non-volatile. Particle emissions during real driving were unevenly distributed, were not excessively different from the Artemis cycle, and were highest for gasoline, lower for E15, lower for 25% n-butanol, and lowest for 25% isobutanol, with most of the reductions taking place during high-power operation.

Overall, both n-butanol and isobutanol blends yielded a considerable reduction in particle number emissions relative to both gasoline and E15.