Effect of Ethanol-Diesel Fuel Blend on Diesel Engine Emissions Produced by Different Bus Fleets

The major regulated pollutants emitted by a diesel urban bus are nitrogen oxides (NOx) and particulate matter (PM). These emissions depend on the engine and its strategies (injection, exhaust-gas recirculation, after-treatment devices, etc.), altitude, weather conditions, route, and driver. This work studies the effect of two fuels, one of them oxygenated, on both NOx emissions and particle-size distributions in comparison with a diesel fuel used as reference. The study was carried out with buses operating in two different cities, one of them located at around 650 m above sea level and the other near sea level. The test fuels were a binary blend of ethanol and diesel fuel (denoted as ED) and a diesel fuel without biodiesel (denoted as D). Emissions were measured using a Horiba OBS-1300 gas analyzer and a TSI engine exhaust particle sizer spectrometer. Results showed a reduction in both NOx emissions and total particle number concentrations with altitude, independently of fuel tested, and an increase in geometrical mean diameter. Effective density was used as a particle-diameter-conversion factor to estimate particle mass concentration. However, the negative effect of ED on NOx emissions and the positive effect on PM were both attenuated by altitude. (C) 2015 American Society of Civil Engineers.