| description abstract | 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. | |
