Idle emission characteristics of a light-duty diesel van at various altitudes

As operating conditions producing severe pollution, high altitude conditions need more attention. In this present paper, regulated emissions and particulate matter distributions of a light-duty diesel van at idle at different altitudes were measured and discussed. Seven altitudes varying from 70 m to 3200 m were introduced and investigated. It was found that CO emission increased corresponding to an increase in altitude. In the cases where altitude was lower than 2400 m, the mass flows of hydrocarbon emissions were quite similar. And the hydrocarbon emissions at 3200 m were much higher than that at lower altitudes. NO_x and NO emissions at high altitude were rather close to that near sea level. NO₂ ascended when altitude was rising in the cases where the altitude was lower than 2400 m; but a decrease at 3200 m was observed. Generally, particulate matter positively correlated to the increased altitude despite the slight fluctuation at relatively low altitudes. Number distribution of particulate matter manifested that a majority of particles were with relatively small aerosol diameters. With the rising of altitude, the percentage of small particles became lower in the total particulate matter. In average, larger number of particles was exhausted at high altitude. With regard to mass distribution, larger particles hold larger percentages by weight than smaller particles at all investigated altitudes. The percentage shared by PM_2.5 in the total particulate matter varied from 48.3% to 74.8% in the tests at different altitudes.