Abstract: The PM emissions from the heavy-duty vehicles which were compliant to the China emission standard stageⅡand stage Ⅲ were tested on the road with the city bus driving cycle. The particle size distributions of the PM emissions in the range of 0.007~10 μm were measured by an electrical low pressure impactor. The test results showed that the average number concentration of the PM emissions with the size under 0.3 μm from the stage Ⅲ vehicles was higher by 23.8% than that from the stage Ⅱ vehicles. For the particles with the size above 0.3 μm, the average mass concentration of the PM emissions from the stage Ⅲ vehicles was lower by 65.4% than that from the stage Ⅱ vehicles, and average number concentration was lower by 27.4%.

Key words: power machinery and engineering, heavy-duty diesel vehicle, PM emission, road test, size distribution