国六重型车实际道路上污染物和温室气体排放特性研究

Controlling on-road greenhouse gas (GHG) emissions from heavy-duty vehicles is imperative. In order to study the on-road emission characteristics of GHG (CO₂, N₂O, CH₄) and regulated emissions (NO_x, CO, NH₃) from China-Ⅵ heavy -duty vehicles, five typical China-Ⅵ heavy -duty diesel and heavy-duty liquid natural gas (LNG) vehicles were selected to conduct on-road emission tests according to the on-road emission test protocol of China-Ⅵ emission regulation. The results show that the CO ₂ emissions of China-Ⅵ heavy-duty vehicles decreased with the increased engine load. The CO₂-specific emissions of diesel and LNG vehicles under highway conditions were reduced by 23.55% and 25.80%, respectively, compared with the urban condition. The CO₂-specific emissions of LNG vehicles were significantly lower than those of diesel vehicles. The CO₂ emissions from LNG vehicles have decreased by 15.68%, 21.58% and 12.17% under urban, suburb, and motorway driving conditions, respectively, indicating that LNG vehicles have significant CO₂ emission reduction advantages compared to diesel vehicles. The CH₄ emissions of LNG vehicles were significantly higher than those of diesel vehicles, with CH₄-specific emissions ranging from 750.75 mg/(kW·h) to 1915.08 mg/(kW·h). On the contrary, the N₂O emissions of diesel vehicles were higher than those of LNG vehicles, which is related to the adoption of the selected catalytic reduction (SCR) system to control NO_x emissions. Considering the significant GHG effects of CH₄ and N₂O, attention should be paid to the N₂O and CH₄ emissions of China-Ⅵ heavy -duty vehicles. Different technical routes taken by diesel vehicles and LNG vehicles can effectively control NO_x emissions. The CO emissions of diesel vehicles were much lower than the NO_x limit of China-Ⅵ emission regulations, while the CO emission control of LNG vehicles nearly failed. In addition, diesel vehicles can effectively control the on-road NH₃ emissions, but the NH₃specific emissions of LNG vehicles were 431.92-1286.45 mg/(kW·h). Taking effective measures to ensure the closed-loop accuracy of the air-fuel ratio is the prerequisite for reducing CO and NH₃ emissions from LNG vehicles. The research results show that although LNG vehicles have CO₂ emission reduction advantages compared with diesel vehicles, the greenhouse effect intensity of the two is similar. Considering that the on-road NO_x and NH₃ emissions of LNG vehicles are significantly higher than those of diesel vehicles, and NO_x and NH₃ are essential precursors of ozone and secondary aerosols in the atmosphere, it is not a reasonable to replace China-Ⅵ heavy -duty diesel vehicles with China-Ⅵ heavy -duty LNG vehicles, and it is not conducive to the control of ozone and particulate matter in the atmospheric environment.