国道和乡村道路条件下三轮汽车的排放特性

为了分析实际道路行驶时三轮汽车的排放特征,该研究利用车载排放测试系统(portable emission measurement system,PEMS)对国道和乡村道2种道路条件下的10辆三轮汽车的常规气态污染物和颗粒物进行了排放测试。结果发现:在2种道路条件下的3种行驶工况(加速工况、匀速工况和减速工况)中,三轮汽车在加速工况下的各项排放因子均高于其他工况;加速工况下,CO的平均排放因子高出匀速工况和减速工况的0.7倍和1.7倍;3种工况条件下,三轮汽车在乡村道上行驶产生的排放均高于国道;对比速度、加速度和排放速率等高线图发现,在不同道路条件下CO、HC和PM排放速率峰值出现在车速较低而加速度较大的区域;对比国道和乡村道上颗粒物数量浓度分布发现,2种道路条件的分布规律相似,以核模态和积聚模态颗粒为主;在乡村道上行驶时,粗粒子模态颗粒数量浓度高于国道上的。该研究成果为三轮汽车的排放控制提供了参考。

Characteristics of emissions for tri-wheel vehicle under national road and rural road conditions

Abstract: With considerable population and high emission rates, tri-wheel vehicles contribute to significant pollution throughout China. The first-phase and second-phase emission standards for rural vehicles were introduced in 2006 and 2007. However, the effectiveness of the standards is unknown due to the lack of relevant research. In this study, a Portable Emission Measurement System (PEMS), which is comprised of a regulated gaseous emission analyzer (SEMTECH-DS) and an electrical low pressure impactor (ELPI), was introduced to characterize the emissions of tri-wheel vehicles in real-world operating conditions. Carbon monoxide (CO), hydrocarbons (HC), NOx and PM emissions of 10 tri-wheel vehicles were measured on planned routes, which contained both national roads and rural roads. The results showed that on national roads, there were fewer acceleration and deceleration circumstances than on rural roads. Most of the emission peaks appeared in the acceleration mode. Among the three driving modes (acceleration mode, deceleration mode and cruising mode), distance-based emission factors of CO, HC, NOx and PM for acceleration mode were the highest on national roads and rural roads. For the acceleration mode on national roads, the average distance-based emission factor of CO was 0.7 times greater than in cruising mode and 1.7 times greater than in deceleration mode. Average emission factors of CO, HC, NOx and PM for each driving mode on rural roads were higher than that on national roads. By drawing contour maps of speed, acceleration and pollutant-emission rates, we found that pollutant emission peaks of CO, HC and PM increased at low speed and under high acceleration conditions on both national roads and rural roads. Emission rates of NOx on rural roads were higher than those on national roads. The number-weighted distributions of particles on national roads and rural roads were similar. Most of the particles were in the nuclei mode and the accumulation mode. Number concentrations of coarse-mode particles on rural roads were higher than on national roads. This paper could provide some reference for future emission controls for tri-wheel vehicles.