National Lab of Auto Performance and Emission Test, School of Mechanical and Vehicular Engineering, Beijing Institute of Technology, Beijing 100081, China.
Sci Total Environ. 2011 Mar 15;409(8):1476-80. doi: 10.1016/j.scitotenv.2010.12.042. Epub 2011 Feb 4.
On-road measurement is an effective method to investigate real-world emissions generated from vehicles and estimate the difference between engine certification cycles and real-world operating conditions. This study presents the results of on-road measurements collected from urban buses which propelled by diesel engine in Beijing city. Two widely used Euro III emission level buses and two Euro IV emission level buses were chosen to perform on-road emission measurements using portable emission measurement system (PEMS) for gaseous pollutant and Electric Low Pressure Impactor (ELPI) for particulate matter (PM) number emissions. The results indicate that considerable discrepancies of engine operating conditions between real-world driving cycles and engine certification cycles have been observed. Under real-world operating conditions, carbon monoxide (CO) and hydrocarbon (HC) emissions can easily meet their respective regulations limits, while brake specification nitrogen oxide (bsNO(x)) emissions present a significant deviation from its corresponding limit. Compared with standard limits, the real-world bsNO(x) emission of the two Euro III emission level buses approximately increased by 60% and 120% respectively, and bsNO(x) of two Euro IV buses nearly twice standard limits because Selective Catalytic Reduction (SCR) system not active under low exhaust temperature. Particle mass were estimated via particle size distribution with the assumption that particle density and diameter is liner. The results demonstrate that nanometer size particulate matter make significant contribution to total particle number but play a minor role to total particle mass. It is suggested that specific certified cycle should be developed to regulate bus engines emissions on the test bench or use PEMS to control the bus emissions under real-world operating conditions.
道路行驶测量是一种有效的方法，可以调查车辆产生的实际排放情况，并估计发动机认证周期与实际运行条件之间的差异。本研究介绍了在北京城市中使用便携式排放测量系统（PEMS）测量气体污染物和电动低压冲击器（ELPI）测量颗粒物（PM）数量排放，对由柴油发动机驱动的城市公交车进行的道路行驶排放测量结果。选择了两辆广泛使用的欧 III 排放标准的公共汽车和两辆欧 IV 排放标准的公共汽车，使用便携式排放测量系统（PEMS）测量气体污染物和电动低压冲击器（ELPI）测量颗粒物（PM）数量排放，进行道路行驶排放测量。结果表明，在实际运行条件下，发动机的运行条件与发动机认证周期之间存在相当大的差异。在实际运行条件下，一氧化碳（CO）和碳氢化合物（HC）排放很容易满足各自的法规限制，而制动规范氮氧化物（bsNO(x)）排放则与其相应的限制存在显著偏差。与标准限制相比，两辆欧 III 排放标准的公共汽车的实际 bsNO(x)排放量分别增加了约 60%和 120%，两辆欧 IV 公共汽车的 bsNO(x)排放量接近标准限制的两倍，因为在低排气温度下选择性催化还原（SCR）系统不活跃。通过假设颗粒密度和直径呈线性关系，从颗粒尺寸分布来估计颗粒质量。结果表明，纳米级颗粒物对总颗粒物数量有显著贡献，但对总颗粒物质量的作用较小。建议制定特定的认证周期，以在测试台上调节公共汽车发动机的排放，或在实际运行条件下使用 PEMS 控制公共汽车的排放。
