High NO2/NOx emissions downstream of the catalytic diesel particulate filter: An influencing factor study.
Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NOx) emissions, including nitric oxide (NO) and nitrogen dioxide (NO2). The use of after-treatment devices increases the risk of high NO2/NOx emissions from diesel engines. In order to investigate the factors influencing NO2/NOx emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NOx ratios downstream of the CDPF range around 20%-83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NOx emissions. The maximum NO2/NOx emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NOx ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NOx emissions decreased with increasing space velocity and engine-out PM/NOx ratio. When the CO conversion ratios range from 80% to 90%, the NO2/NOx emissions remain at a high level.
School of Mechanical and Traffic Engineering, Southwest Forestry University, Kunming 650224, China.
Chao
C
He
School of Mechanical and Traffic Engineering, Southwest Forestry University, Kunming 650224, China; National Lab of Auto Performance and Emission Test, Beijing Institute of Technology, Beijing 10081, China.
Jiaqiang
J
Li
School of Mechanical and Traffic Engineering, Southwest Forestry University, Kunming 650224, China.
Zhilei
Z
Ma
National Lab of Auto Performance and Emission Test, Beijing Institute of Technology, Beijing 10081, China.
Jianwei
J
Tan
School of Mechanical and Traffic Engineering, Southwest Forestry University, Kunming 650224, China. Electronic address: hehesmile@gmail.com.
Longqing
L
Zhao
D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000517:prevention & control*; D002248:Carbon Monoxide / Q000737:chemistry; D004784:Environmental Monitoring; D005374:Filtration; D007700:Kinetics; D009585:Nitrogen Dioxide / Q000032:analysis; D009589:Nitrogen Oxides / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry; D013696:Temperature; D001335:Vehicle Emissions / Q000032:analysis*
D000393:Air Pollutants; D009589:Nitrogen Oxides; D052638:Particulate Matter; D001335:Vehicle Emissions; D002248:Carbon Monoxide; D009585:Nitrogen Dioxide
Diesel engine; Diesel particulate filter; Exhaust temperature; Nitrogen dioxide; Space velocity