Real-World PM, PN and NOx Emission Differences among DOC+CDPF Retrofit Diesel-, Diesel- and Natural Gas-Fueled Buses

To reflect the influence of after-treatment system retrofit and natural gas-fueled vehicle replace on exhaust emissions emitted by urban buses, a portable emission measurement system (PEMS) was employed herein to conduct real driving emission measurements. This study investigated the differences in particle number (PN), particle mass (PM), and nitrogen oxides (NOx) emissions from a China IV diesel bus retrofitted by catalyzed diesel particulate filter (CDPF), a China IV diesel bus, and a China V natural gas bus. The results show that both tested diesel buses possess markedly advantages in NOx emission control when compared to the lean-burn natural gas bus equipped without any NOx after-treatment system. As to PN and PM, only the DOC+CDPF retrofitting diesel bus exhibits enormous benefits on emission control related to the natural gas bus, especially the normal diesel bus. Meanwhile, the differences in PM and PN emissions between retrofitted and normal diesel buses generally increase with the increase in vehicle specific power (VSP). Furthermore, the differences in PM emissions, especially those in the higher VSP ranges, are more significant than those in PN. In addition, the maximum peak PN particle size (32 nm) of the retrofitted diesel bus was significantly lower than that of the normal diesel bus (100 nm). These phenomena indicate that the CDPF retrofitting can effectively reduce diesel bus exhaust particle emissions, especially those with large particle sizes.

• Zhiwen Yang
• Jingyuan Li
• Zhenkai Xie
• Jian Ling
• Jiguang Wang
• Mengliang Li

• CDPF
• diesel
• natural gas
• real-world emissions.

[1] Wang M, Huang C, Ren H, Hu Q. Effect of CDPF on the particle size distribution of heavy-duty diesel vehicles. Acta Scientiae Circumstantiae (China). 2021;41:3070-5.
[2] Lou d, Li z, Tan p, Hu z. Effects of DOC + CDPF on particulate matter emission characteristics from heavy-duty diesel vehicles. Environmental Engineering (China). 2018;36:90 ~ 4.
[3] Lv L, Ge Y, Ji Z, Tan J, Wang X, Hao L, et al. Regulated emission characteristics of in-use LNG and diesel semi-trailer towing vehicles under real driving conditions using PEMS. J Environ Sci (China). 2020;88:155-64.
[4] Gómez A, Fernández-Yáñez P, Soriano JA, Sánchez-Rodríguez L, Mata C, García-Contreras R, et al. Comparison of real driving emissions from Euro VI buses with diesel and compressed natural gas fuels. Fuel. 2021;289:119836.
[5] He L, Hu J, Yang L, Li Z, Zheng X, Xie S, et al. Real-world gaseous emissions of high-mileage taxi fleets in China. The Science of the total environment. 2019;659:267-74.
[6] Dimaratos A, Toumasatos Z, Triantafyllopoulos G, Kontses A, Samaras Z. Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car. Transp Res D: Transp Environ. 2020;82:102307.
[7] Huang X, Wang Y, Xing Z, Du K. Emission factors of air pollutants from CNG-gasoline bi-fuel vehicles: Part II. CO, HC and NOx. Sci Total Environ. 2016;565:698-705.
[8] Jiao P, Li Z, Shen B, Zhang W, Kong X, Jiang R. Research of DPF regeneration with NOx-PM coupled chemical reaction. Appl Therm Eng. 2017;110:737-45.
[9] Kontses A, Triantafyllopoulos G, Ntziachristos L, Samaras Z. Particle number (PN) emissions from gasoline, diesel, LPG, CNG and hybrid-electric light-duty vehicles under real-world driving conditions. Atmos Environ. 2020;222:117126.
[10] Huang C, Lou D, Hu Z, Feng Q, Chen Y, Chen C, et al. A PEMS study of the emissions of gaseous pollutants and ultrafine particles from gasoline- and diesel-fueled vehicles. Atmos Environ. 2013;77:703-10.