Characteristics of NOx emission of light-duty diesel vehicle with LNT and SCR system by season and RDE phase

Yongjoo Lee; Seungil Lee; Seunghyun Lee; Hoimyung Choi; Kyoungdoug Min

doi:10.1016/j.scitotenv.2021.146750

Characteristics of NOx emission of light-duty diesel vehicle with LNT and SCR system by season and RDE phase

Sci Total Environ. 2021 Aug 15:782:146750. doi: 10.1016/j.scitotenv.2021.146750. Epub 2021 Mar 26.

Authors

Yongjoo Lee¹, Seungil Lee¹, Seunghyun Lee², Hoimyung Choi³, Kyoungdoug Min⁴

Affiliations

¹ Department of Mechanical Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea.
² Hyundai Motor Company, Hwasung-si, Gyeonggi-Do, 455-963, Republic of Korea.
³ Department of Mechanical Engineering, Gachon University, Gyeonggi 13120, Republic of Korea. Electronic address: hoimyung@gachon.ac.kr.
⁴ Department of Mechanical Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea. Electronic address: kdmin@snu.ac.kr.

PMID: 33839657
DOI: 10.1016/j.scitotenv.2021.146750

Abstract

As the regulations on vehicle emissions have become more stringent internationally and real-driving emissions (RDE) have been established, the on-road characteristics of emissions have gained importance in vehicle research and development. The results of the fuel consumption levels and emissions from on-road tests are affected by many factors, such as driving conditions, routes and environmental conditions. Therefore, more research and analysis are needed for the effects of environmental factors and driving conditions according to RDE phase on the NOx emissions. In this study, RDE tests were conducted by season to analyze the on-road NOx emission characteristics of lean NOx trap (LNT)- and selective catalytic reduction (SCR)-equipped diesel vehicles corresponding to the Euro 6b regulation prior to the application of the RDE regulation. The purpose of this study is to analyze the effects of seasonal factors and phases of the RDE routes on the NOx emission and NOx conversion efficiency of catalyst. In spring/autumn and summer, the engine-out and tail-pipe NOx emissions were higher 1.3-5.9 times for vehicle A and 1.3-28.4 times for vehicle B in the urban phase than in other phases. In the urban phase, the engine bay temperature was probable to rise owing to frequent stops and low-speed driving, leading to a high intake air temperature, which causes excessive NOx emission, particularly in summer. The average air filter temperature in urban phase was 11-15 °C higher than the environment temperature for vehicle A. The NOx conversion efficiency of the LNT was highest at 54.1% on motorway and the efficiency was dependent on the phase of the test route. The NOx conversion efficiency of the SCR, which is dependent on the catalyst temperature, was highest at 98.7% in spring motorway and the efficiency was affected by the combined factors of season and phases.

Keywords: Conversion efficiency; Lean NOx trap; NOx emissions; Real driving emission; Selective catalytic reduction.