energies Article NOx Emission from Diesel Vehicle with SCR System Failure Characterized Using Portable Emissions Measurement Systems Sheng Su 1,2, Yunshan Ge 1,* and Yingzhi Zhang 3,* 1 Xiamen Environment Protection Vehicle Emission Control Technology Center, Xiamen 361000, China;
[email protected] 2 National Lab of Auto Performance and Emission Test, School of Mechanical and Vehicular Engineering, Beijing Institute of Technology, Beijing 100081, China 3 School of Environment, Tsinghua University, Beijing 100084, China * Correspondence:
[email protected] (Y.G.);
[email protected] (Y.Z.); Tel.: +86-10-6891-2035 (Y.G.); +86-10-6894-8486 (Y.Z.) Abstract: Nitrogen oxides (NOx) emissions from diesel vehicles are major contributors to increasing fine particulate matter and ozone levels in China. The selective catalytic reduction (SCR) system can effectively reduce NOx emissions from diesel vehicles and is widely used in China IV and V heavy- duty diesel vehicles (HDDVs). In this study, two China IV HDDVs, one with SCR system failure and the other with a normal SCR system, were tested by using a portable emissions measurement system (PEMS). Results showed that the NOx emission factors of the test vehicle with SCR system failure were 8.42 g/kW·h, 6.15 g/kW·h, and 6.26 g/kW·h at loads of 0%, 50%, and 75%, respectively, which were 2.14, 2.10, and 2.47 times higher than those of normal SCR vehicles. Emission factors, in terms of g/km and g/kW·h, from two tested vehicles were higher on urban roads than those on suburban Citation: Su, S.; Ge, Y.; Zhang, Y.