Can the world harmonized steady cycle (WHSC) accurately reflect real-world driving conditions for heavy-duty diesel engine emission valuations? A comprehensive experimental study
Renhua Feng, Jing Yu, Xing Shu, Banglin Deng, Zhanye Hua
Abstract
In this study, the influence of aftertreatment on emission reduction in heavy-duty diesel engines was experimentally investigated under the world harmonized steady cycle (WHSC) and universal operating conditions. The experimental results indicate that the average aftertreatment purification efficiencies for nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) under WHSC were 97.8%, 90.4%, and 100%, respectively. Engine load significantly affected both raw and post-treated emissions under WHSC conditions. High emission contribution rates before and after the catalyst were primarily observed during the 3rd, 11th, and 12th working conditions, corresponding to low engine loads. In contrast, low contribution rates were mainly concentrated in the 2nd and 5th working conditions, associated with full engine loads. The particle number (PN) rate after catalysis increased as exhaust temperature decreased due to lower catalyst activity and reduced diesel particulate filter (DPF) purification efficiency. Additionally, raw methane (CH 4 ) emissions were predominantly concentrated in low-load, high-speed regions, exhibiting similar behavior to raw HC emissions. The WHSC test cycle primarily operated within medium- and low-engine-speed regions based on comparisons of NOx, CO, HC, and CH 4 emissions between WHSC and the universal characteristics map. Therefore, emissions under WHSC conditions only partially reflect real driving scenarios, highlighting the need for world harmonized transient cycle (WHTC) testing, which will be explored in future work.