Low load running characteristics and NOx emission under low load for heavy-duty diesel vehicles
WANG Xiao-wei1, JING Xiao-jun1, GAO Tao1, LI Gang2, GU Xue-jing2, ZHANG You-yuan3
1. CATARC Automotive Test Center(Tianjin) Co., Ltd., Tianjin 300300, China; 2. Chinese Research Academy of Environmental Sciences, Beijing 100012, China; 3. Dongfeng Liuzhou Motor Co., Ltd., Liuzhou 545000, China
Abstract：The operation and emission performances of a heavy-duty diesel urban vehicle which meets the China VI emission standard have been investigated based on remote monitoring data. Furthermore, a 6L diesel engine which also meets the China VI emission standard has been adopted to carry out the World Harmonized Transient-State Cycle (WHTC) and California Low Load Cycle (LLC) emission tests on an engine test bench using the engine-in-the-loop methodology. The NOx emission characteristics under the low-load conditions have been studied. Results suggest that the heavy-duty diesel urban vehicle tends to run under the low-load conditions, accompanied with a large portion of NOx emitted. The LLC test reveals the fact that the engine spends more time running under the low-load condition, which leads to a low emission temperature as well as low NOx conversion efficiency. The high NOx emission under the LLC test is mainly caused by the low exhaust temperature. China is suggested to develop low-load cycle to control the NOx emissions under such conditions according to the actual driving characteristics of commercial vehicles. The loading setting should be taken into consideration when developing the low-load cycle given the fact that the NOx conversion and emission are significantly affected by the vehicle loading.
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