Abstract
The exhaust temperature closely affects the system's conversion efficiency. Low temperatures can lead to difficulties in the regeneration of the diesel particulate filter (DPF) and insufficient conversion efficiency of the selective catalytic reduction (SCR). To elevate the exhaust temperature under low-load conditions, this study investigates three fuel injection strategies and their impacts on the system's exhaust temperature. These strategies include without postinjection, single postinjection (closed postinjection), and double postinjection (closed postinjection plus late postinjection). The results show that under Worldwide Harmonized Transient Cycle (WHTC), both single and double postinjections effectively increased the exhaust temperature, thereby improving the conversion efficiency for carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NO (x) ). When single postinjection was enabled, the average temperatures at the inlets of the diesel oxidation catalyst (DOC), DPF, and SCR increased by 10, 12, and 10%, respectively, at which the average transformation efficiencies for CO, HC, and NO (x) exceeded 80%. When double postinjection was enabled, the average temperatures at the inlets of the DOC, DPF, and SCR increased by 33, 105, and 108%, respectively, at which the average transformation efficiencies for CO and HC were above 90% and the efficiency for NOx remaining essentially unchanged compared to the scenario without postinjection. In summary, under the WHTC, single postinjection is suitable for low-load situations, and double postinjection is suitable for situations where exhaust temperatures are extremely low. Moreover, when DPF reproduction is necessary, enabling a double postinjection can essentially meet the temperature requirement.