Thermal management strategy for active regeneration of diesel particulate filter

Abstract

The method of diesel oxidation catalyst (DOC) assistance is an effective way to achieve active regeneration of diesel particulate filter (DPF). Therefore, an appropriate DOC inlet temperature is the essential boundary condition for this regeneration process. In this paper, the thermal management measures and a novel strategy based on the requirements of DPF active regeneration have been proposed and studied through experiments. Results show that intake throttling can increase DOC inlet temperature by 45% at high speed and 13% at low speed. However, its effect becomes significant only after the throttle closure exceeds 65%. Near post-injection is a more effective method than intake throttling to increase the DOC inlet temperature, and is suitable for situations where the DOC inlet temperature differs greatly from the target value. Under the premise of economic consideration, the optimal value of near post-injection time is always 20°CA after top dead center (TDC). The near post-injection quantity has a greater effect on DOC inlet temperature than the near post-injection time. However, too large near post-injection quantity can also lead to a sharp deterioration in fuel economy. Meanwhile, a novel thermal management strategy based on engine working zone division is proposed according to the ability of different thermal management measures and the distribution law of original DOC inlet temperature. With this strategy, the DOC inlet temperature in whole engine operating range increases significantly. In steady state, more than 80% of the operating points can reach the target value of 450 ℃. In world harmonized transient cycle (WHTC), the average DOC inlet temperature is also increased by 28.8%.