Experimental Study and Numerical Interpretation on the Temperature Field of DPF during Active Regeneration with Hydrocarbon Injection

Diesel particulate filter (DPF) is indispensable for diesel engines to meet the increasingly stringent emission regulations. Both the peak temperature and the maximum temperature gradient of the DPF during active regeneration should be well controlled in order to enhance the reliability and durability of the filter. In this paper, the temperature field of the DPF during active regeneration with hydrocarbon (HC) injection was investigated with engine bench tests and numerical simulation. For the experimental study, 24 thermocouples were inserted into the DPF channels to measure the inner temperature of the filter to capture its temperature field, and the circumferential, axial and radial distribution of the filter temperature was analyzed to understand the DPF temperature field behavior during active regeneration. The test results show that the peak temperature of the DPF during regeneration usually occurs at the center of the DPF rear end due to the exothermic reactions of soot burning and the sweeping of the exhaust flow, while the maximum temperature gradient usually appears at the DPF periphery due to the heat transfer from the filter to the ambient. The effects of DPF initial soot loading, DPF inlet temperature, and exhaust mass flow during regeneration on DPF peak temperature and maximum temperature gradient were also studied on the engine test bench. Both the peak temperature and the maximum temperature gradient of the filter increased with the increasing of the DPF initial soot loading and DPF inlet temperature, while both of them decreased when exhaust mass flow risen. A three-dimensional DPF regeneration simulation, which takes soot loading distribution and HC nonuniformity into considered, was conducted with AVL FIRE, a commercial computational fluid dynamics (CFD) software, to interpret the DPF temperature field during active regeneration. The simulation results show that the soot loading in the DPF is very uniform, which indicates that it contributes little to the nonuniformity of the DPF temperature field, while the HC uniformity has a significant effect on the DPF temperature distribution. Further simulation demonstrated that both the peak temperature and the maximum temperature gradient of the DPF during active regeneration can be significantly decreased with the optimization of the HC uniformity at the DOC inlet.