Experimental study on the emission characteristics and performance of PNA coupled aftertreatment system with different catalyst loading

In order to meet the strict emission regulations in the future, passive NOx absorber (PNA) and electrically heated catalyst (EHC) will gradually become the necessary technologies for diesel engines. In this paper, based on a diesel engine with PNA, EHC, diesel oxidation catalyst (DOC), selective catalytic reduction catalyst integrated into diesel particulate filter (SDPF) and selective catalytic reduction catalyst (SCR), the impact of PNA emission characteristics and performance with different catalyst loading were investigated. The results showed that EHC was coupled behind the DOC is more conducive to energy conservation and reducing NOx emissions. Compared with EHC was coupled in front of the DOC, the time for SDPF inlet temperature to reach 180 ℃ was reduced by 123 s, the power consumption of EHC was reduced by 0.25 kWh and nitrogen oxide (NOx) conversion efficiency increased by 16.61% in the cold start phase when EHC was coupled behind the DOC. Meanwhile, PNA has a certain adsorption effect on CO, THC, and NOx. When EHC was coupled behind the DOC, the adsorption amount of carbon monoxide (CO), total hydrocarbon (THC), and NOx increases with the increase of PNA catalyst loading. The maximum adsorption time of PNA for NOx reached 171 s. Similarly, the conversion efficiency of CO, THC, and NOx during the cold start stage also increases with the increase of PNA catalyst loading. The maximum average conversion efficiency of CO, THC, and NOx was 60.58%, 88.60%, and 95.72%, respectively. In cold start phase, the PNA50 has achieved high PNA performance, and the gain brought by higher catalyst loading is not obvious. In medium–high temperature phase, due to the high exhaust temperature, PNA has no effect on the conversion efficiency of CO, THC, and NOx. PN conversion efficiency is more than 99% and is not affected by the PNA type. The findings provide the fundamental insights to promote the application of PNA and EHC in diesel engines and reduce emissions of diesel engines under cold start conditions.