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At present, diesel particulate filter (DPF) is the most effective method to reduce PM and PN in diesel engine exhaust. However, after a long period of operation, the DPF wall formed dense ash layer, which seriously affected the normal operation of the DPF. In this paper, Quartet Structure Generation Set is used to add the ash layer micro-structure, and the lattice Boltzmann method is used to explore the influence of ash layer in the ash containing DPF structure on its oxidation and regeneration process. In DPF, the active regeneration of O2 and particle (ΔH1 = −393.5 kJ/mol) and passive regeneration of NO2 and particulate matter (ΔH2 = −277.3 kJ/mol). This article combines the real microstructure of DPF and Arrhenius law to design two micro porous media structure models for DPF. The influence of ash layer on the heat release process of DPF regeneration was studied by analyzing the presence of ash stratification structure and the inlet velocities of structure I and II. It's found that the regeneration temperature of DPF structure with ash layer increases with the increase of exhaust gas inlet velocity, and the regeneration temperature of micro porous media structures at the same position varies greatly; With the increase of exhaust gas inlet velocity, the temperature distribution uniformity of the micro surface of the ash layer decreases, and the relative range increases; The optimal inlet velocity on the structural wall surface is obtained to be 0.15 m/s.

In this study, online ambient volatile organic compounds (VOCs) were collected at an urban site of Zhengzhou in Central China during February 2018. The VOCs characteristics, source contributions and the Chinese New Year (CNY) effects have been investigated. During the sampling period, three haze periods have been identified, with the corresponding VOCs concentrations of (92 ± 45) ppbv, (62 ± 18) ppbv and (83 ± 34) ppbv; in contrast, the concentration during non-haze days was found to be (57 ± 27) ppbv. In addition, the festival effects of the CNY were investigated, and the concentration of particulate matter precursor decreased significantly. Meanwhile, firework-displaying events were identified, as the emission intensity had been greatly changed. Both potential source contribution function (PSCF) and the concentration weighted trajectory (CWT) models results indicated that short-distance transportation was the main influencing factor of the local VOCs pollution, especially by transport from the northeast. Source contribution results by the positive matrix factorization (PMF) model showed that vehicle exhaust (24%), liquid petroleum gas and natural gas (LPG/NG, 23%), coal combustion (21%), industrial processes (16%) and solvent usages (16%) were the major sources of ambient VOCs. Although industry and solvents have low contribution to the total VOCs, their secondary organic aerosol (SOA) contribution were found to be relatively high, especially in haze-1 and haze-3 periods. The haze-2 period had the lowest secondary organic aerosol potential (SOAp) during the sampling period; this is mainly caused by the reduction of industrial and solvent emissions due to CNY.