| Particulate matter is one main pollutant of the Diesel exhaust. Currently wall-flow diesel particulate filter is the most effective post-processing device used to reduce diesel particulate emissions, but its recycling technology is not very mature, seriously hampered it be widespread used. Therefore, thorough study on a more applicable regeneration method of diesel particulate filters has great significance.Summarized the advantages and disadvantages of various existing regeneration methods, propounded a new regeneration technology. In this technology, diesel is injected into diesel engine exhaust prior to the DOC, and then the temperature of diesel engine exhaust is increased to achieve diesel particulate filters regeneration, and this regeneration technology was comprehensively studied. The main contents of this paper are summarized as follows:(1) A regeneration method for wall-flow diesel particulate filters is proposed. According to the advantages and disadvantages of a variety of diesel particulate filters regeneration methods proposed by the domestic and foreign scholars, combined with the domestic diesel engine technology and fuel quality, a regeneration method called DOC assisted DPF regeneration method is proposed. The structure of this regeneration system and it's control process is quite simple. This regeneration method suitable for most diesel cars on the domestic markets; The regeneration method is not demanding quality requirements for diesel, the fuel economy deterioration rate is small, no damage to the engine life.(2) According to a special case of DOC assisted DPF regeneration method, idling regeneration method is proposed. In this method, a small amount of diesel is sprayed into diesel exhaust to increase the temperature of engine exhaust when the load of engine is higher, then let the engine return to idle state, relying on the decrease of engine exhaust flow to further enhance the exhaust temperature, to achieve regeneration of DPF. The fuel economy of this regeneration method is better than DOC assisted DPF regeneration method, and it's control process is easier than DOC assisted DPF regeneration method.(3) The secondary pollution of the regeneration method is investigated. HC and CO is found to be the secondary pollution of DOC assisted DPF regeneration method. The sources of HC and CO are analysised, the HC is mainly produced by the diesel which is not completely oxidized in the DOC. CO is mainly produced by the particulate matter which is not completely combustted in the DPF regeneration process. The factors of HC and CO emission on the regeneration were analyzed. The factors impact CO emission including the the amount of particulate matter in DPF when beginning regeneration,the exhaust gas temperature after DOC during regeneration,the exhaust flow during regeneration,and the oxygen concentration of the engine exhaust gas during regeneration; The factors impact HC emission including the amount of fuel injection, the exhaust gas temperature before DOC and space velocity.(4) The aging of DOC and DPF is investigated. Two methods of regeneration are carried out 40,000km aging test,Studies show that the two regeneration methods all will result in the performance of aging on the DOC and DPF, and the aging magnitude are similar. The degradation of DOC is mainly reflected on the ignition temperature of CO becomes higher, and the catalytic efficiency of HC and particulate matter are become lower;The degradation of DPF is mainly reflected on the trapping efficiency of empty DPF becomes lower. The impact of nonflammable particulate matter on the back pressure of DPF is negligible.In conclusion, the tow regeneration method of diesel particulate filters, DOC assisted DPF regeneration method and the idling regeneration method, are systematically studied in this paper. The fuel economy and the secondary pollution of regeneration methods were comprehensive analysised, the aging of regeneration method to DOC and DPF were in-depth studyed. The results has an important theoretical significance and engineering applications for expanding the applied scope of wall-flow diesel particulate filters in vehicle, reducing diesel particulate matter pollution on the environment.
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