| Diesel Particulate Filter(DPF), one of the most effective aftertreatment technologies, but there are some defects in trapping the nanoscale particles. The charging and agglomerating technology has been a research hotspot as an effective way to control the number of nanoscale particles of diesel engine. The technology is a kind of approaches to promote the growth of fine particulate matter, but there are few studies in the treatment of the diesel particulate matter. Therefore, the research on the mechanism and performance of the charging and agglomerating technology has a high theoretical significance and application value.Based on the basic theory of corona discharge and the mechanism of charge coagulation, the wire-cylinder corona discharge device and coagulation device were designed and manufactured. The online charging and agglomerating test bench was set up to research the charge efficiency of diesel engine particulates. The micro-orifice uniform deposition impactor(MOUDI) was used to collect diesel engine particulates. The charging property and coagulation efficiency of particles before and after charged agglomerator were analyzed. The features of particles were observed by using scanning electron microscope(SEM). In the condition of-15 kV DC voltage and 35L/min sample gas exhaust flow, particulate matter has a significant effect on charge. Precharging can effectively improve the coagulation efficiency of particulates. The coagulation performance was the best when the AC voltage intensity is 6kV. The size distribution curve of particles after charged agglomerator shifted to the right under three kinds of speeds. The median diameter of the mass was increased from 0.78 to 1.4μm. Modal mass ratios of the coarse particles were also increased by 13.9%, 15% and 11.6% respectively. The presence of the particles before and after charge coagulation analyzed by SEM: The particles in original machine are distributed in a large area, and the particles are combined closely. The morphology of particles after the electric charge was showed branch chain loose structure, and the arrangement of particles are dispersive. The morphology of particles after the coagulation was showed clusters like distribution.In this paper, application research on charged agglomerator coupling DPF was carried out. The bench test has been conducted to analyze the effect of DPF install the charged agglomerator on the economy and emission characteristics. The results show that when the engine runs 3000 s, the pressure drop and fuel consumption are decreased by 0.3kPa and 2% respectively. The smoke down significantly when engine under high load. The filtering efficiency increased by 3.1%. The structure and morphology of the particles were analyzed by transmission electron microscope(TEM). Based on the box counting dimension algorithm, geometric analysis of the structure characteristics of the particles was carried out, and density of the particle structures was carried out. The results show that the phenomenon of local area overlap and accumulation of condensed particles is obviously increased after the charged agglomerator. After DPF, the particles showed a small cluster distribution, outer nuclear arrangement is clear, and the carbon spheres improved. Based on the box counting method, after charged agglomerator, fractal dimension of particles were increased. After charged agglomerator coupling DPF, the fractal dimension was decreased, which was consistent with the TEM analysis. |
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