Study On Diesel Wall-flow Filter For Ash Deposition Process

Diesel particulate filter (DPF) is the most effective exhaust aftertreatment device to reduce the emission of diesel engine particulate matters. As the DPF is widely used all over the world, a long life and high durability DPF is demanded. During the long time operation of the DPF, the inlet channel of the filter will be inevitably plugged by ash. Ash, mostly from essential lubricant additives, affects diesel particulate filter pressure drop sensitivity and limits filter service life. One of the most serious problems of DPF durability is the performance deterioration due to the filter aging because of the accumulation of the ash particles.At first, this article analyzed the source of ash and its formative processes in the wall-flow diesel particulate filter. Systematically summarized the physical and chemical properties of ash. The ash deep-bed deposition and cake deposition process in the wall-flow filter were analyzed based on the particulate matter filtration and regeneration mechanism. The article compared the deep-bed deposition process between ash and particulate matter, and a computational model of wall-flow diesel particulate filter for ash deep-bed deposition process was proposed. The effect of ash deposition on the flow resistance of filters was studied. Finally, the methods of reducing the impact of ash deposition on the filter pressure drop were proposed. The main research of the article included the following works:(1) The mechanism of ash deep-bed deposition in the wall-flow filter was studied. The article achieved to quantitatively analyze the characteristics of ash concentration in the filter wall, and a computational model of diesel wall-flow filter for ash depth deposition process was proposed.(2) This article proposed filter flow resistance equation of ash deep-bed deposition and cake deposition respectively. Based on this consideration, the effect of ash mass and deposition pattern on the filter pressure drop was studied.(3) Applied the engine simulation software AVL BOOST to analyze the flow resistance of the conventional filter and asymmetric channel filter, and is helpful for optimization of the structure of wall-flow filter.