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In real-world driving, the exhaust gas conditions in the particulate filter may induce incomplete filter regenerations. The implications of such partial regenerations are examined in this paper in terms of pressure drop and filter thermal loading. The methodology followed is based on a 2-D simulation model of the regeneration process. The model is initially fine-tuned and validated based on experimental results from engine bench testing. The validated model is subsequently employed to simulate a series of regenerations starting from different possible initial soot distribution patterns. The results are evaluated based on the calculated maximum thermal gradient in the filter that would produce the critical thermal stress for filter structural integrity. It is shown that the filter thermal loading can be significantly higher in case of initially non-uniform soot distribution.

A case study of a close-coupled catalyst subjected to exhaust gas conditions typical for a modern engine warm-up phase is studied using a time-efficient 2-dimensional modeling approach. The flow distribution at catalyst inlet is affected by the downstream flow resistance, which is in turn a function of catalyst temperature field. Unlike traditional CFD approaches, the presented model focuses on this interesting coupling between the problems of flow distribution and catalyst thermal response. The results are expressed in terms of time-dependent velocity and temperature distribution as well as conversion efficiency. After a basic understanding of the phenomena, a parametric analysis is performed to assess the significance of various design parameters affecting the cold start performance of close-coupled catalysts. It is shown that the detrimental effect of flow uniformity on light-off is associated to the non-uniform ageing.