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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.

In close-coupled catalytic converter applications, the exhaust gas mass flow may present fluctuations with a timescale in the order of milliseconds, as a result of periodic valve operation. Such flow pulsations are likely to affect catalytic converter performance, due to mass transfer limitations. A fully transient channel model is developed, to study pollutant conversion under pulsating flow conditions. This model is applied to evaluate the effect of pulsations in catalyst conversion. Firstly, the effect of flow pulsations during the warmed-up operation is studied. Then, we focus on the effect of pulsations during the light-off phase, during which significant temperature and therefore activity gradients are observed in the monolith. The new model is also used to assess the accuracy of the traditional “quasi-steady state” approach, when applied to simulate converters under pulsating flow.