(152c) Wrong-Way Behavior of Diesel Particulate Filters

Diesel engines emit particulate matter (PM), which is a health hazard that has to be removed. The current most efficient device for PM removal is a Diesel Particulate Filter (DPF) which consists of thousands of porous parallel channels, with the opposite ends of adjacent channels being plugged. The exhaust gas passes through the filter porous wall into the adjacent channels, while the accumulated PM is periodically removed by combustion. It is known that the exothermic combustion leads in some cases to excessive local temperature rise, which may melt the ceramic filter and destruct the DPF. It is not yet established what causes some times this deleterious temperature rise. The study aim was to investigate if this may be due to a wrong way behavior that is defined a counter-intuitive response to a sudden change in the input to dynamic system. Extensive experimental and theoretical studies have revealed that a wrong-way behavior may occur in packed bed reactors used to conduct an exothermic chemical reaction. Specifically, a sudden decrease in the feed temperature can generate a transient increase in the reactor temperature.

We used IR imaging to study the impact of a sudden decrease in the feed temperature ( that may be caused by a change in the mode of diesel engine operation) on the moving temperature fronts during the regeneration of a DPF. The experiments reveled that similar to the behavior of packed bed reactors, a wrong-way behavior may be encountered during the regeneration of a DPF. The temperature rise of a downstream moving reaction front is larger than that of an upstream moving front. The magnitude of the temperature rise depends on the location of the front at the time at which the front was at the time the exhaust feed temperature was decreased.