Particulate Traps and Regeneration

In diesel engine applications, filters have to satisfy specific requirements. In spite of high-exhaust gas flow rates, the pressure drop over the filter must be low to avoid decreasing engine performance [79]. The filter must 

The most studied and applied particulate trap is the wall flow monolith [82-84]. It consists of a ceramic structure with parallel channels, of which half are closed at the upstream end in an alternate, checkerboard manner, and the other half are closed at the downstream end. Thus, exhaust gases are forced to flow through the porous walls, which then act as filters. 

When using a particulate trap a regeneration technique is necessary to prevent the trap becoming clogged with collected soot which, in the longer term, would result in engine malfunction due to increased back-pressure. Several techniques for removing soot from the particulate trap have been proposed. 

One method involves passive on board continuous trap regeneration using NO/O and NO  

This overall strategy is reminiscent of that employed in the TWC materials detailed above in that two components of the exhaust gas are reacted together. In this instance, though only one of the components forms a benign product, C(s) CO while NO - NO (which is still obviously a pollutant). 

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