Intersting dynamics of soot combustion on a planar diesel particulate filter

Dan  Luss, University of Houston

The dynamic features of soot combustion on a single layer, planar diesel particulate filter (DPF) were studied using IR imaging. At low oxygen concentrations and feed temperature of 635 oC the soot combustion rate was uniform all over the surface . At higher oxygen concentrations local ignition occurred at either one or several locations. The maximum temperature of the moving fronts, that bound the ignited zones was much higher (>100 oC) than those attained during uniform combustion.  The maximum temperature of a downstream moving front exceeded that of the one moving upstream. At soot loading of 10 g/L a hot zone formed close to the end of the DPF and the bounding temperature front propagated upstream until it conquered the whole surface. At soot loading of 20 g/L the position and number of the hot zones strongly depended on the oxygen concentration. As the flow rate per unit filter surface area was increased, the maximum temperature rise attained first a local maximum and later a local minimum. A sudden change from normal to idle conditions can lead to an transient temperature rise higher than that attained under either one of these two states. This behavior has some similarity to the wrong-way behavior known to exist in packed bed reactors

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