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Temperature Excursions during Regeneration of Diesel Particulate Filters

Dan Luss, Chemical Engineering, University of Houston, Houston, TX 77204

The main technology for removal of particulate matter (PM ) emission is by Diesel Particulates Filter (DPF), which is a multi-channeled ceramic filter. The exhaust gases flow through the porous ceramic walls and exit from the surrounding channels, while the PM is deposited in the channels. The accumulated PM increases the pressure drop through the DPF and has to be periodically removed by combustion. The efficient combustion of the PM is still the most challenging aspect of this PM removal technology. The combustion often generates moving high temperature waves, the temperature of which may exceed in some cases the melting temperature of the DPF channels, damaging the DPF.

Infra-red measurements of the spatiotemporal temperature on the surface of a single layer diesel particulate filter showed that the PM combustin may proceed in different some rather intricate, modes. The feed temperature, oxygen concentration and thickness of the deposited PM layer determine the combustion mode. The lowest temperature rise is obtained when the combustion occurs uniformly on the surface. In many cases ignition occurs at several points leading to formation of moving temperature fronts. . The number of ignition points increases as the PM loading is decreased. The velocity of the downwards moving temperature front exceeds that of the upstream front bounding the hot zone The velocity and temperature of a downwards moving temperature front exceeds that moving upstream. Videos of different PM combustion modes will be shown. Avoiding this mode of combustion decreases the probability of excessive hot zone formation during the PM regeneration.