Controlled Energy Deposition in Diesel Particulate Filters During Regeneration by Means of Microwave Irradiation

Control and location of the energy input to a ceramic diesel filter is essential for successful filter regeneration. External heat sources, such as burners or resistance heaters, initiate soot combustion at the inlet face of the filter, and complete regeneration depends on the combustion front propagating throughout the filter. Uneven or uncontrolled soot combustion can cause incomplete filter regeneration and/or filter destruction.

In contrast, it is possible to provide a more uniform energy input to a filter by incorporating microwave-susceptible materials in the filter body and then using RF (microwave) energy to initiate combustion. This method gives improved control over the soot combustion and lower thermal stresses within the filter.

This paper discusses the RF engineering and materials considerations involved in RF-based regeneration of wall-flow and ceramic-foam diesel filters. The development of filters containing susceptors that couple to both electric and magnetic components of an RF field is described, together with results from prototype testing programs in which both filter types have been successfully regenerated by RF heating.