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

Regeneration of a soot-trap ceramic foam by a single-mode microwave cavity

“…Microwave irradiation has been proposed as an effective mean for particulate trap regeneration (Chunrun et al, 1994;Garner and Dent, 1989;Gautam et al, 1999;Ma et al, 1997;Zhi et al,1995;Walton et al, 1990). Water or carbon black are strong absorbers of microwaves, whereas most ceramics are virtually transparent to them.…”

Design and development of a microwave-enhanced diesel soot oxidation system

“…Also, wall-flow filters are not as tolerant of thermal stresses in the radial direction, so uniform heating of the filter inlet face is essential to avoid filter damage. Ceramic foam filters are isotropic, so they can withstand larger temperature gradients than wall-flow filters (Walton et al, 1990).…”

“…Friction between the moving molecules causes the temperature of the substance to increase. Magnetic materials can be heated by both electric and magnetic fields, but diesel soot is not magnetic and hence can only be heated via the electric field of the RF energy (Walton et al, 1990). The dielectric properties of a material are described by the complex permittivity:…”

“…Conductors reflect microwave energy, so microwaves transmitted to metal walls will be reflected. All of these substances are present in a diesel filtration unit, so the geometry of the metal filter housing, the soot loading, and the intensity and spatial distribution of the microwave energy transmitted to the filter face will determine the electric and magnetic field distributions within the filter (Walton et al, 1990 In order provide more even heating of the filter element, a second-generation system was developed. This system differed from the first-generation system in that the waveguide outlet was positioned along the diffuser centerline and the exhaust inlet was placed on the side of the diffuser.…”

“…At the same time, results from a novel microwave regeneration study performed by Walton, Hayward, and Wren (1990) were published. In this study the filter cavity and the filter material were designed to make efficient use of the electric and magnetic fields which are present during the preheating phase of microwave regeneration.…”