A Thermally Regenerated Diesel Particulate Trap Using High-Temperature Glass-Fiber Filters

A novel high-efficiency Pallflex filter has been developed for diesel exhaust after-treatment. The filter media is made of high-melting point boro-silicate glass fibers bonded together to form a paper-like pad that can withstand elevated thermal regeneration temperatures. Each filter element is placed between two fine stainless steel wire meshes, which impart structural rigidity to the fiber matrix and prevent its disintegration. An array of these filter pads, placed 1 cm, apart, is assembled together in an insulated housing. The filters are separated by spacers, which are perforated on one side and plugged on the other side to force the exhaust to flow through the filter elements. Such a trap of a total filter surface area of 1.2 m² and a volume of 14 liters was tested in the laboratory and on the road to determine its filtration efficiency, back pressure characteristics and regenerability. Thermal regeneration was tested by raising the trap temperature either by throttling the engine or using electrical heaters.