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The development of new designs of a diesel particulate control system is discussed herein. The system employs a single high collection efficiency ceramic monolith to filter the particulate emissions of the engine. Regeneration is achieved by intermittent pulses of pressurized reverse-flow air. After every regeneration the soot is collected at the bottom of the device where it is burned in an incinerator chamber. Different configurations of the system were tested satisfactorily for performance and durability for 100 hrs, coupled to a small experimental engine which was sooting at high rates. Subsequently, a system incorporating a long ventless chamber fitted with an electric burner was mounted on a diesel passenger car and tested for on-road performance evaluation and further development.

The development of an Aerodynamically Regenerated Trap (ART) with a flow-through incinerator section is discussed herein. The ART system presented herein employes a single high-collection efficiency ceramic monolith to filter particulate emissions. Regeneration is performed aerodynamically, using compressed air flowing in the direction opposite to the exhaust flow. Dislodged particulates are captured in the incineration section of the trap directly below the ceramic monolith, where they are burned using an electric heater. This work concentrates on the design and development of the incinerator sections of the diesel particulate trap, whose function is to retain the soot from the regeneration air stream, without impeding the flow of the regeneration air itself.

The simultaneous control of diesel engine particulate and NOx emissions was targeted in this study. Particulate control was achieved with a trap that incorporated a high-filtration efficiency ceramic honeycomb monolith. Aerodynamic regeneration was used to periodically backflush the monolith filter. Soot was collected in a metallic chamber and was either incinerated by an electric burner or removed by a vacuum cleaner. NOx emissions were reduced by recirculation of filtered exhaust gases (EGR), which was made possible by the high collection efficiency of the employed monoliths. Tests were conducted on the road, driving a diesel vehicle under various loads and speeds. The levels of NO, CO and O2 at the exhaust were continuously monitored using a portable instrument. The particulate filtration efficiency was in the vicinity of 99% using CeraMem and 97-98% using Panasonic traps, respectively, hence the EGR line was effectively particulate-free.

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.