Search Results

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.

New developments for optimized control of Aerodynamically Regenerated Traps (ART) - Exhaust Gas Recirculation (EGR) integrated systems for diesel engines are presented herein. Such systems employ high-efficiency ceramic monolith filters to retain 99% of the emitted particulates. Regeneration is achieved periodically by short pulses of compressed air, flowing in the opposite direction to the exhaust. The soot is collected in a chamber, outside of the monolith, where it is oxidized with an electric burner. A fraction of the filtered exhaust is returned to the engine and this reduces NOx emissions, typically, by more than 50% at 18% EGR. However, since the amount of EGR, the frequency of regeneration and the frequency and duration of burning have a bearing on the fuel consumption of the engine, their optimization is imperative. Thus, provisions were made to collect intelligent information, leading to continuous assessment of the engine performance and fuel economy.

This work determined the suitability of two silicon carbide (SiC) monoliths (one regular and one coated with a micromembrane), as well as a coated cordierite monolith for use as aerodynamically regenerated particulate filters for diesel engines. These ceramic honeycomb monoliths were tested for their filtration efficiency, their post filtration particulate size distribution and their ability to be aerodynamically regenerated at pre-selected operating temperatures (200, 300 and 400°C). Through combined laboratory and field testing, the uncoated silicon carbide filter produced the most satisfactory results in all of these tests. This filter resulted in excellent regeneration characteristics while maintaining the highest filtration efficiencies at all particle sized tested. All filters were found to clean effectively at all temperatures. However, upon normalization with the volumetric flow rate through the monolith, it was found that the filters were most thoroughly cleaned at 400°C.