Diesel emission technologies at the SAE Congress Regardless of the ups and downs in the fortunes of the SAE World Congress and Exhibition, the diesel emission sessions have enjoyed considerable interest and high attendance for a number of years. It was also the case during this year's Congress, held in Detroit, MI on March 3-6.
Diesel particulate filter technologies, including both filter substrates and systems, were one of the main topics. A number of papers presented by authors from Ibiden and NGK discussed the improvements in silicon carbide (SiC) substrate technologies. Researchers attempted to improve the thermal shock resistance of SiC by either modifying the material properties (composite Si-SiC, paper 2003-01-0384) or by developing of new assembling techniques for SiC filter segments (2003-01-0376). Another trend was to develop SiC materials of increased porosity, up to as much as 65%, to allow for coating with high catalyst/washcoat loadings, as may be needed in catalyzed DPFs or in combined DPF/NOx adsorber devices (2003-01-0377, 2003-01-0383). Silicon nitride, a new filter substrate material, was presented by Japan's Asahi Glass (2003-01-0386). The silicon nitride material was claimed to have temperature resistance and chemical stability comparable to those of SiC, while being endowed with superior thermal shock tolerance, thus potentially eliminating the major drawback of silicon carbide and the need for filter segmentation. Asahi developed a new manufacturing method using silicon metal as the raw material, resulting in costs allegedly comparable or lower than those for SiC parts. Another new material, named DuraTrap AT, was showcased by Corning, but no paper was presented. The DuraTrap AT, designed to combine high thermal capacity and low thermal conductivity, is currently tested with selected Corning customers. Diesel filter systems papers dealt mainly with ongoing improvement and testing of existing concepts, such as those using cerium or iron based fuel additives for regeneration. A new configuration of passively regenerating catalytic filter, maximizing the effect of NO2 regeneration, was suggested by researchers from the University of Delft, where a catalyzed wall-flow filter was proceeded by a catalyzed ceramic foam substrate (2003-01-0379). In comparison to the last year Congress, more NOx adsorber papers were presented, highlighting the ongoing development in this technology, but also identifying many technical problems (such as durability and regeneration/desulfation strategies) that have to be solved before the commercial application of NOx adsorbers in U.S. 2007 compliant engines can be possible. For the first time, some papers presented results from vehicle prototypes, as opposed to laboratory bench tests. For instance, AVL reported a 65% NOx and 90% PM emissions reduction over the FTP-75 test in a 1750 kg vehicle equipped with a NOx adsorber and a DPF (2003-01-0043). An interesting observation was made that the upstream NOx adsorber helped to regenerate the DPF, probably through increasing the NO2/PM ratio. Little new development was reported in the U.S. EPA NOx adsorber demonstration program. However, the EPA is expecting to start road tests of a NOx adsorber/DPF equipped vehicle (5.9 liter engine) in July. The EPA has been also developing an alternative technology--a clean combustion diesel engine meeting the 0.2 g/bhp-hr NOx standard without the use of exhaust aftertreatment. An early prototype of the engine (with most vital organs replaced by dummies) was showcased in the FEV exhibit area, but no technical paper was presented. A NOx emissions map of the engine was shown, with NOx never exceeding 0.2 g. The technology was developed in a 1.9 liter, 4-cylinder TDI engine, apparently not operated in the HCCI mode. The engine was equipped with "hydraulically intensified" high pressure (> 200 MPa) injection system. NOx emissions were controlled by high boost (turbocharger + boost assist device, intercooler) and a low pressure loop EGR. The engine would require exhaust gas aftertreatment for CO, HC, and PM. Technical details on the engine and the system cost vs. performance trade-offs are not known. With the continuing opposition of the EPA against urea-SCR technology, there were fewer SCR reports. The most active company in this area was Siemens (Ceramics GmbH), who presented papers on integrated SCR-based NOx/PM control systems targeting both Euro 4/5 and the US 2007 (2003- 01-0774). ------------------------ Yahoo! Groups Sponsor ---------------------~--> Your own Online Store Selling our Overstock. http://us.click.yahoo.com/rZll0B/4ftFAA/46VHAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
