27 May 2011
The 3rd CTI International Conference: Vehicle Emission Reduction Technologies—Criteria Pollutants and CO2 was held May 16-20, 2011 in Detroit, MI. The five-day program started with a one-day introductory seminar “Basics of Exhaust Systems” (S. Carstens, EngineSens). The themes for the other days were “Technology Approaches to Meet LEV-III Emissions Requirements” for day two, “CO2 Issues and Efficiency Approaches in the LD and HD Vehicle Sectors” for day three and “HD Emissions Technologies to Meet Current and Future Needs” for days four and five.
LEV III/Tier 3 Legislation and Technology. Coverage of California LEV III/EPA Tier 3 technology started with a brief regulatory overview and a summary of important light-duty diesel and gasoline emission technology developments from the past year (T. Johnson, Corning). Measures to address undesirable secondary effects associated with SCR deNOx aftertreatment are progressing—TiO2 is an effective urea decomposition catalyst that can be used to avoid the formation of many undesirable urea decomposition byproducts; ammonia slip catalyst performance is improving to increase ammonia selectivity to N2 and reduce N2O production; and improvements in substrates offer improved SCR reaction kinetics by overcoming diffusion and mass transfer limitations at higher cell densities. New SCR deNOx catalysts formulations are emerging that have improved low temperature conversion (mixed Cu and Fe zeolites) and also show some ability to oxidize carbon (Nb-Ce oxide). Adding an SCR catalyst on a DPF is an effective means to increase SCR catalyst volume and improve NOx conversion. Advances in NOx adsorber + SCR technology have improved performance while reducing PGM costs, improved SCR catalyst durability and reduced the need to use two catalyst beds. Diesel particulate filter advances include membrane filters that show lower activation energy and ignition temperature and aluminum titanate substrates that can be used to increase soot loading capacity or reduce pressure drop. Gasoline particulate filter designs are available with high filtration efficiency that have little impact on performance. LEV III regulations will drive gasoline emission control systems to higher PGM loadings and increased cell density.
Accompanying the LEV III/Tier 3 emission standards are GHG emission standards and/or fuel economy regulations. Studies from a European perspective strongly suggest that diesel powertrains can meet upcoming GHG restrictions more cost effectively than gasoline. In fact, it was suggested by FEV (M. Tatur) that the gasoline powertrain would require hybridization to avoid penalties for exceeding EU CO2 limits while the diesel did not. Some of the identified engine efficiency trends included lower compression ratio in diesel engines to reduce friction and longer stroke to bore ratio in gasoline engines to reduce heat losses and increase turbulence intensity to extended the lean limit or increase EGR tolerance.
Conference website: www.emission-control-systems.com