Characteristics of Unregulated Toxic Emissions from Ultra-High EGR Low Temperature Diesel Combustion and Effects of Exhaust Catalysts

Abstract

Unregulated toxic emissions from a DI diesel engine with ultra-high EGR low temperature combustion at 50% and 65% loads were measured by FTIR, and reduction characteristics of both regulated and unregulated emissions with exhaust catalysts were investigated. All the regulated emissions at 50% load were reduced to near zero levels with low temperature diesel combustion and the catalysts. At 65% load, approximately 50% reduction in THC and CO were obtained with the catalysts but they are still high at the point of smokeless and ultra-low NOx diesel combustion with large rates of cooled EGR. The unregulated emissions increase dramatically with intake oxygen content below 14% due to EGR. These trends correlate very well with those of THC emissions. The catalysts are effective to reduce some unregulated toxic emissions including aldehydes and some unsaturated hydrocarbons. However, aromatics and methane generated from ultra-high EGR low temperature smokeless diesel combustion are hardly reduced with the catalysts, in particular, at higher loads