Extension of Analytical Methods for Detailed Characterization of Advanced Combustion Engine Emissions

Advanced combustion strategies used to improve efficiency, emissions, and performance in internal combustion engines (IC) alter the chemical composition of engine-out emissions. The characterization of exhaust chemistry from advanced IC engines requires an analytical system capable of measuring a wide range of compounds. For many years, the widely accepted Coordinating Research Council (CRC) Auto/Oil procedure[1,2] has been used to quantify hydrocarbon compounds between C₁ and C₁₂ from dilute engine exhaust in Tedlar polyvinyl fluoride (PVF) bags. Hydrocarbons greater than C₁₂₊ present the greatest challenge for identification in diesel exhaust. Above C₁₂, PVF bags risk losing the higher molecular weight compounds due to adsorption to the walls of the bag or by condensation of the heavier compounds. This paper describes two specialized exhaust gas sampling and analytical systems capable of analyzing the mid-range (C₁₀ - C₂₄) and the high range (C₂₄₊) hydrocarbon in exhaust. An automated gas chromatograph equipped with a mass spectrometer (GC-MS) sampling system was used to sample middle range hydrocarbons from raw exhaust. A separate sampling system consisting of a filter and XAD traps was used for the collection of particulate-phase and semi-volatile-phase hydrocarbons up to C₂₄₊ in dilute exhaust. After extraction, hydrocarbons trapped by the particulate filter and the XAD traps were speciated by a two dimensional gas chromatography mass spectroscopy (GCxGC-MS) technique. These two novel systems allowed more than 2000 compounds to be detected in the exhaust thus extended the analytical capacity in emission characterization.