Method and Detailed Analysis of Individual Hydrocarbon Species From Diesel Combustion Modes and Diesel Oxidation Catalyst

Abstract

An undiluted exhaust hydrocarbon (HC) speciation method, using flame ionization detector gas chromatographs, is developed to investigate HC species from conventional and low-temperature premixed charge compression ignition (PCI) combustion pre- and postdiesel oxidation catalyst (DOC) exhaust. This paper expands on previously reported work by describing in detail the method and effectiveness of undiluted diesel exhaust speciation and providing a more detailed analysis of individual HC species for conventional and PCI diesel combustion processes. The details provided regarding the effectiveness of the undiluted diesel exhaust speciation method include the use of a fuel response factor for HC species quantification and demonstration of its linearity, detection limit, accuracy, and precision. The listing of individual HC species provides not only the information needed to design surrogate exhaust mixtures used in reactor tests and modeling studies but also sheds light on PCI combustion and DOC characteristics. Significantly increased engine-out concentrations of acetylene, benzene, and toluene support the theory that net soot reduction associated with PCI combustion occurs due to the reduction of soot formation (as opposed to increased soot oxidation). DOC oxidation behavior differs depending on the combustion characteristics, which change exhaust species and temperature.

Gaseous and Particulate Emissions from Diesel Engines at Idle and under Load: Comparison of Biodiesel Blend and Ultralow Sulfur Diesel Fuels

“…Similar fractions (4−22%) have been reported previously when sampling exhaust using Tenax adsorbents. 23,33−36 …”

Comparison of HC species from diesel combustion modes and characterization of a heat-up doc formulation

“…Higher premixedness of the fuel-air charge and lower combustion temperature of PCI (compared to conventional combustion) cause a different oxidation path of fuel during combustion, which produces higher CO and unburned HC emissions as well as a higher portion of partially oxidized fuel, such as alkenes, alkynes, and aldehydes, especially at low load conditions (Dec et al, 2002;Wagner et al, 2004;Sluder et al, 2004;Lewis et al, 2005;Bohac et al, 2006;Han et al, 2008). Moreover, the aspect of post-flame oxidation that a lot of SI combustion studies have reported on (Kaiser and Siegl, 1994;Bohac et al, 2004) may provide a better understanding of PCI combustion because PCI has a relatively higher expansion gas temperature due to the later fuel injection timing (compared to conventional combustion) and available oxygen during expansion.…”

“…If a C 9 -C 19 HC is detected in the exhaust but not in the fuel, it is partially oxidized fuel; if a C 9 -C 19 HC is detected in the exhaust and in the fuel, it is considered to be unburned fuel. A more detailed description of the engine, GC set-ups, and test fuel is provided by (Bohac et al, 2006;Han et al, 2008).…”

Measuring long chain alkanes in diesel engine exhaust by thermal desorption PTR-MS

“…2 used in the engine exhaust studies were measured by evaporating 5 µL h −1 of whole fuel into 20 slpm of dry nitrogen at an injection manifold temperature of 60 • C. The PTR-MS sampled directly from this flow, bypassing the thermal desorption sampler and water trap. Gasoline is mostly comprised of hydrocarbons in the C 4 to C 10 range while diesel fuel consists of C 8 to C 25 hydrocarbons (Han et al, 2008;Schauer et al, 1999;Lough et al, 2005;Gentner et al, 2012;Wang et al, 2005). Exhaust is a more complex mixture that contains fuel hydrocarbons plus oxygenated compounds such as aldehydes and ketones, and other hydrocarbons such as alkenes, acetylene, and pyrogenic compounds (Schauer et al, 1999(Schauer et al, , 2002.…”

“…IVOCs are defined as having a saturation vapor pressure between 1.33 × 10 −4 and 1.33 × 10 −1 hPa (10 −4 and 10 −1 Torr) at 25 • C (Robinson et al, 2007;Presto et al, 2009). For the n-alkanes this vapor pressure range corresponds to dodecane (C 12 ) through to octadecane (C 18 ) and compounds within this vapor pressure range comprise a large fraction of diesel fuel and exhaust (Han et al, 2008;Schauer et al, 1999;Siegl et al, 1999;Gentner et al, 2012). Laboratory tests have shown significant SOA formation from long chain n-alkanes, branched alkanes, and cyclic alkanes found in diesel engine exhaust (Lim and Ziemann, 2005;Jordan et al, 2008;Samy and Zielinska, 2009;Tkacik et al, 2012).…”