Authors
S.A. Lewis, Sr., J.M.E. Storey, B.G. Bunting, and J.P. Szybist
Publication
SAE Paper No. 2005-01-3737, 2005 SAE Powertrain & Fluid Systems
Conference and Exhibition.
Abstract
A single cylinder engine was operated in HCCI mode with diesel-range
fuels, spanning a range in cetane number (CN) from 34 to 62. In
addition to measurements of standard gaseous emissions (CO, HC, and
NOx), multiple sampling and analysis techniques were used to
identify and measure the individual exhaust HC species including an
array of oxygenated compounds. A new analytical method, using liquid
chromatography (LC) with electrospray ionization-mass spectrometry
(ESI-MS) in tandem with ultraviolet (UV) detection, was developed to
analyze the longer chain aldehydes as well as carboxylic acids.
Results showed an abundance of formic and butyric acid formation at or
near the same concentration levels as formaldehyde and other aldehydes.
Concentrations of all partially-oxidized species were low when the
combustion phasing was advanced, but were much higher at retarded
combustion phasing when the main combustion event was slower due to the
pressure and temperature conditions being less severe. The increased
concentrations at retarded combustion phasing were higher for the high
CN fuels, which exhibited significantly more low temperature heat
release (LTHR) than the low CN fuels. Fuels with high CN had higher
concentrations of aromatic aldehydes in the exhaust than low CN fuels,
even though they had lower aromatic concentrations in the starting
fuel. This study also shows that the high unburned hydrocarbon
emissions associated with HCCI combustion often includes high
concentrations of partially-oxidized species.
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