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Authors
B.H. West, S.P. Huff, J.E. Parks, S.A. Lewis, Sr., J.-S. Choi, W.P. Partridge, J.E. Storey
Publication
SAE Paper 2004-01-3023, Society of Automotive Engineers, 2004
Abstract
Lean NOx trap (LNT) catalysts are capable of reducing
NOx in lean exhaust from diesel engines. NOx is
stored on the catalyst during lean operation; then, under rich exhaust
conditions, the NOx is released from and reduced by the
catalyst. The process of NOx release and reduction is called
regeneration. One method of obtaining the rich conditions for
regeneration is to inject additional fuel into the engine cylinders
while throttling the engine intake air flow to effectively run the
engine at rich air:fuel ratios; this method is called
“in-cylinder” regeneration. In-cylinder regeneration of LNT
catalysts has been demonstrated and is a candidate emission control
technique for commercialization of light-duty diesel vehicles to meet
future emission regulations. In the study presented here, a 1.7-liter
diesel engine with a LNT catalyst system was used to evaluate
in-cylinder regeneration techniques. Characterization of the exhaust
reductant chemistry during in-cylinder regeneration was performed. The
effects of various injection strategies and fuels and the resulting
exhaust chemistry on the performance of the LNT catalyst were
analyzed. In addition, exhaust species measurement of NOx
and select reductants were performed inside of the catalyst cells with
a capillary-based mass spectrometry technique. The effect of various
injection parameters on exhaust chemistry species and LNT performance
are discussed. Results indicate that fuel chemistry does affect
engine-out hydrocarbon (HC) species, but not engine-out carbon monoxide
(CO) or hydrogen (H2) generation. Higher engine-out CO and
H2 correlate to improved NOx reduction,
irrespective of HCs. |
