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Unregulated Emissions with TWC, Gasoline & CNG

Journal Article
ISSN: 1946-3936, e-ISSN: 1946-3944
Published April 12, 2010 by SAE International in United States
Unregulated Emissions with TWC, Gasoline & CNG
Citation: Czerwinski, J., Heeb, N., Zimmerli, Y., Forss, A. et al., "Unregulated Emissions with TWC, Gasoline & CNG," SAE Int. J. Engines 3(1):1099-1112, 2010,
Language: English


Analysis of non-legislated engine-emission components, with different exhaust-gas after-treatment techniques, is an important air quality objective.
This paper reports the results for various nitrogen oxides, ammonia and differentiated hydrocarbons emitted at part load from a small 4-S SI engine. It was operated with gasoline, with CNG and with two different three-way catalytic converters.
CNG produces less HC and less aromatics. But the HC conversion rate is insufficient. This is due to the lower exhaust gas temperatures, at part load with CNG, and due to the higher stability of light HCs.
CNG affects the λ-regulation window, of the investigated system, such that the NOx conversion rate is lowered.
In the rich domain of the λ-regulation window, the NO & NOx emissions after catalyst were lowest, while the NH₃ formation was most intense, and vice versa.
The catalyst type: precious metal, and its content, influences the conversion rates and emissions of the investigated components during light-off.