engleski

New Possibilities of Reducing NOx Emissions in Direct Fuel Injection Otto Engines

Advanced development of motor vehicles has a very important task of reducing the fuel consumption as well as the emissions of harmful components. Recently, the direct fuel-injection system has been introduced into the Otto engine propelled motor vehicles enabling engines running on lean mixture, resulting in reduced fuel consumption. However, the engines running on lean mixtures makes it impossible to use the three-way catalysts which, used in conventional Otto engines that use stoichiometric mixture, very efficiently reduce the emission of all the three harmful components (CO, HC and NOx) contained in the exhaust gases. Therefore, the direct injection Otto engines require another solution for reducing the harmful components in the exhaust gases, primarily referring to nitrogen oxides (NOx). In case of engines running on lean mixtures, the most difficult thing is to reduce the emission of nitrogen oxides. Diesel engines use the oxidation and denox catalytic converters, which reduce NOx emissions to a lesser extent (up to 20 %). In combination with the exhaust gas recirculation (EGR) and denox catalytic converters the reduction of NOx emission of up to 50 % can be achieved. Recently, in order to improve the efficiency of reducing the NOx emissions on vehicles with direct fuel injection engines, adsorber catalytic converters have been developed. They allow adsorbing of nitrogen oxides during engine lean mixture operation, and when the engine is running on the stoichiometric mixture, they release nitrogen oxides, which are subsequently efficiently reduced in the catalytic converter. This article deals with most important characteristics of the NOx-adsorber catalytic converters in use on direct fuel injection Otto engines.

NOx; Emission; Otto Engine

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