The implementation of stringent exhaust emission regulations has led to the development of natural gas powered dual fuel systems with electronic multiport injection. The high compression ratio of the baseline diesel engine was maintained to keep the high thermal efficiency of diesel cycles. The dual fuel system is mainly powered by natural gas and ignited by a diesel pilot. Extensive experimental results indicate that the diesel dual fuel system provides simultaneous reductions in NOx and particulate emissions. The system also has low exhaust THC and CO under heavy-duty operations. With the combined use of exhaust gas recirculation and catalytic converter, low emission operation has been extended to a larger range, from medium to full loads for all testing speeds. However, conventional converters exhibit poor conversion efficiency at low engine loads due to the low exhaust temperature levels. This leads to increased exhaust emissions during low load operations, especially for the non-reactive hydrocarbons, specifically, methane. To solve this problem, a novel automotive exhaust gas aftertreatment system - the reversing flow catalytic converter - has been developed. The prototype Reversing Flow Converter (RFC) consists of a diversion flow valve and a catalytic monolith converter. The diversion valve periodically re-directs the engine exhaust flow through the catalyst in alternative directions. The duration of flow in each direction is determined by engine operating conditions to obtain an ideal temperature profile along the axis of the monolith. The catalytic converter was designed to have high methane conversion efficiency. Associated techniques, such as retarding fuel injection, exhaust gas recirculation, and the variation of diesel pilot to natural gas ratio, can be used to raise exhaust temperature and bring the catalytic converter to light-off temperatures quicker. After light-off, the RFC technique maintains adequate catalyst temperature during low exhaust temperature operations. Engine dynamometer tests showed that CO conversion rate was above 95 % and CH4 conversion was significantly improved.


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    Title :

    Novel catalytic converter for natural gas powered diesel engines to meet stringent exhaust emission regulations


    Additional title:

    Neuer katalytischer Umwandler für erdgasbetriebene Dieselmotoren zur Erfüllung der Umweltgesetzesauflagen


    Contributors:
    Zheng, M. (author) / Mirosh, E.A. (author) / Matros, Y.S. (author) / Sallamie, N. (author) / Checkel, M.D. (author) / Windawi, H. (author) / Bunimovich, G.A. (author)


    Publication date :

    1998


    Size :

    8 Seiten, 6 Bilder, 1 Tabelle, 4 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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