Modern diesel engines employ a multitude of strategies for oxides of nitrogen (NOx) emission abatement, with exhaust gas recirculation (EGR) being one of the most effective technique. The need for a precise control on the intake charge dilution (as a result of EGR) is paramount since small fluctuations in the intake charge dilution at high EGR rates may cause larger than acceptable spikes in NOx/soot emissions or deterioration in the combustion efficiency, especially at low to mid-engine loads. The control problem becomes more pronounced during transient engine operation; currently the trend is to momentarily close the EGR valve during tip-in or tip-out events. Therefore, there is a need to understand the transient EGR behaviour and its impact on the intake charge development especially under unstable combustion regimes such as low temperature combustion.This study describes a zero-dimensional EGR model that enables the estimation of transient (cycle-by-cycle) build-up of EGR and the time (engine cycles) required to reach steady-state EGR operation (intake/exhaust concentrations). The model response is tuned to a multi-cylinder engine by using an overall engine system time-constant. The effect of EGR on the cylinder charge has been examined in terms of the intake charge dilution and the excess-air ratio. The intake dilution has been empirically shown to provide a reliable quantitative measure of the EGR effectiveness in reducing NOx emissions. The EGR analysis is validated against a wide range of engine operations.


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    Title :

    Transient Build-up and Effectiveness of Diesel Exhaust Gas Recirculation


    Additional title:

    Sae Int. J. Engines


    Contributors:
    Tjong, Jimi (author) / Asad, Usman (author)

    Conference:

    SAE 2014 World Congress & Exhibition ; 2014


    Published in:

    Publication date :

    2014-04-01


    Size :

    11 pages




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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