The next stage of the IMO emission standards (Tier III) requires the reduction of nitrogen oxide emissions compared to current engine designs from 2016 by 75% in coastal and designated areas. But IMO Tier II limits continue to apply on the open sea. Against this background, SCR and exhaust gas recirculation got into the focus of marine engine designers. While the switching between the different modes of operation with an SCR catalyst can be regulated by a bypass, the switching is more difficult with an EGR concept. Nevertheless, there is a desire to use the EGR technology in order to avoid a further operating fluid and the large volume of an SCR catalyst. The approach presented in this paper includes two-stage turbo charging with an EGR turbocharger as additional EGR pump. For switching between operating modes, all three charging units need to be coordinated. Simple switching without any additional control leads to extremely high peak cylinder pressures above the mechanical limit. Therefore additional switching control needs to be provided to ensure safe engine operation and an optimal operating range of the charging units. To ensure a good predictive quality for the analysis a DI-jet-model for the prediction of the net heat release rate which was further developed during the research work is used. Furthermore a refined approach for the estimation of nitrogen dioxides, which uses empirical relations for the influence of different operation parameters to estimate the nitrogen dioxide emissions based on one baseline operation point, is used In this study possible strategies including higher variability for the charging system, such as the use of a turbine bypass or variable turbine geometry, and variable valve timing are analyzed and compared critically. However, current engine designs already have cam phasing technologies to switch to low soot operation at low engine load by delaying the inlet valve closing. These can also be used for the switching between IMO Tier II and Tier III operation modes. Therefore the necessity of a fully variable valve actuator and the potential of a simple cam phasing are discussed. Furthermore the benefit of using variable turbine geometry in IMO Tier III operation compared to a simple turbine bypass will be shown.


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    Title :

    Strategies for switching between ECA and nonECA operation for a medium-speed diesel engine with EGR


    Contributors:


    Publication date :

    2013


    Size :

    12 Seiten, 26 Bilder, 9 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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