The results of the joined research project presented in this paper demonstrate the potential of common rail injection systems to implement flexible injection strategies for significantly reduced smoke emissions of marine diesel engines even at conditions of air deficiency. Fuel spray analyses at a pressurised research chamber show that increasing the rail pressure improves the fuel distribution inside the combustion chamber. The higher injection impulse leads to increased spray lengths without significantly reduced spray cone angles. The spray volumes grow leading to better mixing of fuel and air. The expected reduction in soot generation is confirmed by the results of the soot measurements at the test engine. An improved soot oxidation can be obtained by intensifying the transport processes inside the combustion chamber or by increasing the combustion temperature during the final combustion period. This can be reached by increasing the injection pressure or by application of a post injection. An increased injection impulse takes effect up to the late periods of combustion leading to a more even fuel distribution inside the cylinder and, consequently, to a better utilisation of the air available. The injection impulse of a post injection increases the turbulence and improves the mixing processes in the cylinder volume. At the same time, the late combustion of the post injection fuel increases the temperature during the final combustion periods which also intensifies the soot oxidation. The preconditions for a reliable operation of SCR(Selective Catalytic Reduction)-catalysts at medium speed diesel engines running on marine fuels can be greatly improved by the application of modern common rail injection systems. On the one hand, the CR (Common Rail) system allows the reduction of soot and particulate emissions especially during periods of low or transient engine load. These emissions cannot be treated by the SCR system. Soot and particle emission reduction can be obtained by adjusting the rail pressure or applying post injection to improve the soot oxidation process. On the other hand, post injection strategies could become necessary to elevate exhaust gas temperatures during low load engine operation, especially if SCR systems are combined with IMO (International Maritime Organization) Tier 2 diesel engines which feature 2-stage turbo charging. The dynamic properties of the injector play an important role for the application of multiple injections. Substantial research is necessary to transfer the smoke reduction methods described in this paper to HFO (Heavy Fuel Oil) combustion. The influence of fuel quality and fuel quality variations on combustion processes with pre and post injections are largely unknown and need to be analysed. Currently, further research activities with further improved injectors are under way to utilise the potential of directly-actuated common rail injectors for the combustion of HFO.


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    Titel :

    Flexible CR-injection to reduce soot and particle emissions from medium-speed diesel engines. A precondition for reliable exhaust gas treatment


    Weitere Titelangaben:

    Flexible Common Rail-Einspritzung zur Verringerung von Ruß- und Partikelemiisionen von mittelschnelllaufenden Dieselmotoren - eine Vorbedingung für eine zuverlässige Abgasbehandlung


    Beteiligte:


    Erscheinungsdatum :

    2007


    Format / Umfang :

    18 Seiten, 15 Bilder, 20 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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