In the present paper are illustrated the main results of a research programme based on the analysis of the effect of different EGR (Exhaust Gas Recirculation) layouts on the performance, emissions and particle size function of an automotive engine, operating with conventional diesel and premixed combustion calibration. The results highlighted the improvement of LPEGR (Low Pressure EGR) system with respect to the classical HPEGR (High Pressure EGR) one in terms of emission and FC (Fuel Consumption). The comparison between LPEGR and HPEGR circuit in terms of PSDF (Particle Size Distribution Function) characteristics has confirmed some relationships already reported in the literature and has highlighted some interesting characteristics of the LPEGR operating mode. With engine running in conventional diesel mode, the advantages of LPEGR with respect to HPEGR in terms of NOx emission and FC are evident with a marked increase in soot mass and particle number, centred towards higher mean diameter. Notwithstanding, the DPF shows always a very high efficiency (up to 99.8%) in all conditions. However, the penalty of LPEGR should be further checked also taking into account the DPF regeneration process. When in-cylinder PCCI (Premixed Charge Compression Ignition) combustion conditions are performed, the LPEGR system exhibits high benefits on both NOx and PM (Particulate Matter), including PSDF shape that shows a simultaneous reduction in total number and mean particle diameter that always lies in the range of the accumulation mode. From this point of view, LPEGR system seems to be a good solution to decrease NOx, PM mass and particle number. It was observed that with the adopted engine calibrations, all measured particles fall within the accumulation mode range (30-100 nm), and only a small fraction of particles were detected in the nanoparticle range. Specific test at constant EGR rate and varying the ratio between LPEGR and HPEGR flow put into evidence that there is no effect of the in-cylinder recirculated particles from the HPEGR flow on the PSDF shape measured at the engine exhaust. It is conceivable that the most of the recirculated particles are burned during the combustion process. The correlation analysis between PSDF characteristics and dry soot measured by Microsoot sensor confirms the relationship between total particle number and mean particle diameter reported in other literature papers, while a very good correspondence was evidenced between measured soot mass and calculated mass from PSDF through an empirical equation. The trends between total number, mean particle diameter and soot mass were in-line with past observations reported in the literature. Both the total particle number and the mean particle diameter tend to increase for higher soot emissions, but particles always fall within the range of the accumulation mode. It was highlighted that PSDF characteristics detected at the engine exhaust in terms of shape, total number and mean diameter are influenced by the complex in-cylinder processes that control the combustion and that they are engine layout architecture and engine conditions dependent. As an example, the presented results demonstrated that, depending on the engine layout, the influence of lambda and EGR on PSDF is not uniquely known. It was pointed out that the continuous evolution of the LD diesel engine technology, like the LPEGR system in the present case, always opens new opportunities in controlling the pollutant emission, not only in terms of regulated pollutants (NOx, PM mass, etc.), but also on the emerging issues such as the emitted particle number and relative size.


    Zugriff

    Zugriff über TIB

    Verfügbarkeit in meiner Bibliothek prüfen

    Bestellung bei Subito €


    Exportieren, teilen und zitieren



    Titel :

    Soot particle size and pollutant emissions characterisation from an LD diesel engine equipped with high-pressure and low-pressure EGR system and operating with conventional and PCCI combustion


    Weitere Titelangaben:

    Partikelgröße und Charakterisierung der Schadstoffemission eines LD-Dieselmotors mit Hochdruck- sowie Niederdruck-Abgasrückführung und einer konventionellen sowie PCCI-Verbrennung


    Beteiligte:

    Erschienen in:

    Erscheinungsdatum :

    2012


    Format / Umfang :

    22 Seiten, 20 Bilder, 2 Tabellen, 26 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch