Dependence between nonvolatile nucleation mode particle and soot number concentrations in an EGR equipped heavy-duty diesel engine exhaust

T. Lähde (Corresponding Author), T. Rönkkö, A. Virtanen, A. Solla, Matti Kytö, Christer Söderström, J. Keskinen (Corresponding Author)

    Research output: Contribution to journalArticleScientificpeer-review

    50 Citations (Scopus)

    Abstract

    Heavy duty diesel engine exhaust characteristics were studied with direct tailpipe sampling on an engine dynamometer. The exhaust particle size distributions, total particle mass, and gaseous emissions were measured with different load conditions without after-treatment. The measured particle size distributions were bimodal; distinctive accumulation and nucleation modes were detected for both volatile and dry particle samples. The condensing volatile compounds changed the characteristics of the nonvolatile nucleation mode while the soot/accumulation mode characteristics (concentration and diameter) were unchanged. A clear dependence between the soot and the nonvolatile nucleation mode number concentrations was detected. While the concentration of the soot mode decreased, the nonvolatile nucleation mode concentration increased. The soot mode number concentration decrease was related to soot-NOx trade-off; the decrease of the exhaust gas recirculation rate decreased soot emission and increased NOx emission. Simultaneously detected increase of the nonvolatile nucleation mode concentration may be caused by the decrease of the soot mode sink or by changed combustion characteristics. However, the total particle number concentration increased with decreasing soot mode number concentration. The proportion of the particle number concentration between the nonvolatile nucleation and soot mode followed the NO2:NO ratio linearly. While ratio NO2:NO increased the proportion of soot mode number concentration in total number concentration increased. Regardless of the mechanism that causes the balance between the soot mode and the nonvolatile nucleation mode emissions, the changes in the particle number size distribution should be taken into account while the particle mass emissions are controlled with combustion optimization.
    Original languageEnglish
    Pages (from-to)3175-3180
    JournalEnvironmental Science & Technology
    Volume44
    Issue number8
    DOIs
    Publication statusPublished - 2010
    MoE publication typeA1 Journal article-refereed

    Keywords

    • diesel engine exhaust
    • diesel engines
    • diesel exhaust
    • heavy-duty vehicles

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