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    Comparative analysis of metal oxide nanoparticle accumulation in landfill gas engine combustion chambers: Insights from three sites
    (Pergamon-Elsevier Science Ltd, 2025) Somek, Ozge Osturk; Yildiz, Fikret; Sevimoglu, Orhan
    Combustion chamber deposits adversely affect the operating performance of gas engines. In this study, the elemental composition of deposit samples collected from the inner surface of combustion chambers in gas engines across three different facilities was examined using various methods. The proportional changes in metal oxides along the internal cross-sectional surfaces of the deposits were examined to depict the deposit formation process from beginning to end. Additionally, the study investigated the identification of metals accumulated in the engine oil, their contribution to deposit formation, and the accumulation mechanisms of metal oxide nanoparticles on the engine's interior metal surfaces. The main elements identified in the deposits from the Odayeri and Kom & uuml;rc & uuml;oda facilities were Si, S, and Ca, whereas deposits from the Dilovas & imath; facility contained Si and Sb. These major elements, identified by SEM-EDS, were confirmed through XRF analysis. XRD analysis further confirmed the presence of Ca and S as CaSO4 crystals in the deposits. Ca originates from additives used to increase the total base number of engine oil and control the corrosive effects of landfill gas. It has been determined that silicon accumulates in engine oil over time. An important finding is that metal oxides in the combustion chamber primarily accumulate through impaction, sticking, and thermophoresis mechanisms.
  • [ X ]
    Öğe
    Comparative determination of the time-dependent accumulation of metal oxides in the landfill gas combustion chamber deposits using SEM-EDS, XRF and ICP OES
    (Elsevier, 2024) Sevimoglu, Orhan; Somek, Ozge Osturk; Yildiz, Fikret
    Non-purified landfill gas (LFG) leads to the formation of complex deposits in combustion chambers due to impurities such as siloxanes, sulfur compounds, and organometallic compounds containing elements such as Si, S, Sb, Sn. This study focused on identifying the elemental composition of deposits from four combustion chambers using analytical techniques including SEM-EDS, WDXRF, and microwave digestion ICP OES. The dominant element, Si, with concentrations (wt%) in the deposits was measured by SEM-EDS, ICP-OES, and WDXRF, respectively, as follows: 17.04 +/- 8.59, 21.89 +/- 4.39, and 16.63 +/- 0.94 for cylinder head deposits, and 13.28 +/- 6.97, 15.40 +/- 5.40, and 12.64 +/- 1.64 for piston head deposits. Excluding C, O and N, which could not be analyzed by all three techniques, the multi-analytical approaches demonstrated strong correlations between EDS results and those obtained from WDXRF and ICP OES, with R-2 values of 0.9173 and 0.9002 for cylinder head deposits, respectively. It was also revealed that the elemental composition of deposits varied between combustion chambers. The average mass fractions of all deposit surfaces were ranked as follows for elements exceeding 1 %: O (45.38 %) > Si (16.67 %) > Ca (9.87 %) > Sb (7.21 %) > S (5.98 %) > Sn (3.51 %) > C (2.83 %) > P (2.35 %). Elements below 1 % were ranked as: Na (0.91 %) > N (0.80 %) > Al (0.74 %) > Fe (0.48 %) > Mg (0.30 %). Consequently, the multi-spectrometry analysis approach provides a more comprehensive understanding of the deposit composition, enabling the determination of primary contributors and the most elements. Future studies may involve more general determining the concentrations of organometallic compounds in the LFG, which are the source of the elements found in the deposit.