Marine Engineering
Online ISSN : 1884-3778
Print ISSN : 1346-1427
ISSN-L : 1346-1427
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SPECIAL ISSUE : How Much Do We Need to Improve Technology to Achieve Hydrogen-based Marine Society?
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SPECIAL ISSUE : Potential of VR/AR/MR in Marine Engineering
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  • Toshimichi Fukuoka, Masataka Nomura, Ami Nakada
    2019 Volume 54 Issue 5 Pages 758-764
    Published: September 01, 2019
    Released: September 21, 2019
    JOURNALS FREE ACCESS

     Recently, low temperature fluids are used more commonly, and consequently, leakage related accidents become crucial issues. These accidents are mainly due to significant shrinkage of pipe flange connection elements. It has been reported that leakage accidents often occur when low temperature fluids start to flow, or when the flow rate starts to decrease. This is because under these circumstances, the clamping force in bolts connecting a pair of pipe flanges is presumed to decrease significantly. In the previous paper, a numerical approach based on Finite Element method (FEM) was proposed to simulate a simpler flow condition than those in actual pipelines. In this paper, the numerical approach is applied to more realistic conditions by enabling the surface of low temperature fluids to move up and down. When using liquid nitrogen, the bolt force was reduced to less than 40% of its initial value shortly after the fluid started to flow. When applying the numerical method to an LNG pipeline, it was found that the bolt force momentarily showed a significant reduction as was the case with liquid nitrogen.

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  • Yoshifuru Nitta, Yasuhisa Ichikawa, Koichi Hirata, Yudai Yamasaki
    2019 Volume 54 Issue 5 Pages 765-772
    Published: September 01, 2019
    Released: September 21, 2019
    JOURNALS FREE ACCESS

      Marine lean burn gas engines use natural gas as a fuel and contribute to reducing both NOx and CO2 emissions. On the other hand, the slipped methane which is the unburned methane emitted from the marine lean burn gas engines may have an impact on global warming. Palladium (Pd) catalysts for CH4 oxidation are considered to be one of the most effective means to suppress the slipped methane from lean burn gas engines because they are still active in the lower exhaust gas temperature. However, recent studies have shown that water vapor (H2O) inhibits CH4 oxidation on theses catalysts and deactivates their oxidation capacity. When using Pd catalysts for an exhaust gas aftertreatment in order to reduce the volume of slipped methane from lean burn gas engines, we need to overcome the issue of these catalysts deactivation at the time of higher H2O concentration. This paper explored conditions necessary for sound operations of marine lean burn gas engines by investing possible impacts of the temperature and composition of simulated exhaust gas and characterization of Pd catalysts on their CH4 oxidation performance. Our case study also producedan appropriate geometric size as a design parameter for a CH4 converter to be installed on a marine lean burn gas engine to reduce the slipped methane.

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