Propulsion shaft alignment of large vessel is sensitive to draft change from light draft to full load draft. Each initial bearing offset of the shaft alignment changes by the fluctuation of draft level. Especially, it presents vessels such as VLCC and large bulk carrier. The reasons include a propulsion shaft diameter stiffer and an engine main bearing center distance shorter. Those correspond to engine development trend of higher power and more compact size. The initial bearing offset change affects each bearing performance. In some cases, the change causes sever trouble to an engine and propulsion shaft. It is necessary to estimate an engine crankshaft and propulsion shaft alignment against a draft change for both engine development trend and improving reliability of bearings and shafts. Our past study was mainly focused on engine bearings in service condition. Before in service, it is indispensable for users to estimate reliability both of engine and propulsion shaft alignment against a vessel deformation and engine thermal expansion. So, an evaluation method of both engine and propulsion shaft alignment has developed for large vessel such as VLCC and bulk carrier. Input parameters are a vessel deformation information and an engine thermal expansion data. The vessel deformation is able to be given by a vessel deformation result by a FEM analysis, a directly measurement result of shaft alignment of a similar vessel or an inverse calculation result of shaft alignment of a similar vessel by using our developed software. In this study, an inverse calculation result is used. The evaluation values are conventional shaft alignment calculation values and engine crankshaft values. The conventional shaft alignment values include bearing load, propulsion shaft angle at stern tube bearing, shaft bending moment and shaft bending stress. The engine crankshaft values are crankshaft deflection and bearing load. Calculation parameters are intermediate shaft bearing height, engine bearing height and engine inclination, which are decided by a vessel deformation and an engine thermal expansion. The calculation procedures are as follows. (1) A certain shaft alignment for initial condition is set. (2) Shaft alignment after considered a vessel deformation for a vessel draft condition and an engine thermal expansion is calculated. (3) Output values are calculated. (4) Each output value is estimated whether to meet or not with permissible values (5) Permissible vessel deformation and draft level is solved. By calculating the shaft alignment including the whole range of designed draft level, allowable shaft alignment area is able to be solved. The validity of this method is confirmed that the already serviced vessel data are enough for reliability within the allowable area. It is also confirmed that the vessel deformation and engine thermal expansion influence mainly engine aft side bearing. A stern tube bearing performance is determined by initial installation and is not influenced by a vessel deformation and engine thermal expansion. Finally, it is clarified that a conventional design is essential for the stern tube bearing, and it is necessary for engine bearing to consider a vessel deformation. At a vessel under construction, this method is able to indicate the allowable value of intermediate shaft bearing height, engine bearing height and engine inclination. And for in-service vessel, by using the inverse shaft alignment calculation, safety margin of shaft alignment against vessel deformation is able to be indicated.


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    Titel :

    Evaluation method of engine and propulsion shaft alignment for large vessel


    Beteiligte:
    Sugimoto, Iwao (Autor:in) / Nakao, Toru (Autor:in)


    Erscheinungsdatum :

    2010


    Format / Umfang :

    8 Seiten, 12 Bilder, 4 Tabellen, 4 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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