Dimensioning of marine propulsion shafts

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Examensarbete för masterexamen
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2021
Författare
Gunnarsson, Gudni
Sigurdsson, Sindri
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Dimensioning of marine propulsion shafts for new builds is done early in the design phase of a vessel. Thus, often the designer only has the main particulars of the vessel including the general size and power requirements, as well as the intended purpose of the vessel. With the limited information, a shaft line needs to be dimensioned which is fit for purpose, fulfils class requirements as well as showing good vibrational behavior. Until now this has been done safely and successfully using old principles and fundamentally relying on a single formula that is recognized by all the major classification societies for giving a safe design. This method has been shown to give very reliable designs but is however believed to result in overly dimensioned components. By utilizing expertise, access to good data, and a systematic approach in behavior analysis, it is believed to be possible to step away from current methods and provide slimmer and more power-dense shaft lines. This thesis describes the underlying theory of rotating machinery often summarized as rotor dynamics. A comprehensive study of classification rules and requirements governing the design of marine propulsion shafts. Case studies of typical shaft lines for different types of vessels, for those a software tool from DNV-GL is used to simulate the shaft behavior. The simulation software Nauticus Machinery available from DNV-GL is a specialized marine shaft line analysing software, containing few different tools. The tools used during this thesis work are Nauticus Shaft Alignment, Nauticus Torsional Vibration, and approved formulas and equations from classification societies. Using this combination of software and formulas the writers evaluate an improved method to define the minimum shaft diameter.
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propulsion shaft, whirling, torsional vibration, shaft alignment, shaft dimensioning, classification societies
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