Study On Influence Of Large Ship Response In Waves On Propulsion Shaft

Propulsion shaft is an important component of ship propulsion system anddirectly relates to the safe sailing of a ship. During the service life of ships, workingcondition of propulsion system is affected by many factors simultaneously as hulldeformations, hydrodynamic forces from propeller and lubricating oil film etc.Among these factors, overlarge hull deformation will destroy the former shaftingalignment status and then affect dynamic property of shaft. Thus, working efficiencyand service life of propulsion system are both reduced.In recent years, with the fast development of global economy, higher frequencyof international trade and increasing demand of freight transportation, scale andtechnical parameters of main ship types as container ship and tanker etc. have beenconstantly enlarging. Consequently, some key problems become increasinglyprominent. A large-sized ship has relatively weaker stiffness so that it may result inworse hull deformation which has serious impacts on propulsion shaft. Ship in toughseas, suffering from wave load, may have greater hull deformation than that in thestill water. However, the present shafting alignment of ships does not consider hulldeformations at shaft supports. Shaft installation according to such shaftingalignment is obviously not reasonable. Therefore, shafting alignment techniqueneeds to be reassessed and improved.The emphasis of the dissertation is to calculate hull deformations underdifferent loading cases and promote a reasonable, also accurate hull deformationforecasting method.The dissertation is based on a large container ship and a large tanker. The mainwork is as follows:(1) Utilizing finite element software ANSYS, establish the whole ship finiteelement model and the hull-shaft integration model;(2) Utilizing hydrodynamic analysis program AQWA, calculate wave load withthe consideration of hydrodynamic effect, then apply to hull structure finite element model;(3) Basing on three loading cases of no-load floating, ballasted and full-loadedcase, hull deformations at shaft support under different sea statuses are calculated.Results of models with and without shaft are compared and analyzed.The dissertation demonstrates that hull deformations at shaft supports presentcertain rule and affect propulsion system in some degree. The calculation resultsoffer detailed data for improving the shafting alignment technique. The trend andmagnitude of hull deformation curve can be as a reference for estimating hulldeformation of the same or similar ship type.