Torsional Vibration Calculation Of Branched Propulsion System With High Power Output

Ship propulsion shafting is an important part of marine power plant,including the transmission shaft which is from the Main Engine outputthrust bearing to the propeller and the shafting attachment. In thenavigation, complex loads are acting on the propulsion shafting, thus theshafting torsional vibration is an important factors affecting the reliabilityof ship power plant. If the shafting is always working in the dangerouscritical speed region, it may lead to shafting dynamic performancedeclining, shafting distortion and fatigue invalidation, or even shaftingbroken. These all affect the ship navigation performance and security, sothe study of shafting torsional vibration calculation (TVC) has greatsignificance.TVC algorithm and modeling are improved according to thecharacteristics of propulsion system with high power output. And TVCsoftware is developed according these two aspects.The improvements on the modeling include the following aspects.First, the controllable pitch propeller’s excitation torque with high orderparts under all pitches is calculated by the steady surface panel method.Second, the traditional gear box modeling method is improved that boththe gear mesh stiffness and the excitation caused by gear meshing aretaken into account which make the modeling more meticulous. Theequation calculating the stiffness of shaft filling hydraulic oil is introducedunder structural mechanics and viscous fluid theory which fill the blank ofthe standards rule.The improvements on the algorithm include the following aspects.The transfer matrix method’s defect in calculating the branched shaft isdiscovered and studied. The reasons that cause the natural frequencyabsence in free vibration calculating are discovered by both theory sideand example comparison. Then the transfer matrix method is improved.The validity of the improved transfer methods is verified by calculating the propulsion system of an example.A TVC software which includes the improved feature above isdeveloped through the VB.net and matlab. The UI and input part aredeveloped by VB.net and the solver part is developed by matlab. As the UIand solver are separated, VB.net can play its advantage in UI and matlabcan play its advantage in matrix and numeric calculation. A branchedpropulsion system with high power output is calculated by this softwareand a certain software certificated by the ship classification society. Thedeviations between the results computed by the two software areacceptable.The study in this thesis improves traditional TVC in ship criterionand expands its application scope. It also offers sufficient theoretical andapplied support for TVC of complex branched shafting system with highpower output to ensure its reliability.