Long marine shafting alignment and optimization considering propeller hydrodynamic force in wake field

Abstract

ObjectivesThe traditional method of marine propulsion shafting alignment calculation usually ignores the influence of the ship's wake field, causing a large deviation between the computational result of the propeller hydrodynamic force and the real value which results in a decline in alignment accuracy. MethodsTaking a long marine shafting as the research object, a propeller-shafting-hull integrated finite element model and its wake field model are established, and the propeller hydrodynamic force is calculated using the CFD numerical simulation method. The fluid-structure interaction method is used to apply the fluid computing results on the propeller surface for shafting alignment calculation, and the influence law of the propeller hydrodynamic force on the shafting deflection curve and the state parameters of each bearing are obtained. On this basis, in order to solve the problem of excessive load difference between the four bearings at the end of the long marine shafting, a multi-objective optimization algorithm is introduced for alignment calculation.ResultsWhen the propeller hydrodynamic force is considered, the deflection change of the shafting tail decreases. The closer to the propeller, the greater the influence of the bearing load, and the load value decreases with the increase of the advance coefficient. Comparing the alignment state of the shafting before and after multi-objective optimization, the load difference between the bearings is significantly reduced and the running state of the shafting is improved. ConclusionsThe proposed method can provide references for optimizing shafting alignment accuracy by considering the propeller hydrodynamic force.

Keywords

• marine propulsion shafting system
• shafting alignment
• wake field
• propeller-induced hydrodynamic force
• fluid-structure interaction
• multi-objective optimization