Research On Shafting Alignment Of Large Vessel Based On The Comprehensive Effects Of Multi-factors

Ship propulsion shaft connect with main engine and propeller, play a role of transfer the power of main engine and pushing the ship forward, the effects of shafting alignment have a significant influence on the stable and long-term operation. With the appearance of the Very Large Crude Carrier (VLCC), container ship, LNG ship, the rigidity of ship hull reduce and the rigidity of shafting rise, the effects which are neglected in the past have become the main factors of shafting alignment and must take them into consideration in the calculation.This paper takes the detail study of theory and factors of ship propulsion shafting alignment and the results are listed below.Deduce the formulas of Finite Element Method (FEM) and Transfer Matrix Method (TMM), develop the software of ship propulsion shafting alignment with MATLAB and VB.NET.This paper takes the shafting of one tanker into consideration, fore important factors are analyzed:hull deformation, the stiffness of supports, changes in temperature and force of gears.(1) First, this paper calculates the hull deformation and analysis the influence of hull deformation. Hull deformation has a significant influence on the shafting alignment, it must be taken into consideration for the VLCC or ULCC; the middle bearing is the most sensitive for the hull deformation.(2) Then, this paper calculates the oil stiffness and know the influence of oil could not be ignored. This paper coupled analysis of bearing elastic deformation and pressure of oil film, gets the most realistic rigidity of bearing oil film. The uniform regulation of bearing forces can be done when the oli film is considered and guarantee the safety and stable operation of ship shafting.(3) Then, take the environment of shafting installation into analysis. The environment of shafting installation have an important influence on the Aft sterntube bearing, Fwd sterntube bearing, middle bearing, Aft gear bearing, Fwd gear bearing. In china, the report of shafting alignment which contains different install season (summer or winter) must be given to shipyard.(4) Last, take the influence of gear into analysis. The size and direction of the gear force is different by comparing with the normal situation; with the effects of gear force, the force of Fwd gear bearing reduces, it may case the situation of unjoint in the danger, which has a significant bad influence in the stable run of the shafting.