Theoretical Research And Program Development Of Propulsion Shafting Curve Alignment And Whirling Vibration

Propulsion shafting is an important part of marine power plant. The reliable operation of propulsion shafting is the guarantee of ship safety in service. Shaft alignment and whirling vibration analysis are important content of shafting design. Be aimed at the shortage of existing shafting alignment methods and to meet the needs of China's shipbuilding, it's necessary to improve the shafting alignment methods and develop calculation program of shafting alignment and whirling vibration with independent intellectual property rights.This paper puts forward the concept of the curve alignment. After curve alignment, ship shaft axis in operation basically is its deflection curve which meets the need of design, and installing the bearings conforms to the deflection curve. Shafting deflection is not the inducement of whirling vibration. The deflection value and the rotation value of the deflection curve don't have any limit. The load on bearings will be well-distributed. Thus curve alignment can basically eliminate the partial wear of bearing itself.According curve alignment, the relative angle limit value of shaft and the bearing hole is too large, needs to be stricter than 3.5×10-4rad defined by the existing ship standard CB/Z 338-2005.In order to get the relevant parameters and deflection curve needed by curve alignment, the calculation principle of the transfer matrix method and its application in shafting alignment are introduced. Using the transfer matrix method, calculation program of shafting alignment is developed based on MATLAB. Using the calculation program, this paper carries out shafting alignment to two shafting calculation examples and gets a series of parameters including bearing displacement, bearing load, influence coefficient of bearing load, jack-up factor, shafting deflection, shafting rotation, shafting bending, shafting moment and shafting shear. By doing this calculation ability of this program is proved. Meanwhile by comparing the results to the results from other programs, its accuracy and reliability are tested. The effect of propeller thrust, axis tilt, bearing span and aft stern tube bearing deflection on shafting alignment is also discussed. This discussion provides theoretical support to optimize shaft alignment calculation and shafting design.Based on the concept of curve shafting, lumped parameter unit- distribution parameter unit hybrid system model is established for whirling vibration calculation. Calculation program of the shafting whirling vibration natural frequency is developed on the platform of MATLAB using Prohl transfer matrix method and Riccati transfer matrix method. Application to two shafting calculation examples proves the accuracy of this program. The effect of bearing stiffness and the propeller attached water effect etc on characteristic of whirling vibration is also analyzed.In addition, static simulation and dynamic simulation are conducted by ANSYS and ADAMS. It provides new verification idea to shafting alignment calculation and whirling vibration analysis. It has important significance to optimize shafting design and prevent shafting failure.