Vibrational characteristics of a marine shaft coupling system excited by propeller force

Marine propulsion shafting system subjects to various shocks and cycle exciting forces in actual operation. The propeller excitation is an important the marine shafting vibration excitation sources. In this paper, the finite element method is used to calculate a ship propulsion shafting vibration responses under the propeller bearing forces. Propeller bearing forces can be decomposed into components in three directions of forces and three directions of moments, wherein the periodic propeller excitation will cause the longitudinal vibration, torsional vibration and whirling vibration of marine shafting. The mathematical equations governing the dynamics of the circular shaft of regular constant section are derived. Compared with the free vibration systems, it is found that adding the propeller exciting force can greatly change the frequency band for marine shafting vibration isolation

Analysis of longitudinal vibration power-flow in marine propulsion shafting system

Serving as the heart of ship, marine propulsion system is the most important power source. The longitudinal vibration power flow in the marine propulsion shaft-line is investigated theoretically and experimentally in this paper. The longitudinal vibration power flow analysis on marine propulsion shaft-line has been implemented using governing equations of continuum mechanics. In developing the mathematical model of marine propulsion shaft-line, the longitudinal vibration is defined theoretically. The concept of energy flow density and energy flow line are introduced in the models. A simulation model has been established to describe the properties of the longitudinal vibration power flow in the marine propulsion shaft-line. Analysis results show that the power transmission trend is along the shaft-line in longitudinal vibration. The total longitudinal vibration power flow predicted by the developed model was also compared with that tested using a MetaPower device. It was shown that the developed model provides a more accurate prediction of the total longitudinal vibration power flow of marine shafting in the frequency range of interest

Comparison of measured and calculated water film thickness of a water-lubricated elastically supported tilting pad thrust bearing

A xenon induced fluorescence technique is used to measure the water film thickness of a rubber-supported water-lubricated tilting pad thrust bearing (RWTB). Film thickness maps are obtained over a range of speeds and loads. Based on a Thermo-Elasto-Hydrodynamic lubrication model, the calculated film thickness is compared with the measured one. The measurement shows that the lubrication regime of the RWTB can be observed and it can form a convergent wedge of lubricant. The calculated results are on par with the experimental results at low speed condition (200 r·min-1). Generally, the calculated film thickness is larger and the discrepancy between them increases respecting to the speed. The RWTB is in the hydrodynamic lubrication regime when the speed is over 200 r·min-1 and the load is less than 0.25 MPa. The comparison between the measurements and calculations verifies that the fluorescence technique can be used to measure the film thickness of water-lubricated thrust bearings

Review of the evolution and prevention of friction, wear, and noise for water-lubricated bearings used in ships

Abstract With the development of green tribology in the shipping industry, the application of water lubrication gradually replaces oil lubrication in stern bearings and thrust bearings. In terms of large-scale and high-speed ships, water-lubricated bearings with high performance are more strictly required. However, due to the lubricating medium, water-lubricated bearings have many problems such as friction, wear, vibration, noise, etc. This review focuses on the performance of marine water-lubricated bearings and their failure prevention mechanism. Furthermore, the research of marine water-lubricated bearings is reviewed by discussing its lubrication principle, test technology, friction and wear mechanism, and friction noise generation mechanism. The performance enhancement methods have been overviewed from structure optimization and material modification. Finally, the potential problems and the perspective of water-lubricated bearings are given in detail