Research On The Influence Of The Stiffness Characteristics Of Sliding Bearing Liquid Film On The Coupling Vibration Of Propulsion Shafting

Propulsion shafting is the core component of marine power propulsion system,which connects the engine and propeller and occupies an important position in the whole ship structure.The operation status of shafting directly affects navigation safety and work efficiency.The sliding bearings distributed on the shafting are important supporting components.The dynamic characteristics of the bearings,especially the stiffness,have a direct and significant impact on the vibration transmission characteristics of the propulsion shafting.Studying the influence of bearing stiffness characteristics on propulsion shafting-hull coupling vibration is helpful to promote the design optimization of shafting and improve the safety performance of naval vessels,which has important theoretical and application value.In this paper,the fluid film stiffness of thrust bearings and radial sliding bearings is calculated by numerical method in combination with the lubrication theory of journal bearings in the study of coupled shafting-hull vibration.Based on this,the general shafting-hull coupled vibration model is modified,and the vibration energy transfer characteristics caused by the change of fluid film stiffness caused by the change of shafting speed are studied and analyzed emphatically.The influence can provide reference for vibration reduction design and noise diagnosis of propulsion shafting-hull coupling.Firstly,the fluid film stiffness characteristics of journal bearings are analyzed and studied by using FLUENT module in ANSYS.The fluid film stiffness of journal bearings and tilting pad thrust bearings is simulated and calculated based on the lubrication mechanism of journal bearings and tilting pad thrust bearings.Secondly,the dynamic transfer relationship of the longitudinal vibration of the propulsion shafting is analyzed,and the longitudinal vibration model of the propeller-tilting pad bearing-shafting-hull is established by applying the calculation results of the liquid film stiffness of tilting pad bearing under different working conditions and using the wave admittance method.The differential equation of longitudinal vibration is solved,and the influence of the liquid film stiffness characteristics of thrust bearing on the power flow and vibration energy of shafting system is investigated according to the method of vibration power flow.Finally,combined with the stiffness results of radial sliding bearings and thrust bearings before,the bending vibration model of propulsion shafting-hull system is established and revised.The transmission characteristics of bending vibration power flow in the transmission path composed of transmission shafting and its coupling support with hull are studied and analyzed by using MATLAB software.The radial bearings at different rotational speeds are analyzed and summarized.The influence of stiffness coefficient of thrust bearing on power flow transmission and vibration energy of shafting bending vibration.