Research On Vibration Characteristics Of Ship Propulsion Shaft System Based On Dynamic Lubrication Characteristics Of Bearings

The propulsion shafting is not only the transmission and output device of the ship’s main power,but also the main source of vibration when the ship is running.Due to the limitation of design and manufacturing level,the domestic ship propulsion shafting system generally has the problems of large vibration and noise of the shafting system and poor running stability.Therefore,it is necessary to conduct an in-depth study on the vibration characteristics of the propulsion shaft system based on its specific structure and material properties.The bearing is one of the most critical structures on the propulsion shafting,and its bearing performance and arrangement have a significant impact on the shafting vibration.The main types of shaft bearing are divided into thrust bearing and radial sliding bearing.In this paper,the simulation of scaled shafting is taken as the main analysis object.Combined with relevant numerical analysis software,the influence of bearing stiffness,support position and support length on the vibration of propulsion shafting is studied,and the interaction between bearing non-linear bearing characteristics and shafting vibration response is analyzed.The longitudinal and transverse coupling vibration characteristics of the shafting under different factors are explored.The details are as follows:(1)Referring to the actual ship shafting,the appropriate reduction ratio is selected to plan and design the simulation scale bench of the propulsion shafting.The obtained gantry is similar to the original shafting dynamics and statics.Based on this model,the longitudinal and transverse vibration analysis model of the propulsion shafting can be established.(2)According to the specific action form of the bearing in the propulsion shafting,the vibration characteristics of the longitudinal and transverse vibration of the propulsion shafting are analyzed from the aspects of exciting force loading,bearing stiffness,support point position and support length.The results show that different bearing stiffness and configuration can significantly change the natural frequency and vibration response of the shafting.(3)Taking the tail bearing as the research object and based on the fluid dynamic pressure lubrication theory,the calculation method of the bearing equilibrium position and the liquid film bearing stiffness is proposed.The interaction between the vibration of the propulsion shafting and the bearing load-bearing characteristics is studied.The results show that the vibration of the propulsion shafting will cause the fluctuation of bearing load-bearing capacity,and the vibration response under the non-linear condition is stronger than that under the linear condition.(4)According to the principle of longitudinal-transverse coupling of shaft elements,the model of longitudinal-transverse coupling vibration analysis of propulsion shafting considering alignment factors is established and studied.It is concluded that there exists energy leakage of longitudinal and transverse vibration when alignment factors are considered,and the vibration response is more obvious.