| As the core component of the ship’s propulsion shaft system stern bearing,its operating condition is directly related to the ship’s mobility,safety and reliability.The lubrication characteristics and dynamic characteristics of the stern bearing under different operating conditions have been a hot issue of interest to scholars at home and abroad.This paper takes the stern bearing of a type of bulk carrier propulsion shaft system as the research object.Firstly,established the stern bearing oil film mesh model and numerical solution model based on the stern bearing structural parameters and the basic analysis theory of fluid lubrication.Secondly,in order to analyze the influence of different working condition parameters and lubricating medium physical parameters on the stern bearing steady-state lubrication characteristics,the boundary conditions are established according to the stern bearing actual operating conditions and the stern bearing lubrication flow field distribution is solved.Thirdly,the journal misalignment stern bearing trajectory calculation model is established for calculating the trajectory of the stern bearing under different transient loads and the changes in the transient lubrication characteristics.Finally,based on the study of transient lubrication characteristics,the stern bearing dynamic characteristic solution model is established,and the influence of journal axial motion on the stern bearing dynamic characteristics under different journal inclination angles and journal speeds is explored.The main conclusions of this paper are as follows:(1)The oil film pressure distribution law of the stern bearing in stable operation is: the peak oil film pressure area is mainly concentrated in the vicinity of the minimum oil film thickness,the oil film pressure gradually increases in the gap convergence area,and reaches the maximum pressure before the minimum oil film thickness position.In the gap dispersion region,the oil film pressure gradually decreases,when the oil film pressure is less than the cavitation pressure,the oil film ruptures and precipitates gas,forming an air-steam mixing zone.(2)For the stern bearing steady-state lubrication characteristics: journal misalignment angle,journal speed,oil pressure,oil viscosity and other parameters on the misalignment journal stern bearing steady-state lubrication characteristics have a large impact.Among them,journal misalignment angle mainly affects the axial position of the peak oil film point,journal speed mainly affects the peak oil film pressure and bearing load capacity,oil feed pressure mainly affects the overall oil film pressure and cavitation area,and oil viscosity mainly affects the overall oil film pressure,cavitation area and bearing load capacity.(3)For the stern bearing transient lubrication characteristics: when the stern bearing is disturbed by the transient load,the bearing lubrication characteristic parameters and the axial velocity change greatly and show a certain oscillation process until the axis converges to the equilibrium position again.The influence of transient load on the stern bearing working state is transient,and the step load can make the axis converge to the new equilibrium position.In the process of axis convergence to equilibrium position under transient load,the axial velocity oscillation time of step load is the shortest,the time of rectangular pulse load is the longest,and the time of sinusoidal pulse load is slightly shorter than that of rectangular pulse load.(4)For the dynamic characteristics of the stern bearing: under different journal misalignment angles or journal speeds,the journal axial motion has a significant effect on the stern bearing dynamic characteristics.With the aggravation of the journal axial motion,the bearing axial dynamic characteristic coefficient increases gradually.Moreover,the journal axial displacement mainly affects the bearing axial stiffness,and the journal axial velocity mainly affects the bearing axial damping.The influence degree is positively correlated with the journal inclination angle,but has nothing to do with the journal speed. |
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