Study On Static And Dynamic Characteristics Of Water Lubricated Bearings Considering Bending Of Shaft

Water-lubricated bearings are widely used in underwater vehicles due to their energy-saving and environmental protection characteristics.As the shafting system of ship is enlarged,the cantilever effect of the tail-end propeller is enhanced,and the journal of the large-length-diameter water-lubricated stern bearing is often in complex bending state.Previous studies have generally assumed that the axis is parallell or inclined with the bearing hole axis,which is largely different from the actual situation.To this end,this paper takes the water lubricated bearing of the ship propulsion system as the research object,obtains the deflection of the shaft based on the complete shaft contact analysis,and studies the static and dynamic characteristics of the water lubricated stern bearing considering the shaft bending,aiming at provide theoretical support and engineering reference for the tribological and dynamic design of marine water lubricated stern bearings.The specific research content and conclusions are as follows:(1)Calculation of the deflection of the propulsion shafting considering the contact.Based on the basic theory of contact mechanics,the ANSYS software is used to conduct a contact finite element simulation of the ship propulsion shafting,the parameters such as bearing contact pressure and shaft deflection are obtained,and the effects of propeller load,bearing material and front end bearing support stiffness on shaft deflection and journal deflection at the end bearing are investigated.The results show that the journal deflection of the stern bearing is positively correlated with the propeller load and has little relationship with the bearing stiffness of the front tail bearing.(2)Study on static characteristics of water lubricated bearings considering shaft bending.Based on the deflection curve of the shaft,the bearing film thickness equation considering the journal bending is derived,the elastohydrodynamic lubrication model of water lubricated bearings considering shaft bending is established and solved based on finite difference method,the effects of eccentricity and journal bending on bearing lubrication performance are explored.The results show that the journal bending causes the pressure distribution and film thickness distribution of the water-lubricated bearing to shift significantly.The maximum pressure and the minimum film thickness are concentrated in the bending.At the end,the ratio of the maximum pressure to the specific pressure increases rapidly with the increase of the eccentricity,which is the main manifestation of the poor bearing lubrication performance under the partial load.(3)Study on dynamic characteristics of water lubricated bearing considering shaft bending.The calculation model of dynamic characteristics of water-lubricated bearings was developed,and the conventional 8-parameter dynamic characteristic model was extended to a 16-parameter dynamic characteristic model considering bending stiffness and bending damping,a differential method for solving the 16 dynamic characteristic parameters of water lubricated bearings considering shaft bending is studied.The influence of eccentricity and journal bending on the dynamic characteristics of the bearing is studied.The results show that the values of bending stiffness and bending damping are two orders of magnitude less than radial stiffness and radial damping,when the eccentricity and the degree of journal bending change,the changes in bending stiffness and bending damping are similar to radial stiffness and radial damping.(4)Radial bearing dynamic characteristics test considering shaft bending.A double fulcrum test model for radial bearing under shaft bending is established,the identification method of radial bearing dynamic characteristics under shaft bending is studied,and the bearing dynamic characteristics test under different working conditions is carried out based on the test system of shafting dynamic characteristics.The results show that the rotational speed and the degree of journal bending have an effect on the test results,and the excitation mode and the excitation frequency have an influence on the test accuracy.