Research On Dynamic And Static Characteristics Of Water Lubricated Bearings

Bearing is the key supporting component of the rotary mechanical rotor system.In the green industrial era,the bearing with water as the lubricating medium is more energy-saving and environmentally friendly,and the cost is low.Water-lubricated bearings have been widely used due to their simple structure,good load carrying capacity,convenient maintenance,environmental friendliness and anti-burning.Therefore,it is of great significance to comprehensively study the structural characteristics,lubrication mechanism and dynamic and static characteristics of waterlubricated bearings.In this paper,the water-lubricated bearings of three typical structures: cylindrical,elliptical and tilting-pad bearings are numerically calculated to explore their dynamic characteristics and verified by experimental.Water film calculation models with different structural parameters were established,and different types of water-lubricated bearings were systematically calculated and analyzed.The main work and research results of this paper are as follows:1.The development history and current research status of lubrication theory are summarized,and the related researches on the dynamic and static characteristics and bearing capacity of different types of sliding bearings are reviewed.2.For cylindrical water-lubricated bearings,based on the theory of hydrodynamic lubrication,the radius gap,journal speed,load and length-to-diameter ratio are used as variables,combined with finite element,numerical simulation and dynamic mesh technology,the dynamic and static characteristics of the bearing are calculated and verified by experiments.The results show that:(1)When the length-diameter ratio is the same,the smaller bearing radius clearance,the better bearing load carrying capacity,the smaller fluctuation of the shaft trajectory,the more stable the rotor operation,but the temperature rise will increase;(2)The influence of the rotational speed on the bearing is relatively weak,and the high rotational speed is more conducive to improving the load carrying capacity of the bearing,but the stability of the rotor is decreased in general;(3)Applying a small amount of load will have a significant effect on the bearing performance,but as the load increases,the journal eccentricity increases,and the influence of the load increment on the bearing characteristics decreases;(4)When the same radius clearance is used,the increase of the length-to-diameter ratio is beneficial to improve the load carrying capacity of the bearing.However,when the minimum water film thickness is selected as the selection standard,the optimal lengthto-diameter ratio corresponding to different radius clearance is different,and the bearing structure is optimal when the ratio of the clearance ratio to the aspect ratio of the bearing is 0.0065~0.007.3.Elliptical water lubricated bearing is taken as the analysis object.Based on the research of cylindrical water lubricated bearing,the influence of ellipticity on the dynamic and static characteristic of bearing are analyzed.The results show that: When the ellipticity is 2~3,the water film of the bearing is more stable,which can better overcome the instability of the rotor.Higher or lower ellipticity will reduce the stability of the rotor.Therefore,the model with ellipticity of 3 is selected,and the inlet pressure is changed to explore the influence of external conditions on the performance of elliptical water-lubricated bearings.The results show that the inlet pressure has little effect on the performance.In the design optimization process of the bearing,if the bearing performance needs to be improved,the structural parameters should be chosen to improve first.4.Due to the particularity of the structure of the water-lubricated tilting bearing,based on the original design structural parameters,the preload ratio,the pivot biasing ratio,the tile angle and the bearing type are changed respectively to explore the effect of these structural parameters on the dynamic and static characteristics of the bearing.The results show that:(1)The increase of the preload ratio can reduce the unstable vibration of the bearing,enhance the stability of the rotor,and improve the load carrying capacity of the bearing;(2)The water-lubricated tilting pad bearing in the rotor system that does not need to be reversed adopts the fulcrum offset design,which can make the rotor system more stable.When the pivot biasing rate is about 0.6,the bearing performance is optimal;(3)The increase of the angle of the bearing pad increases the bearing capacity of the bearing,but the stability decreases.In general,the angle of the bearing tile can be increased only,and the overall performance of the bearing can be improved;(4)When the load is between the pads,the maximum pressure of the bearing is less than that of the load on the pad,and the pressure distribution is more uniform.However,comparing the Sommerfeld number of the two load-bearing modes,the load acting on the pad exhibits better bearing performance.