Hydrodynamic Lubrication Mechanism And Multi-Objective Driven Optimization Design Of Textured Friction Contacts

With its environmental protection,economy and safety,water-lubricated bearings are gradually used in marine engineering equipment such as dynamic positioning system of deep sea platform and high-tech ship propulsion system.With the development of marine engineering equipment to heavy load,bearing failure caused by improper lubrication often occurs,which seriously threatens the long-term safe operation of such equipment.In order to solve the above problems,supported by the National Natural Science Foundation of China(No.51506225),the key research and development program of Shandong Province(No.2018GHY115018)and the Fundamental Research Funds for the Central Universities(No.18CX02129A),the surface texture is introduced into the water-lubricated friction pairs,and the research progress of its lubrication mechanism and optimization design is summarized:Firstly,based on computational fluid dynamics and fluid structure coupling method,the soft elastohydrodynamic lubrication model of textured friction pairs under water lubrication is established.Based on response surface and non-dominated sorted genetic algorithm,a multi-objective driving optimization system is established,and the results are in good agreement with those in literature.Secondly,in view of the lack of research on the lubrication mechanism of the texture water-lubricated friction pairs,the loading mechanism of the textures is analyzed from the macro and micro perspectives.It is found that the non-uniform superposition effect between the micro-hydrodynamic pressure of textures and the original dynamic pressure effect of bearing determines the loading capacity of the textured journal bearing.The micro-hydrodynamic pressure effect is caused by the surface micro-texture mainly through the inlet suction effect,cavitation effect and inertia effect.In turbulent state,more lubricants flow into the textured zones,and the increase of the flow at the outlet of the textures makes the blocking effect enhanced,so the loading capacity is higher.Thirdly,aiming at the lack of research on the optimization design of textured water-lubricated friction pairs,three typical textured sliding friction pairs are optimized with the highest loading capacity and the lowest friction force as the objectives.It is found that for the simplified conformal parallel contact pair,the loading capacity is most sensitive to the circumferential distance of textures,and the optimal textures depth ratio is between 0.60 and0.65.For thrust bearing,with the decrease of elastic modulus of bearing material,the optimal textured coverage decreases gradually,and the optimal textured depth has no obvious change.Under the same bearing material,the optimal textured coverage and the optimal textured depth interact.For journal bearings,loading capacity is more sensitive to textured distribution parameters than textured structure parameters.Finally,based on the rotor-journal bearing test rig,an experimental study on the dynamic characteristics of the textured journal bearing is carried out,and the multi-objective drive optimization system is verified.It is found that the amplitude of the textured bearing is much smaller than that of the smooth bearing,and the amplitude of the optimized textured bearing is always better than that of the original textured bearing.