Pore Reconstruction And Seepage Behavior Analysis Of Pi Cage

Bearings are the key mechanical components of the momentum wheel in the spacecraft attitude control system,and have an important influence on the index parameters of the spacecraft's maneuverability,operating accuracy,service life and reliability.During service of the spacecraft in orbit,the deterioration of the bearing lubrication state is one of the main reasons for the failure of the momentum wheel.Now,many momentum wheel bearing lubrication designs use polyimide porous oil-containing cages and oil reservoirs to provide trace lubricating oil for the friction interface of the bearing under the working conditions of centrifugal force,temperature,dragging,etc.,in order to meet lubrication requirements of Bearings during service.According to the pore structure characteristics of polyimide press molding,the quartet structure generation set method is selected as the numerical model construction method of porous media.Based on the principle of cellular automata,a parameter analysis program for the numerical model of porous media is developed.After filtering the porous media numerical model,the influence of the initial solid particle generation probability in the quartet structure generation set method on the pore parameters of the numerical model is analyzed,the maximum connected pore in the numerical model is extracted,and the penetration of the maximum connected pore in the model space is discussed.The relationship between the proportion of the largest connected pore and the initial porosity is compared and analyzed.It is verified that the space volume proportion of the largest connected pore is the effective porosity of the model.Based on the pore structure obtained by the quartet structure generation set method,the maximum sphere algorithm is used to characterize and analyze the pore parameters of porous media.The effects of initial probability,porosity and growth probability set in the quartet structure generation set method on the pore structure are studied.Based on the microstructure of polyimide powder and pressed products and the measurement results of mercury porosimeter,the similarity between the quartet structure generation set model and the actual pore parameters is analyzed,and the structural model is closer to the real structure by modifying the model parameters.On this basis,a three-dimensional solid model of polyimide porous material is constructed by combining the quartet structure generation set method and the maximum sphere algorithm.According to the service condition of momentum wheel bearing,the influence of friction power consumption on the temperature change of polyimide porous cage is analyzed.According to the operation condition of bearing,the seepage model of polyimide porous cage is established by using the finite element simulation software,and the macroscopic seepage behavior of polyimide porous cage under different working conditions is analyzed.Based on macro simulation data and three-dimensional solid model of polyimide porous materials,COMSOL is used The multiphysics finite element analysis software simulates the flow behavior of lubricating oil in the micro pore structure,discusses the seepage behavior of lubricating oil in the polyimide pore structure,providing a theoretical basis for the study of the oil storage and supply behavior of polyimide porous materials,and provides guidance for the lubrication optimization design of momentum wheel bearing.