Numerical Analysis Of Foil Aerodynamic Thrust Bearing Based On Slip Model

Foil aerodynamic bearing is an adaptive aerodynamic bearing supported by flexible foil structure.With high speed,low power consumption,relatively simple structure and high stability,it has been widely used in aerospace,high precision machine tools,cryogenic refrigeration and other fields of oil-free lubrication high-speed rotating machinery.Since the 1960 s,the foil supporting structure of foil radial gas bearing has been improved and optimized many times,and its bearing performance has been greatly improved.Because of its complex structure and relatively slow development,the research of foil gas thrust bearing lubrication film is not deep enough.Moreover,with the improvement of modern processing accuracy and the emergence of demand for reduction of bearings,the performance of micro foil gas thrust bearings is more and more affected by the air slip effect.In view of this,this paper takes the waveform foil aerodynamic thrust bearing as the research object,and studies the influence of airflow slip on the performance of the bearing under the small clearance.Firstly,the Reynolds equation of film pressure control suitable for hydrodynamic gas bearings in cylindrical coordinates is established and solved by combining the mixed finite volume method and the SOR iteration method.The accuracy of the program under non-slip boundary conditions is verified by comparing the results with the literatures.Then the first-order slip correction and Wu's new slip correction Reynolds equation of film pressure control are deduced.The modified program is used to solve the equation according to the bearing parameters in literature.The accuracy of the program is verified by comparing the results of the first-order slip correction with those in literature.Based on the design example,the performance of micro foil gas thrust bearing under different structural and working parameters is calculated by using continuous model,first order slip correction model and Wu's new slip correction model.The differences among the models were compared.Then the calculation parameters of the rotor thrust disc under the inclined condition are designed,and three models are used to calculate the bearing performance under different structural parameters and working parameters.The results show that the smaller the foil deformation flexibility coefficient of thrust foil bearing is,the higher the rotational speed is,and the larger the axial bearing capacity is.When the minimum clearance of the bearing is less than 0.5 um and the rotational speed is less than 20 000 r/min,the rarefied gas effect will reduce the bearing capacity of thrust foil bearing,and the pressure and bearing capacity of the first-order slip model and Wu's new slip model are much lower than that of the continuous model,and the results deviation between the models will follow the axis.The bearing clearance,rotational speed and deformable flexibility coefficient of foil decrease and increase gradually.Under the inclined condition,the effect of airflow slip on bearing capacity is greater.The deviation between models decreases with the increase of inclination angle,and increases with the decrease of bearing speed and minimum clearance.