Widespread usage of bump-type foil journal bearing(BFJB) in oil-free microturbomachinery requires accurate predictions of dynamic performance characteristics, although it remains a challenging issue because BFJB refle...Widespread usage of bump-type foil journal bearing(BFJB) in oil-free microturbomachinery requires accurate predictions of dynamic performance characteristics, although it remains a challenging issue because BFJB reflects nonlinear both structurally and aerodynamically.This paper presented a simple experimental method to semi-directly obtain the minimum film thickness and dynamic stiffness of BFJB using the journal orbit. Numerical calculations and simulations are conducted to validate the experimental method. The micro-deformation and interaction of various foils are taken into consideration to improve the model precision. The results from the numerical model regarding the BFJB dynamic characteristics are compared with the experimental results coming from a dedicated test rig, which shows that the experimental results fluctuate obviously and agree not well with the numerical results at the start stage due to the presence of dry friction at that time, nevertheless, they show fantastic agreement as soon as a gas film is gradually generated to separate the shaft from the top foil. Therefore, the proposed experimental method is effective to predict film thickness and dynamic characteristics during the period from the lift-off time to the land-off time. The dynamic characteristics, along with the journal orbits also can be used to rapidly predict the dynamics behavior of rotor-bearing systems.展开更多
Taking bump-type gas foil bearings as the research object,a deformation model of bump foil and a thin-plate finite element model of top foil were proposed.By solving Reynolds equation and energy equation,the pressure ...Taking bump-type gas foil bearings as the research object,a deformation model of bump foil and a thin-plate finite element model of top foil were proposed.By solving Reynolds equation and energy equation,the pressure distribution and the temperature distribution of gas films in foil bearings were obtained.Further,a numerical method for calculating the lubrication performance of gas foil bearings with considering the surface roughness was proposed.With a specific example,effects of the surface roughness on the bearing lubrication performance were parametrically studied.The results indicate that rougher journal surface can lead to larger fluctuation of the lubrication performance,while surface roughness of top foil has few effects on the fluctuation.Moreover,the mean values of performance parameters almost remain constant at different values of surface roughness.展开更多
Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries,theoretical researches on the modeling,performance prediction of compliant foil bearings and the dynamic analysis ...Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries,theoretical researches on the modeling,performance prediction of compliant foil bearings and the dynamic analysis of the related rotor system seem still far behind the experimental investigation because of structural complexity of the foil bearings.A generalized solution of the elasto-aerodynamic lubrication is presented in this paper by introducing both static and dynamic deformations of foils and solving gas-lubricated Reynolds equations with deformation equations simultaneously.The solution can be used for the calculation of dynamic stiffness and damping,as well as the prediction of static performances of foil bearings.Systematical theories and methods are also presented for the purpose of the prediction of dynamic behavior of a rotor system equipped with foil bearings.展开更多
基金funded by the Natural Science Foundation of China (No. 51775025, 51205015)China Key Research and Development Plan (No. 2017YFB0102102, 2018YFB0104100)。
文摘Widespread usage of bump-type foil journal bearing(BFJB) in oil-free microturbomachinery requires accurate predictions of dynamic performance characteristics, although it remains a challenging issue because BFJB reflects nonlinear both structurally and aerodynamically.This paper presented a simple experimental method to semi-directly obtain the minimum film thickness and dynamic stiffness of BFJB using the journal orbit. Numerical calculations and simulations are conducted to validate the experimental method. The micro-deformation and interaction of various foils are taken into consideration to improve the model precision. The results from the numerical model regarding the BFJB dynamic characteristics are compared with the experimental results coming from a dedicated test rig, which shows that the experimental results fluctuate obviously and agree not well with the numerical results at the start stage due to the presence of dry friction at that time, nevertheless, they show fantastic agreement as soon as a gas film is gradually generated to separate the shaft from the top foil. Therefore, the proposed experimental method is effective to predict film thickness and dynamic characteristics during the period from the lift-off time to the land-off time. The dynamic characteristics, along with the journal orbits also can be used to rapidly predict the dynamics behavior of rotor-bearing systems.
文摘Taking bump-type gas foil bearings as the research object,a deformation model of bump foil and a thin-plate finite element model of top foil were proposed.By solving Reynolds equation and energy equation,the pressure distribution and the temperature distribution of gas films in foil bearings were obtained.Further,a numerical method for calculating the lubrication performance of gas foil bearings with considering the surface roughness was proposed.With a specific example,effects of the surface roughness on the bearing lubrication performance were parametrically studied.The results indicate that rougher journal surface can lead to larger fluctuation of the lubrication performance,while surface roughness of top foil has few effects on the fluctuation.Moreover,the mean values of performance parameters almost remain constant at different values of surface roughness.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.50275116 and 50475088)the National High-Tech Research and Development Program of China(Grant No.2002AA503020).
文摘Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries,theoretical researches on the modeling,performance prediction of compliant foil bearings and the dynamic analysis of the related rotor system seem still far behind the experimental investigation because of structural complexity of the foil bearings.A generalized solution of the elasto-aerodynamic lubrication is presented in this paper by introducing both static and dynamic deformations of foils and solving gas-lubricated Reynolds equations with deformation equations simultaneously.The solution can be used for the calculation of dynamic stiffness and damping,as well as the prediction of static performances of foil bearings.Systematical theories and methods are also presented for the purpose of the prediction of dynamic behavior of a rotor system equipped with foil bearings.
