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
This paper presents an efficient three-dimensional(3D)structural model for bump-type gas foil bearings(GFBs)developed by considering friction.The foil structures are modeled with a 3D shell finite element model.Using ...This paper presents an efficient three-dimensional(3D)structural model for bump-type gas foil bearings(GFBs)developed by considering friction.The foil structures are modeled with a 3D shell finite element model.Using the bump foil mechanical characteristics,the Guyan reduction and component mode synthesis methods are adopted to improve computational efficiency while guaranteeing accurate static responses.A contact model that includes friction and separation behaviors is presented to model the interactions of the bump foil with the top foil and bearing sleeve.The proposed structural model was validated with published analytical and experimental results.The coupled elastohydrodynamics model of GFBs was established by integration of the proposed structural model with data on hydrodynamic films,and it was validated by comparisons with existing experimental results.The performance of a bearing with an angular misalignment was studied numerically,revealing that the reaction torques of the misaligned bearing predicted by GFB models with 2D and 3D foil structure models are quite different.The 3D foil structure model should be used to study GFB misalignment.展开更多
Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To anal...Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil bearings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method (NRM) and Finite Difference Method (FDM). The characteristics of an bump foil bearing model were discussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil bearing without nominal radial clearance can provide better stability and greater load capacity. This numerical analytical method also reveals a good convergence in numerical calculation.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This paper presents an efficient three-dimensional(3D)structural model for bump-type gas foil bearings(GFBs)developed by considering friction.The foil structures are modeled with a 3D shell finite element model.Using the bump foil mechanical characteristics,the Guyan reduction and component mode synthesis methods are adopted to improve computational efficiency while guaranteeing accurate static responses.A contact model that includes friction and separation behaviors is presented to model the interactions of the bump foil with the top foil and bearing sleeve.The proposed structural model was validated with published analytical and experimental results.The coupled elastohydrodynamics model of GFBs was established by integration of the proposed structural model with data on hydrodynamic films,and it was validated by comparisons with existing experimental results.The performance of a bearing with an angular misalignment was studied numerically,revealing that the reaction torques of the misaligned bearing predicted by GFB models with 2D and 3D foil structure models are quite different.The 3D foil structure model should be used to study GFB misalignment.
文摘Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil bearings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method (NRM) and Finite Difference Method (FDM). The characteristics of an bump foil bearing model were discussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil bearing without nominal radial clearance can provide better stability and greater load capacity. This numerical analytical method also reveals a good convergence in numerical calculation.
