An Analytic Model of Oil-Film Force on Hydrodynamic Journal Bearing of Finite Length

Abstract

In order to more clearly express the interrelation between the oil-film force on hydrodynamic journal bearing of finite length and the wedging, whiling, and squeezing motions of journals, an analytic model with well-defined physical meaning is proposed in this paper by introducing the non-slip boundary condition for the oil-film velocity gradient without modifying the basic assumption for Reynolds equation to formulate the expression of oil-film pressure distribution, obtaining the analytic solution of oil-film force through integration of circumferential pressure, and defining the effect coefficients for wedging, whirling and squeezing motions, which are related to the clearance ratio and eccentricity ratio of bearings. The proposed model is compared with an existing model to show off its advantage. The proposed model was also applied to a 200MW steam turbine low-pressure rotor-bearing system to simulate the dynamic response of the rotor during the speed-up process. The analytic results of this application proved the validity of the proposed model.