The Effects of Fluid Inertia Forces on the Dynamic Behavior of Short Journal Bearings in Superlaminar Flow Regime

Abstract

The effects of fluid inertia on the dynamic behavior of oil film journal bearings are theoretically investigated. The dynamic oil film forces considering the combined effects of turbulence and fluid inertia are analytically obtained under the short bearing assumption. Based on the linearized analysis, the whirl onset velocity for a balanced rigid rotor supported horizontally in the oil film journal bearings are determined initially in the case of the length-to-diameter ratio of λ = 0.5 for Reynolds numbers of Re = 2750, 4580, and 5500. Moreover, the nonlinear equations of motion for the rotor are solved by the improved Euler’s method, and the relations between the transient journal motion and the pressure distribution corresponding to the above Reynolds numbers are examined. It is found that the fluid inertia significantly affects the dynamic behavior of turbulent journal bearings under certain operating conditions.