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.

Analytical model of a tilting pad bearing including turbulence and fluid inertia effects

“…However, stiness and damping remained closer to the model without the uid inertia eect, which is consistent with the behavior of other bearing models using the uid inertia eect [7,10,11]. The pad preload, the number of pads and the load on pad position were the parameters that most aected the behavior of the rotor.…”

“…model with inertia eect presented higher orbits (closer to the center), which is consistent with the results obtained by Hashimoto et al[10] and Capone and Inuence of radial clearance on rotor behavior at 3, 4 and 5 krad/s (solid linewithout inertia eect; dashed line -with inertia). Preload eect on rotor behavior at 3, 4 and 5 krad/s (solid -without inertia eect;dashed -with inertia).…”

“…The rotor dynamic analysis of the bearing with inertia eect shows results that are compatible with the ones presented to the plain journal bearing [10,11].…”

“…Hashimoto et al [10] proposed a nonlinear short bearing model to analyze the eects of the uid lm inertia in super-laminar ow regime. They showed that the model with inertia and turbulence eects presents a more stable behavior that the one without inertia, which indicates that uid lm inertia should be considered to properly model a bearing operating in the turbulent regime.…”

An extended Reynold equation applicable to high reduced Reynolds number operation of journal bearings

“…The early attempts [12,23,24,25,26,27] to approximate these nonlinear terms entailed assuming the integral of the velocity product was equal to the product of the integral of the velocities,…”