Towards Accurate Prediction of Unbalance Response, Oil Whirl and Oil Whip of Flexible Rotors Supported by Hydrodynamic Bearings

Abstract

Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of prediction of the model at hand depends on its comprehensiveness. In this study, we construct three bearing models of increasing modeling comprehensiveness and use these to predict the response of two different rotor-bearing systems. The main goal is to evaluate the correlation with measurement data as a function of modeling comprehensiveness: 1D versus 2D pressure prediction, distributed versus lumped thermal model, Newtonian versus non-Newtonian fluid description and non-mass-conservative versus mass-conservative cavitation description. We conclude that all three models predict the existence of critical speeds and whirl for both rotor-bearing systems. However, the two more comprehensive models in general show better correlation with measurement data in terms of frequency and amplitude. Furthermore, we conclude that a thermal network model comprising temperature predictions of the bearing surroundings is essential to obtain accurate predictions. The results of this study aid in developing accurate and computationally-efficient models of flexible rotors supported by plain journal bearings.

Application of Artificial Neural Networks forMonitoring Conditions ofLiquid Friction Mechatron Bearing under Temperature-Viscosity WedgeConditions

“…Четвертый тип колебаний наиболее опасен, обычно возникает на удвоенной критической частоте и сопровождается высокими амплитудами, причем колебания не исчезают с ростом частоты вращения. Такое явление в зарубежной литературе называется «oil whip» [11][12][13]. Смазочный слой может являться причиной дробно-частотных колебаний.…”

SBFEM with reduced modal basis for hydrodynamic bearings

“…The latter is a partial differential equation describing the pressure generation in the lubrication gap and is usually solved by means of analytical methods [5][6][7][8][9][10], look-up table techniques [11], or numerical models [12][13][14]. Amongst these approaches, only the numerical solution provides accurate results under general boundary conditions (BCs) and is able to consider shaft tilting [15], mass-conserving cavitation [16], elasto-hydrodynamics [17,18], thermo-hydrodynamics [19], or hydraulic coupling of oil films [20]. Because of the extensive accumulated computational effort for the numerical solution at every time step, a semi-analytical solution was developed as an alternative in [21] based on the scaled boundary finite element method [22] (SBFEM).…”

A New Geometrical Design to Overcome the Asymmetric Pressure Problem and the Resulting Response of Rotor-Bearing System to Unbalance Excitation

“…Their results illustrated that, in comparison with the perfectly balanced system, the unbalance might cause periodic oscillations at different speed ranges at multiple periods of rotation and even chaotic motion. Recently, Eling et al [12] presented an interesting work on predicting the unbalance response of rotors supported on journal bearings considering unbalance force. They explained the interaction between the rotating shaft and the oil film that can result in unstable dynamic behavior characterized by subsynchronous motion, the oil whirl, where the whirl frequency in journal bearing is close to half the rotation speed.…”