Dynamic coefficients and stability analysis of finite-length journal bearings considering approximate analytical solutions of the Reynolds equation

Dyk, Štěpán; Rendl, Jan; Byrtus, Miroslav; Smolík, Luboš

doi:10.1016/j.triboint.2018.09.011

Cited by 29 publications

(14 citation statements)

References 35 publications

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“…These two approximate solutions allow a direct expression of the fluid-film forces. Approximate analytical solutions for finite length journal bearings with length-todiameter ratio around 1 also exist [25,26] . As a representative of this class of hydrodynamic forces, e.g solution introduced in [24] can be mentioned.…”

Section: Linearization Of Fluid-film Forcesmentioning

confidence: 95%

Predictive capability of various linearization approaches for floating-ring bearings in nonlinear dynamics of turbochargers

Dyk

Smolík

Rendl

2020

Mechanism and Machine Theory

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A floating-ring bearing (FRB) is composed of a journal, a floating ring and a housing which are separated by two thin oil films. This system is inherently nonlinear and if it is lightly loaded or operated at high speeds, it is prone to the fluid-induced instability. The threshold speed for the instability of a journal bearing with one oil film can be estimated using linearized forces acting in the film. However, the linear analysis of FRB might be problematic because results of such an analysis are usually difficult to interpret. Nevertheless, the linear analysis can provide some fundamental insights into system behaviour. This work aims to evaluate in detail the use of linear theory in the stability analysis of rotating systems supported on FRBs. Several approaches for the linearization of the forces acting in FRB are proposed and analysed. The results are visualized in the form of a holistic Campbell diagram which together depicts natural frequencies, whirl frequencies, modal damping and precession of mode shapes. Moreover, it is demonstrated that the holistic Campbell diagram can be used to interpret-and to some extent, also to predict-results of nonlinear analysis.

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Section: Linearization Of Fluid-film Forcesmentioning

confidence: 95%

Predictive capability of various linearization approaches for floating-ring bearings in nonlinear dynamics of turbochargers

Dyk

Smolík

Rendl

2020

Mechanism and Machine Theory

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“…Nowadays, journal bearings have been widely used in rotating machinery due to superior durability and load-carrying capacities [1][2][3], such as wind turbines, transmissions and compressors. The dynamic coefficients of journal bearings directly affect the stability performance and unbalance responses of the whole rotor system, including the four stiffness coefficients and four damping coefficients.…”

Section: Introductionmentioning

confidence: 99%

Model updating for rotor-discs system and its application in dynamic coefficients identification of journal bearings

et al. 2021

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An accurate finite element (FE) model of the rotor-discs system is essential on the field identification of dynamic coefficients for journal bearings. This paper proposes a novel model updating method using the measured modal parameters. In this method, system mass and stiffness matrices were firstly updated by the particle swarm optimization (PSO) algorithm, in which the sensitivity analysis was used to select the appropriate variables to be optimized. Based on the updated results, the damping matrix defined as an improved Rayleigh Damping was then determined according to the experimental modal frequencies and damping ratios. To evaluate the effectiveness of this method, the FE model of a dual rotor-discs system was updated. The frequencies responses predicted by the updated model perform a good agreement with that from measured. Moreover, to validate the reliability of the updated model, the identifications of the dynamic coefficients were conducted on the flexible rotor test rig experimentally. The results demonstrated that the updated model has higher accuracy in field identification of dynamic coefficients than the original model, especially the system under critical speed.This study provides a feasibility strategy for updating the rotor-discs system and thereby establishes a foundation for further parameters identification and dynamic analysis.

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“…In a rotor-bearing system, the bearing dynamic coefficients affect the dynamic behaviour of the system directly, such as the critical speed, imbalance response, and stability performance. Many investigations based on the theoretical model have been carried out to calculate the dynamic coefficients [1][2][3][4]. However, the simplification in modeling inevitably leads to errors between the calculated and actual values.…”

Section: Introductionmentioning

confidence: 99%

A Novel Method for the Dynamic Coefficients Identification of Journal Bearings Using Kalman Filter

Kang

Shi

Zhang

et al. 2020

Sensors

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The dynamic coefficients identification of journal bearings is essential for instability analysis of rotation machinery. Aiming at the measured displacement of a single location, an improvement method associated with the Kalman filter is proposed to estimate the bearing dynamic coefficients. Firstly, a finite element model of the flexible rotor-bearing system was established and then modified by the modal test. Secondly, the model-based identification procedure was derived, in which the displacements of the shaft at bearings locations were estimated by the Kalman filter algorithm to identify the dynamic coefficients. Finally, considering the effect of the different process noise covariance, the corresponding numerical simulations were carried out to validate the preliminary accuracy. Furthermore, experimental tests were conducted to confirm the practicality, where the real stiffness and damping were comprehensively identified under the different operating conditions. The results show that the proposed method is not only highly accurate, but also stable under different measured locations. Compared with the conventional method, this study presents a more than high practicality approach to identify dynamic coefficients, including under the resonance condition. With high efficiency, it can be extended to predict the dynamic behaviour of rotor-bearing systems.

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Dynamic coefficients and stability analysis of finite-length journal bearings considering approximate analytical solutions of the Reynolds equation

Cited by 29 publications

References 35 publications

Predictive capability of various linearization approaches for floating-ring bearings in nonlinear dynamics of turbochargers

Predictive capability of various linearization approaches for floating-ring bearings in nonlinear dynamics of turbochargers

Model updating for rotor-discs system and its application in dynamic coefficients identification of journal bearings

A Novel Method for the Dynamic Coefficients Identification of Journal Bearings Using Kalman Filter

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