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Abstract

Journal bearings are the most common type of bearings in which a shaft freely rotates in a metallic sleeve. They find a lot of applications in industry, especially where extremely high loads are involved. Proper analysis of the various bearing faults and predicting the modes of failure beforehand are essential to increase the working life of the bearing. In the current study, the vibration data of a journal bearing in the healthy condition and in five different fault conditions are collected. A feature extraction method is employed to classify the different fault conditions. Automatic fault classification is performed using artificial neural networks (ANN). As the probability of a correct prediction goes down for a higher number of faults in ANN, the method is made more robust by incorporating deep neural networks (DNN) with the help of autoencoders. Training was done using the scaled conjugate gradient algorithm and the performance was calculated by the cross entropy method. Due to the increased number of hidden layers in DNN, it is possible to achieve a high efficiency of 100% with the feature extraction method.

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Authors and Affiliations

T. Narendiranath Babu
Arun Aravind
Abhishek Rakesh
Mohamed Jahzan
D. Rama Prabha
Mangalaraja Ramalinga Viswanathan
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Abstract

Squeeze film dampers (SFDs) are commonly used in turbomachinery in order to introduce external damping, thereby reducing rotor vibrations and acoustic emissions. Since SFDs are of similar geometry as hydrodynamic bearings, the REYNOLDS equation of lubrication can be utilised to predict their dynamic behaviour. However, under certain operating conditions, SFDs can experience significant fluid inertia effects, which are neglected in the usual REYNOLDS analysis. An algorithm for the prediction of these effects on the pressure build up inside a finite-length SFD is therefore presented. For this purpose, the REYNOLDS equation is extended with a first-order perturbation in the fluid velocities to account for the local and convective inertia terms of the NAVIER-STOKES equations. Cavitation is taken into account by means of a mass conserving two-phase model. The resulting equation is then discretized using the finite volume method and solved with an LU factorization. The developed algorithm is capable of calculating the pressure field, and thereby the damping force, inside an SFD for arbitrary operating points in a time-efficient manner. It is therefore suited for integration into transient simulations of turbo machinery without the need for bearing force coefficient maps, which are usually restricted to circular centralized orbits. The capabilities of the method are demonstrated on a transient run-up simulation of a turbocharger rotor with two semi-floating bearings. It can be shown that the consideration of fluid inertia effects introduces a significant shift of the pressure field inside the SFDs, and therefore the resulting damper force vector, at high oil temperatures and high rotational speeds. The effect of fluid inertia on the kinematic behaviour of the whole system on the other hand is rather limited for the examined rotor.
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Bibliography

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  2.  S. Hamzehlouia and K. Behdinan, “Squeeze film dampers supporting high-speed rotors: Fluid inertia effects,” Proc. Inst. Mech. Eng., Part J: J. Eng. Tribol., vol. 234, no. 1, pp. 18–32, 2020.
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Authors and Affiliations

Thomas Drapatow
1
Oliver Alber
2
Elmar Woschke
1
ORCID: ORCID

  1. Institute of Mechanics, Otto von Guericke University Magdeburg, 39106 Magdeburg, Germany
  2. MAN Energy Solutions SE, 86153 Augsburg, Germany
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Abstract

The paper concerns efficiency of active magnetic stabilization in damping of selfexcited vibration of an asymmetric rotor supported on 5-lobe journal bearings with 5 oil gaps. The dependencies describing the pressure distribution in the oil film are presented. The components of the hydrodynamic uplift forces in the bearings are described. Equations of motion are derived using a numerical simulation method. It was found that active magnetic stabilization was effective for symmetric and non-symmetric systems. Exemplary trajectories of the journal bearing motion as well as the time histories are presented.
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Authors and Affiliations

Zbigniew Starczewski
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Abstract

Different configurations of journal bearings have been extensively used in turbomachinery and power generating equipment. Three-lobe bearing is used due to its lower film temperature and stable operation. In this study, static performance of such a bearing has been investigated at different eccentricity ratios considering lubricant compressibility and variable viscosity. The effect of variable viscosity was considered by taking the viscosity as a function of the oil film thickness while Dowson model is used to consider the effect of lubricant compressibility. The effect of such parameters was considered to compute the oil film pressure, load-carrying capacity, attitude angle and oil side leakage for a bearing working at (ε from 0.6 to 0.8) and (viscosity coefficient from 0 to 1). The mathematical model as well as the computer program prepared to solve the governing equations were validated by comparing the pressure distribution obtained in the present work with that obtained by EL-Said et al. A good agreement between the results has been observed with maximum deviation of 3%. The obtained results indicate a decrease in oil film pressure and load-carrying capacity with the higher values of viscosity coefficient while the oil compressibility has a little effect on such parameters.
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Bibliography

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Authors and Affiliations

Mushrek A. Mahdi
1
ORCID: ORCID
Basim Ajeel Abbas
2

  1. University of Babylon, College of Engineering/Al-Musayab, Automobile Engineering Department, Babylon, Iraq
  2. University of Babylon, College of Engineering, Mechanical Engineering Department, Babylon, Iraq

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