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1

CFD analysis of nano-lubricated journal bearing considering variable viscosity and elastic deformation effects

Kadhim Zainab H., Ahmed Saba Y., Abass Basim A.

Diagnostyka

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2022

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Vol. 23, No. 1

art. no. 2022101

EN

The main objective of the present work is to study the behavior of Nano-lubricated journal bearing considering elasticity and variable viscosity effects. A mathematical model for a journal bearing is employed using three-dimensional computational fluid dynamics. The study is implemented for a journal bearing with laminar flow and smooth surfaces lubricated with pure oil as well as lubricants containing different concentrations of Al2O3 Nano-particles. The dependence of the oil viscosity on the temperature is considered by using the modified Krieger Dougherty model. Pressure, temperature and elastic deformation in addition to the bearing load-carrying capacity of the bearing working under different eccentricity ratios (0.1-0.6) have been studied. The mathematical model is confirmed by comparing the results of the pressure and temperature distributions obtained in the current work with those obtained by Ferron et al.(1983) for a bearing lubricated with pure oil. Also, the pressure obtained for the Nano-lubricated bearing of the present work is validated with that obtained by Solighar (2015). The results are found in good agreement with a maximum deviation not exceeding 5%. The obtained results show that the oil film pressure increases by about 17.9% with a slight decrease in oil film temperature and friction coefficient.

2

Theoretical analysis of jornal bearings lubricated with non-Newtonian fluid based Carreau viscosity model

Mongkolwongrojn M., Aiumpornsin Ch.

International Journal of Applied Mechanics and Engineering

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2005

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Vol. 10, no spec

245-253

EN

The static and dynamic characteristics of journal bearings lubricated with non-Newtonian fluids based on Carreau viscosity model have been investigated theoretically. The time-dependent modified Reynolds equation and the adiabatic energy equations have been formulated using Carreau viscosity model. The simultaneous system of modified Reynolds and adiabatic energy equations were solved numerically with boundary conditions using finite difference technique. The linearized bearing reactions and the journal motion can be approximated to obtain the spring and damping coefficient. Static characteristics are presented as pressure profile, temperature profile, load carrying capacity and the coefficient of friction with varying the eccentricity ratio. The stiffness coefficients, damping coefficients and the stability of the journal bearing are investigated with varying the parameters of the non-Newtonian fluid model. In this study, the shear rate of non-Newtonian lubricant and the model parameters have significant effects on the characteristics of journal bearings lubricated with the non-Newtonian fluids.

3

On identyfying the configuration state of rotor bearing systems

Hu W., Feng N. S., Hahn E. J.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 3

803-812

EN

In statically indeterminate rotor bearing systems involving hydrodynamic bearings, the relative lateral alignment of the bearing housings, i.e. the system configuration state, has a significant influence on the system stability and its vibration behaviour. This paper deals with a general identification procedure for determining the configuration state of any statically indeterminate system with hydrodynamic bearings. The technique is illustrated via numerical experiments using a fictitious four bearing system; and utilises the knowledge of the relative motion of the flexible rotors in their respective housing and of the absolute motion of the flexibly supported bearing housings, information which is now frequently available in existing turbomachinery installations. It is shown that acceptable configuration state identification is obtained even with 5% measurement uncertainty, here simulated by truncating all numerical 'measurements' to two significant digits. Since 5% measurement uncertainty is attainable with present measurement instrumentation, the identification technique is expected to be practically realisable.

4

On the influence of labyrinth seals on the dynamic behaviour of rotors

D'Agostino V., Guida D.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 4

1089-1098

EN

The influence of the labyrinth seals on the dynamic behaviour of a flexible rotor in journal bearings is investigated. In particular a code which makes possible the determination of the stiffness and damping coefficients and the calculus of the stability threshold in the absence of unbalance is discussed. The pressure field in journal bearings and in the labyrinth seal is determined using Warner's hypothesis and the bulk-flow model with two-control-volume, respectively.

5

Active magnetic bearings test rig for experimental investigation of seals

D'Agostino V., Guida D.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 4

1099-1107

EN

A test rig for the experimental validation of the rotordynamic coefficients of annular and labyrinth seals using Active Magnetic Bearings (AMBs) exciters is presented. The rotordynamic coefficients for annular and labyrinth seals are obtained, with two computer programs using the Reynolds' gas lubrication equation and the bulk flow model with two volume control, respectively. The AMBs exciters allow the rotor to levitate without contact, and to excite it with user-defined sinusoidal forces at the same time. The dynamic experiments can be conducted at various rotor speeds, whirling speeds, and with different pressure drops across the seal.