The effect of the non-Newtonian behaviour of lubricants, resulting from the addition of polymers, on the performance of hydrodynamic journal bearings was investigated. An empirical fluid flow equation which adequately represents the flow behaviour of lubricant was used to obtain a modified form of Reynolds' equation. Finite difference numerical solutions were obtained for steady state conditions at various width-to-diameter ratios. The results show a strong influence of the width-to-diameter ratio on the load capacity of journal bearings. Linearised stiffness and damping coefficients were evaluated from the fluid film force equations for the unsteady motion of the journal centre and were used to predict the stability limits of a simple rigid rotor-bearing system which showed a reduction in threshold speeds. The steady state load capacity and stability limits were verified experimentally for finite width bearings. © 1977.

S. T.N. Swamy

B. V.A. Rao

FINITE DIFFERENCE TECHNIQUES

FLOW OF FLUIDS - Non Newtonian

LUBRICANTS - Thin Films

MATHEMATICAL TECHNIQUES - Finite Difference Method

Bearings

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

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IIT Madras

Steady state and stability characteristics of a hydrodynamic journal bearing with a non-Newtonian lubricant

Wear

This paper presents a brief summary of the influence of journal bearings in machinery with special reference to rotor dynamic problems. The journal bearings considered are Newtonian, non-Newtonina and magnetohydrodynamic and their influence on the critical speeds and stability of rotors is investigated. © 1981.

Tribology International

Bearing influenced rotor dynamics

Starting from the general shear stress-sheur strain rr.lation of the odd cubic polynomial type considl'ring correlation effect for pspudoplastic (shpar thinning) /ubricunt, a modified form of Ueynolds' e(luation (nonlinear) is derived under conventional hydrodynamic luhrication approximations. The finite difference technique with successive uPl'r relaxation is used adopting the solution of the associated linwr e(lltatio/l as a first approximation to obtain the pressure distributioll of a finite cylindrical journal bearing incorporating Reynolds' boundary conditions. Steady state performance c/wl"(lctpristics such as load capacity, attitude, friction and flow rate are obtained for various vailles of nonlinear parameter and bearing slenderness ratio. The results presl'rlted in IHmdimensional form al'l' compared with established results for Newtonia/l lubricants. The investigatio/l shows a significant effect of corrl'latio/l on the bearing load capucity and flow rute. © 1979 by ASME.

Journal of Tribology

Steady state performance of a hydrodynamic journal bearing with a pseudoplastic lubricant

Starting from the most general fluid flow equation of the power law type expressing rate of shear in terms of powers of shear stress for non-Newtonian lubricants a modified form of Reynolds'equation is derived for dynamically loaded finite width journal bearings. The finite difference technique with successive over relaxation is used incorporating Reynolds' boundary conditions for pressure to obtain the pressure distribution. From the equations of fluid film forces, the values of stiffness and damping coefficients are obtained for a linearised case. The shear thinning effect of non-Newtonian lubricants at higher shear rates is shown to decrease the stiffness and damping values. Finally, the stability limit for such a bearing is obtained for different values of the nonlinear factor. © 1975.

Stiffness and damping characteristics of finite width journal bearings with a non-newtonian film and their application to instability prediction

Starting from the most general type of fluid flow equation connecting cubic shear stress to rate of shear for non-Newtonian lubricants, a modified form of Reynolds' equation was derived for steady finite width journal bearings. The finite difference technique with successive over relaxation was used incorporating Reynolds' boundary conditions for pressure to obtain the pressure distribution and hence the load capacity and the attitude angle. It is shown that the flatter pressure profile and higher load capacity at low eccentricity ratios have practical advantages. The apparent viscosity loss at higher rates of shear decreases the load capacity at higher eccentricity ratios but it is expected that the flatter viscosity temperature slope of the polymer thickened non-Newtonian lubricants will compensate for their apparent viscosity decrease. © 1975.

Journal	Wear
ISSN	00431648
Open Access	No