Finite Width Journal Bearings Research Articles

Analysis of hydrodynamic journal bearings having non-Newtonian lubricants

Commercial lubricants, due to the presence of different types of additives, behave like non-Newtonian fluids. The effect of this nonlinear behaviour on the performance characteristics of finite-width journal bearings is investigated using the Eyring model for the shear stress and shear strain rate. the finite element method using Galerkin's technique has been used to solve the momentum equations and the continuity equation in cylindrical coordinates, representing the flow field in the clearance space of a journal bearing system using Newtonian fluids; the non-Newtonian effect is introduced by modifying the viscosity term for the model in each iteration. The results of static performance characteristics for finite-width journal bearings having non-Newtonian lubricants have been obtained.

An Analysis of Dynamic Characteristics of Turbulent Journal Bearings Considering Inertia Forces

It is a purpose of this paper to present a means of handling both turbulent and inertia effects on the dynamic characteristics of finite width journal bearings. In the analysis turbulence is treated by means of turbulent coefficients and inertia forces are approximated by mean velocities averaged across the fluid film. Assuming a small displacement of journal center, the dynamic coefficients such as spring, damping and acceleration coefficients and the onset whirl frequencies of rotors are computed The results obtained show that the dynamic characteristics as mentioned above are affected by inertia forces.

Analysis of hydrodynamic journal bearings with non-newtonian power law lubricants by the finite element method

Additives cause commercial lubricants to behave as non-newtonian fluids. The effect of this non-linear behaviour on the performance characteristics of finite-width journal bearings was investigated using the power law model. The Navier-Stokes equations representing the flow field in the clearance space of a bearing using newtonian fluids were solved in cylindrical coordinates by the finite element method using Galerkin's technique and the non-newtonian effect was introduced by modifying the viscosity term at each iteration.

Analysis of Hydrodynamic Journal Bearings Having Non-Newtonian Lubricants (Prandtl Model) by a Finite Element Method

Additives are used to improve the performance of commercial lubricants. These lubricants behave like non-Newtonian fluids (shear thinning or shear thickening). The effect of the nonlinear behaviour on the performance characteristics of finite width journal bearings is investigated using the Prandtl model. The finite element method, using Galerkin's technique, has been used to solve the Navier-Stokes equations in cylindrical coordinates, representing the flow-field in the clearance space of a bearing using Newtonian fluids, and the non-Newtonian effect is introduced by modifying the viscosity term for the model in each iteration. The results applicable to shear-thinning (pseudoplastic) and shear-thickening (dilatant) lubricants are compared with the established results for Newtonian lubricants.

Thermohydrodynamic Lubrication of Journal Bearings in Turbulent Flow

This paper presents a study of turbulent lubrication considering thermal effects on lubricant film. By applying a turbulent lubrication equation and an energy equation to finite width journal bearings and analyzing these equations numerically, the bearing performances such as film temperature and pressure are evaluated. Moreover, the dynamic characteristics such as stiffness and damping coefficients of lubricant film and the stability of rotor are also analyzed. The results obtained here show that the thermal effects on the bearing performances and the dynamic characteristics are prominant in the turbulent lubrication.

Turbulent Lubrication Theory Using the Frictional Law : 2nd Report, Its Application to Journal Bearings

In this paper, an application of the turbulent lubrication theory developed in the first paper to the finite width journal bearings is presented. Bearing performances such as film pressure, load capacity, frictional force and rate of flow in turbulent flows are evaluated by the numerical analysis. The effects of pressure flows on the performances not previously encountered are considered from the analytical results, and are discussed comparing with the published papers. Also, an experiment in a range of high eccentricities and of the mean Reynolds numbers up to 5000 is conducted to compare with the theoretical results. From agreement of the experimental results with the analytical ones, the validity of the theory is confirmed.

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 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.

Calculated load capacity of non-newtonian lubricants in finite width journal bearings

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.

Calculated Performance of Greases in Journal Bearings

A digital computer analysis has been made of the effects of non-Newtonianism on the performance of greases in finite width journal bearings. As anticipated, t he extreme nonlinearity of the shear rate-shear stress relation exhibited by greases makes their deviations from “normal” behavior very marked. Among the effects noted are (1) apparent “anisotropic viscosities,” i.e., viscosities in the side leakage direction as much as 30 times as high as those in the direction of motion, (2) reduced side leakage, (3) flatter pressure profiles, (4) reduced sensitivity of load and friction to speed changes relative to Newtonian lubricants, and (5) the occurrence of “cores” of plug flow. Theoretically interesting is the fact that the apparent axial viscosity approaches the true viscosity while the circumferential viscosity approaches the slope of the flow curve. Many of the conclusions obtained here, especially the advantages of greases at low speeds, are confirmed in practice. Contributed to the American Society of ...

Calculated performance of non-newtonian lubricants in finite width journal bearings : H. H. Horowitz and F. E. Steidler. ASLETrans., 4 (1961) 275–281

Calculated performance of non-newtonian lubricants in finite width journal bearings : H. H. Horowitz and F. E. Steidler. ASLETrans., 4 (1961) 275–281

Calculated Performance of Non-Newtonian Lubricants in Finite Width Journal Bearings

A numerical procedure has been developed for the calculation of the performance of non-Newtonian, polymer-thickened lubricants in finite width journal bearings. Such oils were found to act as if they had averaged “anisotropic viscosities,” i.e., different viscosities in the circumferential and side leakage directions, even though the viscosity was taken to have one definite value, a function of the resultant shear stress, at each point in the oil film. Overall, polymer oils carried less load at a given eccentricity, gave less friction and a flatter pressure distribution than mineral oils of the same low shear viscosities. By analogy with the previously calculated infinite width case, which gave similar results, it is expected that the flatter viscosity temperature slope of the polymer oils will compensate for their apparent viscosity decrease. The program has also been adapted to “natural” boundary conditions, which improve upon the delineation of the cavitation region on the inlet side of the bearing. Co...

Theoretical and Experimental Analysis of Hydrodynamic Gas-Lubricated Journal Bearings

Abstract In recent years, gas-lubricated bearings have aroused a great amount of interest. The interest is centered on the advantages of gas bearings for four major applications: (a) High-temperature devices, for which there is yet no lubricant available. (b) Radioactive atmospheres, where conventional lubricants may break down. (c) Applications sensitive to contamination, such as jet engines, where fouling from lubricating oil becomes serious. (d) Low-friction devices—an especially important advantage because of the trend to high-speed machinery. This paper presents a numerical solution for finite-width journal bearings and results of experiments conducted with air-lubricated hydrodynamic journal bearings. Comparison is made between theoretical and experimental results. Design formulas and recommendations for future studies also are included.