CFD analysis of journal bearing hydrodynamic lubrication by Bingham lubricant

A one piece hydrodynamic bearing which can include hydrostatic support features. The pads are supported on a single thin web for pivoting on a support structure which can include one or more beam-like members. The bearings may have hydrostatic and active control attributes and is very attractive in cryogenic applications where it is very difficult to prevent leakage in conventional hydrostatic tilt pad bearings. The hydrostatic feed through the post eliminates this problem completely and prevents the fretting at the pivots common with conventional tilt pad bearings. A cavity provided under a pad support membrane can be used as an active control device. The pressure can cause the bearing set or assembly clearance to be reduced thus providing better damping and centering capability. The preload in the pad can be actively controlled in this manner. The pad has a limiting device to prevent a negative pre-load condition from occurring. This active control of bearing clearance can allow bearings to operate at large spreads in temperatures.

Hydrostatic and active control movable pad bearing

The effects of geometric change due to wear on the dynamic characteristics of journal bearings are determined theoretically in both laminar and turbulent regimes. The dynamic characteristics such as spring and damping coefficients and whirl onset speed of a rigid rotor supported by two identical symmetrically aligned bearings are analyzed by a semianalytical finite element method, and the numerical results for various wear depth parameters are indicated in graphical form. The geometric change due to wear has significant effects on the principal spring coefficients and on the cross-coupled damping coefficients. The whirl onset speed for a worn journal bearing whose wear depth parameter is larger than 0.3 becomes higher than the speed for a nonworn bearing.

Performance Characteristics of Worn Journal Bearings in Both Laminar and Turbulent Regimes. Part I: Steady-State Characteristics

Influence of textured surface on the performance of non-recessed hybrid journal bearing operating with non-Newtonian lubricant

This study is aimed at predicting the non-Newtonian effects of multigrade oils on journal bearing performance. The governing differential equation, similar to the Reynolds equation, is derived using a general apparent-viscosity function as the constitutive equation in order to be able to accommodate different rheological equations. Treatment of the non-Newtonian effects is confined to nonlinear viscous behavior. Oil elasticity and normal stress effects are not considered. The problem formulation resembles that of the THD problem, and the governing differential equation contains non-Newtonian factors based on the cross-film integrals of viscosity. The problem is solved by the finite difference technique, and the results show reasonable agreement with the experimental data available in the literature. In order to represent the rheology of multigrade engine oils, a new non-linear viscous constitutive equation is proposed. This equation is fitted to experimental data on the rheology of two multigrade engine o...

Non-Newtonian Effects of Multigrade Oils on Journal Bearing Performance

Few experimental investigations on the relation between the nonlinearity of lubricants and the performance of bearings have been published. Theoretical analysis of the relation was presented in the first paper, and experimental analysis of this problem is conducted in this paper. The initial viscosity and the coefficient of pseudo-plasticity are given by the investigation of the flow rate of pseudo-plastic fluids obtained by adding polyisobutylene to spindle oils. The coefficient of pseudo-plasticity is a scale to indicate the behavior of this lubricant. Analyzing the experimental results of the performance of bearings using this lubricant, it is found that the film pressure and the load capacity of pseudo-plastic fluids are smaller than those of Newtonian fluids whose viscosity is equal to the initial viscosity. These values become smaller with an increase in nonlinear factor and eccentricity ratio of bearing.

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Hydrodynamic Lubrication of Journal Bearings by Pseudo-Plastic Lubricants : Part 2, Experimental Studies

Application of Finite-Element Method to Hydrodynamic Lubrication Problems : Part 2, Finite-Width Bearings

Few papers which applied the finite-element method to hydrodynamic lubrication have been published, in spite of many literatures introducing the finite-element method in structural problems. In this paper, the applications of the finite-element method for hydrodynamic lubrication of infinite-width bearings are presented. It is claimed that the finite-element method is able to obtain the accurate results by using a few elements. The finite-element solution is compared with an exact solution and a finite-difference solution of step bearings, plane slider learnings and journal bearings.

Application Bulletin of the JSME of Finite-Element Method to Hydrodynamic Lubrication Problems : Part 1, Infinite-Width Bearings

The qualitative analyses for the core formation inherent in a Bingham solid have already been given by the previous investigations for hydrodynamic lubrication of a Bingham solid. However, they don't make clear the behavior of the solid exactly, because the analyses for finite bearings are not sufficient.In this paper, a method of the vector analysis based on the flow characteristics of a Bingham solid, is presented for a finite bearing and shear stress and velocity distribution in the film are obtained.Using this method, we deduced the equivalent Reynolds equation of a Bingham solid and also established the general theory on the core formation. Consequently it became clear that the core formation is determined by the shear stress distribution which depends on the pressure gradient, the film thickness and the velocity of the slider surface.

Behavior of a Bingham Solid in Hydrodynamic Lubrication : Part 1, General Theory

Some investigations about hydrodynamic lubrication of journal bearings using pseudo-plastic fluids were published in the previous papers by authors. In finite bearings, the velocity gradients in circumferential and axial directions are related respectively with the shear stresses in both directions, so that the velocity gradients in circumferen tial and axial directions correlate with each other. In this paper, a more general modified Reynolds equation including the effects of correlation is derived. Applying this theory to journal bearings, the bearing performance, such as pressure distribution, load capacity, frictional force and oil flow, is obtained. It is compared with the previous analysis neglecting the correlation. It is made clear that the effects of correlation are small in the case of a small "nonlinear factor" which is a dimensionless quantity indicating the non-Newtonian characteristics.

Hirotsugu Hayashi

Papers

Hydrodynamic Lubrication of Journal Bearings by Pseudo-Plastic Lubricants : Part 2, Experimental Studies

Application of Finite-Element Method to Hydrodynamic Lubrication Problems : Part 2, Finite-Width Bearings

Application Bulletin of the JSME of Finite-Element Method to Hydrodynamic Lubrication Problems : Part 1, Infinite-Width Bearings

Behavior of a Bingham Solid in Hydrodynamic Lubrication : Part 1, General Theory

Hydrodynamic Lubrication of Journal Bearings by Pseudo-Plastic Lubricants : Part 3, Theoretical Analysis Considering Effects of Correlation