Load Capacity Of Journal Bearings Research Articles

Improving the load capacity of journal bearings with chevron textures on the shaft surface

The manufacturing of texture patterns on the surfaces of lubricated bearings proved to be an interesting way of improving the tribological behavior in such systems. Depending on the adopted texture geometry, one can achieve significant reductions in friction or an improvement of the load-carrying capacity. In the case of journal bearings, the adoption of textures in the static surface of the contact (bearing casing) usually reduces the friction coefficient with the cost of increasing rotor eccentricity (an indication of a lower load capacity). In this work, we investigate the effects of texturing the rotating surface of the journal bearing’s lubricated contact. In this case, by adopting a chevron texture pattern, one can improve the bearing load-carrying capacity with the cost of increasing the bearing friction (opposite effect). The hydrodynamic lubrication is modeled by the Reynolds equation considering mass-conserving cavitation, whose solution is obtained using a moving multigrid algorithm due to the moving nature of the textures on the shaft. The results show that the improvement in load-carrying capacity is caused by a localized pumping effect of the lubricant towards the centerline of the bearing. In addition, the optimization of the texture geometry for different operating conditions leads to a general design guideline for such textures in journal bearings.

Experimental study on the effect of post-injection parameters on performance of extra-high pressure common-rail diesel engine

The application of surface texture technology can cut down the friction of journal bearing in internal combustion engines, so as to reduce energy consumption and improve effective. A three-dimensional simulation model of the lubrication characteristics is established so as to investigate the effect of surface texture on the load capacity of journal bearing. The accuracy of the simulation model is verified by comparing with the test. On this basis, through the establishment of a two-dimensional texture unit lubrication characteristics simulation model, the influence law of four different texture shapes, such as triangle, arc, rectangle and trapezoid, and typical structural parameters on the load capacity of the load capacity is studied. Finally, a three-dimensional simulation model of lubrication characteristics of the rectangular textured journal bearing is established. Based on this model, the effect of texture distribution position on the load capacity is studied. It shows that the position of the texture will affect the load capacity. The maximum pressure and load capacity are increased when the texture is in the wedge gap convergence region, but they will decrease when in the divergence region.

CFD analysis of load capacity of journal bearing with surface texture

The application of surface texture technology can cut down the friction of journal bearing in internal combustion engines, so as to reduce energy consumption and improve effective. A three-dimensional simulation model of the lubrication characteristics is established so as to investigate the effect of surface texture on the load capacity of journal bearing. The accuracy of the simulation model is verified by comparing with the test. On this basis, through the establishment of a two-dimensional texture unit lubrication characteristics simulation model, the influence law of four different texture shapes, such as triangle, arc, rectangle and trapezoid, and typical structural parameters on the load capacity of the load capacity is studied. Finally, a three-dimensional simulation model of lubrication characteristics of the rectangular textured journal bearing is established. Based on this model, the effect of texture distribution position on the load capacity is studied. It shows that the position of the texture will affect the load capacity. The maximum pressure and load capacity are increased when the texture is in the wedge gap convergence region, but they will decrease when in the divergence region.

Performance prediction of externally pressurized gas bearings for high-speed turbo-expander involving hydrogen, helium and air working fluids

High-speed hydrogen turbo-expander is widely employed in hydrogen liquefaction systems due to its high efficiency. The hydrogen bearings in high-speed turbo-expander are usually applied for low viscosity and pollution-free advantages. Nevertheless, the load capacity of hydrogen bearing is low and the research on maximizing the load capacity is limited by the complicated solution process and danger hydrogen experiment. The purpose of the paper is to easily and quickly acquire the load capacity of high-speed orifice externally pressurized hydrogen journal bearing for optimization of bearing performance. A new simple load capacity predicted model, that is universal for various working fluids involving hydrogen, helium and air, was proposed through the hydrostatic and hydrodynamic analysis. In the model, the evaluation indicators of hydrodynamic and hydrostatic effects were proposed. Based on the model, no numerical analysis and computer programming are needed to calculate the load capacity of journal bearing and numerous key design variables are considered. The results from the predicted model agree very well with those obtained from the finite difference method (FDM) technique. In view of the danger of hydrogen bearing experiment, the load capacity predicted model can be used to design the equivalent experiment of load capacity through substituting air for hydrogen working fluid.

Real-gas effects on aerodynamic bearings

Motivated by the use of aerodynamic bearings lubricated with high-pressure gases in energy conversion cycles, the Reynolds equation is adapted in order to include effects of real-gas and turbulence. Three geometries (Rayleigh-step slider, plain and herringbone-grooved journal bearing) serve to investigate real-gas effects on the static and dynamic properties with a wide variety of lubricants and nondimensional operating conditions. Computational results show a depreciation of the load capacity of journal bearings, with cases reaching a reduction of 50% with unequally affected force components. Stability can be affected both positively and negatively. Some stability losses reach nearly 100%, while improvements of several orders of magnitude with the grooved bearing are reported. Results are fluid-independent for similar reduced pressure and temperature.

A new model of water–gas turbulent lubrication for analysis of the static and dynamic characteristics in a journal bearing

A water–gas turbulent lubrication model is established by coupling the generalized Reynolds equation and bubble force equilibrium equation, which includes surface friction force and surface tension of bubbles. The above coupled-equations are solved to obtain load capacity, bubble concentration, and dynamic characteristic for journal bearing. The available experimental results reveal that the load capacity is well predicted by the present model. The theoretical results show that bubble surface tension and low gas volume fraction ( β ≤ 0.1) are beneficial in increasing the load capacity of journal bearing, while high gas volume fraction ( β ≥ 0.2) have opposite effects. The results also show that water–gas turbulent lubrication can decrease the dynamic characteristic parameters of journal bearing, while increasing the instability whirl frequency of journal bearing.

Mathematical models for the viscosity-temperature relationship of the lubricants containing nanoparticles and its applications to journal bearings

In this paper, various mathematical models obtained for relationship between viscosity and temperature for the lubricants containing nanoparticles is presented. These models are used to predict the static performance characteristics of journal bearing operating under lubricants containing nanoparticles. The nanoparticles used for the present work are CuO, CeO2 and Al2O3. Viscosity models for the nanolubricants are developed with the available experimental data. These models are essential for the computation of performance characteristics of journal bearings. The modified Reynolds and energy equations are used to obtain pressure and temperature distribution across the lubricant film and these equations are solved by using the finite-element method and a direct iteration scheme. The static performance characteristics of journal bearing are computed for various values of eccentricity ratios and aspect ratios. The computed results show that addition of nanoparticles increase the viscosity of lubricants and in turn load capacity of journal bearing.

A model for the effect of roughness on the load capacity of journal bearings

The flow generated by a rotating circular cylinder inside a corrugated outer cylinder is considered. The corrugations are small and are used to model roughness. The force on the inner cylinder, as a linear function of displacement, is found. This requires a Stokes expansion to determine a first-order correction in the Reynolds number R R . The result implies as expected that transverse roughness acts to increase the load capacity of the bearing at low R R , which is confirmed by previous numerical experiments. In addition, roughness can induce reversed flow at much smaller displacements than for smooth bearings.

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

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.

Hydrodynamic Lubrication of Journal Bearings by Non-Newtonian Lubricants : Effects of Composite Flow Characteristics

It is found experimentally that the lubricating oils, with high molecular weight polymers, indicate the composite flow characteristics involving pseudo-plastic and dilatant behavior. Applying a polynomial expression for such non-Newtonian characteristics, a modified Reynolds equation is derived, to obtain the pressure distribution and the load capacity of journal bearings. Comparing with experiments, the physical meanings of the composite flow characteristics are made clear. The effects on the bearing performance are discussed, by introducing a ratio of nonlinearity and a rate of nonlinear influence.

Empirical Treatment of Hydrodynamic Journal Bearing Performance in the Superlaminar Regime

The application of a perturbation in terms of simple correlations for friction in turbulent Couette and ‘screw’ flows, together with a further empirical assumption consonant with the experimental work of Smith and Fuller (1), leads to a pressure field equation identical in form with the Reynolds equation. The load capacity of journal bearings throughout most of the superlaminar range may be represented by a single curve, and existing laminar solutions may be applied with the parameters modified by Reynolds number. The theory is compared with published experimental results, and with the most successful theoretical treatment (4). The correlations obtained confirm the adequacy of the theory to predict performance in the superlaminar régime.

The Performance of Externally Pressurized Bearings Using Simple Orifice Restrictors

The load capacity and vibration characteristics of externally pressurized thrust and journal bearings have been investigated. The bearings used orifices sufficiently recessed back from the bearing surface to ensure that the area of the orifice is the minimum presented to the gas flow. The journal bearings consist of plain cylinders with one or two rows of eight orifices, and the thrust plates of plain discs with six orifices drilled in equispaced circumferential grooves. The load capacity of the thrust plates agrees with that calculated but the vibrations are greater than predicted. The load capacity of journal bearings is about half that calculated assuming axial flow conditions in the bearing, but circumferential flow can account for the difference. Synchronous and half-speed vibrations of a shaft rotating within these bearings have been measured and found to agree with those calculated on the assumption that the gas films behave as linear springs. *Presented as an American Society of Lubrication Engine...