An Analysis of Stress Relaxation in Elastico-Viscous Fluid Lubrication of Journal Bearings

1978 ◽  
Vol 100 (2) ◽  
pp. 287-294 ◽  
Author(s):  
A. Harnoy
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Load Capacity ◽  
Experimental Studies ◽  
Relaxation Effect ◽  
Journal Bearings ◽  
Friction Torque ◽  
Hydrodynamic Theory ◽  
Lubrication Film ◽  
Bearing Load

The hydrodynamic theory of lubrication in journal bearings is extended to elastico-viscous lubricants. The stress relaxation effect upon flow, pressure distribution, friction, and bearing load capacity is considered. This analysis deals with the case of a small relaxation time compared with the transit time required for the lubricant to pass through the bearing. A lubricant model is assumed with a constant relaxation time and without any cross stresses. It is found that the bearing load capacity of an elastic liquid lubrication film is higher than that of a Newtonian one, while the friction torque remains unchanged. Existing experimental studies have shown considerable improvement in journal bearing performance with elastico-viscous lubricants. This analysis suggests stress relaxation to be one of the factors giving rise to this improvement.

Numerical and experimental studies on the thermal and static characteristics of multi-leaf foil thrust bearing

2021 ◽  
pp. 135065012110110
Author(s):  
Yu Guo ◽  
Yu Hou ◽  
Qi Zhao ◽  
Xionghao Ren ◽  
Shuangtao Chen ◽  
...  
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Failure Process ◽  
Experimental Studies ◽  
Elastic Model ◽  
Static Characteristics ◽  
Bearing Load ◽  
Foil Thrust Bearing ◽  
Cooling Air

Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

An Approximate THD Theory for Journal Bearings

1990 ◽  
Vol 112 (2) ◽  
pp. 224-229 ◽  
Author(s):  
G. Gupta ◽  
C. R. Hammond ◽  
A. Z. Szeri
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Pressure Coefficient ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Substantial Agreement ◽  
Interactive Mode ◽  
Lubricant Flow ◽  
Bearing Load ◽  
Sophisticated Model

The aim of this paper is to make available to the industrial designer results of the thermohydrodynamic theory of journal bearings, by providing a simplified, yet accurate model of journal bearing lubrication that can be implemented on a personal computer and be used in an interactive mode. The simplified THD theory we propose consists of two coupled ordinary differential equations for pressure and energy and an algebraic equation for viscosity, which are to be solved iteratively. Bearing load capacity, maximum bearing temperature, maximum pressure, coefficient of friction and lubricant flow rate calculated from this simplified theory compare well with results from a more sophisticated model. We also make comparisons with experimental data on full journal bearings, demonstrating substantial agreement between experiment and simplified theory.

Static thermal performance evaluation of elliptical journal bearings with nanolubricants

2020 ◽  
pp. 135065012097074
Author(s):  
Rajeev Kumar Dang ◽  
Amit Chauhan ◽  
SS Dhami
Keyword(s):  
Thermal Performance ◽  
Load Capacity ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Stable Operation ◽  
Base Oil ◽  
Lubrication Film ◽  
Mineral Oils ◽  
Appreciable Increase ◽  
Thermo Physical Properties

Journal bearings of different configurations have been extensively used in turbomachinery and power generating equipments. Although circular bearings have simplest configuration and commonly used journal bearings, non-circular bearings such as multi-lobe and elliptical bearings have an added advantage of lower lubrication film temperature alongwith stable operation. In this study, static thermal performance of pure elliptical bearing lubricated with nanoparticles based mineral oils has been studied at different eccentricity ratios and bearing speeds. Two types of nanoparticles, namely, CuO and TiO2 with 0.5, 1.0 and 2.0 wt.% concentrations have been separately added in three different viscosity grades of oils. The effect of nanoparticles on thermo-physical properties of oil was considered to compute bearing performance parameters (pressure distribution, load capacity, oil temperature and power losses). Bearing model was generated by taking into account the modified Krieger Dougherty method to determine viscosity at different combinations of oils and nanoparticles. The findings indicate the increase in maximum pressure and load capacity with addition of nanoparticles and this increase was more pronounced at higher concentrations of nanoparticles and at higher viscosity grade oils. Load capacity was found to be increased by 14.24% and 9.21% with 2 wt% concentration of TiO2 and CuO nanoparticles respectively in base oil (AW68) at eccentricity ratio of 0.7. An increase in load capacity with nanolubricants was achieved without an appreciable increase in oil temperature.

Measurement of Oil Aeration Effects in Journal Bearings

2002 ◽  
Author(s):  
J. L. Nikolajsen ◽  
D. Dong ◽  
M. J. Goodwin
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Damping Capacity ◽  
Bearing Load ◽  
Bearing Stiffness

Preliminary measurements have been conducted to determine the effect of oil aeration on journal bearing performance. Oil aeration was observed to reduce the bearing load capacity and to increase the bearing stiffness. Also, the bearing damping capacity was improved significantly by oil aeration.

THD Analysis in Tilting-Pad Journal Bearings Using Multiple Orifice Hybrid Lubrication

1999 ◽  
Vol 121 (4) ◽  
pp. 892-900 ◽  
Author(s):  
I. F. Santos ◽  
R. Nicoletti
Keyword(s):  
Load Capacity ◽  
Flow Behavior ◽  
Journal Bearings ◽  
Operational Conditions ◽  
Tilting Pad ◽  
Bearing Load ◽  
Cooling Effects ◽  
Experimental Values ◽  
Oil Injection ◽  
Tilting Pad Journal Bearings

Tilting pad journal bearings (TPJB) using multiple orifice hybrid lubrication are analyzed applying a thermohydrodynamic (THD) theory. Adiabatic boundary conditions are adopted, and a two-dimensional model is used to represent the fluid flow behavior in the bearing gap. The influence of operational conditions on the temperature distribution and on the bearing load capacity is discussed and compared to theoretical and experimental values for a conventional hydrodynamic case (without radial oil injection). To improve the cooling effects, as well as rotor attitudes, the best location for orifices is the area near the pad edges.

Condensing Vapor Lubrication of Self-Acting Long Journal Bearings

1966 ◽  
Vol 88 (1) ◽  
pp. 236-245 ◽  
Author(s):  
W. Unterberg ◽  
J. S. Ausman
Keyword(s):  
Load Capacity ◽  
Saturation Pressure ◽  
Journal Bearings ◽  
Variable Pressure ◽  
Maximum Pressure ◽  
Two Phase ◽  
Bearing Load ◽  
Phase Liquid ◽  
High Pressure Region ◽  
Vapor Region

This is a theoretical investigation into the behavior of self-acting long journal bearings lubricated with vapor which may partially condense in the high-pressure region of a loaded bearing. Thermohydrodynamic considerations indicate that the lubricant temperature remains constant throughout the bearing. When the maximum pressure in the bearing reaches the saturation vapor pressure at the constant temperature, a further increase in bearing load then causes partial condensation instead of a rise in maximum pressure. In the partial condensation regime, the fluid annulus is made up of (a) a single-phase vapor region with variable pressure, and (b) a two-phase liquid-vapor region at constant saturation pressure. The regional interface locations and the bearing pressure distribution are obtained by “linearized ph” methods under the restrictions or boundary conditions of saturation pressure at the interfaces and constant lubricant mass content. It is shown that complete condensation cannot occur, so that the maximum pressure in the condensing vapor-lubricated bearing is limited to the saturation pressure. For this reason, the resulting load capacity always lies below that of a corresponding bearing lubricated with a noncondensing gas.

Surface Finish and Clearance Effects on Journal-Bearing Load Capacity and Friction

1959 ◽  
Vol 81 (2) ◽  
pp. 245-252 ◽  
Author(s):  
F. W. Ocvirk ◽  
G. B. DuBois
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
Surface Finish ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Oil Film ◽  
Bearing Clearance ◽  
Bearing Load

A method of relating surface finish to minimum oil-film thickness and the corresponding load capacity of plain journal bearings is presented with supporting experimental data. The effect of clearance on load capacity and friction are shown on graphs indicating an optimum bearing clearance.

Static Characteristics of Journal Bearings With Square Dimples

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Hiroyuki Yamada ◽  
Hiroo Taura ◽  
Satoru Kaneko
Keyword(s):  
Hydrodynamic Lubrication ◽  
Numerical Models ◽  
Experimental Studies ◽  
Surface Texturing ◽  
Hydrodynamic Pressure ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Conditions ◽  
Static Characteristics ◽  
Lubrication Performance

Surface texturing is a technique for improving frictional and hydrodynamic performances of journal bearings because microtextures can serve as reservoirs for oil or traps for debris and may also generate hydrodynamic pressure. Over the past two decades, many researchers have experimentally demonstrated that texturing of various tribological elements can reduce friction force and wear, contributing to improvement of lubrication performance. Some numerical studies have examined the hydrodynamic lubrication conditions and reported that surface texturing affects the static characteristics of journal bearings, such as their load carrying capacity and friction torque. However, the validity of these numerical models has not been confirmed because of a lack of experimental studies. This study proposes a numerical model that includes both inertial effects and energy loss at the edges of dimples on the surface of a journal bearing in order to investigate the bearing's static characteristics. Experimental verification of journal bearings is also conducted with a uniform square-dimple pattern on their full-bearing surface. The results obtained by the model agree well with those of experiment, confirming the model's validity. These results show that under the same operating conditions, textured bearings yield a higher eccentricity ratio and lower attitude angle than the conventional ones with a smooth surface. This tendency becomes more marked for high Reynolds number operating conditions and for textured bearings with a large number of dimples.

An Improved Analytical Solution for Self-Acting, Gas-Lubricated Journal Bearings of Finite Length

1961 ◽  
Vol 83 (2) ◽  
pp. 188-192 ◽  
Author(s):  
J. S. Ausman
Keyword(s):  
Analytical Solution ◽  
Finite Length ◽  
Load Capacity ◽  
Journal Bearings ◽  
Perturbation Solution ◽  
Order Perturbation ◽  
Small Eccentricity ◽  
First Order ◽  
Bearing Load ◽  
First Order Perturbation

An improved analytical solution designated the “linearized ph” solution is obtained for gas-lubricated journal bearings of finite length. Whereas the older first-order perturbation solution is useful for small eccentricity ratios (ε < 1/2), the linearized ph solution may be used for high eccentricity ratios. As such it permits estimation of ultimate bearing load capacity. The linearized ph solution is expressed in the form of simple corrections to the first-order perturbation solution, and as such can be computed quickly and easily.

The Importance of the Heat Capacity of Lubricants With Nanoparticles in the Static Behavior of Journal Bearings

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Rodrigo Nicoletti
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Load Capacity ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Volumetric Heat Capacity ◽  
Static Behavior ◽  
Load Carrying ◽  
Bearing Load ◽  
Interesting Solution

Nanoparticle additives increase the viscosity of lubricants, thus being an interesting solution for improving the load carrying capacity of hydrodynamic bearings. But, nanoparticles also change the thermal properties of the lubricant. Would these thermal properties be important to the static characteristics of lubricated bearings? The answer is yes, being the volumetric heat capacity an important parameter. In this work, the static behavior of journal bearings is studied when nanoparticles are added to the lubricant. A thermohydrodynamic analysis is performed with oil ISO VG68 (base fluid) and six different nanoparticles are considered as additives: Si, SiO2, Al, Al2O3, Cu, and CuO. The numerical results show that the bearing load capacity can be increased up to 10%, not only because of the higher viscosity, but also because of the higher volumetric heat capacity of the lubricant with nanoparticles. Higher volumetric heat capacity of the lubricant decreases temperature development in the bearing gap, thus resulting in higher viscosity distribution for the same operating conditions. In fact, the best results were obtained with ISO VG68 + copper oxide (CuO), whose volumetric heat capacity is the highest among the tested nanofluids. Such results were not equaled when only the viscosity of the lubricant had been changed.

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