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.

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.

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.

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.

Geometrical analysis of elliptical journal bearings and its effects on friction and load capacity

2019 ◽  
Vol 234 (5) ◽  
pp. 743-750
Author(s):  
Ali Ebrahimi ◽  
Saleh Akbarzadeh ◽  
Hassan Moosavi
Keyword(s):  
Friction Force ◽  
Reynolds Equation ◽  
Load Capacity ◽  
Major Axis ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Geometrical Parameters ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Lower Temperature

Elliptical bearings are one type of non-circular journal bearings which has two main advantages over the conventional circular bearings: lower temperature rise and lower vibrations. In this study, the energy equation and Reynolds equation are simultaneously solved under adiabatic boundary conditions. The predicted pressure and temperature are compared to the results of published literature for verification purposes. A parametric study is then conducted on the effect of geometrical parameters of the elliptical journal bearing on the load capacity, friction force, pressure, and oil temperature. Effect of geometric parameters of the bearing on the performance is studied. The results show that non-circularity parameter is the most influential parameter in the bearing, and an increase in the non-circularity results in the decrease in maximum pressure and temperature as well as the friction force. Increasing the eccentricity ratio, on the other hand, will cause an increase in the pressure, temperature, and the friction force. Changes in the angle between the major axis of the bearing and load direction decrease the load-carrying capacity and the non-dimensional pressure and results in an increase in the friction coefficient.

Prediction of the Onset of Flow Instability in a Single Horizontal Microtube With an Inlet Orifice

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
YanFeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Flow Instability ◽  
Saturation Pressure ◽  
Absolute Error ◽  
Heating Condition ◽  
Two Phase ◽  
Mass Fluxes ◽  
Upstream Pressure ◽  
Phase Liquid

A methodology to predict the onset of flow instability (OFI) in a single horizontal microtube with an inlet orifice is developed based on the predication of pressure drop. The predictive methodology states, for the same flow rate, the flow instability occurs as the single-phase liquid pressure drop under no heating condition equals the two-phase pressure drop under heating condition in a single microtube. The addition of inlet orifice increases the heat flux at the onset of flow instability by increasing the upstream pressure. The present methodology is validated by comparing the predicted heat flux at the onset of flow instability with our previous experimental data in the microtubes with three sizes of inlet orifices. The results show that the present method can predict the heat flux at the onset of flow instability with a deviation of 30% and mean absolute error of 13% at mass fluxes from 700 to 3000 kg/m2 s. The effects of inlet orifice size and saturation pressure on the onset of flow instability are also studied based on the present methodology. It is found that, at mass fluxes from 100 to 2000 kg/m2 s, the area ratio less than 15% eliminates the flow instability completely before the critical heat flux occurs.

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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