Theoretical and experimental investigation of the effect of oil aeration on the load-carrying capacity of a hydrodynamic journal bearing

2007 ◽  
Vol 221 (7) ◽  
pp. 779-786 ◽  
Author(s):  
M. J. Goodwin ◽  
D Dong ◽  
H Yu ◽  
J. L. Nikolajsen
Keyword(s):  
Carrying Capacity ◽  
Lubricating Oil ◽  
Hydrodynamic Effect ◽  
Air Bubbles ◽  
Load Carrying Capacity ◽  
Hydrodynamic Bearing ◽  
Low Viscosity ◽  
Discernible Effect ◽  
Load Carrying ◽  
Bearing Load

It is widely assumed that the presence of air bubbles in the lubricating oil of a hydrodynamic bearing gives rise to a reduced load-carrying capacity, because of the high compressibility and low viscosity of the air and its tendency, therefore, to upset the hydrodynamic effect. The aim of the work described in the current paper was to investigate the accuracy of this assumption by theoretical and experimental means, and also to provide quantitative data relating to the concentration of air bubbles and their size that are required for any discernible effect. The paper has the following three main contributions: (a) a theoretical model based on Reynolds equation, but modified to allow for the effect of aeration on lubricant viscosity and density, is proposed; (b) a novel method of injecting air bubbles into lubricating oil and for measuring their size and concentration was developed; and (c) an experimental hydrodynamic bearing test rig was implemented and run with both aerated and non-aerated lubricating oil, and in each case measurements of the load-carrying capacity for various operating speeds were made. The results from both theoretical and experiment work show that the presence of air bubbles in the lubricating oil leads to a slight decrease in bearing load-carrying capacity at high operating speeds. For normal operating speeds, however, (i.e. those resulting in eccentricity ratios greater than 0.6) results show that the presence of air bubbles has little effect on bearing load-carrying capacity.

Geometry Optimization of Textured Three-Dimensional Micro- Thrust Bearings

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
C. I. Papadopoulos ◽  
E. E. Efstathiou ◽  
P. G. Nikolakopoulos ◽  
L. Kaiktsis
Keyword(s):  
Carrying Capacity ◽  
Stokes Equations ◽  
Load Capacity ◽  
Three Dimensional ◽  
Load Carrying Capacity ◽  
Thrust Bearings ◽  
Micro Channels ◽  
Wide Range ◽  
Load Carrying ◽  
Bearing Load

This paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as micro-channels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.

Matching the relationship between rotational speed and load-carrying capacity on high-speed and heavy-load hydrostatic thrust bearing

2018 ◽  
Vol 70 (1) ◽  
pp. 8-14 ◽  
Author(s):  
Xiao-dong Yu ◽  
Lei Geng ◽  
Xiao-jun Zheng ◽  
Zi-xuan Wang ◽  
Xiao-gang Wu
Keyword(s):  
Carrying Capacity ◽  
Rotational Speed ◽  
Thrust Bearing ◽  
Lubricating Oil ◽  
Load Carrying Capacity ◽  
Average Pressure ◽  
Content Type ◽  
Oil Film ◽  
Hydrostatic Bearing ◽  
Load Carrying

Purpose Rotational speed and load-carrying capacity are two mutual coupling factors which affect high precision and stable operation of a hydrostatic thrust bearing. The purpose of this paper is to study reasonable matching relationship between the rotational speed and the load-carrying capacity. Design/methodology/approach A mathematical model of relationship between the rotational speed and the load-carrying capacity of the hydrostatic bearing with double-rectangle recess is set up on the basis of the tribology theory and the lubrication theory, and the load and rotational speed characteristics of an oil film temperature field and a pressure field in the hydrostatic bearing are analyzed, reasonable matching relationship between the rotational speed and the load-carrying capacity is deduced and a verification experiment is conducted. Findings By increasing the rotational speed, the oil film temperature increases, the average pressure decreases and the load-carrying capacity decreases. By increasing the load-carrying capacity, the oil film temperature and the average pressure increases and the rotational speed decreases; corresponding certain reasonable matching values are available. Originality/value The load-carrying capacity can be increased and the rotational speed improved by means of reducing the friction area of the oil recess by using low-viscosity lubricating oil and adding more oil film clearance; but, the stiffness of the hydrostatic bearing decreases.

Dynamic stability analysis of noncircular two-lobe journal bearings with couple stress lubricant regime

2020 ◽  
pp. 135065012094551
Author(s):  
Mahdi Zare Mehrjardi
Keyword(s):  
Steady State ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Journal Bearings ◽  
Lubricating Oil ◽  
Couple Stress Fluid ◽  
Load Carrying Capacity ◽  
Stress Parameter ◽  
Attitude Angle ◽  
Load Carrying

In this research, the steady state and dynamic performances of two-lobe noncircular journal bearings with couple stress lubricant are presented. The lubricating oil, containing additives and contaminants, is modeled as the couple stress fluid. The modified Reynolds equation is obtained using the couple stress lubrication theory and is then solved by finite element method as an efficient numerical technique. The steady-state characteristics of bearings, including the load carrying capacity and attitude angle, are determined for various values of the couple stress parameter. The results show that applying the couple stress fluid improves the efficiency of two-lobe bearings in terms of an increased load carrying capacity and reduced attitude angle. Also, the stability performance of the investigated bearings is studied using rotor motion equations based on linear and nonlinear dynamic methods. The results indicate that any increase in the lubricant couple stress parameter enhances the bearing ability to damp the rotor perturbations. In other words, by varying the lubricant from Newtonian oil to the couple stress type and upgrading its properties, the curves of the critical mass parameter and whirl frequency ratio have an increasing and decreasing trend, respectively. Based on the fourth-order Runge–Kutta method results, the dynamic trajectory of the rotor center in the bearing space changes with increasing the couple stress parameter from diverging disturbances and limits the cycle perturbations around the bearing center to converging oscillations to the static equilibrium point. Moreover, the effect of changing lubricant properties on the two-lobe bearing’s performance is more pronounced at higher values of the couple stress parameter, especially with an increase in the noncircularity of bearings’ geometry.

On the Combined Effects of Lubricant Inertia and Viscous Dissipation in Long Bearings

1997 ◽  
Vol 119 (1) ◽  
pp. 76-84 ◽  
Author(s):  
E. Kim ◽  
A. Z. Szeri
Keyword(s):  
Carrying Capacity ◽  
Journal Bearings ◽  
Isothermal Flow ◽  
Nonisothermal Flow ◽  
Combined Effects ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Bearing Load ◽  
The Stability ◽  
Rate Of Dissipation

We have demonstrated earlier that for laminar, isothermal flow of the lubricant in the non-cavitating film of long journal bearings, inertia has negligible effect on the load-carrying capacity and influences only the stability characteristics of the bearing. The question we pose in the present paper is: “will these conclusions remain valid for nonisothermal flow, or will lubricant inertia and dissipation interact and result in significant changes in bearing performance?” The results obtained here assert that the effect of lubricant inertia on load-carrying capacity remains negligible, irrespective of the rate of dissipation. The stability of the bearing is, however, affected by lubricant inertia. These results, although obtained here for long bearings and noncavitating films, are believed to be applicable to some practical bearing operations and suggest that for these, bearing load may be calculated from classical, i.e., noninertial theory.

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