Physical Concepts of the Establishment of the Lubricating Oil Wedge and its Associated Load Carrying Capacity for the Mating Tooth Surfaces of High-Speed Gears

2009 ◽  
pp. 14-14-6
Author(s):  
Ernest K. Gatcombe
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Lubricating Oil ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Tooth Surfaces

The Granular Lubricated Journal Bearing: Evidence of Lift Formation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Venkata K. Jasti ◽  
Martin C. Marinack ◽  
Deepak Patil ◽  
C. Fred Higgs
Keyword(s):  
Carrying Capacity ◽  
Granular Flow ◽  
High Speed ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Flow Behavior ◽  
Extreme Environments ◽  
Granular Flows ◽  
Load Carrying Capacity ◽  
Load Carrying

This work demonstrates that granular flows (i.e., macroscale, noncohesive spheres) entrained into an eccentrically converging gap can indeed actually exhibit lubrication behavior as prior models postulated. The physics of hydrodynamic lubrication is quite well understood and liquid lubricants perform well for conventional applications. Unfortunately, in certain cases such as high-speed and high-temperature environments, liquid lubricants break down making it impossible to establish a stable liquid film. Therefore, it has been previously proposed that granular media in sliding convergent interfaces can generate load carrying capacity, and thus, granular flow lubrication. It is a possible alternative lubrication mechanism that researchers have been exploring for extreme environments, or wheel-regolith traction, or for elucidating the spreadability of additive manufacturing materials. While the load carrying capacity of granular flows has been previously demonstrated, this work attempts to more directly uncover the hydrodynamic-like granular flow behavior in an experimental journal bearing configuration. An enlarged granular lubricated journal bearing (GLJB) setup has been developed and demonstrated. The setup was made transparent in order to visualize and video capture the granular collision activity at high resolution. In addition, a computational image processing program has been developed to process the resulting images and to noninvasively track the “lift” generated by granular flow during the journal bearing operation. The results of the lift caused by granular flow as a function of journal rotation rate are presented as well.

Influence of geometric parameters on the bump foil bearing performance

2019 ◽  
Vol 234 (7) ◽  
pp. 1017-1026
Author(s):  
Sadanand Kulkarni ◽  
Soumendu Jana
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
System Development ◽  
Load Capacity ◽  
Radial Clearance ◽  
Load Carrying Capacity ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Load Carrying ◽  
Lift Off

High-speed rotating system development has drawn considerable attention of the researchers, in the recent past. Foil bearings are one of the major contenders for such applications, particularly for high speed and low load rotating systems. In foil bearings, process fluid or air is used as the working medium and no additional lubricant is required. It is known from the published literature that the load capacity of foil bearings depend on the operating speed, viscosity of the medium, clearance, and stiffness of the foil apart from the geometric dimensions of the bearing. In case of foil bearing with given dimensions, clearance governs the magnitude of pressure developed, whereas stiffness dictates the change in radial clearance under the generated pressure. This article deals with the effect of stiffness, clearance, and its interaction on the bump foil bearings load-carrying capacity. For this study, four sets of foil bearings of the same geometry with two levels of stiffness and clearance values are fabricated. Experiments are carried out following two factor-two level factorial design approach under constant load and in each case, the lift-off speed is measured. The experimental output is analyzed using statistical techniques to evaluate the influence of parameters under consideration. The results indicate that clearance has the maximum influence on the lift-off speed/ load-carrying capacity, followed by interaction effect and stiffness. A regression model is developed based on the experimental values and model is validated using error analysis technique.

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.

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.

The Effects of Fluid Inertia Forces on the Static Characteristics of Sector-Shaped, High-Speed Thrust Bearings in Turbulent Flow Regime

1989 ◽  
Vol 111 (3) ◽  
pp. 406-412 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Experimental Results ◽  
Polar Coordinates ◽  
Load Carrying Capacity ◽  
Static Characteristics ◽  
Fluid Inertia ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Inertia Forces

This paper describes a study on the performance characteristics of sector-shaped, high-speed thrust bearings subjected to the effects of both turbulence and fluid inertia forces. The basic lubrication equations are derived by integrating the momentum and continuity equations in the polar coordinates including the full inertia terms throughout the film thickness; and a numerical calculation technique combining the control volume integration and the Newton-Raphson linearization method is applied to solve the equations. The static characteristics such as the load carrying capacity and the pressure center are calculated for various values of pad extent angle and inner-to-outer radius ratio of a pad. The theoretical results of the load carrying capacity are compared with the experimental results. It was found that the fluid inertia forces have significant effects on the static characteristics of the bearings. Good agreement was obtained between theoretical and experimental results.

On the Performance of Hybrid Foil-Magnetic Bearings

1999 ◽  
Vol 122 (1) ◽  
pp. 73-81 ◽  
Author(s):  
H. Heshmat ◽  
H. Ming Chen ◽  
J. F. Walton,
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Magnetic Elements ◽  
Load Carrying ◽  
Hybrid Bearing

Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each other’s weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both. To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed. [S0742-4795(00)01201-1]

A Segregated SUPG/FEM for THDL Analysis In High Speed Slider Bearings With Injection Effect

2000 ◽  
Vol 123 (4) ◽  
pp. 732-741
Author(s):  
B. V. Rathish Kumar
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
Nonlinear Partial Differential Equations ◽  
Weight Functions ◽  
Load Carrying Capacity ◽  
Slider Bearing ◽  
Frictional Drag ◽  
Load Carrying ◽  
Injection Effect ◽  
Oil Injection

In this study, a segregated Finite Element Method (FEM) in the Petrov Galerkin framework with suitably defined Streamline Upwind Petrov Galerkin (SUPG) weight functions for a non-isothermal flow with temperature dependent density and viscosity in a high speed slider bearing has been proposed. The nonlinear partial differential equations (PDEs) governing the mass, momentum and energy conservations in thermohydrodynamic lubrication (THDL) of a high speed slider bearing with injection effects has been numerically analyzed for temperature, velocity and pressure fields. To assess the influence of the injection boundary condition on load generation and frictional drag in a slider bearing results have been compared with those from a study devoid of injection effects. Further the influence of consideration of fore-region pressure, geometrical configuration of a slider bearing, Peclet Number and thermoviscosity co-efficient in conjunction with oil injection effect on the load carrying capacity has been investigated. Oil injection is observed to bring in not only a gain in load carrying capacity but also a reduction in frictional drag and a reduction in the temperature specially in the vicinity of pad.

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