Elastohydrodynamic analysis of one-layered journal bearings

1998 ◽  
Vol 212 (3) ◽  
pp. 193-205 ◽  
Author(s):  
M Lahmar ◽  
A Haddad ◽  
D Nicolas
Keyword(s):  
Reynolds Equation ◽  
Mathematical Problem ◽  
Elastohydrodynamic Lubrication ◽  
Stability Margin ◽  
Journal Bearings ◽  
Perturbation Approach ◽  
Variable Approach ◽  
Load Carrying ◽  
Fast Solution ◽  
The Stability

Steady state and dynamic solutions to the problem of isothermal elastohydrodynamic lubrication of single-layered journal bearings are derived and presented. The mathematical problem comprises two parts: fluid and elasticity. The elasticity problem is governed by the elastostatic equations which are solved by application of a complex variable approach using the complex Kolosov-Muskhelishvili potentials. The fluid problem is described by the two-dimensional Reynolds equation which is discretized using a finite difference approach and solved by application of the Gauss-Seidel scheme with the Swift-Stieber boundary conditions. The fluid-structure coupling is achieved by an iterative procedure with an under-relaxation algorithm. The dynamic coefficients are obtained by use of a first-order perturbation approach. The results obtained show that the proposed elasticity model permits a fast solution of the problem, particularly under dynamic conditions. They also show that, under the effect of coating elastic deformation, the contact geometry is modified and the load-carrying capacity decreases while the stability margin of the journal bearing system increases.

The Effect of Journal Bearing Misalignment on Load and Cavitation for Non-Newtonian Lubricants

1986 ◽  
Vol 108 (4) ◽  
pp. 645-654 ◽  
Author(s):  
R. H. Buckholz ◽  
J. F. Lin
Keyword(s):  
Reynolds Equation ◽  
Numerical Solutions ◽  
Journal Bearings ◽  
Surface Boundary ◽  
Film Rupture ◽  
Aspect Ratios ◽  
Free Surface Boundary Condition ◽  
Load Carrying ◽  
Boundary Location ◽  
Surface Boundary Condition

An analysis for hydrodynamic, non-Newtonian lubrication of misaligned journal bearings is given. The hydrodynamic load-carrying capacity for partial arc journal bearings lubricated by power-law, non-Newtonian fluids is calculated for small valves of the bearing aspect ratios. These results are compared with: numerical solutions to the non-Newtonian modified Reynolds equation, with Ocvirk’s experimental results for misaligned bearings, and with other numerical simulations. The cavitation (i.e., film rupture) boundary location is calculated using the Reynolds’ free-surface, boundary condition.

Stability of Flexibly Supported Oil Journal Bearings Using Non-Newtonian Lubricants: Linear Perturbation Analysis

2000 ◽  
Vol 123 (3) ◽  
pp. 651-654 ◽  
Author(s):  
K. Raghunandana ◽  
B. C. Majumdar, and ◽  
R. Maiti
Keyword(s):  
Power Law ◽  
Perturbation Analysis ◽  
Perturbation Technique ◽  
Stability Margin ◽  
Journal Bearings ◽  
Diameter Ratio ◽  
Linear Perturbation ◽  
Flexible Support ◽  
The Stability ◽  
Power Law Index

The purpose of this paper is to study the effect of non-Newtonian lubricant on the stability of oil film journal bearings mounted on flexible support using linear perturbation technique. The model of non-Newtonian lubricant developed by Dien and Elrod is taken into consideration. The dynamic co-coefficients are calculated for different values of power law index and length to diameter ratio. These are then used to find stability margin for different support parameters to study the effect of the non-Newtonian lubricant.

Dynamic stability of micropolar lubricated hydrodynamic offset-halves journal bearings

2020 ◽  
pp. 135065012093685
Author(s):  
Sanyam Sharma ◽  
Chimata M Krishna
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Critical Mass ◽  
Journal Bearings ◽  
Aspect Ratios ◽  
Input Parameters ◽  
Output Characteristics ◽  
The Stability ◽  
Offset Factor

The plain circular journal bearings are not found to be stable by researchers when used in high speed rotating machineries. Hence, extensive research in the study of stability characteristics of non-circular bearings or lobed bearings assumed importance, of late. Present article deals with the stability analysis of non-circular offset bearing by taking selected set of input and output parameters. Modified Reynolds equation for micropolar lubricated rigid journal bearing system is solved using finite element method. Two kinds of input parameters namely, offset factors (0.2, 0.4) and aspect ratios (1.6, 2.0) have been selected for the study. The important output characteristics such as load, critical mass, whirl frequency ratio, and threshold speed are computed and plotted for various set of values of input parameters. The results obtained indicate that micropolar lubricated circular offset bearing is highly stable for higher offset factor and higher aspect ratio.

On the linear stability analysis of finite-hydrodynamic porous journal bearings under coupled stress lubrication

2007 ◽  
Vol 221 (7) ◽  
pp. 831-840 ◽  
Author(s):  
S. K. Guha ◽  
A. K. Chattopadhyay
Keyword(s):  
Reynolds Equation ◽  
Dynamic Performance ◽  
Slip Flow ◽  
Tangential Velocity ◽  
Continuum Theory ◽  
Transient State ◽  
Velocity Slip ◽  
Journal Bearings ◽  
The Stability ◽  
Coupled Stress

The objective of the present investigation is to study theoretically, using the finite-difference techniques, the dynamic performance characteristics of finite-hydrodynamic porous journal bearings lubricated with coupled stress fluids. In the analysis based on the Stokes micro-continuum theory of the rheological effects of coupled stress fluids, a modified form of Reynolds equation governing the transient-state hydrodynamic film pressures in porous journal bearings with the effect of slip flow of coupled stress fluid as lubricant is obtained. Moreover, the tangential velocity slip at the surface of porous bush has been considered by using Beavers-Joseph criterion. Using the first-order perturbation of the modified Reynolds equation, the stability characteristics in terms of threshold stability parameter and whirl ratios are obtained for various parameters viz. permeability factor, slip coefficient, bearing feeding parameter, and eccentricity ratio. The results show that the coupled stress fluid exhibits better stability in comparison with Newtonian fluid.

Influence of Surface Roughness and Its Orientation on Partial Elastohydrodynamic Lubrication of Rollers

1983 ◽  
Vol 105 (4) ◽  
pp. 591-597 ◽  
Author(s):  
J. Prakash ◽  
H. Czichos
Keyword(s):  
Reynolds Equation ◽  
Complete Solution ◽  
Elastohydrodynamic Lubrication ◽  
Coupled System ◽  
Line Contact ◽  
Roughness Parameters ◽  
Regime Changes ◽  
Lubrication Regime ◽  
Elasticity Equation ◽  
The Stability

In this paper, a complete solution for a rough, isothermal elastohydrodynamic line contact operating in the partial lubrication regime is presented. The semianalytical EHD line contact model developed recently [12], is used in solving the coupled system of average Reynolds equation and the elasticity equation. The effects of various operating parameters and the roughness parameters are investigated with an emphasis on the outlet behavior. The results indicate that in the partial lubrication regime changes in the outlet may play an important role on the stability of elastohydrodynamic films.

Thermal Elastohydrodynamic Lubrication of Non-Newtonian Fluids With Rough Surfaces

1997 ◽  
Vol 119 (4) ◽  
pp. 605-612 ◽  
Author(s):  
J. M. Wang ◽  
V. Aronov
Keyword(s):  
Surface Roughness ◽  
Shear Flow ◽  
Reynolds Equation ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Newtonian Fluids ◽  
Perturbation Approach ◽  
Correction Factors ◽  
Power Law Fluids

The characteristics of thermal elastohydrodynamic lubrication by non-Newtonian fluids for rough surfaces is investigated theoretically. The general Reynolds equation for two-sided striated roughness lubricated by power law fluids is established using a perturbation approach. New correction factors for the pressure flow and the shear flow are derived; these factors integrate both lubricant rheology and surface roughness characteristics. A more effective numerical algorithm is adopted to obtain the solutions for wide ranges of operating conditions. Observations and discussion lead to further understanding of the various interactions among different factors in a elastohydrodynamic lubrication process.

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.

Stability Analysis of a Complex Geared Rotor-Bearing System in a Turbine Reduction Gearbox

2013 ◽  
Author(s):  
Yuanhong Guan ◽  
Edward W. Sieveking ◽  
Varad Sampathkumar
Keyword(s):  
Stability Analysis ◽  
High Speed ◽  
Low Frequency ◽  
Stability Margin ◽  
Journal Bearings ◽  
Root Cause ◽  
Rotor Bearing ◽  
Noise Vibration ◽  
The Stability ◽  
Load Conditions

It is well known that the rotor system will meet several critical speeds or unstable regions as its rotation speed increases, especially when the rotor system is supported by journal bearings, since there exists a strong fluid-structure coupling which is rather prone to stability issues. Stability analysis of rotor-bearing systems (such as turbine-compressor) has been extensively studied in the literatures over the past 50 years. However, few studies have been performed on geared rotor-bearing systems, especially for complex multi-stage gear train systems. In this paper, the abnormal noise/vibration problem on a high speed 2 stage epicyclic reduction gearbox of a turbine-generator system is studied. This gearbox showed abnormal low frequency vibrations at low speed cranking and high speed partial load conditions. Further detailed probe testing showed that the gear bodies which were supported by 6 journal bearings had quite large sub-synchronized vibrations and shaft whirls were developed when the abnormal noise was present. In order to better understand the root cause and to fully eliminate such low frequency noise/vibration, a detailed finite element model for the whole turbine-gearbox-generator was developed under different speed / load conditions. The linearized journal bearing stiffness and damping matrix were calculated using a separate tool and then plugged into the above FE model. The gears are modeled as rigid bodies and connected by gear mesh stiffness. Gyroscopic force terms have also been included in the model. The stability of the whole system was evaluated by a complex eigenvalue analysis and the stability margin evaluated by the corresponding damping factor (or log decrement). The model predicts a range of instability regions and has good correlation with testing data. The root cause of this abnormal noise/vibration is due to the strong torsional-lateral coupling of gear systems, and further coupling with the fluid dynamics of the journal bearings under certain speed/load conditions. Some sensitivity studies are also performed in order to increase the stability margin and eliminate the sub-synchronized vibrations.

Stability analysis of a rigid rotor supported by two-lobe hydrodynamic journal bearings operating with a non-Newtonian lubricant

2018 ◽  
Vol 233 (6) ◽  
pp. 884-898 ◽  
Author(s):  
Saurabh K Yadav ◽  
Arvind K Rajput ◽  
Nathi Ram ◽  
Satish C Sharma
Keyword(s):  
Reynolds Equation ◽  
Pressure Field ◽  
Equation Of Motion ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Linear Finite Element ◽  
Runge Kutta Method ◽  
The Stability ◽  
Ellipticity Ratio ◽  
Bearing System

In the present work, an investigation has been performed on a rigid rotor supported by two-lobe journal bearings operating with a non-Newtonian lubricant. The governing Reynolds equation for pressure field is solved by using non-linear finite element method. Further to study the dynamic stability of the bearing system, governing equation of motion for the rotor position is solved by fourth order Runge–Kutta method. Bifurcation and Poincaré maps of two-lobe bearings are presented for different values of the non-Newtonian parameter and bearing ellipticity ratio. The numerical results illustrate that the ellipticity of a bearing with a dilatant lubricant improve the stability of the rotordynamic system.

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