scholarly journals Bifurcation Analysis of Rotor/Bearing System using Third Order Journal Bearings Stiffness and Damping Coefficients

2021 ◽  
Author(s):  
Tamer Elsayed ◽  
Hussein Sayed
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Third Order ◽  
The Third ◽  
Bifurcation Stability ◽  
Jeffcott Rotor ◽  
Load Carrying ◽  
Proper Design ◽  
Rotor Stiffness ◽  
Stiffness And Damping

Abstract Journal bearings have many applications in industry due to its high load carrying capacity. In addition proper design of journal bearings enables safe operation at very high speeds. However, they are susceptible to oil whirl instability which may cause bearing failure. The fluid film pressure distribution inside the journal bearing is described by Reynolds equation. Many studies had been done to approximate the bearing performance using first order bearing coefficients. Although this analysis is stable for evaluating the threshold speed but it is insensitive to limit cycles above the threshold speed. Mush literature show that above the threshold speed, subcritical or supercritical bifurcations may be observed. Therefore, the aim of the present paper is to evaluate the third order bearing coefficients for a finite length journal bearing using finite perturbation method. The values of these coefficients are evaluated using infinitesimal perturbation analysis. These values are used to investigate the bifurcation stability of flexible Jeffcott rotor supported by two symmetric journal bearings. The effect of rotor stiffness ratio on the bifurcation stability of the system is investigated. The results of this work show that the third order parameters can be used to evaluate the type of bifurcation above the threshold speed.

scholarly journals Bifurcation analysis of rotor/bearing system using third-order journal bearing stiffness and damping coefficients

2021 ◽  
Author(s):  
T. A. El-Sayed ◽  
Hussein Sayed
Keyword(s):  
Equations Of Motion ◽  
Journal Bearings ◽  
Third Order ◽  
Damping Coefficients ◽  
The Third ◽  
Rotor Bearing ◽  
Bearing Stiffness ◽  
Rotor Stiffness ◽  
Stiffness And Damping ◽  
Bearing System

AbstractHydrodynamic journal bearings are used in many applications which involve high speeds and loads. However, they are susceptible to oil whirl instability, which may cause bearing failure. In this work, a flexible Jeffcott rotor supported by two identical journal bearings is used to investigate the stability and bifurcations of rotor bearing system. Since a closed form for the finite bearing forces is not exist, nonlinear bearing stiffness and damping coefficients are used to represent the bearing forces. The bearing forces are approximated to the third order using Taylor expansion, and infinitesimal perturbation method is used to evaluate the nonlinear bearing coefficients. The mesh sensitivity on the bearing coefficients is investigated. Then, the equations of motion based on bearing coefficients are used to investigate the dynamics and stability of the rotor-bearing system. The effect of rotor stiffness ratio and applied load on the Hopf bifurcation stability and limit cycle continuation of the system are investigated. The results of this work show that evaluating the bearing forces using Taylor’s expansion up to the third-order bearing coefficients can be used to profoundly investigate the rich dynamics of rotor-bearing systems.

scholarly journals Evaluation of static and dynamic characteristics of hydrodynamic spiral-grooved journal bearings using the CFD

2019 ◽  
Vol 39 (2) ◽  
pp. 197-204
Author(s):  
Janardhan Chander Matlapudi ◽  
Prudhvi Kanth Gunti ◽  
Datta Sriram Sigatapu ◽  
Niranjana Behera
Keyword(s):  
Cross Sections ◽  
Carrying Capacity ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Rotor Surface ◽  
Computational Fluid Dynamics Cfd ◽  
Predicted Values ◽  
Stiffness And Damping

Performance of plain journal bearings can be different by inserting inserting grooves of different cross-sections either on the journal or a bearing surface. This paper presents the prediction of load carrying capacity, stiffness, and damping coefficients of spiral-grooved bearing using the Computational Fluid dynamics (CFD) technique. The spiral grooves have been provided on the rotor surface. The error between the predicted values of these parameters using the CFD and the experimental value is low. A comparative analysis of performance has also been carried out between a grooved journal bearing and a plain journal bearing. The load carrying capacity of plain journal bearing is high when compared to spiral grooved journal bearing. At higher eccentrcity ratios, stability of a spiral-grooved journal bearing is comparatively better than a plain bearing.

The Lubricant Flow Structure and Pressure Generation in a Journal Bearing With Diamond-Knurled Stator Surface

2007 ◽  
Author(s):  
Hongmin Li ◽  
Minel J. Braun
Keyword(s):  
Computational Models ◽  
Journal Bearing ◽  
Stokes Equations ◽  
Journal Bearings ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Load Carrying ◽  
Rotor Surface ◽  
Volume Algorithm ◽  
Stiffness And Damping

Journal bearings are popularly used in turbo machinery. The load carrying capacity and the dynamic behavior, stiffness and damping, of a journal bearing are determined by lubricant and bearing parameters: clearance, and shaft diameter and rotation speed, and surface morphology of the rotor and stator surfaces. It has been found that journal bearings with roughened stator surfaces have better performance. This paper presents a numerical investigation on the flow of lubricant in the knurls, in the fluid film between the rotor and the land of the stator, and the pressure generated on the rotor surface in a knurled journal bearing. Three computational models are developed and compared. The full Navier-Stokes equations are solved with a finite volume algorithm to simulate the fluid flow and the pressure generation. The total forces on the rotor surfaces are correlated to the bearing eccentricity and compared to the forces on the smooth bearing shaft of the same clearance. The effects of knurls on the bearing performance will be analyzed and guidance on further investigations on knurled journal bearing is presented.

Steady-State and Dynamic Behaviour of Multi-Recess Hybrid Oil Journal Bearings

1979 ◽  
Vol 21 (5) ◽  
pp. 345-351 ◽  
Author(s):  
M. K. Ghosh ◽  
B. C. Majumdar ◽  
J. S. Rao
Keyword(s):  
Perturbation Theory ◽  
Steady State ◽  
Theoretical Analysis ◽  
Dynamic Behaviour ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Time Dependent ◽  
Damping Coefficients ◽  
Stiffness And Damping

A theoretical analysis of the steady-state and dynamic characteristics of multi-recess hybrid oil journal bearings is presented. A perturbation theory for small vibrations is used to solve an incompressible, finite journal bearing with a time-dependent term. Load capacity, attitude angle, friction parameter, stiffness and damping coefficients are evaluated for a capillary-compensated bearing.

Controlling Journal Bearing Instability Using Active Magnetic Bearings

2007 ◽  
Author(s):  
A. El-Shafei ◽  
A. S. Dimitri
Keyword(s):  
Journal Bearing ◽  
Magnetic Bearing ◽  
Journal Bearings ◽  
Active Magnetic Bearing ◽  
Rotating Speed ◽  
Damping Characteristics ◽  
Oil Whip ◽  
Novel Approach ◽  
Oil Whirl ◽  
Load Carrying

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

Stability of Jeffcott Rotor Operating in Tilting 3-Pad Journal Bearings with Turbulent Oil Film

2009 ◽  
Vol 147-149 ◽  
pp. 450-455
Author(s):  
Stanislaw Strzelecki ◽  
Sobhy M. Ghoneam
Keyword(s):  
Theoretical Investigation ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Oil Film ◽  
Temperature Distributions ◽  
Jeffcott Rotor ◽  
Oil Flow ◽  
The Stability ◽  
Oil Film Pressure

This paper introduces the results of theoretical investigation on the dynamic characteristics of tilting 3-pad journal bearing that operates with turbulent oil film. The Reynolds, energy, viscosity and geometry equations determine the oil film pressure, temperature distributions, and oil film resultant force that are the grounds for the dynamic characteristics of bearing. These equations were solved simultaneously on the assumption of adiabatic laminar or adiabatic turbulent oil flow in the bearing gap. The stability and system damping of Jeffcott rotor operating in tilting 3-pad journal bearing was determined.

Behavior of Finite Journal Bearings Under Dynamic Loading Conditions

1980 ◽  
Vol 102 (3) ◽  
pp. 333-338 ◽  
Author(s):  
G. S. A. Shawki ◽  
M. O. A. Mokhtar ◽  
Z. S. Safar
Keyword(s):  
Boundary Conditions ◽  
Computer Program ◽  
Variational Methods ◽  
Axial Length ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
The Third ◽  
Dynamic Loading Conditions ◽  
Generalized Reynolds Equation

Performance characteristics for a complete journal bearing of finite axial length are obtained analytically using a new set of boundary conditions. The generalized Reynolds equation is transformed, in the present analysis, into three ordinary differential equations, two of which being readily integrable while the third is solved by variational methods. By the aid of a specially devised computer program, the validity of the analysis has been assured when applied to prescribed journal loci including stationary, circular, elliptical, and linear harmonic journal oscillation.

Designing the Partially Porous Journal Bearings of an Aerostatic Spindle

2017 ◽  
Vol 868 ◽  
pp. 110-117
Author(s):  
Te Yen Huang ◽  
Song Chiang Shen ◽  
Shao Yu Hsu
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Low Cost ◽  
Journal Bearings ◽  
Porous Insert ◽  
Load Carrying ◽  
High Speed Rotation ◽  
Ultra Precision ◽  
Precision Machine Tools ◽  
Aerostatic Spindle

The aerostatic journal bearings are widely used in ultra-precision machine tools. Due to remarkable ability of the porous medium in flow restriction, the porous aerostatic journal bearings are better than other types of aerostatic bearings in load carrying capacity, stiffness, damping and dynamic stability. The partially porous aerostatic journal bearing has the advantages of easy production and low cost. Moreover, the gap between the porous insert and the spindle can be adjusted to reduce the eccentricity due to high speed rotation. In this study, the effects of the size of the porous insert and the thickness of the air gap between the spindle and the housing on the gap pressure, the stiffness and the load carrying capability of the partially porous aerostatic journal bearing were figured out for performance evaluation.

Thermohydrodynamic Analysis for Laminar Flow Journal Bearing

1978 ◽  
Vol 100 (4) ◽  
pp. 510-512 ◽  
Author(s):  
Z. S. Safar
Keyword(s):  
Heat Flow ◽  
Radial Direction ◽  
Energy Equation ◽  
Journal Bearing ◽  
Separation Of Variables ◽  
Isoperimetric Problem ◽  
Momentum Equation ◽  
Journal Bearings ◽  
The Third ◽  
Semianalytical Method

This paper describes a semianalytical method for solving the thermohydrodynamic problem in journal bearings. It is assumed that the shaft is isothermal and the bearing heat flow is in the radial direction. The momentum equation is reduced to ordinary differential equations by separation of variables. Two of the resulting equations are integrated directly, while the third equation is interpreted and solved as an isoperimetric problem. The energy equation with its boundary conditions is solved by the Galerkin Kantarovich method.

Research on the Static and Dynamic Characteristics of Misaligned Journal Bearing Considering the Turbulent and Thermohydrodynamic Effects

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Guohui Xu ◽  
Jian Zhou ◽  
Haipeng Geng ◽  
Mingjian Lu ◽  
Lihua Yang ◽  
...  
Keyword(s):  
Film Thickness ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Static And Dynamic Characteristics ◽  
Oil Film ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Journal Misalignment ◽  
Oil Film Pressure

Journal misalignment usually exists in journal bearings that affect nearly all the bearings static and dynamic characteristics including minimum oil film thickness, maximum oil film pressure, maximum oil film temperature, oil film stiffness, and damping. The main point in this study is to provide a comprehensive analysis on the oil film pressure, oil film temperature, oil film thickness, load-carrying capacity, oil film stiffness, and damping of journal bearing with different misalignment ratios and appropriately considering the turbulent and thermo effects based on solving the generalized Reynolds equation and energy equation. The results indicate that the oil thermo effects have a significant effect on the lubrication of misaligned journal bearings under large eccentricity ratio. The turbulent will obviously affect the lubrication of misaligned journal bearings when the eccentricity or misalignment ratio is large. In the present design of the journal bearing, the load and speed become higher and higher, and the eccentricity and misalignment ratio are usually large in the operating conditions. Therefore, it is necessary to take the effects of journal misalignment, turbulent, and thermal effect into account in the design and analysis of journal bearings.

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