Stability Analysis of a Rough Journal Bearing Considering Cavitation Effects

2005 ◽  
Vol 127 (1) ◽  
pp. 112-119 ◽  
Author(s):  
T. V. V. L. N. Rao ◽  
Jerzy T. Sawicki
Keyword(s):  
Stability Analysis ◽  
Governing Equation ◽  
Journal Bearing ◽  
Numerical Procedure ◽  
Instability Threshold ◽  
Bearing Surface ◽  
Surface Configuration

A modified governing equation is derived incorporating the effects of roughness and cavitation in a journal bearing. The available theories of Reynolds roughness and cavitation algorithm proposed by Elrod are utilized in this work to develop a numerical procedure for stability analysis of a liquid lubricated rough journal bearing. The Elrod generalized theory of Reynolds roughness provides a governing equation based on the surface configuration. The Elrod cavitation algorithm conserves mass throughout the bearing and automatically predicts the full film and cavitation regions using a switch function. The roughness is considered on either or both the bearing and journal surfaces. The instability threshold speed increases significantly for the roughness patterns on the grooved bearing surface only at higher eccentricity ratios. The threshold speed increases significantly with increase in the inclination of herringbone type striated roughness patterns on the journal surface from 110° to 150°.

scholarly journals Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory

Friction ◽  
2020 ◽  
Author(s):  
Yu Huang ◽  
Haiyin Cao ◽  
Zhuxin Tian
Keyword(s):  
Stability Analysis ◽  
Equilibrium Point ◽  
Journal Bearing ◽  
Stability Boundary ◽  
Initial Point ◽  
Journal Bearings ◽  
Bearing Surface ◽  
Rotating Speed ◽  
Stability Threshold ◽  
The Stability

AbstractIn this study, we observe that there are two threshold speeds (stability threshold speed and second threshold speed) for the long journal bearing, which is different for the short bearing. When the rotating speed is below the stability threshold speed, the stability boundary nearly coincides with the clearance circle, and the journal center gradually returns to the equilibrium point after being released at an initial point. If the rotating speed is between the stability threshold speed and the second threshold speed, after being released at an initial point, the journal center converges to a contour containing the equilibrium point. In this situation, for a higher rotating speed, the corresponding contour is also larger. When the rotating speed exceeds the second threshold speed, the journal gradually moves towards the bearing surface after being released at an initial point.

Thermoacoustic Stability Analysis of a Full-Annular Lean Combustor for Heavy-Duty Applications

2021 ◽  
Author(s):  
Daniele Pampaloni ◽  
Antonio Andreini ◽  
Alessandro Marini ◽  
Giovanni Riccio ◽  
Gianni Ceccherini
Keyword(s):  
Stability Analysis ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Numerical Procedure ◽  
Pollutant Emissions ◽  
Computational Time ◽  
Heavy Duty ◽  
Operational Parameters ◽  
3D Fem ◽  
Wide Range

Abstract Thermoacoustic characterization of gas turbine combustion systems is of primary importance for successful development of gas turbine technology, to meet the stringent targets on pollutant emissions. In this context, it becomes more and more necessary to develop reliable tools to be used in the industrial design process. The dynamics of a lean-premixed full-annular combustor for heavy-duty applications has been numerically studied in this work. The well-established CFD-SI method has been used to investigate the flame response varying operational parameters such as the flame temperature (global equivalence ratio) and the fuel split between premixed and pilot fuel injections: such a wide range experimental characterization represents an opportunity to validate the employed numerical methods and to give a deeper insight into the flame dynamics. URANS simulations have been performed, due to their affordable computational costs from the industrial perspective, after validating their accuracy through the comparison against LES results. Furthermore, an approach where the pilot and the premixed flame responses are analyzed separately is proposed, exploiting the independence of their evolution. The calculated FTFs have been implemented in a 3D FEM model of the chamber, in order to perform linear stability analysis and to validate the numerical approach. A boundary condition for rotational periodicity based on Bloch-Wave theory has been implemented into the Helmholtz solver and validated against full-annular chamber simulations, allowing a significant reduction in computational time. The reliability of the numerical procedure has been assessed through the comparison against full-annular experimental results.

Non-linear stability analysis of micropolar fluid lubricated journal bearings with turbulent effect

2019 ◽  
Vol 71 (1) ◽  
pp. 31-39
Author(s):  
Subrata Das ◽  
Sisir Kumar Guha
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Micropolar Fluid ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Content Type ◽  
Non Linear ◽  
The Stability ◽  
Bearing System

Purpose The purpose of this paper is to investigate the effect of turbulence on the stability characteristics of finite hydrodynamic journal bearing lubricated with micropolar fluid. Design/methodology/approach The non-dimensional transient Reynolds equation has been solved to obtain the non-dimensional pressure field which in turn used to obtain the load carrying capacity of the bearing. The second-order equations of motion applicable for journal bearing system have been solved using fourth-order Runge–Kutta method to obtain the stability characteristics. Findings It has been observed that turbulence has adverse effect on stability and the whirl ratio at laminar flow condition has the lowest value. Practical implications The paper provides the stability characteristics of the finite journal bearing lubricated with micropolar fluid operating in turbulent regime which is very common in practical applications. Originality/value Non-linear stability analysis of micropolar fluid lubricated journal bearing operating in turbulent regime has not been reported in literatures so far. This paper is an effort to address the problem of non-linear stability of journal bearings under micropolar lubrication with turbulent effect. The results obtained provide useful information for designing the journal bearing system for high speed applications.

Stresses in Oil Lubricated Bearings

1969 ◽  
Vol 184 (1) ◽  
pp. 69-82 ◽  
Author(s):  
S. M. Ibrahim ◽  
H. Mccallion
Keyword(s):  
Thrust Bearing ◽  
Journal Bearing ◽  
Fluid Pressure ◽  
Temperature Gradients ◽  
Rigid Surface ◽  
Pressure Loading ◽  
Bearing Surface ◽  
Bearing Ring ◽  
Difference Analogue ◽  
Differential Thermal Expansion

Stresses in a bimetal strip of white metal bonded to steel, to simulate a journal bearing shell or a thrust bearing ring, have been calculated for various loading conditions. The stresses arose from: fluid pressure loading on the bearing surface whilst the back was supported on a complete rigid surface; locating and holding forces, e.g. compression due to nipping-up the bearing; elastic deformation of the bearing housing; differential thermal expansion and temperature gradients, and incomplete support of the bearing shell when subjected to fluid pressure on its bearing surface. Points at which fatigue damage is likely to originate are apparent. The stresses were calculated numerically from displacements which were found, by an iterative method, to satisfy a finite difference analogue of the governing differential equations.

Three-Dimensional Finite Element Analysis of Pipe Flange Connections: The Case of Using Compressed Asbestos Sheet Gasket

2002 ◽  
Author(s):  
Tomohiro Takaki ◽  
Toshimichi Fukuoka
Keyword(s):  
Contact Pressure ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Bending Moment ◽  
Elastic Interaction ◽  
Bearing Surface ◽  
Element Analysis ◽  
Bolt Stress ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The most important factor for the leakage problem of pipe flange connections is considered to be contact pressure distribution at the gasket bearing surface in service. In this study, the mechanical behaviors of the pipe flange connection are evaluated using FEM as a three-dimensional contact problem, in which a gasket is modeled as a nonlinear one-dimensional gasket element. Here, the contact pressure distributions at the gasket bearing surface and the variations of the bolt stress are estimated under uniform bolt preloads or nonuniform ones due to the elastic interaction during bolting up. The numerical procedure proposed here can successively deal with the processes of bolt-up, applying inner pressure and applying bending moment. The analytical objects are pipe flanges specified in JIS B 2238 with compressed asbestos sheet gaskets being inserted. The validity of the numerical method is ascertained by experiment.

Stability Analysis of Partial Slip Texture Journal Bearing

2020 ◽  
pp. 217-225
Author(s):  
T. V. V. L. N. Rao ◽  
Ahmad Majdi Abdul Rani ◽  
Norani Muti Mohamed ◽  
Hamdan Haji Ya ◽  
Mokhtar Awang ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Journal Bearing ◽  
Partial Slip

Linear stability analysis of finite hydrodynamic journal bearing under turbulent lubrication with coupled-stress fluid

2016 ◽  
Vol 68 (3) ◽  
pp. 386-391 ◽  
Author(s):  
Abhishek Ghosh ◽  
Sisir Kumar Guha
Keyword(s):  
Stability Analysis ◽  
Newtonian Fluid ◽  
High Speed ◽  
Journal Bearing ◽  
Slenderness Ratio ◽  
Linear Perturbation ◽  
Content Type ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Coupled Stress

Purpose Several researchers have observed that to satisfy modern day’s need, it is essential to enhance the characteristics of journal bearing, which is used in numerous applications. Moreover, the use of Newtonian fluid as a lubricant is diminishing day by day, and the use of Non-Newtonian fluids is coming more into picture. Furthermore, if turbo-machinery applications are taken into account, then it can be seen that journal bearings are used for high speed applications as well. Thus, neglecting turbulent conditions may lead to erroneous results. Hence, this paper aims to present focuses on studying the stability characteristics of finite hydrodynamic journal bearing under turbulent coupled-stress lubrication. Design/methodology/approach First, the governing equation relevant to the problem is generated. Then, the dynamic analysis is carried out by linear perturbation technique, leading to three perturbed equations, which are again discretized by finite difference method. Finally, these discretized equations are solved with the help of Gauss-Seidel Iteration technique with successive over relaxation scheme. Consequently, the film response coefficients and the stability parameters are evaluated at different parametric conditions. Findings It has been concluded from the study that with increase in value of the coupled-stress parameter, the stability of the journal may increase. Whereas, with increase in Reynolds number, the stability of the journal decreases. On the other hand, stability increases with increasing values of slenderness ratio. Originality/value Researches have been performed to study the dynamic characteristics of journal bearing with non-Newtonian fluid as the lubricant. But in the class of non-Newtonian lubricants, the use of coupled-stress fluid has not yet been properly investigated. So, an attempt has been made to perform the stability analysis of bearings with coupled-stress fluid as the advanced lubricant.

Nonlinear Simulation Analysis and Experiment of Fluid Plain Journal Bearing With Incompressible Fluid

2003 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Atsuhiko Shintani ◽  
Koji Yoshioka ◽  
Kouhei Okuno ◽  
Hiroaki Tanaka ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Incompressible Fluid ◽  
Journal Bearing ◽  
Simulation Analysis ◽  
Journal Bearings ◽  
Stable Region ◽  
Flexible Rotor ◽  
Nonlinear Simulation ◽  
Fluid Forces ◽  
The Stability

Recently, in many areas such as computers and information equipments etc., the fluid journal bearings are required to rotate at higher speed. To satisfy this requirement, the strictly stability analysis of the journal is indispensable. In this paper, we investigate the stability analysis of the dynamic behavior of the fluid plain journal bearing with an incompressible fluid considering the nonlinear terms of fluid forces. The stability analysis is examined by the numerical simulations on each model of a rigid rotor and a flexible rotor. The stable regions by nonlinear analysis are compared with the regions by classical linear analysis. Performing the nonlinear simulation analysis, it becomes clear that there is rather a stable region which amplitude does not grow up abruptly, and this phenomenon can not only be pointed out, but also is judged to be unstable by linear stable analysis. Finally, the experiment using actual bearings is performed and compared with the numerical results.

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