Linear stability analysis of double-layered porous journal bearings under coupled-stress lubrication with slip flow and percolation effect of additives

2019 ◽  
Vol 71 (3) ◽  
pp. 447-458 ◽  
Author(s):  
Shitendu Some ◽  
Sisir Kumar Guha
Keyword(s):  
Linear Stability ◽  
Mass Parameter ◽  
Critical Mass ◽  
Slip Flow ◽  
Tangential Velocity ◽  
Journal Bearings ◽  
Content Type ◽  
Percolation Effect ◽  
The Stability ◽  
Coupled Stress

Purpose In the application of hydrostatic double-layered porous journal bearings, instability of bearing systems is a major problem. On the other hand, the use of non-Newtonian fluid as a lubricant is more practical in the present days. Furthermore, in case of porous bearing, neglecting slip effect and percolation effect of additives into the pores may lead to erroneous result. Hence, this paper aims to present the linear stability analysis of finite hydrostatic double-layered porous journal bearings lubricated with coupled-stress lubricant with tangential velocity slip and percolation effect. Design/methodology/approach First, considering the tangential velocity slip, the most general modified Reynolds-type equation has been derived for the film region and the governing equations for flow in the coarse and fine layers of porous medium incorporating the percolation effect. A linearized first-order perturbation method has been applied to obtain the threshold of stability in terms of critical mass parameter. The effect of various parameters on the stability is investigated and represented in the form of graphs. Furthermore, a comparison between the stability of double- and single-layered porous journal bearings has been exhibited. Findings In this paper, threshold of stability has been obtained in terms of critical mass parameter. The effect of slip coefficient, percolation factor, coupled-stress parameter, eccentricity ratio and bearing feeding parameter on the stability has been found. Originality/value There is no literature available so far that addresses the analysis of the linear stability of externally pressurized double-layered porous journal bearings with slip flow, including the percolation effect under coupled-stress lubrication. But in this paper, all these points are included which made this paper valuable in design purpose.

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.

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.

Effect of journal misalignment and coupled-stress lubricant on the film pressure of a double-layered porous journal bearing

2019 ◽  
Vol 72 (3) ◽  
pp. 315-323
Author(s):  
Shitendu Some ◽  
Sisir Kumar Guha
Keyword(s):  
Steady State ◽  
Journal Bearing ◽  
Tangential Velocity ◽  
Velocity Slip ◽  
Content Type ◽  
Porous Bearing ◽  
Pressure Profiles ◽  
Percolation Effect ◽  
Journal Misalignment ◽  
Coupled Stress

Purpose In the application of hydrostatic double-layered porous journal bearings, misalignment of bearing systems is a major problem. On the other hand, the use of coupled-stress fluid as a lubricant is more practical in the present days. Furthermore, in case of porous bearing, neglecting slip effect and percolation effect of additives into the pores may lead to erroneous result. Hence, this paper aims to address the effect of journal misalignment and coupled-stress lubricant on the steady-state film pressure of the double-layered porous journal bearing with tangential velocity slip and percolation effect. Design/methodology/approach First, considering the tangential velocity slip, the most general modified Reynolds type equation has been derived for the film region and the governing equations for flow in the coarse and fine layers of porous medium, incorporating the percolation effect for a double-layered porous bearing. Here, considering the misalignment caused by shaft displacement. Film thickness expression established considering the effect of misalignment. Steady-state film pressures are obtained by solving modified Reynolds equation based on the coupled-stress lubrication theory. Effects of journal misalignment and coupled-stress lubricant on the pressure profiles in the film region are discussed and demonstrated in the graphical form. Findings In this paper, effects of journal misalignment and coupled-stress lubricant on the pressure profiles in the film region are obtained. In general, higher degree of misalignment gives higher steady-state pressure value in the film region, and this pressure increases due to increase in coupled-stress parameter up to a certain limit. Originality/value To the best of the author’s knowledge, there is no literature available, so far, that addresses the analysis of the steady-state pressure in the film region of a doubled–layered porous journal bearing under misaligned condition with coupled-stress lubricant. But in this paper all these points are included, which makes this article valuable in design purpose.

Linear Stability Analysis of Short Porous Journal Bearings—Use of the Brinkman Model

1995 ◽  
Vol 117 (1) ◽  
pp. 199-202 ◽  
Author(s):  
Jaw-Ren Lin ◽  
Chi-Chuan Hwang
Keyword(s):  
Linear Stability ◽  
Flow Model ◽  
Slip Flow ◽  
Journal Bearings ◽  
Shear Stresses ◽  
Brinkman Model ◽  
Stability Threshold ◽  
Viscous Shear ◽  
Shear Effects ◽  
The Stability

On the basis of a Brinkman model (BM), this paper predicts that the effects of viscous shear stresses on the linear stability of short porous journal bearings are apparent and not negligible. Compared with those of the slip-flow model (SFM) and the Darcy model (DM), the viscous shear effects provide a significant increase in the stability threshold speeds of short porous journal bearings.

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.

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.

Static characteristics of hydrostatic doubled-layered porous journal bearings with slip flow including additives percolation into pores under coupled stress lubrication

2017 ◽  
Vol 232 (8) ◽  
pp. 927-939 ◽  
Author(s):  
Shitendu Some ◽  
Sisir K Guha
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Slip Flow ◽  
Journal Bearings ◽  
Static Characteristics ◽  
Governing Equations ◽  
Modified Reynolds Equation ◽  
Film Interface ◽  
Coupled Stress ◽  
Steady State Performance

A theoretical analysis of the steady-state characteristics of finite hydrostatic double-layered porous journal bearings dealing with the effects of slip flow at the fine porous layer–film interface and percolation of additives into pores under the coupled stress fluid lubrication is presented. Based on the Beavers–Joseph’s criterion for slip flow, the modified Reynolds equation applicable to finite porous journal bearings lubricated with coupled stress fluids have been derived. The governing equations for flow in the coarse and fine layers of porous medium incorporating the percolation of polar additives of lubricant and the modified Reynolds equation are solved simultaneously using finite difference method satisfying appropriate boundary conditions to obtain the steady-state performance characteristics for various parameter namely percolation factor, slip coefficient, bearing feeding parameter, coupled stress parameter, and eccentricity ratio. The results are exhibited in the form of graphs, which may be useful for design of such bearing.

Numerical and experimental study on dynamic characteristics of tilting-pad journal bearings considering pivot stiffness in a vertical rotor system

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fan Zhang ◽  
Peng Yin ◽  
Yuyang Liu ◽  
Jianmei Wang
Keyword(s):  
Dynamic Characteristics ◽  
Journal Bearings ◽  
Rotor System ◽  
Obvious Effect ◽  
Content Type ◽  
Vertical Rotor ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
The Stability ◽  
Tilting Pad Journal Bearings

Purpose The purpose of this paper is to study the influence of pivot stiffness on the dynamic characteristics of tilting-pad journal bearings (TPJBs) and the stability of the bearing-rotor system. Design/methodology/approach A theoretical numerical model is established, and the influences of pivot stiffness on TPJBs and a bearing-rotor system are analyzed. Then, two kinds of pivot structures with different stiffness are designed and the vibration characteristics are tested on the vertical rotor bearing test bench. Findings The pivot stiffness has an obvious effect on the dynamic characteristics of the TPJBs and the stability of the bearing-rotor system. As a result of appropriate pivot stiffness, the critical speed and the vibration amplification factor can be reduced, the logarithmic decay rate and the stability of the rotor system can be effectively increased. While the journal whirl orbit is smoother and the rubbing is obviously reduced when the bearings have flexible pivots. Originality/value The influence of pivot stiffness on TPJBs and a vertical rotor-bearing system is studied by theoretical and experimental methods.

Enhanced Groove Geometry for Herringbone Grooved Journal Bearings

2013 ◽  
Author(s):  
J. Schiffmann
Keyword(s):  
Cross Section ◽  
Mass Parameter ◽  
Critical Mass ◽  
Stability Margin ◽  
Design Guidelines ◽  
Journal Bearings ◽  
Diameter Ratio ◽  
Width Ratio ◽  
Constant Pitch ◽  
Order Of Magnitude

Although gas lubricated Herringbone Grooved Journal Bearings (HGJB) are known for high rotordynamic stability thresholds, small clearance to diameter ratios are required for stable rotor operation. Tight clearances not only increase bearing losses but also yield challenging manufacturing and assembly tolerances, which ultimately translate into cost. Traditionally, the grooves of HGJB are of helical nature with constant cross-section and pitch. The current paper aims at increasing the clearance to diameter ratio and the stability threshold of grooved bearings by introducing enhanced groove geometries. The axial evolution of groove width, depth and local pitch are described by individual 3rd order polynomials with four interpolation points. The expression for the smooth pressure distribution resulting from the narrow groove theory is modified to enable the calculation of bearing properties with modified groove patterns. The reduced order bearing model is coupled to a linear rigid body rotordynamic model for predicting the whirl speed map and the corresponding stability. By introducing a critical mass parameter as a measure for stability, a criterion for the instability onset is proposed. The optimum groove geometry is found by coupling the gas bearing supported rotor model with a multi-objective optimizer. By maximizing both the clearance to diameter ratio and the rotordynamic stability it is shown that with optimal groove geometry, which deviates from helicoids with constant pitch and cross-section, the critical mass parameter can be improved by more than one order of magnitude compared to traditional HGJB geometries. The clearance to diameter ratio can be increased by up to 80% while keeping the same stability margin, thus reducing both losses and manufacturing constraints. The optimum groove pattern distributions (width ratio, angle and depth) are summarized for a variety of L/D ratios and for different compressibility numbers in a first attempt to set up general design guidelines for enhanced gas lubricated HGJB.

Non-linear stability analysis of two-layered porous journal bearings with velocity slip and percolation effect of additives of coupled-stress lubricant

2020 ◽  
Vol 235 (1) ◽  
pp. 46-60
Author(s):  
Shitendu Some ◽  
Sisir K Guha
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Journal Bearing ◽  
Velocity Slip ◽  
Operating Conditions ◽  
Graphical Form ◽  
Non Linear ◽  
Percolation Effect ◽  
Coupled Stress

In this paper a non-linear stability analysis of the two-layered porous journal bearing under coupled-stress lubricant has been presented with velocity slip phenomenon and additive’s percolation effect. In this non-linear transient analysis, system stability is determined by tracing the locus of the journal center and various trajectories of journal center locus have been represented in graphical form for different operating conditions. Furthermore, stability characteristics in respect of critical mass parameter and whirl ratio have been studied under various parametric conditions and a comparison between the linear and non-linear stability analysis have been demonstrated. To acquire the non-dimensional pressure values, non-dimensional transient Reynolds equation has been solved and with these pressure values, bearing load carrying capacity are derived. Fourth order Runge-Kutta method is used to solve the second order equations of motion for journal bearing system to obtain the stability characteristics. Results of this analysis may be helpful for designing such bearings.

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