Performance of Two Lobe Multirecess Hybrid Journal Bearing Compensated With Capillary Restrictor

2007 ◽  
Author(s):  
Prashant Kushare ◽  
Satish C. Sharma ◽  
S. C. Jain ◽  
J. Sharana Basavaraja
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Favourable Effect ◽  
Improved Performance ◽  
Stiffness And Damping ◽  
Offset Factor ◽  
Bearing System

Multirecess hydrostatic/hybrid journal bearings are being used in many applications owing to their excellent characteristics. The Noncircular journal bearing configurations too are quite frequently used in high speed machinery as they are efficient, less costly and provide better shaft stability. The Two lobe bearing (elliptical bearing) are among the commonly used noncircular journal bearing configuration. The multilobe multirecess hybrid journal bearings have been developed to combine the features of noncircular and circular hybrid journal bearing configurations. In the present work a theoretical investigation of a two lobe multirecess hydrostatic/hybrid journal bearing system have been carried out. The multilobe journal bearing configuration is designed as an arc of the circle with the centre points placed on the symmetry line of the single lobe. The journal offset has been accounted by defining an offset factor ‘δ’. The finite element method has been used to solve the Reynolds equation governing the flow of lubricant in the clearance space of the journal bearing system. The bearing static and dynamic performance characteristics have been presented for the various values of the offset factors (0.75, 1, 1.25 and 1.50) for hybrid mode of operation of the bearing. The simulated results of the studies reveals that, a two lobe recessed hybrid journal bearing provides an improved performance in respect of fluid film stiffness and damping coefficients as compared to that of circular recessed journal bearing. It has been observed that for a multilobe bearing having offset factor more than one has a favourable effect on the dynamic performance characteristics of the two lobe bearing.

Combined Influence of Wear and Misalignment of Journal on the Performance Analysis of Three-Lobe Three-Pocket Hybrid Journal Bearing Compensated With Capillary Restrictor

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Satish C. Sharma ◽  
Vikas M. Phalle ◽  
S. C. Jain
Keyword(s):  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Fluid Film ◽  
Wear Depth ◽  
Fluid Film Thickness ◽  
Film Stiffness ◽  
Offset Factor ◽  
Bearing System

The multirecess noncircular hybrid journal bearings have been receiving wide importance in order to overcome the adverse effects on performance characteristics of multirecess circular journal bearings. During the lifetime of a machine, bearings are quite often required to be operated over a number of years and are subjected to several start and stop operations. As a consequence of this, the bush becomes progressively worn out and thereby changing the clearance space between journal and bearing. The present paper presents an analytical study investigating the effect of wear along with both aligned and misaligned conditions of journal on the performance of a capillary compensated three-lobe three-pocket hybrid journal bearing system for the various offset factors δ = 0.8,1.0, and 1.2. The wear caused on the bearing surface due to the transient (start/stop) operations has been modeled using Dufrane’s wear model. The modified Reynolds equation governing the flow of lubricant in the clearance space of a three-lobe multirecess worn hybrid journal bearing system along with both aligned and misaligned conditions of journal has been solved using an iterative scheme based on FEM. The influence of offset factor (δ), the wear depth parameter (δ¯w), and journal misalignment factors (σ¯,δ¯) on the performance of the three-lobe three-pocket hybrid journal bearing and three-pocket circular hybrid journal bearing system have been investigated. The results have been presented for the capillary compensated three-lobe three-pocket hybrid journal bearing system. The simulated results suggest that a bearing with a higher value of offset factor (δ>1) provides better static and dynamic performance characteristics as compared with a three-pocket circular journal bearing but the bearing with offset factor (δ < 1) is predominantly affected by the wear defect and misalignment of journal. The numerically simulated results suggest that the wear defect and offset factors significantly affect the bearing performance. Therefore, it becomes imperative to account for the influence of wear and offset factors during the design process so as to generate accurate data of bearing performance. The numerically simulated results have been presented in terms of maximum fluid-film pressure, minimum fluid-film thickness, lubricant flow rate, direct fluid-film stiffness, damping coefficients, and stability threshold speed margin. The present study demonstrates that the performance of bearing is significantly affected by wear along with both aligned and misaligned conditions of journal and the loss is partially compensated by keeping the offset factor δ>1.

A Study of Orifice Compensated Multilobe Hole-Entry Hybrid Journal Bearing

2007 ◽  
Author(s):  
T. Nagaraju ◽  
J. Sharana Basavaraja ◽  
Satish C. Sharma ◽  
S. C. Jain
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Academic Community ◽  
Flow Through ◽  
Direct Stiffness ◽  
Improved Performance ◽  
The Stability ◽  
Offset Factor ◽  
Bearing System

The hydrostatic and hybrid journal bearings are finding increasing applications due to their excellent characteristics. The non-recessed hydrostatic/hybrid journal bearings have been developed so to provide an improved performance over the recessed/pocketed hydrostatic/hybrid journal bearings. The stability and unsteady behavior of the journal bearings is greatly influenced by bearing geometry, and accordingly various designs have been used by designers to achieve the desired objective. The non-circular journal bearings i.e. the multilobe journal bearing exhibits better stability as well as a superior capability to suppress whirl. In the present paper a theoretical study pertaining to a novel journal bearing configuration i.e. two-lobe hole-entry hybrid journal bearing is being presented. The work presented in this paper aims to study the performance of a two-lobe hole-entry hybrid journal bearing system compensated by a orifice restrictors. The Reynolds equation governing the flow of lubricant in the clearance space between the journal and bearing together with the equation of flow through an orifice restrictor has been solved using FEM and Galerkin’s method. The bearing performance characteristics results have been simulated for an orifice compensated non-recessed two-lobe hole-entry hybrid journal bearing symmetric configuration for the various values of offset factor (δ), restrictor design parameter (cS2) and the value external load (Wo). Further, a comparative study of the performance of a two-lobe non-recessed hole-entry hybrid journal bearing system vis a vis circular hole-entry symmetric hybrid journal bearing system have also been carried out so that a designer has a better flexibility in choosing a suitable bearing configuration. The simulated numerical results for the non-recessed two-lobe symmetric hole-entry hybrid journal bearing system with an offset factor (δ) greater than one indicates a significant improvement of the order of 30 to 50 percent in the values of direct stiffness and direct damping coefficients as compared to a circular symmetric hole entry hybrid journal bearing system. The results presented in the paper are expected to be quite useful to the bearing designers as well as for the academic community.

Influence of Wear on the Performance of Multirecess Hydrostatic Journal Bearing Operating With Micropolar Lubricant

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
E. Rajasekhar Nicodemus ◽  
Satish C. Sharma
Keyword(s):  
Journal Bearing ◽  
Dynamic Performance ◽  
Flow Equation ◽  
Performance Characteristics ◽  
Wear Depth ◽  
Damping Coefficients ◽  
Load Line ◽  
Wide Range ◽  
Load Arrangement ◽  
Stiffness And Damping

The objective of the present work is to study theoretically the influence of wear on the performance of four-pocket capillary-compensated hydrostatic journal bearing operating with micropolar lubricant. In the present study, the lubricant containing additives and contaminants is modeled as micropolar fluid. The modified Reynolds equation for micropolar lubricant is solved using finite element method along with capillary restrictor flow equation as a constraint together with appropriate boundary conditions. The performance characteristics of a capillary-compensated four-pocket worn hydrostatic journal bearing operating with micropolar lubricant have been presented for a wide range of values of nondimensional external load, wear depth parameter, and micropolar parameters. The simulated results have also been presented for two different loading arrangements. In arrangement I, the load line acts through centers of the pockets, whereas in arrangement II, the load line bisects the land between two pockets. The simulated results suggest that a bearing lubricated with lubricant having higher micropolar effect has better static and dynamic performance characteristics as compared with Newtonian lubricant but the bearing lubricated with lubricant having higher micropolar effect is predominantly affected by the wear vis a vis static characteristics parameters as compared with Newtonian lubricant for both loading arrangements. However, in the case of stiffness and damping coefficients, loading arrangement II shows a significant higher enhancement in the value of direct stiffness and damping coefficients in z-direction due to micropolar effect as compared with load arrangement I. And also, the effect of wear on stiffness and damping coefficients in z-direction for bearing operating with micropolar lubricant is of same order as Newtonian lubricant for the loading arrangement II. A similar behavior is observed for the case of stiffness and damping coefficients in x-direction for loading arrangement I.

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 Steady State and Dynamic Performance Characteristics of Floating Ring Bearings

1981 ◽  
Vol 103 (3) ◽  
pp. 389-397 ◽  
Author(s):  
Chin-Hsiu Li ◽  
S. M. Rohde
Keyword(s):  
Steady State ◽  
Linear Theory ◽  
High Speed ◽  
Dynamic Performance ◽  
Equations Of Motion ◽  
Nonlinear Behavior ◽  
Journal Bearings ◽  
Transient Problem ◽  
The Stability ◽  
Bearing System

An analysis of the steady state and dynamic characteristics of floating ring journal bearings has been performed. The stability characteristics of the bearing, based on linear theory, are given. The transient problem, in which the equations of motion for the bearing system are integrated in real time was studied. The effect of using finite bearing theory rather than the short bearing assumption was examined. Among the significant findings of this study is the existence of limit cycles in the regions of instability predicted by linear theory. Such results explain the superior stability characteristics of the floating ring bearing in high speed applications. An understanding of this nonlinear behavior, serves as the basis for new and rational criteria for the design of floating ring bearings.

Stability of Multirecess Hybrid-Operating Oil Journal Bearings

1985 ◽  
Vol 107 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Y. S. Chen ◽  
H. Y. Wu ◽  
P. L. Xie
Keyword(s):  
Finite Difference Method ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Design Parameters ◽  
Stability Threshold ◽  
Damping Coefficients ◽  
Hybrid Bearing ◽  
The Stability ◽  
Stiffness And Damping ◽  
Bearing System

An analysis and a numerical solution using finite difference method to predict the dynamic performance of multirecess hybrid-operating oil journal bearings are presented. The linearized stiffness and damping coefficients of a typical capillary-compensated bearing with four recesses are computed for various design parameters. The corresponding stiffness and the stability threshold of the bearing are then obtained, and the opposite influences of the hydrodynamic action on them are demonstrated. The effect of rotor flexibility on the onset of self-excited whirl is discussed, and a method is given to determine the stability threshold of a rotor-hybrid bearing system.

The Rolling-Pad Journal Bearing: A Promising Antiwhirl Configuration

1981 ◽  
Vol 23 (3) ◽  
pp. 131-141
Author(s):  
M. Malik ◽  
R. Sinhasan ◽  
D. V. Singh
Keyword(s):  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Tilting Pad ◽  
The Comparative Study ◽  
Tilting Pad Journal Bearing ◽  
Tilting Pad Journal Bearings ◽  
Theoretical Performance

The rolling-pad journal bearing is a kinematic variation of the well-known tilting-pad journal bearing. In rolling-pad bearings, the pads, instead of tilting about fixed pivots, roll at their back surfaces on the inside surface of a common sleeve to accommodate changes in the operating conditions of the bearing. This paper presents a comparison of the theoretical performance characteristics of rolling-pad journal bearings with those of tilting-pad journal bearings. The comparative study indicates that the dynamic performance characteristics of the rolling-pad bearing configuration are superior to those of the tilting-pad bearing.

Development of Herringbon-Grooved Aerodynamic Journal Bearing Systems for Ultra-High-Speed Rotations

2015 ◽  
Vol 656-657 ◽  
pp. 652-657 ◽  
Author(s):  
Norifumi Miyanaga ◽  
Jun Tomioka
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Journal Bearing ◽  
Damping Properties ◽  
Shaft Rotation ◽  
Ultra High Speed ◽  
The Difference ◽  
The Stability ◽  
Stiffness And Damping ◽  
Bearing System

It is absolutely important for ultra-compact rotational machineries to achieve sable shaft rotation at ultra-high-speed. This paper discussed herringbone-grooved aerodynamic journal bearing systems developed for the purpose. In this system, the bearings are supported by rubber-O-rings for accurate and stable operations. To grasp the possibility for stabilization, two types of O-rings with different stiffness and damping properties under bearing supporting were tested in the experiment. As the results, the bearing system demonstrated the maximum rotational speed over 460,000 rpm without unstable phenomenon called whirl. However, the difference in rubber O-rings definitely affected the stability of the bearing system.

Elastohydrodynamic analysis of double-layered journal bearings lubricated with couple-stress fluids

2005 ◽  
Vol 219 (2) ◽  
pp. 145-165 ◽  
Author(s):  
M Lahmar
Keyword(s):  
Couple Stress ◽  
Journal Bearing ◽  
Perturbation Technique ◽  
Dynamic Performance ◽  
Performance Characteristics ◽  
Transient Pressure ◽  
Variable Theory ◽  
Stress Parameter ◽  
Linear Elastostatics ◽  
Bearing System

Elastohydrodynamic (EHD) analysis of a journal bearing with a realistic model for the bearing made of two distinct layers is extended to include couple-stress effects in lubricants blended with polymer additives. Based on the Stokes microcontinuum theory, a transient pressure differential equation (modified Reynolds' equation) is derived from the fluid motion equations and solved numerically. The elegant and powerful semi-analytical approach based on the complex variable theory developed in an earlier work is extended to solve linear elastostatics problems for a double-layered journal bearing. The EHD solution in isothermal conditions is obtained numerically by means of an iterative procedure. By the finite perturbation technique, the eight fluid-film stiffness and damping coefficients are determined. At the threshold of instability, the dynamic coefficients are used as input data for studying the linear stability of the rotor-bearing system. According to the results obtained, the influence of couple-stress parameter on the static and dynamic performance characteristics of the compliant journal-bearing system is physically apparent and not negligible. Compared with the Newtonian lubricants case, lubricants with couple-stresses provide an increase in the load-carrying capacity and stability, a reduction in the attitude angle and the friction factor. It is also found that the fluid-solid interaction effect on the performance characteristics is more important, especially for high values of couple-stress parameter and relative rigidity of liner-bush assembly.

Performance Characteristics of Two-Lobe Hydrodynamic Journal Bearings

1980 ◽  
Vol 102 (4) ◽  
pp. 425-429 ◽  
Author(s):  
Ashok Kumar ◽  
R. Sinhasan ◽  
D. V. Singh
Keyword(s):  
Temperature Rise ◽  
High Speed ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Design Data ◽  
Detailed Design ◽  
Flow Friction ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Film Stiffness

The performance characteristics of noncircular bearings are known to be superior to those of the circular bearings. The two lobe bearings are finding increasing application in high speed turbomachinery. Using a variational solution, detailed design data have been computed for two-lobe bearings in this paper. The data include Sommerfeld number, equilibrium locus, fluid film stiffness and damping coefficients, end-flow, friction parameter, and temperature rise parameter.

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