An Analytical Study of Starved Porous Bearings

1979 ◽  
Vol 101 (1) ◽  
pp. 38-47 ◽  
Author(s):  
C. Cusano
Keyword(s):  
Analytical Study ◽  
Load Capacity ◽  
Porous Wall ◽  
Velocity Slip ◽  
Diameter Ratio ◽  
Radial Clearance ◽  
Oil Film ◽  
Porous Bearing ◽  
Inside Radius ◽  
Outside Diameter

An analytical solution for the performance characteristics of starved porous bearings is obtained. The solution is based on a finite bearing with an arbitrary wall thickness. The Reynolds equation is modified to include the effect of velocity slip at the interface between the oil film and porous wall. The data presented are for a bearing with a length-to-diameter ratio of 1.0, an outside diameter-to-inside diameter ratio of 1.25 and a radial clearance-to-inside radius ratio of 0.0015. The data are presented in a form such that by knowing the oil supplied externally to the porous bearing or by knowing the active oil film arc, the load capacity and coefficient of friction of the bearing can be obtained for given eccentricity ratios and permeability parameters.

Effect of Slip-Flow in Narrow Porous Bearings

1973 ◽  
Vol 95 (4) ◽  
pp. 518-523 ◽  
Author(s):  
P. R. K. Murti
Keyword(s):  
Friction Force ◽  
Experimental Work ◽  
Reynolds Equation ◽  
Load Capacity ◽  
Slip Flow ◽  
Velocity Slip ◽  
Low Permeability ◽  
Eccentricity Ratio ◽  
Porous Bearing ◽  
Thin Walled

The experimental work of Beavers, et al., established that velocity slip takes place over a permeable boundary. The presence of slip flow is taken into account while deriving the appropriate modified Reynolds equation that governs the flow of lubricant in a finite porous bearing. The performance of a thin-walled bearing is then analyzed making use of the narrow bearing approximation. It is found that slip flow adversely affects the load capacity and reduces the friction force on the journal; the attitude angle, however, is not significantly affected. Also the analysis indicates that the effects of velocity slip are prominent when the bearing operates at a lower eccentricity ratio and/or the bearing-matrix has a low permeability.

Effect of Slip Flow in Narrow Porous Bearings With Arbitrary Wall Thickness

1975 ◽  
Vol 42 (2) ◽  
pp. 305-310 ◽  
Author(s):  
P. R. K. Murti
Keyword(s):  
Wall Thickness ◽  
Reynolds Equation ◽  
Bessel Functions ◽  
Load Capacity ◽  
Slip Flow ◽  
Velocity Slip ◽  
Low Permeability ◽  
Bearing Material ◽  
Porous Bearing ◽  
The Galerkin Method

The experimental work of Beavers, et al., established that velocity slip takes place over a permeable boundary. The Reynolds equation governing the flow of lubricant in a finite porous bearing is appropriately modified to include the effect of velocity slip at the permeable boundary. The performance of a bearing with arbitrary wall thickness is then analyzed adopting the narrow bearing approximation. An exact solution is given for the pressure of the lubricant in the bearing material using modified Bessel functions and the modified Reynolds equation for the problem is solved by the Galerkin method. Numerical results obtained with a digital computer indicate that slip flow adversely affects the load capacity and reduces the friction force on the journal; the attitude angle, however, is not significantly affected. Also, the analysis indicates that the effects of velocity slip are prominent when the bearing operates at a higher eccentricity ratio and/or the bearing matrix has a low permeability. The results are presented in graphical and tabular forms and guidelines are outlined to enable designers in assessing bearing performance using the results.

Behavior of Thermal Effects and Velocity-Slip on Performance of Externally Pressurized Porous Incompressible Gas Thrust Bearing

1979 ◽  
Vol 46 (2) ◽  
pp. 465-468 ◽  
Author(s):  
V. K. Kapur ◽  
J. S. Yadav
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Effects ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Velocity Slip ◽  
Experimental Results ◽  
Slip Condition ◽  
Static Stiffness

In the present analysis, the interactions of thermal effects and velocity slip on the performance of externally pressurized porous incompressible gas thrust bearing have been studied. Numerical results for load capacity, mass flow rate, and static stiffness have been obtained and their behavior is illustrated in figures. The results for slip as well as no-slip condition have also been compared with the experimental results of Gargiulo and Gilmour [7].

Effect of velocity slip in a narrow rough porous journal bearing

2003 ◽  
Vol 217 (1) ◽  
pp. 59-70 ◽  
Author(s):  
K Gururajan ◽  
J Prakash
Keyword(s):  
Porous Material ◽  
Coefficient Of Friction ◽  
Strong Interaction ◽  
Journal Bearing ◽  
Load Capacity ◽  
Tangential Velocity ◽  
Velocity Slip ◽  
Qualitative And Quantitative ◽  
Slip Effects ◽  
Thin Walled

The paper examines the effect of velocity slip in a thin-walled infinitely short rough porous journal bearing operating under steady conditions in a hydrodynamic regime. The analysis extends earlier work [1] in which the tangential velocity at the surface of the porous material was neglected. The problem is solved analytically together with associated boundary conditions. It is found that there exists a strong interaction between roughness and slip effects. A comparison with the case of an infinitely long journal bearing [2] shows that there are significant qualitative and quantitative differences in load capacity and coefficient of friction. However, the slip-induced variations in friction force are similar to those for an infinitely long journal bearing.

Simulation studies on static thermal behaviour of true elliptical and orthogonally displaced non-circular journal bearing

2016 ◽  
Vol 68 (3) ◽  
pp. 349-360 ◽  
Author(s):  
Amit Singla ◽  
Amit Chauhan
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Current Trend ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Film Pressure ◽  
Content Type ◽  
Oil Film ◽  
Ellipticity Ratio ◽  
Oil Film Pressure

Purpose The current trend of modern industry is to use machineries which rotate at high speed along with the capability of carrying heavy rotor loads. This paper aims at static thermal analysis of two different profiles of non-circular journal bearings – a true elliptical bearing and orthogonal bearing. Design/methodology/approach The Reynolds equation has been solved through finite difference method to compute the oil film pressure. Parabolic temperature profile approximation technique has been used to solve the energy equation and thus used for computation of various bearing performance characteristics such as thermo-hydrodynamic oil film pressure, temperature, load capacity, Sommerfeld number and power loss characteristics across the bearing. The effect of ellipticity ratio on the bearing performance characteristics has also been obtained for both the elliptical and vertical offset bearing using three different commercially available grades of oil (Hydrol 32, 68 and 100). Findings It has been observed that the thermo-hydrodynamic pressure and temperature rise of the oil film is less in orthogonal bearing as compared to the true elliptical bearing for same operating conditions. The effect of ellipticity ratio of non-circularity on bearing performance parameters have been observed to be less in case of elliptical bearing as compared to orthogonal bearing. It has been concluded that though the rise in oil film temperature is high for true elliptical bearing, but still it should be preferred over orthogonal profile under study, as it has comparably good load-carrying capacity. Originality/value The performance parametric analysis will help the designers to select such kind of non-circular journal bearing for various applications.

Alignment of carbon nanotubes under the influences of nematic liquid crystals and electric fields — an analytical study

2021 ◽  
Author(s):  
Setia Budi Sumandra ◽  
Bhisma Mahendra ◽  
Fahrudin Nugroho ◽  
Yusril Yusuf
Keyword(s):  
Carbon Nanotubes ◽  
Free Energy ◽  
Electric Field ◽  
Electric Fields ◽  
Analytical Study ◽  
Free Energy Density ◽  
Diameter Ratio ◽  
Order Parameters ◽  
Anchoring Strength ◽  
Length To Diameter Ratio

Carbon nanotubes (CNTs) have benefits in various fields, they are disadvantageous due to their tendency to form aggregates and poorly controlled alignment of the CNT molecules (characterized by order parameters). These deficiencies can be overcome by dispersing the CNTs in nematic liquid crystal (LC) and placing the mixture under the influence of an electric field. In this study, Doi and Landau–de Gennes free energy density equations are used to analytically confirm that an electric field increases the order parameters of CNTs and LCs in a dispersion mixture. The anchoring strength of the nematic LC is also found to affect the order parameters of the CNTs and LC. Further, increasing the length-to-diameter ratio of the CNTs increases their alignment without affecting the LC alignment. These findings indicate that CNT molecular alignment can be controlled by adjusting the CNT length-to-diameter ratio, anchoring the LCs, and adjusting the electric field strength.

STATIC CHARACTERISTICS OF OFFSET 8-LOBE JOURNAL BEARINGS

Tribologia ◽  
2021 ◽  
Vol 295 (1) ◽  
pp. 39-51
Author(s):  
Stanisław Strzelecki
Keyword(s):  
Laminar Flow ◽  
Equilibrium Position ◽  
Iterative Procedure ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Diameter Ratio ◽  
Static Characteristics ◽  
Oil Film ◽  
Cooling Conditions ◽  
Grinding Machines

The 8-lobe journal bearings have found application in the bearing systems of spindles of grinding machines. The design of bearings and the large number of lobes and oil grooves assures good cooling conditions of bearing. These bearings can be manufactured as the bearings with cylindrical, non-continuous operating surfaces separated by six lubricating grooves, bearings with the pericycloidal shape of the bearing bore, and as offset journal bearing. This paper presents the results of the computation of static characteristics of an offset 8-lobe journal bearing operating under the conditions of an aligned axis of journal and bush, adiabatic oil film, and at the static equilibrium position of journal. Different values of bearing length to diameter ratio, relative clearance, and lobe relative clearance were assumed. Reynolds' energy and viscosity equations were solved by means of an iterative procedure. Adiabatic oil film, laminar flow in the bearing gap, and aligned orientation of journal in the bearing were considered.

Influence of geometric parameters on the bump foil bearing performance

2019 ◽  
Vol 234 (7) ◽  
pp. 1017-1026
Author(s):  
Sadanand Kulkarni ◽  
Soumendu Jana
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
System Development ◽  
Load Capacity ◽  
Radial Clearance ◽  
Load Carrying Capacity ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Load Carrying ◽  
Lift Off

High-speed rotating system development has drawn considerable attention of the researchers, in the recent past. Foil bearings are one of the major contenders for such applications, particularly for high speed and low load rotating systems. In foil bearings, process fluid or air is used as the working medium and no additional lubricant is required. It is known from the published literature that the load capacity of foil bearings depend on the operating speed, viscosity of the medium, clearance, and stiffness of the foil apart from the geometric dimensions of the bearing. In case of foil bearing with given dimensions, clearance governs the magnitude of pressure developed, whereas stiffness dictates the change in radial clearance under the generated pressure. This article deals with the effect of stiffness, clearance, and its interaction on the bump foil bearings load-carrying capacity. For this study, four sets of foil bearings of the same geometry with two levels of stiffness and clearance values are fabricated. Experiments are carried out following two factor-two level factorial design approach under constant load and in each case, the lift-off speed is measured. The experimental output is analyzed using statistical techniques to evaluate the influence of parameters under consideration. The results indicate that clearance has the maximum influence on the lift-off speed/ load-carrying capacity, followed by interaction effect and stiffness. A regression model is developed based on the experimental values and model is validated using error analysis technique.

Review of the Study on Load Capacity of Oil-Film Bearings

2014 ◽  
Vol 900 ◽  
pp. 405-409
Author(s):  
Xiang Jun Yu ◽  
Zuo Xin Li ◽  
Ke Nan Shen ◽  
Shuang You ◽  
An Jun Wu
Keyword(s):  
Dynamic Simulation ◽  
Experimental Test ◽  
Load Capacity ◽  
Operating Conditions ◽  
Mechanical Transmission ◽  
Paper Briefly ◽  
Scaled Model ◽  
Oil Film ◽  
Depth Study ◽  
The Stability

The oil-film bearings are widely used in mechanical transmission due to the good performance. In normal operating conditions, the journal and bearing shell are separated by the oil film, which contributes to the reduction of wear. And the stability and reliability of oil film has a great effect on load capacity. The paper briefly introduces research methods of the load capacity of oil-film bearings and points out some aspects of large oil-film bearings for in-depth study. Then combining dynamic simulation with experimental test on the scaled model of whole machine, a dynamic research idea is presented for large oil-film bearings.

Effect of torque ratio on speed regulating start

2018 ◽  
Vol 70 (9) ◽  
pp. 1657-1663
Author(s):  
Qingrui Meng ◽  
Zhao Chenghao ◽  
Tian Zuzhi
Keyword(s):  
Film Thickness ◽  
Theoretical Basis ◽  
Design Methodology ◽  
Load Capacity ◽  
Load Torque ◽  
Content Type ◽  
Oil Film ◽  
Torque Transmission ◽  
Drive Speed ◽  
Starting Process

Purpose Friction pairs of the hydro-viscous drive speed regulating start device should be designed based on the rated torque. To obtain design basis of the rated torque of the hydro-viscous drive speed regulating start device, studies on effect of torque ratio (a ratio of the load torque to the rated torque) on speed regulating start were carried out theoretically and experimentally. Design/methodology/approach Under different torque ratio, the modified Reynolds, the thermal energy and the viscosity-temperature equations were solved simultaneously by using finite element method to reveal variation laws of the oil film load capacity and torque transmission during the starting process. Then, speed regulating start experiments were carried out to study the following performance of the output speed. Findings The results show that oil film thickness decreases with the increase of the torque ratio; when oil film thickness is less than 0.05 mm, oil film temperature increases rapidly with the decrease of oil film thickness, which eventually deteriorates performance of the speed regulating start; when the torque ratio decreases to about 0.3, output speed shows a better following performance. Originality/value It indicates that, to acquire a better speed regulating start, the rated torque of the hydro-viscous drive speed regulating start device should not be less than three times of the load torque. Achievements of this work provide theoretical basis for optimal design of the friction pairs of the hydro-viscous drive speed regulating start device.

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