Effect of couple stress parameter on steady-state and dynamic characteristics of three-lobe journal bearing operating on TiO2 nanolubricant

2019 ◽  
Vol 234 (4) ◽  
pp. 528-540
Author(s):  
Ashutosh Kumar ◽  
SK Kakoty
Keyword(s):  
Steady State ◽  
Couple Stress ◽  
Volume Fraction ◽  
Dynamic Performance ◽  
Significant Rise ◽  
Flow Coefficient ◽  
Performance Parameters ◽  
Stress Parameter ◽  
Load Carrying ◽  
Stiffness And Damping

Steady-state and dynamic performance parameters of three-lobe fluid film bearing, operating on TiO2 nanolubricant have been obtained. The effective viscosity for a given volume fraction of TiO2 nanoparticle in base fluid is obtained by using Krieger–Dougherty viscosity model. Various bearing performance parameters are obtained by solving remodeled Reynolds equation, which includes couple stress parameter. The stiffness and damping coefficients are also obtained for different values of the couple stress parameter. Results show a significant rise in the nondimensional load-carrying capacity and flow coefficient while there is a decrease in friction variable. It also reveals a significant improvement in the dynamic coefficient of bearing.

A Variable Viscosity Approach for the Analysis of Steady State and Dynamic Characteristics of Two-Lobe Journal Bearing With TiO2 Based Nanolubricant

2017 ◽  
Author(s):  
Ashutosh Kumar ◽  
Sashindra Kumar Kakoty
Keyword(s):  
Steady State ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Flow Coefficient ◽  
Viscosity Model ◽  
Nano Lubricant ◽  
The Stability ◽  
Stiffness And Damping

Steady-state and dynamic characteristics of two-lobe journal bearing, operating on TiO2 based Nano-lubricant has been obtained. The effective viscosity is obtained by using Krieger-Dougherty viscosity model for a given volume fraction of nanoparticle in the base fluid. Various bearing performance characteristics are then obtained by solving modified Reynolds equation for variable viscosity model and couple stress model. The stiffness and damping coefficients are also determined for various values of the volume fraction of the nanoparticle in the nanofluid. Results reveal that load carrying capacity and flow coefficient increase whereas friction variable decreases without affecting the stability condition of two-lobe journal bearing operating on TiO2 based nanolubricant. On the other hand attitude angle and dynamic coefficients remains constant for all the values of volume fraction of nanoparticle.

Dynamic stability analysis of noncircular two-lobe journal bearings with couple stress lubricant regime

2020 ◽  
pp. 135065012094551
Author(s):  
Mahdi Zare Mehrjardi
Keyword(s):  
Steady State ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Journal Bearings ◽  
Lubricating Oil ◽  
Couple Stress Fluid ◽  
Load Carrying Capacity ◽  
Stress Parameter ◽  
Attitude Angle ◽  
Load Carrying

In this research, the steady state and dynamic performances of two-lobe noncircular journal bearings with couple stress lubricant are presented. The lubricating oil, containing additives and contaminants, is modeled as the couple stress fluid. The modified Reynolds equation is obtained using the couple stress lubrication theory and is then solved by finite element method as an efficient numerical technique. The steady-state characteristics of bearings, including the load carrying capacity and attitude angle, are determined for various values of the couple stress parameter. The results show that applying the couple stress fluid improves the efficiency of two-lobe bearings in terms of an increased load carrying capacity and reduced attitude angle. Also, the stability performance of the investigated bearings is studied using rotor motion equations based on linear and nonlinear dynamic methods. The results indicate that any increase in the lubricant couple stress parameter enhances the bearing ability to damp the rotor perturbations. In other words, by varying the lubricant from Newtonian oil to the couple stress type and upgrading its properties, the curves of the critical mass parameter and whirl frequency ratio have an increasing and decreasing trend, respectively. Based on the fourth-order Runge–Kutta method results, the dynamic trajectory of the rotor center in the bearing space changes with increasing the couple stress parameter from diverging disturbances and limits the cycle perturbations around the bearing center to converging oscillations to the static equilibrium point. Moreover, the effect of changing lubricant properties on the two-lobe bearing’s performance is more pronounced at higher values of the couple stress parameter, especially with an increase in the noncircularity of bearings’ geometry.

Analysis of Static and Dynamic Performance Parameters of Two-Lobe Journal Bearing Operating With Non-Newtonian Lubricant

2019 ◽  
Author(s):  
Ashutosh Kumar ◽  
Sashindra Kumar Kakoty
Keyword(s):  
Couple Stress ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Variable Viscosity ◽  
Dynamic Performance ◽  
Load Carrying Capacity ◽  
Performance Parameters ◽  
Noticeable Increase ◽  
Load Carrying ◽  
Nano Lubricant

Abstract Static and dynamic performance parameters of two-lobe journal bearing, working with non-Newtonian lubricant has been obtained. Krieger-Dougherty model is used to obtain the effective viscosity of nano-lubricant for a given concentration of solid-particle in base lubricant. Modified Reynolds equation is solved to obtain bearing performance parameters for couple stress model and variable viscosity model. Dynamic coefficients are also determined for various couple stress parameter. Results reveal a noticeable increase in flow co-efficient and load carrying capacity while there is a decrease in friction variable. It also reveals a significant betterment in dynamic co-efficient of bearing.

scholarly journals Effect of Dam Depth and Relief Track Depth on Steady-State and Dynamic Performance Parameters of 3-Lobe Pressure Dam Bearing

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Ashutosh Kumar ◽  
S. K. Kakoty
Keyword(s):  
Steady State ◽  
Dynamic Performance ◽  
Performance Characteristics ◽  
Performance Parameters ◽  
Effect Of Pressure ◽  
And Performance

The present study analyzes the effect of pressure dam depth and relief track depth on the performance of three-lobe pressure dam bearing. Different values of dam depth and relief track depth are taken in nondimensional form in order to analyze their effect. Results are plotted for different parameters against eccentricity ratios and it is shown that the effect of pressure dam depth and relief track depth has great significance on stability and other performance parameters. Study of stability and performance characteristics is undertaken simultaneously.

Performance of Lightly Loaded Gas Journal Bearings in the Slip-Flow and Turbulent-Flow Regimes

1968 ◽  
Vol 10 (4) ◽  
pp. 363-366
Author(s):  
M. D. Wood
Keyword(s):  
Steady State ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Reynolds Equation ◽  
Dynamic Performance ◽  
Slip Flow ◽  
Flow Regimes ◽  
Journal Bearings ◽  
Performance Parameters ◽  
Existing Data

The note compares recently published versions of the governing gas film equations for slip-flow and turbulent flow with Reynolds equation for laminar flow. The comparison shows how approximate values of steady-state and dynamic performance parameters may be deduced for the new conditions from existing data.

Flow and heat transfer of couple stress nanofluid sandwiched between viscous fluids

2019 ◽  
Vol 29 (11) ◽  
pp. 4262-4276 ◽  
Author(s):  
C. Jawali Umavathi ◽  
Mikhail Sheremet
Keyword(s):  
Heat Transfer ◽  
Couple Stress ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Viscous Fluids ◽  
Temperature Fields ◽  
Content Type ◽  
Stress Parameter ◽  
Transfer Behavior ◽  
Velocity And Temperature Fields

Purpose The purpose of this study is a numerical analysis of steady-state heat transfer behavior of couple-stress nanofluid sandwiched between viscous fluids. It should be noted that this research deals with the development of a cooling system for the electronic devices. Design/methodology/approach Stokes model is used to define the couple-stress fluid and the single-phase nanofluid model is used to define the nanofluid transport processes. The fluids in all regions are assumed to be incompressible, immiscible and the transport properties in all the three layers are assumed to be constant. The governing coupled linear ordinary differential equations are made dimensionless by using appropriate fundamental quantities. The exact solutions obtained for the velocity and temperature fields are evaluated numerically for various model parameters. Findings The results are demonstrated using different types of nanoparticles such as copper, silver, silicon oxide (SiO2), titanium oxide (TiO2) and diamond. The investigations are carried out using copper–water nanofluid for different values of couple-stress parameter a with a range of 0 = a = 12, solid volume fraction ϕ with a range of 0.0 ≤ ϕ ≤ 0.05, Eckert number Ec with a range of 0.001 ≤ Ec ≤ 6 and Prandtl number Pr with a range of 0.001 ≤ Pr ≤ 6. It was found that the Nusselt number increases by increasing the couple stress parameter, Eckert number and Prandtl number and it decreases with a growth of the solid volume fraction parameter. It was also observed that using SiO2–water nanofluid, the optimal Nusselt number is obtained. Further, using copper, silver, diamond and TiO2, nanoparticles and water as a base fluid does not show any significant changes in the rate of heat transfer. The couple-stress parameter enhances the velocity and temperature fields whereas the solid volume fraction suppresses the flow field for both Newtonian and couple-stress fluid. Originality/value The originality of this work is to analyze the heat transfer behavior of couple-stress nanofluid sandwiched between viscous fluids. The results would benefit scientists and engineers to become familiar with the analysis of convective heat transfer and flow structures in nanofluids and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

Analysis of dynamic characteristics of spiral groove liquid film seal under thermal–fluid–solid coupling

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Bo Yu ◽  
Muming Hao ◽  
Sun Xinhui ◽  
Zengli Wang ◽  
Liu Fuyu ◽  
...  
Keyword(s):  
Steady State ◽  
Liquid Film ◽  
Dynamic Characteristics ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Analysis Model ◽  
Spiral Groove ◽  
Content Type ◽  
Sealing Performance ◽  
Stiffness And Damping

Purpose The purpose of this paper is to investigate the dynamic characteristics of spiral groove liquid film seal under the effect of thermal–fluid–solid coupling. Design/methodology/approach The dynamic analysis model of spiral groove liquid film seal under the effect of thermal–fluid–solid coupling was established by perturbation method. The steady-state and perturbation Reynolds equations were solved, and the steady-state sealing performance and dynamic characteristic coefficients of the liquid film were obtained. Findings Compared with the liquid film without coupling method, a divergent seal gap is formed between the seal rings under the effect of thermal–fluid–solid coupling, the minimum liquid film thickness decreases, the dynamic stiffness and damping coefficients of the liquid film are increased and the thermoelastic deformation of the end-face improves the dynamic performance of the liquid film seal. Originality/value The dynamic characteristics of the spiral groove liquid film seal under the effect of thermal–fluid–solid coupling are studied, which provides a theoretical reference for optimizing the dynamic performance of the non-contacting liquid film seal.

A Comparison of the Steady-State and Dynamic Performance of First- and Second-Generation Foil Bearings

2010 ◽  
Author(s):  
M. J. Conlon ◽  
A. Dadouche ◽  
W. M. Dmochowski ◽  
R. Payette ◽  
J.-P. Be´dard
Keyword(s):  
Steady State ◽  
Experimental Evaluation ◽  
First Generation ◽  
Second Generation ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Stiffness And Damping

Oil-free foil bearing technology has advanced intermittently over the years, driven by research efforts to improve both steady-state and dynamic performance characteristics, namely: load capacity, stiffness, and damping. Bearing designs are thus classified according to “generation”, with first-generation bearings being the most primitive. This paper presents an experimental evaluation of a first- and a second-generation foil bearing, and aims to provide the high-fidelity data necessary for proper validation of theoretical predictive models of foil bearing performance. The aforementioned test bearings were fabricated in-house, and are both 70mm in diameter with an aspect ratio of 1; bearing manufacturing details are provided. The work makes use of a facility dedicated to measuring both the steady-state and dynamic properties of foil bearings under a variety of controlled operating conditions. The bearing under test is placed at the midspan of a horizontal, simply-supported, stepped shaft which rotates at up to 60krpm. Static and dynamic loads of up to 3500N and 450N (respectively) can be applied by means of a pneumatic cylinder and two electrodynamic shakers. The bearings’ structural (static) stiffnesses are highly nonlinear, and this affects the accuracy of the dynamic coefficient determination. Both dynamic stiffness and damping are found to vary nonlinearly with excitation frequency, and are over-predicted by a structural experimental evaluation — the film plays an important role in bearing dynamics. The second-generation bearing is found to have a higher load capacity, dynamic stiffness, and damping than the first-generation bearing.

scholarly journals Non-Newtonian couple-stress squeeze film behaviour between oscillating anisotropic porous circular discs with sealed boundary

2020 ◽  
Vol 21 (3) ◽  
pp. 311
Author(s):  
Bilal Boussaha ◽  
Mustapha Lahmar ◽  
Benyebka Bou-Said ◽  
Hamid Boucherit
Keyword(s):  
Couple Stress ◽  
Base Fluid ◽  
Volume Fraction ◽  
Low Frequency ◽  
Continuum Theory ◽  
Squeeze Film ◽  
Squeezing Flow ◽  
Concentrated Suspension ◽  
Stress Parameter ◽  
Porous Disc

The thrust of this paper is to investigate theoretically the non-Newtonian couple stress squeeze film behaviour between oscillating circular discs based on V. K. Stokes micro-continuum theory. The lubricant squeezed out between parallel porous and rigid facings is supposed to be a concentrated suspension which consists of small particles dispersed in a Newtonian base fluid (solvent). The effective viscosity of the suspension is determined by using the Krieger-Dougherty viscosity model for a given volume fraction of particles in the base fluid. For low frequency and amplitude of sinusoidal squeezing where cavitation as well as turbulence are unlikely, the governing equations including the modified Reynolds equation coupled with the modified Darcy's equation are derived and solved numerically using the finite difference method and a sub-relaxed iterative procedure. The slip velocity at the porous-fluid interface is directly evaluated by means of the modified Darcy's law considering laminar and isothermal squeezing flow. For a given volume fraction, the couple stress effects on the squeeze film characteristics are analyzed through the dimensionless couple stress parameter ℓ˜ considering sealed and unsealed boundary of the porous disc. The obtained relevant results reveal that the use of couple stress suspending fluids as lubricants and the effect of sealing the boundary of the porous matrix improves substantially the squeeze film behaviour by increasing the squeeze film force. On the other hand, side leakage flow calculated in the sealed case remains constant in comparison to that of open end (unsealed) porous disc for all values of couple stress parameter and volume fraction of particle.

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