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Article
Publication date: 9 August 2013

H.C. Garg and Vijay Kumar

This paper aims to investigate the effect of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing…

Abstract

Purpose

This paper aims to investigate the effect of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing system operating with Newtonian and non‐Newtonian lubricants. The analysis considers the generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor. The non‐Newtonian lubricant is assumed to follow the power law. The performance characteristics are computed for the two values of power law index (n=1.0 and 0.566). The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well‐designed non‐recessed hole‐entry hybrid journal bearing.

Design/methodology/approach

Finite element method has been used to solve generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor.

Findings

The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well‐designed non‐recessed hole‐entry hybrid journal bearing. The bearing configuration with plugged holes provides sufficient fluid film thickness and low power requirement as less lubricant is required to be pumped in the bearing.

Originality/value

To the best of the author's knowledge, no study which considers the influence of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing system operating with Newtonian and non‐Newtonian lubricant is yet available in the literature.

Details

Industrial Lubrication and Tribology, vol. 65 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 September 2006

Jaw‐Ren Lin, Tsu‐Liang Chou and Ming‐Hsiung Ho

On the basis of the powerlaw fluid model, the rheological effects of an isothermal incompressible non‐Newtonian laminar lubricating film on the steady and dynamic characteristics…

Abstract

Purpose

On the basis of the powerlaw fluid model, the rheological effects of an isothermal incompressible non‐Newtonian laminar lubricating film on the steady and dynamic characteristics of finite slider bearings are presented in the absence of fluid inertia and cavitation.

Design/methodology/approach

To account for the motion that the pad undergoes prescribed small‐amplitude oscillations in a direction perpendicular to itself, the non‐Newtonian dynamic Reynolds equation including the squeezing‐action effect is obtained. Both the steady pressure and the perturbed pressure are numerically solved and used to evaluate the steady‐state performance and dynamic characteristics.

Findings

According to the results, higher steady load‐carrying capacity, dynamic stiffness and damping coefficients are predicted for the finite bearing with small wedge parameter and high viscosity‐shear rate index. In addition, the effects of non‐Newtonian powerlaw lubricants on the bearing characteristics are more pronounced when the bearing width becomes large.

Originality/value

The paper provides useful information on the dynamic characteristics of finite bearings lubricated by a non‐Newtonian powerlaw fluid.

Details

Industrial Lubrication and Tribology, vol. 58 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 9 March 2010

Li‐Ming Chu, Wang‐Long Li, Yuh‐Ping Chang and Hsiang‐Chen Hsu

The purpose of this paper is to analyze and discuss the coupled effects of surface roughness and flow rheology for a homogeneous mixture of Newtonian base oil and power law fluids…

Abstract

Purpose

The purpose of this paper is to analyze and discuss the coupled effects of surface roughness and flow rheology for a homogeneous mixture of Newtonian base oil and power law fluids on the performance of elastohydrodynamic lubrication (EHL) circular contact problems.

Design/methodology/approach

The average flow model is adapted for the interaction of the flow rheology of lubricant and surface roughness. The average Reynolds type equation (ARTE) and the related flow factors (which describes the coupled effects of surface roughness and flow rheology of a mixture), the viscosity‐pressure and density‐pressure relations equations, the elastic deformation equation, and the force balance equation are then solved simultaneously. The multilevel multi‐integration algorithm and Gauss‐Seidel iteration method are utilized to calculate the film thickness and pressure distributions of the EHL circular contact problems effectively.

Findings

The effects of volume fraction, flow index of power law fluid, and surface roughness parameters (Peklenik number, standard deviation of composite surface roughness) on the film thickness and pressure distributions are discussed. The results show that the effects of surface roughness should be considered especially in EHL contact problems.

Originality/value

The EHL of circular contacts lubricating with mixture of two lubricants is first analyzed. The coupling effects of surface roughness and flow rheology of mixture (a Newtonian fluid and a powerlaw fluid) on the EHL performance are first discussed in this paper.

Details

Industrial Lubrication and Tribology, vol. 62 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 12 March 2018

Li-Ming Chu, Jaw-Ren Lin and Cai-Wan Chang-Jian

The modified Reynolds equation for non-Newtonian lubricant is derived using the viscous adsorption theory for thin-film elastohydrodynamic lubrication (TFEHL) of circular…

Abstract

Purpose

The modified Reynolds equation for non-Newtonian lubricant is derived using the viscous adsorption theory for thin-film elastohydrodynamic lubrication (TFEHL) of circular contacts. The proposed model can reasonably calculate the phenomenon in the thin-film lubrication (TFL) unexplained by the conventional EHL model. The differences between classical EHL and TFEHL with the non-Newtonian lubricants are discussed.

Design/methodology/approach

The power-law lubricating film between the elastic surfaces is modeled in the form of three layers: two adsorption layers on each surface and one middle layer. The modified Reynolds equation with power-law fluid is derived for TFEHL of circular contacts using the viscous adsorption theory. The finite difference method and the Gauss–Seidel iteration method are used to solve the modified Reynolds equation, elasticity deformation, lubricant rheology equations and load balance equations simultaneously.

Findings

The simulation results reveal that the present model can reasonably calculate the pressure distribution, the film thickness, the velocity distribution and the average viscosity in TFL with non-Newtonian lubricants. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction.

Originality/value

The present model can reasonably predict the average viscosity, the turning point and the derivation (log film thickness vs log speed) phenomena in the TFEHL under constant load conditions.

Details

Industrial Lubrication and Tribology, vol. 70 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 10 July 2017

Khalid Mahmood, Muhammad Sajid, Nasir Ali and Tariq Javed

An attempt is made to study magnetohydrodynamic viscous fluid impinging orthogonally toward a stagnation point on a vertical surface lubricated with power law fluid. It has been…

Abstract

Purpose

An attempt is made to study magnetohydrodynamic viscous fluid impinging orthogonally toward a stagnation point on a vertical surface lubricated with power law fluid. It has been assumed that the surface temperature varies linearly with the distance from the stagnation point. The problem is governed by system of partial differential equations for both the base fluid and the lubricant. The continuity of velocity and shear stress is assumed at the interface layer between the base fluid and the lubricant. Dimensionless variables are introduced to transform original problem into ordinary differential equations. An implicit finite-difference scheme known as the Keller-Box method is implemented to obtain the numerical solutions. The influence of various important parameters is presented in the form of graphs and tables. The limiting cases for full and no-slip conditions are deduced from the present solutions. A comparison of the present results with the existing results in the special case validates the obtained numerical solutions. The purpose of this study is to see the behaviour of flow characteristics in the presence of lubrication.

Design/methodology/approach

The authors’ problem is governed by system of partial differential equations for both the base fluid and the lubricant. Dimensionless variables are introduced to transform original problem into ordinary differential equations. The obtained ordinary differential equation along with boundary conditions are highly nonlinear and coupled. An implicit finite-difference scheme known as the Keller-Box method is implemented to obtain the numerical solutions.

Findings

Some findings of this study are that the lubricant increases the velocity of the base fluid inside the boundary layer. In the case of full slip, the effects of viscosity are suppressed by the lubricant. The temperature of the base fluid decreases by increase in lubrication on the surface. By increasing the slip on the surface, the skin friction decreases and local Nusselt number increases, but the rate of increase or decrease is less in magnitude for the case of opposing flow. The similarity solutions only exist for n = 1/2. A non-similar solution is obtained for the other values of the power-law index n.

Originality/value

The study of flow phenomenon over a lubricated surface has important applications in machinery components such as fluid bearings and mechanical seals. Coating is another major application of lubrication including the preparation of thin films, printing, painting, etc. The authors hope that the current study will provide the roadmap for the future studies in this direction.

Details

Industrial Lubrication and Tribology, vol. 69 no. 4
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 13 April 2015

Venkata Subrahmanyam Sajja and Dhaneshwar Prasad

The purpose of this paper is to deal with the qualitative analysis of hydrodynamic lubrication of asymmetric rollers with non-Newtonian incompressible power law lubricants

Abstract

Purpose

The purpose of this paper is to deal with the qualitative analysis of hydrodynamic lubrication of asymmetric rollers with non-Newtonian incompressible power law lubricants including Newtonian.

Design/methodology/approach

The fluid flow governing equations such as equation of motion along with continuity and thermal equations are solved first analytically and investigated numerically by the Runge-Kutta Fehlberg method.

Findings

As a result of this work, it is found that there is a significant change in temperature, pressure, load and traction with Newtonian and non-Newtonian fluids.

Research limitations/implications

The authors considered incompressible hydrodynamic lubrication of two rigid asymmetric rollers, one of them is assumed to be adiabatic. The convection term of the heat flow equation is taken in its average form.

Originality/value

It is a theoretical problem of two heavily loaded rigid cylindrical rollers with cavitations, where the consistency of the power law lubricant is assumed to vary with pressure and the mean film temperature. It has not appeared in the literature.

Details

Industrial Lubrication and Tribology, vol. 67 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 13 November 2017

Chandra B. Khatri and Satish C. Sharma

The aim of the present paper is to study the combined influence of textured surface and micropolar lubricant behaviour on the performance of two-lobe hole-entry hybrid journal…

Abstract

Purpose

The aim of the present paper is to study the combined influence of textured surface and micropolar lubricant behaviour on the performance of two-lobe hole-entry hybrid journal bearing system. The bearing performance parameters of the textured circular/two-lobe hole-entry hybrid journal bearing system have been computed against the constant vertical external load supported by the bearing.

Design/methodology/approach

In this work, Eringen’s micropolar fluid theory has been used to derive the governing Reynolds equation. The consequent solution of the governing Reynolds equation has been obtained by using finite element method (FEM) numerical technique.

Findings

The present study indicates that the use of the textured surface, two-lobe profile of bearing and micropolar lubricant, significantly enhances the bearing performance as compared to non-textured circular journal bearing.

Originality/value

The present study concerning the influence of surface texturing on the behaviour of the two-lobe hole-entry hybrid journal bearing lubricated with micropolar lubricant is original. The theoretically simulated results of the present study will be useful to design an efficient journal bearing system.

Details

Industrial Lubrication and Tribology, vol. 69 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 9 January 2017

Anastasios Zavos and Pantelis Nikolakopoulos

Compression rings are the main sources of frictional losses in internal combustion engines. The present paper aims to present a thermo-mixed hydrodynamic analysis for coated top…

Abstract

Purpose

Compression rings are the main sources of frictional losses in internal combustion engines. The present paper aims to present a thermo-mixed hydrodynamic analysis for coated top compression rings. To understand the coating effects, the main tribological parameters are investigated into a ring-cylinder conjunction in a motorbike engine. Furthermore, flow simulations have been carried out on how different worn profiles on the cylinder inner liner affects friction, lubricant film and localized contact deformation of the coated compression rings.

Design/methodology/approach

In this paper, the basic geometrical dimensions of the top compression ring-cylinder system are obtained from a real motorbike engine. A 2D axisymmetric CFD/FLOTRAN model is created for coated compression rings. Flow simulations are performed by solving the Navier-Stokes and the energy equations. The load capacity of the asperities is also taken into account by Greenwood and Tripp contact model. Realistic boundary conditions are imposed to simulate the in-plane ring motion. The simulation model is validated with analytical and experimental data from the literature. Under thermal considerations, the contribution of worn cylinder profiles in conjunction with different coated compression rings is presented.

Findings

This research shows that because of thermal effects, the boundary friction is higher at reversals and the viscous friction is lower because of reduced oil viscosity. As regards to the isothermal case, the viscous friction is greater because of a higher lubricant viscosity. In the case of chromium-plated ring, boundary friction was 16 per cent lower than a grey cast iron ring taking into account thermal effects. Regarding the localized contact deformation, the coated compression rings showed lower values under different worn cylinder shapes. In particular, hard wear-resistant (Ni-Cr-Mo) coating showed the slighter local deformation. Therefore, the worn cylinder profiles promote boundary/mixed lubrication regime, whereas the lobed profile of cylinder inner liner becomes more wavy.

Originality/value

The solution of the thermo-mixed lubrication model, concerning the piston ring and worn cylinder tribo pair by taking into account the coating of the top compression ring.

Details

Industrial Lubrication and Tribology, vol. 69 no. 1
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 2 October 2007

R. Raghavendra Rao and K. Raja Sekhar

This paper aims to study the effects of couple stresses and surface roughness on the minimum film thickness of heavily loaded rollers and to discuss these by following Grubin's…

Abstract

Purpose

This paper aims to study the effects of couple stresses and surface roughness on the minimum film thickness of heavily loaded rollers and to discuss these by following Grubin's approach and Crook's approximations.

Design/methodology/approach

A generalised form of Reynolds equation for rough surfaces with lubricant as couple stress fluid is derived. This equation is then used to study the combined effect of couple stresses and surface roughness on the roller bearings under heavily loaded conditions. EHD minimum film thickness expressions is obtained by following Grubin's approach and Crook's approximation and it is studied numerically.

Findings

It is found that, as the chain length of the additive molecules increases, the elastohydrodynamic minimum film thickness increases. Also, as the mean height of roughness asperities increases, the elastohydrodynamic minimum film thickness increases for the transversal roughness and it decreases in the case of longitudinal roughness.

Research limitations/implications

These effects are studied theoretically by the mathematical equations in heavily loaded roller bearings.

Practical implications

Reduction of the film thickness in the EHD lubrication between the rollers can be compensated by the use of lubricants containing additives of molecules of size. As a result the bearing performance can be improved.

Originality/value

This research paper provides a closed form of the expressions for the bearings in EHD lubrication and is studied with regard to couple stress parameter. This paper helps to manufacture better bearings.

Details

Industrial Lubrication and Tribology, vol. 59 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 8 April 2014

Shun-Te Hsiao, Yuan Kang, Shyh-Ming Jong, Hsing-Han Lee, De-Xing Peng and Yeon-Pun Chang

This paper aims to study the static characteristics of the hydrostatic conical journal bearings by utilizing single-action membrane restrictors to compensate the working pressures…

Abstract

Purpose

This paper aims to study the static characteristics of the hydrostatic conical journal bearings by utilizing single-action membrane restrictors to compensate the working pressures of recesses.

Design/methodology/approach

The flow resistance network method is used to analyze the influences of load capacity and static stiffness of bearing with the design parameters, including the number of recesses, radial eccentricity ratio, axial displacement ratio, restriction constant, membrane compliance, length-diameter ratio, circumferential land width ratio, axial land width ratio and half of cone angle.

Findings

This study shows the infinite stiffness of the oil produced in the first and second recesses while single-action membrane restriction constant of 2 and 3, respectively, as well as in the fourth recess while single-action membrane restriction constant of 0.01 and 0.1, respectively.

Research limitations/implications

This article provides the hydrostatic conical bearings in static and unbiased states for analyses of design parameters. The analyses ignore dynamic pressure effect and do not use the Reynolds equation, and assuming that each oil recesses pressure is constant.

Practical implications

The influences of the design parameters including the number of recesses, membrane restriction, membrane compliance, length-diameter ratio, half of con-angle, circumferential land width ratio, and axial land width ratio are discussed to the load capacity and static stiffness of conical bearing.

Originality/value

Based on the characteristics of the conical bearing through analysis, this article suggests the front bearing with hard membrane restrictor (capillary) and the back bearing with soft membrane restrictor are the most appropriate for axial stiffness.

Details

Industrial Lubrication and Tribology, vol. 66 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

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