Hydrodynamic lubrication of a porous slider bearing with slip velocity

An inclined porous slider bearing is analysed with slip velocity at the porous boundary considered. The expressions for dimensionless loadcarrying capacity, friction and the centre of pressure are obtained in the form of integrals. Minimization of the slip parameter is essential to increase the load capacity.     

Optimum shape design for surface of a thermohydrodynamic lubrication slider bearing

This paper utilises a thermohydrodynamic model of bearing to optimise the shape of slider bearing. Friction is minimised subject to load and centre of pressure requirements using a sequential quadratic programming algorithm. A generalised Reynolds equation is solved simultaneously with an energy equation using the finite volume method to obtain bearing characteristics, such as friction, load and centre of pressure. Results show that the coefficient of friction is reduced by the optimisation approach. Results also show that larger temperature–viscosity coefficient and inlet viscosity tend to yield smaller optimal friction, whereas larger thermal conductivity tends to yield larger optimal friction. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydromagnetic lubrication equation for an anisotropic porous slider with slip velocity

A general differential equation is derived for the lubrication of an anisotropic porous slider in the presence of a transverse magnetic field. The effect of slip velocity is considered.     

Ferrofluid squeeze film in a long journal bearing

A theoretical study and comparison were made of squeeze film behaviour in an infinitely long journal bearing using the ferrofluid flow models of Neuringer–Rosensweig, Jenkins and Shliomis with uniform and non-uniform magnetic fields. Expressions were obtained for the pressure, load capacity and response time of the squeeze film using the flow models of Jenkins as well as Shliomis. The results corresponding to the Neuringer–Rosensweig model were deduced from the Jenkins model. Computed values of dimensionless load capacity and response time were displayed in tabular form. Their values increased with increasing values of the eccentricity ratio in all the three models. They decreased or increased according to whether the values increased were those of the Jenkins material constant or the rotational viscosity parameter of Shliomis. A uniform magnetic field could not produce magnetic pressure in the Neuringer–Rosensweig model, but it could affect the bearing characteristics in the Shliomis model owing to the rotational viscosity. The load capacity and squeeze time are more in the case of a non-uniform magnetic field than in the case of a uniform magnetic field.     

Numerical investigation of pocketed slip slider bearing with non-Newtonian lubricant

Boundary slip as well as surface texturing is an effective method to improve the tribological performance of lubricated mechanical components. This article analyzes the combined effect of single texturing (pocketing) and wall slip on pressure that strongly related to the load-carrying capacity of slider bearing. The modified Reynolds equation for lubrication with non-Newtonian power-law fluid is proposed. The equation was solved numerically using a finite difference equation obtained by means of the micro-control volume approach. Further, numerical computations for slider bearing with several power-law indexes were compared with the presence of the pocket and slip. The numerical results showed that the characteristic of non-Newtonian is similar to Newtonian fluid with respect to hydrodynamic pressure distribution. The maximum load support is achieved when the pocket depth is equal to the film thickness.     

Analysis of an anisotropic porous slider bearing considering slip velocity

A porous slider bearing with anisotropic permeability and slip velocity is considered. Expressions for the load-carrying capacity, friction, coefficient of friction and the position of the centre of pressure are obtained in integral form. Anisotropic permeability and slip affect these bearing characteristics.     

Optimal design of one-dimensional porous slider bearings using the Brinkman model

On the basis of the Brinkman model, a theoretical study of the optimal load-carrying capacity and friction coefficient for one-dimensional curved porous slider bearings with the gap width varying slowly is presented. The modified Reynolds equation is obtained by applying Brinkman equations to guide oil motion through the porous matrix. By using the technique of calculus of variations, the optimization is performed over a class of step profiles. According to the analysis, the step height ratio and riser location of the optimal geometry are found to depend upon the permeability parameter of the porous matrix. Compared with the inclined-plane bearing case, the stepped porous slider bearing provides an enhancement in the load-carrying capacity as well as a reduction in the friction parameter. An illustrative design example is also included for engineering and industrial applications.     

Lubrication of a long porous slider

The problem of a porous slider where the fluid is injected through the porous bottom is considered. The similarity transformation reduces the governing equations into coupled non-linear ordinary differential equations. The resulting equations are solved using long series with polynomial coefficients. Forty effective terms in the series representing lift and drag coefficients reveal the qualitative features which are comparable to pure numerical results. To this order the number of universal coefficients generated are 3280 in each case. After identifying and estimating the location and nature of singularities, restricting the convergence of these series, the series are recast into new forms, whose validity increases up to moderately large value of Reynolds numbers (R = 5 to R = 16). The variations of lift and drag as functions of R are analysed.     

The squeeze film in an inclined porous slider bearing

The behaviour of a squeeze film in an inclined porous slider bearing is analysed. Expressions for pressure, load capacity, friction, coefficient of friction and the position of the centre of pressure are obtained. Pressure, load capacity and friction are increased as a result of squeeze. The coefficient of friction is decreased and the centre of pressure is unaffected. An expression for the time-height relation is given.     

An inclined porous slider bearing with a transverse magnetic field

A hydromagnetic inclined porous slider bearing with a transverse magnetic field is analysed. Expressions for various bearing characteristics are obtained for large and small Hartmann numbers. The dimensionless load capacity, friction and centre of pressure are computed for large Hartmann numbers in the open-circuit case; the load capacity and friction increase markedly with increasing Hartmann number.     

Ferrofluid lubrication of finite journal bearings using Jenkins model

The present study investigates hydrodynamic lubrication by ferrofluids of finite journal bearings using the Jenkins model. A magnetic field created by displaced finite wire is used. A numerical solution for the modified Reynolds equation using the finite difference method is obtained. Static characteristics of finite journal bearings are analyzed using 2 control parameters: magnetic force coefficient and Jenkins viscosity. The obtained results are compared to those from Neurenger‐Rosensweig model. It is shown that pressure, load capacity, attitude angle, and side leakage increase and friction factor decreases when increasing the value of each control parameter at low and medium eccentricity ratios. However, the Jenkins viscosity parameter decreases the load capacity and increases the friction factor at high eccentricity ratios.     

Analysis of a porous inclined slider bearing with an azimuthal magnetic field

The effects of an applied azimuthal magnetic field and a porous facing of variable thickness on an inclined slider bearing with an electrically conducting lubricant are theoretically investigated. Expressions for pressure, load capacity, friction and the position for the centre of pressure are derived for both open-circuit and short-circuit cases. The case when the magnetic field is absent is also examined.     

Roughness effects in a narrow porous journal bearing with arbitrary porous wall thickness

The paper uses Christensen's stochastic theory to study the effects of surface roughness in a narrow porous journal bearing. An exact solution, valid for arbitrary wall thickness, is given for the film pressure and pressure in the bearing material. The results are compared with the approximate solutions, and the range of various influencing parameters, for which the approximate analysis is satisfactory from a practical point of view is determined.     

Optimum shape design for surface of a porous slider bearing lubricated with couple stress fluid

Porous-bearing performance can significantly benefit from optimally designing the shape of the bearing. The present paper introduces an approach for designing the optimum shape of a slider bearing using an inverse method. The proposed approach utilises a sequential quadratic programming algorithm to minimise friction subject to load and centre of pressure requirements specified by the designer. Bearing characteristics, such as friction, load and centre of pressure, are obtained by solving a modified Reynolds-type equation numerically using the finite difference method. The modified Reynolds equation is derived on the basis of Stokes' microcontinuum theory of couple stress fluids, which is used to study non-Newtonian lubricants. Results show that the optimisation approach reduces the coefficient of friction. In addition, the dimensionless slip parameter is shown to be the most significant parameter affecting optimal friction. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of surface roughness on the static characteristics of inclined plane slider bearing: Rabinowitsch fluid model

In this paper, a theoretical study of the effect of surface roughness on the static characteristics of inclined plane slider-bearing lubricated with Rabinowitsch fluid is analysed. Christensen’s stochastic theory for the lubrication of rough surfaces has been used for the derivation of generalised stochastic Reynolds-type equation. The two types of one-dimensional roughness patterns (Longitudinal and Transverse) are considered. Expressions for pressure, load carrying capacity, frictional force and coefficient of friction are obtained. It is found that the presence of transverse roughness pattern on the bearing surface increases pressure and load carrying capacity. Results are well agreement with smooth case.     

Ferrofluids lubrication: a status report

Ferrofluids (FFs) are stable colloidal suspensions composed of single‐domain magnetic nanoparticles dispersed in a carrier liquid. And it is an intelligent material, exhibiting normal liquid behaviour coupled with superparamagnetic properties. Since the properties and the location of these fluids can easily be influenced by a magnetic field, FFs have recently attracted many scientific, industrial and commercial applications. Lubrication is one of the most important applications for FFs, and the advantage of FFs as lubricant, over the conventional ones, is that the former can be retained at the desired location with moderate magnetic fields. The main focus of this paper is to present a comprehensive review on FFs lubrication theories based on the three flow models of Neuringer–Rosensweig, Shliomis and Jenkins. Besides, a few experimental studies on FFs lubrication are discussed briefly. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of rotation in the lubrication of a porous slider bearing: Small rotation

A mathematical model is developed to investigate the behaviour of a plane-inclined porous slider bearing under the effect of a uniform small rotation. The Beavers-Joseph slip condition was used for the slip velocity at the porous boundary. The expressions for dimensionless pressure distribution, load-carrying capacity and coefficient of friction are obtained. It is concluded that the load-carrying capacity and coefficient of friction depend on the direction and magnitude of rotation. For a negative rotation the load-carrying capacity increases and the coefficient of friction decreases. The load-carrying capacity also decreases with increase in the slip velocity parameter.     

Micropolar fluid squeeze film lubrication of finite porous journal bearing

In this paper, the effect of micropolar fluid on the static and dynamic characteristics of squeeze film lubrication in finite porous journal bearings is studied. The finite modified Reynolds equation is solved numerically using the finite difference technique and the squeeze film characteristics are obtained. According to the results obtained, the micropolar fluid effect significantly increases the squeeze film pressure and the load-carrying capacity as compared to the corresponding Newtonian case. Under cyclic load, the effect of micropolar fluid is to reduce the velocity of the journal centre. Effect of porous matrix is to reduce the film pressure, load-carrying capacity and to increase the journal centre velocity.