scholarly journals Ferrofluid lubrication of circular squeeze film bearings controlled by variable magnetic field with rotations of the discs, porosity and slip velocity

2017 ◽  
Vol 4 (12) ◽  
pp. 170254
Author(s):  
Rajesh C. Shah ◽  
Rajiv B. Shah
Keyword(s):  
Magnetic Field ◽  
Slip Velocity ◽  
Magnetic Particles ◽  
Reynolds Equation ◽  
Variable Magnetic Field ◽  
Squeeze Film ◽  
Design System ◽  
Porous Region ◽  
Different Shapes ◽  
Bearing Design

Based on the Shliomis ferrofluid flow model (SFFM) and continuity equation for the film as well as porous region, modified Reynolds equation for lubrication of circular squeeze film bearings is derived by considering the effects of oblique radially variable magnetic field (VMF), slip velocity at the film–porous interface and rotations of both the discs. The squeeze film bearings are made up of circular porous upper disc of different shapes (exponential, secant, mirror image of secant and parallel) and circular impermeable flat lower disc. The validity of Darcy's Law is assumed in the porous region. The SFFM is important because it includes the effects of rotations of the carrier liquid as well as magnetic particles. The VMF is used because of its advantage of generating maximum field at the required active contact area of the bearing design system. Also, the effect of porosity is included because of its advantageous property of self-lubrication. Using Reynolds equation, general form of pressure equation is derived and expression for dimensionless load-carrying capacity is obtained. Using this expression, results for different bearing design systems (due to different shapes of the upper disc) are computed and compared for variation of different parameters.

Analysis and comparative study of ferrofluid lubricated circular porous squeeze film-bearings

2017 ◽  
Vol 231 (11) ◽  
pp. 1450-1463 ◽  
Author(s):  
Rajesh C Shah ◽  
Dilip B Patel
Keyword(s):  
Magnetic Field ◽  
Reynolds Equation ◽  
Variable Magnetic Field ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Anisotropic Permeability ◽  
Load Carrying ◽  
Design Systems ◽  
Bearing Design ◽  
Maximum Field

Based on ferrohydrodynamic theory by R. E. Rosensweig and continuity equation for film as well as upper and lower porous regions, a general modified Reynolds equation for ferrofluid (FF) lubricated circular discs porous squeeze film-bearings is derived by assuming the validity of the Darcy’s law in the porous regions. The effects of porosity, slip velocity, anisotropic permeability and rotation at both the discs are also included for the study. Here, the FF is controlled by oblique and radially variable magnetic field. The effect of porosity is included because of its advantageous property of self-lubrication, and oblique variable magnetic field is important because of its advantage of generating maximum field at the required active contact zone of the bearing design systems. Using Reynolds equation, different circular porous squeeze film-bearing design systems (e.g. exponential, secant and parallel (flat)) are studied and compared for load-carrying capacity. During the course of investigation, it is observed that uniform magnetic field does not affect on the performances of the bearing systems.

scholarly journals MAGNETIC FLUID-BASED SQUEEZE FILM BETWEEN CURVED POROUS ANNULAR PLATES CONSIDERING THE ROTATION OF MAGNETIC PARTICLES AND SLIP VELOCITY

2020 ◽  
Vol 14 (2) ◽  
pp. 69-82
Author(s):  
Niru C. Patel ◽  
Jimit R. Patel
Keyword(s):  
Slip Velocity ◽  
Magnetic Particles ◽  
Reynolds Equation ◽  
Graphical Representation ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Annular Plates ◽  
Load Carrying ◽  
Porous Interface ◽  
The Impact

The ferrofluid flow model of the Shliomis and continuity equation for the film and porous interface with the theory of Darcy, the modified Reynolds equation for ferrofluid squeeze film between curved annular plates is discussed with the impact of the rotation of Ferro-particles and slip velocity at the boundary. Beavers and Joseph’s slip conditions are adopted to study the impact of slip velocity. The generalized non-dimensional pressure equation is derived and expression for dimensionless load-carrying capacity is obtained for the same. The graphical representation suggests that the bearing's performance enhances due to ferrofluid, considering the appropriate values of parameters for slip velocity and porosity.

On the ferrofluid lubricated exponential squeeze film-bearings

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Rajesh C. Shah ◽  
Dilip B. Patel
Keyword(s):  
Magnetic Field ◽  
Carrying Capacity ◽  
Squeeze Film ◽  
Design System ◽  
Load Carrying Capacity ◽  
Regular Perturbation ◽  
System Variable ◽  
Study Results ◽  
Load Carrying ◽  
Bearing Design

Abstract Based on the ferrohydrodynamic theory by R. E. Rosensweig and continuity equation, ferrofluid (FF) lubricated different exponential squeeze film-bearing designs are studied. Since uniform magnetic field does not effect on the performance of the bearing design system, variable form of magnetic field is considered to control FF flow behaviour. Expressions for pressure and load-carrying capacity are obtained by the methods of averaged inertia and regular perturbation. Results for dimensionless load-carrying capacity are calculated and compared. Some comparisons are also made with the previous study. Results show the significant contribution of FF on the designed problem.

scholarly journals Finite Length Effects on Switching Mechanisms in Chains of Magnetic Particles

2020 ◽  
Vol 6 (4) ◽  
pp. 47
Author(s):  
Dominika Kuźma ◽  
Piotr Zieliński
Keyword(s):  
Magnetic Field ◽  
Ground State ◽  
Magnetic Particles ◽  
Variable Magnetic Field ◽  
Periodic Systems ◽  
Spin Models ◽  
Micromagnetic Simulations ◽  
Equilibrium Configurations ◽  
Chain Axis ◽  
Intermediate Configuration

Periodic systems of magnetic nanoparticles are now of interest as they support GHz spin waves. Their equilibrium configurations, switchable with the external magnetic field, are crucial for such applications. We study infinite and finite chains of particles of two shapes (i) ellipsoidal and (ii) rectangular stripes with long axes perpendicular to the chain axis. A variable magnetic field is applied parallel to the long axes. Micromagnetic simulations are compared with the corresponding discrete spin models (Stoner-Wohlfarth model, S-W). An antiferromagnetic configuration is the ground state for all the systems at vanishing field but a ferromagnetic configuration occurs when the field is strong enough. The switching of the infinite chains to the reversed ferromagnetic configuration proceeds directly for the ellipsoids and by an intermediate configuration, in which the magnetization within the particle is non-uniform, in the case of the stripes. The non-uniform configurations are well represented by tilted states in S-W model. Important differences are found in the finite analogs: the switching of ellipsoids becomes multistage and starts from the innermost particles relatively well reproduced with S-W model, whereas the reversal of the stripes, starts from the outermost particles and has no analog in S-W model. Practical consequences of the findings are discussed.

scholarly journals Improving the Performance of Composite Hollow Fiber Membranes with Magnetic Field Generated Convection Application on pH Correction

Membranes ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 445
Author(s):  
Aurelia Cristina Nechifor ◽  
Alexandru Goran ◽  
Vlad-Alexandru Grosu ◽  
Constantin Bungău ◽  
Paul Constantin Albu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Oil Recovery ◽  
Hollow Fiber ◽  
Power Plants ◽  
Magnetic Particles ◽  
Thermal Power ◽  
Variable Magnetic Field ◽  
Winter Period ◽  
Used Cooking Oil ◽  
Aluminum Ions

The membranes and membrane processes have succeeded in the transition from major technological and biomedical applications to domestic applications: water recycling in washing machines, recycling of used cooking oil, recovery of gasoline vapors in the pumping stations or enrichment of air with oxygen. In this paper, the neutralization of condensation water and the retention of aluminum from thermal power plants is studied using ethylene propylene diene monomer sulfonated (EPDM-S) membranes containing magnetic particles impregnated in a microporous propylene hollow fiber (I-PPM) matrix. The obtained membranes were characterized from the morphological and structural points of view, using scanning electron microscopy (SEM), high resolution SEM (HR-SEM), energy dispersive spectroscopy analysis (EDAX) and thermal gravimetric analyzer. The process performances (flow, selectivity) were studied using a variable magnetic field generated by electric coils. The results show the possibility of correcting the pH and removing aluminum ions from the condensation water of heating plants, during a winter period, without the intervention of any operator for the maintenance of the process. The pH was raised from an acidic one (2–4), to a slightly basic one (8–8.5), and the concentration of aluminum ions was lowered to the level allowed for discharge. Magnetic convection of the permeation module improves the pH correction process, but especially prevents the deposition of aluminum hydroxide on hollow fibers membranes.

Analysis of magneto rheological elastomers for energy harvesting systems

2020 ◽  
Vol 64 (1-4) ◽  
pp. 439-446
Author(s):  
Gildas Diguet ◽  
Gael Sebald ◽  
Masami Nakano ◽  
Mickaël Lallart ◽  
Jean-Yves Cavaillé
Keyword(s):  
Magnetic Field ◽  
Energy Harvesting ◽  
Shear Strain ◽  
Magnetic Induction ◽  
Magnetic Particles ◽  
Homogeneous Magnetic Field ◽  
Electrical Signal ◽  
Harvesting Systems ◽  
Dc Bias ◽  
Magneto Rheological

Magneto Rheological Elastomers (MREs) are composite materials based on an elastomer filled by magnetic particles. Anisotropic MRE can be easily manufactured by curing the material under homogeneous magnetic field which creates column of particles. The magnetic and elastic properties are actually coupled making these MREs suitable for energy conversion. From these remarkable properties, an energy harvesting device is considered through the application of a DC bias magnetic induction on two MREs as a metal piece is applying an AC shear strain on them. Such strain therefore changes the permeabilities of the elastomers, hence generating an AC magnetic induction which can be converted into AC electrical signal with the help of a coil. The device is simulated with a Finite Element Method software to examine the effect of the MRE parameters, the DC bias magnetic induction and applied shear strain (amplitude and frequency) on the resulting electrical signal.

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