Based on ferrofluid flow model given by R.E. Rosensweig, a general equation for different slider squeeze film-bearing design systems, formed by solid upper surface and lower porous plate, is theoretically derived considering the effects of porosity, permeability, squeeze velocity, tangential velocity and oblique variable magnetic field. While deriving the general equation, continuity equation and Darcy’s law are also considered. Expressions for pressure and load-carrying capacity for different squeeze film-bearing design systems are obtained. The results for dimensionless load-carrying capacity are computed and compared with previous results in some cases. The results indicate the better performance of different bearing systems when ferrofluid is used as lubricant. Further, some important conclusions are also made. Two permeability models – globular sphere and capillary fissures are discussed. The variable magnetic field is considered because uniform magnetic field does not enhance bearing performances.
The aim of this paper is to study the impact of various and arbitrary porous structure on the performance of the step bearing lubricated with magnetic fluid. The paper also studied about the effect of squeeze velocity which appears when two lubricated surfaces approaches to each other with a normal velocity. The porous layer (region or wall or matrix) is attached to the lower flat impermeable plate (surface or disc). Two porous structure models given by Kozeny-Carman (a globular sphere model) and Irmay (a capillary fissures model) are considered for the study. The upper surface is a step surface approaching to lower one. The magnetic field considered here is variable and oblique to the lower plate. Expressions for pressure under the step surfaces and load-carrying capacity are obtained. The dimensionless loadcarrying capacity W is calculated for various values of permeability, porous width, length of first step of the bearing, width of the film region, and strength of magnetic field. From the results it is observed that W increases with the increase of the length of the first step and with the increase of K (which leads increase of H) for both the models. It is also observed that permeability and width of porous matrix have almost no effect on W. In the case of width of the film region, it is observed that W attains same behavior whether film thickness is small or large. Moreover, calculation shows that globular sphere model have better performance for W than capillary fissures model. Thus, it is suggested to have a design of porous squeeze step bearing with globular spheres in the porous region considering variable magnetic field strength H of order 10 4 .
This paper discusses about the slider bearing of various shapes stator pad surfaces (e.g. inclined plane, exponential, secant, convex, and parallel) including combined effects of porosity at both the ends, anisotropic permeability, slip velocity, and squeeze velocity. Expression for load capacity is obtained in general and discussed for various cases of stator pad surface to explore its possible effects on the above system for different permeabilities at both the ends. Various sizes of the porous matrix at both the ends are also discussed for the possible optimization of bearing performance. From the study we conclude that better load capacity is obtained when the thickness of both the porous plates are small, and also when both the porous plates are of same size rather than different size.
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