Static and dynamic performances of an offset bearing under a micropolar lubricant

In this research paper, the theoretical performance of a circular offset bearing is evaluated. The objective of this paper is to discuss the effects of eccentricity ratios and micropolarity parameters on the static and dynamic characteristics of an offset bearing with respect to micropolar lubrication. The modified Reynolds' equation for a dynamic state is solved using the finite-element method and Galerkin technique. The performance of an offset bearing is computed for a chosen range of eccentricity ratios (0.4–0.6) and for a length–diameter ratio (2.4). Enhancement in the performance of a bearing system is achieved in terms of increasing load and decreasing whirling at the higher values of eccentricity and offset especially at higher micropolarity.

Analysis of misaligned hydrodynamic porous journal bearings in the steady-state condition with micropolar lubricant

Impregnated porous bearings are used in different machines and other applications. In this work, an analytical work is investigated to evaluate the steady-state characteristics of such self-lubricated porous journal bearings in micropolar lubrication with misalignment. Bi-axial misalignments are considered, namely axial (along the vertical direction) and twisting (along the horizontal direction). Reynolds equation is modified to fit bearing misalignment, by incorporating the effects of micropolarity of the lubricant and porosity of the bush. Darcy’s equation that considers porosity and the misalignment Reynolds’s equation applicable for film region are numerically solved using finite difference method applying successive over-relaxation scheme employing appropriate boundary conditions to obtain the dimensionless fluid film pressure at steady state, which is used to get the steady-state characteristics e.g. load parameter, moment of misalignment, frictional force, and friction parameter.

Analytical analysis of a rigid rotor mounted on three hydrostatic pads lubricated with micropolar fluids

Analytical analysis of rigid rotor set vertically, supported by a new hydrostatic squeeze film damper consisting in three hydrostatic pads fed through three capillary restrictors operating with micropolar lubricant is presented. The modified Reynolds equation is obtained using the micropolar lubrication theory and solving it analytically. The calculation of the flow rate, dimensionless vibratory amplitude and amplitude of transmitted forces are determined by resolving the equations of rotor motion using nonlinear methods. It has been observed that a rigid rotor operating with micropolar lubricant shows an increase in the value of transmitted forces at high speeds and a reduction in the value of vibratory response at critical speed when compared to a corresponding similar rigid rotor operating with Newtonian lubricant.

Performance characteristics of two-lobe pressure dam bearings with micropolar lubrication

A circular bearing experiences the instability problem due to oil whirl, causing violent vibrations at high speed. Two-lobe pressure dam bearing is a solution to the instability arising in high-speed rotating machineries. The paper presents the various static and dynamic characteristics of two-lobe pressure dam bearings, while operating with micropolar fluid. The modified Reynolds equation used to model the lubrication is solved using the finite element method. Performance characteristics such as load, attitude angle, critical mass, threshold speed and whirl frequency are computed, presented graphically and analysed. A detailed comparison of the performance characteristics is done for various micropolar and dam parameters. It is concluded that bearing performance is significantly influenced by dam parameters (dam angles) and micropolar parameters (coupling number and characteristics length).

Numerical analysis of a rigid rotor mounted on four-pad hydrostatic squeeze film damper lubricated with micropolar lubricant

The present work deals with a numerical resolution of the modified Reynolds equation using micropolar lubrication theory to study the effects of coupling number and the characteristic length of the micropolar lubricant on the performance characteristics of hydrostatic squeeze film damper, which consists of four hydrostatic pads fed through four capillary restrictors. According to the results, the bearing operating with micropolar lubricant shows an increase in the value of pressure inside the recess. These results suggest that the influence of micropolar effect on the bearing performance is predominantly affected by the pressure ratio. Therefore, the bearing operator must judiciously choose an appropriate value of the pressure ratio in order to get an overall enhanced bearing performance.