PurposeThe paper seeks to study, theoretically, the performance characteristics of capillary compensated multi‐recessed hydrostatic journal bearings operating with micropolar lubricant. The finite element method is used to solve the modified Reynolds' equation governing the micropolar lubricant flow in the clearance space of a hydrostatic journal bearing. The performance characteristics of bearing operating with micropolar lubricant are presented and compared with that of Newtonian lubricant, for a wide range of non‐dimensional load, capillary restrictor design parameter and micropolar parameters.Design/methodology/approachThe modified Reynolds' equation governing the flow of the micropolar lubricant is solved along with restrictor flow equation by finite element method so as to obtain fluid‐film pressures. The iterative procedure is repeated until the converged solution for the fluid‐film pressure field is obtained.FindingsA study of four‐pocket hydrostatic journal bearing system capillary compensated and operating with micropolar lubricant is presented. The following conclusions are made from the results presented in this study: at a constant load, pocket pressures and minimum film thickness, stiffness coefficients and, the damping coefficients increase with increase in micropolar effect of lubricant as compared to the Newtonian lubricant; the influence of the micropolar parameters of lubricant is more significant upon the minimum fluid‐film thickness at higher values of load and lower values of restrictor design parameter; the non‐dimensional flow decreases with increase in the micropolar effect of the lubricant a given values of restrictor design parameter and load; and the stiffness coefficient in the direction of load is found to be influenced by the micropolar parameters and more significantly at lower values of restrictor design parameter and load.Originality/valueStudies of capillary compensated multi‐recess hydrostatic journal bearing operating with micropolar fluid/lubricant are not available in the existing literature to the best of authors' knowledge. Although, such bearing has been studied with Newtonian lubricant and available in open literature. Therefore, this paper is an original piece of work in the area of micropolar lubrication and compensated hydrostatic bearings.
PurposeThe present work aims to predict accurately the bearing design data for non‐recessed hybrid journal bearings, considering the effect of non‐Newtonian behavior of lubricant for different symmetric and non‐symmetric bearing geometric configurations.Design/methodology/approachThe simultaneous solution of generalized Reynold's equation governing the laminar flow of incompressible lubricant and the equation of flow of lubricant through the capillary restrictor, considering variable viscosity of lubricant following the “Power law”, has been carried out using FEM. For a given set of bearing geometric, operating parameters and for given external vertical load, the values of various performance characteristics have been obtained for a range of values of power law index, after establishing the journal center equilibrium position, the analysis for which has been elaborately explained.FindingsThe results obtained have been presented graphically for various bearing performance characteristics. It has been observed that with decrease in power law index “n”(0
A finite element model is constructed to analyze the effects of steady state temperature field on FGM layer thickness. The first-order shear deformation model is exploited to investigate the uncoupled thermal behavior of functionally graded plates in Abacus environment. The continuum is divided into 540 elements and 541 nodes using two node linear elements. The results show that the temperature distribution in the composite plate is more reasonable with increase in the thickness of FGM layer. The comparison with the non-graded two layered composite plate, the temperature field of the Zirconia/FGM/Aluminum three layered composite plate is in the form of a curve but in case of non-graded two layered composite plate the temperature field is in the form of inclined straight line with sharp bend at the interface of metal and ceramic phase.
Functionally graded materials (FGM) are newly developed materials described by variation in the characteristics gradually over volume. These materials find applications in very high temperature environments namely aerospace industry, nuclear reactors, gas turbines, and electronics cooling. These materials are used in high temperature environments with dynamic load conditions, so their transient thermoelastic analysis under these conditions is necessary. In this paper, transient thermoelastic investigation of FGM is carried out using finite element method (FEM). The effect of temperature dependence is considered in the thermophysical properties of a FGM plate in the direction of its thickness. FEM is applied to solve the thermo mechanical equations and Newmark direct integration scheme is used for obtaining the solution for transient loading. This method improves the accuracy for three dimensional cases and produces solutions directly in time domain. A comparative study is made with some existing methods, and it is found that temperature and thermal stresses remain within safe limits at higher temperatures while preserving the deformation in the structure. The results show that the grading parameter has a dominating effect on transient thermoelastic behavior on FGM plate.
PurposeHybrid bearings have found increasing applications in various machines owing to their large number of favorable characteristics like high load carrying capacity, increased minimum fluid film thickness, long life and increased damping making them attractive for various applications such as turbo machinery, machine tool spindles, precision grinder spindles, etc. A careful design of such bearing for optimum performance has always been among the key issues of the researchers. The present work has been carried out to study the effect of bearing geometric parameters on performance of hybrid journal bearing and supply cut‐off behavior has also been studied for the improved performance.Design/methodology/approachThe generalized Reynold's equation governing the fluid flow in the clearance space between bearing and journal has been solved using finite element method to determine the pressure distribution, subsequently performance of hole‐entry hybrid journal bearing are computed. The journal centre equilibrium position for the given load is computed and the formulation is explained. The geometric parameters include aspect ratio, land width ratio, number of rows and number of holes per row. Further, performance of the bearing is computed with increasing the load, which induces negative pressure or the backpressure at the supply holes subsequently those are plugged to support the higher load.FindingsThe obtained results are presented in graphical form and logical conclusions are drawn and the modified configurations with reduced number of holes are suggested for higher load. It is observed that the bearing configuration with aspect ratio = 1.0 and land width ratio = 0.2 is best for high load support for low power requirement as less lubricant is required to be pumped in the bearing yet it provides sufficient fluid film thickness and lower values of maximum pressure. The load carrying capacity of the bearing can be further increased by plugging the holes on which backpressure is obtained for same bearing configuration. A feedback control with hybrid bearing system will sustain the sudden increase of load by shutting off the supply of the lubricant through supply hole where negative pressure is encountered.Originality/valueThe paper addresses the performance of non recessed hybrid journal bearings with wide range of geometric parameter. The results are quite useful for the bearing designer. The supply cut‐off is another aspect of originality of the paper as it provides the better load support.
The performance characteristics of capillary compensated hole-entry hybrid journal bearing systems have been studied theoretically. The analysis considers the generalized Reynolds equation governing the flow field of lubricant, having variable viscosity, taking the equation of lubricant flow through a capillary restrictor as constraint. The non-Newtonian lubricant is assumed to follow the cubic shear stress law. The results obtained from the study suggest that bearing static performance characteristics can be optimized for the particular bearing operating conditions by proper selection of parameters such as bearing land width ratios (ā b ), the restrictor design parameter (C s2 ), and the non-linearity factor (K ).
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