Purpose The purpose of this study is to improve the tribological performance of meso scale air journal bearing by adopting texture on the bearing surface. Design/methodology/approach The present study is based on numerical analysis. The detailed numerical investigation is carried out using a fluid flow based thin-film model in COMSOL 5.2 software. Findings The influence of texture design parameters: geometry (shape, orientation and slender ratio), and position on the tribological performance of meso scale air journal bearing is investigated. It is found that texture shape has a strong influence on the tribological characteristics such as load capacity and friction coefficient of the bearing. Slender texture improves the load capacity, but it has a negligible effect on the reduction of friction coefficient. In contrast, texture orientation is found to be insignificant for both increasing load capacity and decreasing friction coefficient. Furthermore, the maximum improvement in load capacity is obtained for partially textured bearing, but the minimum friction coefficient is achieved for full texturing. Originality/value The present study investigates the influence of texture design parameters viz geometry (shape, orientation and slender ratio), and position on the tribological performance of meso scale air journal bearing.
In this paper, a square textured parallel slider is considered for a study to improve the hydrodynamic performance of moving parts. The numerical method is employed for the analysis of a square texture with different bottom profiles: flat, triangle T1, triangle T2, and curved. The governing Reynolds equation is solved using a finite difference numerical discretization technique with the Gauss-Seidel iterative scheme. To obtain optimized process parameters, the response surface methodology-based central composite design along with grey relational analysis multi-objective optimization is used. The multi-objective responses are the load capacity and friction coefficient. The triangle T2 bottom profile yields the highest load capacity and the lowest friction coefficient compared to flat, triangle T1, and curved bottom profiles, of which the triangle T1 bottom profile yields the worst results. For the triangle T2 bottom profile, the flow speed is found to be the most significant process parameter, followed by the aspect ratio. Texture density is found to be the least significant parameter based on increasing the load capacity and decreasing the friction coefficient.
The bump-type gas foil bearing (GFB) is widely used in various high-speed oil-free turbomachinery due to its extra features such as high-speed capability without any external oil lubricant. Under the high-speed condition, the performance characteristics of GFB are majorly dependent on its design parameter. Thus, this paper briefly analyzes and optimizes the design parameters of bump-type GFB to improve its performance characteristic. The numerical simulation of bump-type GFB is performed in ANSYS software. The effect of various design parameters such as foil thickness, bump half-length, bump pitch, and bump angle on the output responses are analyzed using a response surface methodology based CCD design matrix. Here, the output responses are structural stiffness and the equivalent stress in foil bearing. To optimize it, the multi-objective GRA technique is used. These results show that the foil thickness is the most influencing and the bump angle is the least influencing design parameter. The optimal value of foil thickness, bump angle, bump half-length and bump pitch are 0.14mm, 63.75 deg., 1.55mm and 4.6mm respectively. At these optimal design parameters, the deviation between the predicted regression model and the numerical results are within 3.5%. Moreover, with these optimal design parameters, the structural stiffness of foil bearings increases by 68.4% and stress distribution reduces by 44.22% compared to the general configuration of foil bearings.
In this paper, the hydrodynamic performance of surface textured meso scale air bearing is evaluated. The effect of texture position is investigated for circular shaped texture. Partially textured zones are modeled along the circumferential direction of the bearing. For this, numerical simulation is carried out using COMSOL Multiphysics 5.2 software. The compressible Reynolds equation is solved using the finite element method for a thin film model. In comparison with plane bearing, the significant improvement in load capacity is observed for textured bearing. Full texturing has obtained 12.80% more load capacity than the plane bearing. Among different partial texture positions, the convergent zone (0°–180°) showed the most promising result. It has obtained 14.02% and 1.25% more load capacity than the plane and fully textured bearings. Moreover, the texture position in the bearing is found to be sensitive. However, surface texture at the outlet of active pressure zone is found to be ineffective for improving load capacity of the bearing.
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