Geometry Optimization of Textured 3-D Micro-Thrust Bearings

Abstract

The paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings, in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as microchannels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems at different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.

An experimental analysis of the hydrodynamic contribution of textured thrust bearings during steady-state operation: A comparison with the untextured parallel surface configuration

“…The best performance, in terms of load-carrying capacity, is obtained with a high density of texture, the textured area extending from 50% to 60% of relative length of the pad. [1][2][3][4] A fully textured pad does not, however, present any interest in terms of loadcarrying capacity. The cavity depth is also an important parameter and depends mainly on minimal film thickness.…”

“…The present experimental investigation uses the optimal geometric parameters determined by Dobrica et al 4 Most of numerical studies have been isothermal. Recently, Papadopoulos et al 3 modeled a partially textured pad with square dimples and performed computational fluid dynamics simulations by taking into account local thermal effects. They showed that the load-carrying capacity decreases when thermal effects are integrated.…”

Preliminary study on mechanism of cavitation in lubricant of textured sliding bearing

“…Sinanoglu et al 14 carried out an experiment of a dimpled shaft, which showed that appropriately dimpled journal shaft can improve the bearing's performances. In 2010, Papadopoulo et al 15 presented a method for optimizing the geometry size of three-dimensional (3D) micro-thrust bearings in a wide range of convergence ratios. In 2011, Qiu and Khonsari 16 studied the cavitation pressure effect on tribological performance of mechanical seal-like thrust bearings with dimples by solving the Reynolds equation with a mass conservative algorithm.…”

The design of hydrodynamic water-lubricated step thrust bearings using CFD method

“…Fluid density [16] used CFD code to analyze the effects of the rolling speed, oil viscosity, and supplying oil concentration on the pressure distributions of oil and water phases. Zhang et al [17], Brajdic-Mitidieri et al [18] and Papadopoulos et al [19] optimized the geometry of inclined thrust bearings, pocketed pad bearings and textured micro-thrust bearings using CFD techniques respectively. CFD widens the range of solvable lubrication problems and makes design process more convenient.…”