Evolutionary Optimization of Micro-Thrust Bearings With Periodic Partial Trapezoidal Surface Texturing

Abstract

An optimization study of trapezoidal surface texturing in slider micro-bearings, via computational fluid dynamics (CFD), is presented. The bearings are modeled as micro-channels, consisting of a moving and a stationary wall. The moving wall (rotor) is assumed smooth, while part of the stationary wall (stator) exhibits periodic dimples of trapezoidal form. The extent of the textured part of the stator and the dimple geometry are defined parametrically; thus, a wide range of texturing configurations is considered. Flow simulations are based on the numerical solution of the Navier–Stokes equations for incompressible isothermal flow. To optimize the bearing performance, an optimization problem is formulated and solved by coupling the CFD code with an optimization tool based on genetic algorithms and local search methods. Here, the design variables define the bearing geometry, while load carrying capacity is the objective function to be maximized. Optimized texturing geometries are obtained for the case of parallel bearings for several numbers of dimples, illustrating significant load carrying capacity levels. Further, these optimized texturing patterns are applied to converging bearings for different convergence ratio values; the results demonstrate that, for small and moderate convergence ratios, a substantial increase in load carrying capacity, in comparison to smooth bearings, is obtained. Finally, an optimization study performed at a high convergence ratio shows that, in comparison to the parallel slider, the optimal texturing geometry is substantially different, and that performance improvement over smooth bearings is possible even for steep sliders.

Geometry Optimization of Textured Three-Dimensional Micro- Thrust Bearings

“…In the present dimensional model, a value of Re ¼ 1 corresponds to a wall velocity U ¼ 0:01785 ms À1 and values of the fluid thermophysical properties equal to those of water at 25 C; see Ref. [19]. Results are presented in non-dimensional form.…”

“…One of the conclusions reported in Ref. [19] is that, in comparison to rectangular texture patterns, the benefits from the introduction of trapezoidal texture geometries are marginal.…”

“…Thus, following the work reported in Ref. [19], in the present study the more realistic three-dimensional slider geometries are considered with the goal of identifying optimal texture patterns of rectangular shape for maximum load carrying capacity. To define the slider geometry, a parametric CAD model is generated, which can account for different bearing width-to-length ratios and roughness geometries of rectangular shape.…”

“…In Ref. [19], the optimization of trapezoidal texture patterns of two-dimensional (infinitely wide) sliders was considered by coupling an optimization approach with CFD simulations. It was concluded that, for parallel and converging sliders, proper texturing results in substantial load capacity levels.…”

Study on Lubrication Characteristics of Trapezoidal Groove for Planetary Gear Sliding Bearing

“…However, the influence of cavitation on the lubrication characteristics is only focused on the mechanical seal [7][8]. A hybrid genetic algorithm method was applied to optimize the irregular trapezoidal cross-section of the grooved thrust bearing [9]. It is concluded that the bearing capacity of the thrust bearing can be maximized by the specific structural parameters, and when the rectangular section was substituted for the trapezoidal section, the geometric carrying capacity of the groove would be enhanced.…”