Biomimetic and optimal designs of grooved aerodynamic thrust bearings for increased load capacity

Download Statistics

Downloads

Downloads per month over past year

Yu, Yunluo (2020). Biomimetic and optimal designs of grooved aerodynamic thrust bearings for increased load capacity. University of Birmingham. Ph.D.

Preview

Yu2020PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (7MB) | Preview

Abstract

This thesis presents a PhD study which aims to develop novel micro surface structures for grooved aerodynamic thrust bearings to achieve a considerable increase in load capacity when operating under a given air film thickness acceptable in engineering practice, which will help widen the application of grooved aerodynamic thrust bearings while ensuring a safe operation. In this study, three approaches are presented: (1) the design of a biomimetic aerodynamic thrust bearing; (2) the optimisation of the groove geometry of spiral-grooved aerodynamic thrust bearings; and (3) the optimisation of the groove configuration of herringbone-grooved aerodynamic thrust bearings.

The novel biomimetic bearing is inspired by the micro surface structures of dragonfly wings; which presumably aid their flying and manoeuvre ability. The topography of the micro surface structures is studied, and the five most representative geometries are extracted before being applied onto bearings for performance evaluation. A computational fluid dynamics (CFD) model is developed to calculate the load capacity of the bearings under different velocities and flow angles. The optimal geometry and velocity angle are selected and manufactured on a bearing surface for experimental tests. The biomimetic bearing is found to increase the load capacity by up to 46.11% in comparison with an optimised conventional spiral-grooved bearing.

The optimisation of the groove geometry of spiral-grooved aerodynamic thrust bearings is presented by combining the chaos-enhanced accelerated particle swarm optimisation (CAPSO) algorithm with the developed CFD model. Both discontinuous and continuous grooves are considered in the proposed method, which differs from existing studies. The optimisation process of an initial spiral-grooved aerodynamic thrust bearing is presented as a case study. The novel optimised grooves are discontinuous groove with completely new geometry. The load capacity of the novel optimised bearing, and that of an initial spiral-grooved bearing are compared experimentally. A 168.68% increase in load capacity has been found after optimisation.

The CAPSO algorithm and the developed CFD model are also combined to find the optimal groove configuration for herringbone-grooved aerodynamic thrust bearings. Different from existing studies, the optimal groove parameters in each section of the bearing are sought independently. An example of an optimised bearing is presented. The optimised herringbone grooves have different parameters in the inner and the outer sections, which is uncommon in existing grooves. The experiment results verified that compared with the non-optimised herringbone-grooved bearing, the new design can increase the load capacity by 30.77%.

In summary, through exploring novel micro surface structures for grooved aerodynamic thrust bearings using biomimetic and optimal design methods, this study presents a novel biomimetic bearing and two optimised aerodynamic thrust bearings with a completely new groove geometry and configuration. The novel designed bearings are found to have an increased load capacity compared to conventional spiral-grooved or herringbone-grooved bearings. The aims of this research have thus been met.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):