Development of a low-cost radial air bearing system

Abstract

The main goal of this master thesis is to develop a new low-cost radial air bearing system for the CT-scanner, which is currently expensive due to the strict tolerances on the large sized porous aerostatic radial air bearings as well as on the counter surface. This thesis has generated several potential low-cost air bearing system concepts. The two most feasible concepts, which are the Multiple Smaller Bearings (MSB) and the hover concept, are investigated on their feasibility, where the latter concept has shown a higher potential. The hover concept is a combination of (a) hover(s) and (an) air bearing(s), which combines the hover's high-load capacity and low-cost characteristics, with the air bearing's high-stiffness characteristics, to create a high-load, high-stiffness and low-cost radial air bearing assembly. To investigate the concept's feasibility, an air bearing and hover model are established. The air bearing model is able to calculate the air bearing performances, where a proposal is made on the race tolerance relaxation factor. Concurrently, a hover model is investigated on its static load capacity, stiffness and flow consumption. From the feasibility study, it was expected that the hover concept consumed a significant amount of flow and required a control system. However, its (costs) potentials have been the tolerance reduction on the counter surface and using significantly smaller sized air bearings. Afterwards, an experimental setup is designed and manufactured, to measure the individual and combined static performances of the air bearing and hover and to verify the results with their models. It is verified that the air bearing model is able to predict the overall trend of the measured air bearing performance. Subsequently, two different hover types are investigated, where the experiments have provided insight into the hover's performance. It is shown that the hover model is able to estimate the load carrying capacity at lower hover heights and is able to estimate the order of magnitude of the hover stiffness, but is insufficient to provide the hover air consumption. For the combined performance, it is observed that the hover is able to carry a partial load of the air bearings and that the combined performance of the air bearing and hover, can be well predicted with the individual air bearing model and the individual hover performance obtained from measurements. Finally, a conceptual design of a new low-cost radial air bearing system, which combines two air bearings and five hovers, is proposed and has its potential to reduce the current radial air bearing system costs by 17 %. The current hover concept is not only potentially applicable for the current CT-scanner but in general for high-load applications, where low friction and a high-stiffness is required, with the focus on a low-cost oriented design.