To date, the approach to gas bearings and seals for this system
has demanded a disproportionate amount of the total research effort.
The closed cycle, small-scale turbo-alternator-compressors
developed for the present demonstration loop are a result of custom
fabrication, and an iterative design and testing process. This
has resulted in a system capable of supporting the necessary thrust
loads, on the order of 400 N, at high speeds, within minimal irreversible
losses. However, there is still considerable room for
improvement. Modeling results indicate that a bearing with smaller
diameter and fewer thrust pads could maintain thrust load
capacity with reduced frictional losses. In addition, incorporation
of geometric features (e.g. chevrons) at the trailing edge of each
thrust pad to expel hot fluid would likely increase load capacity
by enhancing the thermal wedge effect, while improving thermal
management [81]. Experimental work has also demonstrated that
using a stamped manufacturing approach rather than assembling
the thrust bearing manually from many small pieces can attain
tighter engineering tolerances. Smaller engineering tolerances allow
for operation at reduced film thicknesses, increasing load
capacity.