Experiments With Scaled Foil Bearings in a Test Compressor Rotor

Gas bearings are a promising technology for rotor support due to their inherent ability to work with process fluids in gas compression turbomachines. This feature has potential for eliminating oil systems, providing a clean operation and substantially reducing operating costs. This paper presents initial experiments of a 59 kg (130 lb) test compressor rotor supported on a pair of 90.20 mm (3.551 in) diameter metal-mesh foil bearings lubricated with ambient air in a rotordynamic test rig running at 9,000 rpm without gas compression. The configuration includes relocation of the bearing supports inboard of the gas seals to reduce bearing span, favoring a more stable configuration of the rotor-bearing system. Test foil bearings are designed to support static loads due to rotor weight and remnant imbalance levels. Test results show that the bearings are capable of supporting design loads and running at moderate vibration levels. A slow-growing subsynchronous vibration appears after a stable period at full speed as a result of top foil damage in the free end bearing during the run-up. This damage is due to lack of axial rotor constraints. The results of the experiments indicate that metal mesh foil bearings are a promising technology towards oil-free supported turbomachinery at larger scales than previously utilized.