US Patent 8734017 Air bearing shaft

An air bearing shaft for an air cycle machine is provided. The air bearing shaft includes a seal disk and a shaft body. The shaft body includes a first shaft body portion extending from a face of the seal disk to a knife-edge seal. The first shaft body portion includes journal bearing cooling holes positioned axially closer to the knife-edge seal than to the face of the seal disk. The journal bearing cooling holes extend through the first shaft body portion to a hollow interior and have a total cooling area. Start-up holes are positioned axially closer to the face of the seal disk than to the knife-edge seal. The start-up holes extend through the first shaft body portion to the hollow interior. The start-up holes have a total start-up area. A ratio of the total cooling area to the total start-up area is between 2.17 and 4.06.