Journal air bearing with air-film-supply vent
A journal air bearing is provided. The bearing includes a top foil configured to receive the shaft, an intermediate foil disposed radially outboard the top foil, and a journal sleeve disposed radially outboard the intermediate foil. The intermediate foil defines a plurality of holes configured to act as a vent to communicate fluid to an increased supply area to an air film.
1. A journal air bearing, comprising:
a journal sleeve that receives a rotatable shaft, the journal sleeve being spaced apart from the rotatable shaft;
a top foil disposed between the journal sleeve and the rotatable shaft, the top foil and the rotatable shaft defining a gap there between;
an intermediate foil disposed radially outboard of the top foil, the intermediate foil defines a plurality of holes and a notch having a first wall extending from one edge of the intermediate foil towards another edge of the intermediate foil, a second wall extending from the first wall and disposed parallel to the one edge of the intermediate foil, a third wall extending from the second wall towards the one edge of the intermediate foil and is disposed in a non-parallel and non-perpendicular relationship with the one edge of the intermediate foil; and
a bump foil having a plurality of corrugations, the bump foil disposed between the intermediate foil and the journal sleeve, wherein air flows through spaces formed between adjacent corrugations, wherein rotation of the shaft creates an air film that supports the shaft within the journal sleeve and the plurality of holes communicates the air that flows through the spaces formed between adjacent corrugations to the air film; and
a formed key extending radially relative to the rotatable shaft and the holes of the intermediate foil are disposed immediately adjacent to the formed key and the holes are aligned with the first wall of the notch of the intermediate foil.
2. The air-cycle machine of claim 1 , wherein the holes are disposed in a row that extends from the one edge of the intermediate foil to the another edge of the intermediate foil.
3. The air-cycle machine of claim 2 , wherein the row of holes is parallel with a rotational axis of the shaft, the holes are linearly spaced from each other, and end ones of the holes are spaced from respective edges of the intermediate foil.
4. The air-cycle machine of claim 1 , wherein the top foil is joined to the intermediate foil.
5. The journal air bearing of claim 1 , wherein the top foil has a thickness within a range of 0.0076 centimeters (0.003 inches) to 0.0102 centimeters (0.004 inches).
6. The journal air bearing of claim 1 , wherein the bump foil has a pitch within a range of 0.47 centimeters (0.186 inches) to 0.35 centimeters (0.136 inches).
7. The journal air bearing of claim 1 , wherein the top foil has a width of 4.36 centimeters (1.717 inches).
8. The journal air bearing of claim 1 , wherein the intermediate foil has a total thickness variation of 0.00203 centimeters (0.0008 inches).