Foil-air bearing assembly for engine starter
An air turbine starter that includes a turbine member for rotatably extracting mechanical power from a flow of fluid, where the turbine member is coupled to a drive shaft to provide a rotational output. The air turbine starter further includes a foil-air bearing assembly and a thrust bearing that rotatably support the drive shaft.
1. An assembly comprising:
a housing;
a turbine member within the housing;
a shaft operably coupled with the turbine member;
a foil-air bearing assembly configured to rotatably support the shaft at a forward side of the turbine member; and
a stator upstream of the turbine member, the stator having at least one nozzle and at least partially defining a bearing housing for the foil-air bearing assembly.
2. The assembly of claim 1 wherein the foil-air bearing assembly comprises a radial foil bearing and a thrust foil bearing within the bearing housing.
3. The assembly of claim 2 wherein the thrust foil bearing comprises a thrust top foil and a thrust bump foil.
4. The assembly of claim 3 wherein the thrust foil bearing is upstream of the radial foil bearing.
5. The assembly of claim 1 , further comprising a flow path at least partially defined by the housing.
6. The assembly of claim 1 wherein the bearing housing includes an air inlet and an air exhaust fluidly coupled to the at least one nozzle and the foil-air bearing assembly is located fluidly between the air inlet and the air exhaust.
7. The assembly of claim 6 wherein the air exhaust is radially exterior of the air inlet and the foil-air bearing assembly.
8. The assembly of claim 6 , further comprising a shaft extension having a body operably coupled to a forward end of the shaft, the shaft extension journaled within the foil-air bearing assembly.
9. The assembly of claim 8 wherein the shaft extension comprises at least one internal air flow channel and is fluidly located between the air inlet and the foil-air bearing assembly.
10. The assembly of claim 9 wherein the at least one internal air flow channel is a first internal air flow channel and a second internal air flow channel, wherein the first internal air flow channel extends axially within the body and the second internal air flow channel extends radially within the body.
11. The assembly of claim 8 wherein the shaft extension further comprises a flange at the forward end thereof, the flange locating the foil-air bearing assembly within the bearing housing.
12. The assembly of claim 11 wherein the flange is located forward of a foil-air thrust bearing and rotatably coupled to the stator.
13. The assembly of claim 12 , further comprising a plate having an aperture therein mounted to an open end of the bearing housing and wherein one of the shaft extension or the shaft pass through the aperture.
14. The assembly of claim 13 wherein a gap between the plate and the shaft extension defines the air exhaust.
15. The assembly of claim 1 , further comprising at least one thrust bearing configured to rotatably support at least one of the shaft or the turbine member, rear of the turbine member.
16. A method for flowing air through a foil-air bearing assembly located in a bearing housing at least partially defined by a stator located upstream of a turbine to rotatably support of a shaft or a shaft extension received by the foil-air bearing assembly, the method comprising:
flowing air through a flow path;
diverting a portion of the air flowing through the flow path into the stator to define a bearing air flow;
flowing the bearing air flow through an air inlet and at least one internal air flow channel to the foil-air bearing assembly;
flowing the bearing air flow through at least one of a radial foil bearing or a thrust foil bearing of the foil-air bearing assembly; and
exhausting, from the bearing housing in a radial direction, the bearing air flow downstream of the at least one of the radial foil bearing or the thrust foil bearing.
17. The method of claim 16 wherein the flowing of the bearing air flow through the air inlet and the at least one internal air flow channel comprises flowing the bearing air flow axially through a first internal flow channel and radially through a second internal flow channel.
18. The method of claim 16 , further comprising providing a gap via a gas film between the shaft or the shaft extension and a top foil of the radial foil bearing.
19. The method of claim 18 wherein the providing the gap via the gas film further comprises flexing a bump foil or flexible portions of the radial foil bearing to create the gap.
20. The method of claim 16 , further comprising providing pressurized air to an inlet of the flow path of an air turbine starter.