System and method for transporting lubricant through a vane

1. A mid-turbine frame of a gas turbine engine, comprising:

a vane extending from one end to another end along an axis;

a first fitting;

a second fitting spaced apart from the first fitting along the axis;

a tube assembly located within the vane such that a cavity is defined between the vane and the tube assembly, the tube assembly comprising:

an outer tube coupled to the first fitting and extending from the first fitting to the second fitting;

an inner tube located within the outer tube and extending from the first fitting to the second fitting; and

an outer passage defined between the outer tube and the inner tube, and an inner passage defined within the inner tube, wherein the cavity, the outer passage and the inner passage are fluidly isolated from one another, and

the cavity is configured to direct a cooling flow through the cavity, and the outer tube is configured to direct a buffer flow through the outer tube.

2. The mid-turbine frame of claim 1 , wherein the inner tube is configured to direct a lubricant flow through the inner tube.

3. The mid-turbine frame of claim 1 , wherein the inner tube and the outer tube configured without thermal insulation.

4. The mid-turbine frame of claim 1 , wherein, at the second fitting, a plurality of ribs extend between the outer tube and the inner tube and are offset from one another to define a scalloped section with a plurality of openings that are circumferentially spaced apart from one another.

5. The mid-turbine frame of claim 4 , wherein, at the first fitting, one end of a tube-end fitting is fluidly connected to a buffer inlet conduit and another end of the tube-end fitting is fluidly connected to the outer tube.

6. The mid-turbine frame of claim 5 , wherein the tube-end fitting defines a fitting orifice through which a supply inlet conduit extends to fluidly connect with the inner tube.

7. The mid-turbine frame of claim 6 , wherein an air seal is disposed at the fitting orifice to surround the supply inlet conduit at the fitting orifice.

8. A gas turbine engine, comprising:

a high-pressure compressor; and

a mid-turbine frame, comprising:

a vane extending from one end to another end along an axis;

a first fitting;

a second fitting spaced apart from the first fitting along the axis;

a tube assembly located within the vane such that a cavity is defined between the vane and the tube assembly, the tube assembly comprising:

an outer tube coupled to the first fitting and extending from the first fitting to the second fitting;

an inner tube located within the outer tube and extending from the first fitting to the second fitting; and

an outer passage defined between the outer tube and the inner tube, and an inner passage defined within the inner tube, wherein the cavity, the outer passage and the inner passage are fluidly isolated from one another, and

the cavity is configured to direct a cooling flow through the cavity, and the outer tube is configured to direct a buffer flow through the outer tube, and the cooling flow and the buffer flow are bled from the high-pressure compressor.

9. The gas turbine engine of claim 8 , wherein the cooling flow and the buffer flow are both bled from a same stage of the high-pressure compressor.

10. The gas turbine engine of claim 9 , comprising:

a cooling conduit fluidly connected to the high-pressure compressor to supply the cooling flow to the cavity;

a buffer conduit fluidly connected to the high-pressure compressor to supply the buffer flow to the outer passage; and

a heat exchanger fluidly connected to the buffer conduit between the high-pressure compressor and the mid-turbine frame.

11. The gas turbine engine of claim 10 , wherein the inner tube is configured to direct a lubricant flow through the inner tube.

12. The gas turbine engine of claim 10 , wherein the inner tube and the outer tube configured without thermal insulation.

13. The gas turbine engine of claim 10 , wherein, at the second fitting, a plurality of ribs extend between the outer tube and the inner tube and are offset from one another to define a scalloped section with a plurality of openings that are circumferentially spaced apart from one another.

14. The gas turbine engine of claim 13 , wherein, at the first fitting, one end of a tube-end fitting is fluidly connected to a buffer inlet conduit and another end of the tube-end fitting is fluidly connected to the outer tube.

15. The gas turbine engine of claim 14 , wherein the tube-end fitting defines a fitting orifice through which a supply inlet conduit extends to fluidly connect with the inner tube.

16. The gas turbine engine of claim 15 , wherein an air seal is disposed at the fitting orifice to surround the supply inlet conduit at the fitting orifice.

17. A method of transporting lubricant through a service tube of a gas turbine engine, comprising:

transporting a cooling flow, at a first pressure and a first temperature, through a cavity defined within a vane of a mid-turbine frame, the cavity defined between an inner wall of the vane and a service tube extending through the vane;

transporting a buffer flow, at the first pressure and a second temperature that is lower than the first temperature, through an outer passage in the service tube, the outer passage being defined between an outer tube and an inner tube of the service tube; and

transporting a lubricant flow through an inner passage defined within the inner tube of the service tube.

18. The method of claim 17 , comprising transporting the cooling flow at the pressure and the first temperature from a stage of a high-pressure compressor through a cooling conduit and to the cavity.

19. The method of claim 18 , comprising transporting the buffer flow from the stage of the high-pressure compressor, through a buffer conduit, and to the outer passage.

20. The method of claim 19 , comprising transporting the buffer flow through a heat exchanger fluidly coupled to the buffer conduit between the high-pressure compressor and the mid-turbine frame, whereby the buffer flow is at the pressure and the second temperature that is lower than the first temperature.