MID-TURBINE FRAME WITH TENSIONED SPOKES

• US 20140102110A1
• Filed: 07/13/2012
• Published: 04/17/2014
• Est. Priority Date: 07/13/2012
• Status: Active Grant

• Current Assignee: Rtx Corporation
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: Farah, Jorge I., Sanchez, Paul K., Burdick, Andrew D.
• Granted Patent: US 9,217,371 B2
• Time in Patent Office: Days
• US Class Current: 60/772
• CPC Class Codes: F01D 25/162 Bearing supports
• CPC Class Codes: F01D 25/28 Supporting or mounting arrangements, e.g. for turbine casing
• CPC Class Codes: F02C 7/06 Arrangements of bearings bearings F16C; Lubricating of turbo machines F01D25/18; of machines or engines in general F01M
• CPC Class Codes: F02C 7/20 Mounting or supporting of plant; Accommodating heat expansion or creep
• CPC Class Codes: F05D 2260/31 Retaining bolts or nuts
• CPC Class Codes: F05D 2260/941 particularly aimed at mechanical or thermal stress reduction

Abstract

A mid-turbine frame located in a gas turbine engine axially aft of a high-pressure turbine and fore of a low-pressure turbine includes an outer frame case, an inner frame case, and at least a first spoke connecting the outer frame case to the inner frame case. The first spoke is tightened so as to be in tension during substantially all operating conditions of the gas turbine engine.

Claims

1. A gas turbine engine comprising:

a combustor;

a first turbine section in fluid communication with the combustor;

a second turbine section in fluid communication with the first turbine section; and

a mid-turbine frame located axially between the first turbine section and the second turbine section, the mid-turbine frame comprising;

an outer frame case;

an inner frame case; and

at least a first spoke connecting the outer frame case to the inner frame case, wherein the first spoke is tightened so as to be in tension during substantially all operating conditions of the gas turbine engine.

2. The gas turbine engine of claim 1, wherein the first spoke comprises:

a tie rod having a first threaded surface; and

a retaining nut having a second threaded surface engaged with the first threaded surface.

3. The gas turbine engine of claim 2, wherein the retaining nut comprises a flange extending outward from an outer surface of the retaining nut.

4. The gas turbine engine of claim 3, wherein the retaining nut is positioned in a hole of the outer frame case, with the flange positioned radially outward of the outer frame case and the second threaded surface positioned radially inward of the outer frame case.

5. The gas turbine engine of claim 3, wherein a bolt extends through the flange into the outer frame case.

6. The gas turbine engine of claim 2, wherein the first threaded surface is on an outer surface of the tie rod, wherein the second threaded surface is on an inner surface of the retaining nut, and wherein the first and second threaded surfaces overlap partially but not completely.

7. The gas turbine engine of claim 2, wherein the tie rod comprises a flange bolted to an outer diameter portion of the inner frame case.

8. The gas turbine engine of claim 2, wherein the retaining nut is a first retaining nut and wherein the tie rod comprises a third threaded surface at a first end of the tie rod opposite a second end of the tie rod having the first threaded surface, the gas turbine engine further comprising:

a second retaining nut having a fourth threaded surface engaged with the third threaded surface.

9. The gas turbine engine of claim 8, wherein the tie rod extends through a hole in the inner frame case such that the first end of the tie rod and the second retaining nut are positioned radially inward of the inner frame case.

10. The gas turbine engine of claim 9, wherein the first threaded surface is positioned radially between the inner frame case and the outer frame case.

11. The gas turbine engine of claim 1, wherein the first spoke is one of a plurality of spokes tightened so as to be in tension during substantially all operating conditions of the gas turbine engine.

12. The gas turbine engine of claim 1, wherein the first spoke extends through a hole in at least one of the inner frame case and the outer frame case.

13. The gas turbine engine of claim 1, wherein the first spoke extends through a hole in the inner frame case and a hole in the outer frame case.

14. The gas turbine engine of claim 1, wherein the first spoke extends through an airfoil having a hollow interior.

15. A mid-turbine frame located in a gas turbine engine axially aft of a high-pressure turbine and fore of a low-pressure turbine, the mid-turbine frame comprising:

an outer frame case;

an inner frame case; and

at least a first spoke connecting the outer frame case to the inner frame case, wherein the first spoke is tightened so as to be in tension during substantially all operating conditions of the gas turbine engine.

16. The mid-turbine frame of claim 15, wherein the first spoke comprises:

a tie rod having a first threaded surface; and

a retaining nut having a second threaded surface engaged with the first threaded surface and a flange extending outward from an outer surface of the retaining nut.

17. A method of operating a gas turbine engine having a mid-turbine frame located in a gas turbine engine axially aft of a high-pressure turbine and fore of a low-pressure turbine, the method comprising:

tightening a plurality of spokes connecting an inner frame case to an outer frame case of the mid turbine frame so as to be in tension during substantially all operating conditions of the gas turbine engine; and

operating the gas turbine engine such that the plurality of spokes do not have a zero load at any time during operation of the gas turbine engine.

18. The method of claim 17, wherein tightening the plurality of spokes comprises:

rotating spoke retaining nuts threadedly engaged with spoke tie rods so as to increase tension.

19. The method of claim 17, wherein each of the plurality of spokes extends through a hole in at least one of the inner frame case and the outer frame case.

20. The method of claim 17, wherein the plurality of spokes consists of an odd number of spokes in the mid-turbine frame, and further comprising:

tightening the plurality of spokes so as to center the inner frame case with the outer frame case.