FILM RIDING PRESSURE ACTUATED LEAF SEAL ASSEMBLY

• US 20110304101A1
• Filed: 06/11/2010
• Published: 12/15/2011
• Est. Priority Date: 06/11/2010
• Status: Active Grant

• Current Assignee: CMG Tech, LLC
• Original Assignee: CMG Tech, LLC
• Inventors: Grondahl, Clayton M., Dudley, James Carlton, Smith, Richard Lee
• Granted Patent: US 8,474,827 B2
• Time in Patent Office: Days
• US Class Current: 277/411
• CPC Class Codes: F01D 11/001 for sealing space between stator blade and rotor
• CPC Class Codes: F01D 11/02 by non-contact sealings, e.g. of labyrinth type for sealing space between rotor blade tips and stator F01D11/08
• CPC Class Codes: F05D 2240/57 Leaf seals
• CPC Class Codes: F16J 15/164 the sealing action depending on movements; pressure difference, temperature or presence of leaking fluid
• CPC Class Codes: F16J 15/3292 Lamellar structures
• CPC Class Codes: F16J 15/445 with means for adjusting the clearance
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

In accordance with embodiments of this invention, a pressure actuated leaf seal assembly is provided that includes film riding, hydrodynamic/hydrostatic runners under seal member leaf ends. Leaf seal assemblies according to embodiments of this invention maintain the runner away from a rotating body until adequate rotating speed is present to generate lift required to allow the runner to float on a thin film of operating fluid on the rotating body, so that the runner does not rub the rotating body. In addition, runners are attached, or added, to leaf seal members such that the runners move in a radial direction, while remaining parallel to the rotating body. In one embodiment, a runner can comprise a separate structure coupled to a leaf seal member, and in another embodiment, a runner can comprise a wear-resistant pad on a distal end of a leaf seal member.

Claims

1. A leaf seal assembly for use between a rotating component and a stationary component in a turbomachine, the leaf seal assembly comprising:

a leaf seal including at least one set of leaf seal members, each leaf seal member having a planar surface having an areal dimension; and

a runner coupled to a distal end of at least one leaf seal member of the at least one set of leaf seal members, wherein the at least one leaf seal member maintains the runner in a first position away from the rotating component in an unpressurized inoperative state and moves the runner to a second position, close to, but not contacting, the rotating component in a pressurized operative state.

2. The leaf seal assembly of claim 1, wherein the at least one leaf seal member is configured to maintain the runner substantially parallel to the rotating component in both the operative and inoperative states.

3. The leaf seal assembly of claim 1, wherein a clearance between the runner and the rotating component in the pressurized operative state is approximately 90% less than a clearance between the runner and the rotating component in the unpressurized inoperative state.

4. The leaf seal assembly of claim 1, wherein the runner includes a plurality of arcuate runner segments circumferentially disposed about the rotating component.

5. The leaf seal assembly of claim 1, wherein the at least one set of leaf seal members includes a plurality of sets of leaf seal members, the plurality of sets of leaf seal members being axially spaced relative to the rotating component, each pair of sets of leaf seal members having a space therebetween.

6. The leaf seal assembly of claim 5, wherein the runner includes at least one opening extending radially through the runner, whereby the operating fluid of the turbomachine flows through the at least one opening into the space between a pair of sets of leaf seal members, and wherein, in an operative state, a pressure in the space between the pair of sets of leaf seal members is less than a pressure upstream of the plurality of leaf seal members and greater than a pressure downstream of the plurality of sets of leaf seal members.

7. The leaf seal assembly of claim 6, wherein, in an operative state, the pressure in the space between the pair of sets of leaf seal members is substantially equivalent to an average of the upstream pressure and the downstream pressure.

8. The leaf seal assembly of claim 5, wherein each set of leaf seal members includes a substantially equal longitudinal length, and wherein at least one leaf seal member in each set of leaf seal members is coupled to the runner.

9. The leaf seal assembly of claim 5, wherein the plurality of sets of leaf seal members includes two sets of axially spaced leaf seal members, including one upstream set of leaf seal members and one downstream set of leaf seal members, and a set of sealing leaf seal members, wherein the set of sealing leaf seal members is positioned between the set of upstream leaf seal members and the set of downstream leaf seal members, and wherein only the set of upstream leaf seal members and the set of downstream leaf seal members are coupled to the runner.

10. The leaf seal assembly of claim 1, wherein the at least one leaf seal member is pivotally coupled to the runner.

11. The leaf seal assembly of claim 10, wherein the at least one leaf seal member includes a curled end and the runner includes a pocket, wherein the curled end mates with the pocket such that the runner is pivotally coupled to the at least one leaf seal member while allowing the at least one leaf seal member to pivot relative to the runner.

12. The leaf seal assembly of claim 1, wherein, in the pressurized operative state, the runner floats on a film of operating fluid of the turbomachine between the runner and the rotating component.

13. The leaf seal assembly of claim 12, wherein a thickness of the film of operating fluid is approximately 1 mils to approximately 20 mils.

14. The leaf seal assembly of claim 1, wherein the runner includes a Rayleigh step proximate to an upstream end of the runner.

15. The leaf seal assembly of claim 1, wherein the runner comprises one of the following materials:

a stainless steel or a nickel-based alloy.

16. The leaf seal assembly of claim 1, wherein an inner radius of the runner is greater than an outer radius of the rotating component.

17. The leaf seal assembly of claim 1, wherein a radius at a leading edge of the runner is greater than a radius at a trailing edge of the runner.

18. The leaf seal assembly of claim 1, further including a retaining strip disposed on an outer diameter of the runner, wherein the retaining strip is coupled to the runner and includes at least one slot between the retaining strip and the runner, and wherein each slot is configured to matingly engage a distal end of a respective leaf seal member.

19. The leaf seal assembly of claim 1, further including a wear resistant pad positioned along at least a portion of an inner diameter surface of the runner, the wear resistant pad proximate to the rotating component in the pressurized operative state.

20. The leaf seal assembly of claim 19, wherein the wear resistant pad comprises a plasma, vapor deposition or flame sprayed metal powder coating, and wherein the coating comprises one of the following:

titanium carbide, nickel-aluminum composite, tungsten carbide, molybdenum disulfide, polytetrafluoroethylene (PTFE), tungsten disulfide, titanium nitride or amorphous diamond wear coating.

21. A leaf seal assembly for use between a rotating component and a stationary component in a turbomachine, the leaf seal assembly comprising:

a leaf seal including at least one set of leaf seal members, each leaf seal member having a planar surface having an areal dimension, wherein the at least one set of leaf seal members is configured to move between a first position in an unpressurized inoperative state and a second position in a pressurized operative state, and wherein at least one leaf seal member of the at least one set of leaf seal members, includes a distal end angled such that at least one surface of the distal end is substantially parallel to the rotating component in the second position;

a wear resistant pad positioned on the at least one surface of the distal end, such that in an unpressurized inoperative state, the at least one leaf seal member maintains the wear resistant pad away from the rotating component, and in the pressurized operative state, the at least one leaf seal member maintains the wear resistant pad close to, but not contacting, the rotating component.

22. The leaf seal assembly of claim 21, wherein the wear resistant pad comprises a plasma, vapor deposition or flame sprayed metal powder coating.

23. The leaf seal assembly of claim 21, wherein the wear resistant pad comprises one of the following materials:

titanium carbine, nickel-aluminum composite or tungsten carbide, and wherein a thickness of the wear resistant pad is approximately 0.02 inches.

24. The leaf seal assembly of claim 21, wherein the wear resistant pad comprises one of the following materials:

molybdenum disulfide, polytetrafluoroethylene (PTFE), tungsten disulfide, titanium nitride or an amorphous diamond wear coating, and wherein a thickness of the wear resistant pad is less than approximately 0.001 inch.

25. The leaf seal assembly of claim 21, wherein, in the pressurized operative state, the wear resistant pad floats on a film of operating fluid of the turbomachine between the wear resistant pad and the rotating component.

26. The leaf seal assembly of claim 21, wherein the wear resistant pad includes a Rayleigh step proximate to an upstream end of the wear resistant pad.

27. The leaf seal assembly of claim 21, wherein the wear resistant pad includes at least one arced surface on an upstream face of the wear resistant pad.

28. The leaf seal assembly of claim 21, further including a polymer member disposed along an upstream face of the at least one leaf seal member.

29. The leaf seal assembly of claim 21, wherein the angled distal end includes at least one curled portion on a high pressure side of the angled distal end.

30. The leaf seal assembly of claim 21, further including an articulated attachment positioned between the wear resistant pad and the distal end, the articulated attachment having a first portion that is substantially planar and a second portion that is curled, wherein the wear resistant pad is positioned on the first portion, and wherein the distal end is configured to matingly engage the second portion, allowing the articulated attachment to rotate with respect to the distal end.

31. The leaf seal assembly of claim 21, wherein the angled distal end includes a plurality of bends.