Hybrid seal and system and method incorporating the same

1. A system, comprising:

a first structure in communication with a first medium; and

a second structure housing a seal assembly between the first and second structures, the seal assembly comprising:

an interface seal disposed against the first structure; and

a flexible seal pressuringly biased against the second structure and the interface seal by a second medium; wherein the flexible seal comprises a metal.

2. The system of claim 1 , wherein the first structure is an inner shroud and the second structure is an outer shroud.

3. The system of claim 1 , wherein the first medium is hot gas and the second medium is a cooling gas.

4. The system of claim 1 , wherein the system comprises a gas turbine engine.

5. The system of claim 1 , wherein the interface seal comprises a ceramic material.

6. The system of claim 1 , wherein the interface seal comprises a rope seal.

7. The system of claim 1 , wherein the interface seal comprises a block seal.

8. The system of claim 1 , wherein the interface seal comprises a plurality of seal members.

9. The system of claim 1 , wherein the flexible seal comprises a C-shaped structure.

10. The system of claim 1 , wherein the flexible seal comprises a U-shaped structure.

11. The system of claim 1 , wherein the flexible seal comprises a W-shaped structure.

12. The system of claim 1 , wherein the seal assembly is preloaded by the second medium.

13. A seal, comprising:

a first seal mechanism adapted for insertion between a first structure and a second structure, wherein the first structure is in communication with a first medium and the second structure is in communication with a second medium; and

a second seal mechanism, which is pressuringly biasable against the first seal mechanism and against the second structure by the second medium; wherein the second seal mechanism comprises a C-shaped structure, or a U-shaped structure, or a W-shaped structure, or any combination thereof.

14. The seal of claim 13 , wherein the first structure is an inner shroud and the second structure is an outer shroud.

15. The seal of claim 13 , the first medium is a hot gas and the second medium is a purge gas relatively colder than the hot gas.

16. The seal of claim 13 , wherein the first seal mechanism comprises a ceramic material.

17. The seal of claim 13 , wherein the first seal mechanism comprises a rope seal structure.

18. The seal of claim 13 , wherein the first seal mechanism comprises a block seal structure.

19. The seal of claim 13 , wherein the first seal mechanism comprises a plurality of seal members.

20. The seal of claim 13 , wherein the second seal mechanism comprises a metal.

21. The seal of claim 13 , wherein the second seal mechanism comprises the C-shaped structure.

22. The seal of claim 13 , wherein the second seal mechanism comprises the U-shaped structure.

23. The seal of claim 13 , wherein the second seal mechanism comprises the W-shaped structure.

24. A system, comprising:

means for sealingly interfacing a first structure adjacent a second structure, wherein the first structure is in communication with a first medium and the second structure is in communication with a second medium; and

means for pressurably and sealingly interfacing both the second structure and the means for sealingly interfacing the first structure to provide a pressure-loaded seal with both the first structure and the second structure, wherein the second medium is relatively cooler than the first medium.

25. The system of claim 24 , wherein the first structure is an inner shroud and the second structure is an outer shroud.

26. The system of claim 24 , wherein the first medium is hot gas and the second medium is a purge gas relatively cooler than the hot gas.

27. The system of claim 24 , wherein the system comprises a gas turbine engine.

28. A method, comprising:

engaging a first seal against a first structure adjacent a second structure, wherein the first structure is in communication with a first medium and the second structure is in communication with a second medium;

pressuringly biasing a second seal against the first seal and against the second structure with pressure of the second medium; and

preloading the second seal by the second medium.

29. The method of claim 28 , wherein engaging the first seal comprises interfacing a rope seal against the first structure.

30. The method of claim 28 , wherein engaging the first seal comprises interfacing a block seal against the first structure.

31. The method of claim 28 , wherein engaging the first seal comprises interfacing a plurality of seal members against the first structure.

32. The method of claim 28 , wherein pressuringly biasing the second seal comprises pressuring a C-seal flexibly against the first seal and against the second structure.

33. The method of claim 28 , wherein pressuringly biasing the second seal comprises pressuring a U-seal flexibly against the first seal and against the second structure.

34. The method of claim 28 , wherein pressuringly biasing the second seal comprises pressuring a W-seal flexibly against the first seal and against the second structure.

35. A method, comprising:

providing a first seal engagable with a first structure adjacent a second structure, the first structure being adapted to communicate with a first medium and the second structure being adapted to communicate with a second medium separate from the first medium; and

providing a second seal pressurably biasable by the second medium against the first seal and against the second structure, wherein the first seal comprises metal, ceramic, or a combination thereof.

36. The method of claim 35 , wherein providing the first seal comprises providing a rope seal.

37. The method of claim 35 , wherein providing the first seal comprises providing a block seal.

38. The method of claim 35 , wherein providing the first seal comprises providing a plurality of seal members.

39. The method of claim 35 , wherein providing the second seal comprises providing a C-shaped seal.

40. The method of claim 35 , wherein providing the second seal comprises providing a U-shaped seal.

41. The method of claim 35 , wherein providing the second seal comprises providing a W-shaped seal.

42. The method of claim 35 , wherein the second seal comprises a metal.

43. A system for pneumatically sealing a gas path in an engine, comprising:

a rope seal adapted for insertion between an inner shroud and an outer shroud of the engine, wherein the inner shroud is in communication with a hot gas and the outer shroud is in communication with a purge gas relatively colder than the hot gas; and

a C-shaped seal, which is pressuringly biasable against the rope seal and against the outer shroud by the purge gas.

44. The system of claim 43 , wherein a concave surface of the C-shaped seal is disposed against the rope seal.

45. The system of claim 44 , wherein a convex surface of the C-shaped seal is disposed against the rope seal.

46. A system for pneumatically sealing a gas path in an engine, comprising:

a rope seal adapted for insertion between an inner shroud and an outer shroud of the engine, wherein the inner shroud is in communication with a hot gas and the outer shroud is in communication with a purge gas relatively colder than the hot gas; and

a U-shaped seal, which is pressuringly biasable against the rope seal and against the outer shroud by the purge gas.

47. A system for pneumatically sealing a gas path in an engine, comprising:

a ceramic block seal adapted for insertion between an inner shroud and an outer shroud of the engine, wherein the inner shroud is in communication with a hot gas and the outer shroud is in communication with a purge gas relatively colder than the hot gas; and

a U-shaped seal, which is pressuringly biasable against the ceramic block seal and against the outer shroud by the purge gas.

48. A system for pneumatically sealing a gas path in an engine, comprising:

a rope seal adapted for insertion between an inner shroud and an outer shroud of the engine, wherein the inner shroud is in communication with a hot gas and the outer shroud is in communication with a purge gas relatively colder than the hot gas; and

a W-shaped seal, which is pressuringly biasable against the rope seal and against the outer shroud by the purge gas.