Lean direct injection atomizer for gas turbine engines

• US 20060248898A1
• Filed: 04/06/2006
• Published: 11/09/2006
• Est. Priority Date: 05/04/2005
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Delavan Incorporated and Rolls-Royce PLC
• Inventors: Williams, Brandon P., Bretz, David H., Buelow, Philip E.O., Gill, Helen, Spooner, Michael, Mohamed, Caroline
• Granted Patent: US 7,779,636 B2
• Time in Patent Office: Days
• US Class Current: 60/776
• CPC Class Codes: F23D 2900/11101 Pulverising gas flow impinging on fuel from pre-filming surface, e.g. lip atomizers
• CPC Class Codes: F23R 3/14 by using swirl vanes
• CPC Class Codes: F23R 3/28 characterised by the fuel supply burners F23D
• CPC Class Codes: F23R 3/286 having fuel-air premixing devices F23R3/30 takes precedence
• CPC Class Codes: F23R 3/343 Pilot flames, i.e. fuel nozzles or injectors using only a very small proportion of the total fuel to insure continuous combustion ignition in gas-turbine plants F02C7/264; pilot flame igniters F23Q9/00

Abstract

A lean direct injection fuel nozzle for a gas turbine is disclosed which includes a radially outer main fuel delivery system including a main inner air swirler defined in part by a main inner air passage having a radially inner wall with a diverging downstream surface, an intermediate air swirler radially inward of the main inner air swirler for providing a cooling air flow along the downstream surface of the radially inner wall of the main inner air passage, and a radially inner pilot fuel delivery system radially inward of the intermediate air swirler.

Claims

1. A lean direct injection fuel nozzle for a gas turbine comprising:

a) a radially outer main fuel delivery system including a main inner air swirler defined in part by a main inner air passage having a radially inner wall with a diverging downstream surface;

b) an intermediate air swirler radially inward of the main inner air swirler for providing a cooling air flow along the downstream surface of the radially inner wall of the main inner air passage; and

c) a radially inner pilot fuel delivery system radially inward of the intermediate air swirler.

2. A lean direct injection fuel nozzle as recited in claim 1, wherein the main fuel delivery system is of a pre-filming air-blast type and includes a main fuel swirler radially outward of the main inner air swirler, a main outer air swirler radially outward of the main fuel swirler, and an outer air cap radially outward of the main outer air swirler

3. A lean direct injection fuel nozzle as recited in claim 1, wherein the pilot fuel delivery system is of a simplex air-blast type, which includes a pressure swirl atomizer.

4. A lean direct injection fuel nozzle as recited in claim 3, wherein the pilot fuel delivery system includes a pilot outer air swirler, and a pilot fuel swirler radially inward of the pilot outer air swirler.

5. A lean direct injection fuel nozzle as recited in claim 1, wherein the pilot fuel delivery system is of a pre-filming air-blast type.

6. A lean direct injection fuel nozzle as recited in claim 5, wherein the pilot fuel delivery system includes a pilot outer air swirler, a pilot fuel swirler radially inward of the pilot outer air swirler, and a pilot inner air swirler extending along a central axis of the fuel nozzle.

7. A lean direct injection fuel nozzle as recited in claim 1, wherein the intermediate air swirler includes a set of swirl vanes oriented at an angle sufficient to ensure that the cooling air remains attached to the diverging downstream surface of the radially inner wall of the main inner air passage.

8. A lean direct injection fuel nozzle as recited in claim 7, wherein the intermediate air swirler includes a set of swirl vanes oriented at an angle of between about 35°

to about 60°

relative to a central axis of the fuel nozzle.

9. A lean direct injection fuel nozzle as recited in claim 7, wherein the swirl vanes of the intermediate air swirler are oriented to impart swirl in one of a clockwise direction and a counter-clockwise direction relative to a central axis of the fuel nozzle.

10. A lean direct injection fuel nozzle as recited in claim 9, wherein a swirl direction of the intermediate air swirler is co-rotational with respect to a swirl direction of the main inner air swirler.

11. A lean direct injection fuel nozzle as recited in claim 9, wherein a swirl direction of the intermediate air swirler is counter-rotational with respect to a swirl direction of the main inner air swirler.

12. A lean direct injection fuel nozzle as recited in claim 2, wherein a leading edge of the radially inner wall of the main air passage is located downstream from a leading edge of the outer air cap.

13. A lean direct injection fuel nozzle as recited in claim 2, wherein a leading edge of the radially inner wall of the main air passage is located upstream from a leading edge of the outer air cap.

14. A lean direct injection fuel nozzle as recited in claim 6, wherein the pilot inner air swirler includes a set of swirl vanes oriented to impart swirl in one of a clockwise and a counter-clockwise direction relative to a central axis of the fuel nozzle.

15. A lean direct injection fuel nozzle as recited in claim 14, wherein the pilot outer air swirler includes a set of swirl vanes oriented to impart swirl in one of a clockwise and a counter-clockwise direction relative to a central axis of the fuel nozzle.

16. A lean direct injection fuel nozzle as recited in claim 15, wherein the swirl vanes of the pilot outer air swirler are configured as axial swirl vanes.

17. A lean direct injection fuel nozzle as recited in claim 15, wherein the swirl vanes of the pilot outer air swirler are configured as radial swirl vanes.

18. A lean direct injection fuel nozzle as recited in claim 15, wherein a swirl direction of the pilot outer air swirler is co-rotational with respect to a swirl direction of the pilot inner air swirler.

19. A lean direct injection fuel nozzle as recited in claim 15, wherein a swirl direction of the pilot outer air swirler is counter-rotational with respect to a swirl direction of the pilot inner air swirler.

20. A lean direct injection fuel nozzle as recited in claim 2, wherein the main inner air swirler includes swirl vanes oriented at angle of between about 20°

to about 50°

relative to a central axis of the fuel nozzle.

21. A lean direct injection fuel nozzle as recited in claim 20, wherein the swirl vanes of the main inner air swirler are oriented to impart swirl in one of a clockwise direction and a counter-clockwise direction relative to a central axis of the fuel nozzle.

22. A lean direct injection fuel nozzle as recited in claim 2, wherein the main outer air swirler includes swirl vanes oriented at angle of between about 45°

to about 60°

relative to a central axis of the fuel nozzle.

23. A lean direct injection fuel nozzle as recited in claim 22, wherein the swirl vanes of the main outer air swirler are oriented to impart swirl in one of a clockwise direction and a counter-clockwise direction relative to a central axis of the fuel nozzle.

24. A lean direct injection fuel nozzle as recited in claim 22, wherein the swirl vanes of the main outer air swirler are configured as axial swirl vanes

25. A lean direct injection fuel nozzle as recited in claim 22, wherein the swirl vanes of the main outer air swirler are configured as radial swirl vanes.

26. A lean direct injection fuel nozzle as recited in claim 2, wherein a swirl direction of the main outer air swirler is co-rotational with respect to a swirl direction of the main inner air swirler.

27. A lean direct injection fuel nozzle as recited in claim 2, wherein a swirl direction of the main outer air swirler is counter-rotational with respect to a swirl direction of the main inner air swirler.

28. A lean direct injection fuel nozzle for a gas turbine comprising:

a) a radially outer main fuel delivery system having an outer air cap and including;

i) a main outer air swirler radially inward of the outer air cap;

ii) a main fuel swirler radially inward of the main outer air swirler; and

iii) a main inner air swirler radially inward of the main fuel swirler, and defined in part by a main inner air passage having a radially inner wall with a diverging downstream surface;

b) an intermediate air swirler radially inward of the main inner air swirler for providing a cooling air flow along the downstream surface of the radially inner wall of the main inner air passage; and

c) a radially inner pilot fuel delivery system having a converging pilot air cap radially inward of the intermediate air swirler.

29. A lean direct injection fuel nozzle as recited in claim 28, wherein the pilot fuel delivery system is of a simplex air-blast type, which includes a pressure swirl atomizer.

30. A lean direct injection fuel nozzle as recited in claim 29, wherein the pilot fuel delivery system includes a pilot outer air swirler, and a pilot fuel swirler radially inward of the pilot outer air swirler.

31. A lean direct injection fuel nozzle as recited in claim 28, wherein the pilot fuel delivery system is of a pre-filming air-blast type.

32. A lean direct injection fuel nozzle as recited in claim 31, wherein the pilot fuel delivery system includes a pilot outer air swirler, a pilot fuel swirler radially inward of the pilot outer air swirler, and a pilot inner air swirler extending along a central axis of the fuel nozzle.

33. A lean direct injection fuel nozzle as recited in claim 28, wherein a leading edge of the radially inner wall of the main air passage is located downstream from a leading edge of the outer air cap.

34. A lean direct injection fuel nozzle as recited in claim 28, wherein a leading edge of the radially inner wall of the main air passage is located upstream from a leading edge of the outer air cap.

35. A lean direct injection fuel nozzle as recited in claim 28, wherein a leading edge of the radially inner wall of the main air passage is coincident with a leading edge of the outer air cap.

36. A method of injecting fuel into a gas turbine comprising the steps of:

a) providing an inboard pilot combustion zone;

b) providing a main combustion zone outboard of the pilot combustion zone; and

c) mechanically separating the main combustion zone from the pilot combustion zone in such a manner so as to delay mixing of hot combustion products from the pilot combustion zone into the main combustion zone.

37. A method according to claim 36, further comprising the step of supporting a weak central recirculation zone within the pilot combustion zone.

38. A method according to claim 36, wherein the step of mechanically separating the main combustion zone from the pilot combustion zone includes confining an inner air flow of a pre-filming air-blast atomizer by providing an inner air passage having a conically expanding radially inner downstream wall which extends at least to a leading edge of the fuel pre-filmer.

39. A method according to claim 38, further comprising the step of flowing cooling air over the conically expanding radially inner wall of the inner air passage of the pre-filming air-blast atomizer.

40. A method of managing airflow through the inner air circuit of a pre-filming air-blast atomizer comprising:

forming a flow passage of the inner air circuit, in an area downstream from a minimum area location thereof, in such a manner so that there is an increase in pressure from the minimum area location to a downstream exit of the inner air circuit, for air flows that remain attached to the walls of the passage.

41. A method according to claim 40, further comprising confining the air flow exiting the inner air circuit within a conically expanding annular passage downstream from the minimum area location of the inner air circuit.

42. A method according to claim 41, further comprising sizing the conically expanding annular passage to obtain a desired mass flow rate through the inner air circuit.

43. A method of managing airflow through the inner air circuit of a pre-filming air-blast atomizer comprising:

forming the inner air circuit with a conically expanding annular passage, downstream from an air swirler located within the inner air circuit, in such a manner so that there is an increase in pressure within the inner air circuit from the air swirler to a downstream exit of the conically expanding annular passage, for air flows that remain attached to the walls of the conically expanding annular passage.

44. A method according to claim 43, further comprising selecting a gap size for the conically expanding annular passage to obtain a desired mass flow rate through the inner air circuit.