Apparatus for mixing fuel in a gas turbine nozzle

1. A combustion turbine engine having a combustor that includes a fuel nozzle in which a supply of compressed air and fuel are mixed for combustion, wherein the fuel nozzle further includes:

a fuel plenum defined between a circumferentially extending shroud and axially by a forward tube-sheet and an aft tube-sheet; and

a mixing-tube that extends across the fuel plenum that defines a passageway connecting an inlet formed through the forward tube-sheet and an outlet formed through the aft tube-sheet, the mixing-tube comprising one or more fuel ports that fluidly communicate with the fuel plenum;

wherein the mixing-tube, comprises a plurality of grooves on an outer surface;

wherein the mixing-tube is attached to the forward tube-sheet and aft tube-sheet along an interface that comprises a fail-safe leakage path;

wherein the interface includes shoulders formed within each of the inlet and the outlet that engages a correspondingly shaped tip face formed on the mixing-tube, such that the mixing-tube is mechanically trapped therebetween.

2. The combustion turbine engine according to claim 1 , wherein the inlet shoulder comprise a radially jutting step that narrows the inlet such that further migration of the mixing-tube in the direction of insertion is halted once engaged.

3. The combustion turbine engine according to claim 1 , wherein the fail-safe leakage path comprises an interface that defines a path connecting the fuel plenum to the passageway defined by the mixing-tube.

4. The combustion turbine engine according to claim 1 , wherein the shoulder of the inlet and the tip face comprises corresponding planar surfaces each of which have an annular profile.

5. The combustion turbine engine according to claim 1 , wherein the forward tube-sheet comprises a forward axial boundary of the fuel nozzle; and

wherein the fuel plenum extends uninterrupted axially between a first end that is defined by the forward tube-sheet and a second end that is defined by the aft tube tube-sheet.

6. The combustion turbine engine according to claim 5 , wherein the aft tube-sheet comprises an aft axial boundary of the fuel nozzle, and wherein, on a hot side, the aft tube-sheet borders a combustion zone of the combustor.

7. The combustion turbine engine according to claim 1 , wherein the outlet shoulder comprises a radially jutting step that narrows the outlet such that further migration of the mixing-tube in the direction of insertion is halted once engaged; and

wherein the fail-safe leakage path comprises an interface that defines a path connecting the fuel plenum to the passageway of the mixing-tube.

8. The combustion turbine engine according to claim 1 , wherein the grooves comprise a plurality of circumferentially extending grooves that are axially spaced on the outside surface of the mixing-tube.

9. The combustion turbine engine according to claim 8 , wherein the grooves comprise one of a semi-circular and semi-oval cross-sectional shape.

10. The combustion turbine engine according to claim 9 , wherein one of the grooves is positioned adjacent to a joint edge formed between the mixing-tube and forward tube-sheet.

11. The combustion turbine engine according to claim 8 , wherein the fuel plenum comprises a cylindrical shape and connects to a fuel conduit that extends from a combustor end cap;

wherein the fuel nozzle comprises a plurality of separated mixing-tubes, each of the mixing-tubes comprising a cylindrical shape; and

wherein each mixing-tube comprises a plurality of axially spaced fuel ports.

12. A fuel nozzle for a combustor of a combustion turbine engine, the fuel nozzle comprising:

a fuel plenum defined by a shroud that extends between a forward tube-sheet and an aft tube-sheet;

a plurality of mixing-tubes, each of which defines an enclosed passageway extending across the fuel plenum from an inlet formed through the forward tube-sheet to an outlet formed through the aft tube-sheet, wherein each of the mixing-tubes includes a plurality of fuel ports that fluidly connects the enclosed passageway to the fuel plenum;

wherein each of the mixing-tubes comprises a plurality of grooves formed on an outer surface, the plurality of grooves configured to increase a compliancy of each mixing-tube; and

wherein the mixing-tube comprises a non-integral component to both the forward tube-sheet and the aft tube-sheet, wherein the mixing-tube is mechanically trapped therebetween via a first tip face of the mixing-tube engaging a recessed seat formed in the inlet and a second tip face of the mixing-tube engaging a recessed seat formed in the outlet.

13. The fuel nozzle according to claim 12 , wherein the recessed seat in the inlet includes a shoulder that narrows the inlet so that migration of the mixing-tube in the direction of insertion is prevented upon engagement of the shoulder by the first tip face; and

wherein the recessed seat in the outlet includes a shoulder that narrows the outlet so that migration of the mixing-tube in the direction of insertion is prevented upon engagement of the shoulder by the second tip face.

14. The fuel nozzle according to claim 13 , wherein the recessed seat in the inlet comprises one positioned within a thickness of the forward tube-sheet; and

wherein the recessed seat in the outlet comprises one positioned within a thickness of the aft tube-sheet.

15. The fuel nozzle according to claim 13 , wherein the grooves comprise a plurality of circumferentially extending grooves that are axially spaced on the outside surface of the mixing-tube.

16. The fuel nozzle according to claim 15 , wherein the grooves comprise one of a semi-circular and semi-oval cross-sectional shape.

17. The fuel nozzle according to claim 15 , wherein one of the grooves is positioned adjacent to a joint edge formed between each of the mixing-tubes and the forward tube-sheet.

18. The fuel nozzle according to claim 15 , wherein one of the grooves is positioned adjacent to a joint edge formed between each of the mixing-tubes and the forward tube-sheet; and

wherein a second of the grooves is positioned adjacent to a joint edge formed between each of the mixing-tubes and the aft tube-sheet.