Turbine combustor system having aerodynamic feed cap

1. A system, comprising:

a turbine combustor, comprising:

a fuel nozzle comprising an inner shell and an outer shell;

a feed cap disposed about the fuel nozzle comprising an outer wall and a back plate, wherein the back plate meets respective upstream end termini of the outer shell of the fuel nozzle and the outer wall of the feed cap; and

a pressurized chamber surrounding the fuel nozzle, wherein the outer wall of the feed cap, the outer shell of the fuel nozzle, and the back plate form three walls of the pressurized chamber;

wherein the turbine combustor is configured to flow a first pressurized air from a first source at a first pressure via a fluid path extending along the outer wall of the feed cap, the back plate of the feed cap, and into the fuel nozzle, wherein the fluid path comprises a segment between the back plate of the feed cap and an end plate of a head end chamber of the turbine combustor, wherein the segment is substantially free of flow-impeding surfaces between the back plate and the end plate;

wherein the turbine combustor is configured to flow a second pressurized air from a second source at a second pressure, greater than the first pressure, into the pressurized chamber.

2. The system of claim 1 , wherein the back plate of the feed cap is configured to maintain flow along the back plate to impede recirculation of a fluid mixture comprising the first pressurized air and a fuel along the back plate.

3. The system of claim 1 , wherein the back plate excludes any obstructions or recesses between the outer shell and the outer wall.

4. The system of claim 1 , wherein the turbine combustor comprises a combustion chamber and a divider plate separating the combustion chamber from the head end chamber, wherein the divider plate forms a fourth wall of the pressurized chamber surrounding the fuel nozzle.

5. The system of claim 4 , wherein the back plate comprises a flat cross-sectional geometry that is oriented substantially parallel with respect to the end plate of the head end chamber and a rounded cross-sectional geometry at its edges where the back plate merges with the outer wall of the feed cap and the outer shell of the fuel nozzle, and wherein the flat and rounded cross-sectional geometries are along an axial direction of the turbine combustor.

6. The system of claim 4 , wherein at least a portion of the fluid path is defined by the inner and outer shells of the fuel nozzle, the end plate of the head end chamber, the back plate of the feed cap, and the outer wall of the feed cap.

7. The system of claim 4 , wherein the outer wall of the feed cap and the outer shell of the fuel nozzle are each attached to the divider plate to form the pressurized chamber.

8. The system of claim 7 , wherein the turbine combustor is configured to flow only the second pressurized air to the pressurized chamber.

9. The system of claim 1 , wherein the turbine combustor comprises a fuel injector along the fluid path upstream from the fuel nozzle and the back plate.

10. The system of claim 1 , wherein the turbine combustor comprises a divider plate between a combustion chamber and the head end chamber, wherein the fuel nozzle is disposed in the head end chamber between an end plate and the divider plate, wherein the outer wall of the feed cap, the back plate of the feed cap, and the outer shell of the fuel nozzle are configured to maintain a sufficient flow along all boundaries to impede combustion in the head end chamber.

11. A system, comprising:

a turbine combustor, comprising:

a combustion chamber;

a head end chamber separated from the combustion chamber by a divider plate;

a pressurized chamber disposed in the head end chamber and about a fuel nozzle, wherein the pressurized chamber comprises a back plate that meets an upstream end terminus of an outer shell of the fuel nozzle;

wherein the turbine combustor comprises a first fluid path configured to flow a mixture of fuel and a first pressurized air from a first source at a first pressure along an outer surface of the pressurized chamber, and the outer surface of the pressurized chamber comprises a first outer surface of a feed cap disposed around the fuel nozzle, a second outer surface of the back plate, and a third outer surface of the outer shell of the fuel nozzle; and

wherein the turbine combustor comprises a second fluid path configured to flow a second pressurized air from a second source at a second pressure, greater than the first pressure, into the pressurized chamber.

12. The system of claim 11 , wherein the turbine combustor comprises the fuel nozzle comprising an inner shell and the outer shell, and the turbine combustor is configured to flow the mixture through the first fluid path along the first outer surface of the feed cap and into the fuel nozzle, and the first fluid path is substantially free of flow impeding surfaces.

13. The system of claim 11 , wherein the back plate of the pressurized chamber joins the upstream end terminus of the outer shell of the fuel nozzle and another upstream end terminus of the feed cap disposed about the fuel nozzle.

14. The system of claim 13 , wherein the head end chamber comprises an end plate positioned substantially parallel with respect to the divider plate, wherein the back plate comprises a flat wall or a curved wall that is curved toward the end plate.

15. The system of claim 11 , wherein the back plate of the feed cap is configured to maintain flow along the back plate to impede recirculation of the mixture along the back plate.

16. A system, comprising:

a turbine combustor, comprising:

a combustion chamber;

a head end chamber separated from the combustion chamber by a divider plate;

a fluid path disposed in the head end chamber and configured to flow a first pressurized air from a first source at a first pressure into a fuel nozzle, wherein the fluid path comprises:

a first segment disposed between a flow sleeve of the turbine combustor and an outer wall of a feed cap;

a second segment disposed downstream of and in fluid communication with the first segment and between a back plate of the feed cap and an end plate of the head end chamber, wherein the back plate meets a head end terminus of the outer wall of the feed cap and the second segment is substantially free of any flow-impeding surfaces between the back plate and the end plate; and

a third segment disposed downstream of and in fluid communication with the second segment and between inner and outer shells of the fuel nozzle; and

a pressurized chamber formed by the divider plate, the back plate of the feed cap, the outer wall of the feed cap, and the outer shell of the fuel nozzle, wherein the pressurized chamber is configured to receive only a second pressurized air from a second source at a second pressure.

17. The system of claim 16 , wherein the fluid path is configured to receive the first pressurized air from an annulus defined by the flow sleeve and a flow liner of the turbine combustor, and wherein the fluid path is configured to mix the first pressurized air with a fuel injected by a quaternary fuel injector to produce a pressurized fuel-air mixture at a third pressure.

18. The system of claim 17 , wherein the second pressure is greater than the third pressure.

19. The system of claim 16 , wherein the second segment of the fluid path is configured to be substantially free of a crosswise flow of the first pressurized air, wherein the crosswise flow comprises a flow direction oriented crosswise with respect to the end plate of the head end chamber.