Turbine nozzle with inner band and outer band cooling

1. A turbine nozzle, comprising:

an airfoil that extends in span from an inner band to an outer band, the inner band and the outer band define inner and outer flow boundaries of the turbine nozzle;

one or more inner plates at least partially covering a gas side surface of the inner band;

a plurality of cooling channels formed within the gas side surface of the inner band beneath the one or more inner plates;

one or more outer plates at least partially covering a gas side surface of the outer band;

a plurality of cooling channels formed within the gas side surface of the outer band beneath the one or more outer plates, the plurality of cooling channels of the outer band comprising at least one serpentine shaped cooling channel defined between a pressure side wall of the airfoil and a pressure side wall of the outer band and at least one cooling channel oriented to follow a curvature of the pressure side wall of the airfoil;

a first aperture defining a flow path for a cooling medium to flow into the at least one serpentine shaped cooling channel;

a second aperture defining a flow path for the cooling medium to flow into the at least one cooling channel oriented to follow the curvature of the pressure side wall of the airfoil;

a plurality of exhaust ports defined in the one or more inner plates, each of the plurality of exhaust ports extending radially outward through a corresponding inner plate of the one or more inner plates from a corresponding one of the plurality of cooling channels of the inner band; and

a plurality of exhaust ports defined in the one or more outer plates, each of the plurality of exhaust ports extending radially inward through a corresponding outer plate of the one or more outer plates from a corresponding one of the plurality of cooling channels of the outer band.

2. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the outer band comprises at least one serpentine shaped cooling channel defined between a leading edge portion of the airfoil and a forward wall of the outer band.

3. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the inner band comprises at least one serpentine shaped cooling channel.

4. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the inner band comprises at least one serpentine shaped cooling channel defined between a leading edge portion of the airfoil and a forward wall of the inner band.

5. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the inner band comprises at least one serpentine shaped cooling channel defined between a pressure side wall of the airfoil and a pressure side wall of the outer band.

6. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the inner band comprises at least one cooling channel disposed along a leading edge portion of the inner band and extending between a pressure side wall and a suction side wall of the inner band.

7. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the outer band comprises a group of densely spaced cooling channels and a group of sparsely spaced cooling channels.

8. The turbine nozzle as in claim 1 , wherein the plurality of cooling channels of the inner band comprises a group of densely spaced cooling channels and a group of sparsely spaced cooling channels.

9. A gas turbine, comprising:

a compressor;

a combustor downstream from the compressor; and

a turbine disposed downstream from the combustor, wherein the turbine comprises a stage having a row of turbine nozzles and a row of turbine rotor blades, at least one turbine nozzle comprising:

an airfoil that extends in span from an inner band to an outer band, wherein the inner band and the outer band define inner and outer flow boundaries of the turbine nozzle;

one or more inner plates at least partially covering a gas side surface of the inner band;

a plurality of cooling channels formed within the gas side surface of the inner band beneath the one or more inner plates, the plurality of cooling channels of the inner band comprising at least one serpentine shaped cooling channel defined between a leading edge portion of the airfoil and a forward wall of the inner band and at least one cooling channel disposed along a leading edge portion of the airfoil and extending between a pressure side wall and a suction side wall of the airfoil;

a first aperture defining a flow path for a cooling medium to flow into the at least one serpentine shaped cooling channel;

a second aperture defining a flow path for the cooling medium to flow into the at least one cooling channel disposed along the leading edge portion of the airfoil;

one or more outer plates at least partially covering a gas side surface of the outer band;

a plurality of cooling channels formed within the gas side surface of the outer band beneath the one or more outer plates;

a plurality of exhaust ports defined in the one or more inner plates, each of the plurality of exhaust ports extending radially outward through a corresponding inner plate of the one or more inner plates from a corresponding one of the plurality of cooling channels of the inner band; and

a plurality of exhaust ports defined in the one or more outer plates, each of the plurality of exhaust ports extending radially inward through a corresponding outer plate of the one or more outer plates from a corresponding one of the plurality of cooling channels of the outer band.

10. The gas turbine as in claim 9 , wherein the plurality of cooling channels of the outer band comprises at least one serpentine shaped cooling channel.

11. The gas turbine as in claim 9 , wherein the plurality of cooling channels of the outer band comprises at least one serpentine shaped cooling channel defined between a leading edge portion of the airfoil and a forward wall of the outer band.

12. The gas turbine as in claim 9 , wherein the plurality of cooling channels of the outer band comprises at least one serpentine shaped cooling channel defined between a pressure side wall of the airfoil and a pressure side wall of the outer band.

13. The gas turbine as in claim 9 , wherein the plurality of cooling channels of the inner band comprises at least one serpentine shaped cooling channel defined between a pressure side wall of the airfoil and a pressure side wall of the outer band.

14. The gas turbine as in claim 9 , wherein the plurality of cooling channels of the outer band comprises a group of densely spaced cooling channels and a group of sparsely spaced cooling channels.

15. The gas turbine as in claim 9 , wherein the plurality of cooling channels of the inner band comprises a group of densely spaced cooling channels and a group of sparsely spaced cooling channels.

16. A turbine nozzle, comprising:

an airfoil that extends in span from an inner band to an outer band, the inner band and the outer band define inner and outer flow boundaries of the turbine nozzle;

one or more inner plates at least partially covering a gas side surface of the inner band;

a plurality of cooling channels formed within the gas side surface of the inner band beneath the one or more inner plates, the plurality of cooling channels of the inner band comprising at least one serpentine shaped cooling channel defined between a leading edge portion of the airfoil and a forward wall of the inner band and at least one cooling channel disposed along a leading edge portion of the airfoil and extending between a pressure side wall and a suction side wall of the airfoil;

a first aperture defining a flow path for a cooling medium to flow into the at least one serpentine shaped cooling channel;

a second aperture defining a flow path for the cooling medium to flow into the at least one cooling channel disposed along the leading edge portion of the airfoil;

one or more outer plates at least partially covering a gas side surface of the outer band;

a plurality of cooling channels formed within the gas side surface of the outer band beneath the one or more outer plates;

a plurality of exhaust ports defined in the one or more inner plates, each of the plurality of exhaust ports extending radially outward through a corresponding inner plate of the one or more inner plates from a corresponding one of the plurality of cooling channels of the inner band; and

a plurality of exhaust ports defined in the one or more outer plates, each of the plurality of exhaust ports extending radially inward through a corresponding outer plate of the one or more outer plates from a corresponding one of the plurality of cooling channels of the outer band.

17. The turbine nozzle as in claim 16 , wherein the plurality of cooling channels of the outer band comprises at least one serpentine shaped cooling channel defined between a pressure side wall of the airfoil and a pressure side wall of the outer band and at least one cooling channel oriented to follow a curvature of the pressure side wall of the airfoil.

18. The turbine nozzle as in claim 16 , wherein the plurality of cooling channels of the outer band comprises a group of densely spaced cooling channels and a group of sparsely spaced cooling channels.

19. The turbine nozzle as in claim 16 , wherein the plurality of cooling channels of the inner band comprises a group of densely spaced cooling channels and a group of sparsely spaced cooling channels.