Combustor liner cooling system

1. A combustor liner comprising:

an upstream portion;

a downstream end portion extending from the upstream portion along a generally longitudinal axis, the downstream end portion including an inner surface and an outer surface, the inner surface defining a plurality of microchannels, each of the plurality of microchannels extending longitudinally along the inner surface, the downstream end portion further defining a plurality of passages extending between the inner surface and the outer surface, wherein the plurality of microchannels are fluidly connected to the plurality of passages such that each of the plurality of passages is directly connected to one of the plurality of microchannels; and

a cover layer associated with the inner surface of the downstream end portion,

wherein the plurality of microchannels are configured to flow a cooling medium therethrough, cooling the combustor liner.

2. The combustor liner of claim 1 , wherein the cover layer is one of a metal coating, a bond coating, or a thermal barrier coating.

3. The combustor liner of claim 1 , further comprising a thermal barrier coating disposed adjacent the cover layer.

4. The combustor liner of claim 3 , further comprising a bond coating disposed between the thermal barrier coating and the cover layer.

5. The combustor liner of claim 1 , wherein the downstream end portion comprises a combustor liner substrate.

6. The combustor liner of claim 1 , wherein the downstream end portion comprises a combustor liner substrate and a bond coating, and wherein the plurality of microchannels are defined in the bond coating.

7. The combustor liner of claim 6 , wherein the cover layer comprises a thermal barrier coating.

8. The combustor liner of claim 1 , wherein the downstream end portion comprises a combustor liner substrate, a bond coating, and a first thermal barrier coating, and wherein the plurality of microchannels are defined in the first thermal barrier coating.

9. The combustor liner of claim 8 , wherein the cover layer comprises a second thermal barrier coating.

10. The combustor liner of claim 1 , wherein the plurality of microchannels extend linearly with respect to the longitudinal axis.

11. The combustor liner of claim 1 , wherein the plurality of microchannels extend helically with respect to the longitudinal axis.

12. The combustor liner of claim 1 , wherein the outer surface of the downstream end portion defines a plurality of channels, each of the plurality of channels configured to flow cooling medium therethrough, cooling the combustor liner, and wherein at least a portion of the plurality of passages are further fluidly connected to at least a portion of the channels.

13. The combustor liner of claim 1 , wherein cooling medium is exhausted directly from the plurality of microchannels.

14. The combustor liner of claim 1 , wherein the cover layer defines a plurality of exhaust passages, each of the plurality of exhaust passages fluidly connected to one of the plurality of microchannels and configured to accept cooling medium from the microchannel and exhaust cooling medium adjacent the cover layer.

15. The combustor liner of claim 1 , wherein the inner surface of the downstream end portion further defines a plenum, the plenum configured to accept cooling medium from the plurality of microchannels.

16. The combustor liner of claim 15 , wherein the cover layer defines a plurality of exhaust passages, each of the plurality of exhaust passages fluidly connected to the plenum and configured to accept cooling medium from the plenum and exhaust cooling medium adjacent the cover layer.

17. A combustor comprising:

a combustor liner at least partially defining a hot gas path, the combustor liner including an upstream portion and a downstream end portion extending from the upstream portion along a generally longitudinal axis, the downstream end portion including an inner surface and an outer surface, the inner surface defining a plurality of microchannels, each of the plurality of microchannels extending longitudinally along the inner surface, the downstream end portion further defining a plurality of passages extending between the inner surface and the outer surface, wherein the plurality of microchannels are fluidly connected to the plurality of passages;

a cover layer associated with the inner surface of the downstream end portion;

a transition piece coupled to the combustor liner and further defining the hot gas path; and

a sealing ring providing a seal between the combustor liner and the transition piece,

wherein the plurality of microchannels are configured to flow a cooling medium therethrough, cooling the combustor liner.

18. The combustor of claim 17 , the sealing ring defining a plurality of feed passages, the feed passages configured to flow cooling medium therethrough, and wherein at least a portion of the passages defined in the downstream end portion are configured to accept cooling medium from the plurality of feed passages.

19. The combustor of claim 17 , further comprising an annular wrapper disposed between the combustor liner and the sealing ring, the annular wrapper defining a plurality of feed passages, the plurality of feed passages configured to flow cooling medium therethrough.

20. The combustor of claim 17 , wherein the outer surface of the downstream end portion defines a plurality of channels, each of the plurality of channels configured to flow cooling medium therethrough, cooling the combustor liner, and wherein at least a portion of the plurality of passages are further fluidly connected to at least a portion of the channels.