We Claim:
1. A system comprising:
a turbine comprising:
an expansion section configured to expand an exhaust flow in a downstream direction, wherein the expansion section comprises a plurality of stages; and
a diffuser section coupled downstream of the expansion section, wherein the diffuser section is configured to receive the exhaust flow along an exhaust path and an energizing flow along a wall, and the diffuser section comprises:
the wall comprising an inner surface, wherein the wall is disposed about the exhaust path; and
an energizing port disposed in the wall at or downstream of a last stage of the plurality of stages of the expansion section, wherein the energizing port is configured to direct the energizing flow along the inner surface of the wall to energize a boundary layer along the wall, and a first pressure of the energizing flow is greater than a second pressure of the exhaust flow at the energizing port.
2. The system as claimed in claim 1, wherein the energizing flow comprises steam or carbon dioxide.
3. The system as claimed in claim 1, comprising a cooling manifold coupled to the turbine, wherein the cooling manifold is configured to direct a cooling flow toward a turbine casing disposed about the plurality of stages of the expansion section, and the energizing port is configured to receive at least a portion of the cooling flow from the cooling manifold as the energizing flow.
4. The system as claimed in claim 3, comprising a compressor coupled to the turbine, wherein the turbine is configured to drive the compressor, and the cooling flow comprises a bleed flow from the compressor.
5. The system as claimed in claim 3, comprising a compressor coupled to the turbine and a turbine discharge casing, wherein the turbine is
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configured to drive the compressor, the turbine discharge casing is configured to receive a compressed air flow from the compressor, and the turbine discharge casing is disposed about the cooling manifold and the expansion section of the main turbine casing.
6. The system as claimed in claim 5, comprising an enclosure, wherein the turbine comprises an aero-derivative gas turbine, and the compressor discharge casing is disposed within the enclosure.
7. The system as claimed in claim 6, wherein the cooling flow and the compressed air flow are isolated from the enclosure.
8. The system as claimed in claim 1, comprising a downstream system coupled to the downstream section, wherein the downstream system is configured to extract energy from the exhaust flow and the energizing flow.
9. The system as claimed in claim 8, wherein the downstream system comprises a heat recovery steam generator (HRSG).
10. The system as claimed in claim 1, wherein an inner diameter of the wall increases in the downstream direction, and an angle between the wall and an axis of the diffuser section is approximately 5 to 30º.
11. A method comprising:
expanding an exhaust gas through a plurality of turbine stages of a turbine section, wherein the exhaust gas flows in a downstream direction through the plurality of turbine stages;
receiving the exhaust gas in a diffuser section downstream of the turbine section; and
energizing a boundary layer downstream of an energizing port of the diffuser section, wherein the boundary layer is disposed along a wall of the diffuser section, the energizing flow has a higher pressure than the exhaust gas at the energizing port, and the boundary layer is configured to reduce a pressure loss of the exhaust gas through the diffuser section.
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12. The method as claimed in claim 11, comprising:
extracting energy from the energizing flow and the exhaust gas via a downstream system coupled to the diffuser section.
13. The method as claimed in claim 12, wherein the downstream system comprises a heat recovery steam generator (HRSG).
14. The method as claimed in claim 13, wherein the energizing flow comprises a steam flow, and the steam flow is received from the HRSG.
15. The method as claimed in claim 11, comprising cooling the turbine section via a cooling flow, wherein the energizing port is configured to receive the cooling flow as the energizing flow.
16. The method as claimed in claim 15, wherein cooling the turbine section comprises directing the cooling flow through a cooling manifold toward a turbine casing disposed about the plurality of turbine stages, and the cooling manifold is configured to direct the cooling flow from the turbine casing to the energizing port.
17. The method as claimed in claim 16, comprising controlling a clearance between the turbine casing and rotating components of the turbine section via cooling the turbine casing with the cooling flow.
18. A gas turbine system comprising:
a cooling manifold disposed about an expansion section of a turbine, wherein the cooling manifold is configured to direct a cooling flow toward a turbine casing of
the expansion section; and
a diffuser section coupled to the cooling manifold, wherein the diffuser section is configured to receive an exhaust gas from the expansion section and the cooling flow from the cooling manifold, and the diffuser section comprises an energizing port configured to energize a boundary layer with the cooling flow between a wall and the exhaust gas.
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19. The gas turbine system as claimed in claim 18, wherein the cooling flow comprises a steam flow.
20. The gas turbine system as claimed in claim 18, comprising
a compressor discharge casing disposed about a combustor of the gas turbine system, the cooling manifold, and the expansion section, wherein the compressor discharge casing is configured to receive a compressed air flow and to direct the compressed air flow to the combustor, and the compressor discharge casing is configured to isolate the cooling flow, the compressed air flow, and the exhaust gas from an external environment about the compressor discharge casing.