Gas turbine

Abstract

 A gas turbine is provided, including a turbine, an exhaust diffuser (26), and a plasma actuator (60). The turbine releases an exhaust gas. The exhaust diffuser (26) receives the exhaust gas from the turbine (24). The exhaust diffuser has an inlet (40) and an outlet (42), and at least one wall (48,52) that is disposed between the inlet (40) and the outlet (42). The plasma actuator (60) produces a plasma along the at least one wall (48,50) of the diffuser (24).

Description

BACKGROUND OF THE INVENTION

[0001] The subject matter disclosed herein relates to a gas turbine, and more specifically to a gas turbine exhaust diffuser having a plasma actuator for producing a plasma.

[0002] Gas turbines generally include a compressor, a combustor, one or more fuel nozzles, a turbine and an exhaust diffuser. Air enters the gas turbine through an air intake and is compressed by the compressor. The compressed air is then mixed with fuel supplied by the fuel nozzles. The air-fuel mixture is supplied to the combustors at a specified ratio for combustion. The combustion generates pressurized exhaust gases, which drive blades of the turbine. An exhaust diffuser may be utilized to improve efficiency of the last stage turbine blade, which is also referred to as a last stage bucket, by decreasing the static pressure at the turbine exit.

[0003] The exhaust diffuser generally consumes a large amount of space. The exhaust diffuser includes an inlet and an outlet that are located between diverging walls of the exhaust diffuser. An axial length of the exhaust diffuser is measured between the inlet and the outlet of the exhaust diffuser. If the axial length of the diffuser is not sufficient and is too short, flow separation may occur at the diverging walls of the exhaust diffuser, which results in pressure losses.

BRIEF DESCRIPTION OF THE INVENTION

[0004] According to one aspect of the invention, a gas turbine is provided, including a turbine, an exhaust diffuser, and a plasma actuator. The turbine releases an exhaust gas. The exhaust diffuser receives the exhaust gas from the turbine. The exhaust diffuser has an inlet and an outlet, and at least one wall that is disposed between the inlet and the outlet. The plasma actuator produces a plasma along the at least one wall of the diffuser.

[0005] These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

[0006] The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a partially cross-sectioned schematic view of an exemplary gas turbine system having a compressor;

FIG. 2 is a cross-sectioned view of an exhaust diffuser shown in FIG. 1;

FIG. 3 is a cross-sectioned view of the exhaust diffuser shown in FIG. 2 along section lines 3-3;

FIG. 4 is a cross-sectioned view of an exhaust strut shown in FIG. 2 along section lines 4-4; and

FIG. 5 is an enlarged view of a plasma actuator as shown in FIGS. 2-4.

[0007] The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0008] FIG. 1 illustrates a schematic exemplary power generation system indicated by reference number 10. The power generation system 10 is a gas turbine system having a compressor 20, a combustor 22, a turbine 24, and an exhaust diffuser 26. Air enters the power generation system 10 though an air intake 30 connected to the compressor 20, and is compressed by the compressor 20. The compressed air is then mixed with fuel by a fuel nozzle 34 in a specific ratio for combustion. The combustion generates hot pressurized exhaust gas that drives blades (not shown) that are located within the turbine 24. The exhaust gas is sent from the turbine 24 to the exhaust diffuser 26.

[0009] FIG. 2 is an exemplary illustration of a side view of the exhaust diffuser 26. The exhaust diffuser 26 includes an inlet 40, an outlet 42, an inner diffuser 44 and an outer diffuser 46. The inner diffuser 44 includes an inner wall 48 and the outer diffuser 50 includes an outer wall 52. The inner wall 48 and the outer wall 52 are both located between the inlet 40 and the outlet 42. The inner wall 48 of the inner diffuser 44 is generally concentric with the outer wall 52 of the outer diffuser 46. Both the inner diffuser 44 and the outer diffuser 46 are oriented about an axis A-A. In the embodiment as shown, the outer wall 52 of the outer diffuser 46 includes a generally diverging configuration. The inlet 40 of the exhaust diffuser 26 receives an exhaust gas 56 from the turbine 24 (shown in FIG. 1). A plasma generator or actuator 60 is located on an outer surface 54 of the inner wall 48, and a plasma actuator 62 is located on an outer surface 58 of the outer wall 52. It should be noted that while FIG. 2 illustrates the plasma actuator 60 on the inner wall 48 as well as the plasma actuator 62 located on the outer wall 52, only one of the inner wall 48 or the outer wall 52 may include one of the plasma actuators 60 and 62 as well.

[0010] FIG. 3 is a sectional view of the exhaust diffuser 26 taken along section line 3-3. As seen in FIG. 3, both the inner wall 48 and the outer wall 52 include a 360° configuration. Specifically, referring now to FIG. 2-3, the inner wall 48 of the inner diffuser 44 includes a generally annular configuration, and the outer wall 52 of the outer diffuser 46 includes a generally conical configuration. A series of manways 68 are located between the inner wall 48 and the outer wall 52. The manways 68 provide personnel access to the inner diffuser 44. In the embodiment as shown in FIG. 3, the manways 68 are each spaced at about a 120° configuration apart from one another, however it is to be understood that the manways 68 may be arranged in a variety of configurations as well. An outer surface 70 of each of the manways 68 may include a plasma actuator 72 as well. The outer surface 70 of each of the manways 68 are exposed to the exhaust gas 56 from the turbine 24 (shown in FIG. 1).

[0011] Referring back to FIG. 2, an exhaust strut 80 is located within the exhaust diffuser 26 between the inner wall 48 and the outer wall 52. The exhaust strut 80 includes a cross-section which is indicated by section line 4-4. Referring now to FIG. 4, which is an illustration of the exhaust strut 80 at section 4-4, the exhaust frame strut 80 includes a cross-section that is shaped as a cambered airfoil. The airfoil includes an upper camber portion 82 and a lower camber portion 84. The exhaust strut 80 has an outer surface 86, where a plasma actuator 88 may be located on the upper camber portion 82 or the lower camber portion 84 along the outer surface 86. It should be noted that while FIG. 4 illustrates a cambered airfoil, it is to be understood that the airfoil may include a generally symmetrical configuration as well.

[0012] FIG. 5 is an enlarged view of an exemplary plasma actuator 90, which may be used along the inner wall 48, the outer wall 52, along the outer surface 70 of the manways 68, or on the outer surface 86 of the exhaust strut 80 (shown in FIG. 2). The plasma actuator 90 includes an inner electrode 92, an outer electrode 94, and a dielectric material 96. The dielectric material 96 is configured for conforming to a conical or generally curved surface. That is, the dielectric material 96 is configured for conforming to a non-planer surface. Therefore, the plasma actuator 90 is configured for conforming to an outer surface of an object that is conical or includes a generally curved profile. For example, referring now to FIG. 2, the plasma actuator 60 is disposed along a generally annular outer surface 54, and the plasma actuator 62 is disposed along a generally conical outer surface 58.

[0013] Referring back to FIG. 5, an AC power supply 100 is connected to both the inner electrode 92 and the outer electrode 94. The AC power supply 100 provides AC power to the inner electrode 92 and the outer electrode 94. In one exemplary embodiment, the power consumption of the plasma actuator 90 is 15 Watts per linear foot of plasma. When the amplitude of the AC voltage reaches a threshold value, the exhaust gas 56 from the turbine 24 (shown in FIG. 1) ionizes in a region of the largest electric potential to form a plasma 102. The plasma 102 begins at an edge 104 of the outer electrode 94 and spreads over an area 106 projected by the outer electrode 94 that is adjacent the dielectric material 96. The plasma 102 produces a force on the exhaust gas 56, which in turn causes a change in the pressure distribution along a curved surface 110. The change in pressure distribution generally reduces or substantially prevents flow separation when the plasma actuator 90 is energized by the AC power supply 100. Thus, in the embodiments as shown in FIGS. 2-5, the plasma actuator 90 improves efficiency of the last stage turbine blade (not shown) or last stage bucket of the turbine 24 (shown in FIG. 1) by increasing the static pressure of the exhaust gas 56.The plasma actuators as illustrated in FIGS. 2-5 provide a robust design that is relatively simple, and also provides a relatively low amount of power consumption with real-time control.

[0014] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. A gas turbine, comprising:

a turbine (24) releasing an exhaust gas;

an exhaust diffuser (26) for receiving the exhaust gas from the turbine (24), the exhaust diffuser (26) having an inlet (40), an outlet (42) and at least one wall (48,52) that is disposed between the inlet (40) and the outlet (42); and

a plasma actuator (60) producing a plasma along the at least one wall (48,52) of the diffuser (26).

2. The gas turbine of claim 1, wherein the exhaust diffuser (26) includes an inner diffuser (44) and an outer diffuser (46), wherein the inner diffuser (44) is generally concentric with the outer diffuser (46).

3. The gas turbine of claim 2, wherein the inner diffuser (44) includes an inner wall (48), and wherein the plasma actuator (60) is disposed along the inner wall (48) of the inner diffuser (44).

4. The gas turbine of claim 2 or 3, wherein the outer diffuser (46) includes an outer wall (52), and wherein the plasma actuator (60) is disposed along the outer wall (52) of the outer diffuser (46).

5. The gas turbine of any of claims 2 to 4, wherein the inner diffuser (44) includes a generally annular configuration.

6. The gas turbine of any of claims 2 to 5, wherein the outer diffuser (46) includes a generally conical configuration.

7. The gas turbine of any of claims 2 to 6, comprising at least one manway (68) located between the inner diffuser (44) and the outer diffuser (46), wherein the at least one manway (68) includes an outer manway surface (70), and wherein another plasma actuator (60) is located along the outer manway surface (70).

8. The gas turbine of any preceding claim, comprising an exhaust strut (80) that is located between an inner wall (48) and an outer wall (52) of the exhaust diffuser (26), the exhaust strut (80) having a cross-section, wherein the cross-section of the exhaust strut (80) includes an airfoil shape.

9. The gas turbine of claim 8, comprising an exhaust strut plasma actuator (88) that is disposed along an outer surface of the exhaust strut (80).

10. The gas turbine of claim 1, wherein the plasma actuator (90) includes an inner electrode (92), an outer electrode (94), and a dielectric material (96).

Drawing