Mitigation of rotating stall in turbine exhaust section using segmented auxiliary strut

Abstract

To mitigate rotating stall in a turbine exhaust section using a segmented auxiliary strut.SOLUTION: A system includes a turbine exhaust section having an exhaust flow path, an inner exhaust wall radially disposed along the exhaust flow path, and an outer exhaust wall radially disposed along the exhaust flow path, the outer exhaust wall disposed radially outward from the inner exhaust wall. The turbine exhaust section includes an auxiliary strut (50) extending from the inner exhaust wall to the outer exhaust wall. The auxiliary strut (50) is segmented. The auxiliary strut (50) includes: an inner portion (282); a central portion (284) disposed radially outward from the inner portion (282); and an outer portion (286) disposed radially outward from the central portion (284). The inner portion (282), the outer portion (286), or both of the portions (282, 286) are configured to rotate to an angled position.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The subject matter disclosed herein relates to alleviating the formation of rotating stall in the low-pressure turbine section of a turbine (e.g., an expansion turbine of a gas turbine engine) or in the exhaust section downstream of the turbine. The exhaust section of a gas turbine engine is provided with a split auxiliary strut having one or more portions rotatable to a certain angular position to alleviate the formation of rotating stall cells that may occur during low-flow operating conditions of the gas turbine engine.

Background Art

[0002] Gas turbine engines operate under various conditions (steady-state conditions, transient conditions (e.g., startup or shutdown), full-load conditions, or part-load conditions, etc.). Unfortunately, when operating under low-flow operating conditions (e.g., transient conditions or part-load conditions), a gas turbine engine is prone to enter a rotating stall state. In the rotating stall state, rotating stall cells are formed in the low-pressure turbine section of the gas turbine engine, causing reverse flow. The rotating stall cells rotate at a fraction of the rotational speed of the gas turbine engine (i.e., at a low frequency), thereby causing asynchronous high-cycle fatigue in the turbine blades of the low-pressure turbine section. Therefore, there is a need to at least alleviate or prevent the rotating stall state in a gas turbine engine.

Summary of the Invention

[0003] Specific embodiments corresponding to the scope of the present invention as originally claimed are summarized below. These embodiments are not intended to limit the scope of the claimed invention, and these embodiments are only intended to provide a brief overview of possible forms of the invention. In fact, the present invention can encompass various forms similar to or different from the embodiments shown below.

[0004] In one embodiment, the system includes a turbine exhaust section having an exhaust flow path, an inner exhaust wall disposed radially along the exhaust flow path, and an outer exhaust wall disposed radially along the exhaust flow path, the outer exhaust wall being disposed radially outside the inner exhaust wall. The turbine exhaust section includes auxiliary struts extending from the inner exhaust wall to the outer exhaust wall. The auxiliary struts are split, and the auxiliary struts include an inner portion, a central portion disposed radially outside the inner portion, and an outer portion disposed radially outside the central portion. The inner portion, the outer portion, or both are configured to rotate to a certain angular position. The auxiliary struts are circumferentially disposed between adjacent struts of the turbine exhaust section.

[0005] In another embodiment, the system includes a turbine exhaust section having an exhaust flow path, an inner exhaust wall disposed radially along the exhaust flow path, an outer exhaust wall disposed radially along the exhaust flow path, and auxiliary struts extending from the inner exhaust wall to the outer exhaust wall. The auxiliary struts are split, and the auxiliary struts include an inner portion, a central portion disposed radially outside the inner portion, an outer portion disposed radially outside the central portion, an inner operating assembly configured to operate the inner portion to rotate the inner portion to an inner angular position, and an outer operating assembly configured to operate the outer portion to rotate the outer portion to an outer angular position. The auxiliary struts are circumferentially disposed between adjacent struts of the turbine exhaust section.

[0006] In another embodiment, the system includes a turbine exhaust section having an exhaust flow path, an inner exhaust wall disposed radially along the exhaust flow path, an outer exhaust wall disposed radially along the exhaust flow path, and an auxiliary strut extending from the inner exhaust wall to the outer exhaust wall. The auxiliary strut is split and includes an inner portion, a central portion disposed radially outside the inner portion, and an outer portion disposed radially outside the central portion. The inner portion, the outer portion, or both are configured to rotate to a certain angular position. The auxiliary strut is circumferentially disposed between adjacent struts of the turbine exhaust section. When the inner portion rotates to an inner angular position, it is configured to substantially expand over an inner circumferential distance between adjacent struts. When the outer portion rotates to an outer angular position, it is configured to substantially expand over an outer circumferential distance between adjacent struts.

Brief Description of the Drawings

[0007] These features, aspects, and advantages of the present disclosure, as well as other features, aspects, and advantages, can be further understood by reading the following embodiments for carrying out the invention with reference to the drawings. In the drawings, like reference numerals represent like parts throughout the drawings.

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[0008] One or more specific embodiments of the present disclosure will be described below. For the sake of brevity in describing these embodiments, not all features of an actual implementation are described herein. It should be understood that in the development of any such actual implementation, as in various engineering projects or design projects, a number of implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related constraints and business-related constraints that are considered to vary from implementation to implementation. Further, although such development efforts may be complex and time-consuming, it should be understood that they are routine in the business of design, fabrication, and manufacture for those skilled in the art to benefit from the present disclosure.

[0009] When introducing elements of various embodiments of the present disclosure, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of such elements. "Comprising," "including," and "having" are inclusive and are intended to mean that additional elements other than the recited elements may exist.

[0010] As described in more detail below, the disclosed embodiments can mitigate rotating stall conditions in the low pressure turbine section of a gas turbine engine by mitigating the formation of reverse flow and rotating stall cells downstream of the final stage blade of the gas turbine engine. For example, certain embodiments include a plurality of inner flow control vanes (e.g., radially inner vanes) disposed on the inner exhaust wall (e.g., inner diameter) of the exhaust section of the gas turbine engine. The plurality of inner flow control vanes are aligned such that their axial positions are aligned (e.g., a common axial position) and form a segmented inner dam (e.g., a segmented inner annular flow barrier wall). The inner dam is configured to separate reverse flow of the exhaust gas (e.g., the exhaust flow path) into upstream and downstream vortices. The upstream vortex maintains a tangential velocity, thereby reducing the velocity gradient of the shear layer located immediately downstream of the blades of the final stage of the turbine section (e.g., the final stage of the turbine blades). By reducing the velocity gradient of the shear layer, the likelihood of a rotating stall condition in the low pressure turbine section is reduced. In certain embodiments, the inner dam can be combined with a segmented outer dam (e.g., a segmented outer annular flow barrier wall having a plurality of outer flow control vanes) disposed on the outer exhaust wall of the exhaust section. The outer dam is configured to constrict the exhaust flow path, thereby improving the effectiveness of the inner dam.

[0011] In certain embodiments, auxiliary struts (e.g., radial auxiliary struts) circumferentially arranged between adjacent struts (e.g., radial diffuser struts) in the exhaust section of a gas turbine engine can be used to mitigate the formation of rotating stall. In certain embodiments, the auxiliary strut can include an inner portion (e.g., radial inner flow control vane), a central portion (e.g., radial intermediate flow control vane), and an outer portion (e.g., radial outer flow control vane). The inner and outer portions (e.g., flow control vanes) are configured to rotate about a pivot to a certain angular position in the circumferential direction, while the central portion is configured to remain stationary and avoid rotation. By the rotation of the inner and outer portions of the auxiliary strut, the exhaust flow path is blocked immediately below the outer exhaust wall and immediately above the inner exhaust wall, thereby increasing the tangential velocity of the reverse flow in the exhaust flow path and decreasing the velocity gradient of the shear layer adjacent to the last stage blade (e.g., the last stage of the turbine blade). By decreasing the velocity gradient of the shear layer, the possibility of forming a rotating stall cell in the low-pressure turbine section immediately upstream of the exhaust section is reduced.

[0012] In certain embodiments, the formation of rotating stall can be mitigated using flow direction conversion vanes (e.g., flow control vanes, mixing vanes) configured to direct a portion of the high-speed free flow near the outer exhaust wall (e.g., outer diameter) towards the reverse flow at the inner exhaust wall (e.g., inner diameter). When the high-speed free flow is added to the reverse flow, the tangential velocity of the reverse flow increases near the last stage blade (e.g., the last stage of the turbine blade), thereby reducing the velocity gradient of the shear layer and reducing the risk of forming a rotating stall. The flow direction conversion vanes can be configured to be stored in a recess disposed in the outer exhaust wall during normal operating conditions of the gas turbine engine.

[0013] Figure 1 is a schematic flow diagram of one embodiment of a turbine system 10 having a gas turbine engine 12 with a recirculation obstruction system 11 (e.g., a rotating stall prevention system). As will be described in detail below, the recirculation obstruction system 11 includes one or more sets of flow control vanes 13 (see FIG. 2) configured to prevent the flow of exhaust gas from recirculating (e.g., flowing backward) to the final turbine stage, thereby reducing the risk of a rotating stall condition. In a particular embodiment, the turbine system 10 can be used in an aircraft, a locomotive, a power generation system, or a combination thereof. The illustrated gas turbine engine 12 includes, in the order in which fluid continuously flows, an intake section 16, a compressor or compressor section 18, a combustor or combustor section 20, a turbine or turbine section 22 (i.e., an expansion turbine), and an exhaust section 24. The turbine section 22 is coupled to the compressor 18 via a shaft 26.

[0014] As shown by the arrow, air flows through the intake section 16 and into the gas turbine engine 12, and into the compressor 18, which compresses the air before it flows into the combustor section 20. The illustrated combustor section 20 includes a combustor housing 28 arranged concentrically or annularly with respect to the shaft 26 between the compressor 18 and the turbine section 22. Compressed air from the compressor 18 flows into the combustor section 20, where the compressed air and fuel are mixed and burned in the combustor to drive the turbine section 22. High-temperature combustion gases flow from the combustor section 20 through the turbine section 22 and drive the compressor 18 via the shaft 26. For example, power can be applied to the turbine blades in the turbine section 22 by the combustion gases to rotate the shaft 26. After flowing through the turbine section 22, the high-temperature combustion gases can flow through the exhaust section 24 and be discharged from the gas turbine engine 12. As will be described later, the recirculation prevention system 11 can include one or more flow control vanes 13 (see FIG. 2) arranged in the exhaust section 24 so as to be close to at least the last turbine stage of the turbine section 22 (for example, arranged between the last turbine stage of the turbine section 22 and a plurality of struts of the exhaust section 24). The gas turbine engine 12 can be described by a longitudinal direction, i.e., the axis 32 (for example, the axial direction), a radial direction, i.e., the axis 34, and a circumferential direction, i.e., the axis 36.

[0015] FIG. 2 is a side cross-sectional view of one embodiment of the gas turbine engine 12 of FIG. 1 cut along the longitudinal axis 32, showing one embodiment of the recirculation prevention system 11. As described above with respect to FIG. 1, air can flow through the intake section 16 and into the gas turbine engine 12, where it can be compressed by the compressor 18. The compressed air from the compressor 18 is then directed to the combustor section 20, where the compressed air can be mixed with fuel. The combustor section 20 includes one or more combustors 38. In certain embodiments, the gas turbine engine 12 can include a plurality of combustors 38 arranged in a ring. Further, each combustor 38 can include a plurality of fuel nozzles 40 attached to or near the head end of each combustor 38 in a ring or other arrangement. In operation, the fuel nozzles 40 can inject a fuel-air mixture into the combustor 38 at a ratio suitable for optimal combustion, emissions, fuel consumption, and power output. Within the combustor section 20, the fuel-air mixture burns to produce high-temperature pressurized combustion gases. After combustion, the high-temperature pressurized combustion gases flow through the transition piece 42 and from the combustor section 20 to the turbine section 22. Within the turbine section 22, the pressurized combustion gases rotate blades 44 (e.g., rotating turbine blades) that extend radially within the turbine section 22 and are disposed between vanes 46 (e.g., stationary turbine vanes), rotating the shaft 26, and then flow through the exhaust section 24 and are discharged as exhaust gases.

[0016] In certain embodiments, the turbine section 22 can include one or more turbine stages (e.g., 1, 2, 3, 4, or more turbine stages) disposed at different axial positions along the longitudinal axis 32 of the turbine section 22. Each turbine stage has a plurality of blades 44 (e.g., rotating turbine blades) spaced from each other in a circumferential direction centered on the longitudinal axis 32 of the turbine section 22 at a common axial position, and the blades 44 are coupled to a central turbine rotor or shaft of the turbine section 22. Similarly, each turbine stage has a plurality of vanes 46 (e.g., stationary turbine vanes) spaced from each other in a circumferential arrangement centered on the longitudinal axis 32 of the turbine section 22 at a common axial position offset from the blades 44, and the vanes 46 are coupled to an outer casing or outer wall of the turbine section 22. In operation, the pressurized combustion gas continuously flows through each turbine stage to drive the turbine section 22 to rotate. Thus, one or more upstream turbine stages can be regarded as high-pressure (HP) turbine stages, one or more intermediate turbine stages can be regarded as intermediate-pressure (IP) turbine stages, and one or more downstream turbine stages can be regarded as low-pressure (LP) turbine stages. The LP turbine stage 72 can include one or more LP turbine stages having blades 44 and vanes 46, and includes a last turbine stage 74 upstream of the exhaust section 24. The recirculation prevention system 11 is configured to prevent recirculation (e.g., backflow) of the exhaust gas in the LP turbine stage 72, particularly the last turbine stage 74, thereby reducing the possibility of a rotating stall condition in the turbine section 22 when the gas turbine engine 12 is operating under low flow rate operating conditions.

[0017] In the illustrated embodiment, the recirculation prevention system 11 includes a plurality of sets of flow control vanes 13. The exhaust section 24 can include at least one strut 48 (e.g., a radial diffuser strut) downstream of the blades 54 of the final stage of the turbine section 22 (e.g., the blades 44 of the final turbine stage 74), and each strut 48 extends radially between an inner exhaust wall 56 (e.g., an inner diameter wall, an inner annular wall, or an inner hub) and an outer exhaust wall 58 (e.g., an outer diameter wall or an outer annular wall) of the exhaust section 24 (e.g., an annular exhaust duct). For example, the exhaust section 24 can include 2, 3, 4, 5, 6, 7, 8, 9, 10, or more struts 48 spaced circumferentially from each other about the longitudinal axis 32 of the turbine section 22 at a common axial position downstream of the final stage blades 54. The plurality of sets of flow control vanes 13 can be arranged as one or more sets at one or more axial positions relative to the longitudinal axis 32, and the axial positions can include one or more intermediate axial positions disposed between the blades 44 and the vanes 46 of the final turbine stage 74 (and / or other low pressure turbine stages 72) of the turbine section 22, one or more intermediate axial positions downstream of the blades 54 of the final stage of the turbine section 22 and upstream of at least one strut 48, and / or other axial positions suitable for preventing reverse flow of the exhaust gas to the blades 54 of the final stage.

[0018] As shown in FIG. 3, one set of the flow control vanes 13 includes flow control vanes 92 and 94, and the flow control vanes 92 and 94 are respectively disposed on the inner exhaust wall 56 and the outer exhaust wall 58 of the exhaust section 24 in the axial range between the last turbine blade 54 and at least one exhaust strut 48. Additionally or alternatively, the turbine section 22 can include another set of flow control vanes 13 (i.e., flow control vanes 132, 95), and the flow control vanes of the other set are respectively disposed on the inner turbine wall 78 of the turbine 22 and the outer turbine wall 76 of the turbine 22 in the axial range between the last turbine nozzle 46 and the last turbine blade 54. Each set of the flow control vanes 13 can include a plurality of flow control vanes spaced apart from each other in the circumferential direction centered on the longitudinal axis 32 of the turbine 22 at a common axial position, and the flow control vanes 13 can be configured to extend or retract according to the operating conditions (for example, extend under low flow operating conditions (such as partial load and / or transient operating conditions), and retract under normal steady conditions and / or full load operating conditions). As shown, at least one set of the flow control vanes 13 (for example, flow control vanes 92, 132) can be disposed on the inner exhaust wall 56 of the exhaust section 24 and / or the inner turbine wall 78 of the turbine section 22, and in certain embodiments, at least one set of the flow control vanes 13 (for example, flow control vanes 94, 95) can be disposed on the outer exhaust wall 58 of the exhaust section 24 and / or the outer turbine wall 76 of the turbine section 22.

[0019] In certain embodiments, one or more sets of the flow control vanes 13 are circumferentially disposed at 36 between the struts 48 and can at least partially axially overlap with the struts 48 along the longitudinal axis 32. For example, the recirculation prevention system 11 can include at least one auxiliary strut 50 (e.g., a radial auxiliary strut) having one or more flow control vanes 13. Each auxiliary strut 50 extends radially at 34 between the inner exhaust wall 56 and the outer exhaust wall 58 of the exhaust section 24, and each auxiliary strut 50 is circumferentially disposed at 36 between adjacent struts 48 and struts 48. For example, the exhaust section 24 can include two, three, four, five, six, seven, eight, nine, ten, or more auxiliary struts 50 spaced apart from each other in the circumferential direction centered on the longitudinal axis 32 of the turbine section 22 at a common axial position that at least partially axially overlaps with the struts 48.

[0020] For example, the leading edge of the auxiliary strut 50 can be axially aligned with the leading edge of the strut 48, while the trailing edge of the auxiliary strut 50 can be positioned axially upstream from the trailing edge of the strut 48. Thus, the auxiliary strut 50 can be shorter than the strut 48 in the axial direction along the longitudinal axis 32. Each auxiliary strut 50 can include one or more flow control vanes 13 configured to rotate (e.g., rotate circumferentially at 36) between an axial orientation aligned with the longitudinal axis 32 and an orientation intersecting the longitudinal axis 32 at an angle. As will be discussed in more detail below, the flow control vanes 13 of each auxiliary strut 50 can include a radially inner flow control vane located near the inner exhaust wall 56 and a radially outer flow control vane located near the outer exhaust wall 58. Various aspects of the flow control vanes 13 and auxiliary struts 50 of the recirculation prevention system 11 will be described in more detail below.

[0021] In various embodiments, as shown in FIG. 2, the recirculation prevention system 11 also includes a controller 60, which monitors the operating conditions of the turbine system 10 and controls the position of the flow control vane 13 to prevent backflow of the exhaust gas and can be configured to at least mitigate or prevent a rotating stall condition in the turbine section 22. In certain embodiments, the controller 60 can include a processor 62, a memory 64, instructions 66 stored in the memory 64 and executable by the processor 62, and a communication circuit 68 configured to communicate with an actuator 70 coupled to the flow control vane 13. Examples of the actuator 70 can include an electric actuator (e.g., an electric motor or an electric drive device), a fluid actuator (e.g., a pneumatic actuator or a hydraulic actuator), or any combination thereof. In certain embodiments, each set of the flow control vanes 13 can be coupled to a single actuator 70 or a plurality of actuators 70 (e.g., one actuator per vane 13, or one actuator per subset of a plurality of vanes 13), and the controller 60 can operate one or more actuators 70 to move the flow control vane 13 between an extended position and a retracted position in response to the operating conditions of the turbine system 10.

[0022] For example, the controller 60 can control one or more actuators 70 such that the flow control vane 13 moves to the extended position in response to sensor feedback indicating reverse flow of the exhaust gas, a low flow state (e.g., a flow state during part load conditions and / or transient operating conditions), or a rotating stall state. However, the controller 60 can control one or more actuators 70 such that the flow control vane 13 moves to the retracted position when there is no such aforementioned state, such as in response to sensor feedback indicating normal downstream flow of the exhaust gas and / or a normal flow state (e.g., a flow during full load conditions and / or steady state operating conditions). In some embodiments, one or more sets of the flow control vanes 13 can be operated passively in response to operating conditions, such as by moving from the retracted position to the extended position in response to reverse flow. Various aspects of the operation of the flow control vane 13 are described in further detail below.

[0023] FIG. 3 is a side cross-sectional view taken along line 3-3 of one embodiment of the turbine system 10 of FIG. 2, further showing aspects of the recirculation obstruction system 11 disposed in the exhaust section 24 and the turbine section 22. The turbine section 22 includes a hot gas flow path disposed radially between an inner turbine wall 78 and an outer turbine wall 76. Similarly, the exhaust section 24 includes an exhaust flow path disposed radially between an inner exhaust wall 56 and an outer exhaust wall 58, where the inner exhaust wall 56 is a radially inner wall (e.g., an inner diameter wall or an inner annular wall) and the outer exhaust wall 58 is a radially outer wall (e.g., an outer diameter wall or an outer annular wall). As shown and discussed in further detail below, the flow control vane 13 includes one or more sets of the flow control vanes 13 of the turbine section 22 and / or the exhaust section 24 (e.g., inner flow control vanes 92 and 132 and outer flow control vanes 94 and 95). The exhaust section 24 includes struts 48 and, in certain embodiments, auxiliary struts 50 having flow control vanes 13.

[0024] Each set of flow control vanes 13 (e.g., 92, 94, 95, 132) can include a plurality of flow control vanes spaced from each other circumferentially about the longitudinal axis 32 of the turbine section 22 at a common axial position, and the flow control vanes 13 can be configured to selectively extend or retract in response to operating conditions (e.g., extend in low flow operating conditions (such as part load and / or transient operating conditions) and retract in normal steady state conditions and / or full load operating conditions). For example, each flow control vane 13 disposed adjacent to a wall (e.g., the inner turbine wall 78 and outer turbine wall 76 of the turbine section 22 or the inner exhaust wall 56 and outer exhaust wall 58 of the exhaust section 24) is, in the retracted position, substantially parallel to or flush with the respective wall and / or axially oriented along the longitudinal axis 32, whereas each flow control vane 13, in the extended position, projects at an angle with respect to the wall in a substantially lateral or angled orientation from the wall. For example, the angle can be 90 degrees. In many embodiments, the angle is an acute angle and can be an angle of 10 degrees to 89 degrees, 20 degrees to 80 degrees, 30 degrees to 70 degrees, or 40 degrees to 60 degrees. Each flow control vane 13 can be configured to selectively move between the retracted position and the extended position by a movement oblique to the wall (e.g., a movement oblique to the longitudinal axis 32 or a movement along the radial axis 34), an axial movement parallel to the wall (e.g., a movement parallel to the longitudinal axis 32), a rotational movement, or a combination of these movements.

[0025] The movement of the flow control vane 13 can be actively operated by an actuator 70 coupled to the controller 60 and / or can be passively operated in response to the flow conditions (e.g., reverse flow) in the turbine section 22 (e.g., the last turbine stage 74) and / or the exhaust section 24. For example, the flow control vane 13 can be biased towards the retracted position by one or more springs, and when the reverse flow of the exhaust gas overcomes the spring force, the flow control vane 13 can be moved from the retracted position to the extended position. In a further example, the flow control vane 13 can be biased towards the extended position by one or more springs, and when the normal flow of the exhaust gas overcomes the spring force, the flow control vane 13 can be moved from the extended position to the retracted position, and also, in the case of low flow rate and / or reverse flow of the exhaust gas, the flow control vane 13 can be held in the extended position by the spring force.

[0026] The flow control vane 13 coupled to the auxiliary strut 50 can operate in a similar manner such that the flow control vane 13 can selectively move between the extended position and the retracted position. For example, the flow control vane 13 can be oriented axially along the longitudinal axis 32 in the retracted position (e.g., the axial position), while the flow control vane 13 can be oriented in a direction intersecting the longitudinal axis 32 (e.g., oriented in the circumferential direction 36) in the extended position (e.g., the circumferential position). The flow control vane 13 coupled to the auxiliary strut 50 may be actively operated by the actuator 70 and the controller 60 as described above, or the flow control vane 13 may be passively operated in response to the operating conditions (e.g., reverse flow and / or low flow rate of the exhaust gas). Various aspects of the flow control vane 13 coupled to the auxiliary strut 50 will be described in more detail below.

[0027] As shown in FIG. 3, the inner flow control vane 92 extends radially outward from the inner exhaust wall 56 at an axial position (e.g., the axial position measured from the downstream edge 99 adjacent to the inner exhaust wall 56) that is downstream by an inner axial distance 96 in the longitudinal direction 32 from the downstream edge 99 (e.g., the trailing edge) of the blade 54 of the final stage. The inner axial distance 96 is shorter than the axial length 98 between the downstream edge 99 (e.g., the trailing edge) of the blade 54 of the final stage and the upstream edge 101 (e.g., the leading edge) of the strut 48 and / or the auxiliary strut 50. For example, the inner axial distance 96 can be in the range of 10 to 90 percent, 15 to 85 percent, 20 to 80 percent, 25 to 75 percent, 30 to 70 percent, 35 to 65 percent, 40 to 60 percent, or 45 to 55 percent of the axial length 98. In some embodiments, the inner axial distance 96 may be shorter than, equal to, or longer than the value of 10, 20, 30, 40, 50, 60, or 70 percent of the axial length 98, while the inner control vane 92 is located upstream of the strut 48 and / or the auxiliary strut 50. For example, the inner axial distance 96 may be a value of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 percent of the axial length 98, or a value plus or minus about 1, 2, 3, 4, 5 percent of the axial length 98.

[0028] The radial length 100 of the inner flow control vane 92 (e.g., a height of 34 in the radial direction) is shorter than the radial width 102 extending from the inner exhaust wall 56 to the outer exhaust wall 58 (e.g., the radial width 102 measured from the axial position of the inner flow control vane 92). For example, the radial length 100 of the inner control vane 92 can be in the range of 10 to 20 percent, 10 to 30 percent, 10 to 40 percent, 10 to 50 percent, or 10 to 60 percent of the radial width 102. In some embodiments, the radial length 100 may be shorter than, equal to, or longer than a value of 5 percent, 10 percent, 15 percent, 20 percent, 25 percent, 30 percent, 35 percent, 40 percent, 45 percent, 50 percent, 55 percent, or 60 percent of the radial width 102, but the radial length 100 is shorter than the radial width 102. For example, the radial length 100 may be a value of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of the radial width 102, or a value plus or minus about 1, 2, 3, 4, 5 percent of the radial width 102.

[0029] In certain embodiments, the exhaust section 24 includes one or more sets of outer flow control vanes 94 disposed on the outer exhaust wall 58. The outer flow control vanes 94 extend radially inwardly from the outer exhaust wall 58 at an axial position (e.g., an axial position measured from the downstream edge 99 (e.g., trailing edge) of the final stage blade 54) that is downstream by an outer axial distance 104 in the longitudinal direction 32 by an outer axial distance 104. The outer axial distance 104 is shorter than the axial length 98 between the downstream edge 99 (e.g., trailing edge) of the final stage blade 54 and the upstream edge 101 (e.g., leading edge) of the strut 48 and / or the auxiliary strut 50. For example, the outer axial distance 104 can range from 10 to 90 percent, 15 to 85 percent, 20 to 80 percent, 25 to 75 percent, 30 to 70 percent, 35 to 65 percent, 40 to 60 percent, or 45 to 55 percent of the axial length 98. In some embodiments, the outer axial distance 104 may be shorter than, equal to, or longer than the value of 10, 20, 30, 40, 50, 60, or 70 percent of the axial length 98, while the outer control vane 94 is located upstream of the strut 48 and / or the auxiliary strut 50. For example, the outer axial distance 104 may be a value of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 percent of the axial length 98, or a value plus or minus about 1, 2, 3, 4, 5 percent of the axial length 98.

[0030] In certain embodiments, the outer flow control vanes 94 can be axially (e.g., in the longitudinal direction 32) aligned with respect to the inner control vanes 92 such that the inner axial distance 96 and the outer axial distance 104 are the same as each other and the axial positions of the vanes 92 and 94 are the same as each other. However, in some embodiments, one or more sets of the outer flow control vanes 94 can be arranged at an upstream position, a downstream position, and / or an axially aligned position with respect to the axial positions of one or more sets of the inner flow control vanes 92.

[0031] The radial length 106 of the outer flow control vane 94 (e.g., the height in the radial direction 34) is shorter than the radial width 102 that extends between the inner exhaust wall 56 and the outer exhaust wall 58 (e.g., the radial width 102 measured from the axial position of the outer flow control vane 94). For example, the radial length 106 of the outer flow control vane 94 can be in the range of 10 to 20 percent, 10 to 30 percent, 10 to 40 percent, 10 to 50 percent, or 10 to 60 percent of the radial width 102 at the axial position of the outer flow control vane 94. In some embodiments, the radial length 106 is shorter than, equal to, or longer than a value of 5 percent, 10 percent, 15 percent, 20 percent, 25 percent, 30 percent, 35 percent, 40 percent, 45 percent, 50 percent, 55 percent, or 60 percent of the radial width 102, and the radial length 106 is shorter than the radial width 102. For example, the radial length 106 may be a value of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of the radial width 102, or a value plus or minus about 1, 2, 3, 4, 5 percent of the radial width 102.

[0032] In certain embodiments, the radial lengths 100 and 106 may be the same as or different from each other. For example, the radial length 106 of one or more sets of the outer flow control vanes 94 may be shorter than, equal to, or longer than the radial length 100 of one or more sets of the inner flow control vanes 92. In embodiments where the axial positions of the inner flow control vanes 92 and the outer flow control vanes 94 are aligned, the radial lengths 100, 106 of each control vane of the inner flow control vanes 92 and the outer flow control vanes 94 are shorter than 40 percent of the radial width 102.

[0033] The inner flow control vane 92 is configured to divide a hub vortex (or reverse flow 113) into an upstream hub vortex 112 and a downstream hub vortex 114 with respect to the downstream direction 109 of the exhaust gas flowing through the turbine section 22 and the exhaust section 24, in order to suppress the formation of a hub vortex (for example, a vortex adjacent to the inner exhaust wall 56 or the hub) caused by the reverse flow 113 that occurs behind the final stage blade 54 (for example, behind the final turbine stage 74). As shown in the figure, the inner flow control vane 92 is configured to separate the reverse flow 113 (for example, the exhaust gas flowing in the direction opposite to the downstream direction 109) into the downstream hub vortex 114 (for example, a vortex having a low tangential velocity) and the upstream hub vortex 112. By separating the upstream hub vortex 112 and the downstream hub vortex 114 by the inner flow control vane 92, the upstream hub vortex 112 can maintain a high tangential velocity, thereby reducing the velocity gradient in the shear layer 116 located immediately downstream of the final stage blade 54. By reducing the velocity gradient in the shear layer 116, the possibility of forming a fairly large non-axisymmetric stall cell is reduced.

[0034] In a particular embodiment, the upstream surface 118 of the inner flow control vane 92 is smooth in order to reduce the friction between the upstream hub vortex 112 and the inner flow control vane 92, thereby reducing the decrease in the tangential velocity of the upstream hub vortex 112. Additionally or alternatively, the downstream surface 120 of the inner flow control vane 92 can include a swirler feature (for example, a protruding turning vane and / or a concave turning slot) configured to increase the tangential velocity of the reverse flow 113 flowing towards the upstream hub vortex 112, as will be described in more detail below. For example, as will be described in more detail below, the turning vanes 210 of FIGS. 6-8 and / or the flow control vane 13 of FIG. 11 can be oriented to induce and / or increase the tangential velocity of the upstream hub vortex 112.

[0035] In certain embodiments, the turbine section 22 includes one or more sets of outer flow control vanes 95 disposed on an outer turbine wall 76 within the turbine section 22. As shown, the outer flow control vanes 95 extend radially inwardly from the outer turbine wall 76 at an intermediate position within the final turbine stage 74 (e.g., an intermediate axial position between the final stage vanes 108 (e.g., vanes 46 of the final turbine stage 74) and the final stage blades 54 (e.g., blades 44 of the final turbine stage 74) of the turbine section 22). In the illustrated embodiment, the radial length 110 (e.g., height in the radial direction 34) of the outer flow control vanes 95 is shorter than the radial width 111 that extends from the inner turbine wall 78 to the outer turbine wall 76 of the turbine section 22 within the final turbine stage 74. For example, the radial length 110 of the outer flow control vanes 95 can range from 10 to 20 percent, 10 to 30 percent, 10 to 40 percent, 10 to 50 percent, or 10 to 60 percent of the radial width 111 at the axial position of the outer flow control vanes 95. In some embodiments, the radial length 110 is shorter than, equal to, or longer than a value of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of the radial width 111, and the radial length 110 is shorter than the radial width 111. For example, the radial length 110 may be a value of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of the radial width 111, or a value plus or minus about 1, 2, 3, 4, 5 percent of the radial width 111.

[0036] In the illustrated embodiment, the outer flow control vanes 95 are disposed between the final stage vanes 108 and the final stage blades 54 of the final turbine stage 74, but the outer flow control vanes 95 can be disposed on the outer turbine wall 76 between the blades 44 and the vanes 46 in a pair of adjacent blades 44 and vanes 46 spaced axially apart within the turbine section 22 (e.g., within the same turbine stage or between different turbine stages).

[0037] The outer flow control vane 95 is configured to divide a toroidal vortex (or the reverse flow 121), for example, a vortex adjacent to the outer turbine wall 76 in the final turbine stage 74, into an upstream toroidal vortex 122 and a downstream toroidal vortex 124 in order to suppress the formation of a toroidal vortex (for example, a vortex adjacent to the outer turbine wall 76 in the final turbine stage 74) due to the reverse flow 121 behind the final stage vane 108. The reverse flow 121 has a high tangential velocity due to the rotation of the final stage blade 54. As shown, the outer flow control vane 95 is configured to separate the downstream toroidal vortex 124 (for example, a vortex having a high tangential velocity due to the rotation of the final stage blade 54) from the upstream toroidal vortex 122 (for example, a vortex having a low tangential velocity adjacent to the final stage vane 108). By separating the upstream toroidal vortex 122 and the downstream toroidal vortex 124 by the outer flow control vane 95, the upstream toroidal vortex 122 can reduce its tangential velocity to achieve a low tangential velocity adjacent to the final stage vane 108, thereby reducing the velocity gradient in the shear layer 126 located immediately downstream of the final stage vane 108. By reducing the velocity gradient in the shear layer 126, the possibility of forming a fairly large non-axisymmetric stall cell in the final turbine stage 74 is reduced.

[0038] In certain embodiments, the upstream surface 128 and / or the downstream surface 130 of the outer flow control vane 95 includes swirling features (for example, counter-swirling features and / or reverse-swirling features) configured to oppose the tangential velocity of the reverse flow 121, thereby reducing, making zero, or making negative the tangential velocity of the upstream toroidal vortex 122 adjacent to the final stage vane 108. For example, as will be described in more detail below, the swirling vanes 210 of FIGS. 6-8 and / or the flow control vane 13 of FIG. 11 can be oriented to reduce the tangential velocity of the upstream toroidal vortex 122. In some embodiments, the downstream surface 130 of the outer flow control vane 95 is smooth so that the tangential velocity of the downstream toroidal vortex 124 is maintained in the same rotational direction as the final stage blade 54, which will be described in more detail below.

[0039] In certain embodiments, the outer flow control vane 94 is configured to change the orientation of the exhaust flow path 90, and the outer flow control vane 94 changes the exhaust flow path 90 inwardly between the inner flow control vane 92 and the outer flow control vane 94. By changing the exhaust flow path 90 inwardly, the effect of the inner flow control vane 92 can be further improved. In some embodiments, using the same principle, the effect of the outer flow control vane 95 can be further improved by one or more sets of inner flow control vanes 132 axially disposed on the inner turbine wall 78 between the final stage vane 108 and the final stage blade 54. In certain embodiments, the recirculation obstruction system 11 can include any number and configuration of sets of flow control vanes 13 (e.g., 92, 94, 95, 132, etc.) provided along the inner turbine wall 78 and the outer turbine wall 76 of the final turbine stage 74 and / or along the inner wall 56 and the outer wall 58 of the exhaust section 24 and / or coupled to the auxiliary struts 50 between adjacent struts 48. However, in certain embodiments, certain flow control vanes 13 can be optionally provided and / or certain flow control vanes 13 can be excluded. For example, the outer flow control vanes 94 and 95 and the inner flow control vane 132 can be omitted from the recirculation obstruction system 11 in certain embodiments.

[0040] The turbine section 22 and / or the exhaust section 24 can include a combination of flow control vanes 13 (e.g., inner flow control vanes 92 and 132 and outer flow control vanes 94 and 95). In this case, among different sets of the flow control vanes 13, the number, radial length, circumferential spacing, shape, and other characteristics of the flow control vanes 13 may be the same as or different from each other. In a particular embodiment, the exhaust section 24 can include the inner flow control vane 92. In other embodiments, the exhaust section 24 can include both control vanes, the inner flow control vane 92 and the outer flow control vane 94. In a particular embodiment, the turbine section 22 can include the outer flow control vane 95. In other embodiments, the turbine section 22 can include the outer flow control vane 95 and the inner flow control vane 132. In a particular embodiment, the exhaust section 24 can include the inner flow control vane 92 and the outer flow control vane 94, and the turbine section 22 can include the outer flow control vane 95 and the inner flow control vane 132. In each of these embodiments, the exhaust section 24 may or may not include the flow control vane 13 coupled to the auxiliary strut 50.

[0041] In a particular embodiment, the turbine section 22 may include the flow control vanes 95 and / or 132, and the exhaust section 24 may not include the flow control vanes. That is, in a particular embodiment, the flow control vane 13 may be arranged longitudinally between the final stage vane 108 and the final stage blade 54, but may not be arranged between the final stage blade 54 and the strut 48. The flow control vanes 95, 132 that can be arranged in the turbine section 22 will be described in more detail herein.

[0042] FIG. 4 is a side cross-sectional view of the recirculation prevention system 11 of FIG. 2 taken along the longitudinal axis 32, showing a plurality of flow control vanes 13 configured to move between a retracted position and an extended position relative to a wall 151 (e.g., the inner turbine wall 78 and / or the outer turbine wall 76 of the turbine section 22, and / or the inner exhaust wall 56 and / or the outer exhaust wall 58 of the exhaust section 24). The flow control vanes 13 can include one or more sets of flow control vanes 140, one or more sets of flow control vanes 142, one or more sets of flow control vanes 144, and one or more sets of flow control vanes 146, and each set of flow control vanes 140, 142, 144, and 146 includes a plurality of flow control vanes (e.g., at least 5, 10, 15, 20, 30, 40, 50, 100, or more flow control vanes) spaced circumferentially from each other about the longitudinal axis 32 at a common axial position. One or more sets of the illustrated flow control vanes 13 (e.g., 140, 142, 144, and 146) can be used independently of, or in combination with, any of the flow control vanes described herein (e.g., 92, 94, 95, and 132).

[0043] The flow control vanes 13 (e.g., 140, 142, 144, and 146) are shown in the extended position, in which position the flow control vanes 13 are used to prevent backflow of the exhaust gas and to separate vortices (e.g., hub vortices or torus vortices) as described above. The flow control vanes 13 (e.g., 140, 142, 144, and 146) are configured to move between the extended position and the retracted position by active control by the actuator 70 and the controller 60, or by passive control in response to a low flow rate and / or backflow of the exhaust gas. As shown, the flow control vanes 13 can be extended by an actuator 70 (e.g., an electric actuator, a pneumatic actuator, a hydraulic actuator, etc.), and the actuator 70 is coupled to the flow control vanes 13 and communicatively coupled to the controller 60.

[0044] The flow control vanes 13 (e.g., 140, 142) are configured to move between a retracted position and an extended position relative to the wall 151 by an axial movement (e.g., radial direction 34) across the wall 151, both towards and away from the wall 151. In certain embodiments, the flow control vanes 13 (e.g., 140, 142) extending radially outward from the wall 151 can include extending linearly from a recess 150 disposed in the wall 151. In the illustrated embodiment, the flow control vanes 13, 140 extend and retract perpendicular (e.g., 90 degrees) to the recess 150 of the wall 151, and the flow control vanes 13, 142 can extend and retract at an angle 154 to the recess 150 of the wall 151. Thus, the flow control vane 140 and its recess 150 can be perpendicular to the wall 151, while the flow control vane 142 and its recess 150 can be inclined at an angle 154 to the wall 151.

[0045] In each configuration, the flow control vanes 13 (e.g., 140, 142) move linearly or axially in and out of the recess 150. The recess 150 is sized to accommodate a single flow control vane 13 (e.g., 140, 142), in which case the wall 151 can define a corresponding plurality of recesses 150. As an alternative, the recess 150 can be sized to accommodate a plurality of flow control vanes 13 (e.g., 140, 142), in which case the number of recesses 150 disposed circumferentially in the wall 151 is less than the number of flow control vanes 13. In yet another embodiment, the recess 150 can be an annular recess sized to accommodate a circumferential array of flow control vanes 150. The wall 151 can include an inner turbine wall 78, an outer turbine wall 76, an inner exhaust wall 56, or an outer exhaust wall 58, and thus the flow control vanes 13 (e.g., 140, 142) can extend radially inward or radially outward in the illustrated extended position.

[0046] In certain embodiments, the flow control vane 13 (e.g., 142) is oriented at an angle 154 measured in a counterclockwise direction 156 from the wall 151 to the flow control vane 13 (i.e., in the angular direction from the longitudinal axis 32 to the radial axis 34), and the angle 154 can be in the range of 10 degrees to 90 degrees, 20 degrees to 80 degrees, 30 degrees to 70 degrees, or 40 degrees to 60 degrees. For example, the angle 154 can be less than, equal to, or greater than 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, or 90 degrees, and can be an angle plus or minus 5 degrees or 10 degrees from that angle. In the illustrated embodiment, the angle 154 of the flow control vane 13 (e.g., 142) is a fixed angle. In some embodiments, the angle 154 of the flow control vane 13 (e.g., 142) can be a variable angle.

[0047] The flow control vanes 13, 144 are configured to move between a retracted position and an extended position relative to the wall 151 by rotational movement. In certain embodiments, the radial extension of the flow control vanes 13, 144 can include the rotation of the flow control vane 13 about a pivot 158 (e.g., a pivot joint, a rotary joint, or a hinge) that extends in the lateral direction 159 (e.g., the circumferential direction 36) of the exhaust portion 24. In the illustrated embodiment, the flow control vanes 13, 144 are configured to rotate from a recess 160 in the wall 151 to an upright (e.g., extended) position at an angle 145 relative to the wall 151. As shown, the actuator 70 can be coupled to the controller 60 and configured to drive the flow control vane 13 by a curved arm 162 that extends from and retracts into a curved recess 164. Additionally or alternatively, the actuator 70 can be coupled to the pivot 158 and configured to directly operate the pivot 158 by the torque applied to the axis of rotation of the pivot 158.

[0048] The rotation of the flow control vane 13 about the pivot 158, by which the flow control vane 13 extends radially, will be described in more detail herein. In the illustrated embodiment, the pivot 158 is disposed at the upstream end 161 of the flow control vane 13, and the flow control vane 13 is configured to rotate in the upstream direction while extending. In a particular embodiment, the pivot 158 may be disposed at the downstream end 163 of the flow control vane 13, and the flow control vane 13 may be configured to rotate in the downstream direction while extending.

[0049] In a particular embodiment, the angle 145 of the flow control vane 13 (e.g., 144) in the extended position may be a preset (e.g., a fixed angle) or variable (e.g., a continuously variable angle or a plurality of different preset angles). The angle 145 can be in the range of 10 degrees to 90 degrees, 20 degrees to 80 degrees, 30 degrees to 70 degrees, or 40 degrees to 60 degrees. For example, the angle 145 may be less than, equal to, or greater than 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, or 90 degrees, and may be an angle plus or minus 5 degrees or 10 degrees from that angle. In a particular embodiment, the controller 60 can control the actuator 60 such that the angle 145 in the extended position is adjusted based on various operating conditions (e.g., low flow rate and / or reverse flow rate, what percentage of load conditions of partial load conditions, etc.).

[0050] The flow control vanes 13, 146 are configured to move between a retracted position and an extended position relative to the wall 151 by axial movement along the wall 151 (e.g., along the longitudinal axis 32) towards and away from the radial wall 165. The radial wall 165 can extend radially away from the wall 151 at an angle (such as an angle less than, equal to, or greater than 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, or 90 degrees). The radial wall 165 can be associated with a folded or bent portion of the exhaust section 24 (e.g., the rotating duct portion). In certain embodiments, the radial extension of the flow control vanes 13, 146 can include axial movement in the upstream direction 169 from recesses 166 disposed in the radial wall 165 (e.g., struts 48, struts 50). In certain embodiments, the bottom 167 of the flow control vane 13 (e.g., 146) can be a rail 168 disposed on the wall 151 and can be coupled to a rail 168 (e.g., an axial guide) that extends away from the recesses 166 of the radial wall 165 in the upstream direction 169.

[0051] For example, the rail 168 extends in the axial direction 32 and includes a male rail portion coupled to the female rail portion, and the rail 168 enables the flow control vanes 13, 146 to move axially while preventing them from moving in the radial direction 34 and the circumferential direction 36. The female rail portion may be disposed on the wall 151, while the male rail portion may be disposed on the flow control vanes 13, 146, or the male rail portion may be disposed on the wall 151 and the female rail portion may be disposed on the flow control vanes 13, 146. In any configuration, the rail 168 includes mating first and second rail portions, each disposed on the wall 151 and the flow control vanes 13, 146. In a particular embodiment, the rail 168 includes one or more wheels disposed within the rail (e.g., an axial rail). In a particular embodiment, the flow control vanes 13, 146 can be configured to extend from the recess 166 by sliding along the rail 168 in the upstream direction 169 away from the radial wall 165.

[0052] The flow control vanes 13, 146 can be actuated to move axially along the rail 168 by one or more actuators 70 coupled to the controller 60 and / or by passive operation. In a particular embodiment, the axial movement of the flow control vanes 13, 146 can be by passive operation (such as low flow operating conditions (e.g., part load or transient operating conditions), backflow of exhaust gas, or a combination thereof) based on one or more operating conditions of the turbine system 10. For example, the flow control vanes 13, 146 can extend axially in the upstream direction 169 from the retracted position of the recess 166 to the extended position in response to the backflow of exhaust gas exceeding a threshold velocity.

[0053] In certain embodiments, the flow control vanes 13, 146 are spring-biased downstream towards the recess 166 by one or more springs, and if the backflow of the exhaust gas overcomes the spring force, the flow control vane 13 can move upstream in the upstream direction 169 and move from the retracted position to the extended position. In certain embodiments, the flow control vanes 13, 146 can be spring-biased upstream away from the recess 166 in the upstream direction 169, in which case, if the normal downstream flow of the exhaust gas (e.g., during normal full load, steady state conditions of the turbine system 10) overcomes the spring force, the flow control vane 13 can move downstream and move from the extended position to the retracted position, and if the exhaust gas is of low flow rate and / or the exhaust gas is flowing back, it is insufficient to overcome the spring force, and thus, due to the spring force, the flow control vane 13 can move upstream in the upstream direction 169 and move from the retracted position to the extended position.

[0054] Each set of flow control vanes 13 (e.g., 140, 142, 144, and 146) is configured to move between a stowed position and an extended position relative to the wall 151 by active control by the actuator 70 and the controller 60 and / or passive control (e.g., biasing the flow control vanes 13 to move in response to flow conditions such as low exhaust gas flow and / or exhaust gas backflow). In certain embodiments, the actuator 70 (e.g., an actuator assembly) can be operated to extend or retract the flow control vanes 13 in response to receiving an instruction (e.g., a signal) from the controller 60. In certain embodiments, the controller 60 is configured to instruct the actuator 70 based on one or more operating conditions of the exhaust section 24 (e.g., low exhaust gas flow and / or exhaust gas backflow), operating conditions of the turbine system 10 (e.g., full load condition, partial load condition, steady state condition, transient condition, etc.). For example, the controller 60 can instruct the actuator 70 to extend the flow control vanes 13 in response to a decrease in the speed of the gas turbine engine 12 to a partial speed (e.g., a low speed in a partial load condition), and can instruct the actuator 70 to retract the flow control vanes 13 in response to the gas turbine engine 12 operating at a full speed (e.g., a full speed in a full load condition). Additionally or alternatively, the flow control vanes 13 can be operated passively and / or manually (e.g., by operator input).

[0055] In certain embodiments, any embodiment regarding extending the flow control vane 13 (e.g., extending linearly, rotating about a pivot, moving axially) may be used alone or in combination with other embodiments. It should be understood that these embodiments are applicable to each control vane of the inner flow control vane 13 (e.g., 92, 132) and the outer flow control vane 13 (e.g., 94, 95). In certain embodiments, one embodiment of extending the flow control vane 13 (e.g., 140, 142, 144, and 146) may be employed at one location, and another embodiment of extending the flow control vane 13 (e.g., 140, 142, 144, and 146) may be employed at another location. For example, each inner flow control vane can rotate about a pivot, while the outer flow control vane can extend linearly from the recess.

[0056] FIG. 5 is a cross-sectional view taken along the radial axis 34 of an embodiment of the gas turbine engine 12 of FIG. 2, showing the flow control vanes 13 of the recirculation prevention system 11 in the inner exhaust wall 56 and the outer exhaust wall 58 of the turbine section 22 (e.g., the final turbine stage 74) and / or the exhaust section 24. In the illustrated embodiment, the flow control vane 13 includes a plurality of inner flow control vanes 92 arranged circumferentially about the longitudinal axis 32. The plurality of inner flow control vanes 92 align their axial positions to a common axial position (e.g., the axial position relative to the longitudinal axis 32) along the inner exhaust walls 78, 56 (e.g., the inner diameter) of the turbine section 22 and / or the exhaust section 24 to form an inner dam 190 (e.g., a segmented inner dam, a segmented inner ring).

[0057] As shown, while the inner flow control vanes 92 are disposed in the extended position, the upstream surface 118 and the downstream surface 120 (e.g., the surface with respect to the axial direction) of each inner flow control vane 92 are configured such that the adjacent upstream surface 118 and the downstream surface 120 (e.g., the adjacent surface with respect to the axial direction) of the adjacent inner flow control vane 92 overlap (e.g., contact) in the circumferential direction. In a particular embodiment, each inner flow control vane 92 can be configured such that the downstream surface 120 of each inner flow control vane 92 partially overlaps (e.g., underlaps) under the upstream surface 118 of the first adjacent inner flow control vane 92 in the circumferential direction 36, and the upstream surface 118 of each inner flow control vane 92 can partially overlap (e.g., overlaps) over the downstream surface 120 of the second adjacent inner flow control vane 92 in the circumferential direction 36, and the first and second inner flow control vanes 92 are disposed on opposite sides in the circumferential direction of each respective inner flow control vane 92. For example, the first and second inner flow control vanes 92 are arranged in opposite directions, clockwise and counterclockwise, or counterclockwise and clockwise, on opposite sides in the circumferential direction of each respective inner flow control vane 92 to define the overlap and / or underlap of the upstream surface 118 and the downstream surface 120, and the overlap and / or underlap of the upstream surface 118 and the downstream surface 120 can be defined.

[0058] In a particular embodiment, when the exhaust flow has a tangential flow in the circumferential direction 36 and a reverse flow in the upstream direction 169, the flow control vane 92 can be configured to overlap the upstream surface 120 over the downstream surface 118 in the same circumferential direction 36 (e.g., clockwise or counterclockwise) as the tangential flow to prevent the reverse flow in the upstream direction 169. In other words, each pair of adjacent inner flow control vanes 92 overlaps the upstream surface 118 and the downstream surface 120 along an overlap region (see FIG. 8) oriented on the side opposite to the circumferential direction 36 of the tangential flow, thereby blocking the leakage of the exhaust flow in the upstream direction 169. In other words, the aforementioned overlapping direction of the inner flow control vanes 92 can be based on the circumferential direction 36 of the flow (e.g., tangential flow) in the exhaust flow path 90 (e.g., the overlapping direction opposite to the direction of the tangential flow in the exhaust flow path 90).

[0059] For example, when the exhaust gas flow path 90 has a counterclockwise tangential flow in the reverse flow (e.g., the upstream direction 169), each inner flow control vane 92 can be configured to overlap with the adjacent inner flow control vane 92 in the clockwise direction 192. Since the overlapping direction is opposite to the direction of the tangential flow in the exhaust gas flow path 90, the reverse flow of the exhaust gas does not flow into the gap formed by the overlapping inner flow control vanes 92, but flows over the overlapping portion of the inner flow control vanes 92. However, the inner flow control vanes 92 may overlap with each other adjacent to the opposite side in the circumferential direction with the first and second inner flow control vanes 92 in any manner suitable for preventing the reverse flow of the exhaust gas. In certain embodiments, the inner flow control vanes 92 may operate passively, actively, or manually (e.g., operated by user input).

[0060] In the illustrated embodiment, the flow control vane 13 includes a plurality of outer flow control vanes 94 arranged in a circumferential direction about the longitudinal axis 32. The plurality of outer flow control vanes 94 are aligned in an axial position common to an axial position (e.g., an axial position relative to the longitudinal axis 32) along the outer exhaust wall 58 (e.g., outer diameter) to form an outer dam 194 (e.g., a segmented outer dam, a segmented outer ring). As shown, while the outer flow control vanes 94 are in the extended position, the upstream surface 196 and the downstream surface 198 (e.g., surfaces with respect to the axial direction) of each outer flow control vane 94 are configured such that the adjacent upstream surface 196 and the downstream surface 198 (e.g., adjacent surfaces in the axial direction) of the adjacent outer flow control vane 94 overlap in the circumferential direction. The circumferential overlap of the outer flow control vanes 94 is substantially the same as that discussed in detail with reference to the inner flow control vane 92. In a particular embodiment, the direction of overlap of the outer flow control vanes 94 may be opposite to the circumferential component of the flow in the exhaust passage 90, as detailed above with reference to the inner flow control vane 92. In a particular embodiment, the outer flow control vanes 94 may operate passively, actively, or manually (e.g., actuated by user input).

[0061] Furthermore, the flow control vane 13 can include a plurality of flow control vanes (e.g., inner flow control vane 132, outer flow control vane 95) axially arranged between the blades and vanes of the turbine section 22 of the last turbine stage 74. The plurality of flow control vanes 13 (e.g., 132) can form an inner dam so that their axial positions are aligned to a first common axial position (e.g., the axial position with respect to the longitudinal axis 32) along the inner exhaust wall 56 (e.g., inner diameter), and the plurality of flow control vanes 13 (e.g., 95) can form an outer dam by aligning their axial positions to a second common axial position (e.g., the axial position with respect to the longitudinal axis 32) along the outer exhaust wall 58 (e.g., outer diameter). The first common axial position may or may not be the same as the second common axial position. The circumferential overlap of the flow control vanes 13 (e.g., 95, 132) is substantially the same as that described in detail above with reference to the inner flow control vane 92. In a particular embodiment, the overlap direction of the flow control vanes 13 (e.g., 95, 132) can be opposite to the circumferential component of the flow in the exhaust passage 90, as described in detail above.

[0062] In the illustrated embodiment, 15 flow control vanes 13 arranged along the inner exhaust wall 56 and 32 flow control vanes 13 arranged along the outer exhaust wall 58 are shown, but it should be understood that any number of flow control vanes 13 can be arranged on the inner exhaust wall 56, or on the outer exhaust wall 58, or between the blades and vanes of the turbine section 22 (e.g., the last turbine stage 74). For example, at least 5, 10, 15, 30, 50, or 100 flow control vanes 13 can be arranged on the inner exhaust wall 56, or on the outer exhaust wall 58, or between the blades and vanes of the turbine section 22 (e.g., the last turbine stage 74).

[0063] FIG. 6 is a rear cross-sectional view taken along line 6-6 of an embodiment of the flow control vane 13 (e.g., 92, 94, 95, 132) of FIG. 5, showing the turning vane 210 on the downstream surface 212 of the flow control vane 13. In the illustrated embodiment, the turning vane 210 is angled circumferentially (e.g., in the circumferential direction 36) with respect to the radial direction 34 and is configured to induce circumferential swirl in the flow of exhaust gas in the exhaust passage. In a particular embodiment, the direction in which the turning vane 210 is angled is based on the position of the flow control vane 13. For example, in a particular embodiment, the inner flow control vane 13 (e.g., 92) and / or the outer flow control vane 13 (e.g., 94) located downstream of the final stage blade 54 may include a turning vane 210 angled in the same circumferential direction as the circumferential velocity component (e.g., tangential flow) of the reverse flow (e.g., upstream direction 169) in the exhaust passage. That is, if the exhaust passage has a circumferential velocity component (e.g., tangential flow) in the circumferential direction 36 (e.g., clockwise or counterclockwise), the turning vane 210 can be angled in the same circumferential direction 36 to increase the tangential velocity of the reverse flow in the exhaust passage (e.g., the velocity in the shaft rotation direction). It can be understood that by increasing the tangential velocity of the reverse flow in the exhaust passage, the velocity gradient of the shear layer in the exhaust passage located behind the final stage blade can be reduced, reducing or preventing the formation of rotating stall cells in the final stage turbine stage 74.

[0064] In certain embodiments, the inner flow control vane 13 (e.g., 132) and / or the outer flow control vane 13 (e.g., 95) disposed in the turbine section 22 (e.g., the final turbine stage 74) can include a turning vane 210 angled in a circumferential direction opposite to the circumferential velocity component (e.g., tangential flow) of the exhaust flow path. That is, when the exhaust flow path has a circumferential velocity component (e.g., tangential flow) in the circumferential direction 36 (e.g., clockwise or counterclockwise), the turning vane 210 can be angled in the opposite circumferential direction 36 (e.g., counterclockwise or clockwise). This is to reduce the tangential velocity (e.g., the velocity in the shaft rotation direction) of the reverse flow in the exhaust flow path before the reverse flow in the exhaust flow path impinges on the downstream edge (e.g., the trailing edge) of the final stage vane 108. In certain embodiments, it is desirable to slightly reverse the tangential direction component (e.g., the circumferential component) of the reverse flow in the exhaust flow path to better match the reverse flow to the shape (e.g., the airfoil shape) of the final stage vane 108.

[0065] In the illustrated embodiment, the turning vane 210 is shown as having a constant thickness 216 along the central axis 218 of the turning vane 210. In certain embodiments, the thickness 216 of the turning vane 210 may vary along the central axis 218. For example, the thickness 216 may increase or decrease from the inner radius 220 (e.g., radially inward) to the outer radius 222 (e.g., radially outward) of the flow control vane 13. Further, the thickness 216 may increase or decrease linearly, curvilinearly, and / or in a segmented manner. In certain embodiments, the turning vane 210 can include protrusions and / or recesses with respect to the downstream surface 212 of the flow control vane 13.

[0066] In certain embodiments, the swivel vane 210 can be folded into a recess disposed in the downstream surface 212 of the flow control vane 13. In certain embodiments, the swivel vane 210 may be used for all of the flow control vanes 13 or for a combination of the flow control vanes 13. In certain embodiments, the swivel vane 210 can be configured to extend in response to receiving an instruction (e.g., a signal) from the controller 60 through an actuator (e.g., an electric actuator, a pneumatic actuator, or a hydraulic actuator). In certain embodiments, the controller 60 can be configured to instruct the actuator based on one or more operating conditions of the turbine system 10. For example, the controller 60 can instruct the actuator to extend the swivel vane 210 in response to the speed of the gas turbine engine dropping to a partial speed (e.g., a low speed under partial load conditions), and can instruct the actuator to retract the swivel vane 210 in response to the gas turbine engine operating at full speed (e.g., full speed under full load conditions). Additionally or alternatively, the flow control vane 13 can be operated passively and / or manually (e.g., through operator input).

[0067] As shown in FIG. 6, the flow control vane 13 has circumferentially opposite surfaces 224 and 226, which are configured to overlap with adjacent flow control vanes 13 as described above with reference to FIG. 6. For example, the surface 224 of the illustrated flow control vane 13 overlaps with the surface 226 of the first adjacent flow control vane 13, and the surface 226 of the illustrated flow control vane 13 overlaps with the surface 224 of the second adjacent flow control vane 13. The circumferential overlap portion of the adjacent surfaces 224, 226 extends from the inner radius 220 to the outer radius 222, and the circumferential overlap portion is the portion between the upstream and downstream surfaces of the adjacent flow control vanes 13. In certain embodiments, as will be described later with reference to FIG. 8, the circumferential overlap between adjacent flow control vanes 13 can be angled at least partially.

[0068] FIG. 7 is a side cross-sectional view of one embodiment of the flow control vane 13 of FIG. 5 taken along line 7-7 of FIG. 6, showing one of the plurality of swivel vanes 210 protruding from the downstream surface 212 of the flow control vane 13. In the illustrated embodiment, the swivel vane 210 extends in the longitudinal direction 32 from the downstream surface 212 in the axial direction. In the illustrated embodiment, the height 230 of the swivel vane 210 is constant in the direction of the central axis 218 of the swivel vane 210. In a particular embodiment, the height 230 of the swivel vane 210 may vary along the central axis 218 of the swivel vane 210. For example, the height 230 can increase and / or decrease from the inner radius 220 to the outer radius 222 of the flow control vane 13. Further, the height 230 of the swivel vane 210 can increase and / or decrease linearly, curvilinearly, and / or in a segmented manner.

[0069] FIG. 8 is a top view of one embodiment of the flow control vane 13 of FIGS. 2-7, showing a portion (e.g., three) of a set of flow control vanes 13 that are in contact in the circumferential direction 36 to define a segmented annular dam 240 (e.g., an inner dam, an outer dam). In the illustrated embodiment, the flow control vane 13 is illustrated as having a bevel 242 (e.g., angled surfaces 224, 226) that overlaps (e.g., contacts, spreads over, or spreads under an adjacent flow control vane) an adjacent flow control vane 13. For example, the angled surface 242 can be oriented at an angle with respect to the longitudinal axis 32, and the angle can be between 10 and 80 degrees, 20 and 70 degrees, 30 and 60 degrees, or 40 and 50 degrees. In a particular embodiment, the upstream surface 118 and the downstream surface 120 of each flow control vane 13 can partially overlap the upstream surface 118 or the downstream surface 120 of an adjacent flow control vane 13 as described herein. In the illustrated embodiment, a plurality of swivel vanes 210 are present across the circumferential dimension 244 (e.g., width) of each flow control vane 13. In a particular embodiment, the plurality of swivel vanes 210 may be present over a portion of the circumferential dimension 244 such that a space is provided where the upstream surface 118 and the downstream surface 120 of adjacent flow control vanes 13 overlap.

[0070] In the illustrated embodiment, the flow control vane 13 is disposed axially upstream of the strut 48 and the auxiliary strut 50 with respect to the downstream direction 109 of the exhaust gas flowing from the turbine section 22 to the exhaust section 24. Although one strut 48 and one auxiliary strut 50 are shown in FIG. 8 for simplicity, the exhaust section 24 may include any number of struts 48 and auxiliary struts 50 in the circumferential direction about the longitudinal axis 32. Under certain operating conditions of the turbine system 10, the exhaust gas may be in a low flow state and / or a reverse flow state (i.e., a flow in the upstream direction 169 opposite to the downstream direction 109). For example, the low flow state and / or the reverse flow state may be caused by partial load conditions, transient conditions (e.g., start-up, shutdown, or other variable operations), or the operation of the turbine system 10 in other states that reduce the flow rate of the turbine section 22 and the exhaust section 24. The reverse flow state may include a reverse flow of the exhaust gas between the strut 48 and the auxiliary strut 50, as indicated by the arrow 246.

[0071] The reverse flow 246 has a flow that substantially coincides with the longitudinal axis 32 in the upstream direction 169. The reverse flow 246 substantially does not include a circumferential flow (e.g., a tangential flow) in the circumferential direction 36 in the region downstream of the flow control vane 13 (e.g., the segmented annular dam 240). However, the reverse flow 246 may include some circumferential flow. When the reverse flow 246 of the exhaust gas contacts the turning vane 210 disposed on the downstream surface 120 of the flow control vane 13 (e.g., the segmented annular dam 240), it is substantially directed (e.g., turned) in the circumferential direction 36, and a circumferential flow (e.g., a tangential flow) as indicated by the arrow 248 is obtained and / or increased on the upstream side of the flow control vane 13 (e.g., the segmented annular dam 240). In a particular embodiment, the turning vane 210 is angled in the same circumferential direction 36 as the rotational direction of the final stage blade 54 of the final turbine stage 74, thereby reducing the velocity gradient between the reverse flows 246, 248 and the final stage blade 54. By reducing the velocity gradient, the risk of forming a rotating stall cell in the final turbine stage 74 can be reduced.

[0072] In the illustrated embodiment, four turning vanes 210 disposed on the downstream surface 120 of each flow control vane 13 are shown, but any number of turning vanes 210 can be disposed on the downstream surface 120 of each flow control vane 13. For example, at least two, four, eight, ten, or twenty turning vanes 210 may be disposed on the downstream surface 120 of each flow control vane 13. Further, the number of turning vanes 210 disposed on the downstream surface 120 of each flow control vane 13 may be different for each flow control vane 13 and / or for each set of flow control vanes 13.

[0073] FIG. 9 is a perspective view of one embodiment of a set of flow control vanes 13 of FIGS. 2-5 in an extended position (e.g., a deployed configuration), each flow control vane 13 of the plurality of flow control vanes 13 includes a curved vane, and the plurality of flow control vanes 13, in total, define a curved annular dam. For example, each flow control vane 13 of the plurality of flow control vanes 13 may be curved radially (e.g., curved in the radial direction 34), may be curved circumferentially (e.g., curved in the circumferential direction 36), and / or may be curved axially (e.g., curved in the axial direction 32). The curved shape of the flow control vanes 13 is configured to allow the flow control vanes 13 to fold and deploy between a stored position and an extended position while allowing the flow control vanes 13 to slide smoothly relative to each other. In the illustrated embodiment, the upstream surface 118 and the downstream surface 120 of each flow control vane 13 are configured to overlap the adjacent upstream surface 118 and the adjacent downstream surface 120 of the adjacent flow control vane 13 while the flow control vane 13 is disposed in the extended position. As illustrated, the flow control vanes 13 are configured to rotate about a pivot 158 (e.g., a pivot joint, a rotary joint, or a hinge). In the illustrated embodiment, the pivot 158 is disposed at the upstream end 161 of the flow control vane 13. In a particular embodiment, the pivot 158 is disposed at the downstream end 163 of the flow control vane 13. The illustrated embodiment shows inner flow control vanes 13 (e.g., 92, 132), but this embodiment can also be used for flow control vanes 13 disposed elsewhere (e.g., outer flow control vanes 94, 95).

[0074] FIG. 10 is a perspective view of one embodiment of the set of flow control vanes 13 of FIGS. 5 and 9 in the storage position (e.g., the folded configuration). In the illustrated embodiment, the upstream surface 118 and the downstream surface 120 of each flow control vane 13 are configured to slide (e.g., move in a sliding manner) along the adjacent upstream surface 118 and the adjacent downstream surface 120 of the adjacent flow control vane 13 in order to transition from the extended position of FIG. 9 to the storage position of FIG. 10. As shown, the radially outer surface 260 of the flow control vane 13 has a curved annular shape configured to provide a substantially smooth surface across which exhaust gas can flow while the flow control vane 13 is in the storage position. For example, the curved annular shape can have a variable diameter in the longitudinal direction 32 since the set of curved flow control vanes 13 is folded or stored. The illustrated embodiment shows the inner flow control vanes 13 (e.g., 92, 132), but this embodiment can also be used with flow control vanes 13 located elsewhere (e.g., the outer flow control vanes 94, 95).

[0075] FIG. 11 is a top view of an embodiment of a set of flow control vanes 13 of FIGS. 2-7, the flow control vanes 13 being spaced from each other in a circumferential direction about the longitudinal axis 32 of the turbine section 22, and the flow control vanes 13 being angled with respect to the longitudinal axis 32 such that swirl (e.g., circumferential flow or tangential flow) is induced in the upstream exhaust gas backflows 246, 248 in the upstream direction 169 opposite the downstream direction 109. In the illustrated embodiment, the flow control vanes 13 are oriented at an angle 270 with respect to the longitudinal axis 32 in the circumferential direction 36. The angle 270 can be between 10 and 80 degrees, 20 and 70 degrees, 30 and 60 degrees, or 40 and 50 degrees. For example, the angle 270 can be less than, equal to, or greater than 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, or 80 degrees, and can be plus or minus 5 degrees or 10 degrees from that angle. Further, the plurality of flow control vanes 13 can be spaced from each other by a circumferential spacing 272 (e.g., a circumferential gap, distance, or separation). In some embodiments, the circumferential spacing 272 is uniform among all of the flow control vanes 13 of a particular set of flow control vanes 13 or a plurality of sets of flow control vanes 13. However, in some embodiments, the circumferential spacing 272 is variable between the flow control vanes 13 within a particular set or between different sets of flow control vanes 13. Further, in a particular embodiment, adjacent flow control vanes 13 at least partially overlap each other circumferentially between the upstream end 161 and the downstream end 163, and the terms "upstream" and "downstream" are relative to the flow of exhaust gas from the turbine section 22. However, each pair of adjacent flow control vanes 13 defines an intermediate flow path 274 that is oriented at the angle 270 such that swirl in the upstream exhaust gas backflows 246, 248 in the upstream direction 169 is induced.

[0076] In the illustrated embodiment, the flow control vane 13 is disposed axially upstream of the strut 48 and the auxiliary strut 50 with respect to the downstream direction 109 of the exhaust gas flowing from the turbine section 22 to the exhaust section 24. Although one strut 48 and one auxiliary strut 50 are shown in FIG. 11 for simplicity, the exhaust section 24 can include any number of struts 48 and auxiliary struts 50 arranged in a circumferential direction about the longitudinal axis 32. Under certain operating conditions of the turbine system 10, the exhaust gas may be in a low flow state and / or a reverse flow state due to the operation of the turbine system 10 under partial load conditions or transient conditions (e.g., start-up, shutdown, or other variable operation). The reverse flow state may include a reverse flow of exhaust gas between the strut 48 and the auxiliary strut 50, as indicated by the arrow 246.

[0077] The reverse flow 246 is in a flow that substantially coincides with the longitudinal axis 32 in the upstream direction 169, and the reverse flow 246 substantially does not include a circumferential flow (e.g., a tangential flow) in the circumferential direction 36 in a region downstream of the flow control vane 13 (e.g., the segmented annular dam 240). However, the reverse flow 246 may include some circumferential flow. When the reverse flow 246 of the exhaust gas contacts the angled flow control vane 13, it is substantially directed (e.g., swirled) in the circumferential direction 36, and a circumferential flow (e.g., a tangential flow) is obtained and / or increased as indicated by the arrow 248 on the upstream side of the flow control vane 13. In a particular embodiment, the flow control vane 13 is angled in the same circumferential direction 36 as the rotational direction of the final stage blade 54 of the final turbine stage 74, thereby reducing the velocity gradient between the reverse flows 246, 248 and the final stage blade 54. By reducing the velocity gradient, the risk of forming a rotating stall cell in the final turbine stage 74 can be reduced. In a particular embodiment, the flow control vane 13 has an airfoil shape between the downstream end 163 (e.g., the leading edge with respect to the reverse flow 246) and the upstream end 161 (e.g., the trailing edge with respect to the reverse flow 246).

[0078] In certain embodiments, the flow control vanes 13 with an angle 270 and a circumferential spacing 272 can be applied to the inner flow control vanes 13 (e.g., 92, 132) and / or the outer flow control vanes 13 (e.g., 94, 95). In certain embodiments, for each set of flow control vanes 13 (e.g., 92, 94, 95, 132), a combination of the characteristics of the flow control vanes (such as the combinations of characteristics shown in FIGS. 2-11) can be used. For example, one or more sets of the flow control vanes 13 in FIG. 11 may be used in combination with one or more sets of the flow control vanes 13 in FIGS. 6-8. Further, any of the embodiments of FIGS. 4, 9, and 10 may be used for the flow control vanes 13 of any configuration of the flow control vanes 13.

[0079] In other examples, the inner flow control vanes 13 (e.g., 92, 132) can include turning vanes 210 disposed on the downstream surface 212 of the inner flow control vanes 13 as shown in FIGS. 6-8, and the outer flow control vanes 13 (e.g., 94, 95) can include the flow control vanes 13 with an angle 270 and a circumferential spacing 272 as shown in FIG. 11, or vice versa. Further, the direction of turning imparted by the turning vanes 210 in FIGS. 6-8 and / or the flow control vanes 13 in FIG. 11 can be adjusted (e.g., clockwise or counterclockwise) according to the installation position in the turbine section 22 (e.g., the flow control vanes 95, 132) or the exhaust section 24 (e.g., the flow control vanes 92, 94). For example, the turning direction for the flow control vanes 13 in the exhaust section 24 can be the same as the rotation direction of the turbine section 22, while the turning direction for the flow control vanes 13 in the turbine section 22 (e.g., the final turbine stage 74) can be opposite to the rotation direction of the turbine section 22.

[0080] FIG. 12 is a cross-sectional view of an embodiment of a plurality of struts 48 and a plurality of auxiliary struts 50 (e.g., auxiliary airfoils), showing that the auxiliary strut 50 has a flow control vane 13 in a stowed position 278 (e.g., an axially aligned position) relative to the central engine axis 280. The flow control vane 13, while being part of the auxiliary strut 50, is configured to block reverse flow of exhaust gas in substantially the same manner as described in detail above. In the illustrated embodiment, the struts 48 and the auxiliary struts 50 extend radially 34 from an inner exhaust wall 56 (e.g., inner diameter) to an outer exhaust wall 58 (e.g., outer diameter). In the illustrated embodiment, the auxiliary struts 50 are circumferentially disposed (e.g., spaced apart or offset) between adjacent struts 48 (e.g., adjacent struts 287 and 289) of the exhaust section 24. As shown, each auxiliary strut 50 of the plurality of auxiliary struts 50 is disposed in a position sufficiently close to one of the adjacent struts 48 (e.g., the adjacent strut 287).

[0081] In certain embodiments, each of the plurality of struts 48 and the plurality of auxiliary struts 50 has an airfoil shape (e.g., a radial airfoil shape). As shown, the auxiliary strut 50 is divided to include an inner portion 282, a central portion 284 disposed radially outward of the inner portion 282, an outer portion 286 disposed radially outward of the central portion 284, and one or more strut pivots 288 (e.g., pivot joints, rotary joints, or hinges) radially coupled to the inner portion 282, the outer portion 286, and (in certain embodiments) the central portion 284. In the illustrated embodiment, the inner radial extent 290 (e.g., radial length) of the inner portion 282 and the outer radial extent 292 (e.g., radial length) of the outer portion 286 are shorter than the intermediate radial extent 294 (e.g., radial length) of the central portion 284. In certain embodiments, the inner radial extent 290 and the outer radial extent 292 are equal to, or longer than, the intermediate radial extent 294.

[0082] In certain embodiments, one or more of the inner portion 282, the central portion 284, and the outer portion 286 include or embody the flow control vane 13, which is adjustable or movable between a stowed position 278 shown in FIGS. 12 and 14 and an extended position 304 shown in FIGS. 13 and 15. For example, the inner portion 282 and the outer portion 286 of each auxiliary strut 50 can be adjustable between the stowed position 278 and the extended position 304, and each of the inner portion 282 and the outer portion 286 aligns with the longitudinal axis 32 and the central engine axis 280 at the stowed position 278 (e.g., an axially aligned position, a parallel position, or a folded position), and each of the inner portion 282 and the outer portion 286 extends circumferentially 36 between adjacent struts 48 (e.g., adjacent struts 287 and 289) at the extended position 304 (e.g., an angular position, a circumferential extended position, or a deployed position).

[0083] In some embodiments, the inner portion 282 and the outer portion 286 of each auxiliary strut 50 (and each set of auxiliary struts 50) can be adjustable between the extended position 278 and the stowed position 304 independently of each other and / or in synchronization with each other. Further, by making the inner portion 282 and the outer portion 286 of each auxiliary strut 50 (and each set of auxiliary struts 50) adjustable to different extended positions 304, different amounts of coverage (e.g., blocking the flow) can be achieved circumferentially along the inner exhaust wall 56 and the outer exhaust wall 58. Accordingly, the inner portion 282 and the outer portion 286 of each auxiliary strut 50 (and each set of auxiliary struts 50) may be coupled to independent actuators 70 independently controlled by the controller 60, or the inner portion 282 and the outer portion 286 of each auxiliary strut 50 (and each set of auxiliary struts 50) may be coupled to a common actuator 70 jointly controlled by the controller 60.

[0084] In the illustrated embodiment, eight struts 48 and eight auxiliary struts 50 arranged circumferentially are shown in the exhaust section 24, but any number of struts 48 and auxiliary struts 50 can be arranged in the exhaust section 24. For example, at least two, four, six, eight, ten, twelve, fourteen, sixteen, eighteen, twenty, or more struts 48 and auxiliary struts 50 may be arranged in the exhaust section 24. In the illustrated embodiment, there are the same number of auxiliary struts 50 as the struts 48, and one auxiliary strut 50 is arranged between two adjacent struts 48. In a particular embodiment, the number of auxiliary struts 50 can be a multiple of the number of struts 48. For example, at least two, three, or four auxiliary struts 50 can be arranged circumferentially between two adjacent struts 48.

[0085] FIG. 13 is a cross-sectional view of an embodiment of a plurality of struts 48 and a plurality of auxiliary struts 50, showing that the auxiliary strut 50 has a flow control vane 13 in an extended position 304 (e.g., a circumferential extended position, an angular position, or a deployed position) relative to the central engine axis 280. As shown, the inner portion 282, the outer portion 286, or both are configured to rotate about one or more strut pivots 288 from a stowed position 278 to an extended position 304. In the illustrated embodiment, the central portion 284 remains in a stationary position rather than rotating about one or more strut pivots 288. As shown, while the inner portion 282 is in the extended positions 304, 306, the inner portion 282 is configured to substantially expand (e.g., substantially block) across an inner circumferential distance 310 between adjacent struts 48. Further or alternatively, while the outer portion 286 is in the extended positions 304, 308, the outer portion 286 is configured to substantially expand (e.g., substantially block) across an outer circumferential distance 312 between adjacent struts 48. That is, the inner portion 282 is configured to at least substantially block (e.g., mostly block) an inner region 314 of the exhaust flow path 90 that is disposed directly radially outward from the inner exhaust wall 56, and the outer portion 286 is configured to at least substantially block (e.g., mostly block) an outer region 316 of the exhaust flow path 90 that is disposed directly radially inward from the outer exhaust wall 58.

[0086] In certain embodiments, gaps 318 (FIG. 16) can be disposed on both circumferential sides of the inner portion 282 or the outer portion 286. In the illustrated embodiment, the inner portion 282 and the outer portion 286 are configured to form an axially disposed axial opening 320 between the inner portion 282 and the outer portion 286, and the exhaust path can pass through the axial opening 320. In the illustrated embodiment, the inner portion 282 and the outer portion 286 are shown to curve circumferentially (e.g., curve in the circumferential direction 36). For example, the inner portion 282 can have a curvature (e.g., radius) that matches or substantially conforms to the curvature (e.g., radius) of the inner exhaust wall 56, and the outer portion 286 can have a curvature (e.g., radius) that matches or substantially conforms to the curvature (e.g., radius) of the outer exhaust wall 58. In certain embodiments, the inner portion 282 and the outer portion 286 can be substantially linear (e.g., straight, flat) in the circumferential direction 36.

[0087] FIG. 14 is a cross-sectional view of one embodiment of an auxiliary strut 50 circumferentially disposed between adjacent struts 48 shown in FIG. 12, showing the inner portion 282 and outer portion 286 of the auxiliary strut 48 in a stowed position 278 (e.g., an axially aligned position, a parallel position, or a folded position). Each auxiliary strut 50 has an upstream edge or leading edge 330 and a downstream edge or trailing edge 334, and each strut 48 has an upstream edge or leading edge 332 and a downstream edge or trailing edge 336. In the illustrated embodiment, the leading edge 330 of the auxiliary strut 50 is axially aligned with the leading edge 332 of adjacent struts 48 (e.g., adjacent struts 287 and 289). For example, the leading edges 330, 332 can be disposed at a common axial position on the longitudinal axis 32 and the central engine axis 280. In some embodiments, the leading edge 330 of the auxiliary strut 50 may be disposed upstream and / or downstream of the leading edge 332 of the strut 48. However, at least a portion of the auxiliary strut 50 is disposed downstream of the leading edge 332 of the strut 48. As shown, at least a portion of the inner portion 282, the central portion 284, the outer portion 286, and one or more strut pivots 288 are disposed downstream of the leading edge 332 of adjacent struts 48 (e.g., adjacent struts 287 and 289).

[0088] In the illustrated embodiment, the auxiliary strut 50 is shown as having an airfoil shape, and the leading edge 330 of the auxiliary strut 50 is disposed upstream of the trailing edge 334. In certain embodiments, the auxiliary strut 50 can have a rectangular shape, an elliptical shape, a polygonal shape, or an irregular curved shape. In the illustrated embodiment, the auxiliary strut 50 has an axial length 338 (e.g., the length from the leading edge 330 to the trailing edge 334) that is shorter than the axial length 340 (e.g., the length from the leading edge 332 to the trailing edge 336) of adjacent struts 48 (e.g., adjacent struts 287 and 289). In certain embodiments, the axial length 338 may be substantially equal to the axial length 340 of adjacent struts 48 (e.g., adjacent struts 287 and 289).

[0089] In the illustrated embodiment, the inner portion 282, the central portion 284, and the outer portion 286 have a substantially equal axial length 338. In certain embodiments, the axial lengths 338 of the inner portion 282, the central portion 284, and the outer portion 286 may be different from each other. In certain embodiments, the axial length 338 of the inner portion 282, the central portion 284, and / or the outer portion 286 of each auxiliary strut 50 may be shorter than the axial length 340 of the strut 48, may be equal to the axial length 340 of the strut 48, or may be longer than the axial length 340 of the strut 48. For example, each axial length 338 can be a length between 10 and 90 percent, 20 and 80 percent, 30 and 70 percent, or 40 and 60 percent of the axial length 340 of the strut 48. In other examples, the axial length 338 may be shorter than, equal to, (longer or shorter by 5 or 10 percent of the axial length 340) about 10, 20, 30, 40, 50, 60, or 70 percent of the axial length 340.

[0090] In the illustrated embodiment, when the inner portion 282 and the outer portion 286 are disposed in the storage position 278, the profile 342 (e.g., inner profile, perimeter, or airfoil portion) of the inner portion 282, the profile 344 (e.g., central profile, perimeter, or airfoil portion) of the central portion 284, and the profile 346 (e.g., outer profile, perimeter, or airfoil portion) of the outer portion 286 are configured to coincide with each other in the radial direction (e.g., in the radial direction 34). That is, in the illustrated embodiment, the profile 342 is substantially equal to the profiles 344 and 346. In certain embodiments, the profiles 342, 344, 346 may not be equal in shape and / or size. As shown, when the inner portion 282, the central portion 284, and the outer portion 286 are each disposed in the storage position 278 (e.g., an axially aligned position), the inner longitudinal axis 348 of the inner portion 282, the central longitudinal axis 350 of the central portion 284, and the outer longitudinal axis 352 of the outer portion 286 are substantially coaxial (e.g., coincident) and parallel with the corresponding longitudinal axis 354 of adjacent struts 48 (e.g., adjacent struts 287 and 289). However, at the storage position 278, the axes 348, 350, 352 of each auxiliary strut 50 are aligned with each other, defining a first radius passing through the auxiliary strut 50 between the central engine axis 280 and the outer exhaust wall 58, while the axis 354 of each strut 48 is aligned with a second radius offset in the circumferential direction 36 from the first radius, and the second radius can be defined to pass through the strut 48 between the central engine axis 280 and the exhaust wall 58. Thus, the first radius and the second radius may not be exactly parallel to each other.

[0091] FIG. 15 is a cross-sectional view of an embodiment of an auxiliary strut 50 between adjacent struts 48 (e.g., adjacent struts 287 and 289) shown in FIG. 13, and the central portion 284 of the auxiliary strut 50 is aligned with the longitudinal axis 32 and the central engine axis 280 in the axial direction, further showing that the inner portion 282 and the outer portion 286 are arranged at the extended position 304. As shown, when the inner portion 282 and the outer portion 286 are respectively arranged at the extended position 304, the inner longitudinal axis 348 of the inner portion 282 and the outer longitudinal axis 352 of the outer portion 286 are angled with respect to the corresponding longitudinal axis 354 of the adjacent struts 48 (e.g., adjacent struts 287 and 289).

[0092] In a particular embodiment, the inner angle 356 is the angle defined between the inner longitudinal axis 348 of the inner portion 282 and the central longitudinal axis 350 of the central portion 284, and the inner angle 356 is different from the outer angle 358 defined between the outer longitudinal axis 352 of the outer portion 286 and the central longitudinal axis 350 of the central portion 284. For example, the inner angle 356 may be greater than or less than the outer angle 358. That is, in a particular embodiment, the extended position 306 of the inner portion 282 may be angularly different from the extended position 308 of the outer portion 286.

[0093] In a particular embodiment, the inner angle 356 between the inner longitudinal axis 348 of the inner portion 282 and the central longitudinal axis 350 of the central portion 284 is substantially equal to the outer angle 358 between the outer longitudinal axis 352 of the outer portion 286 and the central longitudinal axis 350 of the central portion 284. That is, in a particular embodiment, the extended position 306 of the inner portion 282 may be substantially equivalent to the extended position 308 of the outer portion 286. The inner angle 356 and the outer angle 358 can each be an angle in the range of 10 degrees to 90 degrees, 20 degrees to 80 degrees, 30 degrees to 70 degrees, or 40 degrees to 60 degrees.

[0094] In certain embodiments, the controller 60 can control one or more actuators 70 to adjust the inner angle 356 and the outer angle 358 to be the same angle or different angles from each other in a continuously varying manner or a stepwise manner (e.g., varying the angle continuously or varying the angle in increments). In certain embodiments, the controller 60 can control one or more actuators 70 to move the inner portion 282 from the stowed position 278 to the extended position 304 while holding the outer portion 286 in the stowed position 278, or while moving the outer portion 286 from the extended position 304 to the stowed position 278, or vice versa. In certain embodiments, the inner angle 356 and / or the outer angle 358 can be an angle based on one or more operating conditions of the gas turbine engine. For example, the inner angle 356 and / or the outer angle 358 can be changed based on a low flow rate and / or a reverse flow condition in the exhaust section 24, the operating conditions of the turbine system 10 (e.g., part load, full load, steady state conditions, transient conditions (e.g., start or stop), or any combination thereof).

[0095] In certain embodiments, the inner portion 282 and the outer portion 286 can be configured to rotate simultaneously about one or more strut pivots 288 (e.g., equivalent kinematic trajectories). That is, the inner longitudinal axis 348 of the inner portion 282 and the outer longitudinal axis 352 of the outer portion 286 are configured to coincide radially while the inner portion 282 and the outer portion 286 are rotating.

[0096] In certain embodiments, the inner portion 282 and the outer portion 286 can be configured to rotate in a non-simultaneous manner (e.g., asynchronously). For example, the inner portion 282 can be configured to rotate from the stowed position 278 (e.g., the axially aligned position) to the extended position 304 before or after the outer portion 286 rotates from the stowed position 278 (e.g., the axially aligned position) to the extended position 304. In certain embodiments, the inner portion 282 and the outer portion 286 are configured to rotate about one or more strut pivots 288 independently of each other. For example, the inner portion 282 may or may not be internally coupled to the outer portion 286 (e.g., via one or more strut pivots 288).

[0097] FIG. 16 is a front view in line 16-16 of one embodiment of an auxiliary strut 50 between adjacent struts 48 of FIG. 13, and as shown in FIG. 15, the central portion 284 of the auxiliary strut 50 is axially aligned with the longitudinal axis 32 and the central engine axis 280, further showing that the inner portion 282 and the outer portion 286 of the auxiliary strut 50 are disposed in the extended position 304. In the illustrated embodiment, the recirculation obstruction system 11 includes an inner actuation assembly 370 (e.g., actuator 70) that operates the inner portion 282 such that the inner portion 282 rotates about one of the one or more strut pivots 288. Further, the recirculation obstruction system 11 includes an outer actuation assembly 372 (e.g., actuator 70) that operates the outer portion 286 such that the outer portion 286 rotates about one of the one or more strut pivots 288. In the illustrated embodiment, the inner actuation assembly 370 and the outer actuation assembly 372 are shown as being coupled to the same strut pivot 288 of the one or more strut pivots 288. In certain embodiments, the inner actuation assembly 370 can be directly coupled to the inner portion 282. Additionally or alternatively, the outer actuation assembly 372 can be directly coupled to the outer portion 286.

[0098] In the illustrated embodiment, the controller 60 instructs the inner motion assembly 370 to rotate the inner portion 282 about one or more pivots 288 based on one or more operating conditions of the turbine system 10 as described above. For example, the controller 60 can instruct the inner motion assembly 370 to rotate the inner portion 282 about one or more pivots 288 based on a low flow condition and / or a reverse flow condition of the exhaust gas. Further, the controller 60 instructs the outer motion assembly 372 to rotate the outer portion 286 about one or more pivots 288 based on one or more operating conditions of the turbine system 10. For example, the controller 60 can instruct the outer motion assembly 372 to rotate the outer portion 286 about one or more pivots 288 based on a low flow condition and / or a reverse flow condition of the exhaust gas. In certain embodiments, the inner motion assembly 370, the outer motion assembly 372, or both assemblies may operate actively, passively (e.g., operate at pressure or speed against a spring force), or both.

[0099] In the illustrated embodiment, the inner portion 282 is configured to substantially expand (e.g., substantially block) across an inner circumferential distance 310 between adjacent struts 48 while disposed in the extended position 306. Additionally or alternatively, the outer portion 286 is configured to substantially expand (e.g., substantially block) across an outer circumferential distance 312 between adjacent struts 48 while disposed in the extended position 308. That is, the inner portion 282 is configured to at least substantially block (e.g., mostly block) an inner region 314 of the exhaust flow path that is disposed radially outwardly directly from the inner exhaust wall 56, and the outer portion 286 is configured to at least substantially block (e.g., mostly block) an outer region 316 of the exhaust flow path 90 that is disposed radially inwardly directly from the outer exhaust wall 58.

[0100] In certain embodiments, the gap 318 can be disposed on both sides in the circumferential direction of the inner portion 282 or the outer portion 286. In the illustrated embodiment, the inner portion 282 and the outer portion 286 are configured to form an axial opening 320 disposed radially therebetween, and the exhaust flow path 90 can pass through the axial opening 320. In the illustrated embodiment, the inner portion 282 and the outer portion 286 are shown linearly in the circumferential direction. In certain embodiments, the inner portion 282 and the outer portion 286 may be substantially curved in the circumferential direction 36.

[0101] When the inner portion 282 and the outer portion 286 are disposed at the extended positions 306 and 308, the auxiliary strut 50 can separate the hub vortex and / or the torus vortex, as described in detail above. For example, the inner portion 282 of the auxiliary strut 50 disposed at the extended position 306 can function substantially the same as described in detail above with reference to the inner flow control vane 92, while the outer portion 286 of the auxiliary strut 50 disposed at the extended position 308 can function substantially the same as described in detail above with reference to the outer flow control vanes 94, 95. In other examples, the inner portion 282 of the auxiliary strut 50 disposed at the extended position 306 is configured to separate the reverse flow into a downstream hub vortex 114 (e.g., a vortex having a low tangential velocity) and an upstream hub vortex 112 (a vortex having a high tangential velocity), as described above with reference to FIG. 3. The auxiliary strut 50 can be used separately or in combination with flow control vanes 13 (such as the inner flow control vanes 92, 132 (e.g., inner dams) and the outer flow control vanes 94, 95 (e.g., outer dams) described herein).

[0102] FIG. 17 is a cutaway schematic view of an embodiment of the recirculation prevention system 11 of FIG. 2, showing a flow direction changing vane 390 (e.g., flow control vane 13) disposed in a storage position 392 within a recess 394 of an outer exhaust wall 58 of the recirculation prevention system 11. In the illustrated embodiment, the recirculation prevention system 11 includes an exhaust section 24. The exhaust section 24 includes an inner exhaust wall 56 (e.g., an inner diameter wall) that defines a radially inner boundary of the exhaust flow path 90, and an outer exhaust wall 58 that is located radially outward from the inner exhaust wall 56 and that defines a radially outer boundary of the exhaust flow path 90. The exhaust section 24 also includes a flow direction changing vane 390 disposed downstream of the final stage blade 54 (e.g., the final turbine stage 74) of the turbine section 22 and upstream of the strut 48 and / or auxiliary strut 50 of the exhaust section 24. The flow direction changing vane 390 includes a narrow end 396 and a wide end 402, as further described herein.

[0103] In the illustrated embodiment, the recirculation prevention system 11 includes a flow direction changing pivot 398 (e.g., a pivot joint, a rotary joint, or a hinge) coupled to the narrow end 396 of the flow direction changing vane 390. Further, the exhaust section 24 includes one or more flow direction changing actuators 400 (e.g., actuator 70), and the one or more flow direction changing actuators 400 are configured such that the wide end 402 of the flow direction changing vane 390 rotates relative to the narrow end 396, such that the flow direction changing vane 390 moves radially in the radial direction 34 of the exhaust section 24, or both. In the illustrated embodiment, the one or more flow direction changing actuators 400 are shown coupled to the flow direction changing pivot 398, but in a particular embodiment, the one or more flow direction changing actuators 400 may be coupled to one or more different portions of the flow direction changing vane 390.

[0104] FIG. 18 is a schematic cutaway view of an embodiment of the recirculation obstruction system 11 of FIGS. 2 and 17, showing the flow direction changing vane 390 extended into the exhaust section 24 in the extended position 401. In the illustrated embodiment, the narrow end 396 is disposed on the outer exhaust wall 58, and the wide end 402 is offset circumferentially 36 and axially 32 from the narrow end 396. Further, the wide end 402 is disposed radially 404 inward of the narrow end 396. In the illustrated embodiment, when the flow direction changing vane 390 is disposed in the extended position 401, the wide end 402 contacts the inner exhaust wall 56. In certain embodiments, the wide end 402 is disposed sufficiently close to the inner exhaust wall 56 but radially offset from the inner exhaust wall 56. In the illustrated embodiment, the wide end 402 is shown as being disposed upstream 169 of the exhaust section 24 with respect to the narrow end 396. In certain embodiments, the wide end 402 may be disposed downstream of the narrow end 396 or may be axially aligned with the narrow end 396.

[0105] In the illustrated embodiment, the radial extent 406 (e.g., radial width) of the wide end 402 is greater than the radial extent 408 of the narrow end 396. Further, the radial extent 406 of the wide end 402 is radially inward of the radial extent 408 of the narrow end 396. As shown, the flow direction turning vane 390 includes a curved wall 410 (e.g., a wall obtained by lofting) extending from the narrow end 396 to the wide end 402. In a particular embodiment, the curved wall 410 includes a loft 412 (e.g., a substantial loft) of a cross-section 414 along a curve 416 from the narrow end 396 to the wide end 402. That is, the cross-section 414 has a shape along the curve 416 from the narrow end 396 to the wide end 402, and the curved wall 410 is formed. As shown, the cross-section 414 (e.g., cross-sectional shape) includes a radial portion 418 extending substantially in the radially inward direction 404 and an axial portion 420 extending in a direction (e.g., perpendicular, orthogonal) intersecting from the radially outer edge 422 of the radial portion 418. As shown, the axial portion 420 extends substantially upstream in the direction 169 of the exhaust portion 24. Further, one or more dimensions of the cross-section 414 may vary from the narrow end 396 to the wide end 402. In the illustrated embodiment, the extent 426 (e.g., radial extent) of the radial portion 418 increases from the narrow end 396 to the wide end 402. In a particular embodiment, the extent 428 of the axial portion 420 varies (e.g., increases) from the narrow end 396 to the wide end 402.

[0106] In the illustrated embodiment, curve 416 includes a first curved portion 430 extending in the downstream direction of exhaust portion 24 from the narrow end 396 (e.g., the first end), and a second curved portion 431 extending in the upstream direction of exhaust portion 24 from the first curved portion 430. As shown, the first concave surface 432 and the second concave surface 433 of the first curved portion 430 are directed (e.g., face) in the upstream direction 169 of exhaust portion 24. As shown, the radius of curvature 434 of curve 416 increases from the narrow end 396 toward the wide end 402. That is, curve 416 curves further from the narrow end 396 toward the wide end 402. In the illustrated embodiment, the tangent line 436 (e.g., tangent line: tangent) of curve 416 is an acute angle clockwise with respect to the radially inward direction 404 and has a component in the upstream direction 169. In a particular embodiment, the tangent line 436 may have a component in the radial direction 404.

[0107] The flow direction conversion vane 390 captures a part of the exhaust flow path 90 having a high tangent velocity (e.g., free flow) from the outer exhaust wall 58, changes the direction, and mixes with the reverse flow 113 of the exhaust flow path 90 along the inner exhaust wall 56, thereby increasing the tangent velocity of the reverse flow 113 and reducing the velocity gradient of the shear layer 116 behind the final stage blade 54 of the turbine section 22 (e.g., the final turbine stage 74). In a particular embodiment, the flow direction conversion vane 390 can be used separately or in combination with the flow control vane 13 associated with the auxiliary strut 50 and / or the flow control vane 13 (e.g., the inner flow control vanes 92, 132 and / or the outer flow control vanes 94, 95) described herein.

[0108] FIG. 19 is a schematic cross-sectional view of the radial axis 34 at the storage position 392 of FIG. 17 of one embodiment of the set of flow direction conversion vanes 390 of FIGS. 17 and 18. In the illustrated embodiment, each flow direction conversion vane 390 is disposed radially outside the outer exhaust wall 58 while being disposed at the storage position 392. In certain embodiments, the flow direction conversion vane 390 is coupled to the inner exhaust wall 56, and the flow direction conversion vane 390 can retract radially inward of the inner exhaust wall 56 while being disposed at the storage position 392. That is, in certain embodiments, the flow direction conversion vane 390 can retract into a recess disposed in the inner exhaust wall 56. Regardless of the attachment position (i.e., the inner exhaust wall 56 or the outer exhaust wall 58), the flow direction conversion vane 390 is configured to curve circumferentially about the central engine axis 280 of the exhaust section 24 while being disposed at the storage position 392.

[0109] In the illustrated embodiment, a direction conversion actuator 400 is coupled to each flow direction conversion vane 390. As shown, the direction conversion actuator 400 is coupled to the direction conversion pivot 398 and the flow direction conversion vane 390. In certain embodiments, the direction conversion actuator 400 is coupled to either the direction conversion pivot 398 or the flow direction conversion vane 390. In the illustrated embodiment, each flow direction conversion vane 390 is operated by a separate direction change actuator 400. In certain embodiments, the direction conversion actuator 400 can be configured to operate two or more flow direction conversion vanes 390 (e.g., two flow direction conversion vanes, three flow direction conversion vanes, etc.). In certain embodiments, the flow direction conversion vane 390 can be operated by a single direction conversion actuator 400. As shown, the controller 60 is communicatively coupled to each individual direction conversion actuator 400. In certain embodiments, one or more direction conversion actuators 400 can be daisy chain connected and / or the controller 60 can be communicatively coupled to a subset of the direction conversion actuators 400.

[0110] In the illustrated embodiment, the exhaust section 24 includes four flow direction conversion vanes 390. In certain embodiments, the exhaust section 24 can include two or more flow direction conversion vanes 390 (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, or more flow direction conversion vanes). In the illustrated embodiment, the wide end 402 of each flow direction conversion vane 390 is arranged counterclockwise (e.g., in the circumferential direction 36) with respect to the narrow end 396 in the circumferential direction. In certain embodiments (not shown), the wide end 402 of each flow direction conversion vane 390 is arranged clockwise with respect to the narrow end 396 in the circumferential direction.

[0111] FIG. 20 is a schematic cross-sectional view of the radial axis 34 at the extended position 401 of FIG. 18 for an embodiment of the flow direction conversion vane 390 of FIGS. 17-19. In the illustrated embodiment, the curved wall 416 (e.g., a wall obtained by lofting) of the flow direction conversion vane 390 is configured to curve circumferentially about the central engine axis 280 of the exhaust section 24. As shown, when the flow direction conversion vane 390 is arranged at the extended position 401 (e.g., in the extended state), the curved wall 416 curves radially inward from the narrow end 396 to the wide end 402.

[0112] The flow direction conversion vane 390 is configured to selectively enter (e.g., selectively act on) the exhaust flow path 90 of the exhaust section 24 by a direction conversion actuator 400 (e.g., actuator 70). In certain embodiments, the direction conversion actuator 400 can be configured to move 460 the flow direction conversion vane 390 in the radial direction 34 of the exhaust section 24. Additionally or alternatively, the direction conversion actuator 400 can be configured to rotate 462 the wide end 402 relative to the narrow end 396. That is, the direction conversion actuator 400 can be configured to rotate the flow direction conversion vane 390 about the direction conversion pivot 398. In some embodiments, the movement 460 may precede the rotation 462, and in other embodiments, the rotation 462 may precede the movement 460.

[0113] In certain embodiments, the diverter pivot 398 can contribute to both the movement 460 and rotation 462 of the flow diverter vane 390. For example, the diverter pivot 398 can be configured to move (e.g., slide) within the slot 464. The diverter actuator 400 can be configured such that the flow diverter vane 390 moves 460 as the flow diverter vane 390 travels within the slot 464. It should be understood that the movement 460 and rotation 462 of the flow diverter vane 390 can be performed by the same diverter actuator 400 or different diverter actuators 400.

[0114] FIG. 21 is a perspective view of one embodiment of the flow diverter vane 390 of FIGS. 17 - 20. In the illustrated embodiment, the flow diverter vane 390 includes a one-piece body (i.e., a one-piece) that extends from the narrow end 396 to the wide end 402. In certain embodiments, the flow diverter vane 390 can be constructed of metal (e.g., aluminum, steel) or a durable composite material (e.g., carbon fiber reinforced polymer). As shown previously, the diverter pivot 398 is disposed at the narrow end 396 of the flow diverter vane 390.

[0115] In the illustrated embodiment, the flow direction turning vane 390 includes a curved wall 410 (e.g., a wall obtained by lofting) extending from the narrow end 396 to the wide end 402. In a particular embodiment, the curved wall 410 includes a loft 412 (e.g., a substantial loft) of a cross-section 414 along a curve 416 from the narrow end 396 to the wide end 402. That is, the cross-section 414 has a shape along the curve 416 from the narrow end 396 to the wide end 402, and the curved wall 410 is formed. As shown, the cross-section 414 (e.g., cross-sectional shape, profile) includes an L-shaped profile 470. In the illustrated embodiment, the L-shaped profile 470 includes a radial portion 418 and an axial portion 420 extending in a direction (e.g., perpendicular, orthogonal) intersecting from the radially outer end 422 (FIG. 18) of the radial portion 418. Further, one or more dimensions of the cross-section 414 may vary from the narrow end 396 to the wide end 402. In the illustrated embodiment, the extent 426 (e.g., radial extent) of the radial portion 418 increases from the narrow end 396 toward the wide end 402.

[0116] FIG. 22 is a schematic cross-sectional view of one embodiment of the recirculation obstruction system 11 of FIG. 2 taken along line 22-22 of FIG. 3. In the illustrated embodiment, the cross-sectional cut plane is orthogonal to the radial direction 34 and intersects the final stage vane 108, the outer flow control vane 95, the final stage blade 54, and the strut 48. As shown, the outer flow control vane 95 is disposed downstream of the final stage vane 108 and upstream of the final stage blade 54. The outer flow control vane 95 is disposed on the outer turbine wall within the final turbine stage 74 of the turbine section 22. In a particular embodiment, the angle 480 formed by the central axis 482 of the outer flow control vane 95 and the longitudinal axis 32 is a positive acute angle. By having the outer flow control vane 95 at an angle 480 with respect to the longitudinal axis 32, the direction of the reverse flow 121 is changed in the circumferential direction 484 (e.g., in a direction opposite to the rotational direction of the blade) such that the direction of the changed reverse flow 486 is sufficiently aligned with the trailing edge portion 488 of the final stage vane 108. By changing the direction of the reverse flow 121, the direction of the changed reverse flow 486 can be sufficiently aligned with the outer contour 490 of the final stage vane 108, thereby reducing the turbulent flow that would otherwise occur by the reverse flow 121 (e.g., a reverse flow that does not change direction) contacting the final stage vane 108.

[0117] As described herein, the outer flow control vane 95 can mitigate the formation of the toroidal vortex between the final stage vane 108 and the final stage blade 54. In certain embodiments, any number of outer flow control vanes 95 may be disposed between the final stage vane 108 and the final stage blade 54. For example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 50, 100, or more flow control vanes 95 (e.g., flow control vanes spaced circumferentially about the longitudinal axis 32) can be disposed between the final stage vane 108 and the final stage blade 54. Similar to the inner flow control vanes, the plurality of outer flow control vanes 95 can be aligned (e.g., at a common axial position) such that their axial positions are aligned within the turbine section 22 and can form an outer dam (e.g., an outer annular dam). In certain embodiments, the outer flow control vane 95 can be disposed between the blades from the second stage to the final stage and the final stage vane 108, between the vanes from the second stage to the final stage and the blades from the second stage to the final stage, or between adjacent sets of blades and vanes of the turbine section 22.

[0118] As shown in FIG. 3, the turbine section 22 can also include one or more inner flow control vanes 132 disposed on the inner turbine wall 78 between the final stage vane 108 and the final stage blade 54 of the turbine section 22, the one or more inner flow control vanes 132 extending radially outward from the inner turbine wall 78 of the turbine section 22. In certain embodiments, the one or more inner flow control vanes 132 and the outer flow control vanes 95 can be disposed at a common axial position along the longitudinal axis 32. As described with reference to FIG. 4, the outer flow control vanes 95 can be configured to extend radially inward from a recess (e.g., 150) disposed in the outer turbine wall 76. Additionally or alternatively, the inner flow control vanes 132 can be configured to extend radially outward from a recess (e.g., 150) disposed in the inner turbine wall 78. The operating configurations (e.g., linear extension, rotation about a pivot, etc.) described with reference to FIG. 4 can be applied to the outer flow control vanes 95 and / or the inner flow control vanes 132 disposed in the turbine section 22.

[0119] As a technical effect of the disclosed embodiments, there is the ability to mitigate the formation of rotating stall cells in the exhaust section of a gas turbine engine. In particular, the disclosed embodiments reduce the velocity gradient of the shear layer that exists immediately behind the final stage blades of the turbine section. For example, in one embodiment, an inner dam (e.g., a dam including a plurality of inner flow control vanes) disposed on the inner exhaust wall divides the reverse flow of the exhaust gas into an upstream vortex and a downstream vortex. The upstream vortex maintains a high tangential velocity adjacent to the final stage blades, thereby reducing the velocity gradient of the shear layer. In certain embodiments, an auxiliary strut disposed between adjacent main struts can include an inner portion, a central portion, and an outer portion. The inner and outer portions (e.g., flow control vanes) can be configured to rotate to a certain angular position in the circumferential direction, thereby directing a significant proportion of the free flow towards the reverse flow, thereby increasing the tangential velocity of the reverse flow and reducing the velocity gradient of the shear layer adjacent to the final stage blades. In certain embodiments, flow direction changing vanes are used to move a portion of the exhaust flow having a high tangential velocity near the outer exhaust wall to the reverse flow near the inner exhaust wall. By adding the high-speed flow to the reverse flow, the overall tangential velocity of the reverse flow increases near the final stage blades, thereby reducing the velocity gradient of the shear layer. In certain embodiments, one or more outer flow control vanes and / or inner flow control vanes can be disposed downstream of the final stage vanes of the turbine and upstream of the final stage blades of the turbine. The outer flow control vanes can be disposed on the outer wall of the turbine and can be configured to mitigate the formation of the toroidal vortex between the final stage vanes and the final stage blades.

[0120] The subject matter detailed above can be defined by one or more embodiments as shown below. [Embodiment 1] According to a first aspect, the system includes a turbine exhaust section having an exhaust passage, an inner exhaust wall disposed radially along the exhaust passage, and an outer exhaust wall disposed radially along the exhaust passage and located radially outside the inner exhaust wall. The turbine exhaust section includes auxiliary struts extending from the inner exhaust wall to the outer exhaust wall. The auxiliary struts are divided and include an inner portion, a central portion disposed radially outside the inner portion, and an outer portion disposed radially outside the central portion. The inner portion, the outer portion, or both are configured to rotate to a certain angular position. The auxiliary struts are circumferentially disposed between adjacent struts of the turbine exhaust section. [Embodiment 2] In an axially aligned position, the inner leading edge of the inner portion has a circumferentially aligned position with respect to the inner trailing edge of the inner portion, and in an axially aligned position, the central leading edge of the central portion has a circumferentially aligned position with respect to the central trailing edge of the central portion, and in an axially aligned position, the outer leading edge of the outer portion has a circumferentially aligned position with respect to the outer trailing edge of the outer portion. The system according to Embodiment 1. [Embodiment 3] The central portion is configured to remain stationary in an axially aligned position. The system according to Embodiment 1 or 2. [Embodiment 4] When the inner portion and the outer portion are disposed in an axially aligned position, the first profile of the inner portion, the second profile of the central portion, and the third profile of the outer portion are configured to coincide radially. The system according to any one of Embodiments 1 to 3. [Embodiment 5] The leading edge of the auxiliary strut has an axially common position with respect to the leading edge adjacent to the adjacent diffuser strut. The system according to any one of Embodiments 1 to 4. [Embodiment 6] The system according to any one of Embodiments 1 to 5, wherein the inner part, the outer part, or both are configured to rotate to respective angular positions about one or more pivots radially coupled to the inner part and the outer part. [Embodiment 7] The system according to any one of Embodiments 1 to 6, wherein the inner part and the outer part are configured to rotate independently of each other about the one or more pivots. [Embodiment 8] When the inner part is disposed at the certain angular position, the inner longitudinal axis of the inner part forms an angle with the corresponding longitudinal axis of the adjacent strut. The system according to any one of Embodiments 1 to 7, wherein when the outer part is disposed at the certain angular position, the outer longitudinal axis of the outer part forms an angle with the corresponding longitudinal axis of the adjacent strut. [Embodiment 9] An inner angle is defined between the inner longitudinal axis of the inner part and the central longitudinal axis of the central part, and an outer angle is defined between the outer longitudinal axis of the outer part and the central longitudinal axis of the central part, and the inner angle is equal to the outer angle. The system according to any one of Embodiments 1 to 8. [Embodiment 10] In a second aspect, the system includes a turbine exhaust section having an exhaust flow path, an inner exhaust wall disposed radially along the exhaust flow path, an outer exhaust wall disposed radially along the exhaust flow path, and an auxiliary strut extending from the inner exhaust wall to the outer exhaust wall. The auxiliary strut is split and includes an inner portion, a central portion disposed radially outside the inner portion, an outer portion disposed radially outside the central portion, an inner operating assembly configured to operate the inner portion to rotate the inner portion to an inner angular position, and an outer operating assembly configured to operate the outer portion to rotate the outer portion to an outer angular position. The auxiliary strut is circumferentially disposed between adjacent struts of the turbine exhaust section. [Embodiment 11] It includes a controller having one or more processors. The controller is configured to instruct the inner operating assembly to rotate the inner portion to the inner angular position based on one or more operating conditions of the turbine exhaust section, to instruct the outer operating assembly to rotate the outer portion to the outer angular position based on one or more operating conditions of the turbine exhaust section, or to perform a combination of instructing the inner operating assembly and instructing the outer operating assembly, the system according to any of Embodiments 1 to 10. [Embodiment 12] The auxiliary strut is circumferentially offset from a first adjacent strut among the adjacent struts, and the auxiliary strut is substantially closer to the first adjacent strut than a second adjacent strut among the adjacent struts, the system according to any of Embodiments 1 to 11. [Embodiment 13] An inner angle is defined between an inner longitudinal axis of the inner portion and a central longitudinal axis of the central portion. An outer angle is defined between the outer longitudinal axis of the outer portion and the central longitudinal axis of the central portion, and the inner angle, the outer angle, or both angles are based on one or more operating conditions of the turbine exhaust section, the system according to any one of Embodiments 1 to 12. [Embodiment 14] The inner portion is configured to at least substantially block an inner region of the exhaust passageway that is disposed radially outward directly from the inner exhaust wall, and the outer portion is configured to at least substantially block an outer region of the exhaust passageway that is disposed radially inward directly from the outer exhaust wall, the system according to any one of Embodiments 1 to 13. [Embodiment 15] The inner angular position and the outer angular position are different positions from each other, the system according to any one of Embodiments 1 to 14. [Embodiment 16] The system includes a turbine exhaust section having an exhaust passageway, an inner exhaust wall disposed radially along the exhaust passageway, an outer exhaust wall disposed radially along the exhaust passageway, and an auxiliary strut extending from the inner exhaust wall to the outer exhaust wall. The auxiliary strut is divided, and the auxiliary strut includes an inner portion, a central portion disposed radially outward of the inner portion, and an outer portion disposed radially outward of the central portion. The inner portion, the outer portion, or both are configured to rotate to a certain angular position. The auxiliary strut is circumferentially disposed between adjacent struts of the turbine exhaust section. When the inner portion is disposed at the inner angular position, it is configured to substantially extend over the inner circumferential distance between adjacent struts. When the outer portion is disposed at the outer angular position, it is configured to substantially extend over the outer circumferential distance between adjacent struts. [Embodiment 17] The central portion remains stationary and is configured to prevent rotation, the system according to any one of Embodiments 1 to 16. [Embodiment 18] When the inner part and the outer part are arranged at positions aligned in the axial direction, the inner profile of the inner part, the central profile of the central part, and the outer profile of the outer part are configured to coincide in the radial direction, the system according to any one of Embodiments 1 to 17. [Embodiment 19] When the inner part rotates to the inner angular position and the outer part rotates to the outer angular position, the inner part and the outer part are configured to form an axial opening arranged radially between the inner part and the outer part, the system according to any one of Embodiments 1 to 18. [Embodiment 20] An inner angle is defined between the inner longitudinal axis of the inner part and the central longitudinal axis of the central part, An outer angle is defined between the outer longitudinal axis of the outer part and the central longitudinal axis of the central part, and the inner angle is equal to the outer angle, the system according to any one of Embodiments 1 to 19.

[0121] The description provided herein discloses the present invention (including the best mode) using examples, and anyone skilled in the art can practice the present invention (including manufacturing and using an apparatus or system and performing an incorporated method). The patentable scope of the present invention is defined by the claims and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims or if they include equivalent structural elements that do not have a substantial difference from the literal language of the claims.

Description of Reference Numerals

[0122] 11 System 22 Turbine section 24 Turbine exhaust section 48, 50 Exhaust diffuser strut 54 Final stage blade 56, 151 Inner exhaust wall 58 Outer exhaust wall 60 Controller 62 Processor 70, 370 Operating assembly 90 Exhaust flow path 92 Inner flow control vane 100 Inner radial range 102 Radial distance 118, 120 Axial planes 150, 166 Recesses 158 Pivot 159 Lateral direction 194 Outer dam 196, 198 Axial planes 212 Downstream surface

Claims

1. A system (11) comprising a turbine exhaust section (24), said turbine exhaust section (24) comprising an exhaust flow path (90), an inner exhaust wall (56) arranged radially along said exhaust flow path (90), an outer exhaust wall (58) arranged radially along said exhaust flow path (90), said outer exhaust wall (58) being arranged radially outside said inner exhaust wall (56), and an auxiliary strut (50) extending from said inner exhaust wall (56) to said outer exhaust wall (58), said auxiliary strut (50) being split, said auxiliary strut (50) comprising an inner portion (282), a central portion (284) arranged radially outside said inner portion (282), and an outer portion (286) arranged radially outside said central portion (284) wherein the auxiliary strut (50) comprises and further comprising wherein said inner portion (282), said outer portion (286), or both (282, 286) are configured to rotate to a certain angular position, wherein said auxiliary strut (50) is circumferentially arranged between adjacent diffuser struts (48) of said turbine exhaust section (24), the system (11).

2. an inner operating assembly (70, 370) configured to operate said inner portion (282) to rotate said inner portion (282) to an inner angular position, and an outer operating assembly (70, 372) configured to operate said outer portion (286) to rotate said outer portion (286) to an outer angular position wherein the system (11) according to claim 1 further comprises

3. wherein said inner angular position and said outer angular position are different positions from each other, the system (11) according to claim 2

4. comprising a controller (60) having one or more processors (62), said controller being configured to instruct said inner operating assembly (70, 370) to rotate said inner portion (282) to said inner angular position based on one or more operating conditions of a turbine system (10) comprising said turbine exhaust section (24), instruct said outer operating assembly (70, 372) to rotate said outer portion (286) to said outer angular position based on one or more operating conditions of said turbine system (10) comprising said turbine exhaust section (24), or A combination of instructing the inner motion assembly (70, 370) and instructing the outer motion assembly (70, 372) The system (11) according to claim 2, which is configured to perform the above.

5. The system according to claim 1 or 2, wherein the inner part (282), the outer part (286), or both (282, 286) are configured to rotate to respective angular positions about one or more pivots (288) radially coupled to the inner part (282) and the outer part (286).

6. The system according to claim 5, wherein the inner part (282) and the outer part (286) are configured to rotate independently of each other about the one or more pivots (288).

7. When the inner part (282) is disposed at the certain angular position, the inner longitudinal axis (348) of the inner part (282) forms a certain angle with the corresponding longitudinal axis (354) of the adjacent diffuser strut (48). The system according to claim 1, wherein when the outer part (286) is disposed at the certain angular position, the outer longitudinal axis (352) of the outer part (286) forms a certain angle with the corresponding longitudinal axis (354) of the adjacent diffuser strut (48).

8. An inner angle (356) is defined between the inner longitudinal axis (348) of the inner part (282) and the central longitudinal axis (350) of the central part (284). An outer angle (358) is defined between the outer longitudinal axis (352) of the outer part (286) and the central longitudinal axis (350) of the central part (384), and the inner angle (356) is equal to the outer angle (358). The system according to claim 7.

9. At an axially aligned position, the inner front edge (330) of the inner part (282) has a circumferentially aligned position with respect to the inner rear edge (334) of the inner part (282). At an axially aligned position, the central front edge (330) of the central part (284) has a circumferentially aligned position with respect to the central rear edge (334) of the central part (284). At an axially aligned position, the outer front edge (330) of the outer part (286) has a circumferentially aligned position with respect to the outer rear edge (334) of the outer part (286). The system according to claim 1 or 2.

10. The system according to claim 9, wherein the central portion (284) is configured to remain stationary at an axially aligned position.

11. The system according to claim 9, wherein when the inner portion (282) and the outer portion (286) are arranged at an axially aligned position, the first profile (342) of the inner portion (282), the second profile (344) of the central portion (284), and the third profile (346) of the outer portion (286) are configured to coincide radially.

12. The system according to any one of claims 1 to 11, wherein the auxiliary strut (50) is circumferentially offset from a first adjacent diffuser strut (48) among the adjacent diffuser struts (48), and the auxiliary strut (50) is substantially closer to the first adjacent diffuser strut (48) than a second adjacent diffuser strut (48) among the adjacent diffuser struts (48).

13. The system according to any one of claims 1 to 12, wherein a leading edge (330) of the auxiliary strut (50) is axially aligned with a leading edge (332) adjacent to the adjacent diffuser strut (48).

14. The system according to claim 2, wherein the inner portion (282) is configured to at least substantially block an inner region (314) of the exhaust passage (90) that is arranged radially outward directly from the inner exhaust wall (56), and the outer portion (286) is configured to at least substantially block an outer region (316) of the exhaust passage (90) that is arranged radially inward directly from the outer exhaust wall (58).

15. The system according to claim 14, wherein when the inner portion (282) rotates to the inner angular position and the outer portion (286) rotates to the outer angular position, the inner portion (282) and the outer portion (286) are configured to form an axial opening (320) arranged radially between the inner portion (282) and the outer portion (286).

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