Fluid injection system and method for mitigating turbine engine rotational stall

Abstract

The invention discloses a fluid injection system and method for mitigating turbine engine rotational stall. A stall mitigation system (11) for a gas turbine engine (12) includes a turbine exhaust section (24) downstream of an expansion turbine (22). The turbine exhaust section (24) includes an inner wall (86) and an opposing outer wall (88) disposed radially along an exhaust flow path (84). The system (11) also includes a fluid injection system (38) configured to inject a fluid (73) into a chamber (89) located between the inner wall (86) and the outer wall (88) via a plurality of inner ports (54, 134) disposed in the inner wall (86) and / or a plurality of ports (146) disposed in struts (90, 92) extending from the inner wall (86) to the outer wall (88). The plurality of inner ports (54, 134) and the plurality of ports (146) are disposed downstream of a last stage blade (91) of the expansion turbine (22).

Description

BACKGROUND OF THE INVENTION

[0001] The subject matter disclosed herein relates to mitigating the formation of rotating stall in the low-pressure turbine section of a turbine engine.

[0002] A gas turbine engine can operate under various conditions, such as steady-state conditions, transient conditions (e.g., startup or shutdown), full-load conditions, or part-load conditions. Unfortunately, when operating under low-flow conditions (e.g., transient or part-load conditions), a gas turbine engine can be susceptible to rotating stall conditions. A rotating stall condition involves the formation of rotating stall cells in the low-pressure turbine section of the gas turbine engine, resulting in reverse flow. The rotating stall cells rotate at a fraction of the rotational speed of the gas turbine engine (e.g., low frequency), thereby causing asynchronous high-cycle fatigue on the turbine blades in the low-pressure turbine section. Accordingly, there is a need to at least mitigate or prevent rotating stall conditions in a gas turbine engine. SUMMARY OF THE INVENTION

[0003] Certain embodiments are outlined below that are equivalent in scope to the originally claimed invention. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are only intended to provide a brief overview of possible forms of the invention. Indeed, the invention can include various forms that may be similar to or different from the embodiments set forth below.

[0004] In one embodiment, a system includes a turbine exhaust section downstream of a turbine. The turbine exhaust section includes an exhaust flow path. The turbine exhaust section further includes an inner wall radially disposed along the exhaust flow path. The turbine exhaust section further includes an outer wall radially outward from the inner wall and along the exhaust flow path. The system further includes a fluid injection system configured to inject fluid into a chamber radially disposed between the inner wall and the outer wall via a plurality of inner ports disposed in the inner wall. The plurality of inner ports are disposed downstream of a downstream edge of a last-stage turbine blade.

[0005] In another embodiment, a system includes a turbine exhaust section. The turbine exhaust section includes an exhaust flow path, an inner wall radially disposed along the exhaust flow path, an outer wall radially outward from the inner wall and along the exhaust flow path, and struts radially extending from the inner wall to the outer wall. The system further includes a fluid injection system configured to inject fluid into a chamber radially disposed between the inner wall and the outer wall via a plurality of ports disposed in a front end portion of the struts. The plurality of ports are disposed downstream of a downstream edge of a last turbine blade.

[0006] In another embodiment, the system includes a turbine exhaust section downstream of the turbine. The turbine exhaust section includes an exhaust flow path, an inner wall disposed radially along the exhaust flow path, and an outer wall disposed radially outward from the inner wall and along the exhaust flow path. The system also includes a fluid injection system. The fluid injection system includes a fluid supply device configured to supply one or more fluids to the turbine exhaust section. The fluid injection system further includes a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to control the injection of the one or more fluids into a chamber radially disposed between the inner wall and the outer wall via a plurality of inner ports integrally formed in the inner wall. The plurality of inner ports are disposed downstream of the downstream edge of the last stage turbine blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features, aspects, and advantages of the present system and method will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein:

[0008] Figure 1 is a schematic flow diagram of an embodiment of a turbine system having a gas turbine engine, the gas turbine engine having a stall mitigation system having a fluid injection system;

[0009] Figure 2 is a cross-sectional side view of an embodiment of a gas turbine engine taken along a longitudinal axis, showing an embodiment of the fluid injection system of the stall mitigation system; Figure 1 showing the fluid injection system discharging fluid into the gas turbine engine;

[0010] Figure 3 is a cross-sectional side view of an embodiment of a gas turbine engine taken along line 3-3, Figure 2 showing the fluid injection system discharging fluid into the gas turbine engine; Figure 2 through

[0011] Figure 4 is a cross-sectional view of an embodiment of a gas turbine engine taken along line 4-4, Figure 3 showing fluid injection ports disposed in an upstream portion of a plurality of struts of the gas turbine engine and also disposed in the inner wall and the outer wall of the gas turbine engine;

[0012] Figure 5 is along Figure 4 is a cross-sectional view of an embodiment of a strut and an auxiliary strut taken along line 5-5, Figure 3 showing fluid injection ports disposed in a front end portion of the strut and a front end portion of the auxiliary strut;

[0013] Figure 6 is alongFigure 4 taken along line 6-6 of Figure 4 Cross-sectional view of an embodiment of a strut, showing independent control of fluid entry via each fluid injection port;

[0014] Figure 7 is along Figure 4 taken along line 7-7 of Figure 4 Cross-sectional view of an embodiment of a fluid injection port, showing a fluid manifold fluidly coupled to each row of fluid injection ports;

[0015] Figure 8 is along Figure 7 taken along line 8-8 of Figure 7 Cross-sectional view of an embodiment of a row of fluid injection ports, showing the circumferential angling of each fluid injection port;

[0016] Figure 9 Cross-sectional side view of an embodiment of a steam turbine engine taken along a longitudinal axis, showing an exemplary fluid flow produced by an embodiment of a fluid injection system; and

[0017] Figure 10 is along Figure 3 taken along line 10-10 of Figure 2 Cross-sectional schematic view of an embodiment of a stall mitigation system. DETAILED DESCRIPTION

[0018] One or more specific embodiments of the systems and methods of the present invention will now be described. To provide a concise description of these embodiments, not all features of actual implementations may be described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints, which may vary from one implementation to another. Additionally, it should be understood that such development work may be complex and time-consuming, but would still be a routine task of design, fabrication, and manufacture for those of ordinary skill in the art who have benefited from this disclosure.

[0019] When introducing the elements of the various embodiments of the present invention, the articles "a", "an", "the", and "said" are intended to mean that there is one or more of the elements. The terms "comprising", "including", and "having" are intended to be inclusive and mean that there may be additional elements other than those listed.

[0020] As used throughout the specification and claims, approximating language may be used to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function associated therewith. Accordingly, values modified by terms such as "about," "approximately," and "substantially" are not limited to the precise values specified. In at least some instances, the approximating language may correspond to the precision of the instrument used to measure the value. Throughout this specification and the claims, where range limitations may be combined and / or interchanged, such ranges are identified and include all the subranges subsumed therein, unless the context or language indicates otherwise. When applied to a particular value, "substantially" may indicate a + / - 10% variation of that value, and, and when used in the context of an angle, may indicate a + / - 10-degree variation greater or less than the angle or direction. For example, "substantially vertical" includes a direction within ten degrees of vertical in any direction (e.g., clockwise or counterclockwise). For example, an axis or feature that is "substantially perpendicular" includes an axis or element that intersects at an angle between 80 degrees and 100 degrees, and thus should be interpreted more broadly than the unmodified term "perpendicular," which is defined as a 90-degree intersection between axes or elements.

[0021] As described in more detail below, the embodiments disclosed herein include a stall mitigation system configured to mitigate a rotating stall condition in the low-pressure turbine section of a turbine (e.g., a gas turbine engine or a steam turbine) by mitigating the formation of rotating stall cells and reverse flow downstream of the turbine's last-stage blades. For example, certain embodiments of the stall mitigation system include a fluid injection system configured to inject fluid into a hub chamber downstream of the turbine's last-stage blades via the fluid injection system. In some embodiments, the fluid injection system may include fluid injection ports disposed on an inner wall (e.g., an inner annular wall) of the turbine and downstream of the last-stage blades. Additionally or alternatively, the fluid injection system may include fluid injection ports disposed on an outer wall (e.g., an outer annular wall) of the turbine and downstream of the last-stage blades. In some embodiments, the fluid injection ports may be circumferentially angled in a direction opposite to the direction of rotation of the rotating stall cells. In some embodiments, the stall mitigation system includes a fluid extraction system having an ejector configured to extract or discharge exhaust gas from the chamber through an orifice in the outer wall, inner wall, or any suitable location to help mitigate or prevent a rotating stall condition.

[0022] In some embodiments, a fluid injection system may include a fluid injection port integrally disposed in an upstream portion of a diffuser strut in a turbine exhaust section. The fluid injection port may be disposed on an inner radial portion of the upstream portion of the diffuser strut and, in some embodiments, may be angled in a direction opposite to the direction of rotation of a rotating stall cell. Additionally or alternatively, the fluid injection system may include an auxiliary fluid injection port integrally disposed in an upstream portion of an auxiliary diffuser strut in an exhaust section of a gas turbine engine. The auxiliary diffuser strut may be axially aligned with the diffuser strut and circumferentially offset from the diffuser strut. The auxiliary fluid injection port may be disposed on an inner radial portion of the upstream portion of the auxiliary diffuser strut and, in some embodiments, may be angled in a direction opposite to the direction of rotation of the rotating stall cell.

[0023] Figure 1 FIG. 4 is a schematic flow diagram of an embodiment of a turbine system 10 having a gas turbine engine 12 with a stall mitigation system 11 configured to reduce rotating stall conditions. As discussed further below, the stall mitigation system 11 includes a fluid injection system 38 configured to inject a fluid (e.g., compressor bleed gas, exhaust gas, carbon dioxide, etc.) into an area experiencing reverse flow (e.g., flow recirculation, vortex formation, etc.) to help reduce the reverse flow and / or inhibit rotating stall conditions. In some embodiments, the turbine system 10 may include an aircraft, a locomotive, a power generation system, or a combination thereof, but a power generation system is shown here. The illustrated gas turbine engine 12 includes an inlet section 16, a compressor or compressor section 18, a combustor or combustor section 20, a turbine or turbine section 22 (e.g., an expansion turbine), and an exhaust section 24. The turbine 22 is coupled to the compressor 18 via a shaft 26.

[0024] As indicated by the arrows, air can enter the gas turbine engine 12 through the intake section 16 and flow into the compressor 18, which compresses the air before it enters the combustor section 20. The illustrated combustor section 20 includes a combustor housing 28 that is disposed concentrically or annularly about the axis 26 between the compressor 18 and the turbine 22. Compressed air from the compressor 18 enters the combustor 40, where the compressed air can be mixed with and burned with fuel within the combustor 40 to drive the turbine 22. The hot combustion gases flow from the combustor section 20 through the turbine 22 and drive the compressor 18 via the shaft 26. For example, the combustion gases can apply a motive force to the turbine rotor blades within the turbine 22 to cause the shaft 26 to rotate. After flowing through the turbine 22, the hot combustion gases can leave the gas turbine engine 12 through the exhaust section 24. The exhaust section 24 can include a plurality of struts, including main support struts and auxiliary struts, that are located downstream of the turbine 22, such as within a diffuser section of the exhaust section 24. The gas turbine engine 12 can be described in terms of a longitudinal or axis 32 (e.g., axial), a radial or axis 34, and a circumferential or axis 36.

[0025] As discussed further below, the fluid injection system 38 of the stall mitigation system 11 can include fluid injectors or injection ports at a plurality of axial positions relative to the longitudinal 32, a plurality of radial positions relative to the radial 34, and / or a plurality of circumferential positions relative to the circumferential 36 within the turbine 22 and / or the exhaust section 24. For example, the fluid injectors or injection ports of the fluid injection system 38 can be disposed in one or more downstream or low-pressure turbine stages (e.g., the last turbine stage) of the turbine 22, axially between the last turbine stage of the turbine 22 and the plurality of struts, directly on the plurality of struts, and / or circumferentially between the plurality of struts.

[0026] Additionally, the fluid injection through the fluid injectors or injection ports can be selectively controlled based on the operating conditions of the turbine system 10. For example, during operating conditions that are conducive to flow reversal and rotating stall conditions (e.g., low flow conditions associated with a partial load or transient condition of the turbine system 10), the fluid injection system 38 can be controlled to provide fluid injection to counteract or inhibit flow reversal and thus reduce the likelihood of a rotating stall condition. However, during normal operating conditions (e.g., full load and / or steady-state operating conditions), the fluid injection system 38 can be controlled to reduce or stop fluid injection.

[0027] Figure 2 is a cross-sectional side view of an embodiment of the gas turbine engine 12 taken along the longitudinal axis 32, showing an embodiment of the fluid injection system 38 coupled to the turbine 22 and the exhaust section 24. As described above with respect to Figure 1 Figure 1 ​As described, air can enter the gas turbine engine 12 through the intake section 16 and can be compressed by the compressor 18. Then, the compressed air from the compressor 18 can be directed into the combustor section 20, where the compressed air can be mixed with fuel. The combustor section 20 includes one or more combustors 40. In some embodiments, the gas turbine engine 12 can include a plurality of combustors 40 arranged in an annular configuration. Alternatively, the combustor section 20 can include an annular combustor (not shown). Additionally, each combustor section 20 can include a plurality of fuel nozzles 42 attached to the head end of or near each combustor section 20 in an annular or other arrangement.

[0028] During operation, the fuel nozzles 42 can inject the fuel-air mixture into the combustor 40 at a suitable ratio to achieve optimal combustion, emissions, fuel consumption, and power output. Within the combustor section 20, the fuel-air mixture can combust to produce hot, pressurized combustion gases. After combustion, the hot pressurized combustion gases can leave the combustor section 20 and flow through the transition piece 44 to the turbine 22. Within the turbine 22, the pressurized combustion gases can cause the blades 45 that radially extend within the turbine 22 and are disposed between the stationary vanes 46 to rotate, causing the shaft 26 to rotate, and then leave as exhaust through the exhaust section 24.

[0029] In an exemplary embodiment, the fluid injection system 38 includes a fluid supply device 48, a fluid line 50 (e.g., a conduit, pipe, or tubing), a fluid injector or injection port 54, and a controller 56. In certain embodiments, the controller 56 may include a processor 58, a memory 60, instructions 62 stored on the memory 60 and executable by the processor 58, and a communication circuit 64 configured to communicate with the fluid supply device 48 and various sensors throughout the turbine system 10. In the exemplary embodiment, the fluid supply device 48 includes a compressor 66, an ejector 68, a manifold 70, and a valve 72. As shown, the fluid supply device 48 is configured to draw in a fluid 73 (e.g., a gas) from one or more fluid sources 74. The fluid source 74 may include a tank, a container, a device having a fluid in the turbine system 10, an air separation unit (ASU), a pipeline, or a connection to other parts of the turbine system 10 (e.g., compressor 18). The ASU may be configured to separate air into oxygen and nitrogen for use in the turbine system 10. The fluid source 74 may include air 76, an inert gas 78, other gases 80, compressor bleed 82 from the compressor 18 of the gas turbine engine 12, or a combination thereof. For example, the inert gas 78 may include nitrogen from an ASU or another source, or another inert gas. The other gases 80 may include exhaust gas drawn from the exhaust section 24, carbon dioxide captured in a carbon capture system, or other gases. The compressor bleed 82 may include compressed air or exhaust gas recirculation (EGR) gas, where the EGR gas is recirculated from the exhaust section 24 to the compressor 18 as part of an EGR system.

[0030] The fluid supply device 48 is configured to receive fluid from one or more of the fluid sources 74 via a plurality of fluid lines 83 having respective valves 85, which are coupled to and controlled by the controller 56. Thus, the controller 56 is configured to selectively control the valves 85 and the fluid supply device 48 to control the fluid supply from the fluid source 74 to the respective injectors or injection ports 54. For example, the controller 56 may selectively open and close the various valves 85 to provide only one or a combination of fluids (e.g., air, inert gas, other gases, compressor bleed, or any combination thereof) from the fluid source 74 to the various injectors or injection ports 54. The compressor 66 of the fluid supply device 48 may be configured to compress and / or boost the pressure of any one or more of the fluid sources 74. The ejector 68 may operate using high and low pressure gases associated with a venturi section 69 ( Figure 3 ) such that the fluid injection system 38 may use the fluid line 50 and the injection port 54 to draw and / or inject fluid. Thus, in certain embodiments, the injection port 54 may be used as an injection port or a draw port, and the fluid line 50 may be used as an injection line or a draw line. Various details of the ejector 68 are discussed below.

[0031] The manifold 70 may include a fluid injection manifold configured to distribute various fluids from a fluid source 74 to an injector or injection port 54. In some embodiments, the manifold 70 may also include a fluid extraction manifold coupled to an ejector 68 and one or more sets of ports 54 (e.g., extraction ports). A valve 72 may also be coupled to the fluid line 50 and the manifold 70 to assist in controlling the distribution of fluid through the fluid injection system 38 to the injector or injection port 54.

[0032] In the illustrated embodiment, the exhaust section 24 includes an exhaust flow path 84 (e.g., an annular exhaust flow path), an inner wall 86 (e.g., an inner annular wall, an inner exhaust wall) disposed radially along the exhaust flow path 84, and an outer wall 88 (e.g., an outer annular wall, an outer exhaust wall) disposed radially outward from the inner wall 86 and along the exhaust flow path 84. The inner wall 86 and the outer wall 88 may also define an exhaust diffuser (or exhaust diffuser section) of the exhaust section 24, wherein the cross-sectional area of the exhaust diffuser expands to assist in reducing the exhaust pressure and diffusing the exhaust flow. The exhaust section 24 further includes a chamber 89 (e.g., an annular chamber, an annular exhaust chamber) disposed radially between the inner wall 86 and the outer wall 88 and axially downstream of the last stage blades 91 (or last stage blade set) of the turbine 22.

[0033] In some embodiments, the exhaust section 24 further includes one or more struts 90 (e.g., diffuser struts in the exhaust diffuser section). The struts 90 may include main struts 92 (e.g., main structural support struts) and / or auxiliary struts 93. In the illustrated embodiment, the main struts 92 and the auxiliary struts 93 extend from the inner wall 86 to the outer wall 88 in a radial direction 34. In some embodiments, the main struts 92 and / or the auxiliary struts 93 may extend only partially or fully between the inner wall 86 and the outer wall 88. For example, the main struts 92 may extend fully between the inner wall 86 and the outer wall 88, while the auxiliary struts 93 may extend only partially (but not fully) between the inner wall 86 and the outer wall 88. Although the following discussion may only refer to the struts 90 (e.g., 92, 93), the features of the disclosed fluid injection system 38 are intended to apply to any number of struts 90, such as at least equal to or greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20 or more struts 92 and 93. In the illustrated embodiment, the exhaust section 24 includes a manhole 94 (e.g., a hollow radial manhole structure that enables access by a user) fluidly coupled to a passage 96 disposed in the inner wall 86. The passage 96 is fluidly coupled to the chamber 89.

[0034] The fluid injection system 38 is configured to inject fluid 73 into the chamber 89 via the fluid injection port 54, as described in more detail herein. As discussed further below in more detail, the injector or injection port 54 may include one or more sets of injection ports disposed in the inner wall 86, outer wall 88, struts 90 (e.g., 92, 93), or any combination thereof. For example, the injector or injection port 54 may include one or more sets of injection ports 54 circumferentially arranged in the circumferential direction 36 about the longitudinal axis 34, wherein each set of injection ports 54 is disposed at a different axial position along the longitudinal axis 34 (e.g., the first set at the first axial position, the second set at the second axial position, etc.). By additional example, the foregoing sets of injection ports 54 may be disposed on the inner wall 86 and / or outer wall 88 downstream of the turbine 22 or in a low-pressure turbine stage (e.g., the last turbine stage), in the exhaust section 24 between the last turbine stage and the struts 90, on the struts 90, circumferentially between the struts 90, or any combination thereof. Thus, the injection ports 54 may be disposed at different radial positions, such as along the inner radius of the inner wall 86, along the outer radius of the outer wall 88, or along one or more intermediate radial positions of the struts 90 between the inner wall 86 and the outer wall 88.

[0035] In some embodiments, each strut 90 may include any number of injection ports 54 (e.g., at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) distributed uniformly or non-uniformly between the inner wall 86 and the outer wall 88 in the radial direction 34. In some embodiments, the injection ports 54 may be at an acute or perpendicular angle relative to a surface or wall (e.g., the inner wall 86, outer wall 88, or the wall of the strut 90). For example, the angle of the injection ports 54 relative to an adjacent surface or wall may be less than, equal to, or greater than 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 85 degrees, or 90 degrees, plus or minus 5 degrees. Relative to the downstream direction of the exhaust flow through the turbine 22 and the exhaust section 24, the injection ports 54 may point upstream, downstream, and / or in a cross direction. For example, the position, angle, and direction of the injector or injection port 54 may be selected to counteract, inhibit, or interrupt the reverse flow (or recirculation) of the exhaust, particularly the reverse flow associated with large-scale vortex structures in the flow, thereby helping to inhibit or prevent the formation of rotating stall cells in the turbine 22. Various aspects of the fluid injection system 38 are discussed in detail below.

[0036] Additionally, the controller 56 is configured to control the fluid injection system 38 based on the operating conditions of the turbine system 10 to help inhibit or prevent the formation of rotating stall cells in the turbine 22. For example, when the operating conditions of the turbine system 10 indicate a low flow condition or other conditions conducive to the formation of rotating stall cells (e.g., a low flow condition associated with a partial load or transient condition (e.g., startup, shutdown, or other transient behavior) of the turbine system 10), the controller 56 can selectively actuate or turn on the fluid injection performed by the fluid injection system 38. In some embodiments, the controller 56 can receive sensor feedback from the turbine 22 and / or the exhaust section 24 that indicates a low flow rate, reverse flow, vibration, or other conditions indicative of rotating stall. By additional example, when the operating conditions of the turbine system 10 indicate a normal flow condition or other conditions not conducive to the formation of rotating stall cells (e.g., a high flow or normal flow condition associated with a full load or steady state condition of the turbine system 10), the controller 56 can selectively reduce the flow rate, deactivate, or stop the fluid injection performed by the fluid injection system 38. The controller 56 can selectively control the fluid injection into and / or the fluid extraction from the respective ports 54 based on the severity of the operating conditions conducive to rotating stall.

[0037] Figure 3 is taken along line 3-3 Figure 2 cross-sectional side view of an embodiment of a gas turbine engine 12, showing fluid injection into the turbine 22 and the exhaust section 24 through Figure 2 the fluid injection system 38. In the illustrated embodiment, the fluid injection system 38 includes fluid lines 50 (e.g., fluid lines 120, 122, 124, 126, 128, and 130) fluidly coupled to a plurality of fluid sources 74 (e.g., external gas 132 and compressor bleed 82). The fluid lines 50 can be fluid inlet or supply lines, fluid extraction or withdrawal lines, or a combination thereof. Although the illustrated embodiment shows the external gas 132 and the compressor bleed 82, it should be appreciated that a combination of one or more of the fluid sources 74 described herein can be coupled to the fluid injection system 38. Specifically, the external gas 132 can be air 76, an inert gas 78, or other gas 80, as discussed above with reference to Figure 2 . The fluid lines 50 are fluidly coupled to fluid injection ports 54. The fluid injection ports 54 include an inner port 134, outer ports 136 (e.g., outer ports 138, 140, 142, and 144), and strut ports 146 (e.g., strut ports 148, 150, 152, and 154) disposed in the main strut 92, the auxiliary strut 93, or both.

[0038] In an exemplary embodiment, fluid line 120 is fluidly coupled to manhole 94 of exhaust section 24. Manhole 94 is fluidly coupled to passage 96 disposed in inner wall 86. As shown, passage 96 is fluidly coupled to inner opening 134, which is integrally disposed in inner wall 86. Inner opening 134 is disposed downstream (e.g., in the longitudinal direction 32) (e.g., downstream of the last stage of the turbine) of downstream edge 156 of the last stage blades 91 of turbine 22. Inner opening 134 is configured to allow (e.g., inject) fluid 73 to enter chamber 89. Inner opening 134 may also be described as a radial inner opening, an inner radius opening, an inner wall opening, or an inner hub opening. Inner opening 134 may include one or more sets of a plurality of inner openings 134, which are circumferentially arranged and spaced apart from each other at a common axial position, wherein the plurality of inner openings 134 of each respective set may be disposed at different axial positions. For example, the plurality of inner openings 134 of each set may include at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500 or more inner openings 134, which are circumferentially arranged and spaced apart evenly or unevenly. Inner opening 134 may be at an acute angle or a perpendicular angle with respect to inner wall 86 and / or longitudinal axis 32.

[0039] In an exemplary embodiment, inner opening 134 is disposed at an axial distance 158 downstream of downstream edge 156 of the last stage blades 91. As shown, distance 158 falls within the range of axial distance 160 with respect to the axial distance 162 (e.g., total distance or spacing) spanned in the downstream direction from downstream edge 156 of the last stage blades 91 towards the upstream edge 164 of strut 90 of exhaust section 24. For example, when measured as a percentage of axial distance 162 from downstream edge 156 in the downstream direction, the range of axial distance 160 may be about 5% to 95%, 10% to 90%, 15% to 85%, 20% to 80%, 25% to 75%, 30% to 70%, 35% to 65% or 40% to 60%. In certain embodiments, a first set of inner openings 134 (e.g., circumferentially arranged) may be disposed at a first axial distance 158, a second set of inner openings 134 (e.g., circumferentially arranged) may be disposed at a second axial distance 158, a third set of inner openings 134 (e.g., circumferentially arranged) may be disposed at a third axial distance 158, a fourth set of inner openings 134 (e.g., circumferentially arranged) may be disposed at a fourth axial distance 158, and so on. Different distances 158 may be incrementally spaced apart from downstream edge 156 of the last turbine blade 91 at a uniform or non-uniform spacing. During operation, allowing fluid 73 to enter via inner opening 134 can alleviate the formation of rotating stall cells (e.g., stall cells generated by hub vortices) in chamber 89 adjacent to turbine 22 (e.g., the last stage of the turbine).

[0040] In an exemplary embodiment, the fluid inlet line 122 is fluidly coupled to the outer port 138. As shown, the outer port 138 is integrally disposed in the outer wall 88 and is downstream of the downstream edge 156 of the last stage blade 91. The outer port 138 may include one or more sets of outer ports 138 (e.g., circumferentially arranged) that are located at one or more respective axial distances, such as the axial distance from the downstream edge 156 of the last stage blade 91. Similar to the inner port 134, the outer port 138 may be spaced apart at one or more axial distances between the downstream edge 156 of the last stage blade 91 and the upstream edge 164 of the strut 90. In certain embodiments, the range of the axial distance of the outer port 138 may be the same as that discussed above with reference to the inner port 134. The outer port 138 is configured to allow the fluid 73 to enter the chamber 89 from the outer wall 88. It should be appreciated that allowing the fluid 73 to enter via the outer port 138 may alleviate the formation of rotating stall (e.g., hub vortex stall) in the chamber 89 downstream of the turbine 22.

[0041] In an exemplary embodiment, the fluid lines 124, 126, and 128 are fluidly coupled to the outer ports 140, 142, and 144, respectively. As shown, the outer port 140 is integrally disposed in the outer wall 88 and is axially disposed between the penultimate stage guide vane 166 of the turbine 22 and the penultimate stage blade 168 of the turbine 22. The outer port 140 is configured to allow fluid to enter or be injected into the penultimate toroidal chamber 174 that is axially disposed between the penultimate stage guide vane 166 and the penultimate stage blade 168. Additionally, the outer port 142 is integrally disposed in the outer wall 88 and is axially disposed between the penultimate stage blade 168 of the turbine 22 and the last stage guide vane 170. Additionally, the outer port 144 is integrally disposed in the outer wall 88 and is axially disposed between the last stage guide vane 170 and the last stage blade 91. In the exemplary embodiment, each of the outer ports 136 is shown to be independently controllable via a valve 172 (e.g., valve 72) such that any combination of the outer ports 138, 140, 142, or 144 may allow fluid to enter the turbine 22 and / or the exhaust section 24. It should be appreciated that allowing the fluid 73 to enter via the outer ports 140, 142, and 144 may alleviate the formation of rotating stall (e.g., toroidal vortex stall) in the turbine chamber 174 (e.g., toroidal chamber) disposed between the blades 45 and the guide vanes 46 of the turbine 22. Further, it should be appreciated that the outer port 136 may include any combination of the outer ports 138, 140, 142, and 144.

[0042] The outer ports 138, 140, 142, and 144 may be described as radial outer ports, outer radius ports, or outer wall ports. The outer ports 138, 140, 142, and 144 may include one or more sets of a plurality of outer ports that are circumferentially arranged and spaced apart from each other at a common axial position about the longitudinal axis 32, wherein the plurality of outer ports of each respective set may be disposed at different axial positions. For example, the plurality of outer ports 138, 140, 142, and 144 of each set may include at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500, or more outer ports that are circumferentially arranged and spaced apart evenly or unevenly. The outer ports 138, 140, 142, and 144 may be at an acute or perpendicular angle relative to the outer wall 88 and / or the longitudinal axis 32.

[0043] In the illustrated embodiment, the fluid line 130 is disposed inside the strut 90 (e.g., main strut 92, auxiliary strut 93) and is fluidly coupled to the strut port 146. As shown, the strut port 146 is integrally disposed in the front end portion 176 (e.g., upstream end portion) of the strut 90. The strut port 146 is configured to allow fluid 73 to enter the chamber 89 from the front end portion 176 of the strut 90. In the illustrated embodiment, the strut port 146 is radially disposed relative to the inner wall 86 below or within a radial height 178 (e.g., radius threshold or radial range). In some embodiments, the radial height 178 is less than half of the total height 180 (e.g., total radius or radial length) of the strut 90 extending from the inner wall 86 to the outer wall 88. Allowing fluid 73 to enter via the strut port 146 can mitigate the formation of rotating stall (e.g., hub vortex stall) in the chamber 89 downstream of the turbine 22. The strut port 146 will be described in further detail herein.

[0044] The fluid injection port 54 may include any combination of the inner port 134, the outer port 136, and the strut port 146. For example, in some embodiments, the fluid injection system 38 may include the inner port 134 and the strut port 146 while omitting the outer port 136. In some embodiments, the controller 56 may be configured to independently control the flow of fluid into the inner port 134, the outer port 136, and the strut port 146 simultaneously and / or sequentially based on operating conditions. The operating conditions may include an operating mode (e.g., steady state, full load, partial load, or transient (e.g., startup, shutdown, etc.)) or sensor feedback (e.g., pressure, flow rate, flow velocity, flow direction, etc.). For example, the sensor feedback may indicate a flow reversal and / or a stall condition.

[0045] In the illustrated embodiment, the ejector 68 is fluidly coupled to the chamber 89 via a fluid line 182 that is coupled to the outer wall 88. As described above, the ejector 68 can operate using high and low pressure gases associated with the venturi section 69 such that the fluid injection system 38 can draw and / or inject fluid. In the illustrated embodiment, the ejector 68 includes an annular body 184 along a central axis 186, where the annular body 184 includes an axial fluid inlet 188, a radial fluid inlet 190, an axial fluid outlet 192, and a venturi section 69 between the axial fluid inlet 188 and the axial fluid outlet 192. The venturi section 69 includes an annular converging wall portion or passage 194, an annular diverging wall portion or passage 196, and an annular throat 198 between the passages 194 and 196. The ejector 68 is configured to receive a high pressure flow (e.g., motive fluid or drive fluid) through the axial fluid inlet 188 and a low pressure flow (e.g., driven fluid or suction fluid) through the radial fluid inlet 190. In the illustrated embodiment, the high pressure flow can be compressor bleed 82; however, the ejector 68 can also use other high pressure gases. The low pressure flow can be exhaust from one or more regions of the turbine 22 and / or the exhaust section 24 that are susceptible to stall conditions, such as between the last stage blades 91 and the struts 92 along the outer wall 88.

[0046] Thus, in the illustrated embodiment, the ejector 68 is configured to discharge a portion of the exhaust from the chamber 89 between the turbine 22 and the exhaust section 24 by using compressor bleed 82 as the high pressure flow. For example, the compressor bleed 82 can be used in conjunction with the ejector 68 to create a suction force to draw the exhaust from the chamber 89. The ejector 68 can also output a fluid flow (e.g., a mixture of exhaust and compressor bleed flow) to another location in the exhaust section 24, such as downstream of the strut 90. In some embodiments, in addition to and independent of allowing flow through the inner port 134, the outer port 136, and / or the strut port 146, the ejector 68 can also be used to draw or remove exhaust, thereby helping to reduce or eliminate flow reversal and stall conditions.

[0047] Figure 4 is taken along line 4-4 Figure 3Cross-sectional view of an embodiment of a gas turbine engine 12, showing a fluid injection port 54 disposed in an upstream portion 200 (e.g., front end portion) of a plurality of main struts 92 of the gas turbine engine 12 and also disposed in an inner wall 86 and an outer wall 88 of the gas turbine engine 12. In the illustrated embodiment, the fluid injection system 38 includes an inner port 134 disposed in the inner wall 86 (e.g., inner annular wall) and an outer port 136 disposed in the outer wall 88 (e.g., outer annular wall). In some embodiments, the inner port 134 is configured to allow fluid 73 to enter the chamber 89 by injecting fluid 73 radially outward (e.g., in a radially outward direction) through the inner port 134. Additionally or alternatively, the outer port 136 is configured to allow fluid 73 to enter the chamber 89 by injecting fluid 73 radially inward (e.g., in a radially inward direction) through the outer port 136. In the illustrated embodiment, the inner port 134 is circumferentially angled in a direction opposite to the direction of rotation of the turbine blades (e.g., the direction of rotational stall motion). For example, if the blades rotate circumferentially 36 (e.g., the counterclockwise direction shown), the inner port 134 may be angled in the clockwise direction, or vice versa. In certain embodiments, the outer port 136 may additionally be circumferentially angled in a direction opposite to the direction of blade rotation. The circumferential angling of the inner port 134 will be described in further detail herein.

[0048] In the illustrated embodiment, the fluid injection system 38 of the exhaust section 24 includes a strut port 146 (e.g., main strut port 202) integrally disposed in an upstream portion 200 of the main strut 92 (e.g., exhaust strut, diffuser strut). As shown, the fluid injection system 38 is configured to inject fluid 73 into the chamber 89 via the main strut port 202. As shown, the main strut 92 extends radially from the inner wall 86 to the outer wall 88. In the illustrated embodiment, each main strut 92 includes four main strut ports 202 disposed on an inner radial portion 204 of the upstream portion 200 (e.g., front end) of the main strut 92. In certain embodiments, the main strut 92 may include more or fewer than four main strut ports 202 (e.g., 1, 2, 3, 5, 6, 7, 8, 9, 10 or more). As discussed in further detail herein, the main strut port 202 is angled relative to the longitudinal axis (e.g., radial axis) of the main strut 92. Although the illustrated embodiment shows each main strut 92 having the same number of strut ports 146, the number of strut ports 146 may vary between the main struts 92.

[0049] In an exemplary embodiment, the fluid injection system 38 of the exhaust section 24 includes a strut port 146 (e.g., an auxiliary strut port 206) integrally disposed in an upstream portion 205 (e.g., a front end portion) of an auxiliary strut 93 (e.g., an auxiliary exhaust strut, an auxiliary diffuser strut). As shown, the auxiliary strut 93 extends radially 34 from the inner wall 86 to the outer wall 88 of the gas turbine engine 12 and is offset circumferentially (e.g., spaced apart in the circumferential direction 36) from the main strut 92. In certain embodiments, the auxiliary circumferential thickness 208 of the auxiliary strut 93 may be less than the circumferential thickness 210 of the main strut 92 in the circumferential direction 36. However, in some embodiments, the auxiliary circumferential thickness 208 may be equal to or greater than the main strut circumferential thickness 210.

[0050] As shown, the fluid injection system 38 is configured to inject fluid 73 into the chamber 89 via the auxiliary strut port 206. In the exemplary embodiment, each auxiliary strut 93 includes four auxiliary strut ports 206 disposed on an inner radial portion 208 of the upstream portion 205 (e.g., the auxiliary front end) of the auxiliary strut 93. As discussed in further detail herein, the auxiliary strut ports 206 are angled relative to the longitudinal axis of the auxiliary strut 93. In certain embodiments, the auxiliary strut 93 may include more or fewer than four auxiliary strut ports 206 (e.g., 1, 2, 3, 5, 6, 7, 8, 9, 10 or more). While the exemplary embodiment shows each auxiliary strut 93 having the same number of auxiliary strut ports 206, the number of auxiliary strut ports 206 may vary between the auxiliary struts 93.

[0051] It should be appreciated that while the exemplary embodiment shows evenly spaced inner ports 134, outer ports 134, and strut ports 146, in certain embodiments, they may be non-uniformly spaced. Additionally or alternatively, in certain embodiments, the fluid injection system 38 may include more or fewer inner ports 134, outer ports 134, and / or strut ports 146 than shown in the exemplary embodiment.

[0052] Figure 5 is taken along line 5-5 Figure 3Cross-sectional view of an embodiment of the main strut 92 and the auxiliary strut 93, showing fluid inlets 54 provided in the upstream portion 200 of the main strut 92 and the upstream portion 205 of the auxiliary strut 93. In the illustrated embodiment, the main strut 92 includes a nose portion 230 of the upstream portion 200, a central portion 232, a central support 234 provided in the central portion 232, and a tail portion 236 of the downstream portion 235. As shown, the nose portion 230 of the upstream portion 200 includes one or more main strut ports 202 provided in the nose wall 238 of the nose portion 230, where the main strut ports 202 are fluidly coupled to a fluid passage 237 (e.g., a radial fluid passage) in the nose portion 230. In the illustrated embodiment, the auxiliary strut 93 includes a fluid passage 239 (e.g., a radial fluid passage) provided in the upstream portion 205 of the auxiliary strut 93. The fluid passage 239 may be configured to convey fluid 73 radially along the radial direction 34 to the auxiliary strut port 206.

[0053] In the illustrated embodiment, the auxiliary longitudinal length 241 (e.g., the axial length) of the auxiliary strut 93 is shorter than the longitudinal length 243 (e.g., the axial length) of the main strut 92 in the axial direction 32. For example, the auxiliary longitudinal length 241 may be greater than or equal to about 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80% of the longitudinal length 243. In certain embodiments, the auxiliary longitudinal length 241 may be substantially equal to the longitudinal length 243.

[0054] In the illustrated embodiment, the longitudinal central axis 242 passes through the main strut 92 and extends from the leading edge 244 to the trailing edge of the tail portion 236. The longitudinal central axis 242 intersects the leading edge 244 at the central upstream edge or the first intersection point. Each main strut port 202 includes a central axis 240 that is angled with respect to the longitudinal central axis 242 of the main strut 92. In certain embodiments, the angle 245 between the central axis 240 and the longitudinal central axis 242 may vary from 0 degrees to 80 degrees. For example, the angle 245 may be less than or equal to 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees or 80 degrees. In the illustrated embodiment, the central axis 240 is offset from the longitudinal central axis 242 at the leading edge 244 of the nose portion 230 of the main strut 92. In the illustrated embodiment, the central axis 240 is substantially perpendicular to the tangent 246 of the nose wall 238 at the second intersection point 248 of the central axis 240 and the nose wall 238 (i.e., the main strut port 202 is perpendicular to the surface of the nose wall 238 at the position of the main strut port 202). In certain embodiments, the central axis 240 may not be perpendicular to the tangent 246 (i.e., the main strut port 202 may be oriented at an angle other than 90 degrees with respect to the surface of the nose wall 238).

[0055] In an exemplary embodiment, the auxiliary longitudinal center axis 250 extends through the auxiliary strut 93 from the leading edge 252 to the trailing edge opposite the leading edge. The longitudinal center axis 250 intersects the leading edge 252 at a center upstream edge or a first intersection point. Each auxiliary strut port 206 includes an auxiliary center axis 249 that is angled relative to the auxiliary longitudinal center axis 250 of the auxiliary strut 93. As shown, the auxiliary longitudinal center axis 250 is substantially parallel to the longitudinal center axis 242. In certain embodiments, the angle 251 between the auxiliary center axis 249 and the auxiliary longitudinal center axis 250 can vary from 0 degrees to 80 degrees. For example, the angle 245 can be less than or equal to 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, or 80 degrees. In the exemplary embodiment, the auxiliary center axis 249 is offset from the auxiliary longitudinal center axis 250 at the leading edge 252 of the auxiliary strut 93. In the exemplary embodiment, the auxiliary center axis 249 is substantially perpendicular to the tangent 286 of the outer surface 254 at a second intersection point 258 of the auxiliary center axis 248 and the outer surface 254 (i.e., the auxiliary strut port 206 is perpendicular to the surface of the upstream portion 205 at the location of the auxiliary strut port 206). In certain embodiments, the auxiliary center axis 249 may not be perpendicular to the tangent 256 (i.e., the auxiliary strut port 206 may be oriented at an angle other than 90 degrees relative to the surface of the upstream portion 205).

[0056] In certain embodiments, the controller 56 can independently control the flow to the main strut port 202 and the auxiliary strut port 206. That is, the main strut port 202 and the auxiliary strut port 206 can be controlled to inject fluid simultaneously or at different times based on the operating conditions and sensor feedback indicating a need to reduce reverse flow and / or stall conditions. In certain embodiments, in the case where flow is introduced through the inner exhaust wall 86 or the outer exhaust wall 88, the main strut port 202, the auxiliary strut port 206, or both can be omitted. For example, in some embodiments, the exhaust section 24 can include both the main strut 92 and the auxiliary strut 93, and although the main strut 92 may not include the main strut port 202, the auxiliary strut 93 can include the auxiliary strut port 206.

[0057] Figure 6 is taken along line 6-6 Figure 4Cross-sectional view of an embodiment of a strut 90 (e.g., main strut 92, auxiliary strut 93), showing independent control of fluid entry via each fluid inlet port. In the illustrated embodiment, the strut 90 includes strut ports 146 (e.g., main strut port, auxiliary strut port). The strut ports 146 are each fluidly coupled to separate fluid channels 288 (e.g., fluid channels 290, 292, 294, and 296). The fluid channels 288 are disposed within the interior 291 of the strut 90. In the illustrated embodiment, the fluid channels 288 extend from the front wall 297 (e.g., nose wall) of the strut 90 to the outer wall 88 (e.g., outer exhaust wall) of the gas turbine engine 12. In some embodiments, the fluid channels 288 may extend from the front wall 297 to the inner wall 86 of the gas turbine engine 12.

[0058] In the illustrated embodiment, each of the fluid channels 288 is coupled to a valve 298 (e.g., valves 300, 302, 304, and 306). As shown, the valve 298 (e.g., Figure 2 valve 72 in ) is fluidly coupled to a fluid source 74 and communicatively coupled to a controller 56 configured to independently control each of the valves 298 (for simplicity, only the coupling between the controller 56 and the valve 306 is shown). In some embodiments, the controller 56 may be configured to set different flow rates for each valve 298. For example, the controller 56 may control the valve 306 such that fluid 73 travels through the fluid channel 296 and is allowed to enter the chamber 89 via the strut port 154 at a high flow rate. The controller 56 may be configured to vary the flow rate of the fluid 73 from one strut port 146 to another. That is, the controller 56 may control the valves 298 such that the flow rate of the fluid 73 injected into the chamber 89 decreases from the strut port 154 to the strut port 148 (i.e., decreases in the radially outward direction). In some embodiments, the controller 56 may control the valves 298 such that the flow rate of the fluid 73 injected into the chamber 89 increases from the strut port 154 to the strut port 148 (i.e., increases in the radially outward direction). As shown, each of the strut ports 146 (e.g., strut ports 148, 150, 152, and 154) is disposed at a different radial distance from the inner wall 86. In operation, the controller 56 is configured to selectively control the valves 298 (e.g., valves 300, 302, 304, and 306) to regulate the fluid flow rate at different radial distances via different strut ports 146.

[0059] In the illustrated embodiment, each strut port 146 is fluidly coupled to a separate fluid passage 288. In some embodiments, a fluid passage 288 may be fluidly coupled to more than one strut port 146. For example, one fluid passage 288 may be fluidly coupled to strut ports 148 and 150, and another fluid passage 288 may be fluidly coupled to strut ports 152 and 154. In some embodiments, each strut port 146 may be fluidly coupled to the same fluid passage 288. It should be appreciated that while the illustrated embodiment shows four strut ports 146, four fluid passages 288, and four valves 298, the main strut 92 may include more or fewer strut ports 146, fluid passages 288, and / or valves 298 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more). The embodiments described herein regarding independent control of the strut ports 146 may apply to the main strut, the auxiliary strut, or both.

[0060] Figure 7 is a cross-sectional view of an embodiment of a fluid injection port 54 in the inner wall 86 or the outer wall 88 taken along Figure 4 line 7-7, showing a manifold 70 (e.g., an annular manifold, a fluid manifold) that is fluidly coupled to each group or row 332 of fluid injection ports 54 (e.g., a circumferential arrangement of ports at a particular axial location). In the illustrated embodiment, each of the manifolds 70 (e.g., fluid manifolds 334, 336, and 338) is fluidly coupled to a separate group or row 332 of fluid injection ports 54 (e.g., rows 340, 342, and 344). In the illustrated embodiment, each row 332 of fluid injection ports 54 extends circumferentially 36 about the central rotational axis of the gas turbine engine 12. As shown, the rows 332 are axially spaced from each other longitudinally 32 of the gas turbine engine 12. Each manifold 70 is fluidly coupled to each fluid injection port 54 belonging to a particular row 332. For example, fluid manifold 334 may be fluidly coupled to row 340, fluid manifold 336 may be coupled to row 342, and fluid manifold 338 may be coupled to row 344.

[0061] In the illustrated embodiment, each row 332 of fluid is fluidly coupled to a separate row of valves 346 (e.g., rows of valves 348, 350, and 352). The row of valves 346 is communicatively coupled to a controller 56. The controller 56 is configured to independently control the injection of fluid 73 into the chamber 89 through each row 332 of the fluid injection ports 54. The controller 56 may be configured to vary (e.g., increase or decrease) the flow rate of the fluid 73 from one row 332 to another row. That is, the controller 56 may control the row of valves 346 such that the flow rate of the fluid 73 injected into the chamber 89 decreases from row 340 to row 344. In some embodiments, the controller 56 may control the row of valves 346 such that the flow rate of the fluid 73 injected into the chamber 89 increases from row 340 to row 344. The fluid injection ports 54 in the illustrated embodiment may include an inner port 134, an outer port 136, or both.

[0062] Figure 8 is taken along line 8-8 Figure 7 Cross-sectional view of an embodiment of row 342 of the fluid injection port 54, showing that each fluid injection port 54 is circumferentially angled in the circumferential direction 36. In the illustrated embodiment, the fluid injection ports 54 (e.g., fluid injection ports 362, 364, and 366) are disposed in a wall 368 (e.g., inner wall 86, outer wall 88). As shown, the port center axis 370 of the fluid injection port 54 (e.g., port center axes 372, 374, and 376) forms an angle 378 (e.g., angles 380, 382, and 384) with a radial axis 386 (e.g., radial axes 388, 390, and 392) that extends from the central axis of rotation of the gas turbine engine 12 to the intersection 394 (e.g., intersections 396, 398, and 400) of the radial axis 386, the port center axis 370, and the surface 402 (e.g., inner surface, outer surface) of the wall 368. In some embodiments, the fluid injection ports 54 are angled in the opposite direction of the rotation of the turbine blade (e.g., the direction of rotational stall). For example, if the turbine blade rotates in the circumferential direction 36 as shown by arrow 403, the fluid injection ports 54 may be angled in the circumferential direction 36 opposite to arrow 403, thereby causing the fluid 73 to be directed in an angled direction 405 having a circumferential component. The fluid inlet 54 may be angled in the circumferential direction 36 in a clockwise or counterclockwise orientation. In some embodiments, the angle 378 may be in the range of 0 degrees to 80 degrees. For example, the angle 378 may be less than, equal to, or greater than 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, or 80 degrees.

[0063] In an illustrative embodiment, each fluid injection port 54 includes an inlet 404 (e.g., inlets 406, 408, and 410) and an outlet 412 (e.g., outlets 414, 416, and 418). As shown, the angling of the port center axis 370 results in a circumferential offset of the outlet 412 relative to the inlet 404. In an illustrative embodiment, the fluid injection port 54 includes a side surface 420 (e.g., side surfaces 422, 424, and 426). The side surface may have a uniform cross-section 428 extending from the inlet 404 to the outlet 412. For example, the cross-section 428 may be circular, oval, square, rectangular, etc. In an illustrative embodiment, the cross-section 428 is shown to linearly translate along the port center axis 370 from the inlet 404 to the outlet 412 to form the fluid injection port 54. In certain embodiments, the fluid injection port 54 may be curved. That is, the cross-section 428 may translate along a curve extending from the inlet 404 to the outlet 412.

[0064] Figure 9 is a cross-sectional side view of an embodiment of a steam turbine engine 440 taken along the longitudinal axis 32, showing an embodiment of the fluid injection system 38. In an illustrative embodiment, the fluid injection system 38 includes fluid lines 442 (e.g., fluid inlet lines 446, 448, and 450) fluidly coupled to a steam source 452 and an external auxiliary boiler 454. Although the illustrated embodiment shows a steam source 452 and an external auxiliary boiler 454, combinations of one or more of the fluid sources described herein may also be used. The fluid lines 442 are fluidly coupled to a fluid injection port 456. The fluid injection port 456 includes an inner port 458 and an outer port 460 (e.g., outer ports 462, 464, and 466).

[0065] In an illustrative embodiment, the inner port 458 is disposed at a distance 468 downstream of the downstream edge 470 of the last stage blade 472. As shown, the distance 468 falls within a range of a distance 474 that is within one-quarter to one-half of the width 476 spanning the downstream edge 470 of the last stage blade 472 and the rear wall 478 of the steam turbine engine 440. In certain embodiments, the inner port 458 may include one or more rows of axial ports (e.g., a circumferential row of ports). It should be appreciated that allowing fluid 73 to enter via the inner port 458 can mitigate the formation of rotating stall (e.g., hub vortex stall) in the chamber 480 downstream of the turbine 482 of the steam turbine engine 440.

[0066] In an exemplary embodiment, fluid inlet line 446 is fluidly coupled to outer port 462. As shown, outer port 462 is integrally disposed in outer wall 484 and is downstream of the downstream edge 470 of the last stage blade 472. Outer port 462 may include one or more rows of axial ports (e.g., a circumferential row of ports). Outer port 462 is configured to allow fluid 73 to enter chamber 480 from outer wall 484. It should be appreciated that allowing fluid 73 to enter via outer port 462 may mitigate the formation of rotating stall (e.g., hub vortex stall) in chamber 480 downstream of turbine 482.

[0067] In an exemplary embodiment, fluid lines 448 and 450 are fluidly coupled to outer ports 464 and 466, respectively. As shown, outer port 464 is integrally disposed in outer wall 484 and is axially disposed between the penultimate (second from the last) stage blade 486 of turbine 482 and the last (final) stage guide vane 488 of turbine 482. Outer port 464 is configured to allow fluid 73 to enter the second toroidal chamber 490 axially disposed between the penultimate stage blade 486 and the last stage guide vane 488 of turbine 482. Additionally, outer port 466 is integrally disposed in outer wall 484 and is axially disposed between the last stage guide vane 488 and the last stage blade 472 of turbine 482. Outer port 466 is configured to allow fluid 73 to enter the last toroidal chamber 491 axially disposed between the last stage guide vane 488 and the last stage blade 472 of turbine 482.

[0068] In an exemplary embodiment, each of outer ports 460 is shown to be independently controllable via valve 492 coupled to controller 56 such that any combination of outer ports 462, 464, and 466 may allow fluid to enter turbine 482 and / or chamber 480. Allowing fluid 73 to enter via outer ports 462, 464, and 466 may mitigate the formation of rotating stall (e.g., toroidal vortex stall) in toroidal chambers 490 and 491 (e.g., turbine chambers) and chamber 480. Additionally, outer ports 460 may include any combination of outer ports 462, 464, and 466. Although outer ports 462, 464, 466 may be singular in form herein, it should be understood that multiple circumferentially arranged outer ports 462, 464, 466 may be used.

[0069] Figure 10 is taken along Figure 3 line 10-10 of Figure 2Cross-sectional schematic view of an embodiment of a stall mitigation system. In the illustrated embodiment, the cutting plane of the cross-section is orthogonal to the radial direction 34 and intersects the last-stage guide vane 170 of the turbine 22, the last-stage blade 91 of the turbine 22, and the main strut 92 of the exhaust section 24. As shown, fluid 73 is injected (e.g., allowed to enter) through one or more fluid inlets 136 (e.g., the outer inlet 144 mentioned in Figure 3 ), which are positioned downstream of the axial position of the last-stage guide vane 170 and upstream of the axial position of the last-stage blade 91, such that the fluid 73 is axially injected between the last-stage guide vane 170 and the last-stage blade 91. Additionally, one or more fluid inlets 498 are configured to inject the fluid 73 circumferentially 175 (e.g., in a direction opposite to the blade rotation direction of the last-stage blade 91). In certain embodiments, the one or more fluid inlets 498 may include Figure 3 the fluid inlets 136, 144 of

[0070] . The injected fluid 73 is applied to the reverse flow 500 of the exhaust, causing the reverse flow 500 to deflect in the direction 175. The deflected reverse flow 502 is more closely aligned with the rear portion 504 of the last-stage guide vane 170. Injecting the fluid 73 in the direction 175 causes the deflected reverse flow 502 to be more closely aligned with the outer contour 506 of the last-stage guide vane 170, thereby mitigating the turbulence that might otherwise be caused by the reverse flow 121 (e.g., undeflected) contacting the last-stage guide vane 170 with greater orthogonality. Figure 3 As discussed herein, injecting the fluid 73 through the outer inlet 144 between the last-stage guide vane 170 and the last-stage blade 91 can mitigate the formation of toroidal vortices between the last-stage guide vane 170 and the last-stage blade 91. Any number of outer inlets 498 can be provided between the last-stage guide vane 170 and the last-stage blade 91. For example, 2, 3, 4, 5, 6, 7, 9, 15, 20, 30, 50, 100, or more outer inlets 498 can be provided between the last-stage guide vane 170 and the last-stage blade 91. Similar to the inner inlets, the outer inlets 498 can be axially aligned in the turbine 22. In certain embodiments, with reference to Figure 3 , the outer inlets 498 can be axially (e.g., longitudinally) provided as the outer inlet 142 between the penultimate-stage blade 168 and the last-stage guide vane 170, the outer inlet 140 between the penultimate-stage guide vane 166 and the penultimate-stage blade 168, or the outer inlet between any suitable blade and guide vane of the turbine 22. As

[0071] shown, the turbine 22 may also include one or more inner inlets 134 longitudinally (e.g., axially) disposed between the last-stage guide vane 170 and the last-stage blade 91 of the turbine 22 for injecting the fluid 73 between the last-stage guide vane 170 and the last-stage blade 91. In certain embodiments, the one or more inner inlets 134 may be in the same axial position as the outer inlet 136.The technical effects of the disclosed embodiments include the ability to mitigate the formation of rotating stall cells in a turbine section, such as the exhaust section of a gas turbine engine or a steam turbine. Specifically, the disclosed embodiments can interrupt the forward and / or reverse flow of the exhaust, thereby reducing the velocity gradient of the shear layer directly downstream of the last stage blades of the corresponding turbine. For example, in one embodiment, an inner fluid injection port disposed on the inner wall of the turbine exhaust section is configured to inject fluid into the reverse flow path of the exhaust, thereby reducing the velocity of the reverse flow before it reaches the last stage blades. Additionally, when the exhaust changes from forward flow to reverse flow due to being blocked by a strut, a strut fluid injection port disposed in the upstream portion of the main diffuser strut and / or the auxiliary diffuser strut injects fluid into the exhaust path. Like the inner fluid injection port, the strut fluid injection port reduces the velocity of the reverse flow before it reaches the last stage blades, thereby reducing the velocity gradient of the shear layer.

[0072] As set forth below, the subject matter described in detail above can be defined by one or more clauses.

[0073] The system includes a turbine exhaust section downstream of the turbine. The turbine exhaust section includes an exhaust flow path. The turbine exhaust section further includes an inner wall radially disposed along the exhaust flow path. The turbine exhaust section further includes an outer wall radially outward from the inner wall and along the exhaust flow path. The system further includes a fluid injection system configured to inject fluid into a chamber radially disposed between the inner wall and the outer wall via a plurality of inner ports disposed in the inner wall. The plurality of inner ports are disposed downstream of the downstream edge of the last stage blades of the turbine.

[0074] The system according to the preceding clause, wherein the plurality of inner ports are disposed at a distance downstream of the downstream edge of the last stage blades of the turbine, wherein the distance is between 25% and 50% of the width spanning from the downstream edge of the last stage blades to the upstream edge of the struts of the turbine exhaust section.

[0075] The system according to any one of the preceding clauses, wherein the fluid injection system is configured to inject the fluid into the chamber via a plurality of first outer ports disposed in the outer wall.

[0076] The system according to any one of the preceding clauses, wherein the fluid injection system is configured to inject the fluid into a turbine chamber radially disposed between the inner wall and the outer wall and axially disposed between the guide vanes and the blades of the turbine via a plurality of second outer ports integrally disposed in the outer wall.

[0077] The system according to any one of the preceding clauses, wherein the central axis of the inner port among the plurality of inner ports is circumferentially angled with respect to a radial axis extending from the longitudinal central axis of the turbine exhaust section to the central axis of the inner port.

[0078] The system according to any one of the preceding clauses, wherein the fluid injection system includes an ejector fluidly coupled to one or more fluid ports in the outer wall, and wherein the ejector is configured to aspirate exhaust gas from the chamber.

[0079] The system according to any one of the preceding clauses, wherein the fluid includes bleed air from a compressor of the turbine, external gas, inert gas, or a combination thereof.

[0080] The system includes a turbine exhaust section. The turbine exhaust section includes an exhaust gas flow path, an inner wall radially disposed along the exhaust gas flow path, and an outer wall radially outward from the inner wall and along the exhaust gas flow path, and struts radially extending from the inner wall to the outer wall. The system further includes a fluid injection system configured to inject fluid into a chamber radially disposed between the inner wall and the outer wall via a plurality of ports disposed in a front end portion of the struts. The plurality of ports are disposed downstream of a downstream edge of the last turbine blade of the turbine.

[0081] The system according to the preceding clause, wherein the plurality of ports are disposed on an inner radial portion of the front end portion of the strut, and wherein the central axis of the port among the plurality of ports is angled with respect to the longitudinal central axis of the strut.

[0082] The system according to any one of the preceding clauses, the system includes auxiliary struts extending from the inner wall towards the outer wall, wherein the auxiliary struts are circumferentially offset from the struts.

[0083] The system according to any one of the preceding clauses, wherein the fluid injection system is configured to inject the fluid into the chamber via a plurality of auxiliary ports disposed in an auxiliary front end portion of the auxiliary struts.

[0084] The system according to any one of the preceding clauses, wherein the plurality of auxiliary ports are disposed on an auxiliary inner radial portion of the auxiliary front end portion of the auxiliary strut, and wherein the auxiliary central axis of the auxiliary port among the plurality of auxiliary ports is angled with respect to the auxiliary longitudinal central axis of the auxiliary strut.

[0085] The system according to any one of the preceding clauses, wherein the central axes of the plurality of ports are offset from the longitudinal central axis of the strut, wherein the auxiliary central axis is offset from the auxiliary longitudinal central axis, or wherein the central axis and the auxiliary central axis are offset from the longitudinal central axis and the auxiliary longitudinal central axis, respectively.

[0086] The system according to any one of the preceding clauses, wherein the fluid injection system includes a controller configured to: independently control the flow to different ones of the plurality of ports to inject the fluid into the chamber, independently control the flow to different ones of the plurality of auxiliary ports to inject the fluid into the chamber, or both.

[0087] The system includes a turbine exhaust section downstream of the turbine. The turbine exhaust section includes an exhaust flow path, an inner wall disposed radially along the exhaust flow path, and an outer wall disposed radially outward from the inner wall and along the exhaust flow path. The system further includes a fluid injection system. The fluid injection system includes a fluid supply device configured to supply one or more fluids to the turbine exhaust section. The fluid injection system further includes a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to control the injection of the one or more fluids into a chamber radially disposed between the inner wall and the outer wall via a plurality of inner ports integrally formed in the inner wall. The plurality of inner ports are disposed downstream of the downstream edge of the turbine last stage blade.

[0088] The system according to the preceding clause, wherein the fluid injection system is configured to inject the one or more fluids into the chamber via a plurality of first outer ports disposed in the outer wall.

[0089] The system according to any one of the preceding clauses, wherein the fluid injection system is configured to inject the one or more fluids radially between the inner wall and the outer wall and axially between the guide vanes and the blades of the turbine via a plurality of second outer ports integrally provided in the outer wall.

[0090] The system according to any one of the preceding clauses, wherein the plurality of inner ports, the plurality of first outer ports, the plurality of second outer ports, or a combination thereof include multiple rows of ports circumferentially arranged at different axial positions, wherein the controller is configured to independently control the injection of the one or more fluids through each of the multiple rows.

[0091] The system according to any one of the preceding clauses, wherein the fluid injection system includes an ejector fluidly coupled to one or more fluid ports in the outer wall, wherein the ejector is configured to aspirate exhaust gas from the chamber.

[0092] The system according to any one of the preceding clauses, wherein the controller is configured to: independently control the injection of the one or more fluids via the plurality of inner ports, the plurality of first outer ports, the plurality of second outer ports, or combinations thereof, control the suction of exhaust from the chamber independently of the injection of the one or more fluids, or both.

[0093] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any combined method. The scope of the invention for which patent protection may be sought is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not materially different from the literal language of the claims, then such other examples are intended to be within the scope of the claims.

Claims

1. A stall mitigation system (11) for a gas turbine engine (12), the system (11) comprising: A turbine exhaust section (24) downstream of the expansion turbine (22), the turbine exhaust section (24) comprising: an exhaust flow path (84); an inner wall (86) disposed radially along the exhaust gas flow path (84), the inner wall (86) defining a plurality of inner ports (54, 134); and an outer wall (88) disposed radially outward from the inner wall (86) and along the exhaust gas flow path (84); and a fluid injection system (38) configured to inject a fluid (73) into a chamber (89) radially disposed between the inner wall (86) and the outer wall (88) via the plurality of inner ports (54, 134); The plurality of inner ports (54, 134) are disposed downstream of a downstream edge (156) of a last-stage blade (91) of the expansion turbine (22).

2. The system (11) of claim 1, wherein the plurality of inner ports (54, 134) are disposed at a distance downstream of the downstream edge (156) of the last stage blade (91) of the expansion turbine (22), wherein the distance is between 25% and 50% of a width spanning from the downstream edge (156) of the last stage blade (91) to the upstream edge (164) of the strut (90) of the turbine exhaust section (24).

3. The system (11) of claim 1, wherein the fluid injection system (38) is configured to inject the fluid (73) into the chamber (89) via a plurality of first external ports (136) disposed in the outer wall (88).

4. The system (11) of claim 3, wherein the fluid injection system (38) is configured to inject the fluid (73) into a turbine chamber (174) via a plurality of second external ports (140, 142, 144) integrally disposed in the outer wall (88), the turbine chamber being radially disposed between the inner wall (86) and the outer wall (88) and axially disposed between the guide vanes (46) and the blades (45) of the expansion turbine (22).

5. The system (11) according to claim 4, comprising: A controller (56) having a processor (58), a memory (60), and instructions (62) stored on the memory (60) and executable by the processor (58) to independently control the injection of the fluid (73) into the chamber (89) radially disposed between the inner wall (86) and the outer wall (88) via the plurality of inner ports (134), the plurality of first outer ports (136), and the plurality of second outer ports (140, 142, 144).

6. The system (11) of claim 5, wherein the plurality of inner ports (134), the plurality of first outer ports (136), the plurality of second outer ports (140, 142, 144), or a combination thereof comprises a plurality of rows (332) of ports arranged circumferentially at different axial locations; and wherein the controller (56) is configured to independently control the injection of the fluid (73) through each row (340, 342, 344) of the plurality of rows (332), to control the extraction of exhaust gas from the chamber (89) independently of the injection of the fluid (73), or both.

7. The system (11) of claim 1, wherein a central axis (370) of an inner port (134) of the plurality of inner ports (134) is circumferentially angled relative to a radial axis (386) extending from a longitudinal central axis of the turbine exhaust section (24) to the central axis (370) of the inner port (134).

8. The system (11) of claim 1, wherein the fluid injection system (38) comprises an ejector (68) fluidly coupled to one or more fluid ports (136) in the outer wall (88), wherein the ejector (68) is configured to draw exhaust gas from the chamber (89).

9. The system (11) of claim 1, wherein the fluid (73) comprises bleed air (82) from a compressor (18) of the gas turbine engine (12), external gas (132), an inert gas (78), or a combination thereof.

10. A stall mitigation system (11) for a gas turbine engine (12), the system (11) comprising: A turbine exhaust section (24), the turbine exhaust section comprising: an exhaust flow path (84); an inner wall (86) disposed radially along the exhaust gas flow path (84); an outer wall (88) disposed radially outward from the inner wall (86) and along the exhaust gas flow path (84); and struts (90, 92) extending radially from the inner wall (86) to the outer wall (88); and A fluid injection system (38) configured to inject a fluid (73) into a chamber (89) radially disposed between the inner wall (86) and the outer wall (88) via a plurality of ports (146) disposed in a front end portion (176) of the struts (90, 92), the plurality of ports (146) being disposed downstream of a downstream edge (470) of a last turbine blade (91, 472) of an expansion turbine (22).

11. The system (11) of claim 10, wherein the plurality of ports (146) are disposed on an inner radial portion (204, 208) of the front end portion (176) of the strut (90, 92), and wherein a center axis of a port in the plurality of ports (146) is angled relative to a longitudinal center axis of the strut (90, 92).

12. A system (11) according to claim 10, comprising an auxiliary support (93) extending from the inner wall (86) toward the outer wall (88), wherein the auxiliary support (93) is offset circumferentially from the support (90); and wherein the fluid injection system (38) is configured to inject the fluid (73) into the chamber (89) via a plurality of auxiliary ports (146, 206) provided in an auxiliary front end portion (205) of the auxiliary support (93).

13. A system (11) according to claim 12, wherein the plurality of auxiliary ports (146, 206) are arranged on the auxiliary inner radial portion (208) of the auxiliary front end portion (205) of the auxiliary support (93), and wherein the auxiliary center axis (249) of the auxiliary ports (146, 206) among the plurality of auxiliary ports (146, 206) is angled relative to the auxiliary longitudinal center axis (250) of the auxiliary support (93).

14. A system (11) according to claim 13, wherein the central axis (240) of the multiple ports (146) is offset from the longitudinal central axis (242) of the pillars (90, 92), wherein the auxiliary central axis (249) is offset from the auxiliary longitudinal central axis (250) of the auxiliary pillar (93), or wherein the central axis (240) and the auxiliary central axis (249) are offset from the longitudinal central axis (242) and the auxiliary longitudinal central axis (250), respectively.

15. The system (11) of claim 12, wherein the fluid injection system (38) includes a controller (56) configured to: independently controlling flow to different ones of the plurality of ports (146) to inject the fluid (73) into the chamber (89); independently controlling flow to different auxiliary ports of the plurality of auxiliary ports (146, 206) to inject the fluid (73) into the chamber (89); or both.

Images