Patent Publication Number: US-10316746-B2

Title: Turbine system with exhaust gas recirculation, separation and extraction

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and benefit of U.S. Provisional Patent Application No. 62/112,123, entitled “TURBINE SYSTEM WITH EXHAUST GAS RECIRCULATION, SEPARATION AND EXTRACTION,” filed on Feb. 4, 2015, which is incorporated by reference herein in its entirety for all purposes. 
    
    
     BACKGROUND 
     The subject matter disclosed herein relates to gas turbine engines, and more particularly, to systems for exhausting combustion gases from gas turbine engines. 
     Gas turbine engines are used in a wide variety of applications, such as power generation, aircraft, and various machinery. Gas turbine engines generally combust a fuel with an oxidant (e.g., air) in a combustor section to generate hot combustion products, which then drive one or more turbine stages of a turbine section. In turn, the turbine section drives one or more compressor stages of a compressor section, thereby compressing oxidant for intake into the combustor section along with the fuel. Again, the fuel and oxidant mix in the combustor section, and then combust to produce the hot combustion products. These combustion products may include unburnt fuel, residual oxidant, and various emissions (e.g., nitrogen oxides) depending on the condition of combustion. Gas turbine engines typically consume a vast amount of air as the oxidant, and output a considerable amount of exhaust gas into the atmosphere. In other words, the exhaust gas is typically wasted as a byproduct of the gas turbine operation. 
     BRIEF DESCRIPTION 
     Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below. 
     In one embodiment, a system includes a turbine combustor having a first volume configured to receive a combustion fluid and to direct the combustion fluid into a combustion chamber. The turbine combustor includes a second volume configured to receive a first flow of an exhaust gas and to direct the first flow of the exhaust gas into the combustion chamber. The turbine combustor also includes a third volume disposed axially downstream from the first volume and circumferentially about the second volume. The third volume is configured to receive a second flow of the exhaust gas and to direct the second flow of the exhaust gas out of the turbine combustor via an extraction outlet, and the third volume is isolated from the first volume and from the second volume. 
     In one embodiment, a system includes a turbine combustor having a housing, a liner defining a combustion chamber, and a flow sleeve disposed about the liner. The turbine combustor also includes a first volume disposed in a head end of the combustion chamber, wherein the first volume is configured to receive a combustion fluid and to provide the combustion fluid to the combustion chamber. The turbine combustor also includes a second volume disposed downstream of the first volume and defined between the flow sleeve and the housing. The second volume is configured to receive a first flow of recirculated combustion products and to direct the first flow of recirculated combustion products out of the combustor via an extraction conduit. A flange extends between the flow sleeve and the housing, and the flange is configured to block flow of the combustion fluid into the second volume and to block flow of the first flow of recirculated combustion products into the first volume. 
     In one embodiment, a method includes combusting an oxidant and a fuel in a combustion chamber of a turbine combustor to generate combustion products. The method also includes compressing at least some of the combustion products generated by the combustor to generate compressed combustion products. The method further includes cooling a liner of the turbine combustor using a first flow of the compressed combustion products and isolating a second flow of the compressed combustion products within the turbine combustor from the oxidant, the fuel, and the first flow of the compressed combustion products. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become 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: 
         FIG. 1  is a schematic diagram of an embodiment of a gas turbine system configured to recirculate combustion products generated by a turbine combustor; 
         FIG. 2  is a cross-sectional side view schematic of an embodiment of the turbine combustor of  FIG. 1 ; 
         FIG. 3  is a cross-sectional side view schematic of an embodiment of a flow sleeve of the turbine combustor of  FIG. 2 ; and 
         FIG. 4  is a cutaway perspective view of an embodiment of a flow sleeve of the turbine combustor of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     Detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Embodiments of the present invention may, however, be embodied in many alternate forms, and should not be construed as limited to only the embodiments set forth herein. 
     Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are illustrated by way of example in the figures and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the present invention. 
     The terminology used herein is for describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Although the terms first, second, primary, secondary, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, but not limiting to, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any, and all, combinations of one or more of the associated listed items. 
     Certain terminology may be used herein for the convenience of the reader only and is not to be taken as a limitation on the scope of the invention. For example, words such as “upper”, “lower”, “left”, “right”, “front”, “rear”, “top”, “bottom”, “horizontal”, “vertical”, “upstream”, “downstream”, “fore”, “aft”, and the like; merely describe the configuration shown in the FIGS. Indeed, the element or elements of an embodiment of the present invention may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations. 
     As discussed in detail below, the disclosed embodiments relate generally to gas turbine systems with exhaust gas recirculation (EGR), and particularly stoichiometric operation of the gas turbine systems using EGR. The gas turbine systems disclosed herein may be coupled to a hydrocarbon production system and/or include a control system, a combined cycle system, an exhaust gas supply system, and/or an exhaust gas processing system, and each of these systems may be configured and operated as described in U.S. Patent Application No. 2014/0182301, entitled “SYSTEM AND METHOD FOR A TURBINE COMBUSTOR,” filed on Oct. 30, 2013, and U.S. Patent Application No. 2014/0123660, entitled “SYSTEM AND METHOD FOR A TURBINE COMBUSTOR,” filed on Oct. 30, 2013, both of which are hereby incorporated by reference in its entirety for all purposes. For example, the gas turbine systems may include stoichiometric exhaust gas recirculation (SEGR) gas turbine engines configured to recirculate the exhaust gas along an exhaust recirculation path, stoichiometrically combust fuel and oxidant along with at least some of the recirculated exhaust gas, and capture the exhaust gas for use in various target systems. The recirculation of the exhaust gas along with stoichiometric combustion may help to increase the concentration level of carbon dioxide (CO 2 ) in the exhaust gas, which can then be post treated to separate and purify the CO 2  and nitrogen (N 2 ) for use in various target systems. The gas turbine systems also may employ various exhaust gas processing (e.g., heat recovery, catalyst reactions, etc.) along the exhaust recirculation path, thereby increasing the concentration level of CO 2 , reducing concentration levels of other emissions (e.g., carbon monoxide, nitrogen oxides, and unburnt hydrocarbons), and increasing energy recovery (e.g., with heat recovery units). Furthermore, the gas turbine engines may be configured to combust the fuel and oxidant with one or more diffusion flames (e.g., using diffusion fuel nozzles), premix flames (e.g., using premix fuel nozzles), or any combination thereof. In certain embodiments, the diffusion flames may help to maintain stability and operation within certain limits for stoichiometric combustion, which in turn helps to increase production of CO 2 . For example, a gas turbine system operating with diffusion flames may enable a greater quantity of EGR, as compared to a gas turbine system operating with premix flames. In turn, the increased quantity of EGR helps to increase CO 2  production. Possible target systems include pipelines, storage tanks, carbon sequestration systems, and hydrocarbon production systems, such as enhanced oil recovery (EOR) systems. 
     In particular, present embodiments are directed toward gas turbine systems, namely stoichiometric exhaust gas recirculation (SEGR) systems having features configured to recirculate combustion products and to direct the recirculated combustion products to various locations within a combustor of the engine. For example, a combustion fluid (e.g., a mixture of oxidant and fuel) may combust within a combustion chamber of the combustor, and the hot combustion gases (e.g., combustion products) drive rotation of a turbine. At least some of the combustion products may be recirculated through the combustor, i.e., exhaust gas recirculation (EGR). In some cases, the combustion products may be directed from the turbine to a recirculating fluid compressor (e.g., EGR compressor) that compresses the combustion products, thereby generating compressed combustion products (e.g., a recirculating fluid or EGR fluid). Some of the recirculating fluid (e.g., a first flow of the recirculating fluid) may pass through an impingement sleeve in a transition piece of the combustor and travel along a combustor liner, thereby cooling the combustor liner. The first flow of the recirculating fluid may then enter the combustion chamber via one or more openings in a forward portion (e.g., upstream portion) of the combustor liner and mix with the combustion fluids in the combustion chamber. In certain embodiments, some of the recirculating fluid (e.g., a second flow of the recirculating fluid) may be directed toward and extracted through an extraction conduit. The recirculating fluid extracted via the extraction conduit may be used in any of a variety of downstream processes, such as enhanced oil recovery (EOR), carbon sequestration, CO 2  injection into a well, and so forth. 
     The gas turbine system may be configured to operate in a stoichiometric combustion mode of operation (e.g., a stoichiometric control mode) and a non-stoichiometric combustion mode of operation (e.g., a non-stoichiometric control mode), such as a fuel-lean control mode or a fuel-rich control mode. In the stoichiometric control mode, the combustion generally occurs in a substantially stoichiometric ratio of a fuel and oxidant, thereby resulting in substantially stoichiometric combustion. In particular, stoichiometric combustion generally involves consuming substantially all of the fuel and oxidant in the combustion reaction, such that the products of combustion are substantially or entirely free of unburnt fuel and oxidant. One measure of stoichiometric combustion is the equivalence ratio, or phi (Φ), which is the ratio of the actual fuel/oxidant ratio relative to the stoichiometric fuel/oxidant ratio. An equivalence ratio of greater than 1.0 results in a fuel-rich combustion of the fuel and oxidant, whereas an equivalence ratio of less than 1.0 results in a fuel-lean combustion of the fuel and oxidant. In contrast, an equivalence ratio of 1.0 results in combustion that is neither fuel-rich nor fuel-lean, thereby substantially consuming all of the fuel and oxidant in the combustion reaction. In context of the disclosed embodiments, the term stoichiometric or substantially stoichiometric may refer to an equivalence ratio of approximately 0.95 to approximately 1.05. However, the disclosed embodiments may also include an equivalence ratio of 1.0 plus or minus 0.01, 0.02, 0.03, 0.04, 0.05, or more. Again, the stoichiometric combustion of fuel and oxidant in the turbine-based service system may result in products of combustion or exhaust gas with substantially no unburnt fuel or oxidant remaining. For example, the exhaust gas may have less than 1, 2, 3, 4, or 5 percent by volume of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NO X ), carbon monoxide (CO), sulfur oxides (e.g., SO X ), hydrogen, and other products of incomplete combustion. By further example, the exhaust gas may have less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 parts per million by volume (ppmv) of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NO X ), carbon monoxide (CO), sulfur oxides (e.g., SO X ), hydrogen, and other products of incomplete combustion. However, the disclosed embodiments also may produce other ranges of residual fuel, oxidant, and other emissions levels in the exhaust gas. As used herein, the terms emissions, emissions levels, and emissions targets may refer to concentration levels of certain products of combustion (e.g., NO X , CO, SO X , O 2 , N 2 , H 2 , HCs, etc.), which may be present in recirculated gas streams, vented gas streams (e.g., exhausted into the atmosphere), and gas streams used in various target systems (e.g., the hydrocarbon production system). 
     In the disclosed embodiments, various flow separating and flow guiding elements are provided to separate the combustion fluid (e.g., fuel, oxidant, etc.), the first flow of recirculating fluid (e.g., EGR fluid), and the second flow of recirculating fluid (e.g., EGR fluid) from one another and to direct these fluids to appropriate locations. For example, a flow sleeve may separate the first flow of the recirculating fluid that flows along the combustor liner from the second flow of the recirculating fluid that flows toward the extraction conduit. By way of another example, a flange may extend radially outward from the flow sleeve toward a combustor housing (e.g., case), thereby separating the second flow of the recirculating fluid from the combustion fluid in a head end of the combustor. The disclosed embodiments may advantageously recirculate the combustion products for cooling the combustion liner and for combustion, as well as for any of a variety of downstream processes (e.g., enhanced oil recovery, CO 2  injection into a well, etc.). Such recirculation techniques may reduce emissions of nitrous oxides and carbon monoxide from the engine. Furthermore, the disclosed embodiments may advantageously provide components configured to separate the various fluids (e.g., combustion fluids and recirculating fluids) from one another within the engine and to efficiently direct the various fluids to appropriate locations. 
     Turning now to the drawings,  FIG. 1  illustrates a block diagram of an embodiment of a gas turbine system  10 . The system  10  may include a stoichiometric exhaust gas recirculation gas turbine engine, as discussed below. As shown, the system  10  includes a primary compressor  12 , a turbine combustor  14  (e.g., combustor), and a turbine  16 . The primary compressor  12  is configured to receive oxidant  18  from an oxidant source  20  and to provide pressurized oxidant  22  to the combustor  14 . The oxidant  18  may include air, oxygen, oxygen-enriched air, oxygen-reduced air, or any combination thereof. Any discussion of air, oxygen, or oxidant herein is intended to cover any or all of the oxidants listed above. Additionally, a fuel nozzle  24  is configured to receive a liquid fuel and/or gas fuel  26 , such as natural gas or syngas, from a fuel source  28  and to provide the fuel  26  to the combustor  14 . Although one combustor  14  and one fuel nozzle  24  are shown for clarity, the system  10  may include multiple combustors (e.g., 2 to 20)  14  and/or each combustor  14  may receive fuel  26  from multiple fuel nozzles  24  (e.g., 2 to 10). 
     The combustor  14  ignites and combusts the mixture of the pressurized oxidant  22  and the fuel  26  (e.g., a fuel-oxidant mixture), and then passes hot pressurized combustion gases  30  into the turbine  16 . Turbine blades are coupled to a shaft  32 , which may be coupled to several other components throughout the turbine system  10 . As the combustion gases  30  pass through the turbine blades in the turbine  16 , the turbine  16  is driven into rotation, which causes the shaft  32  to rotate. Eventually, the combustion gases  30  exit the turbine  16  via an exhaust outlet  34 . As shown, the shaft  32  is coupled to a load  40 , which is powered via rotation of the shaft  32 . For example, the load  40  may be any suitable device that may generate power or work via the rotational output of the system  10 , such as an electrical generator. 
     Compressor blades are included as components of the primary compressor  12 . In the illustrated embodiment, the blades within the primary compressor  12  are coupled to the shaft  32 , and will rotate as the shaft  32  is driven to rotate by the turbine  16 , as described above. The rotation of the blades within the compressor  12  compresses the oxidant  18  from the oxidant source  20  into the pressurized oxidant  22 . The pressurized oxidant  22  is then fed into the combustor  14 , either directly or via the fuel nozzles  24  of the combustors  14 . For example, in some embodiments, the fuel nozzles  24  mix the pressurized oxidant  22  and fuel  26  to produce a suitable fuel-oxidant mixture ratio for combustion (e.g., a combustion that causes the fuel to more completely burn) so as not to waste fuel or cause excess emissions. 
     In the illustrated embodiment, the system  10  includes a recirculating fluid compressor  42  (e.g., EGR compressor), which may be driven by the shaft  32 . As shown, at least some of the combustion gases  30  (e.g., exhaust gas or EGR fluid) flow from the exhaust outlet  34  into the recirculating fluid compressor  42 . The recirculating fluid compressor  42  compresses the combustion gases  30  and recirculates at least some of the pressurized combustion gases  44  (e.g., recirculating fluid) toward the combustor  14 . As discussed in more detail below, a first flow of the recirculating fluid  44  may be utilized to cool a liner of the combustor  14 . A portion of the first flow may be subsequently directed into a combustion chamber of the combustor  14  for combustion, while another portion of the first flow may be directed toward an extraction conduit  46  (e.g., exhaust gas extraction conduit). Additionally, a second flow of the recirculating fluid  44  may not flow along the liner, but rather, may flow between a flow sleeve and a housing of the combustor toward the extraction conduit  46 . The recirculating fluid  44  may be used in any of a variety of manners. For example, the recirculating fluid  44  extracted through the extraction conduit  46  may flow to an extraction system  45  (e.g., an exhaust gas extraction system), which may receive the recirculating fluid  44  from the extraction conduit  46 , treat the recirculating fluid  44 , and then supply or distribute the recirculating fluid  44  to one or more various downstream systems  47  (e.g., an enhanced oil recovery system or a hydrocarbon production system). The downstream systems  47  may utilize the recirculating fluid  44  in chemical reactions, drilling operations, enhanced oil recovery, CO 2  injection into a well, carbon sequestration, or any combination thereof. 
     As noted above, the gas turbine system  10  may be configured to operate in a stoichiometric combustion mode of operation (e.g., a stoichiometric control mode) and a non-stoichiometric combustion mode of operation (e.g., a non-stoichiometric control mode), such as a fuel-lean control mode or a fuel-rich control mode. In the stoichiometric control mode, the combustion generally occurs in a substantially stoichiometric ratio of the fuel and oxidant, thereby resulting in substantially stoichiometric combustion. In context of the disclosed embodiments, the term stoichiometric or substantially stoichiometric may refer to an equivalence ratio of approximately 0.95 to approximately 1.05. However, the disclosed embodiments may also include an equivalence ratio of 1.0 plus or minus 0.01, 0.02, 0.03, 0.04, 0.05, or more. Again, the stoichiometric combustion of fuel and oxidant in the combustor  14  may result in products of combustion or exhaust gas (e.g.,  42 ) with substantially no unburnt fuel or oxidant remaining. For example, the recirculating fluid  44  may have less than 1, 2, 3, 4, or 5 percent by volume of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NO X ), carbon monoxide (CO), sulfur oxides (e.g., SO X ), hydrogen, and other products of incomplete combustion. By further example, the recirculating fluid  44  may have less than approximately 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 parts per million by volume (ppmv) of oxidant (e.g., oxygen), unburnt fuel or hydrocarbons (e.g., HCs), nitrogen oxides (e.g., NO X ), carbon monoxide (CO), sulfur oxides (e.g., SO X ), hydrogen, and other products of incomplete combustion. The low oxygen content of the recirculating fluid  44  may be achieved in any of a variety of manners. For example, in some cases, a stoichiometric mixture or approximately stoichiometric mixture of combustion fluids burn to generate combustion gases  30  having the low oxygen content. Additionally or alternatively, in some embodiments, various filtering or processing steps (e.g., oxidation catalysts or the like) may be implemented between the exhaust outlet  34  and/or the recirculating fluid compressor  42 , or at any other suitable location within the system  10 , to generate the low oxygen recirculating fluid  44 . As noted above, the pressurized, low oxygen recirculating fluid  44  may be used for cooling a liner of the combustor  14 , may be provided to the combustor for combustion, and/or may be extracted from the combustor for use in various chemical reactions, drilling operations, enhanced oil recovery (EOR), carbon sequestration, CO 2  injection into a well, and so forth. 
       FIG. 2  is a cross-sectional side view schematic of an embodiment of the combustor  14  of  FIG. 1 . The combustor  14  may be described herein with reference to an axial axis or direction  48 , a radial axis or direction  50 , and a circumferential axis or direction  52 . The combustor  14  extends from an upstream end  54  to a downstream end  56 . As shown, the combustor  14  includes a combustion chamber  60  defined by a liner  62 . The combustor  14  also includes a flow sleeve  64  disposed circumferentially about at least a portion of the liner  62 . The combustion chamber  60 , the liner  62 , and the flow sleeve  64  are disposed within a combustor housing  66  (e.g., case). 
     A cap  68  is positioned at a forward end  69  of the flow sleeve  64 . In some embodiments, the cap  68  may be coupled to the forward end  69  of the flow sleeve  64  to form a seal  71  via any suitable technique (e.g., bolted, welded, or the like). A combustion fluid  70  (e.g., the fuel  26 , the pressurized oxidant  22 , and/or a mixture thereof) is directed into a head end  72  of the combustor  14  and into the combustion chamber  60 . For example, in the illustrated embodiment, one or more fuel nozzles  24  disposed within the head end  72  of the combustor  14  provide a first flow  74  of the combustion fluid  70  into the combustion chamber  60 . Additionally, a second flow  80  of the combustion fluid  70  flows into a first generally annular volume  76  between a forward portion  78  of the flow sleeve  64  and the case  66 , and then subsequently flows radially into the combustion chamber  60  via one or more first openings  82  (e.g., conduits or holes) in the flow sleeve  64  and one or more second openings  84  (e.g., conduits or holes) in the liner  62 . As shown, the second flow  80  of the combustion fluid  70  may enter the combustion chamber  60  downstream of the first flow  74  of the combustion fluid  70  in a direction that is generally transverse (e.g., a radial direction) to a flow direction  86  within the combustor  14 . 
     The combustor  14  ignites and combusts the combustion fluid  70  in the combustion chamber  60  and passes the hot pressurized combustion gases  30  into the turbine  16 . The combustion gases  30  are passed through the exhaust outlet  34 , and at least some of the combustion gases  30  are directed into the recirculating fluid compressor  42 . In the illustrated embodiment, the recirculating fluid compressor  42  compresses the combustion gases  30  and directs the compressed combustion gases  44  (e.g., recirculating fluid or EGR fluid) toward the combustor  14 . As shown, a first flow  88  of the recirculating fluid  44  passes through an impingement sleeve  90  (e.g., a perforated sleeve) of a transition piece  91  of the combustor  14  and into a second generally annular volume  92  between the liner  62  and the flow sleeve  64 . The first flow  88  of the recirculating fluid  44  may cool the liner  62  as the first flow  88  flows lengthwise along the liner  62  toward the upstream end  54  of the combustor  14 . The first flow  88  may then flow radially into the combustion chamber  60  via one or more openings  93  in the liner  62 , where the first flow  88  is mixed with the combustion fluid  70 . 
     A second flow  94  of the recirculating fluid  44  does not pass through the impingement sleeve  90 , but rather, is directed toward the fluid extraction conduit  46 . In the illustrated embodiment, the second flow  94  of the recirculating fluid  44  flows into a third generally annular volume  96  between the flow sleeve  64  and the case  66 . As shown, the third generally annular volume  96  extends around at least a portion of the second generally annular volume  92  (e.g., the second generally annular volume  92  and the third generally annular volume  96  may extend about an axis of the combustor and/or are coaxial). As used herein, the terms annular, generally annular, or generally annular volume may refer to an annular or non-annular volume having various arcuate surfaces and/or flat surfaces. The second flow  94  flows generally toward the upstream end  54  of the combustor  14  within the third generally annular volume  96  and eventually flows into the extraction conduit  46 . An aft end  97  of the flow sleeve  64  is coupled to the impingement sleeve  90  via a ring  99 , and an aft portion  98  of the flow sleeve  64  separates the second generally annular volume  92  from the third generally annular volume  96 . Thus, once the first flow  88  of the recirculating fluid  44  passes through the impingement sleeve  90  and into the second generally annular volume  92 , the first flow  88  and the second flow  94  of the recirculating fluid  44  are separated (e.g., isolated) from one another. Additionally, as discussed below, the second flow  94  of the recirculating fluid  44  within the combustor  14  is separated (e.g., isolated) from the combustion fluid  70 . 
     The impingement sleeve  90  may be configured to enable a particular volume or percentage of the recirculating fluid  44  into the second generally annular volume  92 . Thus, the first flow  88  of the recirculating fluid  44  may be any suitable fraction of the recirculating fluid  44  output by the recirculating fluid compressor  42 . For example, approximately 50 percent of the recirculating fluid  44  may flow into the second generally annular volume  92 , while approximately 50 percent of the recirculating fluid  44  may flow into the third generally annular volume  96 . In other embodiments, approximately 10, 20, 30, 40, 60, 70, 80, 90 percent or more of the recirculating fluid  44  output by the recirculating fluid compressor  42  may flow through the impingement sleeve  90  and into the second generally annular volume  92 . In some embodiments, approximately 10-75 percent, 20-60 percent, or 30-50 percent of the recirculating fluid  44  output by the recirculating fluid compressor  42  may flow through the impingement sleeve  90  and into the second generally annular volume  92 . 
     In the illustrated embodiment, the fluid extraction conduit  46  is positioned axially between the impingement sleeve  90  and the upstream end  54  of the combustor  14  (e.g., upstream from the impingement sleeve  90  and downstream of the head end  72 ), although the fluid extraction conduit  46  may be disposed in any suitable position for directing the recirculating fluid  44  away from the recirculating fluid compressor  42  and/or from the combustor  14 . In certain embodiments, it may be desirable for the second flow  94  of the recirculating fluid  44  to maintain a relatively high pressure as the second flow  94  flows toward the extraction conduit  46 . Thus, the third generally annular volume  96  may have a relatively large cross-sectional area (e.g., a flow area) configured to maintain the relatively high pressure of the second flow  94 . As space within the combustor  14 , and particularly space between the liner  62  and the case  66  may be limited, the flow area of the third generally annular volume  96  may be greater than a flow area of the second generally annular volume  92  along a length of the third generally annular volume  96  to facilitate maintenance of the high pressure of the second flow  94 . For example, the flow area of the third generally annular volume  96  may be approximately 10, 20, 30, 40, 50, 60 and/or more percent larger than the flow area of the second generally annular volume  92  along the length of the second generally annular volume  92 . Such a configuration may enable a compact design of the combustor  14  and efficient fluid flow, while also maintaining a relatively high pressure of the second flow  94  of the recirculating fluid  44  as this fluid travels toward the extraction conduit  46 . 
     Additionally, in the illustrated embodiment, a flange  100  extends between the flow sleeve  64  and the case  66 . The flange  100  is configured to separate the second flow  94  of the recirculating fluid  44  in the third generally annular volume  96  from the combustion fluid  70  in the first generally annular volume  76 . The flange  100  may have any suitable form for separating these fluids. As shown, the flange  100  extends radially outward from and circumferentially about the flow sleeve  64  (e.g., the flange  100  is annular). The flange  100  may be integrally formed with the flow sleeve  64  from a single piece of material, or the flange  100  may be welded to the flow sleeve  64 . In other embodiments, the flange  100  may be coupled to the flow sleeve  64  via any suitable fasteners (e.g., a plurality of threaded fasteners, such as bolts). The flange  100  may also be coupled to the case  66  via any suitable technique. The flange  100  may be integrally formed with the case  66  from a single piece of material, or the flange  100  may be welded to the case  66 . In other embodiments, the flange  100  may be coupled to the case  66  via any suitable fasteners (e.g., a plurality of threaded fasteners, such as bolts). The flange  100  blocks the flow of the combustion fluid  70  and the second flow  94  of the recirculating fluid  44  across the flange  100 . Additionally, the seal  71  between the cap  68  and the forward end  69  of the flow sleeve  64  blocks the first flow  88  of the recirculating fluid  44  from entering the head end  72  of the combustor  14 . Thus, the cap  68 , the seal  71 , the forward portion  78  of the flow sleeve  64 , and the flange  100  generally separate the combustion fluid  70  and the recirculating fluid  44  from one another. Furthermore, the first flow  88  of the recirculating fluid  44  is at a higher pressure than the combustion fluid  70  flowing from the first annular space  76  into the combustion chamber  60 , and this pressure differential blocks the combustion fluid  70  from flowing downstream into the second generally annular volume  92 . 
       FIG. 3  is a cross-sectional side view schematic of the flow sleeve  64  of the combustor  14 , and  FIG. 4  is a cutaway perspective view of the flow sleeve  64  of the combustor  14 , in accordance with an embodiment. The flow sleeve  64  extends between the forward end  69  and the aft end  97 . The forward end  69  of the flow sleeve  64  is configured to be coupled to the cap  68  to form the seal  71 , while the aft end  97  of the flow sleeve  64  is configured to be coupled to the impingement sleeve  90  via the ring  99 , as shown in  FIG. 2 . The flange  100  extends radially outward from and extends circumferentially about the flow sleeve  64 . As discussed above, the flange  100  is configured to extend between the flow sleeve  64  and the case  66 , thereby separating the first generally annular volume  76  that is configured to receive the combustion fluid  70  from the third generally annular volume  96  that is configured to receive the second flow  94  of the recirculating fluid  44 , as shown in  FIG. 2 . The forward portion  78  of the flow sleeve  64  includes the openings  82  to enable the combustion fluid  70  to flow radially inward from the first generally annular volume  76  toward the combustion chamber  60 . Additionally, in the illustrated embodiments, one or more bosses  114  are provided in the forward portion  78  of the flow sleeve  64 . The one or more bosses  114  may enable placement of hardware through the flow sleeve  64  and into the combustion chamber  60 . As shown, the one or more bosses  114  may include floating collars  116  to block fluid flow through the one or more bosses  114 . Furthermore, as shown in  FIG. 4 , the flange  100  may have apertures  118  that are configured to receive suitable fasteners (e.g., a plurality of threaded fasteners, such as bolts) to couple the flange  100  to the case  66 . In some embodiments, the forward end  69  of the flow sleeve  64  may include apertures  120  that are configured to receive suitable fasteners (e.g., a plurality of threaded fasteners, such as bolts) to couple the flow sleeve  64  to the cap  68 . 
     Technical effects of the disclosed embodiments include systems for controlling the flow of the combustion fluid  70  and the recirculating fluid  44  within the engine  10 . The disclosed embodiments recirculate combustion gases  30 , which may be used to cool the combustor liner  62  and/or may be extracted for other purposes, for example. The first flow  88  of the recirculating fluid  44  may flow along the liner  62 , thereby cooling the liner  62 , while the second flow  94  of the recirculating fluid  44  may be extracted from the combustor  14 . The first flow  88  and the second flow  94  of the recirculating fluid  44  may be separated from one another via the flow sleeve  64 . Additionally, the recirculating fluid  44  may be separated from the combustion fluid  70  via the cap  68 , the forward portion  78  of the flow sleeve  64 , the flange  100 , and/or the pressure differential between the first flow  88  of recirculating fluid  44  and the combustion fluid  70 . The disclosed embodiments may advantageously reduce emissions via recirculating the combustion gases  30 . Additionally, the disclosed embodiments may provide a compact system for efficiently separating and directing various fluids within the combustor  14 . 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may 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 with insubstantial differences from the literal languages of the claims. 
     ADDITIONAL DESCRIPTION 
     The present embodiments provide a system and method for gas turbine engines. It should be noted that any one or a combination of the features described above may be utilized in any suitable combination. Indeed, all permutations of such combinations are presently contemplated. By way of example, the following clauses are offered as further description of the present disclosure: 
     Embodiment 1 
     A system, comprising: a turbine combustor, comprising: a first volume configured to receive a combustion fluid and to direct the combustion fluid into a combustion chamber; and a second volume configured to receive a first flow of an exhaust gas and to direct the first flow of the exhaust gas into the combustion chamber; and a third volume disposed axially downstream from the first volume and circumferentially about at least a portion of the second volume, wherein the third volume is configured to receive a second flow of the exhaust gas and to direct the second flow of the exhaust gas out of the turbine combustor via an extraction outlet, and the third volume is isolated from each of the first volume and from the second volume. 
     Embodiment 2 
     The system of embodiment 1, comprising: a housing; a flow sleeve disposed within the housing, wherein the third volume is defined between an aft portion of the flow sleeve and the housing; and a flange extending radially outward from the flow sleeve to the housing, wherein the flange isolates the third volume from the first volume. 
     Embodiment 3 
     The system defined in any preceding embodiment, wherein the extraction outlet is positioned between a transition piece and a head end of the combustor. 
     Embodiment 4 
     The system defined in any preceding embodiment, comprising: a housing, a liner disposed within the housing; a flow sleeve disposed within the housing and radially outward of the liner, wherein the second volume is defined between the liner and the flow sleeve, the third volume is defined between the flow sleeve and the housing, and an aft portion of the flow sleeve isolates the first volume from the second volume. 
     Embodiment 5 
     The system defined in any preceding embodiment, comprising an exhaust gas compressor configured to compress and to route the exhaust gas to the turbine combustor. 
     Embodiment 6 
     The system defined in any preceding embodiment, comprising a gas turbine engine having the turbine combustor, wherein the gas turbine engine is a stoichiometric exhaust gas recirculation gas turbine engine. 
     Embodiment 7 
     The system defined in any preceding embodiment, comprising an exhaust gas extraction system coupled to the extraction conduit, and a hydrocarbon production system coupled to the exhaust gas extraction system. 
     Embodiment 8 
     The system defined in any preceding embodiment, wherein the first volume is disposed within a head end of the turbine combustor. 
     Embodiment 9 
     The system defined in any preceding embodiment, comprising: a liner defining a combustion chamber of the turbine combustor; a flow sleeve disposed radially outward of the liner; and a cap positioned proximate to the head end of the turbine combustor and coupled to a forward end of the flow sleeve to form a seal; wherein the second volume is defined between the liner and flow sleeve, and the seal is configured to block the first flow of the second fluid from flowing into the head end of the turbine combustor. 
     Embodiment 10 
     The system defined in any preceding embodiment, wherein a forward portion of the flow sleeve comprises one or more openings configured to enable the first fluid to flow radially inward through the flow sleeve and toward the combustion chamber. 
     Embodiment 11 
     The system defined in any preceding embodiment, wherein a first cross-sectional flow area of the second volume is less than a second cross-sectional flow area of the third volume. 
     Embodiment 12 
     A system, comprising: a turbine combustor, comprising: a housing; a liner defining a combustion chamber; a flow sleeve disposed about the liner; a first volume disposed in a head end of the combustion chamber, wherein the first volume is configured to receive a combustion fluid and to provide the combustion fluid to the combustion chamber; a second volume disposed downstream of the first volume and defined between the flow sleeve and the housing, wherein the second volume is configured to receive a first flow of recirculated combustion products and to direct the first flow of recirculated combustion products out of the combustor via an extraction conduit; and a flange extending between the flow sleeve and the housing, wherein the flange is configured to block flow of the combustion fluid into the second volume and to block flow of the first flow of recirculated combustion products into the first volume. 
     Embodiment 13 
     The system defined in any preceding embodiment, comprising a third volume defined between the liner and the flow sleeve, wherein the third volume is configured to receive a second flow of recirculated combustion products and to direct the second flow of recirculated combustion products into the combustion chamber, and the flow sleeve isolates the second volume from the third volume. 
     Embodiment 14 
     The system defined in any preceding embodiment, comprising a transition piece having an impingement sleeve, wherein the impingement sleeve enables the second flow of recirculated combustion products to flow into the third volume. 
     Embodiment 15 
     The system defined in any preceding embodiment, wherein the extraction conduit is positioned between a transition piece and a head end of the turbine combustor. 
     Embodiment 16 
     The system defined in any preceding embodiment, comprising an exhaust gas compressor configured to compress and to route the recirculated combustion products to the turbine combustor. 
     Embodiment 17 
     The system defined in any preceding embodiment, comprising an exhaust gas extraction system coupled to the extraction conduit, and a hydrocarbon production system coupled to the exhaust gas extraction system. 
     Embodiment 18 
     The system defined in any preceding embodiment, comprising a gas turbine engine having the turbine combustor, wherein the gas turbine engine is a stoichiometric exhaust gas recirculation gas turbine engine. 
     Embodiment 19 
     A method, comprising: combusting an oxidant and a fuel in a combustion chamber of a turbine combustor to generate combustion products; compressing at least some of the combustion products generated by the combustor to generate compressed combustion products; cooling a liner of the turbine combustor using a first flow of the compressed combustion products; and isolating a second flow of the compressed combustion products within the turbine combustor from the oxidant, the fuel, and the first flow of the compressed combustion products. 
     Embodiment 20 
     The method or system defined in any preceding embodiment, wherein combusting the oxidant and the fuel comprises operating the turbine combustor in a stoichiometric combustion mode of operation. 
     Embodiment 21 
     The method or system defined in any preceding embodiment, comprising directing the first flow of the compressed combustion products into the combustion chamber. 
     Embodiment 22 
     The method or system defined in any preceding embodiment, comprising extracting the second flow of the compressed combustion products out of the turbine combustor. 
     Embodiment 23 
     The method or system defined in any preceding embodiment, wherein extracting the second flow of the compressed combustion products out of the combustor occurs between a transition piece and a head end of the turbine combustor. 
     Embodiment 24 
     The method or system defined in any preceding embodiment, wherein the first flow of the compressed combustion products comprises approximately 50 percent of the compressed combustion products output by the compressor. 
     Embodiment 25 
     The method or system defined in any preceding embodiment, wherein the compressed combustion products output by the compressor comprise less than 5 percent by volume of oxygen.