Recirculation system for gas turbine engine

Abstract

A recirculation system (206, 306) for a gas turbine engine (100) includes a mixing chamber (208) including an inlet end (210) to receive an exhaust gas (30) containing unburned fuel and an outlet end (214); and at least one recirculation conduit (220) including an inlet opening (222) in fluid communication with the mixing chamber (208) proximate the outlet end (214) and an outlet opening (226) in fluid communication with the mixing chamber (208) proximate the inlet end (210). The recirculation system (206, 306) also includes a fan (232). The fan (232) is operable to receive at least one of a substantially fuel-free exhaust gas flow (40) and a fresh air flow (60) present within the at least one recirculation conduit (220) and to direct at least one of a portion (50) of the substantially fuel-free exhaust gas flow (40) and a portion (70) of the fresh air flow (60) into the mixing chamber (208) to reduce an amount of unburned fuel in the exhaust gas (30).

Description

Technical Field

[0001] This disclosure relates to a recirculation system for a gas turbine engine, an exhaust system for a gas turbine engine, and a method for recirculating gases associated with a gas turbine engine. Background Technology

[0002] Gas turbine engines can operate on a variety of fuels. Each fuel may have a different energy density, and therefore the amount of fuel required to run a gas turbine engine may also vary. For example, as the energy density of a fuel decreases, a gas turbine engine may require more fuel to maintain the same load.

[0003] In certain situations, gas turbine engines may experience ignition failures, ignition delays, or shutdowns during operation. During such situations, a significant amount of unburned fuel may be present in the exhaust gases. Depending on the air-fuel ratio in the exhaust gases, unintended knocking and / or ignition may occur in the exhaust pipe from the gas turbine engine.

[0004] Therefore, it is desirable to find a feasible system that can maintain the air-fuel ratio below a predetermined value and also retain the heat of the exhaust gas from the gas turbine engine, while solving the aforementioned problems.

[0005] U.S. Patent No. 8,926,917 describes systems and methods for oxidizing gases. In some embodiments, a reaction chamber is configured to receive fuel gas and maintain the gas within the reaction chamber at a temperature above its auto-ignition temperature. The reaction chamber may also be configured to maintain the reaction temperature within the reaction chamber below its quenching temperature. In some embodiments, heat and product gases from the oxidation process may be used, for example, to drive a turbine or a reciprocating engine and injected back into the reaction chamber. Summary of the Invention

[0006] In one aspect of this disclosure, a recirculation system for a gas turbine engine is provided. The recirculation system includes a mixing chamber having an inlet end and an outlet end. The inlet end of the mixing chamber is in fluid communication with the gas turbine engine to receive exhaust gas from the gas turbine engine. The exhaust gas contains unburned fuel. The recirculation system also includes at least one recirculation duct connected to the mixing chamber. The at least one recirculation duct includes an inlet opening in fluid communication with the mixing chamber near the outlet end. The at least one recirculation duct also includes an outlet opening in fluid communication with the mixing chamber near the inlet end. The recirculation system further includes a fan disposed within the at least one recirculation duct. The fan is operable to receive at least one of a fresh air flow and a substantially fuel-free exhaust gas flow present near the outlet end of the mixing chamber within the at least one recirculation duct, via the inlet opening of the at least one recirculation duct. The fan is also operable to direct at least one of a portion of the substantially fuel-free exhaust gas flow and a portion of the fresh air flow into the mixing chamber via the outlet opening of the at least one recirculation duct. Furthermore, at least one of the portion of the substantially fuel-free exhaust gas flow and the portion of the fresh air flow mixes with the exhaust gas present in the mixing chamber near the inlet end of the mixing chamber to reduce the amount of unburned fuel in the exhaust gas.

[0007] In another aspect of this disclosure, an exhaust system for a gas turbine engine is provided. The exhaust system includes an engine exhaust port defining an exhaust interface. The exhaust system also includes a recirculation system in fluid communication with the exhaust interface of the engine exhaust port. The recirculation system includes a mixing chamber having an inlet end and an outlet end. The inlet end of the mixing chamber is in fluid communication with the exhaust interface of the engine exhaust port to receive exhaust gas from the exhaust interface. The exhaust gas contains unburned fuel. The recirculation system also includes at least one recirculation duct connected to the mixing chamber. The at least one recirculation duct includes an inlet opening in fluid communication with the mixing chamber near the outlet end. The at least one recirculation duct also includes an outlet opening in fluid communication with the mixing chamber near the inlet end. The recirculation system further includes a fan disposed within the at least one recirculation duct. The fan is operable to receive at least one of a fresh air flow and a substantially fuel-free exhaust gas flow present near the outlet end of the mixing chamber within the at least one recirculation duct, via the inlet opening of the at least one recirculation duct. The fan is also operable to direct at least one of a portion of the substantially fuel-free exhaust gas flow and a portion of the fresh air flow into the mixing chamber via the outlet opening of the at least one recirculation duct. Furthermore, at least one of the portion of the substantially fuel-free exhaust gas flow and the portion of the fresh air flow mixes with the exhaust gas present in the mixing chamber near the inlet end of the mixing chamber to reduce the amount of unburned fuel in the exhaust gas.

[0008] In another aspect of this disclosure, a method for recirculating gas associated with a gas turbine engine is provided. The method includes providing a mixing chamber including an inlet end and an outlet end. The inlet end of the mixing chamber is in fluid communication with the gas turbine engine to receive exhaust gas from the gas turbine engine. The exhaust gas contains unburned fuel. The method also includes providing at least one recirculation conduit connected to the mixing chamber. The at least one recirculation conduit includes an inlet opening in fluid communication with the mixing chamber near the outlet end. The at least one recirculation conduit also includes an outlet opening in fluid communication with the mixing chamber near the inlet end. The method further includes operating a fan while the gas turbine engine is running. The fan is disposed within the at least one recirculation conduit. The method includes, based on the operation of the fan, receiving at least one of a fresh air flow and a substantially fuel-free exhaust gas flow present near the outlet end of the mixing chamber via the inlet opening of the at least one recirculation conduit. The method also includes, based on the operation of the fan, guiding at least one of a portion of the substantially fuel-free exhaust gas flow and a portion of the fresh air flow into the mixing chamber via the outlet opening of the at least one recirculation duct. Furthermore, at least one of the portion of the substantially fuel-free exhaust gas flow and the portion of the fresh air flow mixes with the exhaust gas present in the mixing chamber near the inlet end of the mixing chamber to reduce the amount of unburned fuel in the exhaust gas.

[0009] Other features and aspects of this disclosure will become apparent from the following description and accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of an exemplary gas turbine engine according to an example of this disclosure;

[0011] Figure 2 Examples of this disclosure include those for use with respect to the present disclosure. Figure 1 A schematic diagram of the exhaust system of the gas turbine engine's recirculation system;

[0012] Figure 3 It is an example of the use of this disclosure Figure 1 A schematic diagram of the recirculation system of a gas turbine engine; and

[0013] Figure 4 It is a recycling and, according to the example of this disclosure Figure 1 A flowchart of a method for handling gases associated with a gas turbine engine. Detailed Implementation

[0014] In all the accompanying drawings, use the same reference numerals to denote the same or similar parts whenever possible.

[0015] Figure 1 This is a schematic diagram of an exemplary gas turbine engine 100. For clarity and ease of illustration, some surfaces of the gas turbine engine 100 have been omitted or enlarged. Furthermore, this disclosure may refer to forward and backward directions. Generally, all references to "forward" and "backward" relate to the direction of primary airflow (i.e., the air used in the combustion process), unless otherwise specified. For example, forward is "upstream" relative to the primary airflow, while backward is "downstream" relative to the primary airflow.

[0016] Furthermore, this disclosure may generally refer to the rotational central shaft "A1" of the gas turbine engine 100. The central shaft "A1" may be shared or used with various other concentric engine components. Unless otherwise specified, all references to radial, axial, and circumferential directions and measurements refer to the central shaft "A1," and terms such as "inner" and "outer" generally indicate smaller or larger radial distances from the central shaft, wherein the radial direction "D1" may be any direction perpendicular to and radiating outward from the central shaft "A1."

[0017] The gas turbine engine 100 includes an inlet 102, a compressor 104, a combustor 106, a turbine 108, an exhaust system 200, and a power output coupler 112. The compressor 104 includes one or more compressor rotor assemblies 114. The combustor 106 includes one or more injectors 116 and one or more combustion chambers 118. The turbine 108 includes one or more turbine rotor assemblies 120. The exhaust system 200 includes an exhaust diffuser 122. Furthermore, the exhaust system 200 includes an engine exhaust port 202 defining an exhaust interface 204. The gas turbine engine 100 also includes a shaft 126 supported by a plurality of bearing assemblies 128. The shaft 126 extends along a central axis “A1”.

[0018] like Figure 1 As illustrated, the compressor rotor assembly 114 and the turbine rotor assembly 120 are axial-flow rotor assemblies. Each turbine rotor assembly 120 includes a rotor disk (not shown) circumferentially mounted with corresponding turbine blades (not shown). Additionally, each compressor rotor assembly 114 may also include a rotor disk (not shown) circumferentially mounted with corresponding compressor blades (not shown).

[0019] Gas (typically air 10) enters at inlet 102 as the "working fluid" and is compressed by compressor 104. In compressor 104, the working fluid is compressed within an annular flow channel 130 by a series of compressor rotor assemblies 114. Specifically, air 10 is compressed in numbered "stages," which are associated with each compressor rotor assembly 114. For example, "second stage air" might be associated with the second compressor rotor assembly 114. Similarly, each turbine rotor assembly 120 can be associated with a numbered stage. For example, the first stage turbine rotor assembly 132 is at the very front of turbine rotor assembly 120, the second stage rotor assembly 134 is downstream of the first stage turbine rotor assembly 132, and so on. However, other numbering / naming rules may also be used.

[0020] Compressed air 10 exiting compressor 104 enters combustor 106, where it is diffused and fuel is added. In some examples, the fuel may include diesel and kerosene, etc. In other examples, the fuel may include natural gas, hydrogen, refinery gas, and syngas, etc. Air 10 and fuel are injected into combustion chamber 118 via one or more injectors 116 for ignition. After the combustion reaction, energy is extracted from the combusted fuel / air mixture by each stage of a series of turbine rotor assemblies 120 via turbine 108. Exhaust gas 30 can then diffuse in exhaust diffuser 122. Furthermore, exhaust gas 30 can be discharged from gas turbine engine 100 via exhaust port 204.

[0021] In some examples, exhaust gas treatment system 217 (such as...) Figure 2 The exhaust gas treatment system 217 (shown) can be configured in fluid communication with the engine exhaust port 202 to receive exhaust gas 30 from the engine exhaust port. For example, the exhaust gas treatment system 217 may include a waste heat recovery system, a selective catalytic reduction (SCR) module (not shown), a carbon capture system, etc. For example, the exhaust gas 30 can be treated to reduce harmful emissions / products present in the exhaust gas, for example, in the SCR module or carbon capture system. Furthermore, the exhaust gas 30 can be treated to recover heat from the exhaust gas 30 in the waste heat recovery system. The waste heat recovery system can recover waste heat from the exhaust gas 30, and the recovered waste heat can be used for various applications, such as in cogeneration applications, where the waste heat can be used to boil water to flow through a steam turbine (not shown).

[0022] Figure 2 yes Figure 1A schematic diagram of the exhaust system 200 of a gas turbine engine 100. The exhaust system 200 includes a recirculation system 206 in fluid communication with an exhaust port 204 of the engine exhaust port 202. In some examples, the recirculation system 206 provides dilution of the exhaust cloud discussed herein. In some examples, it may be desirable to dilute the exhaust cloud to or below a predetermined limit. In various examples, this predetermined limit may be below the lower flammability limit, the knock transition limit, or other fuel concentration limits or ranges relative to the fuel-air ratio. In some examples, the fuel-air ratio may be determined not only based on the composition of the exhaust cloud but also based on the temperature of the fuel. The target fuel-air ratio will be determined by the fuel composition, engine operating characteristics, and downstream exhaust configuration. In some examples, the target dilution ratio will result in a final concentration below the lower flammability limit and unignitable. In another example, the target dilution ratio will keep the concentration within the knock range, thereby preventing a transition to a fast flame. In yet another example, the exhaust cloud is not diluted. This may be because the fuel-air ratio already meets emission standards or the predetermined limits discussed above.

[0023] The recirculation system 206 includes a mixing chamber 208. The mixing chamber 208 includes an inlet end 210 and an outlet end 214. The inlet end 210 of the mixing chamber 208 is connected to the gas turbine engine 100 (see...). Figure 1 The mixing chamber 208 is in fluid communication with the exhaust port 204 of the gas turbine engine 100 to receive exhaust gas 30 from the exhaust port. The exhaust gas 30 contains unburned fuel. Specifically, the exhaust gas 30 may contain a significant amount of unburned fuel during ignition, delayed ignition, or flameout events. Furthermore, the outlet end 214 of the mixing chamber 208 is in fluid communication with the exhaust gas treatment system 217 associated with the gas turbine engine 100.

[0024] The mixing chamber 208 defines an inlet section 212 including an inlet end 210. The mixing chamber 208 also defines an outlet section 216 including an outlet end 214. The mixing chamber 208 further defines an intermediate section 218 extending between the inlet section 212 and the outlet section 216. The mixing chamber 208 defines a first length L1. Specifically, the inlet section 212, the outlet section 216, and the intermediate section 218 of the mixing chamber 208 collectively define the first length L1. The inlet section 212, the outlet section 216, and the intermediate section 218 may be integrally formed as a single component. Alternatively, the inlet section 212, the outlet section 216, and the intermediate section 218 may be formed as separate components, which may be coupled to each other using mechanical fasteners and welding, etc.

[0025] The recirculation system 206 also includes one or more recirculation conduits 220 connected to the mixing chamber 208. The one or more recirculation conduits 220 define a second length L2. The one or more recirculation conduits 220 include an inlet opening 222 that is in fluid communication with the mixing chamber 208 at an outlet end 214 near the mixing chamber 208. The one or more recirculation conduits 220 also include an outlet opening 226 that is in fluid communication with the mixing chamber 208 at an inlet end 210 near the mixing chamber 208. An intermediate section 218 of the mixing chamber 208 is in fluid communication with each of the inlet opening 222 and the outlet opening 226 of the recirculation conduits 220. Figure 2 In the illustrated embodiment, the inlet opening 222 is always in direct fluid communication with the outlet opening 226.

[0026] Furthermore, one or more recirculation ducts 220 include an inlet duct portion 224 having an inlet opening 222. Additionally, one or more recirculation ducts 220 include an outlet duct portion 228 having an outlet opening 226. One or more recirculation ducts 220 also include an intermediate duct portion 230 extending between the inlet duct portion 224 and the outlet duct portion 228. A second length L2 is formed by each of the inlet duct portion 224, the outlet duct portion 228, and the intermediate duct portion 230. A first length L1 of the mixing chamber 208 and a second length L2 of the one or more recirculation ducts 220 are determined to facilitate mixing of a portion 50 of the substantially fuel-free exhaust gas flow 40 with the exhaust gas 30 within the mixing chamber 208.

[0027] It should be noted that, as used herein, the term "essentially fuel-free exhaust gas" refers to exhaust gas that contains little or no unburned fuel. In some examples, the inlet duct section 224, the outlet duct section 228, and the intermediate duct section 230 may be manufactured as a single, integral component. Alternatively, the inlet duct section 224, the outlet duct section 228, and the intermediate duct section 230 may be formed as separate components, which may be coupled to each other using mechanical fasteners and welding, among other methods. Figure 2 In the illustrated embodiment, one or more recirculation lines 220 include a single recirculation line 220. However, depending on the application requirements, the recirculation system 206 may include multiple recirculation lines (e.g., two recirculation lines similar to recirculation line 220) coupled to the mixing chamber 208.

[0028] exist Figure 2In the illustrated embodiment, the recirculation system 206 includes a fan 232 disposed within one or more recirculation ducts 220. However, in other embodiments, the fan 232 may be omitted from the recirculation system 206. The fan 232 is disposed in an intermediate duct portion 230 of one or more recirculation ducts 220. The fan 232 is operable to receive, within one or more recirculation ducts 220, a substantially fuel-free exhaust gas flow 40 or fresh air flow (not shown in this embodiment) present near the outlet end 214 of the mixing chamber 208 via an inlet opening 222 of one or more recirculation ducts 220. Figure 2 In the illustrated embodiment, fan 232 is operable to receive, within one or more recirculation ducts 220, a substantially fuel-free exhaust gas flow 40 present near the outlet 214 of mixing chamber 208 via inlet openings 222 of one or more recirculation ducts 220. In other words, when fan 232 is operated, fan 232 draws the substantially fuel-free exhaust gas flow 40 into one or more recirculation ducts 220 via inlet openings 222.

[0029] Furthermore, fan 232 is operable to direct a portion 50 of the substantially fuel-free exhaust gas flow 40 and a portion of the fresh air flow into the mixing chamber 208 via one or more outlet openings 226 of the recirculation duct 220. Figure 2 In the illustrated embodiment, fan 232 is operable to direct only a portion 50 of the substantially fuel-free exhaust gas flow 40 into mixing chamber 208. In other words, a portion 50 of the substantially fuel-free exhaust gas flow 40 within one or more recirculation ducts 220 is directed into mixing chamber 208 via outlet opening 226. Furthermore, the portion 50 of the substantially fuel-free exhaust gas flow 40 and a portion of the fresh air flow mix with exhaust gas 30 present in mixing chamber 208 near inlet end 210 of mixing chamber 208 to reduce the amount of unburned fuel in exhaust gas 30. Specifically, in Figure 2 In the illustrated embodiment, a portion 50 of the substantially fuel-free exhaust gas flow 40 is mixed with exhaust gas 30 present in the mixing chamber 208 near the inlet end 210 of the mixing chamber 208 to reduce the amount of unburned fuel in the exhaust gas 30.

[0030] In some examples, fan 232 is made of a high-temperature resistant material. This high-temperature resistant material allows fan 232 to be used in one or more recirculation ducts 220, as the temperature of the exhaust gas 30 can be very high. Furthermore, the material of fan 232 may also have moisture-proof and chemical-resistant properties.

[0031] Although a single fan 232 is illustrated herein, the recirculation system 206 may include multiple fans arranged within one or more recirculation ducts 220 based on factors such as a first length L1, a second length L2, the density of the fuel used in the gas turbine engine 100, the amount of fuel used, and the size of the gas turbine engine 100. It should be noted that when the gas turbine engine 100 starts operating, the fan 232 may be turned on so that if the gas turbine engine 100 encounters an ignition, delayed ignition, or shutdown event, the air-fuel ratio of the exhaust gas 30 in the mixing chamber 208 is always below a predetermined value. Furthermore, the rotational speed of the fan 232 may be set to ensure that the air-fuel ratio of the exhaust gas 30 in the mixing chamber 208 is always below a predetermined value.

[0032] It should be noted that the first length L1, the second length L2, and the rotational speed of the fan 232 can be optimized based on the analysis of the exhaust gas 30. In some examples, computational fluid dynamics (CFD) analysis can be performed to determine the first length L1, the second length L2, and / or the rotational speed of the fan 232.

[0033] It should be noted that the design of one or more recirculation ducts 220 shown herein is merely exemplary, and one or more recirculation ducts 220 may include any other suitable design to allow a portion 50 of the substantially fuel-free exhaust gas flow 40 to be mixed with exhaust gas 30 near the inlet section 212 of the mixing chamber 208.

[0034] Figure 3 A recycling system 306 according to another embodiment of the present disclosure is illustrated. The recycling system 306 can be used with respect to... Figure 2 The recirculation system 206 described herein is substantially similar, with common components indicated by the same reference numerals. The recirculation system 306 also includes a fresh air duct 334 coupled to one or more recirculation ducts 220. The fresh air duct 334 receives fresh air and selectively directs it towards the recirculation duct 306. The fresh air duct 334 may communicate with the environment or a fresh air source (not shown) to direct fresh air towards the recirculation duct 306.

[0035] The recirculation system 306 also includes a valve component 336 disposed in one or more recirculation ducts 220. The valve component 336 may be a three-way valve. Additionally, the valve component 336 may include a solenoid valve actuation component. The valve component 336 provides selective fluid communication between an outlet opening 226 of one or more recirculation ducts 220 and an inlet opening 222 of one or more recirculation ducts 220 or a fresh air duct 334. The valve component 336 is capable of operating in a first configuration and a second configuration.

[0036] In the first configuration, the inlet opening 222 of one or more recirculation pipes 220 is in fluid communication with the outlet opening 226 of one or more recirculation pipes 220 to guide a portion 50 of the substantially fuel-free exhaust gas flow 40 into the mixing chamber 208. In other words, in the first configuration, a portion 50 of the substantially fuel-free exhaust gas flow 40 is introduced into the mixing chamber 208. Therefore, in Figure 3 In the illustrated embodiment, the inlet opening 222 is in fluid communication with the outlet opening 226 only when the valve member 336 is in the first configuration.

[0037] In the second configuration, the fresh air duct 334 is in fluid communication with the outlet opening 226 of one or more recirculation ducts 220 to guide a portion 70 of the fresh air flow 60 into the mixing chamber 208. In other words, in the second configuration, a portion 70 of the fresh air flow 60 is introduced into the mixing chamber 208, instead of a portion 50 of the substantially fuel-free exhaust gas flow 40. Therefore, in Figure 3 In the illustrated embodiment, the fresh air duct 334 is in fluid communication with the outlet opening 226 only when the valve member 336 is in the second configuration. Furthermore, a portion 70 of the fresh air flow 60 mixes with the exhaust gas 30 present in the mixing chamber 208 near the inlet end 210 of the mixing chamber 208 to reduce the amount of unburned fuel in the exhaust gas 30.

[0038] In some examples, the fresh airflow 60 may include ambient air. When the valve member 334 is in the second configuration, the fan 232 draws the fresh airflow 60 into the recirculation duct 206, and a portion 70 of the fresh airflow 60 is further directed into the mixing chamber 208 via the outlet openings 226 of one or more recirculation ducts 220. In other embodiments, the fan 232 may be omitted from the recirculation system 306.

[0039] It should be noted that valve member 336 can switch between a first configuration and a second configuration based on a control signal received from a controller (not shown). The controller can generate the control signal based, for example, input received from the operator of the gas turbine engine 100, to switch valve member 336 between the first configuration and the second configuration (see...). Figure 1 ).

[0040] In some examples, when the exhaust gas treatment system 217 (see...) Figure 1 When the system is in operation, valve component 336 can operate in a first configuration; when the exhaust gas treatment system 217 is closed, valve component 336 can operate in a second configuration. In addition, valve component 336 can also operate in the second configuration when exhaust gas 30 discharged from mixing chamber 208 is to be introduced into the SCR module, or if exhaust system 200 needs to be purged.

[0041] It should be understood that a single feature shown or described for one embodiment may be combined with a single feature shown or described for another embodiment. The above implementations do not limit the scope of this disclosure in any way. Therefore, it should be understood that although some features are shown or described to illustrate the use of this disclosure in the context of a functional section, such features may be omitted from the scope of this disclosure without departing from the spirit of this disclosure as defined in the appended claims.

[0042] Industrial applicability

[0043] This disclosure describes recirculation systems 206 and 306, which may be particularly advantageous for gas turbine engines using hydrogen or other low-density fuels as the primary fuel source for operation. A fan 232, disposed in recirculation duct 220, draws in either a substantially fuel-free exhaust gas stream 40 or a fresh air stream 60 into the recirculation duct 220. Furthermore, the fan 232 also directs a portion 50 of the substantially fuel-free exhaust gas stream 40 or a portion 70 of the fresh air stream 60 into a mixing chamber 208. The portion 50 of the substantially fuel-free exhaust gas stream 40 or the portion 70 of the fresh air stream 60 mixes with the exhaust gas 30 present in the mixing chamber 208 to reduce the amount of unburned fuel in the exhaust gas 30. Therefore, recirculation systems 206 and 306 ensure that the air-fuel ratio in the exhaust gas 30 never exceeds a predetermined value, such that the exhaust gas 30 is either non-flammable or the pressure increase due to detonation is compensated.

[0044] Furthermore, mixing a portion 50 of the essentially fuel-free exhaust gas stream 40 with the exhaust gas 30 maintains a high exhaust temperature for the exhaust gas 30 while keeping the air-fuel ratio below a predetermined value. More specifically, the recirculation system 206 recirculates a portion 50 of the exhaust gas 30 itself, rather than introducing fresh air into the exhaust gas 30, thereby maintaining the high temperature of the exhaust gas 30. Therefore, the heat from the exhaust gas 30 can be recovered and used for other purposes (such as combined heat and power applications).

[0045] Furthermore, in an example where the exhaust gas treatment system 217 is off, the recirculation system 306 may direct a portion 70 of the fresh airflow 60 into the mixing chamber 208 instead of directing a portion 50 of the essentially fuel-free exhaust gas flow 40 into the mixing chamber, because maintaining a high temperature for the exhaust gas 30 may not be necessary when the exhaust gas treatment system 217 is off. In another example where the exhaust gas 30 is directed to the SCR module, the recirculation system 306 may direct a portion 70 of the fresh airflow 60 into the mixing chamber 208 instead of directing a portion 50 of the essentially fuel-free exhaust gas flow 40 into the mixing chamber, because the exhaust gas 30 may require a lower temperature. In yet another example where the exhaust system 200 needs to be purged, the recirculation system 306 may direct a portion 70 of the fresh airflow 60 into the mixing chamber 208 instead of directing a portion 50 of the essentially fuel-free exhaust gas flow 40 into the mixing chamber.

[0046] Furthermore, the outlet opening 226 is positioned sufficiently far along the mixing chamber 208 to ensure that the substantially fuel-free exhaust gas flow 40 entering the recirculation duct 220 contains virtually no unburned fuel during an ignition or flameout event and is located far downstream of the fuel cloud. Additionally, a first length L1 and a second length L2 are defined to ensure that a portion 50 of the substantially fuel-free exhaust gas flow 40 is effectively mixed with the exhaust gas 30 at the inlet of the intermediate section 218.

[0047] Furthermore, the recirculation systems 206 and 306 described herein may be simple in construction, universally applicable to gas turbine engines of different designs, and can be retrofitted into existing gas turbine engines.

[0048] Figure 4 An example of recycling and Figure 1 A flowchart of a method 400 for handling gases associated with a gas turbine engine 100. (See reference...) Figures 1 to 4 At step 402, a mixing chamber 208 is provided. The mixing chamber 208 includes an inlet end 210 and an outlet end 214. The inlet end 210 of the mixing chamber 208 is in fluid communication with the gas turbine engine 100 to receive exhaust gas 30 from the engine. The exhaust gas 30 contains unburned fuel. Step 402 also includes configuring the inlet end 210 of the mixing chamber 208 in fluid communication with an exhaust port 204 of the gas turbine engine 100 to receive exhaust gas 30. Step 402 also includes configuring the outlet end 214 of the mixing chamber 208 in fluid communication with an exhaust gas treatment system 217 associated with the gas turbine engine 100.

[0049] At step 404, one or more recirculation conduits 220 are provided. The one or more recirculation conduits 220 are connected to the mixing chamber 208. The one or more recirculation conduits 220 include an inlet opening 222 that is in fluid communication with the mixing chamber 208 at an outlet end 214 near the mixing chamber 208. The one or more recirculation conduits 220 also include an outlet opening 226 that is in fluid communication with the mixing chamber 208 at an inlet end 210 near the mixing chamber 208. The one or more recirculation conduits 220 include: an inlet conduit portion 224 that includes the inlet opening 222; an outlet conduit portion 228 that includes the outlet opening 226; and an intermediate conduit portion 230 that extends between the inlet conduit portion 224 and the outlet conduit portion 228.

[0050] Furthermore, the mixing chamber 208 defines an inlet section 212 including an inlet end 210, an outlet section 216 including an outlet end 214, and an intermediate section 218 extending between the inlet section 212 and the outlet section 216. Additionally, the intermediate section 218 is in fluid communication with each of the inlet opening 222 and the outlet opening 226 of one or more recirculation pipes 220.

[0051] At step 406, fan 232 is operated while gas turbine engine 100 is running. Fan 232 is disposed in one or more recirculation ducts 220.

[0052] At step 408, one or more recirculation ducts 220 receive, via inlet openings 222, substantially fuel-free exhaust gas flow 40 or fresh air flow 60 present near the outlet end 214 of the mixing chamber 208, based on the operation of the fan 232.

[0053] At step 410, based on the operation of fan 232, a portion 50 of the substantially fuel-free exhaust gas flow 40 or a portion 70 of the fresh air flow 60 is directed into mixing chamber 208 via the outlet opening 226 of one or more recirculation ducts 220. Furthermore, the portion 50 of the substantially fuel-free exhaust gas flow 40 or the portion 70 of the fresh air flow 60 mixes with the exhaust gas 30 present in mixing chamber 208 near the inlet end 210 of mixing chamber 208 to reduce the amount of unburned fuel in the exhaust gas 30. (See now for further details.) Figure 3 and Figure 4 The recirculation system 306 also includes a fresh air duct 334 coupled to one or more recirculation ducts 220 and a valve member 336 disposed in one or more recirculation ducts 220. The valve member 336 provides selective fluid communication between an outlet opening 226 of one or more recirculation ducts 220 and an inlet opening 222 of one or more recirculation ducts 220 or the fresh air duct 334. The valve member 336 is capable of operating in a first configuration and a second configuration.

[0054] In a first configuration, the inlet opening 222 of one or more recirculation ducts 220 is in fluid communication with the outlet opening 226 of one or more recirculation ducts 220 to guide a portion 50 of the substantially fuel-free exhaust gas flow 40 into the mixing chamber 208. In a second configuration, the fresh air duct 334 is in fluid communication with the outlet opening 226 of one or more recirculation ducts 220 to guide a portion 70 of the fresh air flow 60 into the mixing chamber 208.

[0055] While various aspects of this disclosure have been specifically shown and described with reference to the foregoing embodiments, those skilled in the art will understand that various additional embodiments can be conceived through modifications to the disclosed machinery, systems, and methods without departing from the spirit and scope of this disclosure. These embodiments should be understood to fall within the scope of this disclosure as defined by the claims and any equivalents.

Claims

1. A recirculation system (206, 306) for a gas turbine engine (100), said recirculation system (206, 306) comprising: A mixing chamber (208) includes an inlet end (210) and an outlet end (214), wherein the inlet end (210) of the mixing chamber (208) is in fluid communication with the gas turbine engine (100) to receive exhaust gas (30) from the gas turbine engine, and wherein the exhaust gas (30) contains unburned fuel. At least one recirculation conduit (220) connected to the mixing chamber (208), wherein the at least one recirculation conduit (220) includes an inlet opening (222) in fluid communication with the mixing chamber (208) at an outlet end (214) near the mixing chamber (208); and wherein the at least one recirculation conduit (220) further includes an outlet opening (226) in fluid communication with the mixing chamber (208) at an inlet end (210) near the mixing chamber (208); and A fan (232), disposed in the at least one recirculation duct (220), wherein the fan (232) is operable to: Within the at least one recirculation duct (220), at least one of a fresh air flow (60) and a substantially fuel-free exhaust gas flow (40) present at the outlet end (214) near the mixing chamber (208) is received via the inlet opening (222) of the at least one recirculation duct (220); At least one of a portion (50) of the substantially fuel-free exhaust gas flow (40) and a portion (70) of the fresh air flow (60) is directed into the mixing chamber (208) via the outlet opening (226) of the at least one recirculation duct (220), wherein the portion (50) of the substantially fuel-free exhaust gas flow (40) and the portion (70) of the fresh air flow (60) are mixed with the exhaust gas (30) present in the mixing chamber (208) near the inlet end (210) of the mixing chamber (208) to reduce the amount of unburned fuel in the exhaust gas (30).

2. The recirculation system (206, 306) according to claim 1, wherein the fan (232) is made of a high-temperature resistant material.

3. The recirculation system (206, 306) according to claim 1, wherein the inlet end (210) of the mixing chamber (208) is in fluid communication with the exhaust port (204) of the gas turbine engine (100) to receive the exhaust gas (30), and wherein the outlet end (214) of the mixing chamber (208) is in fluid communication with the exhaust gas treatment system (217) associated with the gas turbine engine (100).

4. The recirculation system (206, 306) according to claim 1, wherein the mixing chamber (208) defines an inlet section (212) including the inlet end (210), an outlet section (216) including the outlet end (214), and an intermediate section (218) extending between the inlet section (212) and the outlet section (216), and wherein the intermediate section (218) is in fluid communication with each of the inlet opening (222) and the outlet opening (226) of the at least one recirculation conduit (220).

5. The recirculation system (206, 306) according to claim 1, wherein the at least one recirculation conduit (220) comprises: An inlet pipe section (224) includes an inlet opening (222). The outlet pipe section (228) includes an outlet opening (226); and the intermediate pipe section (230) extends between the inlet pipe section (224) and the outlet pipe section (228).

6. The recirculation system (206, 306) according to claim 5, wherein the fan (232) is disposed in the intermediate duct section (230).

7. The recirculation system (206, 306) according to claim 1, wherein the mixing chamber (208) defines a first length (L1), wherein the at least one recirculation conduit (220) defines a second length (L2), and wherein each of the first length (L1) and the second length (L2) is determined to facilitate the mixing of said portion (50) of said substantially fuel-free exhaust gas flow (40) with said exhaust gas (30) within said mixing chamber (208).

8. The recirculation system (306) according to claim 1, further comprising a fresh air duct (334) coupled to the at least one recirculation duct (220) and a valve member (336) disposed in the at least one recirculation duct (220), wherein the valve member (336) provides selective fluid communication between the outlet opening (226) of the at least one recirculation duct (220) and at least one of the inlet opening (222) of the at least one recirculation duct (220) and the fresh air duct (334), wherein the valve member (336) is capable of operating in a first configuration and a second configuration. in, In the first configuration, the inlet opening (222) of the at least one recirculation pipe (220) is in fluid communication with the outlet opening (226) of the at least one recirculation pipe (220) to guide a portion (50) of the substantially fuel-free exhaust gas flow (40) into the mixing chamber (208); and In the second configuration, the fresh air duct (334) is in fluid communication with the outlet opening (226) of the at least one recirculation duct (220) to guide the portion (70) of the fresh air flow (60) into the mixing chamber (208).

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