Inlet mixer for exhaust gas recirculation in power generation systems

Abstract

An exhaust gas recirculation (EGR) mixer for use in a power generation system is provided. The EGR mixer includes a mixing chamber defining a flow direction and a working fluid inlet coupled to the mixing chamber for introducing a working fluid into the mixing chamber along the flow direction. The EGR mixer also includes exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlets. Each of the exhaust gas injection ducts is oriented to receive exhaust gas recirculated within the power generation system and to inject the exhaust gas into the mixing chamber in a direction transverse to the flow direction to generate turbulence within the mixing chamber. The EGR mixer also includes an outlet coupled to the mixing chamber for delivering the mixture of exhaust gas and working fluid toward a compressor within the power generation system.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to power generation systems, and particularly to systems that use recirculated exhaust gas to increase plant output. [Background technology]

[0002] Gas turbine engines are widely used in industrial and power generation applications. A conventional gas turbine engine includes a compressor section, a combustor section downstream from the compressor section, and a turbine section downstream from the combustor section. A working fluid, such as ambient air, enters the compressor section and is compressed before proceeding through the combustor section. The compressed working fluid is mixed with fuel and combusted in the combustor section to produce combustion gases that expand through the turbine section to rotate a shaft and generate electricity.

[0003] In at least some known gas turbine engines, the compressed working fluid contains an excess amount of oxygen compared to the amount of oxygen required to support combustion. As a result, temperatures within the combustor section can increase, which can result in various undesirable emissions, including, but not limited to, nitrogen oxides (NOx). Adjusting the operating temperature of the gas turbine engine by reducing the available oxygen entering the combustion section can adjust the operating temperature, thereby reducing the production of NOx.

[0004] Various methods for reducing combustion temperatures and NOx production in the combustor section are known in the art. For example, some gas turbine engines utilize an exhaust gas recirculation (EGR) system that captures at least a portion of the combustion exhaust gas exiting the turbine section. The combustion exhaust gas exiting the turbine section generally has a lower oxygen level compared to the working fluid (e.g., ambient air) entering the compressor section. The EGR system mixes the exhaust gas with the working fluid and introduces the mixture into the compressor section. As a result, the high oxygen content of the working fluid entering the compressor is diluted with the lower oxygen content exhaust gas. The ratio of working fluid to exhaust gas in the mixture entering the compressor section is also suitable to maintain sufficient oxygen in the compressed working fluid supplied to the combustor section to support combustion.

[0005] Typically, EGR systems include an absorption chiller that reduces the temperature and moisture concentration in the recirculated exhaust gas before it mixes with the working fluid. However, the cooled exhaust gas may still have a higher temperature than the working fluid (e.g., ambient air) before mixing. Furthermore, the exhaust gas may retain moisture after absorption. As a result, moisture in the exhaust gas may condense when mixed with the cooler working fluid. Compressor operation may be adversely affected by condensation from the working fluid-exhaust gas mixture entering the compressor.

[0006] Additional problems may exist with known exhaust gas recirculation systems. For example, it may be difficult to mix a large amount of exhaust gas with the working fluid before the mixture enters the compressor section to reduce compressor distortion and / or surge. A mixer utilized to mix the exhaust gas and working fluid upstream of the compressor section may require a large footprint to achieve proper mixing. However, increasing the mixer footprint adds cost to the overall power generation system. Alternatively, mixing capacity may be increased within a smaller footprint by supplying exhaust gas at a higher pressure to induce turbulence within the mixer, but this requires higher blower costs in the EGR system upstream of the mixer. Furthermore, known EGR systems typically include a filter media located downstream of the mixer to reduce and / or remove particulates and other contaminants that may be entrained in the working fluid-exhaust gas mixture. Because the filter media is typically downstream of the mixer, the pressure of the working fluid is not reduced before mixing, thus allowing for greater turbulence within the mixer. The filter media increases the pressure drop of the working fluid-exhaust gas mixture entering the compressor, thus reducing the efficiency of the EGR system and / or the compressor. The filter media, which may include, for example, cellulose filter paper, may also be degraded and / or destroyed by condensation caused by the working fluid-exhaust gas mixture.

[0007] Therefore, there is a need for an EGR mixer for generating a working fluid-exhaust gas mixture supplied to a rotary machine that addresses the above-mentioned problems by reducing the footprint of the mixer, eliminating condensation in the working fluid-exhaust gas mixture, minimizing and / or eliminating the pressure drop across the mixer, and / or minimizing damage to the filter media, and that facilitates proper mixing of the working fluid and exhaust gas at lower pressures. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2010 / 142560 Summary of the Invention

[0009] In one aspect, an exhaust gas recirculation (EGR) mixer for use in a power generation system including an EGR system configured to recirculate exhaust gas generated within the power generation system is provided. The EGR mixer includes a mixing chamber defining a flow direction and a working fluid inlet coupled to the mixing chamber for introducing a working fluid into the mixing chamber along the flow direction. The EGR mixer also includes a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet. Each of the plurality of exhaust gas injection ducts is oriented to receive the recirculated exhaust gas and inject the exhaust gas into the mixing chamber in a direction transverse to the flow direction to generate turbulence within the mixing chamber. The EGR mixer also includes an outlet coupled to the mixing chamber downstream of the plurality of exhaust gas injection ducts for delivering a mixture of the exhaust gas and the working fluid toward a compressor within the power generation system.

[0010] In another aspect, a power generation system is provided. The power generation system includes a rotary machine and an exhaust gas recirculation (EGR) system. The rotary machine includes a compressor and a turbine coupled to the compressor and configured to generate exhaust gases. The EGR system is configured to recirculate exhaust gases from the turbine toward the compressor, and the EGR system includes an EGR mixer for mixing the recirculated exhaust gases with a working fluid. The EGR mixer includes a mixing chamber defining a flow direction and a working fluid inlet coupled to the mixing chamber for introducing the working fluid into the mixing chamber along the flow direction. The EGR mixer also includes a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet. Each of the plurality of exhaust gas injection ducts is oriented to receive the recirculated exhaust gases and inject the exhaust gases into the mixing chamber in a direction transverse to the flow direction to generate turbulence within the mixing chamber. The EGR mixer also includes an outlet coupled to the mixing chamber downstream of the plurality of exhaust gas injection ducts for delivering the mixture of exhaust gases and working fluid toward the compressor of the rotary machine.

[0011] In another aspect, a method of operating a power generation system is provided. The power generation system includes an exhaust gas recirculation (EGR) system including an EGR mixer. The EGR mixer includes a mixing chamber, a working fluid inlet coupled to the mixing chamber, a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet, and an outlet coupled to the mixing chamber downstream of the plurality of exhaust gas injection ducts. The method includes generating exhaust gas within the power generation system and recirculating at least a portion of the exhaust gas within the power generation system toward a compressor. The method also includes introducing a working fluid into the mixing chamber of the EGR mixer along a flow direction via the working fluid inlet. The method also includes injecting the recirculated exhaust gas into the mixing chamber of the EGR mixer via the plurality of exhaust gas injection ducts in a direction transverse to the working fluid to generate turbulence in the mixing chamber and generate a mixture of the exhaust gas and the working fluid. The method also includes delivering the mixture toward the compressor via an outlet of the EGR mixer. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of an exemplary power generation system including an exhaust gas recirculation system. [Figure 2] 2 is a perspective view of an exemplary exhaust gas recirculation mixer for mixing the working fluid with the recirculated exhaust gas in the power generation system shown in FIG. 1. FIG. [Figure 3] FIG. 3 is a cross-sectional side view of the exhaust gas recirculation mixer of FIG. 2. [Figure 4] 3 is another perspective view of the exhaust gas recirculation mixer of FIG. 2 with various portions removed to show the interior of the mixer in greater detail. [Figure 5] 5 is an enlarged view of section circle C of FIG. 4 showing in more detail a portion of the exhaust gas injection duct located within the mixing chamber of the exhaust gas recirculation mixer. [Figure 6] 5 is an isolated perspective view of an exemplary exhaust gas injection duct used in the exhaust gas recirculation mixer of FIGS. 2-4 formed with different distributions of injection holes. FIG. [Figure 7]5 is an isolated perspective view of an exemplary exhaust gas injection duct used in the exhaust gas recirculation mixer of FIGS. 2-4 formed with different distributions of injection holes. FIG. [Figure 8] 5A-5C are various exemplary cross-sectional views of exhaust gas injection ducts used in the exhaust gas recirculation mixers of FIGS. 2-4. [Figure 9] 5A-5C are various exemplary cross-sectional views of exhaust gas injection ducts used in the exhaust gas recirculation mixers of FIGS. 2-4. [Figure 10] 5A-5C are various exemplary cross-sectional views of exhaust gas injection ducts used in the exhaust gas recirculation mixers of FIGS. 2-4. [Figure 11] 5A-5C are various exemplary cross-sectional views of exhaust gas injection ducts used in the exhaust gas recirculation mixers of FIGS. 2-4. [Figure 12] 5A-5C are various exemplary cross-sectional views of exhaust gas injection ducts used in the exhaust gas recirculation mixers of FIGS. 2-4. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments described herein relate to power generation systems that use recirculated exhaust gas to increase plant output and / or efficiency. In particular, the disclosed embodiments relate to a power generation system that includes an exhaust gas recirculation (EGR) system that recirculates exhaust gas generated by a turbine of a rotary machine (e.g., a gas turbine engine), mixes it with a working fluid (e.g., ambient air), and then supplies the mixture to a compressor. The EGR system includes an EGR mixer upstream of the compressor that mixes the exhaust gas with the working fluid. The exhaust gas is recirculated and mixed with the working fluid before the mixture is introduced into the compressor. The mixture serves as a diluent for oxygen in the compressed working fluid that is conveyed downstream to a combustion section downstream of the compressor. As a result, the peak combustion temperature of the combustion section can be reduced and / or maintained below a threshold temperature, and / or generated exhaust emissions (e.g., NOx emissions) can be reduced and / or maintained below a threshold level.

[0014] Each exemplary embodiment of an EGR mixer described herein includes a mixing chamber, a working fluid inlet coupled to the mixing chamber, and an outlet coupled to the mixing chamber. A working fluid (e.g., ambient air) introduced into the mixing chamber via the working fluid inlet flows across the mixing chamber in a flow direction toward the outlet. The exemplary EGR mixer embodiment also includes a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet.

[0015] Each of the plurality of exhaust gas injection ducts receives recirculated exhaust gas from a turbine of a rotary machine (e.g., a gas turbine engine) and injects the exhaust gas into the mixing chamber in a direction transverse to the flow direction of the working fluid flowing across the mixing chamber. More specifically, the exhaust gas is injected by the exhaust gas injection duct in a cross-flow relationship with the working fluid so as to generate turbulence in the mixing chamber. The exhaust gas injection ducts may be oriented in a direction generally perpendicular to the flow direction (e.g., parallel and sequential, such as in a vertically stacked orientation), and each duct may include one or more series of holes (i.e., exhaust gas injection locations) spaced apart along the length of the respective exhaust gas injection duct. The holes formed in each exhaust gas injection duct may be shaped, sized, and arranged (e.g., spaced apart) in any shape, size, and / or relative position that facilitates substantially uniform mixing across the cross-sectional area of ​​the mixing chamber.

[0016] Exemplary EGR mixer embodiments may also include one or more drain ports located below the mixing chamber and / or outlet, and the exhaust gas injection duct may be shaped to allow condensate generated during mixing to flow from the exhaust gas injection duct toward the drain port. In some embodiments, the EGR mixer may include a moisture collector to extract condensate from the exhaust gas-working fluid mixture as the mixture exits the mixer, and the extracted condensate may be conveyed to the drain port via a condensate duct. In certain embodiments, a filter media may be utilized to filter particulates from the working fluid, and in such embodiments, the filter media is appropriately positioned upstream of the mixing chamber proximate the inlet. The exhaust gas and working fluid mixture exits the EGR mixer via an outlet and is subsequently directed to the compressor.

[0017] Exemplary EGR mixer embodiments described herein facilitate increasing the efficiency of mixing of exhaust gas with a working fluid, such as an oxidant (e.g., ambient air), in an EGR system for a rotary machine. The EGR mixer generates turbulence by injecting exhaust gas in a cross-flow relationship with the working fluid flowing through the mixing chamber, thereby facilitating increased mixing capacity of the mixer and achieving a uniform mixture of the exhaust gas and working fluid across the cross-sectional area of ​​the mixing chamber. This facilitates reducing compressor strain and / or surge. The EGR mixer advantageously allows for mixing of large volumes of exhaust gas and working fluid at lower pressures, thereby facilitating reduced energy output when supplying the exhaust gas and / or working fluid to the mixing chamber. The EGR mixer may also facilitate removal or extraction of condensate generated by mixing hot, saturated exhaust gas with a cooler working fluid before flowing the exhaust gas / working fluid mixture to the compressor, thereby reducing the risk of water impingement damage within the compressor (e.g., on compressor blades). Preferably, the mixing chamber of the EGR mixer is downstream of a filter media utilized to filter particulates from the working fluid prior to mixing, thereby facilitating reduction or elimination of filter media damage or degradation due to condensation in the exhaust gas / working fluid mixture and reducing the pressure drop across the EGR mixer.

[0018] When introducing elements of various embodiments disclosed herein, the articles "a," "an," "the," and "said" are intended to mean the presence of one or more of the element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0019] Unless otherwise specified, terms expressing approximation, such as "generally," "substantially," and "approximately," used herein indicate that the modified term may apply only to an approximate degree, as recognized by one of ordinary skill in the art, rather than to an absolute or complete degree. Thus, values ​​modified with terms such as "about," "approximately," and "substantially" are not limited to the exact value specified. In at least some instances, approximation language may correspond to the precision of an instrument for measuring the value. Furthermore, unless otherwise indicated, terms such as "first," "second," and the like are used herein merely as labels and do not impose any order, position, or hierarchy requirements on the items they refer to. Furthermore, for example, a reference to a "second" item does not require or exclude, for example, the presence of a "first" or lower-numbered item, or a "third" or higher-numbered item.

[0020] 1 is a schematic diagram of an exemplary power generation system 100. In the exemplary embodiment, power generation system 100 includes a rotary machine 102. In the exemplary embodiment, rotary machine 102 is a gas turbine engine 102. Gas turbine engine 102 includes a compressor 104, one or more combustors 106, and a turbine 108 coupled together in a serial-flow relationship. A shaft 110 extends axially and operably couples compressor 104 to turbine 108. Gas turbine engine 102 may be coupled to a generator 112 via shaft 110 to generate electrical power.

[0021] The power generation system 100 also includes an exhaust gas recirculation (EGR) system 150 downstream from and fluidly coupled to the gas turbine engine 102. The EGR system 150 includes an exhaust gas treatment system 152 that receives the exhaust gas 120 generated by the gas turbine engine 102 through a conduit and channels the treated exhaust gas 122 through an EGR loop 154 ​​where it is recirculated toward the compressor 104, as described in further detail below. A portion of the treated exhaust gas 124 may also be discharged from the exhaust gas treatment system 152 to the atmosphere through an exhaust outlet. In certain embodiments, the exhaust gas treatment system 152 may include multiple treatment units for use in generating the treated exhaust gases 122 and 124, such as a filter unit 156, a selective catalytic reduction unit 158, an absorption unit 160, and / or any other type of exhaust gas treatment unit. The treated exhaust gases 122 and 124 may have a lower temperature and / or lower saturation (eg, moisture content) than the temperature and / or saturation of the exhaust gases 120 exiting the gas turbine engine 102 .

[0022] In some embodiments, the power generation system 100 may be a combined cycle power plant that includes a gas turbine engine 102 and a steam cycle configuration that includes a heat recovery steam generator (HRSG) (not shown) and a steam turbine engine (not shown). The HRSG receives exhaust gases 120 from the gas turbine engine 102, extracts heat from the exhaust gases 120, and exhausts the exhaust gases at a temperature lower than the operating temperature of the exhaust gases 120 exiting the gas turbine engine 102. The HRSG also exhausts steam that is channeled toward the steam turbine engine to enable the steam to perform work in the steam turbine engine. Both the gas turbine engine 102 and the steam turbine engine may be operably coupled to a generator 112 that generates electrical power using a working fluid flowing through each engine.

[0023] Treated exhaust gas 122 is recirculated from exhaust gas treatment system 152 through EGR loop 154 ​​and delivered to EGR mixer 200 upstream of compressor 104. In certain embodiments, EGR mixer 200 may receive treated exhaust gas 122, untreated exhaust gas 120 from gas turbine engine 102, or any other exhaust gas source that may or may not pass through various equipment. For example, in some embodiments, exhaust gas 120 from gas turbine engine 102 may be recirculated through EGR loop 154 ​​to EGR mixer 200 without flowing through exhaust gas treatment system 152. In an exemplary embodiment, EGR system 150 includes a recirculation blower or compressor 162 coupled in EGR loop 154 ​​between exhaust gas treatment system 152 and EGR mixer 200. Blower 162 receives exhaust gas 122 and discharges it toward EGR mixer 200, where it may be compressed. In certain embodiments, EGR system 150 may include a control valve or other control device (e.g., a splitter, not shown in FIG. 1 ) in EGR loop 154 ​​to facilitate control of the amount of exhaust gas 122 recirculated to EGR mixer 200. For example, EGR system 150 may recirculate approximately 0% to approximately 40% of the exhaust gas 120 exiting gas turbine engine 102 through EGR loop 154 ​​to EGR mixer 200, with the remainder of the exhaust gas 120 being discharged as treated exhaust gas 124 or discharged before the gas is delivered to exhaust gas treatment system 152.

[0024] During operation, the combustor 106 receives a compressed working fluid 114 including an oxidant (e.g., compressed air) from the compressor 104 and fuel 116 provided from a fuel supply (not shown). The fuel 116 and the compressed working fluid 114 are mixed and combusted in the combustor 106 to generate combustion gases 118. The combustion gases 118 are channeled through the turbine 108, where they expand and perform work in the turbine 108, causing the shaft 110 to rotate, thereby enabling the generator 112 to generate electrical power. After performing work in the turbine 108, exhaust gases 120 are exhausted from the gas turbine engine 102 and received by the exhaust gas treatment system 152. The treated exhaust gases 122 are recirculated through the EGR loop 154 ​​via a blower 162 to the EGR mixer 200, where the exhaust gases 122 are mixed with a working fluid 164, such as ambient air. A mixture 166 of the exhaust gas 122 and working fluid 164 exiting the EGR mixer 200 is delivered to the compressor 104, which compresses the mixture 166 and delivers it to the combustor 106 as compressed working fluid 114. Mixing the working fluid 164 with the recirculated exhaust gas 122 to form the mixture 166 may dilute the working fluid 164 and reduce the amount of oxygen in the compressed working fluid 114, which may facilitate reducing peak combustion temperatures and / or reducing NOx formation in the combustor 106.

[0025] 2-5, various elements and features of an exemplary EGR mixer 200 are shown in greater detail. In the exemplary embodiment, the EGR mixer 200 includes a housing 202 that encloses an interior 212 and has a first end 204 and a second end 206. The housing 202 extends along a longitudinal axis A between the first end 204 and the second end 206. The housing 202 is open at the first end 204 and the second end 206. The EGR mixer 200 includes a working fluid inlet duct 208 formed in the first end 204 of the housing 202. The working fluid inlet duct 208 allows the working fluid 164 to enter the interior 212 of the housing 202. The EGR mixer 200 also includes a filter 210 within the housing 202 near the first end 204 and in close proximity to the working fluid inlet duct 208. The filter 210 removes particulates or other impurities (e.g., dust, pollen, smoke, bacteria, etc.) entrained within or mixed with the working fluid 164 entering the housing 202. The filter 210 may be any suitable device utilized to filter air, including, but not limited to, a fiberglass filter, a pleated or polyester filter, a cellulose paper filter, a high-efficiency particulate air (HEPA) filter, and / or any suitable device having any suitable penetrating particle size.

[0026] The housing 202 encloses a mixing chamber 214 within an interior 212 downstream of the filter 210. The mixing chamber 214 is defined within the housing 202 where the exhaust gas 122 mixes with the working fluid 164. Locating the mixing chamber 214 downstream of the filter 210 provides several advantages. For example, the working fluid 164 (e.g., ambient air) entering the housing 202 may be at a lower temperature than the exhaust gas 122, which may still be at a relatively high temperature and have a substantial saturation level (e.g., moisture content) even after being processed by the exhaust gas treatment system 152. After mixing with the cooler working fluid 164, the temperature of the exhaust gas 122 decreases, and moisture within the exhaust gas 122 condenses, creating droplets of fluid (e.g., water) within the housing 202. The filter 210, which may include a filter medium susceptible to damage from droplets, is upstream of any droplets formed as a result of mixing, thus reducing or eliminating wetting and / or damage to the filter medium due to condensation. Additionally, locating filter 210 upstream of mixing chamber 214 facilitates reducing the pressure drop caused by EGR mixer 200 in generating mixture 166 delivered to compressor 104. Rather, instead of delivering both working fluid 164 and recirculated exhaust gas 122 through filter 210, only working fluid 164 passes through filter 210. Thus, only the flow of working fluid 164 experiences the pressure drop caused by filter 210. Compared to conventional mixers that may inject exhaust gas upstream of a filter house, EGR mixer 200 that injects exhaust gas 122 downstream of the filter can facilitate an approximately 1.7-inch water column decrease in pressure drop across EGR mixer 200, which corresponds to approximately a 3-megawatt (MW) increase in power output from power generation system 100.

[0027] To inject exhaust gases 122 into mixing chamber 214, EGR mixer 200 includes an exhaust gas inlet duct 216 that extends outward from housing 202 and fluidly couples EGR loop 154 ​​(shown in FIG. 1 ) with mixing chamber 214. Exhaust gas inlet duct 216 is coupled to a side of housing 202 adjacent mixing chamber 214. A plurality of exhaust gas injection ducts 218 that are fluidly coupled with exhaust gas inlet duct 216 extend into and across mixing chamber 214. Each exhaust gas injection duct 218 has an open end 220 (also referred to herein as an inlet of exhaust gas injection duct 218) that faces exhaust gas inlet duct 216, with each open end 220 defining an opening in housing 202 that allows exhaust gases 122 to enter a respective exhaust gas injection duct 218. Furthermore, open end 220 may be substantially flush with or extend outwardly beyond the side of housing 202 coupled to exhaust gas inlet duct 216. Furthermore, because open end 220 is the only opening in housing 202 adjacent to mixing chamber 214, exhaust gas 122 must flow through exhaust gas injection duct 218 to enter mixing chamber 214. In other words, exhaust gas injection duct 218 forms the only flow path for exhaust gas 122 to enter mixing chamber 214 from exhaust gas inlet duct 216. Thus, duct 218 facilitates improved control over the direction of exhaust gas 122 injected into mixing chamber 214.

[0028] In the exemplary embodiment, each exhaust gas injection duct 218 extends transversely relative to longitudinal axis A within mixing chamber 214. Each exhaust gas injection duct 218 includes at least one series of holes 226 extending transversely of the respective duct 218. An end 222 of each exhaust gas injection duct 218 opposite open end 220 (shown in FIGS. 6 and 7 ) may be closed or may be located outside mixing chamber 214 opposite exhaust gas inlet duct 216, such that holes 226 provide the only outlet for exhaust gas 122 injected into mixing chamber 214. In the exemplary embodiment, exhaust gas injection ducts 218 are arranged in series, each extending substantially perpendicular to longitudinal axis A and each substantially parallel to one another. Arranging exhaust gas injection ducts 218 in a substantially parallel series may facilitate reducing the cross-sectional area of ​​mixing chamber 214, which may facilitate reducing the overall footprint of EGR mixer 200. In the exemplary embodiment, exhaust gas injection ducts 218 are vertically stacked in series and oriented horizontally. In other embodiments, exhaust gas injection ducts 218 may be oriented in any other orientation that enables ducts 218 to function as described herein, such as vertically in a horizontally stacked orientation.

[0029] It should be appreciated that exhaust gas inlet duct 216 may be adjacent to mixing chamber 214 and coupled to any side of housing 202, depending on the orientation of exhaust gas injection ducts 218 and the relative position of EGR mixer 200 on EGR loop 154. In the exemplary embodiment, EGR mixer 200 includes 16 exhaust gas injection ducts 218 arranged in parallel series. In other embodiments, any other number of exhaust gas injection ducts 218 may be included that enables EGR mixer 200 to function as described herein. The number of exhaust gas injection ducts 218 may vary based on, for example, the size and operational requirements of EGR mixer 200.

[0030] A plurality of support beams 224 extend across the mixing chamber 214. The support beams 224 extend substantially perpendicular to the longitudinal axis A and substantially perpendicular to the lateral direction of the exhaust gas injection ducts 218. The support beams 224 are fixedly coupled to each duct 218 and to the housing 202. The support beams 224 maintain the relative position of each of the exhaust gas injection ducts 218 within the mixing chamber 214 during operation. Thus, the support beams 224 facilitate preventing misalignment of the ducts 218 due to vibrations, mechanical loads, etc. that may result from the flow and mixing of the exhaust gas 122 and working fluid 164 within the mixing chamber 214.

[0031] The exhaust gas injection ducts 218 are oriented such that the exhaust gas 122 is injected via holes 226 in each duct 218 in a cross-flow relationship relative to the working fluid 164 flowing through the EGR mixer 200. The working fluid 164 enters the mixing chamber 214 along a flow direction X substantially parallel to the longitudinal axis A, and the mixture 166 exits the EGR mixer 200 along the flow direction X via outlets 228 in the open second end 206. The exhaust gas 122 is injected in a direction transverse to the flow direction X (e.g., perpendicular to the flow direction X or at an oblique angle relative to the flow direction X) to define a cross-flow relationship of the injected exhaust gas 122 relative to the working fluid 164. This creates turbulence within the mixing chamber 214 that induces mixing of the working fluid 164 and the injected exhaust gas 122. The turbulence facilitates efficient and substantially uniform mixing of the working fluid 164 and the injected exhaust gas 122 within the mixing chamber 214. In particular, the turbulence created by the cross-flow relationship of the injected exhaust gas 122 relative to the working fluid 164 facilitates creating a uniform distribution of the working fluid 164 and the exhaust gas 122 within the mixture 166, facilitating uniform thermal mixing and reducing the temperature of the exhaust gas 122 so that the mixture 166 exiting the EGR mixer 200 has a substantially stable temperature. The uniform distribution of the mixture 166 facilitates efficient operation of the compressor 104 and downstream combustor 106 that utilize the mixture 166 during operation of the gas turbine engine 102. The reduced temperature of the exhaust gas 122 facilitates the substantial formation of condensates that form as a result of mixing the exhaust gas 122 with the working fluid 164 within the EGR mixer 200. As described in further detail below, the EGR mixer 200 facilitates the removal of condensates formed by mixing before the mixture 166 exits the EGR mixer 200. This substantially removes moisture (e.g., water) from the mixture 166 before it enters the compressor 104. Additionally, the turbulence created by the cross-flow relationship of the injected exhaust gas 122 to the working fluid 164 facilitates reducing the pressure of the exhaust gas 122 at the exhaust gas inlet duct 216 necessary to induce proper mixing.For example, the EGR mixer 200 may facilitate proper mixing of the exhaust gas 122 at 40% recirculation, where the exhaust gas 122 has an inlet pressure of approximately 20 mbar or less at the exhaust gas inlet duct 216. It should be understood that the required inlet pressure of the exhaust gas 122 may be based on the recirculation percentage utilized. The EGR mixer 200 appropriately reduces the required inlet pressure of the exhaust gas 122 to achieve sufficient mixing at various recirculation percentages within the operating range of the EGR system 150, e.g., within a range of approximately 0% to approximately 40% recirculation of the exhaust gas 122. Reducing the inlet pressure of the exhaust gas 122 entering the EGR mixer 200 facilitates reducing energy costs associated with recirculating the exhaust gas 122 (e.g., requiring a lower energy output of the blower 162).

[0032] 5-7 , the shape, size, position, and / or distribution of the series of holes 226 in each of the exhaust gas injection ducts 218 may be any shape, size, relative position, and / or distribution that allows for sufficient mixing between the working fluid 164 and the injected exhaust gas 122. Each of the exhaust gas injection ducts 218 has a front side 232, a rear side 234, and opposing exhaust gas injection sides 236 and 238 extending between the front side 232 and the rear side 234. When the exhaust gas injection ducts 218 are installed within the EGR mixer 200, the front side 232 faces toward the first end 204, the rear side 234 faces toward the second end 206, and the opposing injection sides 236 and 238 extend generally along the longitudinal axis A between the front side 232 and the rear side 234. Thus, opposing injection sides 236 and 238 generally face in a direction transverse to (e.g., perpendicular to) longitudinal axis A when exhaust gas injection duct 218 is installed. In an exemplary embodiment, injection side 236 may form a top side of duct 218 and injection side 238 may form a bottom side of duct 218 when duct 218 is installed in a vertically stacked orientation. In an exemplary embodiment, at least one series of holes 226 includes a first series of holes 226 formed in injection side 236 and a second series of holes 226 formed in opposing injection side 238. Forming the series of holes 226 in opposing injection sides 236 and 238 orients holes 226 to facilitate injecting exhaust gas 122 in a direction transverse to flow direction X (e.g., perpendicular to flow direction X or at an oblique angle relative to flow direction X) when exhaust gas injection duct 218 is installed. In other embodiments, any other number of series of holes 226 may be formed in the inlet sides 236 and 238, for example, two series of holes 226 may be formed in one or each of the inlet sides 236 and 238. In some embodiments, a series of holes 226 may be formed in one of the inlet sides 236 and 238 and not in the other of the inlet sides 236 and 238. Furthermore, in some embodiments, a series of holes 226 may also be formed along the front side 232 and / or the back side 234.The shape of the holes 226 may be, for example, square, circular, oval, triangular, another polygonal shape, or any other shape, and the holes 226 may have any suitable size (e.g., diameter or cross-sectional area) that facilitates injecting the exhaust gas 122 into the mixing chamber 214 at a suitable velocity.

[0033] As shown in FIG. 6 , in some embodiments, the series of holes 226 formed along each of the exhaust gas injection ducts 218 may be evenly distributed along the length of the duct 218 between the open end 220 and the opposing end 222. That is, the series of holes 226 includes pairs of adjacent holes 226, with each pair of adjacent holes 226 spaced a distance apart equal to the distance between adjacent pairs of holes 226 in the series of holes 226. In other embodiments, the series of holes 226 may be unevenly distributed along the length of the duct 218 between the open end 220 and the opposing end 222. For example, as shown in FIG. 7 , adjacent pairs of holes 226 proximate the opposing end 222 may be spaced a smaller distance apart than adjacent pairs of holes 226 proximate the open end 220. Varying the spacing of the holes 226 along the length of the duct 218 may facilitate improved distribution of the injected exhaust gas 122 across the mixing chamber 214. For example, when exhaust gas 122 enters exhaust gas injection duct 218 at open end 220, the exhaust gas 122 injected into mixing chamber 214 may be concentrated in an area within mixing chamber 214 proximate open end 220 because the gas is injected through the forward holes 226 proximate open end 220. Changing the distribution of holes 226 to have greater spacing proximate open end 220, as shown in FIG. 7 , may result in a greater amount of exhaust gas 122 substantially flowing through duct 218 and reaching holes 226 proximate the opposite end 222 of duct 218. As a result, improved distribution of injected exhaust gas 122 within mixing chamber 214 may be achieved.

[0034] It should be understood that a first series of holes 226 in an injection side 236 of a given duct 218 and a second series of holes 226 formed in the opposing injection side 238 need not have the same distribution or arrangement of holes 226. Furthermore, the first series of holes 226 and the second series of holes 226 may include holes of different sizes, shapes, and / or angular orientations through their respective injection sides 236, 238. Furthermore, it should be understood that the size, shape, and arrangement of the first and second series of holes 226 in a given duct 218 may differ in one or more aspects from the size, shape, and arrangement of the first and second series of holes 226 in another duct 218 of the EGR mixer 200.

[0035] 8-12 illustrate various exemplary cross-sections of exhaust gas injection duct 218 along a line parallel to longitudinal axis A when duct 218 is mounted within EGR mixer 200. The cross-sections illustrated in FIGS. 8-12 represent non-limiting examples of cross-sectional shapes that exhaust gas injection duct 218 may embody. In various embodiments, exhaust gas injection duct 218 may have the same or different cross-sectional shapes within the same EGR mixer 200. The cross-sectional shape of exhaust gas injection duct 218 may be selected to, for example, reduce cost, improve aerodynamics within mixing chamber 214, improve flow distribution of exhaust gas 122 injected through and from duct 218, facilitate collection of condensate within duct 218, and facilitate removal of condensate, among other benefits.

[0036] In the exemplary embodiment, as shown in Figure 8, the plurality of exhaust gas injection ducts 218 have a rectangular cross-section, with a front side 232, a rear side 234, and opposing injection sides 236 and 238 of the ducts 218 each being substantially flat. The holes 226 may be formed in each of the injection sides 236 and 238 adjacent the front side 232, as shown in Figure 8, or may be formed in other areas of the sides 236 and 238. In this embodiment, the rectangular cross-section of the ducts 218 may be a low-cost design that is easy to manufacture and / or procure.

[0037] As shown in FIG. 9 , in another embodiment, one or more of the exhaust gas injection ducts 218 may have a cross-section similar to that shown in FIG. 8 , with the additional feature that the injection side 238 slopes upward from the front side 232 to the rear side 234. As mentioned above, in the illustrated embodiment, the injection side 238 may form the bottom side of the duct 218 when attached to the EGR mixer 200. The sloped injection side 238 shown in FIG. 9 may allow condensate collected in each exhaust gas injection duct 218 to exit via a series of holes 226 formed in the side 238. It should be understood that in other orientations of the duct 218, the other side forming the bottom side of the duct 218 may be sloped as shown in FIG. 9 , and holes 226 may be formed in the side forming the bottom of the duct 218 to allow condensate to exit.

[0038] 10-12, in other embodiments, one or more of the exhaust gas injection ducts 218 may have a cross-sectional shape with a curved leading side 232 to facilitate improved aerodynamics within the mixing chamber 214, for example, by allowing the working fluid 164 to flow more easily across the duct 218. The duct 218 may have, for example, an oval or circular cross-section (FIG. 10), a bullet-shaped cross-section (FIG. 11), or a hybrid cross-section similar to the bullet-shaped cross-section of FIG. 11, in which the injection sides 236 and 238 taper inward in a mirror image relationship toward the aft end point 234, forming a V-shape of the duct 218 opposite the leading side 232, as shown in FIG.

[0039] 2-4 , EGR mixer 200 also includes one or more drain ports 240, one or more moisture collectors 242, and a condensate duct 244 that cooperate to extract and remove condensate formed within mixture 166 before mixture 166 exits EGR mixer 200 via outlet 228. Drain ports 240 are suitably formed in a floor 246 of housing 202 below mixing chamber 214 and / or downstream of exhaust gas injection duct 218 (e.g., below moisture collector 242). Drain ports 240 allow condensate that forms within mixing chamber 214 and injection duct 218 as a result of thermal mixing of hot saturated exhaust gas 122 with cold working fluid 164 to exit housing 202.

[0040] The moisture collector 242 is disposed within the housing 202, downstream of the exhaust gas injection duct 218 and upstream of the outlet 228. The moisture collector 242 extracts condensate (e.g., water droplets) from the mixture 166 of the exhaust gas 122 and the working fluid 164 within and / or exiting the mixing chamber 214 before the mixture 166 exits the EGR mixer 200. In particular, the moisture collector 242 includes a sheet or panel of vanes 250 through which the mixture 166 flows between the mixing chamber 214 and the outlet 228. The vanes 250 may be oriented horizontally or vertically. Each of the vanes 250 is shaped and / or designed (e.g., includes protrusions or other moisture-trapping features) to form a serpentine flow path for the mixture 166 to promote condensation, and the condensate is collected on or otherwise captured by the vanes 250. As a result, the condensate is separated from the mixture 166. The moisture collector 242 also allows the collected condensate to flow downward toward the floor 246 and out of the housing 202 via the drain port 240. The moisture collector 242 may alternatively be referred to as a drift eliminator, mist eliminator, vane separator, and / or moisture separator.

[0041] A condensate duct 244 extends between the mixing chamber 214 and the outlet 228. The condensate duct 244 is shaped to convey condensate from the mixture 166 toward a drain port 240 in a floor 246 of the housing 202. In particular, the condensate duct 244 includes a bottom panel 248 that at least initially slopes upward from the floor 246 of the housing 202 toward the outlet 228, the upwardly sloping portion of the bottom panel 248 conveying condensate generated within the mixing chamber 214 and extracted by the moisture collector 242 and / or otherwise removed from the mixture 166 toward the drain port 240 before the mixture 166 exits the EGR mixer via the outlet 228.

[0042] During operation, the EGR mixer 200 receives a flow of exhaust gas 122 recirculated by the EGR system 150, e.g., via an exhaust gas inlet duct 216, from the exhaust gas treatment system 152 and / or directly from the gas turbine engine 102. The EGR mixer also receives a working fluid 164 (e.g., ambient air) via a working fluid inlet duct 208. The working fluid 164 flows across the interior of the housing 202 of the EGR mixer 200 and into a mixing chamber 214 along a flow direction X. Before entering the mixing chamber 214, the working fluid 164 may flow across a filter 210 located proximate the working fluid inlet duct 208, which removes particulates and other impurities from the working fluid 164. The exhaust gas 122 is injected into the mixing chamber 214 via a plurality of exhaust gas injection ducts 218 in a direction transverse to the flow direction X of the working fluid 164. As a result, turbulence is created within the mixing chamber 214, producing a mixture 166 of the working fluid 164 and the exhaust gas 122. During mixing within the mixing chamber 214, condensate may be produced as described above. The condensate may be removed, for example, by one or more moisture collectors 242 that extract condensate from the mixture 166 downstream of the mixing chamber 214 and upstream of the outlet 228 of the EGR mixer 200 due to the shape of the exhaust gas injection duct 218 allowing the condensate collected in the duct 218 to flow therefrom toward a drain port 240 formed in the floor 246 of the housing 202, and / or by a condensate duct 244 that conveys the condensate from the mixture 166 toward the drain port 240. The mixture 166 (with the condensate removed) is then directed to the compressor 104 of the gas turbine engine 102 via the outlet 228 of the EGR mixer 200.

[0043] Exemplary embodiments of an exhaust gas recirculation (EGR) mixer for use in power generation systems utilizing exhaust gas recirculation are described herein. The exemplary EGR mixer embodiments overcome at least some drawbacks of known EGR systems and provide several advantages over conventional designs and processes. The exemplary EGR mixer embodiments facilitate mixing of large volumes of exhaust gas and working fluid (e.g., ambient air) supplied to the EGR mixer at low pressure, thus reducing operating costs (e.g., blower power costs) associated with delivering the exhaust gas and / or working fluid. In particular, the exemplary EGR mixer includes an array of exhaust gas injection ducts that inject exhaust gas into the mixer in a cross-flow relationship with the working fluid flowing through the EGR mixer, thereby creating turbulence and enabling efficient mixing across a reduced cross-sectional area of ​​the mixer. The exemplary EGR mixer embodiments also facilitate reducing the size requirements of the EGR mixer, reducing the overall footprint of the EGR system. Additionally, exemplary EGR mixer embodiments facilitate uniform mixing of the exhaust gas and working fluid to produce a substantially homogeneous and thermally stable mixture, thereby facilitating the reduction or elimination of operational inefficiencies and other undesirable consequences (e.g., compressor strain and / or surge) that may otherwise result from poorly mixed flow. Furthermore, the exemplary EGR mixer is configured to reduce the overall pressure drop of the EGR system, particularly by injecting exhaust gas mixed with the working fluid downstream of a filter media utilized to filter particulates from the working fluid. This configuration facilitates extending the useful life of the filter media, resulting in a significantly lower risk of damage and / or degradation due to condensates (e.g., water droplets) formed in the exhaust gas and working fluid mixture. The exemplary EGR mixer also includes various means for extracting and removing condensates from the exhaust gas and working fluid mixture, thereby reducing or eliminating the possibility that condensates may degrade turbine engine performance or cause other damage downstream of the EGR mixer.

[0044] The above description is intended to be illustrative only, and those skilled in the art will recognize that changes can be made to the described embodiments without departing from the scope of the invention as disclosed. Modifications that fall within the scope of the invention will be apparent to those skilled in the art in light of a review of the present disclosure, and such modifications are intended to fall within the scope of the appended claims. The systems and methods described herein are not limited to the specific embodiments described herein; rather, various system components can be utilized independently and separately from other systems and components described herein. For example, the exhaust gas recirculation mixer can be implemented and utilized in connection with any application where enhanced, uniform mixing and a reduced footprint of the mixer are desired.

[0045] Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. Moreover, references in the above description to "one embodiment" or "exemplary embodiment" are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the invention, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0046] Further aspects of the present invention are provided by the subject matter of the following clauses.

[0047] 1. An EGR mixer for use in a power generation system including an exhaust gas recirculation (EGR) system configured to recirculate exhaust gases generated within the power generation system, the EGR mixer including: a mixing chamber defining a flow direction; a working fluid inlet coupled to the mixing chamber for introducing a working fluid into the mixing chamber along the flow direction; a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet, each of the plurality of exhaust gas injection ducts receiving the recirculated exhaust gases and oriented to inject exhaust gases into the mixing chamber in a direction transverse to the flow direction to generate turbulence within the mixing chamber; and an outlet coupled to the mixing chamber downstream of the plurality of exhaust gas injection ducts for delivering a mixture of exhaust gas and working fluid towards a compressor within the power generation system.

[0048] 2. An EGR mixer as described in clause 1, wherein the plurality of exhaust gas injection ducts are oriented in parallel series, each exhaust gas injection duct extending across the mixing chamber in a direction substantially perpendicular to the flow direction.

[0049] 3. An EGR mixer as described in any one of clauses 1 to 2, wherein the plurality of exhaust gas injection ducts are stacked and oriented vertically in series.

[0050] 4. An EGR mixer as described in any one of clauses 1 to 3, wherein each of the plurality of exhaust gas injection ducts comprises an inlet for receiving recirculated exhaust gas and at least one series of holes for injecting exhaust gas into the mixing chamber.

[0051] 5. An EGR mixer as described in any one of clauses 1 to 4, wherein at least one series of holes comprises a first series of holes and a second series of holes formed on opposite sides of each exhaust gas injection duct, the first series of holes being oriented to inject exhaust gases into the mixing chamber in a first direction transverse to the flow direction, and the second series of holes being oriented to inject exhaust gases into the mixing chamber in a second direction transverse to the flow direction.

[0052] 6. An EGR mixer as described in any one of clauses 1 to 5, wherein each pair of adjacent holes in the at least one series of holes is spaced apart by a distance equal to the distance between each other pair of adjacent holes.

[0053] 7. An EGR mixer as described in any one of clauses 1 to 5, wherein the distance between adjacent pairs of holes in the at least one series of holes varies along the length of each exhaust gas injection duct.

[0054] 8. An EGR mixer as described in any one of clauses 1 to 7, further comprising a drain port below the mixing chamber for receiving condensate from the mixture of exhaust gas and working fluid.

[0055] 9. An EGR mixer as described in any one of clauses 1 to 8, further comprising a moisture collector downstream of the plurality of exhaust gas injection ducts, the moisture collector configured to extract condensate from the mixture of exhaust gas and working fluid.

[0056] 10. An EGR mixer as described in any one of clauses 1 to 9, further comprising a condensate duct extending between the mixing chamber and the outlet, the condensate duct configured to convey condensate from the mixture of exhaust gas and working fluid towards the drain port.

[0057] 11. An EGR mixer as described in any one of clauses 1 to 10, wherein each of the plurality of exhaust gas injection ducts comprises a first series of holes and a second series of holes, and each of the plurality of exhaust gas injection ducts is shaped to allow condensate collected within the respective exhaust gas injection duct to exit via the second series of holes.

[0058] 12. An EGR mixer as described in any one of clauses 1 to 11, further comprising a filter adjacent the working fluid inlet and upstream of the plurality of exhaust gas injection ducts for filtering particulates from the working fluid.

[0059] 13. A power generation system comprising: a rotary machine including a compressor and a turbine coupled to the compressor and configured to generate exhaust gases; and an exhaust gas recirculation (EGR) system configured to recirculate exhaust gases from the turbine toward the compressor, wherein the EGR system comprises an EGR mixer for mixing the recirculated exhaust gases with a working fluid, the EGR mixer including: a mixing chamber defining a flow direction; a working fluid inlet coupled to the mixing chamber for introducing the working fluid into the mixing chamber along the flow direction; a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet, each of the plurality of exhaust gas injection ducts receiving the recirculated exhaust gases and oriented to inject exhaust gases into the mixing chamber in a direction transverse to the flow direction to generate turbulence in the mixing chamber; and an outlet coupled to the mixing chamber downstream of the plurality of exhaust gas injection ducts for delivering the mixture of exhaust gases and working fluid toward the compressor of the rotary machine.

[0060] 14. The power generation system of any one of clauses 1 to 13, wherein the rotary machine comprises a gas turbine engine.

[0061] 15. A power generation system as described in any one of clauses 1 to 14, wherein each of the plurality of exhaust gas injection ducts comprises an inlet for receiving the exhaust gas to be recirculated and at least one series of holes for injecting the exhaust gas into the mixing chamber.

[0062] 16. The power generation system of any one of clauses 1 to 15, wherein the EGR mixer is adjacent to the working fluid inlet and further comprises a filter upstream of the plurality of exhaust gas injection ducts for filtering particulates from the working fluid.

[0063] 17. The power generation system of any one of clauses 1 to 16, wherein the EGR mixer further comprises a moisture collector downstream of the plurality of exhaust gas injection ducts, the moisture collector configured to extract condensate from the mixture of exhaust gas and working fluid.

[0064] 18. A method of operating a power generation system including an exhaust gas recirculation (EGR) system including an EGR mixer including a mixing chamber, a working fluid inlet coupled to the mixing chamber, a plurality of exhaust gas injection ducts extending across the mixing chamber downstream of the working fluid inlet, and an outlet coupled to the mixing chamber downstream of the plurality of exhaust gas injection ducts, the method comprising: generating exhaust gas within the power generation system; recirculating at least a portion of the exhaust gas within the power generation system toward a compressor; introducing a working fluid into the mixing chamber of the EGR mixer along a flow direction via the working fluid inlet; injecting the recirculated exhaust gas into the mixing chamber of the EGR mixer via the plurality of exhaust gas injection ducts in a direction transverse to the working fluid to generate turbulence in the mixing chamber and generate a mixture of the exhaust gas and the working fluid; and delivering the mixture toward the compressor via an outlet of the EGR mixer.

[0065] 19. The method of any one of clauses 1 to 18, further comprising filtering the working fluid before introducing it into the mixing chamber.

[0066] 20. The method of any one of clauses 1 to 19, further comprising removing condensate from the mixture of working fluid and exhaust gas before directing the mixture to the compressor.

[0067] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. [Explanation of symbols]

[0068] 100 Power Generation System 102 Rotating machines, gas turbine engines 104 Compressor 106 Combustor 108 Turbine 110 Shaft 112 Generator 114 Working Fluid 116 Fuel 118 Combustion Gas 120 (untreated) exhaust gas 122 (treated) exhaust gas 124 (treated) exhaust gas 150 Exhaust Gas Recirculation (EGR) System 152 Exhaust Gas Treatment System 154 EGR loop 156 Filter Unit 158 Selective Catalytic Reduction Unit 160 absorption units 162 Recirculation Blower or Compressor 164 Working Fluid 166 mixture 200 Exhaust Gas Recirculation (EGR) Mixer 202 Housing 204 first end 206 Second End 208 Working fluid inlet duct 210 filters 212 Internal 214 Mixing Chamber 216 Exhaust gas inlet duct 218 Exhaust gas injection duct 220 Open end 222 End 224 Support beam 226 holes 228 Exit 232 Front 234 Rear side 236 Exhaust gas injection side 238 Exhaust gas injection side 240 Drain port 242 Moisture Collector 244 Condensate Duct 246 beds 248 bottom panel 250 feathers X flow direction A Longitudinal axis

Claims

1. 1. An EGR mixer (200) for use in a power generation system (100) including an exhaust gas recirculation (EGR) system (150) configured to recirculate exhaust gases (120, 122) generated within the power generation system (100), comprising: a mixing chamber (214) defining a flow direction (X); a working fluid inlet (208) coupled to the mixing chamber (214) for introducing a working fluid (164) into the mixing chamber (214) along the flow direction (X); a plurality of exhaust gas injection ducts (218) extending across the mixing chamber (214) downstream of the working fluid inlet (208), each of the plurality of exhaust gas injection ducts (218) receiving the recirculated exhaust gases (120, 122) and oriented to inject the exhaust gases (120, 122) into the mixing chamber (214) in a direction transverse to the flow direction (X) to create turbulence within the mixing chamber (214); an outlet (228) coupled to the mixing chamber (214) downstream of the plurality of exhaust gas injection ducts (218) for delivering a mixture (166) of the exhaust gases (120, 122) and the working fluid (164) toward a compressor (104) within the power generation system (100); An EGR mixer (200) comprising:

2. 2. The EGR mixer of claim 1, wherein the plurality of exhaust gas injection ducts are oriented in parallel series, each exhaust gas injection duct extending across the mixing chamber in a direction substantially perpendicular to the flow direction.

3. The EGR mixer (200) of claim 2, wherein the plurality of exhaust gas injection ducts (218) are stacked and oriented vertically in series.

4. 2. The EGR mixer of claim 1, wherein each of the plurality of exhaust gas injection ducts comprises an inlet for receiving the recirculated exhaust gas and at least one series of holes for injecting the exhaust gas into the mixing chamber.

5. 5. The EGR mixer of claim 4, wherein the at least one series of holes comprises a first series of holes and a second series of holes formed on opposite sides of each exhaust gas injection duct, the first series of holes being oriented to inject the exhaust gases into the mixing chamber in a first direction intersecting the flow direction, and the second series of holes being oriented to inject the exhaust gases into the mixing chamber in a second direction intersecting the flow direction.

6. 5. The EGR mixer of claim 4, wherein each pair of adjacent holes in the at least one series of holes is spaced apart by a distance equal to a distance between each other pair of adjacent holes.

7. 5. The EGR mixer of claim 4, wherein a distance between adjacent pairs of holes in the at least one series of holes varies along a length of each exhaust gas injection duct.

8. 10. The EGR mixer of claim 1, further comprising a drain port below the mixing chamber for receiving condensate from the mixture of the exhaust gas and the working fluid.

9. 9. The EGR mixer of claim 8, further comprising a moisture collector downstream of the plurality of exhaust gas injection ducts, the moisture collector configured to extract condensate from the mixture of the exhaust gas and the working fluid.

10. 10. The EGR mixer of claim 9, further comprising a condensate duct extending between the mixing chamber and the outlet, the condensate duct configured to convey condensate from the mixture of the exhaust gas and the working fluid toward the drain port.

11. 9. The EGR mixer of claim 8, wherein each of the plurality of exhaust gas injection ducts comprises a first series of holes and a second series of holes, and each of the plurality of exhaust gas injection ducts is shaped to allow condensate collected within a respective exhaust gas injection duct to exit via the second series of holes.

12. 10. The EGR mixer of claim 1, further comprising a filter adjacent the working fluid inlet and upstream of the plurality of exhaust gas injection ducts for filtering particulates from the working fluid.

13. A compressor (104) and a turbine (108) coupled to the compressor (104) and configured to generate exhaust gases (120, 122); a rotary machine (102) comprising: an exhaust gas recirculation (EGR) system (150) configured to recirculate the exhaust gases (120, 122) from the turbine (108) toward the compressor (104); The power generation system (100) comprises: the EGR system (150) comprising an EGR mixer (200) for mixing the recirculated exhaust gas (120, 122) with a working fluid (164), the EGR mixer (200) comprising: a mixing chamber (214) defining a flow direction (X); a working fluid inlet (208) coupled to the mixing chamber (214) for introducing the working fluid (164) into the mixing chamber (214) along the flow direction (X); a plurality of exhaust gas injection ducts (218) extending across the mixing chamber (214) downstream of the working fluid inlet (208), each of the plurality of exhaust gas injection ducts (218) receiving the recirculated exhaust gases (120, 122) and oriented to inject the exhaust gases (120, 122) into the mixing chamber (214) in a direction transverse to the flow direction (X) to create turbulence within the mixing chamber (214); an outlet (228) coupled to the mixing chamber (214) downstream of the plurality of exhaust gas injection ducts (218) for delivering a mixture (166) of the exhaust gases (120, 122) and the working fluid (164) toward the compressor (104) of the rotary machine (102); A power generation system (100) comprising:

14. The power generation system (100) of claim 13, wherein the rotary machine (102) comprises a gas turbine engine.

15. 14. The power generation system (100) of claim 13, wherein each of the plurality of exhaust gas injection ducts (218) comprises an inlet (216) for receiving the exhaust gas (120, 122) to be recirculated and at least one series of holes (226) for injecting the exhaust gas (120, 122) into the mixing chamber (214).

16. 14. The power generation system of claim 13, wherein the EGR mixer further comprises a filter proximate the working fluid inlet and upstream of the plurality of exhaust gas injection ducts for filtering particulates from the working fluid.

17. 14. The power generation system of claim 13, wherein the EGR mixer further comprises a moisture collector downstream of the plurality of exhaust gas injection ducts, the moisture collector configured to extract condensate from the mixture of the exhaust gas and the working fluid.

18. 1. A method of operating a power generation system (100) including an exhaust gas recirculation (EGR) system (150) including an EGR mixer (200) including a mixing chamber (214), a working fluid inlet (208) coupled to the mixing chamber (214), a plurality of exhaust gas injection ducts (218) extending across the mixing chamber (214) downstream of the working fluid inlet (208), and an outlet (228) coupled to the mixing chamber (214) downstream of the plurality of exhaust gas injection ducts (218), comprising: generating exhaust gases (120, 122) within the power generation system (100); recirculating at least a portion of the exhaust gases (120, 122) toward a compressor (104) within the power generation system (100); introducing a working fluid (164) into the mixing chamber (214) of the EGR mixer (200) along a flow direction (X) via the working fluid inlet (208); injecting the recirculated exhaust gases (120, 122) into the mixing chamber (214) of the EGR mixer (200) via the plurality of exhaust gas injection ducts (218) in a direction transverse to the working fluid (164) to generate turbulence in the mixing chamber (214) and generate a mixture (166) of the exhaust gases (120, 122) and the working fluid (164); delivering the mixture (166) towards the compressor (104) via the outlet (228) of the EGR mixer (200); A method comprising:

19. The method of claim 18, further comprising filtering the working fluid (164) before introducing the working fluid (164) into the mixing chamber (214).

20. 20. The method of claim 18, further comprising removing condensate from the mixture (166) of the working fluid (164) and the exhaust gas (120, 122) before delivering the mixture (166) towards the compressor (104).

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