Patent Publication Number: US-11029030-B2

Title: Ducting arrangement with injector assemblies configured to form a shielding flow of air injected into a combustion stage in a gas turbine engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of the Aug. 3, 2016 filing date of U.S. provisional application 62/370,289 which is incorporated by reference herein. 
     The present application is further related to U.S. Patent Application (U.S. 62/370,333) titled “Combustion System with Injector Assemblies Arranged to Recapture Cooling Air in a Combustor Wall to Form a Shielding Flow of Air in a Combustion Stage”; and U.S. Patent Application (U.S. 62/370,342) titled “Method And Computer-Readable Model For Additively Manufacturing Ducting Arrangement With Injector Assemblies Forming A Shielding Flow Of Air”, each filed concurrently herewith and incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     Disclosed embodiments are generally related to combustion turbine engines, such as gas turbine engines and, more particularly, to injector assemblies and/or a ducting arrangement including such injector assemblies, as may be used in a combustion system of a gas turbine engine. 
     2. Description of the Related Art 
     In most large stationary gas turbine engines, fuel is delivered from a fuel source to a combustion section where the fuel is mixed with air and ignited to generate hot combustion products that define working gases. The working gases are directed to a turbine section where they drive the rotation of a turbine rotor. It is known that production of NOx emissions can be reduced by reducing the residence time of the working fluid in the combustion section. One approach to reduce this residence time is to provide and ignite a portion of the fuel and air downstream of the primary combustion stage. This approach is referred to in the art as a distributed combustion system (DCS). See, for example, U.S. Pat. Nos. 8,375,726 and 8,752,386. Each of the above-listed patents is herein incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary schematic of a disclosed ducting arrangement in a combustion system for a combustion turbine engine. The ducting arrangement can benefit from disclosed injector assemblies arranged to inject a respective flow of reactants in a combustion stage to be mixed with a cross-flow of combustion products. 
         FIG. 2  is a cutaway view showing certain non-limiting structural details in connection with a disclosed injector assembly. 
         FIG. 3  is a side view of a disclosed injector assembly. 
         FIG. 4  is a half-sectional view of a disclosed injector assembly showing a path for air flow through a passageway constructed in the injector assembly. 
         FIG. 5  is a simplified schematic for conceptualizing an air shielding effect generated by air flow injected by a disclosed injector assembly. The air flow may be configured to surround the flow of reactants injected by the injector assembly, as the flow of reactants is admitted in the combustion stage. This shielding effect causes an ignition delay to the flow of reactants injected into the combustion stage and allows a relatively longer time interval for enhancing co-flow mixing before the hot cross-flow of combustion products can ignite the flow of reactants. 
         FIG. 6  is a cross-sectional, exploded view of one disclosed combustor wall or any combustor component that conveys the combustion products through the combustor system, such as a transition duct, as may comprise a multi-panel arrangement that includes a plurality of cooling air conduits that may be in flow communication with a disclosed injector assembly to recapture the cooling air to generate the shielding air flow. 
         FIG. 7  is a cross-sectional view of another disclosed combustor wall or any combustor component that conveys the combustion products through the combustor system, such as a transition duct, as may comprise a unitized body that includes the plurality of cooling air conduits. 
         FIG. 8  is a fragmentary, isometric view of a disclosed combustor wall or any combustor component that conveys the combustion products through the combustor system, such as a transition duct, illustrating example locations for interfacing with respective disclosed injector assemblies. 
         FIG. 9  is a zoomed-in view of one of the interface locations shown in  FIG. 8 . 
         FIG. 10  is a fragmentary, isometric view of an injector assembly disposed at the interface location shown in  FIG. 9 . 
         FIG. 11  is a fragmentary, cutaway isometric view showing further structural details of the injector assembly disposed at the location (shown in  FIG. 9 ) for interfacing with a disclosed transition duct. 
         FIG. 12  is an isometric view that shows non-limiting structural details in connection with the outlet side of the passageway constructed in the injector assembly. 
         FIGS. 13-17  are respective isometric views that show further non-limiting structural details in connection with disclosed injector assemblies. 
         FIGS. 18-21  are respective bottom views of disclosed injector assemblies that show further non-limiting structural details in connection with disclosed injector assemblies. 
         FIG. 22  is a flow chart listing certain steps that may be used in a method for manufacturing disclosed ducting arrangements. 
         FIG. 23  is a flow chart listing further steps that may be used in the method for manufacturing disclosed ducting arrangements. 
         FIG. 24  is a flow sequence in connection with the method for manufacturing disclosed ducting arrangements. 
     
    
    
     DETAILED DESCRIPTION 
     The inventors of the present invention have recognized certain issues that can arise in known distributed combustion systems (DCSs) where a number of injector assemblies may be disposed in a combustion stage (also referred to in the art as an axial combustion stage) that may be arranged axially downstream from a main combustion stage of the combustion system. For example, by injecting a flow of reactants (e.g., a mixture of fuel and air) through a number of injector assemblies (as each may comprise an assembly of an air scoop and a fuel nozzle) disposed in the combustion stage downstream from the main combustion stage, one can achieve a decreased static temperature and a reduced combustion residence time, each of which is conducive to reduce NOx emissions to be within acceptable levels at turbine inlet temperatures of approximately 1700° C. (3200° F.) and above. 
     The downstream combustion stage may involve a ducting arrangement that passes a hot-temperature cross-flow of combustion products (e.g., vitiated gases from the main combustion stage) that in certain embodiments can reach relatively high subsonic speeds, which is conducive to further achieve a decreased static temperature and a reduced combustion residence time. 
     The present inventors have recognized that the mixing performance provided by existing injector assemblies between the flow of reactants and the cross-flow of combustion products can benefit from further improvements. More particularly, the present inventors have recognized that the greater the amount of the cross-flow combustion products that can be entrained with the injected flow of reactants prior to ignition of the fuel contained in the injected flow of reactants, the lower the flame temperature will be, and thus the lower the amount of NOx emissions that will be produced. 
     In view of such recognition, the present inventors propose an injector assembly designed to generate a shielding flow of air that surrounds the injected flow of reactants. This air-shielding effect transitorily separates the injected flow of reactants from the cross-flow of combustion products, thereby advantageously delaying ignition of the injected flow of reactants. This delayed ignition allows an incremental amount of cross-flow combustion products to entrain with the flow of reactants prior to stabilizing the flame formed in the downstream combustion stage. 
     The present inventors have further recognized that in a traditional combustion system, cooling air that may be used for cooling certain components of the ducting arrangement is generally ejected into the vitiated cross-flow of combustion products, and is essentially lost, without contributing to the combustion process, which decreases the efficiency of the engine. Accordingly, the present inventors further propose to recapture the cooling air used for cooling such components so that recaptured cooling air is efficiently reutilized to generate the shielding flow of air. 
     The present inventors have yet further recognized that traditional manufacturing techniques may not be necessarily conducive to a cost-effective and/or realizable manufacture of ducting arrangement configurations that may be involved to efficiently implement the foregoing approaches. For example, traditional manufacturing techniques tend to fall short from consistently limiting manufacturing variability; and may also fall short from cost-effectively and reliably producing the relatively complex geometries and miniaturized features and/or conduits that may be involved in such ducting arrangements configurations. 
     In view of this further recognition, in one non-limiting embodiment, the present inventors further propose use of three-dimensional (3D) Printing/Additive Manufacturing (AM) technologies, such as laser sintering, selective laser melting (SLM), direct metal laser sintering (DMLS), electron beam sintering (EBS), electron beam melting (EBM), etc., that may be conducive to cost-effective fabrication of disclosed ducting arrangements that may involve complex geometries and miniaturized features and/or conduits. For readers desirous of general background information in connection with 3D Printing/Additive Manufacturing (AM) technologies, see, for example, a textbook titled “Additive Manufacturing Technologies, 3D Printing, Rapid Prototyping, and Direct Digital Manufacturing”, by Gibson I., Stucker B., and Rosen D., 2010, published by Springer, which is incorporated herein by reference. 
     In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation. 
     Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application. 
     The terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated. Lastly, as used herein, the phrases “configured to” or “arranged to” embrace the concept that the feature preceding the phrases “configured to” or “arranged to” is intentionally and specifically designed or made to act or function in a specific way and should not be construed to mean that the feature just has a capability or suitability to act or function in the specified way, unless so indicated. 
     In one non-limiting embodiment, a disclosed ducting arrangement may comprise a unitized ducting arrangement. The term “unitized” in the context of this application, unless otherwise stated, refers to a structure which is formed as a single piece (e.g., monolithic construction) using a rapid manufacturing technology, such as without limitation, 3D Printing/Additive Manufacturing (AM) technologies, where the unitized structure, singly or in combination with other unitized structures, can form a component of the combustion turbine engine, such as for example respective injector assemblies, or an entire ducting arrangement including such assemblies. 
       FIG. 1  is a simplified fragmentary schematic of a combustor system  10  (e.g., a DCS) for a combustion turbine engine, such as a gas turbine engine. In one non-limiting embodiment, an array of spaced-apart injector assemblies  12  may be circumferentially arranged in a combustion stage (e.g., the axial combustion stage) downstream from a main combustion stage  18  of the combustor system. The downstream combustion stage is fluidly coupled to receive (e.g., through a ducting arrangement  20 , as may involve a number of transition ducts) a cross-flow of hot-temperature combustion products (schematically represented by arrow  21 ). 
     As may be appreciated in  FIG. 1 , in one non-limiting embodiment, injector assemblies  12  may be disposed in a combustor wall or transition duct having a conical section  17  configured to accelerate the cross-flow of combustion products. In one non-limiting embodiment, injector assemblies  12  may be disposed proximate the exit of the conical section of the combustor wall or transition duct. It will be appreciated that injector assemblies  12  are not limited to conical section  17 . For example, as may be further appreciated in  FIG. 1 , injector assemblies  12  may be disposed upstream of conical section  17 . In alternative embodiments, at least some of the array of injector assemblies  12  may be disposed at different axial locations to, for example, form two or more annular rows of injector assemblies  12 . 
     As shown in  FIG. 2 , in one non-limiting embodiment, injector assembly  12  includes a reactant-guiding structure  16  arranged to convey a flow of reactants into the combustion stage (e.g., a mixture of fuel and air, schematically represented by arrow  19 ) for admixing with the cross-flow of combustion products. Injector assembly  12  further includes means for injecting a flow of air (schematically represented by arrows  22  in  FIG. 4 ) into the combustion stage. That is, an additional flow of air which at least initially does not admix with the flow of axial stage reactants  19 . 
     As further shown in  FIG. 2 , in one non-limiting embodiment injector assembly  12  may have an injector assembly body comprising an inner wall  24  and an outer wall  25  that define a passageway  26  having an inlet side  27  and an outlet side  28 . The passageway defined by inner wall  24  and outer wall  25  of the injector assembly body is effective to inject the flow of cooling fluid  22  (e.g., air) into the combustion stage. 
     As may be appreciated in  FIG. 3 , in one non-limiting embodiment, at the inlet side  27  of passageway  26 , injector assembly  12  includes a plurality of circumferentially arranged openings  29  that may be fluidly coupled to an air plenum (not shown); or, as described in greater detail below, may be fluidly coupled to cooling fluid conduits in a combustor wall or transition duct. It will be appreciated that openings  29  are not limited to any particular shape. Thus, the shape illustrated in the drawings for openings  29  should not construed in a limiting sense. 
     Without limiting disclosed embodiments to any particular principle of operation, the flow of air  22  injected into the combustion stage may be conceptualized as effective to condition interaction (e.g., an air shielding effect) of the flow of reactants  19  with respect to the cross-flow of combustion products, as the flow of reactants is admitted into the combustion stage. 
       FIG. 5  is a simplified schematic for conceptualizing the air shielding effect generated by air flow  22  injected by injector assembly  12 . The air flow may be configured to surround the flow of reactants  19  injected by the injector assembly, as the flow of reactants is admitted in the combustion stage. This air shielding effect provides an ignition delay to the flow of reactants injected into the combustion stage and allows a relatively longer time interval for enhancing co-flow mixing (e.g., adjective mixing) before the hot cross-flow of combustion products can ignite the flow of reactants. 
     In operation, a flame  33  generated in the axial combustion stage is incrementally shifted farther downstream than would be the case, if the disclosed air shielding effect was not provided. That is, the shield of air flow surrounding the injected flow of reactants promotes liftoff and/or increases the liftoff distance of the flame, allowing a longer time interval for entrainment of the cross-flow with the injected flow of reactants and this reduces the flame temperature, which in turn reduces the level of NOx emissions. 
       FIG. 6  is a cross-sectional, exploded view of one disclosed combustor wall  40 ′ or transition duct body, such as may comprise a multi-panel arrangement  42 ,  44  that includes a plurality of cooling air conduits  46 .  FIG. 7  is a cross-sectional view of another disclosed combustor wall  40 ″ or transition duct body, such as may comprise a unitized body  49  that includes the plurality of cooling air conduits  46 . Regardless of the specific construction modality of the combustor wall or transition duct body, cooling air conduits  46  may be in flow communication with injector assembly  12  to recapture the cooling air that otherwise would be wasted to generate the shielding air flow, as shown in  FIG. 11 . That is, this arrangement effectively makes dual usage of the air conveyed by cooling air conduits  46 : use for cooling purposes of combustor structures; and use for combustion purposes in the axial stage. 
       FIG. 8  is a fragmentary, isometric view of a combustor wall  40  or transition duct body (e.g., multi-panel arrangement, unitized body, etc.,) illustrating example locations  48  for interfacing with respective injector assemblies.  FIG. 9  is a zoomed-in view of one such interface location  48  where one can see a plurality of outlets  52  for conveying cooling fluid (e.g., air) from a respective combustor wall  40  to a respective injector assembly  12  that may be disposed at the interface location, as seen in  FIG. 10 . Each outlet  52  in the transition duct is positioned to be in correspondence with a respective one of the openings  29  at the inlet side of a respective injector assembly  12 , partially seen in  FIG. 11 . The description below proceeds to describe various non-limiting embodiments that may be optionally implemented in disclosed injector assemblies. 
       FIG. 12  is an isometric view that shows certain details in connection with the outlet side  28  of the passageway  26  constructed in an injector assembly  12 . In this example, the outlet side  28  of passageway  26  comprises a varying cross-sectional profile along a perimeter of the outlet side so that, for example, a velocity and a volume of the injected flow of air can have a desired variation along the perimeter of the outlet side. It will be appreciated that the outlet side of the passageway may have a uniform cross-sectional profile, such as a circular profile. 
     In one non-limiting embodiment, as seen in  FIG. 13 , reactant-guiding structure  16  of injector assembly  12  may include means for swirling  56  the flow of reactants to be injected into the combustion stage. Alternatively, as seen in  FIG. 14 , passageway  26  of injector assembly  12  may include means for swirling  58  the flow of cooling fluid to be injected into the combustion stage. The means for swirling  56 ,  58  may both be respectively included, depending on the needs of a given application. 
     In one non-limiting embodiment, means for swirling  58  may be arranged to provide a swirl to the flow of cooling fluid along a first swirl direction, while the means for swirling  56  may be arranged to provide a swirl to the flow of reactants along a second swirl direction. In one non-limiting embodiment, the first and the second swirl directions may be arranged to provide equal swirling directions relative to one another, as shown in  FIG. 15 . That is, the means for swirling  56 ,  58  may be arranged to provide co-swirling. In another non-limiting embodiment, the first and the second swirl directions may provide opposite swirling directions relative to one another, as shown in  FIG. 16 . That is, the means for swirling  56 ,  58  may be arranged to provide counter-swirling. 
     In one non-limiting embodiment, as seen in  FIG. 17 , a number of orifices  62  may be arranged on the inner wall  24  of injector assembly  14  to provide fluid communication between passageway  26  and reactant-guiding structure  16 . 
       FIGS. 18-21  are respective bottom views of the respective flow outlets of an injector assembly  12  (such as outlet side  28  of passageway  26  that conveys the shielding air flow and the outlet  60  of reactant-guiding structure  16  that conveys the flow of reactants). 
     In one non-limiting embodiment, as seen in  FIG. 18 , the outlet side  28  of passageway  26  may include geometric features  64 , such as a chevron arrangement, a lobe arrangement, serrated arrangement, etc., configured to promote co-flow intermixing of the flow of cooling fluid with the flow of reactants, as each flow is respectively admitted into the combustion stage. 
     In another non-limiting embodiment, as seen in  FIG. 19 , the outlet  60  of reactant-guiding structure  16  may include such geometric features  64 . Alternatively, both the outlet side  28  of passageway  26  and the outlet  60  of reactant-guiding structure  16  can each include respective geometric features  64 , as seen in  FIG. 20 . If desired the respective geometric features  64  may be circumferentially staggered relative to one another as seen in  FIG. 21 . 
       FIG. 22  is a flow chart listing certain steps that may be used in a method for manufacturing disclosed ducting arrangements in a combustion system for a gas turbine engine. As shown in  FIG. 22 , after a start step  200 , step  202  allows generating a computer-readable three-dimensional (3D) model, such as a computer aided design (CAD) model, of the ducting arrangement. The model defines a digital representation of the ducting arrangement, as described above in the context of the preceding figures. Prior to return step  206 , step  204  allows manufacturing the ducting arrangement using an additive manufacturing technique in accordance with the generated three-dimensional model. 
     Non-limiting examples of additive manufacturing techniques may include laser sintering, selective laser melting (SLM), direct metal laser sintering (DMLS), electron beam sintering (EBS), electron beam melting (EBM), etc. It will be appreciated that once a model has been generated, or otherwise available (e.g., loaded into a 3D digital printer, or loaded into a processor that controls the additive manufacturing technique), then manufacturing step  204  need not be preceded by a generating step  202 . It will be further appreciated that the entire ducting arrangement or one or more components of the ducting arrangement, e.g., transition duct, injector assembly, combination of transition duct with the injector assemblies, etc., may be formed as respective unitized structures using additive manufacturing in accordance with the generated three-dimensional model. 
       FIG. 23  is a flow chart listing further steps that may be used in the disclosed method for manufacturing the ducting arrangement. In one non-limiting embodiment, manufacturing step  204  ( FIG. 22 ) may include the following: after a start step  208 , step  210  allows processing the model in a processor into a plurality of slices of data that define respective cross-sectional layers of the ducting arrangement. As described in step  212 , at least some of the plurality of slices may define one or more voids within at least some of the respective cross-sectional layers of the ducting arrangement. (e.g., respective voids that may be used to form hollow portions of ducting arrangement  20 , such as interface locations  48 , cooling air conduits  46  and outlets  52  ( FIG. 9 ), passageway  26  and openings  29  in connection with injection assemblies  12 , ( FIG. 3  and  FIG. 4 )). Prior to return step  216 , step  214  allows successively forming each layer of the ducting arrangement by fusing a metallic powder using a suitable source of energy, such as without limitation, lasing energy or electron beam energy. 
       FIG. 24  is a flow sequence in connection with a disclosed method for manufacturing a 3D object  232 , such as ducting arrangement  20 , injection assemblies  12 , etc. A computer-readable three-dimensional (3D) model  224 , such as a computer aided design (CAD) model, of the 3D object may be processed in a processor  226 , where a slicing module  228  converts model  224  into a plurality of slice files (e.g., 2D data files) that defines respective cross-sectional layers of the 3D object. Processor  226  may be configured to control an additive manufacturing technique  230  used to make 3D object  232 . 
     In operation at least the following advantages are believed to be achieved by disclosed embodiments: 1) The shield of air flow surrounding the flow of reactants is effective to promote liftoff and/or increases the liftoff distance of the flame generated in the downstream combustion stage allowing more time for entrainment of the cross-flow which reduces flame temperature and reduces NOx emissions; 2) autoignition flashback risk reduction and 3) the air flow that forms the shielding air additionally provides a cooling functionality, which maintains the hot side of the injector assembly body at a lower temperature thereby extending the life of the injector assembly. This cooling functionality allows for injector assemblies (e.g., scoops) that can benefit from a wide range of airflows with relatively similar cooling capability. Opposite to disclosed embodiments, the cooling in previous scoop designs was highly dependent on the total scoop flow, and thus limiting the range of airflows that could be used. In operation, disclosed embodiments are expected to be conducive to realizing a combustion system capable of achieving approximately a 65% combined cycle efficiency or greater in a gas turbine engine. Disclosed embodiments are also expected to realize a combustion system capable of maintaining stable operation at turbine inlet temperatures of approximately 1700° C. and higher while maintaining a relatively low level of NOx emissions, and acceptable temperatures in components of the engine without an increase in cooling air consumption. By reusing for combustion purposes air that was previously limited just for cooling the combustor wall, one can enhance the efficiency of the combustion system while maintaining NOx emissions below regulatory limits. 
     While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.