Patent Publication Number: US-9416973-B2

Title: Micromixer assembly for a turbine system and method of distributing an air-fuel mixture to a combustor chamber

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to turbine systems, and more particularly to a micromixer assembly of a gas turbine engine, as well as a method of distributing an air-fuel mixture to a combustor chamber of the gas turbine engine. 
     Gas turbine systems may include a micromixer, where air distribution to an individual air-fuel pipe should remain at a mean average value of the overall flow. The micromixer typically includes a plurality of pipes or tubes, each having an inlet. Due to upstream conditions, such as the flow experiencing a sharp turn just prior to entering the inlets, non-uniform mass flow often prevails, thereby hindering engine performance. Decreased performance is a result of ineffective air-fuel mixing prior to injection to the combustor chamber, thereby increasing NOx emissions, for example. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a micromixer assembly for a turbine system includes a plurality of pipes each having an inlet for receiving an airflow from an annulus defined by an inwardly disposed liner and an outwardly disposed sleeve, each of the plurality of pipes also including an outlet for dispersing an air-fuel mixture into a combustor chamber. Also included is a first portion of each of the plurality of pipes. Further included is a second portion of each of the plurality of pipes, the second portion comprising the inlet for receiving the airflow. Yet further included is at least one fuel receiving path in communication with at least one of the first portion and the second portion. 
     According to another aspect of the invention, a micromixer assembly for a turbine system includes a plurality of pipes each having an inlet for receiving an air-fuel mixture from an annulus defined by an inwardly disposed liner and an outwardly disposed sleeve, each of the plurality of pipes also including an outlet for dispersing the air-fuel mixture into a combustor chamber. Also included is a first portion of each of the plurality of pipes, the first portion comprising a relatively linear region and the outlet. Further included is a second portion of each of the plurality of pipes, the second portion comprising the inlet for receiving the air-fuel mixture and a curved region for redirecting the air-fuel mixture toward the first portion. 
     According to yet another aspect of the invention, a method of distributing an air-fuel mixture to a combustor chamber is provided. The method includes routing an airflow from an annulus defined by an inwardly disposed liner and an outwardly disposed sleeve to a curved region of a pipe. Also included is redirecting an air-fuel mixture to a relatively linear region of the pipe. Further included is dispersing the air-fuel mixture into the combustor chamber through an outlet of the pipe. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic illustration of a gas turbine engine; 
         FIG. 2  is a partial sectional view of a combustor assembly of the gas turbine engine, the combustor assembly having a micromixer assembly; 
         FIG. 3  is a schematic illustration of the micromixer assembly according to a first embodiment; 
         FIG. 4  is an elevational end view of the micromixer assembly according to the first embodiment of  FIG. 3 ; 
         FIG. 5  is a schematic illustration of the micromixer assembly according to a second embodiment; 
         FIG. 6  is a schematic illustration of the micromixer assembly according to a third embodiment; 
         FIG. 7  is a schematic illustration of an end view of the micromixer assembly according to the third embodiment of  FIG. 6 ; 
         FIG. 8  is a perspective view of an inlet region of the micromixer assembly; and 
         FIG. 9  is a flow diagram illustrating a method of distributing an air-fuel mixture to a combustor chamber of the combustor assembly. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a gas turbine engine  10  constructed in accordance with an exemplary embodiment of the present invention is schematically illustrated. The gas turbine engine  10  includes a compressor  12  and a plurality of combustor assemblies arranged in a can annular array, one of which is indicated at  14 . As shown, the combustor assembly  14  includes an endcover assembly  16  that seals, and at least partially defines, a combustor chamber  18 . A plurality of tube bundles  20 - 22  are supported by the endcover assembly  16  and supply fuel to an interior region of the combustor assembly  14 . The tube bundles  20 - 22  receive fuel through a common fuel inlet (not shown) and compressed air from the compressor  12 . The fuel and compressed air are passed into the combustor chamber  18  and ignited to form a high temperature, high pressure combustion product or airstream that is used to drive a turbine  24 . The turbine  24  includes a plurality of stages  26 - 28  that are operationally connected to the compressor  12  through a compressor/turbine shaft  29  (also referred to as a rotor). 
     In operation, air flows into the compressor  12  and is compressed into a high pressure gas. The high pressure gas is supplied to the combustor assembly  14  and mixed with fuel, for example natural gas, fuel oil, process gas and/or synthetic gas (syngas), in the combustor chamber  18 . The fuel/air or combustible mixture ignites to form a high pressure, high temperature combustion gas stream. In any event, the combustor assembly  14  channels the combustion gas stream to the turbine  24  which converts thermal energy to mechanical, rotational energy. 
     Referring now to  FIG. 2 , as noted above, a can annular array of combustor assemblies is arranged in a circumferentially spaced manner about an axial centerline of the gas turbine engine  10 . For illustration clarity, a partial view of a single combustor assembly of the can annular array is shown and includes the combustor chamber  18  and a head end  25 . The head end  25  is disposed at an adjacent upstream location of the combustor chamber  18  and includes a micromixer assembly  30 . The micromixer assembly  30  includes a plurality of pipes  32  that may be appropriated into sectors. In an exemplary embodiment, as shown in  FIG. 4 , the micromixer assembly  30  includes five sectors, with each sector having about 21 pipes. However, it is to be understood that the actual number of sectors and number of pipes within each sector may vary depending on the application of use. Each of the plurality of pipes  32  may vary in dimension. In one embodiment, each pipe comprises an outer diameter of about 0.875″ (about 22.2 mm) and a tube thickness of about 0.049″ (about 1.24 mm). Although referred to throughout the specification as the plurality of pipes  32 , it is to be understood that a plurality of passages are employed for a cast assembly. Therefore, for clarity of description, the term pipes is referenced herein, but the term is to be understood to be used synonymously with passages. 
     The combustor chamber  18  is defined by a liner  34 , such as an inwardly disposed liner. Spaced radially outwardly of the liner  34 , and surroundingly enclosing the liner  34 , is a sleeve  38 , such as a flow sleeve, for example. An airflow  40  flows in an upstream direction within an annulus  42  defined by the liner  34  and the sleeve  38  toward the head end  25  of the combustor assembly  14 . 
     Referring now to  FIGS. 3 and 4 , in conjunction with  FIG. 2 , a first embodiment of the micromixer assembly  30  is illustrated. In the illustrated embodiment, each of the plurality of pipes  32  includes a first portion  50  disposed in a relatively linear orientation and extending from a second portion  52  of the plurality of pipes  32  to an outlet  56 , where the outlet  56  is formed integrally with, or operably coupled to, a face outlet plate  57 . As will be described in detail below, each of the plurality of pipes  32  is configured to route an air-fuel mixture  58  throughout the plurality of pipes to the outlet  56  for distribution to the combustor chamber  18 . The second portion  52  of each of the plurality of pipes  32  extends from an inlet  60  disposed in close proximity to the annulus  42  for receiving the airflow  40  therein. The inlet  60  for each of the plurality of pipes  32  may include a “scooped” region  61  ( FIG. 8 ) that facilitates flow uniformity of the airflow  40  upon entry to the plurality of pipes  32 . The second portion  52  extends from the inlet  60  to the first portion  50  and includes a curved region  62  that redirects the airflow  40 . In the illustrated embodiment, the redirection of the airflow  40  occurs over an angle of about 180 degrees. 
     A fuel plenum  70  is included and is defined, at least in part, by the endcover assembly  16  and a cap structure  72 . The fuel plenum  70  is configured to retain a fuel  74  for delivery to the plurality of pipes  32 . More specifically, the fuel  74  is delivered from the fuel plenum  70  to the second portion  52  of the plurality of pipes  32  through at least one fuel receiving path  76 . The at least one fuel receiving path  76  may simply be a hole extending through the second portion  52  or may be a more elaborate fuel routing system for introduction of the fuel  74  to the second portion  52 . The at least one fuel receiving path  76  may be situated in various locations along or within the plurality of pipes  32 . In an exemplary embodiment, the at least one fuel receiving path  76  is disposed at a location of the second portion  52  upstream of the curved region  62 , however, it is to be appreciated that the at least one fuel receiving path  76  may be disposed at locations within the curved region  62  or downstream of the curved region  62 . Irrespective of the precise configuration and location of the at least one fuel receiving path  76 , the fuel  74  is injected into each of the plurality of pipes  32  for mixing with the airflow  40  to form the air-fuel mixture  58  to be distributed to the combustor chamber  18 . Routing of the air-fuel mixture  58  through the second portion  52  effectively mixes the airflow  40  and the fuel  74  over a short distance prior to distribution to the combustor chamber  18 , which results in beneficial emission performance of the gas turbine engine  10 . 
     Referring now to  FIG. 5 , a second embodiment of the micromixer assembly  30  is illustrated. The second embodiment is similar in many respects to the first embodiment described in detail above, such that duplicative description of each component is not necessary and similar reference numerals are employed where applicable. As shown, the second portion  52  of each of the plurality of pipes  32  route the from the inlet  60  to the first portion  50  over an angle of about 90 degrees, rather than the 180 degrees described above in conjunction with the first embodiment. The inlet  60  is configured to receive the airflow  40  for mixing with the fuel  74  over the curved region  62  of the second portion  52 . Although the first embodiment and the second embodiment illustrate and are described as having a 180 degree turn and a 90 degree turn, respectively, it is to be appreciated that the second portion  52  of each of the plurality of pipes  32  may be configured to turn the air-fuel mixture  58  over numerous turning angles. It is contemplated that any turning angle between about 90 degrees and 180 degrees is suitable for effective mixing of the air-fuel mixture  58 . 
     Referring now to  FIGS. 6 and 7 , a third embodiment of the micromixer assembly  30  is illustrated. The third embodiment is similar in many respects to the first and second embodiments described above, such that duplicative description of each component is not necessary and similar reference numerals are employed where applicable. In the illustrated embodiment, the fuel  74  is distributed into the annulus  42  to form the air-fuel mixture  58  prior to injection of the air-fuel mixture  58  into the inlet  60  of the plurality of pipes  32 . Distribution of the fuel  74  into the annulus  42  for mixing with the airflow  40  is achieved by disposal of a fuel injector arrangement  80 . The fuel injector arrangement  80  is configured to deliver fuel upstream of the inlet  60  of the plurality of pipes  32 . It is to be appreciated that the fuel injector arrangement  80  may be in the form of various geometric configurations. In one embodiment, the fuel injector arrangement  80  comprises at least one airfoil-shaped region  82  having at least one aperture  84  for delivery of the fuel  74  to the annulus  42 . The geometry of the at least one airfoil-shaped region  82  is selected based on the aerodynamic properties of an airfoil to reduce the disturbance on the airflow  40  rushing toward the head end  25  through the annulus  42 . As noted above, other geometric configurations of the fuel injector arrangement  80  are contemplated. For example, a cylindrical peg may be employed. The exemplary embodiments described above are merely illustrative and numerous suitable shapes may be used to reduce the disturbance on the airflow  40 , as described above. 
     The air-fuel mixture  58  is thereby premixed before entering the inlet  60  of the second portion  52  of the plurality of pipes  32 . In the illustrated embodiment, the second portion  52  routes the air-fuel mixture  58  along an angular turn of about 180 degrees to effectively mix the air-fuel mixture  58 . As noted above, the second portion  52  may be configured to turn the air-fuel mixture  58  over numerous angles, such as between about 90 degrees and about 180 degrees. Subsequently, the air-fuel mixture  58  is routed through the first portion  50  of the plurality of pipes  32  for distribution into the combustor chamber  18 . 
     The micromixer assembly  30  of any of the above-described embodiments may be fully or partially formed in a number of processes. In an exemplary embodiment, the micromixer assembly  30  is cast to reduce stresses throughout the structure that may be present with various other processes. Alternatively, the micromixer assembly  30  may be fully or partially brazed or formed with an additive process, such as direct metal laser sintering (DMLS), for example. Additionally, a tube expansion process may be employed, wherein the plurality of pipes are expanded into an opening. 
     As illustrated in the flow diagram of  FIG. 9 , and with reference to  FIGS. 1-8 , a method of distributing an air-fuel mixture to a combustor chamber  100  is also provided. The gas turbine engine  10 , as well as the combustor assembly  14  and the micromixer assembly  30  have been previously described and specific structural components need not be described in further detail. The method of distributing an air-fuel mixture to a combustor chamber  100  includes routing an airflow from an annulus defined by an inwardly disposed liner and an outwardly disposed sleeve to a curved region of a pipe  102 . The air-fuel mixture is then redirected to a relatively linear region of the pipe  104 . The air-fuel mixture is dispersed into the combustor chamber through an outlet of the pipe  106 . 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.