Patent Publication Number: US-9404658-B2

Title: Gas turbine engine fuel air mixer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/772,812 filed Mar. 5, 2013, the contents of which are hereby incorporated in their entirety. 
    
    
     GOVERNMENT RIGHTS 
     The present application was made with the United States government support under Contract No. NNCO8CB09C, awarded by the National Aeronautics and Space Administration. The United States government has certain rights in the present application. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to devices for delivering fuel, and more particularly, but not exclusively, to fuel mixers for gas turbine engines. 
     BACKGROUND 
     Providing a fuel/air mixture to a combustor of an internal combustion engine remains an area of interest. Some existing systems have various shortcomings relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present invention is a unique fuel mixer. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for mixing fuel and air. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts one embodiment of a gas turbine engine. 
         FIG. 2  depicts an embodiment of a fuel/air mixer. 
         FIG. 3  depicts an embodiment of a fuel/air mixer. 
         FIG. 4  depicts an embodiment of a fuel/air mixer. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     With reference to  FIG. 1 , a gas turbine engine  50  is disclosed that includes a compressor  52 , combustor  54 , and turbine  56 . As air enters the gas turbine engine it is compressed by the compressor  52  and mixed with a fuel provided by a fuel mixer  58 . The fuel mixer  58  can be located a variety of places within the gas turbine engine and is not limited to the location depicted in  FIG. 1 . The fuel/air mixture is combusted in the combustor  54  before being delivered to the turbine  56 . As used herein, the term “air” refers to any oxidizer suitable for use with a fuel that is to be combusted in the combustor  54 , whether or not the oxidizer takes the form of atmospheric air. Similarly, the fuel can take a variety of forms suitable for use in gas turbine engines. To set forth just a few non-limiting examples, the fuel can take the form of JP-4, JP-8, and Jet A, the fuel can be a blended fuel, and/or the fuel can include any number and type of additives. 
     Though the gas turbine engine  50  is depicted as having a single compressor and single turbine, in other embodiments the gas turbine engine  50  can have any number of compressors and turbines. In addition, the gas turbine engine  50  can have any number of shafts coupling the compressors and turbines to create separate spools. In a few non-limiting examples of embodiments, the gas turbine engine  50  can take the form of a turboshaft, turboprop, or turbofan engine. In addition, the gas turbine engine  50  can be an adaptive or variable cycle engine. In some forms the gas turbine engine  50  can be an axial flow engine, centrifugal flow engine, or a mixed axial-centrifugal flow engine. In short, the gas turbine engine  50  and/or it&#39;s individual components can take on a variety of forms and be used in a variety of applications. 
     In some applications the gas turbine engine  50  can be used as a powerplant for an aircraft. As used herein, the term “aircraft” includes, but is not limited to, helicopters, airplanes, unmanned space vehicles, fixed wing vehicles, variable wing vehicles, rotary wing vehicles, unmanned combat aerial vehicles, tailless aircraft, hover crafts, and other airborne and/or extraterrestrial (spacecraft) vehicles. Further, the present inventions are contemplated for utilization in other applications that may not be coupled with an aircraft such as, for example, industrial applications, power generation, pumping sets, naval propulsion, weapon systems, security systems, perimeter defense/security systems, and the like known to one of ordinary skill in the art. 
     Turning now to  FIG. 2 , a view of one embodiment of the fuel mixer  58  is shown. The fuel mixer  58  is used to atomize liquid fuel and mix the fuel with an air stream before being combusted in the combustor  54 . In one form the fuel mixer  58  can be used to provide fuel to a lean burning combustor  54  of the gas turbine engine  50 . Generally speaking, the rate of vaporization of a liquid fuel can be enhanced by increasing the total surface area of the liquid fuel in relation to the mass of fuel. For example, by forming the liquid fuel into droplets or forms other than a bulk liquid the rate of vaporization can be increased. Such increase in the surface area relative to its mass can be made possible by atomizing the fuel using a variety of approaches. The fuel mixer  58  of the present application uses plain jet airblast atomizers in some embodiments, in other embodiments the fuel mixer  58  can also include a pressure swirl mixer, and in others can also include fuel filming, some or all of which to be described in some form further below. It will be appreciated, however, that the mixer  58  is not limited to these particular approaches and can include additional and/or alternative forms. 
     In the illustrated form the fuel mixer  58  includes a pilot mixer  60  and a main mixer  62  both of which can be used to provide a mixture of fuel and air to the combustor  54 . In one form the pilot mixer  60  includes a passage  64  through which an air traverses and a swirler  66  structured to change a direction of the air such as by adding a rotational component. The pilot mixer  60  can include a single annular passage  64  or multiple separate passages which can be arranged in an annular configuration, to set forth just a few non-limiting embodiments. Many different types of swirlers can be used in the pilot mixer  60  such as, but not limited to, vane type swirlers and swirlers formed of a plurality of discrete air passages arranged at an angle relative to the direction of incoming airflow. 
     The pilot mixer  60  also includes a fuel aperture  68  through which a fuel can be provided to the fuel mixer  58  at a variety of flow rates, pressures, and temperatures. In the illustrated embodiment the fuel aperture  68  is oriented to provide fuel along an axis of the fuel mixer  58 , and in one non-limiting form the axis can be a central axis of the fuel mixer  58 . In some embodiments the fuel aperture  68  can provide fuel to the pilot mixer  60  other than along the central axis of the fuel mixer  58 . For example, in some forms fuel can be delivered off axis, while in other forms the fuel can be delivered at an angle relative to the central axis, to set forth just a few non-limiting possibilities. In one form the pilot mixer  60  can deliver fuel to be mixed with air using airblast atomization, but other approaches are also contemplated herein. Though the fuel mixer  58  is illustrated as having just a single fuel aperture  68 , other embodiments of the mixer  58  can include one or more apertures  68 . 
     An area change portion  70  is located between the swirlers  66  and an exit  72  of the pilot mixer  60 . The area change portion  70  is used to accelerate the flow of air toward the exit  72  of the fuel mixer  58 . In the illustrated embodiment the area change portion  70  includes a throat which denotes a minimum area of the area change portion  70 . In some embodiments, including the illustrated embodiment, the area change portion  70  also includes a portion beyond the throat which increases in cross sectional area and causes a subsequent slowing of an air toward the exit  72 . Though the swirlers  66  are depicted in the illustrated embodiment as extending to the area change portion  70 , in other embodiments the swirlers  66  can extend into the area change portion and toward the exit  72  any variety of distances. 
     The fuel aperture  68  of the pilot mixer  60  is located near a throat of the area change portion  70  in the illustrated embodiment. In some forms the fuel aperture  68  can be located downstream of the throat, in other forms it is located at the throat, and in still further forms the fuel aperture  68  can be located upstream of the throat. In any event, any variety of spatial relationships are contemplated between the throat of the area change portion  70  and the fuel aperture  68 . 
     The fuel aperture  68  is offset from the exit  72  of the pilot mixer  60  in the illustrated embodiment. The offset can vary from a relatively large amount to a relatively small amount. In some forms the offset can be negligible. Various offset configurations, passage shapes, and exit orientations, among others can be used, some of which are illustrated in  FIGS. 2 and 3 . 
     In the illustrated embodiment the main mixer  62  includes an inner passage  74  and an outer passage  76  both of which are combined into a main passage  78  downstream from each. The passages  74  and  76  are used to provide air to be mixed with fuel in the main mixer  62  The inner passage  74  can include a swirler  80  structured to change a direction of the air such as by adding a rotational component. The passage  74  can be a single annular passage or can take the form of multiple separate passages arranged in an annular configuration, to set forth just a few non-limiting embodiments. The outer passage  76  can additionally and/or alternatively include a swirler  82  structured to change a direction of the air such as by adding a rotational component. The passage  76  can be a single annular passage or can take the form of multiple separate passages arranged in an annular configuration, to set forth just a few non-limiting embodiments. Many different types of swirlers can be used in the main mixer  62  such as, but not limited to, vane type swirlers and swirlers formed of a plurality of discrete air passages arranged at an angle relative to the direction of incoming airflow. Furthermore, any of the swirlers  80  and  82 , and for that matter swirlers  66 , can have any configuration that is unique relative to each other. For example, swirler  66  can have a different geometry than either or both of swirlers  80  and  82 . To set forth another non-limiting example, any of the swirlers can have a different number of passages arranged to change the direction of air traversing the swirlers. Some embodiments, however, can have similar or identical characteristics between the swirlers. Either or both of the swirlers  80  and  82  can extend toward an exit  84  of the main mixer  62  any variety of distances. To set forth just one non-limiting example in this regard, swirler  82  can extend to an end of the member  86  disposed between the inner passage  74  and outer passage  76 . 
     In the illustrated form the main mixer  62  includes a fuel opening  88  arranged to provide fuel coincident with the swirler  80 . The fuel opening  88  is positioned between an upstream side of the swirler  80  and a downstream side, but any position between the two is contemplated. Furthermore, though the fuel opening  68  is configured to provide a jet of fuel in a radially outward direction at this location, other embodiments can provide for delivery of fuel in any variety of other locations and orientations. 
     Depending on relative flow rates, pressures, etc of the fuel and air within the main mixer  62 , in some embodiments and/or modes of operation the fuel emitted from the fuel opening  88  can form a fuel film on a surface of the member  86 . For example, a fuel film can be developed upon the member  86  depending upon a power setting required of the gas turbine engine  50 . As will be appreciated by a review of the figures, such a fuel filming surface is configured to deliver a film of fuel to the confluence of air from the inner passage  74  and the outer passage  76  of the illustrated embodiment. 
     The main passage  78  provides a common pathway for a mixture of fuel and air from the main mixer  62  to the exit  84  of the fuel mixer  58 . In the illustrated embodiment the main passage  78  includes a converging portion which is used to accelerate the flow of air toward the exit  84 . The illustrated embodiment also includes a diverging portion downstream of a minimum area of the main passage  78  forming a converging-diverging main passage  78 . The diverging portion of the main passage  78  can be used to slow a flow of fuel/air mixture as it proceeds toward the exit  84 . Not all embodiments of the main passage  78  need include either or both the converging-diverging portion. 
     As can be seen in the illustrated embodiment, the main passage  78  includes a portion that is turned radially inward toward the pilot mixer  60 , as well as a portion that is turned radially outward away from the pilot mixer  60 . Various embodiments of the main passage  78  can be configured to provide for either or both turning flow and changing a cross sectional area. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.