Patent Publication Number: US-8528337-B2

Title: Lobe nozzles for fuel and air injection

Description:
TECHNICAL FIELD 
     The present application relates generally to gas turbines engines and more particularly relates to lobe-shaped premix injectors for use with fuel and air streams. 
     BACKGROUND OF THE INVENTION 
     In a gas turbine engine, it is common to mix the fuel and the air immediately upstream of a combustion zone. The fuel and the air must be mixed rapidly and sufficiently so as to produce a flow stream suitable for the combustion. The fuel and the air should be mixed, however, without flame holding or without forming recirculation zones. Such recirculation zones potentially could support flame holding or even an autoignition event that could cause damage to the turbine as a whole. 
     Various types of fuel and air injector configurations are now in use. The different configurations may be used to accommodate, in part, the specific nature and quality of the fuel and the combustion process. Each of these injector configurations, however, requires its own set of spare parts as well as specific installation, operation, and repair techniques. Likewise, many known injectors are made of relatively expensive cast parts and assembly processes. 
     There is a desire therefore, for an injection design that can be used across product lines. The injector preferably should be relatively low cost while providing sufficient mixing with a reduced possibility of flame holding or forming recirculation zones. 
     SUMMARY OF THE INVENTION 
     The present application thus describes an injection system for fuel and air. The injection system includes a number of lobes positioned adjacent to each other. Each of the lobes has a trailing end. A number of jets may be positioned adjacent to the trailing end. 
     The present application further describes an injection system for fuel and air. The injection system includes a number of lobes positioned adjacent to each other. Each of the lobes has a trailing end. A number of fuel jets and a number of air jets may be positioned adjacent to the trailing end. 
     The present application further describes an injection system for fuel and air. The injection system includes a number of vanes positioned adjacent to each other with each of the vanes including a trailing end. A number of fuel jets and a number of air jets are positioned adjacent to the trailing end. 
     These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a lobe injection system with a swirl injector as is described herein. 
         FIG. 2  is a side cross-sectional view of a lobe of the lobe injection system of  FIG. 1 . 
         FIG. 3  is a side cross-sectional view of a pair of lobes of the lobe injection system of  FIG. 1 . 
         FIG. 4  is a perspective view of a lobe injection system with a non-swirl injector as is described herein. 
         FIG. 5  is a front plan view of a pair of lobes of the lobe injection system of  FIG. 4 . 
         FIG. 6  is a perspective view of a lobe injection system with a number of nested lobes as is described herein. 
         FIG. 7  is a perspective view of a number of nested lobes with spacers therein. 
         FIG. 8  is a perspective view of a pair of nested lobes with a lobed shape. 
         FIG. 9  is a perspective view of a lobe with an upstream jet. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings in which like numerals refer to like elements throughout the several views,  FIG. 1  shows an example of a lobe injector system  100  as is described herein. In this example, the lobe injector system  100  incorporates a swirl injector  110 . As is known, the swirl injector  110  generally includes a number of vanes or lobes  120 . The lobes  120  may have any desired shape or configuration. Any number of lobes  120  may be used herein. Each pair of the lobes  120  defines an air pathway therebetween. The lobes  120  may be mounted about a hub  130 . 
     Each lobe  120  of the lobe injector system  100  may have a number of large jets  140  positioned on an end plate  125  along a trailing edge  126  thereof. Each lobe  120  of the lobe injector system  100  also may have a number of small jets  150 . The small jets  150  may be positioned at an angle along the end plate  125  or perpendicular to the end plate  125  and positioned adjacent thereto. In this example, an angle of about thirty degrees (30°) is shown. Any angle may be used herein including opposing jets  150  at about ninety degrees (90°) as is explained below. Any number of small jets  150  may be used. Likewise, the small jets  150  may have any size. Fuel therefore may be injected at an angle into the air stream at multiple points along each lobe  120 . Air or an inert diluent also may be injected through one or more of the small jets  150 . Multiple fuels and/or other gases also may be injected through the combined use of the large jets  140  and the small jets  150 . The end plate  125  may or may not be used. Likewise, slot or sheet injection may be used. 
       FIG. 2  shows a further embodiment of a lobe  160 . In this embodiment, the lobe  160  has an air jet  170  and a fuel jet  180 . The fuel jet  180  may be angled with respect to the air jet  170  as is shown. The air jet  170  may be positioned downstream of the fuel jet  180 . The downstream air jet  170  provides for rapid mixing of the fuel. Alternatively, the air jet  170  may be positioned upstream of the fuel jet  180  such that the air can impinge on the fuel jet  180  and further increases the possibility of rapid mixing. 
     The air jet  170  may have a scalloped region  190 . The scalloped region  190  also reduces flame holding potential. The number, size, and orientation of the jets  170 ,  180  may vary. As is shown in  FIG. 3 , opposing lobes  160  may be used so as to enhance further mixing via the air and the fuel streams colliding. 
       FIGS. 4 and 5  show a further embodiment of the lobe injector system  100 . In this example, a non-swirl injector  200  is shown. The non-swirl injector  200  also includes a number of lobes  210 . The lobes  210  may or may not include the air and the fuel jets  170 ,  180  as is described above. Sheet injection with a diluent blanket may be used for high diluent effectiveness. 
     A further example of the lobe injector system  100  is shown in  FIG. 6 . In this example, a nested injector  220  is shown. The nested injector  220  includes a number of lobes  230  nested within each other. The air and/or the fuel jets  170 ,  180  also may be used herein. The lobes  230  may be axially staged for multiple fueling paths. Other configurations may be used herein. A nested outer lobe also may be used for impingement cooling. As is shown in  FIG. 7 , a number of spacers  240  may be used between the lobes  230 . The spacers  240  may provide spacing and structure to the lobes  230  as well as defining flow paths therethrough. The spacers  240  also may enable a means of flow control for diffusion flame configurations. 
     As is shown in  FIG. 8 , the lobes  230  themselves also may have a lobed or a sinusoidal shape. In this example, a number of lobes  250  may have the lobed shape so as to increase mixing at the trailing edge  126  thereof and to provide a stable flame structure. Other shapes may be used herein. The lobes  250  may be nested or unnested. 
     The components of the lobe injector system  100  may be made out of conventional sheet metal or similar materials as well as casting or more expensive techniques or materials. The less expensive materials may be used given the positioning of the jets  170 ,  180  and the lack of flame holding on the metal. The same general design may be used for various types of turbines, including, but not limited to, DLN (Dry Low NO x ) and IGCC (Integrated Gasification Combined Cycle), MNQC (Multi-Nozzle Quiet Combustor), and otherwise. 
     The lobe injector system  100  thus may provide uniformity across product lines and a resulting cost benefit. The lobe injector system  100  may be original equipment or a retrofit and may be scalable. Specifically, the size, number, and positioning of the jets  140 ,  150 ,  170 ,  180  may be changed to accommodate different fuels or gases. The lobe injector system  100  further provides fuel flexibility in that large variations in fuel flows may be accommodated, i.e., low volume/high BTU flows and high volume/low BTU flows may be used. Likewise, the air may be ambient, purge air, steam, nitrogen, other inert gasses, or another fuel stream. 
     By moving the jets  140 ,  150 ,  170 ,  180  to the trailing edge  126  of the lobes  120 , the possibility of flame holding is reduced. Likewise, the fuel-air mixing time likewise is reduced in that the lobe injector system  100  allows for more fuel and air passages to interact, thus providing more fuel injection points so as to provide better mixing. Flame holding margins therefore may be reduced. The lobe injector  100  thus addresses the issue of costs, flame holding, mixing, fuel flexibility, and a unified design. The design is flexible with many variations. 
     The lobes  120  may be segmented to increase design flexibility and durability. As described above, the end plate  125  may or may not be used. The lobes  120  may use outer shells or other structures to aid in directing the airflow therethrough. The outer shells may form lobe module. Although circular structures are shown herein, the lobes  120  may be modular in nature and may take a square shape, a rectangular shape, or any desired shape and structure. Lobes  120  of varying heights also may be used. 
     The lobe injection system  110  also may have additional air jets  260  or fuel jets  270  positioned upstream of the trailing edge  126  as is shown in  FIG. 9 . Upstream injection may be used within the same fuel circuit. For example, natural gas may be injected upstream with a syngas at the trailing edge  126 . Fuel injection upstream of the trailing edge  126  can provide cooling to the lobes  120  and potentially extend the useful lifetime. Likewise, an inert air may be injected upstream to reduce flame holding potential with a syngas. 
     It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.