Patent Publication Number: US-9897321-B2

Title: Fuel nozzles

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to nozzles, and more particularly to fuel nozzles such as those used in combustors of gas turbine engines. 
     2. Description of Related Art 
     A variety of engines typically incorporate fuel injectors or nozzles in their combustion sections in which fuel and air are mixed and combusted. Efficiency of combustion is related to a variety of factors including fuel-to-air ratio, ignition source location and degree of fuel atomization. Fuel is typically sprayed from a pressure atomizer and then mixed with flows of air. 
     Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is an ongoing need in the art for improved fuel nozzles. The present disclosure provides a solution for this need. 
     SUMMARY OF THE INVENTION 
     A nozzle includes a nozzle body defining a longitudinal axis. The nozzle body includes an air passage having a radial swirler and a converging conical cross-section. A fuel circuit is radially outboard from the air passage with respect to the longitudinal axis. The fuel circuit extends from a fuel circuit inlet to a fuel circuit annular outlet. The fuel circuit includes a plurality of helical passages to mitigate gravitational effects at low fuel flow rates. Each helical passage of the fuel circuit opens tangentially with respect to the fuel circuit annular outlet into an outlet of the air passage. 
     In accordance with certain embodiments, the helical passages are defined by helical threads in at least one of a fuel circuit inner wall or a fuel circuit outer wall. Each helical passage can intersect a single cross-sectional plane taken along the longitudinal axis. More than one of the helical passages can intersect each cross-sectional plane taken along the longitudinal axis. Each of the helical passages can complete at least one 360 degree pass through the fuel circuit. 
     The fuel circuit annular outlet can be proximate to the outlet of the air passage. The fuel circuit can be defined between a fuel circuit inner wall and a fuel circuit outer wall. At least a portion of the fuel circuit outer wall can be radially outboard from the fuel circuit inner wall with respect to the longitudinal axis. At least a portion of both the fuel circuit inner wall and outer wall can be conical shapes that converge toward the longitudinal axis. The fuel circuit inlet can include a plurality of circumferentially spaced apart openings in fluid communication with a fuel manifold. A plurality of tubes can be defined through the air passage, each tube connecting the openings to the fuel manifold. 
     It is contemplated that the air passage can be defined between a backing plate and a fuel circuit inner wall downstream from the backing plate. At least a portion of the fuel circuit inner wall can be a conical shape that converges toward the longitudinal axis. The air passage can include an annular inlet. The radial swirler can include radial swirl vanes circumferentially spaced apart from one another about the annular inlet to induce swirl into air entering the annular inlet of the air passage. The tubes are defined within the radial swirl vanes. 
     An outer air passage can be defined radially outboard of the fuel circuit with respect to the longitudinal axis. The outer air passage can be defined between a fuel circuit outer wall and an outer air passage wall. The outer air passage can be a converging non-swirling outer air passage. An annular outlet of the outer air passage can be proximate to the fuel circuit annular outlet. The nozzle body can include an insulation jacket between the air passage and the fuel circuit and/or between the outer air passage and the fuel circuit. The nozzle can include a low-flow fuel nozzle integrated into a backing plate of the nozzle body upstream from the air passage. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a perspective view of an exemplary embodiment of a nozzle constructed in accordance with the present disclosure, showing the swirling air passage and the non-swirling outer air passage; 
         FIG. 2  is a cross-sectional side elevation view of the nozzle of  FIG. 1 , showing the corresponding cross-section indicated in  FIG. 1 ; 
         FIG. 3  is an exploded cross-sectional perspective view of a portion of the nozzle of  FIG. 1 , showing the helical passages of the fuel circuit; 
         FIG. 4  is an upstream elevation view of a portion of the nozzle of  FIG. 1 , showing the circumferentially spaced apart openings of the fuel circuit inlet; 
         FIG. 5  is a perspective view of a portion of the nozzle of  FIG. 1 , showing the vanes of the air passage; 
         FIG. 6A  is a perspective view of another exemplary embodiment of a nozzle constructed in accordance with the present disclosure, showing a low-flow fuel nozzle integrated into the backing plate; and 
         FIG. 6B  is a cross-sectional side elevation view of the nozzle of  FIG. 5 , showing the corresponding cross-section indicated in  FIG. 6A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a nozzle in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments of nozzles in accordance with the disclosure, or aspects thereof, are provided in  FIGS. 2-6B , as will be described. The systems and methods described herein provide for radial swirl nozzles with reduced emissions and improved temperature uniformity over traditional radial swirl nozzles. 
     As shown in  FIGS. 1 and 2 , a nozzle  100  includes a nozzle body  102  defining a longitudinal axis A. Nozzle body  102  includes a fuel circuit  106  radially outboard from an air passage  104  with respect to longitudinal axis A. Fuel circuit  106  is defined between a fuel circuit inner wall  115  and a fuel circuit outer wall  116 . It is contemplated that inner and outer fuel circuit walls  115  and  116 , respectively, can be made from a metallic material. A portion of fuel circuit outer wall  116  is radially outboard from fuel circuit inner wall  115  with respect to longitudinal axis A. A portion of both the fuel circuit inner wall  115  and outer wall  116  are conically shaped and converge toward longitudinal axis A. Fuel circuit annular outlet  110  is proximate to the outlet of air passage  104 . 
     With continued reference to  FIGS. 1 and 2 , air passage  104  is defined between a backing plate  124  and a jacket  134  downstream from backing plate  124 . Those skilled in the art will readily appreciate that backing plate  124  and jacket  134  can be made from thin metallic materials and/or a thicker ceramic material, such as a ceramic-matrix composite (CMC) material, e.g. jacket  134  can be an insulation jacket. Air passage  104  includes a radial swirler  107  at an annular inlet  126 . Radial swirler  107  has radial swirl vanes  128  circumferentially spaced apart from one another about annular inlet  126  to induce swirl into air entering air passage  104 . Large swirl offset and pure radial entry produces very high swirl and high radial pressure gradient at fuel outlet  110 . 
     As shown in  FIG. 2 , an outer air passage  130  is defined radially outboard of fuel circuit  106  with respect to longitudinal axis A. Outer air passage  130  provides non-swirled air. Outer air passage  130  is between a jacket  136  and an outer air passage wall  131 . It is contemplated jacket  136  and an outer air passage wall  131  can be constructed using a thin metallic material and/or thicker ceramic material, e.g. a CMC material. For example, jacket  136  can be a metallic shell and not provide any insulation and/or it can be a ceramic material and be an insulation jacket to insulate fuel circuit  106 . Insulation jackets can be made from a ceramic or a ceramic composite material, both of which tend to reduce thermal growth mismatch. Metallic shells can be designed to mitigate thermal growth effects, e.g. by using slits, multiple pieces, growth gaps etc. 
     In accordance with some embodiments, air passage  104 , e.g. the radial swirler, can contribute 40% to 50% of total air, while outer air passage  130  contributes 50% to 60% of the flow. By using a non-swirling outer air passage  130 , the diameter of nozzle  100  can be reduced and extremely high swirl can be applied to core air flow in swirling air passage  104 . However, while inner air passage  104  is described as a swirling air passage and outer air passage  130  is described as a non-swirling air passage, those skilled in the art will readily appreciate that this can be reversed, or both can be counter-swirled, or the like, as needed to provide a shear layer of air for atomization of the fuel exiting fuel circuit  106 . 
     With continued reference to  FIG. 2 , outer air passage  130  is a converging non-swirling outer air passage  130 . An annular outlet  132  of outer air passage  130  is proximate to a fuel circuit annular outlet  110 . Fuel circuit  106  extends from a fuel circuit inlet  108 , shown in  FIG. 4 , to a fuel circuit annular outlet  110 . Fuel circuit  106  includes a plurality of helical passages  112  to add resistance to fuel flow before exit, thereby mitigating gravitational effects at low fuel flow rates. Traditional fuel distributors tend to drool, e.g. fuel tends to pool at one end, when exposed to similar low flow rates. Starting points for helical passages  112  are spaced apart circumferentially. It is contemplated that the axial distance between passages ranges from 0.030 inches (0.762 mm) to 0.100 inches (2.54 mm). Those skilled in the art will readily appreciate that this distance depends partly on the width of each individual helical passage  112 , which can range from between 0.025 inches (0.635 mm) to 0.05 inches (1.27 mm). The thread pitch for the plurality of helical passages  112 , for example, nine passages of 0.035 inches (0.889 mm) wide, would be 0.405″ (10.29 mm). 
     As shown in  FIG. 2 , the proximity of fuel circuit outlet  110  to swirling air passage  104  and results in an intense mixing being focused on a fuel film exiting from fuel circuit  106 . The high co-swirling core air from air passage  104  is used to distribute swirling fuel from fuel circuit outlet  110  before mixing with unswirled air from outer air passage  130 . Converging outer air from outer air passage  130  and diverging inner flow from air passage  104  squeeze the fuel film at an exit  117  of nozzle  100 . This results in a very thin layer adjacent to the reacting zone such that the flame initially burns rich, but is very quickly quenched to pre-turbine temperature levels (T4), for example, the T4 temperature level for modern engines ranges from 2500 to 3500° F. (1371 to 1926° C.). This results in very hot, evenly distributed, stable temperatures near nozzle outlet  117 , but low emissions due to the quick quench. The hot temperatures at the nozzle outlet  117  assist in stabilizing reactions downstream in the thin mixing layer. 
     Those skilled in the art will readily appreciate that the converging layer of unswirled air exiting from outlet air passage  130  is thinner than the diverging layer of swirling air exiting from inner air passage  104 . Moreover, the fuel film exiting fuel circuit outlet  110  travels a very short distance to reach outlet  132  of outer air passage  130 . Swirling air from air passage  104  continues to squeeze the fuel film downstream into the unswirled converging air layer from outer air passage  130  for an axial distance measured from nozzle outlet  117  of approximately one-half of the diameter of nozzle  100 . It is contemplated that the thin layer of unswirled converging air and the thin fuel film exiting from fuel circuit  106  lead to very rapid mixing of hot reacted gases, fuel and fresh air. Those skilled in the art will readily appreciate that this is different from a premixer since a hot flame zone exists. 
     As shown in  FIG. 3 , each helical passage  112  of fuel circuit  106  opens tangentially with respect to fuel circuit annular outlet  110  into an outlet  114  of air passage  104 . Fuel flow exiting fuel circuit  106  exits from outlet  110  at an extremely large tangential angle, for example, the angle can range from 75 to 88 degrees. Those skilled in the art will readily appreciate that the angle can vary depending on the number of helical passages  112 . The radial pressure gradient resulting therefrom helps to reduce film thickness at annular outlet  110 . Each helical passage  112  intersects a single cross-sectional plane taken along longitudinal axis A, for example the cross-sections shown in  FIGS. 2 and 3 . Multiple helical passages  112  intersect each cross-sectional plane taken along longitudinal axis A. Each of helical passages  112  complete at least one 360 degree pass around fuel circuit  106 . Helical passages  112  are defined by helical threads  113  in a fuel circuit outer wall  116 . 
     With reference now to  FIGS. 3 and 4 , fuel circuit inlet  108  includes a plurality of circumferentially spaced apart openings  118  in fluid communication with a fuel manifold  120 . Those skilled in the art will readily appreciate that while fuel manifold  120  is shown integrally formed with backing plate  124 , it can be formed independent of backing plate  124 . 
     As shown in  FIGS. 2 and 5 , a plurality of cylindrical tubes  122  are defined through air passage  104 . Each tube  122  connects a respective opening  118  to fuel manifold  122 . Tubes  122  can be metallic transfer tubes. It is also contemplated that in place of some of tubes  122 , fasteners can also be used. Vanes, described above, can be hollow and/or ceramic, and are used to insulate tubes  122  as they pass through air passage. 
     As shown in  FIGS. 6A and 6B , nozzle  200  is similar to nozzle  100 . Nozzle  200  includes a low-flow fuel nozzle  201  integrated into a backing plate  224  of nozzle body  202  upstream from air passage  204 . Those skilled in the art will readily appreciate that this will assist with fuel staging, if required. 
     Those skilled in the art will readily appreciate that embodiments of the present invention, e.g. nozzles  100  and  200 , are easily manufactured radial swirlers that are lightweight. Nozzles  100  and  200  can be additively manufactured, for example using direct metal laser sintering, or the like. Moreover, components of nozzle body  102  and  202  can be appropriately spaced to permit thermal expansion and contraction. Additionally, annular fuel outlet  110 , with very limited exposure to the hot surface of air passage  104  outlet  114 , eliminates backflow and flashback possibility that tends to exist if fuel is introduced too early into core. 
     The methods and systems of the present disclosure, as described above and shown in the drawings provide for radial swirl nozzles with superior properties including reduced emissions and improved temperature uniformity. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.