Patent Publication Number: US-9835334-B2

Title: Air entrance effect

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to injectors and nozzles, and more particularly to nozzles and injectors such as used in fuel injection in gas turbine engines. 
     2. Description of Related Art 
     A variety of devices and methods are known in the art for injecting fuel into gas turbine engines. Of such devices, many are directed to injecting fuel into combustors of gas turbine engines. Typical nozzles for fuel injectors incorporate swirlers to induce atomization on liquid fuel issued from the nozzle, as well as effect dispersion of the atomized droplets for good fuel/air mixing. The action of imparting swirl to a flow naturally results in a pressure-loss of the fluid passing through the swirler. This pressure-loss is exacerbated by the presence of flow-separations near the leading-edge of the vane (or entrance to the vaned passage). The pressure-loss which occurs due to the leading-edge flow separations is considered a parasitic loss of energy that could otherwise be used for atomization. Such flow separations also reduce the amount of air which can pass through the swirler passage for a given (fixed) amount of available pressure (pressure-drop through the swirler passage). There is an ongoing desire to reduce the pressure-loss and increase the amount of air flow through fuel nozzles in gas turbine engines. 
     Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is an ongoing need for swirlers with ever lower pressure loss. The present disclosure provides a solution for this need. 
     SUMMARY OF THE INVENTION 
     A nozzle includes a nozzle body defining longitudinal axis with a liquid circuit extending axially in a downstream direction from a liquid inlet to a spray orifice, and an air circuit, e.g. an inner air circuit, extending axially downstream from an upstream air inlet to an air outlet proximate the spray orifice. An air swirler, e.g., an inner air swirler, is mounted in the air circuit, wherein at least a portion of the air swirler is flush with or protrudes axially upstream relative to the air inlet. 
     The air swirler can be an axial swirler with a center body having axial swirl vanes extending outward therefrom. The center body can protrude axially upstream relative to the air inlet, and the axial swirl vanes can each have a respective leading edge that is substantially flush with the air inlet. It is also contemplated that the center body can have an upstream end that is substantially flush with the air inlet. It is also contemplated that the center body can have an upstream end that is downstream of the air inlet. 
     The air circuit can include a converging section that converges from the air inlet down to a non-converging inlet section of the air circuit. The center body and swirl vanes can extend axially through the converging section. 
     In another aspect, the air swirler can be positioned within an inlet section of the air circuit and the air circuit can include an outlet section downstream of the inlet section, the outlet section having a smaller cross-sectional area than the inlet section. The air swirler can have a downstream end positioned within a tapered section of the air circuit that necks down in cross-sectional area from the main section to the outlet section. It is also contemplated that the air swirler can have a downstream end positioned upstream of the necking section. 
     Each of the swirl vanes can have a leading edge that is flat, can be a single lead helical vane, and can have a constant thickness. The swirl vanes can be a full coverage set of vanes. 
     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 nozzle as part of an injector; 
         FIG. 2  is a cross-sectional side elevation view of the nozzle of  FIG. 1 , showing the inner air swirler and inner air circuit; 
         FIG. 3  is a cross-sectional side elevation view of the nozzle of  FIG. 1 , showing another exemplary embodiment of an inner air swirler in the inner air circuit; 
         FIG. 4  is a side elevation view of another exemplary embodiment of an inner air swirler, showing the upstream end of the center body substantially flush with the leading edges of the vanes; and 
         FIG. 5  is a cross-sectional side elevation view of a portion of the nozzle of  FIG. 1 , showing the inner air swirler of  FIG. 4  within the inner air circuit. 
     
    
    
     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. 2-5 , as will be described. The systems and methods described herein can be used to improve performance of swirlers, for example for fuel injection in gas turbine engines. 
     Nozzle  100  includes a nozzle body  102  that depends from an injector feed arm  104 , and includes an outer air cap  106  for air blast atomization. As shown in  FIG. 2 , nozzle body  102  defines longitudinal axis A with a liquid circuit  108 , e.g., for fuel to be injected, extending axially in a downstream direction from a liquid inlet  110  to a spray orifice  112 . Nozzle body  102  also includes an inner air circuit  114  extending axially downstream from an upstream air inlet  116  to an air outlet  118  proximate spray orifice  112 . An inner air swirler  120  is mounted in inner air circuit  114 . 
     Inner air swirler  120  is an axial swirler with a center body  122  having axial swirl vanes  124  extending outward therefrom. At least a portion of inner air swirler  120  is flush with or protrudes axially upstream relative to air inlet  116 . In the example shown in  FIG. 2 , center body  122  protrudes axially upstream relative to air inlet  113 , and the axial swirl vanes  124  each have a respective leading edge  126  that is substantially flush with air inlet  116 . 
     Inner air circuit  114  includes an inlet section  128  extending from air inlet  116  toward an outlet section  130 . Air circuit  114  also includes a tapered section  132  that necks down in area as it extends from inlet section  128  to outlet section  130 . In the example shown in  FIG. 2 , center body  122  and vanes  124  do not extend downstream into tapered section  132  so the downstream ends of center body  122  and vanes  124  end upstream of tapered section  132 . However, as shown in  FIG. 3 , it is also contemplated that a center body  222  and/or swirl vanes  224  of a swirler  220  can extend axially through the inlet section  128 , and center body and/or vanes  224  can have downstream ends that are positioned within tapered section  132  or even further downstream. Swirler  220  is similarly situated at its upstream end to swirler  120  described above, and is essentially extended further axially in length towards the downstream end of inner air passage  114 . 
     Each of the swirl vanes  124  and  224  has a leading edge  126 / 226  that is flat. Vanes  124  and  126  are single lead helical vanes (e.g., have a constant, helical pitch), and have a constant thickness. It is also contemplated that swirl vanes  124  and  224  can each form part of a full coverage set of vanes. 
     With reference now to  FIG. 4 , another exemplary embodiment of a swirler  320  is shown, similar to swirlers  124  and  224  described above, however, in swirler  320 , the center body  322  has an upstream end  323  that is substantially flush with the main portions of leading edges  326  of the helical vanes  324 . The inner portions of leading edges  326  are swept to meet up with the constant diameter portion of center body  322 . As shown in  FIG. 5 , leading edges  326  and upstream end  323  are substantially flush with air inlet  116 . This provides benefits of flush/protruding inner air swirler portions while fitting into the form envelope of inner air circuit  114 . Those skilled in the art will readily appreciate that the upstream end  323  could readily be modified to be downstream of air inlet  116 . 
     Inner air circuit  114  includes a converging section  134  that converges down from air inlet  116  to non-converging inlet section  128  of inner air circuit  114 . The center body  122 ,  222 , and  322 , and swirl vanes  124 ,  224 , and  324  can extend axially through the converging section  134 . This provides for any flow separations incident at leading portions of swirlers  120 ,  220 , and  320  to be positioned upstream of the converging section. The converging flow through converging section  134  reduces these separations compared to traditional swirlers where the separations occur downstream of the converging flow. In this way, swirlers positioned in accordance with this disclosure substantially mitigate such separations and provide reduced flow-losses for a given pressure drop through inner air circuits compared to traditional swirler configurations. Swirler configurations as described herein provide for a larger effective area than traditional swirler configurations. In other words, for a given throat area, swirler configurations as described herein provide for greater flow therethrough than traditional swirler configurations with the same throat area. In embodiments described herein, swirlers extended through converging inlet portions, potentially eliminate the need for small diametral steps to bottom the swirlers for proper positioning when assembling, since the enlarged inlet does not allow the swirler to proceed downstream if it becomes dislodged, for example. 
     While shown an described in the exemplary contest of inner air circuits and inner air swirlers, those skilled in the art will readily appreciate that the systems and methods described herein can readily be applied to outer air circuits and outer air swirlers, intermediate air circuits and intermediate air swirlers, and/or any other suitable air circuits and air swirlers. For example, the leading edges of swirl vanes in outer air cap  106  can be positioned substantially flush with the inlet to outer air cap  106  to reduce pressure loss and/or increase effective area through outer air cap  106  relative to traditional configurations. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for swirlers with superior properties including reduced pressure loss and/or increased effective area relative to traditional configurations. 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 scope of the subject disclosure.