Patent Publication Number: US-10788214-B2

Title: Fuel injectors for turbomachines having inner air swirling

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to turbomachines, more specifically to fuel injector systems for turbomachines. 
     2. Description of Related Art 
     A conventional fuel nozzle air swirler is comprised of a separate air swirler and heat shield element. These parts of traditional injectors are difficult to attach and may experience inadvertent release of the swirler which can affect performance. Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved fuel nozzle/injector systems. The present disclosure provides a solution for this need. 
     SUMMARY 
     A fuel injector for a turbomachine includes an inner heat shield having an air cavity wall defining an air cavity for allowing air to flow therethrough. The inner heat shield includes an integral air swirler forming a downstream end thereof. The integral air swirler extends in an axially downstream direction at least as far as a fuel distribution channel defined on or in a fuel distributor of the injector to direct airflow at an outlet of the fuel distributor. 
     The integral air swirler can include an angled or curved wall extending from the downstream end of the heat shield such that the angled or curved wall extends both axially downstream and radially inward. The angled or curved wall can have a frustoconical shape having a linear inner or outer surface and/or curved inner or outer surface. The angled or curved wall can include a plurality of swirling channels defined therethrough and configured to effuse swirling air. 
     The air swirler can include an upstream extending wall that extends from a downstream end of the angled or curved wall in the axially upstream direction. The upstream extending wall extends both axially upstream and radially inward. The upstream extending wall includes a conical or frustoconical shape. 
     The upstream extending wall can include one or more inner swirling holes configured to effuse swirling air. The upstream extending wall can extend axially upstream beyond the angled or curved wall and into a constant inner diameter area of the heat shield. An outer surface of the heat shield can include an engagement protrusion axially upstream from the air swirler and configured to engage with the fuel distributor to seat the air swirler proximate an outlet of the fuel distributor. 
     In accordance with at least one aspect of this disclosure, an inner heat shield for a fuel injector of a turbomachine can include an air cavity wall defining an air cavity for allowing air to flow therethrough, wherein the inner heat shield includes an integral air swirler forming a downstream end thereof, wherein the air cavity wall and/or the integral air swirler are configured to extend in an axially downstream direction at least as far as a fuel distribution channel defined on or in a fuel distributor of the injector to direct airflow at an outlet of the fuel distributor. The inner heat shield can include any suitable configuration as disclosed above and/or below. 
     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 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, embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a cross-sectional view of an embodiment of a fuel injector/nozzle in accordance with this disclosure; 
         FIG. 2  is a perspective view of an embodiment of an inner heat shield in accordance with this disclosure, e.g., as used in the embodiment of  FIG. 1 ; and 
         FIG. 3  is a partial perspective cutaway view of an embodiment of a multipoint injection/combustor system in accordance with this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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, an illustrative view of an embodiment of a fuel injector (which can also be referred to as a fuel nozzle) in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  200 . Other embodiments and/or aspects of this disclosure are shown in  FIGS. 2-3 . 
     Referring to  FIGS. 1 and 2 , a fuel injector  200  for a turbomachine includes an inner heat shield  213  having an air cavity wall  213   a  defining an air cavity  203  for allowing air to flow therethrough. The inner heat shield  213  includes an integral air swirler  215  forming a downstream end  213   b  of the heat shield  213  as shown. The fuel injector  200  can include an outer heat shield  211  and a fuel distributor  209 . 
     The integral air swirler  215  can extend in an axially downstream direction at least as far as a fuel distribution channel  209   a  defined on or in a fuel distributor  209  of the injector  200  to direct airflow at an outlet of the fuel distributor  209 . For example, the fuel distributor  209  can include one or more fuel distribution channels  209  that are defined circumferentially about the fuel distributor to distribute fuel about the circumference of the fuel distributor  209 . As shown, the air cavity wall  213   a  and/or the integral air swirler  215  are configured to extend at least as axially downstream as the one or more of the fuel distribution channels  209   a  of the fuel distributor  209  of the injector  200  when installed in the outer heat shield  211 . 
     The integral air swirler  215  can include an angled or curved wall  215   a  extending from the downstream end of the heat shield  213  such that the angled or curved wall  215   a  extends both axially downstream and radially inward. The angled or curved wall  215   a  can include any suitable shape that extends axially downstream and radially inward. For example, as shown, the angled or curved wall  215   a  can include a frustoconical shape having a linear inner or outer surface and/or curved inner or outer surface. For example, inner and/or outer surfaces of the angled or curved wall  215  can be linear such that a portion of a cone is formed. In other embodiments, the inner and/or outer surface of the angled or curved wall  215  can be curved such that a portion of a spherical shape is formed. In other suitable shapes are contemplated herein. 
     The angled or curved wall  215   a  can include a plurality of swirling channels  215   c  defined therethrough and configured to effuse swirling air. In certain embodiments, the swirling channels  215   c  are shaped to direct air tangentially, at least partially radially outward, and at least partially axially downstream as shown (e.g., aimed at an expanding section and/or outlet of the fuel distributor  209  to mix with fuel effusing from the fuel distribution channels  209 ). 
     The air swirler  215  can include an upstream extending wall  215   b  that extends from a downstream end of the angled or curved wall  215   a  in axially upstream direction. The upstream extending wall  215   b  can extend both axially upstream and radially inward as shown (e.g., such that it reverses direction). The upstream extending wall  215   b  can include a conical or frustoconical shape as shown. 
     The upstream extending wall  215   b  can include one or more inner swirling holes  215   d  configured to effuse swirling air. The inner swirling holes  215   d  can be configured to aim air at a further downstream location than the swirling channels  215   c.  In certain embodiments, the swirling channels  215   c  and/or swirling holes can include shaped slots and/or round holes, and/or rectangular slots. Any other suitable configuration to effuse and/or swirl air for the inner swirling holes  215   d  and/or swirling channels  215   c  is contemplated herein. 
     The upstream extending wall  215   b  can extend axially upstream beyond the angled or curved wall and into a constant inner diameter area of the inner heat shield  213  as shown. In certain embodiments, the upstream extending wall  215   b  is configured to act as a flow guide and/or reducer that directs airflow (e.g., and/or speeds up airflow) from the air cavity  203  to the swirling channels  215   c.    
     In certain embodiments, the inner heat shield  213  can include a constant diameter inner diameter surface (e.g., cylindrical in shape) for the air cavity wall  213   a.  In certain embodiments, an outer surface  213   b  of the heat shield  213  can include an engagement protrusion  214  axially upstream from the air swirler  215  and configured to engage with the fuel distributor  209  (e.g., an inner diameter of the fuel distributor  209  as shown) to seat the air swirler  215  proximate an outlet of the fuel distributor  209 . 
     The fuel injector  200  can be configured for us with a multipoint injection system (e.g., as shown in  FIG. 3 ) or any other suitable system. The fuel injector  200  can include an interior cavity  205  defined between the inner heat shield  213  and the outer hear shield  211 . A fuel tube  207  can be disposed at least partially within the interior cavity  205  of the body  201 . 
     As shown in  FIG. 2 , the inner heat shield  213  can include a seating flange  216  for seating the inner heat shield  213  within the outer heat shield  211 . The seating flange  216  can include a fuel tube opening  218  for allowing one or more of a fuel tube end and/or a fuel tube connector (e.g., including an elbow) of a fuel manifold to pass through the flange  216  to connect the fuel tube  207 , 
     Referring additionally to  FIG. 3 , the fuel tube  207  can include a first end (not shown) configured to connect to a fuel injector connector (e.g.,  113   a,    113   b,    113   c ) of a fuel manifold (e.g., manifold  100 ). In certain embodiments, the first end can include an elbow (not shown) configured to mate with a fuel injector connector (e.g.,  113   a,    113   b,    113   c ). 
     As shown in Fig,  1 , the fuel tube  207  can include a second end  207   b  configured to connect to a fuel distributor  209  of the fuel injector  200 . The fuel injector  200  can be configured to be disposed at least partially in a combustor dome (e.g., combustor dome  123 ). The fuel tube can be configured to move in an axial direction (e.g., a centerline of the fuel injector  200 ) to allow flexibility between the fuel manifold (e.g., manifold  100 ) and the combustor dome (e.g., combustor dome  123 ). 
     The fuel tube  207  can be a coiled fuel tube  207 . The coiled fuel tube  207  can be configured to axially compress and/or expand between the first end and the second end  207   b  (e.g., like a spring). As shown, the coiled tube  207  can be contained within the interior cavity  205  of the fuel injector  200 . 
     In certain embodiments, the outer heat shield  211  and the inner heat shield  213  can be integrally formed together (e.g., via additive manufacturing). In certain embodiments, the outer heat shield  211  and the inner heat shield  213  can be separate components. In certain embodiments, the air swirler  215  can be a separate component from the air cavity wall  213   a  and can be attached together in any suitable manner (e.g., brazing, bonding, clipping, etc.). In certain embodiments, the inner heat shield  213  can be integrally formed to have the air swirler  215  thereon (e.g., via casting, via additive manufacturing). The inner heat shield can be made from any suitable material (e.g., preferably low alpha, low conductivity material such as ceramic matrix composite). 
     The interior cavity  205  can be formed between the outer heat shield  211  and the inner heat shield  213  such that the coiled fuel tube  207  is disposed between the outer heat shield  211  and the inner heat shield  213 . The outer heat shield  211  can include one or more standoff features  231  for orienting the fuel injector  200  on the combustor dome (e.g., to align with a fuel injector connector  113   a,    113   b,    113   c  of a fuel manifold  100 ). The one or more standoff features  231  can include three standoff features, for example. The fuel distributor  209  can be disposed at least partially within the interior cavity  205  defined between the outer heat shield  211  and the inner heat shield  213 . 
     Embodiments reduce part count and thereby reduce cost. In embodiments, inner air from the air cavity allows energizing of the fuel to produce a very thin circumferential film on a relatively large diameter, e.g., about 50% of the total nozzle air enters through the inner air cavity. The inner air and fuel can then vigorously mix with converging outer air flow (that passes around the outer heat shield  211  through the combustor dome  123 ) to produce near premixed (e.g., ideal) conditions. The mixture can be burned immediately downstream of the nozzle/injector in a lean burn fashion (e.g., which can have low emissions). 
     The large amount of core air, the relatively high pressure drop and high temperature can transmit a substantial amount of unwanted heat to the fuel distributor, however, the core heat shield reduces the convective heat transfer. Certain embodiments eliminate risk of detachment of the air swirler because it is integral with heat shield. Embodiments can also cause radial divergence and swirl at the same time which can improve mixing and efficiency. 
     Embodiments direct air swirling at the outlet such that air is energetically directed radially outwards toward the fuel lip but with substantial tangential velocity component to encourage circumferential uniformity and subsequent mixing with the outer air stream. Embodiments extend axially from a cylindrical heat shield and provide a heat shield all the way in the axial direction of fuel components. Substantial tangential velocity is retained to encourage mixing with the convergent, e.g., unswirling, outer air stream. Embodiments permit a substantial amount of air to enter through the inner channel since the features can be on a relatively large diameter. 
     Any suitable combination(s) of any disclosed embodiments and/or any suitable portion(s) thereof is contemplated therein as appreciated by those having ordinary skill in the art. 
     Those having ordinary skill in the art understand that any numerical values disclosed herein can be exact values or can be values within a range. Further, any terms of approximation (e.g., “about”, “approximately”, “around”) used in this disclosure can mean the stated value within a range. For example, in certain embodiments, the range can be within (plus or minus) 20%, or within 10%, or within 5%, or within 2%, or within any other suitable percentage or number as appreciated by those having ordinary skill in the art (e.g., for known tolerance limits or error ranges). 
     The embodiments of the present disclosure, as described above and shown in the drawings, provide for improvement in the art to which they pertain. While the subject disclosure includes reference to certain 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.