Aircraft fuel nozzle

Abstract

A fuel injector for an aircraft gas turbine engine includes a housing stem, a fuel nozzle coupled to the housing stem, and a fuel conduit extending through the housing stem and into the fuel nozzle where the fuel conduit bends to extend in a longitudinal downstream direction within the fuel nozzle. The fuel conduit is configured to transport bulk fuel flow further along the nozzle before being split downstream in the fuel circuit for final spray distribution, thereby promoting lower fuel temperatures. The fuel nozzle may minimize metal-to-metal contact between an external wall of the nozzle in thermal communication with ambient environment and an internal portion of the nozzle in thermal communication with the fuel circuit to minimize heat pick-up in the fuel. The fuel conduit may include a coiled section within a cavity of the fuel nozzle for compensating for thermal growth mismatches of the fuel injector.

1 . A fuel injector, comprising:
 a housing stem;   a fuel nozzle operatively coupled to the housing stem, the fuel nozzle extending in a longitudinal direction between an upstream end and a downstream discharge end of the fuel nozzle, the fuel nozzle comprising a fuel circuit having an inlet section and an outlet section; and   a fuel conduit extending through the housing stem into the fuel nozzle to form the inlet section of the fuel circuit, and extending through the fuel nozzle in the longitudinal direction toward the downstream discharge end to form an upstream portion of the fuel circuit;   wherein the fuel conduit is configured to provide bulk fuel flow through the housing stem and the upstream portion of the fuel circuit, the fuel conduit fluidly connecting downstream to a fuel manifold located at an intermediate longitudinal position in the fuel nozzle between the upstream end and the downstream discharge end, the fuel manifold being configured to split the bulk fuel flow into a plurality of fuel flow passages in a downstream portion of the fuel circuit for fuel distribution through the outlet section and fuel discharge from the fuel nozzle.   
     
     
         2 . The fuel injector according to  claim 1 ,
 wherein the upstream portion of the fuel circuit provided by the fuel conduit has a surface area to volume ratio of that is less than a surface area to volume ratio of the downstream portion of the fuel conduit provided by the plurality of fuel flow passages.   
     
     
         3 . The fuel injector according to  claim 1 ,
 wherein the upstream portion of the fuel circuit provided by the fuel conduit is confined to a partial angular region on one side of the longitudinal axis as the fuel conduit extends in the longitudinal direction.   
     
     
         4 . The fuel injector according to  claim 1 ,
 wherein the upstream portion provided by the fuel conduit extends through an insulating gap internal to the fuel nozzle, and a major portion of the upstream portion provided by the fuel conduit is spaced apart from one or more walls of the fuel nozzle that are in heat transfer relation to an external environment of the fuel nozzle.   
     
     
         5 . The fuel injector according to  claim 1 , wherein the fuel conduit includes a fuel tube having a coiled section internal to the fuel nozzle, the coiled section at least partially circumscribing a longitudinal axis of the fuel nozzle. 
     
     
         6 . The fuel injector according to  claim 1 , wherein each of the plurality of fuel flow passages of the downstream portion has a cross-sectional area transverse to a direction of fuel flow that is less than a cross-sectional area transverse to a direction of fuel flow of the upstream portion provided by the fuel conduit. 
     
     
         7 . The fuel injector according to  claim 1 , wherein the plurality of fuel flow passages are internal fuel flow passages enclosed by a body portion of the fuel nozzle. 
     
     
         8 . The fuel injector according to  claim 1 ,
 wherein the fuel conduit includes a fuel tube that is segmented into sections, with the sections being fluidly connected together via a fluid connector; or   wherein the fuel conduit includes a single unitary fuel tube.   
     
     
         9 . The fuel injector according to  claim 1 , wherein each of the plurality of fuel flow passages include an outlet that opens into an annulus fluidly connected to the outlet section, the outlets forming an array of outlets circumferentially spaced apart about a longitudinal axis of the fuel nozzle. 
     
     
         10 . The fuel injector according to  claim 9 , wherein the downstream portion of the fuel circuit includes a fuel prefilmer between the outlets of the plurality of fuel flow passages and the outlet section of the fuel circuit, the annulus being an axially extending swirl annulus at an upstream portion of the fuel prefilmer in which the outlets open into the swirl annulus at an angle to provide swirling fuel flow, and the fuel prefilmer having a radially inwardly converging portion at a downstream portion thereof, the fuel prefilmer being configured to terminate at a downstream prefilmer orifice which forms the outlet section of the fuel circuit. 
     
     
         11 . The fuel injector according to  claim 1 , further comprising an inner air swirler, and an outer air swirler outwardly surrounding the inner air swirler, in which the fuel circuit is radially interposed between the inner air swirler and the outer air swirler. 
     
     
         12 . The fuel injector according to  claim 1 ,
 wherein an overall axial distance of the fuel circuit is measured from the axial location of the inlet section where fuel enters the fuel nozzle to the axial location of the outlet section where fuel is distributed from the fuel circuit, and   wherein an axial distance of the upstream portion providing bulk fuel flow is in a range from 30% to 99% of the overall axial distance of the fuel circuit.   
     
     
         13 . The fuel injector according to  claim 1 ,
 wherein the fuel manifold is part of a transition section that is a first point of transition from bulk fuel flow to split flow as fuel flows downstream from a section of the fuel conduit in the housing stem.   
     
     
         14 . A fuel injector, comprising:
 a housing stem;   a fuel nozzle operatively coupled to the housing stem, the fuel nozzle extending in a longitudinal direction between an upstream end and a downstream discharge end of the fuel nozzle; and   a fuel tube extending through the housing stem into the fuel nozzle;   wherein the fuel tube includes a coiled section contained within a portion of the fuel nozzle.   
     
     
         15 . The fuel injector according to  claim 14 ,
 wherein the fuel nozzle includes an inner air heatshield, and   wherein the coiled section is at least partially coiled around the inner air heatshield.   
     
     
         16 . The fuel injector according to  claim 14 ,
 wherein the fuel tube is segmented into sections, with the sections being fluidly connected together via a fluid connector; or   wherein the fuel tube is a single unitary tube.   
     
     
         17 . The fuel injector according to  claim 14 ,
 wherein the fuel tube includes an axially extending section that extends in a longitudinal direction of the fuel nozzle downstream of the coiled section, the axially extending section configured to transport bulk fuel flow through the fuel nozzle.   
     
     
         18 . A fuel injector, comprising:
 a housing stem;   a fuel nozzle operatively coupled to the housing stem, the fuel nozzle including an internal wall in heat transfer relation with fuel flowing through the nozzle, and an external wall in heat transfer relation with ambient environment;   wherein the internal wall and the external wall are coupled together via a plurality of legs that are circumferentially spaced apart from each other about a longitudinal axis of the fuel nozzle.   
     
     
         19 . The fuel injector according to  claim 19 ,
 wherein the plurality of legs are equally spaced apart with gaps between the legs, and   wherein the internal wall is formed by a body portion of the nozzle that encloses one or more fuel flow passages internal to the fuel nozzle.   
     
     
         20 . The fuel injector according to  claim 18 ,
 wherein at least a rearward portion of the external wall is a single wall, and   wherein the plurality of legs are the only coupling points between the inner wall and the external wall.