Fuel/air mixing system for fuel nozzle

Abstract

A system includes a fuel nozzle. The fuel nozzle includes a central hub with a first annular passage extending along a longitudinal axis of the fuel nozzle. A flow conditioner is disposed along the first annular passage. The flow conditioner includes at least one of a straightening vane, a mesh screen, or a multi-passage body having multiple passages generally parallel with the longitudinal axis. An outer shroud is disposed about the central hub to define a second annular passage extending along the longitudinal axis of the fuel nozzle.

1 . A system, comprising:
 a fuel nozzle, comprising:
 a central hub comprising a first annular passage extending along a longitudinal axis of the fuel nozzle and a flow conditioner disposed along the first annular passage, wherein the flow conditioner comprises at least one of a straightening vane, a mesh screen, or a multi-passage body having a plurality of passages generally parallel with the longitudinal axis; and 
 an outer shroud disposed about the central hub to define a second annular passage extending along the longitudinal axis of the fuel nozzle. 
   
     
     
         2 . The system of  claim 1 , comprising a combustor or a gas turbine engine having the fuel nozzle. 
     
     
         3 . The system of  claim 1 , comprising a plurality of premixing tubes downstream from the flow conditioner, wherein each tube of the plurality of premixing tubes comprises an air inlet, a fuel inlet disposed in a side wall, and an air-fuel mixture outlet. 
     
     
         4 . The system of  claim 1 , comprising a plurality of swirl vanes disposed in the second annular passage between the outer shroud and the central hub, wherein an interior of each swirl vane of the plurality of swirl vanes is configured to route a first air flow into the first annular passage, an exterior of each swirl vane of the plurality of swirl vanes is configured to swirl a second air flow along the second annular passage, and the flow conditioner in the first annular passage is disposed between the plurality of swirl vanes and an outlet of the fuel nozzle. 
     
     
         5 . The system of  claim 1 , wherein the flow conditioner comprises a plurality of straightening vanes each gradually turning from a radial direction toward an axial direction along the longitudinal axis in a downstream direction toward an outlet of the fuel nozzle. 
     
     
         6 . The system of  claim 1 , wherein the central hub comprises a first wall extending circumferentially about the longitudinal axis to define a central passage, a second wall extending circumferentially about the first wall to define the first annular passage, and a third wall extending circumferentially about the second wall to define a third annular passage, wherein the first annular passage routes a first air flow along the flow conditioner, and the third annular passage routes a first fuel flow. 
     
     
         7 . The system of  claim 6 , wherein the second annular passage comprises a swirler and the first annular passage comprises a plurality of premixing tubes disposed downstream from the flow conditioner, wherein each tube of the plurality of premixing tubes comprises an air inlet, a fuel inlet in a side wall, and an air-fuel mixture outlet. 
     
     
         8 . The system of  claim 7 , wherein the straightening vane, the perforated sheet or mesh screen, and the multi-passage body are configured to reduce swirl in the first annular passage caused by the swirler in the second annular passage. 
     
     
         9 . A system, comprising:
 a fuel nozzle, comprising:
 a central hub comprising a first annular passage extending along a longitudinal axis of the fuel nozzle, a flow conditioner disposed along the first annular passage, and a plurality of premixing tubes disposed along the first annular passage downstream from the flow conditioner, wherein each tube of the plurality of premixing tubes comprises an air inlet, a fuel inlet, and an air-fuel mixture outlet; 
 an outer shroud disposed about the central hub to define a second annular passage extending along the longitudinal axis of the fuel nozzle; and 
 a plurality of swirl vanes disposed in the second annular passage between the outer shroud and the central hub, wherein an air passage of each swirl vane of the plurality of swirl vanes is configured to route a first air flow into the first annular passage, an exterior of each swirl vane of the plurality of swirl vanes is configured to swirl a second air flow along the second annular passage, and the flow conditioner in the first annular passage is disposed between the plurality of swirl vanes and the plurality of premixing tubes. 
   
     
     
         10 . The system of  claim 9 , comprising a gas turbine engine, wherein the gas turbine engine comprises the fuel nozzle, a combustor having the fuel nozzle, a compressor, and a turbine. 
     
     
         11 . The system of  claim 9 , wherein the flow conditioner comprises a straightening vane, a perforated sheet or mesh screen, or a multi-passage body having a plurality of passages generally parallel with the longitudinal axis. 
     
     
         12 . The system of  claim 9 , wherein the flow conditioner comprises a plurality of straightening vanes each having a turn gradually directed along the longitudinal axis in a downstream direction toward the plurality of premixing tubes. 
     
     
         13 . The system of  claim 9 , wherein the flow conditioner comprises a perforated sheet or mesh screen extending crosswise to the longitudinal axis in the first annular passage. 
     
     
         14 . The system of  claim 9 , wherein the flow conditioner comprises a multi-passage body having a plurality of passages generally parallel with the longitudinal axis. 
     
     
         15 . The system of  claim 9 , wherein the flow conditioner comprises a perforated sheet or mesh screen disposed with the first annular passage upstream of a multi-passage body having a plurality of passages generally parallel with the longitudinal axis. 
     
     
         16 . The system of  claim 9 , wherein the central hub comprises a first wall extending circumferentially about the longitudinal axis to define a central passage, a second wall extending circumferentially about the first wall to define the first annular passage, and a third wall extending circumferentially about the second wall to define a third annular passage, wherein the first annular passage routes the first air flow to the air inlet of each tube of the plurality of premixing tubes, and the third annular passage routes a fuel flow to the fuel inlet of each tube of the plurality of premixing tubes. 
     
     
         17 . A system, comprising:
 a fuel nozzle, comprising:
 a central hub comprising a first annular passage extending along a longitudinal axis of the fuel nozzle and a flow conditioner disposed along the first annular passage, wherein the flow conditioner comprises at least one of a straightening vane, a perforated sheet or mesh screen, or a multi-passage body having a plurality of passages generally parallel with the longitudinal axis; 
 an outer shroud disposed about the central hub to define a second annular passage extending along the longitudinal axis of the fuel nozzle; and 
 a plurality of swirl vanes disposed in the second annular passage between the outer shroud and the central hub, wherein an interior of each swirl vane of the plurality of swirl vanes is configured to route a first air flow into the first annular passage, an exterior of each swirl vane of the plurality of swirl vanes is configured to swirl a second air flow along the second annular passage, and the flow conditioner in the first annular passage is disposed between the plurality of swirl vanes and an outlet of the fuel nozzle. 
   
     
     
         18 . The system of  claim 17 , comprising a gas turbine engine, wherein the gas turbine engine comprises the fuel nozzle, a combustor having the fuel nozzle, a compressor, and a turbine. 
     
     
         19 . The system of  claim 17 , wherein the flow conditioner comprises a plurality of the straightening vanes each having a turn gradually directed along the longitudinal axis in a downstream direction toward the outlet of the fuel nozzle, wherein the flow conditioner comprises the perforated sheet or mesh screen, or the multi-passage body having the plurality of passages generally parallel with the longitudinal axis. 
     
     
         20 . The system of  claim 17 , comprising a plurality of premixing tubes disposed downstream from the flow conditioner, wherein each tube of the plurality of premixing tubes comprises an air inlet, a fuel inlet, and an air-fuel mixture outlet.