Fuel nozzle for gas turbine engine combustor

Abstract

A method and structure for operating a combustion system of a gas turbine engine to mitigate low frequency combustion acoustics is generally provided. The method includes flowing an oxidizer through a fuel nozzle passage defining an inner wall and an outer wall, in which each of the inner wall and the outer wall are contoured from a first radius to a second radius smaller than the first radius; flowing the oxidizer at a higher axial velocity at the inner wall relative to the outer wall upstream of a fuel injection port; flowing a fuel through the fuel injection port to the fuel nozzle passage to mix with the flow of oxidizer to produce a fuel-oxidizer mixture; and igniting the fuel-oxidizer mixture downstream of the fuel injection port.

1 . A combustion system for a gas turbine engine, the combustion system comprising:
 a fuel nozzle comprising an inner wall and an outer wall together defining a fuel nozzle passage through which an oxidizer flows toward a combustion chamber, wherein the inner wall and the outer wall together define a contoured portion from a first radius to a second radius smaller than the first radius, and further wherein the inner wall defines a fuel injection port therethrough in fluid communication with the fuel nozzle passage, and wherein the outer wall defines a throat at the fuel nozzle passage and an exit plane at a downstream end of the outer wall adjacent to the combustion chamber, and wherein the fuel nozzle defines a forward stagnation point of the flow of oxidizer between the throat and the exit plane.   
     
     
         2 . The combustion system of  claim 1 , wherein the fuel nozzle further comprises:
 a plurality of vanes in adjacent circumferential arrangement around a fuel nozzle centerline, wherein each vane is extended between the inner wall and the outer wall upstream of the fuel injection port, and wherein each pair of vanes defines a first cross sectional area circumferentially therebetween proximate to a leading edge and a second cross sectional area proximate to a trailing edge different from the first cross sectional area.   
     
     
         3 . The combustion system of  claim 2 , wherein the plurality of vanes are extended at least partially along a circumferential direction, a tangential direction, or both, relative to the fuel nozzle centerline. 
     
     
         4 . The combustion system of  claim 3 , wherein the plurality of vanes extends the trailing edge to a circumferential location relative to the nozzle centerline different from the leading edge such as to at least partially obscure the second cross sectional area from view along a downstream direction relative to the first cross sectional area. 
     
     
         5 . The combustion system of  claim 1 , wherein the fuel injection port is disposed upstream of the throat defined by the outer wall. 
     
     
         6 . The combustion system of  claim 1 , wherein the fuel nozzle passage defines a region within approximately eight diameter-lengths of a diameter of the fuel injection port upstream of the fuel injection port at which a flow of oxidizer defines a higher axial velocity at the inner wall relative to the outer wall normal to the inner wall.