Gas turbine fuel injector with insulating air shroud

Abstract

A fuel injector for a gas turbine engine is disclosed. The fuel injector includes an injector housing extending from a first end to a second end along a longitudinal axis. The second end of the housing is fluidly coupled to a combustor of the turbine engine and the housing includes a liquid fuel gallery annularly disposed about the longitudinal axis. The fuel injector also includes a stem extending longitudinally from the first end of the housing to a third end. The stem includes a liquid tube configured to deliver liquid fuel to the fuel injector. The fuel injector also includes an annular shell extending along the longitudinal axis from the first end to the third end and circumferentially disposed about the stem. The fuel injector further includes an insulating air shroud formed inside the shell. The air shroud includes a layer of air between the shell and the stem.

1 - 9 . (canceled) 
     
     
         10 . A method of operating a gas turbine engine, comprising:
 delivering liquid fuel to a combustor of the turbine engine through one or more liquid fuel carrying components of a fuel injector coupled to the combustor;   combusting the liquid fuel in the combustor;   providing an insulating air shroud around one or more of the liquid fuel carrying components, the insulating air shroud including a layer of atmospheric air;   generating eddy air currents in the insulating air shroud in response to the combustion, the eddy air currents assisting in expelling heated atmospheric air from the insulating air shroud and drawing cooler atmospheric air into the insulating air shroud; and   maintaining a temperature of the one or more liquid fuel carrying components below a threshold temperature as a result of the generation of the eddy air currents.   
     
     
         11 . The method of  claim 10 , wherein providing an insulating air shroud includes providing an insulating air shroud between the one or more liquid fuel carrying components and a shell. 
     
     
         12 . The method of  claim 11 , wherein the delivering of liquid fuel includes delivering a liquid fuel to the combustor through a liquid fuel tube coupled to the fuel injector. 
     
     
         13 . The method of  claim 12 , wherein the expelling of heated air includes expelling heated air from the insulating air shroud through one or more air gaps formed between the insulating shell and the liquid fuel tube, and the drawing of cooler air includes drawing cooler air into the insulating air shroud through the air gaps. 
     
     
         14 . The method of  claim 10 , wherein providing an insulating air shroud includes providing an insulating air shroud between one or more of the liquid fuel carrying components and an enclosure containing compressed air. 
     
     
         15 . The method of  claim 10 , wherein the maintaining of a temperature includes maintaining a temperature of at least one of the liquid fuel carrying components below about 400° F. (204.4° C.). 
     
     
         16 . The method of  claim 10 , wherein the delivering of liquid fuel to a combustor includes;
 delivering liquid fuel to a liquid fuel gallery of the fuel injector through a liquid tube; and   delivering liquid fuel to a pilot assembly of the fuel injector through a pilot liquid tube.   
     
     
         17 . The method of  claim 16 , wherein the forming of an insulating air shroud includes forming an insulating air shroud over one or more of the liquid fuel gallery, the liquid tube, and the pilot liquid tube. 
     
     
         18 - 20 . (canceled) 
     
     
         21 . A method of operating a gas turbine engine, comprising:
 directing liquid fuel and compressed air to a combustor of the gas turbine engine through a fuel injector, the fuel injector extending from a first end coupled to the combustor to a third end along a longitudinal axis;   directing the liquid fuel to the third end of the fuel injector through a stem, the stem extending along the longitudinal axis from the third end, in a direction away from the first end, to a second end such that the third end is located between the second end and the first end, the stem including a liquid tube configured to pass the liquid fuel therethrough; and   providing an insulating air shroud circumferentially about the stem, the insulating air shroud being formed by a layer of atmospheric air in an annular space between the stem and an annular shell circumferentially disposed about the stem.   
     
     
         22 . The method of  claim 21 , wherein providing the insulating air shroud includes closing the annular space at the third end to prevent flow of the atmospheric air into the combustor. 
     
     
         23 . The method of  claim 22 , wherein providing the insulating air shroud further includes providing one or more openings at the second end to vent the atmospheric air in the annular space to the atmosphere. 
     
     
         24 . The method of  claim 21 , further including providing a covering member at the second end to at least partially cover the annular space between the shell and the stem at the second end. 
     
     
         25 . The method of  claim 21 , wherein providing an insulating air shroud includes shielding the shell from an enclosure of the gas turbine engine containing compressed air using the layer of atmospheric air. 
     
     
         26 . The method of  claim 21 , wherein directing the liquid fuel and compressed air includes directing compressed air from the enclosure into the combustor through the fuel injector. 
     
     
         27 . The method of  claim 21 , further including generating eddy air currents in the insulating air shroud in response to combustion in the combustor, the eddy air currents assisting in expelling heated atmospheric air from the insulating air shroud and drawing cooler atmospheric air into the insulating air shroud. 
     
     
         28 . A method of operating a gas turbine engine, comprising:
 delivering liquid fuel to a combustor of the turbine engine through one or more liquid fuel carrying components of a fuel injector;   delivering compressed air to the combustor through the fuel injector;   combusting a mixture of the liquid fuel and the compressed air in the combustor; and   providing an insulating air shroud around the one or more liquid fuel carrying components of the fuel injector, the insulating air shroud including a layer of atmospheric air that separates the compressed air directed to the combustor from the one or more liquid fuel carrying components.   
     
     
         29 . The method of  claim 28 , further including generating eddy air currents in the insulating air shroud in response to the combustion in the combustor, the eddy air currents assisting in expelling heated atmospheric air from the insulating air shroud and drawing cooler atmospheric air into the insulating air shroud. 
     
     
         30 . The method of  claim 28 , wherein providing an insulating air shroud includes maintaining a temperature of the one or more liquid fuel carrying components below a coking temperature of the liquid fuel. 
     
     
         31 . The method of  claim 28 , wherein providing an insulating air shroud includes preventing the flow of the atmospheric air in the insulating air shroud into the combustor. 
     
     
         32 . The method of  claim 31 , wherein providing an insulating air shroud further includes providing one or more openings to fluidly couple the layer of atmospheric air in the insulating air shroud to the atmosphere.