Closed trapped vortex cavity pilot for a gas turbine engine augmentor

A gas turbine engine exhaust apparatus, comprising:

• an exhaust casing;
• a combustion liner spaced radially inward of the exhaust casing;
• a cooling duct defined by boundaries established radially inward by a first face of the combustion liner, and radially outward by the exhaust casing;
• a core duct defined at least in part by a second face of the combustion liner;
• and
• an augmentor apparatus, including:
• a radial spraybar radially extending into the core duct, the radial spraybar including fuel tubes in communication with a fuel source, the spraybar configured to introduce fuel into the core duct,
• a closed trapped vortex apparatus disposed within the cooling duct, the closed trapped vortex apparatus comprising:
• a tubular structure having a structural wall, the structural wall forming a cavity within the tubular structure, the structural wall having a lower boundary wall forming a boundary between the cavity and the core duct,
• at least one driver hole passing through the structural wall,
• an ignition source communicating with the cavity;
• a fuel source communicating with the cavity;
• and
• a plurality of flame tubes extending through the lower boundary wall of the tubular structure at a plurality of preselected discrete locations providing communication between the cavity and the core duct;
• wherein the closed trapped vortex apparatus of the augmentor apparatus is located radially outward of a combustor liner.

A method of providing pilot ignition for a gas turbine engine augmentor, comprising:

• passing a core flow containing oxygen through a core duct;
• introducing fuel into the core flow to define a combustible mixture;
• maintaining a pilot flame in a closed trapped vortex combustion pattern at a location outside the core duct;
• and
• communicating at least one of the pilot flame and hot gases from the closed trapped vortex combustion pattern to the core flow through a plurality of flame tubes at a plurality of preselected discrete locations around a periphery of the core duct, so as to ignite the combustible mixture.