Augmentor with trapped vortex cavity pilot

A turbofan gas turbine engine comprising:

• a fan section upstream of a core engine;
• the core engine including in serial downstream flow communication a high pressure compressor, a combustor, and a high pressure turbine;
• a low pressure turbine downstream of the core engine;
• an annular bypass duct containing a bypass flowpath circumscribing the core engine;
• a diffuser located radially inwardly of the bypass duct and aft and downstream of the low pressure turbine and including an annular radially outer diffuser liner circumscribing a diffuser duct containing a portion of a core stream flowpath;
• a gas turbine engine augmentor disposed in an exhaust casing of the engine located aft and downstream of the diffuser;
• a combustion liner surrounding a combustion zone of the exhaust flowpath in the exhaust casing;
• the combustion liner having tailpipe liner diameter smaller than a diffuser liner diameter of the outer diffuser liner;
• the augmentor including an annular trapped vortex cavity pilot having a cavity forward wall, a cavity radially outer wall, and a cavity aft wall, and an annular cavity therebetween;
• a cavity opening extending between the cavity forward and aft walls at a radially inner end of the cavity;
• cavity fuel injector tubes operably disposed through the outer wall into the cavity;
• circumferentially spaced apart radial flameholders having integral spraybars integral with the radial flameholders and extending radially inwardly into an exhaust flowpath of the augmentory;
• radial spraybars extending radially inwardly into the exhaust flowpath and being circumferentially interdigitated with the radial flameholders;
• and
• the annular trapped vortex cavity pilot being located just aft and downstream of the radial spraybars and the radial flameholders at a radially outer portion of a combustion zone of the exhaust flowpath.

A method for operating a gas turbine engine augmentor, the method comprising:

• supplying fuel to an annular trapped vortex cavity pilot having a cavity forward wall, a cavity radially outer wall, and a cavity aft wall, an annular cavity therebetween, and a cavity opening extending between the cavity forward and aft walls at a radially inner end of the cavity and open to exhaust flowpath of the augmentor;
• flowing the fuel through cavity fuel injector tubes extending through the outer wall and into the cavity and injecting the fuel directly into the cavity;
• producing at least one annular rotating vortex of a fuel and air mixture and igniting the fuel and air mixture within the cavity;
• and
• injecting the fuel into the exhaust flowpath through radial spraybars and/or integral spraybars extending radially inwardly into the exhaust flowpath wherein the augmentor further includes a plurality of circumferentially spaced apart radial flameholders extending radially inwardly into the exhaust flowpath and the integral spraybars are integral with the radial flameholders and igniting the fuel from the radial spraybars and/or integral spraybars using the trapped vortex cavity pilot.