System for reducing flame holding within a combustor

A combustor comprising:

• a. an end cover coupled to a casing, the end cover and the casing at least partially defining a head end plenum and a high pressure plenum within the combustor;
• b. an annular cap assembly that extends radially within the combustor, wherein the cap assembly comprises a radially extending base plate axially separated from a radially extending cap plate and a shroud that extends from the base plate towards the cap plate, the cap assembly having an inlet port that extends through the shroud, the base plate at least partially defining a fuel nozzle passage;
• c. a primary fuel nozzle that extends downstream from the end cover and at least partially through the fuel nozzle passage, the primary fuel nozzle having an annular burner tube that defines a premix flow passage through the primary fuel nozzle, the burner tube at least partially defining an inlet to the premix flow passage;
• d. an inner plenum at least partially defined by the base plate, the cap plate, the shroud and the burner tube, the inlet port defining a flow path into the inner plenum, the inlet of the burner tube defining a flow path between the inner plenum and the premix flow passage;
• and
• e. a high pressure flow passage and a cooling flow passage at least partially defined within the combustor, the high pressure flow passage being in fluid communication with the inlet port of the cap assembly, the high pressure flow passage defining a flow path between the high pressure plenum and the inner plenum, the cooling flow passage defining a flow path between the high pressure plenum and the head end plenum.

A gas turbine comprising:

• a. a compressor at an upstream end of the gas turbine;
• b. a turbine at downstream end of the gas turbine;
• and
• c. a combustor disposed between the compressor and the turbine, the combustor having an end cover coupled to a casing, the casing being in fluid communication with the compressor, the casing at least partially defining a high pressure plenum that surrounds the combustor, the end cover at least partially defining a head end plenum within the combustor, the combustor including a system for reducing flame holding within the combustor, the system comprising:
• i. a high pressure plenum and a head end plenum at least partially defined between a casing and an end cover of the combustor;
• ii. a cap assembly that extends radially within the combustor, the cap assembly having a base plate positioned downstream from the end cover, a cap plate downstream from the base plate and an annular shroud that extends at least partially therebetween, the base plate and the shroud at least partially defining an inner plenum within the cap assembly, the base plate at least partially defining a fuel nozzle passage;
• iii. a primary fuel nozzle that extends from the end cover through the fuel nozzle passage and through the inner plenum, the primary fuel nozzle having an annular burner tube that at least partially defines a premix flow passage through the cap assembly, the burner tube at least partially defining an inlet to the premix flow passage;
• and
• iv. a high pressure flow passage and a cooling flow passage defined within the combustor, the high pressure flow passage defining a flow path between the high pressure plenum and the inner plenum and the cooling flow passage defining a flow path between the high pressure plenum and the head end plenum.