Patent ID: 8528338

Claim:
A method of cooling a tip end of an air-staged diffusion nozzle disposed in a combustor of a gas turbine with a compressor and a turbine, wherein the nozzle is upstream from a burner tube of the combustor, the method comprising: providing an air-staged diffusion nozzle comprising a nozzle body including a gas-fuel cavity bounded by an outer peripheral wall disposed along a longitudinal axis of the nozzle; an end closure wall, a cooling air chamber disposed within the gas-fuel cavity; an outer swirler supplied by gas-fuel from the gas-fuel cavity and compressed air from an external space surrounding the nozzle body; and a forward projection of the cooling air chamber, extending through the peripheral wall of the within and projecting through an end closure wall of the central fuel chamber; supplying gas-fuel to the gas-fuel cavity from an upstream gas-fuel source; diverting gas-fuel to flow through gas injection holes defined about a periphery of the end closure wall into swirl passages of the outer swirler; mixing the gas-fuel with compressed air from the external space within the outer swirler; discharging the swirled gas-fuel and compressed air with a rotational direction into a burner tube space downstream from the end closure wall of the nozzle body; and diverting compressed air from the external space surrounding the nozzle body through the cooling air chamber to the burner tube space downstream from the end closure wall of the nozzle body, and the step of diverting the compressed air comprising: flowing compressed air from the external space to the cooling air chamber with tubes fluidly connected through the outer peripheral wall of the gas-fuel cavity to the cooling air chamber and fluidly connected through a peripheral wall of the cooling air chamber to a cooling air cavity within, and the step of diverting comprising: sizing the tubes and penetrations through the peripheral walls of the nozzle body and cooling air chamber to provide sufficient compressed air flow for promoting mixing of gas-fuel and air within the burner space.