A fuel injector is disclosed for reducing flashback. In an embodiment, the fuel injector may comprise an injector head with purge holes on a radial wall along a radial axis between an assembly axis of the fuel injector and a plurality of vanes arranged circumferentially around the assembly axis. In addition, the plurality of vanes may comprise fuel outlets connecting interior fuel passages to spaces between the vanes. The introduction of these purge holes near the bases of the vanes and the configuration and positioning of the fuel outlets in the vanes and elsewhere in the fuel injector may alter the stoichiometry (e.g., fuel-air ratio) within the premix passage of the fuel injector to reduce flashback. A plurality of such fuel injectors may be used in the combustor of a gas turbine engine.

A method and system for cleaning a fuel nozzle during engine operation is provided. Operations include operating the compressor section to provide the flow of oxidizer at a first oxidizer flow condition to the combustion chamber, wherein the first oxidizer flow condition comprises an environmental parameter; operating the fuel system at a first fuel flow condition to produce a fuel-oxidizer ratio at the combustion chamber; comparing the environmental parameter to a first environmental parameter threshold; and transitioning the fuel system to a second fuel flow condition corresponding to a cleaning condition at the fuel nozzle if the environmental parameter is equal to or greater than the first environmental threshold.

A burner for a metal-melting furnace can releasably receive a tapered plug in sealing engagement with an access passage aligned with an air passage. The burner may be configured to extend through a wall of the metal-melting furnace so that the air passage is through a front face within the furnace and so that the access passage is through a rear face outside of the furnace. The access passage may be aligned with the air passage to permit a rigid structure to be passed through the burner from outside the furnace to dislodge build-up of solidified metal from the air passage. The tapered plug may be moveable between a sealing configuration of being received in a seat to seal the access passage during burner operation and a cleaning configuration of being removed from the seat to expose the access passage for insertion of the rigid structure.

A fuel spray nozzle includes a fuel circuit having in series a gallery, circumferentially spaced passages arranged in a row around the nozzle, and an annular spin chamber. Each passage has an inlet for receiving a respective portion of the fuel from the gallery and a metering orifice for discharging its portion of the fuel. The passages are configured such that, when the flow of liquid fuel to the inlet port is shut off, a respective differential static pressure develops across stagnant liquid fuel remaining between the inlet and the metering orifice of each passage, and the passages are further configured such that one or more selected passages develop a different differential static pressure to the remaining passages causing a flow of purging air to enter the gallery from the combustor through the selected passages and exit through the remaining passages, thereby purging the gallery and the passages of fuel.

A fuel system can include a first fuel circuit, a second fuel circuit, and an inert gas purge system operatively connected to both the first fuel circuit and the second fuel circuit to purge at least a portion of either or both of the first and/or second fuel circuit. The first fuel can be a liquid fuel and the second fuel can be a gaseous fuel. The first fuel circuit can include a first fuel manifold configured to fluidly communicate a first fuel supply with at least one dual fuel nozzles downstream of the first fuel manifold.

Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to the combustor by supplying fuel to the first fuel manifold via a first flow divider valve and supplying fuel to the second fuel manifold via a second flow divider valve. While supplying fuel to the combustor by supplying fuel to the first fuel manifold, the method includes stopping supplying fuel to the second fuel manifold and supplying pressurized gas to the second fuel manifold via the second flow divider valve to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated nozzles.

Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to the combustor by supplying fuel to the first fuel manifold via a first flow divider valve and supplying fuel to the second fuel manifold via a second flow divider valve. While supplying fuel to the combustor by supplying fuel to the first fuel manifold, the method includes stopping supplying fuel to the second fuel manifold and supplying pressurized gas to the second fuel manifold via the second flow divider valve to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated nozzles.

A method and system for cleaning a fuel nozzle during engine operation is provided. Operations include operating the compressor section to provide the flow of oxidizer at a first oxidizer flow condition to the combustion chamber, wherein the first oxidizer flow condition comprises an environmental parameter; operating the fuel system at a first fuel flow condition to produce a fuel-oxidizer ratio at the combustion chamber; comparing the environmental parameter to a first environmental parameter threshold; and transitioning the fuel system to a second fuel flow condition corresponding to a cleaning condition at the fuel nozzle if the environmental parameter is equal to or greater than the first environmental threshold.

A fuel nozzle apparatus includes: an outer body having an exterior surface and a plurality of openings in the exterior surface. An inner body is disposed inside the outer body, cooperating with the outer body to define an annular space. A main injection ring is disposed in the annular space and includes an array of fuel posts extending outward therefrom, each fuel post including a perimeter wall defining a lateral surface and a recessed floor. Each fuel post is aligned with one of the openings and separated from the opening by a perimeter gap defined between the opening and the lateral surface. A main fuel gallery extends within the main injection ring. The main injection ring includes plurality of main fuel orifices, each main fuel orifice communicating with the main fuel gallery and extending through one of the fuel posts.

A fuel nozzle apparatus includes: an outer body having an exterior surface and a plurality of openings in the exterior surface. An inner body is disposed inside the outer body, cooperating with the outer body to define an annular space. A main injection ring is disposed in the annular space and includes an array of fuel posts extending outward therefrom, each fuel post including a perimeter wall defining a lateral surface and a recessed floor. Each fuel post is aligned with one of the openings and separated from the opening by a perimeter gap defined between the opening and the lateral surface. A main fuel gallery extends within the main injection ring. The main injection ring includes plurality of main fuel orifices, each main fuel orifice communicating with the main fuel gallery and extending through one of the fuel posts.