Cooling in staged fuel systems
A fuel system includes a fuel supply system. A plurality of fuel nozzles are connected in fluid communication with the fuel supply system to supply fuel from a fuel source to be issued for combustion from the fuel nozzles. A cooling system is included, wherein at least one of the fuel nozzles includes a cooling circuit in addition to a fuel circuit for issuing fuel from the fuel supply system for combustion. The cooling circuit includes an inlet and an outlet. The inlet is in fluid communication with the cooling system for circulation of coolant through the cooling circuit and back to the cooling system out the outlet of the cooling circuit for cooling the fuel circuit with the fuel circuit staged off.
1. A fuel system comprising:
a fuel supply system;
a plurality of fuel nozzles connected in fluid communication with the fuel supply system to supply fuel from a fuel source to be issued for combustion from the plurality of fuel nozzles; and
a cooling system;
wherein the fuel supply system comprises:
a first fuel manifold connected in fluid communication with a first subset of the plurality of fuel nozzles to supply fuel from the fuel source to be issued for combustion from the first subset of the plurality of fuel nozzles; and
a second fuel manifold connected in fluid communication with a second subset of the plurality fuel nozzles to selectively supply fuel from the fuel source to be issued for combustion from the second subset of fuel nozzles of the plurality of fuel nozzles with the second subset of fuel nozzles staged on, wherein each of the fuel nozzles of the second subset includes a cooling circuit in addition to a fuel circuit for issuing fuel from the second fuel manifold for combustion, wherein the cooling circuit includes an inlet and an outlet, wherein the inlet is in fluid communication with the cooling system for circulation of coolant through the cooling circuit and back to the cooling system out the outlet of the cooling circuit for cooling the fuel circuit with the fuel circuits of the second subset of fuel nozzles staged off;
wherein each of the fuel nozzles of the first subset does not include a cooling circuit connected to the cooling system in addition to having the fuel circuit.
2. A fuel system as recited in claim 1 , wherein the cooling system includes a coolant conduit connected for fluid communication of coolant from the outlet of the cooling circuit of a first one of the fuel nozzles of the second subset to the inlet of the cooling circuit of a second one of the fuel nozzles of the second subset.
3. A fuel system as recited in claim 2 , wherein the cooling system includes:
a first coolant manifold connected in fluid communication to supply coolant to the inlet of the cooling circuit of the first one of the fuel nozzles of the second subset; and
a second coolant manifold connected in fluid communication to receive coolant from the outlet of the cooling circuit of another one of the fuel nozzles of the second subset.
4. A fuel system as recited in claim 2 , wherein the cooling system includes:
a first coolant manifold connected in fluid communication to supply coolant to the inlet of the cooling circuit of the first one of the fuel nozzles of the second subset; and
a second coolant manifold connected in fluid communication to receive coolant from the outlet of the cooling circuit of the second one of the fuel nozzles of the second subset.
5. A fuel system as recited in claim 1 , wherein each fuel nozzle of the second subset includes:
a nozzle body defining a longitudinal axis including an air passage;
wherein the fuel circuit is radially outboard from the air passage with respect to the longitudinal axis, the fuel circuit extending from a fuel circuit inlet to a fuel circuit annular outlet, wherein the fuel circuit is defined between a fuel circuit inner wall and a fuel circuit outer wall, wherein at least a portion of the fuel circuit outer wall is radially outboard from the fuel circuit inner wall with respect to the longitudinal axis; and
wherein the cooling circuit is defined within at least one of the fuel circuit inner wall and the fuel circuit outer wall, wherein the cooling circuit extends from an axial position proximate the fuel circuit inlet to an axial position proximate the fuel circuit outlet.
6. A fuel system as recited in claim 1 , wherein each fuel nozzle of the second subset includes a nozzle body defining a longitudinal axis, wherein the nozzle body includes an outer air passage defined radially outboard of the fuel circuit with respect to the longitudinal axis, and wherein the outer air passage is defined between a fuel circuit outer wall and an outer air passage wall, and wherein the outer air passage is a converging non-swirling outer air passage.
7. A fuel system as recited in claim 1 , wherein the cooling system is configured to cool the second subset engine shut down until the temperature proximate the second subset decreases below a predetermined limit to avoid formation of coke during engine cool down.
8. A fuel system as recited in claim 1 , wherein the cooling system is configured to circulate fluid in the cooling circuits prior to start up to help cool residual soakback or preheat the second sunset for cold day starts.