Fuel systems and methods for purging
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.
1 . A non-transitory computer readable medium comprising computer executable instructions, the instructions configured to cause a computer to perform a method, the method comprising:
controlling a purge gas valve of a dual-fuel system of an aircraft and a gaseous fuel valve of the dual-fuel system to cause purging of a gaseous fuel circuit feeding a gaseous fuel to a dual-fuel engine of the aircraft, the purging being performed with a gas from a gas supply of the aircraft; and
simultaneously purging with the gas during shutdown of the dual-fuel engine of the aircraft both the gaseous fuel circuit and a liquid fuel circuit configured to feed a liquid fuel to the dual-fuel engine of the aircraft.
2 . The non-transitory computer readable medium of claim 1 , wherein:
the method includes preventing flashback from a combustor of the dual-fuel engine of the aircraft by purging of the gaseous fuel circuit during starting up and/or shutting down the dual-fuel engine of the aircraft in gaseous fuel operation.
3 . The non-transitory computer readable medium of claim 1 , wherein the gas includes an inert gas.
4 . The non-transitory computer readable medium of claim 1 , wherein controlling the purge gas valve and the gaseous fuel valve includes closing a gaseous fuel shut off valve to shut off gaseous fuel flow at least in part concurrently with opening the purge gas valve in a manner that maintains a higher pressure in the gaseous fuel circuit than in a combustor of the dual-fuel engine of the aircraft and thereby shutting down the dual-fuel engine of the aircraft.
5 . The non-transitory computer readable medium of claim 1 , wherein:
the gas is an inert gas; and
controlling the purge gas valve and the gaseous fuel valve includes progressively opening the purge gas valve and/or progressively closing the gaseous fuel valve while maintaining pressure in the gaseous fuel circuit greater than in a combustor of the dual-fuel engine of the aircraft in order to progressively increase a mixture of the inert gas with the gaseous fuel until flameout, and then closing the purge gas valve and the gaseous fuel valve after flameout.
6 . The non-transitory computer readable medium of claim 1 , wherein:
the gas is an inert gas; and
the method includes purging the liquid fuel circuit with the inert gas when changing from liquid fuel operation to gaseous fuel operation.
7 . The non-transitory computer readable medium of claim 1 , wherein:
the gas is an inert gas;
the method includes:
purging the gaseous fuel circuit of the dual-fuel engine of the aircraft with the inert gas during shutdown of the dual-fuel engine of the aircraft; and
once a flameout in a combustor of the dual-fuel engine of the aircraft has been detected, ceasing to purge the gaseous fuel circuit.