Methods of igniting liquid fuel in a turbomachine

1. A method of igniting liquid fuel in a turbomachine combustor, the method comprising:

initiating a flow of gaseous fuel from a gaseous fuel supply to a gaseous fuel nozzle;

initiating a flow of liquid fuel from a liquid fuel supply to a liquid fuel cartridge, wherein the step of initiating the flow of liquid fuel occurs with or after the step of initiating the flow of gaseous fuel;

after initiating both the flow of gaseous fuel and the flow of liquid fuel, simultaneously igniting the flow of gaseous fuel and the flow of liquid fuel with an igniter; and

terminating the flow of gaseous fuel from the gaseous fuel supply to the gaseous fuel nozzle.

2. The method as in claim 1 , wherein the liquid fuel cartridge is positioned along an axial centerline of the turbomachine combustor, and wherein the gaseous fuel nozzle surrounds the liquid fuel cartridge, the liquid fuel cartridge and the gaseous fuel nozzle being positioned in a head end of the turbomachine combustor.

3. The method as in claim 1 , wherein the step of initiating the flow of gaseous fuel and the step of initiating the flow of liquid fuel are performed simultaneously.

4. The method as in claim 1 , wherein the gaseous fuel supply is one of a main gaseous fuel supply system, an auxiliary gaseous fuel supply system, or both the main auxiliary gaseous fuel supply system and the auxiliary gaseous fuel supply system.

5. The method as in claim 1 , further comprising providing a controller in communication with the igniter, the gaseous fuel supply, and the liquid fuel supply.

6. The method as in claim 5 , further comprising detecting a flame within a combustion chamber of the turbomachine combustor using a flame detector, the flame detector being in communication with the controller.

7. The method as in claim 6 , wherein the step of initiating the flow of gaseous fuel and the step of initiating the flow of liquid fuel occur before the flame detector detects a flame in the combustion chamber.

8. The method as in claim 1 , wherein the step of initiating the flow of gaseous fuel from the gaseous fuel supply is accomplished by controlling a gaseous fuel valve located in a gaseous fuel supply line extending from the gaseous fuel supply.

9. The method as in claim 8 , wherein the step of terminating the flow of gaseous fuel from the gaseous fuel supply is accomplished by controlling the gaseous fuel valve.

10. The method as in claim 1 , wherein the step of initiating the flow of liquid fuel from the liquid fuel supply is accomplished by controlling a liquid fuel valve located in a liquid fuel supply line extending between the liquid fuel supply and the liquid fuel cartridge.

11. A method of starting a gas turbine on liquid fuel, the gas turbine comprising a rotor shaft coupled to a compressor and a turbine, wherein a plurality of combustors is disposed between the turbine and the compressor, the method comprising:

accelerating the rotation of the rotor shaft towards a combustion speed to force air through the gas turbine; and

within each combustor of the plurality of combustors:

initiating a flow of gaseous fuel from a gaseous fuel supply to a gaseous fuel nozzle;

initiating a flow of liquid fuel from a liquid fuel supply to a liquid fuel cartridge, wherein the step of initiating the flow of liquid fuel occurs with or after the step of initiating the flow of gaseous fuel;

after initiating both the flow of gaseous fuel and the flow of liquid fuel, simultaneously igniting the flow of gaseous fuel and the flow of liquid fuel with an igniter; and

terminating the flow of gaseous fuel from the gaseous fuel supply to the gaseous fuel nozzle.

12. The method as in claim 11 , wherein the liquid fuel cartridge is positioned along an axial centerline of each combustor of the plurality of combustors, and wherein the gaseous fuel nozzle surrounds the liquid fuel cartridge, the liquid fuel cartridge and the respective gaseous fuel nozzle being positioned in a head end of each combustor of the plurality of combustors.

13. The method as in claim 11 , wherein the step of initiating the flow of gaseous fuel and the step of initiating the flow of liquid fuel are performed simultaneously.

14. The method as in claim 11 , wherein the gaseous fuel supply is one of a main gaseous fuel supply system, an auxiliary gaseous fuel supply system, or both the main auxiliary gaseous fuel supply system and the auxiliary gaseous fuel supply system.

15. The method as in claim 11 , further comprising providing a controller in communication with the igniter, the gaseous fuel supply, and the liquid fuel supply.

16. The method as in claim 15 , further comprising detecting a flame within a combustion chamber of a combustor of the plurality of combustors using a flame detector, the flame detector being in communication with the controller.

17. The method as in claim 16 , wherein the step of initiating the flow of gaseous fuel and the step of initiating the flow of liquid fuel occur before the flame detector detects a flame in the combustion chamber.

18. The method as in claim 11 , wherein the step of initiating the flow of gaseous fuel from the gaseous fuel supply is accomplished by controlling a gaseous fuel valve located in a gaseous fuel supply line extending from the gaseous fuel supply.

19. The method as in claim 18 , wherein the step of terminating the flow of gaseous fuel from the gaseous fuel supply is accomplished by controlling the gaseous fuel valve.

20. The method as in claim 11 , wherein the liquid fuel cartridge includes a cartridge tip, and wherein the cartridge tip defines rows of liquid fuel injection holes circumferentially spaced apart from one another on the cartridge tip.