Fuel flow control system and method for engine start
Systems and methods for controlling fuel flow to an engine during start are provided. Fuel is caused to be injected into a combustor of the engine according to a first fuel schedule defining a minimum fuel flow limit required to achieve light-off of the engine, the minimum fuel flow limit set at an initial value. Following light-off of the engine, at least one operating parameter of the engine is monitored. Based on the at least one operating parameter, occurrence of flameout in the engine is detected. In response to detecting occurrence of flameout in the engine, the minimum fuel flow limit is increased from the initial value to a first value to obtain an adjusted fuel schedule, and fuel is caused to be injected into the combustor according to the adjusted fuel schedule.
1. A method for controlling fuel flow to an aircraft engine during start, the method comprising:
causing fuel to be injected into a combustor of the aircraft engine, according to an open loop fuel schedule, to achieve a target rotational speed for the aircraft engine, the open loop fuel schedule defining a minimum fuel flow limit required to achieve light-off of the aircraft engine, the minimum fuel flow limit set at an initial value;
monitoring, following light-off of the aircraft engine, at least one operating parameter of the aircraft engine, the at least one operating parameter monitored while fuel is caused to be injected into the combustor, according to a closed loop fuel schedule, to maintain a target acceleration for the aircraft engine;
detecting, based on the at least one operating parameter, occurrence of flameout in the aircraft engine following light-off of the aircraft engine; and
in response to detecting occurrence of flameout in the aircraft engine following light-off of the aircraft engine, increasing the minimum fuel flow limit from the initial value to a first value to obtain an adjusted open loop fuel schedule, and causing fuel to be injected into the combustor according to the adjusted open loop fuel schedule.
2. The method of claim 1 , wherein monitoring the at least one operating parameter of the aircraft engine comprises monitoring an acceleration of the aircraft engine, and wherein detecting occurrence of flameout in the aircraft engine comprises comparing the acceleration to a predetermined threshold and detecting partial flameout in response to determining that the acceleration is below the threshold.
3. The method of claim 1 , wherein the open loop fuel schedule defines a maximum fuel flow limit, and further wherein the first value is lower than the maximum fuel flow limit.
4. The method of claim 3 , further comprising, after causing fuel to be injected according to the adjusted open loop fuel schedule:
detecting occurrence of a subsequent flameout in the aircraft engine;
increasing the minimum fuel flow limit from the first value to a second value lower than the maximum fuel flow limit to obtain a newly adjusted open loop fuel schedule; and
causing fuel to be injected into the combustor according to the newly adjusted open loop fuel schedule.
5. The method of claim 1 , wherein detecting occurrence of flameout in the aircraft engine comprises detecting occurrence of a partial flameout.
6. The method of claim 1 , wherein detecting occurrence of flameout in the aircraft engine comprises detecting occurrence of a complete flameout.
7. The method of claim 1 , wherein fuel is caused to be injected into the combustor according to the adjusted open loop fuel schedule with the aircraft engine on the ground.
8. The method of claim 1 , wherein fuel is caused to be injected into the combustor according to the adjusted open loop fuel schedule while in flight.
9. The method of claim 1 , wherein monitoring the at least one operating parameter of the aircraft engine comprises monitoring an inter-stage turbine temperature of the aircraft engine.
10. A system for controlling fuel flow to an aircraft engine during start, the system comprising:
at least one processing unit; and
at least one non-transitory computer-readable memory having stored thereon program instructions executable by the at least one processing unit for:
causing fuel to be injected into a combustor of the aircraft engine, according to an open loop fuel schedule, to achieve a target rotational speed for the aircraft engine, the open loop fuel schedule defining a minimum fuel flow limit required to achieve light-off of the aircraft engine, the minimum fuel flow limit set at an initial value;
monitoring, following light-off of the aircraft engine, at least one operating parameter of the aircraft engine, the at least one operating parameter monitored while fuel is caused to be injected into the combustor, according to a closed loop fuel schedule, to maintain a target acceleration for the aircraft engine;
detecting, based on the at least one operating parameter, occurrence of flameout in the aircraft engine following light-off of the aircraft engine; and
in response to detecting occurrence of flameout in the aircraft engine following light-off of the aircraft engine, increasing the minimum fuel flow limit from the initial value to a first value to obtain an adjusted open loop fuel schedule, and causing fuel to be injected into the combustor according to the adjusted open loop fuel schedule.
11. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for monitoring the at least one operating parameter of the aircraft engine comprising monitoring an acceleration of the aircraft engine, and for detecting occurrence of flameout in the aircraft engine comprising comparing the acceleration of the aircraft engine to a predetermined threshold and detecting partial flameout in response to determining that the acceleration is below the threshold.
12. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for causing fuel to be injected into the combustor according to the open loop fuel schedule defining a maximum fuel flow limit, the first value being lower than the maximum fuel flow limit.
13. The system of claim 12 , wherein the program instructions are executable by the at least one processing unit for, after causing fuel to be injected according to the adjusted open loop fuel schedule:
detecting occurrence of a subsequent flameout in the aircraft engine;
increasing the minimum fuel flow limit from the first value to a second value lower than the maximum fuel flow limit to obtain a newly adjusted open loop fuel schedule; and
causing fuel to be injected into the combustor according to the newly adjusted open loop fuel schedule.
14. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for detecting occurrence of flameout in the aircraft engine comprising detecting occurrence of a partial flameout.
15. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for detecting occurrence of flameout in the aircraft engine comprising detecting occurrence of a complete flameout.
16. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for causing fuel to be injected into the combustor according to the adjusted open loop fuel schedule with the aircraft engine on the ground.
17. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for causing fuel to be injected into the combustor according to the adjusted open loop fuel schedule while in flight.
18. The system of claim 10 , wherein the program instructions are executable by the at least one processing unit for monitoring the at least one operating parameter of the aircraft engine comprising monitoring an inter-stage turbine temperature of the aircraft engine.
19. A non-transitory computer readable medium having stored thereon program code executable by at least one processor for:
causing fuel to be injected into a combustor of an aircraft engine, according to an open loop fuel schedule, to achieve a target rotational speed for the aircraft engine, the open loop fuel schedule defining a minimum fuel flow limit required to achieve light-off of the aircraft engine, the minimum fuel flow limit set at an initial value;
monitoring, following light-off of the aircraft engine, at least one operating parameter of the aircraft engine, the at least one operating parameter monitored while fuel is caused to be injected into the combustor, according to a closed loop fuel schedule, to maintain a target acceleration for the aircraft engine;
detecting, based on the at least one operating parameter, occurrence of flameout in the aircraft engine following light-off of the aircraft engine; and
in response to detecting occurrence of flameout in the aircraft engine following light-off of the aircraft engine, increasing the minimum fuel flow limit from the initial value to a first value to obtain an adjusted open loop fuel schedule, and causing fuel to be injected into the combustor according to the adjusted open loop fuel schedule.