Systems and methods for fuel-based thermal management

1. A method of fuel-based thermal management for a gas turbine engine, comprising:

receiving, by a controller, a fluid temperature of a flow of a fluid from a fluid temperature sensor upstream of a heat exchanger, the heat exchanger configured to thermally couple the fluid to a fuel;

receiving, by the controller, a first fuel temperature from a first fuel temperature sensor upstream of the heat exchanger;

receiving, by the controller, a flight cycle time;

receiving, by the controller, at least one of an altitude measurement or an ambient pressure measurement;

receiving, by the controller, a dissolved oxygen concentration measurement from an oxygen sensor configured to measure a dissolved oxygen concentration of the fuel;

determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, the flight cycle time, and the at least one of the altitude measurement or the ambient pressure measurement;

determining, by the controller, whether a thermal load from the fluid can be deposited into the fuel based on the determining the updated dissolved oxygen concentration of the fuel; and

modulating, by the controller, the flow of the fluid to the heat exchanger based on the determining, by the controller, whether the thermal load from the fluid can be deposited into the fuel.

2. The method of claim 1 , wherein the determining, by the controller, whether the thermal load from the fluid can be deposited into the fuel comprises:

determining, by the controller, a fuel coking temperature based on the updated dissolved oxygen concentration; and

comparing, by the controller, the fuel coking temperature to the first fuel temperature.

3. The method of claim 2 , wherein the modulating, by the controller, the flow of the fluid to the heat exchanger further comprises:

depositing, using the heat exchanger, the thermal load from the fluid into the fuel;

receiving, by the controller, a second fuel temperature from a second fuel temperature sensor downstream of the heat exchanger;

comparing, by the controller, the fuel coking temperature to the second fuel temperature; and

determining, by the controller, whether to adjust a flow rate of the fluid to the heat exchanger based on the comparing of the fuel coking temperature to the second fuel temperature.

4. The method of claim 3 , wherein the depositing, using the heat exchanger, the thermal load from the fluid into the fuel comprises:

actuating, by the controller, a valve fluidly coupled between a source of the fluid and the heat exchanger.

5. The method of claim 3 , wherein the modulating, by the controller, the flow of the fluid to the heat exchanger further comprises:

decreasing, by the controller, the flow rate of the fluid if the second fuel temperature is greater than the fuel coking temperature.

6. The method of claim 5 , wherein the decreasing, by the controller, the flow rate of the fluid comprises:

actuating, by the controller, a valve fluidly coupled between a source of the fluid and the heat exchanger.

7. The method of claim 1 , wherein the fluid comprises at least one of oil, air, lubricating fluid, fuel, or hydraulic fluid.

8. The method of claim 7 , wherein the fluid is output from a component of the gas turbine engine.

9. A fuel-based thermal management system, comprising:

a heat exchanger configured to thermally couple a fluid and a fuel;

a controller configured to modulate a flow of the fluid to the heat exchanger; and

a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the controller, cause the controller to perform operations comprising:

determining, by the controller, a temperature of the fluid;

receiving, by the controller, a dissolved oxygen concentration measurement from an oxygen sensor configured to measure a dissolved oxygen concentration of the fuel;

receiving, by the controller, a first fuel temperature from a first fuel temperature sensor upstream of the heat exchanger;

determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, a flight cycle time, and at least one of an altitude measurement or an ambient pressure measurement; and

modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration of the fuel.

10. The fuel-based thermal management system of claim 9 , wherein the operation of modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration of the fuel comprises:

determining, by the controller, a fuel coking temperature based on the updated dissolved oxygen concentration of the fuel;

comparing, by the controller, the fuel coking temperature to the first fuel temperature; and

determining, by the controller, whether a thermal load from the fluid can be deposited into the fuel based on the comparing of the fuel coking temperature to the first fuel temperature.

11. The fuel-based thermal management system of claim 10 , wherein the operation of modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration of the fuel further comprises:

receiving, by the controller, a second fuel temperature;

comparing, by the controller, the fuel coking temperature to the second fuel temperature; and

determining, by the controller, whether to adjust a flow rate of the fluid to the heat exchanger based on the comparing of the fuel coking temperature to the second fuel temperature.

12. The fuel-based thermal management system of claim 9 , wherein the operation of modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration of the fuel comprises:

actuating, by the controller, a valve fluidly coupled between a source of the fluid and the heat exchanger.

13. A fuel-based thermal management system for a gas turbine engine, comprising:

a fuel-fluid heat exchange system comprising:

a heat exchanger configured to thermally couple a fluid received from a heat source and a fuel received from a fuel source, and

a valve configured to regulate a flow of the fluid to the heat exchanger;

a controller in operable communication with the valve; and

a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the controller, cause the controller to perform operations comprising:

determining, by the controller, whether a temperature of the fluid is above a predetermined fluid temperature threshold;

receiving, by the controller, a dissolved oxygen concentration measurement from an oxygen sensor configured to measure a dissolved oxygen concentration of the fuel output by the fuel source;

receiving, by the controller, a first fuel temperature from a first fuel temperature sensor upstream of the heat exchanger;

determining, by the controller, an updated dissolved oxygen concentration using the dissolved oxygen concentration measurement received from the oxygen sensor, the first fuel temperature, a flight cycle time, and at least one of an altitude measurement or an ambient pressure measurement; and

modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration.

14. The fuel-based thermal management system of claim 13 , wherein modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration in the fuel comprises:

determining, by the controller, a fuel coking temperature based on the updated dissolved oxygen concentration;

comparing, by the controller, the fuel coking temperature to the first fuel temperature; and

determining, by the controller, whether a thermal load from the fluid can be deposited into the fuel based on the comparing of the fuel coking temperature to the first fuel temperature.

15. The fuel-based thermal management system of claim 14 , wherein modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration in the fuel further comprises:

depositing, using the heat exchanger, the thermal load from the fluid into the fuel;

receiving, by the controller, a second fuel temperature from a second temperature sensor downstream of the heat exchanger;

comparing, by the controller, the fuel coking temperature to the second fuel temperature; and

determining, by the controller, whether to actuate the valve based on the comparing of the fuel coking temperature to the second fuel temperature.

16. The fuel-based thermal management system of claim 15 , wherein depositing, using the heat exchanger, the thermal load from the fluid into the fuel comprises:

actuating, by the controller, the valve to an open position.

17. The fuel-based thermal management system of claim 16 , wherein modulating, by the controller, the flow of the fluid to the heat exchanger based on the updated dissolved oxygen concentration in the fuel further comprises:

actuating, by the controller, the valve to a closed position if the second fuel temperature is greater than the fuel coking temperature.

18. The fuel-based thermal management system of claim 13 , wherein an output flow of the fluid from the heat exchanger is directed to a component of the gas turbine engine.

19. The fuel-based thermal management system of claim 18 , wherein the fluid comprises at least one of oil or air.

20. The fuel-based thermal management system of claim 13 , wherein the dissolved oxygen concentration measurement output from the oxygen sensor corresponds to a pre-flight concentration of dissolved oxygen.