Systems and methods for bleed valve control in fuel systems

1. A fuel system comprising:

a fuel metering unit including a fuel inlet and a fuel outlet defining a flow path therebetween, wherein the fuel outlet is in fluid communication with an engine;

a bleed valve in fluid communication with the flow path of the fuel metering unit, wherein the fuel metering unit includes a temperature sensor positioned between the bleed valve and the engine; and

a controller in communication with the fuel metering unit and the bleed valve to send data thereto and/or receive data therefrom, wherein the controller is in communication with the temperature sensor to receive a fuel temperature measurement therefrom, wherein the bleed valve is configured and adapted to open or close depending on a command from the controller, wherein the flow path is configured and adapted to be in selective fluid communication with a fuel system interstage through the bleed valve, wherein the controller is configured and adapted to be in communication with the fuel system interstage to receive a thermal management system (TMS) bleed demand input therefrom, wherein the controller is in communication with the bleed valve to send a turn-on command to the bleed valve when the TMS bleed demand input is positive and when the fuel temperature measurement is outside of a hysteresis band limit.

2. The system as recited in claim 1 , wherein the fuel metering unit includes a first main stage pump and a second main stage pump upstream from the engine.

3. The system as recited in claim 2 , wherein the bleed valve is downstream from the first and second main stage pumps.

4. The system as recited in claim 2 , wherein the fuel metering unit includes a fuel metering valve between the first and second main stage pumps and the engine.

5. The system as recited in claim 2 , wherein the bleed valve is positioned between the first and second main stage pumps and the engine.

6. The system as recited in claim 1 , wherein the controller is in communication with a speed (N2) sensor to receive an input from the N2 sensor and determine whether a speed of the engine is in an idle state or above, or a below the idle state.

7. The system as recited in claim 6 , wherein the controller is in communication with the bleed valve to send a shut-off command to the bleed valve when the engine is below the idle state.

8. A fuel system comprising:

a fuel metering unit including a fuel inlet and a fuel outlet defining a flow path therebetween, wherein the fuel outlet is in fluid communication with an engine;

a bleed valve in fluid communication with the flow path of the fuel metering unit, wherein the fuel metering unit includes a temperature sensor positioned between the bleed valve and the engine; and

a controller in communication with the fuel metering unit and the bleed valve to send data thereto and/or receive data therefrom, wherein the controller is in communication with the temperature sensor to receive a fuel temperature measurement therefrom, wherein the bleed valve is configured and adapted to open or close depending on a command from the controller, wherein the flow path is configured and adapted to be in selective fluid communication with a fuel system interstage through the bleed valve, wherein the controller is configured and adapted to be in communication with the fuel system interstage to receive a TMS bleed demand input therefrom, wherein the controller is in communication with a second main stage pump, wherein the controller is configured and adapted to send a flood command when the fuel temperature measurement is within of a hysteresis band limit.

9. The system as recited in claim 8 , wherein the controller is in communication with the bleed valve to send a turn-on command to the bleed valve when the TMS bleed demand input is positive and when the fuel temperature measurement is outside of a hysteresis band limit.

10. The system as recited in claim 8 , wherein the fuel metering unit includes a first main stage pump and a second main stage pump upstream from the engine.

11. The system as recited in claim 8 , wherein the bleed valve is downstream from the first and second main stage pumps.

12. The system as recited in claim 8 , wherein the fuel metering unit includes a fuel metering valve between the first and second main stage pumps and the engine.

13. The system as recited in claim 8 , wherein the bleed valve is positioned between the first and second main stage pumps and the engine.

14. The system as recited in claim 8 , wherein the controller is in communication with a speed (N2) sensor to receive an input from the N2 sensor and determine whether a speed of the engine is in an idle state or above, or a below the idle state.

15. The system as recited in claim 14 , wherein the controller is in communication with the bleed valve to send a shut-off command to the bleed valve when the engine is below the idle state.

16. A method for controlling a bleed valve in a fuel system, the method comprising:

receiving a data input with a controller from a speed (N2) sensor of an engine;

determining whether a speed of the engine is at or above an idle state or below the idle state based on the data input from the N2 sensor;

switching the bleed valve on or off depending on whether the speed of the engine is below the idle state OR at or above the idle state;

receiving a positive thermal management system (TMS) demand input with the controller;

measuring a fuel temperature with a temperature sensor and receiving a fuel temperature measurement in the controller; and

at least one of: switching the bleed valve on if the fuel temperature measurement is greater than a hysteresis band limit, or flooding a second stage pump of the fuel system if the fuel temperature measurement is less than or equal to the hysteresis band limit.

17. The method as recited in claim 16 , wherein, if the fuel temperature measurement is less than or equal to the hysteresis band limit, further comprising switching the bleed valve on after flooding the second stage pump.