System and method for operating a precooler in an aircraft

1. An aircraft engine, comprising:

a nacelle with an air inlet and an air outlet;

a cavity defined within the nacelle, the cavity permitting ambient air to pass through the nacelle from the air inlet to the air outlet;

an inner fixed structure dividing the cavity into an engine core compartment and a fan bypass channel;

a compressor region defined within the engine core compartment, the compressor region producing bleed air taken from at least one position between the air inlet and the air outlet;

a precooler disposed within the nacelle, the precooler defining an ambient air passage and a bleed air passage, wherein the ambient air passes to the engine core compartment through the ambient air passage from an ambient air inlet to an ambient air outlet, wherein the bleed air passes through the bleed air passage from a bleed air inlet to a bleed air outlet, and wherein heat is transferred between the ambient air and the bleed air via heat exchange within the precooler;

at least one pressure relief door disposed on the inner fixed structure to create additional engine venting through the pressure relief door, when opened; and

a controller operatively connected to the pressure relief door, wherein the controller at least opens the pressure relief door based on a demand for increased flow of the ambient air through the ambient air passage.

2. The aircraft engine of claim 1 , wherein the at least one pressure relief door comprises a plurality of pressure relief doors.

3. The aircraft engine of claim 1 , wherein the bleed air has a temperature greater than the ambient air.

4. The aircraft engine of claim 3 , wherein the bleed air is cooled to a predetermined temperature within the precooler via the heat exchange with the ambient air.

5. The aircraft engine of claim 4 , wherein the predetermined temperature is between about 200° C. to 232° C.

6. The aircraft engine of claim 1 , wherein the precooler further comprises:

a scoop positioned upstream of the ambient air inlet.

7. The aircraft engine of claim 1 , wherein the ambient air passage and the bleed air passage are separate from one another such that the ambient air and the bleed air are prevented from intermixing during the heat exchange.

8. The aircraft engine of claim 1 , wherein the ambient air passage and the bleed air passage permit intermixing of the ambient air and the bleed air during the heat exchange.

9. The aircraft engine of claim 1 , wherein the bleed air is taken from positions proximate to both a high pressure compressor and a low pressure compressor.

10. The aircraft engine of claim 1 , wherein the demand for increased flow of the ambient air through the ambient air passage is conditioned upon trigger variables, which comprise at least one signal indicative of an engine failure, a bleed air system failure, an ice condition, or an activation of an anti-icing system.

11. The aircraft engine of claim 10 , wherein the trigger variables further comprise at least one signal indicative of flow of the ambient air, flow of the bleed air, pressure at the ambient air inlet, pressure at the ambient air outlet, pressure at the bleed air inlet, pressure at the bleed air outlet, outside air temperature, temperature at the air inlet, temperature at the air outlet, temperature at the bleed air inlet, temperature at the bleed air outlet, differential pressure between the ambient air inlet and the ambient air outlet, differential pressure between the bleed air inlet and the bleed air outlet, weight on wheel off, altitude of the aircraft, and time.

12. The aircraft engine of claim 1 , wherein the controller is operatively connected to the pressure relief door to close the pressure relief door based on a demand for decreased flow of the ambient air through the ambient air passage.

13. A method of operating an aircraft engine comprising a nacelle with an air inlet and an air outlet, a cavity defined within the nacelle, the cavity permitting ambient air to pass through the nacelle from the air inlet to the air outlet, an inner fixed structure dividing the cavity into an engine core compartment and a fan bypass channel, a compressor region defined within the engine core compartment, the compressor region producing bleed air taken from at least one position between the air inlet and the air outlet, a precooler disposed within the nacelle, the precooler defining an ambient air passage and a bleed air passage, wherein the ambient air passes to the engine core compartment through the ambient air passage from an ambient air inlet to an ambient air outlet, wherein the bleed air passes through the bleed air passage from a bleed air inlet to a bleed air outlet, and wherein heat is transferred between the ambient air and the bleed air via heat exchange within the precooler, at least one pressure relief door disposed on the inner fixed structure to create additional engine venting through the pressure relief door, when opened, and a controller operatively connected to the pressure relief door, wherein the controller at least opens the pressure relief door based on a demand for increased flow of the ambient air through the ambient air passage, the method comprising:

receiving, by the controller, trigger variables;

evaluating the trigger variables, by the controller, to determine if the ambient air passing through the ambient air passage is cooling the bleed air passing through the bleed air passage to a predetermined temperature; and

opening the pressure relief door, if the trigger variables require an increased flow of the ambient air through the ambient air passage.

14. The method of claim 13 , further comprising:

closing the pressure relief door, if the trigger variables require a decreased flow of the ambient air through the ambient air passage.

15. The method of claim 13 , wherein the trigger variables comprise at least one signal indicative of an engine failure, a bleed air system failure, an ice condition, and activation of an anti-icing system.

16. The method of claim 15 , wherein the trigger variables further comprise at least one signal indicative of flow of the ambient air, flow of the bleed air, pressure at the ambient air inlet, pressure at the ambient air outlet, pressure at the bleed air inlet, pressure at the bleed air outlet, outside air temperature, temperature at the air inlet, temperature at the air outlet, temperature at the bleed air inlet, temperature at the bleed air outlet, differential pressure between the ambient air inlet and the ambient air outlet, differential pressure between the bleed air inlet and the bleed air outlet, weight on wheel off, altitude of the aircraft, and time.

17. A control system for controlling at least one pressure relief door on an aircraft engine comprising a nacelle with an air inlet and an air outlet, a cavity defined within the nacelle, the cavity permitting ambient air to pass through the nacelle from the air inlet to the air outlet, an inner fixed structure dividing the cavity into an engine core compartment and a fan bypass channel, a compressor region defined within the engine core compartment, producing bleed air taken from at least one position between the air inlet and the air outlet, a precooler disposed within the nacelle, the precooler defining an ambient air passage and a bleed air passage, wherein the ambient air passes to the engine core compartment through the ambient air passage from an ambient air inlet to an ambient air outlet, wherein the bleed air passes through the bleed air passage from a bleed air inlet to a bleed air outlet, wherein heat is transferred between the ambient air and the bleed air via heat exchange within the precooler, the at least one pressure relief door disposed on the inner fixed structure to create additional engine venting through the pressure relief door, when opened, and a controller operatively connected to the pressure relief door, wherein the controller at least opens the pressure relief door based on a demand for increased flow of the ambient air through the ambient air passage, the system comprising:

a controller configured to receive trigger variables;

an actuator operatively connected to the at least one pressure relief door, the actuator being configured at least to open the pressure relief door;

a communication line operatively connecting the controller to the actuator;

wherein, after evaluating the trigger variables and determining if the ambient air passing through the ambient air passage is cooling the bleed air passing through the bleed air passage to a predetermined temperature, the controller sends a signal to open the pressure relief door, if the trigger variables require an increased flow of the ambient air through the ambient air passage.

18. The control system of claim 17 , wherein the controller sends a signal to close the pressure relief door, if the trigger variables require a decreased flow of the ambient air through the ambient air passage.

19. The control system of claim 17 , wherein the trigger variables comprise at least one signal indicative of an engine failure, a bleed air system failure, an ice condition, and activation of an anti-icing system.

20. The control system of claim 19 , wherein the trigger variables further comprise at least one signal indicative of flow of the ambient air, flow of the bleed air, pressure at the ambient air inlet, pressure at the ambient air outlet, pressure at the bleed air inlet, pressure at the bleed air outlet, outside air temperature, temperature at the air inlet, temperature at the air outlet, temperature at the bleed air inlet, temperature at the bleed air outlet, differential pressure between the ambient air inlet and the ambient air outlet, differential pressure between the bleed air inlet and the bleed air outlet, weight on wheel off, altitude of the aircraft, and time.