System and method for operating a precooler in an aircraft

Abstract

A method for controlling a pressure control mechanism in a turbofan engine having a precooler permitting heat exchange between ambient air and bleed air includes detecting at least one of an engine failure or a bleed system failure, detecting at least one of an ice condition or an activation of an anti-ice system, and actuating the pressure control mechanism, thereby altering the heat exchange between the ambient air and the bleed air.

What is claimed is: 
     
         1 . A method for controlling a pressure control mechanism in a turbofan engine having a precooler permitting heat exchange between ambient air and bleed air, the method comprising:
 detecting at least one of an engine failure or a bleed system failure;   detecting at least one of an ice condition or an activation of an anti-ice system; and   actuating the pressure control mechanism, thereby altering the heat exchange between the ambient air and the bleed air.   
     
     
         2 . The method of  claim 1 , wherein the pressure control mechanism comprises a pressure relief door disposed proximate to an outlet of the turbofan engine. 
     
     
         3 . The method of  claim 1 , wherein the pressure control mechanism is actuated upon detection of a combination of at least one of an engine failure and a bleed system failure, and at least one of an ice condition and an activation of the anti-ice system. 
     
     
         4 . The method of  claim 1 , wherein actuating the pressure control mechanism comprises opening a pressure relief door in the turbofan engine. 
     
     
         5 . The method of  claim 2 , wherein:
 the pressure relief door comprises a plurality of pressure relief doors, and   actuating the plurality of pressure relief doors comprises opening the plurality of pressure relief doors.   
     
     
         6 . The method of  claim 1 , wherein the bleed air has a temperature greater than the ambient air. 
     
     
         7 . The method of  claim 6 , wherein the bleed air is cooled to a predetermined temperature within the precooler via the heat exchange with the ambient air. 
     
     
         8 . The method of  claim 7 , wherein the predetermined temperature is between about 200° C. to 232° C. 
     
     
         9 . The method of  claim 1 , further comprising:
 providing an ambient air passage for the ambient air;   providing a bleed air passage for the bleed air; and   separating the ambient air passage and the bleed air passage from one another such that the ambient air and the bleed air are prevented from intermixing during the heat exchange.   
     
     
         10 . The method of  claim 1 , further comprising:
 providing an ambient air passage for the ambient air;   providing a bleed air passage for the bleed air; and   combining the ambient air passage and the bleed air passage to permit intermixing of the ambient air and the bleed air during the heat exchange.   
     
     
         11 . The method of  claim 1 , wherein the bleed air is taken from positions proximate to both a high pressure compressor and a low pressure compressor in the turbofan engine. 
     
     
         12 . The method of  claim 1 , wherein a demand for increased flow of the ambient air is conditioned upon trigger variables, which comprise signals indicative of an engine failure, a bleed air system failure, an ice condition, or an activation of an anti-icing system. 
     
     
         13 . The method of  claim 12 , wherein the trigger variables further comprise signals 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. 
     
     
         14 . The method of  claim 4 , further comprising:
 closing the pressure relief door based on a demand for decreased flow of the ambient air.   
     
     
         15 . The method of  claim 1 , wherein the pressure control mechanism comprises a pressure relief door disposed proximate to an outlet of the turbofan engine, downstream of the precooler, the method further comprising:
 changing a degree of openness of the pressure relief door in response to the detecting, thereby changing an ambient air flow through the precooler.   
     
     
         16 . The method of  claim 15 , wherein actuating the pressure control mechanism includes opening the pressure relief door in the turbofan engine at least in part to satisfy a demand for an increased flow of the ambient air. 
     
     
         17 . The method of  claim 16 , wherein actuating the pressure control mechanism also includes closing the pressure relief door in the turbofan engine at least in part to satisfy a demand for a decreased flow of the ambient air. 
     
     
         18 . 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;   a compressor region defined within the nacelle, 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 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 within the cavity to create additional engine venting proximate to the air outlet; 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.   
     
     
         19 . 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, a compressor region defined within the nacelle, 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 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 within the cavity to create additional engine venting proximate to the air outlet, 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.   
     
     
         20 . 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, a compressor region defined within the nacelle, 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 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, at least one pressure relief door disposed within the cavity to create additional engine venting proximate to the air outlet, 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.