Turbofan engine performance recovery system and method

Abstract

Methods and apparatus are provided for improving engine performance in a turbofan gas turbine engine following foreign object ingestion in turbofan gas turbine engines that include an intake fan that includes a plurality of fan blades, and that is disposed within and surrounded by a fan case. The occurrence of a foreign object ingestion by the turbofan gas turbine engine is detected and, upon detecting that a foreign object has been ingested, air is bled from a region proximate the blades of the intake fan through a slot in the fan case.

1 . A turbofan engine intake assembly, comprising:
 a fan case adapted to be mounted in an engine nacelle assembly, the fan case including an inner surface and an outer surface;   an intake fan mounted within the fan case and including a plurality of radially extending fan blades;   a slot extending through the fan case between the inner and outer surfaces, the slot at least partially extending around the fan case proximate the fan blades; and   an annulus coupled to the outer surface and including an inner surface that defines an annular plenum, the annular plenum in fluid communication with the slot and atmosphere outside the fan case.   
     
     
         2 . The turbofan engine intake assembly of  claim 1 , further comprising:
 a discharge conduit coupled to the annulus and including an inlet port and an outlet port, the inlet port in fluid communication with the annular plenum, the outlet port in fluid communication with the atmosphere outside the fan case.   
     
     
         3 . The turbofan engine intake assembly of  claim 2 , further comprising:
 a valve mounted on the discharge conduit and movable to a plurality of valve positions.   
     
     
         4 . The turbofan engine intake assembly of  claim 3 , further comprising:
 a valve actuator coupled to the valve, the valve actuator adapted to receive valve actuator commands and configured, upon receipt of the valve actuator commands, to selectively move the valve to one of the plurality of valve positions.   
     
     
         5 . The turbofan engine intake assembly of  claim 1 , wherein:
 each fan blade includes a leading edge and a trailing edge; and   the slot is disposed between the leading edge and trailing edge of each fan blade.   
     
     
         6 . A turbofan engine system, comprising:
 a nacelle assembly;   an intake section, a compressor section, a combustion section, and a gas turbine section mounted in the nacelle assembly, the intake section comprising:
 a fan case mounted in the nacelle assembly, the fan case including an inner surface and an outer surface; 
 an intake fan mounted within the fan case and including a plurality of radially extending fan blades; 
 a slot extending through the fan case between the inner and outer surfaces, the slot at least partially extending around the fan case proximate the fan blades; and 
 an annulus coupled to the outer surface and including an inner surface that defines an annular plenum, the annular plenum in fluid communication with the slot and atmosphere outside the fan case. 
   
     
     
         7 . The turbofan engine intake assembly of  claim 6 , further comprising:
 a discharge conduit coupled to the annulus and including an inlet port and an outlet port, the inlet port in fluid communication with the annular plenum, the outlet port in fluid communication with the atmosphere outside the fan case.   
     
     
         8 . The turbofan engine system of  claim 7 , further comprising:
 a valve mounted on the discharge conduit and movable to a plurality of valve positions.   
     
     
         9 . The turbofan engine system of  claim 8 , further comprising:
 a valve actuator coupled to the valve, the valve actuator further coupled to receive valve actuator commands and configured, upon receipt of the valve actuator commands, to selectively move the valve to one of the plurality of valve positions.   
     
     
         10 . The turbofan engine system of  claim 8 , further comprising:
 a pump mounted on the conduit and configured to selectively pump air from the annulus.   
     
     
         11 . The turbofan engine system of  claim 6 , further comprising:
 an engine control coupled to, and configured to selectively supply the valve actuator commands to, the valve actuator.   
     
     
         12 . The turbofan engine system of  claim 11 , wherein the engine control is further configured to detect a foreign object ingestion event. 
     
     
         13 . The turbofan engine system of  claim 12 , wherein the engine control is further configured to supply the valve actuator commands upon detecting the foreign object ingestion event. 
     
     
         14 . The turbofan engine system of  claim 6 , wherein:
 each fan blade includes a leading edge and a trailing edge; and   the slot is disposed between the leading edge and trailing edge of each fan blade.   
     
     
         15 . A method of improving engine performance in a turbofan gas turbine engine following foreign object ingestion, the turbofan gas turbine engine comprising an intake fan and a fan case, the intake fan disposed within and surrounded by the fan case and including a plurality of fan blades, the method comprising the steps of:
 detecting when a foreign object has been ingested by the turbofan gas turbine engine; and   upon detecting that a foreign object has been ingested, bleeding air from a region proximate the blades of the intake fan through a slot in the fan case.   
     
     
         16 . The method of  claim 15 , wherein the step of detecting comprises detecting performance degradation of the turbofan gas turbine engine. 
     
     
         17 . The method of  claim 15 , wherein the step of detecting comprises detecting a change in air pressure around the intake fan. 
     
     
         18 . The method of  claim 15 , wherein the step of bleeding air comprises opening a valve that allows air from the region to flow to atmosphere. 
     
     
         19 . The method of  claim 18 , wherein the valve is opened automatically upon detecting that a foreign object has been ingested. 
     
     
         20 . The method of  claim 15 , wherein the step of bleeding air comprises pumping air from the region.