Flutter sensing and control system for a gas turbine engine

Abstract

A gas turbine engine system includes a nacelle, a fan casing within the nacelle, a variable area fan nozzle, a sensor and a controller. The sensor detects an airfoil flutter condition. The controller communicates with the sensor and is operable to move the variable area fan nozzle to influence a discharge airflow area in response to the detection of the airfoil flutter condition.

1 . A gas turbine engine system, comprising:
 a nacelle;   a fan casing within the nacelle;   a variable area fan nozzle;   a sensor which detects an airfoil flutter condition; and   a controller that communicates with said sensor, wherein said controller is operable to move said variable area fan nozzle to influence a discharge airflow area associated with said variable area fan nozzle in response to the detection of said airfoil flutter condition.   
   
   
       2 . The system as recited in  claim 1 , wherein said sensor is mounted to said fan casing adjacent to a blade tip area of a fan section. 
   
   
       3 . The system as recited in  claim 1 , wherein said airfoil flutter condition comprises self-induced oscillations simultaneously experienced by adjacent airfoils of the gas turbine engine system. 
   
   
       4 . The system as recited in  claim 3 , wherein said adjacent airfoils are circumferentially disposed about a fan section of the gas turbine engine system. 
   
   
       5 . The system as recited in  claim 1 , wherein said controller influences said discharge airflow area by moving said variable area fan nozzle between a first position having a first discharge airflow area and a second position having a second discharge airflow area greater than said first discharge airflow area in response to detection of said airfoil flutter condition. 
   
   
       6 . The system as recited in  claim 1 , wherein said discharge airflow area extends between said variable area fan nozzle and a core engine casing. 
   
   
       7 . A gas turbine engine, comprising:
 a nacelle;   a fan casing within the nacelle;   a variable area fan nozzle moveable to influence a discharge airflow area associated with said variable area fan nozzle;   a fan section within said fan casing;   a compressor section and a turbine section positioned downstream of said fan section;   a combustor section positioned between said compressor section and said turbine section;   a sensor which detects an airfoil flutter condition; and   a controller that communicates with said sensor, wherein said controller is operable to move said variable area fan nozzle in response to the detection of said airfoil flutter condition.   
   
   
       8 . The gas turbine engine as recited in  claim 7 , wherein said variable area fan nozzle includes at least one flap assembly, said at least one flap assembly moveable between a first position having a first discharge airflow area and a second position having a second discharge airflow area greater than said first discharge airflow area. 
   
   
       9 . The gas turbine engine as recited in  claim 8 , comprising an actuator assembly in communication with said controller and operable to move said at least one flap assembly between said first position and said second position. 
   
   
       10 . The gas turbine engine as recited in  claim 7 , wherein said sensor is mounted to said fan casing adjacent to a blade tip area of said fan section. 
   
   
       11 . The gas turbine engine as recited in  claim 10 , wherein said fan section includes a plurality of airfoils circumferentially disposed about said fan section. 
   
   
       12 . The gas turbine engine as recited in  claim 7 , wherein the gas turbine engine is a geared turbofan engine. 
   
   
       13 . The gas turbine engine system as recited in  7 , wherein said airfoil flutter condition comprises self-induced oscillations simultaneously experienced by adjacent airfoils of said fan section. 
   
   
       14 . The gas turbine engine system as recited in  7 , wherein said discharge airflow area extends between said variable area fan nozzle and a core engine casing. 
   
   
       15 . A method for controlling a gas turbine engine, comprising the steps of:
 (a) sensing a flutter condition; and   (b) influencing a discharge airflow area associated with a variable area fan nozzle in response to sensing the flutter condition.   
   
   
       16 . The method as recited in  claim 15 , wherein the flutter condition comprises self-induced oscillations simultaneously experienced by adjacent airfoils of the gas turbine engine. 
   
   
       17 . The method as recited in  claim 15 , wherein said step (a) comprises:
 mounting a sensor to a fan section of the gas turbine engine for sensing the flutter condition.   
   
   
       18 . The method as recited in  claim 15 , wherein the variable area fan nozzle is moveable between a first position having a first discharge airflow area and a second position having a second discharge airflow area greater than the first discharge airflow area, wherein said step (b) comprises:
 influencing the discharge airflow area by moving the variable area fan nozzle from the first position to the second position in response to sensing the flutter condition.   
   
   
       19 . The method as recited in  claim 18 , further comprising the step of:
 (c) returning the variable area fan nozzle to the first position in response to sensing that the flutter condition has ceased.