Geared turbofan gas turbine engine with reliability check on gear connection

Abstract

A gas turbine engine includes a fan and a compressor. A combustor drives a turbine, including a first turbine with a shaft to drive the compressor. A fan drive turbine drives the fan through a speed reduction. A sensor senses a speed of rotation of the fan and communicates sensed speed information to a control. The control develops an expected speed for the fan. A problem is identified should the sensed speed be less than the expected speed by more than a predetermined amount. A method is also described.

1 . A gas turbine engine comprising:
 a fan;   a compressor section having at least one rotor;   a combustor;   a turbine system, including a first turbine including a shaft to drive said least one rotor, and at least a fan drive turbine, said fan drive turbine being operable to drive said fan through a speed reduction; and   a sensor to sense a speed of rotation of said fan and communicate said sensed speed to a control, said control being operable to develop an expected speed for said fan and identify a problem should said sensed speed be less than the expected speed by more than a predetermined amount, said predetermined amount being intended to identify a failure in at least one of gears, a connection and a shaft in said speed reduction, or a shaft driven by said gears and in turn driving said fan.   
     
     
         2 . The gas turbine engine as set forth in  claim 1 , wherein said sensor dynamically determining an angular position of a feature rotating with the fan by measuring the time of arrival of the feature, and this dynamically determined angular position being utilized as the sensed speed, and compared to an expected angular position of the fan feature, said expected angular position being said expected speed. 
     
     
         3 . The gas turbine engine as set forth in  claim 1 , wherein a sensor is associated with said fan drive turbine to sense the angular position of a feature on said fan drive turbine, and the sensed angular position of said fan drive turbine feature being utilized to determine said expected speed of said fan. 
     
     
         4 . The gas turbine engine as set forth in  claim 1 , wherein the expected speed of said fan is calculated based upon engine variables. 
     
     
         5 . The gas turbine engine as set forth in  claim 1 , wherein said engine is shut down should said sensed speed of said fan differ from said expected speed by more than a predetermined amount. 
     
     
         6 . The gas turbine engine as set forth in  claim 1 , wherein said control looks for progressive increase in the difference between the sensed speed and the expected speed. 
     
     
         7 . The gas turbine engine as set forth in  claim 1 , wherein an intermediate turbine is positioned between said first and fan drive turbines, and said intermediate turbine drives a compressor stage. 
     
     
         8 . The gas turbine engine as set forth in  claim 1 , wherein said speed reduction includes at least one of a flexible coupling and a spline connection to drive said fan. 
     
     
         9 . The gas turbine engine as set forth in  claim 8 , wherein said speed reduction directly drives said fan, through a fan shaft. 
     
     
         10 - 12 . (canceled) 
     
     
         13 . A method of operating a gas turbine engine comprising:
 a turbine system having a first turbine including a shaft driving a high pressure compressor, and at least a fan drive turbine driving a fan through a speed reduction; and   sensing a speed of rotation of said fan and comparing a sensed speed to an expected speed for said fan and identifying a problem should said sensed speed of said fan be less than the expected speed by more than a predetermined amount, said predetermined amount being intended to identify a failure in at least one of gears, a connection and a shaft in said speed reduction, or a shaft driven by said gears and in turn driving said fan.   
     
     
         14 . The method as set forth in  claim 13 , wherein said sensed speed of rotation of said fan is sensed by dynamically determining an angular position of a feature rotating with the fan by measuring the time of arrival of the feature, and this dynamically determined angular position being utilized as the sensed speed, and compared to an expected angular position of the fan feature, the expected angular position being said expected speed. 
     
     
         15 . The method as set forth in  claim 14 , wherein sensing the angular position of a feature rotating with said fan drive turbine, and said sensed angular position of said feature on said fan drive turbine being utilized to determine said expected angular position of said feature rotating with said fan. 
     
     
         16 . (canceled) 
     
     
         17 . The method as set forth in  claim 13 , wherein if a progressive increase in the difference between the sensed speed and the expected speed is determined, a problem is identified. 
     
     
         18 . The method as set forth in  claim 13 , wherein said fan drive turbine drives said fan, and an intermediate turbine is positioned between said first and fan drive turbines, and said intermediate turbine drives an intermediate compressor. 
     
     
         19 . The method as set forth in  claim 13 , wherein said speed reduction includes at least one of a flexible coupling and a spline connection to drive said fan through said speed reduction. 
     
     
         20 . The method as set forth in  claim 19 , wherein said speed reduction directly drives said fan through a fan shaft. 
     
     
         21 . The method as set forth in  claim 1 , wherein said connection is a spline and the shaft is flexible. 
     
     
         22 . The gas turbine engine as set forth in claim  10 , wherein said predetermined amount being intended to identify a failure in at least one of gears, a spline connection and a flexible shaft in said speed reduction, or a shaft driven by said gears and in turn driving said fan. 
     
     
         23 . (canceled) 
     
     
         24 . A gas turbine engine comprising:
 a fan;   a compressor section having a first and second rotor;   a combustor;   a turbine system, including:
 a first turbine including a shaft to drive said second rotor, 
 at least a fan drive turbine, said fan drive turbine being operable to drive said fan through a speed reduction; and 
 an intermediate turbine between said first turbine and said fan drive turbine, with 
   said intermediate turbine driving said first rotor; and   a sensor to sense a speed of rotation of said fan and communicate said sensed speed to a control, said control being operable to develop an expected speed for said fan and to identify a problem should said sensed speed be less than the expected speed by more than a predetermined amount, said predetermined amount being intended to identify a failure in at least one of:
 gears, 
 a connection and a shaft in said speed reduction, said connection including at least one of a flexible coupling and a spline connection to drive said fan, said predetermined amount also identifying a failure in said at least one of a flexible coupling and an end said spline connection; or 
 a shaft driven by said gears and in turn driving said fan. 
   
     
     
         25 . The gas turbine engine as set forth in  claim 24 , wherein said sensor dynamically determining an angular position of a feature rotating with the fan by measuring the time of arrival of the feature, and this dynamically determined angular position being utilized as the sensed speed, and compared to an expected angular position of the fan feature, said expected angular position being said expected speed. 
     
     
         26 . The gas turbine engine as set forth in  claim 24 , wherein a sensor is associated with said fan drive turbine to sense the angular position of a feature on said fan drive turbine, and the sensed angular position of said fan drive turbine feature being utilized to determine said expected speed of said fan. 
     
     
         27 . The gas turbine engine as set forth in  claim 24 , wherein said engine is shut down should said sensed speed of said fan differ from said expected speed by more than a predetermined amount. 
     
     
         28 . The gas turbine engine as set forth in  claim 24 , wherein said control looks for progressive increase in the difference between the sensed speed and the expected speed. 
     
     
         29 . The gas turbine engine as set forth in  claim 24 , wherein said speed reduction directly drives said fan, through a fan shaft. 
     
     
         30 . The A method of operating a gas turbine engine comprising:
 providing a turbine system having:
 a first turbine including a shaft driving a high pressure compressor, 
 at least a fan drive turbine driving a fan through a speed reduction; and 
 an intermediate turbine, with said intermediate turbine driving a low pressure compressor; 
   sensing a speed of rotation of said fan and comparing a sensed speed to an expected speed for said fan;   
       identifying a problem should said sensed speed of said fan be less than the expected speed by more than a predetermined amount, said predetermined amount being intended to identify a failure in at least one of:
   gears,   a connection and a shaft in said speed reduction, said connection including at least one of a flexible coupling and a spline connection to drive said fan, said predetermined amount also identifying a failure in said at least one of a flexible coupling and an end said spline connection; or   a shaft driven by said gears and in turn driving said fan.