Geared turbofan with three turbines with first two counter-rotating, and third co-rotating with the second turbine

Abstract

A gas turbine engine has a fan rotor, a first compressor rotor and a second compressor rotor. The second compressor rotor compresses air to a higher pressure than the first compressor rotor. A first turbine rotor drives the second compressor rotor and a second turbine rotor. The second turbine drives the compressor rotor. A fan drive turbine is positioned downstream of the second turbine rotor. The fan drive turbine drives the fan through a gear reduction. The first compressor rotor and second turbine rotor rotate as an intermediate speed spool. The second compressor rotor and first turbine rotor together as a high speed spool, with the high speed spool rotating in an opposed direction to the intermediate speed spool. The fan drive turbine rotates in the same direction as the intermediate speed spool.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 a fan rotor, a first compressor rotor and a second compressor rotor, said second compressor rotor compressing air to a higher pressure than said first compressor rotor;   a first turbine rotor, said first turbine rotor driving said second compressor rotor, and a second turbine rotor, said second turbine driving said first compressor rotor;   a fan drive turbine positioned downstream of said second turbine rotor, said fan drive turbine driving said fan through a gear reduction; and   said first compressor rotor and said second turbine rotor rotating as an intermediate speed spool, and said second compressor rotor and said first turbine rotor rotating together as a high speed spool, with said high speed spool rotating in an opposed direction to said intermediate speed spool, and said fan drive turbine rotating in the same direction as said intermediate speed spool.   
     
     
         2 . The engine as set forth in  claim 1 , wherein said fan rotor is driven by said gear reduction to rotate in the same direction as said high speed spool. 
     
     
         3 . The engine as set forth in  claim 1 , wherein a power density of the engine is greater than or equal to about 1.5 lbs/in 3 , and less than or equal to about 5.5 lbf/in 3 . 
     
     
         4 . The engine as set forth in  claim 3 , wherein said power density is defined as a ratio of thrust produced by said engine expressed in pounds force to a volume of a turbine section incorporating each of said first turbine rotor, said second turbine rotor and said fan drive turbine rotor, expressed in cubic inches. 
     
     
         5 . The engine as set forth in  claim 4 , wherein said ratio is greater than or equal to 2.0. 
     
     
         6 . The engine as set forth in  claim 5 , wherein said ratio is greater than or equal to about 4.0. 
     
     
         7 . The engine as set forth in  claim 6 , wherein said thrust is sea level take-off flat-rated static thrust. 
     
     
         8 . The engine as set forth in  claim 7 , wherein said fan delivering a portion of air into a bypass duct and a portion of air into said first compressor rotor as core flow. 
     
     
         9 . The engine as set forth in  claim 8 , wherein a mid-turbine frame is positioned between said first and second turbine rotors. 
     
     
         10 . The engine as set forth in  claim 9 , wherein a turning vane is positioned between said mid-turbine frame and said second turbine rotor. 
     
     
         11 . The engine as set forth in  claim 10 , wherein a vane is positioned between said second turbine rotor and said fan drive turbine. 
     
     
         12 . The engine as set forth in  claim 8 , wherein a vane is positioned between said second turbine rotor and said fan drive turbine. 
     
     
         13 . The engine as set forth in  claim 1 , wherein a mid-turbine frame is positioned between said first and second turbine rotors. 
     
     
         14 . The engine as set forth in  claim 13 , wherein a turning vane is positioned between said mid-turbine frame and said second turbine rotor. 
     
     
         15 . The engine as set forth in  claim 14 , wherein a vane is positioned between said second turbine rotor and said fan drive turbine. 
     
     
         16 . The engine as set forth in  claim 1 , wherein a vane is positioned between said second turbine rotor and said fan drive turbine. 
     
     
         17 . A gas turbine engine comprising:
 a fan rotor, a first compressor rotor and a second compressor rotor, said second compressor rotor compressing air to a higher pressure than said first compressor rotor;   a first turbine rotor, said first turbine rotor driving said second compressor rotor, and a second turbine rotor, said second turbine driving said first compressor rotor;   a fan drive turbine positioned downstream of said second turbine rotor, said fan drive turbine driving said fan through a gear reduction;   said first compressor rotor and said second turbine rotor rotating as an intermediate speed spool, and said second compressor rotor and said first turbine rotor rotating together as a high speed spool, with said high speed spool rotating in an opposed direction to said intermediate speed spool, and said fan drive turbine rotating in the same direction as said intermediate speed spool;   said fan rotor being driven by said speed reduction to rotate in the same direction as said high speed spool;   a power density of the engine being greater than or equal to about 1.5 lbf/in 3 , and less than or equal to about 5.5 lbf/in 3 ; and   said power density defined as a ratio of thrust produced by said engine expressed in pounds force to a volume of a turbine section incorporating each of said first turbine rotor, said second turbine rotor and said fan driving turbine rotor, expressed in cubic inches.   
     
     
         18 . The engine as set forth in  claim 17 , wherein said ratio is greater than or equal to 2.0. 
     
     
         19 . The engine as set forth in  claim 18 , wherein said ratio is greater than or equal to about 4.0. 
     
     
         20 . The engine as set forth in  claim 19 , wherein said thrust is sea level take-off flat-rated static thrust.