Geared turbofan engine with counter-rotating shafts

Abstract

A mid-turbine frame is incorporated into a turbine section of a gas turbine engine intermediate a high pressure turbine and a low pressure turbine. The high pressure and low pressure turbines rotate in opposite directions. A plurality of vanes redirect the flow downstream of the high pressure turbine as it approaches the low pressure turbine.

1 . A gas turbine engine comprising:
 a fan for delivering air into a low pressure compressor, and into a bypass duct;   a low pressure compressor, a high pressure compressor, a combustion section, a high pressure turbine, and a low pressure turbine;   said high pressure turbine configured to rotate in a first direction about a central axis with said high pressure compressor as a high pressure spool, said low pressure turbine configured to rotate in a second direction, opposed to said first direction, about said central axis with said low pressure compressor as a low pressure spool;   said fan being driven by said low pressure turbine through a speed reduction mechanism, and such that said fan and said low pressure compressor rotate at different speeds;   a mid-turbine frame for said high pressure turbine, said mid-turbine frame including a first bearing supporting said high pressure turbine relative to an outer core housing of the gas turbine engine, said mid-turbine frame including a strut supporting said first bearing at a location intermediate a downstream end of said high pressure turbine and an upstream end of said low pressure turbine; and   a plurality of vanes positioned upstream of a first stage of said low pressure turbine, and said plurality of vanes being separated from said mid-turbine frame.   
     
     
         2 . The engine as set forth in  claim 1 , wherein said high pressure spool is also supported at an upstream end of the high pressure compressor by a second bearing, and supported relative to the outer housing through a second strut in a straddle-mounted arrangement. 
     
     
         3 . The engine as set forth in  claim 1 , having a power density that is greater than or equal to about 1.5 and less than or equal to about 5.5 lbf/cubic inches. 
     
     
         4 . The engine as set forth in  claim 3 , wherein said power density is greater than or equal to about 4.0. 
     
     
         5 . The engine as set forth in  claim 4 , wherein said power density is calculated with a thrust gravity that is sea level take-off, flat-rated static thrust. 
     
     
         6 . The engine as set forth in  claim 1 , said fan having a bypass ratio greater than 6. 
     
     
         7 . The engine as set forth in  claim 1 , wherein said fan rotating in said first direction. 
     
     
         8 . The engine as set forth in  claim 1 , wherein said fan rotating in said second direction. 
     
     
         9 . A gas turbine engine turbine comprising:
 a high pressure turbine configured to rotate with a high pressure compressor as a high pressure spool in a first direction about a central axis;   a low pressure turbine configured to rotate with a low pressure compressor as a low pressure spool in a second direction about said central axis, said high pressure spool operating with gases at a higher pressure than said low pressure spool, and said high pressure spool rotating at a higher speed than said low pressure spool;   a mid-turbine frame for supporting said high pressure turbine, said mid-turbine frame including a first bearing supporting said high pressure turbine, and a strut supporting said first bearing at a location between said high pressure turbine and said low pressure turbine; and   a plurality of vanes associated with a first stage of said low pressure turbine.   
     
     
         10 . The engine as set forth in  claim 9 , wherein said plurality of vanes being incorporated into said mid-turbine frame. 
     
     
         11 . The engine as set forth in  claim 9 , wherein said plurality of vanes are mounted separately from said mid-turbine frame. 
     
     
         12 . The engine as set forth in  claim 9 , wherein a fan is connected to the low pressure spool via a speed changing mechanism. 
     
     
         13 . The engine as set forth in  claim 12 , wherein said fan rotates in said first direction. 
     
     
         14 . The engine as set forth in  claim 12 , wherein said fan rotates in said second direction. 
     
     
         15 . The engine as set forth in  claim 12 , including a power density that is greater than or equal to about 1.5 and less than or equal to about 5.5 lbf/cubic inches. 
     
     
         16 . The engine as set forth in  claim 15 , wherein said power density is greater than or equal to about 4.0. 
     
     
         17 . The engine as set forth in  claim 16 , wherein said power density is calculated with a thrust gravity that is sea level take-off, flat-rated static thrust. 
     
     
         18 . The engine as set forth in  claim 9 , wherein said high pressure spool is also supported at the high pressure compressor by a thrust bearing, and supported relative to the outer housing through a second strut creating a straddle-mounted arrangement of the spool. 
     
     
         19 . The engine as set forth in  claim 9 , wherein a nut secures a plurality of struts from said outer core housing. 
     
     
         20 . The engine as set forth in  claim 9 , wherein said plurality of vanes is configured in a single row.