Gas turbine engine with low stage count low pressure turbine

Abstract

A gas turbine engine according to an example of the present disclosure includes, among other things, a fan section, a low spool that includes a low pressure compressor section, the low pressure compressor section including three (3) or more stages, and a high spool including a high pressure compressor section. The high pressure compressor section includes between eight to thirteen (8-13) stages. A gear train is defined along an engine axis. The low spool is operable to drive the fan section through the gear train.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 a fan section;   a low spool that includes a low pressure compressor section, said low pressure compressor section includes three (3) or more stages;   a high spool that includes a high pressure compressor section, said high pressure compressor section including between eight to thirteen (8-13) stages; and   a gear train defined along an engine axis, said low spool operable to drive said fan section through said gear train.   
     
     
         2 . The engine as recited in  claim 1 , wherein said low pressure compressor includes three (3) stages. 
     
     
         3 . The engine as recited in  claim 1 , wherein said low pressure compressor includes four (4) stages. 
     
     
         4 . The engine as recited in  claim 1 , wherein said high pressure compressor includes eight (8) stages. 
     
     
         5 . The engine as recited in  claim 1 , wherein said low spool includes a low pressure turbine with three to six (3-6) stages. 
     
     
         6 . The engine as recited in  claim 5 , wherein said low pressure turbine defines a low pressure turbine pressure ratio that is greater than about five (5). 
     
     
         7 . The engine as recited in  claim 1 , wherein said low spool includes a low pressure turbine with three to six (3-6) stages, and said low pressure turbine defines a low pressure turbine pressure ratio that is greater than five (5), said low pressure compressor includes three (3) or four (4) stages. 
     
     
         8 . The engine as recited in  claim 7 , wherein said gear train defines a gear reduction ratio of greater than about 2.3. 
     
     
         9 . The engine as recited in  claim 1 , wherein said gear train defines a gear reduction ratio of greater than 2.3. 
     
     
         10 . The engine as recited in  claim 1 , wherein said gear train defines a gear reduction ratio of greater than or equal to about 2.5. 
     
     
         11 . The engine as recited in  claim 1 , wherein said gear train defines a gear reduction ratio of greater than or equal to 2.5. 
     
     
         12 . The engine as recited in  claim 1 , wherein said low spool includes a first turbine section configured to drive said gear train, said first turbine section being one of three turbine rotors, while a second turbine section and another one of said turbine rotors each drives a compressor section. 
     
     
         13 . The engine as recited in  claim 12 , wherein said first turbine section drives a compressor section. 
     
     
         14 . The engine as recited in  claim 13 , wherein said gear train is positioned intermediate said compressor section driven by said first turbine section and said fan section. 
     
     
         15 . The engine as recited in  claim 13 , wherein said gear train is positioned intermediate said first turbine section and said compressor section driven by said first turbine section. 
     
     
         16 . The gas turbine engine as set forth in  claim 1 , further comprising a fan variable area nozzle to vary a fan nozzle exit area and adjust a pressure ratio of a fan bypass airflow of said fan section during engine operation. 
     
     
         17 . The engine as recited in  claim 16 , wherein said fan bypass airflow defines a bypass ratio greater than about six (6). 
     
     
         18 . The engine as recited in  claim 16 , wherein said fan bypass airflow defines a bypass ratio greater than ten (10). 
     
     
         19 . The engine as recited in  claim 16 , further comprising:
 a controller operable to control said fan variable area nozzle to vary a fan nozzle exit area and adjust the pressure ratio of the fan bypass airflow to reduce a fan instability.   
     
     
         20 . A gas turbine engine comprising:
 a gear train defined along an engine axis, said gear train defines a gear reduction ratio of greater than about 2.3; and   a spool along said engine axis which drives said gear train, said spool includes a low pressure turbine with three to six (3-6) stages and a low pressure compressor with between three (3) and four (4) stages.   
     
     
         21 . The engine as recited in  claim 20 , wherein said low pressure turbine defines a low pressure turbine pressure ratio that is greater than five (5). 
     
     
         22 . The engine as recited in  claim 20 , wherein said gear train drives a fan section to generate a fan bypass airflow having a bypass ratio greater than ten (10). 
     
     
         23 . The engine as recited in  claim 20 , wherein said gear train defines a gear reduction ratio of greater than or equal to 2.5. 
     
     
         24 . The engine as recited in  claim 20 , wherein said low pressure turbine defines a low pressure turbine pressure ratio that is greater than five (5), said gear train defines a gear reduction ratio of greater than or equal to 2.5 to drive a fan section and generate a fan bypass airflow having a bypass ratio greater than ten (10).