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, and a low spool including a low pressure compressor section and a low pressure turbine. A high spool includes a high pressure compressor section. A gear arrangement is defined along an engine axis. The low spool is operable to drive the fan section through the gear arrangement. A mount system includes an aft mount configured to react at least a portion of a thrust load at an engine case generally parallel to an engine axis.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 a fan section;   a low spool including a low pressure compressor section and a low pressure turbine, said low pressure compressor section including three (3) or more stages, and said low pressure turbine including three to six (3-6) stages;   a high spool including a high pressure compressor section, said high pressure compressor section including eight to thirteen (8-13) stages;   a gear arrangement defined along an engine axis, said low spool operable to drive said fan section through said gear arrangement; and   a mount system including an aft mount configured to react at least a portion of a thrust load at an engine case generally parallel to an engine axis, said engine case defined about said engine axis.   
     
     
         2 . The engine as recited in  claim 1 , wherein said aft mount is attachable to a mid-turbine frame contained at least partially within said engine case. 
     
     
         3 . The engine as recited in  claim 2 , wherein said mid-turbine frame supports at least one bearing. 
     
     
         4 . The engine as recited in  claim 2 , wherein said fan section is configured to deliver a portion of air into said low pressure compressor section, and a portion of air into a bypass duct, and wherein a bypass ratio, which is defined as a volume of air passing to said bypass duct compared to a volume of air passing into said low pressure compressor section, is greater than ten (10). 
     
     
         5 . The engine as recited in  claim 1 , comprising a forward mount located forward of said aft mount relative to said engine axis, said forward mount configured to react at least a vertical load. 
     
     
         6 . The engine as recited in  claim 5 , wherein said forward mount is attachable to an engine intermediate case. 
     
     
         7 . The engine as recited in  claim 5 , wherein said forward mount is configured to react a side load. 
     
     
         8 . The engine as recited in  claim 1 , wherein said low pressure compressor includes between three and four (3-4) stages. 
     
     
         9 . The engine as recited in  claim 8 , wherein said low pressure compressor includes three (3) stages. 
     
     
         10 . The engine as recited in  claim 8 , wherein said high pressure compressor includes eight (8) stages. 
     
     
         11 . The engine as recited in  claim 10 , wherein said low pressure turbine includes three (3) stages, and said low pressure turbine defines a low pressure turbine pressure ratio that is greater than about five (5). 
     
     
         12 . The engine as recited in  claim 8 , wherein a pressure ratio across said fan section is less than about 1.45. 
     
     
         13 . The engine as recited in  claim 1 , wherein said low pressure turbine includes three (3) stages, said high spool includes a high pressure turbine with two (2) stages, said low pressure compressor includes three (3) stages, and said high pressure compressor includes eight (8) stages. 
     
     
         14 . The engine as recited in  claim 13 , wherein said low pressure turbine defines a low pressure turbine pressure ratio that is greater than five (5), and said gear arrangement defines a gear reduction ratio that is greater than about 2.3. 
     
     
         15 . The engine as recited in  claim 1 , wherein said gear arrangement defines a gear reduction ratio that is greater than or equal to about 2.5. 
     
     
         16 . A method of designing a gas turbine engine comprising:
 providing a fan section including a fan;   providing a low spool including a low pressure compressor section and a low pressure turbine, said low pressure compressor section including three (3) or more stages, and said low pressure turbine including three to six (3-6) stages;   providing a high spool including a high pressure compressor section and a high pressure turbine, said high pressure compressor section including thirteen (13) or fewer stages;   providing a gear arrangement defined along an engine axis, said low spool operable to drive said fan section through said gear arrangement; and   providing a mount system including an aft mount located aft of said high pressure turbine relative to said engine axis, said aft mount configured to react at least a portion of a thrust load at an engine case generally parallel to said engine axis.   
     
     
         17 . The method as recited in  claim 16 , wherein said aft mount is attachable to a mid-turbine frame contained at least partially within said engine case, said mid-turbine frame supporting at least one bearing. 
     
     
         18 . The method as recited in  claim 17 , wherein said at least one bearing includes a first bearing and a second bearing. 
     
     
         19 . The method as recited in  claim 16 , comprising providing a forward mount located forward of said aft mount relative to said engine axis, wherein said forward mount is configured to react at least one of a vertical load and a side load, and said forward mount is attachable to an engine intermediate case. 
     
     
         20 . The method as recited in  claim 19 , wherein said low pressure turbine defines a low pressure turbine pressure ratio that is greater than five (5), and said gear arrangement defines a gear reduction ratio that is greater than or equal to about 2.5.