Gas turbine engine with fan tied compressor

Abstract

A turbofan engine according to an example of the present disclosure includes, among other things, a fan including fan blades, an outer housing that surrounds the fan to define a bypass flow path, a compressor section in fluid communication with the fan, the compressor section including a low pressure compressor section and a high pressure compressor section, a turbine section including a fan drive turbine section driving the fan and the low pressure compressor section and a high pressure turbine section driving the high pressure compressor section. A gear reduction including an epicyclic gear train is between the fan drive turbine section and the low pressure compressor section such that the low pressure compressor section and the fan are rotatable at a common speed and such that the fan is rotatable at a lower speed than the fan drive turbine section. The fan drive turbine section has a first exit area at a first exit point and is rotatable at a first speed, the high pressure turbine section has a second exit area at a second exit point and is rotatable at a second speed, which is higher than the first speed. A first performance quantity is defined as a product of the first speed squared and the first area, a second performance quantity is defined as a product of the second speed squared and the second exit area and a performance ratio of the first performance quantity to the second performance quantity is between 0.2 and 0.8.

What is claimed is: 
     
         1 . A turbofan engine comprising:
 a fan including fan blades, an outer housing that surrounds said fan to define a bypass flow path, and a low fan pressure ratio between 1.2 and 1.45 across said fan blades alone at a cruise condition;   a compressor section in fluid communication with said fan, said compressor section including a low pressure compressor section and a high pressure compressor section;   a combustion section in fluid communication with said compressor section;   a turbine section in fluid communication with said combustion section;   wherein said turbine section includes a fan drive turbine section driving said fan and said low pressure compressor section, and includes a high pressure turbine section driving said high pressure compressor section;   a gear reduction including an epicyclic gear train between said fan drive turbine section and said low pressure compressor section, such that said low pressure compressor section and said fan are rotatable at a common speed, and such that said fan is rotatable at a lower speed than said fan drive turbine section;   wherein said fan drive turbine section has a first exit area at a first exit point and is rotatable at a first speed;   wherein said high pressure turbine section has a second exit area at a second exit point and is rotatable at a second speed, which is higher than said first speed;   wherein a first performance quantity is defined as a product of the first speed squared and said first area;   wherein a second performance quantity is defined as a product of the second speed squared and said second exit area; and   wherein a performance ratio of said first performance quantity to said second performance quantity is between 0.2 and 0.8.   
     
     
         2 . The turbofan engine as set forth in  claim 1 , wherein said turbofan engine is a two-spool turbofan engine including a low spool and a high spool, wherein said low spool comprises said low pressure compressor section and said fan drive turbine section, and said high spool comprises said high pressure compressor section and said high pressure turbine section. 
     
     
         3 . The turbofan engine as set forth in  claim 2 , wherein said fan has 26 or fewer blades. 
     
     
         4 . The turbofan engine as set forth in  claim 3 , further comprising a bypass ratio greater than 10 and less than 22 at said cruise condition. 
     
     
         5 . The turbofan engine as set forth in  claim 4 , wherein said high pressure turbine section is a two stage turbine section. 
     
     
         6 . The turbofan engine as set forth in  claim 4 , wherein a gear ratio of said gear reduction is greater than 2.3 and less than 5.0. 
     
     
         7 . The turbofan engine as set forth in  claim 6 , wherein said fan drive turbine section has at least three stages and has up to six stages. 
     
     
         8 . The turbofan engine as set forth in  claim 7 , wherein said low pressure compressor section includes a plurality of stages. 
     
     
         9 . The turbofan engine as set forth in  claim 8 , wherein said performance ratio is less than or equal to 0.5. 
     
     
         10 . The turbofan engine as set forth in  claim 9 , wherein said second speed is greater than twice said first speed and is less than four times said first speed. 
     
     
         11 . The turbofan engine as set forth in  claim 7 , wherein:
 said fan drive turbine section includes an inlet, an outlet and a pressure ratio of greater than 5, and wherein the pressure ratio of said fan drive turbine section is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet.   
     
     
         12 . The turbofan engine as set forth in  claim 11 , wherein said gear reduction is a planetary gear reduction. 
     
     
         13 . The turbofan engine as set forth in  claim 11 , wherein said low spool is rotatable in a first direction, and said high spool is rotatable in a second direction opposed to said first direction. 
     
     
         14 . The turbofan engine as set forth in  claim 13 , wherein said bypass ratio is greater than 13 at said cruise condition, and said gear ratio is greater than 2.5. 
     
     
         15 . The turbofan engine as set forth in  claim 14 , wherein said second speed is less than three times said first speed. 
     
     
         16 . The turbofan engine as set forth in  claim 14 , wherein said performance ratio is less than or equal to 0.5. 
     
     
         17 . The turbofan engine as set forth in  claim 16 , wherein said low pressure compressor section is a three stage compressor section. 
     
     
         18 . The turbofan engine as set forth in  claim 17 , wherein said second speed is between three and four times said first speed. 
     
     
         19 . The turbofan engine as set forth in  claim 18 , wherein:
 a low fan pressure ratio is less than 1.35 across said fan blades alone at said cruise condition; and   a low corrected fan tip speed of each of said fan blades is less than 1150 ft/second at said cruise condition.   
     
     
         20 . The turbofan engine as set forth in  claim 2 , wherein said gear reduction is a planetary gear reduction. 
     
     
         21 . The turbofan engine as set forth in  claim 20 , wherein said fan drive turbine section has at least three stages and has up to six stages. 
     
     
         22 . The turbofan engine as set forth in  claim 21 , wherein said low pressure compressor section includes three stages. 
     
     
         23 . The turbofan engine as set forth in  claim 22 , wherein said fan drive turbine section includes an inlet, an outlet and a pressure ratio of greater than 7.5, and wherein the pressure ratio of said fan drive turbine section is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet. 
     
     
         24 . The turbofan engine as set forth in  claim 23 , wherein said high pressure turbine section is a two stage turbine section. 
     
     
         25 . The turbofan engine as set forth in  claim 24 , further comprising a bypass ratio greater than 10 and less than 22 at said cruise condition. 
     
     
         26 . The turbofan engine as set forth in  claim 25 , wherein said fan has 26 or fewer blades, and said bypass ratio is greater than 13 at said cruise condition. 
     
     
         27 . The turbofan engine as set forth in  claim 26 , wherein a gear ratio of said gear reduction is greater than 2.3 and less than 5.0. 
     
     
         28 . The turbofan engine as set forth in  claim 27 , wherein said second speed is between three and four times said first speed. 
     
     
         29 . The turbofan engine as set forth in  claim 28 , wherein said performance ratio is less than 0.5. 
     
     
         30 . The turbofan engine as set forth in  claim 29 , wherein a low fan pressure ratio is less than 1.35 across said fan blades alone at said cruise condition.