Turbine section of high bypass turbofan

Abstract

A turbofan engine comprises a fan having fan blades. A compressor is in communication with the fan section. The fan is configured to communicate a portion of air into a bypass path defining a bypass area outwardly of the compressor and a portion into the compressor. A bypass ratio is defined as air communicated through the bypass path relative to air communicated to the compressor being greater than about 6.0. A combustor is in fluid communication with the compressor. A turbine is in communication with the combustor. The turbine has a first turbine section that includes two or more stages and a second turbine section that includes at least two stages. A ratio of airfoils in the first turbine section to the bypass ratio is less than about 170. The first turbine section includes a maximum gas path radius. A ratio of the maximum gas path radius to a maximum radius of the fan blades is less than about 0.50. A speed reduction mechanism is coupled to the fan and rotatable by the turbine.

1 . A turbofan engine comprising:
 a fan having fan blades;   a compressor in communication with the fan section, wherein the fan is configured to communicate a portion of air into a bypass path defining a bypass area outwardly of the compressor and a portion into the compressor and a bypass ratio defined as air communicated through the bypass path relative to air communicated to the compressor is greater than about 6.0;   a combustor in fluid communication with the compressor;   a turbine in communication with the combustor, the turbine having a first turbine section that includes two or more stages and a second turbine section that includes at least two stages, wherein a ratio of airfoils in the first turbine section to the bypass ratio is less than about 170 and the first turbine section includes a maximum gas path radius and a ratio of the maximum gas path radius to a maximum radius of the fan blades is less than about 0.50; and   a speed reduction mechanism coupled to the fan and rotatable by the turbine.   
     
     
         2 . The turbofan engine as recited in  claim 1 , wherein the compressor includes a first compressor section and a second compressor section, wherein the second compressor section operates at a pressure higher than the first compressor section. 
     
     
         3 . The turbofan engine as recited in  claim 2 , wherein the first compressor section includes at least four stages. 
     
     
         4 . The turbofan engine as recited in  claim 3 , wherein the second compressor section includes at least eight stages. 
     
     
         5 . The turbofan engine as recited in  claim 4 , wherein the second turbine section comprises a high pressure turbine and the first turbine section comprises a low pressure turbine that operates at a pressure lower than the high pressure turbine section and the low pressure turbine includes an airfoil count below about 1600. 
     
     
         6 . The turbofan engine as recited in  claim 5 , wherein a hub-to-tip ratio (Ri:Ro) of the low pressure turbine section is between about 0.4 and about 0.5 measured at a maximum Ro axial location within the low pressure turbine. 
     
     
         7 . The turbofan engine as recited in  claim 6 , wherein the low pressure turbine includes more than four stages. 
     
     
         8 . The turbofan engine as recited in  claim 6 , wherein the speed reduction mechanism comprises an epicyclic gearbox. 
     
     
         9 . The turbofan engine as recited in  claim 8 , wherein the epicyclic gearbox provides a speed reduction ratio is between about 2:1 and about 5:1. 
     
     
         10 . The turbofan engine as recited in  claim 1 , wherein there is a third turbine section. 
     
     
         11 . A turbofan engine comprising:
 a fan having fan blades;   a compressor in communication with the fan section wherein the compressor includes a first compressor section including at least two stages and a second compressor section including at least five stages, wherein the second compressor section is configured to operate at a higher pressure than the first compressor section, wherein the fan is configured to communicate a portion of air into a bypass path defining a bypass area outwardly of the compressor and a portion into the compressor and a bypass ratio defined as air communicated through the bypass path relative to air communicated to the compressor is greater than about 6.0;   a combustor in fluid communication with the compressor;   a turbine in communication with the combustor, the turbine having a first turbine section and a second turbine section, wherein a ratio of airfoils in the first turbine section to the bypass ratio is less than about 170 and the first turbine section includes a maximum gas path radius and a ratio of the maximum gas path radius to a maximum radius of the fan blades is less than about 0.50; and   a speed reduction mechanism coupled to the fan and rotatable by the turbine.   
     
     
         12 . The turbofan engine as recited in  claim 11 , wherein the first turbine section includes three or more stages. 
     
     
         13 . The turbofan engine as recited in  claim 12 , wherein the first turbine section includes four or more stages. 
     
     
         14 . The turbofan engine as recited in  claim 13 , wherein the second turbine section comprises a high pressure turbine and the first turbine section comprises a low pressure turbine that operates at a pressure lower than the high pressure turbine section and the low pressure turbine includes an airfoil count below about 1600. 
     
     
         15 . The turbofan engine as recited in  claim 14 , wherein a hub-to-tip ratio (Ri:Ro) of the low pressure turbine section is between about 0.4 and about 0.5 measured at a maximum Ro axial location within the low pressure turbine. 
     
     
         16 . The turbofan engine as recited in  claim 15 , wherein the bypass ratio is greater than about 8.0. 
     
     
         17 . The turbofan engine as recited in  claim 16 , wherein a fan pressure ratio across the fan is less than about 1.45. 
     
     
         18 . The turbofan engine as recited in  claim 17 , wherein the speed reduction mechanism comprises an epicyclic gearbox. 
     
     
         19 . The turbofan engine as recited in  claim 18 , wherein the epicyclic gearbox provides a speed reduction ratio between about 2:1 and about 5:1.