A fan drive gear system for driving a fan in a gas turbine engine having a high bypass ratio

Abstract

A gas turbine engine includes a fan section that includes a fan rotatable about an axis of rotation of the gas turbine engine. A speed reduction device is connected to the fan. The speed reduction device includes a star drive gear system with a star gear ratio of at least 1.5. A bypass ratio is greater than about 11.0.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 a fan section including a fan rotatable about an axis of rotation of the gas turbine engine; and   a speed reduction device connected to the fan, wherein the speed reduction device includes a star drive gear system with a star gear ratio of at least 1.5, wherein a bypass ratio is greater than about 11.0.   
     
     
         2 . The gas turbine engine of  claim 1 , wherein the speed reduction device includes a star gear system gear ratio of at least 2.6. 
     
     
         3 . The gas turbine engine of  claim 2 , wherein the speed reduction device includes a system gear ratio less than or equal to 4.1. 
     
     
         4 . The gas turbine engine of  claim 3 , including the bypass ratio is less than about 22.0. 
     
     
         5 . The gas turbine engine of  claim 4 , wherein the fan blade tip speed of the fan section is greater than about 1000 ft/sec and less than about 1400 ft/sec. 
     
     
         6 . The gas turbine engine of  claim 1 , wherein the star system includes a sun gear, a plurality of star gears, a ring gear, and a carrier. 
     
     
         7 . The gas turbine engine of  claim 6 , wherein each of the plurality of star gears includes at least one bearing. 
     
     
         8 . The gas turbine engine of  claim 7 , wherein the carrier is fixed from rotation. 
     
     
         9 . The gas turbine engine of  claim 8 , wherein a low pressure turbine is mechanically attached to the sun gear. 
     
     
         10 . The gas turbine engine of  claim 9 , wherein a fan section is mechanically attached to the ring gear. 
     
     
         11 . The gas turbine engine of  claim 1 , wherein an input of the speed reduction device is rotatable in a first direction and an output of the speed reduction device is rotatable in a second direction opposite to the first direction. 
     
     
         12 . The gas turbine engine of  claim 11 , including a low pressure turbine section in communication with the speed reduction device, wherein the low pressure turbine section includes at least three stages. 
     
     
         13 . The gas turbine engine as recited in  claim 1 , further comprising a low pressure turbine which is one of three turbine rotors, and the low pressure turbine drives the fan section and the other two of the three turbine rotors each drive a compressor section. 
     
     
         14 . The gas turbine engine as recited in  claim 1 , further comprising a high pressure turbine, with each of a low pressure turbine and the high pressure turbine driving a compressor rotor. 
     
     
         15 . The gas turbine engine as recited in  claim 14 , wherein the speed reduction device is positioned intermediate a compressor rotor driven by the low pressure turbine and the fan section. 
     
     
         16 . The gas turbine engine as recited in  claim 14 , wherein the speed reduction device is positioned intermediate the low pressure turbine and the compressor rotor driven by the low pressure turbine. 
     
     
         17 . A fan drive gear module for a gas turbine engine comprising:
 a star drive gear system with a speed reduction ratio of at least 1.5, wherein the star drive gear system for driving a gas turbine engine with a bypass ratio greater than about 11.0.   
     
     
         18 . The fan drive gear module of  claim 17 , wherein the speed reduction ratio is greater than about 2.6 and less than or equal to 4.1. 
     
     
         19 . The fan drive gear module of  claim 17 , wherein the star drive gear system is configured to drive a fan section with a fan blade tip speed greater than about 1000 ft/sec and less than about 1400 ft/sec. 
     
     
         20 . The fan drive gear module of  claim 17 , wherein the bypass ratio is less than about 22.0. 
     
     
         21 . The fan drive gear module as recited in  claim 17 , further comprising a low pressure turbine which is one of three turbine rotors, and the low pressure turbine drives a fan section and the other two of the three turbine rotors each drive a compressor section. 
     
     
         22 . The fan drive gear module as recited in  claim 17 , further comprising a high pressure turbine, with each of a low pressure turbine and the high pressure turbine driving a compressor rotor. 
     
     
         23 . The fan drive gear module as recited in  claim 22 , wherein the speed reduction device is positioned intermediate a compressor rotor driven by the low pressure turbine and a fan section. 
     
     
         24 . The fan drive gear module as recited in  claim 22 , wherein the speed reduction device is positioned intermediate the low pressure turbine and the compressor rotor driven by the low pressure turbine.