Geared turbofan gas turbine engine architecture

Abstract

A gas turbine engine includes a very high speed low pressure turbine such that a quantity defined by the exit area of the low pressure turbine multiplied by the square of the low pressure turbine rotational speed compared to the same parameters for the high pressure turbine is at a ratio between about 0.5 and about 1.5.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 a fan section including less than 18 fan blades, with a low fan pressure ratio of less than about 1.45, the low fan pressure ratio measured across the fan blades alone;   a bypass ratio greater than 10;   a gear train having a gear ratio greater than about 2.3;   a compressor section;   a combustor in fluid communication with the compressor section;   a turbine section in fluid communication with the combustor and including a fan drive turbine and a second turbine, the fan drive turbine driving a fan rotor through the gear train wherein:
 the engine includes a power density greater than 4.0 lbf/in3 wherein power density is defined as Sea Level Takeoff Thrust in lbf produced divided by a volume of the turbine section in cubic inches; 
 the fan drive turbine includes at least one rotor having a live rim radius (r) and a bore width (W), and a ratio of W/r is between 4.65 and 5.55; 
 the fan drive turbine includes an inlet, an outlet, and a fan drive turbine pressure ratio greater than 5, wherein the fan drive turbine pressure ratio is a ratio of a pressure measured prior to the inlet as related to a pressure at the outlet prior to any exhaust nozzle; 
 the fan drive turbine has a first exit area and is configured to rotate at a first speed, the second turbine has a second exit area and is configured to rotate at a second speed, which is faster than the first speed, wherein a first performance quantity is defined as the product of the first speed squared and the first area, a second performance quantity is defined as the product of the second speed squared and the second area, and a performance ratio of the first performance quantity to the second performance quantity is between 0.5 and 1.5; and 
 the fan drive turbine has a number of fan drive turbine stages, and a ratio between a number of the fan blades and the number of fan drive turbine stages is between 2.5 and 8.5. 
   
     
     
         2 . The gas turbine engine set forth in  claim 1 , wherein the performance ratio is greater than or equal to 0.8. 
     
     
         3 . The gas turbine engine set forth in  claim 2 , wherein the power density is less than or equal to 5.5 lbf/in3. 
     
     
         4 . The gas turbine engine set forth in  claim 3 , wherein the second turbine is a one stage turbine, and the gear train is a planetary gear system. 
     
     
         5 . The gas turbine engine set forth in  claim 2 , wherein the power density is less than or equal to 5.5 lbf/in3, and the performance ratio is greater than or equal to 1.0. 
     
     
         6 . The gas turbine engine set forth in  claim 1 , wherein the second turbine is a two stage turbine. 
     
     
         7 . The gas turbine engine set forth in  claim 6 , wherein the fan section has a low corrected fan tip speed less than 1150 ft/sec, wherein the low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]̂0.5. 
     
     
         8 . The gas turbine engine set forth in  claim 7 , wherein the gear train is a planetary gear system. 
     
     
         9 . The gas turbine engine set forth in  claim 8 , further comprising a mid-turbine frame between the fan drive turbine and the second turbine, the mid-turbine frame supporting at least one bearing assembly and including at least one vane. 
     
     
         10 . The gas turbine engine set forth in  claim 8 , wherein the at least one rotor having a bore radius (R), and a ratio of r/R is between 2.00 and 2.30. 
     
     
         11 . A gas turbine engine comprising:
 a fan section including a plurality of fan blades and with a low fan pressure ratio of less than about 1.45, the low fan pressure ratio measured across the fan blades alone;   a bypass ratio greater than 10;   a gear train having a gear ratio greater than about 2.3;   a compressor section;   a combustor in fluid communication with the compressor section;   a turbine section in fluid communication with the combustor and including a fan drive turbine and a second turbine, the fan drive turbine driving a fan rotor through the gear train wherein:
 the engine includes a power density greater than 4.0 lbf/in3 wherein power density is defined as Sea Level Takeoff Thrust in lbf produced divided by a volume of the turbine section in cubic inches; 
 the fan drive turbine includes at least one rotor having a live rim radius (r) and a bore width (W), and a ratio of W/r is between 4.65 and 5.55; 
 the fan drive turbine includes an inlet, an outlet, and a fan drive turbine pressure ratio greater than 5, wherein the fan drive turbine pressure ratio is a ratio of a pressure measured prior to the inlet as related to a pressure at the outlet prior to any exhaust nozzle; 
 the fan drive turbine has a first exit area and is configured to rotate at a first speed, the second turbine has a second exit area and is configured to rotate at a second speed, which is faster than the first speed, wherein a first performance quantity is defined as the product of the first speed squared and the first area, a second performance quantity is defined as the product of the second speed squared and the second area, and a performance ratio of the first performance quantity to the second performance quantity is between 0.5 and 1.5; and 
 the fan drive turbine has a number of fan drive turbine stages, and a ratio between a number of the fan blades and the number of fan drive turbine stages is between 2.5 and 8.5. 
   
     
     
         12 . The gas turbine engine set forth in  claim 11 , wherein the second turbine is a one stage turbine, and the gear train is a planetary gear system. 
     
     
         13 . The gas turbine engine set forth in  claim 12 , wherein the fan section has a low corrected fan tip speed less than 1150 ft/sec, wherein the low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]̂0.5. 
     
     
         14 . The gas turbine engine set forth in  claim 13 , wherein the plurality of fan blades is less than 18 fan blades. 
     
     
         15 . The gas turbine engine set forth in  claim 14 , wherein the performance ratio is greater than or equal to 0.8. 
     
     
         16 . The gas turbine engine set forth in  claim 11 , wherein the gear train is a planetary gear system, and the second turbine is a two stage turbine. 
     
     
         17 . The gas turbine engine set forth in  claim 16 , wherein the fan section has a low corrected fan tip speed less than 1150 ft/sec, wherein the low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]̂0.5. 
     
     
         18 . The gas turbine engine set forth in  claim 17 , wherein the performance ratio is greater than or equal to 0.8. 
     
     
         19 . The gas turbine engine set forth in  claim 18 , wherein the power density is less than 5.5 lbf/in3. 
     
     
         20 . The gas turbine engine set forth in  claim 11 , wherein the at least one rotor having a bore radius (R), and a ratio of r/R is between 2.00 and 2.30. 
     
     
         21 . The gas turbine engine set forth in  claim 20 , wherein the power density is less than 5.5 lbf/in3. 
     
     
         22 . A gas turbine engine comprising:
 a fan section including a plurality of fan blades;   a gear train having a gear ratio greater than about 2.3;   a compressor section;   a combustor in fluid communication with the compressor section;   a turbine section in fluid communication with the combustor and including a fan drive turbine and a second turbine, the fan drive turbine driving a fan rotor through the gear train wherein:
 the engine includes a power density greater than 4.0 lbf/in3 wherein power density is defined as Sea Level Takeoff Thrust in lbf produced divided by a volume of the turbine section in cubic inches; 
 the fan drive turbine has a first exit area and is configured to rotate at a first speed, the second turbine has a second exit area and is configured to rotate at a second speed, which is faster than the first speed, wherein a first performance quantity is defined as the product of the first speed squared and the first area, a second performance quantity is defined as the product of the second speed squared and the second area, and a performance ratio of the first performance quantity to the second performance quantity is between 0.5 and 1.5; and 
 the fan drive turbine has a number of fan drive turbine stages, and a ratio between a number of the fan blades and the number of fan drive turbine stages is between 2.5 and 8.5. 
   
     
     
         23 . The gas turbine engine set forth in  claim 22 , wherein the plurality of fan blades is less than 18 fan blades, and the second turbine is a one stage turbine. 
     
     
         24 . The gas turbine engine set forth in  claim 22 , wherein the plurality of fan blades is less than 18 fan blades, and the second turbine is a two stage turbine. 
     
     
         25 . The gas turbine engine set forth in  claim 22 , wherein the fan section is configured to include a low fan pressure ratio of less than 1.45 at cruise at 0.8 Mach and 35,000 feet, the low fan pressure ratio measured across the fan blades alone. 
     
     
         26 . The gas turbine engine set forth in  claim 25 , further comprising a bypass ratio greater than 10 at cruise at 0.8 Mach and 35,000 feet. 
     
     
         27 . The gas turbine engine set forth in  claim 26 , wherein the fan drive turbine includes an inlet, an outlet, and a fan drive turbine pressure ratio greater than 5, wherein the fan drive turbine pressure ratio is a ratio of a pressure measured prior to the inlet as related to a pressure at the outlet prior to any exhaust nozzle. 
     
     
         28 . The gas turbine engine set forth in  claim 27 , wherein the plurality of fan blades is less than 18 fan blades. 
     
     
         29 . The gas turbine engine set forth in  claim 27 , wherein the fan section has a low corrected fan tip speed less than 1150 ft/sec, wherein the low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]̂0.5. 
     
     
         30 . The gas turbine engine set forth in  claim 27 , wherein the performance ratio is greater than or equal to 0.8, and the fan drive turbine includes at least one rotor having a bore radius (R) and a live rim radius (r), and a ratio of r/R is between 2.00 and 2.30.