Low noise turbine for geared turbofan engine

Abstract

A turbine module according to an example of the present disclosure includes, among other things, a fan drive rotor having a plurality of blade rows each including a number of blades. A majority of the blade rows are capable of rotating at a rotational speed, so that when measuring the rotational speed in revolutions per minute: (number of blades×the rotational speed)/60≧about 5500 Hz.

1 . A gas turbine engine comprising:
 a fan and a turbine having a fan drive rotor, there also being a second turbine rotor;   a gear reduction effecting a reduction in a speed of said fan relative to an input speed from said fan drive rotor;   said fan drive rotor having a number of turbine blades in a majority of a plurality of blade rows of said fan drive rotor, and said turbine blades configured to operate at least some of the time at a rotational speed, and said number of turbine blades in said majority of said blade rows and said rotational speed being such that the following formula holds true for each row of said majority of said blade rows of the fan drive turbine:
   (number of blades×speed)/60≧about 5500 Hz; and
 
   said rotational speed being in revolutions per minute.   
     
     
         2 . The gas turbine engine as set forth in  claim 1 , wherein the formula results in a number greater than or equal to about 6000 Hz. 
     
     
         3 . The gas turbine engine as set forth in  claim 2 , wherein said gas turbine engine is rated to produce 15,000 pounds of thrust or more. 
     
     
         4 . The gas turbine engine as set forth in  claim 1 , wherein the formula holds true for all of said blade rows of the fan drive rotor. 
     
     
         5 . The gas turbine engine as set forth in  claim 1 , wherein the formula does not hold true for all of said blade rows of the fan drive rotor. 
     
     
         6 . The gas turbine engine as set forth in  claim 1 , wherein the formula results in a number less than or equal to about 7000 Hz, said rotational speed being an approach speed. 
     
     
         7 . The gas turbine engine as set forth in  claim 1 , wherein the formula results in a number less than or equal to about 10000 Hz, said rotational speed being a takeoff speed. 
     
     
         8 . The gas turbine engine as set forth in  claim 1 , wherein said turbine section having a higher pressure turbine rotor and a lower pressure turbine rotor, with said fan drive rotor being said lower pressure turbine rotor and said second turbine rotor is said higher pressure turbine rotor. 
     
     
         9 . The gas turbine engine as set forth in  claim 1 , wherein there is a third turbine rotor, with said fan drive turbine being a most downstream of said three turbine rotors. 
     
     
         10 . A method of designing a gas turbine engine comprising the steps of:
 including a gear reduction between a fan drive turbine rotor and a fan, and selecting a number of blades in a majority of blade rows of the fan drive turbine rotor, in combination with a rotational speed of the fan drive turbine rotor, such that the following formula holds true for each row of said majority of blade rows of the fan drive turbine rotor:
   (number of blades×speed)/60≧about 5500 Hz;
 
   said rotational speed being in revolutions per minute; and   including a second turbine rotor.   
     
     
         11 . The method of designing a gas turbine engine as set forth in  claim 10 , wherein the formula results in a number greater than or equal to about 6000. 
     
     
         12 . The method of designing a gas turbine engine as set forth in  claim 11 , wherein said gas turbine engine is rated to produce 15,000 pounds of thrust or more. 
     
     
         13 . The method as set forth in  claim 10 , wherein the formula holds true for all of the blade rows of the fan drive turbine. 
     
     
         14 . The method as set forth in  claim 10 , wherein the formula does not hold true for all of the blade rows of the fan drive turbine. 
     
     
         15 . The method as set forth in  claim 10 , wherein the formula results in a number less than or equal to about 7000 Hz, and said rotational speed is an approach speed. 
     
     
         16 . The method as set forth in  claim 10 , wherein the formula results in a number less than or equal to about 10000 Hz, and said rotational speed is a takeoff speed. 
     
     
         17 . The method as set forth in  claim 10 , wherein a turbine section including a higher pressure turbine rotor and a lower pressure turbine rotor, and said fan drive turbine rotor being said lower pressure turbine rotor. 
     
     
         18 . A turbine module comprising:
 a fan drive rotor having a plurality of blade rows each including a number of blades, a majority of the blade rows being capable of rotating at a rotational speed, so that when measuring said rotational speed in revolutions per minute:
   (number of blades×said rotational speed)/60≧about 5500 Hz.
 
   
     
     
         19 . The turbine module as set forth in  claim 18 , wherein the formula results in a number greater than or equal to about 6000. 
     
     
         20 . The turbine module as set forth in  claim 18 , wherein the formula does not hold true for all of the blade rows of the fan drive rotor. 
     
     
         21 . The turbine module as set forth in  claim 18 , wherein the formula holds true for all of the blade rows of the fan drive rotor. 
     
     
         22 . The turbine module as set forth in  claim 21 , wherein a pressure ratio across said fan drive rotor is greater than about 5:1. 
     
     
         23 . The turbine module as set forth in  claim 21 , wherein the formula results in a number less than or equal to about 7000 Hz, and the rotational speed is an approach speed. 
     
     
         24 . The turbine module as set forth in  claim 21 , wherein the formula results in a number less than or equal to about 10000 Hz, and the rotational speed is a takeoff speed. 
     
     
         25 . The turbine module as set forth in  claim 18 , wherein there being a higher pressure turbine rotor and a lower pressure turbine rotor, and said fan drive rotor being said lower pressure turbine rotor.