Geared gas turbine engine with reduced fan noise

1. A gas turbine engine comprising:

a fan section having a rotor with a plurality of fan blades, said plurality being equal to or less than 26, said fan section having a low fan pressure ratio of less than 1.45, wherein the low fan pressure ratio is measured across said fan blades alone;

a geared arrangement that drives said fan rotor;

a compressor section including a first compressor section and a second compressor section;

a turbine section including a first turbine section that drives said first compressor section, and a second turbine section that drives said second compressor section and said geared arrangement with said geared arrangement providing a gear reduction;

a plurality of exit guide vanes positioned downstream of said fan blades;

wherein a first ratio of a number of exit guide vanes to a number of fan blades being between 0.8 and 2.0; and

each of said exit guide vanes defines a hollow opening covered by an acoustic liner having a perforated face sheet with a plurality of holes, said face sheet has a thickness, and a diameter of said plurality of holes in said face sheet is less than or equal 0.3 of the thickness;

wherein said plurality of holes in said face sheet extend over at least 5% of a total surface area of said face sheet;

said geared arrangement has a gear reduction ratio greater than or equal to 2.3;

wherein the second turbine section includes an inlet, an outlet and a pressure ratio of greater than 5, the pressure ratio being pressure measured prior to the inlet as related to pressure at the outlet prior to any exhaust nozzle; and

wherein the fan section has a low corrected fan tip speed of less than 1150 ft/sec, and said low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]{circumflex over ( )}0.5.

2. The gas turbine engine as set forth in claim 1 , wherein said diameter is less than or equal to 0.2 of the thickness.

3. The gas turbine engine as set forth in claim 2 , wherein said exit guide vanes are provided with sweep and lean.

4. The gas turbine engine as set forth in claim 3 , wherein sweep means that: (a) an outer periphery of said exit guide vane is positioned to be downstream of a location of an inner periphery of said exit guide vane; and (b) a sweep angle is between 0 degrees and 30 degrees.

5. The gas turbine engine as set forth in claim 4 , wherein lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 0 degrees and less than or equal to 15 degrees.

6. The gas turbine engine as set forth in claim 3 , wherein lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 0 degrees and less than or equal to 15 degrees.

7. The gas turbine engine as set forth in claim 1 , wherein said exit guide vanes are provided with sweep and lean.

8. The gas turbine engine as set forth in claim 7 , wherein sweep means that: (a) an outer periphery of said exit guide vane is positioned to be downstream of a location of an inner periphery of said exit guide vane; and (b) a sweep angle is between 0 degrees and 30 degrees.

9. The gas turbine engine as set forth in claim 8 , wherein lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 0 degrees and less than or equal to 15 degrees.

10. The gas turbine engine as set forth in claim 7 , wherein lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 0 degrees and less than or equal to 15 degrees.

11. A gas turbine engine comprising:

a fan section having a plurality of fan blades, said fan section having a low fan pressure ratio of less than 1.45 measured across said fan blades alone;

a geared arrangement that drives said fan section;

a compressor section including a first compressor section and a second compressor section;

a turbine section including a first turbine section that drives said first compressor section, and a second turbine section that drives said second compressor section and said geared arrangement;

a plurality of exit guide vanes positioned downstream of said fan blades;

wherein a first ratio of a number of exit guide vanes to a number of fan blades being between 0.8 and 2.0;

said geared arrangement has a gear reduction ratio greater than or equal to 2.3;

wherein the second turbine section includes an inlet, an outlet and a pressure ratio of greater than 5, the pressure ratio being pressure measured prior to the inlet as related to pressure at the outlet prior to any exhaust nozzle;

wherein the fan section has a low corrected fan tip speed of less than 1150 ft/sec, and said low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]{circumflex over ( )}0.5 and said fan section has 20 or fewer fan blades; and

wherein said exit guide vanes are provided with sweep, wherein sweep means that: (a) an outer periphery of said exit guide vane is positioned to be downstream of a location of an inner periphery of said exit guide vane; and (b) a sweep angle is between 0 degrees and 30 degrees;

each of said exit guide vanes defines a hollow opening covered by an acoustic liner having a perforated face sheet with a plurality of holes;

said face sheet has a thickness, and a diameter of said plurality of holes in said face sheet is selected to be less than or equal to 0.3 of the thickness; and

said plurality of holes in said face sheet extend over at least 5% of a total surface area of said face sheet.

12. The gas turbine engine as set forth in claim 11 , wherein said sweep angle is greater than or equal to 15 degrees.

13. The gas turbine engine as set forth in claim 12 , wherein said exit guide vanes are provided with lean, and lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 0 degrees and less than or equal to 15 degrees.

14. The gas turbine engine as set forth in claim 13 , wherein said lean angle is greater than or equal to 2 degrees.

15. The gas turbine engine as set forth in claim 14 , wherein said diameter is less than or equal to 0.2 of the thickness.

16. The gas turbine engine as set forth in claim 13 , wherein said diameter is less than or equal to 0.2 of the thickness.

17. The gas turbine engine as set forth in claim 11 , wherein said exit guide vanes are provided with lean, and lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 0 degrees and less than or equal to 15 degrees.

18. The gas turbine engine as set forth in claim 17 , wherein said diameter is less than or equal to 0.2 of the thickness.

19. The gas turbine engine as set forth in claim 18 , wherein said lean angle is greater than or equal to 2 degrees.

20. The gas turbine engine as set forth in claim 11 , wherein said geared arrangement is between said fan section and said second compressor section.

21. A gas turbine engine comprising:

a fan section having a plurality of fan blades;

a geared arrangement that drives said fan section;

a compressor section including a first compressor section and a second compressor section;

a turbine section including a first turbine section that drives said first compressor section, and a second turbine section that drives said second compressor section and said geared arrangement;

a plurality of exit guide vanes positioned downstream of said fan blades;

wherein a first ratio of a number of exit guide vanes to a number of fan blades being between 0.8 and 2.0;

wherein said exit guide vanes are provided with lean, wherein lean means that: (a) an outer periphery of said exit guide vane is positioned at a greater circumferential distance than an inner periphery of said exit guide vane in a direction of rotation of said fan blades; and (b) a lean angle is greater than or equal to 2 degrees and less than or equal to 15 degrees;

each of said exit guide vanes defines a hollow opening covered by an acoustic liner having a perforated face sheet with a plurality of holes;

said face sheet has a thickness, and a diameter of said plurality of holes in said face sheet is selected to be less than or equal to 0.3 of the thickness; and

wherein said fan section has 20 or fewer fan blades.

22. The gas turbine engine as set forth in claim 21 , wherein said exit guide vanes are provided with sweep and sweep means that: (a) an outer periphery of said exit guide vane is positioned to be downstream of a location of an inner periphery of said exit guide vane; and (b) a sweep angle is between 0 degrees and 35 degrees.

23. The gas turbine engine as set forth in claim 22 , wherein said diameter is less than or equal to 0.2 of the thickness.

24. The gas turbine engine as set forth in claim 23 , wherein:

said geared arrangement has a gear reduction ratio greater than or equal to 2.3;

wherein the second turbine section includes an inlet, an outlet and a pressure ratio of greater than 5, the pressure ratio being pressure measured prior to the inlet as related to pressure at the outlet prior to any exhaust nozzle; and

wherein the fan section has a low corrected fan tip speed of less than 1150 ft/sec, and said low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]{circumflex over ( )}0.5.

25. The gas turbine engine as set forth in claim 21 , wherein:

said geared arrangement has a gear reduction ratio greater than or equal to 2.3;

wherein the second turbine section includes an inlet, an outlet and a pressure ratio of greater than 5, the pressure ratio being pressure measured prior to the inlet as related to pressure at the outlet prior to any exhaust nozzle; and

wherein the fan section has a low corrected fan tip speed of less than 1150 ft/sec, and said low corrected fan tip speed is an actual fan tip speed divided by [(Tram ° R)/(518.7° R)]{circumflex over ( )}0.5.

26. The gas turbine engine as set forth in claim 21 , wherein said lean angle is greater than or equal to 2 degrees.

27. The gas turbine engine as set forth in claim 26 , wherein said plurality of holes in said face sheet extend over at least 5% of a total surface area of said face sheet.

28. The gas turbine engine as set forth in claim 21 , wherein said plurality of holes in said face sheet extend over at least 5% of a total surface area of said face sheet.

29. The gas turbine engine as set forth in 28 , wherein said geared arrangement is between said fan section and said second turbine section.

30. The gas turbine engine as set forth in claim 21 , wherein said geared arrangement is between said fan section and said second turbine section.