Geared Architecture for High Speed and Small Volume Fan Drive Turbine
A gas turbine engine includes a gear system that provides a speed reduction between a fan drive turbine and a fan rotor. Aspects of the gear system are provided with defined flexibility. The fan drive turbine has a first exit area and rotates at a first speed. A second turbine section has a second exit area and rotates at a second speed, which is faster than said first speed. A performance quantity can be defined for both turbine sections as the products of the respective areas and respective speeds squared. A performance quantity ratio of the performance quantity for the fan drive turbine to the performance quantity for the second turbine section is between 0.5 and 1.5.
1 . A gas turbine engine comprising:
a fan shaft driving a fan;
a plurality of gears in driving engagement with said fan shaft;
a first turbine section providing a drive input into said plurality of gears and having between three and six stages;
a two stage second turbine, and
wherein said first turbine section has a first exit area at a first exit point and rotates at a first speed,
wherein said second turbine section has a second exit area at a second exit point and rotates at a second speed,
wherein a first performance quantity is defined as the product of said first speed squared and said first area,
wherein a second performance quantity is defined as the product of said second speed squared and said second area,
a performance quantity ratio of said first performance quantity to said second performance quantity is greater than or equal to 0.5 and less than or equal to 1.075.
2 . The gas turbine engine as set forth in claim 1 , wherein a gear ratio of said plurality of gears is greater than 2.3.
3 . The gas turbine engine as set forth in claim 2 , wherein said plurality of gears provide an epicylic gear system, said epicyclic gear system including a ring gear having a ring gear lateral stiffness and a ring gear transverse stiffness and said epicyclic gear system having a gear mesh lateral stiffness and a gear mesh transverse stiffness, and at least one of said ring gear lateral stiffness and said ring gear transverse stiffness being less than 12% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
4 . The gas turbine engine as set forth in claim 3 , wherein there being a flexible support to support said epicyclic gear system, said flexible support having a flexible support lateral stiffness and a flexible support transverse stiffness, and at least one of said flexible support lateral stiffness and said flexible support transverse stiffness being less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
5 . The gas turbine engine as set forth in claim 4 , wherein a flexible connection connects a sun gear of said epicyclic gear system to be driven by said first turbine section, and a frame which supports said fan shaft, and said flexible connection having at least one of a flexible connection lateral stiffness and a flexible connection transverse stiffness that is less than 11% of a respective one of a frame lateral stiffness and a frame transverse stiffness.
6 . The gas turbine engine as set forth in claim 5 , wherein at least one of said flexible support lateral stiffness and said flexible support transverse stiffness being less than 11% of a respective one of said frame lateral stiffness and said frame transverse stiffness, and said second speed is greater than twice said first speed.
7 . The gas turbine engine as set forth in claim 3 , wherein a flexible connection connects a sun gear of said epicyclic gear system to be driven by said first turbine section, and said flexible connection having at least one of a flexible connection lateral stiffness and a flexible connection transverse stiffness that is less than 5% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
8 . The gas turbine engine as set forth in claim 7 , wherein a power ratio of a flat-rated Sea Level Take-Off thrust provided by said engine in lbf, to a volume of a turbine section including both said first and second turbine sections in inch 3 being greater than or equal to 1.5 lbf/inch 3 .
9 . The gas turbine engine as set forth in claim 8 , wherein said power ratio being less than or equal to 5.5 lbf/inch 3 .
10 . The gas turbine engine as set forth in claim 2 , wherein a power ratio of flat-rated Sea Level Take-Off thrust provided by said engine in lbf, to a volume of a turbine section including both said first and second turbine sections in inch 3 being greater than or equal to 4.0 lbf/inch 3 .
11 . The gas turbine engine as set forth in claim 10 , wherein said plurality of gears provide an epicylic gear system, said epicyclic gear system including a ring gear having a ring gear lateral stiffness and a ring gear transverse stiffness and said epicyclic gear system having a gear mesh lateral stiffness and a gear mesh transverse stiffness, and at least one of said ring gear lateral stiffness and said ring gear transverse stiffness being less than 12% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
12 . The gas turbine engine as set forth in claim 11 , wherein a flexible connection connects a sun gear of said epicyclic gear system to be driven by said first turbine section, and said flexible connection having at least one of a flexible connection lateral stiffness and a flexible connection transverse stiffness that is less than 5% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
13 . The gas turbine engine as set forth in claim 12 , wherein there being a flexible support to support said epicyclic gear system, said flexible support having a flexible support lateral stiffness and a flexible support transverse stiffness, and at least one of said flexible support lateral stiffness and said flexible support transverse stiffness being less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
14 . The gas turbine engine as set forth in claim 1 , wherein there is a flexible connection connecting said first turbine to drive said plurality of gears, said plurality of gears having a gear mesh lateral stiffness and a gear mesh transverse stiffness, and said flexible coupling having a flexible coupling lateral stiffness and a flexible coupling transverse stiffness, and at least one of said flexible coupling lateral and transverse stiffnesses being less than or equal to 5% of a respective one of said gear mesh lateral and transverse stiffnesses, and said second speed being greater than twice said first speed.
15 . A gas turbine engine comprising:
a fan shaft driving a fan having fan blades;
an epicyclic gear system having a gear ratio greater than 2.3, and in driving engagement with said fan shaft and having a gear mesh lateral stiffness and a gear mesh transverse stiffness;
said epicyclic gear system having a ring gear, and at least one of a ring gear lateral stiffness and a ring gear transverse stiffnesses being less than 12% of a respective one of said gear mesh lateral and transverse stiffnesses; and
a first turbine section providing a drive input into said epicyclic gear system;
a second turbine section,
wherein said first turbine section has a first exit area at a first exit point and rotates at a first speed,
wherein said second turbine section has a second exit area at a second exit point and rotates at a second speed,
wherein a first performance quantity is defined as the product of said first speed squared and said first area,
wherein a second performance quantity is defined as the product of said second speed squared and said second area,
wherein a performance quantity ratio of the first performance quantity to said second performance quantity is between 0.5 and 1.075.
16 . The gas turbine engine as set forth in claim 15 , wherein there being a flexible support to support said epicyclic gear system, said flexible support having a flexible support lateral stiffness and a flexible support transverse stiffness, and at least one of said flexible support lateral stiffness and said flexible support transverse stiffness being less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
17 . The gas turbine engine as set forth in claim 16 , wherein a power ratio of a flat-rated Sea Level Take-Off thrust provided by said engine in lbf, for a volume of a turbine section including both said first and second turbine sections in inch 3 being greater than or equal to 1.5 lbf/inch 3 .
18 . The gas turbine engine as set forth in claim 17 , wherein said power ratio being less than or equal to 5.5 lbf/inch 3 .
19 . The gas turbine engine as set forth in claim 17 , wherein said power ratio being greater than or equal to 4.0 lbf/inch 3 .
20 . The gas turbine engine as set forth in claim 15 , wherein there being a flexible support to support said epicyclic gear system, and a frame which supports said fan shaft, and at least one of a flexible support lateral stiffness and a flexible support transverse stiffness being less than 11% of a respective frame lateral stiffness and a frame transverse stiffness.
21 . The gas turbine engine as set forth in claim 20 , wherein said first turbine has between three and six stages and said second turbine is a two stage second turbine.
22 . The gas turbine engine as set forth in claim 21 , wherein a flexible connection connects a sun gear of said epicyclic gear system to be driven by said first turbine section, and said flexible connection having at least one of a flexible connection lateral stiffness and a flexible connection transverse stiffness that is less than 11% of a respective one of said frame lateral stiffness and said frame transverse stiffness.
23 . The gas turbine engine as set forth in claim 15 , wherein a low fan pressure ratio across the fan blades alone is less than 1.45.
24 . The gas turbine engine as set forth in claim 23 , wherein a power ratio of a flat-rated Sea Level Take-Off thrust provided by said engine in lbf, for a volume of a turbine section including both said first and second turbine sections in inch 3 being greater than or equal to 1.5 lbf/inch 3 .
25 . The gas turbine engine as set forth in claim 24 , wherein said power ratio being greater than or equal to 4.0 lbf/inch 3 .
26 . The gas turbine engine as set for in claim 25 , wherein said second speed is more than twice said first speed.
27 . The gas turbine engine as set forth in claim 23 , wherein a flexible connection connects a sun gear of said epicyclic gear system to be driven by said first turbine section, and a frame which supports said fan shaft, and said flexible connection having at least one of a flexible connection lateral stiffness and a flexible connection transverse stiffness that is less than 5% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness, and wherein at least one of said flexible connecting lateral stiffness and said flexible connecting transverse stiffness being less than 11% of a respective frame lateral stiffness and a frame transverse stiffness.
28 . The gas turbine engine as set forth in claim 15 , wherein a power ratio of flat-rated Sea Level Take-Off thrust provided by said engine in lbf, to a volume of a turbine section including both said first and second turbine sections in inch 3 being greater than or equal to 4.0 lbf/inch 3 .
29 . The gas turbine engine as set forth in claim 28 , wherein there being a flexible support to support said epicyclic gear system, said flexible support having a flexible support lateral stiffness and a flexible support transverse stiffness, and at least one of said flexible support lateral stiffness and said flexible support transverse stiffness being less than 8% of a respective one of said gear mesh lateral stiffness and said gear mesh transverse stiffness.
30 . The gas turbine engine as set forth in claim 29 , wherein a flexible connection connects a sun gear of said epicyclic gear system to be driven by said first turbine section, and a frame which supports said fan shaft, and said flexible connection having at least one of a flexible connection lateral stiffness and a flexible connection transverse stiffness that is less than 11% of a respective one of a frame lateral stiffness and a frame transverse stiffness.