FLEXIBLE SUPPORT STRUCTURE FOR A GEARED ARCHITECTURE GAS TURBINE ENGINE
A gas turbine engine according to an example of the present disclosure includes, among other things, a fan shaft driving a fan having fan blades, a fan shaft support that supports the fan shaft and a gear system connected to the fan shaft. The gear system includes a ring gear defining a ring gear lateral stiffness, a gear mesh defining a gear mesh lateral stiffness, and a reduction ratio greater than 2.3. A bypass ratio is greater than 10 (10). The ring gear lateral stiffness is less than 12% of the gear mesh lateral stiffness.
1 . A gas turbine engine, comprising:
a fan shaft driving a fan having fan blades;
a fan shaft support that supports said fan shaft;
a gear system connected to said fan shaft, said gear system includes a ring gear defining a ring gear lateral stiffness, a gear mesh defining a gear mesh lateral stiffness, and a reduction ratio greater than 2.3;
a bypass ratio greater than ten (10); and
wherein said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness.
2 . The gas turbine engine of claim 1 , further comprising a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across the fan blades alone.
3 . The gas turbine engine of claim 2 , further comprising a low pressure turbine with an inlet, an outlet, and a low pressure turbine pressure ratio greater than 5:1, wherein said low pressure turbine pressure ratio is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet prior to any exhaust nozzle.
4 . The gas turbine engine of claim 3 , further comprising a low corrected fan tip speed less than about 1150 ft/second, wherein said low corrected fan tip speed is an actual fan tip speed at an ambient temperature divided by [(Tram ° R)/(518.7° R)]0.5, where T represents said ambient temperature in degrees Rankine.
5 . The gas turbine engine of claim 4 , further comprising a gear system input to said gear system defining a gear system input lateral stiffness and said fan shaft support defining a fan shaft support lateral stiffness, wherein said gear system input lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
6 . The gas turbine engine of claim 5 , wherein said gear system input defines a gear system input lateral stiffness and wherein said gear system input lateral stiffness is less than 5% of said fan shaft support lateral stiffness.
7 . The gas turbine engine of claim 6 , further comprising a two stage high pressure turbine.
8 . The gas turbine engine of claim 2 , wherein said ring gear defines a ring gear transverse stiffness and said gear mesh defines a gear mesh transverse stiffness and said ring gear transverse stiffness is less than 20% of said gear mesh transverse stiffness.
9 . The gas turbine engine of claim 8 , wherein said ring gear transverse stiffness is less than 12% of said gear mesh transverse stiffness.
10 . The gas turbine engine of claim 9 , further comprising a low pressure turbine with an inlet, an outlet, and a low pressure turbine pressure ratio greater than 5:1, wherein said low pressure turbine pressure ratio is a ratio of a pressure measured prior to said inlet as related to a pressure at said outlet prior to any exhaust nozzle.
11 . The gas turbine engine of claim 10 , further comprising a low corrected fan tip speed less than about 1150 ft/second, wherein said low corrected fan tip speed is an actual fan tip speed at an ambient temperature divided by [(Tram ° R)/(518.7° R)]0.5, where T represents said ambient temperature in degrees Rankine.
12 . The gas turbine engine of claim 11 , further comprising a gear system input defining a gear system input lateral stiffness and said fan shaft support defining a fan shaft support lateral stiffness, wherein said gear system input lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
13 . The gas turbine engine of claim 12 , wherein said gear system input lateral stiffness is less than 11% of said gear mesh lateral stiffness.
14 . The gas turbine engine of claim 13 , wherein the fan shaft support includes a K-frame bearing support.
15 . The gas turbine engine of claim 11 , wherein the gear system is a planetary gear system.
16 . The gas turbine engine of claim 12 , further comprising a mid-turbine frame including at least one airfoil extending into a flow path.
17 . The gas turbine engine of claim 1 , further comprising a flexible support which supports said gear system and defines a flexible support lateral stiffness and said fan shaft support defines a fan shaft support lateral stiffness, wherein the flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
18 . The gas turbine engine of claim 17 , wherein said flexible support defines a flexible support transverse stiffness, said fan shaft support defines a fan shaft support transverse stiffness and said flexible support transverse stiffness is less than 20% of said fan shaft support transverse stiffness.
19 . The gas turbine engine of claim 18 , further comprising a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across the fan blades alone.
20 . The gas turbine engine of claim 19 , further comprising a low corrected fan tip speed less than about 1150 ft/second, wherein said low corrected fan tip speed is an actual fan tip speed at an ambient temperature divided by [(Tram ° R)/(518.7° R)]0.5, where T represents said ambient temperature in degrees Rankine.
21 . The gas turbine engine of claim 20 , further comprising a mid-turbine frame including at least one airfoil extending into a flow path.
22 . The gas turbine engine of claim 20 , further comprising a two stage high pressure turbine.
23 . The gas turbine engine of claim 19 , wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
24 . The gas turbine engine of claim 23 , wherein said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness and said gear system input both transfers torque and facilitates segregation of vibrations.
25 . The gas turbine engine of claim 23 , wherein said gear mesh defines a gear mesh transverse stiffness and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness.
26 . The gas turbine engine of claim 25 , further comprising a low corrected fan tip speed less than about 1150 ft/second, wherein said low corrected fan tip speed is an actual fan tip speed at an ambient temperature divided by [(Tram ° R)/(518.7° R)]0.5, where T represents said ambient temperature in degrees Rankine.
27 . The gas turbine engine of claim 23 , wherein said gear system input defines a gear system input lateral stiffness and said fan shaft support defines a fan shaft support lateral stiffness and said gear system input lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
28 . The gas turbine engine of claim 27 , further comprising a two stage high pressure turbine.
29 . The gas turbine engine of claim 27 , wherein said gear system input defines a gear system input transverse stiffness and said fan shaft support defines a fan shaft support transverse stiffness and said gear system input transverse stiffness is less than 20% of said fan shaft support lateral stiffness.
30 . The gas turbine engine of claim 19 , wherein said ring gear defines a ring gear transverse stiffness and said gear mesh defines a gear mesh transverse stiffness and said ring gear transverse stiffness is less than 12% of said gear mesh transverse stiffness.