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 defining a fan shaft support lateral stiffness and a fan shaft support transverse stiffness and a gear system connected to the fan shaft. A flexible support supports the gear system and defines a flexible support lateral stiffness and a flexible support transverse stiffness. A low fan pressure ratio of less than 1.45 measured across the fan blades alone. At least one of the flexible support lateral stiffness is less than 11% of the fan shaft support lateral stiffness and the flexible support transverse stiffness is less than 20% of the fan shaft support transverse 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 defining a fan shaft support lateral stiffness and a fan shaft support transverse stiffness;
a gear system connected to said fan shaft;
a flexible support supporting said gear system defining a flexible support lateral stiffness and a flexible support transverse stiffness;
a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across the fan blades alone; and
wherein at least one of said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness and said flexible support transverse stiffness is less than 20% of said fan shaft support transverse stiffness.
2 . The gas turbine engine of claim 1 , wherein said gear system includes a gear mesh defining a gear mesh lateral stiffness and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
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 and 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.
4 . The gas turbine engine of claim 3 , further comprising a bypass ratio greater than ten ( 10 ) and a two stage high pressure turbine.
5 . The gas turbine engine of claim 4 , 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, wherein the gear system is a planetary gear system having a reduction ratio greater than 2.3 and said flexible support lateral stiffness and said flexible support transverse stiffness is less than 11% of a respective one of said fan shaft support lateral stiffness and said fan shaft support transverse stiffness.
6 . The gas turbine engine of claim 2 , further comprising a gear system input to said gear system defining a gear system input lateral stiffness, wherein said gear system input lateral stiffness is less than 11% of said fan shaft support lateral stiffness and said gear system includes a reduction ratio greater than 2.3.
7 . The gas turbine engine of claim 6 , wherein said flexible support transverse stiffness and said gear system input transverse stiffness are less than 11% of said fan shaft support transverse stiffness.
8 . The gas turbine engine of claim 7 , wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness and said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
9 . The gas turbine engine of claim 8 , 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.
10 . 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 and said gear system is a planetary gear system.
11 . The gas turbine engine of claim 10 , further comprising a two stage high pressure compressor and 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 1 , further comprising a mid-turbine frame.
13 . The gas turbine engine of claim 12 , 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 and said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
14 . The gas turbine engine of claim 13 , wherein said gear system includes a gear mesh defining a gear mesh lateral stiffness and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
15 . The gas turbine engine of claim 14 , 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.
16 . The gas turbine engine of claim 15 , wherein said flexible support transverse stiffness is less than 20% of said fan shaft support transverse stiffness.
17 . The gas turbine engine of claim 16 , further comprising a bypass ratio greater than ten (10) and a two stage high pressure turbine, wherein said gear system includes a reduction ratio greater than 2.3 and said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
18 . The gas turbine engine of claim 17 , further comprising an inner shaft and an outer shaft concentric with said inner shaft that both rotate via at least one bearing system, wherein said mid-turbine frame includes at least one airfoil extending into a flow path.
19 . The gas turbine engine of claim 17 , further comprising a gear system input to said gear system defining a gear system input lateral stiffness, wherein said gear system input lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
20 . The gas turbine engine of claim 1 , wherein said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
21 . The gas turbine engine of claim 20 , 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 and said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
22 . The gas turbine engine of claim 21 , further comprising a two stage high pressure turbine and a bypass ratio greater than ten (10), wherein said gear system includes a gear mesh defining a gear mesh lateral stiffness and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
23 . The gas turbine engine of claim 22 , further comprising a gear system input to said gear system defining a gear system input lateral stiffness, wherein said gear system input lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
24 . The gas turbine engine of claim 23 , wherein said gear system input defines a gear system input transverse stiffness and said gear system input transverse stiffness is less than 11 of said fan shaft support transverse stiffness.
25 . The gas turbine engine of claim 22 , 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 and 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 mid-turbine frame including at least one airfoil extending into a flow path.
27 . The gas turbine engine of claim 1 , wherein said gear system includes a gear mesh defining a gear mesh transverse stiffness and said flexible support transverse stiffness is less than 11% of said gear mesh transverse stiffness.
28 . The gas turbine engine of claim 27 , wherein said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
29 . The gas turbine engine of claim 28 , 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 and said gear mesh defines a gear mesh lateral stiffness, said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness, and said gear system includes a reduction ratio greater than 2.3.
30 . The gas turbine engine of claim 29 , further comprising a two stage high pressure turbine, a bypass ratio greater than ten (10), and 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 and said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness and said gear system is a planetary gear system.