GEARED ARCHITECTURE FOR HIGH SPEED AND SMALL VOLUME FAN DRIVE TURBINE
A gas turbine engine includes a fan shaft that has fan blades. A fan shaft is drivingly connected to the fan. A fan shaft support supports the fan shaft and defines a fan shaft support lateral stiffness. A gear system is connected to the fan shaft and driven through an input. A gear system flex mount arrangement accommodates misalignment of the fan shaft and the input during operation and includes a flexible support that defines a flexible support lateral stiffness that is less than 11% of the shaft support lateral stiffness.
1 . A gas turbine engine, comprising:
a fan shaft drivingly connected to a fan, said fan having fan blades;
a fan shaft support supporting said fan shaft and defining a fan shaft support lateral stiffness;
a gear system connected to said fan shaft and driven through an input; and
a gear system flex mount arrangement, wherein said flex mount arrangement accommodates misalignment of said fan shaft and said input during operation, and includes a flexible support defining a flexible support lateral stiffness that is less than 11% of said shaft support lateral stiffness.
2 . The gas turbine engine of claim 1 , further comprising a ring gear defining a ring gear lateral stiffness and a gear mesh defining a gear mesh lateral stiffness and said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness.
3 . The gas turbine engine of claim 2 , wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
4 . The gas turbine engine of claim 3 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 measured across said fan blades alone, and 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.
5 . The gas turbine engine of claim 1 , further comprising a gear mesh defining a gear mesh lateral stiffness, wherein said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
6 . The gas turbine engine of claim 5 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 measured across said fan blades alone, 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 a mid-turbine frame including a bearing support structure supporting a bearing system.
7 . The gas turbine engine of claim 6 , further comprising a core flow path, a fan tip speed of less than 1150 ft/second and said mid-turbine frame includes at least one airfoil in said core flow path and directing air flow around said bearing support structure.
8 . The gas turbine engine of claim 5 , further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 measured across said fan blades alone, and 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, said flexible support defines a flexible support transverse stiffness and said fan shaft support defines a fan shaft support transverse stiffness with said flexible support transverse stiffness less than 11% of said fan shaft support transverse stiffness, and said gear system has a gear reduction ratio of greater than 2.3, and a gear mesh defines a gear mesh transverse stiffness with said flexible support transverse stiffness less than 8% of said gear mesh transverse stiffness.
9 . The gas turbine engine of claim 1 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across said fan blades alone, and 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.
10 . The gas turbine engine of claim 9 , wherein a gear mesh defines a gear mesh lateral stiffness and said flexible support lateral stiffness less than 8% of said gear mesh lateral stiffness.
11 . The gas turbine engine of claim 10 , wherein said input defines an input lateral stiffness that is less than 11% of said fan shaft support lateral stiffness.
12 . The gas turbine engine of claim 11 , wherein said gear system includes a ring gear defining a ring gear lateral stiffness and said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness.
13 . The gas turbine engine of claim 10 , wherein said flexible support defines a flexible support transverse stiffness and said fan shaft support defines a fan shaft support transverse stiffness and said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
14 . The gas turbine engine of claim 1 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across said fan blades alone, and a gear mesh defines 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 flexible support defines a flexible support transverse stiffness and said fan shaft support defines a fan shaft support transverse stiffness and said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
16 . The gas turbine engine of claim 1 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across said fan blades alone, and said flexible support defines a flexible support transverse stiffness and said fan shaft support defines a fan shaft support transverse stiffness and said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
17 . A gas turbine engine comprising:
a fan shaft drivingly connected to a fan, said fan having fan blades;
a gear system connected to said fan shaft and driven through an input, a gear system flex mount arrangement, wherein the flex mount arrangement accommodates misalignment of said fan shaft and said input during operation, and a ring gear defining a ring gear lateral stiffness and a gear mesh defining a gear mesh lateral stiffness, wherein said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness.
18 . The gas turbine engine of claim 17 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 and said low fan pressure ratio is measured across said fan blades alone, and 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.
19 . The gas turbine engine of claim 18 , further comprising a mid-turbine frame supporting a bearing system and having at least one airfoil in a core flow path.
20 . The gas turbine engine of claim 19 , wherein said flex mount arrangement includes a flexible support defining a flexible support lateral stiffness, said fan shaft support defines a fan shaft support lateral stiffness, and said flexible support lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
21 . The gas turbine engine of claim 18 , wherein said flex mount arrangement includes a flexible support defining a flexible support lateral stiffness, said fan shaft support defines a fan shaft support lateral stiffness, 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 fan shaft support that supports said fan shaft and defines a fan shaft support lateral stiffness, wherein said input defines an input lateral stiffness that is less than 11% of said fan shaft support lateral stiffness.
23 . The gas turbine engine of claim 22 , 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 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.
25 . The gas turbine engine of claim 24 , further comprising a fan shaft support that supports said fan shaft defining a fan shaft support transverse stiffness, wherein said input defines an input transverse stiffness, said fan shaft support define a fan shaft support transverse stiffness, and said input transverse stiffness is less than 11% of said fan shaft support transverse stiffness.
26 . The gas turbine engine of claim 25 , further comprising a fan tip speed of less than 1150 ft/second and a mid-turbine frame including at least one airfoil in a core flow path.
27 . A gas turbine engine comprising
a fan shaft drivingly connected to a fan, said fan having fan blades;
a fan shaft support that supports said fan shaft defining a fan shaft support lateral stiffness;
a gear system connected to said fan shaft and driven through an input, said input defining an input lateral stiffness that is less than 11 % of said fan shaft support lateral stiffness; and
a gear system flex mount arrangement, wherein said flex mount arrangement accommodates misalignment of said fan shaft and said input during operation.
28 . The gas turbine engine of claim 27 , wherein said flex mount arrangement includes a flexible support defining a flexible support lateral stiffness that is less than 11% of said fan shaft support lateral stiffness.
29 . The gas turbine engine of claim 28 , further comprising a ring gear defining a ring gear lateral stiffness, a gear mesh defining a gear mesh lateral stiffness, and said ring gear lateral stiffness is less than 12% of said gear mesh lateral stiffness.
30 . The gas turbine engine of claim 29 , wherein said gear system has a gear reduction ratio of greater than 2.3, and further comprising a gear reduction ratio of greater than 2.3, a bypass ratio greater than ten (10), a low fan pressure ratio of less than 1.45 measured across said fan blades alone, and 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 8% of said gear mesh lateral stiffness.