FLEXIBLE SUPPORT STRUCTURE FOR A GEARED ARCHITECTURE GAS TURBINE ENGINE
A gas turbine engine includes a propulsor that has propulsor blades, a propulsor shaft for driving the propulsor, a propulsor shaft support that supports said propulsor shaft, said propulsor shaft support defining a propulsor shaft support transverse stiffness, a gear system connected to said propulsor shaft, said gear system includes a gear mesh defining a gear mesh transverse stiffness, and a flexible support which supports said gear system relative to a static structure and defines a flexible support transverse stiffness, wherein said flexible support transverse stiffness is less than 11% of said propulsor shaft support transverse stiffness and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness.
1 . A gas turbine engine, comprising:
a propulsor having propulsor blades;
a propulsor shaft for driving the propulsor;
a propulsor shaft support that supports said propulsor shaft, said propulsor shaft support defining a propulsor shaft support transverse stiffness;
a gear system connected to said propulsor shaft, said gear system includes a gear mesh defining a gear mesh transverse stiffness; and
a flexible support which supports said gear system relative to a static structure and defines a flexible support transverse stiffness, wherein said flexible support transverse stiffness is less than 11% of said propulsor shaft support transverse stiffness and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness.
2 . The gas turbine engine of claim 1 , wherein said propulsor shaft support defines a propulsor shaft support lateral stiffness and said flexible support defines a flexible support lateral stiffness and said flexible support lateral stiffness is less than 11% of said propulsor shaft support lateral stiffness.
3 . The gas turbine engine of claim 2 , wherein the propulsor is a fan, and comprising a fan case surrounding the fan.
4 . The gas turbine engine of claim 1 , further comprising a mid-turbine frame including at least one airfoil extending into a flow path, and wherein said propulsor shaft support is a K-frame bearing support.
5 . The gas turbine engine of claim 1 , wherein the gear system has a reduction ratio greater than 2.3.
6 . The gas turbine engine of claim 5 , wherein said gear mesh defines a gear mesh lateral stiffness and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
7 . The gas turbine engine of claim 6 , further comprising a high speed spool including a two stage high pressure turbine, and a low speed spool including 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.
8 . The gas turbine engine of claim 7 , wherein said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness.
9 . The gas turbine engine of claim 8 , further comprising an input coupling defining an input coupling transverse stiffness, wherein said input coupling transverse stiffness is less than 20% of said propulsor shaft support transverse stiffness.
10 . The gas turbine engine of claim 9 , wherein said input coupling transverse stiffness is less than 11% of said propulsor shaft support transverse stiffness.
11 . The gas turbine engine of claim 10 , wherein said input coupling defines an input coupling lateral stiffness and said input coupling lateral stiffness is less than 11% of said fan shaft support lateral stiffness.
12 . The gas turbine engine of claim 1 , wherein said flexible support transverse stiffness is less than 11% of said propulsor shaft support transverse stiffness.
13 . A gas turbine engine, comprising:
propulsor means for providing propulsion;
a propulsor shaft driving the propulsor means;
a propulsor shaft support that supports said propulsor shaft, said propulsor shaft support defining a propulsor shaft support transverse stiffness;
a reduction means for reducing a rotational speed of an output that drives the propulsor means relative to an input, said reduction means includes a gear mesh means defining a gear mesh lateral stiffness; and
a flexible support means for supporting said reduction means relative to a static structure, the flexible support means defining a flexible support transverse stiffness and a flexible support lateral stiffness, wherein said flexible support transverse stiffness is less than 11% of said propulsor shaft support transverse stiffness, and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness.
14 . The gas turbine engine of claim 13 , wherein said gear mesh means defines a gear mesh transverse stiffness and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness.
15 . The gas turbine engine of claim 14 , further comprising compression means for compressing airflow from the propulsor means, and expansion means for driving the compression means in response to expanding airflow across the expansion means.
16 . The gas turbine engine as recited in claim 15 , wherein the compression means includes a plurality of compression stages, and the expansion means includes a plurality of expansion stages.
17 . The gas turbine engine of claim 16 , wherein the compression means is a three stage compressor, and the expansion means is a two stage turbine.
18 . The gas turbine engine of claim 17 , further comprising a mid-turbine frame including at least one airfoil extending into a flow path.
19 . The gas turbine engine of claim 18 , wherein the input is an input coupling that has an input coupling transverse stiffness, wherein said input coupling transverse stiffness is less than 20% of said propulsor shaft support transverse stiffness.
20 . The gas turbine engine of claim 19 , wherein the reduction means includes an epicyclic gear train that has a gear reduction ratio of greater than 2.5.