# US 11,111,818 B2 · Flexible support structure for a geared architecture gas turbine engine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,111,818 B2 - Document ID: US11111818B2 - Status: Granted - Kind: B2 - Application number: 16/667,154 - Filed: 2019-10-29 - Published: 2020-07-23 - Granted: 2021-09-07 - Earliest claimed: 2011-06-08 - Assignees: Raytheon Technologies Corporation - Applicants: Raytheon Technologies Corporation - Inventors: Michael E. McCune; Jason Husband - Web page: https://patentgrep.com/patent/US11111818B2 ## CPC - F01D 25/164: {Flexible supports; Vibration damping means associated with the bearing} - F01D 5/06: Rotors for more than one axial stage, e.g. of drum or multiple disc type; Details thereof, e.g. shafts, shaft connections {(F01D5/022, F01D5/023 take precedence)} - F01D 9/02: Nozzles; Nozzle boxes; Stator blades; Guide conduits {, e.g. individual nozzles (nozzle boxes F01D9/047)} - F01D 15/12: Combinations with mechanical gearing (driven by multiple engines F01D13/00) - F01D 25/16: Arrangement of bearings; Supporting or mounting bearings in casings (bearings per se F16C) - F01D 25/28: Supporting or mounting arrangements, e.g. for turbine casing - F02C 7/32: Arrangement, mounting, or driving, of auxiliaries - F02C 7/36: Power transmission arrangements between the different shafts of the gas turbine plant, or between the gas-turbine plant and the power user ({F02C3/107 - F02C3/13 and} F02C7/32 take precedence; couplings for transmitting rotation F16D; gearing in general F16H) - F02K 3/06: with front fan - F04D 19/02: Multi-stage pumps - F04D 25/045: {the pump wheel carrying the fluid driving means, e.g. turbine blades} - F04D 29/053: Shafts - F04D 29/056: Bearings - F04D 29/321: {for axial flow compressors} - F04D 29/325: {for axial flow fans (blade mountings F04D29/34, blades F04D29/38)} - F05D 2220/32: in gas turbines - F05D 2240/60: Shafts - F05D 2260/40311: of the epicyclical, planetary or differential type - F05D 2260/96: Preventing, counteracting or reducing vibration or noise - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - Y10T 29/49321: Assembling individual fluid flow interacting members, e.g., blades, vanes, buckets, on rotary support member - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - F02K: JET-PROPULSION PLANTS (features of jet-propulsion plants common to gas-turbine plants, air intakes or fuel supply control of air-breathing jet-propulsion plants F02C7/00, F02C9/00) - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A gas turbine engine includes a fan shaft that drives a fan that has fan blades. An outer housing surrounds the fan. A bypass flow path is within the outer housing. A fan shaft support that supports the fan shaft defines a fan shaft support transverse stiffness. A gear system is connected to the fan shaft. The gear system includes a gear mesh that defines a gear mesh transverse stiffness. A flexible support which supports the gear system relative to a static structure defines a flexible support transverse stiffness. The flexible support transverse stiffness is less than 11% of the fan shaft support transverse stiffness. The flexible support transverse stiffness is less than 8% of the gear mesh transverse stiffness. ## Claims ### Claim 1 A gas turbine engine, comprising: a fan shaft driving a fan having fan blades; an outer housing surrounding the fan, and a bypass flow path within said outer housing; a fan shaft support that supports said fan shaft, said fan shaft support defining a fan shaft support transverse stiffness; a gear system connected to said fan 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 fan shaft support transverse stiffness and said flexible support transverse stiffness is less than 8% of said gear mesh transverse stiffness. ### Claim 2 (depends on 1) The gas turbine engine of claim 1, wherein said fan shaft support defines a fan 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 fan shaft support lateral stiffness. ### Claim 3 (depends on 2) The gas turbine engine of claim 2, further comprising a fan section having a low fan pressure ratio of less than 1.45, wherein said low fan pressure ratio is measured across the fan blades alone. ### Claim 4 (depends on 3) The gas turbine engine of claim 3, further comprising a low corrected fan tip speed less than 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. ### Claim 5 (depends on 4) The gas turbine engine of claim 4, further comprising a mid-turbine frame including at least one airfoil extending into a flow path, and wherein said fan shaft support is a K-frame bearing support. ### Claim 6 (depends on 3) The gas turbine engine of claim 3, and a reduction ratio greater than 2.3. ### Claim 7 (depends on 6) The gas turbine engine of claim 6, 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. ### Claim 8 (depends on 7) The gas turbine engine of claim 7, 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. ### Claim 9 (depends on 8) The gas turbine engine of claim 8, further comprising a two stage high pressure turbine, and a low corrected fan tip speed less than 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. ### Claim 10 (depends on 7) The gas turbine engine of claim 7, further comprising an input coupling defining an input coupling transverse stiffness, wherein said input coupling transverse stiffness is less than 20% of said fan shaft support transverse stiffness. ### Claim 11 (depends on 10) The gas turbine engine of claim 10, wherein said input coupling transverse stiffness is less than 11% of said fan shaft support transverse stiffness. ### Claim 12 (depends on 11) The gas turbine engine of claim 11, 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. ### Claim 13 (depends on 10) 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. ### Claim 14 (depends on 3) The gas turbine engine of claim 3, further comprising a low corrected fan tip speed less than 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 further comprising at least one bearing system, a high speed spool including an outer shaft and a low speed spool including an inner shaft, wherein said gear system includes a planet carrier and said fan shaft is mounted to said planet carrier and said inner shaft and outer shaft are concentric and rotate via said at least one bearing system about a longitudinal axis of said engine. ### Claim 15 A gas turbine engine, comprising: a fan shaft driving a fan having fan blades; an outer housing surrounding the fan, and a bypass flow path within said outer housing; a fan shaft support that supports said fan shaft, said fan shaft support defining a fan shaft support transverse stiffness; a gear system connected to said fan shaft, said gear system includes a gear mesh defining a gear mesh lateral stiffness; at least one bearing system, a high speed spool including an outer shaft and a low speed spool including an inner shaft, wherein said gear system includes a planet carrier and said fan shaft is mounted to said planet carrier and said inner shaft and outer shaft are concentric and rotate via said at least one bearing system about a longitudinal axis of said engine; and a flexible support which supports said gear system relative to a static structure and defines a flexible support transverse stiffness and a flexible support lateral stiffness, wherein said flexible support transverse stiffness is less than 11% of said fan shaft support transverse stiffness, and said flexible support lateral stiffness is less than 8% of said gear mesh lateral stiffness. ### Claim 16 (depends on 15) The gas turbine engine of claim 15, 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. ### Claim 17 (depends on 16) The gas turbine engine of claim 16, further comprising a low pressure turbine driving said gear system having 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 an exhaust nozzle. ### Claim 18 (depends on 17) The gas turbine engine of claim 17, further comprising a low corrected fan tip speed less than 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. ### Claim 19 (depends on 18) The gas turbine engine of claim 18, wherein said gear system drives a compressor rotor at a common speed with said fan shaft. ### Claim 20 (depends on 19) The gas turbine engine of claim 19, further comprising a three stage low pressure compressor, and a two stage high pressure turbine. ### Claim 21 (depends on 15) The gas turbine engine of claim 15, further comprising a fan section having a low fan pressure ratio of less than 1.45, said low fan pressure ratio measured across the fan blades alone and a reduction ratio greater than 2.3. ### Claim 22 (depends on 21) The gas turbine engine of claim 21, further comprising a low corrected fan tip speed less than 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. ### Claim 23 (depends on 22) The gas turbine engine of claim 22, further comprising a mid-turbine frame including at least one airfoil extending into a flow path. ### Claim 24 (depends on 22) The gas turbine engine of claim 22, further comprising an input coupling defining an input coupling transverse stiffness, wherein said input coupling transverse stiffness is less than 11% of said fan shaft support transverse stiffness. ### Claim 25 (depends on 24) The gas turbine engine of claim 24, wherein said input coupling both transfers torque and facilitates the segregation of vibrations. ### Claim 26 (depends on 21) The gas turbine engine of claim 21, further comprising an input coupling defining an input coupling transverse stiffness, wherein said input coupling transverse stiffness is less than 20% of said fan shaft support transverse stiffness. ### Claim 27 (depends on 26) The gas turbine engine of claim 26, further comprising said input coupling defining an input coupling lateral stiffness and said fan shaft support defining a fan shaft support lateral stiffness, wherein said input coupling lateral stiffness is less than 11% of said fan shaft support lateral stiffness. ### Claim 28 (depends on 27) The gas turbine engine of claim 27, wherein said input coupling transverse stiffness is less than 11% of said fan shaft support transverse stiffness.