# US 11,306,682 B2 · Concentric turbomachine with trailing edge > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,306,682 B2 - Document ID: US11306682B2 - Status: Granted - Kind: B2 - Application number: 16/527,905 - Filed: 2019-07-31 - Published: 2020-04-02 - Granted: 2022-04-19 - Earliest claimed: 2018-08-22 - Assignees: ROLLS-ROYCE plc - Applicants: ROLLS-ROYCE plc - Inventors: Giles E Harvey - Web page: https://patentgrep.com/patent/US11306682B2 ## CPC - B64C 11/001: {Shrouded propellers} - B64C 11/48: Units of two or more coaxial propellers - B64D 27/33: Hybrid electric aircraft - B64D 27/34: All-electric aircraft - B64D 35/04: characterised by the transmission driving a plurality of propellers or rotors - B64D 35/06: the propellers or rotors being counter-rotating - F02C 6/00: Plural gas-turbine plants; Combinations of gas-turbine plants with other apparatus; Adaptations of gas-turbine plants for special use - F02K 3/06: with front fan - F02K 3/072: with counter-rotating {, e.g. fan} rotors - F02K 3/077: the plant being of the multiple flow type, i.e. having three or more flows - F02K 5/00: Plants including an engine, other than a gas turbine, driving a compressor or a ducted fan - F05D 2220/32: in gas turbines - F05D 2220/76: an electrical generator - F05D 2250/70: Shape - Y02T 50/50: On board measures aiming to increase energy efficiency - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - B64C: AEROPLANES; HELICOPTERS - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT - 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) - 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 ## Abstract An axial flow turbomachine (102) for producing thrust to propel an aircraft is shown. The turbomachine has an inner duct (202) and an outer duct (204), both of which are annular and concentric with one another. An inner fan (206) is located in the inner duct, and is configured to produce a primary pressurised flow (P). An outer fan (207) is located in an outer duct, and is configured to produce a secondary pressurised flow (S). The outer fan has a hollow hub (208) through which the inner duct passes. A swept area of the outer fan is from 2 to 20 times greater than a swept area of the inner fan. ## Claims ### Claim 1 An axial flow turbomachine for producing thrust to propel an aircraft, the turbomachine comprising: an inner duct and an outer duct, both of the inner duct and the outer duct are annular and concentric with one another; an inner fan located in the inner duct, the inner fan being configured to produce a primary pressurized flow; and an outer fan located in the outer duct, the outer fan being configured to produce a secondary pressurized flow and having a hollow hub through which the inner duct passes; wherein a duct length is defined by a length of a trailing edge of the outer duct located axially downstream of the inner duct, a swept area of the outer fan is from 2 to 20 times greater than a swept area of the inner fan, and the duct length is defined by a range between 6 times a tip radius of the inner fan and 8 times the tip radius of the inner fan. ### Claim 2 (depends on 1) The turbomachine of claim 1, wherein the swept area of the outer fan is from 4 to 17 times greater than the swept area of the inner fan. ### Claim 3 (depends on 1) The turbomachine of claim 1, wherein the swept area of the outer fan is from 7.5 to 13 times greater than the swept area of the inner fan. ### Claim 4 (depends on 1) The turbomachine of claim 1, wherein the swept area of the outer fan is equal to 9 times greater than the swept area of the inner fan. ### Claim 5 (depends on 1) The turbomachine of claim 1, wherein, in operation, the primary pressurized flow enters the inner duct and the secondary pressurized flow enters the outer duct, the primary pressurized flow and secondary pressurized flow respectively exit the inner duct and the outer duct, such that the secondary pressurized flow substantially shrouds the primary pressurized flow. ### Claim 6 (depends on 1) The turbomachine of claim 1, wherein the inner fan is configured to rotate counter to the outer fan. ### Claim 7 (depends on 1) The turbomachine of claim 1, wherein the inner fan is configured to rotate at a rate greater than a rate of the outer fan. ### Claim 8 (depends on 1) The turbomachine of claim 1, further comprising a first electric machine configured to drive the inner fan and a second electric machine configured to drive the outer fan. ### Claim 9 (depends on 1) The turbomachine of claim 1, further comprising a first electric machine configured to drive the inner fan, the first electric machine having a rotor integral with a hub of the inner fan and a stator located radially inward of the rotor. ### Claim 10 (depends on 9) The turbomachine of claim 9, further comprising a second electric machine is-configured to drive the outer fan, the second electric machine having a rotor integral with the hub of the outer fan and a stator located radially inward of the rotor of the second electric machine and radially outward of the inner duct. ### Claim 11 (depends on 1) The turbomachine of claim 1, wherein the inner fan and the outer fan partially or fully overlap in an axial direction. ### Claim 12 (depends on 1) The turbomachine of claim 1, wherein a hub-tip ratio of the outer fan is from 1.6 to 2.2 times a hub-tip ratio of the inner fan. ### Claim 13 (depends on 1) The turbomachine of claim 1, wherein a diameter of the outer fan is from 2.5 to 3.5 times a diameter of the inner fan. ### Claim 14 (depends on 13) The turbomachine of claim 13, wherein the diameter of the outer fan is equal to 3.2 times greater than the diameter of the inner fan. ### Claim 15 (depends on 1) The turbomachine of claim 1, wherein the inner fan is configured to operate at a tip speed from 1 to 3 times a tip speed of the outer fan. ### Claim 16 (depends on 15) The turbomachine of claim 15, wherein the inner fan is configured to operate at the tip speed from 1.3 to 2.5 times the tip speed of the outer fan. ### Claim 17 (depends on 1) The turbomachine of claim 1, wherein the inner fan is configured to operate at a rate of rotation of from 3 to 8 times that a rate of rotation of the outer fan. ### Claim 18 (depends on 17) The turbomachine of claim 17, in which the inner fan is configured to operate at the rate of rotation from 5 to 7 times the rate of rotation of the outer fan. ### Claim 19 (depends on 1) An aircraft comprising one or more turbomachines according to claim 1.