# US 2020/0400036 A1 · Gas turbine engine system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0400036 A1 - Document ID: US20200400036A1 - Status: Published application - Kind: A1 - Application number: 16/449,554 - Filed: 2019-06-24 - Published: 2020-12-24 - Earliest claimed: 2019-06-24 - Assignees: Pratt & Whitney Canada Corp. - Applicants: Pratt & Whitney Canada Corp. - Inventors: Timothy REDFORD; David MENHEERE - Web page: https://patentgrep.com/patent/US20200400036A1 ## CPC - F01D 15/12: Combinations with mechanical gearing (driven by multiple engines F01D13/00) - B64D 41/00: Power installations for auxiliary purposes - F01D 15/10: Adaptations for driving, or combinations with, electric generators - F01D 25/36: using electric motors - F02C 3/04: having a turbine driving a compressor (power transmission arrangements F02C7/36; control of working fluid flow F02C9/16) - F02C 7/32: Arrangement, mounting, or driving, of auxiliaries - F16H 48/10: with orbital spur gears - B64D 13/06: the air being conditioned (pressurising B64D13/02) - B64D 2013/0603: {Environmental Control Systems} - F05D 2220/32: in gas turbines - F05D 2220/50: for auxiliary power units (APU's) - F05D 2220/76: an electrical generator - F05D 2260/40311: of the epicyclical, planetary or differential type - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - 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) - F16H: GEARING - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS ## Abstract A gas turbine engine system includes, in serial flow communication, an engine compressor configured to compress air, a combustor in which the compressed air is mixed with fuel and ignited to generate a stream of combustion gases, and a turbine configured to extract energy from the combustion gases. An electric generator is configured to be driven by the turbine and generate electric energy during use. An electric motor is configured to be driven by electric energy generated by the electric generator. The electric motor is configured in use to drive the engine compressor. ## Claims ### Claim 1 A gas turbine engine system, comprising: an engine compressor, a combustor, and a turbine in serial flow communication; an electric generator configured to be driven by the turbine; and an electric motor configured to be driven by electric energy generated by the electric generator, the electric motor configured in use to drive the engine compressor. ### Claim 2 (depends on 1) The system of claim 1, comprising a differential gear train having an input drivingly coupled to the turbine and a first output, the electric generator being drivingly coupled to the first output of the differential gear train. ### Claim 3 (depends on 2) The system of claim 2, wherein the first output is drivingly coupled to a load compressor configured to generate compressed air for an environmental control system of an aircraft. ### Claim 4 (depends on 2) The system of claim 2, wherein the differential gear train has a second output that is drivingly coupled to the engine compressor. ### Claim 5 (depends on 1) The system of claim 1, wherein the engine compressor is a first engine compressor, and the system includes a second engine compressor operatively disposed downstream from the first engine compressor. ### Claim 6 (depends on 2) The system of claim 2, wherein the differential gear train includes an epicyclic gear set. ### Claim 7 (depends on 2) The system of claim 2, wherein the differential gear train includes a compound epicyclic gear set. ### Claim 8 (depends on 2) The system of claim 2, wherein the first output is drivingly coupled to a propeller. ### Claim 9 A method of operating a gas turbine engine, comprising: using an engine compressor to compress air; generating a stream of combustion gases by igniting the compressed air mixed with fuel; extracting energy from the combustion gases with a turbine; driving an electric generator with the turbine to generate electric energy; and driving the engine compressor using an electric motor driven by the electric energy generated by the electric generator. ### Claim 10 (depends on 9) The method of claim 9, comprising driving the electric generator via a first output of a differential gear train. ### Claim 11 (depends on 10) The method of claim 10, comprising driving the engine compressor via a second output of the differential gear train. ### Claim 12 (depends on 10) The method of claim 10, comprising generating compressed air for an environmental control system of an aircraft using a load compressor driven via the first output of the differential gear train. ### Claim 13 (depends on 12) The method of claim 12, comprising maintaining a substantially constant operating speed of the electric generator while varying an operating speed of the turbine. ### Claim 14 (depends on 12) The method of claim 12, comprising maintaining a substantially constant operating speed of the load compressor while varying an operating speed of the turbine. ### Claim 15 (depends on 12) The method of claim 12, comprising controlling the electric generator to maintain a desired operating speed of the load compressor. ### Claim 16 (depends on 10) The method of claim 10, comprising maintaining a substantially constant operating speed of the electric generator while varying an operating speed of the turbine. ### Claim 17 An auxiliary power unit comprising: an engine compressor, a combustor, and a turbine in serial flow communication; a differential gear train having an input shaft drivingly coupled to the turbine, a first output shaft and a second output shaft, the differential gear train configured to apportion an input torque from the turbine between a first output torque applied to the first output shaft and a second output torque applied to the engine compressor via the second output shaft; an electric generator drivingly coupled to the first output shaft of the differential; and an electric motor configured to be driven by electric energy generated by the electric generator, the electric motor configured in use to drive the compressor. ### Claim 18 (depends on 17) The auxiliary power unit of claim 17, further comprising a load compressor drivingly coupled to the first output shaft of the differential gear train. ### Claim 19 (depends on 17) The auxiliary power unit of claim 17, wherein the engine compressor is a first engine compressor, and the auxiliary power unit includes a second engine compressor operatively disposed downstream from the first engine compressor. ### Claim 20 (depends on 18) The auxiliary power unit of claim 18, wherein the differential gear train includes an epicyclic gear set.