# US 2025/0154902 A1 · Propulsion system comprising a hydrogen-burning 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 2025/0154902 A1 - Document ID: US20250154902A1 - Status: Published application - Kind: A1 - Application number: 18/916,983 - Filed: 2024-10-16 - Published: 2025-05-15 - Earliest claimed: 2023-11-14 - Assignees: ROLLS-ROYCE plc - Applicants: ROLLS-ROYCE plc - Inventors: Michael C WILLMOT; Richard PEACE - Web page: https://patentgrep.com/patent/US20250154902A1 ## CPC - B64D 37/30: Fuel systems for specific fuels - F02C 7/22: Fuel supply systems - B64G 1/402: {Propellant tanks; Feeding propellants} - F02C 7/268: Starting drives for the rotor {, acting directly on the rotor of the gas turbine to be started} - F17C 9/02: with change of state, e.g. vaporisation - H01M 8/04201: {Reactant storage and supply, e.g. means for feeding, pipes} - F02C 3/22: the fuel or oxidant being gaseous at standard temperature and pressure (F02C3/28 takes precedence) - F02C 7/224: Heating fuel before feeding to the burner - F05D 2220/323: for aircraft propulsion, e.g. jet engines - F05D 2260/213: by the provision of a heat exchanger within the cooling circuit - F17C 2221/012: Hydrogen - F17C 2223/0161: cryogenic, e.g. LNG, GNL, PLNG - F17C 2223/033: Small pressure, e.g. for liquefied gas - F17C 2225/0123: gaseous, e.g. CNG, GNC - F17C 2227/0311: Air heating - F17C 2227/0323: in a closed loop - F17C 2265/066: for feeding engines for propulsion - F17C 2270/0189: Planes - H01M 2250/20: Fuel cells in motive systems, e.g. vehicle, ship, plane - Y02T 90/40: Application of hydrogen technology to transportation, e.g. using fuel cells - 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) - B64G: COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR - F17C: VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES (storing fluids in natural or artificial cavities or chambers in the earth B65G5/00; construction or assembling of bulk storage containers employing civil-engineering techniques E04H7/00; variable-capacity gas-holders F17B; liquefaction or refrigeration machines, plants, or systems F25) - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - 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 A propulsion system comprises a propulsive hydrogen-burning gas turbine engine, a first tank storing liquid hydrogen with an ullage and a first fuel line including a fuel pump and a vaporiser, the first fuel line providing gaseous hydrogen to the engine during operation of the system. A second tank storing gaseous hydrogen is coupled by a second fuel line to the first fuel line at a position thereon between the vaporiser and the engine, providing for engine start-up (when the vaporiser is inoperative) and power-boosting during operation of the system. A duct connects gaseous hydrogen within the second tank to the ullage in the first tank in order maintain pressure in the first tank as liquid hydrogen within it is depleted, preventing cavitation of liquid hydrogen within the fuel pump. ## Claims ### Claim 1 A propulsion system comprising: (i) a propulsive, hydrogen-burning gas turbine engine; (ii) a first tank arranged to store liquid hydrogen with an ullage; (iii) a first fuel line arranged to convey hydrogen from the first tank to combustion apparatus of the propulsive, hydrogen-burning gas turbine engine, the first fuel line including a fuel pump and a vaporiser, wherein the fuel pump is arranged to transport liquid hydrogen from the first tank to the vaporiser and the vaporiser is arranged to vaporise the liquid hydrogen utilising heat from the propulsive, hydrogen-burning gas turbine engine and provide resulting gaseous hydrogen to combustion apparatus of the propulsive, hydrogen-burning gas turbine engine and wherein the propulsion system further comprises: (iv) a second tank arranged to store compressed gaseous hydrogen; (v) a second fuel line arranged to convey gaseous hydrogen between the second tank and the first fuel line at a position thereon intermediate the vaporiser and the combustion apparatus; and (vi) a duct which in operation of the propulsion system connects pressurised gaseous hydrogen stored in the second tank to the ullage of the first tank. ### Claim 2 (depends on 1) A propulsion system according to claim 1 further comprising a fuel cell stack and a third fuel line arranged to convey gaseous hydrogen from the second tank to the fuel cell stack and wherein the fuel pump is an electric pump and the fuel cell stack is arranged to provided electrical power to the fuel pump. ### Claim 3 (depends on 1) A propulsion system according to claim 1 further comprising a fuel cell stack and a third fuel line arranged to convey gaseous hydrogen from the second tank to the fuel cell stack and wherein the fuel cell stack is arranged to provide electrical power to an electric starter-motor comprised in the propulsive hydrogen-burning gas turbine engine. ### Claim 4 (depends on 3) A propulsion system according to claim 3 wherein the fuel pump is an electric pump and the fuel cell stack is arranged to provide electrical power to the fuel pump. ### Claim 5 (depends on 1) A propulsion system according to claim 1 wherein the first tank and a portion of the first fuel line extending from the first tank to the vaporiser are contained within a first volume which is arranged for evacuation during operation of the fuel system. ### Claim 6 (depends on 5) A propulsion system according to claim 5 further comprising a fuel cell stack and a third fuel line arranged to convey gaseous hydrogen from the second tank to the fuel cell stack and an electric vacuum pump arranged to receive electrical power from the fuel cell stack and substantially evacuate the first volume. ### Claim 7 (depends on 6) A propulsion system according to claim 6 wherein: (i) the fuel pump is an electric pump and the fuel cell stack is arranged to provide electrical power to the fuel pump; and/or (ii) the fuel cell stack is arranged to provide electrical power to an electric starter motor comprised in the propulsive hydrogen-burning gas turbine engine. ### Claim 8 (depends on 1) A propulsion system according to claim 1 further comprising apparatus for maintaining an inert atmosphere within a second volume which includes a portion of the first fuel line including the vaporiser. ### Claim 9 (depends on 8) A propulsion system according to claim 8 wherein said apparatus comprises a third tank arranged to store compressed gaseous nitrogen and a duct (166) coupling the third tank to said second volume. ### Claim 10 (depends on 9) A propulsion system according to claim 9 further comprising apparatus arranged to selectively convey gaseous hydrogen from the second tank and gaseous nitrogen from the third tank to the first fuel line at a position thereon between the first tank and the fuel pump. ### Claim 11 (depends on 1) A propulsion system according to claim 1 further comprising a third tank arranged to store gaseous nitrogen and apparatus arranged to selectively convey gaseous hydrogen from the second tank and gaseous nitrogen from the third tank to the first fuel line at a position thereon between the first tank and the fuel pump. ### Claim 12 (depends on 1) A propulsion system according to claim 1 further comprising a fuel cell stack, a third fuel line arranged to convey gaseous hydrogen from the second tank to the fuel cell stack and an electrical power distribution system, the fuel cell stack being arranged to provide electrical power to the electrical power distribution system. ### Claim 13 (depends on 1) A propulsion system according to claim 1 further comprising power distribution system, an auxiliary hydrogen-burning gas turbine engine, a third fuel line arranged to convey gaseous hydrogen from the second tank to combustion apparatus of the auxiliary hydrogen-burning gas turbine engine and an electrical generator arranged to be driven by the auxiliary hydrogen-burning gas turbine engine and provide electrical power to the power distribution system. ### Claim 14 (depends on 1) A propulsion system according to claim 1 wherein the vaporiser comprises a heat exchanger arranged to receive compressor bleed air from the propulsive hydrogen-burning gas turbine engine and transmit heat from the compressor bleed air to liquid hydrogen within the first fuel line. ### Claim 15 (depends on 1) A propulsion system according to claim 1 wherein the vaporiser comprises a heat-exchanger arranged to transmit heat from oil within an oil system of the propulsive gas turbine engine to liquid hydrogen within the first fuel line. ### Claim 16 (depends on 1) A propulsion system according to claim 1 wherein the vaporiser comprises a heat-exchanger arranged to transmit heat from the exhaust flow of the propulsive gas turbine engine to liquid hydrogen within the first fuel line. ### Claim 17 (depends on 1) An aircraft comprising a propulsion system according to claim 1. ### Claim 18 (depends on 17) An aircraft according to claim 17 wherein the aircraft is an aeroplane or a helicopter.