US-12618361-B2 - Hydrogen fuelled gas turbine engine

Abstract

A fuel system for a gas turbine engine configured to combust hydrogen fuel. The fuel system includes a main fuel conduit, a fuel pump configured to operate on hydrogen within the fuel conduit to provide pressurised fuel to a core combustor of the gas turbine engine, an auxiliary combustor downstream in fuel flow of the fuel pump, and configured to combust a portion of fuel diverted from the main fuel conduit and to heat a remainder of fuel in the main fuel conduit, and a fuel turbine downstream in fuel flow of the auxiliary combustor. The fuel turbine is configured to be driven by the heated fuel from the auxiliary combustor and configured to power the fuel pump. The fuel system includes a turbine bypass conduit configured to selectively bypass fuel around the fuel turbine. A method of operation is also described.

Inventors

• Martin K Yates

Assignees

• ROLLS-ROYCE PLC

Dates

Publication Date

20260505

Application Date

20250211

Priority Date

20240305

Claims (20)

1. 1 . A fuel system for a gas turbine engine configured to combust a hydrogen fuel, the fuel system comprising: a main fuel conduit; a fuel pump configured to operate on the hydrogen fuel within the fuel conduit to provide a pressurized fuel to a core combustor of the gas turbine engine; an auxiliary combustor downstream in a fuel flow of the fuel pump, configured to combust a portion of the hydrogen fuel directly routed from the main fuel conduit to the auxiliary combustor, by a fuel flow valve, to heat a remainder of the hydrogen fuel in the main fuel conduit; a fuel turbine downstream in a fuel flow of the auxiliary combustor, the fuel turbine being configured to be driven by the heated fuel from the auxiliary combustor and configured to power the fuel pump; a turbine bypass conduit configured to selectively bypass the fuel around the fuel turbine, wherein; one end the turbine bypass conduit is connected to both (1) a point on the main conduit between the fuel pump and the fuel turbine and (2) the auxiliary combustor.
2. 2 . The fuel system according to claim 1 , wherein the fuel turbine is configured to mechanically drive the fuel pump, and/or to drive an electrical generator.
3. 3 . The fuel system according to claim 1 , wherein fuel pump is coupled to an electric motor.
4. 4 . The fuel system according to claim 1 comprising a fuel storage unit configured to store cooled hydrogen, the cooled hydrogen being liquid hydrogen or cryogenically cooled compressed gaseous or supercritical hydrogen.
5. 5 . The fuel system according to claim 4 , wherein the fuel storage unit is configured to store the hydrogen as a liquid at a temperature of less than 30 Kelvin (K).
6. 6 . The fuel system according to claim 5 , wherein the fuel storage unit is configured to store the hydrogen at a temperature up to 25 Kelvin (K).
7. 7 . The fuel system according to claim 5 , wherein the fuel storage unit is configured to store the hydrogen at a pressure of between 1 and 4 Bar.
8. 8 . The fuel system according to claim 1 , wherein the fuel pump is configured to provide a maximum pressure ratio of between 10:1 and 100:1.
9. 9 . The fuel system according to claim 8 , wherein the fuel pump is configured to provide a maximum pressure ratio of between 15:1 and 60:1.
10. 10 . The fuel system according to claim 9 , wherein the fuel pump is configured to provide the maximum pressure ratio at 20:1.
11. 11 . The fuel system according to claim 1 comprising an actively controllable turbine bypass valve configured to control a mass flow rate and/or a pressure of the hydrogen fuel flowing through the fuel turbine bypass conduit.
12. 12 . The fuel system according to claim 11 comprising a controller configured to control at least the auxiliary combustor and the turbine bypass valve.
13. 13 . The fuel system according to claim 12 , wherein the controller is configured to operate at least one of the auxiliary combustor and the turbine bypass valve to provide a constant fuel pump rotational speed.
14. 14 . The fuel system according to claim 12 , wherein the controller is configured to operate at least one of the auxiliary combustor and the turbine bypass valve to provide a variable fuel pump rotational speed, which varies in accordance with a schedule in accordance with a fuel flow demand.
15. 15 . The fuel system according to claim 12 , wherein the controller is configured to control an electric motor, a turbine inlet valve and/or a turbine outlet valve to control a pressure, a temperature and a flow rate of the fuel within the fuel system.
16. 16 . The fuel system according to claim 15 , wherein the controller is configured to operate the electric motor, the turbine inlet valve and/or the turbine outlet valve to provide a constant fuel pump rotational speed.
17. 17 . The fuel system according to claim 15 , wherein the controller is configured to operate the electric motor, the turbine inlet valve and/or the turbine outlet valve to provide a variable fuel pump rotational speed, which varies in accordance with a schedule in accordance with a fuel flow demand.
18. 18 . The fuel system according to claim 1 comprising a turbine inlet valve provided upstream in hydrogen a fuel flow of the fuel turbine configured to control a mass flow rate and/or a pressure of the fuel flowing into the fuel turbine.
19. 19 . The fuel system according to claim 1 comprising a turbine outlet valve provided downstream in a fuel flow of the fuel turbine configured to control a mass flow rate and/or a pressure of the fuel flowing out of the fuel turbine.
20. 20 . A gas turbine engine comprising the fuel system according to claim 1 .

Description

TECHNICAL FIELD This disclosure relates to a fuel system for a hydrogen fueled gas turbine engine, a gas turbine engine including such a fuel system, aircraft comprising such engines, and methods of controlling such fuel systems and engines. BACKGROUND Hydrogen fueled aircraft have been proposed, in which the hydrogen is stored in the form of a liquid, in order to improve density of the fuel. However, such hydrogen must first be warmed to higher temperatures and pumped to high pressures at high flow rates prior to combustion. Challenges in conditioning the liquid hydrogen include the high power required to raise the temperatures and pressures at the required flow rate, as well as controlling complex pumping and heating systems such that the required flow, pressures and temperatures can be produced at all phases of flight. SUMMARY In a first aspect, there is provided a fuel system for a gas turbine engine configured to combust hydrogen fuel, the fuel system comprising: a main fuel conduit;a fuel pump configured to operate on hydrogen within the fuel conduit to provide pressurised fuel to a core combustor of the gas turbine engine;an auxiliary combustor downstream in fuel flow of the fuel pump, and configured to combust a portion of fuel diverted from the main fuel conduit and to heat a remainder of fuel in the main fuel conduit; anda fuel turbine downstream in fuel flow of the auxiliary combustor, the fuel turbine being configured to be driven by the heated fuel from the auxiliary combustor and configured to power the fuel pump; whereinthe fuel system comprises a turbine bypass conduit configured to selectively bypass fuel around the fuel turbine. Advantageously, the fuel system conditions fuel in an efficient, controllable manner. The provision of a fuel turbine provides for efficient driving power to enable operation of the pump, to raise the pressure of the fuel, while the auxiliary combustor both raises the temperature of the fuel and provides enthalpy to drive the turbine. The provision of the turbine bypass conduit which provides for selective bypass of the fuel turbine provides for independent control of the turbine driven fuel pump, which in turn allows for independent temperature and pump pressure control. The fuel turbine may be configured to mechanically drive the fuel pump, and/or may be configured to drive an electrical generator. Advantageously, excess energy from the fuel turbine can be utilised by the aircraft. The fuel pump may be coupled to an electric motor. Advantageously, where the fuel turbine cannot provide sufficient power to fully operate the fuel pump, power can be introduced by the electric motor. The fuel system may comprise a fuel storage unit configured to store cooled hydrogen, which may be configured to store liquid hydrogen or cryogenically cooled compressed gaseous or supercritical hydrogen. The fuel storage unit may be configured to store hydrogen as a liquid at a temperature of less than 30 Kelvin (K), and may be configured to store hydrogen at a temperature less than 25K, and may be configured to store hydrogen at a pressure of between 1 and 4 Bar. The fuel pump may be configured to provide a maximum pressure ratio of between 10:1 and 100:1, and may be configured to provide a maximum pressure ratio of between 15:1 and 60:1, and may be configured to provide a maximum pressure ratio of approximately 20:1. The fuel system may comprise an actively controllable turbine bypass valve configured to control mass flow rate and/or pressure of fuel flowing through the fuel turbine bypass conduit. The fuel system may comprise a turbine inlet valve provided upstream in hydrogen fuel flow of the fuel turbine configured to control mass flow rate and/or pressure of fuel flowing into the fuel turbine. The fuel system may comprise a turbine outlet valve provided downstream in hydrogen fuel flow of the fuel turbine configured to control mass flow rate and/or pressure of fuel flowing out of the fuel turbine. Advantageously, further control of the fuel turbine can be provided, either concurrently or redundantly with the turbine bypass. The fuel system may comprise a controller configured to control at least the auxiliary combustor and turbine bypass valve and, optionally, the electric motor, turbine inlet and/or turbine outlet valve to control pressure, temperature and flow rate of fuel within the fuel system. The controller may be configured to operate at least one of the auxiliary combustor and turbine bypass valve and, optionally, the electric motor, turbine inlet and/or turbine outlet valve to provide a constant fuel pump rotational speed. Advantageously, as input power by the turbine varies, pump speed is kept constant by additional torque input by the electric motor. Alternatively, the controller may be configured to operate at least one of the auxiliary combustor and turbine bypass valve and, optionally, the electric motor, turbine inlet and/or turbine outlet valve to provide a variable