Compressed air system for aircraft

1 . A system for an aircraft, comprising:

an engine;

a nacelle housing the engine;

a fuel system including a fuel circuit, a fuel source, a heat exchanger and a turboexpander, the fuel circuit configured to direct fuel in a liquid phase from the fuel source, through the heat exchanger and the turboexpander, to the engine for combustion, the fuel being in a gaseous phase when the fuel exits the heat exchanger, and the heat exchanger configured to transfer heat energy from combustion products generated by the combustion of the fuel in the engine into the fuel in the fuel circuit;

an air system discrete from the engine, the air system including an air compressor and the turboexpander, and the air system configured to expand the fuel directed across the turboexpander by the fuel circuit to power operation of the air compressor;

an engine inlet fluidly coupling the engine to an environment external to the aircraft; and

an air circuit inlet fluidly coupling the air compressor to the environment external to the aircraft;

wherein the engine inlet and the air circuit inlet are each independently fluidly coupled to the environment external to the aircraft; and

wherein the air compressor is located within an interior of a wing.

2 . The system of claim 1 , wherein

the fuel comprises hydrogen fuel; and

the fuel source comprises a hydrogen fuel reservoir.

3 . The system of claim 1 , wherein the fuel system is configured to store the fuel within the fuel source as a cryogenic liquid.

4 . The system of claim 1 , wherein

the heat exchanger is configured to facilitate changing the fuel from the liquid phase to the gaseous phase; and

the air system is configured to expand the fuel in the gaseous phase across the turboexpander before delivering the fuel in the gaseous phase to the engine.

5 . The system of claim 1 , wherein the engine comprises a gas turbine engine.

6 . The system of claim 1 , wherein

the engine includes a compressor section, a combustor section, a turbine section and a flowpath extending through the compressor section, the combustor section and the turbine section from the engine inlet into the flowpath to an exhaust from the flowpath; and

the heat exchanger is arranged along the flowpath between the combustor section and the exhaust from the flowpath.

7 . The system of claim 6 , wherein the heat exchanger is arranged along the flowpath between the turbine section and the exhaust from the flowpath.

8 . The system of claim 1 , further comprising a pneumatic system including an air circuit, the pneumatic system configured to receive compressed air through the air circuit from the air compressor.

9 . The system of claim 8 , wherein the pneumatic system includes a bleed air circuit, the pneumatic system is configured to receive additional compressed air from the bleed circuit fluidly coupled to the engine.

10 . The system of claim 1 , wherein the air compressor is fluidly decoupled from the engine.

11 . The system of claim 1 , further comprising a propulsor rotor coupled to and configured to be driven by the engine.

12 . A system for an aircraft, comprising:

an engine;

an engine inlet fluidly coupling the engine to an environment external to the aircraft;

a pneumatic system;

an air system including an air compressor and a turboexpander, the air system configured to expand fuel directed across the turboexpander to power operation of the air compressor, and the air compressor configured to provide compressed air for delivery to the pneumatic system;

an air system inlet fluidly coupling the air compressor to the environment external to the aircraft, the air system inlet fluidly coupling the air compressor to the environment external to the aircraft independently from the engine inlet fluidly coupling the engine to the environment external to the aircraft; and

a fuel system including a fuel circuit, a heat exchanger and the turboexpander, the fuel circuit configured to direct the fuel through the heat exchanger to the turboexpander and to the engine for combustion, and the heat exchanger configured to increase a temperature and a pressure of the fuel;

wherein the pressure of the fuel entering the turboexpander is a first pressure and the pressure of the fuel exiting the turboexpander is a second pressure less than the first pressure; and

wherein the fuel circuit is further configured to deliver the fuel from the turboexpander to the engine for combustion at the second pressure;

wherein the aircraft comprises a first aircraft structure and a second aircraft structure, the first aircraft structure comprises the engine, and the second aircraft structure comprises at least one of a fuselage or a wing; and

wherein the air compressor and the turboexpander are arranged within the second aircraft structure.

13 . The system of claim 12 , wherein the pneumatic system comprises a pneumatic anti-icing system.

14 . The system of claim 12 , wherein the pneumatic system comprises a pneumatic actuator.

15 . The system of claim 12 , wherein the pneumatic system comprises an environmental control system for the aircraft.

16 . A system for an aircraft, comprising:

a fuselage;

a gas turbine engine including a compressor section, a combustor section, a turbine section and a flowpath extending through the compressor section, the combustor section and the turbine section from an engine inlet into the flowpath to an exhaust from the flowpath, the engine inlet fluidly coupling the gas turbine engine to an environment external to the aircraft;

a fuel system configured to deliver fuel to the combustor section, the fuel system including a fuel circuit, a fuel source, a heat exchanger and a turboexpander, the fuel circuit fluidly coupling the fuel source to the combustor section, and the fuel circuit extending sequentially through the heat exchanger, the turboexpander between the fuel source and the combustor section, and to the combustor section; and

an air system including an air compressor and the turboexpander, the air compressor fluidly independent of the flowpath, and a turboexpander rotor in the turboexpander coupled to and configured to drive rotation of an air compressor rotor in the air compressor, the air compressor comprising an air compressor inlet fluidly coupling the air compressor to the environment external to the aircraft;

wherein the fuel system is configured such that the heat exchanger provides the fuel to the turboexpander as warm and high pressure gaseous fuel, and the turboexpander expands the warm and high pressure gaseous fuel to provide low pressure gaseous fuel;

wherein the fuel system is further configured to deliver the low pressure gaseous fuel to one or more fuel injectors in the combustor section;

wherein the engine inlet and the air compressor inlet are each separately fluidly coupled to the environment external to the aircraft; and

wherein the air system is located within an interior portion of the fuselage.