Aircraft and a retrofit cryogenic fuel system

1. An aircraft, comprising:

a turbine engine having a bleed air output line;

a cryogenic fuel system having a cryogenic fuel tank for storing cryogenic fuel and a supply line operably coupling the tank to the turbine engine, the cryogenic fuel tank being located within a compartment;

an on board inert gas generating system (OBIGGS) fluidly coupled to the bleed air output line and having a nitrogen rich stream output line and an oxygen rich stream output line, the nitrogen rich stream output line being fluidly coupled with the compartment; and

a pressure regulation system configured to selectively increase or decrease a pressure in said nitrogen rich stream output line, the pressure regulation system comprising;

a control valve;

a low pressure line;

a high pressure line; and

an expansion valve or turbine fluidly coupled to the low pressure line upstream of the compartment for lowering a pressure of the nitrogen rich stream provided to the compartment.

2. The aircraft of claim 1 , further comprising a heat exchanger fluidly connected between the turbine engine and the OBIGGS and wherein the bleed air output line routes through the heat exchanger.

3. The aircraft of claim 1 wherein the compartment comprises an overboard vent.

4. The aircraft of claim 1 , wherein said pressure regulation system further comprises:

a motor-driven, gear-driven, shaft-driven or turbine-driven compressor fluidly coupled to the high pressure line;

wherein said high pressure line is fluidly coupled with the supply line located upstream of the cryogenic fuel tank.

5. The aircraft of claim 4 wherein the control valve controls the flow of nitrogen to each of said low pressure line and said high pressure line.

6. The aircraft of claim 1 wherein the aircraft is a dual fuel aircraft fueled by both cryogenic fuel and a kerosene based jet fuel.

7. An aircraft having a retrofit cryogenic fuel system, a cargo bay and a turbine engine fueled by the cryogenic fuel, comprising:

an evacuated enclosure within the cargo bay;

a cryogenic fuel tank located within the evacuated enclosure, the cryogenic fuel tank being located within a compartment;

at least one vent line or fuel supply line fluidly coupled to the evacuated enclosure;

an on board inert gas generating system (OBIGGS) fluidly coupled to a bleed air output line and having a nitrogen rich stream output line and an oxygen rich stream output line, the nitrogen rich stream output line being fluidly coupled with the compartment; and

a pressure regulation system configured to selectively increase or decrease the pressure of said nitrogen rich stream, the pressure regulation system comprising;

a control valve;

a low pressure line;

a high pressure line; and

an expansion valve or turbine fluidly coupled to the low pressure line upstream of the compartment for lowering a pressure of the nitrogen rich stream provided to the compartment.

8. The aircraft of claim 7 wherein at least one of the vent line and the fuel supply line are continuous without a joint.

9. The aircraft of claim 7 wherein the at least one vent line is fluidly coupled to ambient air external to the cargo bay when the evacuated enclosure is received within the cargo bay.

10. The aircraft of claim 7 wherein the at least one vent line comprises an ejector coupling, with the ejector coupling configured to create a suction and an evacuated pressure condition within the line and the evacuated enclosure.

11. The aircraft of claim 7 , wherein said nitrogen rich stream output line is selectively coupled to the at least one fuel supply line to purge said at least one fuel supply line.

12. An aircraft, comprising:

a turbine engine having a bleed air output line;

a cryogenic fuel system having a cryogenic fuel tank for storing cryogenic fuel and a supply line operably coupling the tank to the turbine engine, the cryogenic fuel tank being located within a compartment;

an on board inert gas generating system (OBIGGS) fluidly coupled to the bleed air output line and having a nitrogen rich stream output line and an oxygen rich stream output line, the nitrogen rich stream output line being fluidly coupled with the compartment;

a water and particle filter upstream of said on board inert gas generating system (OBIGGS); and

a pressure regulation system configured to selectively increase or decrease the pressure of said nitrogen rich stream, the pressure regulation system comprising;

a low pressure line;

a high pressure line; and

an expansion valve or turbine fluidly coupled to the low pressure line upstream of the compartment for lowering a pressure of the nitrogen rich stream provided to the compartment.

13. The aircraft of claim 12 , further comprising a control valve fluidly coupled to said nitrogen rich stream output line;

wherein said control valve is configured to control the flow of nitrogen in said nitrogen rich stream to each of said low pressure line and said high pressure line.

14. The aircraft of claim, 13 wherein said pressure regulation system is downstream of said control valve and upstream of each of said low pressure line and said high pressure line.

15. The aircraft of claim 14 further comprising:

a cargo bay;

an evacuated enclosure within the cargo bay; and

at least one vent line coupled to the evacuated enclosure;

wherein said cryogenic fuel tank is located within the evacuated enclosure.

16. The aircraft of claim 15 wherein said high pressure line is fluidly coupled to said fuel supply line.

17. The aircraft of claim 16 wherein the aircraft is a dual fuel aircraft fueled by both cryogenic fuel and a kerosene based jet fuel.

18. The aircraft of claim 17 further comprising a heat exchanger upstream of said water and particle filter.