Aircraft Fuel Tank Flammability Reduction Method and System

• US 20140053726A1
• Filed: 08/24/2012
• Published: 02/27/2014
• Est. Priority Date: 08/24/2012
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Jojic, Ivana, Evosevich, Barbara J.
• Granted Patent: US 9,061,249 B2
• Time in Patent Office: Days
• US Class Current: 95/54
• CPC Class Codes: B01D 2053/224 with hollow fibres
• CPC Class Codes: B01D 2256/10 Nitrogen
• CPC Class Codes: B01D 2257/104 Oxygen
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 67/0067 by carbonisation or pyrolysis
• CPC Class Codes: B01D 71/0212 Carbon nanotubes
• CPC Class Codes: B64D 37/32 Safety measures not otherwise provided for, e.g. preventing explosive conditions extinguishing or preventing fires in aircraft A62C
• CPC Class Codes: Y02T 50/40 Weight reduction

Abstract

An aircraft fuel tank flammability reduction method includes feeding pressurized air into an air separation module containing a carbon membrane, the air feed exhibiting a normal pressure of no more than 55 psig and the carbon membrane containing at least 95 weight percent carbon. The method includes producing nitrogen-enriched air from the air separation module as a result of removing oxygen from the air feed. An aircraft fuel tank flammability reduction system includes a source for pressurized air, an air separation module configured to receive air feed from the pressurized air source, and a carbon membrane containing at least 95 weight percent carbon. The carbon membrane is configured to permeate oxygen from the air feed through the carbon membrane at a temperature of at least 120° C. (248° F.) and to produce nitrogen-enriched air from the air separation module as a result of removing oxygen from the air feed.

Claims

1. An aircraft fuel tank flammability reduction method comprising:

feeding pressurized air into an air separation module containing a carbon membrane, the air feed exhibiting a normal pressure of no more than 55 psig and the carbon membrane containing at least 95 weight percent carbon;

contacting the carbon membrane with the air feed, permeating oxygen from the air feed through the carbon membrane, and producing nitrogen-enriched air from the air separation module as a result of removing oxygen from the air feed; and

feeding the nitrogen-enriched air into the fuel tank on board the aircraft.

2. The method of claim 1 wherein the carbon membrane comprises a carbon hollow fiber, a spiral wound carbon fiber sheet, a carbon nanotube sheet, or combinations thereof.

3. The method of claim 1 wherein the carbon membrane comprises a pyrolyzed polymer hollow fiber.

4. The method of claim 1 wherein the air feed exhibits a temperature of at least 120°

C. (248°

F.).

5. The method of claim 1 wherein the air feed exhibits a temperature from 120°

C. to 195°

C. (248°

F. to 383°

F.).

6. The method of claim 1 further comprising feeding the pressurized air from a source for the pressurized air into the air separation module without substantially cooling the air feed in a heat exchanger.

7. The method of claim 1 further comprising substantially cooling the nitrogen-enriched air in a heat exchanger before feeding the nitrogen-enriched air from the air separation module into the fuel tank.

8. An aircraft fuel tank flammability reduction method comprising:

feeding pressurized air into an air separation module containing a pyrolyzed polymer hollow fiber, the air feed exhibiting a temperature from 120°

C. to 195°

C. (248°

F. to 383°

F.), the hollow fiber containing at least 95 weight percent carbon, and the hollow fiber exhibiting a selectivity ratio of oxygen permeability to nitrogen permeability of at least 9 and a permeance of at least 80 gas permeation units when measured at an operating temperature of 160°

F.;

contacting the hollow fiber with the air feed, permeating oxygen from the air feed through the hollow fiber, and producing nitrogen-enriched air from the air separation module as a result of removing oxygen from the air feed;

substantially cooling the nitrogen-enriched air from the air separation module in a heat exchanger; and

feeding the cooled nitrogen-enriched air into the fuel tank on board the aircraft.

9. The method of claim 8 wherein the air feed exhibits a normal pressure of no more than 55 psig.

10. An aircraft fuel tank flammability reduction system comprising:

a source for pressurized air;

an air separation module configured to receive air feed from the pressurized air source;

a carbon membrane containing at least 95 weight percent carbon in the air separation module, the carbon membrane being configured to permeate oxygen from the air feed through the carbon membrane at a temperature of at least 120°

C. (248°

F.) and to produce nitrogen-enriched air from the air separation module as a result of removing oxygen from the air feed; and

a fuel tank on board the aircraft and configured to receive the nitrogen-enriched air.

11. The system of claim 10 wherein the carbon membrane comprises a carbon hollow fiber, a spiral wound carbon fiber sheet, a carbon nanotube sheet, or combinations thereof.

12. The system of claim 10 wherein the carbon membrane comprises a pyrolyzed polymer hollow fiber.

13. The system of claim 10 wherein the carbon membrane is configured to permeate oxygen from the air feed through the carbon membrane at a temperature from 120°

C. to 195°

C. (248°

F. to 383°

F.).

14. The system of claim 10 wherein the carbon membrane is configured to permeate oxygen from the air feed through the carbon membrane at a normal pressure of no more than 55 psig.

15. The system of claim 10 wherein the system lacks a cooling heat exchanger downstream of the pressurized air source before the air separation module.

16. The system of claim 10 further comprising a heat exchanger configured to cool substantially the nitrogen-enriched air from the air separation module and to provide cooled nitrogen-enriched air into the fuel tank.

17. The system of claim 10 wherein the carbon membrane exhibits a selectivity ratio of oxygen permeability to nitrogen permeability of at least 9 when measured at an operating temperature of 160°

F.

18. The system of claim 10 wherein the carbon membrane exhibits a permeance of at least 80 gas permeation units when measured at an operating temperature of 160°

F.

19. The system of claim 10 wherein the carbon membrane has an operational surface area that is at least 50% less than an operational surface area of a polymer hollow fiber membrane operating under the same conditions and producing the same nitrogen-enriched air output.

20. The system of claim 10 wherein the carbon membrane exhibits a service life that is at least 1.5 times a service life of a polymer hollow fiber membrane operating under the same conditions and producing the same nitrogen-enriched air output.