Carbon Membrane Air Separation for Aircraft Fuel Tank Inerting

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing aircraft fuel tank inerting systems using polymer hollow fiber membranes have limited service life and operating conditions due to material limitations, leading to reduced performance and increased weight and drag from larger heat exchangers and higher air supply demands.

Innovation Solution

The use of carbon membranes, such as carbon hollow fibers or pyrolyzed polymer hollow fibers, in air separation modules that operate at higher temperatures and lower pressures, allowing for increased permeability and selectivity while reducing the system's weight and size, and extending service life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polymer hollow fiber membranes are used in air separation modules, then oxygen permeation is achieved, but service life and operating conditions are limited due to material limitations

Engineering Contradiction:

Improveservice lifeVSAvoidoperating conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the fundamental material parameter from polymer to carbon, which has inherently different thermal and mechanical properties. This parameter change enables the membrane to withstand higher temperatures and pressures, directly resolving the limitation on operating conditions while maintaining long service life.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs carbon membranes that may be integrated with supporting structures to create a composite air separation module. This composite approach allows the carbon membrane to function at elevated temperatures and pressures while the supporting structure provides mechanical integrity, thus expanding adaptable operating conditions without compromising reliability.

Inventive Principle:

Principle #40Composite materials

2Productivity

If higher pressure air feed is used to increase oxygen permeation, then separation efficiency improves, but system weight and drag increase due to larger heat exchangers and higher air supply demands

Engineering Contradiction:

Improveseparation efficiencyVSAvoidsystem weight

Core Design Contradiction:

ProductivityVSWeight of moving object

Solution Approach 1:

The patent changes the operating pressure parameter by utilizing lower pressure air feed (up to 380 kPa gauge) made possible by the carbon membrane's superior permeability. This parameter change reduces the need for high-pressure compressors and smaller heat exchangers, directly reducing system weight while maintaining separation efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the need for high-pressure mechanical compression systems with a carbon membrane-based separation system that achieves efficient oxygen permeation at lower pressures. This substitution eliminates or reduces the size of heavy mechanical components like compressors and large heat exchangers, thereby reducing overall system weight.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Duration of action of stationary object

If polymer membranes operate at lower temperatures to maintain material integrity, then service life is extended, but permeability and selectivity are reduced

Engineering Contradiction:

Improveservice lifeVSAvoidpermeability

Core Design Contradiction:

Duration of action of stationary objectVSQuantity of substance

Solution Approach 1:

The patent changes the temperature operating parameter by utilizing the carbon membrane's thermal stability to operate at higher temperatures (120°C to 195°C). This parameter change simultaneously improves permeability and selectivity while the carbon material's inherent thermal resistance ensures extended service life, resolving the trade-off between temperature and performance.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the efficiency and reliability of aircraft fuel tank inerting systems by increasing permeability, reducing the need for larger heat exchangers, and extending the service life of the air separation modules, leading to improved fuel efficiency and reduced maintenance costs.

Implementation Method 1

permeating oxygen from the air feed through the carbon membrane

Methodology Applied

Scientific EffectPermeation: Permeation

Data Source

PatentEP2888168B1Aircraft fuel tank flammability reduction method and system

Publication Date: 2016.06.22 THE BOEING CO

Figure 1~2
Figure 3~4

AI summary

An aircraft fuel tank flammability reduction method includes feeding pressurized air into an air separation module (12) containing a carbon membrane (13), 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 (12) 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 (12) configured to receive air feed from the pressurized air source, and a carbon membrane (13) containing at least 95 weight percent carbon. The carbon membrane (13) 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 (12) as a result of removing oxygen from the air feed.